WO2009075408A1 - Light diffusion sheet comprising light diffusion layer formed in same sheet, and manufacturing method for the sheet - Google Patents

Light diffusion sheet comprising light diffusion layer formed in same sheet, and manufacturing method for the sheet Download PDF

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Publication number
WO2009075408A1
WO2009075408A1 PCT/KR2008/000946 KR2008000946W WO2009075408A1 WO 2009075408 A1 WO2009075408 A1 WO 2009075408A1 KR 2008000946 W KR2008000946 W KR 2008000946W WO 2009075408 A1 WO2009075408 A1 WO 2009075408A1
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WO
WIPO (PCT)
Prior art keywords
light diffusion
layer
pores
light
layers
Prior art date
Application number
PCT/KR2008/000946
Other languages
French (fr)
Inventor
Sung Woon Cha
Kyung Soo Lee
Byung Joo Jeon
Original Assignee
Industry-Academic Cooperation Foundation, Yonsei University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Industry-Academic Cooperation Foundation, Yonsei University filed Critical Industry-Academic Cooperation Foundation, Yonsei University
Publication of WO2009075408A1 publication Critical patent/WO2009075408A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
    • G02B5/0278—Diffusing elements; Afocal elements characterized by the use used in transmission
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0215—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having a regular structure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0221—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having an irregular structure
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • G02B5/0226—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures having particles on the surface
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/0236—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element
    • G02B5/0242—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element by means of dispersed particles
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/0236—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element
    • G02B5/0247—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element by means of voids or pores
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0268—Diffusing elements; Afocal elements characterized by the fabrication or manufacturing method
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133606—Direct backlight including a specially adapted diffusing, scattering or light controlling members

Definitions

  • the present invention relates to a light diffusion sheet; and; more particularly, to alight diffusion sheet provided with a plurality of light diffusion layers forming pores therein so as to obtain a desired light diffusion efficiency using a foaming technique and a method for manufacturing the same.
  • LCD Liquid Crystal Display
  • the LCD is in the limelight as a display of several kinds of portable image display devices or fixed image display devices since the LCD is capable of being manufactured in small and ultra-thin and realizing image quality with high definition while consuming few current.
  • a luminescent type related to such an additional luminescent device is classified as a front-light type and a back-light type mainly.
  • the front-light type is a type for improving brightness of a display surface by mounting a light source on a front surface or a front side surface of the display.
  • realizing a technique for evenly distributing light emitted from a light source to a surface of the display becomes difficult as the size of the display becomes larger and there are problems that reflected light is generated from the surface of the display and a design of a front surface of the display is limited since the light source is irradiated from a front-side direction.
  • the back-light type is an indirect lighting type in which light generated from a light source of a unit of a back-light mounted on a rear surface of a display device reaches an opposite side through a light guide plate and the light is emitted to a front surface by reflecting on a reflector such as a metal deposition plate or an opaque white plate, thus improving brightness of a display screen.
  • a plan may be considered for arranging a plurality of light sources on a unit of back light so as to provide with a clear and bright image and enhancing an output of the light source itself.
  • a case raises problems incidentally to shorten the life time of product by increasing a caloric value and a power consumption of the unit of back light and to reduce an operation time once particularly for a moving image display device.
  • the present invention is different from the conventional technique technically in that the present invention relates to a technique for distributing pores inside unlike the conventional light diffusion sheet in which granules are distributed.
  • the light diffusion sheet in accordance with the present invention has the following objects to solve problems mentioned in the background of the related art.
  • a light diffusion sheet comprising a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer of a plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
  • each of the plurality of layers of the light diffusion sheet in accordance with the present invention is divided from each other in the same sheet by foaming.
  • the light diffusion sheet capable of improving light diffusion efficiency by making the average size and average density of pores to be same or different in a plurality of light diffusion layers in which the pores are distributed while the weight of the sheet is reduced by distributing the pores inside the light diffusion sheet.
  • Hg. 1 and Rg. 2 are cross-section diagrams showing the light diffusion sheet including three layers in accordance with embodiments of the present invention.
  • Rg. 3 and Rg. 4 are cross-section diagrams showing the light diffusion sheet including five layers in accordance with embodiments of the present invention.
  • Rg. 5 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with the present invention.
  • Hg. 6 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a first embodiment of the present invention
  • Rg. 7 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a second embodiment of the present invention.
  • Rg. 8 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a third embodiment of the present invention. Best Mode for Carrying Out the Invention
  • a light diffusion sheet comprising a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer of a plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
  • each of the plurality of layers of the light diffusion sheet in accordance with the present invention is divided from each other in the same sheet by foaming.
