KR20050108440A - A manufacturing method of diffusing film for flat panel display - Google Patents

Abstract

The present invention relates to a method of manufacturing a light diffusing film for a flat panel display, comprising: introducing a transparent base film into a reaction chamber generating plasma by a high frequency power source applied to an electrode (S1); (S2) treating the surface of the transparent base film by injecting an inert gas into the reaction chamber and applying a predetermined power to an electrode to generate a plasma; (S3) applying a mixed solution of a semi-crystalline crystalline oligomer having a photoinitiator and a UV functional group on the surface of the plasma-treated transparent substrate film; And (S4) curing the crystalline oligomer by irradiating UV to the transparent base film to which the mixed solution is applied. According to the production method of the present invention, a light diffusing film having excellent light transmittance while uniformly diffusing incident light can be produced by a simple and economical method.

Description

A manufacturing method of diffusing film for flat panel display}

The present invention relates to a method for producing a light diffusing film used in various flat panel displays such as liquid crystal display devices.

As multimedia technologies are developed, the use of flat panel displays, such as liquid crystal displays, has been expanded from notebook computer monitors to desktop computer monitors, TVs, and the like, and thus, large screens, low power consumption, and high brightness are required. In order to meet this demand, the efficiency of the backlight unit for supplying the light source of the display must be maximized.

1 is an exploded perspective view schematically illustrating a configuration of an edge-light backlight unit in a backlight unit constituting a liquid crystal display device. Referring to FIG. 1, a conventional backlight unit 10 includes a light source 12 such as a fluorescent lamp, a light guide plate 14 for scattering and homogenizing light emitted from the light source 12, a light guide plate 14, and a liquid crystal panel. The light diffusing film 18 disposed between the first and second sides of the light diffusing film 18 to increase the uniformity of light incident on the liquid crystal panel 16 and the light guide plate 14 therebetween. One or two pieces of reflecting plate 20 to prevent exposure to the outside of the light generated from 12 and changing the path of the light emitted from the light diffusing film 18 and deriving the brightness of the light. A prism sheet 22 and a protective sheet 24 for protecting the prism sheet 22 are provided. As shown in FIG. 2, the light diffusion film 18 used in the backlight unit 10 is a light diffusion coating film made of a transparent resin in which light diffusion beads 17 are dispersed on a surface of the transparent base film 19. 21 is formed (FIG. 2A), or the light diffusing beads 17 are dispersed in the transparent base film 19.

In the above-described backlight unit, in order to maximize the efficiency of the backlight unit, the light diffusing film should be excellent in light transmittance while uniformly diffusing the incident light. In order to provide sufficient light diffusivity of a light diffusing film using a conventional light diffusing bead, the density of the light diffusing bead must be increased.Increasing the density of the light diffusing bead also increases the scattering and diffuse reflection of light by the light diffusing bead and transmits the light. The amount of light lost increases. That is, since the light transmittance through the light diffusion film is reduced, it is difficult to implement a flat panel display showing high brightness.

Therefore, there is an urgent need for a light diffusion film that is excellent in light diffusivity and capable of maintaining high light transmittance.

The technical problem to be achieved by the present invention is to solve the above problems and to provide a method of manufacturing a light diffusing film for flat panel display that can be produced in a simple and economical way to uniformly diffuse the incident light and excellent light transmittance. It is.

In order to achieve the above technical problem, a method of manufacturing a light diffusing film for flat panel display according to the present invention comprises the steps of: injecting a transparent base film into a reaction chamber for generating a plasma by a high frequency power applied to the electrode (S1); (S2) treating the surface of the transparent base film by injecting an inert gas into the reaction chamber and applying a predetermined power to an electrode to generate a plasma; (S3) applying a mixed solution of a semi-crystalline crystalline oligomer having a photoinitiator and a UV functional group on the surface of the plasma-treated transparent substrate film; And (S4) curing the crystalline oligomer by irradiating UV to the transparent base film to which the mixed solution is applied.

Hereinafter, a method of manufacturing a light diffusing film for flat panel display according to the present invention will be described in detail.

First, a transparent base film is introduced into a reaction chamber for generating plasma by a high frequency power source applied to an electrode (S1). 3 shows a plasma apparatus capable of plasma treating a surface of a plastic transparent film. It is to be understood that the present invention is not limited to the configuration of the illustrated plasma device, and that various modifications can be made within the scope of achieving the object of the present invention.

Referring to the illustrated plasma reactor, a first electrode 31, which is one of the parallel plate electrodes, is installed in the reaction chamber 30, and a second electrode 32 is installed on the upper portion opposite thereto. The object to be processed 100 is placed on the electrode 31. The to-be-processed object 100 may be used as a transparent base film as long as the support having excellent light transmittance. Specifically, a film made of polycarbonate, polypropylene, polyethylene terephthalate, polyethylene, or the like may be used. The thickness of the base film to be used can be adjusted according to the application. When used with a light guide plate in a general backlight, it is preferable to use a transparent base film between 0.5 mm and 200 mm, and the light guide plate as in a direct light type backlight. When not using, it is preferable to use a transparent substrate film (sheet) of 1.5 mm to 3 mm.

