JP4371290B2 - Hologram light guide plate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hologram light guide plate, and more particularly to a hologram light guide plate used for a front light and a backlight for a liquid crystal display device.
[0002]
[Prior art]
A light guide plate is used for a front light and a backlight of a liquid crystal display device. The light guide plate for backlight can improve uniformity by a scattering plate or the like, but in the case of the light guide plate for front light, it is necessary to be transparent in order to observe the display surface through the light guide plate.
[0003]
In Japanese Patent Application Laid-Open No. 11-109338, the present applicant illuminates propagation light by providing a reflection or transmission hologram on one surface of a light guide plate that propagates light while repeating total reflection as a front light guide plate. A hologram light guide plate that emits light is proposed.
[0004]
It is also clear that such a hologram light guide plate can be used as a light guide plate for backlight.
[0005]
[Problems to be solved by the invention]
When this hologram light guide plate is used as a light guide plate for a liquid crystal display device, it is not easy to perform uniform illumination due to repeated reflection and end face reflection.
[0006]
The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a configuration that enables uniform and bright illumination in a hologram light guide plate.
[0007]
[Means for Solving the Problems]
The hologram light guide plate of the present invention that achieves the above object comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source arranged in the vicinity of one end of the plate-like body is plate-like. A hologram light guide plate configured to be propagated while being repeatedly totally reflected in the body, and a part of the propagated light is diffracted to the outside of the plate-like body by the hologram; An absorption layer that absorbs the propagating light is provided at the end opposite to the light source.
[0008]
Another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body passes through the plate-like body. In the hologram light guide plate configured to be propagated while being repeatedly totally reflected and diffracted to the outside of the plate-like body by the hologram, the light source of the plate-like body is The opposite end is configured to taper in a cross section perpendicular to the end, and a reflective layer is provided on the surface of the tapered portion opposite to the side from which the diffracted light from the hologram is emitted. It is characterized by that.
[0009]
Another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body passes through the plate-like body. In a hologram light guide plate configured to propagate while repeatedly being totally reflected, and to be diffracted to the outside of the plate-like body by the hologram, the surface of the plate-like body facing the light source The front surface and the back surface of the plate-like body are formed in a wedge shape that forms an angle with each other within a cross section perpendicular to the end portion.
[0010]
Another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body passes through the plate-like body. In a hologram light guide plate configured to propagate while being repeatedly totally reflected and diffracted part of the propagated light to the outside of the plate-like body by the hologram, the thickness of the plate-like body is 0 It is characterized by being 5 mm or less.
[0011]
Still another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body is contained in the plate-like body. In a hologram light guide plate configured to be diffracted to the outside of the plate-like body by the hologram in the light source of the plate-like body. A polarization separation element is arranged at the facing end, a specific linearly polarized component is selectively introduced into the plate-like body, and a linearly polarized component orthogonal thereto is reflected to the light source side. It is.
[0012]
In this case, it is desirable that the linearly polarized light transmission direction of the polarization separation element is S-polarized light.
[0013]
Still another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body is contained in the plate-like body. Is propagated while being repeatedly totally reflected, and a part of the propagated light is diffracted to the outside of the plate-like body by the hologram, and at least on the illumination light incident side on the diffracted light exit side In the hologram light guide plate in which the liquid crystal display element having a polarizing plate is arranged, the direction of the transmission axis of the polarizing plate is made to coincide with the direction in which the polarization component of the diffracted light by the hologram is large.
[0014]
In this case, it is desirable that the direction in which the polarization component of the diffracted light by the hologram is large is the polarization direction of S-polarized light.
[0015]
Still another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body is contained in the plate-like body. Is propagated while being totally reflected repeatedly, and a part of the propagated light is diffracted to the outside of the plate-like body by the hologram, and a reflective liquid crystal display element is provided on the diffracted light exit side. In the hologram light guide plate to be disposed, the direction of the diffracted light is set to be oblique with respect to the surface of the transparent plate-like body, and the light reflected from the reflective layer of the reflective liquid crystal display element is substantially Further, it does not advance in the direction opposite to the diffracted light.
