JP3137435B2 - Liquid crystal panel and liquid crystal projection television using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel for use in a liquid crystal projection type television and a liquid crystal projection type television mainly for enlarging and projecting an image displayed on a small liquid crystal panel onto a screen.

[0002]

2. Description of the Related Art A liquid crystal display device is useful because it has many features such as light weight and thinness, and research and development thereof have been active. However, there are many problems such as difficulty in increasing the screen. Therefore, in recent years, a liquid crystal projection television that obtains a large-screen display image by enlarging and projecting a display image of a small liquid crystal panel with a projection lens or the like has been attracting attention. At present, a commercially available liquid crystal projection television uses a twisted nematic (hereinafter referred to as TN) liquid crystal panel utilizing the optical rotation characteristics of liquid crystal.

First, a general liquid crystal panel will be described. FIG. 9 is a plan view of the liquid crystal panel. In FIG.
Reference numeral 91 denotes a glass substrate (hereinafter, referred to as an array substrate) on which a thin film transistor (hereinafter, referred to as a TFT) as a switching element is formed, and 92, a substrate on which a transparent electrode made of ITO or the like is formed (hereinafter, referred to as an opposite substrate) ), 96 is a drive IC (hereinafter, referred to as a gate drive IC) for applying a signal for controlling on / off of a TFT connected to a gate signal line on the array substrate 91, and 95 is a source signal line on the array substrate 91. A drive IC (hereinafter referred to as a source drive IC) for applying a data signal to the device, a polarizing film 93, a sealing resin 94 for sealing a liquid crystal, and a liquid crystal panel is constituted by these components. ing. In the following, the components denoted by the same reference numerals have the same content, the same configuration, or an approximate configuration.

FIG. 10A is a plan view of one pixel portion of a conventional liquid crystal panel. FIG. 10 (b) shows the D-
It is sectional drawing in the D 'line. However, in the drawings, unnecessary portions are omitted for ease of explanation, and the drawings are modeled. The above applies to the following drawings.

In FIGS. 10A and 10B, reference numeral 12 denotes a source signal line, one end of which is connected to a source drive I in FIG.
It is connected to C95. Reference numeral 11 denotes a gate signal line, one end of which is connected to the gate drive IC 96 in FIG. 16 is a first electrode, that is, a pixel electrode made of ITO
Reference numeral 14 denotes the formed array substrate. Reference numeral 13 denotes a TFT forming position. Next, in FIG. 11, 21 is a counter substrate, 111 is a layer made of TN liquid crystal (hereinafter referred to as a TN liquid crystal layer), and its film thickness is about 5 μm. A light-shielding layer (black matrix) 112 is formed on the counter electrode 22, and an alignment film (not shown) made of an organic material such as a polyimide resin is formed on the counter electrode 22 and the pixel electrode 14. . Note that the size of one pixel is about 500 μm to 30 μm.

FIG. 12 is a diagram illustrating the operation of a TN liquid crystal panel, which is a conventional liquid crystal panel. In FIG. 12, 121 is a polarizing plate, 122 is a polarization direction, 123 is a transparent electrode, 124 is a liquid crystal molecule, 125 is a signal source, and 126 is a switch. In the off state of the liquid crystal panel including the above components, incident light is
It rotates 90 degrees and transmits without rotating in the on state. Therefore, if the polarization directions of the two polarizing plates 121 are orthogonal,
In the off state, light is transmitted, and in the on state, light is blocked. However, the opposite is true if the polarization directions are parallel to each other. As described above, the TN liquid crystal panel modulates light to display an image.

Hereinafter, a conventional liquid crystal projection television using the above liquid crystal panel will be described with reference to FIG. Figure
FIG. 13 is a configuration diagram of a conventional liquid crystal projection television. In FIG. 13, 131 is a condensing optical system, 132 is an infrared cut mirror for transmitting infrared light, 133a is a blue light reflecting dichroic mirror (hereinafter referred to as BDM), and 133b is a green light reflecting dichroic mirror (hereinafter referred to as GDM). , 133c are red light reflecting dichroic mirrors (hereinafter referred to as RDMs), 13c
4a, 134b, 134c, 136a, 136b, 136c are polarizing plates, 135a, 13
5b and 135c are transmission type conventional TN liquid crystal panels, 137a and 137
b and 137c are projection lens systems. Note that components unnecessary for the description, such as a field lens, are omitted from the drawings.

A conventional liquid crystal projection television comprising the above-described components will be described below with reference to FIG. 13 regarding the relationship and operation of each component. First, white light emitted from the condensing optical system 131 is converted into blue light (hereinafter, referred to as blue light) by the BDM 133a.
B light) is reflected, and this B light is incident on the polarizing plate 134a. The light transmitted through the BDM 133a reflects the green light (hereinafter referred to as G light) by the GDM 133b to the polarizing plate 134b, and reflects the red light (hereinafter referred to as R light) by the RDM 133c and enters the polarizing plate 134c. You. Each polarizing plate 134
In a, 134b, and 134c, only one of the longitudinal wave component and the transverse wave component of each color light is transmitted, and the liquid crystal panels 135a, 135b, and 135c are irradiated with the polarization direction of the light aligned. At this time, 50%
The above light is absorbed by the polarizing plates 134a, 134b, 134c, and the brightness of the transmitted light is reduced to half or less at the maximum.

