JP2002116309A - White diffusion plate and reflection type liquid crystal display device using the same - Google Patents

Abstract

(57) [Problem] To provide a white diffusion plate capable of observing white in a desired observation region and a reflection type liquid crystal display device using the same as a reflection plate. SOLUTION: This is a white diffusion plate 10 that diffracts illumination light incident at a predetermined incident angle into a specific angle range and looks white, and is composed of a two-dimensional array of minute cells A, and each cell has a lattice spacing. A two-dimensional transmission-type or reflection-type two-dimensional diffraction grating that continuously changes two-dimensionally, for example, a white diffusion plate composed of a partial region of a Fresnel zone plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white light diffusing plate and a reflection type liquid crystal display device using the same, and more particularly, to a white light diffusing plate capable of observing white in a desired observation region and a reflection using the same as a reflecting plate. The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a computer generated hologram which can be used as a reflection diffuser by being arranged on the back of a reflection type liquid crystal display device. For example, Japanese Patent Application Laid-Open Nos. H11-183716 and H11-296054 propose a computer generated hologram having a phase distribution that diffracts light incident at a predetermined oblique incident angle into a predetermined observation area.

[0003]

The problem to be solved by the present invention is disclosed in JP-A-11-18 / 1999.
The computer-generated hologram proposed in No. 3716 and Japanese Patent Application Laid-Open No. H11-296054 is a type in which a reflective layer is provided on a relief pattern, or a transmission type hologram, so that diffraction occurs in a wide wavelength range. For this reason, when the observation area is set to be narrow for the purpose of improving brightness or the like, there is a problem that a color observed at each observation position changes due to a difference in diffraction angle depending on a wavelength.

The present invention has been made in view of such problems of the prior art, and has as its object to provide a white diffuser plate capable of observing white in a desired observation region and a reflection type diffuser plate using the same as a reflector plate. It is to provide a liquid crystal display device.

[0005]

According to a first aspect of the present invention, there is provided a white diffuser plate according to the present invention, wherein illumination light incident at a predetermined incident angle is diffracted into a specific angle range and looks white. The white diffusing plate is formed of a two-dimensional array of minute cells, and each cell is formed of a transmission type or reflection type two-dimensional diffraction grating in which the grating interval changes two-dimensionally and continuously.

In this case, it is desirable that the two-dimensional diffraction grating is composed of a partial area of a transmission type or reflection type Fresnel zone plate.

Further, the ratio between the maximum lattice spacing d _max and the minimum lattice spacing d _min in a cross section of the two-dimensional diffraction grating including the direction of incidence of the illumination light is determined by the relationship between the red wavelength λ _R and the blue wavelength λ _B.
It is desirable that the ratio be larger than the ratio.

In this case, it is desirable that the red wavelength λ _R is 650 nm and the blue wavelength λ _B is 450 nm.

Preferably, the two-dimensional diffraction grating comprises a phase grating, and is blazed so as to diffract to a specific order at least in a cross section including the direction of incidence of the illumination light.

In this case, the two-dimensional diffraction grating has, in a direction orthogonal to the cross section including the direction of incidence of the illumination light, a beam of a specific order that is blazed positively and a beam that is negatively blazed are substantially equal. It is desirable to have.

A display device according to the present invention is characterized in that the above-mentioned white diffusion plate is used as a transmission type or reflection type screen.

Further, the reflection type liquid crystal display device of the present invention is characterized in that the above-mentioned white diffusion plate is disposed on the back surface as a reflection plate.

Another reflection type liquid crystal display device of the present invention is characterized in that the above-mentioned white diffusion plate is arranged as a reflection plate between a liquid crystal layer and a back substrate.

In this case, the reflection plate may be made of a semi-transparent material, and a light source may be provided on the back side.

