WO2008066221A1

WO2008066221A1 - Backlight unit and method of manufacturing an optical sheet included in the same

Info

Publication number: WO2008066221A1
Application number: PCT/KR2007/001871
Authority: WO
Inventors: Seong-Sik Kim; Sang-Dae Park; Jae-Woon Kim
Original assignee: Dinos Co., Ltd.
Priority date: 2006-11-29
Filing date: 2007-04-17
Publication date: 2008-06-05

Abstract

A backlight unit of the present invention includes a light guide plate; and a first prism sheet disposed on the light guide plate, and configured to condense a light outputted from the light guide plate. The first prism sheet includes a prism base and first prism patterns. The first prism patterns are disposed on a first surface of surfaces of the prism base, and configured to have a mountain shape. Here, when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude. In the prism sheet of the backlight unit, pitches between the prism patterns are different one another. Accordingly, the moire phenomenon, the wet-out phenomenon and the imprinting phenomenon are not occurred in the LCD using the backlight unit.

Description

BACKLIGHT UNIT AND METHOD OF MANUFACTURING AN OPTICAL SHEET INCLUDED IN THE SAME

Technical Field

[I] Example embodiments of the present invention relate to backlight unit and a method of manufacturing the same, more particularly relate to backlight unit for preventing a moire phenomenon and a wet-out phenomenon and an imprinting phenomenon. Background Art

[2] A liquid crystal display (hereinafter, referred to as "LCD") as a display device is not self-emitting device, and thus should include a backlight unit for providing a light to a LCD panel.

[3] FlG. 1 is a view illustrating a common LCD.

[4] In FlG. 1, the LCD includes a LCD panel 100 and a backlight unit 102.

[5] The backlight unit 102 provides a light, e.g. white light to the LCD panel 100. In the case, the LCD panel 100 displays a certain image using the provided light in accordance with data inputted from an outside apparatus (not shown).

[6] Hereinafter, the structure of the backlight unit 102 will be described.

[7] FlG. 2 is a perspective view illustrating the backlight unit. FlG. 3 is a sectional view illustrating a prism sheet in FlG. 2.

[8] In FlG. 2, the backlight unit 102 includes a light source section 200, a light guide plate 202, an optical sheet and a reflection sheet 206.

[9] The light source section 200 has a light source 220, and provides a light emitted from the light source 220 to the light guide plate 202.

[10] The light guide plate 202 outputs the light provided from the light source section 200 to the optical sheet 204 through an upper surface thereof. Particularly, the light provided from the light source section 200 is diffused by total reflection in the light guide plate 202 so that the provided light is uniformly diffused in the light guide plate 202. In this process, the provided light is outputted through the upper surface of the light guide plate 202.

[II] The reflection sheet 206 reflects a light leaked from the light guide plate 202 in a direction of the light guide plate 202 to reduce the consumption of the light.

[12] The optical sheet 204 includes a diffusion sheet 210 and a prism sheet 212.

[13] The diffusion sheet 210 diffuses uniformly the light outputted from the light guide plate 202. [14] The prism sheet 212 condenses the light diffused by the diffusion sheet 210 in a direction of the LCD panel 100. [15] In brief, the light emitted from the light source section 200 is incident to the LCD panel 100 through the light guide plate 202, the diffusion sheet 210 and the prism sheet 212.

[16] Hereinafter, the prism sheet 212 will be described in detail.

[17] The prism sheet 212 has a prism base 230 and prism patterns 232 as shown in FlG. 3.

[18] The prism patterns 232 are formed repeatedly with the same shape on the prism base

230. In addition, pitches P between the prism patterns 232 have the same length. In this case, since the prism patterns 232 and pixels included in the LCD panel 100 are respectively regular, a moire phenomenon which is generated by two regular patterns is occurred to the LCD panel 100.

[19] Further, the prism pattern 232 may be contacted with a lower surface of the LCD panel 100, e.g. lower polarization film by various causes, and so a wet-out phenomenon and an imprinting phenomenon are occurred to the LCD panel 100. Here, the wet-out phenomenon means a phenomenon that a specific part of the LCD panel 100 is brighter than the other parts, and the imprinting phenomenon indicates a phenomenon that a pattern similar to a stain is occurred to a part of the LCD panel 100. Disclosure of Invention Technical Problem

[20] Accordingly, the present invention is provided to substantially obviate one or more problems due to limitations and disadvantages of the related art.

[21] Example embodiments of the present invention provide a backlight unit for preventing moire phenomenon, wet-out phenomenon and imprinting phenomenon and a method of manufacturing the same. Technical Solution

[22] A prism sheet according to one example embodiment of the present invention includes a prism base; and first prism patterns disposed on a first surface of surfaces of the prism base, and configured to have a mountain shape. Here, when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[23] One or more of pitches between the first prism patterns have different length from the other pitches.

[24] The pitches have the length between about 5D and about 100D.

[25] The first prism patterns are disposed on an imaginary curve on the basis of the imaginary curve, wherein at least one of heights between the first prism patterns and the imaginary curve have different length from the other heights.

[26] The heights have the length in the range of about 0.1D and about 15D. [27] At least one of vertex angles of the first prism patterns has different magnitude from the other vertex angles.

[28] The vertex angles have the angle between about 80° and about 120°.

[29] An imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[30] One or more of pitches between valleys of the first prism patterns have different length from the other pitches.

[31] The prism sheet further includes diffusion sections disposed on a second surface of the surfaces of the prism base, and configured to have a hemisphere shape, wherein the second surface is different from the first surface.

[32] At least one of the diffusion sections includes a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index. Here, the first refractive layer is higher than the second refractive layer.

[33] The first refractive layer is made up of polymer having the first refractive index between about 1.49 and about 1.63, and the second refractive layer is made up of silica (SiO2) having the second refractive index of about 1.45.

[34] A length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[35] The prism pattern further includes second prism patterns disposed between the first prism patterns, and configured to have a hemisphere shape.

[36] A prism sheet according to another example embodiment of the present invention includes a prism base; a curved surface layer configured to have a curved surface shape, disposed on a first surface of surfaces of the prism base, and made up of a first substance; and first prism patterns disposed on the curved surface layer, configured to have a mountain shape, and made up of a second substance. Here, when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[37] The first substance is substantially identical to the second substance.

[38] At least one of pitches between the first prism patterns have different length from the other pitches.

[39] One or more of heights between the first prism patterns and the curved surface layer have different length from the other heights.

[40] At least one of vertex angles of the first prism patterns have different magnitude from the other vertex angles.

[41] An imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape. [42] The prism sheet further includes diffusion sections disposed on a second surface of the surfaces of the prism base, and configured to have a hemisphere shape, wherein the at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index. Here, the first refractive layer is higher than the second refractive layer.

[43] The first refractive layer is made up of polymer having the first refractive index between about 1.49 and about 1.63, and the second refractive layer is made up of silica (SiO2) having the second refractive index of about 1.45.

[44] A length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[45] The prism pattern further includes second prism patterns disposed between the first prism patterns, and configured to have a hemisphere shape.

[46] A backlight unit according to one example embodiment of the present invention includes a light guide plate; and a first prism sheet disposed on the light guide plate, and configured to condense a light outputted from the light guide plate. Here, the first prism sheet includes a prism base; and first prism patterns disposed on a first surface of surfaces of the prism base, and configured to have a mountain shape, wherein when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[47] At least one of pitches between the first prism patterns have different length from the other first prism patterns, one or more of vertex angles of the first prism patterns have different magnitude from the other vertex angles, and at least one of heights of the first prism patterns have different length from the other heights.

[48] The backlight unit further includes diffusion sections disposed on a second surface of the prism base, and configured to have a hemisphere shape. Here, wherein at least one of the diffusion sections includes a first refractive layer configured to have a first refractive index; and a second refractive layer configured to have a second refractive index smaller than the first refractive index.

[49] An imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[50] A length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[51] The backlight unit further includes second prism patterns disposed between the first prism patterns in the same direction as the first prism patterns, and configured to have a hemisphere shape.

