JPH0980428A - Liquid crystal display device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display which is bright and does not require a back light by forming interference filters consisting of multiple layers of metallic compd. thin-film layers on electrodes as optical thin films and utilizing the interference colors of these thin films in effecting coloration. SOLUTION: A light controllable layer 8 consisting of a high polymer and liquid crystals held between substrates 1 and 2 is driven by the optical thin films 5, an oriented film 6 and transmission or pixel electrodes 4. This light controllable layer allows the transmission of incident light in the state that an electric field is not applied thereon. The layer scatters the incident light when the electric field is applied thereon. The light controllable layer does not exert any action on the incident light at all when the light controllable layer is combined with the optical thin films. The incident light is mostly absorbed by a light absorber or is reflected by a light reflector in the case the incident light is transmitted through this layer and, therefore, the interference light does not arrive at an observer and an element appears dark. The incident light is scattered by the light controllable layer when the light controllable layer attains the scattering state and, therefore, the light interfered by the optical thin films is again scattered by the light controllable layer and its progressing direction is changed. This light arrives at the observer and the element appears colored.

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 device and electronic equipment equipped with the liquid crystal display device. More specifically, the present invention relates to electronic devices such as liquid crystal projectors and liquid crystal displays.

[0002]

2. Description of the Related Art Conventionally, a so-called polymer dispersion type liquid crystal display device has been developed in which a liquid crystal and a polymer are combined and light scattering is used as an electro-optical element which does not use a polarizing plate (US Patent No. 3600060, NO). .4435047,
NO. 4688900, NO. 4891152, NO.
4994204, NO. 5188760). US Patent No. 4435047, NO. 3600060, N
O. 4688900, NO. The polymer-dispersed liquid crystal display device disclosed in U.S. Pat. No. 4,891,152 has a configuration in which liquid crystal molecules are sandwiched between liquid crystal droplets formed of a polymer, and the liquid crystal droplets are arranged in the polymer. In such a liquid crystal display device, since liquid crystal molecules are randomly arranged on the surface of the sphere of the liquid crystal droplets, the liquid crystal droplets surrounded by the polymer scatter light when no electric field is applied, and thus white display is performed. can get. Then, when an electric field is applied, the liquid crystals in the liquid crystal droplets are aligned in the direction of the electric field, so that the liquid crystal becomes transparent. Since black paper, plate, etc. are arranged on the back surface of the liquid crystal display device, a black display is obtained in a transparent state, and a display with contrast can be obtained (hereinafter, such a mode of the liquid crystal display device will be referred to as a normal mode). Called).

However, in this display mode, the liquid crystal molecules located near the surface of the sphere made of a polymer in the liquid crystal droplet cannot be easily aligned in the electric field direction due to the influence of the polymer, and some scattering occurs. As a result, there was a problem that a good transparent state could not be obtained unless a very high voltage was applied.

Also, US Pat. 4994204,
NO. In the polymer-dispersed liquid crystal display device disclosed in 5188760 and the like, when the electric field is applied, the refractive index of the polymer matrix and the refractive index of the liquid crystal substantially match, so that the element scatters light and a white display is obtained. When no electric field is applied, it becomes transparent and the black paper, plate, etc. behind the element can be seen, and thus a display can be obtained.

However, since this liquid crystal display device scatters only the polarized light in a specific direction, it is necessary to increase the thickness of the liquid crystal cell in order to improve the scattering degree and the white turbidity. There was a problem that the drive voltage increased.

Also, US Pat. 5384067,
NO. In the elements disclosed in Japanese Patent No. 52008845 and Japanese Patent Publication No. 6-507505, the liquid crystal layer itself having a spiral structure has the property of selective reflection. However, since this spiral structure changes with temperature, the ambient temperature When it changes, there is a problem that the wavelength of light that is selectively reflected changes, and the display color changes.

[0007]

The liquid crystal display device of the present invention has been made in order to solve the above problems and has the following features.

