JPH1069232A - Diffusion plate, illumination device and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to efficiently utilize the light from a light source by allowing the particles formed by coating the surfaces of pearl gloss pigments with polymers to exist in uniform dispersion at a diffusion plate. SOLUTION: The particles 11 formed by coating the surfaces of mica 10 with titanium dioxide 12 and coating the surfaces of the titanium dioxide 12 with the polymers 15 exist in uniform dispersion on the diffusion plate 34. Even if the particles 11 exist at the diffusion plate 34 constituted in such a manner in the state of maintaining contact therewith, the spacings of at least twice the thickness of the polymer layers are eventually generated between the pearl gloss pigments and the pearl gloss pigments by the polymers 15 with which the pearl gloss pigments are coated. Incident light 14, therefore, passes the polymers 15 and can pass, as scattered light, the diffusion plate 34 even if the particles 11 exist in the state of maintaining the contact. As a result, the loss of the incident light 14 is made smaller in comparison with the nonmodified pearl gloss pigments.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diffuser, a lighting device and a liquid crystal display.

[0002]

2. Description of the Related Art In recent years, liquid crystal displays have been used in various fields because they are lightweight and thin. In particular, it is widely used in the electronic industry such as notebook personal computers and portable liquid crystal televisions. However, the liquid crystal display needs to have low power consumption when used for a portable type or a vehicle-mounted liquid crystal display. Therefore, in a transmission type liquid crystal display, it is desired to reduce the power consumption of a backlight (illumination device) which occupies most of the power consumption.

[0003] In order to reduce the power consumption of the backlight, efficient use of light from the backlight has been studied. Conventionally, as a technique for diffusing light from a backlight, for example, fine irregularities for diffusing light are formed on the surface of a transparent substrate made of one kind of polymer material selected from inorganic glass, polyester or polypropylene. Diffusion plates which are provided or in which acrylic beads or pearlescent pigments are dispersed are well known.

[0004]

However, the diffusing plate using the irregularities cannot diffuse incident light satisfactorily. In addition, the provision of the irregularities may cause the diffusion plate to be easily damaged. In addition, it is very difficult to finish these irregularities uniformly, so that advanced technology is required.

On the other hand, the diffusion plate using the acrylic beads cannot satisfactorily diffuse incident light. Therefore, conventionally, it is conceivable to increase the addition amount of the acrylic beads or increase the thickness of the diffusion plate. However, when the addition amount of the acrylic beads is increased or the thickness of the diffusion plate is increased, most of the light is reflected light.

On the other hand, if the amount of acrylic beads added is reduced or the thickness of the diffusion plate is reduced, most of the light is not diffused but becomes transmitted light. In a diffusion plate using the pearlescent pigment, for example, as shown in FIG.
If the pearl luster pigments 62 are in contact with each other, the incident light 14 may be blocked by the pearl luster pigments 62 and may not be able to pass through the diffusion plate 60.

As described above, satisfactory diffusion and transmission properties of light could not be obtained in any case. The present invention has been made in view of the circumstances of the related art, and an object of the present invention is to provide a diffuser, a lighting device, and a liquid crystal display that can efficiently use light from a light source.

[0008]

In order to achieve the above object, a diffusion plate according to the present invention is a diffusion plate that transmits incident light as scattered light. It is characterized by being dispersed. In the diffusion plate, the layer thickness of the polymer coated on the surface of the pearlescent pigment was 0.1 to 200 μm.
m is preferable.

The pearlescent pigment is a titanium mica pigment in which mica surface is coated with titanium dioxide,
It is preferable that the layer thickness of the titanium dioxide coated on the mica surface is such that interference light having a wavelength range substantially the same as the absorption wavelength range of the pearlescent pigment can be obtained. The pearlescent pigment is preferably a colored pearlescent pigment in which mica surface is coated with titanium dioxide, and furthermore, titanium dioxide surface is coated with a titanium-based composite oxide. Also,
The layer thickness of the total titanium oxide coated on the mica surface,
It is preferable that the layer thickness be such that interference light of a desired color can be obtained.

Preferably, the polymer is one selected from acrylic, polymethacrylate and styrene. The pearlescent pigment surface has a polymer-coated particle content of 1 to 70% by weight.
It is preferred that In order to achieve the above object, the lighting device according to the present invention is a light source that emits a light beam, a diffuser that transmits light from the light source as scattered light,
In the lighting device provided with (1), the diffuser plate is characterized in that particles having a pearlescent pigment surface coated with a polymer are uniformly dispersed.

