JP3082303B2 - LCD projector - 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 display and a liquid crystal projector.

[0002]

BACKGROUND OF THE INVENTION Conventional twisted nematic liquid crystal display device, the absorption axis of the incident side polarizing plate and the outgoing-side polarizing angle theta ₁ of the optical plate absorption axis of the angle formed by the rubbing direction of the two glass substrates θ ₂ and had been substantially match.

Further, a conventional liquid crystal projector has a plurality of the above-mentioned conventional liquid crystal display devices as light valves, and illuminates an image generated by the plurality of liquid crystal display devices with a light source and uses a projection lens. It was projected on the screen.

[0004]

However, the conventional technique has a problem that the contrast is low. Therefore, the present invention solves such a problem, and an object of the present invention is to provide a liquid crystal display device and a liquid crystal projector with an image quality with higher contrast.

[0005]

[0006]

According to the present invention, there is provided a liquid crystal projector comprising: a light source; the above liquid crystal display device for modulating light from the light source; and projection optical means for projecting light modulated by the liquid crystal display device. It is characterized by having. More specifically, a light source, a plurality of light valves for modulating light from the light source, a combining means for combining the light modulated by the plurality of light valves, and a projection for projecting the light combined by the combining means Optical means, wherein the plurality of light valves have a first type light valve and a second type light valve, and a light beam modulated by the first type light valve and the second type light valve. In a liquid crystal projector in which the modulated light flux and the modulated light flux are guided to the projection optical unit in an inverting relationship with each other, each of the light valves includes a liquid crystal panel having a liquid crystal sandwiched between a pair of rubbed substrates, and an incident light. An angle θ1 between an absorption axis of the incident-side polarizing plate and an absorption axis of the emission-side polarizing plate, and a rabbit of the pair of substrates. And the sign of the difference Δθ between the angle θ1 and the angle θ2 is opposite between the first type light valve and the second type light valve. . In each of the light valves, a difference Δθ between the angle θ1 and the angle θ2 is 0 °.
<| △ θ | <4 °. Further, the light valve of the first type and the light valve of the second type have a difference between the angle θ1 and the angle θ2.
It is characterized in that the absolute values of θ are substantially equal.

[0007]

[Action] In conventional absorption axis of the incident side polarizing plate such as a liquid crystal display device the angle between the absorption axis of the exit-side polarizing plate theta ₁ between two and the angle theta ₂ of the rubbing direction of the glass substrate of matches The contrast in the clear viewing direction is high, but the contrast in the reverse clear viewing direction is low.

[0008] The reason is that there is light leakage in the reverse clear vision direction. The incident light contains light rays of various angle components, and the contrast is determined by the sum of the contrasts of the individual light rays. Therefore, if the contrast as a whole can be increased even if the contrast in the clear vision direction is slightly sacrificed, the use of the liquid crystal display device (for example, the liquid crystal display device may be used by other persons from various directions, such as a large display device). This is extremely effective in some cases (such as when viewing a display device).

For this purpose, the angle θ ₁ formed by the absorption axis of the incident side polarizing plate and the absorption axis of the output side polarizing plate is different from the angle θ ₂ formed by the rubbing direction of the two glass substrates. Thus, the difference Δθ between those angles is 0 ゜ <| Δθ | <
It is effective to satisfy the relationship of 4 ゜.

Also, in the case of a liquid crystal projector, since the light source is not usually a point light source, light beams of various angle components are mixed in the light beams incident on a plurality of liquid crystal display devices used as light valves. By adopting the above configuration in the liquid crystal display device, the contrast of the liquid crystal projector can be increased.

Further, in the case of a liquid crystal projector, since a plurality of liquid crystal display devices are arranged at mirror-symmetric positions, the value of Δθ is determined to be either positive or negative depending on the position of the liquid crystal display device. It is particularly effective to make the absolute values substantially equal (both color display and monochrome display). In this case, the contrast of each color is similarly increased, and the white balance is not degraded.

FIG. 1 is used in the projector of the present invention.
FIG. 4 is a perspective view showing a reference example of a liquid crystal light valve . 11
Is a light incident side polarizing plate, and 12 is a light emitting side polarizing plate. In actual use, a liquid crystal panel enters between these polarizing plates.

