JPH05313147A - Liquid crystal panel and liquid crystal projection type television using the panel - Google Patents

Abstract

PURPOSE:To provide the liquid crystal panel of a high brightness and high contrast display. CONSTITUTION:A thin film 17 is formed of a material having the specific dielectric constant lower than the specific dielectric constant of high-polymer dispersed liquid crystals 15 on a counter electrode 13. The refractive index of the thin film 17 is made to coincide approximately with the ordinary ray refractive index no of the liquid crystals. A refractive index difference n is generated between the polymers and water-drop-like liquid crystals in the liquid crystal layer 15 and the incident light is scattered when a voltage is not impressed to the liquid crystal layer 15. The liquid crystal molecules orient and the refractive index of the liquid crystal layer turns to the ordinary ray refractive index no when several V or higher voltage is impressed to the liquid crystal layer. The incident light, then, advances rectilinearly and is emitted from picture element electrodes 14. Electric lines of force are generated within the liquid crystal layer 15 when 5 to 3V voltage is impressed to the liquid crystal layer 15, but the dielectric constant of the thin film 17 is low and, therefore, the electric lines of force bend near the thin film 17. The liquid crystal molecules orient along the electric lines of force if the electric lines of force have the prescribed intensity or above. The liquid crystal molecules orienting in the horizontal direction of the substrate 11 increase and the refractive index of the liquid crystals 15 increases and the n increases as well if the electric lines of force bend. Then, the scattering performance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projection television for mainly magnifying and projecting an image displayed on a small liquid crystal panel on a screen, and a liquid crystal panel mainly used for the liquid crystal projection television.

[0002]

2. Description of the Related Art Since a liquid crystal panel has many features such as a light weight and a thin shape, research and development have been actively conducted. However, there are many problems such as difficulty in increasing the screen size. Therefore, in recent years, a liquid crystal projection television, which enlarges and projects a display image of a small liquid crystal panel by a projection lens or the like to obtain a large-screen display image, has been suddenly attracting attention. At present, commercially available liquid crystal projection televisions use twisted nematic (hereinafter referred to as TN) liquid crystal panels that utilize the optical rotation characteristics of liquid crystals. An example of a liquid crystal projection television and a liquid crystal panel used for the television is described in, for example, "Flat Color Display '" 91 P194 to P205, published by Nikkei BP.

A conventional liquid crystal panel will be described below. However, the unnecessary parts are omitted in the explanation.
It is drawn as a model to make the drawings easier to see. The above also applies to the subsequent drawings.

FIG. 8 is a sectional view of a conventional liquid crystal panel. The array substrate 72 and the counter electrode substrate 71 are held at a distance of 4 to 6 μm, and the TN liquid crystal 76 is injected between the substrates. The periphery of the display area is sealed with a sealing resin (not shown). Reference numeral 78 is a black matrix formed of chromium or the like, 73 is a counter electrode formed of a transparent material such as ITO, 75 is a pixel electrode, 74 is a thin film transistor (hereinafter referred to as TFT), and 77a and 77b are alignment films.

A conventional method for manufacturing a liquid crystal panel will be described below. First, the array substrate 72 and the counter electrode substrate 71
Alignment films 77a and 77b are applied to the film, and an alignment process is performed by a rubbing process. After that, the sealing resin is applied to the peripheral portion of the array substrate 72 while leaving the injection port of the TN liquid crystal 76. Also, beads for obtaining a uniform liquid crystal film thickness are scattered on the counter electrode substrate 71. Next, the counter electrode substrate 71 and the array substrate 72 are bonded together. After that, irradiate with ultraviolet rays,
Alternatively, the sealing resin is cured by heating. Next, the bonded substrates are put into a vacuum chamber, and the array substrate 72
After the inside of the gap between the counter electrode substrate 71 and
Dip the liquid crystal inlet into the liquid crystal. After that, when the vacuum in the vacuum chamber is broken, the liquid crystal is injected into the gap through the injection port. Finally, the injection port is sealed and completed.

A conventional liquid crystal projection television will be described below with reference to the drawings. FIG. 9 is a configuration diagram of a conventional liquid crystal projection television. In FIG. 9, 81 is a condensing optical system, and 82 is UV that transmits infrared rays and ultraviolet rays.
IR cut mirror, 83a is a blue light reflection dichroic mirror (hereinafter referred to as BDM), 83b is a green light reflection dichroic mirror (hereinafter referred to as GDM), 83c is a red light reflection dichroic mirror (hereinafter referred to as RDM), 84a. , 84b, 84c, 86a, 86b, 86
Reference numeral c is a polarizing plate, 85a, 85b and 85c are transmissive TN liquid crystal panels, and 87a, 87b and 87c are projection lens systems.

