JPH06222362A - Illumination device for liquid crystal display device - Google Patents

Abstract

PURPOSE:To enhance the utilizing efficiency of illumination light by collimating the illumination light of a liquid crystal display device and making it incident on a liquid crystal display panel or a hologram for spectrum. CONSTITUTION:The illumination light emitted from a light source 17 is made incident on one end parts of respective optical fibers 15 and guided to the other end parts by being guided in the fibers 15. The divergent light emitted from one end part with one end part of the fiber 15 as a secondary point light source is converted to the collimated beam of light 3 by the lens surface of the micro- convex lens of a micro-convex lens array 4 and made incident on the corresponding microhologram of the hologram 2. The spectrally split light of R, G and B is passed through a liquid crystal cell and made incident on color filter cells R, G and B. Then, the bright color display is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device for a liquid crystal display device, and more particularly, to use the illumination light by collimating the illumination light and making the parallel light incident on a liquid crystal display panel or a hologram for spectroscopy. The present invention relates to a device for improving efficiency.

[0002]

2. Description of the Related Art The applicant of the present invention discloses in Japanese Patent Application Nos. 5-12170 and 5-12171 that a backlight is efficiently dispersed and incident on each of R, G and B cells of a color filter of a color liquid crystal display device. In order to improve the light utilization efficiency, a method using a hologram was proposed. The principle will be briefly described. In the case of FIG. 6A, a parallel backlight 3 is incident on a hologram 5 having no wavelength selectivity and a spectral property, and R split by the hologram 5,
The light of G and B is 1 of the color filter 1 of the liquid crystal display panel.
The light is made incident on the color filter cells R, G, and B that form pixels to improve the utilization efficiency of the backlight. In the case of FIG. 6B, diffraction is performed on a specific wavelength like a Lippmann hologram. Using the wavelength-selective holograms 6 and 7, the blue light diffracted by the hologram 6 is put into the color filter cell B, the red light diffracted by the hologram 7 is put into the color filter cell R, and the holograms 6 and 7 are put together. The remaining complementary color component (green) that is not diffracted by is made incident on the color filter cell G,
It is intended to improve the utilization efficiency of the backlight.

Further, conventionally, a liquid crystal display device used for a projection device has been illuminated with parallel light and enlarged and projected on a screen.

[0004]

However, in the illuminating device using the hologram, if the backlight of the current liquid crystal flat display is used as it is, the expected effect cannot be obtained. This is because although the hologram originally has a severe incident angle selectivity, the back light of the liquid crystal flat display is scattered light of about ± 50 °, so that high diffraction efficiency cannot be obtained, and This is because the phenomenon that the diffracted light of the original color does not enter the color filter cell of a predetermined color occurs, and the utilization efficiency of the backlight cannot be improved as expected.

The present invention has been made in view of such a situation, and an object thereof is to make illumination light of a liquid crystal display device parallel and to make the parallel light incident on a liquid crystal display panel or a hologram for its spectrum. Therefore, the utilization efficiency of the illumination light is improved.

[0006]

In a lighting device for illuminating a liquid crystal display device from the back, a lighting device for a liquid crystal display device according to the present invention which achieves the above object is arranged at the focal point of a micro-converging lens array and each micro-focusing lens. And emitting parallel light.

In this case, the minute converging lens is composed of a rotationally symmetric lens, the minute secondary light source is composed of one end of an optical fiber, and the light from the light source is introduced into the other end of each optical fiber to emit light from the one end. Alternatively, the minute secondary light source is constituted by a minute aperture provided on the reflecting surface of the waveguide, and light from the light source is introduced into one end of the waveguide to cause the minute aperture to emit light. You can also do so.

Further, the minute converging lens is composed of a cylindrical lens, the minute secondary light source is provided on the reflecting surface of the waveguide, and is constituted by a slit opening parallel to the generatrix of the cylindrical lens, and one end of the waveguide is formed. It is also possible to introduce light from a light source into the slit to cause the slit opening to emit light.

In these, the liquid crystal display device is
In a color liquid crystal display device in which color filter cells of different colors are periodically arranged with respect to adjacent liquid crystal cells and a backlight is emitted from the back side to perform color display, between a micro-convergent lens array and an array of color filter cells. It is also possible to dispose a hologram that disperses substantially parallel light from the micro-convergent lens array and makes it enter the color filter cell position of the corresponding color.

