JP2000298203A - Optical diffusion plate, illuminating device and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a optical diffusion plate, having high brightness and high light-diffusing property by forming a light-diffusing layer consisting of a light- transmitting resin containing silicone-based polymer particles and silica particles as light-scattering particles on a transparent substrate surface. SOLUTION: An optical diffusion plate 18 has a structure of a light-diffusing layer 10 consisting of a light-transmitting resin 16, light-scattering particles 14a (silicone-based polymer particles) and light-scattering particles 14b (silica particles) formed on the surface of a transparent substrate 12. Therefore, the optical diffusion plate 18 passes the light from an inner light source through the transparent substrate 12 and the light-diffusing layer 10, while dispersing the passing light in a good state by the light-scattering particles 14a, 14b in the optical diffusion layer 10. The compounding weight ratio of the silicone- based polymer particles 14a to the silica particles 14b in the optical diffusion layer 10 is preferably in the range of 99/1 to 1/99. The compounding weight ratio is more preferably 90/10 to 70/30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing plate, an illuminating device and a liquid crystal display device using the same, and more particularly to an improvement in brightness and light diffusibility of the light diffusing plate.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices have been used as displays for portable telephones, electronic organizers, etc. because of their thinness and lightness. These liquid crystal display elements are
Unlike a plasma display or the like, it does not emit light by itself. Therefore, display is performed by controlling transmission / non-transmission of light from an internal or external light source by a liquid crystal shutter. That is, in a liquid crystal display element using an internal light source, a light diffusion plate is usually inserted on the back side of the liquid crystal cell, and the internal light entering from the back side of the liquid crystal plate is transmitted while being diffused and supplied to the liquid crystal plate, Transmission / non-transmission is controlled by a liquid crystal shutter. As described above, there is a transmission type liquid crystal display element as a type using only an internal light source. As a type in which the internal light source / external light is selectively used depending on the ON / OFF of the internal light source, there is a transflective liquid crystal display element. When the internal light source is turned on, display is performed in the same manner as the transmissive liquid crystal display element, but when the internal light source is turned off, external light entering from the liquid crystal panel surface side is diffused by the light diffusion plate. The light is reflected and returned to the liquid crystal plate, and transmission / non-transmission is controlled by a liquid crystal shutter.

In these liquid crystal display devices, a light diffusing plate is provided to diffuse light from an internal light source and make an image of the light source invisible. A light diffusion plate having such a function is required to be bright, uniform and have a high light diffusion property. To this end, a high total light transmittance and a high haze (diffuse light transmittance / total light transmittance) are required. is necessary. Conventionally, these light diffusing plates have been disclosed in JP-A-8-2203.
As disclosed in Japanese Patent Application Laid-Open No. 10, a structure having a structure in which a light diffusion layer composed of a light transmitting resin and light scattering particles such as acrylic particles and silica particles is formed on the surface of a transparent substrate has been used.

[0004]

However, a light diffusing plate using acrylic particles or silica particles as light scattering particles has a high total light transmittance but has a low haze and thus performs a sufficient function as a light diffusing plate. I couldn't say.
As a result, conventional lighting devices (backlight units) using these light diffusion plates have insufficient light diffusion performance,
Even with a liquid crystal display element using this, it has been difficult to perform bright, bright and easy-to-view display. The present invention has been made in view of the above problems, and has as its object to provide a light diffusion plate having high luminance and high light diffusion, a high-luminance lighting device using the same, and a liquid crystal display element having a bright and easy-to-view display. It is in.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a light-diffusing resin composed of a light-transmitting resin containing a mixture of silicone-based polymer particles and silica particles as light-scattering particles. By forming a layer on the surface of the transparent substrate, it has been found that a light diffusion plate having high luminance and high light diffusion can be obtained, and the present invention has been accomplished.

That is, a light diffusion plate according to the present invention is a light diffusion plate having a structure in which a light diffusion layer comprising a light transmitting resin and light scattering particles is formed on the surface of a transparent substrate. It is characterized by containing a mixture of a system polymer particle and a silica particle. Further, in the light diffusion plate according to the present invention, the blending weight ratio of silicone polymer particles / silica particles in the light diffusion layer is 99/1 to 1/9.
Preferably, it is 9.

In the light diffusion plate according to the present invention, it is more preferable that the blending ratio by weight of the silicone polymer particles / silica particles in the light diffusion layer is 90/10 to 70/30. Further, in the light diffusion plate according to the present invention, the silicone-based polymer particles have a particle size of 0.5 to 50 μm.
It is preferred to include m spherical particles.

