JPH0743741A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the contrast of the liquid crystal display element oriented and dispersed with liquid crystals and high-polymer particles and to improve the visibility thereof. CONSTITUTION:This liquid crystal display element is constituted by orienting and dispersing the liquid crystals 106 contg. dichromatic dyestuff and the high- polymers 105 having refractive index anisotropy with each other and clamping these liquid crystals and high polymers between two sheets of substrates 101, 110 which have pixel electrodes 103 and wirings for transmitting electric signals to these pixel electrodes 103 and at least one of which are transparent. The pixel electrodes 109 of the rear side substrate 101 is formed of a reflective material and the parts between the pixel electrodes are subjected to a light absorbing treatment or light shielding treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display element which constitutes a display portion of information equipment terminals, televisions, home electric appliances and the like.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for miniaturization and portability of information equipment, a reflective liquid crystal display element is indispensable from the viewpoint of power saving required for displays in this field. The TN method has been widely used for wrist watches, calculators and the like, and the STN method has been used for large capacity display as a reflection type liquid crystal display device for notebook personal computers, word processors and the like. Furthermore, on the reflective liquid crystal display device,
Applications for combining an information input device such as a tablet are expanding, and a reflective liquid crystal display element is required to have good brightness and visibility. Recently, in such a field, a liquid crystal display device using a polymer-dispersed liquid crystal in which a liquid crystal and a polymer are mutually dispersed without using a polarizing plate has attracted attention.

The principle of operation of this liquid crystal display element utilizes the difference in the refractive index between the liquid crystal and the polymer, and when the refractive index of the liquid crystal and that of the polymer match due to the application of an electric field, a transmissive state is exhibited.
This is because when the refractive index changes due to the removal of the electric field, a scattering state is exhibited. NCAP (invention of Ferguson et al .: Japanese Patent Publication No. 58-501631), LCPC (Asahi Glass Co., Ltd .:
US Patent 4,818,070), PDLC (Kent State University: US Patent 4,685,771), PNL
C (Dainippon Ink and Chemicals, Inc .: European open patent E
PAs 313 and 053) are based on the above operation principle. On the other hand, a liquid crystal display device using a polymer dispersed liquid crystal of a reverse mode (hereinafter referred to as a reverse type) that transmits when no electric field is applied and scatters when an electric field is applied (Kent State University: US Pat. No. 4,994,204, Philips: published in Europe). Patent EP 0451905 A1) is also disclosed.

[0004]

However, in the liquid crystal display element of the TN type and the STN type using the conventional polarizing plate, since the utilization efficiency of light is low, it is dark when it is a reflection type, and it is difficult to use as an information input device such as a tablet. When combined, it became a very dark display, which was a problem. Also, in the TN method and the STN method, since the reflector is arranged over the polarizing plate on the back surface of the substrate on the back side, there is a double image of the display,
Small letters were hard to see, and visibility was a problem. On the other hand, according to the technique of European Patent Publication EP0488116A2, when a dichroic dye is contained in the liquid crystal, light absorption without application of an electric field and switching of white turbid light scattering with application of an electric field are possible, resulting in a bright reflective type. It was possible to manufacture a display. Furthermore, when the light reflecting surface is also used as the pixel electrode, a bright reflective display without a double image of the display was possible.

However, although this conventional technique can solve the problems of the conventional display method using a polarizing plate,
Since the pixel electrode also serves as the reflecting surface, light leaks from between the pixel electrodes, and there is a problem that the back side is transparent, and as a result, there is a problem that contrast and color difference are reduced. When the addition amount of the dichroic dye is increased in order to prevent the floating of the display in the off state, the light resistance is deteriorated, the dye is deposited, and the specific resistance value of the liquid crystal is lowered. There was a problem that caused it.

The present invention has been made in order to solve such a problem, and an object of the present invention is to block stray light from between the pixels of the back substrate so that dichroic dye of An object of the present invention is to provide a reflection-type liquid crystal display element that suppresses the floating of the display when it is off, has a high contrast ratio, and has a large color difference without increasing the addition amount.