[52] The backlight unit further includes a second prism sheet disposed on the first prism sheet, and configured to have third prism patterns crossing over the first prism patterns and the second prism patterns.

[53] The backlight unit further includes diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[54] The backlight unit further includes a second prism sheet disposed on the first prism sheet, and configured to have second prism patterns crossing over the first prism patterns.

[55] The backlight unit further includes diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[56] The backlight unit further includes a diffusion sheet located between the light guide plate and the first prism sheet, and configured to provide the light outputted from the light guide plate to the first prism sheet.

[57] A backlight unit according to another example embodiment of the present invention includes a light guide plate; and a first prism sheet located on the light guide plate, and configured to condense a light outputted from the light guide plate, wherein the first prism sheet includes a prism base; a curved surface layer configured to have a curved surface shape, disposed on a first surface of surfaces of the prism base, and made up of a first substance; and first prism patterns configured to have a mountain shape, disposed on the curved surface layer, and made up of a second substance. Here, when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[58] At least one of pitches between the first prism patterns have different length from the other first prism patterns, one or more of vertex angles of the first prism patterns have different magnitude from the other vertex angles, and at least one of heights of the first prism patterns have different length from the other heights.

[59] The backlight unit further includes diffusion sections disposed on a second surface of the prism base, and configured to have a hemisphere shape, wherein at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer disposed in the first refractive layer, and configured to have a second refractive index smaller than the first refractive index.

[60] An imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[61] A length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[62] The backlight unit further includes second prism patterns disposed between the first prism patterns in the same direction as the first prism patterns, and configured to have a hemisphere shape. [63] The backlight unit further includes a second prism sheet disposed on the first prism sheet, and configured to have third prism patterns crossing over the first prism patterns and the second prism patterns. [64] The backlight unit further includes diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape. [65] The backlight unit further includes a second prism sheet disposed on the first prism sheet, and configured to have second prism patterns crossing over the first prism patterns. [66] The backlight unit further includes diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[67] The first substance is substantially identical to the second substance.

[68] A one body type optical sheet according to one example embodiment of the present invention includes a first base section; a second base section; an adhering section located between the first base section and the second base section, and configured to adhere the second base section to the first base section; and first prism patterns disposed on the second base section. [69] The optical sheet further includes diffusion sections disposed on a surface opposed to a surface corresponding to the adhering section of surfaces of the first base section, and configured to have hemisphere shape. [70] At least one of the diffusion sections includes a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index, wherein the first refractive index is higher than the second refractive index. [71] The adhering section is made up of an ultraviolet curing resin (UV resin) or a curing resin containing a diffusion agent. [72] The first base section is a film made up of a polyethylene terephthalate PET, a poly methyl meta acrylate PMMA or a polycarbonate. [73] The first base section is made up of a diffusion plate.

[74] One or more of pitches between the first prism patterns have different length from the other pitches. [75] At least one of heights of the first prism patterns have different length from the other heights. [76] When a vertex angle of at least one of the first prism patterns is halved on the basis of a normal of the second base section, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[77] The first prism patterns are disposed on an imaginary curve.

[78] An imaginary line generated by connecting vertexes of some of the first prism patterns has mountain shape. [79] The optical sheet further includes second prism patterns disposed between the first prism patterns, and configured to have hemisphere shape. [80] The optical sheet further includes a curved surface layer disposed between the second base section and the first prism patterns, and configured to have curved surface shape. [81] The optical sheet is employed in a direct-lighting type backlight unit.

[82] A method of manufacturing a one body type optical sheet according to one example embodiment of the present invention includes forming a first structure by coating a curing resin on a first surface of surfaces of a first base section; curing firstly the first structure; forming a second structure by attaching a second base section to the first structure, wherein prism patterns are formed on the second base section; and forming the optical sheet by curing secondly the second structure. [83] The method further includes forming diffusion sections disposed on a second surface of the surfaces of the first base section, wherein the second surface is different from the first surface, [84] The first base section is a film made up of a polyethylene terephthalate PET, a poly methyl meta acrylate PMMA or a polycarbonate. [85] The first base section is made up of a diffusion plate.

Advantageous Effects [86] In the prism sheet of the backlight unit of the present invention, pitches between the prism patterns are different one another. In addition, heights of the prism patterns are different one another. Accordingly, the moire phenomenon, the wet-out phenomenon and the imprinting phenomenon are not occurred in the LCD using the backlight unit. [87] Further, in the backlight unit of the present invention, the curved surface layer having lens shape is formed on the prism sheet, and thus the concentration efficiency of the backlight unit is increased. [88] Additionally, in the prism sheet in the backlight unit of the present invention, the imaginary line formed by connecting the vertexes has mountain shape, and sub-angles generated by the halving the vertex angle have the same magnitude. Therefore, the concentration efficiency of the backlight unit is increased. [89] Moreover, an optical sheet included in a backlight unit of the present invention is one body type sheet, and so the thickness of the backlight unit and the loss of a light may be reduced. [90] In addition, a method of manufacturing an optical sheet of the present invention man- ufactures the optical sheet by attaching a UV resin and a prism structure to a film or a diffusion plate moving along a guide line, and thus the optical sheet is easily manufactured and a cost needed to manufacture the optical sheet is reduced.

Brief Description of the Drawings [91] Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which: [92] FlG. 1 is a view illustrating a common LCD;

[93] FlG. 2 is a perspective view illustrating the backlight unit;

[94] FlG. 3 is a sectional view illustrating a prism sheet in FlG. 2;

[95] FlG. 4 is a view illustrating a liquid crystal display employing a backlight unit according to one example embodiment of the present invention; [96] FlG. 5 is a perspective view illustrating the backlight unit according to a first example embodiment of the present invention; [97] FlG. 6 to FlG. 8 are sectional views illustrating the prism sheet according to one example embodiment of the present invention; [98] FlG. 9 is a perspective view illustrating a backlight unit according to a second example embodiment of the present invention;

[99] FlG. 10 and FlG. 11 are sectional views illustrating a prism sheet in FlG. 9;

[100] FlG. 12 is a sectional view illustrating a prism sheet employed in a backlight unit according to a third example embodiment of the present invention; [101] FlG. 13 is a sectional view illustrating a prism sheet employed in a backlight unit according to a fourth example embodiment of the present invention; [102] FlG. 14 is a sectional view illustrating a prism sheet employed in a backlight unit according to a fifth example embodiment of the present invention; [103] FlG. 15 is a perspective view illustrating a backlight unit according to a sixth example embodiment of the present invention; [104] FlG. 16 to FlG. 21 are sectional views illustrating prism sheets included in backlight units according to a seventh to twelfth example embodiments of the present invention; [105] FlG. 22 is a sectional view illustrating a backlight unit according to a fifteenth example embodiment of the present invention;

[106] FlG. 23 is a sectional view illustrating a diffusion section in FlG. 22; [107] FlG. 24 to FlG. 29 are views illustrating a first process of manufacturing the optical sheet according to one example embodiment of the present invention; [108] FlG. 30 is a view illustrating a second process of manufacturing the optical sheet according to another example embodiment of the present invention; [109] FlG. 31 is a sectional view illustrating an optical sheet according to a sixteenth example embodiment of the present invention;

[110] FlG. 32 to FTG. 34 are views illustrating an optical sheet according to a seventeenth embodiment of the present invention;

[111] FlG. 35 is a sectional view illustrating an optical sheet according to an eighteenth example embodiment of the present invention;

[112] FTG. 36 is a sectional view illustrating an optical sheet according to a nineteenth example embodiment of the present invention; and

[113] FTG. 37 is a sectional view illustrating an optical sheet according to a twentieth example embodiment of the present invention. Mode for the Invention

[114] Example embodiments of the present invention are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments of the present invention, however, example embodiments of the present invention may be embodied in many alternate forms and should not be construed as limited to example embodiments of the present invention set forth herein.