In order to achieve the above object, a liquid crystal display according to the present invention comprises a light source for emitting a light beam, a diffusion plate for transmitting light from the light source as scattered light, and a light transmission plate for transmitting light from the diffusion plate. A liquid crystal panel that controls whether to shut off or cut off by changing the voltage applied to the liquid crystal layer, wherein the diffuser plate is formed by uniformly dispersing particles having a pearlescent pigment surface coated with a polymer. It is characterized by existing.

The term "liquid crystal panel" used herein means that when a voltage is applied to a liquid crystal layer sandwiched between two alignment films, for example,
When the arrangement of the liquid crystal molecules changes, the vibration direction of the light beam from the diffusion plate changes. A polarizing plate that passes linearly polarized light in a predetermined vibration direction among the light beams that have passed through the subsequent alignment film is provided, and by changing the voltage applied to the liquid crystal layer, the light beam can be passed or blocked. Means that can be controlled.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The diffusion plate according to the present invention, as described above, has a structure in which particles coated with a polymer are uniformly dispersed on the surface of the pearlescent pigment, so that the incident light can be further diffused. It is possible to That is, the light beam incident on the diffusion plate is diffused at the boundary between the substrate and the polymer and at the boundary between the polymer and the pearlescent pigment. Moreover, even if the particles coated with the polymer are in contact with the surface of the pearlescent pigment, the incident light can pass through the polymer and exit the diffusion plate as scattered light. Can be greatly reduced.

Further, it is preferable that the layer thickness of the polymer coated on the surface of the pearlescent pigment is 0.1 to 200 μm. That is, when the layer thickness of the polymer coated on the surface of the pearlescent pigment is less than 0.1 μm, most of the light is transmitted without being diffused. On the other hand, the layer thickness of the polymer coated on the surface of the pearlescent pigment is 200 μm.
This is because, when the value exceeds 1, most of the light is scattered and absorbed inside the diffusion plate.

Further, the pearlescent pigment has a mica surface coated with titanium dioxide, and the layer thickness of the titanium dioxide coated on the mica surface is adjusted to be substantially the same wavelength range as the absorption wavelength range of the pearlescent pigment. By setting the layer thickness so as to obtain the interference color described above, it becomes possible to supplement light in a specific wavelength range that is absorbed by the pearlescent pigment. In addition, the pearlescent pigment is a colored pearlescent pigment in which mica surface is coated with titanium dioxide and further titanium dioxide surface is coated with a titanium-based composite oxide, whereby titanium dioxide-coated mica originally had. It is possible to obtain transmitted light of a similar color to the interference color.

Further, by using one kind of polymer selected from acrylic, polymethacrylate, and styrene, it is possible to obtain a diffusion plate with low light loss. Further, by setting the content of the pearlescent pigment to 1 to 70% by weight, light can be diffused favorably and the transmission performance is not impaired. That is, when the amount of the pearlescent pigment is less than 1% by weight, most of the incident light is transmitted through the diffusion plate without being diffused.

On the other hand, the content of the pearlescent pigment is 70% by weight.
When the value exceeds, most of the incident light is reflected and cannot pass through the diffusion plate. By using a diffuser plate in which the particles coated with the polymer on the surface of the pearlescent pigment are uniformly dispersed and used for a lighting device and a liquid crystal display, light from a light source can be efficiently used. Because it is possible, a bright and beautiful image can be obtained. In addition, as a method of producing particles having a polymer coated on the surface of the pearlescent pigment, particles of the pearlescent pigment are dispersed in a monomer solution, and the polymer generated in the surface layer of the particles uniformly covers the surface layer. For example, a method of adding a polymerization initiator and the like under the polymerization conditions and encapsulating the mixture is exemplified.

Another example is a method in which pearlescent pigment particles are dispersed in a polymer solution, and the solubility of the polymer is lowered to precipitate the particles on the particle surface. Further, as an example, a method of physically mixing pearlescent pigment particles and polymer particles and adsorbing the polymer particles on the surface of the particles is exemplified. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a schematic configuration of a liquid crystal display using a diffusion plate according to an embodiment of the present invention. The liquid crystal display module 22 shown in the figure includes a case 27, a bezel 26 serving as a frame of an LCD panel, a light source 28, a reflection plate 30, a light guide plate 32, and a diffusion plate 34.
, Polarizing plate 38, glass substrate 40, transparent electrode 42
, An alignment film 44, a liquid crystal layer 46, an alignment film 48, a transparent electrode 50, a glass substrate 52, and a polarizing plate 56.

