KR20090022312A - Diffuse-film with self-surface protection function - Google Patents

Abstract

A light diffusion film having surface protecting function is provided to reduce the manufacturing cost by using the light diffusion film with no protective film. A multilayer light diffusion film comprises a core layer(11) and a skin layer(12). The emboss pattern is molded in the surface of the skin layer. The core layer is made of the thermoplastic resin. The thermoplastic resin is the methacrylic resin, styrene resin, cycloolefin based resin, and polycarbonate. The skin layer is made of the Acryl resin. The Acryl resin is selected from the group consisting of the methylmethacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethylacrylate, propyl methacrylate, butyl acrylate, 2- ethylhexylacrylat, 2- hydroxy ethyl acrylate, 2- hydroxyproylacrylate, monoglycerol acrylate, acrylamide, metacryl amide, the alicyclic Acryl resin and their mixture.

Description

Light Diffusion Film with Surface Protection {DIFFUSE-FILM WITH SELF-SURFACE PROTECTION FUNCTION}

The present invention relates to a light diffusing film having a surface protection function by itself without a separate protective film.

In modern display systems, for example liquid crystal displays (LCDs), it is common to have a diffuser film, and a light diffuser film for a liquid crystal display (LCD) is commonly used to send or diffuse light in a backlight unit. Light diffusing film refers to a wide range of products used to maintain the overall light transmittance while uniformly distributing light to the observer and concealing defects caused by light guiding.

In general, such a light diffusion film for a liquid crystal display device requires a protective film to prevent minute scratches occurring during the manufacturing process and scratches that may occur before post-processing.

For example, in the case of a single layer polycarbonate light diffusing film, an embossed pattern is applied to a surface through an extrusion process and a polishing roll, and then a process of attaching a protective film for surface protection is required. This is because polycarbonate resin is excellent in impact resistance, transparency, and heat resistance, but its surface hardness and scratch resistance are not good.

In order to improve the surface properties of the film, a method of coating a heat curable resin or a light curable resin on the film surface has been studied, but these methods did not show satisfactory results in terms of cost reduction or productivity improvement.

There is a need for a light diffusing film that does not require a protective film at present for the cost of using such a protective film, the problem of surface damage of the counterpart member to which the protective film is in contact, and the simplification of the manufacturing process.

An object of the present invention is to provide a light diffusion film that does not require a protective film by laminating a skin layer having a constant embossed pattern on at least one side of the core layer.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, 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,

The multilayer light-diffusion film containing the core layer and the skin layer in which the embossed pattern is formed in the surface can be presented.

In addition, according to another aspect of the present invention,

The manufacturing method of the multilayer light-diffusion film which laminated | stacked the core layer and the skin layer in which the embossed pattern is formed by coextrusion molding can be proposed.

Hereinafter, the present invention will be described in more detail. First, the layer constituting the multilayer light diffusing film of the present invention and its components will be described with reference to the drawings.

Core layer

The resin constituting the core layer 11 of the multilayer light diffusing film of the present invention is not particularly limited as long as it is a thermoplastic resin.

Examples thereof include polyacetal resin, acrylic resin, polycarbonate resin, styrene resin, polyester resin, vinyl resin, polyphenylene ether resin, polyolefin resin, acrylonitrile-butadiene-styrene copolymer resin, polyarylate Resin, polyether sulfone resin, polyphenylene sulfide resin, and fluorine resin.

Preferably, in consideration of physical properties and the like of the thermoplastic resin composition, transparent high molecular resins such as methacrylic resins, styrene resins, cycloolefin resins, and polycarbonate resins can be used. Moreover, these resin can also be mixed and used.

Most preferably, an aromatic polycarbonate resin having a weight average molecular weight in the range of 15,000 to 40,000 can be used.

In the present invention, the thickness of the core layer can be varied depending on the use, it is preferable to form so as to be 36 ~ 445 ㎛. If the thickness of the core layer is smaller than 36 μm, the total thickness of the light diffusing film to be produced is too thin, and curling is likely to occur, and impact resistance may be reduced. If the thickness of the core layer exceeds 445 μm, the total thickness of the light diffusing film to be manufactured is thick, which increases the thickness of the backlight unit and is not desirable for the thinning demand of the liquid crystal display device.

Skin layer

The skin layer 12 is laminated to protect the surface of the core layer 11, and may be laminated on one side of the core layer as shown in FIG. 1A or on both sides of the core layer as shown in FIG. 1B. As for the component which forms a skin layer, acrylic resin is preferable among thermoplastic resins. By way of example, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate and butyl methacrylate; Acrylic esters such as methyl acrylate, ethyl acrylate, propyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate; Esters containing hydroxy groups such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and monoglycerol acrylate; Acrylamide, methacrylamide, alicyclic acrylic resin, etc. are mentioned, These resin can also be used individually or in mixture of 2 or more. As said acrylic resin, it is more preferable to use methyl methacrylate and methyl acrylate. Also most preferably, polymethylmethacrylate (PMMA) resins having a weight average molecular weight in the range of 30,000 to 300,000 can be used.

