JP3528994B2 - Parallel light source for liquid crystal display device and liquid crystal display device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel light source for a liquid crystal display device and a liquid crystal display device using the same, and more particularly, a shallow and compact parallel light source for a backlight for a liquid crystal display device employing a hologram color filter. And a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Conventionally, a backlight for display has been indispensable in a high-brightness liquid crystal color display device. However, in the liquid crystal display device using the color filter, the poor utilization efficiency of the backlight has been a problem. The main reasons are as follows.

The area occupied by the black matrix other than the cells of each color is large, and the light impinging on it is wasted. Of the white light that enters each cell, the color components that pass through the R (red), G (green), and B (blue) color filters are limited to one color, and the other complementary color components are wasted. . Each color filter causes a loss due to absorption of light.

As a solution to these problems, as shown in FIG. 16, for example, a microlens array 2 is installed in front of the color filter 1, and a white light backlight 3 is provided in the color filter cells R and G, respectively. , B to avoid the black matrix 4 to illuminate the backlight 3 to improve the efficiency of use of the backlight 3 (eg, “Display and Imaging”, 1992, Vol. .1, N
o. 1, pp. 33-38).

Further, a method of efficiently dividing white light into R, G, and B by utilizing the spectrum of a hologram and reducing the absorption by the black matrix and the color filter for the above items (1) to (5), The applicants of the present invention filed Japanese Patent Application Nos. 5-12170-1, 5-14573, and 5-12573.
No. 97517, No. 5-149211, etc. For example, there is a method of combining a hologram having a spectral function without diffraction wavelength dependence and a microlens array having a condensing function, a method of using a hologram having a diffracted wavelength and angle selectivity which are multiplexed or laminated, and a method having a spectral function and a collective function. There is a method of using a hologram having both optical functions.

Further, as a parallel light source for a backlight having a small depth and a compact size for a liquid crystal display device using such a hologram color filter, the applicant of the present invention has disclosed a microlens array and its application in Japanese Patent Application No. 12554/1993. We proposed a micro secondary light source placed at the focal point of each lens.

[0007]

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

Conventionally, collimated light is used as a backlight used in a projector type liquid crystal display device or the like. However, since the distance between the light source and the collimated light is long, the device is large and bulky. Therefore, it cannot be used for a liquid crystal flat display device which should be compact.

The parallel light source according to Japanese Patent Application No. 5-125454 described above is one proposal, and there is a possibility that a parallel light source with a shallow depth for a liquid crystal display device can be constructed.

Therefore, the present invention has been made in order to explore this possibility, and an object thereof is still another form of a parallel light source for a backlight, which is compact and has a small depth for a liquid crystal display device using a hologram color filter. And to propose a liquid crystal display device using the same.

[0011]

[0012]

[0013]

A parallel light source for a liquid crystal display device of the present invention that achieves the above object uses a hologram color filter as a color filter for diffracting and splitting substantially parallel light into a spectral pixel of a corresponding color. In a parallel light source for a liquid crystal display device, a fine converging lens array and a fine secondary light source arranged at a focal point of each fine lens or an off-axis position thereof are provided, and the fine secondary light source has a high refractive index core and a low refractive index core. It consists of a high-refractive-index part provided in the low-refractive-index clad of a waveguide consisting of a refractive-index clad. It is characterized in that it is converted into substantially parallel light which is made incident on the hologram color filter by a converging lens array.

[0014]

In this case, it is desirable that the material of the high refractive index core or the material of the waveguide is a light scattering polymer which is transparent and has a light scattering property, and domains having different refractive indexes are phase-separated.

[0016]

[0017]

[0018]

[0019]

The above parallel light source for liquid crystal display devices can be used for other liquid crystal display devices which do not use the hologram color filter.

Further, in the liquid crystal display device according to the present invention, the parallel light source and the liquid crystal display panel are arranged in this order from the light source side, and the incident side of the liquid crystal display panel, the inside of the liquid crystal display panel, and the emission of the liquid crystal display panel. A diffuser plate is disposed on the side, and the above parallel light source for liquid crystal display device is used as a parallel light source.

Another liquid crystal display device according to the present invention is
From the light source side, a parallel light source, a hologram color filter for diffracting substantially parallel light to be incident on a spectral pixel of a corresponding color, and a liquid crystal display panel are arranged in this order. Inside the liquid crystal display panel, the hologram color filter and the A diffuser plate is disposed between the liquid crystal display panels or on the exit side of the liquid crystal display panel, and the parallel light source for a liquid crystal display device is used as a parallel light source.

