Liquid crystal display module

The present invention relates to a liquid crystal display module including a surface light source device that emits light in a planar manner using a light guide plate.

Conventionally, as a backlight or the like of a transmissive liquid crystal display device, a side light type surface light source device in which light source light is incident from an end surface of a light guide plate and light is emitted in a planar shape from one main surface has been used. In this side light type surface light source device, light incident from an end surface is diffusely reflected by a main surface opposite to the light emitting surface and emitted from the light emitting surface. As shown in the prior art of No. 1 (see FIG. 1), it is formed on a smooth surface.

Therefore, when the above-mentioned side light type surface light source device is installed on the liquid crystal display element in which the polarizing plates are arranged on the front side and the rear side of the display of the liquid crystal cell, respectively, the light emitting surface of the light guide plate is smooth. The normally smooth rear polarizing plate surface of the liquid crystal display element comes into contact with the entire surface or a part of the polarizing plate.

When the smooth surfaces come into contact with each other as described above, the contact area is in a completely adhered state without an air layer, and the non-contact area around the contact area is a gap space in which an air layer exists. , The boundary between both optically different regions is easily recognized visually from the observation side, and the display quality is significantly deteriorated.

Further, in many cases, an appropriate number of optical sheets are interposed between the light guide plate and the liquid crystal display element in order to suppress the loss of the emitted light from the light guide plate and to make the intensity distribution uniform. However, if the surface of the optical sheet in contact with the surface of the rear polarizing plate is smooth, the same problem occurs. When the optical sheet is an optical element that generates interference fringes (moire) such as a prism sheet, the moiré further lowers the display quality.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2003-167251</text></patcit>

<p> In the present invention, although the surface light source device using the light guide plate is used as the backlight, deterioration of the display quality due to the gap between the liquid crystal display element and the backlight is surely prevented, and good display quality is stably maintained. An object of the present invention is to provide a transmissive liquid crystal display module that can be obtained.</p>

<p> In order to solve the above problems, the liquid crystal display module of the present invention has a front side, which is an observation side of a liquid crystal cell display formed by sandwiching a liquid crystal between a pair of substrates, and a rear side opposite to the front side. A liquid crystal display element in which a front polarizing plate and a rear polarizing plate are arranged, a light source, and light emitted from the light source are incident on the liquid crystal display element, and the rear polarizing surface is projected from a light emitting surface facing the rear polarizing plate of the liquid crystal display element. A liquid crystal display module having a backlight including a light guide plate that emits light toward the plate, and the surface of the rear polarizing plate facing the light emitting surface of the light guide plate is a uniform uneven surface. It is a liquid crystal cell characterized by this.</p>

<p> According to the liquid crystal display module of the present invention, by making the surface of the rear polarizing plate a uniform uneven surface, the surface of the rear polarizing plate and the light emitting surface of the light guide plate or the surface of the optical sheet that are in opposition to the surface of the rear polarizing plate are made uniform. By making point contact, it is possible to reliably prevent the occurrence of a problem in which a surface contact area is partially generated and the boundary between the surface contact area and the surrounding non-contact area is visually recognized, so that a transparent display of good quality is stabilized. It will be possible to obtain it.</p>

In the liquid crystal display module of the present invention, as a rear polarizing plate, an uneven coating layer made of a material in which fine particles having a substantially uniform particle size are dispersed and mixed in a base resin liquid is laminated on one surface of a polarizing element. It is preferable to use an anti-glare polarizing plate formed by the above method, which makes it possible to easily manufacture a polarizing plate having a concave-convex surface having a uniform surface.

In addition, an optical sheet for making the intensity distribution of the emitted light from the light guide plate uniform between the rear polarizing plate and the light emitting surface of the light guide plate and suppressing the loss of the emitted light so that the light is efficiently incident on the rear polarizing plate. This can prevent not only the boundary between the surface contact region and the non-contact region between the rear polarizing plate and the optical sheet but also the occurrence of moire caused by the optical sheet, and the brightness distribution can be increased. It is possible to easily obtain a transmissive liquid crystal display module that is uniform and has improved display quality.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is an exploded perspective view showing a transmissive liquid crystal display module as an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view thereof.

A liquid crystal cell C is formed by sandwiching a liquid crystal layer (not shown) between a pair of transparent glass substrates 1 and 2. The front polarizing plate 3 is installed on the outer surface opposite to the surface (hereinafter referred to as the inner surface) of the glass substrate 1 on the front side, which is the observation side of the display in the liquid crystal cell C, and is on the non-observation side. A rear polarizing plate 4 is installed on the outer surface of the rear glass substrate 2 to form a liquid crystal display element Lc.

Here, the surface of the rear polarizing plate 4 is formed into a uniform uneven surface. In the present embodiment, a uniform uneven surface is obtained by so-called anti-glare treatment. That is, as shown in FIG. 3, a hard coat obtained by dispersing and mixing silicic acid fine powder having a uniform particle size in a silicone-based hard coat liquid on one surface of a polarizing film 4a having a transmission axis and an absorption axis in directions orthogonal to each other. By applying the mixed solution, an anti-glare hard coat layer 4b having a uniform uneven surface is formed.

