KR100446044B1 - protecting film for prism - Google Patents

Abstract

In the prism protective film for liquid crystal display, the composition which disperse | distributed the light-diffusion agent of average particle diameter 3-30 micrometers in binder resin in one surface of the synthetic resin film of thickness 100-200 micrometers, and thickness is 10-50 micrometers, and surface roughness 0.05- A light diffusing layer having a thickness of 5 μm was formed, and on the other side of the synthetic resin film, a diffusion backing layer having a thickness of 1 μm to 10 μm and a surface roughness of 0.001 μm to 1.0 μm with a composition in which a light diffusing agent having an average particle diameter of 1 μm to 5 μm was dispersed in a binder resin. It relates to a formed prism protective film.

The prism protective film for liquid crystal displays of this invention is excellent in light diffusivity and the shielding against prism peak, and has the effect which is excellent in workability, without causing prism peak and blocking.

Description

Prism protective film {protecting film for prism}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism protective film used in a flat panel display such as a liquid crystal display (hereinafter referred to as LCD) and a light emitting diode (hereinafter referred to as LED).

Unlike other flat panel display methods, the liquid crystal display method uses a liquid crystal itself, and thus an additional light emitting device is required to improve the brightness of the display screen. Such light emitting devices include a front light method and a back light method, and the backlight method is a light source of a backlight unit (Back Light Unit) attached to the back of the display device as shown in FIG. The light generated from 1) is led to the opposite side through the light guide plate 2, and is reflected to a light reflecting film 2 such as a metal deposited film or an opaque white reflecting film so that light is emitted to the front surface and at the same time, the prism 5 This is an indirect lighting method that improves the brightness of the display screen using. In such a backlight method, high luminance can be expressed using the light diffusing film 4 and the prism 5.

The prism used in the backlight method is configured by regularly arranging fine prisms on the surface of a thin synthetic resin sheet, and the prism peak is formed of an acute angle and may be easily damaged even from a small impact from the outside. There is a need for a prism protective film that can protect the surface of the prism.

Since the prism protective film should be high in brightness and excellent in shielding against prism peaks after being installed on the prism sheet, it must be processed through various processes such as printing, cutting, and processing, and should be excellent in workability. Various properties are required that must not themselves damage the surface of the prism.

Therefore, there is a need for the development of a prism protective film having low surface roughness without impairing display screen brightness, providing shielding against prism peaks, and no blocking with prism peaks.

In the present invention, the shielding property against the prism peak means the degree to which the prism peak is visible by visually observing the prism protective film on the prism sheet of the liquid crystal backlight unit.

At this time, it is determined that the prism peak is not visible, but the prism peak is not shielded, and the prism peak itself is displayed on the final screen as it is, so that the uniformity of the image is reduced.

In addition, the prism peak and blocking refers to a phenomenon in which the prism protection film is in close contact with the prism peak. When the prism protection film is in close contact with the prism peak, light interference occurs at the interface, resulting in a rainbow-colored stain. .

An object of the present invention is to provide a prism protective film having excellent light diffusivity and shielding against prism peaks and excellent workability without causing prism peaks and blocking. The inventors formed a light diffusion layer composed of a light diffusing agent and a binder resin having an average particle diameter of 3 to 30 μm on one surface of a synthetic resin film having a thickness of 100 to 200 μm and having a surface roughness of 0.05 to 5 μm and having a surface roughness of 0.05 to 5 μm. Another aspect of the present invention is to form a prism protective film by forming a diffusion backing layer composed of a light diffusing agent and a binder resin having an average particle diameter of 1 ~ 5㎛ 1 ~ 10㎛ thickness and a surface roughness of 0.001 ~ 1.0㎛ It was confirmed that the prism protective film can be achieved to achieve the present invention was completed.

1 is a diagram illustrating a backlight type LCD structure and a traveling direction of light therein.

Explanation of symbols on main parts of drawing-

1: light source 2: light reflecting film

3: light guide plate 4: light diffusing film

5: prism 6: prism protective film

According to the present invention, one side of the substrate diffuses light incident from the light source to provide high luminance and shielding against prism peaks, and to improve surface roughness (Ra) to improve processability such as printing, cutting, and hole processing. ) Is provided so that the light diffusing layer is in the range of 0.05 to 5.0 μm, and on the other side, the surface roughness (Ra) is 0.001 so as not to directly block the prism peak and to prevent damage to the prism during vibration. It is characterized by providing a diffusion back so as to be in the range of 1.0 to 1.0㎛.

When the surface roughness of the light diffusing layer is less than 0.05 µm, the workability is very poor in printing, cutting and hole processing, so that the product yield is notably reduced, the light diffusivity is lowered, and the shielding against prism peaks is insufficient. . In addition, when the surface roughness of the light diffusion layer is more than 5㎛ there is a problem that the light transmittance is lowered and the brightness is lowered eventually.