[0023]

In the present invention, since the parallel light source can be formed in a flat plate shape with a shallow depth, by incorporating this into a liquid crystal display device employing a hologram color filter,
It is possible to configure a color liquid crystal display device having a shallow depth, a compact size, a wide viewing angle, and a bright color.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Prior to the description of embodiments of a parallel light source for a backlight according to the present invention, the principle of a typical hologram color filter proposed by the present applicant will be described with reference to the drawings. . First, the principle and operation of the previously proposed first embodiment color filter will be described with reference to the cross-sectional view of the liquid crystal display device of FIG. In the figure, a hologram array 5 that constitutes the previously proposed color filter is spaced apart from the side of the liquid crystal display element 6 on which the liquid crystal display element 6 is incident, which is regularly divided into the liquid crystal cells 6 '. On the back surface of the liquid crystal display element 6, there are arranged color filters 1'of R, G, B colors similar to FIG. 16 aligned with the respective liquid crystal cells 6'and a color filter 1 consisting of a black matrix 4 provided therebetween. Alternatively, the coloring cell 1'is omitted and only the black matrix 4 is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6.

The hologram array 5 corresponds to the repeating period of the R, G, and B color-separating pixels, that is, each set of three liquid crystal cells 6'adjacent to each other in the in-plane direction of the liquid crystal display element 6. It is composed of minute holograms 5'arranged in an array at the same pitch as the repeating pitch, and the minute holograms 5'are aligned in groups of three liquid crystal cells 6'adjacent to each other in the direction of the paper surface of the liquid crystal display element 6 to form one group. The micro holograms 5'are arranged one by one, and each micro hologram 5'corresponds to the micro hologram 5'the light of the green component in the backlight 3 which is incident at an angle θ with respect to the normal line of the hologram array 5. It is formed in a Fresnel zone plate shape so as to collect light on the colored cell 1 ′ or the liquid crystal cell 6 ′ at the center of the three color-dividing pixels R, G, and B. The minute hologram 5'is formed of a transmission hologram such as a relief hologram, a phase hologram, or an amplitude hologram, which has little or no wavelength dependency of diffraction efficiency. Here, the fact that the diffraction efficiency has no or little wavelength dependence means that it is not a type that diffracts only a specific wavelength and does not diffract other wavelengths like a Lippmann hologram. The wavelength also means that it is diffracted, and the diffraction grating having no wavelength dependence of the diffraction efficiency diffracts at different diffraction angles depending on the wavelength.

With such a configuration, when the white backlight 3 which is incident at an angle θ with respect to the normal line from the surface of the hologram array 5 on the side opposite to the liquid crystal display element 6 is incident, the wavelength is changed. The diffraction angles of the minute holograms 5'are different depending on the wavelengths, and the focusing positions for each wavelength are dispersed in the direction parallel to the surface of the hologram array 5. Among them, the red wavelength component is at the position of the color filter cell R or the liquid crystal cell 6'displaying red, the green component is at the position of the color filter cell G or the liquid crystal cell 6'displaying green, and the blue component. Is a color filter cell B or a liquid crystal cell 6'displaying blue
By arranging the hologram array 5 so as to diffract and collect light at respective positions, the respective color components are hardly attenuated by the respective color filter cells R, G, B and the black matrix 4, and the respective liquid crystal cells 6 are arranged. It is possible to perform color display according to the state of the liquid crystal cell 6'at the corresponding position after passing through the ??? The incident angle θ of the backlight 3 on the hologram array 5 is determined by various conditions such as hologram recording conditions, the thickness of the hologram array 5, and the distance between the hologram array 5 and the liquid crystal display element 6.

As described above, by using the hologram array 5 as a color filter, each wavelength component of the conventional color filter backlight can be made incident on each color cell without waste, and the utilization efficiency thereof is greatly improved. be able to.

Further, a modification of the above-mentioned first form can be considered. This will be described with reference to FIG. The principle and operation of the previously proposed modified color filter of the first embodiment will be described with reference to the same sectional view of FIG.
In the figure, color filters 30 using holograms already proposed are spaced apart from each other on the incident side of the backlight 3 of the liquid crystal display element 6 which is regularly divided into liquid crystal cells 6 '. On the back surface of the liquid crystal display element 6, there are arranged color filters 1'of R, G, B colors similar to FIG. 16 aligned with the respective liquid crystal cells 6'and a color filter 1 consisting of a black matrix 4 provided therebetween. Or colored cell 1 '
Is omitted, and only the black matrix 4 is arranged.
In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6.