In a liquid crystal display device in which a dimming layer is sandwiched between a pair of substrates having electrodes on the inner surfaces of opposing substrates, the dimming layer is composed of liquid crystal molecules and polymers, and the polymers are An interference filter formed by being dispersed in a liquid crystal layer composed of the liquid crystal molecules and having a function of reflecting light of a specific wavelength on the electrode formed on the one substrate. Is characterized by.

The interference filter referred to in the present invention is made up of one or a plurality of thin films having a thickness of about the wavelength of light, and the reflected lights from the upper and lower surfaces of the thin film interfere with each other to cause coloring. It refers to the thin film. When the light control layer has no effect on the incident light and transmits the incident light, the incident light is almost absorbed by the light absorbing layer or reflected by the interference filter in a specific direction. Does not reach the observer, and the device looks dark. When the light control layer is in a scattering state, the incident light is scattered by the light control layer, so the light interfered by the interference filter is again scattered by the light control layer and the traveling direction changes to reach the observer, and the element is colored. You can see it. In this way, the dark state and the colored state can be controlled by the electric field applied to the light control layer.

The light control layer scatters light when an electric field is applied between the first transparent electrode layer and the second transparent electrode layer, and transmits light when no electric field is applied. It has the function of

Further, the interference filter has a function of reflecting visible light and absorbing light of a wavelength having a complementary color relationship with the visible light. Full-color display is possible by allocating a portion that selectively reflects green light, a portion that selectively reflects blue light, and a portion that selectively reflects red light to each pixel.

Further, the interference filter has a function of absorbing light having a wavelength of 600 nm or more and reflecting light having a complementary color relationship with the light having a wavelength of 600 nm or more. Therefore, the light scattered by the light control layer and reflected by the interference filter looks white or bluish white, resulting in very good contrast. The wavelength of light that is selectively absorbed is more preferably a wavelength of 630 nm or more.

A color filter is arranged on the first substrate or the second substrate. As described above, a reflective full-color display with good contrast becomes possible by combining a liquid crystal element capable of black-and-white display with good contrast with a color filter.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

 (First Mode) The first mode of the present invention will be described below.

FIG. 1 is a sectional view of a liquid crystal display device according to the first embodiment of the present invention. In the figure, 1 is an upper substrate, 2 is a lower substrate, 3 is an active element, 4 is a pixel electrode, 5 is an interference filter, 6 is an alignment film, 7 is a polymer, 8 is a polymer and a liquid crystal, which are aligned and dispersed with each other. A light control layer (hereinafter, referred to as a light control layer) 9 is a light absorption layer. The light control layer is in a light transmitting state when no voltage is applied, and the interference filter 5 does not act except when forming a specific angle with the light source. Therefore, the light is absorbed by the rear light absorbing layer 9 and thus appears black. When an electric field is applied, incident light is scattered by the light control layer, so that light of a specific wavelength is selectively reflected by the interference filter, and the light of a specific wavelength appears to be colored.

This liquid crystal display device was prepared as follows. A TFT element and a pixel electrode were formed on a substrate by a usual method, and an interference filter (laminated metal thin film) formed on the pixel electrode was formed as follows. First, ITO was formed on a glass substrate as a pixel electrode by 2000Å vapor deposition. MgF2 1090Å, Ta2 on ITO element electrode
O5 was formed by vapor deposition at 680Å.

Next, after the substrate is laminated with a counter substrate so as to have a gap of 6 μm and subjected to an alignment treatment, a mixture of a nematic liquid crystal (E8, manufactured by Merck & Co.) and an ultraviolet curable resin (E
8: UV curable resin = 75 parts by weight: 25 parts by weight) is vacuum-sealed, and the ultraviolet curable resin is cured by irradiating with ultraviolet rays at 2000 mJ / cm2, and the polymer (polymer layer) and liquid crystal molecules (liquid crystal layer) are separated. A liquid crystal display device (also referred to as a liquid crystal display device or a liquid crystal cell) having an aligned light control layer was formed. Further, the interference filter absorbs light of 600 nm or more,
Light having a wavelength of 600 nm or more could be irradiated from above and below the filter so as to reflect light having a complementary color relationship with m light. The obtained liquid crystal display device was almost black because light was absorbed by the light absorption layer 9 when no voltage was applied, and when a voltage was applied, a pale display was obtained due to selective reflection of the interference filter. The transmittance curve when voltage is applied is shown in FIG. 2, and the relationship between voltage and reflectance is shown in FIG. The contrast is 1:14
Met.