The first electrode 31 is connected to the drawing electrode 33 extending out of the reaction chamber 30, and the drawing electrode 33 is connected to the power source 35 again to receive a high frequency power source for generating plasma. . The lead electrode 33 is insulated from the reaction chamber 30 by the insulating unit 34. In addition, a second electrode is provided on the side opposite to the first electrode 31 in the reaction chamber 30 to excite an inert gas in the reaction vessel 30 to generate a plasma as described later. In the reaction chamber 30, an inlet 36 for introducing an inert gas for plasma generation and an outlet 37 for discharging the reacted gases are formed.

Subsequently, an inert gas such as Ar or Ne is introduced into the reaction chamber 30 and a predetermined power is applied to the electrode to generate a plasma to treat the surface of the transparent base film (S2). The surface of the plasma-treated transparent base film is removed foreign matter present on the surface, and in the subsequent process to allow the crystallization during the photocuring of the crystalline oligomer applied to the surface of the plasma-treated transparent base film to proceed well. If the photocuring process is performed by coating a crystalline oligomer on the surface of the transparent base film not subjected to plasma treatment, crystallization does not occur easily.

Then, a mixture of a photoinitiator and a semi-crystalline crystalline oligomer having a UV functional group is coated on the surface of the plasma-treated transparent substrate film (S3). Here, the "UV functional group" means a functional group that reacts to allow the polymerization of the crystalline oligomer to proceed by the action of a photoinitiator by UV irradiation. Examples of such UV functional groups include acrylates and oxides. can do. When applying the radical polymerization may include an acrylate functional group, when applying a cationic polymerization, it is preferable to include an oxide functional group. In addition, the "semicrystalline state" refers to a haze (cloudy state) when observed with the naked eye at 40% or more, and the "crystalline oligomer" means, such as ethylene, acetal, ester, propylene, glycol, It refers to an oligomer in which periodic repeating units exist in the molecular structure of the oligomer so as to form a crystallized polymer during polymerization. Examples of the crystalline oligomer in the semi-crystalline state having such a UV functional group may include tripropylene glycol diacrylate, but are not limited thereto. The preferred thickness of the applied liquid mixture is 1 µm to 20 µm.

Subsequently, UV is irradiated to the transparent base film coated with the mixed solution to cure the crystalline oligomer (S4). The wavelength of UV selects an appropriate region depending on the type of photoinitiator applied.

In the light diffusing film 18 for flat panel display manufactured as described above, a crystalline polymer light diffusion film 40 is formed on the surface of the transparent base film 19 (see FIG. 4). It has a semicrystalline structure having a micron crystalline domain size, and the incident light is refracted at a predetermined angle relative to the crystal direction of each crystalline region. That is, there is little scattering or diffuse reflection of the incident light, and the light loss is minimized by simply refracting only the light path in various directions. Therefore, according to the manufacturing method of the present invention, it is possible to easily and economically produce a light diffusing film for display and a light diffusing film using conventional light diffusing beads with a light diffusivity that is comparable to each other, and that the light transmittance is remarkably high.

In the manufacturing method of the light-diffusion film for display of the present invention, the above-mentioned crystalline polymer light-diffusion film may be separately formed and peeled on a support, and then adhered to the transparent base film surface using an adhesive. That is, a support (polycarbonate film, etc.) is introduced into a reaction chamber that generates plasma by a high frequency power source applied to the electrode, and the surface of the support is plasma treated, and then the photoinitiator and UV are applied to the surface of the plasma treated support. The mixed solution mixed with the crystalline oligomer in the semi-crystalline state having the functional group is applied and irradiated with UV to cure the crystalline oligomer. Upon obtaining the support having the crystalline polymer light diffusion film formed on the surface according to the curing reaction, the crystalline polymer light diffusion film is peeled off from the support, and the peeled crystalline polymer light diffusion film is adhered to the transparent base film with an adhesive including an adhesive film. The light-diffusion film for flat panel displays can be manufactured by the method.

Hereinafter, examples will be described in detail to help understand the present invention. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Comparative Examples 1 to 4

As shown in FIG. 2A, a conventional light diffusing film having an optical acid coating film in which light diffusing beads are dispersed in a transparent resin, that is, D-series of Tsujiden Corporation was purchased and evaluated. As the transparent base film, a polyethylene terephthalate (PET) film having a thickness of 120 to 140 μm was used. Haze and light transmittance of the light diffusing film depended on the diameter of the light diffusing beads, which are described in Table 1 by measuring the diameter of the light diffusing film used in Comparative Examples 1 to 4 and the haze and light transmittance of the light diffusing film. . Haze is a value indicating the magnitude of light diffusivity.