The color filter 30 of the modification of the first embodiment proposed above comprises a hologram 27 and a microlens array 28, and the microlens 28 'constituting the microlens array 28 is divided into R, G, and B components. Corresponding to the repeating period of the color pixels, that is, each set of three liquid crystal cells 6'adjacent to each other in the direction of the paper surface of the liquid crystal display element 6, they are arranged in an array at the same pitch as the repeating pitch. Further, the hologram 27 is formed of uniform interference fringes acting as a diffraction grating, and is formed of a transmission hologram such as a relief type, a phase type, or an amplitude type which has little or no wavelength dependence of diffraction efficiency.

Due to such a configuration, the hologram 2
When the backlight 3 is made incident from the surface of the liquid crystal display 7 on the side opposite to the liquid crystal display element 6 at an angle θ, the light is diffracted at different angles depending on the wavelength and dispersed on the exit side of the hologram 27. It By the microlens 28 'arranged on the incident side or the emitting side of the hologram 27, the dispersed light is separated into wavelengths and condensed on its focal plane. Among them, the red wavelength component is at the position of the color filter cell R or the liquid crystal cell 6'displaying red, the green component is at the position of the color filter cell G or the liquid crystal cell 6'displaying green, and the blue component. So as to diffract and collect at the position of the color filter cell B or the liquid crystal cell 6'displaying blue,
By arranging the color filters 30, the respective color components pass through the respective liquid crystal cells 6 ′ with almost no attenuation in the respective color filter cells R, G, B and the black matrix 4, and the liquid crystal cells at the corresponding positions. Color display can be performed according to the state of 6 '. The incident angle θ of the backlight 3 on the hologram 27 is determined by various conditions such as the hologram recording condition, the thickness of the hologram 27, and the distance between the hologram 27 and the liquid crystal display element 6.

In such an arrangement, the hologram 27
As a transmission hologram, which has no or little wavelength dependence of diffraction efficiency, which is not a light-collecting property and has uniform interference fringes, can be used, the hologram 27 is aligned with each microlens 28 ′ of the microlens array 28. The features are that they do not need to be aligned, and that the pitch of the microlens array 28 is three times that of the conventional case of FIG. 16, making it easy to fabricate and align.

Next, the principle and operation of the previously proposed second embodiment color filter will be described with reference to the same sectional view of FIG. In the figure, the hologram array 15 constituting the already proposed color filter is spaced apart on the side of the liquid crystal display element 6 on which the liquid crystal display element 6 is incident, which is regularly divided into the liquid crystal cells 6 '. Liquid crystal display element 6
On the back side, a color filter 1 composed of R, G, B colored cells 1 ′ similar to FIG. 16 aligned with each liquid crystal cell 6 ′ and a black matrix 4 provided between them is arranged, or The coloring cell 1'is omitted and only the black matrix 4 is arranged. In addition to the above, polarizing plates (not shown) are arranged on both sides of the liquid crystal display element 6.

