JP2827653B2 - Projection type liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device.

[0002]

2. Description of the Related Art Recently, as a liquid crystal display device for displaying a television image or the like using a liquid crystal display panel, a device which enlarges a display image of the liquid crystal display panel with a projection lens and projects and displays the image on a screen has been developed.

Conventionally, as this projection type liquid crystal display device,
A transmissive liquid crystal display panel is used. Light is incident on the liquid crystal display panel from a light source arranged opposite the light incident surface, and light transmitted through the liquid crystal display panel, that is, image light, is transmitted to the liquid crystal display panel. Is known in which the light is made incident on a projection lens arranged so as to face the light exit surface and is enlarged and projected on a screen.

[0004]

However, the above-mentioned conventional projection type liquid crystal display device has a problem that the contrast of an image projected and displayed on a screen is poor.
This is because the contrast of the image light transmitted through the transmission type liquid crystal display panel is poor.

That is, the liquid crystal display panel displays an image by controlling the electric field applied to the internal liquid crystal to select each of the pixel display portions of the liquid crystal display panel into a state of transmitting light and a state of blocking light. However, this liquid crystal display panel has a pixel display unit selected to be in a light transmitting state and a pixel display unit selected to be in a light blocking state in order to generate a certain amount of light leakage even in a state where light is blocked. Is small, the contrast of the image light transmitted through the transmissive liquid crystal display panel is low, and the contrast of the image projected and displayed on the screen is also low.

The present invention has been made in view of the above circumstances, and has as its object to provide a projection type liquid crystal capable of converting an image projected on a screen into a high quality image with good contrast. A display device is provided.

[0007]

According to the present invention, in order to achieve the above object, a liquid crystal display panel is a reflection type liquid crystal display panel having a reflection surface on a back surface thereof, and light is transmitted between a light source and the liquid crystal display panel. An optical member for refraction is arranged, and light from the light source is refracted by the optical member to form a liquid crystal display.
While the light is incident on the display panel from the front side, the image light reflected by the reflection surface on the back side and emitted to the front side of the liquid crystal display panel is reflected again by the optical member.
The light is incident on the projection lens .

[0008]

With such a configuration, even if the light incident on the liquid crystal display panel from the front surface side and transmitted through the liquid crystal display panel and converted into image light is image light having a low contrast as described above, This image light is reflected by the reflection surface on the back surface of the liquid crystal display panel, passes through the liquid crystal display panel again, and exits to the front surface side of the liquid crystal display panel. Become.

This is because light incident on the liquid crystal display panel passes through the liquid crystal display panel twice and exits from the liquid crystal display panel, and image light emitted from the liquid crystal display panel passes twice through the liquid crystal display panel. Light, the light leakage of the pixel display unit selected in the light-blocking state is considerably reduced, so that image light with good contrast is obtained.Therefore, if this image light is made incident on the projection lens and enlarged and projected on the screen, it is projected on the screen. The projected image can be a high-quality image with good contrast. Further, an optical member for refracting light is disposed between the light source and the liquid crystal display panel, and light from the light source is refracted by the optical member.
The liquid crystal display panel is caused to enter the liquid crystal display panel from the front side, and the image light reflected by the reflection surface on the back side and emitted to the front side of the liquid crystal display panel is again transmitted to the optical member.
The light from the light source incident on the liquid crystal display panel and the light emitted from the liquid crystal display panel can be reduced, so that image light with higher contrast can be projected. can do.

The present invention will be described below with reference to the drawings.
First, FIGS. 1 and 2 show a reflection type projection type liquid crystal display device.
This is a reflection type projection type liquid crystal display
The basic configuration of the device will be described.

In FIG. 1, reference numeral 1 denotes an apparatus case,
A transmission screen 2 is provided in a display window opened on the front surface of the case 1. Reference numeral 10 denotes a dot matrix liquid crystal display panel for displaying a television image or the like disposed at a lower portion in the case 1.
Is a reflection type having a reflection surface on its back surface.