[0016]
Still another hologram light guide plate of the present invention comprises a transparent plate-like body, a hologram is provided on one surface thereof, and light introduced from a light source disposed in the vicinity of one end of the plate-like body is contained in the plate-like body. Is propagated while being totally reflected repeatedly, and a part of the propagated light is diffracted to the outside of the plate-like body by the hologram, and a reflective liquid crystal display element is provided on the diffracted light exit side. In the hologram light guide plate to be disposed, the direction of the diffracted light is set obliquely with respect to the surface of the transparent plate-like body, and the diffracted light is used as a reflective layer of the reflective liquid crystal display element. A reflective optical layer directed in the front direction of the reflective liquid crystal display element is used.
[0017]
In this case, a reflective hologram or a reflective computer generated hologram can be used as the reflective optical layer. Further, a reflecting mirror having a sawtooth cross section can be used.
[0018]
In the above hologram light guide plate, it is desirable to provide an antireflection layer on both sides or one side thereof.
[0019]
Moreover, it is desirable to provide a protective layer on both sides or one side of the hologram light guide plate.
[0020]
In the present invention, uniform and bright illumination is possible with a configuration such as providing an absorption layer that absorbs light propagating through the end of the hologram light guide plate opposite to the light source of the transparent plate-like body, A light guide plate for a liquid crystal display device or the like that can display a bright, high-contrast display with high transparency of the hologram light guide plate itself can be realized.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the hologram light guide plate of the present invention will be described based on examples.
[0022]
First, basic configurations of a front light hologram light guide plate and a backlight hologram light guide plate for a liquid crystal display device will be described.
[0023]
FIG. 6A is a schematic cross-sectional view of a reflective liquid crystal display device using the front light hologram light guide plate 1, and the reflective liquid crystal display element 20 is slightly spaced on the back side of the front light hologram light guide plate 1. The reflective liquid crystal display element 20 is, for example, a TN liquid crystal display element, and a liquid crystal layer 23 is sandwiched between the transparent substrates 21 and 22 and sealed. A transparent pixel electrode is provided on the inner surface of one of the transparent substrates 21 and 22 on the liquid crystal layer 23 side, a transparent counter electrode is provided on the other side, an alignment film is provided thereon, and the transparent substrates 21 and 22 are provided. Polarizers 24 and 25 are arranged outside the plate in a parallel Nicols state or a crossed Nicols state. A reflective layer 26 is provided on the back surface of the polarizing plate 25 on the back surface side. In the case of color display, a color filter is disposed on the transparent counter electrode.
[0024]
The front light hologram light guide plate 1 includes a transparent plate-like body 2 made of plastic or the like, and a transmission hologram 3 is disposed in close contact with or adhered to the back surface thereof. Similar to the transmission hologram disclosed in Japanese Patent Application Laid-Open No. 11-109338, the transmission hologram 3 guides light that is guided in the transparent plate 2 and is incident on the transmission hologram 3 at a predetermined angle greater than the critical angle. It has a characteristic of diffracting as diffracted light 6 out of the back surface of the body 2. The diffraction efficiency of the transmission hologram 3 is set lower as it gets closer to the light source 4 on average, and is set higher as the distance from the light source 4 increases. In order to have such a distribution of diffraction efficiency, one means is to provide a distribution so that a desired diffraction efficiency can be obtained in the light intensity of the object light and the reference light at the time of hologram photography. However, the transmission hologram 3 may be an aggregate of fine holograms patterned in a halftone dot shape, and the area ratio of the fine holograms may be smaller as it is closer to the light source 4 and larger as it is farther from the light source 4. For details, see JP-A-11-109338.
