TWI431331B - A diffuser sheet in a back light module - Google Patents

Description

Diffusion sheet for backlight module

The present invention relates to a diffusion sheet, and more particularly to a diffusion sheet for a backlight module that can be prevented from being thermally deformed.

Liquid crystal displays have the advantages of low power consumption, small size, long life, and the like, and are attracting attention as various image output devices. Liquid crystal display (LCD) is different from other self-illuminating displays. The liquid crystal itself is a non-illuminating material, so an external light source is required to make it visible. The part for providing the light source of the liquid crystal display is called a backlight module, and the backlight module has an optical film for improving the uniformity of the backlight and the central brightness.

The main components of the backlight module include an incident light source, a reflector, a light guide plate or a diffusion plate, a diffusion film, a brightness enhancement film, etc., and The position of the light source can be divided into (1) side light source structure, that is, the incident light source is disposed on the side of the light guide plate. This type is usually applied to a notebook computer or a desktop monitor because of its thin thickness; (2) a direct-lit light source structure, that is, the incident light source is disposed under the diffusing plate. Usually, the type of use is applied to a large-sized monitor or television, and because of its large size, it provides appropriate brightness. A plurality of incident light sources are disposed below the diffuser plate. However, whether it is a side light source type or a direct type structure, the light source transmits light or directly penetrates the diffusion plate, and there may be uneven brightness and darkness. Therefore, several optical films must be disposed on the light guide plate or the diffusion plate to The light passing through the light guide plate or the diffusion plate is made uniform.

The optical film includes a diffusion sheet and a brightness enhancement sheet. The diffuser function is to shield the light guide plate dots and turns to make the light uniform. The function of the brightness enhancement is to concentrate the uniform diffusion light source toward the normal direction of the panel, and enhance the brightness to save energy and save electricity.

Referring to FIG. 1 , it is a schematic diagram of a composition of a conventional diffusion sheet. As shown in the figure, the diffusion sheet 10 mainly comprises a transparent substrate 11 and a first adhesive layer 12 adhered to the front and back surfaces of the transparent substrate 11 . It is composed of a second rubber layer 13. When the diffusion sheet 10 is produced, organic or inorganic beads as light diffusion particles are usually added to the first adhesive layer 12, and are coated on the light-transmitting substrate 11 to have light diffusion. effect. However, the light-diffusing particles added by the diffusion sheet 10 are often detached, and the detached light-diffusing particles move and rub between the cymbal sheet and the diffusion sheet 10, thereby causing scratches and affecting the quality of the display.

Referring to FIG. 2, it is a schematic diagram of the composition of another conventional diffusion sheet. As shown in the figure, the diffusion sheet 20 is mainly composed of a light-transmitting substrate 21 and a coating layer adhered to the front and back surfaces of the light-transmitting substrate 21. 22 is composed of an anti-adhesive layer 23. The coating layer 22 is a transparent coating layer of a viscous resin, and the light-diffusing particles are not added, and the occurrence of the light-diffusing particles falling off can be avoided. The surface of the coating layer 22 is distributed by means of rolling to distribute the pattern of the unevenness and the rough surface, and a diffusion effect is produced by the rough surface. The surface of the anti-adhesive layer 23 is distributed in a pattern of unevenness by means of rolling, and the uneven pattern has the same depth gap so that it does not generate static electricity and adheres to the light guide plate. However, whether it is the rough surface of the coating layer 22 or the surface of the embossing layer of the anti-adhesion layer 23, the rough surface of the rolling roller is usually produced by a beading method or an etching method, and then applied to the light-transmitting substrate. . Neither of these methods can control the uniformity of surface roughness, and it is easy to produce bright spots and light and dark bands, so it is difficult to be practical. Furthermore, since the coating layer 22 of the front and back surfaces of the light-transmitting substrate 21 is different from the material of the anti-adhesion layer 23, the coefficient of thermal expansion is different, so that the coating layer 22 and the anti-adhesion layer 23 receive the light source. When the high heat is dissipated, the diffusion sheet 20 is warped, affecting the quality of the display and its optical performance.

As described above, how to make the diffusion sheet can maintain or even increase the optical performance under the premise of being affected by the high heat of the light source is actually a practical thinking direction.

Therefore, the main object of the present invention is to provide a diffusion sheet for a backlight module to achieve an optical performance that is not affected by the high heat of the light source.

A diffusion sheet for a backlight module according to the present invention is mainly composed of a light-transmitting substrate and a first adhesive layer and a second adhesive layer respectively coated on the upper and lower surfaces of the transparent substrate. The composition of the first adhesive layer and the second adhesive layer are substantially the same, and the material thereof comprises a monomer, an oligomer and a photoinitiator, and the monomer component comprises a monofunctional group. Any one of a monomer and a polyfunctional monomer, the oligomer component comprising urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate and pure acrylic resin In any one of the components, the photoinitiator comprises 1-yl-cyclohexyl-phenyl ketone, 2-yl-2-methyl-1-phenyl-1-propanone, benzophenone, benzoin And any of the mercaptophosphine oxides.

