JP3007536B2 - 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. More specifically, the present invention relates to a bright reflective liquid crystal display device for displaying images.

[0002]

2. Description of the Related Art In recent years, application of a liquid crystal display device has been expanded from a calculator to a display of a word processor or a personal computer due to a remarkable improvement in display performance due to the progress of liquid crystal display technology. further,
Expectations for market expansion as a display for portable information devices are increasing. For portable applications, it is an important issue to reduce power consumption because it is driven by a battery. Therefore, a reflection type liquid crystal display device that consumes a large amount of power and does not use a backlight is often used as the liquid crystal display device.

A conventional reflection type liquid crystal display device will be described below. FIG. 3 is a diagram showing a sectional configuration diagram of a conventional reflection type liquid crystal display device. The liquid crystal layer 31 is sealed between two substrates 33 each having a transparent electrode 32 formed on the inner surface thereof, and inside a seal resin 34 formed by printing and forming around the substrates. The liquid crystal layer is aligned in a predetermined direction by performing an alignment process on an alignment film 35 formed by printing on the transparent electrode.
Further, a polarizing plate 36 is provided outside the upper and lower substrates, a retardation plate 37 is provided between the polarizing plate and the liquid crystal layer, and a reflecting plate 38 is provided outside one of the polarizing plates.
Is pasted. In consideration of cost and display performance, one or two retardation plates 37 are used, and even in the case of two retardation plates 37, a configuration in which they are moved to one side and a configuration in which they are vertically distributed are devised. An on / off display voltage signal is applied to the transparent electrode from an external drive circuit device, thereby realizing display of a bright state and a dark state.

[0004]

However, the transmittance of the polarizing plate is about 90% even when linearly polarized light is incident parallel to the polarization axis, and in the conventional panel configuration using two polarizing plates. I can't get enough brightness. There is a problem that the displayed image is dark. In particular, in the case of a reflective panel, a backlight is not used, and light passes through the polarizing plate four times, so that there is a problem of attenuation of the light amount.

An object of the present invention is to provide a bright reflective liquid crystal display device in order to solve the conventional problems.

[0006]

In order to solve the above-mentioned problems, a reflection type liquid crystal display device according to the present invention is characterized in that substrates with electrodes having an alignment film layer formed on the surface thereof are opposed to each other, and the peripheral portions are bonded with a sealing resin. A liquid crystal layer having a twisted structure therein, a polarizing plate provided on one side outside the liquid crystal layer, and a reflection plate disposed on the other side, wherein the liquid crystal layer and the polarization off having a twisted structure in the opposite direction between the plates
A liquid crystal layer for optical compensation of a film-like liquid crystalline polymer material is provided, and the product Δn · d of the thickness d of the two liquid crystal layers and the birefringence Δn is 700 nm or more and 950 nm
It is characterized by the following.

[0007]

According to the reflection type liquid crystal display device of the present invention described above, the substrates with electrodes having the alignment film layer formed on the surface thereof are opposed to each other, and the liquid crystal layer having a twisted structure inside by bonding the peripheral portion with a sealing resin. And a reflection type liquid crystal display device provided with one polarizing plate on one of the outside of the liquid crystal layer and a reflection plate on the other side, wherein the liquid crystal layer and the polarizing plate have a reverse twisted structure. film-like liquid crystal comprises a liquid crystal layer for light <br/> Science compensation of the polymeric material, and the thickness d of the two liquid crystal layers, the product [Delta] n · d of birefringence [Delta] n is 700 nm or more 950 nano When it is less than or equal to meters , a bright reflective liquid crystal display device can be realized. That is, when the polarizing plate is 1
Since only one sheet is used, in the off-voltage state, light that has passed through the two liquid crystal layers that are in an optical compensation relationship with each other while being in an elliptically polarized state is close to an incident linearly polarized state and is reflected by the reflector. After passing through the two liquid crystal layers again, the state returns to the incident linear polarization state again. Therefore, the light is emitted in the state where the light absorption by the polarizing plate is the least, and the light state is obtained. In the on-voltage state, the effective birefringence decreases because the liquid crystal molecules of the driven liquid crystal layer undergo orientation deformation. The incident light is affected by the birefringence corresponding to the difference in the amount of birefringence between the driven liquid crystal layer and the liquid crystal layer for optical compensation, and the returned light is elliptically polarized unlike the off-voltage state. Becomes When the voltage is adjusted so that the difference in the amount of birefringence becomes about 140 nm, that is, an amount corresponding to a quarter of the central light wavelength in visible light, the light that has been reflected and passed through the liquid crystal layer again is incident straight. The state is close to linearly polarized light in a direction orthogonal to the polarization state. Therefore, a dark state can be realized at this time. An advantage of the present invention is that the reflectance can be improved by using only one polarizing plate, which has been conventionally used in two sheets.

In the above, the optical compensation liquid crystal layer is formed of a film made of a liquid crystalline polymer material .
It becomes practical.