FIG. 2 is an enlarged view of a part of the reflection type liquid crystal display panel 10. In the figure, reference numerals 11a and 11b denote a pair of front and back transparent substrates (glass plates) facing each other with a liquid crystal sealing gap. A large number of narrow stripe-shaped transparent signal electrodes 12 are formed in parallel on the inner surface of one substrate, for example, the front substrate 11a, and are arranged in parallel with the signal electrodes 12 on the inner surface of the other rear substrate 11b. A large number of narrow stripe-shaped transparent scanning electrodes 13 are arrayed in parallel,
The portions where the scanning electrodes 13 and the signal electrodes 12 cross and face each other constitute a pixel display portion D.

A red filter RF, a green filter GF, and a red filter RF are provided above or below one of the scanning electrode 13 and the signal electrode 12 (in this embodiment, the signal electrode 12).
Blue filters BF are alternately formed, and the liquid crystal display panel 10 displays a full-color image by a combination of red, green, and blue pixels alternately displayed on each pixel display portion D. It has become.

The liquid crystal display panel 10 is of the TN type, and the liquid crystal LC sealed between the substrates 11a and 11b is 90 degrees by the alignment films 14a and 14b formed on the electrode forming surfaces of the substrates 11a and 11b. Or, they are twisted at 270 degrees, and polarizing plates 15a and 15b are provided on the outer surfaces of both substrates 11a and 11b, respectively. In addition,
The polarizing plates 15a and 15b are provided with their polarization axes parallel or orthogonal.

Reference numeral 16 denotes a reflecting plate provided on the outer surface of the back-side polarizing plate 15b.
Light incident from the front side and transmitted through the liquid crystal display panel 10 is reflected by the reflection surface of the reflection plate 16, transmitted through the liquid crystal display panel 10 again, and emitted to the front side.

On the other hand, in FIG. 1, reference numeral 3 denotes a light source for making light incident on the reflective liquid crystal display panel 10. The light source 3 includes a light source lamp and a parabolic mirror reflector that reflects light emitted from the light source lamp. The reflector has a parabolic surface that reflects light emitted from the light source lamp as parallel light. It is a mirror reflector. The light source 3 is installed so as to face the surface of the reflective liquid crystal display panel 10 so that light is incident from a direction slightly inclined with respect to a line perpendicular to the liquid crystal display panel surface.

4 is a projection lens and 5 is a circular lens.
The full-color image light emitted from the liquid crystal display panel 10 is incident on the projection lens 4 by the condenser lens 5 and is enlarged and projected by the projection lens.

Reference numerals 6 and 7 denote projection mirrors for guiding the image light projected by the projection lens 4 toward the transmissive screen 2 on the front of the case. The image light passing through the projection lens 4 receives the first projection mirror. The light is reflected by the second projection mirror 7 toward the second projection mirror 7, and further reflected by the second projection mirror 7 toward the screen 2 to be projected and displayed on the screen 2.

In this projection type liquid crystal display device, light a ₁ from a light source 3 is made incident on a reflection type liquid crystal display panel 10, and image light a ₂ emitted from the liquid crystal display panel 10 is projected by a projection lens 4 onto a projection mirror 6. The image is projected onto the transmission screen 2 on the front of the case from the rear side through 7 through the rear side, and the image projected on the transmission screen 2 is observed from the front side of the apparatus.

In the projection type liquid crystal display device, the liquid crystal display panel 10 is provided with a reflection plate 16 on its back surface.
And a reflection type liquid crystal display panel provided with
₁ is incident on the liquid crystal display panel 10 from the front side thereof, and image light a ₂ reflected by the reflector 16 on the rear surface and emitted to the front side of the liquid crystal display panel 10 is incident on the projection lens 4. Therefore, the image projected on the screen 2 can be a high-quality image with good contrast.

That is, the light that enters the liquid crystal display panel 10 from the front side and passes through the liquid crystal layer of the liquid crystal display panel 10 and the rear side polarizing plate 15b and becomes image light is converted into a pixel selected in a light blocking state. Due to light leakage of the display unit, image light having low contrast similar to image light transmitted through the transmission type liquid crystal display panel is obtained.
Of the liquid crystal display panel 1
Image light a ₂ emitted from the liquid crystal display panel 10 in order to pass through
Becomes image light with good contrast.

