JP2916039B2 - Projection type image display device - 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 image display device such as a projection television and an overhead projector.

[0002]

2. Description of the Related Art There is an increasing demand for liquid crystal display devices as projection display devices for projection televisions and the like. When a liquid crystal display device is used as a projection type, a small and high-definition display is required for the liquid crystal display device in terms of cost and specifications. However, when the arrangement of the picture elements of the liquid crystal display element is increased in order to provide a small and high-definition display, the area of a portion other than the picture elements such as wiring with respect to the display area becomes relatively large, which contributes to display. The area of the picture element is reduced. As a result, the aperture ratio defined by the area ratio of the pixel opening to the display area decreases. When the aperture ratio is small, the light use efficiency is deteriorated, so that the projection screen becomes dark and the image quality is reduced. This problem is particularly serious in an active matrix type liquid crystal display device.

In order to prevent such a decrease in aperture ratio due to an increase in the number of picture elements, a method has been proposed in which a microlens array is formed on one surface of a liquid crystal display device (Japanese Patent Laid-Open No. 60-165621-165624). issue). FIG. 7 is a cross-sectional view of a liquid crystal display device having a microlens array in a liquid crystal display element. This liquid crystal display device has a liquid crystal display element 101 in which support substrates 103 and 104 are disposed opposite to each other with a liquid crystal layer 102 interposed therebetween.
A color filter 105 is formed on the liquid crystal layer 102 side of the liquid crystal display element 1, and a microlens array 106 is formed on the other (upper) support substrate 104 on the side opposite to the liquid crystal layer 102.
01 is formed in a position arrangement corresponding to each pixel.

In the liquid crystal display device having the above-mentioned structure, as shown in FIG. 8, the incident light travels along the optical path 111, so that the light-collecting state can be improved. That is, the micro lens array 106
In the structure having no pixel, the incident light travels like the optical path 112 and reaches other than the picture element opening 113. However, by providing the microlens array 106, the incident light travels through the optical path 111 and the picture element opening 113. Is collected. As a result, a small and bright display has become possible.

[0005]

The problem of the brightness of the display screen has been solved by incorporating the microlens array into the image display device, but the problem of the display quality still remains. Among the components of the projection type image display device, a microlens array, a liquid crystal display element, and the like generate less heat due to light absorption, but a color filter, a polarizing plate, and the like generate more heat due to light absorption. Therefore, in the image display device, the temperature rises due to a polarizing plate or the like. Since the color filter generates a large amount of heat due to light absorption, the temperature of the substrate provided with the color filter rapidly rises when the color filter is incorporated in a projection type image display device. Moreover, since the illuminance distribution of the light source is not uniform, the temperature rise varies depending on the location. Accordingly, for example, uneven temperature distribution occurs on the surface of the glass substrate on which the color filter is formed, and as a result, anisotropic stress is generated in the glass substrate due to a temperature gradient. The optical anisotropy due to the anisotropic stress, so-called photoelasticity, causes a partial decrease in contrast and adversely affects display quality.

The present invention has been made in view of the above circumstances, and it is possible to reduce contrast unevenness due to photoelasticity, and to prevent a decrease in screen brightness due to a decrease in aperture ratio, thereby achieving a uniform image. It is an object of the present invention to provide a projection type image display device having a bright screen.

[0007]

The projection type image display device of the present invention has a light source and a plurality of light paths through which light from the light source is guided, and a light absorbing film is arranged around the light path. A parallel light selecting means for converting the light from the light source into substantially parallel light by absorbing the light that has reached the light absorbing film; and a plurality of picture elements arranged on the light emitting side of the parallel light selecting means. A display element, and a microlens array arranged on the light incident side of the display element and condensing and guiding light substantially collimated by the parallel light selecting means to an opening of the picture element of the display element. And the effective angle of the microlens array
Is the focal length F of the microlens array,
Of the opening of the picture element corresponding to the microlens array
In relation to the magnitude H, if defined by Equation 1
^{Moni, | θ | ≦ tan -1 (} H / 2F) ··· ( Equation 1) wherein the effective angle of the microlens array | 0 | 4 °
It is characterized by the following, thereby achieving the above object.

Preferably, the shape of the cross section of the light path of the parallel light selecting means is similar to the shape of the picture element of the display element.