  • the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.
  • the average size of the pores preferably is in the range of 5 /M to 150/M
  • a transmissivity of a total light ray preferably is in the range of 40% to 80%
  • a trans- missivity of a parallel light ray preferably is less than 6.5%.
  • a method for manufacturing the light diffusion sheet in accordance with the present application oomprises a saturation process for saturating a part or the whole of the light diffusion sheet by inputting the light diffusion sheet formed of the same sheet in a high pressure chamber and injecting a high pressure gas; and a foaming process for forming pores by the gas infiltrated into the light diffusion sheet by heat treating the saturated light diffusion sheet.
  • the light diffusion layer in which pores are distributed is formed and when the light diffusion layer is plural, it is preferable that the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.
  • the gas injected during the saturation process in accordance with the present invention preferably is more than any one selected from a group consisting of a CO gas, an N and a combination gas thereof as an inert gas.
  • the light diffusion sheet when the light diffusion sheet includes three layers, it is possible that a first layer disposed closest to a light source and a third layer disposed farthest to the light source are formed of light diffusion layers and a central second layer is formed of a light transmitting layer.
  • the whole light diffusion sheet is saturated with an injection gas within the high pressure chamber and the gas saturated in the first layer and the third layer except for a central second layer is discharged in the air in a saturation process and pores are formed in the second layer by heat treating the light diffusion sheet in a foaming process.
  • the light diffusion sheet when the light diffusion sheet includes five layers with a first layer to a fifth layer, it is preferable that in a saturation process, the other region except for a central third layer of the light diffusion sheet is saturated with the injection gas within the high pressure chamber and the gas saturated in the external first and fifth layers is discharged in the air and in the foaming process, pores in the a second layer and the fourth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet.
  • the average size of the pores in the second layer disposed close to the light source is larger than the average size of the pores in the fourth layer disposed far from the light source and the average density of the pores in the second layer disposed close to the light source is lower than the average density of the pores in the fourth layer disposed far from the light source.
  • Hg. 1 and Rg. 2 are cross-section diagrams showing the light diffusion sheet including three layers in accordance with embodiments of the present invention and Rg. 3 and Rg. 4 are cross-section diagrams showing the light diffusion sheet including five layers in accordance with embodiments of the present invention.
  • the light diffusion sheet 100 in accordance with the present invention 100 is made of a light transmitting material and has a plurality of layers.
  • the layers are not conjugated with each other but the layers are divided from each other by processing the same sheet through a foaming process.
  • a light diffusion sheet provided with light diffusion layer formed in the same sheet in accordance with the present invention includes a light diffusion sheet 100 made of a light transmitting material and including a plurality of layers, a light diffusion layer 200 to constitute at least one layer among a plurality of layers of the light diffusion sheet in which a plurality of pores 210 are distributed by foaming and a light transmitting layer 300 as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
  • the pores formed and distributed in the light diffusion layer 200 in accordance with the present invention perform functions of light diffusion, reflection and scattering sources.
  • Each of the plurality of layers of the light diffusion sheet 100 in accordance with the present invention is discriminated in the same sheet by foaming and when the light diffusion layer 200 is plural, it is preferable that the average size of pores 210 of the light diffusion layers 200 disposed close to a light source is equal to or larger than the average size of pores 210 of the light diffusion layers 200 disposed far from the light source and the average density of pores 210 of the light diffusion layers 200 disposed close to the light source is equal to or lower than the average density of pores 210 of the light diffusion layers 200 disposed far from the light source.
  • the average size of the pores 210 of the light diffusion layer 200 in accordance with the present invention preferably is in the range of 5 /M to 150/M.
  • perpendicular transmitted light When light reaches a substance, some light is reflected, other light input into the substance is absorbed by the substance and the other light becomes a transmitted light. And the transmitted light is classified into diffusion- transmitted-light diffused by the substance and parallel transmitted light going right on in the incidence direction(when the light is input in a specimen perpendicularly, it is referred to as perpendicular transmitted light).
  • There are three transmissivities such as a whole light ray trans- missivity(Tt) to represent a whole amount of the transmitted light ray, a diffusion transmissivity(Td), and a parallel light ray transmissivity(Tp). Correlation of parameters is as follows.
  • Tp% (parallel transmissivity) Tt - Td
  • Tt% (total light ray transmissivity) Tp + Td
  • the total light ray transmissivity of the light diffusion sheet 100 in accordance with the present invention preferably is in the range of 40% to 80% and the parallel light ray transmissivity thereof preferably is less than 6.5%.
  • an embodiment of the light diffusion sheet in accordance with the present invention is capable of being realized in a three- layer- structure.
