KR101541279B1 - An optical film, a backlight unit having the optical film, and an LCD device having the backlight unit - Google Patents

Abstract

The present invention provides a light emitting device comprising: a base layer made of a light-transmitting material; A microlens array layer including a plurality of microlenses arranged on one side of the base layer; A light reflection layer formed to be spaced apart from the microlens array layer and reflecting light incident on the base layer; A light absorbing layer formed on one side of the light reflecting layer facing the microlens array layer, the light absorbing layer absorbing light; And a light transmitting portion formed through the light reflecting layer and the light absorbing layer at focal positions of the plurality of microlenses, a backlight unit including the optical film, and an LCD device having the backlight unit Lt; / RTI >

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film, a backlight unit having the optical film, and an LCD device having the backlight unit,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit used in a flat panel display device, and more particularly, to an optical film having improved light-convergence degree, a backlight unit having the optical film, and an LCD device having the backlight unit.

The flat panel display device includes a light emitting device that emits light by itself to form an image, and a light receiving device that receives light from the outside to form an image. For example, a liquid crystal display (LCD) device is a light receiving flat panel display device. Thus, the LCD device requires a separate light source, for example a lighting device such as a backlight unit.

Such a backlight unit is a direct type in which a light source is placed on the back surface of an LCD panel to directly illuminate the entire surface of the LCD panel and a light source is disposed on one side or both sides of the LCD panel, And an edge type that diffuses by diffusion. Direct type can be placed on a large display such as an LCD TV because a light source can be arranged in a large area freely and effectively, and the edge type is arranged at a limited position where a light source is a side surface of a light guide plate, but the volume can be reduced. It is mainly used in displays.

Among liquid crystal modes of an LCD panel, for example, liquid crystal of a TN mode is widely used for a high yield and a low manufacturing cost, but it is pointed out that a relatively narrow viewing angle is a disadvantage. An optical film such as a wide view film may be used to alleviate the relatively narrow viewing angle problem. Recently, a so-called collimation LCD which diffuses light transmitted through an LCD panel by placing a light diffusing plate in front of the LCD panel has been studied. The collimation LCD has a structure in which a light path from a backlight unit to an LCD panel It is important that the light is collimated and incident on the LCD panel.

The present invention provides an optical film having improved light collecting degree, a backlight unit having the optical film, and an LCD device having the backlight unit.

The present invention provides a light emitting device comprising: a base layer made of a light-transmitting material; A microlens array layer including a plurality of microlenses arranged on one side of the base layer; A light reflection layer formed to be spaced apart from the microlens array layer and reflecting light incident on the base layer; A light absorbing layer formed on one side of the light reflecting layer facing the microlens array layer, the light absorbing layer absorbing light; And a light transmitting portion formed through the light reflecting layer and the light absorbing layer at focal positions of the plurality of microlenses.

According to one embodiment of the present invention, when the distance from one side of the base layer to the light transmitting portion is T, the thickness of the microlens is h, and the radius of curvature of the microlens is r, T + h = 3r Lt; / RTI >

According to an embodiment of the present invention, six microlenses 13 may be arranged at regular intervals around any one microlens of the microlens array layer.

According to an embodiment of the present invention, the surface of the reflective layer may be curved or irregular so that the angle of incidence of the light incident on the reflective layer and the reflection angle of the light reflected by the reflective layer are not equal to each other.

According to an embodiment of the present invention, the light absorbing layer and the light reflection layer may be formed on a side opposite to one side of the base layer on which the microlens array layer is formed.

According to an embodiment of the present invention, the light absorbing layer, the light reflecting layer, and the light transmitting portion may be formed inside the base layer.

According to an embodiment of the present invention, the light transmitting portion may be a light transmitting layer passing through the light reflecting layer and the light absorbing layer.

According to an embodiment of the present invention, the light transmitting portion may include a reflection type polarizing layer that transmits one direction of polarized light and reflects another direction of polarized light.

