KR101038660B1 - Diffuser sheet having 2 type uv stabilizer - Google Patents

Abstract

The present invention relates to a three-layer diffuser plate having a skin layer formed on both sides of the base layer, and more particularly, contains a UV stabilizer in the coating layer of the diffuser of the core-shell type, which is effective as a small amount of UV stabilizer. The present invention relates to a diffuser plate capable of blocking a wavelength.

The present invention is a diffusion plate of a three-layer structure in which a skin layer is formed on both sides of the base layer; A first diffusion agent added to the base layer and having a coating layer including a benzotriazole-based UV stabilizer; And a second diffusion agent added to the skin layer and having a coating layer including an oxanilide UV stabilizer.

The present invention relates to a diffuser plate using a diffusing agent, comprising a UV stabilizer in the shell layer (coating layer) of the core-shell type diffuser, by using a small amount of UV stabilizer to enable effective diffusion of the blocking plate. to provide.

Diffusion Plate, Diffusion Agent, UV Stabilizer

Description

Diffusion plate containing heterogeneous heat stabilizer in base layer and skin layer {DIFFUSER SHEET HAVING 2 TYPE UV STABILIZER}

The present invention relates to a three-layer diffuser plate having a skin layer formed on both sides of the base layer, and more particularly, contains a UV stabilizer in the coating layer of the diffuser of the core-shell type, which is effective as a small amount of UV stabilizer. The present invention relates to a diffuser plate capable of blocking a wavelength.

Since a liquid crystal display device is not a self-luminous device such as a plasma display panel (PDP) or an organic light emission diode (OLED), surface light is incident on the rear surface and light is generated by a change in liquid crystal according to a predetermined signal. It operates on the principle of displaying a predetermined screen by adjusting the open / close of this moving passage.

As such, since the liquid crystal display is not a self-luminous element, a surface light source generator called a backlight unit is required on the rear side thereof. The backlight unit of the liquid crystal display may be divided into an edge method in which the light source is disposed at one side and a direct method in which the light source is disposed below, according to the arrangement of the light source.

The double edge type is mainly used for notebook or desktop computer monitors, and the direct type is mainly used for large area such as LCD TV.

The direct type backlight unit includes a fluorescent lamp for generating light, a reflecting plate for reflecting the generated light in a direction in which the panel is located, and a diffusion plate. Such a direct type backlight unit has a diffusion plate, which diffuses the light generated from the fluorescent lamp and serves to uniformize the light throughout the panel.

As the base resin, transparent thermoplastic resins such as methacryl resin, styrene resin, cyclic olefin resin, and polycarbonate resin are mainly used as the base resin.

The base resin is added with a light transmission effect that transmits light such as direct sunlight or fluorescent light with high transmittance, and a hiding power such that the light source is invisible to the naked eye, and a light diffusion effect that diffuses light.

As a diffusing agent, inorganic or organic materials having a difference in refractive index between 0.02 and 0.13 are generally used. As the inorganic fine particles, calcium carbonate, barium sulfate, titanium dioxide, aluminum hydroxide, silica, glass, talc and mica are used. , White carbon, magnesium oxide, zinc oxide, and the like, and silicon-based, teflon-based, acrylic-based, styrene-based, etc. are used as the organic fine particles.

As other additives, UV stabilizers may be added to prevent color deformation due to ultraviolet rays emitted from the backlight lamp, and lubricants and antioxidants are added.

Existing UV stabilizer technology is to compress the UV stabilizer in the form of a master batch on the diffuser plate and then blend it onto the diffuser plate to reduce the efficiency caused by the excessive input of the UV diffuser, and the color coordinates of the diffuser plate. There were disadvantages such as change.

The present invention is applied to the core-shell type diffusion agent that can absorb the selective UV wavelength for each layer in the diffusion plate of the three-layer structure in which the skin layer is formed on both sides of the base layer, improving color coordinates and The aim is to achieve effective UV stabilization and cost reduction.

The present invention can be applied to the functional group (modified group) modified in the shell portion of the diffusion agent to improve the compatibility with the base layer or skin layer can prevent the impact resistance due to the diffusion agent is prevented.

The present invention is a diffusion plate of a three-layer structure in which a skin layer is formed on both sides of the base layer; A first diffusion agent added to the base layer and having a coating layer including a benzotriazole-based UV stabilizer; And a second diffusion agent added to the skin layer and having a coating layer including an oxanilide UV stabilizer.

The present invention relates to a diffuser plate using a diffusing agent, comprising a UV stabilizer in the shell layer (coating layer) of the core-shell type diffuser, by using a small amount of UV stabilizer to enable effective diffusion of the blocking plate. to provide.

In the present invention, a diffusing agent for selectively absorbing UV wavelengths emitted from the backlight is added to the skin layer, and a diffusing agent for selectively absorbing UV wavelength bands in which the polystyrene as the base resin is weak is added to the base layer.

Therefore, the present invention is effective UV blocking using a small amount of the UV stabilizer than to apply the UV stabilizer throughout the diffusion plate.

