JP3698321B2 - Parallel light source for liquid crystal display device and liquid crystal display device using the same - Google Patents

Description

  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 in particular, a liquid crystal display device using a hologram color filter and a shallow parallel light source for a backlight and a liquid crystal display using the same. Relates to the device.

  Conventionally, in a high-brightness liquid crystal color display device, a backlight for display has become indispensable. 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.

  (1) The area occupied by the black matrix other than the cells of each color is large, and the light hit there is wasted.

  (2) Among the white light incident on each cell, the color components that pass through the R (red), G (green), and B (blue) color filters are each limited to one color, so the other complementary color components are It becomes useless.

  (3) A loss occurs due to light absorption in each color filter.

  Among these problems, as a solution of (1), as shown in FIG. 16, for example, a microlens array 2 is installed on the front surface of the color filter 1, and a white light backlight 3 is provided in the color filter cells R and G, respectively. A method of increasing the utilization efficiency of the backlight 3 by illuminating the light by condensing it to B and avoiding the black matrix 4 is known (for example, Non-Patent Document 1).

  Further, white light is efficiently divided into R, G, and B by using the spectrum by hologram, and the above-mentioned (1) to (3) are also reduced in absorption by the black matrix and color filter to increase efficiency. The present applicant has proposed the method in Japanese Patent Application Nos. 5-12170-1, 5-14573, 5-97517, and 5-149 211. For example, a method of combining a hologram having a spectral function without diffraction wavelength dependence and a microlens array having a condensing function, a method using multiplexed or stacked holograms having diffraction wavelength and angle selectivity, a spectral function and a collection There is a method using a hologram having both optical functions.

In addition, as a parallel light source for a backlight having a shallow depth for a liquid crystal display device using such a hologram color filter, the present applicant has disclosed a microlens array and its respective lenses in Japanese Patent Application No. 5-12554. We proposed a microsecondary light source placed at the focal point.
“Display and Imaging”, 1992, Vol. 1, No. 1 1, pp. 33-38

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

  Conventionally, parallel light is used as a backlight used in projector-type liquid crystal display devices, etc., but since the distance between the light source and the parallel light is long, the device is large and bulky. It cannot be used for liquid crystal flat display devices that should be compact.

  Further, the parallel light source according to the above-mentioned Japanese Patent Application No. 5-12554 is one proposal, and there is a possibility that a parallel light source with a small depth for a liquid crystal display device can be configured.

  Therefore, the present invention has been made in order to explore this possibility, and its purpose is to provide still another form of a compact parallel light source for a backlight having a shallow depth for a liquid crystal display device using a hologram color filter. It is to propose a liquid crystal display device used.

  A parallel light source for a liquid crystal display device according to the present invention that achieves the above object is a parallel light source for a liquid crystal display device using a hologram color filter that diffracts and divides substantially parallel light into a corresponding color spectral pixel as a color filter. And a micro-converging lens array and a micro-secondary light source disposed at the focal point of each micro-lens or an off-axis position thereof, the micro-secondary light source having a micro-convex surface on both sides and a valley between the convex surfaces of one surface The light is emitted from a white light source at one end of the waveguide and is leaked from the valley by the micro-converging lens array. The light beam is converted into substantially parallel light incident on the hologram color filter.

  In the first parallel light source for a liquid crystal display device, the material of the high refractive index core or the material of the waveguide may be made of a light scattering polymer that is transparent and has light scattering properties, and domains having different refractive indexes are phase-separated. desirable.

  Further, the minute convergence lens array may be composed of a gradient index lens array.

  The above parallel light source for liquid crystal display devices can of course be used for other liquid crystal display devices that do not use a hologram color filter.

  The liquid crystal display device according to the present invention is arranged in the order of the parallel light source and the liquid crystal display panel from the light source side, and diffuses to the incident side of the liquid crystal display panel, the inside of the liquid crystal display panel, and the emission side of the liquid crystal display panel. A plate is arranged, and the parallel light source for liquid crystal display device described above is used as a parallel light source.