Each liquid crystal panel modulates the transmitted light according to a video signal. The modulated light passes through each of the polarizing plates 136a, 136b, and 136c according to the degree of modulation, and the light is projected through each of the projection lens systems 137a, 137.
The light enters the lenses 7b and 137c and is enlarged and projected on a screen (not shown) by the lens system.

[0010]

As is apparent from the above description, the liquid crystal panels 135a, 135b, and 13 using TN liquid crystal are used.
In 5c, linearly polarized light needs to be incident. Therefore, it is necessary to arrange the polarizing plates 134a, 134b, 134c, 136a, 136b, 136c before and after the TN liquid crystal panels 135a, 135b, 135c. The polarizer described above theoretically absorbs more than 50% of the light. Therefore, as a conventional problem, there is a problem that only a low-luminance screen can be obtained when enlarged projection is performed on a screen.

The present invention takes into account the foregoing, ie, T
When N liquid crystal is used, 50% or more of the light is absorbed by the polarizing plate. Therefore, there is a problem that the light utilization rate is low and high-luminance display cannot be performed. The object of the present invention is to provide a liquid crystal panel and a liquid crystal projection television having a high luminance display and a high contrast.

[0012]

In order to achieve the above object, a liquid crystal panel according to the present invention has a structure in which at least one of two opposing substrates is transparent, and the opposing surfaces of the two substrates are opposed to each other. An electrode layer having a light-transmitting property is formed on the substrate; a polymer-dispersed liquid crystal layer is sandwiched between the two substrates;
A plurality of projections are formed on a surface of at least one of the substrates facing the polymer-dispersed liquid crystal layer with an isotropic medium having a light transmitting property, and the liquid crystal between the projections is oriented in a certain direction. And the projections are formed using a polymer material forming a polymer dispersed liquid crystal layer.

In the liquid crystal projection television according to the present invention, at least one of the two opposing substrates is transparent, and an opposing electrode layer is formed on the opposing surfaces of the two substrates. A polymer-dispersed liquid crystal layer sandwiched between the two substrates, and a light-transmitting isotropic surface on at least one of the two substrates facing the polymer-dispersed liquid crystal layer. Forming a plurality of protrusions in a conductive medium, the electrode layer between the protrusions is in contact with the polymer-dispersed liquid crystal layer, and at least the liquid crystal between the protrusions is oriented in a certain direction. A liquid crystal panel, a light generating means, and a projection lens, and a stripe-shaped projection formed in the liquid crystal panel as a first optical element component for guiding the light emitted by the light generating means to the liquid crystal panel. In the direction parallel to and perpendicular to the object Different rates, includes an anamorphic lens having a large curvature the vertical direction. In the liquid crystal projection television of the present invention, at least one of the two opposing substrates is transparent, and an electrode layer having light transmittance is formed on the opposing surfaces of the two substrates,
A polymer-dispersed liquid crystal layer is sandwiched between the two substrates, and at least one of the two substrates has a light-transmitting isotropic surface on a surface facing the polymer-dispersed liquid crystal layer. A plurality of protrusions are formed in a medium, and the electrode layer between the protrusions is in contact with the polymer-dispersed liquid crystal layer, and at least the liquid crystal between the protrusions is oriented in a certain direction. A liquid crystal panel, light generating means, and a projection lens are provided, and as a second optical element component for projecting light modulated by the liquid crystal panel, a modified stop having an aperture diameter different depending on a direction is provided.

At least one of the liquid crystal panels used for red, blue, and green has the pitch or height of the projections of another liquid crystal panel changed.

[0015]

The present inventors have considered using a polymer-dispersed liquid crystal. Since a liquid crystal panel using a polymer-dispersed liquid crystal does not use a polarizing plate, the light use efficiency can be extremely increased.

Hereinafter, the polymer dispersed liquid crystal will be described. Polymer-dispersed liquid crystals are roughly classified into two types depending on the dispersion state of the liquid crystal and the polymer. One is a type in which a liquid crystal in the form of water droplets is dispersed in a polymer. The liquid crystal is
It exists in a discontinuous state in a polymer. Hereinafter, such a liquid crystal is referred to as a PDLC, and a liquid crystal panel using the liquid crystal is referred to as a PD liquid crystal panel. The other type adopts a structure in which a polymer network is stretched around a liquid crystal layer. It looks just like a sponge with liquid crystal. Liquid crystals exist continuously without being in the form of water droplets. Hereinafter, such a liquid crystal is called a PNLC, and a liquid crystal panel using the liquid crystal is called a PN liquid crystal panel. In order to display an image on the two types of liquid crystal panels, scattering and transmission of light are controlled.

The PD liquid crystal panel utilizes the property that the refractive index varies in the direction in which the liquid crystal is oriented. In the state where no voltage is applied, the respective liquid crystal droplets are oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer and the liquid crystal, and the incident light is scattered. Here, when a voltage is applied, the alignment directions of the liquid crystals are aligned. If the refractive index when the liquid crystal is aligned in a certain direction is adjusted in advance to the refractive index of the polymer, incident light is transmitted without being scattered.