FIG. 2A is a plan view when the rubbing direction of the glass on the incident side of the glass sandwiching the liquid crystal of the liquid crystal panel of FIG. 1 is viewed from the incident side. FIG. 2B is a plan view when the rubbing direction of the exit side glass of the glass sandwiching the liquid crystal of the liquid crystal panel of the first embodiment is viewed from the incident side. Reference numeral 21 denotes a direction in which the glass is rubbed during rubbing.

A liquid crystal projector usually uses a halogen lamp or a metal halide lamp as a light source. In these light sources, the light emitting portion has a certain spread rather than one point. Therefore, the light rays condensed by the reflector and the like are a set of light rays having various angle components with respect to the optical axis.

As described above, the angle θ ₁ between the rubbing direction shown in FIG. 2A and the rubbing direction shown in FIG.
The conventional liquid crystal display device is obtained by combining a liquid crystal panel having an angle of 90 ° and a polarizing plate having an angle θ ₂ between the absorption axis of the incident-side polarizing plate and the absorption axis of the emission-side polarizing plate of 90 °.

In this case, the angle θ ₁ formed by the absorption axis of the incident side polarizing plate and the absorption axis of the output side polarizing plate substantially coincides with the angle θ ₂ formed by the rubbing direction of the two glass substrates. I have.

When a voltage is applied to the liquid crystal panel of the conventional liquid crystal display device to block light rays, light leakage from the reverse clear viewing direction has a large effect, and the overall contrast is low.

Therefore, in order to suppress this leaked light in the conventional liquid crystal display device, in the present invention, the directions of the absorption axes of the two polarizing plates were adjusted to search for the optimum value.

That is, the angle between the absorption axis of the incident-side polarizing plate 11 and the orientation direction of the light-incident side glass of the liquid crystal panel is α.
Then, the contrast was measured by rotating the angle formed between the absorption axis of the output-side polarizing plate 12 and the orientation direction of the output-side glass of the liquid crystal panel from left to right as viewed from the incident direction of light from α.

FIG. 3 shows the experimental results when α is 90 °.

Referring to the value of the rotation angle θ, as can be seen in FIG. 3, by setting the value of the rotation angle θ in the range of 0 ° <θ <4 °, the contrast in the reverse clear vision direction is increased. Thus, an image having a sufficiently high contrast on the screen (relative contrast of 1 or more in FIG. 3) was obtained.

Further, regarding the direction of the rotation angle,
When viewed along the traveling direction of the light θ, the direction of the absorption axis of the output-side polarizing plate is set in the reference direction (the input-side polarizing plate) in the direction opposite to the direction in which the polarized light transmitted through the input-side polarizing plate rotates. angle of the absorption axis of the absorption axis and the outgoing side polarizing plate of the direction of rotating the two rubbing directions of the angle theta ₂ is the same as the above direction of the glass substrate) is high becomes the direction of the contrast.

FIG. 3 shows an example in which α is 90 °. However, it is limited to the case where α is 90 °.
5 °, 60 °, -30 °, -45 °, -60 °, -90
Similar results were obtained in the case of ゜.

Although the present invention has been described above with reference to a normally white mode TN type liquid crystal display device having a 90 ° twist as an example, the technology of the present invention is not limited to this case. Liquid crystal display device, 200
(4) It is effective for all liquid crystal display devices that use the optical rotation of liquid crystal as a display principle, such as a so-called STN liquid crystal display device twisted or more, a polymer dispersion type liquid crystal display device, and the like.

FIG. 4 shows an embodiment of the liquid crystal projector of the present invention .
It is a top view of the optical system in an example . Here, 41 is a light valve for green, 42 is a light valve for red, and 43 is a light valve for blue. Each light valve was a liquid crystal display device including a liquid crystal panel, an incident side polarizing plate, and an outgoing side polarizing plate, which was confirmed to have high contrast in the same manner as in the reference example .

FIG. 5 is a perspective view when the absorption axis of the entrance side polarizing plate 51 and the exit side polarizing plate 52 are taken out of the light valve 42 for red. Here, an angle theta ₁ of the absorption axis of the incident side polarizing plate 51 emission side polarization plate 52, it is adjusted so that the contrast is improved most.