[0025]
With such a configuration, when illumination light enters from one end of the transparent plate-like body 2 from the light source 4, the air of the transmission hologram 3 that is in close contact with or adhered to the front surface and the back surface of the transparent plate-like body 2 The illumination light 5 is guided toward the other end of the transparent plate-like body 2 while repeating total reflection with the interface. Since the transmission hologram 3 has the above-described configuration, an angle component satisfying the diffraction condition of the transmission hologram 3 in the illumination light 5 is diffracted by the transmission hologram 3 during the light guide, and is diffracted light 6 as the back surface side. Illuminated light that uniformly illuminates the entire surface of the reflective liquid crystal display element 20 that is diffracted toward the transmission hologram 3 and is disposed close to the transmission hologram 3 from its surface side. The diffracted light 6 is reflected by the reflective layer 26 on the back surface according to the display state of the reflective liquid crystal display element 20, exits from the reflective liquid crystal display element 20 to the front side, and is placed in front of the transmission hologram 3. Thus, the transparent plate-like body 2 is transmitted as display light 27, and the reflection light liquid crystal display device capable of efficiently taking in the illumination light from the light source 4 to illuminate the screen uniformly and displaying brightly.
[0026]
FIG. 6B is a schematic cross-sectional view of a transmissive liquid crystal display device using a backlight hologram light guide plate 1 ′. In this case, the backlight hologram light guide plate 1 ′ is an arrangement position of the transmission hologram 3. Only differs from FIG. That is, the transmission hologram 3 is disposed in close contact with or adhered to the surface of the transparent plate 2 such as plastic.
[0027]
A transmissive liquid crystal display element 20 ′ is arranged at a slight interval on the surface side of the transmissive hologram 3, and the transmissive liquid crystal display element 20 ′ is, for example, a TN liquid crystal display element, and a transparent substrate 21. The liquid crystal layer 23 is sandwiched and sealed between. A transparent pixel electrode is provided on the inner surface of one of the transparent substrates 21 and 22 on the liquid crystal layer 23 side, a transparent counter electrode is provided on the other side, an alignment film is provided thereon, and the transparent substrates 21 and 22 are provided. Polarizers 24 and 25 are arranged outside the plate in a parallel Nicols state or a crossed Nicols state. In the case of color display, a color filter is disposed on the transparent counter electrode.
[0028]
Also in this case, when illumination light enters from one end of the transparent plate-like body 2 of the backlight hologram light guide plate 1 ′ from the light source 4, the transmission type is disposed in close contact with or adhered to the back surface of the transparent plate-like body 2 and the surface thereof. The illumination light 5 is guided toward the other end of the transparent plate-like body 2 while repeating total reflection between the hologram 3 and the interface with air, and the transmission hologram 3 in the illumination light 5 is guided during the light guide. The angle component satisfying the diffraction condition is diffracted by the transmission hologram 3 and is diffracted to the front surface side as diffracted light 6 so that the entire surface is uniform from the rear surface side of the transmission liquid crystal display element 20 ′ disposed close to the transmission hologram 3. It becomes the illumination light to illuminate. Therefore, a transmissive liquid crystal display device capable of efficiently taking in illumination light from the light source 4 to illuminate the screen uniformly and brightly and capable of bright display is obtained.
[0029]
In the case of the front light hologram light guide plate 1, instead of the transmission hologram 3 being adhered or adhered to the back surface of the transparent plate-like body 2, a reflection hologram is adhered or adhered to the front surface, and the backlight hologram is provided. Instead of closely attaching or adhering the transmissive hologram 3 to the surface of the transparent plate 2 in the case of the light guide plate 1 ′, a reflective hologram is closely attached or adhered to the rear surface of the transparent plate 2 so as to totally reflect within the transparent plate 2. In the meantime, the light 5 guided may be diffracted by the reflection hologram and emitted to the back side or the front side of the transparent plate 2 to be used as illumination light. Similar to the reflection hologram disclosed in JP-A-11-109338, this reflection hologram transmits light that is guided in the transparent plate-like body 2 and is incident on the reflection hologram at a predetermined angle greater than the critical angle. 2 has a characteristic of diffracting as diffracted light 6 to the back surface or the front surface, and for details, see JP-A-11-109338.
[0030]
The present invention relates to the hologram light guide plate 1 for front light and the hologram light guide plate 1 'for backlight as described above, but both differ in whether display light from a liquid crystal display element is transmitted. Since the other configurations are substantially the same, the front light hologram light guide plate 1 will be described unless otherwise specified in the following description.