In the case of the diffused back layer, when the surface roughness is less than 0.001 μm, blocking with a prism peak occurs, causing a rainbow caused by interference of light, resulting in an uneven part of the image. In addition, when the surface roughness of the diffusion backing layer exceeds 1.0 μm, the prism peak due to the irregularities of the diffusion backing surface is damaged during vibration.

Hereinafter, the present invention will be described in detail.

As the base film used in the present invention is required to have high transparency, a film made from a high transparent polymer resin such as polyolefin resin, polyester resin, polyacrylic resin, polycarbonate resin, or the like can be used.

Among them, polyethylene terephthalate (hereinafter referred to as PET) film having high transparency, good mechanical strength and excellent workability and strong resistance to light and heat emitted from the backlight unit is most preferred.

In the present invention, as the light diffusing agent of the light diffusing layer, an inorganic or organic light diffusing agent having an average particle diameter in the range of 3 to 30 μm may be used alone or as a mixture of two or more kinds. Examples of the inorganic light diffusing agent particles include silica, zirconia, and carbonic acid. Calcium, barium sulfate, titanium oxide, and the like, and examples of the organic light diffusing agent particles include styrene, melamine formaldehyde, benzoguanamine formaldehyde, benzoguanamine melamine formaldehyde, propylene, ethylene, silicone, urethane, and methyl (meth Homopolymers or copolymers obtained by using monomers such as acrylates, and the like, and those in the monodisperse or polydisperse forms.

As the light diffusing agent of the diffusion back layer, the above light diffusing agent having an average particle diameter of 1 to 5 µm is used.

Moreover, as an organic binder resin used for this invention, for example

Thermosetting or ultraviolet curing such as polyvinyl resin, acrylic resin, polyester resin, styrene resin, alkyd resin, amino resin, polyurethane resin, epoxy resin, and the like.

In forming the light diffusion layer and the diffusion backing layer using the light diffusing agent and the binder resin in the present invention, it is necessary to adjust the use ratio of the light diffusing agent and the binder resin.

When the use ratio of the binder resin is too low, the adhesion to the base film is bad, and when the use ratio of the binder resin is too high, the light diffusivity and the uniformity of the brightness is inferior.

The present inventors have sufficient adhesion to the base film when the light diffusing layer is composed of 50 to 150% by weight of the light diffusing agent to the binder resin and the diffusing back layer is composed of 1 to 20% by weight of the light diffusing agent to the binder resin. It can be seen that it is possible to maintain excellent brightness and uniformity of brightness while maintaining.

Method for producing a prism protective film according to the object of the present invention is as follows.

First, the light diffusing layer or the diffusion backing layer composition including the light diffusing agent particles and the binder resin is used in the binder resin by using a disperser such as a bead mill using glass or zirconium beads or a roll mill using horizontal or vertical rolls. The diffusing agent particles are dispersed to be uniformly distributed.

At this time, a dispersant containing a modified polysiloxane or polycarboxylic acid is used in order to make the dispersion better.

A binder resin solution in which the light diffusing agent particles are uniformly dispersed is applied onto a base film, preferably a PET film, and then dried to form a prism protective film.

The method of applying the light diffusing layer or the diffusion back layer composition to the base film may be adopted without particular limitation as long as it is a method commonly known in the art, and for example, an air knife according to the material and shape of the base film. ), Gravure, Meyer Bar, reverse roll or spray (spray) method can be used arbitrarily selected.

Hereinafter, an Example is given and this invention is demonstrated concretely.

Example 1

The light diffusing layer composition of the prism protective film having the following composition was circulated milled for about 60 minutes using a zirconium bead mill so as to sufficiently disperse the light diffusing agent in the binder resin, and then a PET film having a thickness of 125 μm using a 0.4 mm mayer bar ( A brand name: HPE-125 (manufactured by Teijin Co., Ltd., Japan) was applied, and dried at 120 ° C. for 3 minutes to form a light diffusion layer having a thickness of 30 μm. In addition, a prism protective film was manufactured by forming a diffusion backing layer having a thickness of 5 μm on the opposite side using the same manufacturing method as the light diffusion layer (only using 0.15 mm Meyer Bar). Thus, the properties of the prepared prism protective film was evaluated and shown in the following [Table 1].