The light source 28 emits a light beam. This light source 28
As cold cathode fluorescent lamp, hot cathode fluorescent lamp, EL
(Electroluminescence), an LED (light emitting diode), an incandescent lamp, or the like can be used. Light guide plate 32
Causes the light beam from the light source 28 to enter the diffusion plate 34. As the light guide plate 32, a white pigment which scatters light on the surface of a substrate made of an acrylic resin, or a plate in which ink to which transparent beads are added is printed in a dot shape can be used.

The reflection plate 30 reflects the light beam from the light source 28 and makes it incident on the light guide plate 32. As the reflection plate 30, a metal deposition film, a polished metal plate, foamed polyester, or the like can be used. Further, as the reflection plate 30, a reflection plate in which a pearlescent pigment is very densely present in a transparent film can be used. The diffusion plate 34 diffuses the light flux from the light guide plate 32 at random.

In this embodiment, the diffusion plate 34 is
The titanium dioxide is coated on the mica surface, and the polymer-coated particles 11 on the titanium dioxide surface are uniformly dispersed. In addition, the particle 11 has a layer thickness of titanium dioxide coated on the surface of the mica, which has interference light in a wavelength region substantially the same as the absorption wavelength region of the titanium dioxide-coated mica. The polarizing plate 38 is fixed to the lower surface of the glass substrate 40 in the drawing, and the polarizing plate 56 is fixed to the upper surface of the glass substrate 54 in the drawing by an adhesive, so that the luminous flux passing through the diffusing plate 34 is light in a predetermined vibration direction. .

The transparent electrodes 42 and 50 are made of, for example, an ITO film whose main component is indium oxide, and are patterned according to the purpose. This transparent electrode 42 is a glass substrate 4
0, the transparent electrode 50 is provided on the lower surface of the glass substrate 52 in the figure. By applying a voltage to the transparent electrodes 42 and 50 by the power source 58, the alignment film 4
The liquid crystal molecules 46 between the substrate 4 and the alignment film 48 can be arranged in a certain form. The liquid crystal layer 46 is provided with, for example, a nematic liquid crystal with a layer thickness of about 6 μm. In order to keep this interval constant, beads-like fine particles (not shown) made of, for example, silicon dioxide are used as the spacer material.

The liquid crystal display module 22 according to the present invention is generally configured as described above, and its operation will be described below. First, the light beam from the light source 28 directly enters the light guide plate 32 provided in the front or enters the light guide plate 32 via the reflector 30 provided in the rear. The light beam incident on the light guide plate 32 is reflected by the lower surface in the figure and emitted in a substantially vertical direction. The light beam passing through the light guide plate 32 enters a diffusion plate 34 provided in front.

The luminous flux passing through the diffusion plate 34 is favorably diffused by the particles 11 having a mica surface coated with titanium dioxide and a polymer coated on the titanium dioxide surface.
That is, it is actually very difficult to apply the pearlescent pigment so that the pearlescent pigment is uniformly dispersed and present, so that the distribution of the pearlescent pigment becomes uneven, and as shown in FIG. It may exist in a state where it was done. Then, as shown in FIG. 1, if the particles of the pearlescent pigment 62 are in contact with the diffusion plate 60, the incident light 14 is blocked by the pearlescent pigment 62 and passes through the diffusion plate 60. May not be possible.

Therefore, in the present embodiment, the diffusion plate 3
Instead of using an unmodified pearlescent pigment for 4, a particle 11 having a mica 10 surface coated with titanium dioxide 12 and a titanium dioxide surface 12 coated with a polymer 15 is used as shown in FIG. It is. As a result, FIG.
As shown in FIG. 5, even if the particles 11 are in contact with each other, the polymer 15 coated on the pearlescent pigment 17 causes at least a polymer layer thickness between the pearlescent pigments 17. That is, a gap twice as large as that shown in FIG.