The skin layer of the present invention is embossed to have a uniform surface roughness for the expression of excellent optical properties as well as surface protection function, the embossed pattern may be formed in a uniform shape or have an amorphous pattern It may be.

In the present invention, the skin layer is preferably formed so that the thickness is 5 ~ 50 ㎛, 40% or less of the total film thickness. If the thickness of the skin layer is less than 5 μm, due to the interlayer thickness difference of the light diffusing film to be produced not only the interface unstable phenomenon, but also does not perform the surface protection function properly. On the other hand, when the thickness of the skin layer exceeds 50 ㎛ or more than 40% of the total thickness, the surface hardness and scratch resistance of the light diffusing film to be produced may be improved, but the impact resistance may be lowered.

additive

In the resin forming the core layer or skin layer of the present invention, additives such as talc, silica, mica, and alumina may be used, and when the inorganic filler is added, physical properties such as mechanical strength and heat deformation temperature may be improved. have. In addition, UV absorbers, heat stabilizers, antioxidants, flame retardants, lubricants, dyes and / or pigments may be further included. These additives are known to those skilled in the art, their amount or use.

Manufacturing method

In order to manufacture the light-diffusion film provided with the core layer and skin layer of this invention, the co-extrusion shaping | molding method which has a polishing roll to which the embossed pattern was provided is used. Referring to FIGS. 1 and 2, the resin constituting the core layer and the resin constituting the skin layer are melted and kneaded in each of the extruders 21 and 22 and then supplied to the feed block dyna multi manifold die 23. . By discharging this to the cooling rolls 25, 26, and 27 through the die 24, the multilayer light-diffusion film of this invention in which the skin layer 12 which has an embossed pattern was laminated | stacked on at least one surface of the core layer 11 was obtained. Manufacture.

Skin layer 12 having an embossed pattern in the present invention, due to the embossed shape of the surface, to give a uniform roughness to the surface of the light diffusion film, which has the effect of achieving a high haze and total light transmittance.

For the purpose of expressing such optical properties, in order to form a certain level of embossed pattern, the present invention uses sand blasting treatment to have a film embossed shape on the surface of the cooling roll 26 used in the extrusion process of the film. Although the method of clamping with the roll 25 is employ | adopted, it is not limited to this, The rubber roll 25 can also be given a pattern or emboss shape by methods, such as sandblasting or surface coating.

FIG. 1A shows a light diffusing film having a two-layer structure in which the skin layer 12 is laminated on one side of the core layer 11, and FIG. 1B shows that the skin layer 12 is on both sides of the core layer 11. The light-diffusion film which has a laminated 3-layered structure is shown.

It is preferable that the total thickness (sum of the thickness of a core layer and the thickness of a skin layer) of the said light-diffusion film is 60-450 micrometers. If the thickness is less than 60 μm, curling is liable to occur because the thickness is too thin. If the thickness is more than 450 μm, the thickness of the backlight unit becomes large and it is difficult to satisfy the thinning demand of the liquid crystal display.

In addition, the thickness of the skin layer 12 is laminated in the range of 5 ~ 50 ㎛ on the basis of the cross-section, it is good not to exceed 40% of the total film thickness (sum of the thickness of the core layer and the skin layer thickness).

 An object of the present invention is to provide a light diffusion film that does not require a protective film by laminating a skin layer having a constant embossed pattern on at least one side of the core layer. Accordingly, the high cost problem caused by the use of the protective film is solved, and the production process can be simplified, thereby improving productivity.

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 here will be omitted if they are technically inferred by those skilled in the art.

Example  One

The film was manufactured by the molding machine provided with the apparatus as shown in FIG. Polymethyl meta was melt-kneaded at 270 ° C. of polycarbonate (PC) resin (Chimei, PC-110 grade) constituting the core layer in the extruder 1 (21) and skinned in the extruder 2 (22). The methacrylate (PMMA) resin (MG-5 grade from Sumitomo) was melt kneaded at 240 ° C. and then laminated on a feed block. At this time, the thickness of each resin layer was adjusted so that a polycarbonate resin layer might be 115 micrometers, and a PMMA resin layer might be 15 micrometers. The resin layer discharged through the T die was then passed between the rolls 25 and 26 to impart an embossed shape to the PMMA resin layer surface.

The T die was 600 mm wide, and the first (25), second (26), and third (27) cooling rolls used rubber rolls, sand blasted rolls, and steel rolls, respectively. The temperature of the T die was set to 250 ° C, the first, second and third roll temperatures to 100 ° C, 140 ° C and 130 ° C, respectively.