On the other hand, a PN liquid crystal panel uses the irregularity of the alignment of liquid crystal molecules. Irregular orientation state,
That is, the incident light is scattered when no voltage is applied. On the other hand, when a voltage is applied to make the arrangement state regular, light is transmitted. The above description of the movement of the liquid crystal of the PD liquid crystal panel and the PN liquid crystal panel is based on a model. Although the present invention is not limited to one of a PD liquid crystal panel and a PN liquid crystal panel, a PD liquid crystal panel will be described as an example for ease of explanation.
The PD liquid crystal panel and the PN liquid crystal panel are collectively referred to as a polymer dispersed liquid crystal panel. Further, liquids containing liquid crystal to be injected into the polymer dispersed liquid crystal panel are collectively referred to as liquid crystal solution or resin, and a state in which the resin component in the liquid crystal solution is polymerized and cured is referred to as polymer.

As the polymer matrix in the polymer-dispersed liquid crystal layer which becomes the liquid crystal layer of such a dispersion type liquid crystal display element, basically, if it is transparent, it can be either a thermoplastic resin or a thermosetting resin. Although not available, UV-curable resins are the simplest, have good performance, and are commonly used. The reason is that the conventional method of manufacturing a TN mode liquid crystal panel can be applied as it is. As a conventional method of manufacturing a liquid crystal panel, first, a predetermined electrode pattern is formed on two upper and lower substrates in advance, and the two substrates are overlapped so that the electrodes face each other. At this time, a spacer having a predetermined size and a uniform particle size is sandwiched between the substrates, and the two substrates are fixed with an epoxy resin sealing material in a state where a gap between the two substrates can be maintained. Next, a manufacturing method of injecting a liquid crystal into the empty cell thus obtained is often used.

In order to manufacture a dispersion type liquid crystal panel by applying this manufacturing method, if the material of the polymer matrix is an ultraviolet-curable resin, particularly an acrylic resin as an example, the monomer can be used before the injection. And / or exists as a relatively low viscosity precursor such as an oligomer, and the blend with the liquid crystal has sufficient fluidity to be injected at room temperature. If a method of forming a polymer-dispersed liquid crystal layer by irradiating light after injection and promoting a curing reaction is used, a dispersion-type liquid crystal panel can be easily formed.

Further, by irradiating the panel with ultraviolet rays after the injection, only the resin causes a polymerization reaction to become a polymer, and only the liquid crystal is phase-separated. Liquid crystal droplets are formed,
On the other hand, when the amount of the liquid crystal is large, the polymer matrix exists in the liquid crystal material in the form of particles or a network, and the liquid crystal is formed so as to form a continuous layer. At this time, the particle size of the liquid crystal droplet,
Alternatively, if the pore diameter of the polymer network is somewhat uniform and the size is not in the range of 0.1 μm to several μm, the light scattering property is poor and the contrast does not increase. For this purpose, the material must be a material that can be cured in a relatively short time, and an ultraviolet curable resin is desirable.

FIG. 14 shows the operation of the polymer dispersed liquid crystal panel.
A brief description will be given using (a) and (b). FIG. 14 (a) (b)
FIG. 4 is an explanatory diagram of the operation of the polymer dispersed liquid crystal panel. Fig. 14
14A and 14B, reference numeral 141 denotes an array substrate, 142 denotes a pixel electrode, 143 denotes a counter electrode, 144 denotes a liquid crystal in the form of droplets, 145 denotes a polymer, and 146 denotes a counter substrate. The pixel electrode 142 has a TFT
And the like, and a voltage is applied to the pixel electrode by turning on and off the TFT, and the direction of liquid crystal alignment on the pixel electrode is changed to modulate light. As shown in FIG. 14A, when no voltage is applied, each of the liquid crystal droplets 144 is oriented in an irregular direction. In this state, a difference in refractive index occurs between the polymer 145 and the liquid crystal, and the incident light is scattered. Here Figure 14
As shown in (b), when a voltage is applied to the pixel electrode, the directions of the liquid crystals are aligned. If the refractive index when the liquid crystal is oriented in a certain direction is adjusted in advance to the refractive index of the polymer, the incident light is emitted from the array substrate 141 without being scattered.

As described above, since the polymer-dispersed liquid crystal panel does not use a polarizing plate, the light use efficiency is high and a display image with extremely high luminance can be obtained. However, when the above-mentioned liquid crystal is used for a liquid crystal panel, there are the following problems.

One is separation of the polymer dispersed liquid crystal layer from the counter electrode or pixel electrode. This occurs because the degree of adhesion between the electrode composed of ITO or the like and the polymer dispersed liquid crystal layer is low. In a liquid crystal projection television, a temperature of 50 to 60 degrees is applied to the liquid crystal panel when a lamp as a light source is turned on, and a room temperature of 10 to 30 degrees when turned off. Therefore, when the power of the liquid crystal projection television is turned on / off, the liquid crystal panel is exposed to a severe condition such as a heat shock test. The above-described peeling occurs due to this heat shock state or the like.

