Liquid crystal display device

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device in which a film-like member such as a protective film for a polarizing element and a retardation film is used.

Liquid crystal display devices are widely used as display devices in various information processing devices such as computers and televisions, and in recent years, demand has been rapidly increasing especially in the fields of liquid crystal televisions and the like. With the expansion of the market for such liquid crystal display devices, there is a strong demand for further improvement in display image quality and reduction in manufacturing costs.

Under such circumstances, a so-called vertical orientation (VA) mode liquid crystal display device has been proposed as an effective technique for improving display image quality (see, for example, Patent Documents 1 to 3). The VA mode liquid crystal display device vertically aligns liquid crystals having negative permittivity anisotropy between opposing substrates in a state where no voltage is applied. According to the VA mode liquid crystal display device, the liquid crystal display cell shows almost no birefringence or optical rotation in the front direction. Therefore, by arranging two polarizing elements orthogonally on both sides of the liquid crystal display cell, the voltage is increased. In the non-applied state, a substantially perfect black display can be realized and a very high contrast can be obtained. However, in the oblique direction, the liquid crystal display cell exhibits birefringence, so that there is an apparent phase difference, and the geometric relative relationship between the two polarizing elements is not apparently orthogonal, so that light leakage occurs. Will occur and the contrast will drop. Therefore, in the VA mode liquid crystal display device, it is a technical issue to expand the viewing angle. On the other hand, there is known a technique of providing a retardation film in a liquid crystal display device in VA mode for the purpose of canceling the phase difference of a liquid crystal display cell in an oblique direction and maintaining the orthogonality of a polarizing element. For example, in Patent Documents 1 to 3 and the like, polarizing elements are arranged on both sides of a liquid crystal display cell in VA mode, and at least one retardation film is arranged between the polarizing element and the liquid crystal display cell, and a viewing angle is provided. Is disclosed to expand.

Further, as a technique effective for improving the display image quality, a so-called horizontal electric field (IPS) mode liquid crystal display device has been proposed (see, for example, Patent Documents 4 and 5). In the IPS mode liquid crystal display device, a horizontal electric field is applied to a horizontally oriented liquid crystal display cell in which a liquid crystal is sandwiched between two upper and lower substrates whose surfaces have been subjected to parallel alignment treatment, and liquid crystal molecules are substantially parallel to the substrate. It is displayed by rotating it in a parallel plane. In the IPS mode liquid crystal display device, the liquid crystal molecules are always substantially parallel to the substrate, and the display is performed by changing the angle formed by the liquid crystal molecules and the polarizing element. Therefore, the birefringence of the liquid crystal display cell changes even in an oblique direction. It has the advantage of being small and having a wide viewing angle. However, even in the IPS mode liquid crystal display device, as in the VA mode liquid crystal display device, since the two polarizing elements are arranged orthogonally, the geometrical relative relationship between the two polarizing elements is different in the oblique direction. Since it is not apparently orthogonal, light leakage occurs and the contrast is lowered. In order to suppress this decrease in contrast, it is being studied to provide a retardation film also in an IPS mode liquid crystal display device. For example, Patent Document 5 and the like disclose a technique for arranging a retardation film in which the phase difference in the in-plane direction and the thickness direction is controlled between the polarizing element and the liquid crystal display cell.

In these liquid crystal mode liquid crystal display devices, as a polarizing element, a dichroic substance such as iodine or a dichroic dye is adsorbed on a transparent polymer film such as a polyvinyl alcohol-based resin film molecularly oriented in one direction. Oriented ones are generally used. However, such a polarizing element has room for improvement in terms of mechanical strength, heat resistance and moisture resistance. Therefore, in general, a transparent protective film is attached to both sides or one side of the polarizing element via an adhesive layer or the like to ensure the durability of the polarizing element. Therefore, the retardation film as described above is usually attached to the outside of the protective film attached to the polarizing element via an adhesive layer.

Conventionally, as a protective film, a triacetyl cellulose film (hereinafter, also referred to as "TAC") is widely used. However, since the TAC film has high moisture permeability, there is room for further improvement in order to sufficiently secure the moisture resistance of the polarizing element. Therefore, in order to further improve the durability of the polarizing element under high temperature and high humidity, a technique of using a film having better water vapor permeability than a TAC film such as a film made of norbornene resin as a protective film is used. Has been proposed (see, for example, Patent Documents 6 to 11). Further, for the purpose of reducing the number of constituent films and improving the display quality, a technique has been proposed in which a protective film has the function of a retardation film by using a film made of a norbornene resin or the like. (See, for example, Patent Documents 12 and 13). It should be noted that the retardation film is also disclosed to reduce the water absorption rate and the photoelastic coefficient from the viewpoint of stability of birefringence (phase difference) characteristics (see, for example, Patent Document 15). However, in order to further improve the display image quality of the liquid crystal display device, there is still room for improvement in the durability of the polarizing element.

Further, when a protective film is attached to a polarizing element made of a polyvinyl alcohol-based resin film, the polyvinyl alcohol-based resin becomes brittle in a dry state. Therefore, when a TAC film is used as the protective film, moisture is added to the polarizing element. A method of laminating in a soaked state and then drying and removing water after laminating is preferably used. However, when a film having low moisture permeability such as a film made of norbornene resin is used as the protective film, there is room for ingenuity in that it becomes difficult to dry and remove the moisture after bonding.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 11-258605</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 10-153802</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2000-131693</text></patcit><patcit num="4"><text>Japanese Patent Application Laid-Open No. 6-160878</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 11-305217</text></patcit><patcit num="6"><text>Japanese Unexamined Patent Publication No. 2004-309717</text></patcit><patcit num="7"><text>Japanese Unexamined Patent Publication No. 6-51117</text></patcit><patcit num="8"><text>Japanese Unexamined Patent Publication No. 2002-196132</text></patcit><patcit num="9"><text>Japanese Unexamined Patent Publication No. 2001-235625</text></patcit><patcit num="10"><text>Japanese Patent Application Laid-Open No. 2002-21619</text></patcit><patcit num="11"><text>Japanese Unexamined Patent Publication No. 2002-174729</text></patcit><patcit num="12"><text>Japanese Unexamined Patent Publication No. 11-223728</text></patcit><patcit num="13"><text>Japanese Unexamined Patent Publication No. 8-43812</text></patcit><patcit num="14"><text>Japanese Unexamined Patent Publication No. 8-240714</text></patcit><patcit num="15"><text>Japanese Unexamined Patent Publication No. 2001-91744</text></patcit>

<p>The present invention has been made in view of the above situation, and an object of the present invention is to provide a liquid crystal display device in which a polarizing element has high durability and excellent durability of display quality.</p>

