KR100563239B1 - Transparent sheet excellent in diffuse reflection effect and scratch resistance and manufacturing method - Google Patents

Abstract

The present invention provides a transparent sheet which can be mass-produced by a simple method and excellent in diffuse reflection effect and scratch resistance of a liquid crystal display device, and separately prepared an ultraviolet curable resin composition and a silica dispersion composition, and when the two compositions are mixed with a diluent, It is an object of the present invention to provide a transparent sheet manufacturing method that can freely control the diffuse reflection effect of the transparent sheet by adjusting the mixing ratio.

The transparent sheet manufacturing method according to the present invention comprises the steps of preparing an ultraviolet curable resin composition such that the ratio of 20 to 80% by weight of the ultraviolet curable acrylic urethane resin, 0.1 to 10% by weight of the photopolymerization initiator, and 10 to 70% by weight of the solvent; Preparing a silica dispersion composition such that 20 to 80% by weight of an acrylic resin containing a hydrophilic group in the molecule, 5 to 30% by weight of silica particles, 0.1 to 5% by weight of a dispersant, and 10 to 75% by weight of a solvent; ; Mixing the ultraviolet curable resin composition and the silica dispersion composition with a diluent to form a coating solution; Applying the coating solution to any one of a high transparency and an ultraviolet ray base sheet selected from the group comprising a polyester film, a polycarbonate film, a polyacryl film, a polyamide film, or a triacetate cellulose film; And drying the coating liquid applied to the base sheet, and then irradiating ultraviolet rays to harden the coating to prepare a transparent sheet having a coating layer having a predetermined thickness.

Description

Transparent sheet excellent in diffuse reflection effect and scratch resistance and manufacturing method

The present invention relates to a transparent sheet having excellent diffuse reflection effect and scratch resistance, and to a method of manufacturing the same, and particularly to a liquid crystal display device having excellent diffuse reflection effect and scratch resistance, which can prevent glare due to reflection of external light and screen. It relates to a transparent sheet and a method of manufacturing the same.

In general, the diffuse reflection sheet serves to prevent glare caused by reflected light by scattering light incident from the outside. In particular, in the case of the diffuse reflection sheet used in the liquid crystal display device, since it is placed on the front of the liquid crystal display device, it is necessary to have a protective property against external stimulus and environmental changes. Therefore, the diffuse reflection sheet is required to have excellent scratch resistance together with the diffuse reflection characteristics.

Conventionally diffuse reflection processing workpieces include (1) mat-shaped workpieces having irregularities on the surface of the base sheet with uneven rollers to give diffuse reflection effect, (2) diffusion-type workpieces using a difference in compatibility or crystallinity of the resin, or ( 3) Workpieces made of thin coatings of inorganic compounds are known. However, in order to manufacture the workpiece of (1) of the above workpiece, the surface of the substrate sheet has to be soft, so scratch resistance is inferior to the surface of the substrate sheet, and the workpiece of (2) has the compatibility of the resin according to the temperature change and the solvent and There is a disadvantage that a change in crystallization characteristics may occur, and the workpiece of (3) is formed by forming a single layer or a multilayer inorganic thin layer on the surface of the substrate sheet according to the wavelength of light, and thus the range of the substrate sheet that can be used is limited. Since the process of thinning the inorganic material is required, additional devices are required and the manufacturing process is complicated.

Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a transparent sheet which can be mass-produced by a simple method and excellent in diffuse reflection effect and scratch resistance of a liquid crystal display device.

Another object of the present invention is to prepare a transparent sheet manufacturing method that can freely control the diffuse reflection effect of the transparent sheet by adjusting the mixing ratio of the two compositions when the UV curable resin composition and the silica dispersion composition are separately prepared by mixing the two compositions with a diluent. It is.

In order to achieve the above object, the transparent sheet according to the present invention is characterized in that a coating layer in which an ultraviolet curable resin composition and a silica dispersion composition are mixed is laminated on a base sheet.

The ultraviolet curable resin composition contains an ultraviolet curable acrylic urethane resin, a photopolymerization initiator, a solvent, and the like, and the silica dispersion composition is composed of an acrylic resin, a silica particle, a dispersant, a solvent, and the like containing a hydrophilic group in a molecule.

A diluent is also used to make a coating liquid for coating the ultraviolet curable resin composition and the silica dispersion composition on the base sheet. That is, the diluent is an organic solvent added to control the viscosity and solids content of the coating solution.

In order to manufacture the transparent sheet according to the present invention, a general solution coating method can be used as a method of applying the coating liquid obtained by mixing the ultraviolet curable resin composition, the silica dispersion composition and the diluent in an appropriate ratio on the base sheet. In other words, if the coating solution is applied using a gravure coater, reverse coater, spray coater, slot orifice coater, etc., it is possible to coat in large quantities and mass production is possible.

