KR20090069758A - Master batch composition for preparing diffuser sheet with high luminance and low yellow index and diffuser sheet comprising the same - Google Patents

Abstract

A resin composition for a light diffusion plate is provided to overcome disadvantages of a polystyrene resin, to express excellent light stability, luminance and color coordinate, and to be used in a manufacturing process of a base material layer of a light diffusion plate. A resin composition for a light diffusion plate comprises a polystyrene-based resin; a light diffusing agent; a photostabilizer 0.1-10 parts by weight having the greatest absorption wavelength of 250~320 nm based on the polystyrene-based resin 100.0 parts by weight; and further an HALS-based auxiliary stabilizer 0.1-10 parts by weight based resin 100.0 parts by weight. The photostabilizer is a diamine-based compound, a benzophenone-based compound, a cyanoacrylate-based compound, and a nickel complex compound.

Description

Resin composition for light diffusion plate base layer having high brightness and low yellowing and light diffusion plate including same {MASTER BATCH COMPOSITION FOR PREPARING DIFFUSER SHEET WITH HIGH LUMINANCE AND LOW YELLOW INDEX AND DIFFUSER SHEET COMPRISING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition used to manufacture a base layer of a light diffusion plate used for a backlight unit, an illumination device, or the like of a liquid crystal display device.

The light diffusing plate is mainly used for a component of a backlight unit of a liquid crystal display (LCD) or a lighting device, and may have a single layer of only a base layer as a main layer or a multilayer structure of a base layer and a coating layer.

Since the shielding ability (the ability to cover the light source of the backlight unit) and the light transmittance, which are the main capabilities of the light diffusion plate, depend on the light diffusion effect in the base layer, the components of the base layer affecting the light diffusion effect are important. .

Resin components used as the main material of the light diffusion plate include methacrylic resins, styrene resins, cyclic olefin resins, polycarbonate resins, and the like. Among them, PS-based (polystyrene-based) resin is the most competitive in terms of cost and excellent in workability and optical properties, but it is a prerequisite to expand it to the application range of large TVs where PC resin is currently used. There is.

First of all, there is a problem in that UV stability is deteriorated for a long time due to the characteristics of the PS resin itself which is weak to heat during extrusion molding of the resin composition. In particular, in recent years, flat panel display devices are becoming more and more large, and thus the light quantity of the light source is increased, because the temperature during use becomes higher at higher temperatures.

In addition, CCFL, which is a light source generally used in a liquid crystal display device, exhibits a dual wavelength region of 320 nm or less and a 340 nm or more main absorption wavelength band, and thus can absorb a wavelength band of more than 340 nm in currently commercially available diffuser plates. A benzotriazole-based UV stabilizer and a UV stabilizer that can absorb a wavelength range of 320 nm or less are used together.

However, these stabilizers are yellowish due to their physical properties or their interaction with the resin, resulting in a yellowish color, which leads to high YI values and increases in L, a, and b values when the color coordinates are analyzed. This is observed, which is directly connected to the problem of luminance deterioration.

In addition, organic and inorganic beads having a difference in refractive index of about 0.02 to 0.13 are used as a diffusing agent in order to provide a concealing power such that the light source is not visible to the naked eye while maintaining the light transmission effect of transmitting direct light or fluorescent light at high transmittance. (JP JP 10172801, 6-13308, 7-218705, 9-113708, 11-160505, etc.), PS resins under the influence of residual monomers and impurities in these diffusers or in the interaction of the diffusion agent surface with the PS resin Has a problem of causing yellowing of the benzene ring.

Therefore, in order to economically manufacture a light diffusion plate exhibiting excellent shielding properties and luminance, there is a need for a technology development that can complement the low color coordinate / YI / UV stability of PS resin.

It is an object of the present invention to provide a resin composition for a light diffusion plate base layer that overcomes the above-mentioned disadvantages of the PS resin and expresses excellent light stability / luminance / color coordinates.

Still another object of the present invention is to provide a light diffusing plate for a backlight unit or an illumination manufactured using the resin composition.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object,

According to one aspect of the invention,

In the resin composition for a light diffusion plate base layer comprising a polystyrene resin, a light diffusing agent and a light stabilizer, a wavelength region of maximum wavelength of 250 to 320 nm with respect to 100 parts by weight of the polystyrene resin. Optical diffuser resin composition containing 0.1 to 10 parts by weight of the light stabilizer having a peak) can be presented.

