KR19980018024A - Manufacturing method of diffuse reflection sheet - Google Patents

Abstract

The present invention is a method of manufacturing a diffuse reflection sheet mounted on a liquid crystal display device used in an electronic calculator, an electronic clock, an automobile instrument panel, a liquid crystal television, a notebook computer, and the like, and has physicochemical characteristics such as diffuse reflection effect and scratch resistance compared to a conventional sheet. It was devised to improve overall.

In order to achieve the above object, the present invention is characterized by a diffuse reflection characterized in that the coating composition containing UV curable acrylic urethane resin, particles and solvents is coated on a base sheet after milling or sonication, followed by drying and curing under UV curing. The present invention provides a method for manufacturing a sheet, and the diffuse reflection sheet thus prepared has particularly excellent reflection reflection effect and other physicochemical properties as a whole.

Description

Manufacturing method of diffuse reflection sheet

The present invention is used in a liquid crystal display device and relates to a method of manufacturing a diffuse reflection sheet having particularly excellent anti-reflective effect for preventing glare from light reflected from the outside and excellent physical and chemical properties such as scratch resistance and chemical resistance in general. will be.

Conventional anti-glare (anti-glare) workpieces include mat-shaped workpieces (1) having an opaque surface, diffused workpieces (2) utilizing differences in compatibility or crystallinity of resins, and workpieces coated with a thin layer of inorganic compound (3). Etc. are known.

Among these workpieces, (1) has a complicated manufacturing process and requires a long time, and also has a difficulty in using the durability of the mold used or separating the molding resin from the mold, and (2) has a problem in the durability of the workpiece itself. The workpiece of (3) is formed by forming a single layer or a multi-layer coating layer on the surface of the substrate in accordance with the wavelength level of the light beam, and has a disadvantage in that the substrate used is limited and the manufacturing process is complicated and the apparatus is complicated.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing a sheet having particularly excellent diffuse reflection effect in addition to the physical and chemical properties.

In order to achieve the above object, the present invention provides a coating composition containing an ultraviolet curable acrylic urethane-based resin, silica particles, and a solvent, which is coated on a substrate sheet after milling or sonication, followed by drying to produce an ultraviolet curable sheet. It provides a manufacturing method.

Hereinafter, the present invention will be described in detail.

UV curable acrylic urethane resins used in the present invention are generally obtained by reacting an isocyanate monoma with a polyester polyol, which has a urethane bond in the molecular skeleton and at the same time an acrylate or any position in the molecule (most preferably, the molecular end). It is preferred to use those having derived acrylates. In addition, the acrylic urethane resin uses a mixture of a monomer having a molecular weight of less than 500 and an oligomer having a molecular weight of 500 to 5,000. When the molecular weight of the oligomer exceeds 5,000, the viscosity of the coating liquid increases even if the amount of solids is kept constant, and the film is coated. The surface roughness of the decreases the diffuse reflection effect, and this causes a problem that the sharpness of the film is lowered when the particle content is increased. Monomers used generally have 2 to 4 functional groups and oligomers have 3 to 6 functional groups. When the molecular weight of the oligomer exceeds 5,000, the number of functional groups in the polymer is relatively small and the hardness decreases. Thus, by using the acrylic urethane resin which has a urethane bond, UV curing of a composition becomes possible and the cured film excellent in scratch resistance is obtained.

The silica particles used in the present invention are composed of silicon dioxide (SiO ₂ ), and those having amorphous and porous properties are used. After the milling of such silica particles, the particle size is preferably about 1 to 15 µm (more preferably, 2 to 10 µm). When the particle size is less than 1 µm, the surface energy increases as the volume to surface area ratio of the particles increases. There is a disadvantage in that aggregation occurs easily. In addition, when the particle size is larger than 15㎛, there is a disadvantage that the coating property is poor, the surface state is rough.

Silica particles are often aggregated together by sharing oxygen on the particle surface. To show good optical properties after coating, silica particles must be evenly dispersed in the coating solution. As a method used to improve the dispersibility of silica particles, a milling method such as a ball mill or a sand mill is used, and this milling method is generally used when the particle size is 15 µm or more. The narrower the particle distribution after milling, the better the performance. Specifically, the size of the particles corresponding to 80% is preferably less than twice the average particle diameter. In addition, in the present invention, in order to improve the dispersibility of the fine particles, it is also possible to sonicate the coating liquid made by mixing a resin, silica and a solvent, the sonication time is sonicated for 10 to 100 minutes depending on the degree of dispersion. If the ultrasonic treatment is performed for less than 10 minutes, the particles are not dispersed properly, and if the ultrasonic treatment is performed for more than 100 minutes, reaggregation of the dispersed particles occurs.

In addition, since the silica particles are porous, it is preferable to disperse the solution in a low viscosity state so that liquids such as resin easily enter the pores, and it is not preferable to wet the solvent in advance or disperse it with the solvent.

Anti-glare property is provided by the unevenness | corrugation which arose in the hardened film by using a silica particle, At this time, it is preferable to keep light transmittance as possible and to reduce light reflectance. Such characteristics are determined by the concentration of the composition coated on the base sheet, the coating thickness, the type and size of the silica particles, the amount of addition thereof, and the like.