[0007]

In order to solve the above problems, the liquid crystal display device of the present invention has the following constitution.

(1) A liquid crystal containing a dichroic dye and a refractive index anisotropy are provided between two substrates at least one of which has a pixel electrode and a wiring for transmitting an electric signal to the pixel electrode and at least one of which is transparent. In a liquid crystal display element in which a polymer having is aligned and dispersed with each other and is sandwiched, the pixel electrodes on the back substrate are formed of a reflective material, and light absorption treatment is performed between the pixel electrodes. And

(2) In the above liquid crystal display element, the pixel electrodes on the back substrate are formed of a reflective material, and light-shielding treatment is performed between the pixel electrodes.

(3) A nonlinear element is formed on at least one of the substrates.

(4) The non-linear element is a two-terminal element.

(5) The non-linear element is a three-terminal element.

[0013]

【Example】

(Embodiment 1) Hereinafter, in this embodiment, a configuration of a two-terminal element (MIM element) in which a light absorption layer is provided between pixels is shown. FIG. 1 shows a cross-sectional view of the liquid crystal display element of this example. The substrate 110 on the back side was a MIM facing substrate, and an alloy of aluminum and magnesium was formed on the glass substrate by sputtering to have a thickness of about 2000 angstroms, followed by patterning to form striped reflective electrodes 109. Continuing,
A color mosaic CK (manufactured by Fuji Hunt Co., Ltd.) is applied as an organic resist (black) by a coating device of about 5000 angstrom spin coater, and then patterned to form a reflective electrode 1.
The light absorption layer 108 was formed between the 09 stripes. Subsequently, polyimide was formed as the alignment film 107 and subjected to rubbing treatment. The MIM element 10 is provided on the substrate 101.
2. The ITO pixel electrode 103 and the signal wiring are formed, and polyimide is formed as the alignment film 104 on the surface and then a rubbing process is performed. These two substrates were fixed by bonding the peripheries of the substrates with a gap of 5 μm. The rubbing direction was shifted by 90 ° between the substrates. Next, the liquid crystal and polymer precursor mixture sealed between the substrates will be described. Liquid crystal TL-202 (Merck) and M
J92786 (manufactured by Merck) was mixed and used at 7: 3,
R1011 (Merck) as a chiral component
0.5% by weight and S-344 (Mitsui Toatsu dye) as a dichroic dye were mixed at 2% by weight and used. As the polymer precursor, terphenyl methacrylate was used in an amount of 5% by weight based on the above liquid crystal mixture. The above was mixed by heating and vacuum-sealed in the empty panel described above. After that, the panel at 50 ℃
3mW (350nm) per square cm while maintaining
Was irradiated with the ultraviolet rays of 10 minutes to precipitate the polymer from the liquid crystal, and the liquid crystal display element of this example was completed. Between the substrates, the polymer 105 and the liquid crystal 106 are aligned with each other,
With the dispersed structure, black display was obtained by absorption of the dichroic dye when the voltage was off. When a sufficient voltage was applied, the liquid crystal 106 was oriented in the direction of the electric field, and discontinuity of the refractive index occurred in the medium, resulting in a light scattering state. At this time, since the absorption of the dichroic dye was very small, white display was obtained.

When the liquid crystal display device thus obtained was driven by MIM, the contrast was 11. In this example, the visibility was significantly improved as compared with the conventional liquid crystal display element (contrast 6) in which the light absorption layer was not arranged between the pixel electrodes. Furthermore, when the surface of this liquid crystal display element was subjected to a non-glare treatment and a non-reflective coating, the reflection of the scenery was reduced and the visibility was significantly improved.

In this embodiment, other than the MIM element, a lateral MIM element, a back-to-back MIM element, an MSI element, a diode ring element, a varistor element or the like can be used as the two-terminal nonlinear element.