<p>The present inventors have studied various liquid crystal display devices having at least one film-like member such as a retardation film in the region between the liquid crystal display cell and the polarizing element, and as a result, there is room for improvement in the durability of the polarizing element. We focused on the fact that it is possible to further improve the display quality. For example, the liquid crystal display device shown in FIG. 5 has an adhesive layer 42 having a thickness of about 20 μm, a retardation film 62 made of polycarbonate (hereinafter, also referred to as PC) or the like, and a thickness of about 20 μm on both sides of the liquid crystal display cell 10. Adhesive layer 42, protective film 61 made of TAC, adhesive layer 41, polarizing elements 21,22 based on polyvinyl alcohol (hereinafter, also referred to as "PVA"), adhesive layer 41, and protective film 61 made of TAC. Of these, the adhesive layer 42, the retardation film 62 made of PC, etc., and the protective film 61 made of TAC all have low durability such as heat resistance and moisture resistance. There was a risk of adversely affecting the durability of the polarizing elements 21 and 22.</p><p>On the other hand, the present inventors have (1) a retardation film 62 made of a PC or the like and a retardation film 35 made of a norbornene-based resin or the like having more excellent durability, as in the liquid crystal display device shown in FIG. (2) As in the liquid crystal display device shown in Fig. 7, in addition to the configuration of (1) above, the protective film 61 made of TAC is replaced with a protective film made of norbornen resin, etc., which has better durability. Replace with 36, (3) Like the liquid crystal display device shown in Fig. 8, in addition to the configuration of (2) above, a protective film made of norbornen-based resin or the like also functions as a retardation film. We have been studying reducing the phase difference film and the pressure-sensitive adhesive layer one by one. Then, the film-like member in the region between at least one liquid crystal display cell and the polarizing element has an absolute value of the photoelastic coefficient of 10 × 10.^-8cm²It was found that the durability of the film-like member can be sufficiently improved and the display characteristics of the liquid crystal display device can be improved by satisfying less than / N and the water absorption rate of less than 2.0%.</p><p>Further, the present inventors have made it possible to further improve the durability of the polarizing element by further reducing the moisture absorption in the adhesive layer or the adhesive layer between the polarizing element and the protective film in addition to the above-mentioned configuration. I found that it would be. That is, when the film-like member is attached to the polarizing element via an adhesive layer and / or an adhesive layer having a thickness of less than 10 μm, and is bonded to another film-like member, another film. A liquid crystal display device having excellent durability of the polarizing element and excellent display characteristics is provided by adopting a structure in which the shape member is bonded via an adhesive layer and / or an adhesive layer having a thickness of less than 10 μm. We have found that we can do this, and have come up with the idea that we can solve the above problems brilliantly, and have arrived at the present invention.</p><p>That is, in the present invention, there is a liquid crystal display cell in which a liquid crystal is sandwiched between two opposing substrates, a polarizing element provided on each side of the liquid crystal display cell, and between at least one liquid crystal display cell and the polarizing element. A liquid crystal display device having at least one film-like member provided in a region, wherein the polarizing element is made of a polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorption-oriented, and the film-like member is a film-like member. When the polarizing element is bonded to the polarizing element via an adhesive layer and / or an adhesive layer having a thickness of less than 10 μm and is bonded to another film-like member, the other film-like member is also bonded. It is bonded via an adhesive layer and / or an adhesive layer with a thickness of less than 10 μm, and in the above liquid crystal display device, a film-like member in a region between at least one liquid crystal display cell and a polarizing element has a photoelastic coefficient. The absolute value of is 10 × 10^-8cm²A liquid crystal display device that satisfies less than / N and a water absorption rate of less than 2.0%.</p><p>In the present invention, a film-like member is attached to a polarizing element (polarizer) or another film-like member via an adhesive layer and / or an adhesive layer having a thickness of less than 10 μm. A film made of different materials such as different resins (here, including the substrate glass that constitutes the liquid crystal display cell) is laminated and bonded using an adhesive layer or an adhesive layer, and a durability test is performed in a high temperature and high humidity environment. If this is done, problems such as foaming and delamination are likely to occur. This defect is caused by the fact that films made of different materials expand and contract differently, so that the adhesive layer or the adhesive layer located between them is distorted, and water enters the resulting gaps between the layers or between the layers. Is the main cause. Further, for the same reason, when a pressure-sensitive adhesive or an adhesive adjacent to a polarizing element made of a polyvinyl alcohol-based resin film in which iodine or a dichroic dye is adsorbed and oriented absorbs water, the polarizing element swells or dissolves, resulting in polarization. Problems such as decolorization of the element and reduction of the degree of polarization are likely to occur. For this reason, it is preferable to use as thin an adhesive layer or an adhesive layer as possible, which is difficult to absorb moisture even in a high temperature and high humidity environment, for bonding each member constituting the liquid crystal display device, and the adhesive layer and / or the adhesive layer. By setting the thickness of the polarizing element to less than 10 μm, the durability of the polarizing element can be made sufficient. The more preferable thickness of the adhesive layer and the adhesive layer is less than 2 μm.</p><p>Adhesion is a state in which the surfaces of solids of the same type or different types are bonded and integrated. Normally, the adhesive layer is a liquid that is fluid at the time of bonding, but after that, it changes to a solid by heat treatment or a chemical reaction to exert adhesive force. On the other hand, adhesiveness is a state in which adhesiveness can be achieved by applying a slight pressure at room temperature for a short period of time, and can be peeled off from a hard smooth surface. Usually, the adhesive layer is a soft jelly-like solid, and exhibits adhesive strength without causing a change in state like an adhesive.</p><p>In the present invention, it is preferable that the film-like member is bonded to the polarizing element or other film-like member via an adhesive layer having a thickness of less than 10 μm. If the adhesive layer is too thin, sufficient adhesive strength cannot be obtained. Therefore, in order to pass the durability test required for liquid crystal display devices, a thickness of 20 to 50 μm is usually selected, and if it is thinner than 10 μm, it adheres. Since the force is low, the adhesive force may not be sufficient in a general liquid crystal display device. On the other hand, in the adhesive layer, sufficient adhesive strength that can withstand practical use can be obtained even with a thickness of 10 μm or less. Further, in many cases, it is desirable that the members constituting the liquid crystal display device are not delaminated. From these viewpoints, in the present invention, when thinning the adhesive layer or the adhesive layer, it is preferable to select the adhesive layer rather than the adhesive layer.</p><p>However, when a polarizing film or a retardation film is attached to a liquid crystal display cell, the liquid crystal display cell is usually several times more expensive than the film, so if there is a bonding error, only the film is peeled off. Therefore, the convenience of being able to reuse (also referred to as "rework") the liquid crystal display cell is emphasized, and an adhesive layer is preferably used for bonding instead of an adhesive layer. Therefore, in the present invention, an adhesive layer having a thickness of 10 μm or more may be used for bonding to the liquid crystal display cell, but for other bonding, an adhesive layer having a thickness of less than 10 μm and / Alternatively, an adhesive layer is used. Therefore, in the present invention, the total number of layers of the adhesive layer or the adhesive layer having a thickness of 10 μm or more existing in the region between the observation surface side substrate and the observation surface side polarizing element of the liquid crystal display cell is 1 or less. Similarly, the total number of layers of the adhesive layer or the adhesive layer having a thickness of 10 μm or more existing in the region between the back side substrate and the back side polarizing element of the liquid crystal display cell is 1 or less.</p><p>In the above liquid crystal display device, the film-like member in the region between at least one liquid crystal display cell and the polarizing element has an absolute value of the photoelastic coefficient of 10 × 10.^-8cm²Satisfy less than / N and water absorption less than 2.0%. The absolute value of the photoelastic coefficient of the film-like member is 10 × 10.^-8cm²When it is less than / N, it is possible to sufficiently reduce the characteristic change such as the phase difference change of the film-like member when it is placed in a high temperature environment, and it is possible to realize a liquid crystal display device having excellent durability. it can. As the absolute value of the photoelastic coefficient, a value measured with light having a wavelength of 550 nm at room temperature (about 23 ° C) can be used. A more preferable upper limit of the absolute value of the photoelastic coefficient is 5 × 10.^-8cm²/ N. In addition, since the water absorption rate is less than 2.0%, the moisture absorption of the film-like member when placed in a high-humidity environment is suppressed, and characteristic changes such as phase difference changes in the film-like member and defects in the polarizing element are sufficient. It is possible to realize a liquid crystal display device having excellent durability. For the water absorption rate, the rate of change in mass measured after immersion in water at 23 ° C for 24 hours can be used based on JIS K 6911 General test method for thermosetting plastics. A more preferable upper limit of the water absorption rate is 1.0%.</p><p>The absolute value of the above photoelastic coefficient is 10 × 10^-8cm²Examples of the film-like member having a water absorption rate of less than / N and a water absorption rate of less than 2.0% include a protective film made of a norbornene-based resin (hereinafter, also referred to as norbornene film). According to norbornene film, etc., it is possible to double as a protective film and a retardation film, and since the phase difference change due to the influence of heat and moisture is small, the moisture and heat resistance of the display quality of the liquid crystal display device is effectively improved. You can also do it.