The hologram array 15 is formed by superimposing two holograms 16 and 17, or is formed by superposing two holograms 16 and 17 in a single layer on a single photosensitive material so as to be multi-recorded. , R, G, B, the repetition cycle of the color-separated pixels, that is, each set of three liquid crystal cells 6'adjacent to each other in the direction of the paper surface of the liquid crystal display element 6, is arrayed at the same pitch as the repetition pitch. It is composed of minute holograms 15 'arranged in a circle. Micro hologram 1
5'are arranged in alignment with each set of three liquid crystal cells 6'adjacent to each other in the direction of the plane of the liquid crystal display element 6, and one portion is arranged in each minute hologram 15 '. , A color filter cell of a set of three liquid crystal cells 6'corresponding to the minute hologram 15 'by selectively diffracting the red wavelength component in the white backlight 3 which is incident on the hologram array 15 almost vertically. It is formed in a Fresnel zone plate having wavelength selectivity so as to collect light at the position of the liquid crystal cell 6'displaying R or red, and the portion of each minute hologram 15 'belonging to the hologram 17 is: A set of three liquid crystal cells 6'corresponding to the minute hologram 15 'is selectively diffracted by selectively diffracting the blue wavelength component in the white backlight 3 which is incident on the hologram array 15 almost vertically. It is formed in the Fresnel zone plate-like with a wavelength selectivity so as to condense the position of the liquid crystal cell 6 'to display a color filter cell B or blue. Here, the hologram having wavelength selectivity is a type in which only a specific wavelength is diffracted and other wavelengths are transmitted without being diffracted, like a Lippmann hologram. Therefore, most of the blue wavelength component in the white backlight 3 which is vertically incident on the color filter 15 from the back of the liquid crystal display device is diffracted and condensed by the blue hologram 17 to display the color filter cell B or blue. Then, most of the red wavelength component is diffracted and condensed by the red hologram 16 and enters the color filter cell R or the position of the liquid crystal cell 6'displaying red.
The green component which is not diffracted and condensed by the holograms 17 and 16 passes straight through the hologram array 15 and is incident on the color filter cells R, G and B or the liquid crystal cell 6'displaying those colors one by one. However, the light incident on the color filter cells R and B is blocked by the filter at that position (when the colored cell 1'of the color filter is omitted, the green component is located at the position of the liquid crystal cell 6'which displays blue and red. Since it will be incident, the saturation will be higher if three holograms described below are overlapped or triple-recorded.), And it is effective only at the position of the color filter cell G or the liquid crystal cell 6'displaying green. Incident. The respective wavelength components pass through the respective liquid crystal cells 6'with almost no attenuation, and color display can be performed according to the state of the liquid crystal cells 6'at the corresponding positions. Instead of this, a Fresnel zone plate-shaped hologram for green, which also has wavelength selectivity, is additionally added or triple-recorded, and each of the three holograms corresponds to a corresponding color filter cell or liquid crystal cell 6 '. The wavelength components may be diffracted and condensed and made incident. In this case, although the number of holograms or the number of times of multiple recording increases, each wavelength component of the backlight 3 is not wasted and each color cell R, G, B is lost. Alternatively, since it can be made incident on the liquid crystal cell 6 ', its utilization efficiency is further improved.

By the way, in the above-mentioned FIG. 3,
A Fresnel zone plate-shaped micro hologram 15 'corresponding to each set of three color filter cells R, G, B or three liquid crystal cells 6'adjacent to each other in the direction of the paper.
2 are arranged side by side, but as in the case of FIG. 2, a similar microlens array is formed on two or three holograms in the shape of a uniform diffraction grating having wavelength selectivity or superposed. Similarly, in combination, the wavelength selectivity of diffraction of the hologram can be utilized to significantly improve the utilization efficiency of the liquid crystal display backlight.

By the way, the parallelism of the luminous flux required for the white backlight 3 for illuminating the hologram color filters 5, 30 and 15 as described above is as follows.
When the two-dimensional arrangement of the R, G, and B color separation pixels of the color filter is a stripe type, it may be about ± 40 ° in the X direction where the color separation pixels of the same color are arranged, but In the Y direction in which the color separation pixels are periodically repeated, it is preferably ± 10 ° or less, more preferably 5 ° or less. Also,
When the two-dimensional arrangement of the R, G, and B color separation pixels is a delta type or other type, it is preferably ± 10 ° or less, preferably 5 ° or less in either X or Y direction. Now,
An embodiment of a shallow and compact parallel light source according to the present invention for the white backlight 3 having such parallelism will be described below.

The parallel light source according to Japanese Patent Application No. 5-12554 filed previously is arranged at the focal point of each lens of the microlens array with a minute aperture provided at the tip of the optical fiber and the reflecting surface of the waveguide as a minute secondary light source. However, the white parallel light for backlight is generated from the microlens array, but in the example of FIG. 4, a special waveguide 32 is arranged in parallel behind the microlens array 31. The waveguide 32 is formed by coating a flat plate forming a core 33 having a high refractive index with a clad 34 having a low refractive index on both sides. The microlens array 31 has the same pitch as the two-dimensional pitch of the microlens array 31. The high-refractive index portions 35 are periodically provided on the side clad 34. The refractive index of the high refractive index portion 35 is set equal to or higher than the refractive index of the core 33.
In this way, the light introduced from the white light source 10 to one end of the waveguide 32 is totally reflected at the interface between the core 33 and the clad 34, and guided inside the waveguide 32 along the core 33 without leaking to the outside. , The guide light leaks out from the high refractive index portion 35 of the clad 34 on the microlens array 31 side,
The high refractive index portion 35 serves as a secondary light source. Therefore, by making each high refractive index portion 35 coincide with the focal point of each lens of the microlens array 31, the parallel backlight 3 can be generated in front of the microlens array 31.