[115] Accordingly, while the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like numbers refer to like elements throughout the description of the figures.

[116] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[117] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.). [118] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising,", "includes" and/or "including", when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[119] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[120] FTG. 4 is a view illustrating a liquid crystal display employing a backlight unit according to one example embodiment of the present invention.

[121] In FlG. 4, the liquid crystal display (hereinafter, referred to as "LCD") includes a LCD panel 400 and the backlight unit 402.

[122] The backlight unit 402 provides a light having a certain wavelength to the LCD panel 400.

[123] The LCD panel 400 includes a lower polarization film 404, an upper polarization film 406, a lower substrate 408, an upper substrate 410, a color filter 412, a black matrix 414, a pixel electrode 416, a common electrode 418, a liquid crystal layer 420 and a TFT array 422.

[124] The polarization films 404 and 406 polarize the light provided from the backlight unit 402. For example, the polarization films 404 and 406 pass a traverse wave of the provided light, and cut off a longitudinal wave of the provided light.

[125] The TFT array 422 as switching device switches the pixel electrode 416.

[126] The liquid crystal layer 420 includes liquid crystals disposed corresponding to voltage difference between the pixel electrode 416 and the common electrode 418. In this case, the light provided from the backlight unit 402 is incident to the color filter 412 through the liquid crystals.

[127] The color filter 412 has sub-color filters corresponding to red light, green light and blue light as shown in FIG. 4. Here, the incident light passes through the color filter 412.

[128] The upper substrate 410 is disposed on the color filter 412.

[129] The backlight unit 402 provides the light, e.g. white light to the LCD panel 400, and will be described below with reference to accompanying drawings.

[130] FlG. 5 is a perspective view illustrating the backlight unit according to a first example embodiment of the present invention.

[131] In FlG. 5, the backlight unit 402 of the present embodiment includes a light source section 428, a light guide plate 434, a reflection sheet 436 and an optical sheet 438.

[132] The light source section 428 is located at one side of the light guide plate 434, and includes at least one light source 430 and a packing section 432. Here, the light source 430 according to one embodiment of the present invention may be point light source such as light emitting diode (LED), etc, or a surface light source such as external electrode fluorescent lamp (EEFL), Cold Cathode Fluorescent Lamp (CCFL), etc.

[133] It is desirable that the surface light source is used as the light source 430 in case that the backlight unit 402 is employed in a large size LCD panel. However, it is desirable that the point light source is used as the light source 430 in case that the backlight unit 402 is employed in a small size LCD panel. Here, the light source 430 is not limited to LED, CCFL and EEFL.

[134] The packing section 432 packages the light source 430, and reflects a light emitted from the light source 430 so that the emitted light is incident to one side of the light guide plate 434. This packing section 432 is made up of a material having high re- flexibility, and so a silver Ag may be coated on a surface of the packing section 432.

[135] The reflection sheet 436 is located under the light guide plate 434, and reflects a light leaked from the light guide plate 434 in a direction of the light guide plate 434. This reflection sheet 436 may be manufactured by coating a silver Ag on a base made up of aluminum, etc. Here, a process of manufacturing the reflection sheet 436 may include further a titanium coating process so as to prevent the deformation of the refection sheet 436 due to a heat.

[136] The light guide plate 434 outputs the light provided from the light source section 428 in a direction of the LCD panel 400, and is made up of for example a transparent acrylic resin such as poly methyl meta acrylate (PMMA).

[137] The optical sheet 438 is located on the light guide plate 434, and includes a diffusion sheet 500, a prism sheet 502 and a protection sheet 504.

[138] The diffusion sheet 500 is disposed on the light guide plate 434, and diffuses or condenses the light outputted from the light guide plate 434 to diffuse uniformly the light outputted from the light guide plate 434.

[139] The prism sheet 502 is disposed on the diffusion sheet 500, and condenses the light passing through the diffusion sheet 500 in a direction of the LCD panel 400 by using for example below prism patterns.

[140] The protection sheet 504 protects the prism sheet 502 from a dust, etc, and prevents a damage of an outside object due to the prism patterns. However, the protection sheet 504 is not essential element of the present backlight unit.

[141] In above description, the edge-light type backlight unit 402 where the light source 430 is disposed at a side of the light guide plate 434 is mentioned. However, a direct- lighting type backlight unit where a light source is disposed under a light guide plate may be used as the backlight unit 402 of the present embodiment.

[142] Hereinafter, the prism sheet 502 of the present embodiment will be described in detail with reference to accompanying drawings FlG. 6 to FTG 8.

[143] FlG. 6 to FlG. 8 are sectional views illustrating the prism sheet according to one example embodiment of the present invention.

[144] In FlG. 6, the prism sheet 502 includes a prism base 600 and prism patterns 602.

[145] The prism base 600 supports the prism patterns 602.

[146] The prism patterns 602 have mountain shape, and are formed with a certain pattern on an imaginary curve 610. Particularly, at least one of vertex angles, e.g. αl, α2, α3, α4, etc. of the prism patterns 602 may be different from the other vertex angles as shown in FlG. 6. In addition, in case of halving the vertex angle on the basis of a normal of the prism base 600, sub-angles generated by the halving have the same magnitude as shown in α3 in FlG. 6. Here, the vertex angles, e.g. αl, α2, α3, α4, etc. have for example an angle between about 80° and about 120°. It is desirable that sub- angles generated by halving the vertex angle on the basis of the normal of the prism base 600 have the same magnitude, and the vertex angles have about 90° for maximum light efficiency.

[147] Further, an imaginary line 606 connecting vertexes 604 of the prism patterns 602 is disposed repeatedly with mountain shape on the prism base 600.

[148] In one embodiment of the present invention, at least one of pitches, e.g. Pl, P2, P3, P4, etc. between the vertexes 604 of the prism patterns 602 have different length from the other pitches as shown in FlG. 6. It is desirable that the pitches have values between about 5D and about 100D. Additionally, at least one of pitches (not shown) between valleys 612 of the prism patterns 602 have different length from the other pitches.

[149] In another embodiment of the present invention, at least one of distances between the imaginary curve 610 and the vertexes 604, i.e. heights hi, h2, h3, h4, etc. may have different length from the other heights as shown in FlG. 6. Here, it is desirable that the heights have values between about 0.1D and about 15D.

[150] Hereinafter, the effect of the above prism sheet 502 will be described in detail.

[151] In a first effect, the prism patterns 602 do not have constant pitch or height, i.e. have irregular disposition unlike prism patterns in the Related Art. Accordingly, a moire phenomenon by regular patterns is not occurred to the LCD panel 400.

[152] In a second effect, the imaginary line 606 has mountain shape as shown in FlG. 6. That is, the heights of the vertexes 604 on the basis of the prism base 600 have different lengths, respectively. Hence, in the backlight unit 402 not having the protection sheet 504, only a part of the vertexes 604 of the prism patterns 602 are contacted with the lower polarization film 404 unlike that in Related Art in case that the vertexes 604 are contacted therewith due to various causes. Accordingly, in the LCD panel 400, an imprinting phenomenon is not occurred, or its occurrence probability becomes low.

[153] In a third effect, only a part of the vertexes 604 may be contacted with a lower surface of the protection sheet 504 or the lower polarization film 404. Accordingly, in the LCD panel 400 unlike in the Related Art, a wet-out phenomenon is not occurred, or its occurrence probability becomes low.

[154] In a fourth effect, in the prism patterns 602, the sub-angles generated by halving each of the vertex angles on the basis of the normal of the prism base 600 have the same magnitude as shown in (a) of FIG. 7. In the prism patterns 602 according to another embodiment of the present invention, sub-angles generated by halving each of the vertex angles on the basis of the imaginary curve 610 may have the same magnitude as shown in (b) of FlG. 7. However, the prism patterns 602 shown in (a) of FIG. 7 condense better than the prism patterns 602 in (b) of FIG. 7 as see in a light (Φ) in FlG. 7. Accordingly, it is desirable that the prism patterns 602 shown in (a) of FlG. 7 are employed in the backlight unit 402 of the present embodiment.

