KR20140084617A

KR20140084617A - Optical Sheet

Info

Publication number: KR20140084617A
Application number: KR1020120154266A
Authority: KR
Inventors: 김경종; 남시욱; 신진호; 황홍구; 김경화
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2012-12-27
Filing date: 2012-12-27
Publication date: 2014-07-07

Abstract

The present invention relates to an optical sheet. More specifically, an optical sheet includes a substrate layer; a diffusion layer formed on a surface of the substrate layer; and an intaglio pattern layer which is formed on the other surface of the substrate layer and forms an intaglio pattern. The optical sheet has excellent viewing angle properties and concealment while minimizing the reduction in luminance.

Description

Optical Sheet {Optical Sheet}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an optical sheet that can be used for a liquid crystal display (PDP) or the like.

BACKGROUND ART An LCD used as an optical display device is an indirect light emitting type in which an image is displayed by adjusting the transmittance of an external light source, and a backlight unit as a light source device is used as an important component for determining the characteristics of an LCD.

In particular, with the development of LCD panel manufacturing technology, there has been a demand for a thin and bright LCD display. Accordingly, various attempts have been made to increase the brightness of a backlight unit. For example, a monitor, a PDA Is a measure of its superiority in that a liquid crystal display used as a light source emits bright light from a small energy source. Therefore, the front brightness of LCD is very important.

Since the structure of the LCD diffuses the light passing through the light diffusion layer in all directions, the light exerted on the front surface is very scarce, and thus efforts to develop higher luminance with less power consumption are continuing. In addition, efforts are being made to enlarge the viewing angle so that more users can view the display as the size becomes larger.

If the backlight power is increased for this purpose, the power consumption increases and the power loss due to heat increases. As a result, the battery capacity and the battery life of the portable display are reduced.

In order to improve luminance, various lens sheets have been developed as a method for giving directionality to light, and composite sheets in which a plurality of sheets are integrated have been developed. However, these sheets may be advantageous in terms of cost and productivity, .

In recent years, the use of LEDs as a light source of an LCD BLU (Backlight Uint) has been increasing. As the LED light source is used, the luminance lines of the LEDs are visually recognized in the BLU, and the uniformity of light emitted from the BLU is reduced. And concealment at the same time.

An object of the present invention is to provide an optical sheet capable of improving viewing angle and occlusion characteristics and minimizing luminance reduction.

Accordingly, the present invention provides, as a first preferred embodiment, a substrate layer; A diffusion layer formed on one surface of the substrate layer; And an engraved pattern layer formed on the other surface of the base layer and having a relief pattern formed thereon.

The engraved pattern according to this embodiment may be a microlens shape.

The engraved pattern according to this embodiment may have a width of 10 to 80 탆 and a height of 5 to 40 탆.

The engraved pattern according to the embodiment may have an interval between adjacent engraved patterns of 0 to 5 μm.

The engraved pattern layer according to the embodiment may be selected from epoxy-based acrylate, vinyl ether-based acrylate, urethane-based acrylate, and mixtures thereof.

The optical sheet according to the present invention exhibits excellent luminance characteristics, viewing angle characteristics and concealment characteristics at the same time, and can improve the light uniformity of the BLU.

1 is a cross-sectional view of an optical sheet according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a substrate layer (10); A diffusion layer (20) formed on one surface of the substrate layer; And an engraved pattern layer 30 formed on the other surface of the base layer and having an engraved pattern (Fig. 1).

The substrate layer

The substrate layer may be any film made of a transparent resin used in an optical sheet such as a conventional prism sheet or a prism film. For example, a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, a polyethylene film, a polystyrene film or a polyepoxy film.

Diffusion layer

The diffusion layer is formed on one surface of the substrate layer and includes a binder resin and a light diffusing agent. Specifically, the diffusion layer may include 100 to 500 parts by weight of a light diffusing agent based on 100 parts by weight of the binder resin. If the content is more than 100 parts by weight, the luminance is lowered. If the content is more than 500 parts by weight, the diffusion agent may be separated from the coating layer.

The binder resin may be selected from the group consisting of a polymer selected from the group consisting of a methyl methacrylate resin, an acrylate resin, a polyamide resin, an epoxy resin and a urethane resin, and a mixture thereof .

The light diffusing agent may be selected from poly methyl methacrylate (PMMA), polybutyl methyacrylate (PBMA), silicone, polystyrene, polyurethane, nylon, and mixtures thereof.

The diffusion layer may further contain additives such as a surfactant, an antistatic agent, a dispersant, a light stabilizer, a heat stabilizer, and the like depending on the coating process and coating composition.

Intaglio pattern layer

The engraved pattern layer is formed on the other surface of the base layer, not on one surface of the base layer where the diffusion layer is formed. The engraved pattern layer is formed with a number of engraved patterns. The resin composition is composed of an oligomer of a UV-curable radically polymerized acrylate compound And a UV curable material mainly composed of a monomer, and may be selected from a mixture of an oligomer such as an epoxy-based acrylate, a vinyl ether-based acrylate or a urethan-based acrylate and a monomer of the mono acrylate series. It is preferable to contain an additive for UV curing such as UV curing.

The engraved pattern may be in the form of a spherical micro lens having a width of 10 to 80 μm and a height of 5 to 40 μm. If the width is less than 10 μm or the height is less than 5 μm, There is a problem such as a white point in the appearance of the sheet, and when the width exceeds 80um or the height exceeds 40um, the hiding ability is reduced.

