KR20140087291A - Optical Member and Backlight Unit Comprising the Same - Google Patents

Abstract

The present invention relates to an optical member and a backlight unit comprising the same and, more specifically, to an optical member including a base layer; a resin curing layer which is formed on at least one surface of the base layer; and a structure layer which is formed on one surface of the resin curing layer and in which a plurality of structures are arranged, wherein the resin curing layer has a coefficient of thermal expansion (CTE) greater than a CTE of the base layer and smaller than a CTE of the structure layer so as to improve wrinkle and flexural properties and have high reliability, and a backlight unit including the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical member and a backlight unit including the optical member.

The present invention relates to an optical member used in a backlight unit.

The LCD, which is a liquid crystal display device, is a non-light emitting type electronic display device, and a separate light source, that is, a backlight, must be provided to realize a vivid natural color of a moving image with high quality. The composite that irradiates the light from the rear side of the liquid crystal module is called BLU, and it is divided into two types of direct type BLU and edge type BLU according to the irradiation method. In the small and medium type LCD backlight unit An edge type using a metering lamp is applied.

The conventional LCD backlight unit includes a light source, a light guide plate for guiding light emitted from the light source, and a plurality of diffusion plates and a brightness enhancement film (BEF). Such a large number of optical sheets are components that make the emitted light uniform and have high luminance characteristics in consideration of the fact that the characteristics of the light generated by the edge method or the direct method determine the quality of the image .

Such a large number of optical sheets may be warped or wrinkled due to heat generated from the BLU light source, but they are brought into close contact with the upper and lower optical members due to wrinkles or warpage generated thereby causing secondary defects such as adhesion failure.

Also, the wrinkles and warpage of the optical members may cause a phenomenon of distorted images by obstructing the function of adjusting the direction of the light emitted from the light source of the backlight unit and collecting the light in the visual field direction of the user. Among the optical members, the films classified into the sheet are often composed of the base film and the upper and lower acrylic type structures. Due to such a structure, different kinds of materials have structural weaknesses showing different amounts of deformation due to heat at the same temperature range, so that wrinkles and warpage easily occur and the reliability is lowered.

In order to improve heat resistance characteristics for optical members, polymers having improved heat resistance characteristics by combination of acrylate monomers, aromatic vinylated monomers and methacrylic acid monomers have been developed. However, polymers which are unsuitable for application to the coating process of optical substrates There is a problem in that the use thereof is limited.

In addition, a method for realizing the heat resistance characteristic of the coating has been disclosed. However, this method is a method using a vacuum sputtering process using an oxide-based composition, which is also unsuitable for application to an optical member using a film. The reliability can be improved, but there is a problem that the luminance is lowered by the oxide beads.

SUMMARY OF THE INVENTION The present invention provides an optical member having improved reliability and wrinkle and warping characteristics.

The present invention also provides a backlight unit including the optical member.

Accordingly, the present invention provides, as a first preferred embodiment, a substrate layer; A resin cured layer formed on at least one side of the substrate layer; And a resin layer formed on one surface of the resin cured layer and having a plurality of structures arranged therein, wherein the CTE of the resin cured layer is smaller than a CTE of the substrate layer, The optical member being characterized by being large.

The CTE difference between the substrate layer and the resin cured layer according to the embodiment is 1 to 5 ppm / ° C, and the CTE difference between the resin cured layer and the structural layer may be 1 to 5 ppm / ° C.

The resin cured layer according to the embodiment may be made of a resin selected from an ultraviolet curing resin, a thermosetting resin and a mixed resin thereof.

The structure according to the above embodiment may have a longitudinal cross section selected from a triangle, a semicircle, an ellipse, and a lenticular.

The present invention also provides, as a second preferred embodiment, a backlight unit including the optical member.

The optical member of the present invention improves the corrugation and warpage characteristics without lowering the luminance, has high reliability, can provide an excellent image when applied to a display, and contributes to prolongation of the life of the display.

1 is a cross-sectional view of an optical member according to an embodiment of the present invention, in which the longitudinal section of a structure formed on the structural layer is triangular.
2 is a cross-sectional view of an optical member according to another embodiment of the present invention, in which a longitudinal section of a structure formed on the structural layer is semicircular.

