Manufacturing method for anisotropically diffusing medium

The present invention relates to a method for producing an anisotropic diffusion medium in which the diffusion characteristics of transmitted light change depending on the angle of incidence.

Light diffusing members have long been used not only in lighting equipment and building materials, but also in recent displays, especially LCDs. The light diffusion manifestation mechanism of these members includes scattering due to irregularities formed on the surface (surface scattering), scattering due to the difference in refractive index between the matrix resin and the filler dispersed therein (internal scattering), and surface scattering. It may be due to both internal scattering. However, the diffusing performance of these light diffusing members is generally isotropic, and even if the incident angle is slightly changed, the diffusing characteristics of the transmitted light do not differ significantly.

However, an optical control panel has been proposed that can selectively scatter only incident light from a specific angle (see, for example, Patent Document 1). This special light diffusing member, which is an optical control plate, is used in a specific direction for a resin composition composed of a plurality of compounds having one or more photopolymerizable carbon-carbon double bonds in molecules having different refractive indexes. It is a plastic sheet that has been cured by irradiating it with ultraviolet rays, and selectively scatters only incident light that forms a specific angle with respect to the sheet.

As a material for producing this optical control plate, the above-mentioned "resin composition composed of a plurality of compounds having one or more photopolymerizable carbon-carbon double bonds in molecules having different refractive indexes" described above. In addition to the above, compositions containing urethane acrylate oligomers are disclosed (see, for example, Patent Documents 2 to 4). Further, a combination of compound A having a polymerizable carbon-carbon double bond in the molecule and compound B having no polymerizable carbon-carbon double bond having a refractive index difference of 0.01 or more from this A, or a molecule. Compounds having a plurality of polymerizable carbon-carbon double bonds and having a refractive index difference of 0.01 or more before and after curing are listed (see, for example, Patent Document 5), and further, with radically polymerizable compounds. A combination with a cationically polymerizable compound having a vinyl ether as a functional group is also disclosed (see, for example, Patent Document 6).

Further, as a method for manufacturing the optical control plate, a method of stacking optical control plates having different angular characteristics to generate selective scattering at a plurality of angles (see, for example, Patent Document 7), or at least a plurality of divided regions. One area is irradiated with light from a linear light irradiation source, and the other area is irradiated with light from a linear light irradiation source or a point light source from another angle, and various areas with different scattering angle ranges. (See, for example, Patent Document 8), a method of simultaneously irradiating light from a plurality of linear irradiation light sources arranged apart from each other (see, for example, Patent Document 9), and a photopolymerizable composition. A continuous production method (see, for example, Patent Document 10) has been proposed in which a linear light source is arranged in the width direction of the film-like body and the film-like body is moved in the length direction.

However, as illustrated in Patent Document 2, the incident angle dependence of the scattering characteristic that these optical control plates can selectively scatter only the incident light from a specific angle is exhibited by the optical control plates. This is observed when the optical control plate is rotated around a line projected on the surface of the optical control plate with a linear light source arranged in the sky at the time of fabrication. That is, when it is rotated around a line orthogonal to the projection line of the linear light source, there is almost no dependence of the scattering characteristics on the incident angle, or when it is rotated around the projection line of the linear light source. Will have very different scattering characteristics depending on the angle of incidence.

A schematic diagram of such a conventional optical control panel is shown in FIG. As shown in FIG. 1, in the conventional optical control board, it is said that plate-shaped regions having different refractive indexes are formed in parallel with each other in a sheet-shaped substrate. An electron micrograph of the AA line cross section in FIG. 1 is shown in FIG. 2 (a), and an electron micrograph of the BB line cross section is shown in FIG. 2 (b). As shown in the figure, in the conventional optical control panel, regions having different refractive indexes appear alternately when viewed in the AA line cross section, but there is no change in the refractive index when viewed in the BB line cross section. , Homogeneous. That is, the incident angle dependence is seen in the AA line cross section, but the incident angle dependence is hardly seen in the BB line cross section.

Although the principle of forming these optical control plates has not always been clarified, it is described that "the regions having different refractive indexes are cured so as to exist in a certain direction" (for example, Patent Documents). 11), It is considered that in the photopolymerization process of the photopolymerizable composition, the reaction proceeds spatially non-uniformly to form microstructures having different refractive indexes. Here, in order to show the incident angle dependence of the scattering characteristic that only the incident light from a specific angle can be selectively scattered, regions having different refractive indexes are oriented in a certain direction with regularity. It seems that light irradiation with a linear light source is indispensable for that purpose. That is, it becomes transparent because the microstructure is not formed by the surface light source or the diffused light source irradiation, and the microstructure is formed by the point light source or the parallel light irradiation, but the light scattering is not directional because there is no regularity. (See, for example, Patent Documents 8, 12, and 13).