</p><p>The configuration of the liquid crystal display device of the present invention is not particularly limited as long as it includes the above-mentioned configuration as an indispensable configuration and has a configuration normally possessed by the liquid crystal display device, and is not particularly limited in other configurations. For example, the present invention is not particularly limited by the driving method of the liquid crystal, and the liquid crystal is sandwiched between the pair of substrates, and the liquid crystal is displayed by applying a voltage between the electrodes formed on the respective substrates. It can be applied to all display devices.</p><p>The preferred embodiment of the liquid crystal display device of the present invention will be described in detail below. In the liquid crystal display device, the contrast ratio in the normal direction with respect to the observation surface side substrate of the liquid crystal display cell is CR (0), and the contrast ratio in the direction inclined by 60 ° from the normal direction in the azimuth angle Φ direction is CR ( When defined as Φ, 60), it is preferable that CR (Φ, 60) / CR (0) 0.025 is satisfied at all azimuth angles of Φ = 0 to 360 °. As a result, the viewing angle characteristics required for the liquid crystal display device can be sufficiently satisfied. Examples of the liquid crystal display device satisfying the above contrast characteristics include a device in which a retardation film is arranged in a region between a liquid crystal display cell in VA mode or IPS mode and at least one polarizing element. A more preferable lower limit of the value of [CR (Φ, 60) / CR (0)] is 0.040.</p><p>In the present invention, the number of film-like members arranged in the region between the liquid crystal display cell and the polarizing element is small in order to improve the durability of the polarizing element, reduce the thickness, and reduce the manufacturing cost. Is preferable. Therefore, the protective film of the polarizing element has a function as a retardation film, and has a role of protecting the polarizing element and a role of canceling the phase difference of the liquid crystal display cell in the oblique direction and maintaining the orthogonality of the polarizing element. It is preferable to have them at the same time. That is, the film-like member attached to the polarizing element is preferably a protective film exhibiting birefringence. As a result, the protective film of the polarizing element also functions as a retardation film, making it possible to reduce the thickness and cost of the liquid crystal display device, and reduce the number of adhesive layers that easily absorb moisture to improve reliability. Is possible. Further, in this case, it is more preferable that no other film-like member exhibiting birefringence is arranged in the region between at least one liquid crystal display cell and the polarizing element. In the liquid crystal display device of the present invention, the phase difference in the thickness direction of the film-like member bonded to the polarizing element is the phase difference value in the thickness direction of the liquid crystal display cell and the arrangement form of each of the other film-like members. It is determined in consideration of the phase difference value in the thickness direction and the like as a whole, and is not particularly limited. Further, the phase difference in the in-plane direction is also determined in consideration of the entire liquid crystal display device as well as the phase difference in the thickness direction.</p><p>The absolute value of the above photoelastic coefficient is 10 × 10^-8cm²It is particularly preferable that the film-like member having a water absorption rate of less than / N and a water absorption rate of less than 2.0% is arranged on the back surface side of the liquid crystal display cell. That is, in the liquid crystal display device, the absolute value of the photoelastic coefficient is 10 × 10 at least in the region between the back side substrate and the back side polarizing element of the liquid crystal display cell.^-8cm⁸It is preferable that only a film-like member having a water absorption rate of less than / N and a water absorption rate of less than 2.0% is provided. This is because in a transmissive type and a transmissive / reflective type (semi-transmissive type) liquid crystal display device, the back side of the liquid crystal display cell is closer to the backlight than the observation surface side of the liquid crystal display cell, so that it is exposed to a high temperature environment. This is because Further, the film-like member satisfying the above characteristics includes a region between the back surface side substrate and the back surface polarizing element of the liquid crystal display cell and a region between the observation surface side substrate and the observation surface side polarizing element of the liquid crystal display cell. According to the configuration provided in the above, since the film-like member which is sensitive to heat and moisture is not contained at all, the durability of the display quality of the liquid crystal display device can be particularly effectively improved.</p><p>In the liquid crystal display device, the first protective film is on the liquid crystal display cell side of the polarizing element on the observation surface side, the second protective film is on the observation surface side, and the third protective film is on the liquid crystal display cell side of the polarizing element on the back side. However, it is preferable that a fourth protective film is attached to the back surface side via an adhesive layer and / or an adhesive layer having a thickness of less than 10 μm, respectively. According to this form, the durability of the polarizing elements on the observation surface side and the back surface side can be effectively improved. Examples of such a form include the forms shown in FIGS. 1 (a) to 1 (c). In the present invention, as described above, the absolute value of the photoelastic coefficient is 10 × 10.^-8cm²Film-like members having a water absorption rate of less than / N and a water absorption rate of less than 2.0% may be arranged on both sides of the liquid crystal display cell (Fig. 1 (a)), or only on the observation surface side of the liquid crystal display cell. It may be a form arranged in (FIG. 1 (b)) or a form arranged only on the back side of the liquid crystal display cell (FIG. 1 (c)). Further, it is preferable that the first and third protective films exhibit birefringence and also have a function as a retardation film.</p><p>In the liquid crystal display device, at least one of the combination of the first protective film and the second protective film and the combination of the third protective film and the fourth protective film may be made of resins having different moisture permeability. preferable. As a result, even when a protective film made of a resin having low moisture permeability is attached to one of the polarizing elements, the moisture inside the polarizing element can be easily removed, and the handleability of the polarizing element is ensured. At the same time, it is possible to sufficiently secure the adhesive strength between the polarizing element and the protective film. Since the PVA constituting the polarizing element is very brittle in a dry state and difficult to handle, it is usually attached to a protective film in a state of being moistened with a large amount of water. Further, a protective film made of a resin having a small water absorption rate and a small phase difference change due to the influence of moisture, such as a norbornene resin, generally has a low moisture permeability. Therefore, when such a film having low moisture permeability is used as a protective film for a polarizing element, the moisture resistance of the polarizing element is improved, but if the moisture permeability of the protective films on both sides is too low, the moisture at the time of bonding is sufficient. It cannot be removed and remains inside, and the adhesive strength between the protective film and the polarizing element may not be sufficiently obtained. On the other hand, in the above-described embodiment, a film made of a resin other than norbornene-based resin or the like is attached to one surface of the polarizing element as a protective film, so that the protective films have different moisture permeability and moisture is released. It makes it difficult for it to remain inside. For the above moisture permeability (water vapor permeability), the value measured after leaving for 24 hours under the conditions of temperature 40 ° C and humidity 90% based on JIS K 7129 "Water vapor permeability test method for plastic films and sheets" can be used. it can. The difference in moisture permeability between the protective films in the above combination is 200 g / m.² It is preferable that it is 24 hours or more. The moisture permeability of the protective film on the low moisture permeability side is 100 g / m.² It is preferably 24 hours or less, and the moisture permeability of the protective film on the side with high moisture permeability is 300 g / m.² It is preferable that it is 24 hours or more.</p><p>The liquid crystal display device preferably satisfies at least one of the following formula (1) and the following formula (2). Moisture Permeability of First Protective Film &lt;Moisture Permeability of Second Protective Film (1) Moisture Permeability of Third Protective Film &lt;Moisture Permeability of Fourth Protective Film (2) Moisture Permeability of First Protective Film It has a structure of a protective film / polarizing element / protective film because it is smaller than the moisture permeability of the second protective film or the moisture permeability of the third protective film is smaller than the moisture permeability of the fourth protective film. After the laminated film is attached to the liquid crystal display cell, it becomes possible to release the moisture inside the polarizing element to the outside, and while ensuring the handleability of the polarizing element, the adhesive strength between the polarizing element and the protective film is more sufficient. It will be possible to secure it.</p><p>In the liquid crystal display cell, most of the liquid crystal molecules are oriented substantially perpendicular to the substrate, and black display is performed in a state where the in-plane phase difference is substantially zero. The liquid crystal display device has the following formula (3). When the corrected thickness direction retardation R is defined by, the corrected thickness direction retardation R1 of the first protective film, the corrected thickness direction retardation R3 of the third protective film, and the liquid crystal in the black display state. It is preferable that the corrected thickness direction phase difference Rlc of the display cell satisfies the relationship of the following equation (4). R = (1.3-0.6 × na) × Rxz + (0.7-0.3 × na) × Rxy (3) In the above equation (3), na represents the average refractive index for light with a wavelength of 550 nm, and Rxz for light with a wavelength of 550 nm. Represents the thickness direction phase difference, and Rxy represents the in-plane direction phase difference for light with a wavelength of 550 nm. 0nm R1 + R3-Rlc 35nm (4)</p><p>The average refractive index na is defined by the following equation (5), the in-plane direction phase difference Rxy is defined by the following equation (6), and the thickness direction retardation Rxz is defined by the following equation (7). Defined. na = (nx + ny + nz) / 3 (5) Rxy = (nx-ny) × d (6) Rxz = (nx-nz) × d (7) In the above equations (5) to (7), nx , Ny represents the main refractive index (nx ny) in the in-plane direction with respect to light having a wavelength of 550 nm, nz represents the main refractive index in the thickness direction with respect to light having a wavelength of 550 nm, and d represents the thickness.