KR101785329B1 - Liquid crystal display reflector - Google Patents

Abstract

The present invention relates to a reflective film for a display, comprising: an optically clear adhesive (OCA) film layer; A white resin film layer laminated on the optical transparent adhesive film; And an aluminum evaporated film layer laminated on the white resin film layer.

Description

Reflective film for display. {LIQUID CRYSTAL DISPLAY REFLECTOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a reflective film for a display, and more particularly, to a reflective film that can be applied to a display with improved light efficiency and luminance.

In recent years, as UHD (Ultra-HD) TV has been developed, demands for high-resolution and high-brightness devices to realize clearer picture quality have been developed recently in LCD and OLED displays. Is increasing.

In general, the reflection film applied to a TV display has a side light structure in which a backlight unit (BLU) emits light from the left and right sides of the light guide plate, so that there is a limit to realizing high reflectance and light diffusion performance. Therefore, researches and developments are being conducted on reflective films suitable for realizing high optical efficiency and reflectance while reducing the number of BLUs by designing the direct-type structure.

As such a reflective film, for example, in Korean Patent Registration No. 10-1186833, a white polyester film including a polyester layer having fine bubbles is applied, thereby providing a reflector applicable to a direct-type structure. Korean Patent Laid-Open Publication No. 10-2014-0123560 discloses a reflection film in which reflectance and light diffusion efficiency are improved by limiting porosity, organic content, and inorganic particle content as a reflection film in which a first portion and a second portion are laminated .

Korean Patent Laid-Open Publication No. 10-2016-0135531 discloses a reflection plate including a heat conduction layer as a reflection plate excellent in heat radiation effect and shielding effect.

However, these conventional technologies are difficult to realize a high luminance and chromaticity difference, and thus they are limited in application to high-end TVs such as recently developed UHD-TV.

Korean Patent Publication No. 10-1186833 Korean Patent Publication No. 10-2014-0123560 Korean Patent Publication No. 10-2016-0135531

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflective film for a display having improved light efficiency such as luminance, chromaticity and uniformity.

In particular, it is an object of the present invention to provide a reflective film for display having optical characteristics applicable to a display to which a BLU of a direct-type structure is applied.

According to an aspect of the present invention, there is provided a reflective film for display comprising: an optically clear adhesive (OCA) film layer; A white resin film layer laminated on the optical transparent adhesive film; And an aluminum evaporated film layer laminated on the white resin film layer.

At this time, the optical transparent adhesive film layer is formed by forming a coating layer comprising a polyester resin, an acrylic resin and wax on the surface of the aromatic polyester film, and the optical transparent adhesive film layer is composed of two kinds of optical transparent adhesive Films may be stacked and constructed.

The resin constituting the white resin film layer may be a polyester resin, a polystyrene resin, a polyacrylic resin, a polycarbonate resin or a polyethylene terephthalate resin.

The reflective film according to the present invention has improved light efficiency such as luminance, chromaticity, and uniformity, and thus can be applied to high-end TV displays such as UHD-TV.

Further, it is possible to provide a reflective film for display having optical characteristics applicable to a display to which a BLU of a direct-type structure is applied.

Hereinafter, the present invention will be described in more detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

The reflective film for display of the present invention comprises an optically clear adhesive (OCA) film layer; A white resin film layer laminated on the optical transparent adhesive film; And an aluminum evaporated film layer laminated on the white resin film layer.

In the present invention, the OCA film layer is formed by laminating two different OCA films, and each of the films is formed by forming a coating layer including a polyester resin, an acrylic resin and a wax on the surface of the aromatic polyester film.

At this time, the aromatic polyester film is biaxially stretched so as to have a thickness of 50 to 200 탆, and a coating layer comprising the polyester resin, acrylic resin and wax is formed on one side or both sides of the aromatic polyester film.

The polyester resin forming the coating layer is a polyester polymer comprising a polybasic acid component and a polyol component, and examples thereof include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 1,4-cyclohexanedicarboxylic acid, adipic acid, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1, 2-hexanediol, 1, 2-butanediol, 1, 2-butanediol, 2-ethylhexanetetracarboxylic acid, sebacic acid, trimellitic acid, pyromellitic acid, , 4-cyclohexanedimethanol, and the like.

The acrylic resin is one having a glass transition point (Tg) of 25 占 폚 or less and obtained by copolymerizing one or more kinds of acrylic monomers. Examples of such an acrylic monomer include a hydroxyl group such as alkyl acrylate, alkyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate Containing monomer; Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; Monomers containing a carboxyl group or a salt thereof such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof; Acrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate, N-alkoxyacrylamide, N-alkoxymethacryl Amide, N, N-dialkoxyacrylamide, N, N-dialkoxymethacrylamide, acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide, N- And monomers containing an amide group such as phenyl methacrylamide.

