KR20090054299A - Light diffusion film for liquid crystal display - Google Patents

Abstract

Disclosed is a light diffusing film for liquid crystal display devices. The light diffusion film for a liquid crystal display device is a transparent base material; A high refractive index layer formed on one surface of the transparent substrate; And a low refractive index layer which is alternately arranged with the high refractive index layer and has a refractive index that is 0.01 to 0.1 less than the refractive index of the high refractive index layer.

Description

Light Diffusion Film for Liquid Crystal Display {LIGHT DIFFUSION FILM FOR LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device, and more particularly, to a light diffusion film for a liquid crystal display device.

Recently, cathode ray tubes (CRTs), which are representative of display devices, have been used for flat panel display devices such as liquid crystal displays (LCDs), organic light emitting displays (OLEDs), and plasma display devices. Flat Panel Display (FPD). Among them, liquid crystal displays capable of realizing high resolution and being capable of miniaturization as well as miniaturization are widely used.

The liquid crystal display according to the background art includes a backlight unit and a liquid crystal panel.

The backlight unit may be disposed on the rear surface of the liquid crystal panel and may emit light according to the driving power applied.

The liquid crystal panel displays an image by using light emitted from the backlight unit, and includes a color filter substrate, a thin film transistor substrate, and a liquid crystal layer interposed between the two substrates.

Here, the liquid crystal layer is composed of nematic liquid crystal molecules having dielectric anisotropy and refractive index anisotropy, wherein the nematic liquid crystal molecules are arranged in a specific direction according to an electric field between electrodes formed on each of the two substrates.

In this case, due to the refractive anisotropy of the nematic liquid crystal molecules, the phase difference of the liquid crystal layer may vary according to the position of the liquid crystal display facing the liquid crystal display, which may be recognized as a color deviation according to a viewing angle.

Accordingly, an object of the present invention is to provide a light diffusion film for a liquid crystal display device which can minimize color deviation due to the viewing angle of the liquid crystal display device.

Other problems to be solved by the present invention are not limited to the above-mentioned problems, and other tasks not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

The light diffusing film for a liquid crystal display device according to an embodiment of the present invention for achieving the problem to be solved is a transparent substrate; A high refractive index layer formed on one surface of the transparent substrate; And a low refractive index layer which is alternately arranged with the high refractive index layer and has a refractive index that is 0.01 to 0.1 less than the refractive index of the high refractive index layer.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings.

According to the present invention, the light emitted from the liquid crystal display can be diffused and / or mixed by using the total reflection characteristic of the light due to the difference in refractive index between the alternating high refractive index layer and the low refractive index layer. The deviation can be minimized.

Hereinafter, a light diffusion film for a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals refer to like elements throughout.

The light diffusion film for a liquid crystal display according to the exemplary embodiment of the present invention may be disposed on the entire liquid crystal panel provided in the liquid crystal display. The light diffusing film diffuses and / or mixes the light emitted from the liquid crystal display, that is, the light emitted from the backlight unit included in the liquid crystal display and passed through the liquid crystal panel, thereby minimizing color deviation that may occur depending on the viewing angle. can do. Accordingly, when viewing vehicles located at different angles look at the liquid crystal display including the light diffusing film, the same color may be recognized for each viewer.

1 is a cross-sectional view illustrating a configuration of a light diffusing film for a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the light diffusing film 100 for a liquid crystal display according to an exemplary embodiment of the present invention includes a transparent substrate 110, a high refractive index layer 120, and a low refractive index layer 130.

The transparent substrate 110 is not particularly limited because it only needs transparency, but a transparent plastic film may be used. The transparent plastic film is, for example, polyethylene terephthalate, polysulfone, polyether sulfone, polystyrene, polyethylene naphthalate, polyarylate, polycarbonate, polypropylene, polyimide, triacetyl cellulose, polymethyl methacrylate, It may include one or more selected from the group consisting of epoxy acrylate and brominated acrylate.

The high refractive index layer 120 may be formed on one surface of the transparent substrate 110. Since the refractive index of the high refractive index layer 120 is greater than the refractive index of the low refractive index layer 130, the refractive index is not particularly limited, but may be, for example, 1.4 to 1.6.

The high refractive index layer 120 may satisfy the refractive index range and include a photocurable resin having transparency. As said photocurable resin, 1 or more types can be used from the group which consists of polyester type, an epoxy type, (meth) acrylate type, urethane acrylate type, or epoxy acrylate type resin, for example. Preferably, a urethane acrylate-based or epoxy acrylate-based resin having a refractive index adjusted at about 1.55 may be used as the photocurable resin.

The high refractive index layer 120 may further include light diffusing particles such as acrylic, silicone, nylon, soft microcapsule type, melamine based, styrene beads, etc., in addition to the photocurable resin.