Therefore, even if the incident light 14 exists in a state where the particles 11 are in contact with each other, the incident light 14 can pass through the polymer 15 and pass through the diffusion plate 34 as the scattered lights 19 and 21. Can significantly reduce the loss of incident light 14 compared to unmodified pearlescent pigments. Moreover, as shown in FIG. 4, a part of the light beam 14 incident on the diffusion portion 13 is formed at a boundary between the substrate portion 13 and the polymer 15, a boundary between the polymer 15 and the titanium dioxide 12, and a boundary between the titanium dioxide 12 and the mica 10. It will be spread well.

As described above, in this embodiment, the incident light 14
As a result, the incident light is more diffused as compared with mere acrylic beads or pearlescent pigments. Moreover, in this embodiment, since the light diffusion performance is improved, even if a small amount of pearlescent pigment is used as compared with the conventional one, it is the same as or similar to a conventional diffusion plate using only acrylic beads or pearlescent pigment. More light can be diffused.

By the way, a part of the luminous flux which has passed through the polymer 15 does not reflect at the boundary between the polymer 15 and the titanium dioxide 12 or at the boundary between the titanium dioxide 12 and the mica 10, and is in a specific wavelength range by the pearlescent pigments 10 and 12. Is absorbed. Therefore, in the present embodiment, the layer thickness of the titanium dioxide 12 coated on the surface of the mica 10 is not changed to the pearlescent pigment
The layer thickness is such that interference light in a wavelength region substantially the same as the absorption wavelength region 2 can be obtained. Thereby, pearlescent pigment 1
Since it emits interference light in the same wavelength range as the specific wavelength range absorbed by 0, 12, the color tone lost by the light absorption of the pearlescent pigments 10, 12 can be complemented.

The light that has passed through the diffusion plate 34 enters a polarizing plate 38. The light beam that has passed through the polarizing plate 38 becomes linearly polarized light in a predetermined vibration direction. Here, as shown in FIG. 5A, when no voltage is applied, the liquid crystal molecules 46 are aligned with the alignment films 44 and 4.
It is gradually twisted by the eight grooves. In this case, the luminous flux is
Since the vibration direction is changed along the twist of the liquid crystal molecules 46 and the liquid crystal molecules 46 pass through the polarizing plate 56, this portion appears white to the user.

On the other hand, as shown in FIG.
When a voltage is applied to the transparent electrodes 42 and 50 before and after the alignment films 44 and 48, the liquid crystal molecules 46 are aligned in the long axis direction. In this case, since the vibration direction of the light beam passing through the liquid crystal layer 46 does not change, the light beam is blocked by the front polarizing plate 56, and this portion appears black to the user.

As described above, in the liquid crystal display according to this embodiment, the mica surface is coated with titanium dioxide,
Further, since it is determined that the particles coated with the polymer are uniformly dispersed, the incident light can be further diffused. That is, the incident light can pass through the polymer and pass through the diffuser as scattered light, even if the particles are present in contact with each other. Thereby, the loss of incident light can be greatly reduced as compared with the unmodified pearlescent pigment. In addition, a part of the light beam 14 incident on the diffusion unit 13 is well diffused at the boundary between the substrate 13 and the polymer 15, the boundary between the polymer 15 and the titanium dioxide 12, and the boundary between the titanium dioxide 12 and the mica 10. , The incident light will be diffused three times, compared to just acrylic beads or pearlescent pigments,
Incident light can be further diffused.

As described above, in the liquid crystal display according to the present embodiment, light from the light source can be used efficiently, and a bright and beautiful image can be obtained. The light diffusion plate, the lighting device, and the liquid crystal display of the present invention are not limited to the above-described configurations, and various modifications are possible within the scope of the invention. That is, the diffusion plate according to this embodiment can be used for a TN type liquid crystal display, an STN type display, a DSTN type display, an F-STN type display, a CSH type display, a ferroelectric liquid crystal type liquid crystal display, and the like.

Further, in the above-described embodiment, the case where the pearlescent pigment which diffuses the incident light to the diffusion plate and has the interference light in the substantially same wavelength region as the absorption wavelength region is used has been described. Colored pearlescent pigments coated with titanium and a titanium-based composite oxide are present in a uniformly dispersed state, and it is necessary to use incident light that transmits the same color as the interference color of titanium dioxide-coated mica. In such a case, a new effect of obtaining transmitted light of a desired color even when white light is incident can be obtained by appropriately changing the layer thickness of total titanium oxide coated on the mica surface.