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

The present invention relates to a substrate layer; A resin cured layer formed on at least one side of the substrate layer; And a structure layer formed on one surface of the resin cured layer and having a plurality of structures arranged therein, wherein a CTE of the resin cured layer is larger than a CTE of a substrate layer, And an optical member which is small in size.

[CTE]

In the optical member of the present invention, the resin cured layer formed on at least one surface of the base layer

The optical member can be prevented from being deformed by an external environment such as heat due to the formation of the resin cured layer between the structure layer and the base layer while the difference from the CTE of the base layer is small on at least one surface of the base layer, The occurrence of wrinkles and warpage can be reduced.

The structure of the optical film is largely composed of a substrate and a structure layer. In the case of different kinds of materials, materials with different thermal expansion coefficients under the same temperature range are deformed due to different dimensional deformation. The distorted shape appears as wrinkles or warpage of the optical member, which appears on the screen of the display.

Therefore, in order to minimize this, a buffer layer for dimensional change is required. To solve this problem, a resin cured layer having a CTE value between the substrate layer and the structure layer is introduced. More specifically, the CTE difference between the substrate layer and the resin cured layer is 1 to 5 ppm / ° C, and the CTE difference between the resin cured layer and the structural layer may be 1 to 5 ppm / ° C.

[Resin Cured Layer]

The resin cured layer may be formed of a curable resin composition. In this case, the curable resin is a thermosetting resin or a photo-curable resin which is cured by heating or irradiation of light, which is typified by acrylic resin.

Specifically, the resin cured layer may be formed of a resin selected from an ultraviolet-curable resin, a thermosetting resin, and a mixed resin thereof in the photo-curing resin.

The photo-curable resin may be an ultraviolet (UV) curable resin. Specifically, the ultraviolet curable resin may be an unsaturated polyester resin, a polyfunctional acrylate resin, an epoxy resin, an epoxy acrylate resin and a mixed resin thereof.

The thermosetting resin may be selected from a condensation polymerization type resin, an addition polymerization type resin and a mixed resin thereof. The condensation type resin may be a phenol resin, a melted resin, a melamine resin, etc. The addition polymerization type resin is an epoxy resin , A polyester resin, or the like. In the present invention, these may be used alone or in combination.

In particular, in order for the CTE of the resin cured layer to be smaller than the CTE of the base layer and to have a value larger than the CTE of the structure layer, the resin cured layer is formed of urethane acrylate, epoxy acrylate, (meth) acrylate, hydroxyl acrylate And can be preferably formed of one or more monofunctional urethane acrylate and methacrylate.

[Structure layer]

In the optical member according to the present invention, the optical member according to the embodiment may further include a structure layer formed on one side of the resin cured layer and having a plurality of structures arranged (FIGS. 1 and 2) . At this time, the structure may have a triangular, semicircular, elliptical, or lenticular shape in its longitudinal section, but the present invention is not limited thereto.

An optical member including a structure layer formed on the upper surface of the resin cured layer, wherein the resin cured layer is formed on both sides of the base layer when the optical member includes the structure layer; An optical member including a substrate layer, a resin cured layer formed on the upper surface of the substrate layer, and a structure layer formed on the upper surface of the resin cured layer; An optical member including a resin cured layer, a base layer formed on the upper surface of the resin cured layer, and a structure layer formed on the upper surface of the base layer.

By including the structural layer in the optical member, it is possible not only to improve the wrinkle and the warpage property but also to secure the concealment due to the interface distinguished from the structural layer.

The optical member according to the present invention can be manufactured by wet-coating. Specifically, a resin cured layer is formed on at least one surface of a substrate layer using gravure, and a structure layer having a structure formed on one surface of the resin cured layer is formed Thus, an optical member can be manufactured.

Such an optical member can be applied to a backlight unit.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are not to be construed as limiting of invention, Of course.

Comparative Example 1

As an optical member, a prism film (Kolon) including a base layer and a structure layer having a CTE as shown in Table 1 was prepared.

Example 1

An optical member comprising a base layer having a CTE as shown in Table 1, a resin cured layer and a structural layer was prepared in the following manner.

As the substrate layer, a PET film (thickness 188 탆, Kolon) was prepared.