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 10 µm; trade name MX-1000, manufactured by Sokken Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 3 µm; trade name MX-300, manufactured by Japan Soken Company)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 2

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 45 μm and a thickness of 5 μm of a diffusion back surface was manufactured using the light diffusion layer and the diffusion back composition as described below. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 25 mu m; trade name MX-2500, manufactured by Sokken Japan)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 3 µm; trade name MX-300, manufactured by Japan Soken Company)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 3

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 3 μm of a diffusion back was prepared using the light diffusion layer and the diffusion back composition as described below. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 10 µm; trade name MX-1000, manufactured by Sokken Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 1.8 mu m; trade name MX-180, manufactured by Sokken Japan)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 4

Using the same device and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 5 μm of a diffusion back surface was manufactured using the light diffusion layer and the diffusion back composition as follows. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethylmethacrylate polydisperse light diffusing agent 17 〃

(Average particle size 12 µm; trade name MBX-12, manufactured by Sekisui Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion 2 〃

(Average particle size 3 µm; trade name MX-300, manufactured by Japan Soken Company)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 5

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 3 μm of a diffusion back was prepared using the light diffusion layer and the diffusion back composition as described below. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethyl methacrylate polydisperse light diffusing agent 17 〃

(Average particle size 12 mu m; trade name MBX-12, manufactured by Sekisui, Japan)

Polyester resin 13 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 1.8 mu m; trade name MX-180, manufactured by Sokken Japan)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 6

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 3 μm of a diffusion back was prepared using the light diffusion layer and the diffusion back composition as described below. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethylmethacrylate polydisperse light diffusing agent 17

(Average particle size 12 µm; Brand Name-12, manufactured by Sekasui Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethyl methacrylate polydisperse light diffusing agent 2 〃

(Average particle size 2 µm; trade name MA-1002, manufactured by Nippon Catalyst Co., Ltd.)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Example 7

Using the same device and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 5 μm of a diffusion back surface was manufactured using the light diffusion layer and the diffusion back composition as follows. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 30.5 parts by weight

Toluene 30.5 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 10 µm; trade name MX-1000, manufactured by Sokken Co., Ltd.)

Polyester resin 18 〃

(Binder resin, brand name Niporan 125, product of Nippon Polyurethane company)

Hardener 4 〃

(Product name coronate HX, product of Nippon Polyurethane company)

Diffusion Back Layer Composition

Methyl ethyl ketone 33.5 parts by weight

Toluene 33.5 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 3 µm; trade name MX-300, manufactured by Japan Soken Company)

Polyurethane Resin 26

(Binder resin, brand name Niporan 125, product of Nippon Polyurethane company)

Hardener 5 〃

(Product name coronate HX, product of Nippon Polyurethane company)

Example 8

A prism protective film having a thickness of 30 μm and a thickness of 5 μm of a diffusion back layer by irradiating 300mj / sq.cm of ultraviolet rays with the light diffusion layer and the diffusion back composition as follows using the same apparatus and method as in Example 1 Was prepared. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Isopropyl alcohol 57.5 parts by weight

n-butyl acetate 8.2 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 10 µm; trade name MX-1000, manufactured by Sokken Co., Ltd.)

Binder Resin 17.3

(Uni-17K, manufactured by Japan DIC Corporation)

Diffusion Back Layer Composition

Isopropyl alcohol 64.7 parts by weight

n-butyl acetate 9.3 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 3 μm; trade name MX-300, manufactured by Soken, Japan)

Polyester resin 24 〃

(Uni-17K, manufactured by Japan DIC Corporation)

Comparative Example 1

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 25 μm and a thickness of 5 μm of a diffusion back surface was manufactured using the light diffusion layer and the diffusion back composition as follows. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Melamine-formaldehyde polydisperse light diffuser 17 〃

(Average particle size 0.3 µm; trade name Epostar S3, manufactured by Nippon Catalyst Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 3 µm; trade name MX-300, manufactured by Japan Soken Company)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

In this comparative example, the average particle diameter of the light diffusing agent constituting the light diffusing layer was so small that the surface roughness was too low to obtain good shielding and workability.

Comparative Example 2

Using the same apparatus and method as in Example 1, a prism protective film having a thickness of 30 μm and a thickness of 17 μm of a diffusion back was prepared using the light diffusion layer and the diffusion back composition as described below. The properties of the prism protective film thus produced were evaluated and shown in the following table.

Light Diffusion Layer Composition

Methyl ethyl ketone 35 parts by weight

Toluene 35 〃

Polymethyl methacrylate monodisperse light diffusing agent 17 〃

(Average particle size 10 µm; trade name MX-1000, manufactured by Sokken Co., Ltd.)

Polyester resin 13

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

Diffusion Back Layer Composition

Methyl ethyl ketone 40 parts by weight

Toluene 40 〃

Polymethylmethacrylate Monodisperse Light Diffusion Agent 2 〃

(Average particle size 15 µm; trade name MX-1500, manufactured by Sokken Japan)

Polyester resin 18 〃

(Binder resin, brand name Byron 200, product of Toyobo, Japan)

As a comparative example, when the average particle diameter of the light diffusing agent constituting the diffusion back layer is too large and the illuminance is increased, it was possible to diffuse the result of damaging the prism during vibration.