[155] In a fifth effect, the vertexes 604 of the prism patterns 602 are disposed with mountain shape, and so the efficiency of the light is increased. In particularly, in the prism sheet in the Related Art, in case that a light incident to prism pattern is outputted through a side of a prism pattern, the outputted light runs in a direction different from the LCD panel 100. As a result, the efficiency of the light in the Related Art is not good. However, in the prism sheet 502 of the present invention, a light outputted through a side of a first prism pattern is condensed in a direction of the LCD panel 400 by a second prism pattern which is adjacent to the first prism pattern and is higher than the first prism pattern as see from a light (©) in (a) of FlG. 7. Accordingly, the loss of the light is reduced, i.e. the efficiency of the light is increased.

[156] Hereinafter, a substance of the prism sheet 502 will be described in detail with reference to FIG. 6.

[157] The prism base 600 may be a thermoplastic polymer film which is transparent and flexible, and has an excellent processability. Here, the polymer may be one selected from a group comprising of acrylate, polycarbonate, polyester and polyvinyl chloride. In addition, a first multi-layered film or a second multi-layered film may be employed as the polymer film. Here, the first multi-layered film has structure that an acrylate is laminated on a polycarbonate, and the second multi-layered film has structure that an acrylate is laminated on polyester.

[158] The prism patterns 602 according to one embodiment of the present invention may be made up of an electrolytic dissociated-radioactive ray hardening resin. Here, a composition mixing prepolymer, olygomer and/or monomer having polymerizable unsaturated bond or epoxy group may be employed as the hardening resin.

[159] An unsaturated polyester resin class such as condensate of carboxylic acids and polyhydric alcohols, etc, a methacrylate class such as epoxy resin, polyester methacrylate, polyethyl methacrylate, etc, an acrylate class such as polyester acrylate, epoxy acrylate, urethane acrylate, polyethyl acrylate, polyol acrylate, melamine, etc. and the others are employed as the prepolymer and olygomer. A styrene monomer such as styrene, α-methyl styrene, etc, an esther acrylate class such as 2-ethyl methyl acrylate, methoxyethyl acrylate, butylacrylate, etc, a methacrylic acid ester class such as methylmethacrylate, ethylmethacrylate, methacrylic acid methoxy ethyl, methacrylic acid ethoxy methyl, etc, a substitution aminoalcohol-esther class of unsaturated acid such as acrylic acid-2-(N, N-methylamino)ethyl, etc, a unsaturated calbon acid amid such as acrylamide, methacrylamide, etc, a multifunctional comp ound such as propylene glycol acrylate, ethylene glycol acrylate, propylene glycol methacrylate, ethylene glycol methacrylate, etc, a vinyl pyrrolidinone and/or a polythiols compound having at least two thiol groups of molecule, e.g. trimethy- lolpropane trithiocrylate, trimethylolpropane trithiopropylate, etc, are employed as the monomer. A polyester resin, acrylic resin, polystyrene resin, polyvinyl chloride resin, polyethylene resin, polypropylene-based resin, polyurethane resin, polyamide resin, epoxy resin, cellulose resin, polyimide resin, etc may be used as the light-passing resin. Here, it is desirable that the polyester resin of the above resins is used as the light- passing resin when lightfast, transparency, etc of the rein are considered.

[ 160] Hereinafter, the structure of the upper surface of the prism patterns 602 of the present embodiment will be described in detail with reference to FlG. 8.

[161] As shown in FIG. 8, in one side of the prism pattern, the length of a part of the prism pattern 630a may be different from that of other part 630b. Here, a line formed by sides of the prism pattern is changed with zigzag, and a valley between two prism patterns is formed in a straight line.

[ 162] In another embodiment of the present invention, in one side of the prism pattern, the length of a part of the prism pattern 640a may be different from that of other part 640b. Here, a line formed by sides of the prism pattern is disposed in a straight line, and a valley between two prism patterns is changed with zigzag. In addition, the height of the prism pattern may be changed in a longitudinal direction of the prism pattern.

[ 163] That is, the length of one side of the prism pattern may be changed in a longitudinal d irection of the prism pattern. Here, unlike the above embodiments, each of a line formed by sides of the prism pattern and a valley between two prism patterns may be disposed in a straight line, but are not shown.

[164] FlG. 9 is a perspective view illustrating a backlight unit according to a second example embodiment of the present invention. FlG. 10 and FlG. 11 are sectional views illustrating a prism sheet in FlG. 9.

[165] In FlG. 9, the backlight unit 402 of the present embodiment includes a light source section 900, a light guide plate 902, a reflection sheet 904 and an optical sheet 906. Here, the optical sheet 906 has a prism sheet 910, a protection sheet 912 and a dual brightness enhancement film layer (hereinafter, referred to as "DBEF layer") 914.

[ 166] Since the elements of the present embodiment except the prism sheet 910 and the DBEF layer 914 are the same as in the first embodiment, any further detailed description concerning the same elements will be omitted.

[ 167] Firstly, the DBEF layer 914 will be described in detail.

[168] The DBEF layer 914 reflects a part of a light diffused by the protection sheet 912 in a direction of the light guide plate 902, and provides the other part of the light to the LCD panel 400. This is because the LCD panel 400 uses only a part of a light provided from the backlight unit 402, and polarizes the other part of the light. Hence, the DBEF layer 914 is employed in the backlight unit 402 in order to use the polarized light. For example, the DBEF layer 914 passes a longitudinal wave of the light diffused by the protection sheet 912, and reflects a traverse wave of the light. The reflected traverse wave is reflected again by the light guide plate 902 or the reflection sheet 904. In this case, the reflected traverse wave is changed into a light having a longitudinal wave and a traverse wave. The changed light is incident again to the DBEF layer 914 through the prism sheet 910 and the protection sheet 912. Subsequently, a longitudinal wave of the incident light is provided to the LCD panel 400, and a traverse wave of the incident light is reflected by the DBEF layer 914. Then, the reflected traverse wave is reflected again by the light guide plate 902 or the reflection sheet 904. The above process is repeatedly performed, and so the efficiency of the light provided to the LCD panel 400 from the backlight unit 402 is enhanced. However, the protection sheet 912 and the DBEF layer 914 are not essential elements of the backlight unit 402 of the second embodiment.

[169] Hereinafter, the prism sheet 910 will be described in detail.

[170] As shown in FIG. 10, the prism sheet 910 in the second embodiment includes further diffusion sections 1002 compared with the first embodiment, wherein the diffusion sections 1002 are formed on one side of a prism base 1000, preferably a lower surface thereof.

[171] Each of the diffusion sections 1002 has hemisphere shape and a multi-layered structure as shown in FIG. 11. In particular, each of the diffusion sections 1002 includes a first refractive layer 1010 having a first refractive index and a second refractive layer 1012 having a second refractive index. Here, the second refractive layer 1012 is formed in the first refractive layer 1010, and the second refractive index is smaller than the first refractive index. For instance, the first refractive layer 1010 is made up of a polymer having the first refractive index in the range of about 1.49 and 1.63, and the second refractive layer 1012 is made up of a silica SiO2 having the second refractive index of about 1.45. On the other hand, the refractive layers 1010 and 1012 may be made up of various substances as long as the second refractive index could be smaller than the first refractive index.

[172] In brief, each of the diffusion sections 1002 has a plurality of layers, wherein a first layer of the layers has refractive index smaller than a second layer thereof located outside of the first layer. In this case, a light incident to the diffusion sections 1002 from the light guide plate 902 is diffused when the light passes through the second refractive layer 1012 in accordance with the Snell's law. Accordingly, since the diffusion sections 1002 functions as a diffusion sheet in the backlight unit 402 of the second embodiment, extra diffusion sheet is not required for the backlight unit 402.

[173] In the above description, each of the diffusion sections 1002 has two refractive layers 1010 and 1012. However, each of the diffusion sections 1002 may be made up of at least three refractive layers.