The lighting device according to the present invention is also provided with an internal light source for emitting a light beam and a light diffusion plate for diffusing the light beam from the internal light source, wherein the light diffusion plate is provided on the surface of the transparent substrate. A light diffusion layer formed of a light transmitting resin and light scattering particles is formed, and the light scattering particles include a mixture of silicone-based polymer particles and silica particles.

Further, the transmission type liquid crystal display element according to the present invention comprises: an internal light source for emitting a light beam; a light diffusion plate for diffusing the light beam from the light source;
In a transmissive liquid crystal display device comprising a liquid crystal panel capable of controlling a non-transmissive state by an electric signal, the light diffusing plate includes a light diffusing layer comprising a light transmissive resin and light scattering particles on a transparent substrate surface. The light-scattering particles comprise a mixture of silicone-based polymer particles and silica particles.

Further, the transflective liquid crystal display element according to the present invention has an internal light source for emitting a light beam, and diffuses and transmits the light beam when the light beam is emitted from the internal light source, and the internal light source emits the light beam. Is stopped, a semi-transmissive light diffusion plate that diffuses and reflects external light incident from the side opposite to the internal light source, and a transmission / non-transmission state of light from the light diffusion plate is controlled by an electric signal. A transflective liquid crystal display device comprising a liquid crystal panel capable of transmitting light, wherein the light diffusing plate has a structure in which a light diffusing layer comprising a light transmitting resin and light scattering particles is formed on a transparent substrate surface; The scattering particles include a mixture of silicone-based polymer particles and silica particles.

[0011]

Embodiments of the present invention will be described below in detail. The light diffusing plate according to the present invention is shown in FIG. That is, the light diffusion plate 18 has a structure in which the light diffusion layer 10 formed of the light transmissive resin 16, the light scattering particles 14a (silicone polymer particles), and the light scattering particles 14b (silica particles) is formed on the surface of the transparent substrate 12. Consists of Therefore, the light diffusing plate 18 according to the present invention allows the light taken from the internal light source (the lower part in FIG. 1) to pass through the transparent substrate 12 and the light diffusing layer 10 so that the passing light in the light diffusing layer 10 The light can be satisfactorily diffused by the light scattering particles 14a and 14b.

[0012]Transparent substrate  Light transmittance is used as a base of the transparent substrate used in the present invention.
Is preferable, and polyethylene terephthalate is preferred.
(PET), polycarbonate, polymethyl methacrylate
(PMMA), triacetyl cellulose (TA
C), perfluoro resins (FEP, PFA, ETFE),
Polyvinyl chloride, polystyrene, polypropylene (P
P) and the like. The shape is a film or plate
Used.

[0013]Light transmitting resin  The light-transmitting resin used as a binder in the present invention
Acrylic resin, polycarbonate, polyvinyl chloride
, Polystyrene, polyester, polyurethane, tri
Acetyl cellulose (TAC), polypropylene (P
P) and transparent resins such as fluorine synthetic polymers.

[0014]Light scattering particles  Can the light-scattering particles used in the present invention be made?
Spherical silicone polymer particles and silica particles
A mixture of offspring is used. With silicone polymer particles
Can use a normal silicone resin
The particle size is preferably 0.5 to 50 μm, and 0.5 to 24 μm
Is more preferred. Light diffusion is high when it is smaller than 0.5 μm.
However, the brightness in the frontal direction may be reduced.
Not good. When it is larger than 50 μm, the front luminance is high.
Although it is not possible to obtain sufficient light diffusion
It is not preferable because there is.

The particle size of the silica particles is preferably 0.5 to 24 μm. When the diameter is smaller than 0.5 μm, the light diffusion property is high, but it is difficult to contribute to the improvement of the luminance in the front direction, which is not preferable. On the other hand, if it is larger than 24 μm, the brightness in the front direction is high, but sufficient light diffusivity may not be obtained, which is not preferable.

[0016]Light diffusion layer  In the light diffusion plate according to the present invention, mixing in the light diffusion layer
Weight of product, silicone polymer particles / silica particles
The ratio is preferably from 99/1 to 1/99, more preferably
90/10 to 70/30. Silicone polymer
If the proportion of particles is too high, the total light transmittance will decrease,
The brightness of the display or liquid crystal display element
Is not preferred. Also, the ratio of silica particles is large.
If it breaks, haze decreases, and sufficient light diffusion performance can be obtained.
It is not preferable because it may not be possible.