In this embodiment, the interference filter is 60
It has a property of absorbing light of 0 nm or more and reflecting light having a complementary color to it, but it is not particularly limited to this, and an appropriate material may be used so as to reflect light having a predetermined wavelength. The film thickness can be set.

Compounds that can be used in the interference filter are TiO2, ZnS, CeO2, ZrO2, Sb2O.
3, Nd2O3, SiO, CeF, Al2O3, HfO
2, LiF, MgF2, Ta2O3, MgO2 and the like. The wavelength to be reflected (and the wavelength to be transmitted) can be set by changing the film thickness of each material.

The light absorption layer may be formed between the transparent electrode layer of the lower substrate and the interference filter.

(Modification 1) A modification of the above-described first embodiment is shown below.

In this example, the MIM which is a two-terminal element
The device was formed on the lower substrate. The MIM element and the interference filter (or referred to as a laminated metal thin film) were formed as follows.
First, 1090Å MgF2 and Ta2O5 on the pixel electrode.
Were formed by vapor deposition. Next, ITO was formed on the glass substrate as a counter electrode by 2000Å vapor deposition. Further, an ITO film was formed in stripes on the opposing substrate. A liquid crystal display device was produced in exactly the same manner as the first embodiment except the above. The obtained liquid crystal display device was almost black because light was absorbed by the light absorber when no voltage was applied, and when a voltage was applied, a pale display was obtained due to selective reflection of the interference filter. The transmittance curve when a voltage is applied is shown in FIG. 2, and the relationship between voltage and reflectance is shown in FIG. The contrast was 1:14. The transmittance curve when a voltage is applied is shown in FIG. The contrast was 1:10.

When used as a reflection type liquid crystal display device,
It is also possible to form the pixel electrode connected to the MIM element with a material having a reflection characteristic such as Cr.

(Modification 2) Another modification of the first embodiment of the present invention will be described below. In this example, in order to enable color display, red (hereinafter, R), green (hereinafter, G), and blue (hereinafter, B) light is selectively reflected and is complementary to the R, G, and B lights. An interference filter that absorbs light having a relationship of is used.

FIG. 4 is a sectional view of a substrate having an interference filter of this example. In FIG. 4, 10 is a lower substrate, and 11
Is a transparent electrode, and the substrate on which 12, 13, and 14 are shown is an interference filter, of which 12 is a portion for selectively reflecting red, 13 is a portion for selectively reflecting blue, and 14 is for selectively reflecting green. The part is. In this example, an element substrate having TFT elements was prepared in the same manner as in the first embodiment of the present invention. The counter substrate was a counter substrate having ITO formed on the entire surface, and an optical thin film made of an organic material was further formed. A photocurable resin DMP-128 (manufactured by Polaroid Co., Ltd.) was applied onto the counter substrate by spin coating so that the film thickness was about 2 μm. After that, in order to form this photo-curable resin (optical thin film) as a mosaic interference filter (color filter), R is a light having a wavelength of 600 to 700 nm, and G is a light at a desired location of R, G, and B. Wavelength 500
˜600 nm of light and B of 400 to 500 nm in wavelength were irradiated from above and below the substrate to cure the photocurable resin. R,
Except for the portions corresponding to G and B, a liquid crystal display device was prepared in the same manner as in the first embodiment to obtain a direct-view liquid crystal display device.

When an electric field is applied to the liquid crystal panel having the color-colored portion thus obtained, the applied portion is in a colored display state. When no electric field is applied, it looks black except in a specific positional relationship between the light source and the liquid crystal panel.

In the description, a liquid crystal display device having a TFT element is shown as an example, but an active element such as MIM can be used.

