JP3226521B2 - Reflective liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have made remarkable progress, and have been actively applied to notebook personal computers, small TVs, and the like. The reflective liquid crystal display device has attracted attention because it does not require a backlight as a light source, and thus can consume less power and can be thinner and lighter than the transmissive liquid crystal display device.

In a reflection type liquid crystal display device, a reflection plate for reflecting light incident from the outside is indispensable. However, in order to obtain a bright display without any blur from any angle, reflection and scattering are required. It is necessary to provide an uneven scattering reflective electrode having both functions adjacent to the liquid crystal layer, optimize the uneven shape, and efficiently reflect incident light from all directions toward the front of the liquid crystal display device.

[0004] As a conventional example of a reflection type liquid crystal display device using a light scattering layer, there is one using an uneven scattering reflection electrode described in JP-A-58-125084. Irregularity scattering reflective electrodes are realized by forming irregularities made of a polymer resin by photolithography technology and forming a metal film as a reflective film thereon.

[0005]

However, in the reflection type liquid crystal display device of the prior art having a structure in which the irregularities on the surface of the reflection plate are regularly arranged in the same shape, interference of reflected light occurs, There is a problem that coloring occurs on the plate.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a reflection type liquid crystal display device in which the reflection plate is not colored.

[0007]

In order to achieve the above object, a reflection type liquid crystal display device according to the present invention comprises a first substrate having a transparent electrode and a second substrate having a pixel electrode comprising an uneven scattering reflection electrode. In a reflective liquid crystal display device in which a liquid crystal is interposed between a substrate and a substrate, a formation region of the concave / convex scattering / reflection electrode in a unit pixel, a region where convex portions or concave portions are regularly arranged, and convex portions or concave portions are randomly arranged. And a plurality of regions, and the plurality of regions are arranged in a matrix.

[0008] According to this configuration, it is possible to obtain a reflector having no coloring due to interference of reflected light.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view of an uneven scattering reflective electrode of a unit pixel of a reflective liquid crystal display device according to an embodiment of the present invention. Here, the concavo-convex scattering reflection electrode in the unit pixel is composed of four regions having different standard deviations in the center-to-center distance distribution of concave portions or convex portions (represented by circles) adjacent to each other.

FIG. 2 shows a method of forming the uneven scattering reflective electrode. First, as shown in FIG. 2A, an acrylic resin (Japanese synthetic rubber, trade name PC335) is spin-coated on the glass substrate 1 at 1000 rpm for 30 seconds to form the photosensitive organic insulating film 2. After pre-baking at 90 ° C. for 2 minutes, as shown in FIG. 2B, UV exposure was performed using a mask 3 and, as shown in FIG. The part 2a is formed. next,
As shown in FIG. 2D, 160
Post bake for 2 minutes at ℃ and rounded convex part 2b
Then, main curing is performed at 220 ° C. for 1 hour. FIG. 2
As shown in (e), an aluminum film is formed by sputtering to form a metal thin film of about 200 nm, and the uneven scattering reflective electrode 4 is formed. The reflection surface of the concave / convex scattering / reflection electrode 4 is a concave / convex surface having a predetermined shape.

FIG. 3 shows the measurement results of the reflection characteristics of the uneven scattering reflection electrode thus formed. From this result, it can be seen that the uneven scattering reflective electrode according to the present embodiment is very bright. In addition, when the uneven scattering reflective electrode thus formed was observed under a white lamp, no coloring due to interference was observed.

The scattering and reflection characteristics greatly depend on the distance between adjacent projections. When the projections are arranged in a state where the distance is constant and regularly arranged, the scattering and reflection characteristics are optimal, but coloring due to interference occurs. Occur. Therefore, a region where the distance between adjacent convex portions where the optimal scattering and reflection characteristics are obtained is substantially constant,
By mixing regions in which the distance between adjacent convex portions varies greatly, it is possible to obtain a reflective electrode that is very bright and has no coloring due to interference.

Further, in order to suppress coloring due to interference, an odd-numbered row and an even-numbered area are arranged in a matrix in which a plurality of regions having different standard deviations in the center-to-center distance distribution of adjacent concave portions or convex portions are arranged in a matrix. It is desirable that the unevenness distribution shape of the uneven scattering reflective electrodes in the rows or odd columns and the even columns be different.

FIG. 4 shows a cross section of a reflection type liquid crystal display device according to an embodiment of the present invention. In FIG. 4, 5 is a polarizing plate, 6 is a birefringent film, 7 is an upper transparent substrate, 8 is a color filter, 9 is a transparent electrode, 10 is an alignment film, 11 is a liquid crystal layer, 12 is an uneven scattering reflective electrode, and 13 is The photosensitive organic insulating film 14 is a lower substrate. Here, a glass substrate was used as the upper transparent substrate 7 and the lower substrate 14.

After a polyimide resin is printed on the transparent electrode 9 and the uneven scattering / reflection electrode 12 and cured by heat, an alignment process is performed by a rubbing method using a rayon cloth so that the rubbing is antiparallel to each other. The film 10 was formed.