  • a layer disposed close to the light source is a first layer 110 and a second layer and a third layer are put sequentially.
  • a first layer 110 disposed closest to the light source and a third layer 130 disposed farthest from the light source are formed of light diffusion layers 200 and a central second layer 120 is formed of a light transmitting layer 300.
  • the first layer 110 performs function of low reflection as a first diffusion layer mainly and the third layer 130 performs function of diffusion as a second diffusion layer mainly.
  • a first layer 110 disposed closest to the light source and a third layer 130 disposed farthest from the light source are formed of light diffusion layers 200 and a central second layer 120 is formed of a light diffusion layer 300.
  • a first layer 110 disposed closest to a light source, a central third layer 130 and a fifth layer 150 disposed farthest from the light source are formed of light diffusion layers 200 and a second layer 120 and a fourth layer 140 disposed in the center are formed of light transmitting layers 300.
  • a first layer 110 disposed closest to a light source, a central third layer 130 and a fifth layer 150 disposed farthest from the light source are formed of light transmitting layers 300 and a second layer 120 and a fourth layer 140 disposed in the middle are formed of light diffusion layers 200.
  • the three-layer structure and the five-layer structure are described as representative embodiments in the present specification for convenient description, but it will be apparent to those skilled in the art that various structures such as a two-layer structure, a four-layer structure, a six-layer structure, a seven-layer structure, or the like may be made.
  • the light diffusion sheet 100 in accordance with the present invention preferably is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
  • a method for manufacturing the light diffusion sheet in accordance with the present application comprises a saturation process for saturating a part or the whole of the light diffusion sheet 100 by inputting the light diffusion sheet 100 formed of the same sheet in a high pressure chamber 400 and injecting a high pressure gas 410; and a foaming process for forming pores by the gas infiltrated into the light diffusion sheet 100 by heat treating the saturated light diffusion sheet 100.
  • a light diffusion layer in which pores 210 are distributed is formed.
  • the average size of pores 210 of the light diffusion layers 200 disposed close to a light source is equal to or larger than the average size of the pores 210 of the light diffusion layers 200 disposed far from the light source and the average density of the pores 210 of the light diffusion layers 200 disposed close to the light source is equal to or lower than the average density of the pores 210 of the light diffusion layers 200 disposed far from the light source.
  • the gas injected in the saturation process of the light diffusion sheet in accordance with the present invention preferably is more than any one selected from a group consisting of a CO gas, an N gas and a combination gas thereof as an inert gas.
  • each injected gas preferably is not a supercritical state and when the injected gas is gas combined with the CO gas and the N gas, only the CO gas of the combined gas preferably is not a supercritical state.
  • the injected gas is the CO gas and the N gas, injecting each gas in several orders is possible. Ibr example, injecting each gas is possible in an order of CO gas ⁇ N gas, N gas ⁇ CO gas, CO gas ⁇ N gas ⁇ CO gas, N gas ⁇ GO gas ⁇ N
  • the light diffusion sheet 100 preferably is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
  • the light diffusion sheet 100 when the light diffusion sheet 100 includes three layers with a first layer to a third layer, it is preferable that a region corresponding to the first layer and the third layer of the light diffusion sheet is saturated with the injected gas in a high pressure chamber 400 in a saturation process and the pores in the first and third layers are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
  • the average size of the pores in the first layer disposed close to the light source is larger than the average size of the pores in the third layer disposed far from the light source and the average density of the pores in the first layer disposed close to the light source is lower than the average density of the pores in the third layer disposed far from the light source.
  • the heat treatment in the foaming process in accordance with the present invention preferably is performed by any one selected from a group consisting of a heat plate, an infrared ray heater, a heat blast device and a liquid heat source.
  • the pore 210 are formed by heat treating by compressing the heat plate on the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas.
  • the pores formed in the first layer and the third layer may be formed to have different average size and average density.
  • pore 210 are formed by heat treating by disposing the infrared ray heater or the heat blast device 530 close to the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas.
  • the pores in the first layer and the third layer may be formed to have different average size and the average density.
  • pore 210 are formed by immersing in the liquid heat source 540 the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas.
  • the heat added to the first layer and the third layer is same and therefore the average size and the average density of the pores 210 formed in the first and third layers may become same.
  • the foaming process in accordance with the present invention is performed in an incomplete saturated condition.
  • a region corresponding to the first layer to the third layer of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 in a saturation process and pores in the first layer and the third layer are formed to have same or different average size and average density by heat treating the light diffusion sheet in a foaming process, wherein if the average size and the average density of the pores are different from each other, the average size of the pores in the first layer disposed close to a light source is larger than the average size of the pores in the third layer disposed far from the light source and the average density of the pores in the first layer disposed close to the light source is lower than the average density of the pores in the third layer disposed far from the light source.
