JP3649360B2 - Hologram color filter system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hologram color filter system, and in particular, when used in a color liquid crystal display device or the like, color purity and color reproducibility are good by diffracting and diffracting each color component of illumination light at substantially the same ratio. The present invention relates to a hologram color filter system that greatly improves the use efficiency of illumination light that allows light to be incident substantially perpendicularly to a filter surface.
[0002]
[Prior art]
Conventionally, a backlight is indispensable for display in a color liquid crystal display device using an absorption color filter such as a pigment or a dye. However, just using white light as it is from behind the color liquid crystal display device, its utilization efficiency is very low. The main reasons are as follows.
[0003]
(1) The area occupied by the black matrix other than the cells of each color is large, and the light hitting it is wasted.
(2) Among white light incident on each pixel, the color components that pass through the color filters of R (red), G (green), and B (blue) are limited, so other complementary color components are wasted. End up.
(3) There is a loss due to absorption by the color filter.
[0004]
In order to solve such problems, for example, a microlens array is installed in front of the color filter, and the backlight of the white light is condensed on the color filter cells R, G, and B, respectively. Methods for increasing the utilization efficiency have been conventionally known.
[0005]
However, even with this method, since the white light 3 cannot be applied to each color filter cell R, G, B by being split, it is impossible to solve the problem (2).
[0006]
Furthermore, Japanese Patent Laid-Open No. 4-60538 proposes a liquid crystal projector that improves the light utilization efficiency by using three dichroic mirrors and a microlens array without using such a color filter. In this case, the absorption color filter using the above-mentioned pigments, dyes and the like is not necessary, and the above problems (1) to (3) are solved and the brightness of the color image is improved, but three dichroic mirrors are used. Since this is necessary, the optical system / device becomes large and bulky. In addition, there is a problem that the cost becomes high.
[0007]
In view of such circumstances, the present applicant used a color filter using a hologram and the same in Japanese Patent Application No. 5-12170 in order to greatly improve the utilization efficiency of a backlight for liquid crystal display and the like. A liquid crystal display device was proposed.
[0008]
Further, a liquid crystal projection display device that displays a bright color image on a screen by changing the liquid crystal display device using such a hologram color filter to a projection type has been proposed in Japanese Patent Application No. 5-242292.
[0009]
Hereinafter, a liquid crystal display device and a liquid crystal projection display device using such a hologram color filter will be briefly described.
First, a liquid crystal display device using a first type hologram color filter will be described with reference to a cross-sectional view of FIG. In the figure, a hologram array 5 constituting a color filter is arranged on the backlight 3 incident side of a liquid crystal display element 6 regularly divided into liquid crystal cells 6 '(pixels). On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is disposed. In addition to the above, polarizing plates (not shown) are disposed on the incident side of the hologram array 5 and the emission side of the liquid crystal display element 6. In addition, an absorption color filter that passes light of colors corresponding to R, G, and B color separation pixels is additionally arranged between the black matrix 4 as in the conventional color liquid crystal display device. You may do it.
[0010]
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 condense on the liquid crystal cell G 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 it is not a type that diffracts only a specific wavelength and hardly diffracts other wavelengths like a Lippmann hologram. The diffraction grating whose diffraction efficiency has little wavelength dependency diffracts at different diffraction angles depending on the wavelength.
[0011]
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 liquid crystal cell R that displays red, the green component is at the position of the liquid crystal cell G that displays green, and the blue component is at the position of the liquid crystal cell B that displays blue. By arranging the hologram array 5 so as to be diffracted and condensed, each color component passes through each liquid crystal cell 6 'with almost no attenuation in the black matrix 4, and the liquid crystal cell 6' at the corresponding position is passed through. Color display according to the state 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.
[0012]
As described above, by using the hologram array 5 as a color filter, each wavelength component of the conventional color filter backlight can be incident on each liquid crystal cell 6 'without absorption without any waste. Can be improved.