The optical control panel described above exhibits peculiar light diffusivity, but as described above, it shows the incident angle dependence of the scattering characteristics only when it is rotated in a specific direction. It is only used as a building material to limit.

An optical film called a light control film or a louver film, which has the property of transmitting only incident light in a certain angle range and blocking other incident light, is also known, and in the old days, the back surface of the instrument panel. It has been used for lighting and, recently, for controlling the viewing angle of a display, that is, for preventing peeping. This is obtained by flat-cutting a block produced by alternately laminating and crimping a large number of transparent plastic layers and colored plastic layers at a right angle to the plastic layer or at a predetermined angle (for example, Patent Document). See 14,15.). Since this louver film has a structure in which colored louvers are arranged at equal intervals at a constant inclination in the film thickness direction, light rays substantially parallel to the direction of the louvers are transmitted, but pass through a plurality of adjacent louvers. Light incident at such an angle is absorbed by the louver and cannot be transmitted.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 1-77001</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 1-147405</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 1-147406</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2-54201</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 3-109501</text></patcit><patcit num="6"><text>Japanese Patent Application Laid-Open No. 6-9714</text></patcit><patcit num="7"><text>Japanese Unexamined Patent Publication No. 63-309902</text></patcit><patcit num="8"><text>Japanese Unexamined Patent Publication No. 1-40903</text></patcit><patcit num="9"><text>Japanese Unexamined Patent Publication No. 1-40905</text></patcit><patcit num="10"><text>Japanese Unexamined Patent Publication No. 2-67501</text></patcit><patcit num="11"><text>Japanese Unexamined Patent Publication No. 2-51101</text></patcit><patcit num="12"><text>Japanese Unexamined Patent Publication No. 1-40906</text></patcit><patcit num="13"><text>Japanese Unexamined Patent Publication No. 3-87701</text></patcit><patcit num="14"><text>Japanese Patent Application Laid-Open No. 50-92751</text></patcit><patcit num="15"><text>Patent No. 3043069</text></patcit>

<p> However, although this louver film also exhibits the anisotropy of transmitting only incident light from a specific angle, when the film is rotated around the direction in which the louver is provided, like the previous optical control plate. Only the change in light transmission is observed, and even if the film is rotated around a straight line orthogonal to the louver, the incident angle dependence of the transmitted light is not observed.</p><p> The present inventor aims to improve the anisotropic diffusion medium based on the above prior art, and can be seen only when the incident angle dependence of the scattering characteristics is rotated around a specific straight line in the anisotropic diffusion medium. An anisotropic diffusion medium that exhibits the same scattering characteristics depending on the incident angle even when rotated about any other straight line, and a manufacturing method thereof have already been provided in Japanese Patent Application No. 2004-074180. .. However, the manufacturing method shown here has used a point light source. When a point light source is used as the light source, it is possible to produce a small area, but it is difficult to continuously produce a large area anisotropic diffusion medium.</p><p> Therefore, in the present invention, it is an anisotropic diffusion medium having a resin layer made of a cured product of a composition containing a photocurable compound, and an aggregate of a plurality of rod-shaped cured regions is formed inside the resin layer. Therefore, it is possible to provide a production method capable of continuously producing an anisotropic diffusion medium having a structure in which all of the plurality of rod-shaped cured regions extend parallel to a predetermined direction P over a large area. I am aiming.</p>

<p> That is, in the present invention, the composition containing the photocurable compound is provided in the form of a sheet, and the sheet is irradiated with parallel light from a predetermined direction P to cure the composition and spreads inside the sheet in parallel with the direction P. A method for producing an anisotropic diffusion medium that forms an aggregate of a plurality of existing rod-shaped hardened regions, in which an aggregate of tubular objects arranged parallel to the direction P is formed between a linear light source and a sheet. The present invention provides a method for producing an anisotropic diffusion medium, which comprises interposing and irradiating light through the tubular object.</p><p> The anisotropic diffusion medium produced by the method of the present invention is an anisotropic diffusion medium having a resin layer made of a cured product of a composition containing a photocurable compound, and has a plurality of rods inside the resin layer. An aggregate of cured regions is formed, and the plurality of rod-shaped cured regions all extend parallel to a predetermined direction P, from any direction at any point on one side of the anisotropic diffusion medium. When the amount of linearly transmitted light corresponding to each incident direction of the incident light is vector-displayed in the emission direction starting from the emission point corresponding to the above-mentioned arbitrary point in the space on the other side of the anisotropic diffusion medium, these The curved surface obtained by connecting the tips of the vectors is a bell-shaped curved surface having an axis of symmetry in a predetermined direction P.</p><p> In such an anisotropic diffusion medium, an aggregate of a plurality of rod-shaped cured regions extending in parallel to a predetermined direction P having a different refractive index is formed inside the anisotropic diffusion medium, so that the anisotropic diffusion medium has a predetermined direction. The amount of linearly transmitted light corresponding to the incident light from P shows the minimum value in or near the predetermined direction P, and the amount of linearly transmitted light corresponding to the incident light from an angle inclined from the predetermined direction P has a large inclination angle. It increases as it becomes, and above a certain angle, the increase stops and shows a saturation value. That is, the incident angle dependence of the amount of linearly transmitted light exhibits the same property on any incident surface including a predetermined direction P. Therefore, when the linear transmitted light amount of transmitted light corresponding to the incident light from all directions incident on an arbitrary point O is represented by a vector, the curved surface obtained by connecting the tips of these vectors is as shown in FIG. It has a curved surface with a bell shape.</p><p> As shown in FIGS. 4 and 5, according to the production method of the present invention, a set of tubular objects arranged parallel to the direction P between the linear light source and the composition containing the sheet-shaped photocurable compound. Is intervening, and light is irradiated through this cylinder. Therefore, a part of the light from the linear light source is blocked, and only the light in the direction parallel to the tubular object passes through the tubular object and irradiates the object to be cured, so that the sheet-shaped photocurable compound. The irradiation conditions at any one point of the composition containing the above are equivalent to those received light irradiation from a conventional point-like light source. Therefore, it is possible to continuously produce an anisotropic diffusion medium having the same internal structure and optical characteristics as the anisotropic diffusion medium produced by irradiation with a conventional point light source over a large area.</p>