The coated coating liquid is cured by ultraviolet rays, and thus, by using the ultraviolet curing method, continuous line formation can be achieved, which facilitates mass production and is advantageous in terms of cost.

In addition, according to the present invention, since the UV curable resin composition and the silica dispersion composition are separately prepared, a method of mixing the two compositions is used, and thus, the diffuse reflection effect of the desired sheet can be easily controlled by adjusting the mixing ratio of these compositions. Has characteristics.

In addition, it is important to increase the dispersion stability of the silica particles contained in the silica dispersion composition so that the silica particles do not sink even after long-term storage.

The ultraviolet curable urethane resin contained in the ultraviolet curable resin composition containing the transparent sheet of the present invention is made by reacting an isocyanate monomer or a polypolymer with a polyester polyol and reacting an acrylate or methacrylate monomer containing a hydroxyl group thereto. You can get it. This acrylic urethane-based resin has a urethane bond in the molecular skeleton and at the same time has an acrylic group or an acrylate group derived from an acrylate or methacrylate monomer at any position in the molecule, preferably at the terminal of the molecule. Isocyanate monomers or prepolymers that react with the polyester polyols include isocyanate prepolymers polymerized with toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, diol or diamine and the like. Examples of the acrylate or methacrylate monomer having a hydroxyl group include 2-hydroxyethyl acrylate and 2-hydroxypropyl methacrylate. By using the above acrylic urethane resin, ultraviolet curing with respect to a resin composition becomes possible, and the cured film excellent in scratch resistance can be obtained.

In addition, the photoinitiator is used in order to increase curability among the components of an ultraviolet curable resin composition. General photoinitiators can be used, such as benzophenone, benzyl ketone, 2-chloro- thioxanthone, 2,4-diethyl- thioxanthone, benzoin ethyl ether, diethoxyacetophenone, benzyl methyl ketal, 2- Hydroxy-2-methylpropiophenone, 1-hydroxy-cyclohexyl petyl ketone and the like. In addition, amines, urea compounds, etc. can also be used together as a photosensitizer.

The solvent used in the ultraviolet curable resin composition should be inert to the material used as the base material, and the compatibility with a composition such as resin should be good. The solvent which can be used here is toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, etc., These solvents can be used individually or in mixture.

Content of each component in an ultraviolet curable resin composition is as follows. 20-80 weight% of ultraviolet curable acrylic urethane type resins, 0.1-10 weight% of photoinitiators, and 10-70 weight% of solvents with respect to all the resin compositions.

In the present invention, the silica dispersion composition is mixed with the ultraviolet curable resin composition in order to impart a diffuse reflection effect to the transparent sheet, and is composed of acrylic resin, silica particles, dispersant, solvent and the like containing a hydrophilic group in the molecule.

The acrylic resin is a film adjusting agent, and serves to enable the resin composition to form a film, and serves to reduce the influence of oxygen during ultraviolet curing. In addition, this acrylic resin acts as a thickener for maintaining the viscosity of the coating liquid at a predetermined level or more, and has a hydrophilic group in the molecule, thereby serving to improve the dispersion stability of the silica particles. The acrylic resin used in the present invention preferably has a refractive index of about 1.45, which is similar to that of the silica particles.

As an acrylic monomer which can form such an acrylic resin, alkyl acrylates, such as ethyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, and methyl methacrylate, or methacrylate and hydroxyethyl acryl Acrylates having hydroxyl groups such as acrylate, 2-hydroxypropyl acrylate and 2-hydroxyethyl methacrylate, or non-functional monomers such as methacrylate, vinyl acetate, styrene and acrylonitrile, or acrylic acid and methacryl Functional monomers, such as an acid and glycidyl methacrylate. Although acrylic resins using these monomers alone or in combination of two or more thereof are possible, in the present invention, in order to enhance dispersion stability of silica particles, it is preferable to use together monomers which may include a hydrophilic group in the acrylic resin molecule.

In the present invention, a method is used in which irregularities are formed in the cured film using silica particles, and the diffuse reflection effect is imparted by the irregularities. The silica particles used in the silica dispersion composition consist of silicon dioxide and have an amorphous, porous feature. The shape of the silica particles is spherical, and the refractive index is preferably about 1.46. And it is preferable that the size of a silica particle is 1-15 micrometers. When the size of the silica particles is less than 1㎛, the surface area to the volume of the silica particles increases, and thus the surface energy increases, so that aggregation occurs easily, and the addition amount of the silica particles must be increased to obtain a certain level of diffuse reflection effect. . On the contrary, when the size of the silica particles is larger than 15 μm, the coating property is inferior, the surface state of the coating film is also rough, and the sharpness is poor.

Silica particles are often agglomerated between particles by sharing oxygen on the surface of the particles, but in order for the coating to exhibit excellent optical properties, the silica particles must be evenly dispersed in the coating solution.