[0031]
FIG. 1A is a sectional view of a hologram light guide plate 1 according to an embodiment of the present invention, and FIG. 1B is a partially enlarged view thereof. The hologram light guide plate 1 is formed by placing the transmission hologram 3 as described above in close contact with or adhering to the back surface 2 d of the transparent plate-like body 2, facing the one end 2 a of the transparent plate-like body 2, and the light source 4. When the illumination light enters from one end 2a of the transparent hologram element 2, the entire surface 2c of the transparent plate-like body 2 and the air interface of the transmission hologram 3 disposed in close contact with or adhered to the back surface 2d are disposed. The illumination light 5 is guided toward the other end 2b of the transparent plate-like body 2 while repeating the reflection. During the light guide, an angle component satisfying the diffraction condition of the transmission hologram 3 in the illumination light 5 is diffracted by the transmission hologram 3 and diffracted as the diffracted light 6 to the back surface 2d side, and FIG. As described with respect to b), the entire surface of the reflective liquid crystal display element 20 or the transmissive liquid crystal display element 20 ′ is illuminated uniformly. The portion of the illumination light 5 that does not satisfy the diffraction conditions of the transmission hologram 3 or has not been diffracted reaches the other end 2b, and is reflected by the other end 2b. The light is guided toward one end 2a. When the return light 5n is incident on the transmission hologram 3, the angle component satisfying the diffraction condition of the transmission hologram 3 is diffracted by the transmission hologram 3, and this time, the diffracted light is opposite to the diffracted light 6 (on the surface 2c side). It is diffracted as 6n and exits to the surface 2c side of the transparent plate-like body 2.
[0032]
The reason will be described with reference to the enlarged view of FIG. Since the transmission hologram 3 is a volume hologram, in order to diffract the light 5 propagating in the transparent plate-like body 2 as the diffracted light 6 to the back surface 2d side, interference fringes as shown in FIG. 3a is recorded. On the other hand, the return light 5n that is reflected by the other end 2b of the transparent plate-like body 2 and travels to the opposite side is indicated by a broken line in the drawing that travels in the opposite direction to the light 5 incident on the interference fringes 3a and diffracted. Ingredients are also present. The return light 5n indicated by the broken line is diffracted light 6n which is diffracted by the interference fringes 3a and exits to the surface 2c side opposite to the diffracted light 6. As shown in FIG. 6A, the diffracted light 6 diffracted to the back surface 2d side of the hologram light guide plate 1 is illumination that uniformly illuminates the entire surface of the reflective liquid crystal display element 20 arranged in proximity. Depending on the display state, the light is reflected by the reflective layer 26 on the back surface thereof, exits from the reflective liquid crystal display element 20 to the front surface side, and passes through the hologram light guide plate 1 disposed in front of it to become display light 27. Therefore, although it is an effective portion as illumination light, the diffracted light 6n that suddenly emerges from the hologram light guide plate 1 toward the surface 2c does not contribute to the illumination of the reflective liquid crystal display element 20, and conversely the display light 27 (FIG. This diffracted light 6n overlaps 6 (a)) and becomes noise light, which makes it difficult to see the display.
[0033]
Therefore, in the present invention, as shown in FIG. 1, illumination light reaching the other end 2b by providing an absorption layer 7 made of black paint or the like on the other end 2b opposite to the light source 4 side of the transparent plate-like body 2 is provided. 5 is absorbed to prevent generation of the undesirable return light 5n as described above.
[0034]
Instead, as shown in FIG. 2, the other end 2b opposite to the light source 4 side of the transparent plate-like body 2 is included in a cross section including the normal line of the surface of the transparent plate-like body 2 and perpendicular to the end portion 2b (see FIG. 2 side) is tapered and tapered, and is opposite to the reflective liquid crystal display element 20 or the transmissive liquid crystal display element 20 ′ (FIG. 6B) disposed close to the transmissive hologram 3. A reflective layer 8 is provided on the side tapered surface. If comprised in this way, the illumination light 5 which goes to the other end 2b of the transparent plate-shaped body 2 will be repeatedly reflected by this taper part, and the total reflection conditions on the interface of the transparent plate-shaped body 2 or the transmission hologram 3 and air will no longer be satisfied. The light is emitted from the transparent plate 2 as light 9 that illuminates the region near the end of the reflective liquid crystal display element 20 or the transmissive liquid crystal display element 20 ′. Therefore, in this case, the illumination light 5 reaching the other end 2b of the transparent plate-like body 2 is not absorbed but effectively used as part of the illumination light.