  Another liquid crystal display device according to the present invention is arranged from the light source side in the order of a parallel light source, a hologram color filter for diffracting and splitting substantially parallel light into a corresponding color spectral pixel, and a liquid crystal display panel. A diffusion plate is disposed inside the display panel, between the hologram color filter and the liquid crystal display panel, or on the emission side of the liquid crystal display panel, and the above parallel light source for a liquid crystal display device is used as a parallel light source. It is characterized by this.

  In the present invention, since the parallel light source can be configured in a flat plate shape with a shallow depth, by incorporating this into a liquid crystal display device employing a hologram color filter, a compact color liquid crystal display device with a shallow depth and a wide viewing angle is constructed. can do.

  Prior to the description of the embodiment of the parallel light source for backlight according to the present invention, the principle of a typical hologram color filter previously proposed by the applicant will be described with reference to the drawings.

  First, the principle and action of the color filter of the first embodiment proposed above will be described with reference to the cross-sectional view of the liquid crystal display device of FIG. In the figure, the hologram array 5 constituting the previously proposed color filter is arranged at a distance from the incident side of the backlight 3 of the liquid crystal display element 6 regularly divided into liquid crystal cells 6 '. On the back surface of the liquid crystal display element 6, the color filter 1 composed of the R, G, B colored cells 1 'aligned with the respective liquid crystal cells 6' and the black matrix 4 provided therebetween is arranged. Alternatively, the colored cell 1 'is omitted and only the black matrix 4 is arranged. In addition to the above, polarizing plates (not shown) are disposed on both sides of the liquid crystal display element 6.

  The hologram array 5 corresponds to the repetition period of the color separation pixels of R, G, and B, that is, the repetition pitch corresponding to each set of three liquid crystal cells 6 'adjacent in the direction in the plane of the liquid crystal display element 6. The micro holograms 5 'are arranged in an array at the same pitch. The micro holograms 5' are arranged in groups of three liquid crystal cells 6 'adjacent to each other in the direction of the surface of the liquid crystal display element 6 and arranged one by one. Each of the micro-holograms 5 ′ has three components corresponding to the micro-hologram 5 ′ with the green component light in the backlight 3 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 be condensed on the colored cell 1 ′ or the liquid crystal cell 6 ′ at the center of the color separation pixels R, G, B. The micro-hologram 5 'is formed of a transmission type hologram such as a relief type, a phase type, and an amplitude type, which has little or no wavelength dependency of diffraction efficiency. Here, the fact that the diffraction efficiency has no or little wavelength dependency means that the diffraction efficiency is not a type that diffracts only a specific wavelength and the other wavelengths do not diffract, such as a Lippmann hologram. The wavelength also means what is diffracted, and the diffraction grating having no wavelength dependency of the diffraction efficiency diffracts at different diffraction angles depending on the wavelength.

  Because of such a configuration, when the white backlight 3 incident at an angle θ with respect to the normal line is incident from the surface of the hologram array 5 opposite to the liquid crystal display element 6, it depends on the wavelength. The diffraction angles by the micro-hologram 5 ′ are different, and the condensing position for each wavelength is dispersed in a 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 'for displaying red, and the green component is at the position of the color filter cell G or the liquid crystal cell 6' for displaying green. Are arranged in the hologram array 5 so as to be diffracted and condensed at the position of the color filter cell B or the liquid crystal cell 6 'for displaying blue, so that the respective color components are the color filter cells R, G, B and The black matrix 4 passes through each liquid crystal cell 6 'with almost no attenuation, and color display corresponding to the state of the liquid crystal cell 6' at the corresponding position can be performed. The incident angle θ of the backlight 3 on the hologram array 5 is determined by various conditions such as the 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.

  Thus, 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, so that the utilization efficiency can be greatly improved. .

  A modification of the first embodiment is also conceivable. This will be described with reference to FIG. The principle and action of the modified color filter of the first embodiment proposed previously will be described with reference to the same sectional view of FIG. In the figure, the color filter 30 using the already proposed hologram is arranged at a distance from the incident side of the backlight 3 of the liquid crystal display element 6 regularly divided into liquid crystal cells 6 '. On the back surface of the liquid crystal display element 6, the color filter 1 composed of the R, G, B colored cells 1 'aligned with the respective liquid crystal cells 6' and the black matrix 4 provided therebetween is arranged. Alternatively, the colored cell 1 'is omitted and only the black matrix 4 is arranged. In addition to the above, polarizing plates (not shown) are disposed on both sides of the liquid crystal display element 6.