[0009]

According to the present invention, the light from the light source is substantially parallelized by absorbing the light that has reached the light absorbing film by a parallel light selecting means comprising a plurality of light paths around which a light absorbing film is disposed. It can be light. Using this parallel light selecting means, only the parallel light effective for the light condensing effect of the microlens array provided on the light incident side of the display element is selectively used, and this parallel light is used by the microlens array to display the display element. The light is condensed and guided to the opening of the picture element. For this reason, it is possible to efficiently condense light on the picture element of the display element, reduce the total amount of light incident on the display element, and suppress heat generation due to light absorption. As a result, display unevenness due to photoelasticity can be reduced, and the brightness of the display screen can be maintained.
In addition, the effective angle | θ |
As defined by Equation 1, select parallel light according to it
By setting the means, light is more efficiently applied to the picture element of the display element
Focusing, especially when the effective angle | θ | ≦ 4 °
By setting the parallel light selection means so that
Light can be most efficiently condensed on picture elements. Follow
Therefore, according to these configurations, display unevenness due to photoelasticity is reduced.
It is very effective in reducing the brightness and maintaining the brightness of the display screen.
is there. Furthermore, the shape of the cross section of the light path of the parallel light selecting means is
If the shape of the picture element of the display element is similar to that of the picture element,
Light can be more efficiently condensed on the element.

[0010]

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

FIG. 1 shows a configuration diagram of a projection type image display device of the present embodiment. This image display device is provided with a metal hide lamp as a light source 2 at the focal point of the paraboloid of the parabolic mirror 1. Light from the light source 2 is converged by the parabolic mirror 1 into substantially parallel light beams. A filter 3 for condensing the light into a substantially parallel light beam and then cutting off infrared light and ultraviolet light
, The parallel light selecting means 4 and the polarizing plate 5 a as a polarizer, in this order, and incident on the liquid crystal display device 15, and the image passing through the liquid crystal display device 15 is converted into a polarizing plate 5 b as an analyzer, a lens 12 and It is configured to be projected on a screen 14 via a projection lens 13.

The liquid crystal display device 15 has a substrate 6, a microlens array 7, a color filter 8, and a liquid crystal display element 11 from the light incident side to the emission side. Each lens of the micro lens array 7 and each R.R.
G. FIG. B. The filter is aligned with each picture element of the liquid crystal display element 11, and the adhesive 1 is provided between the color filter 8 and the liquid crystal display element 11 via a spacer 9.
0 is attached.

As shown in FIG. 2, for example, the parallel light selecting means 4 is constituted by combining a number of hexagonal cylindrical light paths 4a, and is provided with a black coating around the periphery to absorb light.
A light absorbing film is formed. Therefore, of the incident light, the light that has reached the periphery of the optical path 4a is absorbed, and only substantially parallel light is emitted.

In the projection type image display device having the above structure, the parallel light selecting means 4 is provided between the light source 2 and the polarizing plate 5a.
Only the light with good parallelism effective for the light-condensing effect can be selectively used, and the color filter 8 and the polarizing plates 5a, 5a
The total amount of light incident on an element that generates relatively large heat due to light absorption such as b can be reduced. As a result, the amount of heat generated in the color filter 8, the polarizing plates 5a, 5b, and the like was suppressed, and the display unevenness due to photoelasticity was reduced, and the brightness of the display screen could be maintained.

In order to prove the above-mentioned effects, the display quality of the projection type image display device of the present embodiment is compared with that of the display device of the present invention which has the same configuration as the display device of the present invention but does not include only the parallel light selecting means 4. An experiment was performed.

FIG. 2 shows the shape of the parallel light selecting means 4 used in the experiment. In the experiment, the parallel light selecting means 4 was obtained by coating a black paint for forming a light absorbing film on Hivex (made of aluminum) manufactured by Yokohama Rubber Co., Ltd. The light selecting means having a length L of 30 mm was used. The liquid crystal display element 11 has an aperture ratio of 30%.
The opening was a square having a size of about 100 μm square, the microlens was designed to have a focal length of 700 μm, and focused on the opening of the liquid crystal display element 11. still,
The present invention is not limited to this setting.

Table 1 shows the experimental results.

[0018]

[Table 1]

Here, the CCR value represents uneven illuminance distribution, and is defined as a percentage of the lowest illuminance with respect to the highest illuminance.
The brightness of the display screen is based on the brightness of the display screen of a projection image display device that does not include the microlens array 7 and the parallel light selection means 4.