According to another aspect of the present invention,

The light-diffusion plate which has a base material layer formed from the said resin composition can be presented.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for manufacturing a base layer of a light diffusion plate used in a backlight unit or an illumination device of a liquid crystal display device, and to express excellent transmittance, luminance, and color coordinates using a more economical polystyrene resin. The kind of additive added to a resin composition and its composition ratio are shown.

One aspect of the present invention is a light diffusing plate resin composition comprising a polystyrene resin, a light diffusing agent and a light stabilizer, having a wavelength range of UV 250 to 320 nm with respect to 100 parts by weight of polystyrene resin as a maximum absorption wavelength region. It provides a resin composition comprising 0.1 to 10 parts by weight of a light stabilizer.

As base resin which comprises the base material layer of a light-diffusion plate, resin which has transparency, such as PS (polystyrene), PMMA (polymethyl methacrylate), PC (polycarbonate), can be used. Preferably, PS-based resin having transparency is preferable, but such a transparent PS-based resin preferably contains 80 to 99% by weight of the total light diffusion plate resin composition. As the transparent PS-based resin, optical general PS-based resins, high heat-resistant PS resins copolymerized with methacrylic acid, and the like can be used without limitation. In particular, methacrylic acid copolymer PS resin (high heat resistance PS for optics) is competitive in price and excellent in heat resistance.

Moreover, you may mix and use 2 or more types of resin which has the said transparency. Appropriate mixing of the transparency resin can be easily carried out by those skilled in the art.

The resin composition of the present invention may include a siloxane light diffusing agent as the light diffusing agent. This is a silicone-based resin particles that are solid at room temperature, and include both silicone rubber having low crosslinking density and flexibility and silicone resin having high crosslinking density and rigidity.

Specific examples of the siloxane light diffusing agent include polymethylsilsesquioxane (PMSQ), polydimethylsiloxane (PDMS), copolymers of the PMSQ and PDMS, PMSQ copolymerized with trimethoxysilane, and epoxy in the terminal group. And silicone resins having a three-dimensional network structure such as siloxane.

Since such siloxane-based crosslinked particles are generally excellent in weather resistance, yellowing phenomenon in which the exposed portion turns yellow even when the final resin composition is exposed to light for a long time can be suppressed. On the other hand, the organic fine particles may induce a yellowing phenomenon under the influence of the unreacted monomer and impurities remaining during the polymerization.

The siloxane-based light diffusing agent used in the present invention has a refractive index of 1.39 to 1.46, which is lower than that of other organic crosslinked particles, and thus, even if only a small amount is added, light diffusion and light transmittance equivalent to those of other light diffusing agents can be obtained.

The amount of the light diffusing agent added is 0.1 to 10 parts by weight based on 100 parts by weight of the PS-based resin. If the amount of the siloxane-based light diffusing agent is less than 0.1 part by weight, the light diffusivity of the final resin composition is not sufficient, so it is difficult to see a lamp or to diffuse light, and when the amount is more than 10 parts by weight, the light transmittance is too high. This results in a decrease in brightness.

In addition, the siloxane-based crosslinked particles are preferably particles having an average particle diameter of 1 ~ 10㎛, when the average particle diameter is less than 1㎛ decreases the concealment of the light source, if the average particle diameter is larger than 10㎛ ensures the appropriate light diffusion There is a problem in that an excess light diffusing agent must be added in order to do so.

In general, when processing the resin composition forming the substrate layer, the shielding property and the light transmittance to the light source are directly connected to the input amount of the light diffusing agent, which has become the most important physical property. In order to express the best luminance considering proper shielding, it is recommended to use two or more particles of different sizes. That is, the first silicon particles having a size of 1 to 2 μm and the second particles having a size of 1.5 to 2 times (4 to 6 μm) may be used together. The amount of the second silicon particles used is preferably 0.5 times the amount of the first particles used.

The resin composition of the present invention includes a light stabilizer to absorb ultraviolet rays generated from the light source.