[174] FIG. 12 is a sectional view illustrating a prism sheet employed in a backlight unit according to a third example embodiment of the present invention.

[175] In FIG. 12, the prism sheet included in the backlight unit 402 of the present embodiment has a prism base 1200, a curved surface layer 1202 and prism patterns 1204.

[176] The curved surface layer 1202 has lens shape, and is made up of a first substance.

[177] The prism patterns 1204 are formed on the curved surface layer 1202 with mountain shape, and are made up of a second substance. Here, it is desirable that the second substance is substantially identical to the first substance.

[178] As described above, since the curved surface layer 1202 has lens shape, a light passed through the prism base 1200 is condensed firstly by the curved surface layer 1202, and then is condensed secondly by the prism patterns 1204. As a result, the backlight unit 402 of the present embodiment has concentration efficiency higher than that in the first and second embodiments.

[179] In another embodiment of the present invention, the curved surface layer 1202 may have not a lens shape but a plane shape. In other words, the shape of the curved surface layer 1202 may be modified variously. Accordingly, it will be immediately obvious to those skilled in the art that many modifications for the shape of the curved surface layer 1202 do not have any effect to the scope of the present invention. [180] FlG. 13 is a sectional view illustrating a prism sheet employed in a backlight unit according to a fourth example embodiment of the present invention.

[181] In FlG. 13, a prism sheet employed in the backlight unit 402 of the present embodiment includes a prism base 1400, first prism patterns 1402a and second prism patterns 1402b.

[182] The first prism patterns 1402a have mountain shape like the first to three embodiments.

[183] The second prism patterns 1402b have not mountain shape but curve shape, preferably have hemisphere shape.

[ 184] In one embodiment of the present, the first prism patterns 1402a and the second prism patterns 1402b are formed by turns on the prism base 1400.

[185] In the backlight unit 402 including the above prism sheet, since the second prism patterns 1402b having hemisphere shape are formed on the prism base 1400, the moire phenomenon in the present embodiment may be reduced more than in the first to third embodiments.

[186] FlG. 14 is a sectional view illustrating a prism sheet employed in a backlight unit according to a fifth example embodiment of the present invention.

[187] In FlG. 14, in the prism sheet of the present embodiment unlike the fourth embodiment, the prism patterns 1504a and 1504b are formed on a curved surface layer 1502. Accordingly, the prism sheet in the fifth embodiment may have concentration efficiency higher than that in the fourth embodiment.

[188] FlG. 15 is a perspective view illustrating a backlight unit according to a sixth example embodiment of the present invention.

[189] In FlG. 15, the backlight unit 402 of the present embodiment includes a light guide plate 1600, a reflection sheet 1602 and an optical sheet 1604.

[190] The optical sheet 1604 includes a diffusion sheet 1610, a first prism sheet 1612a, a second prism sheet 1612b and a protection sheet 1614. However, the diffusion sheet 1610 and the protection sheet 1614 are not essential element of the present embodiment.

[191] The optical sheet 1604 of the present embodiment unlike the first to fifth embodiments has at least two prism sheets 1612a and 1612b to increase concentration efficiency. Here, first prism patterns formed on the first prism sheet 1612a cross over second prism patterns formed on the second prism sheet 1612b as shown in FlG. 15. This will be described in detail with reference to accompanying drawings.

[192] FlG. 16 to FlG. 21 are sectional views illustrating prism sheets included in backlight units according to a seventh to twelfth example embodiments of the present invention.

[193] In FlG. 16, a backlight unit 402 of the seventh embodiment includes a first prism sheet 1612a where diffusion sections are not formed and a second prism sheet 1612b where diffusion sections are formed.

[194] In FlG. 17, the backlight unit 402 of the eighth embodiment includes a first prism sheet 1612a where diffusion sections are formed and a second prism sheet 1612b where diffusion sections are not formed.

[195] In FlG. 18, the backlight unit 402 of the ninth embodiment includes a first prism sheet 1612a where diffusion sections are formed and a second prism sheet 1612b where diffusion sections are formed.

[196] In FlG. 19, the backlight unit 402 of the tenth embodiment includes a first prism sheet 1612a where diffusion sections are not formed and a second prism sheet 1612b where diffusion sections are not formed.

[197] In FlG. 20, the backlight unit 402 of the eleventh embodiment includes a first prism sheet 1612a where diffusion sections are not formed and a second prism sheet 1612b where diffusion sections are not formed. Here, first prism patterns having mountain shape and second prism patterns having hemisphere shape are formed on the prism sheets 1612a and 1612b, wherein the prism patterns of mountain shape in the first prism sheet 1612a correspond to the prism patterns of hemisphere shape in the second prism sheet 1612b.

[198] In FlG. 21, the backlight unit 402 of the twelfth embodiment includes a first prism sheet 1612a where diffusion sections are not formed and a second prism sheet 1612b where diffusion sections are formed. Here, first prism patterns having mountain shape and second prism patterns having hemisphere shape are formed on the prism sheets 1612a and 1612b, wherein the prism patterns of mountain shape in the first prism sheet 1612a correspond to the prism patterns of hemisphere shape in the second prism sheet 1612b.

[199] The backlight unit 402 according to a thirteenth embodiment of the present invention may have a first prism sheet 1612a where diffusion sections are formed and a second prism sheet 1612b where diffusion sections are not formed, and is not shown. Here, first prism patterns having mountain shape and second prism patterns having hemisphere shape are formed on the prism sheets 1612a and 1612b.

[200] Additionally, the backlight unit 402 according to a fourteenth embodiment of the present invention includes a first prism sheet 1612a where diffusion sections are formed and a second prism sheet 1612b where diffusion sections are formed. Here, first prism patterns having mountain shape and second prism patterns having hemisphere shape are formed on the prism sheets 1612a and 1612b.

[201] A curved surface layer is not included in the prism sheets of the seventh to fourteenth embodiments. However, the curved surface layer may be formed in each of the prism sheets of the seventh to fourteenth embodiments.

[202] Further, curved surface layers may be formed in some of the prism sheets in the seventh to fourteenth embodiments, and be not formed in the other prism sheets.

[203] As described above, the optical sheet includes at least one prism sheet, a diffusion sheet and/or a protection sheet for the purpose of achieving the objection of the present invention. However, the optical sheet may be one body type sheet as described below. Hereinafter, a direct-lighting type backlight unit will be described as an example of the backlight unit having the one body type optical sheet for convenience of the description.

[204] FlG. 22 is a sectional view illustrating a backlight unit according to a fifteenth example embodiment of the present invention. FlG. 23 is a sectional view illustrating a diffusion section in FIG. 22.

[205] Referring to FTG. 22, the direct-lighting type backlight unit of the present embodiment includes at least one light source 2200, a reflection sheet 2202 and an optical sheet 2204.

[206] The light source 2200 emits a light having a certain wavelength, and may be an LED, and a CCFL, etc.

[207] The reflection sheet 2202 reflects a light emitted from the light sources 2200 in a direction of the optical sheet 2204.

[208] The optical sheet 2204 includes a first base section 2210, an adhering section 2212, a second base section 2214, prism patterns 2216 and diffusion sections 2218.

[209] The first base section 2210 has a transparent structure to pass the light emitted from the light sources 2200, and is a film made up of a polyethylene terephthalate PET, a poly methyl meta acrylate PMMA or a polycarbonate, etc. In another example embodiment of the present invention, the first base section 2210 may be made up of a diffusion plate instead of the film.

[210] The adhering section 2212 adheres the second base section 2214 to the first base section 2210, and is made up of for example an ultraviolet curing resin (hereinafter, referred to as "UV resin") or a curing resin containing a diffusion agent, etc. Here, in case that the adhering section 2212 is made up of the curing resin containing the diffusion agent, the adhering section 2212 diffuses uniformly a light transmitted through the first base section 2210. Accordingly, a uniformity of a light outputted from the optical sheet 2204 may be enhanced.