(Modification 3) This example is an example in which a color filter is arranged on one of the substrates in order to perform color display more clearly in the first embodiment, the modification 1, or the modification 2. . As shown in FIG. 5, 1
The portions indicated by 5, 16 and 17 are color filters, of which 15 is a portion that transmits red, 16 is a portion that transmits blue, and 17 is a portion that transmits green. The substrate facing the substrate on which the color filter was formed had the same structure as that of the first embodiment, and the interference filter was arranged on the pixel electrode of the substrate on which the active element such as the TFT element was formed.

The color filter has R, R
A color filter having G and B color tones was prepared by a so-called pigment dispersion method. In this way, a liquid crystal display device was produced similarly to the first embodiment. In the liquid crystal display device thus obtained, the portion to which the electric field is applied becomes the colored display portion, and the portion to which the electric field is not applied looks black regardless of the positional relationship with the light source.

By changing the characteristics of the interference filter for each pixel electrode, a clear image can be displayed.

(Second Mode) In this example, an example applied to a projector is shown. FIG. 8 shows a simple cross-sectional view when applied to a projector. In the figure, 101 is a liquid crystal display device (liquid crystal panel) in which an interference filter for selectively reflecting a red wavelength component is arranged on a pixel electrode, and 102 is a liquid crystal display device in which an interference filter for selectively reflecting a blue wavelength component is arranged on a pixel electrode. (Liquid crystal panel), 103 is a liquid crystal display device in which an interference filter for selectively reflecting the green wavelength component is arranged,
104 is a dichroic mirror, 105 is a light source, 106
Is a projection lens system.

The liquid crystal display device used in this example can have the above-mentioned structure or the structure of the liquid crystal display device of the present embodiment or later. Further, the interference filter may be formed for each pixel electrode, or may be formed over the front surface of the substrate as shown in FIG. In this example, the interference filter was created as follows.

That is, the silicone resin (TL3951
L, Wacker-Chemi) with 0.2 wt% of a polymerization initiator (Irgacrere 907, Ciba Ge).
(manufactured by Igy) was mixed, and a film was coated on the glass substrate by spin coating. Next, through a mask in which only the portion desired to be the R color filter was exposed to ultraviolet rays, 15 mW of ultraviolet rays were irradiated for 5 minutes at 25 ° C. to cure the R portion. Similarly, the G part is 76 ° C, and the B part is 105 ° C.
By irradiating with ultraviolet light at ℃, each of the RGB interference filters (color filter portion) was created.

The method of producing the interference filter may be the same as that of the modification 2 and is not limited to this embodiment.

When no electric field is applied to any of the liquid crystal display devices 101, 102 and 103, R, G,
Since all the light of B passes through the projection lens system 106, white is displayed. When an electric field is applied to the liquid crystal panel 101 having an interference filter that selectively reflects the red wavelength component, a difference in refractive index occurs between the liquid crystal and the polymer, and the liquid crystal panel 101 becomes cloudy. descend.
Therefore, the component of the light passing through the projection lens system 106 is blue,
Green is increased and cyan is displayed. Similarly, when an electric field is applied to the liquid crystal panel 102, yellow is displayed on the liquid crystal panel 1.
03 when an electric field is applied to the liquid crystal panel, magenta when the electric field is applied to the liquid crystal panels 101 and 102, red when the electric field is applied to the liquid crystal panels 102 and 103, and red when the electric field is applied to the liquid crystal panels 102 and 103. When an electric field is applied to and 103, blue is displayed respectively. As is apparent from FIG. 3, gradation display is possible by adjusting the applied voltage.

(Third Mode) In this example, an example applied to a wristwatch is shown. FIG. 9 shows a simple sectional view of an example applied to a wristwatch. In the figure, 90 is an interference filter, 91 is a dial, 92 is a drive mechanism, 93 is a needle, 94 is a liquid crystal panel,
Reference numeral 95 is a cover glass, and 96 is an outer frame. An interference filter layer was formed on the dial 91 prepared by a conventional method in the same manner as in the first embodiment.

