JP3058378B2 - 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 projection television for enlarging and projecting an image displayed on a small liquid crystal panel onto a screen, and a liquid crystal panel used for the liquid crystal projection television.

[0002]

2. Description of the Related Art Since liquid crystal panels have many features such as light weight and thinness, research and development 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 enlarges and projects a display image of a small liquid crystal panel with a projection lens or the like and obtains a display image of a large screen has been attracting attention. At present, a commercially available liquid crystal projection type television uses a twisted nematic (hereinafter referred to as TN) liquid crystal panel utilizing the optical rotation characteristics of liquid crystal.

FIG. 12 is an equivalent circuit diagram of a liquid crystal panel.
G1 to Gm are gate signal lines, one ends of which are connected to the gate drive IC 121. S1 to Sn are source signal lines, one end of which is connected to the source drive IC 122. Each pixel has a TFT 123 for applying a signal to a pixel electrode, and an additional capacitor 124 for holding a signal is formed. 125
Is a liquid crystal sandwiched between a pixel electrode and a counter electrode, and can be regarded as a capacitor in an electric circuit.

FIG. 10 is a plan view of one pixel portion of an array substrate on which TFTs and the like are formed. However, parts that are not necessary for the description are omitted, and are drawn as models to make the drawings easier to see. The same applies to the following drawings. In FIG. 10, 101 is a gate signal line,
102 is a source signal line, 103 is a pixel electrode, and 10
Reference numeral 4 denotes a TFT.

FIG. 11 is a sectional view of a conventional liquid crystal panel. The space between the array substrate 112 and the counter electrode substrate 111 on which the counter electrode substrate 115 is formed is held at an interval of 4 to 6 μm, and a TN liquid crystal 113 is injected between the substrates. The periphery of the display area is sealed with a sealing resin (not shown). An alignment film (not shown) is formed on the counter electrode 111 and the pixel electrode 103, and a rubbing process is performed.
The liquid crystal molecules of the liquid crystal layer 113 are aligned.

Hereinafter, a conventional liquid crystal projection television will be described with reference to the drawings. FIG. 13 is a configuration diagram of a conventional liquid crystal projection television. In FIG. 13, 131 is a condensing optical system, 132 is a UVI that transmits infrared rays and ultraviolet rays.
An R-cut mirror 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).
c is a red light reflecting dichroic mirror (hereinafter referred to as RDM), 134a, 134b, 134c, 136a, 1
36b and 136c are polarizing plates, 135a, 135b and 13
5c is a transmissive TN liquid crystal panel, 137a, 137b,
137c is a projection lens system.

The operation of this conventional liquid crystal projection television will be described below with reference to FIG. First, white light emitted from the condensing optical system 131 reflects blue light (hereinafter, referred to as B light) by the BDM 133a, and the B light is incident on the polarizing plate 134a. The light transmitted through the BDM 133a reflects green light (hereinafter referred to as G light) by the GDM 133b, and is reflected by the polarizing plate 134b.
Red light (hereinafter, referred to as R light) is reflected by c and is incident on the polarizing plate 134c. Each polarizing plate transmits only one of the longitudinal wave component or the transverse wave component of each color light, and aligns the polarization direction of the light so that each liquid crystal display panel 135a, 135b, 1
Irradiate 35c. At this time, 50% or more of the light is absorbed by the polarizing plate, and the brightness of the transmitted light is reduced to half or less at the maximum.

Each liquid crystal panel 135a, 135b, 135
c modulates the transmitted light by a video signal. The modulated light is applied to each of the polarizing plates 136a, 136b,
136c, and passes through each projection lens system 137a, 137.
b, 137c and is enlarged and projected on a screen (not shown) by the lens system.