The high refractive index layer 120 may include a groove 120a, and the groove 120a may be well-known, such as a heat press method, a casting method, an injection molding method, or the like, using the photocurable resin of the high refractive index layer 120. It can be formed through the method and the like.

The low refractive index layer 130 may be alternately arranged with the high refractive index layer 120 in left, right, and / or vertical directions. In addition, the low refractive index layer 130 and the high refractive index layer 120 may be arranged in any one of a stripe, orthogonal and lattice. Hereinafter, for convenience of description, the low refractive index layer 130 is alternately arranged with the high refractive index layer 120, and the low refractive index layer 130 and the high refractive index layer 120 have a stripe shape. The case of arrangement will be described as an example.

The low refractive index layer 130 may be formed in the groove 120a and alternately arranged with the high refractive index layer 120. Since the refractive index of the low refractive index layer 130 may be smaller than the refractive index of the high refractive index layer 120, the refractive index is not particularly limited, but may be 0.01 to 0.1 smaller than the refractive index of the high refractive index layer 120. If the refractive index of the low refractive index layer 130 is less than the refractive index of the high refractive index layer 120, but the difference is less than 0.01, there is a problem that the total reflection effect of the incident light (L1, L2) is insignificant, if the difference exceeds 0.1 The incident light L1 and L2 are so diffused that the front luminance decreases. Here, the incident light (L1, L2) is when the light diffusion film 100 is disposed in front of the liquid crystal panel of the liquid crystal display device, is emitted from the backlight unit of the liquid crystal display device passes through the liquid crystal panel, and then the light diffusion The light incident on the film 100 is referred to.

The low refractive index layer 130 may include, for example, a photocurable resin having a refractive index of 1.3 to 1.56. As said photocurable resin, 1 or more types can be used, for example from the group which consists of an organosilicon compound, a urethane acrylate type, or an epoxy acrylate type resin. Preferably, a urethane acrylate-based or epoxy acrylate-based resin having a refractive index adjusted at about 1.50 may be used as the photocurable resin.

The low refractive index layer 130 may further include a light absorbing material to improve contrast ratio (CR) of the liquid crystal display by absorbing external environmental light in addition to the photocurable resin. The light absorbing material may be, for example, one or more selected from the group consisting of aniline black, carbon black, and titanium black, but is not limited thereto.

The low refractive index layer 130 may be formed by filling the groove 120a with the photocurable resin of the low refractive index layer 130 by using a wiping method or the like, and then curing it.

FIG. 2 is a plan view illustrating a planar arrangement of the low refractive index layer illustrated in FIG. 1.

Referring to FIG. 2, the low refractive index layer 130 may be formed in a stripe shape along a diagonal line on a plane due to the formation direction of the groove 120a, but is not limited thereto. For example, the low refractive index layer 130 may be formed in a stripe shape along a vertical or horizontal direction on a plane due to the formation direction of the groove 120a.

The cross-section of the low refractive index layer 130 may be wedge-shaped due to the shape of the groove 120a as shown in FIG. 1, but is not limited thereto. For example, the cross-section of the low refractive index layer 130 may be rectangular or square due to the shape of the groove 120a, or the above shapes may be combined. Hereinafter, a case where the low refractive index layer 130 is formed in a wedge shape will be described as an example.

The low refractive index layer 130 may include an upper surface 130a and first and second slopes 130b and 130c extending from the upper surface 130a in cross section. Two angles θ1 and θ2 of the surface 140 perpendicular to the upper surface 130a and the first and second slopes 130b and 130c may be greater than 0 and 45 degrees or less, respectively. θ2 may be the same or different within the range of the two angles θ1 and θ2. When the two angles θ1 and θ2 increase within the range of the two angles θ1 and θ2, the diffusion of incident light L1 and L2 may increase. However, when the two angles θ1 and θ2 exceed 45 degrees, the incident light L1 and L2 are diffused so much that the front luminance decreases.

The light diffusing film 100 for a liquid crystal display according to the exemplary embodiment of the present invention having the above-described configuration has incident light L1 through a difference in refractive index between the high refractive index layer 120 and the low refractive index layer 130 which are alternately formed. , L2) can be diffused and / or mixed by total reflection of the incident light L1 and L2. Here, total reflection means that when light is incident from an optically dense medium (ie, a material having a high refractive index) to a small medium (ie, a material having a small refractive index), if the incident angle is greater than or equal to a certain angle (critical angle), all the light is reflected at the interface. It is said to be.

Accordingly, incident light L1 and L2 incident on the first and second slopes 130b and 130c at a specific angle, that is, the critical angle or more, are totally reflected on the first and second slopes 130b and 130c, and then diffused and And / or mixed to exit upwards. For this reason, the color deviation according to the viewing angle of the liquid crystal display can be reduced.