The material used for the substrate is soda glass,
Quartz, non-alkali glass, silicon single crystal, sapphire substrate, thermosetting polymer, thermoplastic polymer and the like are preferably used. The polymer material is not particularly limited as long as it does not adversely affect the liquid crystal and the polymer sandwiched between the substrates, and PET, polyether sulfone, epoxy curing resin, phenoxy resin, polyallyl ether, etc. are preferably used. It

Although the reflective electrode is a mixture of Al-Mg, a simple metal such as Al, Cr, Mg, Ag, Au and Pt, or a mixture thereof can be used. In particular, a mixture of Al-Mg is preferable in terms of stability and reflectance, and M
The amount of g added is preferably 0.1 to 10% by weight.

The light absorbing layer is an organic resist, but a material having a high light absorbing ability and an excellent patterning property is desirable.
The absorption wavelength is preferably in the entire visible light region (black), and may be combined with the absorption region of the dichroic dye used.

A polyimide film was used as the alignment film.
An iO oblique vapor deposition film, polyvinyl alcohol, or the like can be used. The liquid crystal and the polymer precursor sandwiched between the substrates only need to be aligned when irradiated with ultraviolet rays, and the substrate surface may be rubbed as it is without forming an alignment film. The rubbing angle is not limited to this embodiment.

As the liquid crystal, those used in ordinary liquid crystal display elements can be preferably used, but in order to improve the scattering degree, the birefringence anisotropy Δn of the liquid crystal should be 0.15 or more. desirable. Further, in order to drive with a non-linear element, the specific resistance value of the liquid crystal alone is 1.0 × 10 ⁹ Ω · cm to 1.0 ×.
10 ¹⁰ Ω · cm or more, more preferably 1 × 10 ¹² Ω
-A cm or more is desirable for maintaining a high retention rate and improving display quality.

The chiral component need not be added,
Normal TN, ST added to improve scattering
The material used for N can be preferably used as it is. The amount added is 0.01 to 10% by weight, preferably 0.1 to 5% by weight. If it is 0.01% by weight or less, the effect is small, and if it is 10% by weight or more, the driving voltage becomes high, and it cannot be driven by a normal nonlinear element.

As the dichroic dye, azo type, anthraquinone type, naphthoquinone type, perylene type, quinophthalone type, azomethine type and the like which are used in a normal GH display system are preferably used. Among them, from the viewpoint of light resistance, the anthraquinone type alone or a mixture with other dyes as necessary is particularly preferable. These dichroic dyes are mixed and used depending on the required color.

The polymer precursor may be any polymer as long as it exhibits a refractive index anisotropy after polymerization and is aligned and dispersed with a liquid crystal, but an ultraviolet-curable monomer is preferable from the viewpoint of simplicity of liquid crystal display device production. As the UV-curable monomer, monofunctional methacrylate, bifunctional methacrylate or polyfunctional methacrylate is preferably used. In order to improve the degree of scattering, it is desirable that these monomers contain at least one benzene ring in their molecular structure. These monomers may contain a chiral component. Moreover, these monomers may be polymerized by irradiating with ultraviolet rays after they are used alone or mixed with other monomers.

In this embodiment, the reflection electrode layer and the light absorption layer are arranged on the counter substrate side of the MIM substrate, but the same effect can be obtained by arranging the reflection electrode layer and the light absorption layer on the MIM element substrate side. (Embodiment 2) Hereinafter, in this embodiment, a configuration of a three-terminal element (polysilicon TFT element) having a light absorption layer provided between pixels will be described. FIG. 2 shows a cross-sectional view of the liquid crystal display element of this example. The substrate 211 on the back side is a TFT substrate, and the TFT 210 and the signal line are formed on the quartz substrate.
The reflective electrode 208 is formed via the electrode 9. The reflective electrode is formed of an alloy of aluminum and magnesium by sputtering to have a thickness of about 1000 Å, and is connected to the TFT through a contact hole. A color mosaic CK (manufactured by Fuji Hunt Co., Ltd.) as an organic resist (black) was applied to this substrate by a 5000 angstrom spin coater, and then a light absorption layer 207 was formed between pixels of the reflective electrode 208 by patterning. Subsequently, polyimide was formed as the alignment film 206 and subjected to rubbing treatment. An ITO electrode 202 is formed on the counter substrate 201, and polyimide is formed as an alignment film 203 on the surface, and then rubbing treatment is performed. These two substrates were fixed by bonding the peripheries of the substrates with a gap of 5 μm.
The rubbing direction was shifted by 90 ° between the substrates.