[0009]

As is clear from the above description, in a conventional liquid crystal panel using a TN liquid crystal, it is necessary to make linearly polarized light incident. Therefore, before and after the liquid crystal panel, each of the polarizing plates 134a, 134b, 134c,
136a, 136b, and 136c need to be arranged.
These polarizing plates theoretically absorb 50% or more of the light. Therefore, there is a problem that only a low-luminance screen can be obtained when the image is enlarged and projected on a screen.

An object of the present invention is to provide a liquid crystal panel capable of obtaining a high-luminance screen and a liquid crystal projection television using the same, in consideration of such problems of the conventional liquid crystal liquid crystal projection television. .

[0011]

The liquid crystal panel of the present invention comprises:
Forming a periodic opening in the pixel electrode, generating a potential difference between the pixel electrode and a common electrode formed under the pixel electrode,
The liquid crystal molecules in the liquid crystal layer are aligned along the lines of electric force generated by the potential difference. The strength of the electric lines of force can be adjusted by the voltage applied to the pixel electrode.

A liquid crystal projection television according to the present invention is configured using the liquid crystal panel according to the present invention.

A diffraction grating is generated by forming a periodic refractive index distribution in a liquid crystal layer of a liquid crystal panel. Incident light is diffracted according to the degree of generation of the diffraction grating.

[0014]

The liquid crystal panel of the present invention generates an opening between pixel electrodes and generates lines of electric force between common electrodes. The strength of the electric lines of force is varied by the voltage applied to the pixel. The lines of electric force pass through the liquid crystal layer. In addition, since the lines of electric force are lines of electric force in a direction parallel to the pixel electrode, the liquid crystal molecules are oriented parallel to the pixel electrode. Refractive index of the liquid crystal when oriented parallel to the pixel electrode is the ordinary refractive index of the liquid crystal n _o and extraordinary refractive index _{n e (n o <n e} ) of an average refractive index of value _{n a = (n o + n} e) /
Close to 2. On the other hand, electric lines of force are also generated in the pixel electrode and the counter electrode. Refractive index n _b of the liquid crystal because the electric field lines are perpendicular to the pixel electrode becomes n _o.

If the openings of the pixel electrode are formed periodically,
Since part of the refractive index n _a and n _b are periodically repeated, a diffraction grating. Light incident on the diffraction grating is diffracted according to the diffraction efficiency of the diffraction grating. If the voltage applied to the pixel electrode is changed, the diffraction efficiency also changes, so that the incident light can be modulated according to the voltage applied to the pixel electrode.

In the case of modulating incident light by diffraction, it is not necessary to use linearly polarized light as in a conventional TN liquid crystal panel. Therefore, the light utilization factor is increased, and high-luminance display can be realized.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of an array substrate according to an embodiment of the liquid crystal panel of the present invention. Reference numeral 11 denotes a pixel electrode made of ITO, and the pixel electrode 11 has a stripe-shaped opening 12 formed therein. The pitch of the openings 12 depends on the arc length of the lamp used in the liquid crystal projection television. When a xenon lamp is used as the lamp, the pitch is preferably 30 μm or less.

FIG. 2A is a sectional view taken along the line AA 'in FIG. A common electrode 22 is formed below the pixel electrode 11 with an insulating film 21 interposed therebetween. The common electrode 22 is formed of ITO when the liquid crystal panel is of a transmission type, and is formed of A when the liquid crystal panel is of a reflection type.
It is formed of a metal thin film such as l or Cr. Further, an additional capacitance (refer to a conventional additional capacitor 124) is formed between the common electrode 22 and the pixel electrode 11.

The thickness of the common electrode 22 is 500-2000.
Å, the insulating film 21 is formed of SiO ₂ or SiN _x ,
The film thickness is 500-1500 °, and the film thickness of the pixel electrode 11 is 500-1500 °. Further, alignment films 23a and 23b are formed on the pixel electrode 11 and the counter electrode 115,
The liquid crystal molecules of the liquid crystal layer 113 are aligned. Liquid crystal layer 11
The film thickness of No. 3 is 2 to 5 μm when the liquid crystal panel is a transmission type. Although FIG. 2 shows that there is considerable unevenness,
The actual unevenness is within 0.2 μm, and the alignment treatment of the alignment film 23 can be favorably formed.