<Evaluation method>

Surface roughness

The surface roughness of the light diffusion layer and the diffusion back surface was measured using a surface roughness meter (model name 2D manufactured by Toyo Seiki Co., Ltd., Japan).

Luminance

Place the prism protective film prepared in Example 1-8 and Comparative Example 1-2 on the prism sheet of the liquid crystal backlight unit, and use the luminance meter (Model BM-7 of Topcon Japan) to obtain the luminance at the center of the liquid crystal backlight unit. Was measured.

Shielding

The prism protective films produced in Example 1-8 and Comparative Example 1-2 were placed on the prism sheet of the liquid crystal backlight unit, and when the prism peaks were visible to the naked eye, it was judged to be defective.

Processability

The prism protective films produced in Examples 1-8 and Comparative Examples 1-2 were subjected to printing, cutting, and hole processing, and then surface conditions were observed.

Prism damage

Place the prism protective film prepared in Example 1-8 and Comparative Example 1-2 on the prism sheet of the liquid crystal backlight unit, perform vibration test up, down, left, and right, and then observe whether the prism peak is damaged. If not, it was determined to be good.

Thickness (㎛) Surface Roughness (Ra, ㎛) Luminance (cd / ㎡) Shielding Machinability Prism damage Light diffusion layer Diffusion Backing Layer Light diffusion layer Diffusion Backing Layer Example 1 30 5 0.5 0.03 1834 Good Good Good Example 2 45 5 1.3 0.03 1840 Good Good Good Example 3 30 3 0.5 0.02 1839 Good Good Good Example 4 30 5 0.9 0.03 1832 Good Good Good Example 5 30 3 0.9 0.02 1835 Good Good Good Example 6 30 3 0.9 0.04 1835 Good Good Good Example 7 30 5 0.5 0.03 1837 Good Good Good Example 8 30 5 0.5 0.03 1834 Good Good Good Comparative Example 1 25 5 0.01 0.03 1624 Bad Bad Good Comparative Example 2 30 17 0.5 1.2 1758 Good Good Bad

As can be seen from the results of the present invention, when the surface roughness of the light diffusion layer is in the range of 0.05 to 5 μm and the surface roughness of the diffusion back surface is in the range of 0.001 to 1.0 μm according to the present invention (Example 1-8) Not only does it have good luminance, it also has excellent shielding against prism peaks, and it is easy to print, cut, and cut holes. Also, it does not cause damage to prism peaks even in up, down, left, and right vibrations. It is suitable for use as a display element, especially a prism protective film for a display screen using a liquid crystal display or an LED lamp.

On the contrary, when the surface roughness of the light diffusing layer and the surface roughness of the diffusing back surface fall outside the above ranges (Comparative Example 1-2), the light efficiency is poor, the luminance is insufficient, and the shielding and workability of the prism peak are poor. Prismatic peak damage during vertical, horizontal, left and right oscillations occurs and is not suitable for use for the purposes of the present invention.

The prism protective film for liquid crystal displays of this invention is excellent in light diffusivity and the shielding against prism peak, and has the effect which is excellent in workability, without causing prism peak and blocking.

Claims (4)

In the prism protective film for liquid crystal displays, a composition in which a light diffusing agent having an average particle diameter of 3 to 30 μm is dispersed in a binder resin on one surface of a synthetic resin film having a thickness of 100 to 200 μm, the thickness is 10 to 50 μm, and the surface roughness is 0.05 to 5 μm. A prism having a light diffusing layer formed on the other surface of the synthetic resin film and having a diffused backing layer having a thickness of 1 to 10 μm and a surface roughness of 0.001 to 1.0 μm with a composition in which a light diffusing agent is dispersed in a binder resin with an average particle diameter of 1 to 5 μm. Protective film. The prism protective film according to claim 1, wherein the synthetic resin film is a synthetic resin film made of polyethylene terephthalate, polycarbonate, or polyacrylic resin. The method of claim 1, wherein the light diffusing agent is an inorganic particle of silica, zirconia calcium carbonate or calcium sulfate or styrene, melamine formaldehyde, benzoguanamine formaldehyde, benzoguanamine melamine formaldehyde, propylene, ethylene, silicone, urethane, methyl meth A prism protective film which is an organic particle obtained by superposing | polymerizing an acrylate monomer, and whose binder resin is a polyester resin, a polyurethane resin, an acrylic resin, an alkyd resin, or an epoxy resin. The prism protective film according to claim 1, wherein the light diffusing layer is composed of 50 to 150% by weight of the light diffusing agent relative to the binder resin, and the diffusing back layer is composed of 1 to 20% by weight of the light diffusing agent relative to the binder resin.