Another is that the scattering characteristics are poor. When this polymer-dispersed liquid crystal panel can be put to practical use as a device, it must be driven at a low voltage and have a sufficient contrast. The characteristic that most affects display performance is this contrast, which can be viewed directly.
A ratio of 30: 1 or more and a projection type of 200: 1 or more are desired, and a value larger than 30: 1 results in insufficient display recognition. To increase the contrast, the transmittance at the black level is kept as small as possible. That is, it is necessary to improve the light scattering characteristics. To improve the light scattering performance of polymer dispersed liquid crystal panels, optimization of the particle size of liquid crystal droplets in the polymer matrix, increase of Δn of liquid crystal material, increase of randomness of liquid crystal molecules in liquid crystal droplets, etc. Can be considered. However, at present, the light scattering characteristics of the polymer-dispersed liquid crystal panel are still low, and have not yet reached the perfect diffusion state, which is an ideal scattering state.

In particular, when used as a projection type display, when a projection lens having an F-number of 4 to 5 which is currently generally used is used, white display and black display when the current polymer dispersed liquid crystal panel is used are used. Brightness ratio is about 50: 1
, Resulting in a display with poor contrast.

Here, a liquid crystal panel using a polymer dispersed liquid crystal
Will be described. Polymer refractive index n_p Same as or
A projection is formed of a light-transmitting material having a refractive index near the
Refractive index n of transmissive material_t And In addition, ordinary refraction of liquid crystal
Rate n_o , The extraordinary light refractive index is n_e And n_p = N_o And
When the liquid crystal layer is in the off state as shown in FIG.
Refractive index n as_x Is the macroscopic refractive index of the polymer
n_p , The refractive index n of the liquid crystal_o And n_e Shows the refractive index
You. However, if the liquid crystal is oriented,
The refractive index is (n_o + N_e ) / 2, a large refractive index
It becomes possible to do. Refractive index n of protrusion_t And n_x
Are different from each other, a difference in refractive index occurs between the two. LCD panel
The light incident on is diffracted by the protrusion, and the component that goes straight
Less. In other words, these protrusions are used as diffraction gratings.
(Hereinafter, protrusions are referred to as diffraction gratings). This means
It means that the scattering state is apparently higher. Fig. 14
When the liquid crystal molecules are in the ON state as shown in FIG.
Follow the direction, n_p = N_o = N_x Becomes Therefore,
n_p = N_t = N_x Becomes This means that the refractive index n of the liquid crystal layer is
_x And the refractive index n of the diffraction grating_t That the refractive index difference of
means. Therefore, no diffraction grating is formed
Since the state is the same, the incident light goes straight as it is. liquid
The refractive index difference between the crystal layer and the polymer and between the liquid crystal layer and the diffraction grating is large.
If it is good, its scattering performance and diffraction efficiency will be large.

The formation of the diffraction grating means that irregularities are formed on the counter electrode or the pixel electrode. This enhances the adhesion between the liquid crystal layer and the electrodes. If a light transmitting material is selected as the material of the diffraction grating, the aperture ratio of the pixel does not decrease.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal panel according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a plan view of one pixel of a liquid crystal panel of one embodiment. However, in order to make the drawing easier to see, the counter electrode substrate and the like are omitted from FIG. As described above, the drawings are modeled. For example, the number, width, shape, and the like of diffraction gratings correspond to this. That is, the present invention is not limited to the number, width, and the like. In particular,
The pixel size is 200 ~ 30μm, the pitch P of the diffraction rotator is 30 ~
2 μm. Therefore, the number of diffraction gratings is usually larger than that shown in FIG. FIG. 1B is a sectional view taken along the line AA ′ of FIG.
It is sectional drawing in a line. FIG. 2A is a cross-sectional view when the opposing substrate 21 is mounted on the array substrate 16 of FIG. 1A, and the polymer dispersed liquid crystal 23 is injected between the substrates. FIG.
(A) shows the gate signal line 11, the source signal line 12, and T
Although the black matrix for FT shielding is omitted, it may be provided on the counter substrate 21. 1A and 1B, reference numeral 15 denotes a protrusion (diffraction grating) formed on the array substrate 16. As the material of the diffraction grating, SiOx, SiNx, Ta
Examples include inorganic substances such as Ox and glass-based substances, and organic substances such as polyimide and acrylic resin. The selection of the material is determined according to the refractive index of the polymer of the polymer dispersed liquid crystal layer 23. The refractive index of each material liquid of the ordinary refractive index n _o
It is 1.45 to 1.55, the liquid crystal of the extraordinary refractive index n _e Is 1.65 to 1.80,
Polymer refractive index n _p Of 1.45 to 1.55 is often used. And n _p = N _o It is often kept.

The permittivity of the diffraction grating is preferably larger than the permittivity in the direction perpendicular to the orientation vector of the liquid crystal to be used, and smaller than the permittivity in parallel. Preferably, the dielectric constant in the direction parallel to the orientation vector of the liquid crystal used is made to match. By doing so, a sufficient electric field can be applied to the liquid crystal layer above the diffraction grating, and the direction of the electric field is also perpendicular to the substrate.