In the present invention, since a two-dimensional array of minute cells is formed, and each cell is formed of a transmission type or reflection type two-dimensional diffraction grating whose grating interval continuously changes two-dimensionally, a predetermined incident angle is obtained. There is an angle range where all the light in the wavelength range from red to blue is diffracted when the illumination light is incident, and it can be observed in white in that angle range, and it can be observed even if the viewpoint is moved in that range The color does not change, and is suitable for a reflection plate or the like of a reflection type liquid crystal display device.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the white diffuser according to the present invention will be described below.

In the white diffuser of the present invention, when illumination light is incident on a two-dimensional diffraction grating having a continuously changing grating interval at a predetermined incident angle, the angle range over which all light in the wavelength range from red to blue is diffracted. Utilizing the possibility of existence, such a two-dimensional diffraction grating is configured as a cell and arranged in a two-dimensional array, and when this diffusing plate is observed within the angular range, it looks bright and white.

For the sake of simplicity, the principle of the present invention will be described first using a Fresnel zone plate as a typical example of a two-dimensional diffraction grating in which the grating interval changes continuously. Hereinafter, the zone plate of Fresnel is simply referred to as a zone plate.

As shown schematically in FIG. 6, the zone plate 1 has amplitude-type or phase-type gratings arranged concentrically, and the intervals between the gratings decrease continuously from the center to the outside. (For example, Masao Tsuruta, “Applied Physics Engineering Selection Book 1 Applied Optics I” (1990.7.20 Co., Ltd.)
Published by Baifukan)). The zone plate 1, those having the effect of a positive lens or a negative lens, the focal length f, when the radius of the central portion and s _1, is ^{_{f = ± s 1 2 / λ}} ··· (1) . Here, + is the focal length f for a positive lens, and-is the focal length f for a negative lens. Λ is a wavelength. The zone plate 1 functions as a positive lens when the diffraction order of the zone plate 1 is +1 order, and the zone plate 1 functions as a negative lens when the diffraction order of the zone plate 1 is -1 order.

As is apparent from the above (1), the focal length f of the zone plate 1 is inversely proportional to the wavelength λ, and the longer the wavelength λ, the shorter the focal length f.

Now, as shown in FIG. 4, a case where parallel illumination light 2 is incident on the area A of the zone plate 1 at an incident angle θ will be examined. Figure 4 shows the positive zone plate 1
4 (a) is a vertical sectional view, and FIG.
(B) is a projection view in the horizontal direction.

The focal length of the red wavelength of the zone plate 1 is
f_RAnd the focal length of the blue wavelength is f_BAnd the zone plate
Light incident on the center O of 1 at an incident angle θ and passing without being diffracted
The intersection of line 3 with the focal plane of the red wavelength of zone plate 1
P_R, The intersection with the blue wavelength focal plane is P_BAnd when
Illumination light 2 enters area A below center O of
When incident at an angle of incidence θ, the red wavelength component_ROnce focused
Then the angle range α_RDiverge inside. Of the diffracted light
Of the light diffracted to the top_RUDiffracted to the bottom,
Light 4_RLAnd The blue wavelength component is represented by a point P_BNiichi
And then the angle range α_BDiverge inside. That time
Of the folded light, the light diffracted to the top _BUAt the bottom
4 diffracted light_BLAnd As is clear from this figure
The angle at which both the red and blue wavelength components are diffracted
The range is the light whose upper side is diffracted to the top of the blue wavelength component.
Line 4_BUAnd the lower side is the bottom of the red wavelength component.
Ray 4 folded_RLRange limited by_WAnd this corner
Degree range α_WInside, as you can see from a simple consideration, red
The wavelength component between the wavelength component and the blue wavelength component is also diffracted and enters.
Incident on the area A of the zone plate 1 from above.
When the illumination light 2 is incident at an angle θ, the angle range α_WRed in
Light in the wavelength range from color to blue is all diffracted and looks white
Will be.