</p><p>The present invention can be suitably used for a normally black mode liquid crystal display device provided with a vertical orientation mode (VA mode) liquid crystal display cell, and by satisfying the above equation (4), the viewing angle compensation in the oblique direction is compensated. It is possible to obtain excellent display quality in a wide viewing angle range. That is, the above equation (4) shows a design guideline for the phase difference in the VA mode. In the above equation (4), the corrected thickness direction phase difference R defined in the above equation (3) is used in order to make the viewing angle compensation in the VA mode more effective .</p><p>Here, the reason for using the corrected thickness direction phase difference R defined in the above equation (3) in the above equation (4) will be described in detail. First, one of the main purposes of viewing angle compensation in VA mode is in the black display state of the liquid crystal display cell, which is almost zero when viewed from the front, but is not almost zero when viewed from an oblique direction. It is to cancel the phase difference. In order to achieve this purpose, it is necessary to properly design the phase difference of the retardation film, but in the past, Rxy, which represents the phase difference when viewed from directly above, was viewed from the side (virtually). The design was done by adjusting Rxz, which represents the phase difference at the time, or Rth = [(nx + ny) / 2-nz] × d = Rxz-Rxy / 2. Among them, a method of making the sum of the Rth of the liquid crystal display cell and the Rth of the retardation film almost equal has been particularly often used. However, in the conventional method, in order to realize the original purpose of canceling the phase difference when viewed from an oblique direction, the error between the design value and the actual effect is large. This is because, for example, even if the retardation films have the same Rth, if the Rxy is different, the effective retardation when viewed from an oblique direction is different. Therefore, in order to design with higher accuracy than the actual effect, it is effective to use the effective phase difference R when actually viewed from an oblique direction. In this case, as the diagonal direction, for example, the azimuth angle Φ = 45 °, An elevation angle of Θ = 60 ° (direction tilted by 60 ° from the normal to the substrate surface) is preferable. However, in the panel maker and the retardation film industry, the handling of Rxy, Rxz, and Rth data is practically standardized, and the data sheet attached when the retardation film is delivered also describes these data. .. Therefore, the present inventors have examined an equation for estimating the effective phase difference R from those data for convenience, and have found the above equation (3) from the examination results of various experiments and calculations. However, in the above equation (3), in addition to Rxy and Rxz, the average refractive index na, which can be known as the resin name of the film, is also used. Therefore, in the present invention, for each of the retardation film and the liquid crystal display cell, the effective retardation R is obtained from the above equation (3), and the total sum thereof is within a range satisfying the above equation (4) for practical use. A sufficient viewing angle can be obtained.</p><p>Of the first and third protective films, at least the one with the larger corrected thickness direction phase difference has an absolute value of the photoelastic coefficient of 10 × 10.^-8cm²It is preferably less than / N. The absolute value of the photoelastic coefficient of the protective film is 10 x 10^-8cm²By setting it to less than / N, it is possible to sufficiently reduce characteristic changes such as phase difference changes when placed in a high temperature environment, but the thickness corrected by the first protective film and the third protective film. When the directional phase difference is different, the photoelastic coefficient of the protective film with the larger corrected thickness directional phase difference is made smaller so that the liquid crystal display device as a whole is placed in a high temperature environment. It is possible to suppress the change in the characteristics of the liquid crystal display device particularly effectively, and to improve the durability of the liquid crystal display device particularly effectively.</p><p>Of the first and third protective films, at least the one having a large corrected thickness direction retardation preferably has a water absorption rate of less than 2.0%. By setting the water absorption rate of the protective film to less than 2.0%, it is possible to sufficiently reduce characteristic changes such as phase difference changes when placed in a high humidity environment. When the corrected thickness direction phase difference is different from that of the protective film, the water absorption rate of the protective film having the larger corrected thickness direction phase difference is set to be small so that the liquid crystal display device as a whole has a high water absorption rate. The change in characteristics when placed in a humid environment can be suppressed particularly effectively, and the durability of the liquid crystal display device can be particularly effectively improved.</p><p>At least one of the first to fourth protective films has a moisture permeability of 100 g / m.²-It is preferably 24 hours or less. This makes it possible to reduce the amount of water that permeates the protective film when placed in a high-humidity environment, thus improving the durability of the polarizing element and the stability of the phase difference of the protective film. However, it is possible to realize a liquid crystal display device having excellent durability of display quality. A more preferable upper limit of moisture permeability is 80 g / m.² It is 24hr.</p><p>The above moisture permeability is 100g / m²-It is particularly preferable that the protective film having a length of 24 hours or less is arranged in the region between at least one liquid crystal display cell and the polarizing element. That is, at least one of the first and third protective films has a moisture permeability of 100 g / m.²-It is preferably 24 hours or less. As a result, after the laminated film having the structure of the protective film / polarizing element / protective film is attached to the liquid crystal display cell, it becomes easy to release the moisture inside the polarizing element to the outside, and the handleability of the polarizing element is ensured. At the same time, it is possible to more sufficiently secure the adhesive strength between the polarizing element and the protective film.</p><p>It is preferable that at least one of the first to fourth protective films is made of a norbornene-based resin. According to the protective film made of norbornene-based resin, it is possible to serve as both the protective film and the retardation film. In addition, since the protective film made of norbornene-based resin has characteristics such as photoelasticity coefficient, water absorption rate, and moisture permeability that are suitable for the present invention, it is possible to suppress phase difference changes and moisture absorption due to the influence of heat and moisture. It is possible to realize a liquid crystal display device having excellent moisture and heat resistance of display quality. The norbornene-based resin is a resin containing norbornene or a polymer obtained by polymerizing a derivative or salt thereof as a main component.</p><p>Further, the present inventors have found that when the liquid crystal display device is subjected to a very strict durability test, cracks may gradually occur from the end portion of the polarizing element in the absorption axis direction. Therefore, it is preferable that the liquid crystal display device has a means for preventing the display quality from being deteriorated due to the occurrence of cracks in the outer peripheral region of the polarizing element. The maximum width of the adjacent polarizing element in the absorption axis direction is larger than the maximum width of the display effective area of the liquid crystal display device in that direction. (2) Absorption of the polarizing element having a bezel and adjacent to the protective film. The maximum width in the axial direction is larger than the maximum width of the opening region of the bezel in that direction. (3) The outer peripheral end surface intersecting the absorption axial direction of the polarizing element adjacent to the protective film is coated with a water-repellent sealant. It is preferable that it is in the form of Further, it is more preferable that the form is a combination of (1) to (3). The forms (1) to (3) above have a moisture permeability of 100 g / m.²-It is preferable to apply it to a polarizing element to which a protective film of 24 hours or less is attached. This is because when a protective film having a low moisture permeability is attached, it is necessary to dry the polarizing element to some extent and then attach the polarizing element, and the polarizing element is particularly liable to crack.</p><p>According to the form (1) above, as illustrated in FIG. 2, the maximum width L of the polarizing element 21 is displayed on the screen (liquid crystal display device) in the absorption axis direction of the polarizing element 21 adjacent to the protective film (not shown). By making it larger than the maximum width L'of the display effective region 50), it is possible to prevent cracks generated in the outer peripheral region of the polarizing element from adversely affecting the display quality of the liquid crystal display device. Further, in a liquid crystal display device or the like having a relatively large screen such as a liquid crystal television, the maximum width in the absorption axis direction (hereinafter, simply referred to as absorption axis direction) of the polarizing element adjacent to the protective film is L, and absorption is performed. When the maximum width of the display effective area of the liquid crystal display device in the axial direction is L', it is more preferable to satisfy L-L'4 mm. In this case, the display effective area of the liquid crystal display device is exceeded in the absorption axis direction. The outer peripheral region of the protective film to be formed is preferably 2 mm or more per side. It is more preferable that the liquid crystal display device satisfies L-L' 10 mm.</p><p>According to the form (2) above, as illustrated in FIG. 3, by covering the outer peripheral region of the polarizing element 21 adjacent to the protective film (not shown) with the bezel 51, it is generated in the outer peripheral region of the polarizing element. It is possible to prevent the cracks from adversely affecting the display quality of the liquid crystal display device. Further, in a liquid crystal display device having a relatively large screen such as a liquid crystal television, when the maximum width in the absorption axis direction is L and the maximum width of the opening region of the bezel in the absorption axis direction is l, the liquid crystal display device is It is more preferable to satisfy Ll 4 mm, and in this case, the outer peripheral region of the protective film formed in the absorption axis direction beyond the opening region of the bezel is preferably 2 mm or more per side. It is more preferable that the liquid crystal display device satisfies Ll 10 mm.</p><p>According to the form (3) above, by sealing the end face of the polarizing element adjacent to the protective film, it is possible to prevent the polarizing element from cracking, and the display quality of the liquid crystal display device deteriorates. Can be prevented.</p>