That is, when the optical layer thickness of the total titanium oxide coated on the mica surface is about 20 to 40 μm, it is silver, and when it is about 40 to 90 μm, it is light gold or gold.
Red at ~ 110 μm, violet at about 110-120 μm, blue at about 120-135 μm, about 135-155
At μm, green transmitted light is obtained. Of the diffusion plate, as the transparent substrate portion, glass, polycarbonate film,
A polyester film or the like can be used.

As the polymer coated on the pearlescent pigment, nitrocellulose, acrylic polymer, polycarbonate, polyester, polyurethane and the like can be used. The layer thickness of this polymer is 0.1 to
200 μm is preferred. As the pearlescent pigment, titanium dioxide mica having a scale-like mica surface coated with titanium dioxide, fish scale foil, basic lead carbonate, bismuth trichloride and the like can be used. In addition to the pearlescent pigment, 1 to 50% by weight of a white pigment can be added to the pearlescent pigment for the purpose of adjusting the color tone. Examples of the white pigment include titanium dioxide mica having no interference color, barium sulfate, zinc oxide, and magnesium oxide.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. The present invention is not limited to the embodiments. Example 1 In Example 1, flaky white mica titanium was dispersed in a polymer solution and spray-dried to obtain spherical resin-coated mica titanium. 1.0 g of the obtained spherical resin-coated titanium mica was dispersed in 15 g of nitrocellulose lacquer. This was applied on a polycarbonate film using a bar coater to prepare a diffusion plate. The thickness of the diffusion plate is 200 μm in a dry state, and the thickness of the titanium dioxide is 120
To 135 μm. The performance of the diffuser according to Example 1 was evaluated for the following two items by measuring transmitted light at 550 nm using a spectrophotometer. (1) Light transmittance: total transmittance (T1) including diffused light when an integrating sphere is mounted (2) Light diffusion: total transmittance (T1) and incidence measured without an integrating sphere Ratio (T1 / T2) with transmittance of light in the same direction (T2) As a result, the light diffusing plate according to Example 1 had a light transmitting performance of 67% and a diffusing performance of 12.

Comparison between Example 1 and Conventional Example In contrast, as a conventional example, unmodified pearlescent pigment 1.
A dispersion plate was prepared by applying a dispersion of 0 g in 15 g of nitrocellulose lacquer to a polycarbonate film using a bar coater in the same manner as in Example 1. In the conventional diffusion plate containing the unmodified pearlescent pigment, the light transmission performance was 40% and the diffusion performance was 3. As a result, as compared with a conventional diffusion plate containing an unmodified pearlescent pigment, the diffusion plate containing particles in which the mica surface according to Example 1 was coated with titanium dioxide and further the titanium dioxide surface was coated with polymethyl methacrylate was compared. It can be understood that both the light transmission performance and the diffusion performance are improved despite the fact that the amounts of the pearlescent pigments are the same.

Next, the transmittance of light between the diffusion plate of Example 1 and the conventional diffusion plate was measured using a spectrophotometer equipped with a diffusion sphere. FIG. 6 shows a case where a diffusion plate having a thickness of 120 to 135 μm of titanium dioxide coated on the mica surface of Example 1 was used, and a conventional diffusion plate containing an unmodified pearlescent pigment was used. The comparison result with the case is shown.
As a result, compared to FIG. 1 showing the conventional example, FIG. II showing the first embodiment shows that in the wavelength range of 400 to 700 nm,
It is understood that the light transmittance is almost neutral.

That is, the diffusion plate of Example 1 in which the thickness of the titanium dioxide coated on the mica surface is 120 to 135 μm is not only improved in both light diffusion performance and light transmission performance, but also improved. The light in the absorption wavelength range of the pearlescent pigment is favorably complemented, and when white light is incident, it is possible to obtain high-luminance and beautiful white transmitted light.

Further, as a conventional example, 1.2 g of unmodified pearlescent pigment was dispersed in 15 g of nitrocellulose lacquer. This was applied on a polycarbonate film using a bar coater in the same manner as in Example 1 to prepare a diffusion plate.
Comparing the diffusion efficiency of the diffusion plate according to Example 1 with the diffusion efficiency of the conventional diffusion plate prepared by dispersing 1.2 g of unmodified pearlescent pigment in 15 g of nitrocellulose lacquer, The pearlescent pigment weighs 1.2 g, whereas the mica surface according to Example 1 is coated with titanium dioxide, and the titanium dioxide surface is coated with polymethyl methacrylate. Despite this, the light diffusion efficiencies of both are comparable.