The above is for the vertical direction, but for the horizontal direction, as shown in FIG. 4B, the illumination light 2 is vertically incident on the zone plate 1 on the projection view, and the red wavelength component is P _R once go diverging condensed thereafter the angular range beta _R, the blue wavelength component diverge once condensed thereafter angular range beta in _B to point P _B. Angle range red wavelength component and a blue wavelength component is diffracted both are angular range beta _B diffracted blue wavelength component, the angular range beta all light in the wavelength region ranging from red to blue diffracted in _B And it looks white.

FIG. 5 shows a view similar to FIG. 4 when the zone plate 1 has a negative power. In this case, the only difference is that the area A of the zone plate 1 where the illumination light 2 is incident at the incident angle θ is above the center O, and the result is the same as the case of the positive zone plate 1 in FIG. Description is omitted.

By limiting the diffraction order of the zone plate 1 to only the +1 order or the −1 order, the zone plate 1 having a positive power as shown in FIG. 4 or the zone plate 1 having a negative power as shown in FIG. In order to achieve this, the phase grating may be blazed as schematically shown in FIG.
FIG. 7A is a cross-sectional view of the blazed surface shape when the diffraction order is limited to the + 1st order to obtain the positive power zone plate 1, and FIG. 7B is the diffraction order limited to the −1st order. FIG. 4 is a cross-sectional view of a blazed surface shape when the zone plate 1 has a negative power.

The diffraction order is +1 order or-
In order to configure the primary limited zone plate 1 as a reflection type, a reflection layer 5 made of aluminum or the like may be provided on a blazed relief surface on the back surface as schematically shown in FIG. FIG. 8A shows a zone plate 1 having a positive power.
FIG. 8B is a sectional view of the zone plate 1 having a negative power. However, the inclination of the blazed surface in the case of the reflection type is naturally different from that in the case of the transmission type because light reciprocates in the transparent medium. The reflection layer 5 may be provided not on the relief surface but on a plane on the opposite side, and light may be incident from the relief surface side. FIG. 8 (a) or (b)
Alternatively, light may be directly incident on the reflective layer 5 and reflected. In that case, the configuration of FIG. 8A is a zone plate 1 of negative power, and the configuration of FIG. 8B is a zone plate 1 of positive power.

As described above, when the illumination light 2 is incident from obliquely above the rear side in the case of the transmission type and obliquely above the front side in the case of the reflection type, the vertical angle of the front side is obtained. Within the range α _W and the horizontal angle range α _B , the partial area A of the zone plate 1 having a positive power or a negative power which looks white in a horizontal direction is constituted by fine cells, and these cells are arranged in an array to obtain a desired area. It is possible to form a white diffusion plate in which the entire surface looks white.

FIG. 1 is a schematic diagram showing a case where a white diffusion plate 10 is formed by arranging a partial area A of a zone plate 1 having a positive power as a cell as shown in FIG. FIG. 2 shows a cell of a partial area A ′ of the zone plate 1 having a negative power as shown in FIG. 5 (area A in FIG. 5 but A ′ to distinguish it from partial area A in FIG. 4). White diffuser 1 arranged two-dimensionally in a grid pattern
FIG. 4 shows a schematic diagram when 0 is configured. FIG. 3 shows a case in which the partial region A of the positive power zone plate 1 of FIG. 4 and the partial region A ′ of the negative power zone plate 1 of FIG. FIG. FIG. 10 shows two adjacent cells used for each cell of FIG.
A specific pattern example in which the phase distribution of one cell A is represented by density is shown. FIG. 11 is a view similar to FIG. 10 of two adjacent cells A ′ used for each cell of FIG. 2, and FIG. 12 is a view of FIG. 1 of two adjacent cells A and A ′ used for each cell of FIG.
FIG. In addition, zone plate 1
The two-dimensional array-like arrangement of the partial areas A and A ′ is not limited to a grid pattern, but may be a delta arrangement, a stripe arrangement, or the like.
Any pattern may be used as long as the two-dimensional surface is densely and regularly filled. FIG. 13 shows an arrangement when the shape of each cell A or A 'is hexagonal, FIG. 14 shows an arrangement when each cell A or A' is triangular, and FIG. Is illustrated by way of example when the shape is rectangular.

