JP2003043480A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid moire fringes in a short time and at a low cost compared with a conventional technique by which an optimum condition for avoiding the moire fringes is found by changing the pixel pitch in the internal part of a liquid crystal display element or the prism pitch of a light guide plate through trial and error. SOLUTION: In a reflection type liquid crystal display device formed by combining a reflection type liquid crystal display element 10 having a diffusion layer 121 in a panel and a frontlight unit 20, an outer diffusion layer 30 consisting of a scattering film having no scattering pitch is provided between a viewing surface side transparent substrate 11 of the display element 10 and a light guide plate 21 of the frontlight unit 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device having a front light unit, and more particularly to a technique for avoiding moire fringes.

[0002]

2. Description of the Related Art Reflective liquid crystal display elements have the advantage that they consume less power because they require external light for illumination.
On the other hand, it is difficult to obtain a bright display in a dark environment.

Therefore, in order to obtain a bright display even in a dark environment, a front light unit may be used in combination on the viewing side of the reflective liquid crystal display element for the purpose of lighting. The front light unit used for this is a side light type in which a light source is arranged on the side of the light guide plate, and in many cases, the light guide plate has a prism surface.

However, when a reflection type liquid crystal display device having a diffusion layer inside the panel and a front light unit are combined, the pixel pitch inside the liquid crystal display device and the prism of the light guide plate interfere with each other, and moire fringes often occur. .

[0005]

In order to avoid the occurrence of the moire fringes, the pixel pitch inside the liquid crystal display element or the prism pitch of the light guide plate has been conventionally optimized, but this optimization is performed. It's not easy.

That is, since either the pixel pitch or the prism pitch is changed, and the optimum condition under which the moire fringes are not generated by visual observation is sought by trial and error, a great deal of labor is required. It also costs money.

[0007]

According to the present invention, the above-mentioned problems are solved by providing a light guide plate having a prism surface of a front light unit on the viewing surface side of a reflective liquid crystal display element having a diffusion layer inside the panel. In the arranged reflection type liquid crystal display device, the problem can be solved by providing an external diffusion layer made of a scattering film having no scattering pitch between the transparent substrate on the observation surface side of the liquid crystal display element and the light guide plate.

The haze value of the outer diffusion layer is preferably in the range of 30 to 80%. Here, the haze value H is H
= (Diffuse transmittance / total light transmittance) × 100%. If the haze value is less than 30%, the expected effect of avoiding moire fringes cannot be obtained, and if it exceeds 80%, the display itself is blurred. Particularly preferable range is 40 to 7
It is 0%.

In the present invention, the external diffusion layer may be provided between the transparent substrate on the observation surface side and the light guide plate, for example, between the polarizing plate and the light guide plate, but it is more effective to avoid moire fringes. In order to achieve the objective, it is preferable to provide it between the transparent substrate on the observation surface side and the retardation plate or between the retardation plate and the polarizing plate.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. As shown in FIG. 1, this reflective liquid crystal display device includes a liquid crystal display element 10 and a front light unit 20 arranged on the observation surface side (upper side in FIG. 1).

The liquid crystal display element 10 is a reflection type having a diffusion layer inside the panel. That is, it has the observation surface side transparent substrate 11 and the back surface side transparent substrate 12 which are pressure-bonded via the peripheral sealing material 13, and the diffusion layer 121 is formed on the inner surface of the back surface side glass substrate 12.

The transparent substrate may be either glass or plastic. One transparent electrode 111 is formed on the inner surface of the observation surface side transparent substrate 11, and the rear surface side transparent substrate 12 is diffused. The other transparent electrode 122 is formed on the layer 121.

In this embodiment, the transparent electrode 111 and the transparent electrode 122 are formed as stripe patterns orthogonal to each other, and the display form is full dot display. The liquid crystal is of TN type or STN type.

Although well-known components such as an insulating film and an alignment film are provided on the inner surfaces of the substrates 11 and 12, they are not shown because they are not the gist of the present invention. A retardation plate 14 and a polarizing plate 15 are laminated in this order on the outer surface of the observation surface side transparent substrate 11.