The liquid crystal of the liquid crystal layer is a nematic liquid crystal having positive dielectric is used, if the orientation between the pixel electrode 11 and the counter electrode 115, the incident light, shows the ordinary refractive index n _o, (hereinafter, the refractive It referred to as rate n _a), when oriented in the average to the pixel electrodes 11, showing a refractive index n _b of the average value of the extraordinary refractive index n _e and ordinary index n _o.

The liquid crystal panel of the present invention generates a line of electric force passing through the liquid crystal layer 113 between the pixel electrode 11 and the common electrode 22 to generate a diffraction grating. Therefore, in order to favorably generate the lines of electric force, it is preferable to remove the insulating film 21 between the openings 12 as shown in FIG. This can be realized relatively easily by performing self-alignment using the pixel electrode 11 formed in a comb electrode shape as a mask.

The voltage applied to the pixel electrode 11 is
Perform in step 4. As the voltage applied to the pixel electrode 11 increases, the lines of electric force passing through the liquid crystal layer 113 increase,
It gets weaker as it gets smaller.

Next, the operation of the liquid crystal panel of this embodiment will be described with reference to FIG. Note that the potential of the counter electrode 115 and the common electrode 22 is set to 0 V for ease of description. When a voltage is applied to the pixel electrode 11 by the TFT 104, the lines of electric force 32 move from the pixel electrode 11 to the counter electrode 115.
C, lines of electric force 32a from the pixel electrode 11 to the common electrode 22;
32b occurs. Liquid crystal molecules 31 along each line of electric force
a, 31b and 31c are oriented. Refractive index for incident light from the liquid crystal molecules 31 aligned vertically n _o, and the liquid crystal molecules 31a, 31b becomes _{n b = (n o + n} e) / 2 of the refractive index. The lines of electric force 32a and 32b exert a strong influence on the portion along the array substrate 112, but since the liquid crystal molecules are elastic, the aligned liquid crystal molecules 31a and 31b
And the alignment state of the liquid crystal molecules 31 a and 31 b is aligned to the liquid crystal molecules near the opposing substrate 111. By the generation of the electric lines of force as described above, a refractive index distribution is generated in the liquid crystal layer 113 as shown in FIG. Portion A is a portion indicating a refractive index close to the refractive index n _o, part of the B is a portion indicating a refractive index close to n _b. Since n _o <n _b , a periodic refractive index distribution is generated in the liquid crystal layer 113, and a diffraction grating is generated. The incident light is bent by the diffraction grating. Since the generation state of the diffraction grating changes depending on the voltage applied to the pixel electrode 11, the diffraction efficiency of the diffraction grating can be changed. The voltage applied to the pixel voltage is 0
When the V without lines of electric force generated, the refractive index across all of the liquid crystal layer 113 throughout is n _b, and the diffraction grating disappears.
As described above, the diffraction grating can be generated or extinguished by the voltage applied to the pixel, so that the incident light can be modulated.

An embodiment of the liquid crystal projection television according to the present invention will be described below with reference to the drawings.

FIG. 4 is a schematic diagram conceptually showing the configuration of a liquid crystal projection television of this embodiment using a schlieren optical system. In FIG. 4, the liquid crystal panel 48 of this embodiment is used as a light valve, a schlieren lens 43 is provided between a schlieren input mask 41 and an output mask 42 having a large number of openings, and the image of the input mask 41 is converted to the output mask 4.
A schlieren optical system having a structure for forming an image on the optical system 2 is formed, and the liquid crystal panel 48 is arranged in the schlieren optical system. The concave mirror 46 was used to increase the light use efficiency. In this embodiment, the schlieren lens 4 is used.
The reference numeral 3 is provided between the input mask 41 and the liquid crystal panel 48, but may be provided between the liquid crystal panel 48 and the output mask 42. In addition, the concave mirror 46 is used to increase the light use efficiency, but need not be provided. In that case, the light source 44
Place a condenser lens in front of the.