The liquid crystal material used for the liquid crystal panel is preferably a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal, and may be a mixture containing one or more liquid crystal compounds or a substance other than the liquid crystal compound. In addition, among the liquid crystal materials described above, the extraordinary light refractive index n _e
And the ordinary refractive index n _o Most preferred is a cyanobiphenyl-based nematic liquid crystal having a relatively large difference between the two. As the polymer matrix material, a transparent polymer is preferable, and the polymer may be any of a thermoplastic resin, a thermosetting resin, and a photocurable resin. In view of the above, it is preferable to use an ultraviolet curing type resin. As a specific example, an ultraviolet curable acrylic resin is exemplified, and a resin containing an acrylic monomer or acrylic oligomer which is polymerized and cured by irradiation with ultraviolet light 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. Further, a polymerization initiator may be used in order to quickly carry out the polymerization. For example, 2-hydroxy-2-methyl-1-
Phenylpropan-1-one ("Darocur" manufactured by Merck & Co., Ltd.)
1173 "), 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (" Darocur 1116 ", manufactured by Merck), 1-vidroxycyclohexylphenyl ketone (" Irgacure 184 ", manufactured by Ciba-Geigy)
)), Benzyl methyl ketal (“Irgacure 651” manufactured by Ciba Geigy) and the like.

In addition, a chain transfer agent, a photosensitizer, a dye, a crosslinking agent, and the like can be appropriately used as optional components.
A liquid or viscous material obtained by uniformly dissolving a liquid crystal material in the ultraviolet curable compound is injected between two substrates, and then irradiated with ultraviolet light to cure only the ultraviolet curable compound. Only the material undergoes phase separation to form a polymer dispersed liquid crystal layer.

The proportion of the liquid crystal material in the polymer-dispersed liquid crystal layer is not specified here, but is generally preferably about 20 to 90% by weight, and more preferably about 50 to 70% by weight. 20
When the amount is less than% by weight, the amount of liquid crystal droplets is small, and the scattering effect is poor. When the content exceeds 90% by weight, the polymer and the liquid crystal
The tendency to phase-separate into layers is increased, the proportion of interfaces is reduced and light scattering is reduced. The structure of the polymer-dispersed liquid crystal layer changes depending on the liquid crystal fraction. When the amount is less than about 50% by weight, the liquid crystal droplets exist as independent droplets. When the amount exceeds 50% by weight, a continuous phase is formed in which the polymer and the liquid crystal are intertwined. .

For example, when irradiating ultraviolet rays, a magnetic field is applied in a direction parallel to the substrate surface of the panel, and the liquid crystal molecules injected between the two substrates are irradiated with ultraviolet rays while being oriented in the direction of the magnetic field. The molecule is immobilized, and FIG.
As schematically shown in the perspective view of FIG.
The molecules are aligned with their long axes aligned in parallel. At this time, the apparent refractive index of the liquid crystal layer is (n _o + _Ne ) / 2.

Consider the case where a liquid crystal having a positive dielectric anisotropy is used. Refractive indices n _x of the liquid crystal layer 23 when in the OFF state The (n _o + _Ne ) / 2. N _o reverse at the time of the on-state Becomes Therefore, in order to make the diffraction grating appear when the liquid crystal is in the off state and to make the diffraction grating disappear when the liquid crystal is in the on state, the refractive index n _{t of the} diffraction grating is required. = N _o Alternatively, it may be set to a value in the vicinity thereof. That is, the refractive index of the liquid crystal layer when the liquid crystal is off state n _x The (n _o + _Ne ) / 2, so n _t ≠ n _x , And the difference in refractive index in the diffraction grating 15 and the liquid crystal layer 23 Δn = (n _o -N _e ) / 2 occur. The refractive index of the liquid crystal layer when the liquid crystal is turned on reversed n _o Since the n _o
= N _p And n _t = N _p Becomes That is, the diffraction grating 15
And the liquid crystal layer 23 has no refractive index difference.

If it is considered that the liquid crystal molecules 24 are not oriented but oriented in random directions, the liquid crystal layer 23 in the off state is considered.
Index of refraction _nx Is (2n _o + _Ne ) / 3. Diffraction grating
15 the refractive index difference between the liquid crystal layer 23 Δn = (n _e -N _o ) / 3. In comparison with this, the refractive index difference Δn between the diffraction grating 15 and the liquid crystal layer 23 can be larger when the liquid crystal molecules 24 are aligned. That is, the diffraction efficiency can be increased.

Also, the refractive index n _{t of the} diffraction grating And polymer refractive index n _p Is preferably within 0.1.
Furthermore, materials within 0.1 should be selected. From the above examination, as a material for forming a diffraction grating, SiO _2, which can be easily formed and processed in terms of process, as the current inorganic material, is used. Is considered suitable. SiO ₂ Has a refractive index of 1.45 to 1.
It is about 50. Further, as a forming method, SiO ₂ After vapor deposition, a pattern mask may be formed and etched. As the organic material, it is optimal to use the same transparent polymer as that used for the liquid crystal layer 23. As a method for forming a diffraction grating using the above-described materials, application to a substrate using a roll quarter or a spinner or the like, and polymerization of only necessary portions using a pattern mask may be performed. There is also a method in which a photosensitive resin composed of a polymer and a dopant is spin-coated on a substrate, exposed through a pattern mask, and then subjected to dry development by sublimation of the dopant by heating under reduced pressure.