In this case, the material of the core 33 is transparent and has a light transmitting property and a light scattering property, and has a different refractive index of several tens of μm.
When a light-scattering polymer such as a block polymer or a polymer blend in which domains having a size of m or less are phase-separated, a secondary light source with no loss and uniform brightness is obtained in the high refractive index portion 35. A brighter backlight 3 can be generated.

In the case of FIG. 5, a transparent plate 37 is provided as a waveguide 36 arranged behind the microlens array 31.
On both sides of the micro-lens array 31 at the same pitch as the two-dimensional pitch and on both sides by a half pitch shift
8 is provided, and a waveguide 36 formed by vapor-depositing a metal reflection layer 40 of aluminum or the like on both surfaces is provided except for the valley portion 39 on the side of the microlens array 31 which coincides with the focal point of each lens. Also in this case, the white light source 10 to the waveguide 3
The light introduced to one end of the waveguide 6 passes through the waveguide 36 through the transparent plate 37.
The guide light leaks out from the valleys 39 between the metal reflection layers 40 on the microlens array 31 side, and the valleys 39 serve as a secondary light source for the backlight 3. Moreover, in this case, the metal reflection layer 40 provided on the surface of the minute convex surface 38 serves as a light condensing surface, and light is more efficiently leaked from the valley portion 39. In this case also, the transparent plate 3
As the material of 7, a light-scattering polymer such as a block polymer or a polymer blend, which is transparent and has a light-transmitting property and a light-scattering property, in which domains having different refractive indexes and having a size of several tens of μm or less are phase-separated is used. As a result, a secondary light source that is uniform and has high brightness without loss is obtained in the valley portion 39, and the brighter backlight 3 can be generated.

By the way, at the focal point of each lens of the microlens array, the tip of the optical fiber, the minute aperture provided in the reflecting surface of the waveguide, the high refractive index portion 35 and the valley portion 39 as described above.
Even if the minute primary light sources are directly arranged instead of such minute secondary light sources as described above, a compact parallel light source with a shallow depth can be configured. Below, several examples of arranging this minute primary light source behind the microlens array will be shown.

FIG. 6 shows a case where light of each color of R, G and B is emitted 3
White LED 42 configured by arranging two LEDs close to each other
Are arranged on the substrate 41 at the same pitch as the two-dimensional pitch of the microlens array 31, and the white LEDs 42 are arranged at the focal points of the respective lenses of the microlens array 31 to obtain the white backlight 3 for parallel light.

FIG. 7 shows a white phosphor 44 such as calcium halophosphate, or an R color phosphor such as (Y, Ge) BO ₃ : Eu and a G color phosphor such as Zn ₂ SiO ₄ : Mn and BaMg.
A white phosphor 44 mixed with a B color phosphor such as Al ₁₄ O ₂₃ : Eu is arranged on the substrate 43 at the same pitch as the two-dimensional pitch of the microlens array 31, and the white phosphor 44 is formed.
Is arranged at the focal point of each lens of the microlens array 31, and the white backlight 3 for parallel light is obtained.

In FIG. 8, a pinhole array 47 having the same pitch as the two-dimensional pitch of the microlens array 31 is arranged so that each pinhole is located at the focal point of each lens of the microlens array 31. Four
The white light from the white phosphor layer 48 provided on the substrate 46 behind it is made incident on the microlens array 31 via 7 and the parallel backlight white backlight 3 is obtained.

FIG. 9 shows a thin film phosphor in which the white phosphor 50 as described above is kept in xenon gas, sandwiched by electrodes 51, 51 from both sides thereof, and the white phosphor 50 is made to emit light by ultraviolet rays generated from the xenon gas. Array 52, substrate 49
The thin-film phosphor array 52 is arranged at the same pitch as the two-dimensional pitch of the microlens array 31, and the thin-film phosphor array 52 is arranged so as to match the focal points of the lenses of the microlens array 31 to obtain the white backlight 3 for parallel light. is there.

