JP3708921B2 - LCD projector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection type projector using a liquid crystal panel.
[0002]
[Prior art]
A projection display device is known as a display device capable of displaying a large screen image.
[0003]
As a projection display device, for example, a CRT (cathode ray tube) is used as an image source for displaying an image, and an image displayed on the CRT is enlarged and projected, and for example, a liquid crystal panel is used as an image source. An apparatus that projects an image displayed on a liquid crystal panel in an enlarged manner (a liquid crystal projector) is known.
[0004]
As a projection type liquid crystal projector using a liquid crystal panel, for example, a single plate type or a three plate type constituted by a light source (lamp), an illumination optical system, a color separation optical system, a liquid crystal panel, a color synthesis optical system, a projection optical system, and the like. There is a liquid crystal projector.
[0005]
A three-plate liquid crystal projector uses a color separation optical system to separate white light from a light source (lamp) into three colors of R (red), G (green), and B (blue), and the separated color light. After irradiating three liquid crystal panels for R, G, and B to obtain images for R, G, and B, the images are synthesized by a color synthesizing optical system to form a single color image. (Patent Document 1).
[0006]
When, for example, a well-known TN (twisted nematic) type liquid crystal material is used as the liquid crystal panel, two polarizing plates are arranged at the front and rear stages of the liquid crystal panel. When a liquid crystal panel using a TN type liquid crystal material is used, the above two polarizing plates are usually arranged so that many liquid crystal panels display “white” when not energized and “black” when energized.
[0007]
However, in an actual illumination optical system, not only perfect parallel light but also an oblique light component is present, and birefringence occurs when the oblique light component enters the liquid crystal panel. Birefringence also occurs due to the pretilt state of the nematic liquid crystal in the vicinity of the glass substrate (the state in which the orientation angle changes continuously).
[0008]
Due to the occurrence of birefringence, the polarization axis of the incident light that has been linearly polarized by the incident side polarizing plate is disturbed. Accordingly, when it is desired to output “black”, unnecessary light (non-image light) is not completely blocked by the output side polarizing plate, and light leakage occurs. This light leakage becomes a factor of decreasing the contrast (the luminance ratio between “white” and “black”).
[0009]
In order to suppress a decrease in contrast, it has already been proposed to use an optical compensation film capable of reducing the influence of birefringence in addition to a liquid crystal panel and two polarizing plates (Patent Document 2).
[0010]
However, in a liquid crystal projector, the optical compensation film tends to become high temperature due to light from the light source, and thus distortion due to thermal contraction occurs. For this reason, the optical compensation film has a problem that the performance cannot be sufficiently maintained and the contrast cannot be improved.
[0011]
In addition, regarding the polarizing plate similar in composition to the optical compensation film, there is a proposal of rounding the four ends of the polarizing plate in order to reduce the influence of shrinkage in the stretching axis direction (Patent Document 3).
[0012]
[Patent Document 1]
Japanese Patent No. 3045155 [0013]
[Patent Document 2]
Japanese Patent No. 3118208 [0014]
[Patent Document 3]
JP-A-8-6014 (FIG. 1, abstract)
[0015]
[Problems to be solved by the invention]
As described above, the optical compensation film has a problem that the original characteristics cannot be maintained due to the heat shrinkage caused by the heat from the light source. In particular, when the optical compensation film has a rectangular shape, there is a problem that contrast unevenness occurs in a peripheral portion where stress concentration due to thermal shrinkage is likely to occur. For example, when an image with an aspect ratio of 16: 9 in which the top and bottom of the screen is black is input to a liquid crystal panel with an aspect ratio of 4: 3, the four corners of the screen become brighter than the center of the screen, reducing the image quality. There's a problem.
[0016]
An object of the present invention is to improve contrast unevenness and image quality in a liquid crystal projector using an optical compensation film capable of reducing the influence of birefringence inherent in a liquid crystal panel.