In general, CCFL, a light source used in liquid crystal display devices, exhibits a maximum absorption wavelength region of less than 320 nm and a dual wavelength region of more than 340 nm. As a result, benzotria that can absorb a wavelength region of more than 340 nm is currently available in commercial diffusion plates. The sol-based light stabilizer and the light stabilizer that can absorb a wavelength range of 320 nm or less are used together. However, these added stabilizers had a problem of causing yellowing of the diffusion plate and decrease in brightness.

The present invention discloses that by using only a light stabilizer having a maximum absorption wavelength in the range of 250 to 320 nm, the light resistance of the light diffusion plate can be improved, and the coloring of the diffusion plate due to ultraviolet absorption can be suppressed to express the best luminance. Therefore, it is not preferable to use the benzotriazole-based light stabilizer conventionally used to absorb the wavelength range of 340 nm or more.

As the light stabilizer of the present invention, one or more products capable of absorbing a wavelength of less than 340 nm, preferably 250 to 320 nm can be used. Specific examples thereof include diamine-based, benzophenone-based, cyanoacrylate-based, saricireto-based, and nickel complex salt-based compounds. The trade names include hostavin, tinuvin, and Zika series. In addition, the powder color of the light stabilizer is also preferably a white series. The light stabilizer of the present invention is not limited as long as it satisfies these characteristics, but a diamine-based light stabilizer is particularly preferable. The light stabilizer may be used in an amount of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the PS resin constituting the light diffusion plate resin composition. If the content is less than 0.1 parts by weight, it is not sufficient to express the physical properties. If the content is more than 10 parts by weight, a problem of lowering the luminance is caused.

In addition, in the present invention, an auxiliary stabilizer may be used to supplement the function of the light stabilizer and to impart long-term stability and stability to YI of the diffusion plate resin. The auxiliary stabilizer was used as a radical scavenger hindered amine light stabilizer (HALS), ZIKA-770 or tinuvin 770 is preferred among several HALS series.

The auxiliary stabilizer may be used in an amount of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the PS resin constituting the light diffusion plate resin composition. If the content is less than 0.1 parts by weight, it is not sufficient to express the physical properties. If the content is more than 10 parts by weight, a problem of lowering the luminance is caused.

The resin composition of the present invention may further include other additives within a range that does not affect the intrinsic physical properties of the light diffusion plate. For example, blowing agents, plasticizers, antistatic agents, antioxidants, heat stabilizers, lubricants, flame retardants, fillers, mold release agents, dyes, pigments, fungicides, antidropping agents to prevent appearance defects caused by yellowing due to resin degradation. And one or more of the nucleating agents. These additives are known to those skilled in the art, their amount or use.

The resin composition for the substrate layer of the diffuser plate prepared in one embodiment of the present invention is for evaluation of the specimen and may be different from that applied to the actual diffuser plate. In actual use for the diffusion plate, it is possible to manufacture and use a coating layer for applying the substrate layer, to form a spray coating layer, the number of layers is not limited. In order to manufacture the base material layer and the coating layer, various raw materials such as the above-described PS resin, light diffusing agent, and light stabilizer may be mixed, and injection molding, extrusion molding, vacuum molding, hot press molding, Various molding methods such as coextrusion may be used.

The present invention includes a light diffusion plate having a base layer formed from the resin composition. The light diffusion plate has a PS resin, a light stabilizer having a wavelength range of 250 to 320 nm as a maximum absorption wavelength region, and a Hals-based auxiliary stabilizer, thereby exhibiting excellent brightness and low yellowing property. Or as a component of a lighting device.

As described above, according to the present invention, a resin composition for a light diffusion plate base layer expressing an optimal light stability and luminance by using a light stabilizer that absorbs a UV region of 250 to 320 nm and a radical scavenger of HALS series as an auxiliary stabilizer is used. It can manufacture.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

In manufacture of the resin composition of this invention, the specific specification of each structural component used by the below-mentioned Example and comparative example is as follows.

(a) PS resin used HRM40 of TOYO STYRENE Co., Ltd. as an optical PS resin, and T080 of TOYO STYRENE Co., Ltd. was used as a high heat resistance PS resin copolymerized with methacrylic acid.

(b) Diffusion agent used SL-200M (2 micrometers) and SL-500m (5 micrometers) of Cheil Industries.