According to the Japanese Patent Application No. 5-125454 filed previously, when arranging the tip of the optical fiber and the minute aperture provided on the reflecting surface of the waveguide at the focal point of each lens of the microlens array as a minute secondary light source, And FIG. 4 to FIG. 9 described above.
In the case of, the GRIN lens array in which the gradient index lenses (GRIN lenses) known as trade name SELFOC are arranged in an array may be used instead of the microlens array including the micro-convex lenses used. FIG. 10 shows an example of using the GRIN lens array 54 when the tip of the optical fiber 53 is used as the secondary light source.
One end of the optical fiber 53 is arranged so as to match the focus of each lens of the GRIN lens array 54, and the other end is arranged together with the other end of the other optical fiber 53 on the front surface of the white light source 10. The light introduced at the end is guided through each optical fiber 53,
The light emitted from one end of each optical fiber 53 is converted into parallel light by each GRIN lens of the GRIN lens array 54, and the white parallel backlight 3 is obtained.

When it is necessary to make the backlight 3 incident at an angle θ with respect to the normal line, as in the hologram color filters 5 and 30 of FIGS. 1 and 2,
If the primary light source or the secondary light source to be arranged at the focal point of each lens of the lens arrays 31 and 54 is eccentrically arranged off-axis, the lens arrays 31 and 54 can be arranged parallel to the hologram color filters 5 and 30. it can.

The above is an example of using the lens arrays 31 and 54 to obtain the parallel light 3, but an example of obtaining the parallel backlight 3 using a louver is shown in FIG. The louver 55 is formed by arranging the light absorption layers 56 in parallel in a one-dimensional or two-dimensional manner in the air or a transparent medium such as glass at a slight interval, and the straight-advancing component along the light absorption layer 56. Only the component that passes through is absorbed, and the component that intersects with the light absorption layer 56 is absorbed and not passed through. Therefore, when a white light source 57 such as a fluorescent lamp having a large light emitting area is arranged on one side of the louver 55, a rectilinear component in the direction in which the light absorption layer 56 faces the other side of the louver 55, that is, parallel light. Since it is obtained, it can be used as the white parallel backlight 3.

Further, a Fresnel reflecting mirror can be used to form a parallel light source having a shallow depth. 12A and 12B are views showing an example in which a parabolic Fresnel reflecting mirror 58 having a parabolic surface as a Fresnel reflecting mirror is used. FIG. 12A is a sectional view of a parallel light source, and FIG. It is a top view of the mirror 58. As shown in the figure, the parabolic Fresnel reflecting mirror 58 is a parabolic reflecting mirror having a large number of annular fine reflecting surfaces 59.
It is a combination of the cut white and the sawtooth-shaped cross section, and converts the light diverging from the point-shaped white light source 10 into parallel light 3 and reflects it like a parabolic reflector. is there. Therefore, this reflected light is reflected by the white parallel backlight 3
Can be used as

Further, as shown in the sectional view of FIG. 13, a total reflection Fresnel surface 66 having a sawtooth-shaped cross section is provided on the slope of the tapered light guide 65 made of a transparent material such as glass, and the linear shape is arranged at the focal line. The light from the white light source 11 is converted into parallel light by the gutter-shaped parabolic reflector 12, the parallel light is introduced from the side surface of the tapered light guide 65, and is reflected forward by the total reflection Fresnel surface 66 to guide the tapered light. The white parallel backlight 3 can be obtained by emitting light from the other side surface of the light body 65 at a predetermined angle θ.

A color liquid crystal display device is obtained by combining any one of the parallel light sources proposed above with a liquid crystal display device using the hologram color filters 5, 30, and 15 as shown in FIGS. Is configured as follows. In the following description, any one of the parallel light sources shown in FIGS.
As shown in FIGS. 1 to 3, a display comprising a liquid crystal display element 6, a color filter 1 (or only a black matrix 4) provided on the back surface of the liquid crystal display element, and polarizing plates arranged on both sides thereof. The panel will be referred to as LCD panel 61. Also, the hologram color filter 5,
Any one of 30 and 15 (including deformation) will be referred to as a hologram color filter 62.