The pitch p and height d of the diffraction grating 15 vary considerably depending on the wavelength λ of the light to be modulated, the refractive index of the liquid crystal layer 23, the light directivity of the optical system, the required diffraction efficiency, and the like.
When no voltage is applied, the emitted light beam is affected by scattering and diffraction. For example, as shown in FIG. 1, when the diffraction grating 15 has a rectangular cross section, the diffraction angle θ and the efficiency η _{0 of the 0th-} order diffracted light are obtained. Is given as follows:

Sin θ = mλ / p (where m is the diffraction order) η ₀ = 0.5 * (1 + cos δ) where δ = 2πΔnd / λ Therefore, the pitch p and the height d are the directivity of light of the optical system,
It should be determined by the diffraction angle θ and the wavelength λ. But,
It often depends on the process conditions for forming the diffraction grating. The pitch t is about 2 μm to 60 μm, and most preferably, 4 μm to 20 μm. Although the shape of the diffraction grating is often sinusoidal or trapezoidal due to the process, there is no problem in its effect if it is designed according to the desired diffraction efficiency and diffraction angle. This is the same for the other embodiments described below.

The thickness of the liquid crystal layer is preferably in the range of 5 μm to 25 μm, and more preferably in the range of 8 μm to 15 μm. This is because when the film thickness exceeds 25 μm, the light incident on the liquid crystal panel is in a completely diffused state and the scattering characteristics are good,
High voltage is required for driving. On the other hand, if the film thickness is less than 5 μm, it can be driven at a low voltage, but the scattering characteristics are poor and the contrast is low.

As another method of aligning the liquid crystal molecules 24, the diffraction grating 15 may be directly rubbed with a cloth or the like by a rubbing treatment or the like as conventionally used in a TN mode liquid crystal. Hereinafter, a second embodiment of the present invention will be described.
The description is limited to the differences from the first embodiment. Therefore, items not described are the same as in the first embodiment. The same applies to the following other embodiments. FIG.
(A) is a sectional view of a liquid crystal panel in a second embodiment of the present invention. In the liquid crystal panel according to the second embodiment, also on the pixel electrode between the projections 35 formed on the pixel electrode 14,
The material constituting the protrusion 35 is formed in a thin film shape. The thickness of this portion is preferably about 200 angstroms to about 1 micron. If the thickness is too large, a voltage drop occurs, and no electric field is applied to the liquid crystal, so that the liquid crystal is not driven. By rubbing the space between the projections 35, the liquid crystal molecules 24 are aligned as schematically shown in the perspective view of FIG.

Hereinafter, a third embodiment of the present invention will be described. FIG. 4A is a plan view of one pixel of the liquid crystal panel of the present invention. On the pixel electrode 14, protrusions 45 are formed at regular intervals in a block shape or a column shape. In the first and second embodiments, since the protrusions were formed in a stripe shape, the incident light was diffracted only one-dimensionally. If the projection is formed as in this embodiment, the incident light is diffracted two-dimensionally. By aligning the liquid crystal as in the first or second embodiment, the effects of scattering and diffraction are further enhanced. FIG. 4B is a cross-sectional view of FIG.
It is sectional drawing in the B 'line.

Hereinafter, a liquid crystal projection television according to the present invention will be described with reference to the drawings. FIG. 5 is a configuration diagram of an embodiment of the liquid crystal projection television according to the present invention. However, components unnecessary for the description are omitted. In FIG. 5, reference numeral 51 denotes a condensing optical system, in which a concave mirror and 25
It has a 0 W metal halide lamp. The concave mirror is configured to reflect only visible light. Further, an ultraviolet cut filter is disposed at the emission end of the light collecting optical system 51. An infrared cut mirror 52 transmits infrared light and reflects only visible light. However, it goes without saying that the infrared cut mirror 52 may be arranged inside the condensing optical system 51. 53a is BDM, 53b is GD
M and 53c are RDMs. It should be noted that, from BDM53a to RDM
The arrangement of 53c is not limited to the above-mentioned order, and it goes without saying that 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. The height d of the diffraction grating formed in the liquid crystal panel 54c that modulates the R light of the liquid crystal panel is formed to be 0.2 μm to 1.0 μm higher than the height d of the diffraction gratings of the other liquid crystal panels. This is because the degree of diffraction depends on the wavelength of the light to be modulated. Also, if necessary, the height of the diffraction grating of the liquid crystal panel 54a for blue light modulation may be higher than that for green.
It is formed 0.2 μm to 1.0 μm lower. The liquid crystal panel 54c that modulates the R light has a larger droplet-shaped liquid crystal particle diameter or a larger liquid crystal film thickness than other liquid crystal panels. This is because the scattering characteristic decreases as the light becomes longer in wavelength. The particle size of the water-droplet liquid crystal can be controlled by controlling ultraviolet light at the time of polymerization or by changing the material used. The liquid crystal film thickness can be adjusted by changing the diameter of the beads in the liquid crystal layer. 55a, 55b,
55c, 57a, 57b and 57c are lenses, and 56a, 56b and 56c are apertures as apertures. 55, 56
And 57 constitute a projection lens system. The aperture 56 is provided with an FNo. Obviously this is not necessary when is large.

