KR20120103464A - A resin composition for a light guide plate and a light guide plate - Google Patents

Abstract

PURPOSE: A resin composition is provided to be suitable for manufacturing a light guide plate with excellent light emission efficiency and sufficiently restrained yellowness. CONSTITUTION: A resin composition contains a transparent resin, and silicon resin particles. The average transmittance in a region of 300-800 nm measured in an optical path of 200 nm when the molding with the resin composition is 25-85 %. The content of the silicon resin particles is 0.1-200 ppm based on total weight of the resin composition. The transparent resin is methacrylic resin. The light guide plate consists of the resin composition. A surface light source device comprises the light guide plate.

Description

Resin composition for light guide plate and light guide plate {A RESIN COMPOSITION FOR A LIGHT GUIDE PLATE AND A LIGHT GUIDE PLATE}

This invention relates to the resin composition for light guide plates suitable for preparing the light guide plate in which yellowness is fully suppressed and excellent in the light emission efficiency.

As a backlight, such as a liquid crystal display device or an illuminating device, a light source, such as a cold cathode tube and LED, is arrange | positioned at the side of a light guide plate, for example, and the light from a light source is reflected in the dot pattern, the prism part, etc. which were formed in the back surface of the light guide plate, Background Art A backlight configured to emit light uniformly from the front surface is known.

As a light guide plate for backlights, the light guide plate which disperse | distributed microparticles | fine-particles in transparent resin, such as acrylic resin, is known. As for the light guide plate which disperse | distributed microparticles | fine-particles in transparent resin, transmitted light tends to have a yellow taste (that is, a yellow index (YI) value is high), and the liquid crystal display device using such a light guide plate has an image slightly yellowish taste. It stands out and a high quality image is not obtained.

As a light guide plate which suppresses the yellowishness of transmitted light, Patent Document 1 discloses a light guide plate in which the product of the absolute value of the difference between the refractive index of the transparent resin and the refractive index of the fine particles and the cumulative 50% particle size of the fine particles satisfies a predetermined range.

However, in the light guide plate of this patent document 1, yellowness may not be fully suppressed and light emission efficiency may not be enough.

Japanese Unexamined Patent Publication No. 2010-92755

An object of the present invention is to provide a light guide plate resin composition suitable for producing a light guide plate that is sufficiently suppressed in yellowness and excellent in light emission efficiency.

The resin composition for light guide plates of this invention has the following structures.

(1) A resin composition for light guide plates containing transparent resin and silicone resin fine particles,

300 nm? Measured at an optical path length of 200 mm when the resin composition was used as a molded body. The average light transmittance in the wavelength range of 800 nm is 25? The resin composition for light guide plates which is 85%.

(2) The silicone resin fine particles are 0.1? To the total weight of the resin composition. The resin composition as described in (1) contained in the ratio of 200 ppm.

(3) The resin composition as described in (1) or (2) whose said transparent resin is methacryl resin.

(4) (1) The light guide plate comprised from the resin composition in any one of (3).

(5) The light guide plate as described in (4) used for the liquid crystal display provided with a LED light source.

(6) The surface light source device provided with the light guide plate as described in (4) or (5).

(7) The liquid crystal display device in which the surface light source device according to (6) is arranged on the back side of the liquid crystal panel.

ADVANTAGE OF THE INVENTION According to this invention, the resin composition for light guide plates suitable for manufacturing a light guide plate in which yellowness is fully suppressed and the light emission efficiency is excellent can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical side view which shows one Embodiment of the liquid crystal display device of this invention.
2 shows 300 nm at an optical path length of 200 mm? It is a figure explaining the measuring method of the average light transmittance in a 800 nm wavelength range.
It is a figure explaining the measuring method of the total luminous flux.

<Resin composition for light guide plate>

The resin composition for light guide plates of the present invention (hereinafter may be simply referred to as "resin composition") contains a transparent resin and silicone resin fine particles, and has an optical path length of 200 mm when the resin composition is formed into a molded article. Measured 300 nm? The average light transmittance in the wavelength range of 800 nm is 25? 85%.