[0010]

In the present invention, the micro-convergent lens array and the micro-secondary light source arranged at the focal point of each micro-convergent lens irradiate almost parallel light. Therefore, for example, a liquid crystal display using a spectroscopic hologram is used. In the device, it is possible to surely improve the utilization efficiency of the backlight by the hologram. Also, the degree of parallelism of the illumination light can be freely changed by simply changing the optical system such as the diameter of the divergence point of the minute secondary light source, the focal length of the minute converging lens array, and the distance between the two. In addition to the hologram on the condition that is parallel light, it is also possible to use a hologram in which divergent light and convergent light are reproduction light.

[0011]

Embodiments of the illuminating device for a liquid crystal display device of the present invention will be described below with reference to the drawings. In the color liquid crystal display device as shown in FIG. 6, the holograms 5 to 7 are
When the backlight 3 is incident and reproduced according to the conditions at the time of shooting, the diffraction efficiency, the diffraction angle and the like can be sufficiently exhibited. However, if the reproduction condition is different from that at the time of shooting, the performance will be sharply reduced. For this reason, the effect of using the holograms 5 to 7 is reduced with the conventional illumination light that is scattered light.

Therefore, in the present invention, an illuminating device capable of irradiating uniform plane-emitted parallel light is used, and for example, the efficiency at the time of reproducing a hologram using parallel light as reference light at the time of photographing is increased. Note that, in the following, a configuration in which a backlight is efficiently dispersed and made incident on each cell of a color filter of a color liquid crystal display device by such a hologram is described, but the present invention is not limited to this and is used for a projection device. It can also be used as a lighting device of a liquid crystal display device.

FIG. 1 shows the construction of an illuminating device according to an embodiment of the present invention. In this figure, the spectral effect as shown in FIG. 6A or 6B is aligned with each pixel composed of a set of three color cells R, G, B of the color filter 1 of the color liquid crystal display device. A hologram 2 in which minute holograms that perform the above are arranged in an array at the same pitch as the pixel pitch of the color filter 1 is arranged on the incident side of the backlight 3 of the color filter 1. A liquid crystal display panel (not shown) is arranged between the color filter 1 and the hologram 2 so that the filter cells R, G, B and the liquid crystal cell are aligned. According to the present invention, on the incident side of the hologram 2, a minute convex lens array 4 having a pitch corresponding to the minute hologram array is arranged, and as shown in a partially enlarged view of FIG. Convex lens 1
One end of the optical fiber 15 is attached to the focal position of 4. The surface of the focal plane of each micro-convex lens 14 other than the end portion of the optical fiber 15 is covered with a light shielding film 16 so that external light does not enter. The other ends of the optical fibers 15 corresponding to the respective micro-convex lenses 14 are bundled together and are attached so as to face a light source 17 such as a metal halide lamp.

In such a configuration, the illumination light emitted from the light source 17 is incident on the other end of each optical fiber 15, guided in the optical fiber 15 and guided to one end, and as shown in FIG. In addition, the divergent light emitted from one end of the optical fiber 15 as a secondary point light source is converted into parallel light 3 by the lens surface of the minute convex lens 14 and is incident on the corresponding minute hologram of the hologram 2. The light of R, G, and B dispersed here passes through the liquid crystal cell and enters the color filter cells R, G, and B to perform bright color display. Thus, in the present invention, since the hologram 2 is irradiated with parallel light according to the conditions at the time of shooting, its diffraction efficiency and spectral characteristics are sufficiently exhibited, and high utilization efficiency of illumination light is obtained.

The concrete experimental results are shown below. Size of liquid crystal display panel: Diagonal length 9 inches Center wavelength of each cell of color filter 1: R: 650n
m G: 545 nm B: 460 nm Distance between hologram 2 and color filter 1: 60 μm Hologram 2: Photosensitive material: Photopolymer film thickness: 10 μm Refractive index difference: 0.023 Recording laser: Argon ion laser 5 W Recording wavelength: 514.5 nm Illumination device: Optical fiber 15: Core diameter 50 μm Micro-convex lens 14: Diameter 300 μm Focal length 500 μm In the above configuration, the degree of improvement in the efficiency of use of the backlight is ± 5 as in the conventional case using the hologram 2.
As a result of comparison with an illuminating device that emits divergent light of 0 °, the following results were obtained. However, the magnification is a magnification for improving the utilization efficiency in the case where the liquid crystal display panel is directly irradiated with the illumination light without using the hologram.

Conventional illuminator × 1.15 Illuminator of FIG. 1 × 2.30 From these results, even when the hologram 2 is installed in the liquid crystal display device, when the conventional illuminator is used as it is,
It can be seen that the degree of improvement is small. On the other hand, when the method of the present invention is adopted, the parallelism of the illumination light 3 can be suppressed to about ± 5 °, so it can be said that the performance of the hologram 2 is sufficiently brought out.