Next, a glass fiber having a diameter of 5.7 μm is placed around the display pixel area on the upper transparent substrate 7 by 1.5 μm.
The thermosetting sealing resin mixed by weight% is screen-printed, and resin beads having a diameter of 4.5 μm are sprayed on the lower substrate 14 at a density of 150 / mm ² , and the upper transparent substrate 7 and the lower substrate 14 are dispersed. Were bonded together, and the sealing resin was cured at 150 ° C. Thereafter, a nematic liquid crystal having a refractive index anisotropy Δn of 0.14 was vacuum-injected, sealed with an ultraviolet curable resin, and then cured by irradiating ultraviolet rays.

On the upper transparent substrate 7 of the liquid crystal cell produced by the above-described method, a birefringent film 6 having a retardation value of 490 nm is used.
And a neutral gray polarizing plate as the polarizing plate 5 was bonded thereon such that the absorption axis thereof forms an angle of 45 ° with the rubbing direction of the upper transparent substrate 7.

Light incident from the polarizing plate 5 side passes through the birefringent film 6 and the liquid crystal layer 11 and reaches the uneven scattering reflective electrode 12. Since the difference in retardation between the birefringent film 6 and the liquid crystal layer 11 is set to １ ／ of the wavelength of light,
On the reflection surface, the light is in a circularly polarized state, and when the reflected light reaches the polarizing plate 5 again, the light is in a linearly polarized state in a direction orthogonal to the incident linearly polarized light. At this time, a dark state can be realized.

Further, by applying a voltage to the liquid crystal layer 11, light passing through the liquid crystal layer 11 can be modulated. The effective retardation value of the liquid crystal layer 11 decreases with the applied voltage. When the retardation values of the liquid crystal layer 11 and the birefringent film 6 become equal, when the reflected light reaches the polarizing plate 5 again, it becomes a linearly polarized light in the same direction as the incident linearly polarized light. At this time, a bright state can be realized.

As described above, an extremely bright reflection characteristic was obtained by optimizing the shape of the uneven scattering reflection electrode.

In the embodiment of the present invention, the operation mode of the liquid crystal has been described using an example in which the electric field control birefringence effect is used. However, the present invention is not limited to this operation mode. In the TN mode, the STN mode, the guest-host mode which is an operation mode without using a polarizing plate, the polymer dispersion type liquid crystal mode, and the like, substantially the same effect can be obtained even in the configuration using the uneven scattering reflection surface. it can.

In the embodiment of the present invention, the planar shape of the convex or concave portion of the concave / convex scattering / reflecting electrode is a circle. However, the effect aimed at by the invention is not limited to this. Triangle, square, pentagon,
Similar effects can be obtained with hexagons, octagons, and ellipses.

Further, in the embodiment of the present invention, a reflective electrode using aluminum as a constituent metal is used as the reflective film. However, the effect aimed at by the present invention is not limited to this. The same effect can be obtained by using a reflective electrode made of a constituent metal.

Further, it is clear that the contents of the present invention can be applied to any of simple matrix driving and driving by a switching element such as a TFT.

[0026]

As is apparent from the above description, in the reflection type liquid crystal display device of the present invention, the formation area of the uneven scattering / reflection electrode in the unit pixel is divided into the area where the convex portions or the concave portions are regularly arranged, and the convex area. Alternatively, by forming a plurality of regions including regions in which the concave portions are randomly arranged, it is possible to obtain excellent reflection characteristics that are extremely bright and free from coloring due to interference.

[Brief description of the drawings]

FIG. 1 is a plan view of an uneven scattering reflective electrode of one pixel of a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view illustrating a method for forming a concave-convex scattering reflection electrode according to an embodiment of the present invention.

FIG. 3 is a reflection characteristic diagram of the uneven scattering reflection electrode according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a basic configuration of a reflective liquid crystal display device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Photosensitive organic insulating film 3 Mask 4 Irregular scattering reflective electrode 5 Polarizer 6 Birefringent film 7 Upper transparent substrate 8 Color filter 9 Transparent electrode 10 Alignment film 11 Liquid crystal layer 12 Irregular scattering reflective electrode 13 Photosensitive organic insulating film 14 Lower substrate

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ogawa Tetsudo 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-323371 (JP, A) JP-A-10- 221704 (JP, A) JP-A-8-184846 (JP, A) JP-A-2-280335 (JP, A) JP-A-4-258901 (JP, A) JP-A-11-7032 (JP, A) JP-A-11-52416 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1343 G02F 1/1362 G02F 1/1335

Claims (1)

(57) [Claims] 1. A reflection type liquid crystal display device in which a liquid crystal is interposed between a first substrate having a transparent electrode and a second substrate having a pixel electrode formed of an uneven scattering reflective electrode, wherein the unevenness in a unit pixel is provided. The formation area of the scattering reflection electrode is
A reflection type liquid crystal display comprising a plurality of regions consisting of regions in which projections or depressions are regularly arranged and regions in which projections or depressions are randomly arranged, wherein the plurality of regions are arranged in a matrix. apparatus.