The details and techniques of the present invention are described below:

Referring to FIG. 3, it is a schematic diagram of a diffusion sheet for a backlight module of the present invention. As shown in the figure, the diffusion sheet 30 of the present invention is mainly used for a light-transmitting substrate 31 and separately coated. A first adhesive layer 32 and a second adhesive layer 33 are disposed on the upper and lower surfaces of the transparent substrate 31. In a general case, the first adhesive layer 32 and the second adhesive layer 33 have a transmittance of more than 85%, a haze of between 20% and 85%, and a thickness of between 2 μm and 20 μm. The first adhesive layer 32 and the second adhesive layer 33 may be an ultraviolet curing adhesive, and the transmittance and haze of the first adhesive layer 32 and the second adhesive layer 33 may be adjusted by changing the composition of the ultraviolet curing adhesive. . An antistatic agent may be added to the first adhesive layer 32 and the second adhesive layer 33 to reduce the occurrence of electrostatic adsorption.

When the diffusion sheet is affected by the high heat of the light source, if only one surface of the diffusion sheet is coated with a rubber layer or a coating layer having a different surface coating material, the expansion coefficient of the rubber layer is different from the expansion coefficient of the light-transmitting substrate. The phenomenon that causes the ruffle (or wavy edge) and warpage will affect the quality of the display. The diffusion sheet 30 of the backlight module of the present invention is applied to the first adhesive layer 32 and the second adhesive layer 33 of the same material on the upper and lower surfaces of the transparent substrate 31. Therefore, when the diffusion sheet 30 is affected by the high heat of the light source, The first adhesive layer 32 and the second adhesive layer 33 are equivalent to the stress generated by thermal expansion, and the probability of occurrence of warpage of the diffusion sheet 30 as a whole can be reduced.

The material of the transparent substrate 31 is polyethylene terephthalate (PET), and the first adhesive layer 32 and the second adhesive layer 33 have substantially the same material, and the materials thereof all contain a monomer and an oligomer. And a photoinitiator.

The monomer component comprises a monofunctional monomer or a polyfunctional monomer, whether it is a monofunctional monomer or a polyfunctional monomer, the composition of which is composed of 2-phenoxyethyl acrylate, A group consisting of propylene glycol diacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate trimethylolpropane triacrylate, and ethoxylated trimethylolpropane triacrylate was selected. In addition, the monomer component may also be composed of 2-phenoxyethyl acrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate trimethylolpropane triacrylate, and A monofunctional monomer such as ethoxylated trimethylolpropane triacrylate is composed of a polyfunctional monomer.

The oligomer component comprises any one of urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, and pure acrylic resin. In addition, the oligomer component may also be composed of urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, and pure acrylic resin. Among them, the urethane acrylate has a good ductility, and if it is added in an amount of 5 wt% to 30 wt%, the film surface toughness of the first adhesive layer 32 and the second adhesive layer 33 (ie, the diffusion sheet 30) can be increased. And scratch resistance.

The photoinitiator comprises 1-yl-cyclohexyl-phenyl ketone, 2-yl-2-methyl-1-phenyl-1-propanone, benzophenone, benzoin and decylphosphine oxide Any of the species may also be 1-yl-cyclohexyl-phenyl ketone, 2-yl-2-methyl-1-phenyl-1-propanone, benzophenone, benzoin, and sulfhydryl Made up of phosphine oxides.

Furthermore, in order to reduce the occurrence of electrostatic adsorption, an antistatic agent may be added to the adhesive layer to increase the antistatic function and reduce the problem of surface adsorption. The antistatic agent component is a metal conductive particle, a metal oxide, a quaternary ammonium salt or the like, and may be added in an amount of 3 wt% to 25 wt%.

In terms of macroscopic view, the monomer portion of the first adhesive layer 32 and the second adhesive layer 33 accounts for about 20% by weight to 60% by weight of the whole, and the oligomer portion accounts for about 30% by weight to 70% by weight of the whole, and the light starts. The agent portion accounts for about 3 wt% to 10 wt% of the whole. The ratio and composition can be changed as needed, so that the haze and transmittance of the diffusion sheet 30 also change.

