JPH0728035A - Display device - Google Patents

Abstract

PURPOSE:To improve the contrast and the visibility of the display device formed by orienting and dispersing a liquid crystal and polymer with each other. CONSTITUTION:This display device is constituted by orienting and dispersing liquid crystal 3 mixed with dichromatic dye 4 and polymer 5 between a substrate 1 provided with transparent electrode 2 and a substrate 8 provided with reflection electrode 7. A light absorptive layer 11 is arranged in tight contact with the rear surface of the reflection electrode side substrate 8. As a result, the display device having the good contrast and the good visibility is produced. The reflection type color large-capacity display having good contrast and bright color is produced by combining the display device with a color filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a display device used for a man-machine interface, such as a display unit of an information equipment terminal, a television and a home electric appliance.

[0002]

2. Description of the Related Art In recent years, the need for a bright power-saving display device that does not use a polarizing plate has increased, and research and development of a polymer dispersed liquid crystal display device (abbreviated as PDLC) has been actively conducted as a first candidate. . In particular, a technique for improving contrast and visibility has been developed, and US Patent 485 has been developed.
In 0678, in a PDLC that is transparent when a voltage is applied and scatters when no voltage is applied, a substrate having a light absorbing layer formed on the back side of the light scattering layer with a slight gap on the back side of the light scattering layer as seen from the user It has been proposed to reflect the light that has escaped through the gaps and return it to the light scattering layer (Fig. 2).

[0003]

However, such a P
DLC has a problem that sufficient brightness and contrast cannot be obtained. In order to solve this problem, a liquid crystal display device (abbreviated as GLAD) in which a polymer and a liquid crystal are aligned and dispersed with each other.
Was developed (European published patent EP 0488116
A2). According to this, transparent or light absorption occurs when no electric field is applied, and white light scattering occurs when an electric field is applied. Moreover, since the driving voltage is low and the specific resistance is high, it can be driven by a two-terminal element or a three-terminal element. Therefore, it is possible to manufacture a bright reflective large-capacity display. In GLAD, it is necessary to reduce light reflection between pixels as much as possible in order to improve the contrast. However, the technology disclosed in US Pat. No. 4,850,678 cannot be applied to GLAD. In U.S. Pat. No. 4,850,678, a light absorbing layer is used on the back side for displaying black, whereas in GLAD, a dichroic dye contained in the liquid crystal is used. Further, in US Pat. No. 4,850,678 for white display, only the scattering of the light scattering layer is used, whereas in GLAD, the electrode on the back side is made reflective so that the light passing through the light scattering layer is reflected on the back side by the reflection electrode. All of them are reflected on the front side and are effectively used. As you can see from this, US patent 4
The back electrode used in 850678 must be transparent and the back electrode used in GLAD must be reflective. That is, when the configuration of US Pat. No. 4,850,678 is applied to GLAD, there is a problem that white cannot be displayed. Therefore, the present invention is to solve such a problem, and an object thereof is to improve the contrast and visibility of GLAD.

[0004]

The display device of the present invention has the following features.

In a display device in which a liquid crystal containing a dichroic dye and a polymer are oriented and dispersed with each other between 1.2 substrates with electrodes, the electrodes of the substrate on the back side when viewed from the user are made of a reflective material. It is characterized in that it is formed by, and the portion other than the reflective electrode absorbs light.

2. The substrate on the back side viewed from the user is a light absorbing material.

3. It is characterized in that the surface opposite to the reflective electrode sandwiching the substrate is subjected to a light absorbing treatment.

4. It is characterized in that a light absorbing treatment is performed at least between the reflective electrodes.

5. The display device is driven in a time division manner.

6. An active element is formed on at least one of the substrates.

7. The active element is a TFT, MI
M, a lateral MIM element.

8. A color filter is provided on the front side of the reflective electrode.

9. A non-glare treatment or a non-reflection coating is applied to the surface of the display device on the observer side.

The details will be described in the following examples.