The dimensions of the cells A and A 'constituting the array of such a white diffusion plate are desirably 200 μm or less in length and width in order to make each cell inconspicuous. As will be described later, when this white diffusion plate is used as a reflection diffusion plate of a reflection type liquid crystal display device, it is desirably equal to or less than the size of a pixel of the liquid crystal display device, for example, 80 μm or less.

In the above description, the zone plate has a continuous grid spacing.
Considered as a representative example of a two-dimensional diffraction grating that changes
However, it will be more generalized and examined. The basis of the present invention is
A two-dimensional diffraction grating with a continuously variable lattice spacing
Are arranged in a two-dimensional array.
The lattice spacing changes continuously in each microscopic cell
That the diffraction gratings are closely arranged
No. As shown in FIG. 9, the second order in which the lattice spacing changes continuously
Light at an incident angle θ on a microcell 11 composed of a diffraction grating
12 is assumed to be incident. FIG. 9A shows a vertical section.
FIG. 9B is a horizontal projection view. Small cell
D is the minimum value of the lattice spacing in each direction in _min,Maximum value
To d_maxAnd

As shown in FIG. 9A, the case where the illumination light 12 is incident from an obliquely upward direction at an incident angle θ will be examined. The red wavelength component diffracted by a particular order, for example, the + 1st order, by the grating having the minimum spacing d _min in the cell 11 is 1
3 _minR, a 13 _minB blue wavelength component, and similarly specific order by the grating of the maximum distance d _max in the cell 11, for example, +1 then diffracted red wavelength component 13 _maxR, and a 13 _maxB blue wavelength components, these When the diffraction direction is the direction as shown in FIG. 9A, the red wavelength component in the illumination light 12 has a continuously changing grating interval d _{min to} d in the cell 11.
_{Due to} the diffraction grating of _max, the light rays are distributed continuously in the angle range a between 13 _minR and 13 _maxR , in _terms of angle range, between γ _minR and γ _maxR . On the other hand, the blue wavelength component in the illumination light 12 is a continuously changing lattice spacing d in the cell 11.
Light _beams from 13 _minB to 13 with a diffraction grating of _{min to} d _{max
In terms} of the angle range during _maxB , it is continuously distributed in the angle range b between γ _minB and γ _maxB . Therefore, in the angle range c where the angle ranges a and b overlap, light in the wavelength range from red to blue is all diffracted and looks white.

Therefore, when there is an area c which appears white in the front in the vertical direction when the illuminating light 12 is incident from an obliquely upward direction at an incident angle θ, the light ray 13 _minB (diffraction by the grating with the minimum interval d _{min) is required} . Diffraction angle measured from the 0th-order transmitted light (or 0th-order reflected light) 12 ′ of the blue wavelength component (or the rightward direction from the normal line as shown in the drawing is positive) θ−γ.
_minB is, 13 _maxR (maximum red wavelength component diffracted by the grating spacing d _max) of the 0-order transmission light (or zero order reflected light) 1
When it is larger than the diffraction angle θ-γ _maxR measured from 2 ′, there is an angle range c that looks white. When this is _expressed as a formula, θ−γ _minB > θ−γ _maxR (2) γ _minB <γ _maxR (3) Both γ _minB and γ _maxR are −90 ° ≦ γ _minB and γ _maxR ≤
Since it exists in the range of 90 °, _{sinγ minB} < _{sinγ maxR} (4) On the other hand, from the diffraction equation, sin θ− _{sinγ minB} = λ _B / d _min (5) sin θ− _{sinγ maxR} = λ _R / D _max (6) From equations (4) to (6), sin θ−λ _B / d _min <sin θ −λ _R / d _max ∴d _max / d _min > λ _R / λ _B (7) That is, in order for the region c to appear white in the vertical direction, the cell 11 of the two-dimensional diffraction grating only needs to be configured so as to satisfy Expression (7).