If the transparent resin contained in the resin composition of this invention is transparent, a composition, a weight average molecular weight, etc. will not be specifically limited. For example, methacryl resin (polymethyl methacrylate (PMMA), etc.), polycarbonate resin, acrylonitrile-styrene-butadiene copolymer resin (ABS resin), polystyrene resin, acrylonitrile-styrene copolymer resin ( AS resin), polyolefin resin (polyethylene, polypropylene, etc.) etc. are mentioned. Among these, methacryl resin is preferable.

Silicone resin microparticles | fine-particles contained in the resin composition of this invention are used in order to diffuse the light which permeate | transmits a light guide plate.

Silicone resin microparticles | fine-particles are not specifically limited, such as an average particle diameter and a weight average molecular weight. In order to diffuse light with better efficiency, silicone resin microparticles | fine-particles are 1? It is preferable to have an average particle diameter of 12 µm, and 2? It is more preferable to have an average particle diameter of 6 micrometers.

The silicone resin fine particles are preferably 0.1? It is contained in the ratio of 200 ppm, More preferably, it is 1? 90 ppm, more preferably 1? 50 ppm, particularly preferably 1? It is contained at a rate of 10 ppm.

The resin composition of this invention measured 300 nm-measured at the optical path length of 200 mm when it was set as the molded object. The average light transmittance in the wavelength range of 800 nm is 25? 85%, preferably 40? It is 70%, and high brightness can be aimed at, suppressing the yellowness of the light guide plate obtained by this.

<Light Guide Plate>

The light guide plate of this invention is comprised from the said resin composition. Specifically, the light guide plate of this invention is obtained by shape | molding the said resin composition by the extrusion molding method, the injection molding method, the hot press molding method, etc., for example.

Various additives, such as a ultraviolet absorber, a heat stabilizer, antioxidant, a weathering agent, a light stabilizer, a fluorescent brightener, a processing stabilizer, may be added to the said light guide plate, for example.

Although the thickness of a light guide plate is not specifically limited, Usually, 0.05? 15 mm, Preferably it is 0.1? 10 mm, More preferably, it is 0.5? 5 mm.

<Surface Light Source Device and Liquid Crystal Display Device>

Next, one embodiment of the surface light source device using the light guide plate comprised from the resin composition of this invention, and the liquid crystal display device using the same is shown in FIG.

This liquid crystal display device 1 includes the surface light source device 9 and the liquid crystal panel 30, and the surface light source device 9 is disposed on the back side of the liquid crystal panel 30.

The liquid crystal panel 30 is disposed on the upper and lower sides of the liquid crystal cell 20 and the liquid crystal cell 20 in which the liquid crystal 11 is enclosed between a pair of upper and lower transparent electrodes 12 and 13 spaced apart from each other and arranged in parallel. Arranged polarizing plates 14 and 15 are provided. The image display part is comprised by these liquid crystal 11, the transparent electrodes 12 and 13, and the polarizing plates 14 and 15. As shown in FIG. In addition, the alignment film (not shown) is laminated | stacked on the inner surface (surface of the liquid crystal side) of the transparent electrodes 12 and 13, respectively.

The surface light source device 9 is disposed on the lower surface side (back side) of the polarizing plate 15. This planar light source device 9 has a rectangular box-shaped lamp box 5 that is rectangular in shape in plan view, an open upper surface side (front side), a light guide plate 3 and a light source housed in the lamp box 5. (2) and the light diffusion plate 4 which is arrange | positioned so that the opening surface may be blocked with respect to the lamp box 5, and is fixed. The light source 2 is an LED (light emitting diode) light source etc., for example, and is arrange | positioned at the side position of the light guide plate 3.

The lamp box 5 consists of a white acrylic resin plate. On the back surface 3a of the light guide plate 3, a dot printing part (dot pattern) by white ink is formed, and light incident from one side of the light guide plate 3 into the light guide plate 3 is transferred to the dot printing part. By reflecting by this, it is comprised so that light may be uniformly radiate | emitted from the front surface (namely, the light emission surface 3b) of the light guide plate 3.