  The previously proposed modified color filter 30 of the first embodiment includes a hologram 27 and a microlens array 28, and the microlens 28 'constituting the microlens array 28 includes R, G, and B color separation pixels. Corresponding to each repetition period, that is, each set of three liquid crystal cells 6 ′ adjacent to each other in the direction of the surface of the liquid crystal display element 6, the liquid crystal display elements 6 are arranged in an array at the same pitch as the repetition pitch. The hologram 27 is composed of uniform interference fringes that act as a diffraction grating, and is composed of a relief type, phase type, amplitude type, or other transmission type hologram that has little or no wavelength dependency of diffraction efficiency.

  Due to such a configuration, when the backlight 3 is incident on the hologram 27 from the surface opposite to the liquid crystal display element 6 at an angle θ with respect to the normal line, it is diffracted at different angles depending on the wavelength. And dispersed on the exit side of the hologram 27. The dispersed light is separated and condensed on the focal plane for each wavelength by the micro lens 28 ′ disposed on the incident side or the emission side of the hologram 27. Among them, the red wavelength component is at the position of the color filter cell R or the liquid crystal cell 6 'for displaying red, and the green component is at the position of the color filter cell G or the liquid crystal cell 6' for displaying green. The color filter 30 is constructed and arranged so as to diffract and condense at the position of the color filter cell B or the liquid crystal cell 6 'for displaying blue, so that each color component is each color filter cell R, G, B and The black matrix 4 passes through each liquid crystal cell 6 'with almost no attenuation, and color display corresponding to the state of the liquid crystal cell 6' at the corresponding position can be performed. The incident angle θ of the backlight 3 on the hologram 27 is determined by various conditions such as the hologram recording conditions, the thickness of the hologram 27, and the distance between the hologram 27 and the liquid crystal display element 6.

  In such an arrangement, as the hologram 27, a transmission hologram having no or little wavelength dependency of diffraction efficiency composed of uniform interference fringes rather than light condensing can be used. There is a feature that it is not necessary to align with each of the microlenses 28 'and that the pitch of the microlens array 28 is three times that of the conventional case of FIG. 16, making it easy to make and align.

  Next, the principle and operation of the color filter of the second form proposed previously will be described with reference to the same sectional view of FIG. In the figure, hologram arrays 15 constituting a color filter already proposed are arranged apart from each other on the incident side of the backlight 3 of the liquid crystal display element 6 regularly divided into liquid crystal cells 6 '. On the back surface of the liquid crystal display element 6, the color filter 1 composed of the R, G, B colored cells 1 'aligned with the respective liquid crystal cells 6' and the black matrix 4 provided therebetween is arranged. Alternatively, the colored cell 1 'is omitted and only the black matrix 4 is arranged. In addition to the above, polarizing plates (not shown) are disposed on both sides of the liquid crystal display element 6.