The light from the light source 44 is incident on the liquid crystal panel 48 via the input mask 41 of the schlieren optical system and the schlieren lens 43, and the light of the liquid crystal panel 48 is diffracted according to the projected image to open the output mask 42. The image is projected on a screen 45 via a projection lens 47 as light leaking from the pattern.

FIG. 5 is a block diagram of a liquid crystal projection television for explaining the above embodiment more specifically. However, components unnecessary for the description are omitted. In FIG. 5, 51
Denotes a condensing optical system, which has a concave mirror and a metal halide lamp or a xenon lamp as light generating means inside. Preferably, the lamp has a short arc as much as possible.
The xenon lamp preferably has an arc length of 2 mm or less. Arc length is 4m for metal halide lamp
m or less. The concave mirror is configured to reflect only visible light. Further, a UVIR cut mirror 52 is arranged at an emission end of the light collecting optical system 51. However, it is needless to say that the UVIR cut mirror 52 may be disposed inside the condensing optical system 51.
53a is BDM, 53b is GDM, 53c is RD
M. Note that the arrangement of the BDM 53a to the RDM 53c is not limited to the above order, and the last RD
M53c may be replaced by a total reflection mirror.

Reference numerals 48a, 48b and 48c are liquid crystal panels of this embodiment. 41a, 41b and 41c are input masks, 42a, 42b and 43c are output masks, 43a,
43b and 43c are schlieren lenses. In addition,
The input mask 41, the schlieren lens 43, and the output mask constitute a schlieren optical system. 47a,
47b and 47c are projection lenses. The F value of the projection lens is selected to be F8 or more, preferably F10 or more.

The operation of the liquid crystal projection television according to this embodiment will be described below. Since the respective modulation systems for red (R), green (G), and blue (B) light are almost the same operation, the modulation system for B light will be described by way of 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 enters the liquid crystal panel 48a through the input mask 41a and the schlieren lens 43a. The liquid crystal panel controls the refractive index of the liquid crystal layer by a signal applied to the pixel electrode, and modulates light. When the diffraction grating disappears, the incident light goes straight, and the straight light is blocked by the output mask 42a. Conversely, when a diffraction grating is formed in the liquid crystal layer, the incident light is diffracted according to the diffraction efficiency and passes through the output mask 42a. I do. The light thus modulated is enlarged and projected on a screen (not shown) by the projection lens 47a. As described above, the B light component of the image is displayed on the screen. Similarly, the liquid crystal panel 48b modulates the light of the G light component, and the liquid crystal panel 48c modulates the light of the R light component, so that a color image is displayed on the screen.

FIG. 6 is a schematic structural view of a liquid crystal projection television according to a second embodiment which is a second embodiment of the present invention. A fly-eye lens 61 is arranged between the light source 44 and the input mask 41. The fly-eye lens 61 is designed and arranged so that a light source image is formed at the opening of the input mask 41 by the lens, and serves to form a minute light source array.
It is desirable to provide a field lens array (not shown) near the input mask 41. Other configurations are the same as those of the first embodiment of the present invention shown in FIG. The liquid crystal panel 48 as a light valve is the liquid crystal panel of the present invention used in the first embodiment. FIG. 7 shows a plan view of the fly-eye lens 61. The fly-eye lens 61 is an aggregate of an array of minute lenses 71, and each of the minute lenses 71 is configured to correspond to each of the openings of the input mask 41. As a result, light emitted from the light source 44 passing through one microlens 71 passes through one opening of the input mask 41 and passes through the schlieren lens 43 and the liquid crystal panel 4.
8 and the output mask 42, and is projected by the projection lens 47. Considering this optical path as one optical system, the F-number is large and the contrast can be high,
Since this optical system is regarded as one system in which many optical systems are gathered, the brightness is not reduced. In other words, the front surface of the pupil is used when the liquid crystal panel 48 is in the transmission state, and the pupil area is effectively reduced by the output mask 42 during diffraction.