A resin cured layer was formed on one side of the substrate layer, and a crude liquid prepared by using a raw material of a Japanese pyrotechnical grade was used as a mixed resin used for the resin cured layer. Specifically, 20 parts by weight of urethane acrylate (R-526, 10 parts by weight and HX-220 by 10 parts by weight), 75 parts by weight of acrylate (R-712, 30 parts by weight, R-167 25 parts by weight, R-128, 20 parts by weight), and 5 parts by weight of additives including a photoinitiator and a stabilizer.

The coating solution of the prepared mixed resin was diluted with a ratio of methyl ethyl ketone 7 and mixed resin 3 as a solvent in order to improve coatability, passed through a drying zone of 100 degrees after gravure coating, and ultraviolet cured to form a resin cured layer.

95 parts by weight of acrylate and 5 parts by weight of a photoinitiator were coated on one surface of the cured resin layer and exposed to ultraviolet rays to form a prism structure having a vertex angle of 90 degrees, a pitch of 50 占 퐉 and a height of 25 占 퐉 to form a structure layer Thus, an optical member was produced.

Example 2

An optical member was produced in the same manner as in Example 1 except that a resin cured layer was formed on the upper surface of the PET film and a structure layer was formed on the resin cured layer.

Example 3

An optical member was produced in the same manner as in Example 1, except that a resin cured layer was formed on the upper and lower surfaces of the PET film and a structure layer was formed on the resin cured layer on the upper surface.

CTE (ppm / ° C) The substrate layer Resin cured layer Structure layer MD TD Comparative Example 1 22.4 23.4 - 28.6 Example 1 21.3 24.6 25.0 27.5 Example 2 22.0 23.1 24.7 28.0 Example 3 21.4 22.9 23.8 27.8

CTE, warpage and wrinkles of the optical members of Examples and Comparative Examples were measured in the following manner, and the results are shown in Table 2.

CTE

The coefficient of thermal expansion was measured in tensile mode using TMA from Perkin Elmer. The film-shaped test piece was measured for the elongation percentage of the test piece at a temperature of 30 to 120 DEG C at a heating rate of 5 DEG C / min under an atmosphere of nitrogen of 100 ml / min at a thickness of 215 mu m * 3 mm * 12 mm and a tension of 215 mN, The average thermal expansion coefficient of TD (Transverse Direction) was calculated.

warp

A film of 100 mm * 100 mm in size was suspended in an oven at a temperature of 60 ° C and a humidity of 85%, and allowed to stand for 96 hours. After leaving for 30 minutes at room temperature, the film was placed on a tray and the warping height of the film was measured.

wrinkle

The optical member having a size of 400 mm * 200 mm was placed in an oven at a temperature of 60 ° C and a humidity of 85%, and then allowed to stand for 96 hours. After leaving for 30 minutes at room temperature, the optical members were placed on a tray, The highest height at which wrinkles occurred was measured.

CTE (ppm / ° C) Bending (mm) Wrinkles (ea, mm) MD TD Comparative Example 1 22.4 28.8 2.4 3ea, 2.7mm Example 1 20.0 25.1 1.7 2ea, 2.0mm Example 2 21.3 23.4 1.5 2ea, 1.8mm Example 3 18.1 19.0 1.2 1ea, 1.2mm

As a result of measurement of the physical properties of the optical members of Examples and Comparative Examples, as shown in Table 2, in the case of the optical member including the resin cured layer having lower CTE than the base layer (Examples 1 to 3) The CTE of the optical member itself is lower than that of the optical member (Comparative Example 1) which does not include the optical member (Comparative Example 1), and the warping property and the wrinkle property are improved.

10: base layer, 20: resin cured layer, 30: structural layer

Claims (5)

A base layer;
A resin cured layer formed on at least one side of the substrate layer; And
A resin layer formed on one side of the resin cured layer and having a plurality of structures arranged therein,
Wherein the resin cured layer has a coefficient of thermal expansion (CTE) thereof larger than a CTE of the base layer and smaller than a CTE of the structure layer. The method according to claim 1,
The CTE difference between the base layer and the resin cured layer is 1 to 5 ppm /
Wherein the CTE difference between the resin cured layer and the structural layer is 1 to 5 ppm / ° C. The method according to claim 1,
Wherein the resin cured layer is made of a resin selected from an ultraviolet curing resin, a thermosetting resin and a mixed resin thereof. The method according to claim 1,
Wherein the structure is selected from a triangular, semicircular, elliptic, and lenticular profile in its longitudinal section. A backlight unit comprising the optical member according to any one of claims 1 to 4.

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