Referring to FIG. 4, it is a schematic diagram of the surface texture of the first adhesive layer of the present invention. As shown in the figure, since the first adhesive layer 32 and the second adhesive layer 33 have substantially the same material, the surface is uniformly distributed with uneven texture. That is, its surface roughness distribution is fairly uniform, and it will not easily produce bright spots and light and dark bands. In order to make the surface of the first adhesive layer 32 and the second adhesive layer 33 embossed (roughness) uniform, the diffusion sheet 30 of the present invention can control the surface roughness of the roller by precisely controlling the plating time, the plating current and the chemical composition ( The surface of the precision plated roller is rolled, and then pressed onto the surfaces of the first adhesive layer 32 and the second adhesive layer 33, so that the unevenness (roughness) distribution is uniform. Therefore, by using a precision plating roller and pressing it on the first adhesive layer 32 and the second adhesive layer 33 to form a concave-convex texture (rough surface), we can control the surface roughness of the first adhesive layer 32 and the second adhesive layer 33. And its components to achieve the desired haze.

While the present invention has been described above in terms of the preferred embodiments thereof, it is not intended to limit the present invention, and it is to be understood that those skilled in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

10. . . Diffusion sheet

11. . . Light transmissive substrate

12. . . First glue layer

13. . . Second glue layer

20. . . Diffusion sheet

twenty one. . . Light transmissive substrate

twenty two. . . Coating layer

twenty three. . . Anti-adhesion layer

30. . . Diffusion sheet

31. . . Light transmissive substrate

32. . . First glue layer

33. . . Second glue layer

Figure 1 is a schematic diagram showing the composition of a conventional diffusion sheet;

Figure 2 is a schematic view showing the composition of another conventional diffusion sheet;

Figure 3 is a schematic view of a diffusion sheet for a backlight module of the present invention;

Figure 4 is a schematic view showing the surface texture of the first adhesive layer of the present invention.

30. . . Diffusion sheet

31. . . Light transmissive substrate

32. . . First glue layer

33. . . Second glue layer

Claims (12)

A diffusion sheet for a backlight module, which is mainly composed of a light-transmitting substrate and a first adhesive layer and a second adhesive layer respectively coated on the upper and lower surfaces of the transparent substrate, and is characterized in that: The first adhesive layer and the second adhesive layer are substantially the same material, and the material thereof comprises a monomer, an oligomer and a photoinitiator, and the monomer component comprises a monofunctional monomer and a Any one of the polyfunctional monomers, the oligomer component comprising any one of urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, and pure acrylic resin And the component of the photoinitiator comprises 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzophenone, benzoin and sulfhydryl Any one of the phosphine oxides; wherein the monomer portion accounts for 20% by weight to 60% by weight of the first adhesive layer and the second adhesive layer, and the oligomer portion accounts for the first adhesive layer and the first The entire second adhesive layer is 30% by weight to 70% by weight, and the photoinitiator portion accounts for 3% by weight to 10% by weight of the first adhesive layer and the second adhesive layer. The diffusion sheet for a backlight module according to claim 1, wherein the first adhesive layer and the second adhesive layer have a thickness of between 2 μm and 20 μm. The diffusion sheet for a backlight module according to claim 1, wherein the monofunctional monomer and the polyfunctional monomer comprise 2-phenoxyethyl acrylate and dipropylene glycol diacrylic acid. Ester, tripropylene glycol Any of acrylate, 1,6-hexanediol diacrylate trimethylolpropane triacrylate, and ethoxylated trimethylolpropane triacrylate. The diffusion sheet for a backlight module according to claim 1, wherein the monomer is composed of 2-phenoxyethyl acrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and 1 6-hexanediol diacrylate trimethylolpropane triacrylate and ethoxylated trimethylolpropane triacrylate. The diffusion sheet for a backlight module according to claim 1, wherein the oligomer is composed of urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate. And the composition of pure acrylic resin. The diffusion sheet for a backlight module according to claim 5, wherein the urethane acrylate is added in an amount of 5 wt% to 30 wt% of the entire oligomer. The diffusion sheet for a backlight module according to claim 1, wherein an antistatic agent may be added to the first adhesive layer and the second adhesive layer to increase an antistatic function. The diffusion sheet for a backlight module according to claim 7, wherein the antistatic agent is composed of metal conductive particles, a metal oxide, and a quaternary ammonium salt. The diffusion sheet for a backlight module as described in claim 7 of the patent application, The antistatic agent is added in an amount of 3 wt% to 25 wt% of the entire first adhesive layer and the second adhesive layer. The diffusion sheet for a backlight module according to claim 1, wherein the photoinitiator is composed of 1-hydroxy-cyclohexyl-phenyl ketone and 2-hydroxy-2-methyl- 1-phenyl-1-propanone, benzophenone, benzoin and decylphosphine oxide. The diffusion sheet for a backlight module according to the first aspect of the invention, wherein the first adhesive layer and the surface of the second adhesive layer are uniformly distributed with a concave-convex texture. The diffusion sheet for a backlight module according to claim 11, wherein the embossed surface of the first adhesive layer and the surface of the second adhesive layer is first formed by precision plating to form a surface roughness of the roller, and then It is formed by pressing it to the first adhesive layer and the second adhesive layer.