[0017]
[Means for Solving the Problems]
The present invention has been made based on the above-described problems. In a liquid crystal projector having a light source and a liquid crystal panel, projecting image light that irradiates the liquid crystal panel with light from the light source and transmits the liquid crystal panel. A first polarizing plate disposed on the incident side of the liquid crystal panel, a second polarizing plate disposed on the output side of the liquid crystal panel, and between the liquid crystal panel and the first polarizing plate, or An optical compensation film disposed between the liquid crystal panel and the second polarizing plate, wherein the optical compensation film has a substantially rectangular shape, and part of the corners thereof are cut off. It has a cut part , and the cut part has a shape cut out inward from an end part intersecting two adjacent sides of the optical compensation film .
[0018]
The liquid crystal projector of the present invention also includes a light source, a color separation device that separates light from the light source into a plurality of color lights, and a plurality of color lights from the color separation device that are incident on each other, and color light modulated by a video signal. A plurality of liquid crystal panels each emitting light, a first polarizing plate disposed on an incident side of the plurality of liquid crystal panels, a second polarizing plate disposed on an output side of the plurality of liquid crystal panels, An optical compensation film disposed between a plurality of liquid crystal panels and at least one of the first polarizing plate or the second polarizing plate disposed opposite to the liquid crystal panel, and the second polarizing plate. A color synthesizer that synthesizes the light emitted from the individual liquid crystal panels, and projection optical means that projects the light synthesized by the color synthesizer. A shape having a cutout which is partially cut in the corner portion, the cut portion is a shape notched inwardly from the end portion intersecting the two adjacent sides of the optical compensation film It is characterized by that.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0020]
FIG. 1 schematically shows the configuration of a three-plate liquid crystal projector to which the embodiment of the present invention can be applied. The present invention is not limited to this, and a single-plate liquid crystal projector may be used.
[0021]
As shown in FIG. 1, the liquid crystal projector 1 (three-plate type liquid crystal projector) includes an optical box 100 including a liquid crystal display unit 150, which will be described below, a lamp (light source) unit 200, and an output from the liquid crystal display unit 150. For example, a projection lens 300 that projects an image on a screen is provided.
[0022]
The optical box 100 includes first and second dichroic mirrors 104 and 108 (colors) that separate white light from a lamp unit 200 described below into three colors of R (red), G (green), and B (blue). Separation optical system), an R liquid crystal panel 107 irradiated with R light separated by a dichroic mirror 104, a G liquid crystal panel 110 irradiated with G light separated by a dichroic mirror 108, and a dichroic mirror 108 And a B liquid crystal panel 116 irradiated with the transmitted B light, and a dichroic prism 118 (color combining optical system) that combines the R light, G light, and B light transmitted through each liquid crystal panel.
[0023]
A first polarizing plate 120 and a second polarizing plate 121 are disposed on the light incident side and the light emitting side of the R liquid crystal panel 107, respectively. Similarly, a first polarizing plate 122 and a second polarizing plate 123 are disposed on the light incident side and the light emitting side of the G liquid crystal panel 110, respectively. A first polarizing plate 124 and a second polarizing plate 125 are disposed on the light incident side and the light emitting side of the B liquid crystal panel 116, respectively.
[0024]
Between each of the liquid crystal panels and the first polarizing plate, that is, between the first polarizing plate 120 for R and the liquid crystal panel 107, between the first polarizing plate 122 for G and the liquid crystal panel 110, B Between the first polarizing plate 124 and the liquid crystal panel 116, a sheet-like or film-like optical compensation member (hereinafter referred to as an optical compensation film) that can reduce the influence of birefringence inherent to the liquid crystal panel described later. 126 to 128). Each of the optical compensation films 126 to 128 may be provided between the liquid crystal panels 107, 110, and 116 and the corresponding second polarizing plates 120, 123, and 125. Further, the respective optical compensation films 126 to 128 may be directly attached to the liquid crystal panels 107, 110 and 116 or the polarizing plates 120 to 125.
[0025]
As the optical compensation films 126, 127, and 128, for example, a trade name “WV Film Wide View A” (Fuji Photo Film Co., Ltd.) or the like can be used.