Example  2

The method of manufacturing the film was basically the same as the method of Example 1, but a film was prepared in which the thickness of the PC resin layer was 100 µm and the thickness of the PMMA resin layer was 30 µm.

Comparative example  One

The method of manufacturing the film was basically the same as the method of Example 1, but a film made of only a PC resin layer without a PMMA resin layer was prepared.

Comparative example  2

The method of manufacturing a film was basically the same as that of Example 1, but a film having a thickness of the PC resin layer of 125 μm and a PMMA resin layer of 3 μm was prepared.

Comparative example  3

The method of manufacturing the film was basically the same as the method of Example 1, but a film was prepared in which the thickness of the PC resin layer was 70 μm and the thickness of the PMMA resin layer was 60 μm.

Property evaluation test

The measurement of the surface hardness was carried out using the pencil scratch test (JIS-K-5401), and the scratch resistance measurement was performed using JIS-K-5400. Impact resistance was measured by a falling ball impact test. The method was to drop a 40 g spherical iron ball onto the specimen at a height of 50 cm and then evaluate the specimen for cracking. Good results should be such that there are no cracks in the specimen. The results are shown in Table 1.

From the above results, it can be seen that the light diffusing films of Examples 1 and 2 simultaneously exhibit excellent surface hardness, scratch resistance and impact resistance of H or higher. The film of Comparative Example 1, which was composed of only a core layer without a skin layer, had a low surface hardness and resulted in poor scratch resistance. Due to the low skin layer thickness, the film of Comparative Example 2 exhibited interfacial instability, poor thickness smoothness, low surface hardness, and poor scratch resistance. The film of Comparative Example 3 in which the thickness of the skin layer exceeds 40% of the total film thickness had good surface hardness and scratch resistance, but had poor impact resistance.

In conclusion, the multilayer light diffusing film produced according to the method of the present invention can express good optical properties while having a level of surface properties without a protective film.

While the embodiments of the present invention have been described with reference to the accompanying tables, the present invention is not limited to the above embodiments, but may be embodied in various forms, and a person of ordinary skill in the art to which the present invention pertains. It will be appreciated that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

1A is a multilayer light diffusing film having a two-layer structure, manufactured according to one embodiment of the present invention,

1B is a multilayer light diffusing film having a three layer structure, manufactured according to one embodiment of the present invention.

11: core layer

12: skin layer given the embossed pattern on the surface

2 is a schematic diagram of an extrusion process facility used to make a multilayer film according to one embodiment of the present invention.

21 extruder 1 (main extruder)

22 extruder 2 (sub extruder)

23: feed block

24: die

25: rubber roll (or sandblasted steel roll)

26: sandblasted steel rolls

27: steel roll

Claims (14)

The multilayer light-diffusion film containing a core layer and the skin layer in which the embossed pattern is formed in the surface. The multilayer light diffusing film of claim 1, wherein the core layer is made of a thermoplastic resin. The multilayer light diffusing film of claim 2, wherein the thermoplastic resin is selected from the group consisting of methacryl resin, styrene resin, cycloolefin resin, polycarbonate resin, and mixtures thereof. The multilayer light diffusing film of claim 1, wherein the skin layer is made of an acrylic resin. The method of claim 4, wherein the acrylic resin is methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl methacrylate, butyl acrylate, 2- Multilayer, selected from the group consisting of ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, acrylamide, methacrylamide, alicyclic acrylic resins and mixtures thereof Light diffusing film. The multilayer light diffusing film of claim 1 comprising at least one skin layer. The multilayer light diffusing film of claim 1, wherein the total thickness of the film is 60 to 450 μm. The multilayer light diffusing film of claim 1, wherein the skin layer has a thickness of 5 to 50 μm and is 40% or less of the total film thickness. The manufacturing method of the multilayer light-diffusion film which laminates the core layer and the skin layer in which the embossed pattern is formed in the surface by co-extrusion molding. The method for producing a multilayer light diffusing film according to claim 9, wherein the core layer is made of a thermoplastic resin selected from the group consisting of methacryl resin, styrene resin, cycloolefin resin, polycarbonate resin, and mixtures thereof. . The method of claim 9, wherein the skin layer is methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl methacrylate, butyl acrylate, 2-ethyl Hexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, acrylamide, methacrylamide, alicyclic acrylic resin and mixtures thereof. The manufacturing method of the multilayer light-diffusion film which consists of. The method of claim 9, laminated to include one or more skin layers. The method of claim 9, wherein the total thickness of the film is 60 to 450 μm. The method of claim 9, wherein the skin layer has a thickness of 5 to 50 μm and is 40% or less of the total film thickness.

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