  • the whole of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 and the gas saturated in the first layer and the third layer except for a central second layer is discharged in the air in a saturation process and pores in the second layer are formed by heat treating the light diffusion sheet in a foaming process.
  • the whole of the light diffusion sheet 100 is saturated with an injected gas in a high pressure chamber 400, the gas saturated in the other layers except for a central third layer is discharged in the air and a region corresponding to the first layer and the fifth layer of the light diffusion sheet is saturated with the injected gas in the high pressure chamber 400 again in a saturation process.
  • pores in the first, third and fifth layers are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
  • the average size of the pores in the layer disposed close to the light source is larger than the average size of the pores in the layer disposed far from the light source and the average density of the pores in the layer disposed close to the light source is lower than the average density of the pores in the layer disposed far from the light source.
  • the light diffusion sheet 100 includes five layers with a first layer to a fifth layer in the method for manufacturing the light diffusion sheet in accordance with the present invention
  • a region corresponding to the other layers except for a central third layer of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 and the gas saturated in the external first and fifth layers is discharged in the air in a saturation process.
  • pores in a second layer and the fifth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
  • the average size of the second layer disposed close to the light source is larger than the average size of the fourth layer disposed far from the light source and the average density of the second layer disposed to the light source is lower than the average density of the fourth layer disposed far from.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Nonlinear Science (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Dispersion Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)

Abstract

In accordance with the present invention, there is provided a light diffusion sheet provided with a light diffusion layer formed in a same sheet, comprising a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer among the plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed, wherein each of the plurality of layers of the light diffusion sheet is discriminated from each other in the same sheet by foaming and when the light diffusion layer is plural, the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.

Description

Description
LIGHT DIFFUSION SHEET COMPRISING LIGHT DIFFUSION LAYER FORMED IN SAME SHEET, AND MANUFACTURING METHOD FOR THE SHEET
Technical Field
[1] The present invention relates to a light diffusion sheet; and; more particularly, to alight diffusion sheet provided with a plurality of light diffusion layers forming pores therein so as to obtain a desired light diffusion efficiency using a foaming technique and a method for manufacturing the same. Background Art
[2] Recently, a light diffusion device for Liquid Crystal Display(LCD) has been widely used. The LCD is in the limelight as a display of several kinds of portable image display devices or fixed image display devices since the LCD is capable of being manufactured in small and ultra-thin and realizing image quality with high definition while consuming few current.
[3] However, it is technical reality that an additional luminescent device is required so as to improve brightness of a display screen since a display type using a liquid crystal does not have luminescence itself unlike other flat panel display types.
[4] A luminescent type related to such an additional luminescent device is classified as a front-light type and a back-light type mainly. The front-light type is a type for improving brightness of a display surface by mounting a light source on a front surface or a front side surface of the display. However, realizing a technique for evenly distributing light emitted from a light source to a surface of the display becomes difficult as the size of the display becomes larger and there are problems that reflected light is generated from the surface of the display and a design of a front surface of the display is limited since the light source is irradiated from a front-side direction.
[5] In contrast, the back-light type is an indirect lighting type in which light generated from a light source of a unit of a back-light mounted on a rear surface of a display device reaches an opposite side through a light guide plate and the light is emitted to a front surface by reflecting on a reflector such as a metal deposition plate or an opaque white plate, thus improving brightness of a display screen.
[6] In such a back- light type, a plan may be considered for arranging a plurality of light sources on a unit of back light so as to provide with a clear and bright image and enhancing an output of the light source itself. However, such a case raises problems incidentally to shorten the life time of product by increasing a caloric value and a power consumption of the unit of back light and to reduce an operation time once particularly for a moving image display device.
[7] Therefore, other techniques capable of improving an illumination of LCD have been required. As one of such techniques, a light diffusion sheet capable of diffusing light emitted from a light source lamp uniformly while passing the light without loss has been developed.
[8] Most conventional light diffusion sheets have a technical characteristic to distribute granules for diffusing light inside the light diffusion sheet so as to diffuse light uniformly. In such a case, there was a development task of development with regard to a material and a type of granules for diffusing light to be applied, or the like.
[9] In such a conventional technique, there were problems to increase the weight of the light diffusion sheet and manufacturing cost since inorganic based granules with a great density are used under the circumstance that the light diffusion sheet became bigger as the LCD became larger.