[0013]
Next, a liquid crystal display device using a second type hologram color filter will be described with reference to a sectional view of FIG. In the figure, the second type hologram color filter 10 comprises a hologram 7 and a condensing microlens array 8, and the microlens 8 ′ constituting the microlens array 8 has R, G, and B color separations. Corresponding to each set of three liquid crystal cells 6 'adjacent in the direction of pixel repetition, that is, in the direction of the liquid crystal display element 6, the liquid crystal display element 6 is arranged in an array at the same pitch. The hologram 7 is composed of parallel and uniform interference fringes acting as a diffraction grating, and is composed 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. On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is disposed. In addition to the above, polarizing plates (not shown) are disposed on both sides of the liquid crystal display element 6. In addition, an absorption color filter that passes light of colors corresponding to R, G, and B color separation pixels is additionally arranged between the black matrix 4 as in the conventional color liquid crystal display device. You may do it.
[0014]
Due to such a configuration, when the backlight 3 is incident on the hologram 7 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. , Dispersed on the exit side of the hologram 7. The dispersed light is separated and condensed on the focal plane by the microlens 8 ′ disposed on the incident side or the exit side of the hologram 7. Among them, the red wavelength component is at the position of the liquid crystal cell R that displays red, the green component is at the position of the liquid crystal cell G that displays green, and the blue component is at the position of the liquid crystal cell B that displays blue. By arranging the color filter 10 so as to be diffracted and condensed, each color component passes through each liquid crystal cell 6 'with almost no attenuation in the black matrix 4, and the liquid crystal cell 6' at the corresponding position passes through. Color display according to the state can be performed.
[0015]
In such an arrangement, the hologram 7 can be a transmission hologram that is not condensing but has a uniform interference fringe and has little wavelength dependency of diffraction efficiency. It is not necessary to align with the lens 8 ', and the pitch of the microlens array 8 is three times that of the conventional case where one microlens is arranged corresponding to each liquid crystal cell 6', making it easy to make. And it is easy to align.
[0016]
As a modification of FIG. 5, as shown in FIG. 6, the arrangement of the microlens array 8 and the liquid crystal display element 6 is as shown in FIG. 5, and the hologram 7 is formed of parallel and uniform interference fringes that act as a diffraction grating. Is separated from the microlens array 8 and arranged in the backlight 3 so as to be substantially perpendicular to the traveling direction thereof, similarly, each wavelength component of the backlight is absorbed without waste without being absorbed into each liquid crystal cell 6 '. It is possible to realize a color filter that can be made incident and whose utilization efficiency is greatly improved.
[0017]
Further, the liquid crystal display device using the hologram color filter having the configuration shown in FIGS. 4 to 6 is used as it is as a direct-view type liquid crystal display device or as a spatial light modulation element for projection display. It can be used as a projection display device. FIG. 7 is a cross-sectional view when the liquid crystal display device of FIG. 4 is configured as a liquid crystal projection display device (the same applies to FIGS. 5 and 6), and the first polarized light is close to or integrated with the incident side of the hologram array 5. A second polarizing plate 13 is disposed close to or integrally with the plate 12 on the exit side of the liquid crystal display element 6. The color liquid crystal display device 11 is illuminated by the white parallel backlight 3 from the illumination device 14 composed of a combination of, for example, a metal halide lamp 15 and a parabolic mirror 16, and is modulated by the color liquid crystal display device 11. The image passes through a field lens 17 disposed in the vicinity of the liquid crystal display device 11 and is magnified by the projection lens 18 and magnified on the screen 19 to obtain a bright projected image.