Hereinafter, a more specific configuration of the liquid crystal projection television according to the present invention of Embodiment 2 will be described. FIG. 8 is a configuration diagram of a liquid crystal projection television according to the second embodiment of the present invention. As shown in the drawing, the configuration is almost the same as that of FIG. 5 described above, except that a fly-eye lens 61 is provided. In addition, the fly-eye lens 61 and the input mask 41 may be collectively disposed between the condensing optical system 51 and the dichroic mirror 48a. Further, the schlieren lens 43 may be provided between the liquid crystal panel 48 and the output mask 42.

Next, the operation of the liquid crystal projection television of this embodiment will be described. 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 white light B
The light component is reflected by the BDM 53a. The B light enters the liquid crystal panel 48a through the fly-eye lens 61a, the input mask 41a, and the schlieren lens 43a.
The liquid crystal panel 48a controls the diffraction state of the incident light by a signal applied to the pixel electrode, and modulates the light. The diffracted light is blocked by the output mask 42a, and conversely, parallel light or light within a predetermined angle passes through the output mask 42a. The modulated light is screened (not shown) by the projection lens 47a.
The projection is enlarged. As described above, the B light component of the image is displayed on the screen. Similarly, the liquid crystal panel 48b
Modulates the light of the G light component, and the liquid crystal panel 48c
By modulating the light of the light component, a color image is displayed on the screen. As a result, a high-contrast full-color display can be realized on the screen. Aperture opening diameter D
The contrast can be improved by reducing. However, the image brightness on the screen decreases.

The thickness of the liquid crystal layer of the liquid crystal panel of the present invention is 1
At 0 to 15 μm, the contrast is 12 at the center of the screen.
0: 1, and when projected on a 40-inch screen with a rear television, the screen gain was 200 [ft] or more with a screen gain of 5, and a screen luminance equal to or greater than that of a CRT projection television could be obtained. .

The projection lens system in the liquid crystal projection type television of the present invention is not limited to this. For example, a central shielding type optical system that shields parallel light with a light shield and projects scattered light on a screen is used. Needless to say, this may be done.

In the embodiment of the liquid crystal projection television of the present invention, the rear liquid crystal projection television is described as an example. However, the present invention is not limited to this, and the front liquid crystal projection television for projecting an image on a reflection screen is used. Needless to say, it can be a TV.

In the liquid crystal projection television of this embodiment, one projection lens is provided for each of the R, G, and B light modulation systems. However, the present invention is not limited to this. Needless to say, 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, the present invention is not limited to providing a liquid crystal panel for modulating each of R, G, and B lights. For example, a television that attaches a mosaic color filter to one liquid crystal panel and projects an image of the panel may be used.

Furthermore, although the liquid crystal panel of the present invention has been described as a transmission type liquid crystal panel, the present invention is not limited to this, and may be formed as a reflection type liquid crystal panel. In that case, the common electrode may be formed of a metal material and used as a reflective electrode. An example of the projection optical system in this case is the optical system shown in FIG.

Here, the projection light emitted from the projection light source 93 is focused on the mirror 92 by the condenser lens 94.
The condensed light is reflected by the mirror 92 and is
At 5, the light becomes parallel rays and enters the liquid crystal panel of the present invention.
The light incident on the pixel where the diffraction grating is completely generated is diffracted, enlarged by the schlieren lens 95, and projected on the screen 91. The light incident on the pixel where the diffraction grating has completely disappeared is reflected as it is, and is shielded by the 92 mirror / schlieren stop. In the intermediate state between the generation and disappearance of the diffraction grating, light according to the diffraction state is projected on the screen 91.