[211] The second base section 2214 is made up of a PET, etc, and supports the prism patterns 2216.

[212] The prism patterns 2216 has mountain shape, and are disposed on the second base section 2214 with regular pattern or irregular pattern. Further, the prism patterns 2216 condense the light transmitted through the second base section 2214. The structure of these prism patterns 2216 will be described in detail with reference to accompanying drawings. [213] The diffusion sections 2218 form on a surface opposed to a surface corresponding to the adhering section 2212 of surfaces of the first base section 2210, and diffuse the light emitted from the light sources 2200 so that the light is uniformly dispersed.

[214] To provide the mentioned diffusion function, one or more of the diffusion sections

2218 is made up of refractive layers 2300 and 2302 having hemisphere shape as shown in FIG. 23.

[215] In particular, each of the diffusion sections 2218 includes a first refractive layer 2300 having a first refractive index and a second refractive layer 2302 having a second refractive index. That is, each of the diffusion sections 2218 has a plurality of layers, wherein a first layer of the layers has refractive index smaller than a second layer located outside of the first layer. In this case, a light incident to the diffusion sections 2218 from the light guide sources 2200 is diffused in accordance with the Snell's law when the light is transmitted through the second refractive layer 2302.

[216] As mentioned above, the optical sheet 2204 included in the backlight unit of the present embodiment is one body type sheet unlike the optical sheet in Related Art. Hence, the thickness of the optical sheet 2204 of the present embodiment is smaller than that of the optical sheet in Related Art.

[217] In addition, in the optical sheet in Related Art, since there is some space between the sheets, every of a light emitted from the light source is not transmitted to the sheets. In other words, some of the light is leaked at the space between the sheets. However, in the optical sheet 2204 of the present embodiment, since the optical sheet 2204 is one body type sheet, the light emitted from the light sources 2200 is not leaked. Accordingly, the loss of the light in the optical sheet 2204 is smaller than that in the optical sheet in Related Art.

[218] The backlight unit described above is a direct-lighting type backlight unit. However, the present embodiment may be employed in an edge-light type backlight unit. That is, an optical sheet included in the edge-light type backlight unit may be one body type sheet.

[219] Additionally, the backlight unit of the present embodiment may be employed in a large backlight unit or a small backlight unit.

[220] Hereinafter, a process of manufacturing the optical sheet 2204 will be described in detail.

[221] FIG. 24 to FIG. 29 are views illustrating a first process of manufacturing the optical sheet according to one example embodiment of the present invention. FIG. 30 is a view illustrating a second process of manufacturing the optical sheet according to another example embodiment of the present invention.

[222] In FIG. 24 to FIG. 29, the film 2400 which is made up of the PET, the PMMA, or the polycarbonate, etc exists in the shape of a roll as shown in FIG. 24. Here, the film 2400 has for example 1.5T of a thickness. In addition, a diffusion agent, e.g. silica-based material may be coated on a backside of the film 2400.

[223] The film 2400 is scribed to a size corresponding to the optical sheet 2204 in a later process, and so is converted into the first base section 2210. Hereinafter, the first base section 2210 is assumed as the film 2400 for convenience of the description.

[224] Subsequently, the first base section 2210 is moved along a guide line as shown in FlG. 24.

[225] Then, an ultraviolet curing resin injecting apparatus 2402 coats an UV curing resin 2212 on the moved first base section 2210, thereby forming a first structure as shown in FIG. 26. In this case, the UV curing resin 2212 is non-uniformly coated on the first base film 2210.

[226] Subsequently, an extrusion roll 2404 extrudes the first structure so that the UV curing resin 2212 is uniformly coated on the first base section 2210, thereby forming a second structure as shown in FlG. 27.

[227] Then, the second structure is moved to a first curing apparatus 2406. The first curing apparatus 2406 cures firstly the second structure so that moisture, etc contained in the UV curing resin 2212 is removed. However, the UV curing resin is imperfectly cured by the first curing apparatus 2406, for example is half cured. Here, since the UV curing resin 2212 is coated on the first base section 2210, the first curing apparatus 2406 is an ultraviolet irradiating apparatus. However, in case that a material coated on the first base section 2210 is changed, the first curing apparatus 2406 will be changed in accordance with the material.

[228] Subsequently, the second structure cured firstly is moved to an attaching roll 2410.

[229] Then, the attaching roll 2410 attaches a prism structure 2408 to the second structure, thereby forming a third structure as shown in FlG. 28. Here, in the prism patterns 2408, the prism patterns 2216 is formed on the second base section 2214.

[230] Subsequently, the third structure is moved to a second curing apparatus 2412. In this case, the second curing apparatus 2412 cures secondly the third structure. Here, since the UV curing resin 2212 is imperfectly cured when the first structure is firstly cured, the prism structure 2408 is attached to the second structure.

[231] Then, the prism structure 2408 is perfectly attached to the second structure by the second curing.

[232] Subsequently, the diffusion sections 2218 are adhered to a backside of the third structure, and so the optical sheet 2204 of the present embodiment is manufactured. Here, this process is not shown in FlG. 24.

[233] Hereinafter, a second process of manufacturing the optical sheet 2204 when the first base section 2210 is made up of a diffusion plate will be described in detail.

[234] As shown in FIG. 30, a transparent diffusion plate 3000 having for example 2T of a thickness is moved along a guide line. Then, the optical sheet 2204 is manufactured through corresponding steps in the first process mentioned above. In this case, since the first base section 2210 in the second process is made up of the diffusion plate 3000, the optical sheet manufactured by the second process is thicker than that manufactured by the first process. However, the optical sheet manufactured by the second process is firmer than that manufactured by the first process.

[235] As described above, the optical sheet 2204 of the present embodiment is manufactured by performing the step of coating the UV curing resin, the step of extruding, the step of attaching and the step of curing with moving along the guide line.

[236] The manufacture process of the present invention is simple compared with well- known manufacture process (extrusion line process) in Related Art. In addition, a cost needed for manufacturing the optical sheet 2204 is lower than that needed for manufacturing the optical sheet in Related Art.

[237] FTG. 31 is a sectional view illustrating an optical sheet according to a sixteenth example embodiment of the present invention.

[238] In FTG. 31, the optical sheet 3100 of the present embodiment is one body type sheet, and includes a first base section 3102, an adhering section 3104, a second base section 3106, prism patterns 3108 and diffusion sections 3110.

[239] Since the elements of the present embodiment except the prism patterns 3108 are the same as in the fifteenth embodiment, any further description concerning the same elements will be omitted.

[240] The prism patterns 3108 are disposed with irregular pattern unlike the fifteenth embodiment.

[241] Particularly, at least one of pitches (for example Pl, P2, P3, etc) between the vertexes of the prism patterns 3108 may have different length from the other pitches

[242] At least one of heights (for instance hi, h2, h3, etc) of the prism patterns 3108 may have different length from the other heights.

[243] At least one of the vertex angles (for example, αl, α2, α3, etc) of the prism patterns 3108 may have different magnitude from the vertex angles.

[244] FTG. 32 to FTG. 34 are views illustrating an optical sheet according to a seventeenth embodiment of the present invention.

[245] In FTG. 32 and FTG. 33, the optical sheet 3200 of the present embodiment is one body type sheet, and includes a first base section 3202, an adhering section 3204, a second base section 3206, prism patterns 3208 and diffusion sections 3210.

[246] Since the elements of the present embodiment except the prism patterns 3208 are the same as in the fifteenth embodiment, any further detailed description concerning the same elements will be omitted.

[247] The prism patterns 3208 have mountain shape, and are formed with a certain pattern on an imaginary curve 3212. Particularly, at least one of vertex angles, e.g. αl, α2, α3, α4, etc. of the prism patterns 3208 may be different from the other vertex angles. In addition, in case of halving the vertex angle on the basis of a normal of the second base section 3206, sub-angles generated by the halving have the same magnitude as shown in α3 in FlG. 33. Here, the vertex angles, e.g. αl, α2, α3, α4, etc. have for example an angle between about 80° and about 120°. It is desirable that sub-angles generated by halving each of the vertex angles on the basis of the normal of the second base section 3206 have the same magnitude, and the vertex angles have about 90° for maximum light efficiency.