The present invention also provides a light emitting device comprising at least one light source emitting light; The optical film disposed in front of the light source; And a light reflecting surface disposed behind the light source and reflecting the backward light toward the front, and an LCD device having the backlight unit.

The backlight unit according to an embodiment of the present invention may further include an optical diffuser between the light source and the optical film.

Hereinafter, an optical film according to an embodiment of the present invention, a backlight unit including the optical film, and an LCD device including the backlight unit will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an optical film according to a first embodiment of the present invention, and FIG. 2 is a plan view of the optical film of FIG.

1, the optical film 10A according to the first embodiment of the present invention includes a base layer 11 in the form of a film made of a light-transmitting material, A microlens array layer 12 including a plurality of microlenses 13 arranged thereon and a light reflecting layer 13 formed to be spaced apart from the microlens array layer 12 and reflecting light incident on the base layer 11 And a light absorbing layer 17A formed on one side of the light reflecting layer 15A facing the microlens array layer 12 and absorbing light. And a light transmitting portion formed through the light reflecting layer 15A and the light absorbing layer 17A at the focus position of the plurality of microlenses 13. [ The light transmitting portion is a light transmitting hole 18 passing through the light reflecting layer 15A and the light absorbing layer 17A.

The plurality of microlenses 13 are attached to the front surface of the base layer 11 through which light is emitted toward the LCD panel 70 (see FIG. 7). The microlens 13 is incident on the base layer 11 through the light transmission hole 18 on the rear surface of the base layer 11 and is directed forward through the front surface of the base layer 11 In the direction perpendicular to the plane in which the base layer 11 forms the light path.

Referring to FIG. 2, the plurality of microlenses 13 are disposed in close contact with the front surface of the base layer 11 as closely as possible in order to increase the degree of light condensation through the optical film 10A. Therefore, six microlenses 13 are arranged at equal intervals around one arbitrary microlens 13. [ The light transmitting apertures 18 are formed at the central portion where the focal point of each microlens 13 is located. The distance relation between each microlens 13 and the corresponding light transmission hole 18 is expressed by the following equation (1).

T + h = 3r

Here, T denotes a distance from one side of the base layer 11 to which the microlens 13 is attached to the light transmission hole 18, h denotes the thickness of the microlens 13, Means the radius of curvature of the microlens 13.

The base layer 11 may be made of a transparent polymer having good light transmittance, and the microlenses 13 may be made of a polymer material such as glass or polymethly methacrylate (PMMA).

The light absorbing layer 17A and the light reflecting layer 15A are sequentially coated on the rear surface opposite to the front surface of the base layer 11 on which the microlens array layer 12 is formed, or by a method of coating. In the embodiment shown in FIG. 1, the distance T from one side of the base layer 11 to which the microlenses 13 are attached to the light transmitting hole 18 coincides with the thickness of the base layer 11.

7 is an exploded cross-sectional view of an LCD device having the optical film of FIG.

7, the LCD device 100 includes a back light unit 50A having the optical film 10A shown in FIG. 1, an LCD 50A disposed on the front side of the backlight unit 50A, And a panel (70). The backlight unit 50A includes a plurality of light sources 52, an optical film 10A disposed in front of the light source 52, and a light reflection surface 55 disposed behind the light source 52. [ And a first optical diffuser 57 disposed between the light source 52 and the optical film 10A.

The light source 52 emits light including, for example, an LED (Light Emitting Diode) or a CCFL (Cold Cathode Fluorescent Lamp). The light reflection surface 55 reflects the light directed toward the rear of the light source 52 forward, and may include, for example, a reflection film. The first optical diffusing plate 57 diffuses light so that light emitted from the light source 52 is dispersed and incident on the optical film 10A uniformly. The first optical diffusing plate 57 is a so-called " hot spot " spot '.