<p>According to the liquid crystal display device of the present invention, it is possible to improve the durability of a polarizing element made of a PVA-based resin film and provide a liquid crystal display device having excellent durability of display quality.</p>

Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited to these embodiments.

First, the configuration of the liquid crystal display device in this embodiment will be described. The liquid crystal display device according to the present embodiment has a second protective film 32, a first polarizing element 21, a first protective film 31 or 31a, a liquid crystal display cell 10, and a third, as outlined in FIG. The protective film 33 or 33a, the second polarizing element 22 and the fourth protective film 34 are sequentially bonded from the observation surface side via the adhesive 42 or the adhesive 41, and are attached to the effective display area of the liquid crystal display device. It has a basic configuration that is sandwiched and integrated by a bezel (frame-shaped member) having a corresponding opening. The liquid crystal display cell 10 has a structure in which the liquid crystal 12 is sandwiched between the observation surface side substrate 11 and the back surface side substrate 13 facing each other. Hereinafter, each component of the liquid crystal display device according to the present embodiment will be described.

(1-1) Protective film and retardation film In this embodiment, any of the films shown in Table 1 below was used as the first to fourth protective films. In Table 1 below, the resin name NB represents a norbornene-based resin, TAC represents a triacetyl cellulose resin, and PC represents a polycarbonate resin. The average refractive index na, the in-plane direction phase difference Rxy, the thickness direction phase difference Rxz, and the corrected thickness direction phase difference R are defined by the above equations (3) and (5) to (7), respectively. The values of moisture permeability are shown as measured using a film having the thickness shown in Table 1 below. The films shown in Table 1 below are stretched at the time of film formation, such as 1 vertical axis, 1 horizontal axis, 2 vertical and horizontal axes, or 2 vertical and horizontal sequential axes, and the in-plane direction phase difference Rxy. Alternatively, the phase difference Rxz in the thickness direction has been adjusted. Further, the moisture permeability is adjusted by utilizing the fact that the thicker the film is, the lower the moisture permeability is, and the thinner the film is, the higher the moisture permeability is.

<tables num="1"><img file="JP2006201401A_D0001.tif" /></tables>

In the present invention, the material of the film-like member such as the protective film is not particularly limited, but a transparent film resin having both a low water absorption rate (or moisture permeability) and a photoelastic coefficient is preferably used. In general, there is a strong relationship between the water absorption rate and the moisture permeability, and the larger the water absorption rate, the higher the moisture permeability in many cases. Examples of the transparent film resin satisfying the above characteristics include an amorphous polyolefin resin film. The amorphous polyolefin resin has a cyclic olefin such as norbornene or polycyclic norbornene monomer as a polymerization unit. Among them, the (thermoplastically saturated) norbornene resin is particularly widely known and is a product from JSR Corporation. The name "Arton", the product names "ZEONEX" and "ZEONOR" from Nippon Zeon, and the product name "Apel" from Mitsui Chemicals are commercially available. These resins can be formed into a film by a solvent casting method, a melt extrusion method, or the like. In this embodiment, a norbornene-based resin (hereinafter, also referred to as NB) was used as the material for the films N-1 to 17.

Further, in the present invention, as the material of the film-like member such as the protective film, a transparent film resin having a low photoelastic coefficient and a high water absorption rate (or moisture permeability) may be used. Examples of the transparent film resin satisfying the above characteristics include triacetyl cellulose resin (TAC). TAC is used as the most common protective film for polarizing elements. In this embodiment, TAC was used as the material for the films T-1 to T-3. Further, in the present invention, as the material of the film-like member such as the protective film, a transparent film resin having a low water absorption rate (or moisture permeability) and a high photoelastic coefficient may be used. Examples of the transparent film resin satisfying the above characteristics include polycarbonate resin (PC). In this embodiment, PC was used as the material of the film P-1. TAC and PC can be made into a film by a solvent casting method, a melt extrusion method, or the like, respectively.

(1-2) Polarizing element In this embodiment, a PVA-based resin film in which iodine or a dichroic dye is adsorbed and oriented is used as the polarizing element. For PVA-based polarizing elements, a PVA film is stretched 5 times, immersed in a solution containing iodine and potassium iodide for dyeing, and then crosslinked in an aqueous solution consisting of boric acid and potassium iodide. Made by The polarizing element and each protective film are bonded by using a method in which the polarizing element is moistened with some water, laminated through an adhesive containing water as a main solvent, and then the water is dried. I went.

(1-3) Adhesive and Adhesive In this embodiment, an acrylic adhesive was used as the adhesive. The thickness of the pressure-sensitive adhesive layer was 20 μm. Further, as the adhesive, a PVA-based adhesive or a urethane-based adhesive was used. The thickness of the adhesive layer was 1 μm or less.

(1-4) Liquid Crystal Display Cell In the present embodiment, as a liquid crystal display cell, most of the liquid crystal molecules are oriented substantially perpendicular to the substrate, and black display is performed in a state where the in-plane phase difference is substantially zero (vertical orientation (1-4). Among the VA) modes, the one in the multi-domain vertical orientation (MVA) mode in which one pixel is divided into four regions and the liquid crystal molecules are oriented substantially horizontally in each region to display white is used. The thickness direction phase difference Rlc of the liquid crystal display cell was set to either -260 nm, -290 nm, or -320 nm in the black display state. The in-plane phase difference Rxy of the liquid crystal display cell was set to approximately 0 nm in the black display state. The average refractive index na of the liquid crystal display cell was 1.50, and the diagonal length was 30 inches. A glass substrate was used as the substrate.

(1-5) Bezel As shown in Fig. 4-1, the bezel 51 supports and fixes the liquid crystal display cell 10, the polarizing elements 21, 22 and the film-like member (not shown) in the liquid crystal display device. It is a member (case) of. In this embodiment, as shown in FIG. 4-2, a metal bezel 51 having a square opening for exposing the display area of the liquid crystal display device is used. The bezel 51 has a front portion that serves as a frame portion that covers the periphery of the liquid crystal display cell 10, and a side portion that is bent at a right angle to the back side with respect to the front portion around the front portion, and has a substantially cross section. It is formed in an L shape. Therefore, the quadrangular opening is provided on the front surface. Further, the bezel 51 is composed of two parts, an outer frame portion 51a and an inner frame portion 51b, and the liquid crystal display cell 10 is supported and fixed by sandwiching the bezel 51 between the outer frame portion 51a and the inner frame portion 51b. The bezel 51 was formed by press molding.

(1-6) Sealing Agent In some examples of the present embodiment, the outer peripheral end face of the polarizing element, which intersects with the absorption axis direction, is coated with a sealing agent. As the sealing agent, a fluorine-based water-repellent material was used, and the sealant was applied and formed using a brush.

Hereinafter, each embodiment produced by changing each component in the liquid crystal display device of the present embodiment will be described. The configurations of the liquid crystal display devices corresponding to each embodiment are summarized in Tables 2 and 3 below. In the table, the acrylic adhesive layer with a thickness of 20 μm is referred to as A adhesive 20, the PVA adhesive with a thickness of 1 μm or less is referred to as P contact 1, and the urethane adhesive with a thickness of 1 μm or less is referred to as U contact 1. Abbreviated.

<tables num="2"><img file="JP2006201401A_D0002.tif" /></tables>

<tables num="3"><img file="JP2006201401A_D0003.tif" /></tables>

(2-1) When there is one film with a large phase difference (Example 1) In this example, from the observation surface side, T-1 is used as the second protective film, and PVA with a thickness of 1 μm or less is used as the adhesive layer. Adhesive, PVA-based polarizing element with absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the first protective film, thickness as the adhesive layer 20 μm acrylic adhesive, observation surface side substrate, Rlc = -290 nm liquid crystal layer, back surface side substrate, 20 μm thick acrylic adhesive as adhesive layer, N-15 as third protective film, thick as adhesive layer Urethane-based adhesive with a thickness of 1 μm or less, PVA-based polarizing element with an absorption axis angle of 90 ° as the second polarizing element, urethane-based adhesive with a thickness of 1 μm or less as the adhesive layer, and N- as the fourth protective film. A liquid crystal display device formed by laminating 10 in this order was produced.