[10] The present invention is different from the conventional technique technically in that the present invention relates to a technique for distributing pores inside unlike the conventional light diffusion sheet in which granules are distributed.
[11] Meanwhile, some conventional light diffusion sheets to distribute pores inside have been discovered, but such conventional light diffusion sheets have low light diffusion efficiency in that the light diffusion sheets distribute pores with a predetermined size simply, and thus a technique for improving light diffusion efficiency is required. Disclosure of Invention Technical Problem
[12] The light diffusion sheet in accordance with the present invention has the following objects to solve problems mentioned in the background of the related art.
[13] It is, therefore, a primary object of the present invention to provide a light diffusion sheet and a method for manufacturing the same capable of reducing the weight of the light diffusion sheet by distributing not granules but pores inside the light diffusion sheet.
[14] It is another object of the present invention to provide a light diffusion sheet and a method for manufacturing the same capable of improving a light diffusion efficiency by properly arranging light diffusion layers distributed with pores inside the light diffusion sheet and light transmitting layers without the pore.
[15] It is still another object of the present invention to provide a light diffusion sheet and a method for manufacturing the same capable of forming the light diffusion layers and the light transmitting layers constituting the light diffusion sheet in the same material through a foaming process without being joined.
[16] It is still another object of the present invention to provide a light diffusion sheet and a method for manufacturing the same capable of enhancing a light diffusion efficiency by being in different average size and average density of pores in a plurality of light diffusion layers.
[17] Objects of the present invention are not limited to the above described objects and the other objects which were not mentioned may be understood clearly by those skilled in the art through the following description. Technical Solution
[18] In accordance with the present invention, there is provided a light diffusion sheet, comprising a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer of a plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
[19] Herein, each of the plurality of layers of the light diffusion sheet in accordance with the present invention is divided from each other in the same sheet by foaming.
Advantageous Effects
[20] As described above, in accordance with the present invention, the light diffusion sheet capable of improving light diffusion efficiency by making the average size and average density of pores to be same or different in a plurality of light diffusion layers in which the pores are distributed while the weight of the sheet is reduced by distributing the pores inside the light diffusion sheet. Brief Description of the Drawings
[21] Hg. 1 and Rg. 2 are cross-section diagrams showing the light diffusion sheet including three layers in accordance with embodiments of the present invention;
[22] Rg. 3 and Rg. 4 are cross-section diagrams showing the light diffusion sheet including five layers in accordance with embodiments of the present invention;
[23] Rg. 5 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with the present invention.
[24] Hg. 6 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a first embodiment of the present invention;
[25] Rg. 7 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a second embodiment of the present invention; and
[26] Rg. 8 is a schematic diagram showing the method for manufacturing the light diffusion sheet in accordance with a third embodiment of the present invention. Best Mode for Carrying Out the Invention
[27] In accordance with the present invention, there is provided a light diffusion sheet, comprising a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer of a plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
[28] Herein, each of the plurality of layers of the light diffusion sheet in accordance with the present invention is divided from each other in the same sheet by foaming.
[29] When the light diffusion layer in accordance with the present invention is plural, it is preferable that the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.
[30] In the light diffusion layers of the light diffusion sheet in accordance with the present invention, the average size of the pores preferably is in the range of 5 /M to 150/M, a transmissivity of a total light ray preferably is in the range of 40% to 80%, and a trans- missivity of a parallel light ray preferably is less than 6.5%.
[31] A method for manufacturing the light diffusion sheet in accordance with the present application oomprises a saturation process for saturating a part or the whole of the light diffusion sheet by inputting the light diffusion sheet formed of the same sheet in a high pressure chamber and injecting a high pressure gas; and a foaming process for forming pores by the gas infiltrated into the light diffusion sheet by heat treating the saturated light diffusion sheet.
[32] In the foaming process in accordance with the present invention, the light diffusion layer in which pores are distributed is formed and when the light diffusion layer is plural, it is preferable that the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source. [33] The gas injected during the saturation process in accordance with the present invention preferably is more than any one selected from a group consisting of a CO gas, an N and a combination gas thereof as an inert gas.
2
[34] In the method for manufacturing the light diffusion sheet in accordance with the present invention, when the light diffusion sheet includes three layers, it is possible that a first layer disposed closest to a light source and a third layer disposed farthest to the light source are formed of light diffusion layers and a central second layer is formed of a light transmitting layer.
[35] In the method for manufacturing the light diffusion sheet in accordance with the present invention, when the light diffusion sheet includes three layers with a first layer to a third layer, it is possible that the whole light diffusion sheet is saturated with an injection gas within the high pressure chamber and the gas saturated in the first layer and the third layer except for a central second layer is discharged in the air in a saturation process and pores are formed in the second layer by heat treating the light diffusion sheet in a foaming process.