The LCD panel 70 includes a liquid crystal layer 61 injected with a TN mode liquid crystal, a rear polarizer 64 disposed behind the liquid crystal layer 61 and transmitting polarized light in one direction, And a front polarizing plate 63 disposed in front of the rear polarizing plate 61 and transmitting polarized light in one direction different from the polarizing light transmissible through the rear polarizing plate 64. In addition, the LCD device 100 includes a second light diffuser plate 66 in front of the LCD panel 70. The second optical diffusing plate 66 diffuses the path of the light transmitted through the LCD panel 70 to enlarge the viewing angle.

In addition, when the direction of the light emitted from the backlight unit 50A is orthogonal to the LCD panel 70, the contrast ratio of the LCD device 100 is increased and the viewing angle can be expanded. Referring again to FIG. 1, light emitted from the light source 52 (see FIG. 7) enters the light transmitting hole 18 while passing through the focal point of the microlens 13 at the center of the light transmitting hole 18 La1 is refracted by the base layer 11 and proceeds to a microlens 13 paired with the light transmission hole 18 and is condensed by the microlens 13 to form a base layer 11 In a direction orthogonal to the plane formed by the projection lens.

The light La2 entering the light transmission hole 18 along the path deviated from the focus of the microlens 13 at the center of the light transmission hole 18 is refracted by the base layer 11, The light does not advance to the microlenses 13 paired with the holes 18 and proceeds to another microlens 13 adjacent thereto and is totally reflected by the microlenses 13 and absorbed by the light absorbing layer 17A (Absorbed). If the light absorbing layer 17A is absent, the total reflected light is reflected back to the light reflecting layer 15A and can be projected in a diagonal direction without being orthogonal to the plane formed by the base layer 11. [ The light projected in the oblique direction toward the front side deteriorates the degree of condensation of the backlight unit 50A (see Fig. 7).

7) is reflected by the light reflection layer 15A and is reflected toward the back of the light source 52 (see FIG. 7). The light La3 propagates to the light reflection layer 15A due to the light emission of the light source 52 Is again reflected by the light reflection surface 55 disposed in the optical film 10A and then directed to the optical film 10A again. This is also called "recycling" of light. The recycled light is incident on the focal point of the microlens 13 at the center of the light transmitting hole 15A (see La1) or enters the area off the center of the light transmitting hole 15A (see La2) (See La3). These processes have already been described so that redundant descriptions are omitted.

The inventors performed a simulation for comparing the performance of the optical film 10A of the present invention shown in Fig. 1 and the optical film from which the light absorbing layer 17A was removed in the optical film 10A shown in Fig. 1 . In this simulation, it is assumed that the micro lens 13 (see Fig. 1) of the optical film has a radius of curvature r (see Fig. 1) of 0.1 mm and a height h 1) is assumed to be 0.2 mm, the light transmission hole 18 (see Fig. 1) is circular, and the radius thereof is assumed to be 0.1 mm.

The light absorptivity of the light absorbing layer 17A is assumed to be 100%, and the light reflectance of the light reflecting layer 15A is assumed to be two types of 87% and 95%. The following table summarizes the simulation results.

division Before Optical Film Transmission After passing through the comparative optical film (light absorbing layer X, light reflecting layer O) After the optical film of the present invention (the light absorbing layer O, the light reflecting layer O) Light reflectance - 87% 95% 87% 95% Light distribution ± 90 ° ± 18 ° ± 16 ° ± 13.5 ° ± 13.5 ° Illuminance 350 [1m] 250 [1m] 250 [1m] 93 [1m] 110 [1m] Luminance 3500 [nit] 6500 [nit] 7000 [nit] 5800 [nit] 6400 [nit] Effective light quantity - 66% 68% 92% 92%

The light before transmission through the optical film has a Lambertian light distribution with an illuminance of 350 [lm], a luminance of 3500 [nit], and a light distribution of 90 [deg.]. When such an optical film having only a light reflecting layer having a light reflectance of 87% and an optical film having no light absorbing layer is transmitted, the light has an illuminance of 250 [lm], a luminance of 6500 [nit], a light distribution of ± 18 °, A light having a luminance of 7000 [nit] and a light distribution of ± 16 ° is obtained when an optical film having only a light reflection layer having only a light reflection layer and having no light absorption layer is transmitted. At this time, the effective light amount indicating the amount of emitted light within the full width at half maximum is 66% and 68%, respectively. This result is that about 1/3 of the total emitted light amount is emitted to the side of the optical film without being emitted in the direction orthogonal to the plane formed by the optical film, that is, in the front direction, and the light collection and contrast ratio may be deteriorated .