When the maximum width of the polarizing element measured in the absorption axis direction is L and the maximum width of the display effective area of the liquid crystal display device measured in the same direction is L', the first polarizing element has L-L'=. 2 mm, L-L'= 2 mm for the second polarizing element. Further, when the maximum width of the polarizing element measured in the absorption axis direction is L and the maximum width of the opening region of the bezel measured in the same direction is l, the first polarizing element has Ll = 2 mm and the second polarizing element. Then, Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 2) In this embodiment, N-8 is used as the third protective film and T-1 is used as the fourth protective film, and an adhesive layer for adhering the second polarizing element and the fourth protective film. A liquid crystal display device was produced in the same manner as in Example 1 except that a PVA-based adhesive having a thickness of 1 μm or less was used.

(2-2) When there are two films with a large phase difference (Example 3) In this example, N-10 is used as the second protective film and urethane with a thickness of 1 μm or less is used as the adhesive layer from the observation surface side. Adhesive, PVA-based polarizing element with absorption axis angle of 0 ° as the first polarizing element, urethane-based adhesive with a thickness of 1 μm or less as the adhesive layer, N-12 as the first protective film, thickness as the adhesive layer 20 μm acrylic adhesive, observation surface side substrate, Rlc = -290 nm liquid crystal layer, back surface side substrate, 20 μm thick acrylic adhesive as adhesive layer, N-12 as third protective film, thick as adhesive layer Urethane-based adhesive with a thickness of 1 μm or less, PVA-based polarizing element with an absorption axis angle of 90 ° as the second polarizing element, urethane-based adhesive with a thickness of 1 μm or less as the adhesive layer, and N-10 as the fourth protective film. , A liquid crystal display device formed by laminating in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 4) In this embodiment, N-5 as the first protective film, N-5 as the second protective film, N-5 as the third protective film, and N-1 as the fourth protective film. A liquid crystal display device was produced in the same manner as in Example 3 except that the above was used. (Example 5) In this embodiment, N-5 as the first protective film, T-1 as the second protective film, N-5 as the third protective film, and T-1 as the fourth protective film. A PVA-based adhesive having a thickness of 1 μm or less as an adhesive layer for adhering the first polarizing element and the second protective film and an adhesive layer for adhering the second polarizing element and the fourth protective film. A liquid crystal display device was produced in the same manner as in Example 3 except that the above was used.

(2-3) When the NB-based protective film is not selectively arranged on the side where the corrected thickness direction retardation R is large or the back side (Example 6) In this embodiment, the second protection is provided from the observation surface side. T-1 as a film, PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, PVA-based polarizing element with an absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, T-3 as the first protective film, 20 μm thick acrylic adhesive as the adhesive layer, observation surface side substrate, Rlc = -290 nm liquid crystal layer, back side substrate, 20 μm thick acrylic adhesive as the adhesive layer , N-1 as the third protective film, urethane-based adhesive with a thickness of 1 μm or less as the adhesive layer, PVA-based polarizing element with an absorption axis angle of 90 ° as the second polarizing element, thickness of 1 μm or less as the adhesive layer A liquid crystal display device formed by laminating and arranging PVA-based adhesive and T-1 as a fourth protective film in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, Ll = 2 mm for the first polarizing element and Ll = 2 mm for the second polarizing element. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 7) In this embodiment, N-8 is used as the first protective film and T-1 is used as the third protective film, and an adhesive layer for adhering the first polarizing element and the first protective film is used. A urethane-based adhesive having a thickness of 1 μm or less was used, and a PVA-based adhesive having a thickness of 1 μm or less was used as an adhesive layer for adhering the second polarizing element and the third protective film. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. Other than that, a liquid crystal display device was produced in the same manner as in Example 6.

(2-4) When the phase difference is designed near the limit where a sufficient viewing angle can be secured with one NB protective film having a large phase difference (Example 8) In this example, from the observation surface side. , T-1 as the second protective film, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, PVA-based polarizing element with an absorption axis angle of 0 ° as the first polarizing element, and the adhesive layer with a thickness of 1 μm or less Urethane-based adhesive, N-1 as the first protective film, acrylic adhesive with a thickness of 20 μm as the adhesive layer, observation surface side substrate, liquid crystal layer of Rlc = -290 nm, back surface side substrate, thickness of 20 μm as the adhesive layer Acrylic adhesive, N-6 as the third protective film, urethane adhesive with a thickness of 1 μm or less as the adhesive layer, PVA adhesive with an absorption axis angle of 90 ° as the second polarizing element, as the adhesive layer A liquid crystal display device formed by laminating and arranging a PVA-based adhesive having a thickness of 1 μm or less and T-1 as a fourth protective film in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 9) In this example, a liquid crystal display device was produced in the same manner as in Example 8 except that N-3 was used as the third protective film.

(2-5) When two NB protective films with a large phase difference are used and the phase difference is designed near the limit where a sufficient viewing angle can be secured (Example 10) In this example, the first and the first A liquid crystal display device was produced in the same manner as in Example 8 except that N-16 was used as the third protective film.

(2-6) When the Rlc of the liquid crystal display cell is changed (Example 11) In this example, from the observation surface side, T-1 is used as the second protective film, and the adhesive layer is a PVA system with a thickness of 1 μm or less. Adhesive, PVA-based polarizing element with absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the first protective film, thickness 20 μm as the adhesive layer Acrylic adhesive, observation surface side substrate, liquid crystal layer of Rlc = -320, back side substrate, acrylic adhesive with a thickness of 20 μm as an adhesive layer, N-14 as a third protective film, thickness as an adhesive layer Urethane-based adhesive of 1 μm or less, PVA-based polarizing element with absorption axis angle of 90 ° as the second polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the fourth protective film, A liquid crystal display device formed by laminating in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 12) In this embodiment, N-4 is used as the first and third protective films, and urethane having a thickness of 1 μm or less is used as an adhesive layer for adhering the first polarizing element and the first protective film. A system adhesive was used. Other than that, a liquid crystal display device was produced in the same manner as in Example 11. (Example 13) In this example, the liquid crystal display is the same as in Example 11 except that the liquid crystal layer of Rlc = -260 nm is used for the liquid crystal display cell and N-9 is used as the third protective film. The device was made.

(2-7) When cracking measures are taken for the polarizing element (Example 14) In this example, T-1 is used as the second protective film and the adhesive layer is a PVA system with a thickness of 1 μm or less from the observation surface side. Adhesive, PVA-based polarizing element with absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the first protective film, thickness 20 μm as the adhesive layer Acrylic adhesive, observation surface side substrate, liquid crystal layer of Rlc = -290 nm, back surface side substrate, acrylic adhesive with a thickness of 20 μm as an adhesive layer, N-8 as a third protective film, thickness as an adhesive layer Urethane-based adhesive of 1 μm or less, PVA-based polarizing element with absorption axis angle of 90 ° as the second polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the fourth protective film, A liquid crystal display device formed by laminating in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 10 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Example 15) In this example, N-1 is used as the second and fourth protective films, N-5 is used as the first and third protective films, and urethane having a thickness of 1 μm or less is used as all the adhesive layers. A system adhesive was used. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 10 mm, and the second polarizing element was set to Ll = 10 mm. No sealing treatment was performed on any of the first and second polarizing elements. Other than that, a liquid crystal display device was produced in the same manner as in Example 14.

(Example 16) In this example, N-1 is used as the second and fourth protective films, N-5 is used as the first and third protective films, and urethane having a thickness of 1 μm or less is used as all the adhesive layers. A system adhesive was used. Also, in the second polarizing element, L-L'= 2 mm. Further, the absorption axis angle of the first polarizing element was set to 45 °, and the absorption axis angle of the second polarizing element was set to 135 °. Then, both the first and second polarizing elements were sealed. Other than that, a liquid crystal display device was produced in the same manner as in Example 14.