[0026]
The lamp unit 200 includes an arc tube 201 such as a halogen lamp or an Xe (xenon) lamp, a reflector 202, and a support 203, and directs light (white light) from the arc tube 201 to the filter 101 of the optical box 100. And exit. Light from the lamp unit 200 is removed unnecessary light such as infrared rays and ultraviolet rays by the filter 101, and is condensed on the liquid crystal panel by the condenser lens 102. The light that has passed through the condenser lens 102 is reflected by the reflection mirror 103 and guided to the dichroic mirror 104.
[0027]
Light from the lamp unit 200 is separated into R light and GB light by the dichroic mirror 104. The R light separated by the dichroic mirror 104 is reflected by the mirror 105 and guided to the first polarizing plate 120 positioned in front of the R liquid crystal panel 107 via the field lens 106.
[0028]
The GB light separated by the dichroic mirror 104 is further separated into G light and B light by the dichroic mirror 108.
[0029]
The G light separated by the dichroic mirror 108 is guided to the first polarizing plate 122 positioned on the front surface of the G liquid crystal panel 110 via the field lens 109.
[0030]
The B light separated by the dichroic mirror 108 is guided in order by the relay lens 111, the reflection mirror 112, the relay lens 113, the reflection mirror 114, and the relay lens 115, and is positioned on the front surface of the B liquid crystal panel 116. Guided to the polarizing plate 124.
[0031]
The light of each color incident on the polarizers 120, 122 and 124 is guided to the liquid crystal panels 107, 110 and 116 for the respective colors through the optical compensation films 126, 127 and 128.
[0032]
The light transmitted through the liquid crystal panels 107, 110, and 116 is guided to the second polarizing plates 121, 123, and 125 arranged on the emission side.
[0033]
The light of each color (R, G, and B) that has passed through the second polarizing plates 121, 123, and 125, that is, video light of three colors, is guided to the dichroic prism 118.
[0034]
The image light synthesized by the dichroic prism 118 is projected onto a screen (not shown) by the projection lens 300.
[0035]
The liquid crystal panels 107, 110, and 116 for R, G, and B are image control devices (not shown) to which video signals (R, G, and B primary color signals) that are information for generating video light are input. Connected with. Since the transmittance of each color liquid crystal panel is selectively changed based on the video signal supplied from the image control device, three color images corresponding to the video signal are obtained and synthesized by the dichroic prism 118. As a result, a full-color image can be obtained.
[0036]
Incidentally, in a liquid crystal panel, particularly a liquid crystal panel using a TN (twisted nematic) type liquid crystal material, it is necessary to consider the influence of double bending described below with reference to FIG. Since the liquid crystal panels 107, 110 and 116 described with reference to FIG. 1 are substantially the same liquid crystal panel, hereinafter, the liquid crystal panel is denoted by reference numeral 21, the first polarizing plate is denoted by reference numeral 22, and the second. The polarizing plates will be described with reference to FIG.
[0037]
As shown in FIG. 2, the liquid crystal panel 21 has first and second polarizing plates 22 and 23 arranged on the incident side and the emission side so that the transmission axes are orthogonal to each other. In the liquid crystal panel 21, nematic liquid crystal is sealed between glass substrates 21A and 21B.
[0038]
When no voltage is applied to the cells of the liquid crystal panel 21 (FIG. 2A), the orientation direction of the liquid crystal material is parallel to the glass substrate 21, and the polarization direction and orientation of the incident side polarizing plate 22 are 90 degrees. It has a twisted twist orientation. The incident light that has been linearly polarized by the incident side polarizing plate 22 has its polarization plane rotated 90 degrees along the twist of the crystal of the liquid crystal, and thus can pass through the outgoing side polarizing plate 23 and display “white”.
[0039]
On the other hand, as shown in FIG. 2B, when a high voltage is applied to the liquid crystal cell, the crystal of the liquid crystal has an orientation (homeotropic orientation) along an electric field perpendicular to the glass substrates 21A and 21B. Become. For this reason, the polarization plane of the light that has been linearly polarized by the incident-side polarizing plate 22 is not rotated because the crystal is not twisted. Thereby, the incident light is blocked by the output side polarizing plate 23 and displayed as “black”. The liquid crystal crystals in the vicinity of the glass substrates 21A and 21B are in a pretilt state (tilt orientation).