On the contrary, when the optical film (10A, see FIG. 1) of the present invention having a light reflecting layer having a light reflectance of 87% and a light absorbing layer having a light absorbing ratio of 100% is passed through, the illuminance is 93 [ (See FIG. 1) having the light reflecting layer 15A having a light reflectance of 95% and the light absorbing layer 17A having a light absorbing rate of 100%, which have optical characteristics of 90% A light intensity distribution of 110 [lm], a luminance of 6400 [nit], a light distribution of ± 13.5 °, and an effective light amount of 92%.

Compared with the optical characteristics of the light transmitted through the optical film without the light absorbing layer, the illuminance decreased to about 60%, but the luminance decreased only about 10%. This means that the light absorbed by the light absorbing layer 17A largely reduces the illuminance but the light absorbed in the light absorbing layer 17A is mostly light emitted to the side surface rather than the light emitted to the front surface of the optical film. The result that the effective light amount reaches 92% also indicates that the optical film 10A of the present invention has a high condensing effect. By reducing the width a of the light transmitting hole 18 and reducing the amount of light traveling to the adjacent microlens 13 other than the microlens 13 paired with the light transmitting hole 18, have.

In the optical film 10A of the present invention, the light distribution of the outgoing light is equal to +/- 13.5 DEG regardless of the light reflectance of the light reflection layer 15A. This is because the light absorbing layer 17A absorbs all the light traveling in the lateral direction, not the front direction, and the light distribution of the outgoing light can be adjusted only by adjusting the width a of the light transmitting hole 18 .

FIGS. 3 and 4 are cross-sectional views showing optical films according to second and third embodiments of the present invention, and FIG. 8 is an exploded cross-sectional view of an LCD device having optical films of FIGS.

3 and 4, the optical films 10B and 10C according to the second and third embodiments of the present invention are also similar to the optical film 10A (see Fig. 1) of the first embodiment, A microlens array layer 12 including a plurality of microlenses 13, light reflecting layers 15B and 15C, light absorbing layers 17B and 17C and a light transmitting hole 18 are provided. On the other hand, the surface of the light reflection layer 15B of the optical film 10B according to the second embodiment is a curved surface that is not flat and curved, and the surface of the light reflection layer 15C of the optical film 10C according to the third embodiment is It is an irregular aspect that is intentionally formed to cause diffuse reflection.

The light Lb1 and Lc1 incident on the central portion of the light transmitting hole 18 are condensed by the microlenses 13 to be incident on the plane formed by the base layer 11 The lights Lb2 and Lc2 projected in the direction orthogonal to each other and entering the region deviated from the central portion of the light transmission hole 18 are absorbed by the light absorption layers 17B and 17C. Light beams Lb3 and Lc3 traveling to the light reflection layers 15B and 15C are reflected by the light reflection layer 15A to perform recycling of light. Since the light reflection layers 15B and 15C are not smooth planes, the reflection angle and the incident angle of the light reflected by the light reflection faces 15B and 15C are different from each other, and the light scattering degree of the light reflection layers 15B and 15C is increased . 8) between the optical films 10B and 10C of the backlight unit 50B and the light source 52 as shown in Fig. 8 because there is a large degree of scattering of light to be recycled .

8 includes a liquid crystal layer 61 and a rear polarizing plate 64 disposed behind the liquid crystal layer 61 and transmitting a polarized light in one direction, as in the LCD device 100 of Fig. A front polarizing plate 63 disposed in front of the liquid crystal layer 61 and transmitting polarized light in one direction different from the polarized light transmissible through the rear polarizing plate 61 and a front polarizing plate 63 disposed in front of the LCD panel 70 66). The light diffusing plate 66 spreads the path of the light transmitted through the LCD panel 70 to enlarge the viewing angle.