The coating composition in the present invention is made by uniformly mixing an acrylic urethane resin, an acrylic resin, and silica particles with a solvent. As a solvent used at this time, an inert thing is used with respect to a base material, It is good to use that the usage-amount so that solid content concentration may be about 20 to 80 weight%. Conventionally used solvents are mixed solvents of BA (butyl acetate) and MEK (methyl ethyl ketone) or mixed solvents of IPA (isopropyl alcohol) and BA (butyl acetate). The latter is more suitable. It is effective to make mixing ratio into about 30-100 weight part of BA per 100 weight part of IPA. Since IPA does not dissolve the acrylic urethane resin well, when the amount of BA is less than 30 parts by weight, the amount of IPA is relatively large, and the resin cannot be uniformly mixed in the composition liquid. In addition, when the amount of BA is used in excess of 100 parts by weight, the effect of replacing the solution with IPA is reduced, so there is no big difference from the existing method.

Various additives, for example, pigments, dyes, antistatic agents, and the like can be added to the coating composition as long as the object of the invention is not impaired. In particular, an initiator is used for ultraviolet curing, and aceto may be used as an initiator. Phenones, benzophenones, benzyls, benzoin and the like.

The coating composition prepared according to the present invention is usually coated in a thickness of about 5 to 20㎛ by a general coating method such as spray method, gravure method on the base sheet and cured by irradiation with ultraviolet rays after heat drying.

As the base sheet, TAC (TriAcetate Cellulose) is usually used. In addition, a plastic sheet such as a transparent polyester resin, polycarbonate resin, polyacrylic resin, or vinyl chloride resin may be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Examples 1 to 4 Comparative Examples 1 and 2]

As shown in Table 1 below, the coating composition subjected to the composition and the ultrasonic treatment was coated on a TAC resin sheet at a line speed of 10 m / min, and thermally dried at 100 ° C. for 3 minutes, followed by an ozone type high pressure mercury lamp (80 W / cm, 15 cm condensing type). Ultraviolet rays were irradiated with to obtain an antiglare sheet having an average coating thickness of 5 μm, and the physical properties thereof were shown in Table 1.

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 2 Acrylic Urethane Resin 100 100 100 100 100 100 Polyisocyanate (g) One One One One One One Silica particles (g) 5 5 5 5 5 5 Photopolymerization Initiator (G) 5 5 5 5 5 5 Solvent (g) IPA / BA = 2/1 170 170 170 170 170 170 Milling time 0 min 1 minute 5 minutes 10 minutes 30 minutes 60 minutes Silica Particle Size (㎛) 7.2 3.4 2.1 1.6 1.3 0.6 Particle dispersibility Bad Good Good Good Good Bad Haze (%) 25 22 21 20.3 18 10

[Examples 5 to 8 Comparative Examples 3 to 4]

Using the composition as shown in Table 2, and was carried out in the same manner as in Example 1 except that the ratio of BA / IPA was modified, the physical properties are shown in Table 2.

Comparative Example 3 Example 5 Example 6 Example 7 Example 8 Comparative Example 4 Acrylic Urethane Resin (g) 100 100 100 100 100 100 Polyisocyanate (g) One One One One One One Silica particles (g) 5 5 5 5 5 5 Photopolymerization initiator (g) 5 5 5 5 5 5 Solvent BA / IPA (%) 0 30 50 70 100 150 Haze (%) (Hazmeter, NDH 20D) 14.7 15.2 16.0 15.0 14.5 14.8 Glossiness (incident angle 60 degrees) 60.0 42.1 39.3 45.3 46.2 54.3

[Examples 9 to 11 and Comparative Example 5]

As shown in Table 3 below, the change in physical properties according to the molecular weight distribution of the acrylic urethane resin was measured and the results were compared.

Example 9 Example 10 Example 11 Comparative Example 5 Acrylic Urethane Resin Molecular Weight 500 500-2,000 42,000-5,000 8,000 to 12,000 Acrylic Urethane Resin Usage (g) 100 100 100 100 Silica particles (g) 5 5 5 5 Photopolymerization Initiator (g) 5 5 5 5 Haze (%) 30.2 30.5 29.7 30.5 definition(%) 40.5 42 37 27 Surface hardness 3H 3H 3H 2H or less Scratch Resistance Great Great Great Bad

As described above, the diffuse reflection sheet manufactured by the present invention has good anti-glare property due to the cured film containing silica, and since the ultraviolet cured film uses acrylic urethane resin, it exhibits excellent properties in chemical resistance and durability. It shows excellent performance when used for applications requiring diffuse reflection effect and scratch resistance.

Claims (5)

A coating composition containing an acrylic urethane resin, a silica particle, and a solvent, which is prepared by reacting an isocyanate monomar to a polyester polyol and is a mixture of a monomer having 2 to 4 functional groups and an oligomer having a molecular weight of 500 to 5000 having 3 to 6 functional groups. Method of producing a diffuse reflection sheet, characterized in that the coating on the substrate sheet after milling or sonication, and then cured by ultraviolet curing after drying. The method for producing a diffuse reflection sheet according to claim 1, wherein the average particle size of the silica particles after milling is in the range of 1 to 15 µm. The method for producing a diffuse reflection sheet according to claim 1, wherein the solvent is a mixed solvent of isopropyl alcohol and butyl acetate. The method for producing a diffuse reflection sheet according to claim 1, wherein the ultrasonic treatment is performed for 10 to 100 minutes. The method for producing a diffuse reflection sheet according to claim 1, wherein the amount of the solvent used is such that the solid content concentration in the coating composition is 20 to 80% by weight.