[0040]
FIG. 3 is a refractive index ellipsoid model for explaining the birefringence of liquid crystal molecules, and shows that the nematic liquid crystal is an optically positive uniaxial substance.
[0041]
As shown in FIG. 3, the nematic liquid crystal can be expressed as a refractive index ellipsoid of, for example, a rugby ball type, and is incident obliquely with light 31 incident parallel to the optical axis passing through the liquid crystal panel (perpendicular to the liquid crystal panel). Considering the light beams 32 and 33, birefringence occurs with respect to the light beams 32 and 33 incident obliquely.
[0042]
FIG. 4 is a refractive index ellipsoid model diagram of the material used for the optical compensation film, and shows that the optical compensation film has optically negative uniaxiality.
[0043]
In FIG. 4, when the light 41 incident parallel to the optical axis passing through the liquid crystal panel (perpendicular to the liquid crystal panel) and the obliquely incident lights 42 and 43 are considered, Birefringence occurs.
[0044]
As is clear from FIG. 4, the optical compensation film having optically negative uniaxial property has a property opposite to the positive uniaxial property of the nematic liquid crystal, so The direction of refraction is opposite to the direction of birefringence generated in the liquid crystal shown in FIG. 3, and therefore the influence of birefringence inherent in the nematic liquid crystal can be canceled out in the image.
[0045]
FIG. 5 is a schematic view for explaining an optical compensation film used in this example. In addition, since the optical compensation films 126 to 128 described with reference to FIG. 1 are substantially the same, hereinafter, the optical compensation film will be described with reference numeral 50.
[0046]
The optical compensation film 50 includes a support 51 including a material having an optically negative uniaxial property, and a coating layer (optical anisotropic layer) 52. The coating layer 52 is arranged corresponding to the pretilt state of the liquid crystal crystals sealed in the individual liquid crystal panels, and can cancel birefringence caused by the pretilt state caused by the liquid crystal crystals.
[0047]
As described above, the required contrast can be obtained by using an optical compensation film that cancels birefringence generated by oblique light incident on the liquid crystal panel or by a pretilt state.
[0048]
By the way, in the projection type liquid crystal projector previously described with reference to FIG. 1, the optical compensation films 126 to 128 are positioned in the optical box 100 integrated with the lamp unit 200. It becomes a high temperature of about 85 ° C. Further, although controlled by the environment in which the projector is installed, the room temperature reaches about 90% RH. For this reason, the optical compensation films 126 to 128 are contracted by heat, and the contrast is lowered particularly in the peripheral portion as already described.
[0049]
Hereinafter, an embodiment of the present invention that can suppress a decrease in contrast even when the optical compensation film contracts due to heat will be described with reference to FIG.
[0050]
FIG. 6 is a front view of an optical compensation film incorporated in a liquid crystal projector. Since the optical compensation films 126 to 128 described with reference to FIG. 1 are substantially the same, hereinafter, the optical compensation film will be described with reference numeral 60.
[0051]
The optical compensation film 60 has a substantially rectangular shape, and is attached to, for example, a glass substrate 61.
[0052]
The optical compensation film 60 has a cut portion 60a formed so as to have a corner portion having a non-acute angle (obtuse angle) and a straight line. The optical compensation film 60 also includes an edge area 60A that is a peripheral portion of the area 62 of the illumination light that has passed through the first polarizing plate and is not directly irradiated with the illumination light.
[0053]
The size of the optical compensation film 60 is set so as to be able to absorb distortion due to thermal shrinkage in the edge area 60A and not to undesirably increase the size of the optical compensation film (or glass substrate). The The size of the edge area 60A is, for example, 10% or more compared to the width 60c of the short side of the optical compensation film 60 when expressed by a distance 60b from the outermost part of the illumination light area 62 to the outermost part of the optical compensation film 60. Set to However, in order not to undesirably increase the size of the optical compensation film (or glass substrate), the distance 60b is preferably limited to about 15% compared to the short side width 60c of the optical compensation film 60. .