In addition, as for the light guide plate 3 to be used, as shown in FIG. 2, the peripheral side surface 51 may be grind | polished and the light-diffusion process for making uniform light to the light emission surface 3b may be given, do. In addition, instead of dot printing using a white ink or the like, the back surface 3a of the light guide plate 3 may be subjected to light diffusion treatment such as prism formation, or to a surface other than the light exit surface 3b of the light guide plate, Light reflection layers, such as a silver vapor-deposited sheet and a film, may be formed.

Since the liquid crystal display device 1 of this invention is comprised in this way, since the light with high whiteness which is not substantially yellowish is emitted from the surface light source device 9 toward the liquid crystal panel 30 with high brightness, The color of the liquid crystal panel 30 can be accurately reproduced. Therefore, a natural, high quality bright color display can be realized without having a yellowish taste.

In the liquid crystal display device 1 shown in FIG. 1, although the structure which the light source 2 was arrange | positioned among the four side surfaces of the light guide plate 3 is employ | adopted, it is not specifically limited to such a structure. For example, you may employ | adopt the structure in which the light source 2 is arrange | positioned at the pair of opposing side surfaces in the light guide plate 3, respectively.

In addition, it does not specifically limit as the light source 2, For example, linear light sources, such as a cold cathode tube, a hot cathode tube, an external electrode fluorescent lamp (EEFL), and point light sources, such as a light emitting diode (LED), etc. are mentioned.

ADVANTAGE OF THE INVENTION According to this invention, the resin composition for light guide plates suitable for manufacturing a light guide plate in which yellowness is fully suppressed and the light emission efficiency is excellent can be provided. Therefore, the present invention is useful in the field of liquid crystal display devices and the like. The light guide plate of this invention is especially used suitably for the liquid crystal display provided with the LED light source of the big screen like a television.

Example

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples.

(Example 1)

(Preparation of plate-shaped sample (light guide plate))

PMMA (manufactured by Sumitomo Chemical Co., Ltd., "Smibex EXN", refractive index: 1.49) to cross-linked silicon fine particles (Momentive Performance Materials Japan Co., Ltd. product, "Tospearl 145", refractive index: 1.42, average Particle size: 4 m) were mixed at a rate of 10 ppm. Subsequently, using a single screw extruder (screw diameter 20 mm), melt-kneading so that the resin temperature is 250 ° C, extruded into strands, water-cooled and cut with a strand cutter, thereby pelletizing methacrylic resin composition (resin composition for light guide plate) )

160 g of the obtained pellet-like resin composition was heat-compression-molded, and the 210-mm square plate-like sample (light guide plate) which has a thickness of 3 mm was prepared.

(Example 2)

Except having mixed "Tospearl 145" in the ratio of 1 ppm, it carried out similarly to Example 1, the methacrylic resin composition was obtained, and the plate-shaped sample was prepared.

(Comparative Examples 1 and 2)

Instead of the crosslinked silicon fine particles "Tospearl 145", polystyrene fine particles (Sekisui Kasei Kogyo Co., Ltd. product, "SBX-12", refractive index: 1.59, average particle diameter: 12 ㎛) mixed in the ratio shown in Table 1 A methacrylic resin composition was obtained in the same manner as in Example 1 except that a plate-like sample was prepared.

Using the plate-shaped samples obtained in Example 1 and Comparative Examples 1 and 2, the average light transmittance, the yellow index (YI) and the total amount of light flux were evaluated. The evaluation method is as follows.

<Measurement of Average Light Transmittance of Visible Light at an Optical Path Length of 200 mm>

As shown in FIG. 2, the obtained plate-shaped sample was cut | disconnected in the magnitude | size of width 50mm x length 200mm. Next, the four side surfaces 51 were polished with a polishing machine (manufactured by Mega Technica Co., Ltd., "Pra Beauty PB-500") to obtain a test piece 50.