Further, polymethyl methacrylate particles having a particle size of 1 to 100 μm may be mixed in an amount of 10 to 20% by weight based on the mixture of the silicone polymer particles and the silica particles. The light diffusion layer has a thickness of 1 to 100 μm.

[0018]Lighting device and liquid crystal display device  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
You. FIG. 2 shows a light diffusion plate according to an embodiment of the present invention.
The schematic configuration of the liquid crystal display element is shown.

The liquid crystal display element 22 shown in FIG.
7, a bezel 26 serving as a frame of the LCD panel, and a light source 28
, A reflection plate 30, a light guide plate 32, a light diffusion plate 18, a polarizing plate 38, a glass substrate 40, a 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.

The light guide plate 32 causes the light beam from the light source 28 to enter the light diffusion plate 18. As the light guide plate 32, a plate in which a white pigment that scatters light or an ink to which transparent beads are added is printed in a dot shape on the surface of a substrate portion made of an acrylic resin can be used. Reflector 3
Numeral 0 reflects the light flux from the light source 28 or the external light and makes it incident on the light guide plate 32.

As the reflection plate 30, for example, a metal vapor-deposited film of aluminum or the like, a polished metal plate, foamed polyester, or the like, or a plate in which pearl luster pigments are very densely used can be used. The light diffusion plate 18 includes a light guide plate 32.
The light flux from is diffused at random. This light diffusion plate 18
As shown in FIG. 1, a light diffusion layer 10 made of a light-transmitting resin 16 including light-scattering particles 14 made of silicone-based polymer particles 14a and silica particles 14b is formed on the surface of a transparent substrate 12. .

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 by the bonding agent. And the light. Transparent electrode 42,
Numeral 50 is made of, for example, an ITO film containing indium oxide as a main component, and is patterned according to the purpose. The transparent electrode 42 is provided on the upper surface of the glass substrate 40 in FIG.
Numerals 0 are provided on the lower surface of the glass substrate 52 in the drawing.

The voltage from the power source 58 is applied to the transparent electrodes 42 and 50.
, The arrangement of the liquid crystal molecules 46 between the alignment films 44 and 48 is changed. 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 device according to the present invention is configured as described above. When the liquid crystal display element of the present invention is used as a transflective liquid crystal display element, display can be performed with either internal light or external light. Therefore, the operation of the light diffusion plate of the present invention in each case will be described below. When an internal light source is used, the light flux from the light source 28 directly enters the light guide plate 32 provided in the front or enters the light guide plate via the reflector 30 provided in the rear. Then, 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 that has passed through the light guide plate 32 enters the light diffusion plate 18 provided in front. The luminous flux passing through the light diffusion plate 18 is satisfactorily diffused by the light scattering particles 14 composed of silicone polymer particles and silica particles. The light that has passed through the light diffusion plate 18 enters the 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. 3A, when no voltage is applied, the liquid crystal molecules 46 are gradually twisted by the grooves of the alignment films 44 and 48. In this case, the luminous flux is the liquid crystal molecules 4
6 is changed in its vibration direction along the twist of
This part appears to be colored to the user because it passes through 6. On the other hand, when a voltage is applied to the transparent electrodes 42 and 50 before and after the alignment films 44 and 48 by the power source 58, the liquid crystal molecules 46 are aligned in the long axis direction as shown in FIG.

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. When an external light source is used, light taken in from the outside (front) is diffused and reflected by the light diffusion plate 18 and is reflected by the polarization plate 38.
Is displayed in the same manner as when internal light is used. Therefore, in the case of a transflective liquid crystal display element,
When a light beam is emitted from the internal light source, the light beam from the internal light source diffuses and transmits through the light diffusion plate 18 to display a liquid crystal. When the internal light source stops emitting the light beam and the outside is relatively bright, In this case, liquid crystal display is performed by the external light being diffusely reflected by the light diffusion plate 18.

Although the transflective liquid crystal display element of the present invention has been described, it goes without saying that a transmissive liquid crystal display element exclusively used for an internal light source can be formed by using the light diffusing plate of the present invention. Further, the light diffusion plate according to the present invention,
The lighting device and the liquid crystal display element using the same are not limited to the above-described configuration, and various modifications are possible within the scope of the invention.

That is, the light diffusing plate according to the present embodiment is a TN type liquid crystal display, an STN type display,
DSTN type display, F-STN type display,
It can be used for a CSH type display, a ferroelectric liquid crystal type liquid crystal display and the like. Further, the light diffusion plate, the lighting device and the liquid crystal display element using the light diffusion plate according to the present invention can be used for applications such as lighting fixtures, illuminated signboards, front projection screens, and liquid crystal displays.