Hereinafter, the light diffusing film for liquid crystal display device according to the exemplary embodiment of the present invention will be described in more detail with reference to Examples. However, the following Examples are intended to describe the light diffusing film for liquid crystal display of the present invention in more detail, and therefore the contents of the present invention are not limited to the following Examples.

EXAMPLE

Example  One

An epoxy acrylate resin having a refractive index of 1.55 was applied to one surface of a polyethylene terephthalate film having a thickness of 125 μm to a thickness of 150 μm. Subsequently, the coated epoxy acrylate resin was pressed using a mold having a trapezoidal pattern having a bottom side of 20 μm, an upper side 12 μm, and a height of 100 μm repeated at intervals of 70 μm, and then hardening the coated epoxy acrylate resin to form a groove having a high refractive index layer. Formed. Subsequently, after filling the urethane acrylate resin having a refractive index of 1.54 in the groove by using the wiping method, the light diffusing film was manufactured by forming a low refractive index layer by curing the groove.

Example  2

A light diffusing film was prepared in the same manner as in Example 1, but a urethane acrylate resin having a refractive index of 1.50 was used as the photocurable resin of the low refractive index layer.

Color deviation  evaluation

After attaching the light diffusing films prepared in Examples 1 and 2 to the front of the liquid crystal panel so that the linear direction of the low refractive index layer is 45 degrees, the white color coordinates according to the left and right viewing angles are measured on the xy color coordinates using a luminance meter. Next, the color deviation x (Δx) according to the left / right viewing angle is calculated and shown in FIG. 3 (a), and the color deviation y (Δy) according to the left / right viewing angle is calculated to refer to FIG. ). Here, the color deviation x (Δx) is the color coordinate x minus the color coordinate x at a specific left / right viewing angle, and the color deviation y (Δy) is the color coordinate at a specific left / right viewing angle from the color coordinate y at the front. minus y.

As a comparative example of the said Example 1 and 2, the said light-diffusion film did not adhere, the liquid crystal panel was employ | adopted. That is, when the light diffusion film is not attached to the liquid crystal panel, a white color coordinate according to left / right viewing angle is measured on an xy color coordinate using a luminance meter, and then color deviation x (Δx) according to left / right viewing angle is measured. The calculation is shown in (a) of FIG. 3, and the color deviation y (Δy) according to the left / right viewing angle is calculated and shown in (b) of FIG. 3.

3 is a graph illustrating color deviation according to a viewing angle of a liquid crystal display device having a light diffusion film for a liquid crystal display device according to an exemplary embodiment of the present invention.

Referring to FIG. 3, it could be seen that color deviations according to left / right viewing angles of the liquid crystal panel to which the light diffusing films prepared in Examples 1 and 2 are attached are smaller than those of the comparative example. Particularly, when the left / right viewing angles are 30 degrees and 60 degrees, it was found that the light diffusing film of Example 2 exhibited better characteristics than the light diffusing film of Example 1.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can realize that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. I can understand that.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

1 is a cross-sectional view illustrating a configuration of a light diffusing film for a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 2 is a plan view illustrating a planar arrangement of the low refractive index layer illustrated in FIG. 1.

3 is a graph illustrating color deviation according to a viewing angle of a liquid crystal display device having a light diffusion film for a liquid crystal display device according to an exemplary embodiment of the present invention.

{Description of symbols for main parts of the drawing}

100: light diffusing film 110: transparent substrate

120: high refractive index layer 130: low refractive index layer

Claims (6)

Transparent substrates; A high refractive index layer formed on one surface of the transparent substrate; And A low refractive index layer which is alternately arranged with the high refractive index layer and has a refractive index that is 0.01 to 0.1 smaller than the refractive index of the high refractive index layer. Light diffusion film for a liquid crystal display comprising a. The method of claim 1, The high refractive index layer and the low refractive index layer is a light diffusion film for a liquid crystal display device, characterized in that arranged in any one of a stripe, orthogonal and lattice. The method of claim 1, The cross-section of the low refractive index layer is at least one of a rectangular, square and wedge shape light diffusion film for a liquid crystal display device. The method of claim 1, The low refractive index layer includes a top surface and first and second slopes extending from the top surface in a cross section, and an angle between a surface perpendicular to the top surface and each of the first and second slopes is greater than 0 and 45 degrees or less. Light-diffusion film for liquid crystal display devices characterized by the above-mentioned. The method of claim 1, The low refractive index layer is a light diffusion film for a liquid crystal display, characterized in that formed along the oblique direction on a plane. The method of claim 1, The low refractive index layer is a light diffusion film for a liquid crystal display characterized in that it comprises a light absorbing material.

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