[248] Further, an imaginary line 3214 connecting vertexes of the prism patterns 3208 is disposed repeatedly with mountain shape on the second base section 3206.

[249] In one embodiment of the present invention, at least one of pitches, e.g. Pl, P2, P3, P4, etc. between the vertexes of the prism patterns 3208 have different length from the other pitches. It is desirable that the pitches have values between about 5D and about 10OD. Additionally, at least one of pitches (not shown) between valleys of the prism patterns 3208 have different length from the other pitches.

[250] In another embodiment of the present invention, at least one of distances between the imaginary curve 3212 and the vertexes, i.e. heights hi, h2, h3, h4, etc. may have different length from the other heights. Here, it is desirable that the heights have values between about 0.1 D and about 15D.

[251] Hereinafter, the effect of the above one body type optical sheet 3200 will be described in detail.

[252] In a first effect, since the optical sheet 3200 is one body type sheet, the thickness of the backlight unit 302 employing the optical sheet 3200 may be reduced.

[253] In a second effect, the prism patterns 3208 do not have constant pitch or height, i.e. have irregular disposition unlike prism patterns in the Related Art. Accordingly, a moire phenomenon generated by regular patterns is not occurred to the LCD panel 400.

[254] In a third effect, the imaginary line 3212 has mountain shape as shown in FTG. 32. That is, the heights of the vertexes on the basis of the second base section 3206 have different lengths, respectively. Hence, in the backlight unit of the present embodiment, only a part of the vertexes of the prism patterns 3208 are contacted with the lower polarization film 404 unlike that in Related Art in case that the vertexes are contacted with the lower polarization film 404 due to various causes. Accordingly, in the LCD panel 400, an imprinting phenomenon is not occurred, or its occurrence probability becomes low.

[255] In a fourth effect, in the prism patterns 3208, the sub-angles generated by halving each of the vertex angles on the basis of the normal of the second base section 3206 have the same magnitude as shown in (a) of FlG. 34. In the prism patterns 3208 according to another embodiment of the present invention, sub-angles generated by halving each of the vertex angles on the basis of the imaginary curve 3212 may have the same magnitude as shown in (b) of FlG. 34. However, the prism patterns 3208 shown in (a) of FlG. 34 condense better than the prism patterns 3208 in (b) of FlG. 7 as see in a light (®) in FlG. 34. Accordingly, it is desirable that the prism patterns 3208 shown in (a) of FlG. 34 are employed in the backlight unit of the present embodiment.

[256] In a fifth effect, the vertexes of the prism patterns 3208 are disposed with mountain shape, and so the efficiency of the light is increased. In particularly, in the prism sheet in the Related Art, in case that a light incident to prism pattern is outputted through a side of a prism pattern, the outputted light runs in a direction different from the LCD panel 100. As a result, the efficiency of the light in the Related Art is not good. However, in the prism sheet 3208 of the present embodiment, a light outputted through a side of a first prism pattern is condensed in a direction of the LCD panel 400 by a second prism pattern adjacent to the first prism pattern, wherein the second prism pattern is higher than the first prism pattern as see from a light (@) in (a) of FIG. 34. Accordingly, the loss of the light is reduced, i.e. the efficiency of the light is enhanced.

[257] FlG. 35 is a sectional view illustrating an optical sheet according to an eighteenth example embodiment of the present invention.

[258] Referring to FlG. 35, the optical sheet 3500 of the present embodiment is one body type sheet, and includes a first base section 3502, an adhering section 3504, a second base section 3506, a curved surface layer 3508, prism patterns 3510 and diffusion sections 3512.

[259] Since the elements of the present embodiment except the curved surface layer 3508 and the prism patterns 3510 are the same as in the fifteenth embodiment, any further detailed description concerning the same elements will be omitted.

[260] The curved surface layer 3508 has lens shape, and is made up of a first substance.

[261] The prism patterns 3510 are formed on the curved surface layer 3508 with mountain shape, and are made up of a second substance. Here, it is desirable that the second substance is substantially identical to the first substance.

[262] As described above, since the curved surface layer 3508 has lens shape, a light transmitted through the second base section 3506 is condensed firstly by the curved surface layer 3508, and then is condensed secondly by the prism patterns 3510. As a result, the backlight unit of the present embodiment may have concentration efficiency higher than that in the fifteenth to seventeenth embodiments.

[263] In another embodiment of the present invention, the curved surface layer 3508 may have not lens shape but plane shape. In other words, the shape of the curved surface layer 3508 may be modified variously. Accordingly, it will be immediately obvious to those skilled in the art that many modifications for the shape of the curved surface layer 3508 do not have any effect to the scope of the present invention. [264] FlG. 36 is a sectional view illustrating an optical sheet according to a nineteenth example embodiment of the present invention. [265] In FlG. 36, the optical sheet 3600 of the present embodiment includes a first base section 3602, an adhering section 3604, a second base section 3606, prism patterns

3608 and diffusion sections 3610. [266] Since the elements of the present embodiment except the prism patterns 3608 are the same as in the fifteenth embodiment, any further detailed description concerning the same elements will be omitted. [267] The prism patterns 3608 includes first prism patterns 3608a having mountain shape and second prism patterns 3608b having for example hemisphere shape. [268] In one embodiment of the present, the first prism patterns 3608a and the second prism patterns 3608b are formed by turns on the second base section 3606. [269] In the backlight unit including the above prism sheet, since the second prism patterns

3608b having hemisphere shape are formed on the second base section 3606, the moire phenomenon in the present embodiment may be reduced more than in the fifteenth embodiment to eighteenth embodiment. [270] As mentioned above, the prism patterns 3608a and 3608b have irregular pattern.

However, the prism patterns 3608a and 3608b may have regular pattern. [271] FlG. 37 is a sectional view illustrating an optical sheet according to a twentieth example embodiment of the present invention. [272] As shown in FIG. 37, first prism patterns having a mountain shape and second prism patterns having a hemisphere shape are formed on an imaginary curve. [273] In addition, the first prism patterns and the second prism patterns may be formed on a curved surface layer.

Claims

[ 1 ] A prism sheet comprising : a prism base; and first prism patterns disposed on a first surface of surfaces of the prism base, and configured to have a mountain shape, wherein when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[2] The prism sheet of claim 1, wherein one or more of pitches between the first prism patterns have different length from the other pitches.

[3] The prism sheet of claim 2, wherein the pitches have the length between about 5D and about 10OD.

[4] The prism sheet of claim 1, wherein the first prism patterns are disposed on an imaginary curve on the basis of the imaginary curve, wherein at least one of heights between the first prism patterns and the imaginary curve have different length from the other heights.

[5] The prism sheet of claim 4, wherein the heights have the length in the range of about 0.1D and about 15D.

[6] The prism sheet of claim 1 , wherein at least one of vertex angles of the first prism patterns have different magnitude from the other vertex angles.

[7] The prism sheet of claim 6, wherein the vertex angles have the angle between about 80° and about 120°.

[8] The prism sheet of claim 1, wherein an imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[9] The prism sheet of claim 1, wherein one or more of pitches between valleys of the first prism patterns have different length from the other pitches.

[10] The prism sheet of claim 1, further comprising: diffusion sections disposed on a second surface of the surfaces of the prism base, and configured to have a hemisphere shape, wherein the second surface is different from the first surface.

[11] The prism sheet of claim 10, wherein the at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index, wherein the first refractive layer is higher than the second refractive layer.

[12] The prism sheet of claim 11, wherein the first refractive layer is made up of polymer having the first refractive index between about 1.49 and about 1.63, and the second refractive layer is made up of silica (SiO2) having the second refractive index of about 1.45.

[ 13] The prism sheet of claim 1 , wherein a length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[14] The prism pattern of claim 1, further comprising: second prism patterns disposed between the first prism patterns, and configured to have a hemisphere shape.

