JPH04248519A - Liquid crystal electrooptical element - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display body consisting of a high-polymer/liquid crystal composite film (hereafter abbreviated as PDLC) which is bright and does not require a back light by forming many layers of metallic thin-film layers on reflection electrodes and using these layers as interference layers to prevent the electrodes from acting like mirrors. CONSTITUTION:This element has a reflection film 8 on one side of the PDLC 1 and is further laminated with many layers of the metallic thin-film layers 10 on this reflection plate 8 in such a manner that these films are commonly used as the electrodes. The interference effect by the metallic thin-film layers cannot be expected while voltages are not impressed to the PDLC 1 and, therefore, the display element is white. The PDLC 1 becomes transparent when the voltage is impressed to the PDLC 1 to put the PDLC into a light transparent state. Visible light, therefore, arrives at the metallic thin-film layers 10 and the interference meeting the number of layers and film thicknesses of the formed metallic thin-film layers 10 and the refractive indices of the constituting metals thereof takes place and these layers are colored. The layers turn black to dark purple if optimum conditions are selected. Namely, the black to dark purple display is possible if the voltage is impressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid crystal electro-optical devices such as liquid crystal televisions, liquid crystal projectors, and liquid crystal displays.

0002

2. Description of the Related Art A polymer/liquid crystal composite film 1 (hereinafter referred to as PDLC) has a structure in which particulate or three-dimensional network structured polymers 6 are dispersed in a nematic liquid crystal material 5, as shown in FIG. The PDLC1 changes from a light scattering state to a light transmitting state as voltage is applied.

In order to use this PDLC as a display, conventionally, as shown in FIG. Display is possible by sandwiching the PDLC 1 between the electrodes 7 and controlling the amount of transmitted light using an applied voltage. When PDLC is used as a display, a polarizing plate, which is essential to conventional liquid crystal display elements, becomes unnecessary, so it is possible to obtain a bright display element.

0004

[Problems to be Solved by the Invention] When a conventional liquid crystal electro-optical device using PDLC is applied to a reflective liquid crystal display device, a white display can be obtained because the PDLC scatters light when no voltage is applied. However, when applying voltage, PD
When the LC is placed in a light transmitting state, light directly hits the reflective electrode behind the PDLC and is reflected. As a result, the electrode section becomes like looking into a mirror, and in extreme cases, the entire liquid crystal display element becomes mirror-like, making it extremely unsightly.

[0005] The present invention has been made to solve these problems, and consists of forming a multilayer metal thin film layer on a reflective electrode and using this as an interference layer to prevent the electrode from becoming mirror-like. The object of the present invention is to provide a bright PDLC liquid crystal display that does not require a backlight.

[0006]

[Means for Solving the Problems] The liquid crystal electro-optical device of the present invention comprises a polymer/liquid crystal composite film in which nematic liquid crystal is dispersed in a thin polymer film, and electrode substrates placed on both sides of the composite film. The electro-optical element is characterized by having a reflecting plate on one side of the polymer/liquid crystal composite film. Furthermore, the reflective plate is a metal thin film formed on the substrate, and is characterized in that it also serves as an electrode. Furthermore, metal thin films
It is characterized by laminating multiple layers of metal thin films.

[0007]

[Operation] In the present invention, one to more than ten layers of metal thin film are formed on the reflecting plate. These metal thin film layers are completely useless when no voltage is applied to the PDLC. This is because the incident light is scattered by the PDLC, so no interference effect due to the metal thin film can be expected. In this case, the display element is white. Next, consider the case where a voltage is applied to the PDLC to make it into a light transmitting state. Since PDLC is transparent, visible light can reach the metal thin film layer. Then, interference occurs in the formed metal thin film layer depending on the number of layers, film thickness, and refractive index of the constituent metals, resulting in coloring. If you choose the best conditions, black ~
It becomes dark purple. That is, when no voltage is applied to the PDLC, the display is white, and when the voltage is applied, the display becomes black to deep purple.

[0008]

Embodiments (Embodiment 1) FIG. 1 is a sectional view of a liquid crystal electro-optical element according to the present invention. In the figure, 1 is a PDLC, a two-element substrate, 3 is a circuit element, 4 is a counter substrate, 5 is a nematic liquid crystal, 6 is a three-dimensional network polymer matrix, 7 is a counter electrode, 8 is a reflective electrode, and 9 is a sealant , 10 are single-layer or laminated metal thin films. PDLC when no voltage is applied
is in a light scattering state, and changes to a light transmitting state by applying a voltage through a transparent electrode or a TFT element.

[0009] This liquid crystal cell was prepared as follows. A reflective electrode and a laminated metal thin film were formed on the TFT element substrate as follows. First, Al was formed as a reflective electrode on a glass substrate by vapor deposition to a thickness of 2000 Å. M on the Al reflective electrode
A thickness of gF2 of 1090 Å and a thickness of Ta2O5 of 680 Å were formed by vapor deposition. Next, the counter substrate is pasted with a gap of 20 μm, and a mixture of nematic liquid crystal (E8, manufactured by Merck & Co., Ltd.) and ultraviolet curing resin (E8: ultraviolet curing resin = 75 parts by weight: 25 parts by weight) is vacuum-sealed. was irradiated with 2000 mj/cm2 to make a PDLC, and a liquid crystal cell was made.

The obtained liquid crystal cell has P when no voltage is applied.
It is almost white because the incident light is scattered by DLC,
When voltage was applied, a purple display was obtained due to interference between the laminated metal thin films. Figure 2 shows the reflectance curve when voltage is applied. The contrast was 1:10.

(Example 2) A liquid crystal cell was prepared in the same manner as in Example 1, except that MgF2 was formed to a thickness of 1090 Å and Ta2O5 was formed to a thickness of 860 Å on the Al reflective electrode by vapor deposition.

The obtained liquid crystal cell has P when no voltage is applied.
It is almost white because the incident light is scattered by DLC,
When a voltage was applied, a deep purple color was obtained due to interference between the laminated metal thin films. Figure 2 shows the reflectance curve when voltage is applied. The contrast was 1:15.

(Comparative Example) A liquid crystal cell was prepared in the same manner as in Example 1, except that a single Al reflective electrode was used.

The obtained liquid crystal cell has P when no voltage is applied.
The color is almost white because the DLC scatters the incident light. However, when a voltage was applied, the PDLC began to transmit light and the reflective electrode underneath could be seen. However, since the reflective electrode acts as a mirror, the surrounding scenery changes depending on the direction in which it is viewed when in use. The background was reflected in the image, making it extremely difficult to use.

[0015]

As described above, according to the present invention, it is possible to provide a liquid crystal display that does not require a backlight and has good contrast.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross-sectional view of a liquid crystal electro-optical element according to the present invention.

FIG. 2 is a diagram showing a reflectance curve of a laminated metal thin film according to the present invention.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

1 PDLC 2 Element substrate 3 Circuit elements 4 Opposite board 5 Nematic liquid crystal 6 Porous cellulose 7 Counter electrode 8 Reflecting electrode 9 Sealant 10　One to multiple metal thin film layers

Claims (3)

[Claims] 1. A liquid crystal electro-optical element comprising a polymer/liquid crystal composite film in which nematic liquid crystal is dispersed in a polymer thin film and electrode substrates disposed on both sides of the polymer thin film. A liquid crystal electro-optical element characterized by having a reflector on one side. 2. A liquid crystal electro-optical element according to claim 1, wherein the reflection plate is a metal thin film formed on a substrate and also serves as an electrode. 3. A liquid crystal electro-optical element, wherein the metal thin film according to claim 2 is a multilayered metal thin film.