The operation of the conventional liquid crystal projection type television will be described below with reference to FIG. 9 (FIG. 9). First, blue light (hereinafter, referred to as B light) of white light emitted from the condensing optical system 81 is reflected by the BDM 83a, and this B light is incident on the polarizing plate 84a. The light transmitted through the BDM 83a is GD
The M83b reflects green light (hereinafter, referred to as G light) to the polarizing plate 84b, and the RDM 83c reflects red light (hereinafter, referred to as R light) to be incident on the polarizing plate 84c. The polarizing plate 84 transmits only one of the longitudinal wave component and the transverse wave component of each color light, aligns the polarization direction of the light, and irradiates each liquid crystal panel 85. At this time, 50% or more of the light is absorbed by the polarizing plate, and the transmitted light becomes half or less of the incident light.

Each liquid crystal panel modulates the incident light according to a video signal. The modulated light passes through the polarizing plates 86a, 86b, 86c according to the degree of modulation, and the projection lens system 8
It is incident on 7a, 87b, and 87c, and is enlarged and projected on a screen (not shown) by the lens system.

[0009]

As is apparent from the above description, in a liquid crystal panel using TN liquid crystal, it is necessary to make linearly polarized light incident. Therefore, it is necessary to dispose polarizing plates before and after the liquid crystal panel. Theoretically, this polarizing plate absorbs 50% or more of light. Therefore,
When enlarged and reflected on the screen, there is a problem that only a low brightness screen can be obtained. In order to solve this problem, a polymer dispersed liquid crystal is used in the present invention. A liquid crystal panel using polymer-dispersed liquid crystal does not use a polarizing plate, and thus the light utilization efficiency can be made very high. Further, a rubbing process or the like is unnecessary.

The polymer dispersed liquid crystal will be briefly described below. Polymer dispersed liquid crystals are roughly classified into two types depending on the dispersion state of liquid crystals and polymers. One is a type in which liquid crystals in the form of water droplets are dispersed in a polymer. The liquid crystal exists in the polymer in a discontinuous state. Hereinafter, such a liquid crystal will be referred to as a PDLC, and a liquid crystal panel using the liquid crystal will be referred to as a PD liquid crystal panel. The other is a type that has a structure in which a polymer network is stretched around the liquid crystal layer. It looks like a sponge containing liquid crystal. The liquid crystal does not form a water drop but continuously exists. Hereinafter, such a liquid crystal is called PNLC, and
A liquid crystal panel using the liquid crystal is called a PN liquid crystal panel.
In order to display an image with the above-mentioned two types of liquid crystal panels, light scattering and transmission are controlled.

PDLC utilizes the property that the refractive index is different in the direction in which the liquid crystal is aligned. When no voltage is applied, each water droplet liquid crystal is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer and the liquid crystal, and incident light is scattered. When a voltage is applied here, the alignment directions of the liquid crystal are aligned. If the refractive index when the liquid crystal is oriented in a certain direction is matched with the refractive index of the polymer in advance, incident light is transmitted without being scattered.

On the other hand, PNLC uses the alignment irregularity of liquid crystal molecules. The incident light is scattered in the irregular alignment state, that is, in the state where no voltage is applied.
On the other hand, when a voltage is applied and the arrangement state is made regular, light is transmitted. The above description of the movement of the liquid crystal of PDLC and PNLC is merely a model idea. Although the present invention is not limited to one of the PD liquid crystal panel and the PN liquid crystal panel, it is not limited to the PD liquid crystal panel for ease of explanation.
A liquid crystal panel will be described as an example. Further, PDLC and PNLC are collectively referred to as polymer dispersed liquid crystal, and PD liquid crystal panel and PN liquid crystal panel are collectively referred to as polymer dispersed liquid crystal panel. A liquid containing a liquid crystal to be injected into a polymer dispersed liquid crystal panel is generically called a liquid crystal solution, and a state in which a resin component in the liquid crystal solution is polymerized and cured is called a polymer.

Regarding the operation of the polymer dispersed liquid crystal (see FIG. 10)
A brief description will be given using (a) and (b).