Hereinafter, the method for producing the anisotropic diffusion medium of the present invention will be described in detail. In the conventional method for producing an anisotropic diffusion medium, a composition containing a photocurable compound is provided in the form of a sheet, and the sheet is irradiated with parallel ultraviolet rays from a point light source arranged in a predetermined direction P to form the composition. Is cured to form an aggregate of a plurality of rod-shaped cured regions in the sheet. However, with this method, it is difficult to continuously produce a large area, so instead of using a point light source, a linear light source that is often used in coating equipment and printing machines is used to achieve the same internal structure and optical characteristics. This is the result of repeated studies to produce a product having the present invention. That is, in the present invention, a set of tubular objects arranged parallel to the direction P is interposed between the linear light source and the composition containing the sheet-shaped photocurable compound, and light irradiation is performed through the tubular objects. It is characterized by. This tubular object refers to a so-called paper rolled into a cylinder, which is hollow inside and has both ends open. Any composition containing a sheet-like photocurable compound can be obtained by collecting a large number of these tubular objects in the same direction and irradiating the object to be cured with light from a linear light source through the tubular objects. The irradiation conditions at one point are the same as those obtained by light irradiation from a conventional point light source, and therefore the internal structure of the anisotropic diffusion medium obtained thereby is also the same as that produced by conventional point light source irradiation. And its optical characteristics are also the same. Schematic diagrams of light irradiation using such a tubular object are shown in FIGS. 4 and 5.

The cross-sectional shape of the tubular object used in the manufacturing method of the present invention is not particularly specified, such as a circle, a triangle, a quadrangle, a hexagon, or a combination thereof. The size of one tubular object is preferably in the range of a cross-sectional diameter of 1 to 100 mm and a length of 10 to 1000 mm. Further, a relationship of (L / D)&gt; 5, preferably (L / D)&gt; 10, and more preferably (L / D)&gt; 20 is required between the diameter D of the cross section and the length L thereof. If the diameter of the tubular object is smaller than 1 mm, the amount of light passing through the tube is too small, which is not preferable. If the diameter exceeds 100 mm, the parallelism of the light is insufficient and the irradiation condition is equivalent to that of a conventional point light source. It is not preferable because it becomes impossible to satisfy. When the length of the tubular object is shorter than 10 mm, it does not satisfy the irradiation condition equivalent to that of a conventional point light source, while when it exceeds 1000 mm, the light emitted to the composition containing the photocurable compound. It is not preferable because the intensity becomes low and long-time exposure is required.

The set of tubular objects used in the present invention needs to have one end in the immediate vicinity of a linear light source and the other end in the vicinity of a sheet-like composition containing a photocurable compound. is there. When one or both are separated, the light shining on the surface of the composition containing the sheet-like photocurable compound may be linear or adjacent tubular, reflecting the shape of the original linear light source. Light from an object is mixed in, and it is not possible to reproduce the irradiation conditions from the originally preferable point light source, and as a result, the anisotropic diffusion medium of the present invention cannot be produced.

The material of the tubular object and its aggregate used in the present invention is not particularly limited, and glass, ceramics, metal, plastic, etc. can be used, but it is durable against strong light and heat from a linear light source. It is preferable that the material is sexual and has strong physical strength. Specifically, metals and alloys such as SUS, iron, and aluminum, and heat-resistant polymer materials are preferably used. However, it is preferable that the inside of the cylinder that transmits light is coated with black, blackened metal, or electrostatically transplanted so as not to reflect light as much as possible.