A liquid crystal and a polymer precursor mixture similar to those in Example 1 were vacuum-sealed between the substrates, and ultraviolet rays were irradiated in the same manner as in Example 1 to precipitate the polymer. The device was obtained.

When the liquid crystal display device thus obtained was driven by a TFT, the contrast was 12. In this example, the visibility was significantly improved as compared with the conventional liquid crystal display element (contrast 6) in which the light absorption layer was not arranged between the pixel electrodes. Furthermore, when the surface of this liquid crystal display element was subjected to a non-glare treatment and a non-reflective coating, the reflection of the scenery was reduced and the visibility was significantly improved.

The materials used for the substrate of this embodiment are soda glass, quartz, non-alkali glass, silicon single crystal,
Sapphire substrate, thermosetting polymer, thermoplastic polymer and the like are preferably used. The polymer material is not particularly limited as long as it does not adversely affect the liquid crystal and the polymer sandwiched between the substrates, and PET, polyether sulfone, epoxy curing resin, phenoxy resin, polyallyl ether, etc. are preferably used. It

Although the reflective electrode is a mixture of Al-Mg, simple metals such as Al, Cr, Mg, Ag, Au and Pt, or a mixture thereof can be used. In particular, a mixture of Al-Mg is preferable in terms of stability and reflectance, and M
The amount of g added is preferably 0.1 to 10% by weight.

Although the light absorbing layer is an organic resist, a material having a high light absorbing ability and an excellent patterning property is desirable.
The absorption wavelength is preferably in the entire visible light region (black), and may be combined with the absorption region of the dichroic dye used.

A polyimide film was used as the alignment film.
An iO oblique vapor deposition film, polyvinyl alcohol, or the like can be used. The liquid crystal and the polymer precursor sandwiched between the substrates only need to be aligned when irradiated with ultraviolet rays, and the substrate surface may be rubbed as it is without forming an alignment film. The rubbing angle is not limited to this embodiment.

As the liquid crystal, those used in ordinary liquid crystal display elements can be preferably used, but in order to improve the scattering degree, the birefringence anisotropy Δn of the liquid crystal should be 0.15 or more. desirable. Further, in order to drive with a non-linear element, the specific resistance value of the liquid crystal alone is 1.0 × 10 ⁹ Ω · cm to 1.0 ×.
10 ¹⁰ Ω · cm or more, more preferably 1 × 10 ¹² Ω
-A cm or more is desirable for maintaining a high retention rate and improving display quality.

The chiral component need not be added,
Normal TN, ST added to improve scattering
The material used for N can be preferably used as it is. The amount added is 0.01 to 10% by weight, preferably 0.1 to 5% by weight. If it is 0.01% by weight or less, the effect is small, and if it is 10% by weight or more, the driving voltage becomes high, and it cannot be driven by a normal nonlinear element.

As the dichroic dye, azo-based, anthraquinone-based, naphthoquinone-based, perylene-based, quinophthalone-based, azomethine-based and the like which are used in a normal GH display system are preferably used. Among them, from the viewpoint of light resistance, the anthraquinone type alone or a mixture with other dyes as necessary is particularly preferable. These dichroic dyes are mixed and used depending on the required color.

The polymer precursor may be any one as long as it exhibits a refractive index anisotropy after polymerization and is aligned and dispersed with the liquid crystal, but an ultraviolet-curable monomer is preferable from the viewpoint of the ease of manufacturing a liquid crystal display device. As the UV-curable monomer, monofunctional methacrylate, bifunctional methacrylate or polyfunctional methacrylate is preferably used. In order to improve the degree of scattering, it is desirable that these monomers contain at least one benzene ring in their molecular structure. These monomers may contain a chiral component. Moreover, these monomers may be polymerized by irradiating with ultraviolet rays after they are used alone or mixed with other monomers.

In this embodiment, as the three-terminal non-linear element, an amorphous silicon TFT element, a Cd-SeTFT element or the like can be used in addition to the polysilicon TFT element.