FIGS. 10A and 10B are explanatory views of the operation of the polymer dispersed liquid crystal panel. (Fig. 10 (a) (b))
In FIG. 11, reference numeral 91 is an array substrate, 92 is a pixel electrode, 93 is a counter electrode, 94 is a liquid crystal droplet, 95 is a polymer, and 96 is a counter electrode substrate. A TFT (not shown) or the like is connected to the pixel electrode 92, and a voltage is applied to the pixel electrode by turning the TFT on and off to change the liquid crystal alignment direction on the pixel electrode to modulate light. When no voltage is applied as shown in FIG. 10A, each liquid crystal 9
4 is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer 95 and the liquid crystal 94, and incident light is scattered. Here, when a voltage is applied to the pixel electrode as shown in (FIG. 10B), the directions of the liquid crystals are aligned. If the refractive index when the liquid crystal is aligned in a certain direction is matched with the refractive index of the polymer in advance, the incident light is emitted from the array substrate 91 without being scattered.

When it is attempted to construct a high-quality display panel using polymer-dispersed liquid crystal, the amount of light transmitted in the scattered state is
It is necessary to increase the ratio of the amount of transmitted light in the transmitted state (hereinafter referred to as contrast). If the contrast is low, the gradation display characteristics deteriorate. A liquid crystal projection television needs a contrast of 100 or more. The maximum transmittance of the polymer-dispersed liquid crystal panel is regulated by the light being reflected by the ITO film or the like of the counter electrode, but it is about 80 to 85%. However, the light transmission amount at the time of scattering is also large. In order to increase the contrast, it is necessary to reduce the amount of transmission in the scattered state (hereinafter referred to as scattering transmittance). In order to reduce the amount of transmission in the scattering state, it is necessary to increase the film thickness of the liquid crystal layer, but if the thickness is increased, the applied voltage for setting the transmission state becomes high and the liquid crystal cannot be driven. From the above, the brightness can be increased by using the polymer dispersed liquid crystal,
It was difficult to construct a liquid crystal panel and a liquid crystal projection television with good display quality because the contrast could not be increased.

[0016]

When a TN liquid crystal is used, 50% or more of light is absorbed by a polarizing plate, so that the light utilization rate is low and high-luminance image display cannot be performed. Therefore, in the present invention, a polymer dispersed liquid crystal that does not require a polarizing plate is used.

In the liquid crystal panel of the present invention, a thin film made of a substance having a dielectric constant different from that of the liquid crystal is formed on the electrode surface in contact with the polymer dispersed liquid crystal. As an example, it is formed in a stripe shape. That is, the portions where the films having different dielectric constants are formed and the portions where the films are not formed are alternately arranged. The films having different dielectric constants may be formed only on the surface of the counter electrode, or may be formed on both the counter electrode and the pixel electrode.

The liquid crystal projection television of the present invention is constructed using the liquid crystal panel of the present invention. Originally, polymer-dispersed liquid crystal panels had poor scattering properties. However, in the liquid crystal panel of the present invention, by forming films having different dielectric constants,
At a predetermined voltage or less, a horizontal electric field is generated in the liquid crystal layer, and the scattering characteristic can be improved. At a predetermined voltage or higher, the liquid crystal layer is in the incident light transmitting state. Therefore, the contrast can be significantly improved and a high quality image can be displayed.

[0019]

The scattering property of the polymer-dispersed liquid crystal is poor because the difference Δn in the refractive index between the water-drop liquid crystal and the polymer is small. For the purpose of future description, the extraordinary refractive index n _e of liquid crystal and ordinary refractive index n _o , and the refractive index of polymer are n _p . However, n _o ≈n _p . When no voltage is applied to the liquid crystal layer, the refractive index n _on of the water droplet liquid crystal is n _o . Usually, n _e is from 1.70 to 1.85, n _o is the seek △ n = n _off -n _on from the numerical because it is 1.50-1.60 0.1
It becomes the following.

When the liquid crystal molecules having a positive dielectric constant are aligned parallel to the electrode substrate, the refractive index n _a is (n _o + n _e ) / 2. If this can be set to n _off , Δn≈0.15
The refractive index difference is 0.15 / 0.1 = 150%, that is, 5
It improves by 0%. For that purpose, electric force lines parallel to the electrode substrate must be generated.

In the present invention, a film having a dielectric constant different from that of the liquid crystal is formed on the electrode. For example, a film having a lower dielectric constant than liquid crystal (hereinafter referred to as a low dielectric constant film) is formed on the electrode. The low dielectric constant film is less likely to transmit the lines of electric force than the liquid crystal. Therefore, the lines of electric force generated from one electrode are inclined near the low dielectric constant film. The liquid crystal molecules are aligned along the lines of electric force when the strength of the lines of electric force, that is, the electric field is above a predetermined value. If the lines of electric force are inclined, the liquid crystal molecules are also inclined and aligned. When the liquid crystal molecules are vertically aligned, the apparent refractive index is n _o , and when the liquid crystal molecules are horizontally aligned, the refractive index is (n _e + n _o ) / 2. When the inclination is intermediate, the refractive index is intermediate.