The set of tubular objects described above is installed in the vicinity of the composition containing the sheet-shaped photocurable compound, but the light emitted through the set is a set of spot light based on the cross section of the tubular object. , A portion with weak irradiation intensity is generated between each spot. Therefore, it is preferable to move the aggregate of the tubular objects and the composition containing the sheet-shaped photocurable compound relatively to make the overall irradiation intensity uniform. Specifically, a method of reciprocating a set of tubular objects to the left or right with the direction P fixed, or rotating a circular orbit can be mentioned.

In the case of continuous production, in the process of moving a long product of a composition containing a photocurable compound at a constant speed, from a set of linear light sources and tubular objects installed parallel to the width direction of this long product. It suffices to irradiate light. Here, in order to increase the curing speed, it is possible to cope with it by installing a plurality of sets of linear light sources and tubular objects in series. In this case, in order to make the irradiation amount in the width direction more uniform, the directions of the sides of the cylindrical object, such as a triangle, a quadrangle, and a hexagon, are the same as the flow direction of the long product. It is also effective to devise so that the structure does not become the same, or to provide a mechanism for rotating the set of tubular objects to the left and right or in a circular shape as described above.

As the light source for irradiating light, a light source having a rod-shaped light emitting surface is used in the present invention, and specifically, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a xenon flash lamp and the like can be used. As the rod-shaped light source, a light source having a diameter of 20 to 50 mm and a light emitting length of about 100 to 1500 mm is commercially available, and can be appropriately selected according to the size of the anisotropic diffusion medium to be produced.

The light beam that irradiates a sheet of the composition containing the photocurable compound must contain a wavelength at which the photocurable compound can be cured, and usually has a wavelength centered on 365 nm of a mercury lamp. Light is used. When the anisotropic diffusion layer of the present invention is produced using this wavelength band, the illuminance is 0.01 to 100 mW / cm.²It is preferably in the range of 0.1 to 20 mW / cm, more preferably 0.1 to 20 mW / cm.²Is the range of. Illuminance is 0.01mW / cm²If it is less than or equal to the following, it takes a long time to cure, resulting in poor production efficiency and 100 mW / cm.²This is because the photocurable compound cures too quickly to form a structure, and the desired anisotropic diffusion characteristics cannot be exhibited.

Next, the anisotropic diffusion medium that can be produced by the method of the present invention will be described in detail. In the anisotropic diffusion medium produced by the method of the present invention, the incident angle dependence of its diffusion characteristics is substantially the same in any incident surface including a straight line P intersecting the surface of the medium at a predetermined angle, and the straight line P It is characterized by having symmetry around. Generally, the diffusion characteristics are expressed by the diffusion transmittance, parallel light transmittance, and haze indicated by JIS-K7105 and JIS-K7136, but these are under the condition that the sample is brought into close contact with the integrating sphere and there is no light leakage. , It is measured by irradiating light from the normal direction, and measurement by arbitrarily changing the incident angle is not assumed. That is, there is no officially recognized method for evaluating the incident angle dependence of the diffusion characteristics of the anisotropic diffusion medium. Therefore, in the present invention, as shown in FIG. 6, a sample is arranged between a light source (not shown) and the receiver 3, and the sample is transmitted straight through the receiver while changing the angle around the straight line L on the sample surface. We decided to evaluate the incident angle dependence of the amount of linearly transmitted light based on the measurement principle of measuring the amount of light entering 3. As a specific device, a commercially available haze meter, a variable-angle photometer, or a spectrophotometer in which a rotatable sample holder is provided between the light source and the light receiving unit can be used. Although the value of the amount of light obtained here is only relative, it is possible to obtain the measurement result as shown in FIG. 7 as the angle dependence of the amount of linearly transmitted light. The angle dependence of the scattering characteristics will be described below with respect to the amount of linear light transmittance, but the present invention is not limited to this, and values such as diffusion transmittance, parallel ray transmittance, and haze measured by a haze meter are used. It is also possible to substitute.

FIG. 8 shows a schematic view of an embodiment of the anisotropic diffusion medium produced by the production method of the present invention. A large number of minute rod-shaped cured regions 2 are formed inside the sheet-shaped anisotropic diffusion medium 1 made of a cured product of a composition containing a photocurable compound. These rod-shaped cured regions 2 are formed by irradiating ultraviolet rays parallel to each other from a point light source arranged in the normal S direction of the anisotropic diffusion medium 1, and all of these rod-shaped cured regions are in the normal S direction. It is formed in parallel. Electron micrographs of cross sections of such an example of the anisotropic diffusion medium of the present invention are shown in FIGS. 9 (a) and 9 (b). These are the AA line sectional view and the BB line sectional view in FIG. That is, the aggregate of the rod-shaped cured regions referred to in the present invention is schematically shown in FIG. 8, but is based on the electron micrograph shown in FIG. 9, and is formed so as to have such a cross-sectional shape. It means something. Further, the rod shape is estimated from the irradiation light source and is schematically described in a columnar shape in FIG. 8, but it means a state in which the rod shape is formed in the thickness direction, and the shape is circular, polygonal, or indefinite. The shape is not particularly limited.