Next, an embodiment using a waveguide instead of an optical fiber will be described. As shown in the sectional view of FIG. 3 and the perspective view of the main part of FIG. 4, an aperture mask 18 is arranged behind the micro-convex lens array 4, and a waveguide 20 lined with a reflection plate 21 is arranged behind it. The opening mask 18 is
Each minute convex lens 14 forming the minute convex lens array 4 has a minute opening 19 at the focal position, and the other portions are light-shielding and the waveguide 20 side is a reflecting surface. And the waveguide 2
One side of 0 is attached to face the light source 17,
Illumination light from the light source 17 enters the waveguide 20 from the opposite side surfaces of the waveguide 20 and is multiple-reflected between the reflection plate 21 and the reflection surface of the aperture mask 18 to be guided in the waveguide 20. Meanwhile, a part of light leaks from the opening 19 of the opening mask 18. The divergent light emitted from the aperture 19 serving as a secondary point light source is converted into parallel light 3 by the lens surface of the minute convex lens 14, is incident on the corresponding minute hologram of the hologram 2, and is dispersed here by R. The light of G, B passes through the liquid crystal cell and is incident on the color filter cells R, G, B to perform bright color display. Also in this case, since the hologram 2 is irradiated with parallel light according to the conditions at the time of photographing, its diffraction efficiency and spectral characteristics are sufficiently exhibited, and high utilization efficiency of illumination light is obtained.

3 and 4 show the case where the color filter cells R, G, B have an isotropic shape such as a square or a circle, but when this is an elongated shape such as a stripe filter, the opening has a length. It is necessary to make the slit shape equal to. FIG. 5 shows a perspective view of a main part in that case. In this case, instead of the micro-convex lens array, a micro-cylindrical lens array 4'having micro-cylindrical lenses having a length equal to the length of the generatrix in the direction of the stripe filter is used,
The aperture mask 18 'is provided with a slitted aperture 19' at the focal line position of each micro cylindrical lens. Others are shown in Figure 3.
This is similar to the case of FIG.

The illuminating device for a liquid crystal display device of the present invention has been described above based on some embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0020]

As is apparent from the above description, according to the illumination device for a liquid crystal display device of the present invention, in a liquid crystal display device using a hologram for spectroscopy, for example, it is possible to surely improve the utilization efficiency of the backlight by the hologram. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a lighting device for a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a cross-sectional view of another embodiment.

FIG. 4 is a perspective view of an essential part of another embodiment.

5 is a perspective view of a main part of the modified example of FIG.

FIG. 6 is a diagram showing a schematic configuration of an illumination device for a color liquid crystal display device using a hologram proposed by the present applicant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Color filter 2 ... Hologram 3 ... Backlight 4 ... Micro convex lens array 14 ... Micro convex lens 15 ... Optical fiber 16 ... Shading film 17 ... Light source 18 ... Opening mask 19 ... Opening 20 ... Waveguide 21 ... Reflector 4 '... Micro Cylindrical lens array 18 '... Aperture mask 19' ... Slitt aperture

Claims (5)

[Claims] 1. An illumination device for illuminating a liquid crystal display device from behind, comprising a micro-converging lens array and a micro secondary light source arranged at the focal point of each micro converging lens, and irradiates substantially parallel light. Lighting device for liquid crystal display device. 2. The minute converging lens is composed of a rotationally symmetric lens, the minute secondary light source is composed of one end of an optical fiber, and light from the light source is introduced into the other end of each optical fiber to emit light from the one end. The lighting device for a liquid crystal display device according to claim 1. 3. The minute converging lens is composed of a rotationally symmetric lens, and the minute secondary light source is constituted by a minute aperture provided on a reflecting surface of the waveguide, and light from the light source is introduced into one end of the waveguide. The lighting device for a liquid crystal display device according to claim 1, wherein the minute aperture is caused to emit light. 4. The minute converging lens is composed of a cylindrical lens, the minute secondary light source is provided on a reflecting surface of the waveguide, and is constituted by a slit opening parallel to a generatrix of the cylindrical lens, and one end of the waveguide is provided. The lighting device for a liquid crystal display device according to claim 1, wherein light from a light source is introduced into the light source to cause the slit opening to emit light. 5. The liquid crystal display device comprises a color liquid crystal display device in which color filter cells of different colors are periodically arranged with respect to adjacent liquid crystal cells, and a backlight is irradiated from behind to perform color display. A hologram is arranged between the array of minute converging lens arrays and the array of color filter cells, and a hologram is arranged to disperse substantially parallel light from the array of minute converging lenses to be incident on a color filter cell position of a corresponding color. The illumination device for a liquid crystal display device according to any one of claims 1 to 4.