Since the lines of electric force are inclined, the apparent refractive index becomes higher than the random refractive index n _x . Therefore Δn
Becomes larger, the refractive index difference from the refractive index n _{p of the} polymer becomes larger, and the scattering characteristics are improved. When a voltage equal to or higher than a predetermined voltage is applied, a sufficient electric field is applied to the liquid crystal on the low dielectric constant film, and the liquid crystal is vertically aligned. As the electric field becomes stronger, the vertically oriented portion expands. If all are vertically aligned, the total refractive index of the liquid crystal layer is approximately n _on.
= Become regarded as n _o.

[0023] From the above, the refractive index of the liquid crystal layer has a refractive index n _off at a voltage non-application state is n _x, the transverse electric field is generated in the liquid crystal layer As you apply a voltage, the liquid crystal molecules Approaches the refractive index n _a when is oriented parallel to the substrate. Liquid crystal molecules further applying a voltage gradually aligned vertically, the refractive index of the liquid crystal layer becomes n _on = n _o. The scattering characteristic becomes maximum when a predetermined voltage is applied rather than when no voltage is applied. Therefore, it suffices to drive the liquid crystal panel within the voltage range from the maximum scattering characteristics to the minimum scattering characteristics.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal panel of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of one pixel portion of the liquid crystal panel of the present invention. It should be noted that the drawings are drawn as models. For example, the pitch of the low dielectric film 17, the number of manufactured films, the height, etc. are not limited to these. The above also applies to the following drawings.

A pixel electrode 14 made of a transparent material such as ITO, a TFT (not shown) for controlling a signal applied to the pixel electrode, and a source signal line 16 are formed on the array substrate 12.
Etc. are formed. On the other hand, 11 is a counter electrode substrate, and a counter electrode 13 and a low dielectric film 17 are formed on the counter electrode substrate 11. The low dielectric film 17
In the drawings, the rectangular shape is shown, but the shape is not limited to this, and may be a sawtooth shape, a triangular shape, a sine curve shape, a trapezoidal shape, or the like. Further, not only the stripe shape but also a two-dimensional shape such as a dot shape may be used. As an example of the pitch of the low dielectric film 17, 1 μm to 2
The range of 0 μm is preferable. Further, the range of 2 to 10 μm is preferable. The film thickness is preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 0.1 μm to 2 μm.

The material of the low dielectric film 17 is SiOx,
Examples include inorganic substances such as SiNx, TaOx and glass-based substances, materials used as resists, organic substances such as polyimide and acrylic resins. The material is selected according to the refractive index of the polymer of the polymer dispersed liquid crystal layer 15. Ordinary refractive index n _o refractive index of the liquid crystal of each material 1.45 to 1.55, the liquid crystal of the extraordinary refractive index n _e 1.6
5 to 1.80, the refractive index n _{p of the} polymer is 1.45 to 1.80.
The one of 55 is often used. In many cases, n _p ≈n _o . The film thickness of the low dielectric constant film 17 is restricted by the dielectric constant. The film thickness may be smaller as the dielectric constant of the low dielectric constant film 17 is smaller than that of the polymer dispersed liquid crystal 15. If the film thickness of the liquid crystal on the low dielectric constant film 17 is d ₂ , the film thickness of the low dielectric constant film 17 is d ₁ , the dielectric constant of the liquid crystal is ε ₂ , and the dielectric constant of the low dielectric constant film 17 is ε ₁ , then ε _{The value of 2} · d ₁ / (ε ₁ · d ₂ + ε ₂ · d ₁ ) is 1/15 or more, preferably 1/8 or more.

The liquid crystal material used in the liquid crystal panel of the present invention is preferably a nematic liquid crystal, a smectic liquid crystal or a cholesteric liquid crystal, and may be a single or two or more kinds of liquid crystal compounds or a mixture containing a substance other than the liquid crystal compounds. Good. Among the liquid crystal materials described above, a cyanobiphenyl nematic liquid crystal having a relatively large difference between the extraordinary refractive index n _e and the ordinary optical refractive index n _o is most preferable. A transparent polymer is preferable as the polymer matrix material, and the polymer may be any of a thermoplastic resin, a thermosetting resin, and a photocurable resin, but the ease of the manufacturing process, the separation from the liquid crystal phase, etc. From this point, it is preferable to use an ultraviolet curable resin. As a specific example, an ultraviolet-curable acrylic resin is exemplified, and a resin containing an acrylic monomer or an acrylic oligomer that is polymerized and cured by ultraviolet irradiation is particularly preferable.