The present invention is a three-layer diffuser plate in which the skin layer is formed on both sides of the base layer, by adding different UV stabilizers to the base layer and the skin layer, the fragility of the UV wavelength band from the backlight unit and the polystyrene itself as a base resin It provides the effect of protecting the diffusion plate in the wavelength band.

In addition, dispersibility is improved by adding a UV stabilizer to the surface of the diffusing agent, which can effectively absorb the UV wavelength even with a small amount of the UV stabilizer.

In addition, the decrease in the light resistance of the diffuser plate caused by the increase of the amount of refracted / reflected light due to the increase in the amount of diffuser can absorb UV from the diffuser itself. Can be reduced.

In addition, it is possible to omit the process of the master batch to inject the UV stabilizer during the extrusion plate production, it is helpful in cost reduction and production yield improvement.

In addition, the core-shell type diffusing agent is modified to increase the compatibility with the base resin in the shell portion according to the original function, thereby securing impact resistance, which is a weak point of the polystyrene diffuser plate, and the single diffusing agent has a local impact. The risk of acting as a crack point can be minimized.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the diffusion plate according to the present invention.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom.

Therefore, definitions of these terms should be made based on the contents throughout the specification.

1 is a cross-sectional view showing the structure of a diffusion plate according to an embodiment of the present invention.

As shown, the diffusion plate 100 according to the present invention includes a base layer 110 and a skin layer 120 formed on both sides of the base layer 110.

The sum of the thicknesses of the skin layers 120 is preferably in the range of 0.1 to 2% of the thickness of the entire diffusion plate 100.

For example, when the thickness of the entire diffusion plate 100 is 2.0 mm, the sum of the thicknesses of the skin layers on both sides is 20 to 40 μm.

The base layer 110 and the skin layer 120 are all based on polystyrene resin.

Base layer 110 is made of a highly transparent polystyrene resin material in order to maximize the total light transmittance, skin layer 120 is 20 to 50% by weight of methyl methacrylate (methyl methacrylate) to improve the impact resistance It is preferably made of compounded polystyrene material.

The high-transparent polystyrene resin refers to a level of 90% or more of total light transmittance, and at the time of polystyrene polymerization, additives other than monomers such as SM and EB required for polymerization are not added, and Mn: 8.0 * 10 ⁴ to 1.5 * 10 ⁵ level, polydispersity Means that it is 3.0 to 4.0 level. Total light transmittance is measured using 3.2 mm thick injection specimens.

The present invention includes a diffusing agent in the base layer 110 and the skin layer 120, which uses a core-shell type diffuser consisting essentially of a core layer and a shell layer. In addition, the shell of the core-shell type diffusion agent is characterized in that it comprises a UV stabilizer. Hereinafter, the core of the core-shell type diffusing agent is referred to as the core portion and the shell portion is referred to as a coating layer.

The first diffusion agent 115 added to the base layer 110 includes a benzotriazole class UV stabilizer in the coating layer 117 and the second diffusion agent 125 added to the skin layer 120. The coating layer 127 includes an oxanilide class UV stabilizer.

The first diffusion agent 115 and the second diffusion agent 125 preferably have a particle size of 1 ~ 30㎛, the addition ratio of the first diffusion agent 115 and the second diffusion agent 125 is a skin layer ( It is preferable that 0.5 to 2% by weight based on the weight of 120).

As the particle size of the diffusing agent decreases, mechanical properties such as impact strength may be improved. However, when the size of the diffusing agent is smaller than 1 μm, Rayleigh scattering occurs, thereby degrading the performance of the diffusing agent. In addition, when the size is 30㎛ or more, the number of particles of the diffusing agent per unit volume when the same amount of the diffusing agent is added is also poor performance as a diffusing agent.

The benzotriazole-based UV stabilizer added to the coating layer 117 of the first diffusing agent 115 absorbs a wavelength of 300 to 360 nm, which is a sensitive area of the polystyrene resin, and is applied to the coating layer 127 of the second diffusing agent 125. The added oxanilide UV stabilizer absorbs a wavelength of 310-325 nm, which is the maximum emission UV wavelength of the cold cathode fluorescent lamp (CCFL).

UV wavelength range of UV can be largely divided into UV-A, UV-B, UV-C.

UV-A (315-400nm) causes the degradation of some polymers, and UV-B (280-315nm) is the shortest wavelength that reaches the earth's surface, causing most of the degradation. Failure to reach the UV-C (280 nm or less) surface phase, but abnormal reactions may occur.

In the polystyrene resin that is the basis of the base layer 110 and the skin layer 120, the C-H bonds in the benzene ring and the bonding portion are easily deteriorated by ultraviolet rays, and the molecular weight decreases due to photooxidation. This may lead to coloration of the product and deterioration of properties.

Polystyrene used as a substrate of the diffusion plate is not greatly degraded by natural light such as sunlight, but may be damaged by ultraviolet rays emitted from a cold cathode fluorescent lamp (CCFL) used as a light source in the backlight unit. Since this adversely affects the reliability of the product, UV absorbers that can absorb the ultraviolet rays emitted by CCFL are used.