[36] In the method for manufacturing the light diffusion sheet in accordance with the present invention, when the light diffusion sheet includes five layers with a first layer to a fifth layer, it is preferable that in a saturation process, the other region except for a central third layer of the light diffusion sheet is saturated with the injection gas within the high pressure chamber and the gas saturated in the external first and fifth layers is discharged in the air and in the foaming process, pores in the a second layer and the fourth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet.
[37] Further, it is preferable that when the average size and the average density of the pores are different, the average size of the pores in the second layer disposed close to the light source is larger than the average size of the pores in the fourth layer disposed far from the light source and the average density of the pores in the second layer disposed close to the light source is lower than the average density of the pores in the fourth layer disposed far from the light source. Mode for the Invention
[38] Hereinafter, the light diffusion sheet in accordance with the present invention will be described in detail with reference to the accompanying drawings.
[39] Hg. 1 and Rg. 2 are cross-section diagrams showing the light diffusion sheet including three layers in accordance with embodiments of the present invention and Rg. 3 and Rg. 4 are cross-section diagrams showing the light diffusion sheet including five layers in accordance with embodiments of the present invention.
[40] The light diffusion sheet 100 in accordance with the present invention 100 is made of a light transmitting material and has a plurality of layers. The layers are not conjugated with each other but the layers are divided from each other by processing the same sheet through a foaming process.
[41] A light diffusion sheet provided with light diffusion layer formed in the same sheet in accordance with the present invention includes a light diffusion sheet 100 made of a light transmitting material and including a plurality of layers, a light diffusion layer 200 to constitute at least one layer among a plurality of layers of the light diffusion sheet in which a plurality of pores 210 are distributed by foaming and a light transmitting layer 300 as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed.
[42] The pores formed and distributed in the light diffusion layer 200 in accordance with the present invention perform functions of light diffusion, reflection and scattering sources.
[43] Each of the plurality of layers of the light diffusion sheet 100 in accordance with the present invention is discriminated in the same sheet by foaming and when the light diffusion layer 200 is plural, it is preferable that the average size of pores 210 of the light diffusion layers 200 disposed close to a light source is equal to or larger than the average size of pores 210 of the light diffusion layers 200 disposed far from the light source and the average density of pores 210 of the light diffusion layers 200 disposed close to the light source is equal to or lower than the average density of pores 210 of the light diffusion layers 200 disposed far from the light source.
[44] The average size of the pores 210 of the light diffusion layer 200 in accordance with the present invention preferably is in the range of 5 /M to 150/M.
[45] When light reaches a substance, some light is reflected, other light input into the substance is absorbed by the substance and the other light becomes a transmitted light. And the transmitted light is classified into diffusion- transmitted-light diffused by the substance and parallel transmitted light going right on in the incidence direction(when the light is input in a specimen perpendicularly, it is referred to as perpendicular transmitted light). There are three transmissivities such as a whole light ray trans- missivity(Tt) to represent a whole amount of the transmitted light ray, a diffusion transmissivity(Td), and a parallel light ray transmissivity(Tp). Correlation of parameters is as follows.
[46] Tp% (parallel transmissivity) = Tt - Td,
[47] Tt% (total light ray transmissivity) = Tp + Td
[48] The total light ray transmissivity of the light diffusion sheet 100 in accordance with the present invention preferably is in the range of 40% to 80% and the parallel light ray transmissivity thereof preferably is less than 6.5%.
[49] As illustrated in Hg. 1 and Rg. 2, an embodiment of the light diffusion sheet in accordance with the present invention is capable of being realized in a three- layer- structure. In such an embodiment, when there is a light source at the downside of the light diffusion sheet 100, a layer disposed close to the light source is a first layer 110 and a second layer and a third layer are put sequentially.
[50] As illustrated in Hg. 1, in the light diffusion sheet 100 including three layers in accordance with a first embodiment of the present invention, it is possible that a first layer 110 disposed closest to the light source and a third layer 130 disposed farthest from the light source are formed of light diffusion layers 200 and a central second layer 120 is formed of a light transmitting layer 300.
[51] A structure that the farther the layer is from the light source, the smaller the average size of the pores 210 is or the farther the layer is from the light source, the higher the average density of the pores 210 is corresponds to the technical characteristic of the present invention to improve light diffusion efficiency. In the first embodiment of the present invention, the first layer 110 performs function of low reflection as a first diffusion layer mainly and the third layer 130 performs function of diffusion as a second diffusion layer mainly.