As such a polymer-forming monomer,
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, neopentyl glycol acrylate, hexanediol diacrylate, diethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol acrylate and the like.

Examples of the oligomer or prepolymer include polyester acrylate, epoxy acrylate and polyurethane acrylate.

A polymerization initiator may be used to accelerate the polymerization, and as an example, 2-hydroxy-2-
Methyl-1-phenylpropan-1-one (“Darocur 1173” manufactured by Merck & Co., Inc.), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-
On (Merck's "Darocur 1116"), 1-vidroxycyclohexyl phenyl ketone (Ciba-Gaiki "Irgacure 184"), benzyl methyl ketal (Ciba-Geigy "Irgacure 651"), etc. are mentioned. In addition, a chain transfer agent, a photosensitizer, a dye, a cross-linking agent or the like can be appropriately used in combination as an optional component.

Although the proportion of the liquid crystal material in the polymer dispersed liquid crystal layer is not specified here, it is generally about 20 to 90% by weight, preferably about 50 to 80% by weight. When it is 20% by weight or less, the amount of liquid crystal drops is small,
The scattering effect is poor. On the other hand, when the content is 90% by weight or less, the polymer and the liquid crystal are more likely to be phase-separated into upper and lower layers, the ratio of the interface is small, and the scattering property is deteriorated. The structure of the polymer-dispersed liquid crystal layer changes depending on the liquid crystal fraction. When the content is about 50% by weight or less, the liquid crystal droplets exist as independent droplets, and when the content is 50% by weight or more, the polymer and the liquid crystal form a continuous layer. ..

The thickness of the liquid crystal 15 is preferably 5 to 25 μm, more preferably 8 to 15 μm. If the film thickness is thin, the scattering characteristics are poor and the contrast cannot be obtained.

When a liquid crystal material having a positive dielectric anisotropy is used, the refractive index n _off of the liquid crystal phase 15 when the liquid crystal is in the off state is generally represented by (2n _o + n _e ) / 3. When the liquid crystal is in the on state, the refractive index of the liquid crystal layer is n _o , so that if n _o = n _p , then n _k = n _p . That is, there is no difference in refractive index between the low dielectric constant film 17 and the liquid crystal layer 15. Therefore, the light incident on the liquid crystal panel goes straight without being refracted or scattered by the low dielectric constant film 17. It is desirable that the difference between the refractive index n _k of the low dielectric constant film 17 and the refractive index n _p of the polymer be within 0.2, and a material within 0.05 should be selected.
From the above examination, as the material for forming the low dielectric constant film 17,
As the current inorganic material, SiO ₂ is considered to be suitable if it can be easily formed and processed in the process. The refractive index of SiO ₂ is usually about 1.45 to 1.50. As a forming method, SiO ₂ may be deposited, a pattern mask may be formed, and etching may be performed. Alternatively, the low dielectric constant film 17 may be directly formed on the glass substrate by using photolithography and dry etching. Further, it is optimal to use the same transparent polymer as that used for the liquid crystal layer 15 as the organic material. Further, a resist material or the like used for usual semiconductor manufacturing can also be used. For example, the negative type resist has a refractive index of 1.5 to 1.55. The relative permittivity of these materials is 3 to 6, and the relative permittivity of liquid crystal is 1
Small compared to 5-30. Therefore, it can be regarded as a low dielectric constant material. As a method of forming the low dielectric constant film 17 using the above materials, it is possible to apply it on the substrate with a roll quarter, a spinner or the like, and polymerize only a necessary portion using a pattern mask. In addition, spin coating a photosensitive resin consisting of polymer + dopant on the substrate,
There is also a method of performing dry development by exposing through a pattern mask and then sublimating the dopant by heating under reduced pressure.

The operation of the liquid crystal panel of the present invention will be described below with reference to (FIG. 2) and (FIG. 3).
(FIG. 2) and (FIG. 3) are explanatory views for explaining the operation of the liquid crystal panel of the present invention. (Figure 2) and (Figure 3)
In the above, 21a, 21b, 31a and 31b are liquid crystal molecules, and 22a, 22b, 32a and 32b are lines of electric force.