Examples 1-4

As the transparent base film, a polycarbonate film having a thickness of 125 μm was used. After the transparent base film was introduced into the plasma reactor and made into a vacuum state, Ar gas was added at 50 sccm (Standard Cubic Centimeter per Minute (0 ° C., 1 atm)) while maintaining the vacuum in the chamber at 10 ^-3 torr. 1Kw of power was applied to the electrode to generate plasma, and plasma treatment was performed for 5 minutes.

Subsequently, a mixed solution obtained by mixing tripropylene glycol diacrylate as a crystalline oligomer and hydroxy cyclohexyl phenyl ketone as a photoinitiator at a weight ratio of 19: 1 was applied to the plasma-treated transparent base film surface with a thickness of 3 μm.

Thereafter, the coated film was irradiated with UV having a wavelength of 300 to 350 nm to prepare a light diffusing film having a crystalline polymer light diffusing layer formed on a transparent base film surface. In Table 2, haze and light transmittance of the light diffusing film according to the examples were measured and described.

Light diffusion film bead diameter (average, μm) haze (%) Light transmittance (@ 550nm) Comparative Example 1 (Tsujiden-D125) 22.1 89.6 78.23 Comparative Example 2 (Tsujiden-D120Y) 12.2 83.77 85.62 Comparative Example 3 (Tsujiden-D124) 25.5 91.67 75.42 Comparative Example 4 (Tsujiden-D127) 36.3 90.26 69.17

Light diffusion film Thickness of the light diffusion layer Average domain size (㎛) haze (%) Light transmittance (@ 550nm) Example 1 6.4 20.2 89.05 88.40 Example 2 5.2 16.6 85.02 89.67 Example 3 3.5 14.2 83.23 88.44 Example 4 2.6 12.5 80.04 90.14

Referring to the results of Table 1 and Table 2, the conventional light diffusing films according to Comparative Examples 1 to 4 using the light diffusing beads did not have a large light transmittance, and it can be seen that the light transmittance decreases as the haze increases. .

On the other hand, according to the present invention, the light diffusing films of Examples 1 to 4 in which the crystalline polymer light diffusing layer was formed on the surface of the transparent substrate film had a very high light transmittance of 88% or more regardless of the domain size, and the light diffusing degree was also high. It can be seen that good.

As described above, the light diffusing film for flat panel display manufactured according to the manufacturing method of the present invention hardly scatters or diffuses the incident light, and minimizes light loss by simply refracting only the light path in various directions. Let's do it. Therefore, according to the manufacturing method of the present invention, it is possible to easily and economically produce a light diffusing film for display and a light diffusing film using conventional light diffusing beads with a light diffusivity that is comparable to each other, and that the light transmittance is remarkably high.

1 is an exploded perspective view schematically showing the configuration of a typical edge-light backlight unit;

2 (a) and 2 (b) are enlarged cross-sectional views of the portion “A” of FIG. 2,

3 is a cross-sectional view showing an example of a plasma apparatus capable of treating the surface of a transparent base film in the manufacturing method of the present invention;

4 is a cross-sectional view of the light diffusing film formed according to the manufacturing method of the present invention.

Claims (4)

(S1) injecting a transparent base film into the reaction chamber for generating a plasma by a high frequency power applied to the electrode; (S2) treating the surface of the transparent base film by injecting an inert gas into the reaction chamber and applying a predetermined power to an electrode to generate a plasma; (S3) applying a mixed solution of a semi-crystalline crystalline oligomer having a photoinitiator and a UV functional group on the surface of the plasma-treated transparent substrate film; And (S4) a step of curing the crystalline oligomer by irradiating UV to the transparent base film coated with the mixed solution; a manufacturing method of a light diffusing film for a flat panel display comprising a. (S1) injecting a support into the reaction chamber for generating a plasma by a high frequency power applied to the electrode; (S2) treating the surface of the support by injecting an inert gas into the reaction chamber and applying a predetermined power to an electrode to generate a plasma; (S3) applying a mixed solution of a semi-crystalline crystalline oligomer having a photoinitiator and a UV functional group on the surface of the plasma-treated support; (S4) curing the crystalline oligomer by irradiating UV to the support to which the mixed solution is applied to obtain a support having a crystalline polymer light diffusion film formed on its surface; (S5) peeling the crystalline polymer light diffusion film from the support; And (S6) bonding the peeled crystalline polymer light diffusion film to the transparent base film with an adhesive; a manufacturing method of a light diffusing film for a flat panel display comprising a. The method of claim 1, wherein the transparent base film is made of any one polymer selected from the group consisting of polycarbonate, polypropylene, polyethylene terephthalate, and polyethylene. . The method for producing a light diffusing film for flat panel display according to claim 1 or 2, wherein the crystalline oligomer is tripropylene glycol diacrylate.