This is because the light incident on the liquid crystal display panel 10 from the front surface side passes through the liquid crystal display panel 10 twice and is emitted to the front surface side of the liquid crystal display panel 10, and is emitted from the liquid crystal display panel 10. Since the image light a ₂ is light that has passed through the liquid crystal display panel 10 twice, the overall luminance is 1
Although slightly lower than the image light transmitted through the two transmissive liquid crystal display panels, the light leakage of the pixel display unit selected in the light blocking state is considerably small, so that the dark pixels among the pixels of the image light are removed. since darker image light a ₂ emitted from the liquid crystal display panel 10 becomes contrast good image light.

Therefore, the image light a ₂ is transmitted to the projection lens 4.
And projected on the screen 2 in an enlarged manner, the image projected on the screen can be a high-contrast image with good contrast.

In this projection type liquid crystal display device, the light source
3 is made to directly enter the liquid crystal display panel 10.
However, the light from the light source 3 is reflected by the mirror.
To make the light incident on the liquid crystal display panel 10.
it can.

In this projection type liquid crystal display device, the incident path of light a1 incident on the liquid crystal display panel 10 and the exit path of image light a2 emitted from the liquid crystal display panel 10 are different. If the incident angle of light to the liquid crystal display panel 10, that is, the angle with respect to a line perpendicular to the liquid crystal display panel surface is made as small as possible, most of the light reflected by the reflector 16 through each pixel display portion D of the liquid crystal display panel 10 will be described with reference to FIG.
As shown in FIG. 7, light is emitted from the liquid crystal display panel 10 through the same pixel display section D, so that, for example, red light reflected by the reflector 16 through the red pixel display section passes through the adjacent blue or green pixel display section. A color shift occurs, and light reflected by the reflector 16 through the pixel display unit selected in the light transmitting state is blocked through an adjacent pixel display unit selected in the light blocking state, resulting in a decrease in luminance. Few things.

Next, an embodiment of the present invention will be described. Fig. 3
4 and FIG. 4 show a first embodiment of the present invention. This second
In the first embodiment , light a1 from the light source 3 is incident on the reflective liquid crystal display panel 10 through the prism 8 perpendicularly to the panel surface, and the light a1 is emitted from the liquid crystal display panel 10 in a direction perpendicular to the panel surface. The outgoing image light a2 is made to enter the projection lens via the prism 8. In this way, the incident path of the light a1 incident on the liquid crystal display panel 10 and the light emitted from the liquid crystal display panel 10 are emitted. Image light a
2 can be matched with the exit path. In this case, the optical path of light that enters the projection lens 4 from the light source 3 via the reflective liquid crystal display panel 10 may be designed as follows.

That is, as shown in FIG.
The incident angle theta ₁ of the light a _{1, 2} a refraction angle of the incident light theta in the light source facing surface 8a, the incident angle out of light on the display panel opposing surface 8b theta from the light source 3 to the light source facing surface 8a of the
_3. The light source facing surface 8a of the prism 8 and the display panel facing surface 8
Assuming that the angle between b and θ is θ ₄ , θ ₂ and θ ₁ have the following relationship. θ ₂ = sin (90−sin ⁻¹ n sin θ ₁ / n ′) n ′: refractive index of prism n: refractive index outside (air) of prism

Assuming that the angle between the light source facing surface 8a of the prism 8 and the display panel facing surface 8b is θ ₄ , the light is emitted from the display panel facing surface 8b through the prism 8 toward the reflective liquid crystal display panel 10. Light emission angle θ
₃ is θ ₃ = sin ⁻¹ n ′ sin [90− (θ ₂ + θ ₄ ] / n

If the reflection type liquid crystal display panel 10 is arranged so that the panel surface is perpendicular to the emission angle θ ₃ , the incident path of the light a ₁ incident on the liquid crystal display panel 10 and the liquid crystal display panel an exit path of the image light a ₂ emitted from 10 can be matched.

Further, the reflection-type liquid crystal display panel image light a ₂ emitted from 10 is directed to the light source facing surface 8a enters the prism 8 with light a ₁ and the same path from the light source, the image light a ₂ Is smaller than the critical angle, the image light a ₂ is directed toward the projection lens facing surface 8 c of the prism 8 if the incident angle θ ₂ is the same as the refraction of the incident light on the light source facing surface 8 a. Since it is reflected, (90− sin ⁻¹ n sin θ ₁ / n ′) ≦ sin θ ₁ n / n ′

Then, the image light a ₂ emitted from the reflective liquid crystal display panel 10 and incident on the prism 8 along the same path as the light a ₁ from the light source is transmitted to the projection lens facing surface 8 of the prism 8.
c, the image light a ₂ can be projected toward the screen 2.