(c) As a light stabilizer, Tinuvin-P from Ciba, PR-25 from Clariant and B-CAP from Clariant were used as the benzotriazole, and Tinuvin 312 from Ciba as the amine.

(d) Tinuvin-770 from Ciba was used as a HALS co-stabilizer.

Example  One:

According to the composition ratio of Table 1 with respect to 100 parts by weight of the optical PS resin HRM40, 1 part by weight of the silicon-based diffusion agent SL-200M, 0.5 parts by weight of SL-500M, 0.3 parts by weight of Tinuvin 312 as a light stabilizer and 0.3 parts by weight of auxiliary stabilizer Tinuvin-770 The parts were mixed. TWIN SCREW type extrusion drill (40Φ) was used to prepare the specimen. The master batch can be used for the production of the actual diffusion plate, and to evaluate the substrate layer, an optical evaluation was performed by obtaining 2t, 10 x 10 sized injection specimens (see Table 1).

Example  2:

100 parts by weight of a high heat resistance PS resin T080 copolymerized with methacrylic acid was used as the PS resin, and the specimens were prepared in the same manner as in Example 1 except that 3.5 parts by weight of Tinuvin 312 and 2.0 parts by weight of Tinuvin-770 were added.

Comparative example  One:

Specimens were prepared in the same manner as in Example 1 except that 0.3 parts by weight of Tinuvin-P and 0.3 parts by weight of B-CAP were added as the light stabilizer.

Comparative example  2:

100 parts by weight of a high heat resistant PS resin T080 copolymerized with methacrylic acid was used as the PS resin, and the specimens were prepared in the same manner as in Example 1 except that 2.0 parts by weight of Tinuvin-P and 3.5 parts by weight of PR25 were added.

TABLE 1

Test Example  1: optical evaluation

1-1: Light resistance  Measure

In order to evaluate the light resistance of the specimens prepared in Examples and Comparative Examples, using the ATLAS-UVCON, after irradiating ultraviolet rays for 48h at a temperature of 60 ℃, YI (Yellow Index) change was measured. The results are shown in Table 2.

1-2: luminance measurement

In order to measure the brightness of the specimens prepared in Examples and Comparative Examples, the average value was recorded by measuring the luminance value of 5 points after 30 minutes of aging at room temperature using BM-7. The results are shown in Table 2.

1-3: transmittance and HAZE

The permeability and the HAZE of the specimens prepared in Examples and Comparative Examples simultaneously measured the values of 5 points using a haze meter to record the average value. The results are shown in Table 2.

TABLE 2

From the results in Table 2, both the general optical PS (HRM 40) and the high heat resistant PS resin (T080) are light stabilizers having a wavelength range of 250 to 320 nm in the maximum absorption wavelength region without using a benzotriazole light stabilizer. It can be seen that when used in conjunction with Hals series stabilizers it has excellent brightness and low yellowing.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (8)

In the resin composition for a light diffusion plate base layer comprising a polystyrene resin, a light diffusing agent and a light stabilizer, 0.1 light stabilizer having a wavelength range of UV 250 ~ 320 nm in the maximum absorption wavelength region with respect to 100 parts by weight of polystyrene resin. Resin composition for an optical dispersion base material layer containing from 10 parts by weight. The resin composition for a light diffusion plate base layer according to claim 1, further comprising 0.1 to 10 parts by weight of a HALS-based auxiliary stabilizer based on 100 parts by weight of polystyrene resin. The resin composition for an optical spreader base layer according to claim 1, wherein the light stabilizer is a compound of diamine, benzophenone, cyanoacrylate, sarichireto or nickel complex salt. The resin composition of claim 1, wherein the light stabilizer is Tinuvin 312. The resin composition of claim 2, wherein the auxiliary stabilizer is Tinuvin-770. The resin composition for an optical diffuser base layer according to claim 1, wherein the light diffusing agent is a siloxane compound. The resin composition for an optical diffuser base layer according to claim 6, wherein the siloxane light diffusing agent is composed of first silicon particles having an average particle size of 1 to 2 um and second silicon particles having an average particle size of 4 to 6 um. A light diffusion plate comprising a base layer formed from the resin composition of claim 1.