[0018]
In the liquid crystal display device using the hologram color filter as described above, the liquid crystal display element 6 including the black matrix 4 is actually, for example, as shown in a cross section in FIG. It consists of a liquid crystal layer 25 such as twisted nematic sandwiched between two glass substrates 21, 22, and a black matrix 4 and a uniform transparent counter electrode 23 are formed on the inner surface of the glass substrate 21 on the backlight side. A transparent pixel electrode 24 and a TFT (not shown) are provided independently for each of the liquid crystal cells R, G, and B on the inner surface of the glass substrate 22 on the display surface side. Further, an alignment layer (not shown) is also provided on the liquid crystal layer 25 side of the electrodes 23 and 24. Then, the hologram color filter 5 or 10 provided on the liquid crystal display element 6 side surface of the substrate 26 is disposed close to or bonded to the glass substrate 21 on the backlight side, and the polarizing plate 12 is disposed on the backlight side of the substrate 26. Polarizing plates 13 are attached to the outer surface of the observation-side glass substrate 22 of the liquid crystal display element 6, respectively. For example, their transmission axes are arranged to be orthogonal to each other. The polarizing plate 12 on the backlight side is disposed in the optical path of the backlight 3 apart from the hologram color filter 5 as shown by a dotted line in FIG. 8 instead of being attached to the backlight side of the substrate 26. There is also.
[0019]
By controlling the voltage applied between the transparent pixel electrode 24 and the transparent counter electrode 23 for each pixel of the liquid crystal display element 6 as described above to change its transmission state, color display is possible.
[0020]
[Problems to be solved by the invention]
By the way, in the above hologram color filter proposed by the present applicant, a hologram having little or no wavelength dependency of diffraction efficiency is used due to wavelength dispersion. Therefore, the diffraction efficiency differs depending on the wavelength. FIG. 9 shows an example of the diffraction efficiency characteristics with respect to the wavelength. When the wavelength is plotted on the horizontal axis, the curve representing the diffraction efficiency has a mountain shape. 9 shows a micro-hologram 5 ′ (FIG. 9) composed of a single hologram with a refractive index modulation Δn = 0.035 using a single color having a wavelength of 514 nm for a photopolymer having a thickness of 6 μm and an average refractive index n = 1.52. The diffraction efficiency depending on the wavelength when 4) is recorded is shown.
[0021]
In particular, in a hologram color filter for color liquid crystal display with three colors R, G, and B, the peak of diffraction efficiency having a mountain shape is located in the middle wavelength G region as shown in FIG. It is desirable to achieve balance, and the diffraction efficiencies in the R wavelength region and the B wavelength region are lower than in the G wavelength region. For this reason, unevenness in the intensity of the three colors R, G, and B occurs, and appears as a color balance defect when performing color display.
[0022]
In the hologram color filter described above, it is necessary to make the backlight 3 incident on the surface with a large incident angle θ of about 40 °, and the light source is considerably off-axis with respect to the liquid crystal display element 6. In particular, when the hologram color filter described above is used in a direct-view type liquid crystal display device, there is a problem that the overall size becomes large.
[0023]
The present invention has been made in view of the problems of such a conventional hologram color filter, and the purpose thereof is to achieve good color purity and color reproducibility by diffracting each color component of illumination light at substantially the same ratio. Another object of the present invention is to provide a hologram color filter system capable of significantly improving the use efficiency of illumination light that allows illumination light to be incident substantially perpendicular to the filter surface.
[0024]
[Means for Solving the Problems]
The hologram color filter system of the present invention that achieves the above object comprises an array of element condensing holograms, and each element condensing hologram is incident at a predetermined angle with respect to the normal of the hologram recording surface. Hologram color filter that spectrally disperses white light with wavelength dispersion in a direction substantially along the hologram recording surface, or a hologram or diffraction grating composed of parallel uniform interference fringes and element condensing arranged on the incident side or the exit side thereof Each of the element condensing lenses cooperates with the hologram or diffraction grating so that the white light incident on the recording surface of the hologram or diffraction grating at a predetermined angle is incident on the element condensing lens. In a hologram color filter that performs spectral dispersion by wavelength dispersion in a direction substantially along the surface of the array,
A transmissive diffraction grating as a wavelength spectroscopic means for reducing the separation angle between the red component and the blue component separated by the hologram color filter is arranged in the optical path of white light incident on the hologram color filter. The hologram color filter is arranged substantially perpendicularly and is arranged so as to form an angle with respect to the transmission type diffraction grating.