The operation of the liquid crystal projection television according to the present embodiment will be described below. In addition, red (R) green (G), blue (B)
Since the operation of each light modulation system is substantially the same, the modulation system of B light 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 reflected by the BDM 53a. This B light is incident on the polymer dispersed liquid crystal panel 54a. The scattered light is aperture
Conversely, parallel light or light within a predetermined angle passes through the aperture 56a. The modulated light passes through the projection lens 57
The image is enlarged and projected on a screen (not shown) by a. As described above, the B light component of the image is uniformly displayed on the screen. Similarly, the polymer dispersed liquid crystal panel 54b modulates the light of the G light component, and the polymer dispersed liquid crystal panel 54c modulates the light of the R light component, so that a color image is displayed on the screen.

The arrangement of the projection lens system is as follows. First, the polymer dispersed liquid crystal panel 54 of the liquid crystal display device
The distance L between the lens 55 and the lens 55 and the distance between the lens 55 and the aperture 56 are arranged to be substantially equal. The above-described projection lens system plays a role of transmitting parallel rays transmitted through each liquid crystal panel and blocking light scattered by each liquid crystal panel. As a result, a high-contrast full-color display can be realized on the screen. If the aperture diameter D of the aperture is reduced, the contrast is improved. However, the image brightness on the screen decreases.

When the thickness of the liquid crystal layer of the liquid crystal panel of the present invention is 10
In the case of μm to 15 μm, the condensing angle θ of the lens needs to be 8 degrees or less in all angles. Among them, around 6 degrees is optimal, and the contrast is 100: 1 at the center of the screen.
When projected on a 40-inch screen with a rear television, the screen gain was 200 ft-L or more at a screen gain of 5, and a screen luminance equal to or higher than that of a CRT projection television could be obtained. Use a short arc lamp. More specifically, the configuration diagram of FIG. 5 is shown as a perspective view shown in FIG. 6 as an example. In FIG. 6, reference numeral 51 denotes a condensing optical system, 53 denotes a dichroic mirror, 54 denotes a liquid crystal panel of the present invention, 61 and 62 denote lenses, 63 denotes mirrors, and 64a, 64b and 64c denote projection lenses or projection lens systems having apertures. is there.

However, in a polymer dispersed liquid crystal panel having a diffraction grating, the degree of scattering (diffraction) differs depending on the wavefront direction of emitted light. FIG. 7 schematically shows an intensity distribution of light emitted from the liquid crystal panel of the present invention when the panel is OFF. FIG. 7A shows a light intensity distribution of a wavefront in a direction perpendicular to the diffraction grating 15. At this time, the incident light is scattered, diffracted, and emitted. However, FIG.
As shown in (b), the light intensity distribution of the wavefront in the direction parallel to the diffraction grating 15 is not diffracted at all and is only affected by scattering. Thus, there is a difference in the scattering (diffraction) effect in the vibration direction of each light. FIG. 8 shows a second embodiment of the liquid crystal projection television according to the present invention. Before the light enters the panel, anamorphic lenses 88a, 88b and 88c are arranged so that the spread angle of the light has a difference in advance. The light is incident on the panel from above to correct the misdirection of the scattering performance. This correction can also be made by opening the aperture ratios of the apertures 86a, 86b, 86c in different shapes depending on the directions in accordance with the difference in the scattering characteristics of the panels.

The configuration of the liquid crystal panel of the present invention is a TFT panel.
The present invention is not limited to this, and is also effective for a liquid crystal display device using a two-terminal element such as a diode as a switching element.

In FIG. 5 or FIG. 8, the light is incident from the counter substrate side. However, the present invention is not limited to this, and it is apparent that the same effect can be obtained even if the light is incident from the array substrate. . As described above, the liquid crystal panel and the liquid crystal projection television according to the present invention are not affected by the incident direction of light.

In the embodiment of the liquid crystal projection television according to the present invention, the rear liquid crystal projection television is described as an example. However, the present invention is not limited to this. Needless to say, it can be a TV. Furthermore, in the liquid crystal projection television of this embodiment, the color separation is performed by the dichroic mirror. However, the present invention is not limited to this. For example, the color separation may be performed using an absorption color filter.

Although the liquid crystal panel of the present invention has been described as a transmissive liquid crystal panel, the present invention is not limited to this, and may be a reflective liquid crystal panel. In that case, the pixel electrode may be a reflective electrode made of a metal material. The diffraction grating is formed on the counter electrode or the reflection electrode.

In the liquid crystal projection television of this embodiment, one projection lens system is provided for each of the R, G, and B light modulation systems. However, the present invention is not limited to this. It is needless to say that the display image modulated by the liquid crystal panel may be combined into one and then may be incident on one projection lens system and projected. Further, a liquid crystal panel for modulating each of R, G, and B lights is provided, but the present invention is not limited to this. For example, a single-panel projection television that attaches a mosaic color filter to one liquid crystal panel and projects the pixels of the panel may be used.

[0056]

As is clear from the above description of the embodiment, since the liquid crystal panel of the present invention uses a polymer-dispersed liquid crystal, it has a luminance twice or more that of a liquid crystal panel using a TN liquid crystal. You can get the screen. Further, a diffraction grating is formed in the liquid crystal panel, and when the liquid crystal is in the ON state, there is almost no difference in the refractive index from the liquid crystal layer 23, so that no diffraction grating is formed. Therefore, the light incident on the liquid crystal panel goes straight without being diffracted. Conversely, when the liquid crystal is in the off state, a difference in refractive index occurs between the liquid crystal layer 23 and the diffraction grating, and the diffraction grating functions. Therefore, light incident on the liquid crystal panel is diffracted. This means that the amount of light traveling straight is reduced. The contrast of the liquid crystal panel is greatly improved by the above-described diffraction effect.