FIG. 10 shows a schematic cross-sectional view for explaining the incident angle dependence of the amount of linearly transmitted light transmitted through the anisotropic diffusion medium shown in FIG. In FIG. 10, reference numeral 2 is a schematic representation of the rod-shaped cured region, in which the rod-shaped cured region extends in the normal S direction. When light is incident from above the anisotropic diffusion medium and emitted downward, the incident light I is incident from the normal S direction, that is, the extending direction of the rod-shaped hardening region.₀Is strongly diffused as it passes through the anisotropic diffusion medium, so that the corresponding linearly transmitted light amount is small. In Figure 10, this is I₀Transmitted light vector T having the same direction as and having a magnitude proportional to the amount of linear transmitted light₀It is represented by. Next, this incident light I₀Incident light tilted by a certain angle from I₁Since the amount of linear transmitted light corresponding to this increases, the transmitted light vector T₁Is T₀It's getting bigger. In addition, the incident light I₁Incident light from a deeper angle I₂Then, the corresponding transmitted light vector T₂Is T₁It is even bigger than.

Incident light I₀When the amount of transmitted light is expressed by a vector for all the incident light inclined from, and the tip ends of the vector are connected, a curve having symmetry shown by a broken line in FIG. 10 can be obtained. In addition, the incident light I₀When the same examination is performed on other cross sections including, the same broken line curve as in FIG. 10 can be obtained for all the cross sections. That is, by connecting the tips of the transmitted light vectors obtained in all directions, a bell-shaped curved surface having an axis in the normal S direction as shown in FIG. 3 can be obtained.

The anisotropic diffusion medium produced by the method of the present invention is not limited to the above-described embodiment. For example, as shown in FIG. 11, the direction P inclined at an arbitrary angle from the normal S direction is the axis of symmetry. It is also possible to use an anisotropic diffusion medium having an incident light angle dependence.

FIG. 12 shows a schematic cross-sectional view for explaining the incident angle dependence of the amount of linearly transmitted light transmitted through the anisotropic diffusion medium shown in FIG. In FIG. 12, reference numeral 2 schematically represents a rod-shaped cured region. When the same study as above was performed for this anisotropic diffusion medium, the incident light I from the P direction, which is the extending direction of the rod-shaped cured region,₀, Incident light tilted against it I₁, I₂Transmitted light vector T corresponding to each of₀, T₁, T₂By connecting the tips of, the curve shown by the broken line in Fig. 12 is obtained, and the incident light I₀By connecting the tips of the transmitted light vectors in the same way for all the cross sections including, a bell-shaped curved surface having an axis of symmetry in the direction P as shown in FIG. 3 can be obtained.

The optical control plate manufactured based on Patent Document 1 and the like also shows the same incident angle dependence as in FIG. 7, but this is only when the sample is rotated around the specific straight line L shown in FIG. However, when rotated around a straight line orthogonal to the straight line L in the sample plane, the incident angle dependence of the amount of linear transmitted light is hardly shown, or a completely different aspect is exhibited. That is, with respect to the optical control plate produced by irradiating light from a linear light source in the same direction as the straight line L shown in FIG. 13, the angle dependence of the amount of linear transmitted light when the optical control plate is rotated around the straight line L is Although it is shown by the solid line in FIG. 14, when it is rotated around the straight line M that is orthogonal to the straight line L, it shows a completely different angle of incidence dependence as shown by the broken line.

However, the anisotropic diffusion medium produced by the method of the present invention is produced by irradiating a composition containing a photocurable compound with parallel light rays from the direction of a straight line P and curing the composition. The incident angle dependence of the amount of linear transmitted light is almost the same in all the incident planes including this straight line P, and the shape shows symmetry around the straight line P. FIG. 15 shows a straight line P representing the incident direction of the parallel light rays irradiated when the anisotropic diffusion medium produced by the method of the present invention is produced. The intersection of the straight line P with the anisotropic diffusion medium is O, and the incident surface P1 formed by the normal S of the anisotropic diffusion medium and the straight line P is defined, and the incident surface perpendicular to the incident surface P1 and including the straight line P is included. Face P2 is also defined. FIG. 16 shows the incident angle dependence of the amount of linearly transmitted light on these two incident surfaces P1 and P2. Although the direction of the straight line P is set to 0 ° here, the incident angle dependence is almost the same for both incident surfaces, and it is shown that the shape also shows symmetry around the straight line P. This means that if the incident angle dependence of the amount of linear transmitted light is measured and three-dimensionalized for all incident surfaces including the straight line P, a bell-shaped rotating body centered on the straight line P is formed.