[0026]
In this case, the incident angles of the red, green, and blue components of the white light separated by the transmissive diffraction grating to the hologram color filter are changed to the incident angles at which the diffraction efficiency of these components in the hologram color filter becomes substantially peak. It is desirable to match.
[0029]
The present invention also includes the case where the hologram color filter is disposed on the illumination light incident side of the liquid crystal display device and the case where the liquid crystal display device is for projection display that projects the display image onto a screen. It is a waste.
[0030]
In the present invention, the wavelength spectroscopic means having a spectral arrangement that reduces the separation angle between the red component and the blue component that are split by the hologram color filter is arranged in the optical path of white light incident on the hologram color filter. The diffraction efficiencies of the holographic color filters for RGB colors can be set to substantially the same value, so that the color purity and color reproducibility of display can be improved, and the utilization efficiency of illumination light can be greatly improved. In addition, the incident angle of white light with respect to the hologram color filter is reduced by inserting the wavelength spectroscopic means, and the overall size can be reduced particularly when it is configured as a direct-view type liquid crystal display device.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the principle of the hologram color filter system of the present invention and examples thereof will be described.
FIG. 3 shows the relationship between the backlight incident angle of a specific wavelength of one micro-hologram 5 ′ of the hologram color filter 5 as shown in FIG. 4 and the diffraction efficiency of that wavelength. This micro-hologram 5 'has a spectral direction dimension of 270 μm, a direction dimension orthogonal to it of 80 μm, a thickness of 6 μm, a backlight incident angle of 35 ° (in air), a wavelength 545 nm diffracted in the normal direction, and a focal length of 1.14 mm (refractive) Designed in a medium with a rate of 1.5).
[0032]
As is clear from FIG. 3, at a specific incident angle, for example, 35 °, there is a large difference in diffraction efficiency between the R wavelength of 620 nm, the G wavelength of 545 nm, and the B wavelength of 470 nm, and at the same time, It can be seen that the diffraction efficiency is not at the peak value at the wavelengths of B and B. It can also be seen that the 620 nm R wavelength diffraction efficiency peak is near an incident angle of 38 ° and the 470 nm B wavelength diffraction efficiency peak is near an incident angle of 32 °.
[0033]
Therefore, from the viewpoint of diffraction efficiency, as shown in FIG. 2, the incident light is incident on the micro-hologram 5 ′ of the backlight 3 (or a combination of the hologram 7 and the micro-lens 8 ′; hereinafter, represented by the micro-hologram 5 ′). If the angle is smaller than the G component 3G for the B component 3B and larger than the G component 3G for the R component 3R, each of the components 3B, 3G, and 3R becomes the minute hologram 5 ′ at an incident angle at which the diffraction efficiency peaks. Incident light can be diffracted and split at substantially the same rate for each color of RGB. In FIG. 2, the angle at which the B component 3B is reduced relative to the G component 3G and the angle at which the R component 3R is increased relative to the G component 3G are both Δ. In the case of the three wavelengths shown in FIG. 3, Δ is about 3 °.
[0034]
However, in this case, as shown in FIG. 2, separation of the B component 27, the G component 28, and the R component 29 (only the chief rays are shown in the figure) separated by the micro-hologram 5 'is a problem. The angle is smaller than the separation angle θ ₁ when the backlight color components 3B, 3G, and 3R are incident at the same incident angle θ. In the case of the above three wavelengths, the angle δ at which the separation angles of R and G and B and G are reduced is about 1.9 ° (the separation angle θ ₁ at the same incident angle of 35 ° is about 4.5 °). is there.). That is, the direction in which the incident angle of each color component of the backlight 3 is made different so that the diffraction efficiency of each RGB color is substantially the same is the direction in which the separation angle of each color component by the hologram color filters 5 and 10 is reduced. It is to end. Therefore, the B component 27 and the R component 29 are not incident on the corresponding color pixels R and B, but are shifted toward the center pixel G, and the black matrix 4 of the corresponding corresponding pixels R and B is obtained. In this case, the incident color does not enter the aperture, and a crosstalk of display color occurs.