As the copolymerization component, monomers of acid anhydride such as maleic anhydride and itaconic anhydride; Vinyl monomers such as vinyl isocyanate, allyl isocyanate, styrene,? -Methyl styrene, vinyl methyl ether, vinyl ethyl ether, vinyltrialkoxysilane, alkylmaleic acid monoester, alkylpumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, Vinylidene chloride, vinylidene chloride, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene.

The wax may be selected from the group consisting of vegetable waxes such as carnauba wax, candy reel wax, rice wax, wax, jojoba oil, palm wax, rosin-modified wax, ocherite wax, sugar cane wax, asphalt wax and bak wax, polyethylene wax, A synthetic hydrocarbon wax such as polyethylene oxide wax, polypropylene wax, and oxidized polypropylene wax may be used.

In the present invention, the two different types of OCA films vary depending on the composition of the coating layer. Preferably, the OCA film is composed of 60 to 90 parts by weight of a polyester resin, 5 to 30 parts by weight of an acrylic resin, and 0.5 to 10 parts by weight of a wax, Rz) of 20 to 30 nm is laminated on the surface of the OCA film layer to produce an OCA film layer. Due to the difference in surface roughness, the adhesion between the white resin film and the OCA film can be increased due to the difference between the surface roughness of the OCA film and the surface roughness of the outermost surface of the OCA film while reducing the appearance defects .

In the structure in which two types of OCA films are laminated, the OCA film on which the white resin film layers are laminated needs to have a higher surface roughness (Rz) to exhibit good adhesion in the case of lamination. In one embodiment, it is preferable that the surface roughness Rz of one OCA film is 2 nm and the surface roughness of the other OCA film is 25 nm. If the surface roughness of one OCA film is 2 nm and the surface roughness of the other OCA film is 35 nm and the difference in surface roughness of both films exceeds 30 nm, the luminance of the center point of the optical film is decreased by 20% or more On the other hand, even when the surface roughness of one OCA film is 2 nm and the surface roughness of the other OCA film is 20 nm and the difference in surface roughness of the two films is less than 20 nm, Compared with 25%. This is presumably because the difference in the surface roughness of the two kinds of OCA films affects the laminated structure of the OCA films to deteriorate the reflectance.

Further, a white resin film layer is laminated on the optical transparent adhesive film. As the white resin, a white film made of a polyester resin, a polystyrene resin, a polyacrylic resin, a polycarbonate resin, or a polyethylene terephthalate resin can be used, and a polyester resin or a polyethylene terephthalate resin having good mechanical strength and excellent workability It is preferable to use a white film composed of

In this case, the inorganic masking agent may be any one of silica, zirconia, calcium carbonate, barium sulfate, titanium dioxide and silica, or a composite thereof, in an amount of 0.1 to 10 탆. . Particularly, it is preferable to use silica in consideration of cost, durability, light stability, film formability, and optical characteristics. In general, barium sulfate or titanium dioxide particles are often used as inorganic particles having high optical properties. In the present invention, it is preferable to use a silica-titania composite in which the silica and titanium dioxide are combined.

The silica-titania composite is prepared by reacting silica particles with a titanium alkoxide, for example, titanium isopropoxide in an aqueous alcohol solution to hydrolyze and polycondensation the titanium alkoxide, thereby carrying titanium dioxide on the surface of the silica. . In addition, when porous silica is used, a silica-titania composite in which titanium dioxide is supported in the silica particles can be produced. When such a composite is used, the optical properties are further improved.

In one embodiment, silica is dispersed in an isopropanol aqueous solution containing 20 mol% of water, and titanium isophoronoxide is gradually added thereto to cause hydrolysis and polycondensation reaction. The silica is dried and calcined at 400 to 500 ° C. for 0.5 to 1 hour And then calcined to produce a silica-titania composite.

At this time, the silica has a pore size of 10 to 50 nm and an average particle size of 0.1 to 10 탆, whereby the silica-titania composite in which the titania is supported in the surface and pores of the silica particles can be obtained .

In addition, hydrolysis and polycondensation reactions take longer to hydrolyze the titanium alkoxide than the polycondensation reaction, so the hydrolysis reaction is the rate determining step of the overall reaction. Therefore, in order to accelerate the reaction, it is preferable to reflux for 24 hours at 70 to 90 ° C after charging the aqueous alcohol solution.

The amount of the titanium dioxide to be supported is preferably 1 to 10% by weight based on the silica particles.

Further, an aluminum evaporated film layer is laminated on the white resin film layer. The aluminum deposited film constitutes a reflective layer, and the deposition may be performed by any one of physical vapor deposition (PVD), chemical vapor deposition (CVD), and electroplating. Specifically, sputtering, electron beam vapor deposition, thermal vapor deposition, laser molecular beam vapor deposition, pulse laser vapor deposition, and electroplating may be used.

In order to evaluate whether the reflection film manufactured by the present invention can be applied to a direct-type backlight unit, the following test and evaluation were carried out.