[0031]

EXAMPLES Next, examples will be shown to clarify the present invention. The present invention is not limited by these embodiments. The present inventors produced the following light diffusion plate in the course of studying the light diffusion plate according to the present invention. Next, a method for manufacturing the light diffusion plate will be described.

<Production Method> In the examples, light scattering particles were dispersed in an acrylic lacquer (SG700, manufactured by Seiko Advance Co., Ltd.), and a polyethylene terephthalate film (PET Lumirror T6
(A thickness of 0, 75 μm, manufactured by Toray Industries, Inc.) to obtain a light diffusion plate having a light diffusion layer having a thickness of 20 μm in a dry state. However,
The composition of the light diffusion layer is as shown in Table 1. All parts are parts by weight.

[0033]

[Table 1]  Example Light scattering particles Number of parts Light transmitting resin (* 4) No.  Copies Silicone polymer silica PMMA (* 1) (* 2) (* 3)  1 90 10 0 100 270 300 0 100 3 50 500 0 100 4 10 90 0 100 5 90 10 20 100  * 1: Particle size 4.5 μm (Tospearl 145, manufactured by Toshiba Silicone Co., Ltd.) * 2: Particle size 5 μm (Sildex L51, manufactured by Asahi Glass Co., Ltd.) * 3: Particle size 20 μm (MX20G, manufactured by Soken Kagaku) * 4: Acrylic Lacquer (SG700, manufactured by Seiko Advance)

Next, the evaluation of the light diffusion plate manufactured in Table 1 was performed.
went. The evaluation criteria are shown below before the evaluation results.
You.Haze measurement  According to Haze Meter HR100 (Murakami Color Research Laboratory)
In accordance with JIS K7105. Brightness and
For visual evaluation of diffusivity, the light diffusion plate produced
The evaluation was performed by incorporating it into a backlight unit.

Visual evaluation of luminance ( visual evaluation with respect to luminance viewed from the front) ：: Particularly bright feeling ：: Bright feeling Δ: Somewhat bright feeling ×: Dark feeling diffusibility Visual evaluation ( evaluated by visually recognizing the light spot of an LED lamp as a point light source) ：: The light spot was not visible at all ：: The light spot was hardly visible Δ: The light spot was visible ×: Tables in which light spots were clearly visible Table 2 shows the evaluation results of the light diffusion plates shown in Table 1.

[0036]

[Table 2]  Example Total light transmittance Haze Diffusivity of luminance No. (%) (%) Visual evaluation Visual evaluation  1 91.8 93.6 ２ 2 93.0 90.2 ◎ ３ 3 95.5 88.8 ○ 4 95.0 86.0 ○ 5 92.4 91.6 ◎

From the above results, the light diffusing plate according to the present invention has a high total light transmittance indicating the luminance and a high haze value indicating the light diffusing property, and also has excellent visual evaluation of the luminance and diffusing property in the actual liquid crystal display device. You can see that it is. Further, it is understood that the blending weight ratio of silicone polymer particles / silica particles in the light diffusion layer is preferably about 99/1 to 1/99. Further, as can be seen from the fact that the haze of Example 1 and Example 2 is 90% or more, and the visual evaluation of the luminance and diffusivity is particularly good, the most preferable of the silicone-based polymer particles / silica particles in the light diffusion layer is more preferable. 90/10 to 70
/ 30.

Next, as shown in Table 3, as a light scattering particle, a light diffusing plate in which silicone polymer particles and silica particles were not used in combination was prepared as a comparative example and evaluated.

[0039]

[Table 3]  Comparative example Light scattering particles Number of parts Light transmitting resin (* 4) No.  Copies Silicone polymer silica PMMA (* 1) (* 2) (* 3)  1 100 00 100 20 0 100 0 100 300 0 100 100 40 50 50 100  * 1: Particle size 4.5 μm (Tospearl 145, manufactured by Toshiba Silicone Co., Ltd.) * 2: Particle size 5 μm (Sildex L51, manufactured by Asahi Glass Co., Ltd.) * 3: Particle size 20 μm (MX20G, manufactured by Soken Kagaku) * 4: Acrylic Lacquer (SG700, manufactured by Seiko Advance Co., Ltd.) Table 4 shows the evaluation results of the light diffusing plates of Comparative Examples shown in Table 3.
You.