[0035]
Therefore, in order to prevent this problem, as is apparent from FIG. 2, the micro-hologram 5 ′ (distance from the hologram array 5 to the condensing point) or the micro-lens 8 so as to compensate for the above-described shortage δ of the separation angle. It is understood that the focal length of ′ may be extended from the original f ₀ to f ₁ longer than that, and the pixel 6 ′ of the display element is arranged at that position. In the case of the above three wavelengths, f ₀ = 1.14 mm to f ₁ = 2.7 mm.
[0036]
In the present invention, in order to make the incident angle of the backlight 3 different for each color component as described above, a diffraction grating or a hologram diffraction grating is used. That is, a diffraction grating or a hologram diffraction grating having a diffraction angle different for each wavelength is arranged in the backlight 3, and the B component 3B diffracted by the diffraction grating or the hologram diffraction grating as shown in FIG. The diffracted R component 3R is increased by a predetermined angle Δ with respect to the G component 3G, and the incident angle with respect to the hologram color filters 5 and 10 is reduced with respect to 3G. The B component 3B is θ-Δ, the G component 3G is θ, and the R component 3R is θ-Δ.
[0037]
FIG. 1 shows a hologram according to one embodiment of the present invention in which such a wavelength dispersion type transmission diffraction grating (hologram diffraction grating) 30 is arranged in the light path of the backlight 3 of the hologram color filter 5 shown in FIG. FIG. 3 shows a cross-sectional view of a liquid crystal display device using a color filter system. The same applies to the liquid crystal display device using the hologram color filter 10 of FIGS.
[0038]
In FIG. 1, the configuration and arrangement relationship of the hologram array 5 and the liquid crystal display element 6 are the same as those in FIG. That is, the hologram array 5 constituting the color filter is arranged at a distance from the incident side of the backlight 3 of the liquid crystal display element 6 that is regularly divided into liquid crystal cells 6 ′ (pixels). On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is disposed. The spacing between the hologram array 5 and the black matrix 4 is selected so as to substantially match the focal length of the micro-hologram 5 '. In addition to the above, polarizing plates (not shown) are disposed on the incident side of the hologram array 5 and the emission side of the liquid crystal display element 6. In addition, an absorption color filter that passes light of colors corresponding to R, G, and B color separation pixels is additionally arranged between the black matrix 4 as in the conventional color liquid crystal display device. You may do it.
[0039]
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. It consists of minute holograms 5 'arranged in an array at the same pitch. The micro-hologram 5 'is composed 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 it is not a type that diffracts only a specific wavelength and hardly diffracts other wavelengths like a Lippmann hologram. The diffraction grating whose diffraction efficiency has little wavelength dependency diffracts at different diffraction angles depending on the wavelength.
[0040]
In accordance with the present invention, a wavelength dispersion type transmission diffraction grating (hologram diffraction grating) 30 is arranged in the three light paths of the backlight. The diffraction grating 30 has a characteristic of diffracting light having a wavelength of 545 nm of the G component in the vertically incident backlight 3 at a diffraction angle of 21 ° from the normal line. 3 light having a wavelength of 620 nm is a diffraction angle of 24 ° (separation angle + 3 ° with respect to light having a wavelength of 545 nm), and light having a wavelength of 470 nm of B component is having a diffraction angle of 18 ° (light having a wavelength of 545 nm). It has a characteristic of diffracting at a separation angle of -3 °. Then, the hologram array 5 is constructed with the diffraction characteristics shown in FIG. 3 so that the light 3G having a wavelength of 545 nm, which is G component spectrally separated by the diffraction grating 30 in the white backlight 3, is incident on the hologram array 5 at an incident angle of 35 °. The diffraction grating 30 is relatively disposed in Therefore, the R component light 620 nm split by the diffraction grating 30 in the white backlight 3 is incident on the hologram array 5 at an incident angle of 38 °, and the B component light 470 nm light is incident on the hologram array 5. Incidents are incident at an angle of 32 °, and are incident on the hologram array 5 at an incident angle (see FIG. 3) where the diffraction efficiency of each wavelength is at its peak. For this reason, the diffraction efficiency by the hologram color filter 5 of each color of RGB can be set to substantially the same peak value.