In this embodiment, the reflective electrode layer and the light absorption layer are arranged on the TFT element substrate, but the structure of this embodiment is particularly desirable because the aperture ratio of the substrate can be increased.

(Embodiment 3) Hereinafter, in this embodiment, a configuration in a 2-terminal element (MIM element) system in which light is shielded between pixels will be described. FIG. 3 is a sectional view of the liquid crystal display device of this example. On the back side MIM counter substrate 311, a light shielding layer 310 is formed.
As chromium, about 1000 angstrom was formed by sputtering. Then, as the insulating layer 309, about 3000 angstroms of silicon dioxide was formed by sputtering. On this insulating layer, an alloy of aluminum and magnesium is sputtered to about 1
After forming 000 angstrom, patterning was performed to form a stripe-shaped reflective electrode 308. Next, the alignment film 30
After forming polyimide as No. 7, rubbing treatment was performed. The MIM element 302 and the ITO are formed on the substrate 301.
A pixel electrode 303 was formed, and polyimide was formed as an alignment film 304 on the surface, and then rubbing treatment was performed. These two substrates were fixed by bonding the peripheries of the substrates with a gap of 5 μm. The rubbing direction was shifted by 90 ° between the substrates.

The same liquid crystal and polymer precursor mixture as in Example 1 was vacuum-sealed between the substrates, and ultraviolet rays were irradiated in the same manner as in Example 1 to precipitate the polymer, and the liquid crystal display of this example was displayed. The device was obtained.

The liquid crystal display device thus obtained is MIM
The contrast was 11 when driven. In this embodiment,
The visibility is significantly improved as compared with the conventional liquid crystal display element (contrast 6) in which the light shielding layer is not arranged between the pixel electrodes. Furthermore, when the surface of this liquid crystal display element was subjected to a non-glare treatment and a non-reflective coating, the reflection of the scenery was reduced and the visibility was significantly improved.

The material used for the substrate of this embodiment is soda glass, quartz, non-alkali glass, silicon single crystal,
Sapphire substrate, thermosetting polymer, thermoplastic polymer and the like are preferably used. The polymer material is not particularly limited as long as it does not adversely affect the liquid crystal and the polymer sandwiched between the substrates, and PET, polyether sulfone, epoxy curing resin, phenoxy resin, polyallyl ether, etc. are preferably used. It

Although the reflective electrode is a mixture of Al-Mg, a simple metal such as Al, Cr, Mg, Ag, Au and Pt, or a mixture thereof can be used. In particular, a mixture of Al-Mg is preferable in terms of stability and reflectance, and M
The amount of g added is preferably 0.1 to 10% by weight.

Although the light shielding layer is made of chrome, it may be made of any metal material that shields light, and is not particularly limited to chromium.

A polyimide film was used as the alignment film.
An iO oblique vapor deposition film, polyvinyl alcohol, or the like can be used. The liquid crystal and the polymer precursor sandwiched between the substrates only need to be aligned when irradiated with ultraviolet rays, and the substrate surface may be rubbed as it is without forming an alignment film. The rubbing angle is not limited to this embodiment.

As the liquid crystal, those used in ordinary liquid crystal display elements can be preferably used, but in order to improve the scattering degree, the birefringence anisotropy Δn of the liquid crystal should be 0.15 or more. desirable. Further, in order to drive with a non-linear element, the specific resistance value of the liquid crystal alone is 1.0 × 10 ⁹ Ω · cm to 1.0 ×.
10 ¹⁰ Ω · cm or more, more preferably 1 × 10 ¹² Ω
-A cm or more is desirable for maintaining a high retention rate and improving display quality.

The chiral component need not be added,
Normal TN, ST added to improve scattering
The material used for N can be preferably used as it is. The amount added is 0.01 to 10% by weight, preferably 0.1 to 5% by weight. If it is 0.01% by weight or less, the effect is small, and if it is 10% by weight or more, the driving voltage becomes high, and it cannot be driven by a normal nonlinear element.