As a method used to improve the dispersion of silica particles, a milling method such as a ball mill or a sand mill may be considered. Such a milling method is suitable when the particle size is larger than 15 μm, but when the particle size is small, Since reaggregation of particles occurs, it is preferable to use a method of stirring and dispersing at high speed with a stirrer. After dispersion of the silica particles, the dispersion stability of the particles should be excellent so that the dispersed state of the particles can be kept constant. In the present invention, in order to prevent sedimentation of the silica particles, a dispersant such as an acrylic resin containing a hydrophilic group in the molecule, an unsaturated polycarboxylic acid, an unsaturated polyamine amide, a polysiloxane copolymer, a silicone oil, etc. is used in the silica dispersion composition.

As a solvent used to form the silica dispersion composition, one or a mixture of two or more of isopropyl alcohol, methyl ethyl ketone, toluene, ethyl acetate, butyl acetate, and the like may be used. The content of each component in the silica dispersion composition is as follows. The acrylic resin is 20 to 80 wt%, the silica particles are 5 to 30 wt%, the dispersant is 1 to 5 wt%, and the solvent is 10 to 75 wt% based on the total silica dispersion composition.

The diluent used in the present invention is an organic solvent added to adjust the viscosity and solids content of the coating solution, and may be used alone or in combination of two or more kinds of toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, and the like.

In addition to the components added to the above compositions, various additives may be further added without departing from the object of the present invention, and such additives are, for example, pigments, dyes, antistatic agents and the like.

Method for producing a transparent sheet excellent in the diffuse reflection effect and scratch resistance provided by the present invention is as follows.

First, it is manufactured so that it may become a ratio of 20-80 weight% of ultraviolet curing resin composition ultraviolet-ray-curable acrylic urethane resin, 0.1-10 weight% of photoinitiators, and 10-70 weight% of solvents.

The silica dispersion composition was prepared such that 20 to 80% by weight of the acrylic resin containing a hydrophilic group in the molecule, 5 to 30% by weight of silica particles, 0.1 to 5% by weight of the dispersant, and 10 to 75% by weight of the solvent. Prepare a diluent.

The mixing ratio of the silica dispersion composition to the ultraviolet curable resin composition is determined according to the degree of diffuse reflection effect of the desired transparent sheet. The addition amount of the diluent is determined so that the coating liquid can have an appropriate viscosity (3-50 cps Brookfield viscosity at 25 ° C.) and a solid content (5-65 wt%).

In this way, a coating liquid obtained by mixing a UV curable resin composition, a silica dispersion composition and a diluent in an appropriate ratio is applied onto a base sheet. The coating method is a gravure coater, a reverse coater, a spray coder, a slot orifice coater, and the like. Usually, it coats so that the thickness of the film after drying may be 1-10 micrometers, and it irradiates an ultraviolet-ray after heat-drying, and hardens a film.

As the base sheet, any film that is transparent and resistant to ultraviolet rays such as polyester film, polycarbonate film, polyacryl film, and polyamide film can be used, and triacetate is used as a protective film for a polarizing plate which is a part of a liquid crystal display device. Cellulose (TAC) films can also be used.

The method for evaluating the physical properties of the transparent sheet manufactured by the above method is as follows.

Haze indicating the transmittance of the transparent sheet and the degree of diffuse reflection effect is measured with a haze meter (model NDH20D, manufactured by Nippon Denki Kogyo Co., Ltd.), and the glossiness is measured by a gloss meter (Model No. 556, Yasuda Seiki, Japan). Measure at 60 ° / 60 ° angle. And the surface hardness of a cured film is measured with a pencil hardness tester (JIS K 5401).

The manufacturing method of the transparent sheet of the following example demonstrates this invention concretely, but this invention is not limited to these.

<Example 1-7>

48% by weight of acrylic urethane resin (UC33, U3357), 2% by weight of photoinitiator (Ciba Specialty Chemicals, Argacure-184), 50% by weight of mixed solvent of butyl acetate / methyl ethyl ketone Was uniformly mixed to prepare an ultraviolet curable resin composition. Then, 45% by weight of an acrylic resin (BF Goodrich Co., Carbosset 526) containing a hydrophilic group in the molecule, 2% by weight of a dispersant (BYK, anti-terra oil), isopropyl alcohol / methyl ethyl ketone After stirring, adding 10% by weight of silica particles (Fuji Silysia, Silysia 340) little by little to the resin solution prepared by uniformly mixing 45% by weight of the mixed solvent at 1/1 ratio, and after adding all the silica particles The stirrer was stirred at a high speed for 5 hours or more to sufficiently disperse the silica particles, thereby preparing a silica dispersion composition. Then, the silica dispersion composition was uniformly mixed at a ratio of 10 to 70 parts by weight and 65 to 95% by weight of toluene, which is a diluent, to 100 parts by weight of the ultraviolet curable resin composition, and passed through a 10 μm filter to prepare a coating solution. The viscosity of the coating solution thus prepared was 8-10 cps (25 ° C.) with a Brookfield viscometer. The coating solution was coated on a triacetate cellulose film at a line speed of 10 mpm using a gravure coater, dried at 90 ° C., and then irradiated with ultraviolet light using an ultraviolet lamp (high pressure mercury lamp, 80 W / cm) to form a cured film. The transparent sheets of Example 7 were prepared. The physical properties of the transparent sheets of Examples 1 to 7 were evaluated by the above-described evaluation method, and are shown in Table 1 below.