The engraved pattern may have a distance between adjacent engraved patterns of 0 to 5 mu m. If the interval is less than 0 占 퐉, there is a problem that the lenses are overlapped and concealability is reduced, and when the distance exceeds 5 占 퐉, the luminance and concealment are reduced. In this case, the interval of the engraved pattern means the interval between the edges of the individual engraved patterns, and when the distance between the engraved patterns is 0 탆, it means that the form is adjacent without the interval between the engraved patterns.

In the optical sheet as described above, it is possible to form a diffusion layer by using gravure on one side of the base layer, dispersing the light diffusion particles in the binder resin by a milling machine, applying the mixture by using gravure, and drying by hot air to form a diffusion layer .

After applying a resin coating solution to the other surface of the substrate layer, UV light is irradiated while lamination with a positive embossing mold having an engraved pattern shape to be formed, and then a relief mold is released to form an engraved pattern layer including an engraved pattern, A sheet can be produced.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

Example 1

A polyethylene terephthalate film Astroll (Kolon) having a thickness of 188 mu m was used as the substrate layer.

The diffusion layer was formed on one side of the substrate layer so as to have a dry thickness of 8 mu m using gravure. The diffusion layer was prepared by mixing 100 parts by weight of an acrylic resin (SA02, Samhwa Paint), 100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene as a binder resin. 100 parts by weight of the binder resin, And 120 parts by weight of polymethyl methacrylate particles (MX500, Soken) were dispersed by a milling machine and then coated. Coated with gravure and hot air dried at 100 DEG C for 30 seconds to form a diffusion layer.

The engraved pattern layer is formed by applying an acrylic UV-curable resin coating liquid (KR30, Minutatek) to the other surface of the substrate layer, irradiating UV with a lens-shaped embossed mold to be formed, releasing a mold with embossing, Shaped micro lenses. At this time, the width of the intaglio micro lens is 10 mu m, the height is 5 mu m, and the interval between adjacent microlenses is 5 mu m.

Such a base layer; A diffusion layer formed on one surface of the substrate layer; And an engraved pattern layer formed on the other surface of the base layer.

Examples 2 to 5

An optical sheet was prepared in the same manner as in Example 1 except that the shape of the engraved pattern was changed according to Table 1.

Comparative Examples 1 to 5

The optical sheets prepared in Examples and Comparative Examples were measured for brightness, viewing angle, and hiding ability, and the results are shown in Table 2.

Luminance

The optical sheets of the above-prepared examples and comparative examples were stacked and fixed on a backlight unit for a 24-inch liquid crystal display panel, and the luminance at arbitrary 13 points was measured using a luminance meter (Model: BM-7A, TOPCON Japan) And the average value thereof was obtained.

Viewing angle

The viewing angles were measured using a BM-7A of Topcon Co. The values were obtained by fixing the optical sheets prepared in Examples and Comparative Examples in a backlight unit (BLU, 24 inches) and measuring the half-brightness of the front (viewing angle = 0) And a viewing angle at a position having a luminance value was measured.

Concealability

The optical sheets prepared in the examples and comparative examples were fixed to a backlight unit for a 24-inch liquid crystal display panel, and visually observing whether the lamp luminescent lines were not visually observed was evaluated relative to each other as follows.

Non-reflective level: about ← ◎ - ○ - Δ → X → Kang

Intaglio pattern layer width Height Adjacent pattern spacing Remarks Example 1 10 탆 5 탆 5 탆 Example 2 30 탆 15 탆 5 탆 Example 3 50 탆 25 m 5 탆 Example 4 70 탆 35 탆 5 탆 Example 5 80 탆 40 탆 2 탆 Example 6 80 탆 40 탆 5 탆 Comparative Example 1 - - - No pattern Comparative Example 2 80 탆 40 탆 10 탆 Comparative Example 3 90 탆 45 탆 2 탆

Luminance
(cd / m ² ) Viewing angle
( ^O ) Concealability Example 1 3203 45 ◎ Example 2 3210 44 ◎ Example 3 3216 45 ◎ Example 4 3206 44 ○ Example 5 3210 45 ◎ Example 6 3206 45 ○ Comparative Example 1 3200 45 X Comparative Example 2 3216 45 △ Comparative Example 3 3168 45 △

As a result of the physical property measurement, it is confirmed that when the pattern is not formed in the engraved pattern layer or when the size or the interval of the formed pattern is out of the proper range, the concealability is poor and the luminance is lowered somewhat I could.

10: base layer, 20: diffusion layer, 30: engraved pattern layer

Claims

A base layer;
A diffusion layer formed on one surface of the substrate layer; And
And an engraved pattern layer formed on the other surface of the base layer and formed with an engraved pattern.

The method according to claim 1,
Wherein the engraved pattern has a shape of a microlens.

The method according to claim 1,
Wherein the engraved pattern has a width of 10 to 80 占 퐉 and a height of 5 to 40 占 퐉.

The method according to claim 1,
Wherein the engraved pattern has an interval between adjacent engraved patterns of 0 to 5 mu m or less.

The method according to claim 1,
Wherein the engraved pattern layer is made of an epoxy acrylate, a vinyl ether acrylate, a urethane acrylate or a mixture thereof.

The method according to claim 1,
Wherein the diffusion layer comprises 100 to 500 parts by weight of light diffusing particles based on 100 parts by weight of the binder resin.