JP2000250004A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device in which the influence of the intensity of incident light are decreased. SOLUTION: This liquid crystal display device has a light-scattering liquid crystal layer between a transparent substrate 1 in the observer side and a polarizer 9, and this liquid crystal layer is held between a pair of transparent substrates having transparent electrodes 3 on the respective substrates facing each other. Voltage is applied on transparent electrodes 3 to control the scattering degree of the light-scattering liquid crystal layer by the voltage so that the reflection of the ambient scenery does not appear on a reflection layer 4 like a mirror depending on the intensity or angle of light entering the liquid crystal display device. Thus, the appearance of the liquid crystal display device can be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-cost reflective liquid crystal display panel used in a system such as a computer terminal, an image display device, and a shutter.

[0002]

2. Description of the Related Art Liquid crystal display elements are used as displays for portable information terminals because of their low power consumption, low cost, thinness and light weight. However, a reflection-type liquid crystal display element is usually used by sandwiching a liquid crystal cell between two polarizing plates and installing a reflection plate thereunder.

In such a reflection type liquid crystal display device using two polarizing plates, incident light passes through the polarizing plates four times, and therefore becomes dark. Therefore, in order to make the reflective liquid crystal display element brighter, the number of polarizing plates to be used is changed from two to only one on the entire surface side of the liquid crystal display element, and a single polarizing plate sandwiching the liquid crystal cell between one polarizing plate and the reflecting plate is used. A plate configuration has been proposed (for example, JP-A-7-146469).

In this case, since the incident light passes through the polarizing plate only twice, an improvement in transmittance can be expected. This single-polarizer type reflector is provided on a rear-side transparent substrate, and the reflector is patterned with a metal film such as aluminum having a high reflectivity in the form of stripes. It has a structure that also serves as a common electrode.

In the case where a reflector is provided outside, when viewed obliquely, the display may look double or the contrast may be reduced due to the thickness of the rear transparent substrate. This problem can be solved by providing it in the inside. The reflector described above uses an aluminum film to increase the reflection efficiency. Since the aluminum film is a mirror surface, a forward scattering plate is provided between the transparent substrate on the observer side and the polarizing plate, and white light can be emitted by scattering the light specularly reflected by the aluminum film. Alternatively, the incident light is scattered by the scattering layer, and the scattered light is reflected by a mirror surface to produce white light.

The above is an example of the case where a forward scattering plate is used. However, the forward scattering plate can be eliminated by forming the surface of the reflection layer with a scattering reflection film having irregularities.

[0007]

In the conventional liquid crystal display device, the unevenness of the surface of the forward scattering plate or the reflection layer is constant even if the state such as the angle and intensity of the externally incident light changes. There has been a problem that the contrast ratio becomes poor or dark depending on the use environment. Specifically, when viewing a liquid crystal display device with a scattering plate set to be used in a bright place in a dark place, the surrounding area is reflected on the reflective layer as a mirror surface, and the appearance of the liquid crystal display element is improved. There is a problem that the temperature is significantly reduced.

[0008]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention comprises a liquid crystal interposed between a transparent substrate on the observer side and a transparent substrate on the back side, and has a thickness of 240 mm in the thickness direction.
A nematic layer twisted from マ to 260 °, and a liquid crystal display device having a polarizing plate on the outside of the observer-side transparent substrate and having a reflective layer patterned in a stripe between the back-side transparent substrate and the nematic layer, Between the observer side transparent substrate and the polarizing plate, there is a light scattering type liquid crystal layer sandwiched by a pair of transparent substrates and sandwiched by a pair of transparent substrates so that the transparent electrode layer faces the surface, and a voltage is applied to the transparent electrode. By controlling the degree of light scattering of the applied scattering type liquid crystal layer by voltage, the surroundings of the reflective layer are not reflected as a mirror surface due to changes in the intensity or angle of light incident on the liquid crystal display element. The appearance of the element can be made uniform.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a schematic sectional view 1 of a liquid crystal display device of the present invention.
Although a transparent glass plate is used for the transparent substrates 1 and 2 in FIG. 1, a transparent polymer film or a plastic substrate may be used. As the transparent electrode 3 on the observer-side transparent substrate 1, a transparent electrode made of an indium tin oxide (ITO) film was patterned by photolithography. The electrode layer has a graphic pattern or a striped pattern for displaying characters and pictures. A reflective layer 4 made of aluminum is provided on the rear transparent substrate 2, and the reflective layer 4 is patterned and also functions as an electrode.
And intersect with each other to form a pixel. Although the reflection layer 4 is made of an aluminum film, any mirror reflection film such as a nickel film, a chromium film, and a silver film may be used. Further, on the transparent electrode 3 and the reflective layer 4, the alignment film layers 5 and 6 are printed with a polyimide resin, baked, formed into a film, and then subjected to a rubbing treatment so as to be twisted from 240 ° to 260 °. The alignment film layer may be a layer made of a Teflon-based material other than polyimide. The alignment film is formed on almost the entire surface in contact with the liquid crystal material. A sealing agent 7 is applied around these transparent substrates and bonded together, and a nematic liquid crystal material 8 having a positive dielectric anisotropy and added with a chiral material is injected into the gaps between the transparent substrates. Then, the polarizing plate 9 and the phase difference plate 10 were attached to the front surface of the transparent substrate.