As can be seen from Table 1, the parallel light selecting means 4
When the CCR value of light incident on the color filter 8 from the light source 2 is
20% to 30%, minimum contrast 40 to 90
Has been improved. According to this result, the parallel light selecting means 4
Is provided, the CCR value of the light incident on the color filter 8 from the light source 2 can be improved. As a result, the uneven temperature distribution generated in the color filter 8 can be reduced, and the decrease in contrast due to photoelasticity can be prevented. It was proved. The CCR value on the projection screen is 38
%.

With respect to the brightness of the display screen, the display device provided with the parallel light selecting means 4 is slightly darker, 1.6 times, than that of the display device not provided with the parallel light selecting means 4. However, the effect of adding the microlens array 7 is sufficient.

From the above results, it can be said that according to the projection type image display device of the present invention, a uniform and bright display screen can be obtained.

In this experiment, the parallel light selecting means 4 is made of a material having a honeycomb structure, which is metal-processed. However, if the material can selectively extract a component having good parallelism from the light components without loss. Any other plastic material, such as Lumisty, a visibility control plate manufactured by Sumitomo Chemical Co., Ltd., or a light control film manufactured by Sumitomo 3M Limited, could obtain the same effect.

Further, by changing the setting of the diameter D of the light path and the length L of the light path of the parallel light selecting means 4, the light collection efficiency on the microlens array 7 can be easily increased.
The setting method will be described below.

FIG. 3 is a sectional view of the substrate 6 on which the microlens array 7 is formed and the liquid crystal display element 11. As can be seen from FIG. 3, the light ray angle (hereinafter referred to as an effective angle) | θ | effective for light collection by the microlens array 7 is determined by the focal length F of the microlens array 7 and the picture element corresponding to the microlens array 7. Using the size H of the opening, it can be expressed as in Equation 1.

[0026]

(Equation 1)

However, here, it is assumed that the size of the condensed spot of the microlens is small enough to have no area, and that the aperture of the picture element is circular.

Therefore, as can be seen from FIG. 2, the relationship between the maximum value θmax of the effective angle θ and the diameter D of the cross section of the optical path 4a and the length L of the optical path 4a is set as shown in the following equation (2). For example, light beams having an excellent light-condensing effect of the microlens array 7 can be effectively used, and light beams at unnecessary angles can be absorbed by the parallel light selecting means 4.

[0029]

(Equation 2)

From equations (1) and (2), the light path 4a, the microlens array 7, and the liquid crystal display element 11 may be set to satisfy equation (3).

[0031]

(Equation 3)

In the above experiment, the ratio of the length L of the light path to the diameter D of the light path of the parallel light selecting means 4 was set to 1:10. This is set to selectively use light having an effective angle | θ | ≦ 4 °.

On the other hand, when the converging spot has an area,
Although the range of the effective angle θ differs depending on the size of the condensed spot and the illuminance distribution, it is sufficient to design the light spot with approximately the same ray angle as when the condensed spot has no area. FIG. 4 shows the relationship between the ray angle and the light utilization rate (%) in the case where the condensed spot is a point and in the case of this embodiment. In the embodiment, the focal length F is set to 700 μm, and the size H of the opening is set to 1
It was set to 00 μm. As can be seen from FIG. 4, in the present embodiment, if the parallel light selecting means 4 is set so that the effective angle | θ | ≦ 4 °, the total amount of light incident on the element that generates heat by light absorption is suppressed, and The brightness of the display screen can also be secured. However, the present invention is not limited to this set value.

Next, the case where the picture element of the liquid crystal display element 11 has an opening having a special shape will be described. Here, a case where there is a difference in the aspect ratio of the openings will be described as an example. FIG. 5A shows the maximum angle θ that the parallel light selecting means 4 can pass in the vertical direction.
FIG. 5B shows the maximum angle θx that can pass in the horizontal direction. FIG. 6A shows the maximum angle θa of light that can be effectively used in the vertical direction of the opening of the picture element due to the light condensing effect of the microlens array 7, and FIG. 5B shows that the maximum angle can be used effectively in the horizontal direction. Indicates the maximum angle θb of light. In order to use light most efficiently, it is preferable to set θy = θa and θx = θb.