[0035]
By the way, in the case of a plane parallel plate in which the front surface 2c and the back surface 2d of the transparent plate-like body 2 are parallel, the angle component satisfying the diffraction condition of the transmission hologram 3 in the illumination light 5 incident from the one end 2a is first transmitted. Since the light is diffracted at a predetermined ratio at the position where it enters the hologram 3 and goes out as diffracted light 6, the ratio of being totally reflected by the front surface 2c and entering the transmission hologram 3 on the back surface 2d again is lower than the first time. As a result, the ratio of the diffracted light 6 at the second incident position becomes lower and darker. For this reason, the diffracted light 6 emitted from the back surface 2d of the hologram light guide plate 1 has a repeated pattern in the surface.
[0036]
In order to prevent this, as shown in FIG. 1, the surface 2c of the transparent plate-like body 2 is within the cross section (plane of FIG. 1) perpendicular to the end 2a including the normal line of the surface of the transparent plate-like body 2. And the back surface 2d are not parallel but have a fine angle δ, and the transparent plate 2 is wedge-shaped, and every time the total reflection in the transparent plate 2 is repeated, the incident angle (in the case of the interface, As shown in the figure, if the angle measured from θ ₀ → θ ₁ → θ ₂ → θ ₃ → θ ₄ →... Is different, each of the different illumination lights 5 immediately after entering from the end 2a. Since the angle components successively satisfy the diffraction conditions of the transmission hologram 3, a part of the light guided in the hologram light guide plate 1 is gradually diffracted to the outside of the light guide plate 1 and leaks. It becomes difficult to generate the repeated pattern as described above, and the illumination light 5 can be used efficiently.
[0037]
Further, in order to make the above repeated pattern inconspicuous, the distance between the front surface 2c and the back surface 2d of the transparent plate-like body 2, that is, the thinner the thickness of the transparent plate-like body 2, the smaller the total reflection interval. This is desirable because it is shorter and the interval between repeated patterns is smaller. When used in combination with an actual reflective liquid crystal display element or a transmissive liquid crystal display element, such a repetitive pattern becomes inconspicuous if the thickness of the transparent plate-like body 2 is 0.5 mm or less.
[0038]
By the way, as described above, since the transmission hologram 3 is composed of a volume hologram, particularly when the incident angle satisfying the diffraction condition is set to be large, P-polarized light (linearly polarized light within the plane of FIG. 1 and FIG. 2). The diffraction efficiency of the polarized light 6 becomes smaller than the diffraction efficiency of the S-polarized light (polarized light linearly polarized perpendicular to the paper surface of FIGS. 1 and 2), and the diffracted light 6 is mostly S-polarized light. Therefore, in order to efficiently illuminate the reflective liquid crystal display element or the transmissive liquid crystal display element, the illumination light 5 introduced from the light source 4 through the end 2a of the transparent plate-like body 2 is S-polarized light, It is desirable to reflect P-polarized light and return it to the light source 4 side.
[0039]
For this purpose, as shown in FIG. 1, it is desirable to dispose a polarization separation element 10 that transmits S-polarized light and reflects P-polarized light at the illumination light introducing end 2a of the transparent plate-like body 2. One such polarization separation element 10 is made of an interference multilayer film, which uses an anisotropic material as the multilayer film material, transmits one polarization component orthogonal to each other, and transmits the other For example, there is a product name “DBEF” (manufactured by Sumitomo 3M Limited). Then, for example, the surface of a reflection mirror (parabolic mirror or hyperboloid mirror) 11 on the light source 4 side is used as a scattering reflection surface, and P-polarized light reflected and returned by the polarization separation element 10 is scattered to generate random polarization (natural polarization). Is converted back into the polarized light separating element 10 side again, and the S-polarized light therein is introduced into the transparent plate-like body 2 so that the illumination light from the light source 4 is almost S-polarized light and efficiently illuminated. 5 can be set.