  The hologram array 15 is obtained by superimposing two holograms 16 and 17 or by multiplex recording two holograms 16 and 17 in a single photosensitive material. Corresponding to each repetition period of G, B color separation pixels, that is, each set of three liquid crystal cells 6 'adjacent to each other in the direction of the surface of the liquid crystal display element 6, they are arranged in an array at the same pitch as the repetition pitch. It consists of a minute hologram 15 '. The minute holograms 15 'are arranged in groups of three liquid crystal cells 6' adjacent to each other in the direction of the liquid crystal display element 6 in the plane of the sheet, and belong to the hologram 16 in each minute hologram 15 '. The portion selectively diffracts the red wavelength component in the white backlight 3 incident on the hologram array 15 substantially perpendicularly, and the color of the set of three liquid crystal cells 6 'corresponding to the minute hologram 15' is obtained. It is formed in the shape of a Fresnel zone plate having wavelength selectivity so as to be condensed at the position of the filter cell R or the liquid crystal cell 6 'for displaying red, and the portion belonging to the hologram 17 in each micro-hologram 15' Selectively diffracts the blue wavelength component in the white backlight 3 incident on the hologram array 15 substantially perpendicularly, and the three corresponding to the micro-hologram 15 ' It is formed in the Fresnel zone plate-like with a wavelength selectivity so as to condense in the position of 'the liquid crystal cell 6 for displaying the set of color filter cell B or blue' crystal cell 6. Here, the hologram having wavelength selectivity is a type that diffracts only a specific wavelength and transmits other wavelengths without being diffracted like a Lippmann hologram. Therefore, most of the blue wavelength component in the white backlight 3 incident perpendicularly to the color filter 15 from behind the liquid crystal display device is diffracted and condensed by the blue hologram 17 to display the color filter cell B or blue. The most of the red wavelength component is diffracted and collected by the red hologram 16 and enters the color filter cell R or the position of the liquid crystal cell 6 'for displaying red. Green components that are not diffracted and collected by the holograms 17 and 16 pass straight through the hologram array 15 and enter the color filter cells R, G, B, or the liquid crystal cell 6 'for displaying their colors by one third. However, the amount incident on the color filter cells R and B is blocked by the filter at that position (if the colored cell 1 'of the color filter is omitted, the green component is positioned at the position of the liquid crystal cell 6' displaying blue and red. Therefore, the saturation increases when three or more holograms described below are overlapped or recorded in a triple manner.) Effectively only at the position of the color filter cell G or the liquid crystal cell 6 'displaying green. Incident. Each wavelength component passes through each liquid crystal cell 6 'with almost no attenuation, and color display corresponding to the state of the liquid crystal cell 6' at the corresponding position can be performed. Instead of this, a wavelength-selective Fresnel zone plate-shaped green hologram is further added or triple-recorded, and each of the three holograms corresponds to the corresponding color filter cell or liquid crystal cell 6 '. In this case, the number of holograms or the number of times of multiple recording increases, but each wavelength component of the backlight 3 can be used without waste in each color cell R, G, B. Or since it can inject into liquid crystal cell 6 ', the utilization efficiency improves further.

  By the way, in the above-mentioned thing of FIG. 3, it corresponds 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, and a Fresnel zone plate-shaped micro hologram. 15 'are arranged in an aligned manner, but as in the case of FIG. 2, the same microlens is used in which two or three uniform diffraction grating holograms having wavelength selectivity are overlapped or multiplexed. Similarly, the use efficiency of the backlight for liquid crystal display can be greatly improved by using the wavelength selectivity of diffraction of the hologram in combination with the array.

  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 from the back is 2 of the color filter R, G, and B color separation pixels. When the dimensional arrangement is a stripe type, it may be about ± 40 ° in the X direction in which color separation pixels of the same color are arranged, but ± 10 in the Y direction in which the color separation pixels of R, G, and B are periodically repeated. It is preferable that the angle is not more than 5 °, desirably 5 ° or less. When the two-dimensional arrangement of the R, G, and B color separation pixels is a delta type or other types, it is preferably ± 10 ° or less, preferably 5 ° or less in both the X and Y directions.

  Now, an embodiment of a compact parallel light source having a shallow depth 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 earlier has a microsecondary light source arranged at the focal point of each lens of the microlens array as a microsecondary light source at the tip of the optical fiber and the reflection surface of the waveguide. Although white parallel light for backlight is generated from the lens array, 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 low refractive index clad 34 on both sides of a flat plate forming a high refractive index core 33, and the microlens array 31 has the same pitch as the two-dimensional pitch of the microlens array 31. A high refractive index portion 35 is periodically provided on the clad 34 on the side. The refractive index of the high refractive index portion 35 is the same as 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 is guided along the core 33 in the waveguide 32 without leaking outside. The guide light leaks out from the high refractive index portion 35 of the clad 34 on the microlens array 31 side, and the high refractive index portion 35 becomes 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 backlight 3 parallel to the front of the microlens array 31 can be generated.