In this embodiment, the incident path of the light a ₁ incident on the liquid crystal display panel 10 and the liquid crystal display panel 1
Because they are matched with the emission path of the image light a ₂ emitted from 0, LCD all light reflected by the reflecting plate 16 through the respective pixel display portion of the liquid crystal display panel 10 through the same pixel display unit The light is emitted from the display panel 10, and therefore, the above-described color shift and luminance reduction can be completely eliminated.

FIG. 5 shows a second embodiment of the present invention. This embodiment is provided between the prism 8 and the reflection type liquid crystal display panel 10 provided in the second embodiment.
A transparent cooling liquid such as an aqueous solution of ethylene glycol is filled in a container having transparent surfaces, and a display panel cooler 9 having a heat pipe for heat radiation inserted therein is provided in the container.

In the case of this embodiment, the angle of the light a1 emitted from the prism 8 toward the liquid crystal display panel 10 is determined by the refractive index of the display panel cooler 9. by arranging a reflective liquid crystal display panel 10 so that the panel surface is perpendicular Te, the incident path of light a ₁ incident on the liquid crystal display panel 10, and the emission path of the image light a ₂ emitted from the liquid crystal display panel 10 Can be matched. In FIG. 5, for convenience, the optical path of light in that case is shown assuming that the refractive index of the display panel cooler 9 is the same as the refractive index of the prism 8.

In each of the embodiments described above, the projection type liquid crystal display device for projecting the display image of the liquid crystal display panel onto the transmission type screen 2 on the front surface of the case from the back side thereof has been described. The present invention can be applied to a projection-type liquid crystal display device that projects a display image on an external screen separate from the device main body, and the liquid crystal display panel 10 is not limited to a device that displays a full-color image, but can also display a monochrome image such as a monochrome image. A display may be provided, and the reflection surface on the back surface may be formed by forming a reflection film by vapor deposition or the like on the back surface of the panel instead of providing the reflection plate 16.

[0036]

According to the projection type liquid crystal display device of the present invention,
Since the image light emitted from the reflective liquid crystal display panel is light that has passed through the liquid crystal display panel twice, the light leakage of the pixel display unit selected in the light blocking state becomes considerably small, so that image light with good contrast is obtained. If this image light is made incident on the projection lens and enlarged and projected on the screen, the image projected on the screen can be a high-quality image with good contrast. Further, an optical member for refracting light is disposed between the light source and the liquid crystal display panel, and the light from the light source is refracted by the optical member to form the liquid crystal display.
While the light is incident on the display panel from the front side, the image light reflected by the reflection surface on the back side and emitted to the front side of the liquid crystal display panel is reflected again by the optical member.
By making the light incident on the projection lens, the angle between the light from the light source incident on the liquid crystal display panel and the light emitted from the liquid crystal display panel can be reduced, so that image light with higher contrast can be projected.

[Brief description of the drawings]

FIG. 1 is a basic projection type liquid crystal table for explaining the present invention .
FIG.

FIG. 2 is an enlarged sectional view of a part of a reflection type liquid crystal display panel used in the liquid crystal display device.

FIG. 3 is a vertical sectional side view of the projection type liquid crystal display device showing the first embodiment of the present invention .

FIG. 4 is an optical path diagram of light entering and exiting the reflection type liquid crystal display panel.

FIG. 5 is an optical path diagram of light entering and exiting a reflective liquid crystal display panel according to a second embodiment of the present invention .

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/13 G02F 1/1335 G03B 21/00 H04N 5/74

Claims (1)

(57) [Claims] 1. A projection type liquid crystal display device for enlarging and projecting a display image of a liquid crystal display panel onto a screen by a projection lens, wherein said liquid crystal display panel is a reflection type liquid crystal display panel having a reflection surface on a back surface thereof, and a light source and said liquid crystal. An optical member that refracts light is disposed between the display panel and the display panel, and light from the light source is refracted by the optical member.
While being incident on the liquid crystal display panel from the front side, image light reflected by the reflection surface on the back side and emitted to the front side of the liquid crystal display panel is again transmitted by the optical member.
A projection type liquid crystal display device, wherein the light is reflected and made incident on the projection lens .