[0054]
The distance 60d between the linear portion of the cut portion 60a and the diagonal portion of the illumination light area 62 is, for example, such that even if the optical compensation film 60 is thermally contracted, the illumination light area 62 is not affected. Preferably it is the range of 60b <= 60d.
[0055]
Thus, even if the peripheral portion of the optical compensation film 60, that is, the edge area 60A is shrunk by heat from the arc tube 201, the area 62 of the illumination light (passing through the optical compensation film 60) is affected by heat shrinkage. In addition, the image contrast emitted toward the projection lens 300 is improved particularly in the peripheral portion of the optical compensation film 60 because the stress concentration due to thermal shrinkage is formed in a shape that does not exert any effect. Moreover, since the cut part 60a is linear, manufacturing efficiency is also good.
[0056]
FIG. 7 is a schematic diagram illustrating an example of an optical compensation film having a notch having a shape different from that of the optical compensation film shown in FIG. In FIG. 7, the optical compensation film will be described with reference numeral 70 in order to distinguish it from FIG. 6.
[0057]
As shown in FIG. 7, the optical compensation film 70 has a generally rectangular shape, and is cut so that a portion where two adjacent sides intersect does not include the top (corner portion) and is in an arbitrary shape (U-shape). It has a notch 70a. In addition, the optical compensation film 70 is affixed on the glass substrate 71 similarly to the optical compensation film 60 demonstrated previously using FIG.
[0058]
The size of the peripheral portion of the optical compensation film 70, that is, the edge area 70A is expressed by a distance 70b from the outermost part of the illumination light area 72 to the outermost part of the optical compensation film 70, for example. Compared with 70c, it is set to 10% or more. However, in order not to undesirably increase the size of the optical compensation film (or glass substrate), the distance 70b is preferably limited to about 15% as compared to the short side width 70c of the optical compensation film 70. .
[0059]
The distance 70d between the inner edge portion of the cutout portion 70a and the diagonal portion of the illumination light area 72 is, for example, such that even if the optical compensation film 70 is thermally contracted, the illumination light area 72 is not affected. The range is preferably 70b ≦ 70d.
[0060]
Thus, even if the peripheral portion (edge area 70A) of the optical compensation film 70 is shrunk by heat, similarly to the optical compensation film 60 shown in FIG. 6, the area 72 of the illumination light is not affected by the heat shrinkage. In addition, since it is formed in a shape that minimizes stress concentration due to thermal contraction, the image contrast emitted toward the projection lens 300 is improved particularly in the peripheral portion.
[0061]
As described above, the position where the adjacent sides of the optical compensation film 60 (70) intersect is cut linearly, or the portion where the adjacent sides intersect does not include the top (corner) and has any shape ( By providing the notch 60a (70a) cut into a U-shape, the edge area 60A (70A) can absorb the distortion of the area 62 (72) of the illumination light onto which the illumination light is projected. Thereby, the area 12 of the illumination light in which the effect | action of an optical compensation film is provided uniformly can be ensured. Therefore, the unevenness in contrast of the projected image, that is, the output image is reduced.
[0062]
In this embodiment, since the optical compensation film is fixed using a glass frame or the like, it is easy to fix (place) and handle the film when assembling a liquid crystal projector.
[0063]
【The invention's effect】
As described above, according to the present invention, the shape of the peripheral portion of the optical compensation film is set to a shape in which the effect of shrinkage due to heat hardly affects the image, so that the unevenness in the contrast of the output image is reduced. Therefore, even when the peripheral portion (particularly, the four corners) displays a black image, it is possible to eliminate the occurrence of a light / dark difference between the peripheral portion and the central portion of the projected video.
[0064]
Further, since it is not necessary to add a cooling device for cooling the optical compensation film, a liquid crystal projector capable of obtaining an image with improved contrast can be realized without increasing the size.
[Brief description of the drawings]
FIG. 1 is an optical arrangement diagram showing a main part of a liquid crystal projector according to the present invention.