(Example 17) In this example, N-5 was used as the first and third protective films, and a urethane-based adhesive having a thickness of 1 μm or less was used as the adhesive layer. Also, in the first polarizing element, L-L'= 10 mm. Further, the first polarizing element was set to Ll = 10 mm, and the second polarizing element was set to Ll = 10 mm. Then, both the first and second polarizing elements were sealed. Other than that, a liquid crystal display device was produced in the same manner as in Example 14.

Hereinafter, comparative examples and reference examples produced by changing each component in the liquid crystal display device of the present embodiment will be described. The configurations of the liquid crystal display devices corresponding to each comparative example and reference example are summarized in Table 4 below.

<tables num="4"><img file="JP2006201401A_D0004.tif" /></tables>

(3-1) When the polarizing element and the protective film are bonded with an acrylic adhesive having a thickness of 20 μm or more (Comparative Example 1) In this Comparative Example, T- is used as the second protective film from the observation surface side. 1. PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, PVA-based polarizing element with an absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, first protection T-1 as a film, acrylic adhesive with a thickness of 20 μm as an adhesive layer, observation surface side substrate, liquid crystal layer with Rlc = -290 nm, back surface side substrate, acrylic adhesive with a thickness of 20 μm as an adhesive layer, third N-15 as a protective film, acrylic adhesive with a thickness of 20 μm as an adhesive layer, PVA-based polarizing element with an absorption axis angle of 90 ° as a second polarizing element, urethane adhesive with a thickness of 1 μm or less as an adhesive layer, A liquid crystal display device formed by laminating N-10 as a fourth protective film in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Comparative Example 2) In this Comparative Example, N-10 was used as the second protective film and N-12 was used as the first and third protective films, and instead of the adhesive layer, an acrylic pressure-sensitive adhesive having a thickness of 20 μm was used. Was used. Other than that, a liquid crystal display device was produced in the same manner as in Comparative Example 1. (Comparative Example 3) In this Comparative Example, a liquid crystal display device was produced in the same manner as in Comparative Example 2 except that an acrylic adhesive having a thickness of 50 μm was used as the adhesive layer.

(3-2) When two or more adhesive layers having a thickness of more than 10 μm are included between the polarizing elements and TAC is included (Comparative Example 4) In this Comparative Example, the basic configuration of the liquid crystal display device described above is compared with A retardation film was placed between the back surface side substrate and the third protective film via an adhesive. Specifically, from the observation surface side, T-1 is used as the second protective film, PVA-based adhesive with a thickness of 1 μm or less is used as the adhesive layer, and PVA-based polarizing element with an absorption axis angle of 0 ° is used as the first polarizing element. , PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, T-1 as the first protective film, acrylic adhesive with a thickness of 20 μm or less as an adhesive layer, observation surface side substrate, liquid crystal layer with Rlc = -290 nm, Back side substrate, acrylic adhesive with a thickness of 20 μm as an adhesive layer, N-13 as a retardation film, acrylic adhesive with a thickness of 20 μm as an adhesive layer, T-1 as a third protective film, thickness as an adhesive layer PVA-based adhesive with a thickness of 1 μm or less, PVA-based polarizing element with an absorption axis angle of 90 ° as the second polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, and T-1 as the fourth protective film. , A liquid crystal display device formed by laminating in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Comparative Example 5) In this comparative example, with respect to the basic configuration of the liquid crystal display device described above, between the first protective film and the observation surface side substrate, and between the back surface side substrate and the third protective film. A retardation film was placed in the film via an adhesive. Specifically, in the region between the first protective film and the observation surface side substrate, an acrylic adhesive having a thickness of 20 μm as an adhesive layer, N-2 as a retardation film, and acrylic having a thickness of 20 μm as an adhesive layer. A liquid crystal display device was produced in the same manner as in Comparative Example 4, except that an adhesive was used and N-2 was used as the retardation film provided between the back surface side substrate and the third protective film.

(3-3) When a protective film having a large photoelastic coefficient and water absorption rate is used between the polarizing elements (Comparative Example 6) In this Comparative Example, T-1 is adhered as the second protective film from the observation surface side. PVA-based adhesive with a thickness of 1 μm or less as a layer, PVA-based polarizing element with an absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, T as the first protective film -1, Acrylic adhesive with a thickness of 20 μm as an adhesive layer, observation surface side substrate, liquid crystal layer with Rlc = -290 nm, back surface side substrate, acrylic adhesive with a thickness of 20 μm as an adhesive layer, as a third protective film P-1, Urethane-based adhesive with a thickness of 1 μm or less as an adhesive layer, PVA-based polarizing element with an absorption axis angle of 90 ° as a second polarizing element, PVA-based adhesive with a thickness of 1 μm or less as an adhesive layer, Fourth A liquid crystal display device formed by laminating T-1 as a protective film in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Comparative Example 7) In this Comparative Example, T-2 was used as the third protective film, and a PVA-based adhesive having a thickness of 1 μm or less was used as the adhesive layer for adhering the fourth protective film to the second polarizing element. A liquid crystal display device was produced in the same manner as in Comparative Example 6 except for the above.

(3-4) When the Rlc of the liquid crystal display cell is changed (Reference example 1) In this reference example, from the observation surface side, T-1 is used as the second protective film, and the adhesive layer is a PVA system with a thickness of 1 μm or less. Adhesive, PVA-based polarizing element with absorption axis angle of 0 ° as the first polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, T-1 as the first protective film, thickness 20 μm as the adhesive layer The following acrylic adhesive, observation surface side substrate, liquid crystal layer of Rlc = -290 nm, back surface side substrate, acrylic adhesive with a thickness of 20 μm as the adhesive layer, N-11 as the third protective film, thickness as the adhesive layer Urethane-based adhesive with a thickness of 1 μm or less, PVA-based polarizing element with an absorption axis angle of 90 ° as the second polarizing element, PVA-based adhesive with a thickness of 1 μm or less as the adhesive layer, and T-1 as the fourth protective film. , A liquid crystal display device formed by laminating in this order was produced. Further, L-L'= 2 mm was set for the first polarizing element, and L-L'= 2 mm was set for the second polarizing element. Further, the first polarizing element was set to Ll = 2 mm, and the second polarizing element was set to Ll = 2 mm. No sealing treatment was performed on any of the first and second polarizing elements.

(Reference Example 2) In this Reference Example, a liquid crystal display device was produced in the same manner as in Reference Example 1 except that N-17 was used as the third protective film. (Reference Example 3) In this reference example, N-7 is used as the first and third protective films, and a urethane-based adhesive having a thickness of 1 μm or less is used as an adhesive layer for adhering the first protective film to the first polarizing element. A liquid crystal display device was produced in the same manner as in Reference Example 1 except that the above was used.

(Evaluation Method) Next, the evaluation method of the liquid crystal display device obtained in Examples, Comparative Examples and Reference Examples will be described. As evaluation items, the contrast ratio, white spots, moisture resistance, cracking of the polarizing element, and foaming / peeling were confirmed. The results of each evaluation are shown in Table 5.

(4-1) Evaluation of contrast ratio Using a backlight system for a large liquid crystal display device as a light source, black display brightness and white display brightness are obtained at an elevation angle of 0 ° (normal to the substrate surface on the observation surface side). Then, at an elevation angle of 60 ° (a direction tilted 60 ° from the normal direction in the azimuth angle Φ direction), the black display brightness and the white display brightness are changed by changing the azimuth angle Φ from 0 to 360 ° by 5 °, respectively. It was measured. From the ratio of black display brightness to white display brightness (white display brightness / black display brightness), the contrast ratio CR (0) at an elevation angle of 0 ° and the contrast ratio CR (Φ, 60) at an elevation angle of 60 ° are obtained. It was. The contrast ratio CR (Φ, 60) changes depending on the azimuth angle, but Table 5 below shows the minimum value of CR (Φ, 60) / CR (0). When the minimum value of CR (Φ, 60) / CR (0) was 0.025 or more, a practically sufficient viewing angle was obtained.