[0015]

【Example】

(Embodiment 1) In this embodiment, MIM is used as an active element.
An example is shown for the case where an element substrate is used.

FIG. 1 shows a simple sectional view of the display device of this embodiment. First, a panel for enclosing the liquid crystal will be described.
A comb-shaped transparent electrode group 2 was formed on the substrate 1 on the front side, and the surface thereof was subjected to orientation treatment. As the MIM element, the signal electrode 13 was first formed on the backside substrate 8 and then the surface thereof was anodized to form the insulating layer 12. Further, a reflective pixel electrode 7 (here, an aluminum magnesium alloy was used) was formed thereon, and its surface was subjected to orientation treatment. A protective layer may be provided on the surface of the active element.
A black paint was applied as the light absorbing layer 11 to the back surface of the electrode of the substrate 8 and dried. The two substrates thus prepared were fixed by sticking their peripheries with the electrode surface inside and keeping the distance between the substrates about 5 μm. Although the number of pixels is three in FIG. 1, 640 × 480 pixels are actually formed on a 4-inch substrate. Next, the liquid crystal and polymer precursor mixture sealed in this gap will be described. MJ9278 as liquid crystal
6 (manufactured by Merck & Co.) was used and R was added as a chiral component.
1011 (manufactured by Merck) was used as a mixture of 0.5% and 3% of a mixture of M361: SI512: M137 (both manufactured by Mitsui Toatsu Dyes) as a dichroic dye. As a polymer precursor, terphenyl methacrylate was used in an amount of 5% based on the above liquid crystal mixture. The above materials were mixed by heating and vacuum-encapsulated in the empty panel described above. Then, ultraviolet rays of 300 to 400 nm and 3 mW / cm ² were irradiated from the front of the panel at 50 ° C. to precipitate the polymer from the liquid crystal, thus completing the display device of this example.

The display device thus manufactured had a contrast of 10, and was much more visible than when the light absorbing plate was arranged with a gap from the substrate (contrast was 8).

In addition to applying black paint on the back surface of the substrate 8, a black adhesive film is attached without bubbles, or a light absorbing layer is arranged on the back side of the substrate 8 and a refractive index such as matching oil is provided in the gap. The same effect was obtained by enclosing the substance to be combined.

It is desirable that the liquid crystal used here has a high specific resistance and a high reliability in order to be combined with an active element, more preferably T manufactured by Merck.
L202 is used as at least one component.

As the dichroic dye, those having good light resistance are preferably used, and more preferably, anthraquinone or perylene dyes are used.

As the polymer precursor, it is desirable to use a polymer having a large birefringence, and it is desirable that the skeleton of biphenyl, terphenyl, tolan or the like is bonded to a polymerizable group such as a methacryl group.

The inclusion of the chiral component can increase the scattering. Although the kind thereof is not limited, a material having good light resistance and reliability is preferable, and CB15, C1 manufactured by Merck & Co., Inc.
5, S801, R801, S1011 and other CM series manufactured by Chisso Corporation can be used.

In the present embodiment, the lateral back-to-back type MIM element substrate shown in FIG. 3 could be used as the element substrate. By using this element, it is possible to reduce the element capacitance, so that it is possible to secure a large driving margin, and it is possible to perform bright display with good contrast. In addition to this as a two-terminal element, PLZT or PVDF
It is also possible to use a ferroelectric element using, for example. In addition, the substrate on which the active element is formed is disposed on the front side, the counter substrate on which the reflective electrode is formed is disposed on the back side, and the light absorption layer of the present invention is formed on the back side of the counter substrate by adhesion. The effect was obtained.