FIG. 2 shows the case where a voltage at which the liquid crystal starts to be oriented (hereinafter referred to as an orientation start voltage) is applied to the counter electrode. The alignment start voltage depends on the film thickness of the liquid crystal 15 and the film thickness / pitch of the low dielectric constant film 17, but normally 0 to 3
It is V. When a voltage is applied, lines of electric force are generated in the liquid crystal layer. Note that the lines of electric force reach the pixel electrode 14 from the counter electrode 13 for ease of explanation. Since a voltage drop occurs in the low dielectric constant film 17, the number of lines of electric force passing through the film 17 is small. The lines of electric force are well transmitted through the liquid crystal layer due to the relative permittivity. Therefore, the counter electrode 1
The lines of electric force from 3 extend toward the pixel electrode while extending from between the low dielectric constant films 17. The liquid crystal molecules are aligned in the vector direction of the lines of electric force. Liquid crystal molecules 21 in the central portion between the low dielectric constant films 17
b is oriented vertically and its refractive index is n ₀ . Since the lines of electric force 22a are bent, the liquid crystal molecules 21a are also oriented with an inclination with respect to the normal axis of the electrode substrate. Therefore, its refractive index is an intermediate refractive index between n _x and n _a . From the above, when the alignment start voltage is applied, the refractive index of the liquid crystal as a whole becomes high, and the refractive index difference Δn with the polymer becomes large. From this, the scattering performance is improved.

FIG. 3 shows when a voltage is applied to bring the liquid crystal 15 into a transmissive state. This voltage is called the transmission voltage. The transmission voltage depends on the materials of the liquid crystal and polymer, the mixing ratio, and the liquid crystal film thickness.
Is 70 to 80 and the film thickness is 13 μm, it is 6 to 8V. When a transmission voltage or a voltage near it is applied,
A sufficient electric field is applied to the liquid crystal on the low dielectric constant film 17. That is, as shown by the electric force line 32b, the electric force line extends vertically. Therefore, liquid crystal molecules 31b also aligned vertically, the refractive index becomes n _o.

The liquid crystal panel is driven by applying a voltage in the range of an alignment start voltage and a transmission voltage to the pixel electrode. By applying the orientation start voltage, the scattering characteristics are improved as compared to when no voltage is applied, and therefore the contrast is increased.

(FIG. 4) and (FIG. 5) are explanatory views of a liquid crystal panel in another embodiment of the present invention. The description will be centered on the differences from the first embodiment.

In FIG. 4, the low dielectric constant film 41 is formed also on the pixel electrode 14 side. By forming the low dielectric constant films 17 and 41, the pixel electrode 14 is vertically formed from the counter electrode 13.
The lines of electric force reaching to become difficult to exist. When the orientation start voltage is applied, all lines of electric force bend as shown by lines 42 of electric force in FIG. Therefore, as compared with the first embodiment, more liquid crystal is tilted and aligned. The proportion of liquid crystal molecules that are tilted and aligned increases, the refractive index of the liquid crystal layer 15 approaches n _a = (n _o + n _e ) / 2, and the scattering performance improves.

In FIG. 4, the width of the low dielectric constant film in FIG. 5 is widened. By forming the low dielectric constant film in this way, the locus of the lines of electric force 44 in FIG. 5 becomes long, and the vector component of the lines of electric force in the lateral direction with respect to the substrate increases. Therefore, as compared with (FIG. 4), the refractive index of the liquid crystal layer 15 approaches n _a , and the scattering performance is improved.

Although a thin film having a dielectric constant lower than that of the liquid crystal is formed in this embodiment, it is needless to say that the same effect can be obtained by forming a film having a higher dielectric constant than that of the liquid crystal with the same structure. However, the lines of electric force go straight in the thin film and bend in the liquid crystal layer.

In the present embodiment, the low dielectric constant film forming portion and the ratio forming portion are alternately formed, but the thick film portion and the thin film portion may be alternately formed. The generation state of the lines of electric force is the same as in (FIG. 2).

The liquid crystal projection television of the present invention will be described below with reference to the drawings. FIG. 6 is a configuration diagram of the liquid crystal projection television of the present invention. However, components that are unnecessary for the description are omitted. In FIG. 6, reference numeral 51 denotes a condensing optical system, which uses a concave mirror inside and a xenon lamp which is a good point light source as a light generating means. If the power consumption is 250 W to 1 kW, practically sufficient screen brightness can be obtained. Moreover, the concave mirror is configured to reflect only visible light. 52 is a U that transmits infrared rays and ultraviolet rays and reflects only visible light
It is a VIR cut mirror. Also, 53a is BDM, 5
3b is GDM and 53c is RDM. In addition, BDM5
It goes without saying that the arrangement of 3a to RDM 53c is not limited to the above order, and the last RDM 53c may be replaced by a total reflection mirror.