The front light unit 20 is a side light, and includes a light guide plate 21 arranged on the observation surface side of the liquid crystal display element 10, and a light source 22 for irradiating the light guide plate 21 with light from the side. . The light guide plate 21 is made of, for example, a polycarbonate resin plate, and the surface facing the liquid crystal display element 10 is finished as a prism surface 211. Light source 22
Although a light emitting diode (LED) is used for this, another light source may be used.

According to the present invention, in order to avoid the occurrence of moire fringes due to the interference between the pixel pitch inside the liquid crystal display element 10 and the prism of the light guide plate 21, the scattering pitch is provided between the liquid crystal display element 10 and the light guide plate 21. The outer diffusion layer 30 made of a scattering film having no is arranged. Specifically, a scattering film is used in which polymer spheres are dispersed in a resin and light is scattered by the polymer spheres.

The haze value of the outer diffusion layer 30 is 30 to 80.
% (Particularly 40 to 70%) is preferable. In this embodiment, the external diffusion layer 30 is disposed between the retardation plate 14 and the polarizing plate 15, but the observation surface side transparent substrate 11
It may be disposed between the phase difference plate 14 and the retardation plate 14. Further, depending on the case, it may be arranged between the polarizing plate 15 and the light guide plate 21.

As a specific example, the internal pixel pitch is 240
Liquid crystal display element 10 with μm and prism pitch 140 μ
When combined with the m light guide plate 21, moire fringes were remarkably generated.

Therefore, when a scattering film having a haze value of 30 to 80% having no scattering pitch was arranged as the external diffusion layer 30 between the retardation plate 14 and the polarizing plate 15, the moire fringes were largely disappeared. If the haze value is less than 40%, weak moire fringes are generated, and if the haze value exceeds 70%, the display may be slightly blurred, so that the more preferable range of the haze value is 40 to 70%.

[0020]

As described above, according to the present invention,
In a reflection type liquid crystal display device in which a reflection type liquid crystal display element having a diffusion layer inside the panel and a front light unit are combined, a scattering occurs between the transparent substrate on the observation surface side of the liquid crystal display element and the light guide plate of the front light unit. By providing an external diffusion layer consisting of a scattering film that does not have a pitch, it is possible to change the pixel pitch inside the liquid crystal display element or the prism pitch of the light guide plate by trial and error to obtain the optimal condition for avoiding moire fringes. In comparison, it is possible to avoid the generation of moire fringes in a short time and at low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a reflective liquid crystal display device according to an embodiment of the invention.

[Explanation of symbols]

10 Reflective liquid crystal display device 11 Observation side transparent substrate 12 Back side transparent substrate 111, 122 transparent electrodes 121 diffusion layer 14 Phase plate 15 Polarizer 20 Front light unit 21 Light guide plate 211 prism surface 22 Light source 30 external nucleic acid layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13363 G02F 1/13363 G09F 9/00 313 G09F 9/00 313 336 336B 9/30 349 9/30 349Z 9/35 9/35 // F21Y 101: 02 F21Y 101: 02 F term (reference) 2H042 BA02 BA20 2H091 FA08X FA08Z FA11X FA11Z FA21X FA23Y FA41Z FB02 FB07 FD06 LA21 LA30 5C094 AA01 AA22 AA48 EA04 EA05 BA02 CA13 DA19 CA13 DA02 CA13 DA02 ED14 FA01 FA02 5G435 AA01 BB12 BB16 CC09 EE22 FF03 FF05 FF06 FF08 HH04 LL07

Claims (3)

[Claims] 1. A reflection type liquid crystal display device comprising a light guide plate having a prism surface of a front light unit, which is arranged on the observation surface side of a reflection type liquid crystal display element having a diffusion layer inside the panel. An external diffusion layer made of a scattering film having no scattering pitch is provided between the transparent substrate on the observation surface side and the light guide plate. 2. The haze value of the outer diffusion layer is 30 to 8
The reflective liquid crystal display device according to claim 1, wherein the reflective liquid crystal display device is in a range of 0%. 3. A retardation plate and a polarizing plate are laminated on the observation side transparent substrate, and the external diffusion layer is provided between the observation side transparent substrate and the retardation plate or the retardation plate. And a polarizing plate provided between the polarizing plate and the polarizing plate.
The reflective liquid crystal display device according to item 1.