5 is a cross-sectional view showing an optical film according to a fourth embodiment of the present invention. 5, the optical film 10D according to the fourth embodiment of the present invention also includes a base layer 11 and a plurality of microlenses 13, as in the optical film 10A (Fig. 1) A light reflecting layer 15D, a light absorbing layer 17D, and a light transmitting hole 19. The microlens array layer 12 includes a light transmitting layer 19, On the other hand, the light reflection layer 15D, the light absorption layer 17D, and the light transmission hole 19 of the optical film 10D according to the fourth embodiment are not formed on the incident surface of the base layer 11, (11). This increases the amount of light passing through the light transmitting apertures 19 among the light incident on the incident surface of the base layer 11 as compared with the optical film 10A (see Fig. 1) of the first embodiment. That is, in the case of the optical film 10A (see Fig. 1) of the first embodiment, only light incident on the region corresponding to the width a of the light transmission hole 18 (see Fig. 1) In the optical film 10D of the fourth embodiment, light incident on the region (b) wider than the width (a) can pass through the light transmitting hole (19) have.

The light Ld1 passing through the central portion of the light transmitting hole 19 is condensed by the microlenses 13 to be orthogonal to the plane formed by the base layer 11, And the light Ld2 that has been incident on the base layer 11 and passed through the light transmission hole 19 through the region of the light transmission hole 19 deviating from the central portion is absorbed by the light absorption layer 17D Absorption). The light Ld3 traveling to the light reflection layer 15D is reflected by the light reflection layer 15D to perform the light recycling process.

FIG. 6 is a cross-sectional view showing an optical film according to a fifth embodiment of the present invention, and FIG. 9 is an exploded cross-sectional view of an LCD device having the optical film of FIG.

6, the optical film 10E according to the fifth embodiment of the present invention also includes a base layer 11, a plurality of microlenses 13 as well as the optical film 10A (see Fig. 1) A microlens array layer 12, a light reflecting layer 15E, and a light absorbing layer 17E. 1) of the first embodiment is provided with a light transmitting hole 18 (see Fig. 1) as a light transmitting portion, the optical film 10E according to the fifth embodiment is a light transmitting portion, A reflective polarizing layer 20 is provided instead of the light transmitting hole 18 (see FIG. 1). The reflection type polarizing layer 20 has a function of transmitting polarized light in one direction and reflecting polarized light in the other direction.

The light Le-in emitted from the light source 52 (see FIG. 9) and incident on the reflective polarizing layer 20 has polarization characteristics in both directions perpendicular to each other, but passes through the reflective polarizing layer 20, Light Le-trans projected forward of the film 10E has only polarization characteristics in one direction, and light Le-out having polarization characteristics in the other direction is reflected.

9, the LCD device 300 includes a backlight unit 50C having the optical film 10E and an LCD panel 80 disposed in front of the backlight unit 50C. Like the backlight unit 50A shown in FIG. 7, the backlight unit 50C includes a plurality of light sources 52, an optical film 10E disposed in front of the light source, And a first optical diffuser 57 disposed between the light source 52 and the optical film 10A.

The LCD panel 80 includes a liquid crystal layer 61 in which a TN mode liquid crystal is injected and a liquid crystal layer 61 disposed in front of the liquid crystal layer 61 and having a polarization direction different from that of polarized light transmissible through the reflective polarizing layer 20. [ And a front polarizer 63 for transmitting polarized light. In addition, the LCD device 300 includes a second light diffuser plate 66 in front of the LCD panel 80. The second optical diffusing plate 66 diffuses the path of the light transmitted through the LCD panel 80 to enlarge the viewing angle. 9, since the light emitted from the backlight unit 50C is polarized in one direction, the LCD device 300 of FIG. 9 is provided with the rear polarizers 64, See Fig. 7).