Returning to FIG. 2, a side light type surface light source device La is arranged behind the rear polarizing plate 4. The side light type surface light source device La has a tapered transparent light guide plate 5 having a substantially wedge-shaped cross section and a cold cathode fluorescent lamp 6 as a light source arranged to face the end surface 5a of the light guide plate 5 as a light incident surface. , The reflector 7 which is arranged so as to surround the cold cathode fluorescent lamp 6 and reflects the emitted light from the cold cathode fluorescent lamp 6 to the light incident surface 5a, and the side opposite to the light emitting surface 5b facing the liquid crystal cell C of the light guide plate 5. It is composed of a light reflecting plate 8 arranged to face the surface of the light source, and a light reflecting film 9 or the like adhered to an end surface of the light guide plate 5 opposite to the light incident surface 5a. Here, the anti-light emitting surface 5c on the side opposite to the light emitting surface 5b of the light guide plate 5 alternately has two types of slopes 5c1 and 5c2 extending parallel to the longitudinal direction of the light incident surface 5a and having different inclination angles. The continuously formed cross section is formed on a serrated uneven surface. The side light type surface light source device La configured in this way is housed in a box-shaped case 10 having an open upper surface with the light emitting surface 5b of the light guide plate 5 facing up.

Between the light emitting surface 5b of the light guide plate 5 and the rear polarizing plate 4, a reflective polarizing sheet 11 for improving brightness, a λ / 4 retardation film 12, and a light diffusing sheet 13 for making the brightness distribution uniform. A composite optical sheet layer Os is interposed. The composite optical sheet layer Os is interposed so that the reflective polarizing sheet 11 is in opposition to the surface of the anti-glare hard coat layer 4b of the rear polarizing plate 4 and the diffusion sheet 13 is in opposition to the light emitting surface 5b of the light guide plate 5. There is.

Here, the surface of the reflective polarizing sheet 11 that is brought into close contact with the rear polarizing plate 4 is a smooth surface, but since the surface of the post-contact polarizing plate 4 is a uniform uneven surface of the anti-glare hard coat layer 4b, it is a contact surface. A uniform point contact state is formed over the entire surface, and a non-uniform contact state in which a surface contact region is partially generated does not occur. Therefore, the boundary between the partial surface contact area and the non-contact area around the partial surface contact area is visually recognized in the display, and the display quality is not deteriorated.

In the liquid crystal display module configured as described above, the light emitted from the cold cathode tube 6 is directly reflected by the reflector 7 or incident on the light incident surface 5a of the light guide plate 5, and the inside of the light guide plate 5 is the other. While traveling toward the end face, it is incident on the slope 5c1 of the anti-light emitting surface 5c, where it is totally reflected toward the light emitting surface 5b or emitted to the outside. The light emitted to the outside is reflected by the light reflecting plate 8 and re-incidents into the light guide plate 5 and travels toward the light emitting surface 5b.

The light reflected toward the light emitting surface 5b is emitted from the light emitting surface 5b in a planar shape, but the distribution state and the light emitting direction at that time are non-uniform and vary greatly. However, when the light is incident on the diffusion sheet 13 laminated on the light emitting surface 5b, the variation thereof is made uniform. The planar luminous flux having a uniform light intensity distribution and emission direction passes through the λ / 4 retardation plate 12 in the next order and is incident on the reflective polarizing sheet 11. Of the light incident on the reflective polarizing sheet 11, the polarized light component along the transmission axis is transmitted, and the polarized light component along the reflection axis becomes linearly polarized light and is reflected again toward the light reflecting plate 8 to be reflected again toward the light reflecting plate 8. Make one round trip to and from. During this time, the polarization direction of the linearly polarized light is rotated by 90 ° to pass through the λ / 4 retardation plate 12 twice, and the polarization direction becomes linearly polarized light along the transmission axis of the reflection polarizing plate 11. Since it is incident on the polarized light, this polarized light also passes through the reflected polarizing sheet 11. In this way, almost all the light incident on the reflection polarizing sheet 11 is transmitted as linearly polarized light along the reflection axis. Since the polarization directions of the linearly polarized light are also along the transmission axis of the rear polarizing plate 4, substantially all of the incident light passes through the rear polarizing plate 4 and is incident on the liquid crystal cell C.

Therefore, according to the liquid crystal display module of the present embodiment, the light source light emitted from the cold cathode tube 6 is extremely efficiently irradiated to the liquid crystal display element Lc by suppressing the rate of dissipation or absorption and loss as much as possible. As a result, a high and uniform brightness display can be obtained, and the boundary between the surface contact region and the non-contact region around the surface of the polarizing plate 4 and the surface of the reflective polarizing sheet 11 which is brought into contact with the surface of the polarizing plate 4 is visually recognized. Not only does it prevent the occurrence of moire due to transmission through optical sheets such as the reflective polarizing sheet 11 and the λ / 4 retardation plate 12, and extremely high-quality transmission display can be stably obtained. Can be done.

The present invention is not limited to the above-described embodiment. For example, the present invention can be preferably applied even when the rear polarizing plate and the light guide plate on the backlight side are brought into direct facing contact with each other without an optical sheet.

Further, the light source of the backlight is not limited to a line light source such as a cold cathode tube, but a point light source such as an LED (Light-emitting diode) can also be used.

<figref num="1">It is an exploded perspective view which shows one Embodiment of this invention.</figref><figref num="2">It is a schematic cross-sectional view which shows the said embodiment.</figref><figref num="3">It is a partially enlarged sectional view which shows the Q part in FIG. 2 enlarged.</figref>

Code description

1, 2 Glass substrate 3 Front polarizing plate 4 Rear polarizing plate 5 Light guide plate 6 Cold cathode tube 11 Reflective polarizing sheet 12 λ / 4 Phase difference film 13 Light diffusion sheet Lc Liquid crystal display element La Sidelight type surface light source device