An outline of a method for producing a liquid crystal panel to be used next is shown (not shown). ITO (In
about 2,000 by sputtering dium tin oxide)
After forming the angstrom, patterning was performed to form a transparent electrode so that characters, numbers, etc. could be displayed. Next, polyimide was formed as a liquid crystal alignment film on each of these glass substrates, and a rubbing treatment was performed to form the alignment films. After that, by bonding the periphery of the substrates, the two glass substrates were bonded together so that a liquid crystal-filled space having a gap of 5 μm was formed between the two glass substrates to form an empty panel. The rubbing direction is 270
Set in °.

Next, the liquid crystal and polymer precursor mixture sealed in this liquid crystal sealed space will be described. As liquid crystal, TL-202 (manufactured by Merck) and MJ92786 (manufactured by Merck) were mixed at a ratio of 7: 3 (hereinafter referred to as liquid crystal A) and used.
R1011 (Merck) as a chiral component
0.5% by weight, as dichroic dye M361, SI5
12, and M137 (all manufactured by Mitsui Toatsu Pressure Dye Co., Ltd.)
Were used in a mixture of 1.4% by weight, 1.7% by weight and 0.4% by weight, respectively. Biphenyl methacrylate as a polymer precursor, 7% by weight based on the liquid crystal mixture
Using. After the above components were mixed by heating to form a liquid crystal state, they were vacuum sealed in the liquid crystal sealed space of the empty panel.

The liquid crystalline mixed material enclosed in the liquid crystal display (liquid crystal panel) was twisted rightward from the rubbing axis of the upper substrate to the rubbing axis of the lower substrate in an orientation state of 270 °. Then, while maintaining the panel at 50 ° C, the irradiation intensity is 18 mW /
Irradiation intensity uniformity of ± 3 at cm2 (wavelength 350 nm)
% Of ultraviolet light to polymerize the polymer to precipitate the polymer from the liquid crystalline mixed material, whereby the liquid crystal and the polymer are phase-separated to complete the liquid crystal panel.

The liquid crystal panel thus obtained was combined with the dial having the above-mentioned interference filter, the driving mechanism, the hands, the cover glass, the outer frame, etc. to make a wrist watch. When no electric field is applied to the liquid crystal panel, there is no difference in the refractive index between the liquid crystal and the polymer, so the liquid crystal panel is transparent and a high-quality dial is obtained due to the metallic luster of the interference filter. To be When an electric field was applied to the liquid crystal panel, a difference in refractive index was generated between the liquid crystal and the polymer, so that the part to which the electric field was applied became cloudy and characters, numbers, etc. were displayed. The contrast at this time is 1: 8, which is significantly improved compared to the contrast of 1: 3 without the interference filter.
Visibility is improved.

[0041]

With the above-mentioned structure,
Since the interference filter can reflect light of a predetermined wavelength, a clear image display can be obtained. In addition, it is possible to realize a liquid crystal display device with excellent visibility without reflection of surrounding scenery, ceiling, observer's face, and the like. Further, since there is no reflected light in the scattered state, clear white display is possible.

Further, since it is in the reverse mode, it is possible to realize a display device having an excellent contrast characteristic as compared with the prior art. Further, since the interference filter is arranged between the transparent electrode layer and the alignment film, the distance between the interference filter and the display surface is short, so that double display of the display can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing a transmittance curve of an interference filter that acts on light in a red wavelength range used in the present invention.

FIG. 3 is a diagram showing a relationship between reflectance and applied voltage of the liquid crystal display device according to the present invention.

FIG. 4 is a diagram showing a cross-sectional view of a substrate having an interference filter that selectively reflects RGB light according to the present invention.

FIG. 5 is a diagram showing a cross section of a liquid crystal display device in which an interference filter according to the present invention and a pigment dispersion type color filter are combined.

FIG. 6 is a diagram showing a transmittance curve of an interference filter that acts on light in the blue wavelength range used in the present invention.