[0009] In the above, the thickness d of the two liquid crystal layers, the product [Delta] n · d of birefringence <br/> refraction value [Delta] n Oh at 950 nanometers
Runode, it is possible to keep the response speed of the liquid crystal of the liquid crystal layer to the practical level. When the product Δn · d of the thickness d of the two liquid crystal layers and the birefringence value Δn exceeds 950 nm, the thickness d of the liquid crystal layer increases, and the response speed of the liquid crystal in the liquid crystal layer decreases. That is, the response speed of the liquid crystal is inversely proportional to the square of the thickness d of the liquid crystal layer.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same portions are denoted by the same reference numerals.

FIG. 1 is a sectional view showing the configuration of a reflection type liquid crystal display device according to an embodiment of the present invention. The liquid crystal layer 1 is sealed between the two substrates 3 on which the electrodes 2 are formed, and inside a seal resin 4 formed by printing and forming around the substrates. The liquid crystal layer is oriented in a predetermined direction by subjecting the orientation film 5 formed by printing on the electrode to an orientation treatment, and has a twisted structure due to the optical rotatory substance added at the same time. Further, the polarizing plate 6, the polarizing plate 6 and the liquid crystal layer 1
Between them, a liquid crystal layer 7 for optical compensation and a reflector 8 on one outer side. The liquid crystal layer for optical compensation may be a liquid crystal panel sealed between two substrates and inside a sealing resin formed around the substrate, similarly to the liquid crystal layer for driving, A similar effect is obtained even with a film made of a polymer material. However, the twist direction of the liquid crystal twist structure is opposite to the direction of the driving liquid crystal layer. Further, the liquid crystal layers for driving and optical compensation are laminated so that the alignment directions of the liquid crystal molecules adjacent to each other are orthogonal to each other.

Panels having different amounts of birefringence Δn · d in the liquid crystal layer were prepared, and their reflection display characteristics were measured. The birefringence amounts of the driving and optical compensation liquid crystal layers were set to substantially the same value. In addition, measurement was performed for each panel while changing the angle of the polarizing plate, and a configuration having the highest contrast was selected.

FIG. 2 shows a reflection display characteristic diagram. The horizontal axis is the amount of birefringence Δn · d, and the vertical axis is the contrast.
As a result, a practically good contrast was realized when the birefringence of the liquid crystal layer was set to about 700 nm or more.

As described above, the liquid crystal layer 1 for driving and the liquid crystal layer 7 having a twisted structure in the opposite direction for optical compensation are laminated, and the polarizing plate 6 is disposed on one of the outer sides thereof, and the reflecting plate is disposed on the other. 8 was arranged, and the product Δn · d of the layer thickness d of the two liquid crystal layers 1 and 7 and the birefringence value Δn was set to 700 nm or more, whereby a good contrast was realized.

The brightness in the bright state is increased by about 20% as compared with the conventional configuration using two polarizing plates.

In the above embodiment of the present invention, the reflection plate is attached to the outside of the substrate, but can also serve as an electrode formed on the inner surface of the substrate. That is, metal, preferably aluminum, was deposited on the substrate of the driving liquid crystal panel on which the polarizing plate was not attached, and an electrode pattern was formed through a photolithography process. The aluminum electrode functions as a reflector.

[0017]

As described above, according to the present invention, the light use efficiency of the reflection type liquid crystal display device can be increased by using one polarizing plate instead of the conventional two, and the off voltage application state can be improved. Can be improved.

In the above description, a liquid crystal panel driven by a simple matrix has been mainly described as an example. However, it is apparent that the present invention can be easily applied to a liquid crystal panel driven by an active matrix in which an active element such as a thin film transistor is formed in each pixel. is there.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating the reflective display characteristics of a reflective liquid crystal display device according to one embodiment of the present invention.

FIG. 3 is a sectional view of a conventional reflective liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal layer 2 Electrode 3 Substrate 4 Seal resin 5 Alignment film 6 Polarizer 7 Liquid crystal layer for optical compensation 8 Reflector 31 Liquid crystal layer 32 Transparent electrode 33 Substrate 34 Seal resin 35 Alignment film 36 Polarizer 37 Phase difference plate 38 Reflector

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13363

Claims (1)

(57) [Claims] 1. A substrate with an electrode having an alignment film layer formed on the surface thereof is opposed to each other, a peripheral portion is bonded with a sealing resin, and a liquid crystal layer having a twisted structure is interposed therein. with one polarizing plate, a reflection type liquid crystal display device obtained by placing a reflective plate on the other film-like liquid crystalline high fraction of having a twisted structure opposite to the polarizing plates and the liquid crystal layer
A reflective liquid crystal layer comprising a liquid crystal layer for optical compensation of a child material , and a product Δn · d of a layer thickness d and a birefringence value Δn of the two liquid crystal layers is 700 nm or more and 950 nm or less. Liquid crystal display.