[52] As illustrated in Hg. 2, in the light diffusion sheet 100 including three layers in accordance with a second embodiment of the present invention, it is possible that a first layer 110 disposed closest to the light source and a third layer 130 disposed farthest from the light source are formed of light diffusion layers 200 and a central second layer 120 is formed of a light diffusion layer 300.
[53] As illustrated in Hg. 3, in the light diffusion sheet 100 including five layers in accordance with the first embodiment of the present invention, it is possible that a first layer 110 disposed closest to a light source, a central third layer 130 and a fifth layer 150 disposed farthest from the light source are formed of light diffusion layers 200 and a second layer 120 and a fourth layer 140 disposed in the center are formed of light transmitting layers 300.
[54] Further, as illustrated in Hg. 4, in the light diffusion sheet 100 including five layers in accordance with the second embodiment of the present invention, it is possible that a first layer 110 disposed closest to a light source, a central third layer 130 and a fifth layer 150 disposed farthest from the light source are formed of light transmitting layers 300 and a second layer 120 and a fourth layer 140 disposed in the middle are formed of light diffusion layers 200.
[55] In the light diffusion sheet in accordance with the present invention, the three-layer structure and the five-layer structure are described as representative embodiments in the present specification for convenient description, but it will be apparent to those skilled in the art that various structures such as a two-layer structure, a four-layer structure, a six-layer structure, a seven-layer structure, or the like may be made.
[56] Meanwhile, the light diffusion sheet 100 in accordance with the present invention preferably is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
[57] Hereinafter, a method for manufacturing the light diffusion sheet in accordance with the present invention will be described in detail.
[58] A method for manufacturing the light diffusion sheet in accordance with the present application comprises a saturation process for saturating a part or the whole of the light diffusion sheet 100 by inputting the light diffusion sheet 100 formed of the same sheet in a high pressure chamber 400 and injecting a high pressure gas 410; and a foaming process for forming pores by the gas infiltrated into the light diffusion sheet 100 by heat treating the saturated light diffusion sheet 100.
[59] In the foaming process in accordance with the present invention, a light diffusion layer in which pores 210 are distributed is formed. When the light diffusion layer 200 is plural, it is preferable that the average size of pores 210 of the light diffusion layers 200 disposed close to a light source is equal to or larger than the average size of the pores 210 of the light diffusion layers 200 disposed far from the light source and the average density of the pores 210 of the light diffusion layers 200 disposed close to the light source is equal to or lower than the average density of the pores 210 of the light diffusion layers 200 disposed far from the light source. [60] As described above, a structure that the farther the layer is from the light source, the smaller the average size of the pores 210 is or the farther the layer is from the light source, the higher the average density of the pores 210 is corresponds to the technical characteristic of the present invention to improve light diffusion efficiency.
[61] The gas injected in the saturation process of the light diffusion sheet in accordance with the present invention preferably is more than any one selected from a group consisting of a CO gas, an N gas and a combination gas thereof as an inert gas.
[62] When the injected gas is the CO gas or the N gas, each injected gas preferably is not a supercritical state and when the injected gas is gas combined with the CO gas and the N gas, only the CO gas of the combined gas preferably is not a supercritical state.
[63] And the injected gas is the CO gas and the N gas, injecting each gas in several orders is possible. Ibr example, injecting each gas is possible in an order of CO gas → N gas, N gas →CO gas, CO gas → N gas →CO gas, N gas →GO gas →N
2 2 2 2 2 2 2 2 2 gas, or the like.
[64] In the method for manufacturing the light diffusion sheet in accordance with the present invention, the light diffusion sheet 100 preferably is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
[65] In the method for manufacturing the light diffusion sheet in accordance with the present invention, when the light diffusion sheet 100 includes three layers with a first layer to a third layer, it is preferable that a region corresponding to the first layer and the third layer of the light diffusion sheet is saturated with the injected gas in a high pressure chamber 400 in a saturation process and the pores in the first and third layers are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
[66] In the method for manufacturing the light diffusion sheet in accordance with the present invention, it is preferable that when the average size and the average density of the pores are different, the average size of the pores in the first layer disposed close to the light source is larger than the average size of the pores in the third layer disposed far from the light source and the average density of the pores in the first layer disposed close to the light source is lower than the average density of the pores in the third layer disposed far from the light source.
[67] The heat treatment in the foaming process in accordance with the present invention preferably is performed by any one selected from a group consisting of a heat plate, an infrared ray heater, a heat blast device and a liquid heat source.