FIG. 9B shows the horizontal direction. As is apparent from this figure, when changing the grating spacing d _min to d _max of the diffraction grating in the cell 11, the minimum distance d _mi diffraction range of ± 1-order blue wavelength components due to the lattice of _n d
Is the range that appears white. Therefore, in the horizontal direction orthogonal to the direction in which the illumination light 12 is incident, in order to make the angle range that appears white to be a symmetrical left and right angle range ± φ _minB , the maximum grating interval d of the diffraction grating in the cell 11 is set. _max
Is as large as possible, and it is only necessary that the blazed + 1st order and the blazed −1st order be substantially equal in any lattice spacing.

As is clear from the above generalized examination.
The grid spacing used for each cell A, A 'in FIGS.
Of transmission type or reflection type, in which
The partial area A of the zone plate 1
The general lattice spacing is not limited to
Using a transmission-type or reflection-type two-dimensional diffraction grating
The minimum requirement in that case is that the expression
(7) That is, a cross section including the incident directions of the illumination lights 2 and 12
Maximum lattice spacing d at_maxAnd the minimum grid spacing d _min
Is the red wavelength λ_RAnd blue wavelength λ_BGreater than the ratio
I just need to be satisfied. To look white, red waves
Long λ_RIs 650 nm, blue wavelength λ_BIs 450nm
Is sufficient, so λ_R/ Λ_B$ 1.44
d_max/ D_{mi n}Should also be 1.44 or more distribution
become. In addition, in the cross section including the incident direction of the illumination lights 2 and 12,
The angle range that looks white in the direction perpendicular to the left and right
In order to obtain a substantially symmetrical
Make sure that the lazed grating exists almost symmetrically on the left and right.
It would be good.

From the above discussion, it is clear that the transmission or reflection type two-dimensional diffraction grating in which the lattice spacing used for each cell A or A 'of the white diffusion plate 10 according to the present invention continuously changes two-dimensionally is shown in FIG. Various shapes other than the partial area of the zone plate 1 illustrated in FIG. In the example illustrated in FIG. 16, the shape of the grating is formed by a part of an elliptic curve. In this case, it can be said that the zone plate has astigmatism. In the example illustrated in FIG. 17, the lattice spacing does not continuously increase or decrease from one end to the other end in the cell but increases and decreases repeatedly. In addition, although not shown, the shape of the lattice may be a wavy line, a parabola, a hyperbola, a tertiary or higher curve, or the like.

The display of the liquid crystal display element 40 is realized by using the above-mentioned white diffusion plate 10, particularly the reflection type white diffusion plate 10, as the reflection diffusion plate 31 of the reflection type liquid crystal display device shown in FIG. Illumination light 32 incident from the side
Is diffused and reflected only to a predetermined observation area in front of it, and a bright white display is possible in a light place without using a self-luminous backlight. In FIG. 18, a liquid crystal display element 40 is composed of a liquid crystal layer 45 such as twisted nematic sandwiched between two glass substrates 41 and 42, for example. An electrode 44 is provided, and a transparent display electrode 43 and a black matrix (not shown) are provided on the inner surface of the other glass substrate 41 independently for each pixel. In the case of a color display device, the liquid crystal cell R,
A transparent display electrode 43, a color filter, and a black matrix are provided independently for each of G and B. Also,
An alignment layer (not shown) is also provided on the liquid crystal layer 45 side of the electrodes 43 and 44. Further, a polarizing plate 46 is provided on the outer surface of the observation-side glass substrate 41, and an outer surface of the glass substrate 42 on the opposite side to the observation side. , Polarizing plates 47 are adhered, for example, and their transmission axes are arranged to be orthogonal to each other. By controlling the voltage applied between the transparent display electrode and the transparent counter electrode of such a liquid crystal display element 40 to change its transmission state, it is possible to selectively display numbers, characters, symbols, pictures, etc. It is. And the reflection diffuser 3
Reference numeral 1 denotes a reflective white diffuser plate 10 according to the present invention having a structure as shown in FIG. 1, for example, and the reflective diffuser plate 31 is disposed on the opposite side of the liquid crystal display device 40 from the observation side. The illumination light 32 including light in the wavelength range from red to blue incident from the display side of 40 is diffused and reflected forward by the reflection diffusion plate 31 arranged on the back surface, and a self-luminous backlight is used in a bright place. A white display can be made without performing the operation.

