JPH04249218A - Liquid crystal electrooptic element - Google Patents

Abstract

PURPOSE:To offer a high polymer, liquid crystal composite film (PDLC) liquid crystal display body which eliminates the need for a bright back light by forming a multi-layered metallic thin film layer as an interference layer on an element electrode and coloring the interference layer by utilizing an interference color. CONSTITUTION:The element electrode 8 is formed on one side of the PDLC 1 and a multi-layered metallic thin film is laminated on the top or reverse surface of the element electrode 8; and incident light is scattered unless a voltage is applied to the PDLC 1, so a display element is in white. When the PDLC 1 is applied with the voltage and put in a light transmission state, the PDLC 1 becomes transparent, so the visible light reaches the metallic thin film layer 10. Then, interference corresponding to the number of layers, the film thickness, and the constituent metal of the formed metallic thin film layer 10 is caused and the interference color is generated to color the layer. The black - dark purple colors are obtained by selecting optimum conditions. Namely, a black - dark purple display is made by applying the voltage.

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, as shown in FIG. 3, 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. In the case of a direct view type liquid crystal display element, PDL
Black paper or a board was placed on the opposite side of C1 to enable black and white display.

0004

[Problem to be Solved by the Invention] When a conventional PDLC is applied to a liquid crystal electro-optical element, when no voltage is applied, the PDLC
scatters light, resulting in a white display. Furthermore, when a voltage is applied to put the PDLC in a light-transmissive state, black paper, a board, etc. behind the PDLC can be seen, so the display becomes black, and a certain degree of contrast can be obtained.

However, the contrast in this case is P
It depends on the distance between the DLC and the black body. That is, when the distance is short, when no voltage is applied, the black object behind can be seen through to some extent, resulting in a gray display instead of a complete white display. However, when a voltage is applied, the black object behind is clearly visible, so a good black display can be obtained. Conversely, if the distance is increased, a good white display can be obtained without seeing the black body behind when no voltage is applied, but when a voltage is applied, the PDLC becomes 1
It does not transmit 00% of the light, but rather scatters the light to some extent, resulting in a gray display. Moreover, the thickness of the liquid crystal display element itself increases, which is not preferable.

In any case, it has been difficult to obtain good contrast with a liquid crystal display element using conventional PDLC.

The present invention has been made to solve the above problem, and by forming a multilayer metal thin film layer on the element electrode and using this as an interference layer, and coloring it using interference color, To provide a PDLC liquid crystal display that is bright and does not require a backlight.

[0008]

[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 metal thin film on one side of the polymer/liquid crystal composite film. Furthermore, the metal thin film is characterized in that a multilayer metal thin film is laminated.

[0009]

[Operation] In the present invention, one to more than ten layers of metal thin films are formed above or below the element electrodes. These metal thin film layers are P
It is completely useless when no voltage is applied to the DLC. This is because the incident light is scattered by the PDLC, so no interference effect by the metal thin film can be expected. In this case, the display element is white. Next, PDL
Consider the case where a voltage is applied to C to make it into a light transmitting state. P
Since DLC 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, and the metal thin film layer is colored by interference color. If the optimal conditions are selected, the color will be black to dark purple. In other words, when no voltage is applied to the PDLC, it is white.
When a voltage is applied, a black to dark purple display becomes possible.

0010

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, 2 is an element substrate, 3 is a circuit element, 4 is a counter substrate, 5 is a nematic liquid crystal, 6 is a three-dimensional mesh polymer matrix, 7 is a counter electrode, 8 is an element electrode, and 9 is a seal The agent 10 is a single layer or a laminated metal thin film. PDL when no voltage is applied
C is a light-scattering state, and changes to a light-transmitting state by applying a voltage through a transparent electrode or a TFT element.

[0011] This liquid crystal cell was prepared as follows. Element electrodes and laminated metal thin films were formed on the TFT element substrate as follows. First, ITO was formed as a device electrode on a glass substrate by vapor deposition to a thickness of 2000 Å. On the ITO element electrode, MgF2 was deposited to a thickness of 1090 Å, and Ta2O5 was deposited to a thickness of 680 Å. Next, the nematic liquid crystal (E8
, manufactured by Merck & Co.) and a mixture of ultraviolet curing resin (E8: ultraviolet curing resin = 75 parts by weight: 25 parts by weight) was vacuum sealed,
irradiated with ultraviolet rays at 2000mj/cm2 to form PDLC,
It was made into a liquid crystal cell.

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 transmittance curve when voltage is applied. The contrast was 1:10.

(Example 2) Element electrodes on TFT element substrate,
The laminated metal thin film was formed as follows. First, MgF2 was placed on the ITO element electrode at a thickness of 1090 Å and Ta2O5 was placed at a thickness of 680 Å.
Each was formed by vapor deposition. Next, ITO was formed as a device electrode on a glass substrate by vapor deposition to a thickness of 2000 Å. A liquid crystal cell was produced in the same manner as in Example 1 except for the above.

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 transmittance curve when voltage is applied. The contrast was 1:14.

(Example 3) A liquid crystal cell was prepared in the same manner as in Example 1, except that MgF2 was deposited to a thickness of 1090 Å and Ta2O5 was deposited to a thickness of 860 Å on the Al reflective electrode.

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 the ITO element electrode was used alone. A piece of black paper was placed 2 cm behind this liquid crystal cell to form a direct view type liquid crystal display element.

The obtained liquid crystal cell has P when no voltage is applied.
Since the incident light is scattered by DLC, the color is approximately gray to white. When a voltage was applied, the PDLC became transparent and the black paper behind it could be seen. However, it was not completely black, and the contrast was 1:5.

[0019]

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 direct-view liquid crystal electro-optical element.

[Explanation of symbols]

1 PDLC 2 Element substrate 3 Circuit element 4 Counter substrate 5 Nematic liquid crystal 6 Porous polymer 7 Counter electrode 8 Device electrode 9 Sealing agent 10 One to multiple metal thin film layers 11 Transmittance curve 12 of metal thin film in Example 1 Transmittance curve 13 of metal thin film in Example 2 Black body

Claims (2)

[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 metal thin film on one side. 2. A liquid crystal electro-optical element, wherein the metal thin film according to claim 1 is a multilayered metal thin film.