[15] A prism sheet comprising : a prism base; a curved surface layer configured to have a curved surface shape, disposed on a first surface of surfaces of the prism base, and made up of a first substance; and first prism patterns disposed on the curved surface layer, configured to have a mountain shape, and made up of a second substance, wherein when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[16] The prism sheet of claim 15, wherein the first substance is substantially identical to the second substance.

[17] The prism sheet of claim 15, wherein at least one of pitches between the first prism patterns have different length from the other pitches.

[18] The prism sheet of claim 15, wherein one or more of heights between the first prism patterns and the curved surface layer have different length from the other heights.

[19] The prism sheet of claim 15, wherein at least one of vertex angles of the first prism patterns have different magnitude from the other vertex angles.

[20] The prism sheet of claim 15, wherein an imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[21] The prism sheet of claim 15, further comprising: diffusion sections disposed on a second surface of the surfaces of the prism base, and configured to have a hemisphere shape, wherein the at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index, wherein the first refractive layer is higher than the second refractive layer.

[22] The prism sheet of claim 21, wherein the first refractive layer is made up of polymer having the first refractive index between about 1.49 and about 1.63, and the second refractive layer is made up of silica (SiO2) having the second refractive index of about 1.45.

[23] The prism sheet of claim 15, wherein a length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[24] The prism pattern of claim 15, further comprising: second prism patterns disposed between the first prism patterns, and configured to have a hemisphere shape.

[25] A backlight unit comprising: a light guide plate; and a first prism sheet disposed on the light guide plate, and configured to condense a light outputted from the light guide plate, wherein the first prism sheet includes: a prism base; and first prism patterns disposed on a first surface of surfaces of the prism base, and configured to have a mountain shape, wherein when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[26] The backlight unit of claim 25, wherein at least one of pitches between the first prism patterns have different length from the other first prism patterns, one or more of vertex angles of the first prism patterns have different magnitude from the other vertex angles, and at least one of heights of the first prism patterns have different length from the other heights.

[27] The backlight unit of claim 25, further comprising: diffusion sections disposed on a second surface of the prism base, and configured to have a hemisphere shape, wherein at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer configured to have a second refractive index smaller than the first refractive index.

[28] The backlight unit of claim 25, wherein an imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[29] The backlight unit of claim 25, wherein a length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[30] The backlight unit of claim 25, further comprising: second prism patterns disposed between the first prism patterns in the same direction as the first prism patterns, and configured to have a hemisphere shape.

[31] The backlight unit of claim 30, further comprising: a second prism sheet disposed on the first prism sheet, and configured to have third prism patterns crossing over the first prism patterns and the second prism patterns.

[32] The backlight unit of claim 31 , further comprising: diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[33] The backlight unit of claim 25, further comprising: a second prism sheet disposed on the first prism sheet, and configured to have second prism patterns crossing over the first prism patterns.

[34] The backlight unit of claim 33, further comprising: diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[35] The backlight unit of claim 25, further comprising: a diffusion sheet located between the light guide plate and the first prism sheet, and configured to provide the light outputted from the light guide plate to the first prism sheet.

[36] A backlight unit comprising: a light guide plate; and a first prism sheet located on the light guide plate, and configured to condense a light outputted from the light guide plate, wherein the first prism sheet includes: a prism base; a curved surface layer configured to have a curved surface shape, disposed on a first surface of surfaces of the prism base, and made up of a first substance; and first prism patterns configured to have a mountain shape, disposed on the curved surface layer, and made up of a second substance, wherein when halving a vertex angle of at least one of the first prism patterns on the basis of a normal of the prism base, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[37] The backlight unit of claim 36, wherein at least one of pitches between the first prism patterns have different length from the other first prism patterns, one or more of vertex angles of the first prism patterns have different magnitude from the other vertex angles, and at least one of heights of the first prism patterns have different length from the other heights.

[38] The backlight unit of claim 36, further comprising: diffusion sections disposed on a second surface of the prism base, and configured to have a hemisphere shape, wherein at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer disposed in the first refractive layer, and configured to have a second refractive index smaller than the first refractive index.

[39] The backlight unit of claim 36, wherein an imaginary line generated by connecting vertexes of some of the first prism patterns has a mountain shape.

[40] The backlight unit of claim 36, wherein a length of one side of the first prism pattern is changed with enlarged in the longitudinal direction of the first prism pattern.

[41] The backlight unit of claim 36, further comprising: second prism patterns disposed between the first prism patterns in the same direction as the first prism patterns, and configured to have a hemisphere shape.

[42] The backlight unit of claim 41 , further comprising: a second prism sheet disposed on the first prism sheet, and configured to have third prism patterns crossing over the first prism patterns and the second prism patterns.

[43] The backlight unit of claim 42, further comprising: diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[44] The backlight unit of claim 36, further comprising: a second prism sheet disposed on the first prism sheet, and configured to have second prism patterns crossing over the first prism patterns.

[45] The backlight unit of claim 44, further comprising: diffusion sections disposed on at least one of one side of the first prism sheet and one side of the second prism sheet, and configured to have a hemisphere shape.

[46] The backlight unit of claim 36, wherein the first substance is substantially identical to the second substance.

[47] A one body type optical sheet comprising: a first base section; a second base section; an adhering section located between the first base section and the second base section, and configured to adhere the second base section to the first base section; and first prism patterns disposed on the second base section.

[48] The optical sheet of claim 47, further comprising: diffusion sections disposed on a surface opposed to a surface corresponding to the adhering section of surfaces of the first base section, and configured to have hemisphere shape.

[49] The optical sheet of claim 48, wherein at least one of the diffusion sections includes: a first refractive layer configured to have a first refractive index; and a second refractive layer formed in the first refractive layer, and configured to have a second refractive index, wherein the first refractive index is higher than the second refractive index.

[50] The optical sheet of claim 47, wherein the adhering section is made up of an ultraviolet curing resin (UV resin) or a curing resin containing a diffusion agent.

[51] The optical sheet of claim 47, wherein the first base section is a film made up of a polyethylene terephthalate PET, a poly methyl meta acrylate PMMA or a polycarbonate.

[52] The optical sheet of claim 47, wherein the first base section is made up of a diffusion plate.

[53] The optical sheet of claim 47, wherein one or more of pitches between the first prism patterns have different length from the other pitches.

[54] The optical sheet of claim 47, wherein at least one of heights of the first prism patterns have different length from the other heights.

[55] The optical sheet of claim 47, wherein when a vertex angle of at least one of the first prism patterns is halved on the basis of a normal of the second base section, sub-angles generated by the halving the vertex angle have substantially the same magnitude.

[56] The optical sheet of claim 47, wherein the first prism patterns are disposed on an imaginary curve.

[57] The optical sheet of claim 47, wherein an imaginary line generated by connecting vertexes of some of the first prism patterns has mountain shape.

[58] The optical sheet of claim 47, further comprising: second prism patterns disposed between the first prism patterns, and configured to have hemisphere shape.

[59] The optical sheet of claim 47, further comprising: a curved surface layer disposed between the second base section and the first prism patterns, and configured to have curved surface shape.

[60] The optical sheet of claim 47, wherein the optical sheet is employed in a direct- lighting type backlight unit.

[61] A method of manufacturing a one body type optical sheet comprising: forming a first structure by coating a curing resin on a first surface of surfaces of a first base section; curing firstly the first structure; forming a second structure by attaching a second base section to the first structure, wherein prism patterns are formed on the second base section; and forming the optical sheet by curing secondly the second structure.

[62] The method of claim 61 , further comprising : forming diffusion sections disposed on a second surface of the surfaces of the first base section, wherein the second surface is different from the first surface,

[63] The method of claim 61, wherein the first base section is a film made up of a polyethylene terephthalate PET, a poly methyl meta acrylate PMMA or a polycarbonate.

[64] The method of claim 61, wherein the first base section is made up of a diffusion plate.