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

  Next, in the case of FIG. 5, as the waveguide 36 disposed behind the microlens array 31, the both sides of the transparent plate 37 have the same pitch as the two-dimensional pitch of the microlens array 31 and are shifted by a half pitch on both sides. In this example, a micro-convex surface 38 is provided, and a waveguide 36 formed by vapor-depositing a metal reflecting layer 40 such as aluminum on both sides is provided except for the valley 39 that matches the focal point of each lens on the micro-lens array 31 side. is there. Also in this case, the light introduced from the white light source 10 into one end of the waveguide 36 is guided along the transparent plate 37 in the waveguide 36, but the valley between the metal reflection layers 40 on the microlens array 31 side. The guide light leaks out from 39 and the valley 39 becomes a secondary light source for the backlight 3. In addition, in this case, the metal reflection layer 40 provided on the surface of the minute convex surface 38 becomes a condensing surface, and light leaks from the valley portion 39 more efficiently. In this case as well, the transparent plate 37 is made of a block polymer or polymer that is transparent, has light transmission properties, has light scattering properties, and has a phase separation of domains of several tens of micrometers or less having different refractive indexes. When a light scattering polymer such as a blend is used, a secondary light source having no loss and uniform and high brightness can be obtained in the valley portion 39, and a brighter backlight 3 can be generated.

  By the way, instead of a micro secondary light source such as the tip of an optical fiber, a micro aperture provided on a reflection surface of a waveguide, a high refractive index portion 35, or a valley portion 39 as described above, at the focal point of each lens of the micro lens array, Even if the minute primary light source is directly arranged, a compact parallel light source having a shallow depth can be configured. Hereinafter, some examples in which the micro primary light source is arranged behind the microlens array will be described.

  In FIG. 6, white LEDs 42 configured by arranging three LEDs emitting light of R, G, and B in close proximity are arranged on the substrate 41 at the same pitch as the two-dimensional pitch of the microlens array 31. The white LED 42 is arranged at the focal point of each lens of the microlens array 31 to obtain the parallel white light backlight 3.

FIG. 7 shows a white phosphor 44 such as calcium halophosphate, or an R color phosphor such as (Y, Ge) BO ₃ : Eu, a G color phosphor such as Zn ₂ SiO ₄ : Mn, and BaMgAl ₁₄ O ₂₃ : Eu. The white phosphor 44 mixed with the B-color phosphor such as 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 focused on each lens of the microlens array 31. To obtain a white backlight 3 of parallel light.

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

  FIG. 9 shows a thin-film phosphor array 52 in which the white phosphor 50 as described above is kept in xenon gas, sandwiched between electrodes 51 and 51 from both sides, and the white phosphor 50 emits light by ultraviolet rays generated from the xenon gas. The thin-film phosphor array 52 is arranged on the substrate 49 at the same pitch as the two-dimensional pitch of the microlens array 31, and the thin-film phosphor array 52 is arranged in accordance with the focal point of each lens of the microlens array 31, and the parallel white light backlight 3 is provided. To get.

  According to the previously filed Japanese Patent Application No. 5-12554, when a micro aperture provided on the tip of an optical fiber and a reflection surface of a waveguide is arranged as a micro secondary light source at the focal point of each lens of the micro lens array, and the above 4 to 9, a GRIN lens array in which a refractive index distribution lens (GRIN lens) known as a product name SELFOC is arranged in an array is used instead of the microlens array composed of the microconvex lenses used. It may be used. FIG. 10 shows an example in which the GRIN lens array 54 is used when the tip of the optical fiber 53 is a secondary light source. One end of the optical fiber 53 is arranged in accordance with the focal point of each lens of the GRIN lens array 54, and the other end. Are arranged together with the other end of the other optical fiber 53 on the front surface of the white light source 10, and the light introduced from the white light source 10 to the other end of each optical fiber 53 is guided in each optical fiber 53, and from one end of each optical fiber 53. The emitted light is converted into parallel light by each GRIN lens of the GRIN lens array 54, and the white parallel backlight 3 is obtained.