As the dichroic dye, azo type, anthraquinone type, naphthoquinone type, which are commonly used for GH,
Perylene type, quinophthalone type, azomethine type and the like are preferably used. Among them, from the viewpoint of light resistance, the anthraquinone type alone or a mixture with other dyes as necessary is particularly preferable. These dichroic dyes are mixed and used depending on the required color.

The polymer precursor may be any one as long as it exhibits a refractive index anisotropy after polymerization and exhibits alignment dispersion with a liquid crystal, but an ultraviolet-curable monomer is preferable from the viewpoint of ease of manufacturing a liquid crystal display device. As the UV-curable monomer, monofunctional methacrylate, bifunctional methacrylate or polyfunctional methacrylate is preferably used. In order to improve the degree of scattering, it is desirable that these monomers contain at least one benzene ring in their molecular structure. These monomers may contain a chiral component. Moreover, these monomers may be polymerized by irradiating with ultraviolet rays after they are used alone or mixed with other monomers.

In this embodiment, other than the MIM element, a lateral MIM element, a back-to-back MIM element, an MSI element, a diode ring element, a varistor element, etc. can be used as the two-terminal nonlinear element. Further, in this embodiment, the light-shielding layer and the reflective electrode layer are arranged on the MIM counter substrate, but the configuration of this embodiment is particularly preferable from the viewpoint of manufacturing simplicity. Furthermore, the configuration of the present invention has exactly the same effect even in the simple matrix system.

[0049]

As described above, according to the constitution of the liquid crystal display device of the present invention, a bright liquid crystal liquid crystal display device without a polarizing plate can be provided.
In particular, it is possible to provide a liquid crystal display device having a significantly improved contrast by suppressing light leakage from between display pixels, which has been a problem in the past, by a simple method of disposing a light shielding layer or a light absorbing layer. It was Furthermore, since the addition amount of the dichroic dye can be reduced by the present invention, a liquid crystal display element having excellent light resistance and reliability can be provided, and
By active matrix driving, it is possible to provide a reflective large-capacity display with good contrast.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display element of Example 1 of the present invention.

FIG. 2 is a sectional view of a liquid crystal display element of Example 2 of the present invention.

FIG. 3 is a sectional view of a liquid crystal display element of Example 3 of the present invention.

[Explanation of symbols]

 101 Substrate 102 MIM Element 103 ITO Pixel Electrode 104 Alignment Film 105 Polymer 106 Liquid Crystal 107 Alignment Film 108 Light Absorption Layer 109 Reflective Electrode 110 Substrate 111 Gap Retainer 201 Substrate 202 ITO Electrode 203 Alignment Film 204 Polymer 205 Liquid Crystal 206 Alignment Film 207 Light absorbing layer 208 Reflective electrode 209 Insulating layer 210 TFT element 211 Substrate 212 Void retaining material 301 Substrate 302 MIM element 303 ITO pixel electrode 304 Alignment film 305 Polymer 306 Liquid crystal 307 Alignment film 308 Reflective electrode 309 Insulating layer 310 Light shielding layer 311 Substrate 312 Void retaining material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G02F 1/139 (72) Inventor Hidehito Iisaka 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson shares In the company

Claims (5)

[Claims] 1. A liquid crystal containing a dichroic dye and a refractive index anisotropy are provided between two substrates, at least one of which has a pixel electrode and a wiring for transmitting an electric signal to the pixel electrode and at least one of which is transparent. In a liquid crystal display element in which the polymers having the orientation are dispersed and sandwiched with each other, the pixel electrodes on the back substrate are formed of a reflective material, and a light absorption treatment is performed between the pixel electrodes. Liquid crystal display device. 2. The liquid crystal display element according to claim 1, wherein the pixel electrode on the back substrate is formed of a reflective material, and a light-shielding process is performed between the pixel electrodes. 3. The liquid crystal display element according to claim 1, wherein a non-linear element is formed on at least one of the substrates. 4. The liquid crystal display element according to claim 1, wherein the non-linear element is a two-terminal element. 5. The liquid crystal display element according to claim 1, wherein the non-linear element is a three-terminal element.