The shape of the opening of the picture element of the liquid crystal display element 11 may be any shape. If the shape of the opening of the parallel light selecting means 4 is set to be similar to the shape of the opening of the picture element, The light collection efficiency can be increased more efficiently.

[0036]

As is apparent from the above description, according to the projection type image display device of the present invention, the microlens array is provided on the light incident side of the display element, and the microlens array is formed by using the parallel light selecting means. By selectively using only the parallel light effective for the light condensing effect of the lens array, and condensing and guiding this parallel light to the aperture of the picture element of the display element by the microlens array, the picture of the display element can be obtained. It is possible to efficiently condense light on the element, reduce the total amount of light incident on the display element, and suppress heat generation due to light absorption. As a result, a projection-type image display device having a uniform and bright display screen can be obtained by reducing contrast unevenness due to photoelasticity and preventing a decrease in screen brightness due to a decrease in aperture ratio. I can do it. In addition, it has a micro lens array.
Since the effective angle | θ | is defined by the above equation 1,
If the parallel light selection means is set according to the
Light can be more efficiently focused on
Means for selecting parallel light so that the effective angle | θ |
The most efficient way to focus light on the picture elements of the display element
be able to. Therefore, according to these configurations, photoelasticity
To reduce display unevenness and maintain display screen brightness
It is very effective in running. Furthermore, the light of the parallel light selecting means
Make the shape of the passage cross section similar to the shape of the picture element of the display element.
To collect light more efficiently on the picture elements of the display device.
Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of a projection type image display device of the present invention.

FIG. 2 is a perspective view of a parallel light selecting unit.

FIG. 3 is a sectional view of a substrate on which a microlens array is formed and a liquid crystal display element.

FIG. 4 is a diagram illustrating a relationship between a light beam angle and a light utilization rate in a case where a condensing spot of a microlens is a point and in a case of the present embodiment.

5A is a diagram illustrating a maximum angle θy that a parallel light selecting unit can pass in a vertical direction, and FIG. 5B is a diagram illustrating a maximum angle θx that can pass in a horizontal direction.

FIG. 6A shows the maximum angle θa of light that can be effectively used in the vertical direction of the opening of the picture element due to the light condensing effect of the microlens array, and FIG. 6B shows the maximum light angle that can be effectively used in the horizontal direction. FIG. 6 is a diagram illustrating a maximum angle θb.

FIG. 7 is a cross-sectional view of a conventional liquid crystal display device having a microlens array.

8 is a diagram showing an optical path of incident light in the liquid crystal display device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Parabolic mirror 2 Light source 3 Filter 4 Parallel light selection means 4a Optical path 5a, 5b Polarizer 6 Substrate 7 Microlens array 8 Color filter 9 Spacer 10 Adhesive 11 Liquid crystal display element 12 Lens 13 Projection lens 14 Screen 15 Liquid crystal display Device D Diameter of light path L Length of light path F Focal length of microlens array H Size of aperture of picture element

Continued on the front page (72) Inventor Takuji Yamaya 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takeshi Shibuya 22-22 Nagaikecho, Abeno-ku, Osaka-shi Osaka Prefecture Inside Sharp Corporation (56 References JP-A-4-22939 (JP, A) JP-A-4-50817 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/13 G02F 1/1335 G03B 21/00 G03B 21/14 H04N 5/74

Claims (2)

(57) [Claims] 1. A light source, comprising: a plurality of light paths through which light from the light source is guided; a light absorbing film disposed around the light path; and absorbing light reaching the light absorbing film. Parallel light selecting means for converting light from the light source into substantially parallel light; a display element provided on the light emission side of the parallel light selection means and having a plurality of picture elements; and a light element on the light incident side of the display element. And a microlens array for condensing and guiding the light that has been made substantially parallel by the parallel light selecting means to the opening of the picture element of the display element, and an effective angle | of the microlens array. θ | is defined by Equation 1 in the relationship between the focal length F of the microlens array and the size H of the opening of the picture element corresponding to the microlens array, and | θ | ≦ tan ^{− 1} (H / 2F) (Formula 1) The effective angle of ray | θ | is 4 °
A projection type image display device characterized by the following. 2. The projection type image display device according to claim 1, wherein the shape of the cross section of the light path of the parallel light selecting means is similar to the shape of the picture element of the display element.