FIG. 7 is a diagram showing a transmittance curve of an interference filter that acts on light in the green wavelength range used in the present invention.

FIG. 8 is a diagram showing an embodiment of an electronic device of the invention.

FIG. 9 is a diagram showing an embodiment in which a liquid crystal display device is arranged on a display device according to the present invention.

[Explanation of symbols]

1 Upper Substrate 2 Lower Substrate 3 Active Element 4 Transparent Electrode 5 Interference Filter 6 Alignment Film 7 Polymer 8 Dimmer Layer 9 Alignment Dispersion of Polymer and Liquid Crystal 9 Light Absorption Layer 10 Substrate with Counter Electrode and Color Filter 11 Transparent Electrode 12 Part of interference filter part that selectively reflects red 13 Part of interference filter part that selectively reflects blue 14 Part of interference filter part that selectively reflects green 15 Part of color filter , A part that selectively transmits red 16 a part that selectively transmits blue in the part of the color filter 17 a part that selectively transmits green in the part of the color filter 90 Interference filter 91 Dial 92 Drive mechanism 93 Needle 94 Liquid crystal panel 95 Cover glass 96 Outer frame 101 Liquid crystal panel 10 having interference filter that selectively reflects red wavelength component 10 LCD panel 104 mirrors 105 a light source 106 a projection lens system having an interference filter for selectively reflecting liquid crystal panels 103 Green wavelength component having an interference filter for selectively reflecting blue wavelength component

Front page continuation (72) Inventor Masayuki Yazaki 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Corporation

Claims (12)

[Claims] 1. A liquid crystal display device comprising a dimming layer sandwiched between a pair of substrates each having an electrode on the inner surface of the opposing substrate, wherein the dimming layer is composed of liquid crystal molecules and a polymer. The molecules are formed by being dispersed in a liquid crystal layer composed of the liquid crystal molecules, and an interference filter having a function of reflecting light of a specific wavelength is formed on the electrode formed on the one substrate. And a liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the light control layer exhibits a light transmitting state when no electric field is applied and a light scattering state when an electric field is applied. 3. The liquid crystal display device according to claim 1, wherein the interference filter having different characteristics for reflecting a specific wavelength is formed for each of the pixel electrodes. 4. The liquid crystal display device according to claim 1, wherein the interference filter has a characteristic of reflecting light in a visible light region and absorbing light having a wavelength complementary to visible light. 5. The interference filter has a function of absorbing light having a wavelength of 600 nm or more and reflecting light having a complementary color relationship with the light having a wavelength of 600 nm or more. 2. The liquid crystal display device according to item 2. 6. The liquid crystal display device according to claim 1, wherein a color filter is arranged on the one substrate or the other substrate. 7. The liquid crystal display device according to claim 1, wherein a light absorbing layer is disposed on the back surface of the liquid crystal display device. 8. A liquid crystal display according to claim 1, wherein an active element and a pixel electrode connected to the active element are formed on the one substrate, and an interference filter is formed on the pixel electrode. apparatus. 9. The active element is a TFT or M
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is an IM. 10. An electronic device in which the liquid crystal display device is arranged in a display device. 11. The electronic device according to claim 10, wherein the liquid crystal display device is arranged on a display device having a display function. 12. A light source, a color separation means for separating the light from the light source into light of each color element, a color synthesizing means for synthesizing the color-separated color light, and for projecting the light synthesized by the color synthesizing means. In the electronic device including the projection optical means, the color separation means includes a plurality of liquid crystal display devices, and the liquid crystal display device includes a dimming layer between a pair of substrates having electrodes on the inner surfaces of the opposing substrates. The light control layer is sandwiched, and the light control layer is composed of liquid crystal molecules and a polymer, and the polymer is dispersed and formed in a liquid crystal layer composed of the liquid crystal molecules. Is an active element,
A pixel electrode connected to the active element is formed, an interference filter is formed on the pixel electrode, and the interference filter has a characteristic of reflecting light of a specific wavelength. An electronic device characterized in that an interference filter having different characteristics for reflecting light of a specific wavelength is arranged for each.