The optical film of the present invention is excellent in the degree of condensation of outgoing light, so that it is not necessary to use several optical films for condensing in manufacturing an LCD device. Therefore, a collimation LCD device having a high contrast ratio and a large viewing angle can be implemented at a low cost.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

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

2 is a plan view of the optical film of Fig.

3 to 6 are sectional views of optical films according to second to fifth embodiments of the present invention.

7 is an exploded cross-sectional view of an LCD device having the optical film of FIG.

FIG. 8 is an exploded cross-sectional view of an LCD device having the optical film of FIG. 3 or FIG.

FIG. 9 is an exploded cross-sectional view of an LCD device having the optical film of FIG. 6;

Description of the Related Art

10A to 10E ... optical film 11 ... base layer

12 ... microlens array layer 13 ... microlenses

15A to 15E ... light reflecting layers 17A to 17E ... light absorbing layers

18, 19 ... light transmitting hole 20 ... reflective polarizing layer

50A to 50C ... backlight unit 70, 80 ... LCD panel

Claims (16)

A base layer made of a light-transmitting material; A microlens array layer including a plurality of microlenses arranged on one side of the base layer; A light reflection layer formed to be spaced apart from the microlens array layer and reflecting light incident on the base layer; A light absorbing layer formed on one side of the light reflecting layer facing the microlens array layer, the light absorbing layer absorbing light; And And a light transmitting portion formed through the light reflecting layer and the light absorbing layer at focal positions of the plurality of microlenses, Wherein the surface of the light reflection layer is a curved surface or an irregular surface such that an incident angle of light incident on the light reflection layer and a reflection angle of light reflected by the light reflection layer are not equal to each other. The method according to claim 1, Wherein T + h = 3r, where T is a distance from one side of the base layer to the light transmitting portion, h is a thickness of the microlens, and r is a curvature radius of the microlens. The method according to claim 1, Characterized in that six microlenses (13) are arranged at equal intervals around a certain microlens of the microlens array layer. delete The method according to claim 1, Wherein the light absorbing layer and the light reflection layer are formed on a side opposite to one side of the base layer on which the microlens array layer is formed. The method according to claim 1, Wherein the light absorption layer, the light reflection layer, and the light transmission portion are formed inside the base layer. The method according to claim 1, Wherein the light transmission portion is a light transmission hole passing through the light reflection layer and the light absorption layer. The method according to claim 1, Wherein the light transmitting portion includes a reflection type polarizing layer that transmits one direction of polarized light and reflects another direction of polarized light. At least one light source emitting light; An optical film according to any one of claims 1 to 3 or 5 to 8, arranged in front of the light source; And And a light reflecting surface disposed behind the light source and reflecting the backward light toward the front. 10. The method of claim 9, Further comprising an optical diffuser between the light source and the optical film. An optical film according to any one of claims 1 to 3 or 5 to 7, disposed at the front of the light source, at least one light source emitting light, A backlight unit having a light reflecting surface that reflects backward light toward the front; And A back polarizing plate disposed behind the backlight unit and disposed behind the liquid crystal layer and transmitting polarized light in one direction and a polarizing plate disposed in front of the liquid crystal layer and capable of transmitting through the rear polarizing plate, And an LCD panel (liquid crystal display panel) having a front polarizer for transmitting polarized light in one direction. 12. The method of claim 11, Wherein the backlight unit further comprises an optical diffuser between the light source and the optical film. 12. The method of claim 11, Further comprising a light diffusion plate in front of the LCD panel. A light source device comprising: at least one light source emitting light; an optical film of claim 8 arranged in front of the light source; and a light reflecting surface disposed at the rear of the light source for reflecting the backward light toward the front Backlight unit; And An LCD panel having a liquid crystal layer disposed in front of the backlight unit and a front polarizer disposed in front of the liquid crystal layer and transmitting polarized light in one direction different from polarizations transmittable through the reflective polarized layer, crystal display panel. 15. The method of claim 14, Wherein the backlight unit further comprises an optical diffuser between the light source and the optical film. 15. The method of claim 14, Further comprising a light diffusion plate in front of the LCD panel.

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