Example 2 In this example, a TFT element is used as an active element. FIG. 4 shows the TFT element substrate used in this example. Gate electrode 1 on substrate 8
5, gate insulating layer 18, semiconductor layer 16, drain electrode 1
7, the source electrode 14, and the reflective electrode 7 were formed. This surface was subjected to orientation treatment. As the light absorption treatment on the back surface of the substrate 8, a method of sticking a black adhesive film without bubbles was used. A transparent electrode 2 was formed on the counter substrate 1, and its surface was subjected to orientation treatment. Although there are three pixels in FIG. 4, 640 × 480 pixels are actually formed on a 4-inch substrate. A protective layer may be provided on the surface of the active element. The two substrates were bonded together with a gap of 5 μm maintained. The encapsulated liquid crystal mixture is the same as in Example 1. TF
The effect of using the T element is that when an amorphous silicon TFT is used, a high driving voltage can be obtained, and bright display is possible. Also polysilicon TF
When the T element is used, a driver for driving and a controller can be incorporated, and the device can be downsized.

Besides sticking a black film on the back surface of the substrate 8,
Even if a black paint is applied, a black adhesive film is adhered without bubbles, or a light absorbing layer is arranged on the back side of the substrate 8 and a substance such as matching oil for adjusting the refractive index is sealed in the gap. It had a similar effect.

The substrate on which the active element is formed is arranged on the front side, the counter substrate on which the reflective electrode is formed is arranged on the back side, and the light absorption layer of the present invention is formed in close contact with the back side of the counter substrate. Also obtained the same effect.

(Embodiment 3) This embodiment shows an example in which the present invention is applied to a display device of a simple matrix or static drive. FIG. 5 shows a simple sectional view of the display device of this embodiment. The same as Example 1 except that the two-terminal element or the three-terminal element was omitted.

Although the number of pixels is three in FIG. 5, it is actually eight.
× 16 pixels were formed on a 5 cm × 10 cm substrate. As a light absorbing process performed on the back surface of the substrate 8, a light absorbing plate is provided on the substrate 8.
The matching oil (refractive index of about 1.5) was filled in the gap between the substrate 8 and the back surface of the substrate.

As a result, the contrast was remarkably improved (contrast 10) as compared with the conventional reflection type simple matrix or static drive display device (contrast 8). Furthermore, when a non-glare treatment and a non-reflective coating were applied to the surface of this display device, the reflection of the landscape was reduced and the visibility was greatly improved.

As the light absorption treatment to be applied to the back surface of the substrate 8, the same effect can be obtained by applying a black paint or laminating a black adhesive film without bubbles.

(Embodiment 4) In this embodiment, Embodiments 1, 2,
3 shows an example in which a color filter is formed. Figure 6
A simple cross-sectional view of the display device of this example is shown in FIG. Although the color filter 10 is formed between the substrate 1 and the electrode 2, it may be formed on the reflective electrode on the substrate 8. The other points are the same as in Examples 1, 2, and 3.

The display device thus manufactured had a contrast of 20, and was much more visible than when the light absorbing plate was arranged with a gap from the substrate (contrast was 15). Therefore, more vivid color display is possible.

As a light absorption treatment applied to the back surface of the substrate 8, a substance such as applying black paint or disposing a light absorption layer on the back side of the substrate 8 and matching a refractive index such as matching oil into the gap. The same effect was obtained by enclosing.

(Embodiment 5) In this embodiment, Embodiments 1, 2,
3 shows an example in which a light absorbing material is used for the substrate on the back side. FIG. 7 is a diagram simply showing a cross section of the display device of the present embodiment. The second embodiment is the same as the second embodiment except that the substrate 8 is the light absorbing substrate 19 and the light absorbing layer 11 is omitted. With this configuration, the labor for forming the light absorption layer can be saved, and thus the manufacturing method is facilitated. The effects of improving the contrast and the visibility were the same as those of the above-described examples.

The light-absorbing substrate used in this embodiment can be applied to the above-mentioned first and third embodiments without any problem.

(Embodiment 6) In this embodiment, Embodiments 1, 2,
3 shows an example in which the gap between the reflective electrodes formed on the substrate on the back side is subjected to light absorption processing. FIG. 8 is a diagram simply showing a cross section of the display device of the present embodiment. A black polyimide film was formed as the light absorption layer 11 on the substrate 8 and the reflective electrode 7 was formed thereon. Other configurations are the same as those in the first embodiment. The effects of improving the contrast and the visibility were the same as those of the above-described examples.