As shown in FIG. 19, the reflective white diffuser 10 according to the present invention is disposed between the liquid crystal layer 45 of the reflective liquid crystal display device and the rear substrate 42 'as a reflective plate. You may. In this case, the reflection layer 5 (FIG. 8) of the white diffusion plate 10 also functions as the light reflective electrode 44 '.
In this case, the reflection layer 5 is provided on the substrate 21 having the relief surface formed on the surface.

For example, in the configuration shown in FIG. 19, a transflective type is used as the reflective layer 5 (the thickness of the reflective layer 5 is set to, for example, about 250 nm or less). When the illumination light 32 based on the light is absent or slightly dark, the light source on the back side can be turned on to enable a bright display by illumination with the backlight.

Although the white diffusion plate according to the present invention has been described based on the principle and the embodiments, the invention is not limited to these, and various modifications are possible. Further, the white diffusion plate of the present invention,
In addition to a reflection plate for a reflection type liquid crystal display device, it can be used for, for example, a reflection screen and a transmission screen for projection display.

[0040]

As is clear from the above description, according to the white diffuser of the present invention, a two-dimensional array of minute cells is formed, and each cell is a transmission type or a cell in which the lattice interval changes two-dimensionally and continuously. Since it consists of a reflective two-dimensional diffraction grating, there is an angle range in which all light in the wavelength range from red to blue is diffracted when illumination light is incident at a predetermined incident angle, and the angle range is observed in white. It is possible that the observed color does not change even if the viewpoint is moved within the range, and is suitable for a reflection plate or the like of a reflection type liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a white diffusion plate according to one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a white diffusion plate according to another embodiment.

FIG. 3 is a schematic diagram showing a configuration of a white diffusion plate according to another embodiment.

FIG. 4 is a diagram for studying a case where illumination light is made to enter a partial area of a positive power zone plate.

FIG. 5 is a diagram for studying a case where illumination light is made incident on a partial area of a zone plate having a negative power.

FIG. 6 is a diagram schematically showing the shape of a zone plate.

FIG. 7 is a cross-sectional view schematically showing a phase grating of a transmission type zone plate.

FIG. 8 is a cross-sectional view schematically illustrating a phase grating of a reflection type zone plate.

FIG. 9 is a diagram for studying a case where illumination light is incident on a general two-dimensional diffraction grating in which the grating interval changes continuously.

FIG. 10 is a diagram showing a specific pattern example of two adjacent cells used for each cell in FIG. 1;

11 is a diagram showing a specific example of a pattern of two adjacent cells used for each cell of FIG. 2;

12 is a diagram showing a specific example of a pattern of two adjacent cells used for each cell in FIG. 3;

FIG. 13 is a diagram showing an arrangement in a case where the cell shape of the white diffusion plate of the present invention is hexagonal.

FIG. 14 is a diagram showing an arrangement in a case where the cell shape of the white diffusion plate of the present invention is a triangle.

FIG. 15 is a diagram showing an arrangement in a case where the cell shape of the white diffusion plate of the present invention is rectangular.

FIG. 16 is a diagram showing a case where the shape of the two-dimensional diffraction grating is formed by a part of an elliptic curve.

FIG. 17 is a diagram showing a case where the lattice spacing of a two-dimensional diffraction grating repeatedly increases and decreases in a cell.