Reference numerals 54a, 54b and 54c are liquid crystal panels of the present invention. 55a, 55b, 55c, 57a, 57
Reference numerals b and 57c are lenses, and 56a, 56b and 56c are apertures as diaphragms. Note that 55, 56, and 57 form a projection optical system. It is also clear that the aperture is not necessary when the F value of the lens 55 and the like is large, and it is also clear that the projection lens system can be replaced by one lens. The F value of the projection lens type needs to be 8.0 or more.

The projection lens system plays a role of transmitting parallel light rays transmitted through each liquid crystal panel and blocking light scattered by each liquid crystal panel. As a result, high-contrast full-color display can be realized on the screen. Aperture 56
The contrast is improved by decreasing the aperture diameter D of a or increasing the F value of the projection lens. However, the image brightness on the screen is reduced.

The operation of the liquid crystal projection television of the present invention will be described below. Since the R, G, and B light modulation systems have substantially the same operation, the B light modulation system will be described as an example. First, white light is emitted from the condensing optical system 51, and the B light component of the white light is BDM 53.
It is reflected by a. The B light is incident on the polymer dispersed liquid crystal panel 54a. The polymer dispersed liquid crystal panel (see FIG.
As shown in 0 (a) and (b)), the light applied to the pixel electrodes is modulated by controlling the scattering and transmission states of the incident light.

The scattered light is blocked by the aperture 56a, and conversely, the light within a predetermined angle passes through the aperture 56a. The modulated light is enlarged and projected on a screen (not shown) by the projection lens 57a. As described above, the B light component of the image is displayed on the screen. Similarly, the polymer dispersed liquid crystal panel 54b modulates the G light component light, and the polymer dispersed liquid crystal panel 54c modulates the R light component light so that a color image is displayed on the screen. (FIG. 6) can be considered as a simple Schlieren optical system.

In addition to the optical system shown in (FIG. 6), the optical system may be of a reflective type as shown in (FIG. 7).
In FIG. 7, 61 is a liquid crystal panel of the present invention. Light emitted from a light emitting source 65 such as xenon is condensed on a mirror 63 by a lens 64. The condensed light enters the lens 62, and the light illuminates the liquid crystal panel 61. The liquid crystal panel 61 modulates the light and scatters the light in the black display portion.
The incident light is reflected as it is in the portion for displaying white. The scattered or reflected light enters the lens 62 again.
The scattered light is blocked by the mirror 63 and the light blocking plate 66. The straight traveling light is transmitted between the light shielding plate 66 and the mirror 63 and is projected on a screen (not shown) to display an image. In addition, in the drawing, as in the case of the above-described configuration diagram and the like, components unnecessary for the description are omitted. Therefore, in actual construction, a field lens and a projection lens suitable for the projection distance and the projection angle should be arranged.

The projection lens system in (FIG. 6) and (FIG. 7) is not limited to this. For example, a parallel light component is blocked by a light blocking member, and scattered light is projected on the screen. It goes without saying that a system may be used.

Although the liquid crystal projection type television of the present invention is described as a rear type liquid crystal projection type television, the present invention is not limited to this, and a front type liquid crystal projection type for projecting an image on a reflection type screen. It goes without saying that you can use TV. Further, in the liquid crystal projection television of the present embodiment, the color separation is performed by the dichroic mirror, but the present invention is not limited to this. For example, an absorption type color filter may be used to perform the color separation.

Further, in the liquid crystal projection television of the embodiment shown in FIG. 6, one projection lens system is provided for each of the R, G and B light modulation systems, but the present invention is not limited to this. It goes without saying that, for example, the display images modulated by the liquid crystal panel may be combined into one by using a mirror or the like and then projected into one projection lens system. Furthermore, it is not limited to providing three liquid crystal panels that modulate the R, G, and B lights, respectively. For example, a television that projects a picture of the panel by attaching a mosaic color filter to one liquid crystal panel may be used.

[0052]

As described above, since the liquid crystal panel of the present invention uses the polymer-dispersed liquid crystal, it is possible to obtain a high-brightness screen which is more than twice as bright as the liquid crystal panel using the TN liquid crystal. In addition, since a low dielectric constant film is formed in the liquid crystal panel, the amount of straight transmission of light in the off state of the liquid crystal is greatly reduced due to the scattering effect in the liquid crystal layer and the alignment of the liquid crystal due to the horizontal electric field. You can When the liquid crystal is on, there is no difference in the refractive index between the low dielectric constant film and the liquid crystal layer, so that the incident light goes straight without refraction and / or scattering. Therefore, a contrast of 100 or more can be easily achieved, and high-quality image display with very good gradation display characteristics can be realized.