In FIG. 14A, when the hologram color filter 62 requires the backlight 3 from an oblique direction, a parallel light source 60 that emits the parallel light 3 from the emitting surface in an oblique direction is used. FIG. 6 is a diagram showing an arrangement showing the overall configuration of the color liquid crystal display device in the case of performing a parallel light source 60, a hologram color filter 62, an LCD panel 61, and a diffusion plate 63 arranged in parallel from the side of the parallel light source 60 in order to reduce the depth. It is shallow and can be made thin in overall thickness. The diffusion plate 63 is provided inside the LCD panel 61 or the hologram color filter 62 and the LCD.
It may be arranged between the panels 61.

In FIG. 14B, when the hologram color filter 62 requires the backlight 3 from an oblique direction, a parallel light source 60 that emits the parallel light 3 in the vertical direction from its emission surface is used. It is the same figure in a case, and is a parallel light source 60 and the hologram color filter 6.
2. The arrangement order of the LCD panel 61 and the diffusion plate 63 is the same as that shown in FIG. 9A, but the parallel light source 60 and the hologram color filter 62 are not parallel to each other, and a wedge-shaped space must be arranged between them. As a result, the overall thickness becomes slightly thicker.

FIG. 14C shows the case where the hologram color filter 62 requires the backlight 3 from the vertical direction, or the deflection using refraction or reflection as proposed in Japanese Patent Application No. 5-225614. In a case where the backlight 3 is vertically incident on the hologram color filter 61 by using an optical element, a similar diagram when a parallel light source 60 that emits the parallel light 3 in the vertical direction from its emission surface is used. The arrangement order of the parallel light source 60, the hologram color filter 62, the LCD panel 61, and the diffusion plate 63 is the same as that shown in FIG. In this case, the parallel light source 60 can be arranged parallel to the hologram color filter 62, and the depth can be made shallow and the overall thickness can be made thin, as in the case of FIG.

The liquid crystal display device combined with the parallel light source 60 according to the present invention is a hologram color filter 6
It is also possible to block the 0th-order light from 2 and prevent it from entering the LCD panel 61. FIG. 15 shows one of the means, that is, the hologram color filter 62 and the LCD.
Between the panels 61, that is, on the exit side of the hologram color filter 62, a 0th-order light blocking louver 64 configured to cut only light in a predetermined direction is arranged. With such a configuration, since unnecessary light does not reach the viewing side, bright and high-contrast display can be performed.

The parallel light source for a liquid crystal display device of the present invention and the liquid crystal display device using the same have been described above based on some embodiments, but the present invention is not limited to these embodiments and various modifications can be made. It is possible.

[0056]

As is apparent from the above description, according to the parallel light source for a liquid crystal display device of the present invention, the parallel light source can be formed in the shape of a flat plate having a shallow depth. Therefore, the parallel light source adopts a hologram color filter. Incorporation into a color liquid crystal display device having a shallow depth, a compact size, and a wide viewing angle can be configured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining the principle and operation of a color filter of a first mode proposed above.

FIG. 2 is a cross-sectional view for explaining the principle and operation of the modified color filter of the first embodiment.

FIG. 3 is a cross-sectional view for explaining the principle and operation of the previously proposed second embodiment color filter.

FIG. 4 is a sectional view of a first embodiment of a parallel light source according to the present invention.

FIG. 5 is a sectional view of a second embodiment of a parallel light source according to the present invention.

FIG. 6 is a sectional view of a third embodiment of a parallel light source according to the present invention.

FIG. 7 is a sectional view of a fourth embodiment of a parallel light source according to the present invention.

FIG. 8 is a sectional view of a fifth embodiment of a parallel light source according to the present invention.

FIG. 9 is a sectional view of a sixth embodiment of a parallel light source according to the present invention.

FIG. 10 is a sectional view of a seventh embodiment of a parallel light source according to the present invention.

FIG. 11 is a sectional view of an eighth embodiment of a parallel light source according to the present invention.

FIG. 12 is a cross-sectional view of a ninth embodiment of a parallel light source according to the present invention and a plan view of a parabolic Fresnel reflector used therein.

FIG. 13 is a sectional view of a tenth embodiment of a parallel light source according to the present invention.

FIG. 14 is a cross-sectional view showing a configuration example of a liquid crystal display device according to the present invention.

FIG. 15 is a cross-sectional view of a liquid crystal display device configured to block 0th order light from a hologram color filter according to the present invention.

FIG. 16 is a sectional view of a conventional example using a microlens array.