[0041]
Each color component is diffracted and dispersed in different directions by the micro-hologram 5 ′, 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 liquid crystal cell R that displays red, the green component is at the position of the liquid crystal cell G that displays green, and the blue component is at the position of the liquid crystal cell B that displays blue. By determining the configuration of the hologram array 5 and the relative position with the liquid crystal display element 6 so as to be diffracted and condensed, each color component passes through each liquid crystal cell 6 'without being attenuated by the black matrix 4, Color display according to the state of the liquid crystal cell 6 'at the corresponding position can be performed.
[0042]
In this way, the diffraction grating 30 is arranged in the optical path of the backlight 3 incident on the hologram color filters 5 and 10 so that the separation angle of the red component and the blue component separated by the hologram color filters 5 and 10 is reduced. If the relative arrangement is used for spectral incidence, the diffraction efficiency by the hologram color filter 5 for each color of RGB is set to substantially the same peak value, the display color purity and color reproducibility can be improved, and the illumination light utilization efficiency can be greatly improved. Can be made.
[0043]
Further, as apparent from comparison between the arrangement of FIG. 1 and the arrangement of FIG. 4, the incident angle of the backlight 3 with respect to the hologram color filter 5 and the liquid crystal display element 6 becomes much smaller by inserting the diffraction grating 30 (Example) In this case, the degree of off-axis with respect to the liquid crystal display device of the backlight 3 is greatly improved, and the overall size can be reduced particularly when it is configured as a direct-view type liquid crystal display device. .
[0044]
In the embodiment of FIG. 1, the color components 3R, 3G, and 3B dispersed by the diffraction grating 30 are made incident at an angle at which the diffraction efficiency of those wavelength components in the hologram color filter 5 reaches a peak. It is not necessary to match each color component 3R, 3G, 3B to the angle at which it is a peak. In FIG. 1, when the diffraction grating 30 has a characteristic of diffracting light having a wavelength of 545 nm of the G component in the vertically incident backlight 3 with a diffraction angle of 35 ° from the normal line, the diffraction grating 30 and the hologram color filter 5 can be spaced apart in parallel or integrally, and the incident angle of the backlight 3 can be set to 0 °. In that case, the backlight 3 has an in-line arrangement in which the liquid crystal display device is completely perpendicularly incident on the liquid crystal display device, so that the overall size of the liquid crystal display device can be greatly reduced, and is particularly suitable for a direct-view type liquid crystal display device. Become. However, in this case, the relative angle of the B component 3B diffracted by the diffraction grating 30 with respect to the G component 3G and the relative angle of the diffracted R component 3R with respect to the G component 3G are about −5 ° and + 5 °, respectively, which are desirable angles. Since the absolute value is slightly larger than −3 ° and + 3 °, the color components 3R, 3G, and 3B dispersed by the diffraction grating 30 do not enter at an angle at which the diffraction efficiency of those wavelength components in the hologram color filter 5 reaches a peak. Due to the arrangement, the color purity and color reproducibility of the display are deteriorated because the diffraction efficiency is slightly different between the color components as compared with the embodiment of FIG. 1, but it is better than the conventional case where the diffraction grating 30 is not arranged. .
[0045]
In the above-described embodiments, the diffraction grating 30 is a transmission diffraction grating that vertically enters the backlight 3 to obtain a predetermined separation angle, but the transmission angle is other than 90 °. Of course. Further, a reflection type diffraction grating may be used instead of the transmission type diffraction grating. Furthermore, a spectral prism may be used.
[0046]
As described above, the hologram color filter system of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made. Further, the hologram color filter system of the present invention can be applied to either a direct view type or a projection type liquid crystal display device.