The light transmittance in the optical path length of 200 mm of this test piece 50 was measured using a plastic characteristic measurement system (consisting of a U-4000 type spectrophotometer and a large sample chamber integrating device) manufactured by Hitachi, Ltd. Wavelength 300 nm? The arithmetic mean value of the light transmittance obtained by measuring every 5 nm in the range of 800 nm was made into "the average light transmittance of visible light." The results are shown in Table 1.

<Evaluation of Yellow Index (YI)>

The light transmittance in the optical path length of 200 mm of the test piece 50 was measured using the plastics characteristic measuring system at a wavelength of 300 nm? It measured every 5 nm in the range of 800 nm, The XYZ value was calculated | required from the obtained measured value according to the method of JISZ-8722, and yellowness (YI) was computed according to the method of JISK-7105. When YI was less than 10, it evaluated that yellowness was suppressed. The results are shown in Table 1.

<Measurement of total luminous flux>

As shown in FIG. 3, the obtained plate-shaped sample was cut | disconnected in the magnitude | size of width 60mm x length 80mm. Next, four side surfaces 611, 612, 613, and 614 were polished with a polishing machine (manufactured by Mega Technica Co., Ltd., "Pra Beauty PB-500") to obtain a test piece 60.

Of the four side surfaces of the test piece 60, the LED 62 such as 6 is irradiated so as to receive light from only one side surface 611, and the other side surfaces 612, 613, and 614 have a black adhesive surface inside and an outside side. Tape (one sided tape 6370 for reflection and light shielding, manufactured by Teraoka Co., Ltd.) was bonded to each other. By affixing a tape in this way, the quantity of the light which the light irradiated from the side surface 611 emits to the surface direction of the test piece 60 both surfaces can be measured.

Next, the test piece 60 was set in the spherical photometer (model 1500 type, diameter 1500mm) by Nemutech Co., Ltd., and the SLMS software of Diode Array Spectrometer (Model DAS-1100 / 2100) by Labsphere Inc. was used. By 350? The amount of luminous flux in the wavelength region of 800 nm was measured. The results are shown in Table 1.

Particulate Average rays
Transmittance (%) YI Total luminous flux
(lms) Kinds Particle size (㎛) Content (ppm) Example 1 silicon 4 10 62.5 7.1 8 Example 2 silicon 4 One 80.8 5.2 6 Comparative Example 1 polystyrene 12 10 68.2 7.9 4 Comparative Example 2 polystyrene 12 100 29.0 11.8 7

As shown in Table 1, the plate-shaped samples (light guide plate) of Examples 1 and 2 using the resin composition of this invention are understood that yellowness is fully suppressed and the light emission efficiency is excellent. On the other hand, the plate-shaped sample (light guide plate) of the comparative example 1 turns out that the light emission efficiency is low. Moreover, it turns out that the yellowish degree of the plate-shaped sample (light guide plate) of the comparative example 2 is not suppressed.

1: liquid crystal display
2: light source
3: light guide plate
4: light diffuser plate
5: lamp box
9: surface light source device
11: liquid crystal
12, 13: transparent electrode
14, 15: polarizer
20: liquid crystal cell
30 liquid crystal panel
50: test piece (light guide plate)
51: side of the test piece (light guide plate)
60: test piece (light guide plate)
611, 612, 613, 614: side of the test piece (light guide plate)
62: LED

Claims (7)

As a resin composition for light guide plates containing transparent resin and silicone resin microparticles | fine-particles,
300 nm? Measured at an optical path length of 200 mm when the resin composition was used as a molded body. The average light transmittance in the wavelength range of 800 nm is 25? The resin composition for light guide plates which is 85%. The method of claim 1,
The silicone resin fine particles are 0.1? To the total weight of the resin composition. The resin composition contained in the ratio of 200 ppm. The method of claim 1,
Resin composition whose said transparent resin is methacryl resin. The light guide plate comprised from the resin composition of Claim 1. The method of claim 4, wherein
Light guide plate used for liquid crystal display with LED light source. The surface light source device provided with the light guide plate of Claim 4. The liquid crystal display device in which the surface light source device of Claim 6 is arrange | positioned at the back side of a liquid crystal panel.

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