[Explanation of symbols]

R, G, B ... Color filter cell, color separation pixel 1 ... Color filter (absorption type: conventional type) 1 '... Coloring cell 3 ... Backlight 4 ... Black matrix 5 ... Hologram array (previous proposal) 5' ... Micro hologram 6 ... Liquid crystal display element 6 '... Liquid crystal cell 10 ... White light source 11 ... Linear white light source 12 ... Parabolic reflector 15 ... Hologram array (color filter: previous proposal) 15' ... Micro hologram 16, 17 ... Hologram 27 ... Hologram 28 ... Microlens array 28 '... Microlens 30 ... Color filter (previous proposal) 31 ... Microlens array 32 ... Waveguide 33 ... Core 34 ... Cladding 35 ... High refractive index portion 36 ... Waveguide 37 ... Transparent plate 38 ... Micro convex surface 39 ... Valley 40 ... Metal reflective layer 41 ... Substrate 42 ... White LED 43 ... Substrate 44 ... White phosphor 4 Substrate 47 ... Pinhole array 48 ... White phosphor layer 49 ... Substrate 50 ... White phosphor 51 ... Electrode 52 ... Thin film phosphor array 53 ... Optical fiber 54 ... Gradient index lens (GRIN lens) array 55 ... Louver 56 ... Light Absorption layer 57 ... White light source 58 ... Parabolic Fresnel reflecting mirror 59 ... Micro reflecting surface 60 ... Parallel light source 61 ... LCD panel 62 ... Hologram color filter 63 ... Diffuser 64 ... Zero-order light blocking louver 65 ... Tapered light guide 66 ... Total reflection Fresnel surface

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Motohiro Oka 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Within Dai Nippon Printing Co., Ltd. (72) Inventor Miaki Tsuruoka 1-chome, Ichigaya-Kagacho, Shinjuku-ku, Tokyo 1-1-1 Dai Nippon Printing Co., Ltd. (72) Inventor Yoichi Mori 1-1-1 Ichigayaka-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. (56) Reference JP-A-6-230384 (JP, A) JP-A-6-196130 (JP, A) JP-A-5-273941 (JP, A) JP-A-7-43679 (JP, A) JP-A-6-235917 (JP, A) -55133 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/13357 F21V 8/00 G02B 6/00

Claims (5)

(57) [Claims] 1. A micro-converging lens array and a micro secondary light source arranged at the focal point of each micro lens or at an off-axis position thereof, wherein the micro secondary light source comprises a high refractive index core and a low refractive index clad. A high-refractive-index portion provided in a low-refractive-index clad of the waveguide. Light from a white light source is introduced into one end of the waveguide, and light leaked from the high-refractive-index portion is converted into liquid crystal by the minute converging lens array. A parallel light source for a liquid crystal display device, which converts light into substantially parallel light to enter a display device. 2. In a parallel light source for a liquid crystal display device, which uses a hologram color filter as a color filter for diffracting and splitting substantially parallel light into incident spectral pixels of a corresponding color, a micro-converging lens array and focal points of each micro-lens. Or a minute secondary light source arranged at an off-axis position thereof, wherein the minute secondary light source is a high refractive index portion provided in a low refractive index clad of a waveguide including a high refractive index core and a low refractive index clad. And introducing light from a white light source into one end of the waveguide to convert the light leaked from the high refractive index portion into substantially parallel light that is made incident on the hologram color filter by the minute converging lens array. A parallel light source for liquid crystal displays. Wherein the material of the high refractive index core, there is a clear light scattering, claim 1 or different domains of refractive index, comprising the light-scattering polymer obtained by phase separation
2. A parallel light source for a liquid crystal display device according to 2 . 4. A parallel light source and a liquid crystal display panel are arranged in this order from the light source side, and a diffusion plate is arranged on the incident side of the liquid crystal display panel, the inside of the liquid crystal display panel, or the exit side of the liquid crystal display panel. Ri Na is, and the parallel light source
A liquid crystal display device according to any one of claims 1 to 3.
A liquid crystal display device using a parallel light source . 5. A parallel light source, a hologram color filter for diffracting and splitting substantially parallel light into a spectral pixel of a corresponding color, and a liquid crystal display panel are arranged in this order from the light source side.
Interior of the liquid crystal display panel, between the hologram color filter and the liquid crystal display panel, or Ri Na and diffuser plate is disposed on the exit side of the liquid crystal display panel, said flat
The liquid crystal according to claim 1, as a row light source.
A liquid crystal display device using a parallel light source for a display device.