First, a reflective film composed of an OCA film layer, a white resin film layer, and an aluminum evaporated film layer was produced. The OCA film layer was formed by laminating an OCA film having a surface roughness (Rz) of 2 nm and an OCA film having a surface roughness of 25 nm The white resin film layer was formed of a composition for a film in which 13 parts by weight of a polyester resin, 27 parts by weight of a silica-titania composite, and a solvent in which methyl ethyl ketone and toluene were mixed at a weight ratio of 1: 1, Sputtering method, and each layer was laminated so as to have a layer thickness of 180 to 190 mu m (Example 1).

Further, a reflective film was produced in the same manner as in Example 1 except that an OCA film having a surface roughness of 2 nm and an OCA film having a surface roughness of 35 nm were laminated to form an OCA film layer (Comparative Example 1).

A reflective film was prepared in the same manner as in Example 1 except that the OCA film layer was composed of one kind of OCA film having a surface roughness of 5 nm (Comparative Example 2).

A reflective film was prepared in the same manner as in Example 1, except that silica was used as an inorganic masking agent in the white resin film layer (Comparative Example 3).

A reflective film was prepared in the same manner as in Example 1, except that titanium dioxide was used as an inorganic masking agent in the white resin film layer (Comparative Example 4).

Further, a conventional reflective film composed of only a white resin film layer and an aluminum evaporated film layer was evaluated (Comparative Example 5).

For the reflectance measurement, the surface of the flat test piece of 64 x 64 x 1 mm was measured with a magnetic spectrophotometer ("U-3500" manufactured by HITACHI SEISAKUSHO Co., Ltd.) to measure the diffuse reflectance with respect to the light having a wavelength of 460 nm Respectively. At this time, the diffuse reflectance is a relative value when the diffuse reflectance of a standard white plate made of barium sulfate is 100%.

In order to measure the luminance, a reflection film of Examples 1 to 3 was mounted on a Samsung UHD panel, and after a lapse of 30 minutes from the operation of the panel, a luminance meter 15 (topcon BM-7fast) The luminance was measured and the average value measured five times was used as the luminance value. The luminance value was measured as a relative value with the value measured in Example 1 as 100%.

The chromaticity was measured using an integral spherical colorimeter (CM-3700D, Minolta).

The evaluation results of Examples 1 to 5 are shown in Table 1.

reflectivity(%) Luminance Chromaticity L * a * b * Example 1 103 100 87.43 -1.02 -8.05 Comparative Example 1 98 82 86.33 -1.15 -6.92 Comparative Example 2 89 92 81.51 -1.64 -4.32 Comparative Example 3 85 91 82.01 -1.43 -4.52 Comparative Example 4 89 93 83.03 -1.26 -5.68 Comparative Example 5 81 85 80.06 -1.25 -6.01

In Table 1, the reflectance was higher than that of the standard white plate in Example 1, but the reflectance was lowered in Comparative Example 1 in which the surface roughness of the OCA film was not adjusted. In addition, the reflectance of Example 1 was higher than that of Comparative Examples 2 to 5, and the reflectance was remarkably higher than that of Comparative Example 5, which is a typical reflective film without lamination of the OCA film.

In addition, when the surface roughness of the OCA film is not controlled, the luminance value is lowered by about 20%, and the adjustment of the surface roughness during the lamination of the OCA film is a very important factor for improving the luminance . In addition, the luminance value of Example 1 was higher than that of Comparative Examples 2 to 5, and it was confirmed that the luminance value was 15% or more higher than that of Comparative Example 5 which is a general reflective film.

In addition, the chromaticity measurement results showed that the L * value in Example 1 was higher than that in Comparative Examples 1 to 4. The L * value is an index indicating the brightness, and this is a result indicating that the reflection film of Example 1 has a higher reflection luminance as compared with Comparative Examples 1 to 4. [ It is also seen that the reflectance at 450 nm wavelength increases in Example 1, and the absolute value of b * increases in absolute value. From these results, it can be seen that the reflective film of Example 1 is superior in optical characteristics to those of Comparative Examples 1 to 4.

It is to be understood that the present invention is not limited to the above-described embodiments, but is defined by the claims, and those skilled in the art can make various changes and modifications within the scope of the claims It is self-evident.

Claims (4)

Optically Clear Adhesive (OCA) film layer;
A white resin film layer laminated on the optical transparent adhesive film;
An aluminum evaporated film layer laminated on the white resin film layer;
Lt; / RTI >
Wherein the optical transparent adhesive film layer is formed by laminating two kinds of transparent adhesive films for optical use,
Wherein the two kinds of transparent adhesive films for optical use have a difference in surface roughness (Rz) of 20 to 30 nm.
The method according to claim 1,
Wherein the optical transparent adhesive film layer is formed by forming a coating layer comprising a polyester resin, an acrylic resin, and a wax on the surface of the aromatic polyester film.
delete The method according to claim 1,
Wherein the resin constituting the white resin film layer is a polyester resin, a polystyrene resin, a polyacrylic resin, a polycarbonate resin, or a polyethylene terephthalate resin.