[0047]
【The invention's effect】
As is apparent from the above description, according to the hologram color filter system of the present invention, the wavelength spectroscopic means having a spectral arrangement that reduces the separation angle of the red component and the blue component that are separated by the hologram color filter from the hologram. Because it is arranged in the optical path of white light incident on the color filter, the diffraction efficiency of each RGB color filter can be set to approximately the same value, the display color purity and color reproducibility can be improved, and the illumination light utilization efficiency Can be greatly improved. In addition, the incident angle of white light with respect to the hologram color filter is reduced by inserting the wavelength spectroscopic means, and the overall size can be reduced particularly when it is configured as a direct-view type liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid crystal display device of one embodiment using a hologram color filter system of the present invention.
FIG. 2 is a diagram for explaining the principle of a hologram color filter system of the present invention.
FIG. 3 is a diagram showing a relationship between a backlight incident angle of a specific wavelength of a micro hologram constituting the hologram color filter and diffraction efficiency of the wavelength.
FIG. 4 is a schematic cross-sectional view of a liquid crystal display device using a first type hologram color filter.
FIG. 5 is a schematic cross-sectional view of a liquid crystal display device using a second type hologram color filter.
6 is a schematic cross-sectional view of a liquid crystal display device using the hologram color filter modified as shown in FIG.
7 is a cross-sectional view of a liquid crystal projection display device using the liquid crystal display device of FIG.
FIG. 8 is a cross-sectional view of a liquid crystal display element.
FIG. 9 is a diagram illustrating an example of diffraction efficiency characteristics of a hologram color filter.
[Explanation of symbols]
3 ... Backlight 3B ... Backscattered B component 3G ... Backlit dispersed G component 3R ... Backlit dispersed R component 4 ... Black matrix 5 ... Hologram array (hologram color filter)
5 '... micro hologram 6 ... liquid crystal display element 6' ... liquid crystal cell 7 ... hologram 8 ... condensing microlens array 8 '... micro lens 10 ... hologram color filter 11 ... color liquid crystal display devices 12, 13 ... polarizing plate 14 ... Illumination device 15 ... metal halide lamp 16 ... parabolic mirror 17 ... field lens 18 ... projection lens 19 ... screen 21 ... backlight side glass substrate 22 ... display side glass substrate 23 ... transparent counter electrode 24 ... transparent pixel electrode 25 ... liquid crystal Layer 26 ... Substrate 27 ... Split B component 28 ... Split G component 29 ... Split R component 30 ... Wavelength dispersive transmission diffraction grating (hologram diffraction grating)

Claims (4)

It consists of an array of element condensing holograms, and each element concentrating hologram disperses the wavelength of white light incident at a predetermined angle with respect to the normal of the hologram recording surface in a direction substantially along the hologram recording surface. Holographic color filter that divides light, or a hologram or diffraction grating consisting of parallel and uniform interference fringes and an array of element condensing lenses arranged on the entrance side or exit side thereof, and the element condensing lens Each cooperates with the hologram or diffraction grating to disperse the white light incident on the recording surface of the hologram or diffraction grating at a predetermined angle by dispersing the wavelength in a direction substantially along the surface of the array of the element condensing lenses. In hologram color filter,
A transmissive diffraction grating as a wavelength spectroscopic means for reducing the separation angle between the red component and the blue component separated by the hologram color filter is arranged in the optical path of white light incident on the hologram color filter. A hologram color filter system, wherein the hologram color filter system is disposed substantially vertically and the hologram color filter is disposed at an angle with respect to the transmission diffraction grating . The incident angles of the red component, the green component, and the blue component, which are obtained by spectrally dividing the white light with the transmission diffraction grating, into the hologram color filter are such that the diffraction efficiency of those components in the hologram color filter is substantially peaked. The hologram color filter system according to claim 1, wherein: 3. The hologram color filter system according to claim 1, wherein the hologram color filter is disposed on the illumination light incident side of the liquid crystal display device. 4. The hologram color filter system according to claim 3, wherein the liquid crystal display device is for projection display in which a display image is projected onto a screen.

Images