[0040]

[Table 4]  Comparative example Total light transmittance Haze Diffusivity of luminance No. (%) (%) Visual evaluation Visual evaluation  182.2 92.0 △ ○ 296.2 81.2 △ △ 3 95.2 80.0 × × 4 94.3 80.2 △ ×

From the above results, it can be seen that the use of only silicone polymer particles as the light-scattering particles (Comparative Example 1) has a high haze and a good light diffusion property, but has a low total light transmittance and is inferior in visual evaluation of luminance. . On the other hand, in Comparative Examples 2 to 4 in which no silicone-based polymer particles were used, it was found that high haze was not obtained, and thus excellent visual evaluation of luminance and diffusivity as in the present invention was not obtained. Further, silica particles (Comparative Example 2) and polymethyl methacrylate (PMMA:
Comparing Comparative Example 3), it can be seen that silica particles are generally superior. That is, it can be seen that a light diffusion plate having high brightness and good light diffusion as in the present invention can be made for the first time by using silicone-based polymer particles and silica particles as light scattering particles.

[0042]

As described above, according to the light diffusing plate of the present invention, the light diffusing plate having the structure in which the light diffusing layer composed of the light transmitting resin and the light scattering particles is formed on the surface of the transparent substrate. Since the light-scattering particles in the plate include a mixture of the silicone-based polymer particles and the silica particles, a light diffusion plate having high luminance and high light-scattering properties can be obtained. Further, according to the lighting device of the present invention using the light diffusion plate, it is possible to provide bright and easy-to-see illumination. Further, the transmissive liquid crystal display device according to the present invention using the light diffusion plate enables a bright and easy-to-see liquid crystal display. Also,
The transflective liquid crystal display device according to the present invention using the light diffusion plate enables bright and easy-to-see liquid crystal display.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a light diffusion plate according to the present invention.

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

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

[Explanation of symbols]

 Reference Signs List 10 light diffusion layer 12 transparent substrate 14a light scattering particles (silicone polymer particles) 14b light scattering particles (silica particles) 16 light transmissive resin 18 light diffusion plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 BA02 BA15 BA20 2H091 FA14Z FA23Z FA31Z FA41Z FA42Z FA44Z FA45Z FB02 FB12 FB13 LA16

Claims (7)

[Claims] 1. A light diffusion plate having a structure in which a light diffusion layer comprising a light transmitting resin and light scattering particles is formed on the surface of a transparent substrate, wherein the light scattering particles are a mixture of silicone polymer particles and silica particles. A light diffusion plate comprising: 2. The light diffusion plate according to claim 1, wherein the weight ratio of silicone polymer particles / silica particles in the light diffusion layer is 99/1 to 1/99. . 3. The light diffusion plate according to claim 2, wherein the weight ratio of silicone polymer particles / silica particles in the light diffusion layer is 90/10 to 70/30. . 4. The light diffusing plate according to claim 1, wherein the silicone polymer particles have a particle size of 0.5 to 0.5.
A light diffusion plate comprising spherical particles of 50 μm. 5. A lighting device comprising: an internal light source for emitting a light beam; and a light diffusing plate for diffusing the light beam from the internal light source, wherein the light diffusing plate is provided on a transparent substrate surface with a light transmitting resin and a light scattering resin. An illumination device having a structure in which a light diffusion layer composed of conductive particles is formed, and wherein the light scattering particles include a mixture of silicone-based polymer particles and silica particles. 6. An internal light source for emitting a light beam, a light diffusion plate for diffusing the light beam from the light source, and a liquid crystal panel capable of controlling the transmission / non-transmission state of light from the light diffusion plate by an electric signal. In the transmissive liquid crystal display device, the diffusion plate has a structure in which a light diffusion layer composed of a light transmitting resin and light scattering particles is formed on a transparent substrate surface, and the light scattering particles are silicone-based polymer particles. And a mixture of silica particles. 7. An internal light source for emitting a light beam, wherein the internal light source diffuses and transmits the light beam when the internal light source emits the light beam, and the internal light source when the internal light source stops emitting the light beam. A semi-transmissive liquid crystal display device comprising: a light diffusion plate that diffuses and reflects external light incident from the opposite side; and a liquid crystal panel capable of controlling a transmission / non-transmission state of light from the light diffusion plate by an electric signal. The light diffusing plate has a structure in which a light diffusing layer composed of a light transmitting resin and light scattering particles is formed on the surface of a transparent substrate, and the light scattering particles include a mixture of silicone-based polymer particles and silica particles. A transflective liquid crystal display device characterized by the above-mentioned.