FIG. 2 is an operation principle diagram of a liquid crystal panel.
FIG. 3 is a refractive index ellipsoid model showing the birefringence of liquid crystal molecules.
FIG. 4 is an index ellipsoid model showing the birefringence of liquid crystal molecules.
FIG. 5 is an operation principle diagram of a liquid crystal panel.
FIG. 6 is a front view showing an example of an optical compensation film in the liquid crystal projector of the present invention.
FIG. 7 is a front view showing an example of an optical compensation film in the liquid crystal projector of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal projector, 100 ... Optical box, 104, 108 ... Dichroic mirror, 107, 110, 116 ... Liquid crystal panel, 118 ... Dichroic prism, 120-125 ... Polarizing plate, 126-128 ... Optical compensation film, 150 ... Liquid crystal display 200, lamp unit, 201, arc tube, 300, projection lens, 60a, 70a, notch (cutting portion).

Claims (10)

In a liquid crystal projector having a light source and a liquid crystal panel, projecting image light that irradiates the liquid crystal panel with light from the light source and transmits the liquid crystal panel,
A first polarizing plate disposed on the incident side of the liquid crystal panel;
A second polarizing plate disposed on the emission side of the liquid crystal panel;
An optical compensation film disposed between the liquid crystal panel and the first polarizing plate, or between the liquid crystal panel and the second polarizing plate,
The optical compensation film has a substantially rectangular shape, and has a cut portion in which a part of the corner portion is cut. A liquid crystal projector characterized by being cut out toward the inside .     The liquid crystal projector according to claim 1, wherein the optical compensation film is an optical film capable of reducing the influence of birefringence inherent in the liquid crystal panel. 3. The liquid crystal projector according to claim 1, wherein the cut portion has a shape cut out in a U shape toward the inside. The optical compensation film includes an irradiation light area irradiated with light that has passed through the first polarizing plate, and a peripheral portion located around the irradiation light area, and the optical compensation film from the outermost part of the irradiation light area. The first distance to the outermost part of the cutout is smaller than a second distance from an inner edge of the cut portion to a diagonal portion of the irradiation light area. The liquid crystal projector described. 5. The liquid crystal projector according to claim 1, wherein the first distance is not less than 10% and not more than 15% as compared with a width of a short side of the optical compensation film. A light source;
  A color separation device that separates light from the light source into a plurality of color lights;
  A plurality of liquid crystal panels that respectively receive a plurality of color lights from the color separation device and emit color lights modulated by video signals;
  A first polarizing plate disposed on an incident side of each of the plurality of liquid crystal panels;
  A second polarizing plate disposed on the emission side of the plurality of liquid crystal panels,
  An optical compensation film disposed between the plurality of liquid crystal panels and at least one of the first polarizing plate and the second polarizing plate disposed to face each other;
  A color synthesizing device that synthesizes light from individual liquid crystal panels that are transmitted through the second polarizing plates and emitted;
  Projection optical means for projecting the light synthesized by the color synthesis device,
  The optical compensation film has a substantially rectangular shape, and has a cut portion in which a part of the corner is cut, and the cut portion is formed from an end portion that intersects two adjacent sides of the optical compensation film. A liquid crystal projector characterized by being cut out toward the inside. The liquid crystal projector according to claim 6, wherein the optical compensation film is an optical film capable of reducing the influence of birefringence inherent in the liquid crystal panel. The liquid crystal projector according to claim 6, wherein the cut portion has a shape cut out in a U shape toward the inside. The optical compensation film includes an irradiation light area irradiated with light that has passed through the first polarizing plate, and a peripheral portion located around the irradiation light area, and the optical compensation film from the outermost part of the irradiation light area. The first distance to the outermost part of the cut is smaller than a second distance from an inner edge of the cut portion to a diagonal portion of the irradiation light area. The liquid crystal projector described. 10. The liquid crystal projector according to claim 6, wherein the first distance is not less than 10% and not more than 15% compared to a width of a short side of the optical compensation film.

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