The light absorbing layer used here may be any one other than those shown here as long as it is a material capable of forming a reflective electrode thereon. The same effect was obtained even when the light absorption layer was formed only between the reflective electrodes.

If the element substrate is a three-terminal element, Example 2
If a simple matrix or a static drive substrate is used, it can be applied to the third embodiment.

(Embodiment 7) In this embodiment, Embodiments 1, 2,
In 3, 4, 5, and 6, an example in which the surface of the display device is subjected to non-glare treatment is shown. Particularly, Example 1 will be described as an example. Clarex non-glare sheet non-glare No. manufactured by Nitto Jushi Kogyo Co., Ltd. was formed on the display surface side of the display device manufactured according to Example 1. 1 MC001 (2% haze, with antireflection coat) 1 mm thick was used by sticking. As a result, glare due to the reflective electrodes placed on the back surface was suppressed, there was almost no reflection of the scenery, and the display floated and visibility was greatly improved. Non-glare No. without anti-reflection coat. 1
But the visibility was improved.

Similar effects can be expected even if other non-glare processing is performed. Further, as the antireflection coating, a type in which a polymer solution is applied or a type in which an inorganic oxide is vapor-deposited or applied can be used.

[0041]

As described above, according to the present invention, it is possible to improve the display contrast by a very simple method of arranging the light absorption layer in close contact with the back surface of the display device.
By using the present invention, it is possible to easily manufacture a display device having good contrast and good visibility, and by combining a color filter, it is possible to manufacture a bright reflective color large-capacity display having good contrast. is there.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a simple cross section of a display device according to a first embodiment.

FIG. 2 is a diagram showing a simple cross section of a conventional display device.

FIG. 3 is a diagram showing a simple cross section of a display device in Example 1.

FIG. 4 is a diagram showing a simple cross section of a display device according to a second embodiment.

FIG. 5 is a diagram showing a simple cross section of a display device according to a third embodiment.

FIG. 6 is a diagram showing a simple cross section of a display device according to a fourth embodiment.

FIG. 7 is a diagram showing a simple cross section of a display device according to a fifth embodiment.

FIG. 8 is a diagram showing a simple cross section of a display device according to a sixth embodiment.

[Explanation of symbols]

 1 substrate 2 electrode 3 liquid crystal 4 dichroic dye 5 polymer 7 reflective electrode 8 substrate 10 color filter 11 light absorbing layer 12 insulating layer 13 signal electrode 14 source electrode 15 gate electrode 16 semiconductor layer 17 drain electrode 18 gate insulating layer 19 Light absorbing substrate 20 Tantalum layer

Front Page Continuation (72) Inventor Hidehito Iizaka 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation

Claims (9)

[Claims] 1. In a display device in which a liquid crystal and a polymer are dispersed between two substrates with electrodes, the liquid crystal containing the dichroic dye and the polymer are aligned and dispersed with each other, and the back side is seen from the user. A display device characterized in that the electrode of the substrate of (1) is formed of a reflective material, and the portion other than the reflective electrode absorbs light. 2. The display device according to claim 1, wherein the substrate on the back side viewed from the user is a light absorbing material. 3. The display device according to claim 1, wherein a surface opposite to the reflective electrode sandwiching the substrate is subjected to a light absorbing treatment. 4. The display device according to claim 1, wherein a light absorbing treatment is performed at least between the reflective electrodes. 5. The display device according to claim 1, wherein the display device is driven in a time division manner. 6. The display device according to claim 1, wherein an active element is formed on at least one of the substrates. 7. The active element is a TFT, MI
7. The display device according to claim 6, wherein the display device is a M or lateral MIM element. 8. The display device according to claim 1, wherein a color filter is provided on the front side of the reflective electrode. 9. The display device according to claim 1, wherein a non-glare treatment or a non-reflective coating is applied to a surface of the display device on an observer side.