Further, since the diffraction grating is formed of a light transmitting material, the aperture ratio of the pixel does not decrease. According to the present invention, the apparent refractive index can be increased by previously aligning the liquid crystal molecules in the polymer dispersed liquid crystal layer 23, and the refractive index difference between the liquid crystal and the polymer and between the liquid crystal and the diffraction grating can be increased. . This improves the scattering characteristics and the diffraction efficiency, respectively.

When the above-described liquid crystal panel of the present invention is used for the liquid crystal projection television of the present invention, the effect is remarkable. The contrast of the image can be greatly improved by the light diffraction effect. Further, in the present invention, by using the anamorphic lens and the modified stop, it is possible to obtain a uniform screen brightness and a uniform contrast ratio. In addition, a bright display can be obtained because the light use efficiency is improved. Further, in the present invention, the contrast of the entire image can be significantly improved by changing the height of the diffraction grating, the thickness of the liquid crystal layer, or the diameter of the liquid crystal droplets of the liquid crystal panel mainly for the R panel from other panels. it can.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of a first embodiment of a liquid crystal panel of the present invention.

FIG. 2 is a sectional view and a perspective view of a first embodiment of the liquid crystal panel of the present invention.

FIG. 3 is a sectional view and a perspective view of a second embodiment of the liquid crystal panel of the present invention.

FIG. 4 is a plan view and a sectional view of a third embodiment of the liquid crystal panel of the present invention.

FIG. 5 is a configuration diagram of a first embodiment of a liquid crystal projection television according to the present invention.

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

FIG. 7 is an intensity distribution diagram of light emitted from the liquid crystal panel of the present invention.

FIG. 8 is a configuration diagram of a liquid crystal projection television according to a second embodiment of the present invention.

FIG. 9 is a plan view of a conventional liquid crystal panel.

FIG. 10 is a plan view and a sectional view of a conventional liquid crystal panel.

FIG. 11 is a sectional view of a conventional liquid crystal panel.

FIG. 12 is a diagram illustrating the operation of a TN liquid crystal panel.

FIG. 13 is a configuration diagram of a conventional liquid crystal projection television.

FIG. 14 is a diagram illustrating the operation of a polymer dispersed liquid crystal panel.

[Explanation of symbols]

 11 Gate signal line 12 Source signal line 13 TFT formation position 14 Pixel electrode 15 Protrusion 16 Array substrate 21 Counter substrate 22 Counter electrode 23 Polymer dispersed liquid crystal layer 24 Liquid crystal molecules 51 Condensing optical system

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-86731 (JP, A) JP-A-63-137211 (JP, A) JP-A-4-232917 (JP, A) JP-A-3-3 23422 (JP, A) JP-A-62-235924 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1334 H04N 5/66 102 H04N 5/74 G02F 1/13 505

Claims (3)

(57) [Claims] At least one of two opposing substrates is provided.
One of the substrates is transparent, and the opposite surface of the two substrates is
An electrode layer having a light-transmitting property is formed between the two substrates.
A polymer dispersed liquid crystal layer is sandwiched between the two substrates.
At least on one of the substrates,
On the opposite surface, a plurality of projections made of an isotropic medium having optical transparency
And the liquid crystal between the protrusions is oriented in a certain direction.
And the protrusions form a polymer dispersed liquid crystal layer.
A liquid crystal panel characterized by being formed using a polymer material . 2. The method according to claim 1, wherein at least one of the two opposing substrates is provided.
One of the substrates is transparent, and the opposite surface of the two substrates is
An electrode layer having a light-transmitting property is formed between the two substrates.
A polymer dispersed liquid crystal layer is sandwiched between the two substrates.
At least on one of the substrates,
On the opposite surface, a plurality of projections made of an isotropic medium having optical transparency
And the electrode layer between the protrusions is the polymer dispersion.
And at least between the projections
A liquid crystal panel characterized in that the liquid crystal is oriented in a certain direction.
A light source, a light generating means, and a projection lens.
First optics for guiding light emitted by the generating means to the liquid crystal panel
Stripes formed in liquid crystal panels as element parts
The curvature is different in the direction parallel to and perpendicular to the shape of the projection,
Anamorphic curves with greater curvature in the vertical direction
A liquid crystal projection television , comprising a lens . 3. At least one of two opposing substrates.
One of the substrates is transparent, and the opposite surface of the two substrates is
An electrode layer having a light-transmitting property is formed between the two substrates.
A polymer dispersed liquid crystal layer is sandwiched between the two substrates.
At least on one of the substrates,
On the opposite surface, a plurality of projections made of an isotropic medium having optical transparency
And the electrode layer between the protrusions is the polymer dispersion.
And at least between the projections
A liquid crystal panel characterized in that the liquid crystal is oriented in a certain direction.
A liquid generating means, a light generating means, and a projection lens.
Optical element component for projecting light modulated by crystal panel
As an aperture stop with a different aperture diameter depending on the direction
Liquid-crystal projection TV, characterized in that that.