[0040]

As is apparent from the above description,
In the liquid crystal panel of the present invention, since the incident light is modulated by the generation and extinction of the diffraction grating, it is possible to obtain a high brightness screen twice or more as compared with a liquid crystal panel using a conventional TN liquid crystal using polarized light. .

Further, since the diffraction grating is generated by the voltage without forming the uneven diffraction grating on the surface of the liquid crystal layer, the manufacturing is easy and the rubbing treatment can be performed well.

Further, 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 image quality and high luminance.

Furthermore, since the incident light is modulated by using a diffraction grating, excellent black display can be realized, and the contrast is greatly improved as compared with the conventional liquid crystal projection type television. Display can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a liquid crystal panel of the present invention.

FIG. 2 is a sectional view of one embodiment of the liquid crystal panel of the present invention.

FIG. 3 is an explanatory diagram of one embodiment of a liquid crystal panel of the present invention.

FIG. 4 is a configuration diagram of an embodiment of a liquid crystal projection television according to the present invention.

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

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

FIG. 7 is an explanatory diagram of components of a liquid crystal projection television according to the present invention.

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

FIG. 9 is a configuration diagram of a liquid crystal projection television according to another embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional liquid crystal panel.

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

FIG. 12 is an equivalent circuit diagram of a conventional liquid crystal panel.

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

[Explanation of symbols]

11, 103 Pixel electrode 12 Opening 21 Insulating film 22 Common electrode 23a, 23b Alignment film 31a, 31b, 31c Liquid crystal molecules 32a, 32b, 32c Electric lines of force 41, 41a, 41b, 41c Input masks 42, 42a, 42b, 42c Output mask 43, 43a, 43b, 43c Schlieren lens 44 Light source 45, 91 Screen 46 Concave mirror 47, 47a, 47b, 47c Projection lens 48, 48a, 48b, 48c, 96 Liquid crystal panel 51 Condensing optical system 52 UVIR cut mirror 53a, 53b, 53c Dichroic mirror 61, 61a, 61b, 61c Fly-eye lens 71 Micro lens 92 Mirror 93 Projection light source 94 Condenser lens

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1343 G02F 1/136-1/1368 G02F 1/13 505 G02F 1/137

Claims (7)

(57) [Claims] 1. A first substrate on which a pixel electrode, a common electrode disposed on the pixel electrode side, and a switching element connected to the pixel electrode are formed, and a second substrate on which a counter electrode is formed. And a liquid crystal layer sandwiched between the first substrate and the second substrate, wherein the pixel electrode has a periodic opening, and the A line of electric force is generated between the pixel electrode and the common electrode,
The liquid crystal molecules of the liquid crystal layer are aligned by the lines of electric force,
The liquid crystal panel is characterized in that the strength of the lines of electric force can be varied by a voltage applied to the pixel electrode. 2. The liquid crystal panel according to claim 1, wherein the pixel electrode and the common electrode are separated by an insulating film. 3. The liquid crystal panel according to claim 1, wherein the liquid crystal is a nematic liquid crystal. 4. The liquid crystal panel according to claim 1, light generating means, a first optical element component for guiding light generated by the light generating means to the liquid crystal panel, and light modulated by the liquid crystal panel. A liquid crystal projection television, comprising a second optical element part for projecting. 5. The light generated by the light generating means is divided by a color filter into light of three predetermined ranges of wavelengths of blue light, green light and red light, and the liquid crystal panel has a wavelength of the three predetermined ranges. The liquid crystal projection television according to claim 4, wherein the liquid crystal projection television is arranged for at least one of the lights. 6. The liquid crystal projection television according to claim 5, wherein the color filter is a dichroic mirror. 7. An optical image of a liquid crystal panel that modulates blue light, an optical image of a liquid crystal panel that modulates green light, and an optical image of a liquid crystal panel that modulates red light are the same on a screen by an optical element component. 6. The liquid crystal projection television according to claim 5, wherein the projection is performed at a position.