That is, in order to obtain the same light diffusion efficiency as that of the conventional diffusion plate containing the unmodified pearlescent pigment, the amount of the pigment contained in the diffusion plate of Example 1 was increased. Can be reduced by about 20% compared to the existing amount of the pigment contained in the conventional diffusion plate. As described above, the diffusion plate according to Example 1 diffuses light at a level equal to or higher than that of the conventional diffusion plate despite the small amount of the pigment, as compared with the conventional diffusion plate containing the unmodified pearlescent pigment. Can be. Moreover, since the amount of the pigment contained in the diffusion plate can be reduced as described above, the light transmittance is also improved.

[0043]

As described above, according to the diffusion plate of the present invention, the particles coated with the polymer are uniformly dispersed on the surface of the pearlescent pigment.
Compared with the conventional case, the incident light can be diffused more, that is, the light beam incident on the diffusion plate is diffused at least at the boundary between the substrate and the polymer and at the boundary between the polymer and the pearlescent pigment. Moreover, even if the particles coated with the polymer are in contact with the surface of the pearlescent pigment, the incident light can pass through the polymer and exit the diffusion plate as scattered light. In addition, light loss can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a conventional diffusion plate using an unmodified pearlescent pigment.

FIG. 2 is an explanatory diagram of a liquid crystal display module using a diffusion plate according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a liquid crystal display module using a diffusion plate according to one embodiment of the present invention.

FIG. 4 is an explanatory view showing an operation of the diffusion plate shown in FIG. 3;

FIG. 5 is an explanatory view showing an operation of the diffusion plate shown in FIG. 3;

FIG. 6 is a diagram illustrating a comparison of light transmittance between the diffusion plate according to the first embodiment of the present invention and a conventional diffusion plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mica 11 Particles 12 Titanium dioxide 13 Transparent substrate part 15 Polymer 28 Backlight (light source) 34 Diffusion plate 38,56 Polarization plate 44,48 Alignment film 46 Liquid crystal layer

Claims (9)

[Claims] 1. A diffusion plate for transmitting incident light as scattered light, wherein particles having a pearlescent pigment surface coated with a polymer are uniformly dispersed. 2. The diffusion plate according to claim 1, wherein the thickness of the polymer coated on the surface of the pearlescent pigment is 0.1.
A diffusion plate having a thickness of from 200 to 200 μm. 3. The diffusion plate according to claim 1, wherein the pearlescent pigment is a mica titanium-based pigment having a mica surface coated with titanium dioxide, and a layer thickness of the titanium dioxide coated on the mica surface. Wherein the thickness of the layer is such that interference light having a wavelength substantially the same as the absorption wavelength range of the pearlescent pigment can be obtained. 4. The diffusion plate according to claim 1, wherein the pearlescent pigment is a colored pearlescent pigment having a mica surface coated with titanium dioxide and a titanium-based composite oxide coated on the titanium dioxide surface. A diffusion plate, characterized in that: 5. The diffusion plate according to claim 4, wherein the layer thickness of the total titanium oxide coated on the surface of the mica is a layer thickness capable of obtaining interference light of a desired color. . 6. The diffusion plate according to claim 1, wherein the polymer coated on the surface of the pearlescent pigment is one selected from acrylic, methacrylate and styrene. The diffusion plate characterized by the above. 7. The diffusion plate according to claim 1, wherein the amount of particles in which the polymer is coated on the surface of the pearlescent pigment is 1 to 70% by weight. . 8. A lighting device comprising: a light source that emits a light beam; and a diffusion plate that transmits light from the light source as scattered light, wherein the diffusion plate is a particle having a pearlescent pigment surface coated with a polymer. The lighting device characterized in that are dispersed uniformly. 9. A light source that emits a light beam, a diffusion plate that transmits light from the light source as scattered light, and a voltage applied to the liquid crystal layer that determines whether to transmit or block light from the diffusion plate. A liquid crystal display comprising: a liquid crystal panel controlled by a liquid crystal display; and wherein the diffusion plate has particles of a pearlescent pigment coated with a polymer uniformly dispersed therein.