Although it has been stated here that the incident angle dependence of the amount of linear transmitted light is almost the same in all the incident planes including the straight line P, this almost the same will be described. As shown in FIG. 7, the incident angle dependence of the linear transmitted light amount shows a valley shape in which the linear transmitted light amount decreases in a specific incident angle range, and the half width is the incident angle of the anisotropic diffusion characteristic. It can be defined as a range. In the present invention, those having a difference in the incident angle range within 15 ° on different incident surfaces are defined as "almost the same".

Further, in the present invention, it has been described that the shape of the incident angle dependence of the amount of linear transmitted light shows symmetry about a predetermined direction P, but the symmetry referred to here refers to the direction P in FIG. Assuming that the incident angle of the incident light is 0 °, the difference between the maximum and minimum values of the linear transmitted light amount in the region where the incident angle is on the plus side is represented by ΔR, and similarly, that on the minus side is represented by ΔL, 0.5 (ΔR / ΔL). This refers to the case where the relationship of 2 is established.

The anisotropic diffusion medium produced by the method of the present invention is produced by irradiating a composition containing a photocurable compound with parallel light rays from the direction of a straight line P to cure the composition. As the direction of this straight line P, the inclination of the medium from the normal line is required to be within 45 °, preferably within 30 °, and more preferably within 15 °. It is also a preferred embodiment of the present invention that this straight line P coincides with the normal. When light is irradiated from a deep inclination of 45 ° or more, the absorption efficiency of the irradiation light is poor and it is disadvantageous in manufacturing, and the incident angle of the amount of linear transmitted light in an arbitrary incident surface including the straight line P shown in the present invention. It is not preferable because the identity of the dependence cannot be maintained. As is clear from FIG. 12, when the inclination of the direction P with respect to the normal is large, the incident light I is inclined by the same angle with respect to the direction P.₂In any case, the optical path lengths in the anisotropic diffusion medium are significantly different from each other, and the transmitted light T₂This is because there is a difference in the amount of light.

The anisotropic diffusion medium produced by the method of the present invention includes an anisotropic diffusion layer alone made of a cured product of a composition containing a photocurable compound, and the anisotropic diffusion layer laminated on a transparent substrate. It is possible to provide a structure in which transparent substrates are laminated on both sides of the anisotropic diffusion layer. Here, as the transparent substrate, the higher the transparency, the better, and the total light transmittance (JIS K7361-1) is 80% or more, more preferably 85% or more, most preferably 90% or more, and also. , Haze value (JIS Those having K7136) of 3.0 or less, more preferably 1.0 or less, and most preferably 0.5 or less can be preferably used. A transparent plastic film, a glass plate, or the like can be used, but the plastic film is preferable because it is thin, light, hard to break, and excellent in productivity. Specifically, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), polycarbonate (PC), polyarylate, polyimide (PI), aromatic polyamide, polysulfone (PS), polyethersulfone ( Examples thereof include PES), cellophane, polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), cycloolefin resin and the like, and these alone, mixed or laminated can be used. The thickness of the substrate is 1 μm to 5 mm, preferably 10 to 500 μm, and more preferably 50 to 150 μm in consideration of application and productivity.

Next, the anisotropic diffusion medium produced by the method of the present invention contains an anisotropic diffusion layer obtained by curing a composition containing a photocurable compound, and the following combinations are available for this composition. It can be used. (1) Those using a single photopolymerizable compound described later (2) Those using a mixture of a plurality of photopolymerizable compounds described later (3) Not having photopolymerizability with a single or a plurality of photopolymerizable compounds Used by mixing with a polymer compound

In any combination, it seems that micron-order fine structures having different refractive indexes are formed in the anisotropic diffusion layer by light irradiation, whereby the unique anisotropic diffusion characteristics shown in the present invention are exhibited. It seems that it can be expressed. Therefore, in (1) above, it is preferable that the change in refractive index before and after photopolymerization is large, and in (2) and (3), it is preferable to combine a plurality of materials having different refractive indexes. Here, the change in refractive index and the difference in refractive index specifically indicate a change or difference of 0.01 or more, preferably 0.05 or more, and more preferably 0.10 or more.

The photocurable compound, which is an essential material for forming the anisotropic diffusion layer produced by the method of the present invention, is selected from polymers, oligomers, and monomers having a radically polymerizable or cationically polymerizable functional group. It is a material composed of a photopolymerizable compound and a photoinitiator, and polymerizes and solidifies by irradiating with ultraviolet rays and visible light.

The radically polymerizable compound mainly contains one or more unsaturated double bonds in the molecule, and specifically includes epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polybutadiene acrylate, silicone acrylate and the like. Acrylate oligomers called by name, 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-Acryloyloxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct diacrylate of bisphenol A, trimethyl propantriacrylate, EO Examples thereof include acrylate monomers such as modified trimethylol propanetriacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylol propanetetraacrylate, and dipentaerythritol hexaacrylate. Further, these compounds may be used individually or in combination of two or more. Although methacrylate can be used in the same manner, acrylate is generally preferable to methacrylate because it has a faster photopolymerization rate.