[0040]
Further, since the light 6 diffracted from the transmission hologram 3 of the hologram light guide plate 1 to become illumination light is mainly S-polarized light, the reflective liquid crystal display element 20 arranged close to the side from which the diffracted light 6 exits. (FIG. 6A) or the direction of the transmission axis of the polarizing plate 24 or the polarizing plate 25 on the illumination light incident side of the transmissive liquid crystal display element 20 ′ (FIG. 6B) is made to coincide with the direction of the S-polarized light. It is desirable to dispose the reflective liquid crystal display element 20 or the transmissive liquid crystal display element 20 ′ in order to efficiently use the illumination light.
[0041]
Next, the direction of the diffracted light 6 by the transmission hologram 3 will be examined. The diffracted light 6 diffracted from the hologram light guide plate 1 uniformly illuminates the reflective liquid crystal display element 20 disposed close to the hologram light guide plate 1 from the front surface side, and the reflective layer 26 on the back surface thereof according to the display state. Is reflected from the reflection type liquid crystal display element 20 to the front side and is transmitted through the hologram light guide plate 1 to become display light 27 (FIG. 6A). However, as shown in FIG. In the case where 6 is configured to enter the reflective layer 26 of the reflective liquid crystal display element 20 substantially perpendicularly, the light 12 reflected by the reflective layer 26 enters the transmission hologram 3 along an optical path opposite to the diffracted light 6. . When the reflected light 12 follows an optical path opposite to that of the diffracted light 6, a part thereof is re-diffracted by the interference fringes 3 a of the transmission hologram 3 for the same reason as described with reference to FIG. Returning to the plate-like body 2, it becomes impossible to transmit the display light 27 through the hologram light guide plate 1. If such a phenomenon occurs, there is a risk that bright display may not be possible.
[0042]
In order to solve this problem, as shown in FIG. 4, the direction of the diffracted light 6 by the transmission hologram 3 (in particular, the direction of the principal ray) is oblique to the surface 2c or 2d of the transparent plate-like body 2. (Meaning deviating from the normal line direction) is set so that the light 12 reflected from the reflective layer 26 of the reflective liquid crystal display element 20 does not substantially travel in the optical path opposite to the diffracted light 6. .
[0043]
However, in the case of FIG. 4, the direction of the reflected light 12 is also not a front direction of the reflective liquid crystal display element 20 but an oblique direction, and an angle at which the display can be observed becomes an oblique direction. Therefore, it is desirable to use a reflective optical layer that directs the reflected light 12 in the substantially front direction of the reflective liquid crystal display element 20 as the reflective layer 26. Even when the reflected light 12 is directed substantially in the front direction of the reflective liquid crystal display element 20, the reflected light 12 does not travel along the optical path opposite to the diffracted light 6. Can be avoided.
[0044]
In the case of FIG. 5A, a reflection hologram 26 ′ that reflects and diffracts obliquely incident diffracted light 6 in a substantially front direction is used as a reflection layer disposed behind the reflection type liquid crystal display element 20. Such a reflection type hologram 26 'is known, for example, in JP-A-11-125707 and JP-A-11-352329. Alternatively, a reflection type computer generated hologram having similar characteristics may be used. Further, instead, a similar action can be achieved by using a sawtooth reflecting mirror 26 ″ having a cross section as shown in FIG.
[0045]
By the way, in particular, in the case of the front light hologram light guide plate 1, the display image of the reflective liquid crystal display element 20 is viewed through the hologram light guide plate 1, so that it is transmitted through the interface, specifically the surface 2 c of the transparent plate 2. If the interface reflectance is high on the exposed surface of the mold hologram 3, the display becomes dark or the display becomes difficult to see due to the reflected light. Therefore, it is desirable to provide an antireflection layer such as an antireflection film on the surface 2 c of the transparent plate 2 and the exposed surface of the transmission hologram 3.
[0046]
In particular, in the case of the front light hologram light guide plate 1, the surface 2c of the transparent plate-like body 2 is an exposed surface as an observation surface. Therefore, it is desirable to provide a protective layer such as a hard coat layer on the surface 2c of the transparent plate-like body 2 and the exposed surface of the transmission hologram 3 if necessary.