(4-2) Evaluation of white spots After performing a storage test for 1000 hours under 80 ° C dry conditions, 9 points of black in a 3 × 3 matrix including the 4 corners and the center of the display effective area. The display brightness was measured, and the maximum / average value was defined as C1. In addition, after conducting a storage test for 1000 hours under the condition of 60 ° C 90% RH, the same measurement was performed and the maximum value / average value was set to C2. From the values of C1 and C2, the white spots were evaluated based on the following evaluation criteria. As the light source, a backlight system for a large liquid crystal display device was used as in the evaluation of the contrast ratio. : C1 and C2 are both 1.3 or less : C1 and C2 are both 1.7 or less : C1 and C2 are both 2.0 or less ×: Either C1 or C2 is greater than 2.0

(4-3) Evaluation of moisture resistance After performing a storage test for 1000 hours under the condition of 50 ° C95% RH, CR (0) was performed at the center of the effective display area by the same method as in (4-1) Evaluation of contrast ratio above. ) Was measured, and the ratio with CR (0) before the storage test was defined as C3. In addition, the appearance was visually evaluated to confirm the presence or absence of defects such as decolorization at the end of the polarizing element. Based on the C3 value and the result of visual evaluation, the moisture resistance was evaluated based on the following evaluation criteria. : C3 is 0.90 or more and there is no defect at the end : C3 is 0.85 or more and there is no defect at the end : C3 is 0.80 or more and there is no defect at the end ×: C3 is 0.80 Less than or defective at the end

(4-4) Evaluation of cracking of polarizing element (PVA) After conducting a humidification test for 48 hours under 60 ° C 95% RH conditions, -35 ° C (1 hour) and 70 ° C (1 hour) are alternated. The heat shock test repeated in 1 was performed up to 400 cycles. Then, it was visually confirmed whether or not a defect such as cracking of the polarizing element occurred in the display effective region, and the cracking of the polarizing element was evaluated based on the following evaluation criteria. : No defect in the display effective area after 400 cycle test : No defect in display effective area after 300 cycle test : No defect in display effective area after 200 cycle test ×: 200 cycle There is a defect in the display effective area after the test of

(4-5) Evaluation of foaming / peeling (a) Storage test for up to 1000 hours under 80 ° C dry conditions, (b) Storage test for up to 1000 hours under 50 ° C 95% RH conditions, (c) -35 A heat shock test of up to 400 cycles of alternating ° C (1 hour) and 70 ° C (1 hour) was performed using different samples. Then, for each sample after each test, it was visually confirmed whether or not a defect such as foaming / peeling had occurred, and evaluation for foaming / peeling was performed based on the following evaluation criteria. : Foaming / peeling did not occur in all three tests that continued up to the maximum test time / cycle, or occurred only in the end face part outside the display effective area : Half the time / cycle of the maximum test time / cycle No foaming or peeling occurred in all three tests continued up to, or occurred only on the end face outside the display effective area. ×: One of the tests continued up to the maximum test time / half the cycle time / cycle In, foaming / peeling occurred in the display effective area.

<tables num="5"><img file="JP2006201401A_D0005.tif" /></tables>

(Summary of evaluation) As shown in Table 5, in the examples, an adhesive layer having a thickness of 1 μm or less was used for bonding the protective film and the polarizing element, and as the protective film, the absolute value of the photoelastic coefficient, the water absorption rate and the transparency were used. Since an NB-based resin film with low humidity was used, it was overall superior in durability (white spots, moisture resistance, PVA cracking, foaming / peeling) compared to the comparative example. In Examples 3 to 5, 8 to 10, and 12, since the NB resin was used as the first and third protective films, the durability was particularly excellent. In Examples 6 and 7, although the NB resin film was used, the protective film on the side where the corrected thickness direction retardation R is large, or the protective film on the back side (region B) which is easily affected by the heat from the backlight. As a result, since the TAC film was used, the durability was slightly lower than that of the other examples. In Examples 8 to 10, the phase difference design of the NB resin film was changed, and in Examples 11 to 13, the phase difference design of the liquid crystal display cell was changed, but sufficient display quality could be obtained in each case. .. In Examples 14 to 17, since the PVA-based polarizing element was subjected to cracking countermeasures, the evaluation of PVA cracking was particularly high.

On the other hand, in Comparative Examples 1 to 3, since an adhesive layer having a thickness of 20 μm or less was used for bonding the protective film and the polarizing element, the display quality was good, but the evaluation of durability was inferior, and particularly moisture resistance. The evaluation of PVA cracking and foaming / peeling was low. In Comparative Examples 4 and 5, since the TAC film having low heat resistance and moisture resistance was used as the first to fourth protective films and the retardation film, the display quality was good, but the evaluation of durability was inferior, and particularly white spots were formed. And the evaluation of moisture resistance was low. In Comparative Examples 6 and 7, since the TAC film having low moisture resistance and / or the PC film having low heat resistance were used as the first to fourth protective films, the evaluation of durability was inferior, and in particular, white spots appeared. And the evaluation of moisture resistance was low.

As described above, the examples were comprehensively superior to the comparative examples in terms of display quality (contrast ratio in the oblique direction) and durability (white spots, moisture resistance, PVA cracking, foaming / peeling). Further, in the embodiment, since the protective film of the polarizing element also serves as a retardation film, the number of films constituting the liquid crystal display device and the bonding man-hours can be reduced, resulting in low cost and thinness. For the above reasons, it can be seen that it is very effective to configure the liquid crystal display device as in this embodiment. The reference example was generally superior to the comparative example in terms of durability, but the display quality was low because the condition of 0 nm R1 + R3 + Rlc 35 nm was not satisfied.

<figref num="1">It is sectional drawing which shows typically an example of the liquid crystal display apparatus of this invention which has the structure which the protective film is arranged on both sides of a polarizing element, and (a) is the low photoelastic coefficient on the 1st and 3rd protective films. It shows a form in which a film with a low water absorption rate is used, (b) a form in which a film with a low photoelastic coefficient and low water absorption rate is used for the first protective film, and (c) a low in the third protective film. It shows a form in which a film having a photoelastic coefficient and a low water absorption rate is used.</figref><figref num="2">It is a top view for demonstrating the preferable relationship between the maximum width L of a polarizing element 21 and the maximum width L'of a screen (display effective area 50 of a liquid crystal display device) in the liquid crystal display device of the present invention.</figref><figref num="3">It is a top view for demonstrating the preferable relationship between the maximum width L of a polarizing element 21 and the maximum width l of an opening of a bezel 51 in the liquid crystal display device of the present invention.</figref><figref num="4-1">FIG. 5 is a cross-sectional view for explaining a state in which a laminated body composed of a liquid crystal display cell 10 or the like is supported and fixed by a bezel 51 in the liquid crystal display device of the present invention.</figref><figref num="4-2">FIG. 5 is a plan view of a laminated body including a bezel 51 and a liquid crystal display cell 10 used in the liquid crystal display device of the present invention when viewed from the observation surface side.</figref><figref num="5">It is sectional drawing which shows typically an example of the structure of the conventional liquid crystal display device.</figref><figref num="6">It is sectional drawing which shows typically the structure which improved the material of the retardation film with respect to the liquid crystal display device of FIG.</figref><figref num="7">It is sectional drawing which shows typically the structure which improved the material of the protective film of the polarizing element with respect to the liquid crystal display device of FIG.</figref><figref num="8">FIG. 5 is a cross-sectional view schematically showing a configuration in which a protective film for a polarizing element and a retardation film are integrated with respect to the liquid crystal display device of FIG. 7.</figref>

Code description

10: Liquid crystal display cell 11: Observation surface side substrate 12: Liquid crystal 13: Back side substrate 21: (Observation surface side) Polarizing element 22: (Back side) Polarizing element 31: Absolute value of photoelastic coefficient is 10 × 10^-8cm²First protective film with less than / N and less than 2.0% water absorption 31a: Absolute value of photoelastic coefficient is 10 × 10^-8cm²First protective film with / N or more and / or water absorption of 2.0% or more 32: Second protective film 33: Absolute value of photoelastic coefficient is 10 × 10^-8cm²Third protective film with less than / N and less than 2.0% water absorption 33a: Absolute value of photoelastic coefficient is 10 × 10^-8cm²Third protective film with / N or more and / or water absorption rate of 2.0% or more 34: Fourth protective film 35: Phase difference film (NB film) 36: Protective film (NB film) 37: Phase difference and protection Film (NB film) 41: Adhesive layer (thickness 0.5 μm) 42: Adhesive layer (thickness 20 μm) 50: Display effective area of liquid crystal display device 51: Bezel 51a: Bezel outer frame 51b: Bezel inner frame 61: Protective film (TAC film) 62: Phase difference film (PC film)