The light scattering type liquid crystal layer comprises a pair of transparent substrates 11,
It is constituted by holding a scattering type liquid crystal 13 between 12. In order to ensure reliability against high temperature and high humidity, it is desirable to seal the outer peripheral portions of the transparent substrates 11 and 12 with the sealant 14. Here, a method of forming the light scattering type liquid crystal layer will be described. Although the transparent substrates 11 and 12 are made of a smooth glass plate, a transparent polymer film may be used. Next, spacers were scattered so that the cell gap was about 10 microns, and a sealing agent 14 was applied to form cells. In the completed cell, polymer network liquid crystal (PN-LC)
Was injected while maintaining a constant temperature, and irradiated with ultraviolet rays of about 50 mW / cm ² for 1 minute to form a scattering type liquid crystal 13. The scattering liquid crystal layer is not only a polymer network liquid crystal,
Polymer dispersed liquid crystal mode, dynamic scattering liquid crystal mode (DS
M), a thermal writing mode may be used.

In the liquid crystal display device configured as shown in FIG. 1, white light can be produced by scattering light that is specularly reflected by the aluminum film by the scattering type liquid crystal layer. Further, white light can be emitted by reflecting the scattered light obtained by scattering the incident light by the scattering type liquid crystal layer on a mirror surface. When the scattering type liquid crystal layer of the liquid crystal display element shown in FIG. 1 is formed, the degree of scattering of the scattering type liquid crystal layer can be changed by controlling the intensity of the ultraviolet ray when irradiating ultraviolet rays and the liquid crystal temperature.

Next, a method of controlling the degree of scattering by applying a voltage to the scattering type liquid crystal will be described. FIG. 2 shows a liquid crystal display device in which a voltage can be applied to the scattering type liquid crystal layer of the liquid crystal display device described with reference to FIG. A pair of transparent substrates 15 and 16
Transparent electrode layers 17 and 18 were formed thereon, with the transparent electrodes facing each other, and a scattering type liquid crystal layer 19 was sandwiched between transparent substrates. 20 is a sealing agent. As the scattering type liquid crystal layer, in addition to the polymer network liquid crystal, a liquid crystal whose scattering degree can be changed by a voltage may be used as long as it is a polymer dispersed liquid crystal mode or a dynamic scattering liquid crystal mode (DSM).

In the liquid crystal display device constructed as shown in FIG. 2, a voltage is applied to the transparent electrode and the degree of light scattering of the scattering type liquid crystal layer is controlled by the voltage in the range of 0 to 10 (Vrms), thereby obtaining the liquid crystal display. The change in the intensity and angle of the light incident on the element prevented the surrounding area from being reflected on the reflective layer as a mirror surface, thereby making the appearance of the liquid crystal display element uniform.

The applied voltage waveform is not limited as long as its effective value changes. By increasing the degree of scattering of the scattering liquid crystal layer in a dark place, the specular reflection of the reflector could be reduced, and in a bright place, the contrast could be increased by decreasing the degree of scattering. In the liquid crystal display device shown in FIG. 2, the degree of scattering can be changed by utilizing the frequency dependence of the rising voltage of the liquid crystal material. Specifically, the voltage is kept constant, and the frequency of the driving waveform is changed from 32 to 5000.
(Hz), the scattering degree changed.

FIG. 3 is a view for explaining a case where the transparent substrate 1 on the observer side in FIG. 21 in FIG.
Is a transparent substrate, on which a transparent electrode layer 22 is formed. 23 is a transparent electrode layer formed on the observer side transparent substrate. A scattering type liquid crystal layer 24 is sandwiched between the observer side transparent substrate and the transparent substrate. 25 is a sealing agent.
In the liquid crystal display device configured as shown in FIG. 3, the weight of the liquid crystal display device can be reduced by eliminating the thickness of the transparent substrate 12 in FIG. 1 and the thickness of the transparent substrate 16 in FIG.

FIG. 4 is a view for explaining a configuration in which the transparent substrate 1 on the observer side and the transparent substrate 16 in FIG. The adhesive 26 has high transmittance and is ideally transparent, but need not be transparent if sufficient transmittance is obtained. Further, the liquid crystal display element can be colored to perform color correction. In the liquid crystal display device configured as shown in FIG.
By bonding the transparent substrate 1 on the observer side and the transparent substrate 16 with the adhesive 26, the air layer between the transparent substrates is eliminated, and the regular reflection on the transparent substrate surface is eliminated, and the liquid crystal display element can be brightened. Became. Further, the total thickness of the liquid crystal display element can be reduced.