[0047]
As described above, the front light hologram light guide plate 1 has been mainly described in the present invention, but these configurations can also be applied to the backlight hologram light guide plate 1 ′. Further, the present invention can also be applied to a front light hologram light guide plate 1 and a backlight hologram light guide plate 1 ′ that use a reflection hologram instead of the transmission hologram 3. Furthermore, the above various configurations can be used alone or in combination of two or more configurations.
[0048]
As described above, the hologram light guide plate of the present invention has been described based on some embodiments, but the present invention is not limited to these embodiments and can be variously modified.
[0049]
【The invention's effect】
As is apparent from the above description, according to the hologram light guide plate of the present invention, an absorption layer for absorbing light propagating therein is provided at the end of the hologram light guide plate opposite to the light source of the transparent plate-like body. With such a configuration, it is possible to realize a light guide plate for a liquid crystal display device or the like that can perform uniform and bright illumination, has good transparency of the hologram light guide plate itself, and can display bright and good contrast.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a hologram light guide plate of one embodiment.
FIG. 2 is a cross-sectional view of a hologram light guide plate of another embodiment.
FIG. 3 is a diagram for explaining a problem when diffracted light from a hologram light guide plate is incident substantially perpendicularly on a reflection layer of a reflective liquid crystal display element.
4 is a cross-sectional view of a hologram light guide plate of another embodiment of the present invention that solves the problem in the case of FIG.
FIG. 5 is a diagram for explaining still another embodiment of the present invention for solving the problem in the case of FIG. 3;
FIG. 6 is a schematic cross-sectional view of a liquid crystal display device using a hologram light guide plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Front light hologram light-guide plate 1 '... Backlight hologram light-guide plate 2 ... Transparent plate-shaped body 2a ... One end 2b of a transparent plate-shaped body ... The other end 2c of a transparent plate-shaped body ... The surface 2d of a transparent plate-shaped body ... Back surface 3 of transparent plate-like body ... Transmission hologram 3a ... Interference fringe 4 ... Light source 5 ... Illumination light 5n ... Return light 6 ... Diffracted light 6n ... Diffracted light (noise light)
7 ... Absorbing layer 8 ... Reflecting layer 9 ... Area illumination light 10 ... Polarization separating element 11 ... Reflecting mirror (parabolic mirror or hyperboloidal mirror)
DESCRIPTION OF SYMBOLS 20 ... Reflection type liquid crystal display element 20 '... Transmission type liquid crystal display element 21, 22 ... Transparent substrate 23 ... Liquid crystal layer 24, 25 ... Polarizing plate 26 ... Reflection layer 26' ... Reflection type hologram 26 "... Reflection of sawtooth cross section Mirror 27 ... Display light

Claims (4)

A transparent plate is provided, a hologram is provided on one surface, and light introduced from a light source disposed near one end of the plate is propagated repeatedly and totally reflected in the plate. In the hologram light guide plate configured such that a part of the light to be diffracted by the hologram to the outside of the plate-like body, the light is propagated to the end of the plate-like body opposite to the light source. features and sulfo program light guide plate to the absorption layer for absorbing light is provided that. A transparent plate is provided, a hologram is provided on one surface, and light introduced from a light source disposed near one end of the plate is propagated repeatedly and totally reflected in the plate. In the hologram light guide plate configured such that a part of the light to be diffracted to the outside of the plate-like body by the hologram, an end portion of the plate-like body opposite to the light source is the plate-like It is configured to taper in a cross section that includes the normal of the body surface and is perpendicular to the end portion, and a reflective layer is provided on the surface of the tapered portion opposite to the side where the diffracted light from the hologram is emitted features and sulfo program light guide plate that has been. Claim 1, characterized in that the front and back surfaces of the plate-like body is constructed wedge-shaped forming an angle to each other in the plate-like body in the cross section perpendicular to said end includes a normal line of the surface Or the hologram light guide plate of 2. Hologram light guide plate of any one of claims 1-3, wherein the thickness of said plate-like body is 0.5mm or less.

Images