As the cationically polymerizable compound, a compound having one or more epoxy groups, vinyl ether groups, and oxetane groups in the molecule can be used. Examples of compounds having an epoxy group include 2-ethylhexyl diglycol glycidyl ether, biphenyl glycidyl ether, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, and tetramethyl bisphenol F. Diglycidyl ethers of bisphenols such as tetrachlorobisphenol A and tetrabromobisphenol A, polyglycidyl ethers of novolak resins such as phenol novolac, cresol novolac, brominated phenol novolac, orthocresol novolac, ethylene glycol, polyethylene glycol, polypropylene. Diglycidyl ethers of alkylene glycols such as glycols, butanediols, 1,6-hexanediols, neopentyl glycols, trimethylpropane, 1,4-cyclohexanedimethanol, EO adducts of bisphenol A, PO adducts of bisphenol A. Examples thereof include glycidyl esters such as glycidyl ester of hexahydrophthalic acid and diglycidyl ester of dimer acid.

In addition, 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meth-dioxane, di (3,4-Epoxycyclohexylmethyl) adipate, di (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3', 4'-epoxy-6'-methyl Cyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadienediepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis (3,4-epoxycyclohexanecarboxylate), lactone modification 3,4-Epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate, tetra (3,4-epoxycyclohexylmethyl) butanetetracarboxylate, di (3,4-epoxycyclohexylmethyl) -4,5-epoxy An alicyclic epoxy compound such as tetrahydrophthalate can also be mentioned, but is not limited thereto.

Examples of the compound having a vinyl ether group include diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, and trimethyl propantrivinyl ether. , Propenyl ether propylene carbonate and the like, but are not limited thereto. The vinyl ether compound is generally cationically polymerizable, but radical polymerization is also possible by combining it with acrylate.

As the compound having an oxetane group, 1,4-bis [(3-ethyl-3-oxettanylmethoxy) methyl] benzene, 3-ethyl-3- (hydroxymethyl) -oxetane and the like can be used.

The above cationically polymerizable compounds may be used alone or in combination of two or more. Photoinitiators capable of polymerizing radically polymerizable compounds include benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-. Diethoxyacetophenone, benzyldimethylketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2 -Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanol-1, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1 -On, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyr-1-yl) titanium, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone -1,2,4,6-trimethylbenzoyldiphenylphosphine oxide and the like can be mentioned. Further, these compounds may be used alone or in combination of two or more.

The photoinitiator of the cationically polymerizable compound is a compound that generates an acid by light irradiation and can polymerize the above-mentioned cationically polymerizable compound by the generated acid. Generally, an onium salt and a metallocene complex are used. It is preferably used. As the onium salt, a diazonium salt, a sulfonium salt, an iodonium salt, a phosphonium salt, a selenium salt and the like are used, and BF is used as a counterion thereof.₄^-, PF₆^-, AsF₆^-, SbF₆^-And other anions are used. Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl) diphenylsulfonium hexafluoroantimonate, and (4-phenylthiophenyl) diphenyl. Sulfonium hexafluorophosphate, bis [4- (diphenylsulfonio) phenyl] sulfide-bis-hexafluoroantimonate, bis [4- (diphenylsulfonio) phenyl] sulfide-bis-hexafluorophosphate, (4-methoxyphenyl) Diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl) phenyliodonium hexafluoroantimonate, bis (4-t-butylphenyl) iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, Examples thereof include (η5-isopropylbenzene) (η5-cyclopentadienyl) iron (II) hexafluorophosphate and the like, but the present invention is not limited thereto. Further, these compounds may be used individually or in combination of two or more.

In the present invention, the photoinitiator is blended in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the photopolymerizable compound. This is because if the amount is less than 0.01 parts by weight, the photocurability is lowered, and if the amount is more than 10 parts by weight, only the surface is cured and the internal curability is lowered. .. These photoinitiators are usually used by directly dissolving powder in a photopolymerizable compound, but if the solubility is poor, the photoinitiator is previously dissolved in a very small amount of solvent at a high concentration. It can also be used. Examples of such a solvent are more preferably photopolymerizable, and specific examples thereof include propylene carbonate and γ-butyrolactone. It is also possible to add various known dyes and sensitizers in order to improve photopolymerizability. Further, a thermosetting initiator capable of curing the photopolymerizable compound by heating can be used in combination with the photoinitiator. In this case, it can be expected that the polymerization curing of the photopolymerizable compound is further promoted and completed by heating after photocuring.