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

  The above is an example in which the lens arrays 31 and 54 are used to obtain the parallel light 3. Next, an example in which the parallel backlight 3 is obtained using a louver is shown in FIG. The louver 55 is obtained by arranging a light absorption layer 56 in a one-dimensional or two-dimensional shape in parallel in a transparent medium such as air or glass at a slight interval, and a linear component along the light absorption layer 56. Only the component that passes through the light absorption layer 56 is absorbed and the component that crosses the light absorption layer 56 is not allowed to pass through. Therefore, when a white light source 57 such as a fluorescent lamp having a large light emitting area is disposed on one side of the louver 55, a straight component in the direction in which the light absorption layer 56 faces the other side of the louver 55, that is, parallel light. As a result, only the white parallel backlight 3 can be used.

  Further, a Fresnel reflector can be used to construct a parallel light source having a small depth. FIG. 12 is a diagram showing an example using a paraboloidal Fresnel reflector 58 in which the paraboloid is configured as a Fresnel reflector. FIG. 12A is a cross-sectional view of a parallel light source, and FIG. 6 is a plan view of the mirror 58. FIG. As shown in the figure, the paraboloidal Fresnel reflector 58 is formed by combining the paraboloidal reflector so that the cross-section is cut into a large number of ring-shaped micro-reflecting surfaces 59 so that the cross section becomes a sawtooth shape. Similar to the parabolic reflector, the light emitted from the spot-like white light source 10 is converted into parallel light 3 and reflected. Therefore, this reflected light can be used as the white parallel backlight 3.

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

  When a color liquid crystal display device is configured by combining any of the parallel light sources proposed above and a liquid crystal display device using the hologram color filters 5, 30, and 15 as shown in FIGS. It becomes as follows. In the following description, one of the parallel light sources as shown in FIGS. 4 to 13 is aligned with the parallel light source 60, the liquid crystal display element 6 as shown in FIGS. A display panel composed of the color filter 1 (or only the black matrix 4) provided on the both sides and polarizing plates disposed on both sides thereof will be referred to as an LCD panel 61. Any one of the hologram color filters 5, 30, and 15 (including deformation) is referred to as a hologram color filter 62.

  FIG. 14A shows a case in which, 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 an oblique direction from its emission surface is used. It is a figure which shows the arrangement | positioning which shows the structure of the whole color liquid crystal display device, and arrange | positions the parallel light source 60, the hologram color filter 62, the LCD panel 61, and the diffuser plate 63 in order from the parallel light source 60 side in parallel, and has a shallow depth. The thickness can be made thin. The diffusion plate 63 may be disposed inside the LCD panel 61 or between the hologram color filter 62 and the LCD panel 61.

  FIG. 14B is the same as the case where the parallel light source 60 that emits the parallel light 3 in the vertical direction is used as the parallel light source 60 when the hologram color filter 62 requires the backlight 3 from the oblique direction. 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 in FIG. 5A, but the parallel light source 60 and the hologram color filter 62 are not parallel, A wedge-shaped space must be arranged. Accordingly, the overall thickness is slightly increased.

  FIG. 14C shows a deflecting optical element using refraction or reflection when the hologram color filter 62 requires the backlight 3 from the vertical direction or as proposed in Japanese Patent Application No. 5-225614. When the backlight 3 is vertically incident on the hologram color filter 61 using the parallel light source 60, the parallel light source 60 emits the parallel light 3 in the vertical direction. 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 in parallel to the hologram color filter 62, and the depth can be reduced and the overall thickness can be reduced as in FIG.

  Note that the liquid crystal display device combined with the parallel light source 60 according to the present invention can block the zero-order light from the hologram color filter 62 so as not to enter the LCD panel 61. FIG. 15 shows one of the means, and a zero-order light blocking louver 64 configured to cut only light in a predetermined direction between the hologram color filter 62 and the LCD panel 61, that is, on the emission side of the hologram color filter 62. Place. With such a configuration, since unnecessary light does not reach the observation side, a 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 based on several embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible. .

  As is clear 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 configured in a flat plate shape with a shallow depth, and by incorporating this into a liquid crystal display device employing a hologram color filter, A color liquid crystal display device having a shallow depth, a compact size, a wide viewing angle, and a bright color can be configured.