That is, the angle between the absorption axis of the incident-side polarizing plate 51 and the orientation of the light-incident side glass of the liquid crystal panel is 9 degrees.
0 °, and the angle between the absorption axis of the exit-side polarizing plate 52 and the orientation direction of the exit-side glass of the liquid crystal panel was adjusted to a value rotated by 90 ° to the left as viewed from the incident direction of light from 90 ° (θ).
Is set in the range of 0 ° <θ <4 °. ).

In a single-projection liquid crystal projector, three light valves are normally arranged at mirror-symmetric positions as shown in FIG. With mirror symmetry, the image or video generated by each light valve is viewed in the traveling direction of the light beam,
It means left-right symmetry (sometimes vertical symmetry) between each light valve.

In the case of FIG. 4, the green light valve and the blue light valve are arranged at mirror symmetric positions with respect to the red light valve.

Here, the green light valve 41 is disposed at a mirror symmetrical position with respect to the red light valve.
And the light valve 43 for blue is the light valve 4 for red.
Contrary to the case of 2, the angle between the absorption axis of the incident side polarizing plate 51 and the rubbing direction of the light incident side glass of the liquid crystal panel is set to 9
0 degree, and adjust the angle between the absorption axis of the output side polarizing plate 52 and the orientation direction of the output side glass of the liquid crystal panel to a value rotated by 90 degrees to the right as viewed from the light incident direction from 90 degrees (θ
Is set in the range of 0 ° <θ <4 °. (This is the same as adjusting to a value rotated to the left by θ degrees (θ is set in the range of −4 ° <θ <0 °).) By doing so, the contrast of all light valves is increased. As a result, the contrast of the liquid crystal projector as a whole can be increased. In addition, the white balance was not degraded by increasing the contrast in all the colors (red, green and blue) in the same manner (regardless of the color display or black and white display).

[0031]

[0032]

As described above, according to the liquid crystal projector of the present invention, the sign of Δθ is opposite between the light valves arranged at mirror symmetric positions and the absolute value is substantially the same. Therefore, the contrast can be increased in all light valves, and the contrast of the entire liquid crystal projector can be increased. Furthermore, by increasing the contrast in all colors (red, green, blue) in the same manner, there is an effect that the white balance is not lost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a liquid crystal display device according to a reference example of the present invention.

FIG. 2A is a plan view of the rubbing direction of the incident side glass in FIG. 1 when viewed from the incident side. (B) Figure
The direction of rubbing during rubbing of one of the exit-side glass is a plan view when viewed from the incident side.

FIG. 3 is a graph showing a relationship between an angle formed by an absorption axis of an incidence-side polarizing plate and an absorption axis of an emission-side polarizing plate in FIG . 1 and contrast.

FIG. 4 is a plan view of an optical system in the embodiment of the liquid crystal projector of the present invention .

FIG. 5 is a perspective view of an entrance-side polarization plate and an exit-side polarization plate of the red light valve of FIG. 4;

[Explanation of symbols]

 11 Incident side polarizing plate 12 Outgoing side polarizing plate 21 Direction of rubbing when rubbing glass 41 Green light valve 42 Red light valve 43 Blue light valve 44 Light source 51 Red light valve incident side polarizing plate 52 Red Output side polarizing plate of light valve

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337 G02F 1/1335 G02F 1/13 505

Claims (3)

(57) [Claims] 1. A light source, a plurality of light valves for modulating light from the light source, a combining means for combining light modulated by the plurality of light valves, and a projection for projecting the light combined by the combining means An optical means, wherein the plurality of light valves have a first type light valve and a second type light valve, and a light beam modulated by the first type light valve and the second type light valve. In the liquid crystal projector, the modulated light flux is guided to the projection optical unit in an inverting relationship with each other, wherein each of the light valves includes a liquid crystal panel having a liquid crystal sandwiched between a pair of rubbed substrates, An angle θ1 between an absorption axis of the incident-side polarizing plate and an absorption axis of the emission-side polarizing plate, and a rabbit of the pair of substrates. And the sign of the difference Δθ between the angle θ1 and the angle θ2 is opposite between the first type light valve and the second type light valve. LCD projector. 2. The liquid crystal projector according to claim 1, wherein in each of the light valves, a difference Δθ between the angle θ1 and the angle θ2 satisfies a relationship of 0 ° <| △ θ | <4 °. . 3. The light valve of the first type and the light valve of the second type have substantially equal absolute values of a difference Δθ between the angle θ1 and the angle θ2. Or the liquid crystal projector according to 2.