Since the polymer dispersion liquid crystal is used as the liquid crystal, the alignment treatment is unnecessary, so that there is no problem even if there is unevenness such as a low dielectric constant film on the substrate. Moreover, since the low dielectric constant film is formed of a light transmissive material, the aperture ratio of the pixel is not lowered. Further, in the polymer-dispersed liquid crystal panel, the problem of peeling was apt to occur due to the poor adhesion between the liquid crystal layer and the counter electrode. It is possible to improve and eliminate the above-mentioned problems.

In the liquid crystal projection type television of the present invention, since the liquid crystal panel of the present invention is used, it is possible to realize high brightness of image quality and high contrast display, and it is possible to realize high quality image display. Not only can the contrast of the image be greatly improved by the improvement of the scattering performance, but also the problem of peeling between the liquid crystal layer and the counter electrode caused by the heat shock when the power is turned on and off does not occur.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the liquid crystal panel in the embodiment of the present invention.

FIG. 3 is an explanatory diagram of the operation of the liquid crystal panel in the embodiment of the present invention.

FIG. 4 is an explanatory diagram of the operation of the liquid crystal panel in the embodiment of the present invention.

FIG. 5 is an explanatory diagram of the operation of the liquid crystal panel in the embodiment of the present invention.

FIG. 6 is a configuration diagram of a liquid crystal projection television according to an embodiment of the present invention.

FIG. 7 is a configuration diagram of a liquid crystal projection television according to another embodiment of the present invention.

FIG. 8 is a sectional view of a conventional liquid crystal panel.

FIG. 9 is a block diagram of a conventional liquid crystal projection television.

FIG. 10 is an explanatory diagram of the operation of the polymer-dispersed liquid crystal.

[Explanation of symbols]

11 Counter electrode substrate 12 Array substrate 13 Counter electrode 14 Pixel electrode 15 Polymer dispersed liquid crystal 17, 41, 43a, 43b Low dielectric constant film 21a, 21b, 31a, 31b Liquid crystal molecule 22a, 22b, 32a, 32b, 42, 44 Electric Force lines 54a, 54b, 54c, 61 Polymer dispersed liquid crystal panel 56a, 56b, 56c Aperture 62, 64 Lens 63 Mirror 65 Light emission source 66 Light shield plate 76 TN liquid crystal 77a, 77b Alignment film 85a, 85b, 85c TN liquid crystal panel 94 Water drop Liquid crystal 95 polymer

Claims (6)

[Claims] 1. At least one of a first electrode substrate and a second electrode substrate has a light-transmitting property, and a polymer-dispersed liquid crystal is sandwiched between the first and second electrode substrates. First and second
Whether a thin film is formed of a substance having a dielectric constant different from that of the polymer-dispersed liquid crystal on at least one of the electrode substrates and the places where the thin film is formed and the places where the thin film is not formed are alternately repeated. , Or a liquid crystal panel in which portions having different film thicknesses are alternately repeated. 2. At least one of a first electrode substrate and a second electrode substrate has a light-transmitting property, and a polymer-dispersed liquid crystal is sandwiched between the first and second electrode substrates, First and second
A thin film is formed on the electrode substrate of a substance having a dielectric constant different from that of the polymer-dispersed liquid crystal, and a place where the thin film is formed and a place where the thin film is not formed are alternately repeated, or a place where the film thickness is different. Are alternately repeated, and the vertical central axis of the thin film formed on the first substrate and the vertical central axis of the thin film formed on the second substrate are not aligned with each other. LCD panel. 3. The width of a portion where the thin film is formed is wider than the width of a non-formed portion.
The described liquid crystal panel. 4. The liquid crystal panel according to claim 1, wherein the refractive index of the thin film is substantially the same as the apparent refractive index of the polymer dispersed liquid crystal in the transmissive state. 5. The liquid crystal panel according to claim 1 or 2, a light generating means, a first optical element part for guiding the light generated by the light generating means to the liquid crystal panel, and the liquid crystal panel. A liquid crystal projection television, comprising a second optical element component that projects or projects modulated light. 6. An optical image of a liquid crystal panel for modulating blue light,
6. The liquid crystal projection television according to claim 5, wherein the optical image of the liquid crystal panel that modulates the green light and the liquid crystal panel that modulates the red light are projected at the same position on the screen by the composite optical system.