FIG. 18 is a cross-sectional view illustrating a configuration of a reflection type liquid crystal display device to which a white diffusion plate according to the present invention is applied.

FIG. 19 is a cross-sectional view showing the configuration of another reflective liquid crystal display device to which the white diffuser according to the present invention is applied.

[Explanation of symbols]

A, A ': Partial area (cell) of zone plate 1 ... Zone plate 2 ... Illumination light 3 ... Light ray passing through the center of the zone plate 4 _RU ... Light diffracted to the top of red wavelength component 4 _RL ... Red wavelength component the outermost left and right most light 4 _R ... red wavelength components are diffracted on the lower side of the light 4 _BL ... blue wavelength component is most diffracted on the upper side of the lowermost light 4 _BU ... blue wavelength components are diffracted in the Diffracted light 4 _B … Light diffracted to the left and right outermost sides of the blue wavelength component 5… Reflection layer 10… White diffusion plate 11… Cell 12… Illumination light 12 ′… Illumination light 13 _minR ... red wavelength component diffracted by the minimum spacing grating in the cell 13 _minB ... blue wavelength component diffracted by the smallest spacing grating in the cell 13 _maxR ... diffracted by the largest spacing grating in the cell red wavelength component 13 _maxB ... in the cell Blue wavelength component diffracted by the grating at the maximum interval 21 Base material of white diffuser plate 31 Reflective diffuser plate 32 Illumination light 40 Liquid crystal display elements 41 and 42 Glass substrate 42 ′ Back substrate 43 Transparent display electrode 44 ... Transparent counter electrode 44 '... Reflective electrode 45 ... Liquid crystal layer 46,47 ... Polarizing plate

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) G02F 1/13357 G02F 1/1335 530 F-term (Reference) 2H042 BA04 BA14 BA20 2H049 AA04 AA08 AA14 AA55 AA63 AA64 AA65 2H091 FA08X FA08Z FA14Z FA16Z FA19Z FA26X FA41Z

Claims (10)

[Claims] 1. A white diffuser plate which looks white by diffracting illumination light incident at a predetermined incident angle within a specific angle range, wherein the white diffuser plate is composed of a two-dimensional array of minute cells. A white diffusion plate comprising a transmission-type or reflection-type two-dimensional diffraction grating whose grating interval continuously changes two-dimensionally. 2. The white diffusion plate according to claim 1, wherein said two-dimensional diffraction grating comprises a partial area of a transmission type or reflection type Fresnel zone plate. 3. The ratio between the maximum lattice spacing d _max and the minimum lattice spacing d _min in a cross section of the two-dimensional diffraction grating including the direction of incidence of the illumination light is such that the red wavelength λ _R and the blue wavelength λ _B
3. The white diffusion plate according to claim 1, wherein the ratio is larger than 4. The red wavelength λ _R is 650 nm,
4. The white diffusion plate according to claim 3, wherein the blue wavelength [lambda] _B is 450 nm. 5. The apparatus according to claim 1, wherein the two-dimensional diffraction grating comprises a phase grating, and is blazed so as to diffract to a specific order at least in a cross section including the direction of incidence of the illumination light. 5. The white diffusion plate according to any one of 1 to 4. 6. In the two-dimensional diffraction grating, in a direction orthogonal to a cross section including the direction of incidence of the illumination light, a positively blazed and a negatively blazed of a specific order are substantially equal. The white diffusion plate according to claim 5, wherein the white diffusion plate is present. 7. A display device using the white diffusion plate according to claim 1 as a transmission type or reflection type screen. 8. A reflection type liquid crystal display device, wherein the white diffusion plate according to claim 1 is arranged on a back surface as a reflection plate. 9. A reflection type liquid crystal display device, wherein the white diffusion plate according to claim 1 is disposed as a reflection plate between a liquid crystal layer and a back substrate. 10. The reflection type liquid crystal display device according to claim 9, wherein said reflection plate is made of a semi-transmissive material, and a light source is provided on the back side thereof. .