In the present invention, an anisotropic diffusion layer can be formed by curing a composition obtained by using the above photocurable compounds alone or in a mixture of a plurality of the above photocurable compounds. The anisotropic diffusion layer of the present invention can also be formed by curing a mixture of a photocurable compound and a polymer resin having no photocurability. Examples of the polymer resin that can be used here include acrylic resin, styrene resin, styrene-acrylic copolymer, polyurethane resin, polyester resin, epoxy resin, cellulose resin, vinyl acetate resin, vinyl acetate-vinegar vinyl copolymer, and polyvinyl. Butyral resin and the like can be mentioned. These polymer resins and photocurable compounds need to have sufficient compatibility before photocuring, but various organic solvents, plasticizers, etc. are used to ensure this compatibility. It is also possible. When acrylate is used as the photocurable compound, it is preferable to select acrylic resin as the polymer resin from the viewpoint of compatibility.

In the anisotropic diffusion medium produced by the method of the present invention, a composition containing the above-mentioned photocurable compound is provided in a sheet shape, and the composition is cured by irradiating the composition with parallel light rays from the direction of a straight line P. It is manufactured by letting it. Here, as a method for providing the composition containing the photocurable compound in the form of a sheet on the substrate, a normal coating method or a printing method is applied. Specifically, air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating. , Die coating and other coatings, intaglio printing such as gravure printing, and stencil printing such as screen printing can be used. Further, when the composition has a low viscosity, a weir having a constant height can be provided around the substrate, and the composition can be cast in the weir surrounded by the weir.

As described above, according to the present invention, the incident angle dependence of the amount of linear transmitted light has an unprecedented characteristic characteristic that a bell-shaped curved line is formed around a specific straight line in the anisotropic diffusion medium. The anisotropic diffusion medium can be continuously produced in a large area.

<figref num="1">It is a schematic diagram which shows an example of the conventional optical control panel.</figref><figref num="2">(a) It is an electron micrograph which shows the AA line cross section (cross section perpendicular to the direction of a linear light source) in the conventional light diffusion medium of FIG. (b) It is an electron micrograph which shows the BB line cross section (cross section parallel to the direction of a linear light source) in the conventional light diffusion medium of FIG.</figref><figref num="3">It is a schematic diagram explaining the incident angle dependence of the linear transmitted light amount transmitted through the anisotropic diffusion medium of this invention.</figref><figref num="4">It is a schematic cross-sectional view which shows the manufacturing method of the anisotropic diffusion medium of this invention.</figref><figref num="5">It is a schematic diagram which shows the manufacturing method of the anisotropic diffusion medium of this invention.</figref><figref num="6">It is a schematic diagram which shows the evaluation method of the incident angle dependence of the linear transmitted light amount of an anisotropic diffusion medium (when only the linear L is a rotation axis).</figref><figref num="7">It is a graph which shows the relationship between the incident angle and the linear transmitted light amount in the evaluation of the incident angle dependence of the linear transmitted light amount of an anisotropic diffusion medium.</figref><figref num="8">It is a schematic diagram which shows the embodiment of the anisotropic diffusion medium of this invention.</figref><figref num="9">(a) FIG. 8 is an electron micrograph showing an AA line cross section in the anisotropic diffusion medium of the present invention shown in FIG. (b) FIG. 8 is an electron micrograph showing a BB line cross section (a cross section orthogonal to the AA line cross section) in the anisotropic diffusion medium of the present invention shown in FIG.</figref><figref num="10">It is a schematic cross-sectional view explaining the incident angle dependence of the linear transmitted light amount transmitted through the anisotropic diffusion medium of FIG.</figref><figref num="11">It is a schematic diagram which shows the other embodiment of the anisotropic diffusion medium of this invention.</figref><figref num="12">It is a schematic cross-sectional view explaining the incident angle dependence of the linear transmitted light amount transmitted through the anisotropic diffusion medium of FIG.</figref><figref num="13">It is a schematic diagram which shows the evaluation method of the incident angle dependence of the linear transmitted light amount of an anisotropic diffusion medium (when the straight lines L and M are the rotation axes).</figref><figref num="14">It is a graph which shows the relationship between the incident angle and the linear transmitted light amount in the evaluation of the incident angle dependence of the linear transmitted light amount of the conventional light diffusion medium.</figref><figref num="15">It is a schematic diagram explaining the incident angle dependence of the amount of linear transmitted light in the anisotropic diffusion medium of the present invention produced by irradiating parallel light rays from a predetermined straight line P direction.</figref><figref num="16">It is a graph which shows the relationship between the incident angle and the linear transmitted light amount in the evaluation of the incident angle dependence of the linear transmitted light amount of the anisotropic diffusion medium of this invention.</figref>

Code description

1 Anisotropic diffusion medium 2 Rod-shaped hardening region 3 Light receiving part 4 Linear light source 5 Cylindrical cavity 6 Aggregate of tubular objects I Incident light T Transmitted light P Incident direction P1, P2 Incident surface S Anisotropic diffusion medium surface Normal