Highly transparent polystyrene used in the present invention has a Tg (glass transition temperature) of 100 ~ 105 ℃, Tm (Melting temperature) of 240 ℃ level of UV fragile wavelength of the resin itself is 310 ~ 325nm.

Ultraviolet wavelength range from CCFL is widely distributed in 300 ~ 360nm, especially after 350nm, peak in 360nm wavelength. As a result, when UV agents capable of strongly absorbing the 310 ~ 325nm and 360nm wavelength bands, which are weak wavelengths of the polystyrene resin itself, and absorbing the ultraviolet range of 300 ~ 360nm as a whole, a product having more UV stability can be made.

The UV stabilizer used in the present invention is an oxanilide stabilizer and a benzotriazole stabilizer are UV agents that can effectively absorb the above-described wavelength bands while best matching the whiteness required in the diffusion plate.

The oxanilide system has a molar weight (Mw) of 310 to 315 g / mol level of N-H, C═O, C═O, and N—H, which are continuously connected to effectively absorb ultraviolet rays and quickly stabilize it. Absorption wavelength band shows maximum absorption capacity from 310 ~ 320nm

The benzotriazole type uses a molar weight (Mw) of 220-225 g / mol and easily absorbs and stabilizes UV in N-N-N bonds with adjacent ring structures. The wavelength band absorbs a wide range of 300 to 360 nm.

UV stabilizers included in each diffusing agent is preferably included 0.1 to 1% by weight relative to the total weight of the diffusing agent.

<Examples>

 1) YI change with increasing diffusion agent content

 The YI change values of nine specimens (thickness 3.2 mm * 10 cm * 10 cm) that were injected with a core part of acrylic material, a particle size of 5 um diffusion agent, and varying the content of the diffusion agent were measured.

 Exposure level follows 83mW, 100J, 1200s string diffuser exposure criteria.

Example 1 is not an evaluation of the three-layer structure diffusion plate, but looks at the amount of change in the YI value as the diffusion agent input amount increases.

L, a, and b represent colors in three dimensions, and in general, whiteness increases as a and b become closer to the number zero. Increasing the whiteness is to improve the quality of the color of the diffusion agent, so it can be said that a, b is smaller.

In addition, since DELTA YI is YI (YIt) after exposure-YI (YIi) before exposure, it can be judged that a smaller value of DELTA absorbs ultraviolet rays.

1 to 9 were evaluated by adding only a diffusing agent to the base PS resin at a level of 0.1 to 2.0% by weight. As the amount of the diffusing agent increased, the total light transmittance (TT) decreased, and as the amount of the diffusing agent increased, It can be seen that the degree of breakdown of the base resin increases with increasing ΔYI (YIt [YI value after exposure] -YIi [YI value before exposure]). The initial YI value changes according to the whiteness of the diffusing agent itself as the content of the diffusing agent increases, but the ΔYI increases when the amount of the diffusing agent increases.

2) Actual extrusion evaluation result

This is the result of measuring the light resistance by content by mixing and extruding the master batch of the base layer and the skin layer with the base resin.

The content of the masterbatch is 7.3 wt% in the base layer and 1.2 wt% in the skin layer.

 Exposure level follows 83mW, 100J, 1200s string diffuser exposure criteria.

Experimental results show that as the UV stabilizer content increases, the YI increases due to the initial color of the UV stabilizer, but the breakage of the base layer due to reflection / refraction that occurs directly in the diffusing agent decreases, so that △ YI decreases as the diffusing agent content increases. Showed a tendency.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art to which the art belongs can make various modifications and other equivalent embodiments therefrom. I will understand.

Therefore, the true technical protection scope of the present invention will be defined by the claims below.

1 is a cross-sectional view showing the structure of a diffusion plate according to an embodiment of the present invention.

Claims (9)

A diffusion plate having a three-layer structure in which a skin layer is formed on both sides of the base layer; A first diffusion agent added to the base layer and having a coating layer including a benzotriazole-based UV stabilizer; And And a second diffuser added to the skin layer and having a coating layer including an oxanilide UV stabilizer. The method of claim 1, The benzotriazole UV stabilizer of the first diffusing agent absorbs light having a wavelength of 300 to 360 nm. The method of claim 1, The oxanilide UV stabilizer of the second diffusion agent absorbs light having a wavelength of 310 ~ 325nm. The method of claim 1, The skin layer is a diffusion plate, characterized in that 0.1 to 2% of the total thickness of the diffusion plate. The method of claim 1, The base layer comprises 0.5 to 2% by weight of the first diffusing agent, The skin layer is a diffusion plate, characterized in that it comprises 0.5 to 2% by weight of the second diffusion agent. The method of claim 1, The first diffuser and the second diffuser is a diffusion plate, characterized in that each containing 0.1 to 1% by weight UV stabilizer. The method of claim 1, The skin layer is a diffusion plate, characterized in that the polystyrene resin 20 to 50% by weight of methyl methacrylate is mixed. The method of claim 1, The base layer is a diffuser plate, characterized in that the high-transparent polystyrene resin having a total light transmittance of 90% or more. The method of claim 1, The first diffusion agent and the second diffusion agent has a particle size of 1 ~ 30㎛.

Images