TABLE 1

As can be seen from the results in Table 1, the haze and glossiness change depending on the amount of the silica dispersion composition added to the ultraviolet curable resin composition. In other words, as the amount of the silica dispersion composition added increases, the diffuse reflection effect increases, while the transmittance maintains good transmittance without significant change. In addition, it can be seen that the surface hardness results of all the cured films of the transparent sheet according to the embodiments all satisfy 3H or more and thus have excellent scratch resistance.

And the change degree of the haze according to the participation amount of the silica dispersion composition with respect to an ultraviolet curable resin composition is as the graph of FIG. That is, since it is possible to control the haze of the transparent sheet by adjusting the addition amount of the silica dispersion composition, it can be seen that by controlling the addition ratio of the silica dispersion composition to the ultraviolet curable resin composition, the diffuse reflection effect of the desired transparent sheet can be easily controlled. Can be.

The transparent sheet according to the present invention configured as described above has excellent diffuse reflection effect and scratch resistance due to the cured coating film containing silica particles.

In addition, since an acrylic urethane resin is used as the cured coating film, it shows excellent properties in chemical resistance and durability, and thus can be applied to various places where diffuse reflection effect and scratch resistance are required, such as a liquid crystal display device.

In addition, since the UV curable resin composition and the silica dispersion composition are separately prepared, a method of mixing the two compositions with a diluent may be used to adjust the mixing ratio of the two compositions to freely control the diffuse reflection effect of the desired sheet.

Moreover, dispersion stability of a silica particle is high by adding the acrylic resin and a dispersing agent which contain a hydrophilic group in a molecule | numerator to a silica dispersion composition.

1 is a graph showing the degree of change in haze according to the amount of the silica dispersion composition added to the ultraviolet curable resin composition.

Claims (3)

Any one of a high transparency and an ultraviolet ray base sheet selected from the group comprising a polyester film, a polycarbonate film, a polyacryl film, a polyamide film or a triacetate cellulose film; In the base sheet, UV-curable resin composition composed of 20 to 80% by weight of ultraviolet curable acrylic urethane resin, 0.1 to 10% by weight of photopolymerization initiator, 10 to 70% by weight of solvent, To prepare a silica dispersion composition composed of 20 to 80% by weight of an acrylic resin containing a hydrophilic group in the molecule, 5 to 30% by weight of silica particles, 0.1 to 5% by weight of a dispersant and 10 to 75% by weight of a solvent, A coating layer formed by mixing a mixture ratio of the ultraviolet curable resin composition, the silica dispersion composition, and the diluent to 100 parts by weight: 10 to 70 parts by weight: 65 to 95 parts by weight; The transparent sheet excellent in the diffuse reflection effect and scratch resistance characterized by being laminated | stacked. Forming an ultraviolet curable resin composition such that the ratio is 20 to 80 wt% of the ultraviolet curable acrylic urethane resin, 0.1 to 10 wt% of the photopolymerization initiator, and 10 to 70 wt% of the solvent; Preparing a silica dispersion composition such that 20 to 80% by weight of an acrylic resin containing a hydrophilic group in the molecule, 5 to 30% by weight of silica particles, 0.1 to 5% by weight of a dispersant, and 10 to 75% by weight of a solvent; ; Mixing the ultraviolet curable resin composition and the silica dispersion composition with a diluent to form a coating solution; Applying the coating solution to any one of a high transparency and an ultraviolet ray base sheet selected from the group comprising a polyester film, a polycarbonate film, a polyacryl film, a polyamide film, or a triacetate cellulose film; Manufacturing a transparent sheet excellent in diffuse reflection effect and scratch resistance, characterized in that it comprises a step of preparing a transparent sheet having a coating layer of a predetermined thickness by curing the coating by heating and drying the coating solution applied to the base sheet by ultraviolet rays Way. According to claim 2, wherein the coating solution is a transparent excellent excellent reflection and scratch resistance, characterized in that the mixing ratio of the ultraviolet curable resin composition, silica dispersion composition and diluent is 100 parts by weight: 10 to 70 parts by weight: 65 to 95 parts by weight. Sheet manufacturing method.