[0017]

According to the liquid crystal display device of the present invention, a nematic layer in which liquid crystal is sandwiched between a transparent substrate on the observer side and a transparent substrate on the back side and twisted in the thickness direction by 240 ° to 260 °,
In a liquid crystal display device having a polarizing plate on the outside of the observer-side transparent substrate and a reflective layer patterned in a stripe shape between the back-side transparent substrate and the nematic layer, between the observer-side transparent substrate and the polarizing plate, There is a light-scattering liquid crystal layer sandwiched between a pair of transparent substrates and sandwiched between a pair of transparent substrates such that the transparent electrode layer faces the surface, and a voltage is applied to the transparent electrodes so that the light scattering degree of the scattering liquid crystal layer is increased. Is controlled by a voltage, so that the scene around the reflection layer is not reflected as a mirror surface due to a change in the intensity or angle of light incident on the liquid crystal display element, and the appearance of the liquid crystal display element can be made uniform. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the configuration of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic sectional view showing an example of the configuration of a liquid crystal display device according to the present invention.

FIG. 3 is a schematic sectional view showing an example of the configuration of a liquid crystal display device according to the present invention.

FIG. 4 is a schematic sectional view showing an example of the configuration of a liquid crystal display element according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Observer side transparent substrate 2 Back side transparent substrate 3, 17, 18, 22, 23 Transparent electrode 4 Reflective layer 5, 6 Alignment film layer 7, 14, 20, 25 Sealant 8, 13, 19, 24 Liquid crystal material 9 Polarizing plate 10 Retardation plate 11, 12, 15, 16, 21 Transparent substrate 26 Adhesive

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[Procedure amendment]

[Submission date] March 12, 1999 (1999.3.1.
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention comprises a liquid crystal interposed between a transparent substrate on the observer side and a transparent substrate on the back side, and has a thickness of 240 mm in the thickness direction.
A nematic layer twisted from 260 ° to 260 °, a liquid crystal display device including a polarizing plate on the outside of the observer-side transparent substrate, and a reflective layer patterned in a stripe shape between the back-side transparent substrate and the nematic layer, during the viewer side transparent substrate and the polarizing plate, there is a light scattering type liquid crystal layer which is sandwiched between a pair of transparent substrates as the transparent electrode layer on the surface is relative, the voltage is applied to the transparent electrode scattering type liquid crystal layer By controlling the degree of light scattering by voltage, changes in the intensity and angle of light incident on the liquid crystal display element prevent the surrounding scenery from being reflected on the reflective layer as a mirror surface, making the appearance of the liquid crystal display element uniform. be able to.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017]

The liquid crystal display device of the present invention comprises a nematic layer in which liquid crystal is sandwiched between a transparent substrate on the observer side and a transparent substrate on the back side and twisted from 240 ° to 260 ° in its thickness direction.
Equipped with a polarizing plate on the outside of the viewer-side transparent substrate, between the liquid crystal display device provided with a reflective layer which is patterned in a stripe shape between the back-side transparent substrate and the nematic layer, the observer-side transparent substrate and the polarizing plate There is a light scattering type liquid crystal layer sandwiched between a pair of transparent substrates such that the transparent electrode layer faces the surface, and a voltage is applied to the transparent electrode to control the light scattering degree of the scattering type liquid crystal layer by the voltage. In addition, a change in the intensity and angle of light incident on the liquid crystal display element prevents the scene around the reflection layer from being reflected as a mirror surface, thereby making the appearance of the liquid crystal display element uniform.

Claims (5)

[Claims] 1. A liquid crystal is sandwiched between a transparent substrate on the observer side and a transparent substrate on the rear side, and the liquid crystal is sandwiched between 240.degree.
液晶 A twisted nematic layer and a liquid crystal display device comprising a polarizing plate outside the observer-side transparent substrate and a reflective layer patterned in a stripe pattern between the back-side transparent substrate and the nematic layer, A liquid crystal display device comprising a light scattering liquid crystal layer between an observer-side transparent substrate and the polarizing plate. 2. The liquid crystal display device according to claim 1, wherein the light scattering type liquid crystal layer is sandwiched between a pair of transparent substrates, and an outer peripheral portion is surrounded by a sealing agent. 3. The method according to claim 1, wherein the scattering type liquid crystal layer is sandwiched between a pair of transparent substrates so that a transparent electrode layer faces the surface, and a voltage is applied to the transparent electrode. Liquid crystal display element. 4. The liquid crystal display device according to claim 1, wherein the pair of transparent substrates sandwiching the light scattering type liquid crystal layer also serve as the observer side transparent substrate. 5. The liquid crystal display device according to claim 1, wherein a pair of transparent substrates sandwiching the light scattering type liquid crystal layer are bonded to the observer side transparent substrate.