It is sectional drawing for demonstrating the principle and effect | action of the color filter of the 1st form proposed previously. It is sectional drawing for demonstrating the principle and effect | action of the color filter of the deformation | transformation of a 1st form. It is sectional drawing for demonstrating the principle and effect | action of the color filter of the 2nd form proposed previously. It is sectional drawing of 1st Example of the parallel light source by this invention. It is sectional drawing of 2nd Example of the parallel light source by this invention. It is sectional drawing of 3rd Example of the parallel light source by this invention. It is sectional drawing of 4th Example of the parallel light source by this invention. It is sectional drawing of 5th Example of the parallel light source by this invention. It is sectional drawing of 6th Example of the parallel light source by this invention. It is sectional drawing of 7th Example of the parallel light source by this invention. It is sectional drawing of 8th Example of the parallel light source by this invention. It is sectional drawing of 9th Example of the parallel light source by this invention, and a top view of the parabolic Fresnel reflector used therewith. It is sectional drawing of 10th Example of the parallel light source by this invention. It is sectional drawing which shows the structural example of the liquid crystal display device by this invention. It is sectional drawing of the liquid crystal display device of the structure which interrupts | blocks the 0th-order light from a hologram color filter by this invention. It is sectional drawing of the prior art 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 '... colored 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 ... micro lens array 28' ... micro lens 30 ... color filter (previous proposal)
DESCRIPTION OF SYMBOLS 31 ... Microlens array 32 ... Waveguide 33 ... Core 34 ... Cladding 35 ... High refractive index part 36 ... Waveguide 37 ... Transparent plate 38 ... Minute convex surface 39 ... Valley part 40 ... Metal reflective layer 41 ... Substrate 42 ... White LED
43 ... substrate 44 ... white phosphor 46 ... 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 reflector 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

Claims (6)

It consists of a micro-converging lens array and a micro secondary light source arranged at the focal point of each micro lens or its off-axis position, and the micro secondary light source has micro convex surfaces on both sides, and a valley between convex surfaces of one surface The light is emitted from the white light source into one end of the waveguide and the light leaked from the valley is liquid crystal by the micro-converging lens array. A parallel light source for a liquid crystal display device, wherein the light is converted into substantially parallel light incident on the display device. In a parallel light source for a liquid crystal display device using a holographic color filter that diffracts and splits almost parallel light into a corresponding color spectral pixel as a color filter, the focal point of each microlens and the focal point of each microlens or its off-axis position The microsecondary light source is provided with a microconvex surface on both sides, and a waveguide having a metal reflective layer on both sides except for a valley between the convex surfaces of one surface. It comprises a trough, and light from a white light source is introduced into one end of the waveguide, and light leaking from the trough is converted into substantially parallel light that is incident on a hologram color filter by the minute convergence lens array. A parallel light source for a liquid crystal display. 3. The parallel light source for a liquid crystal display device according to claim 1, wherein the waveguide material is made of a light scattering polymer that is transparent and has light scattering properties, and domains having different refractive indexes are phase-separated. The parallel light source for a liquid crystal display device according to any one of claims 1 to 3, wherein the minute converging lens array comprises a refractive index distribution lens array. From the light source side, arranged in the order of a parallel light source and a liquid crystal display panel, a diffusion plate is arranged on the incident side of the liquid crystal display panel, inside the liquid crystal display panel, or on the output side of the liquid crystal display panel, 5. A liquid crystal display device using the parallel light source for a liquid crystal display device according to claim 1 as a parallel light source. From the light source side, a parallel light source, a hologram color filter for diffracting and splitting substantially parallel light into a corresponding color spectral pixel, and a liquid crystal display panel are arranged in this order, and the inside of the liquid crystal display panel, the hologram color filter and the 5. The parallel light source for a liquid crystal display device according to claim 1, wherein a diffusion plate is disposed between the liquid crystal display panels or on an emission side of the liquid crystal display panel, and the parallel light source according to claim 1 is used as the parallel light source. A liquid crystal display device characterized by the above.

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