[68] In an embodiment of a foaming chamber 500(referring to Rg. 6) where pores are formed in a first layer and a third layer among three layers in the foaming process in accordance with the present invention, the pore 210 are formed by heat treating by compressing the heat plate on the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas. Herein, if the condition of heat treatment is changed, the pores formed in the first layer and the third layer may be formed to have different average size and average density.
[69] In another embodiment of the foaming chamber 500(referring to Rg. 7) in accordance with the present invention, pore 210 are formed by heat treating by disposing the infrared ray heater or the heat blast device 530 close to the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas. Herein, if the condition of heat treatment is changed, the pores in the first layer and the third layer may be formed to have different average size and the average density.
[70] In another embodiment of the foaming chamber 500(referring to Rg. 8) in accordance with the present invention, pore 210 are formed by immersing in the liquid heat source 540 the light diffusion sheet 100 of which the first layer and the third layer are saturated with the injected gas. However, in such an embodiment of the liquid heat source, the heat added to the first layer and the third layer is same and therefore the average size and the average density of the pores 210 formed in the first and third layers may become same.
[71] Meanwhile, it is preferable that the foaming process in accordance with the present invention is performed in an incomplete saturated condition.
[72] In the first embodiment(referring to Rg. 1) wherein the light diffusion sheet 100 includes three layers with a first layer to a third layer in the method for manufacturing the light diffusion sheet in accordance with the present invention, a region corresponding to the first layer to the third layer of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 in a saturation process and pores in the first layer and the third layer are formed to have same or different average size and average density by heat treating the light diffusion sheet in a foaming process, wherein if the average size and the average density of the pores are different from each other, the average size of the pores in the first layer disposed close to a light source is larger than the average size of the pores in the third layer disposed far from the light source and the average density of the pores in the first layer disposed close to the light source is lower than the average density of the pores in the third layer disposed far from the light source.
[73] In the second embodiment(referring to Rg. 2) wherein the light diffusion sheet 100 includes three layers with a first layer to a third layer in the method for manufacturing the light diffusion sheet in accordance with the present invention, the whole of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 and the gas saturated in the first layer and the third layer except for a central second layer is discharged in the air in a saturation process and pores in the second layer are formed by heat treating the light diffusion sheet in a foaming process.
[74] In the first embodiment(referring to Rg. 3) wherein the light diffusion sheet 100 includes five layers with a first layer to a fifth layer in the method for manufacturing the light diffusion sheet in accordance with the present invention, the whole of the light diffusion sheet 100 is saturated with an injected gas in a high pressure chamber 400, the gas saturated in the other layers except for a central third layer is discharged in the air and a region corresponding to the first layer and the fifth layer of the light diffusion sheet is saturated with the injected gas in the high pressure chamber 400 again in a saturation process. Further, pores in the first, third and fifth layers are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
[75] When the average size and the average density of the pores are different, it is preferable that the average size of the pores in the layer disposed close to the light source is larger than the average size of the pores in the layer disposed far from the light source and the average density of the pores in the layer disposed close to the light source is lower than the average density of the pores in the layer disposed far from the light source.
[76] In the second embodiment(referring to Rg. 4) wherein the light diffusion sheet 100 includes five layers with a first layer to a fifth layer in the method for manufacturing the light diffusion sheet in accordance with the present invention, a region corresponding to the other layers except for a central third layer of the light diffusion sheet is saturated with an injected gas in a high pressure chamber 400 and the gas saturated in the external first and fifth layers is discharged in the air in a saturation process. Further, pores in a second layer and the fifth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet 100 in a foaming process.
[77] When the average size and the average density of the pores are different, it is preferable that the average size of the second layer disposed close to the light source is larger than the average size of the fourth layer disposed far from the light source and the average density of the second layer disposed to the light source is lower than the average density of the fourth layer disposed far from.
[78] In the method for manufacturing the light diffusion sheet in accordance with the present invention, while the three-layer structure and the five-layer structure are described as representative embodiments in the present specification for convenient description, it will be apparent to those skilled in the art that various structures such as a second-layer structure, a fourth-layer structure, a six-layer structure, a seven-layer structure, or the like by change of conditions of the saturation process and the foaming process may be made.
[79] Ibr example, in the second-layer structure, only a first layer of the light diffusion sheet 100 is saturated with an injected gas in the high pressure chamber 400 in the saturation process, and pores in only the first layer may be formed by heat treating the light diffusion sheet 100 in a foaming process. Further, in the fourth-layer structure, manufacturing in an order of a light diffusion layer 200 - a light transmitting layer 100 - a light diffusion layer 200 - a light transmitting layer 100, or the like is possible.
[80] Further, to realize various optical functions of the light diffusion sheet in accordance with the present invention, arranging reversely unlike the conventional arrangement is also possible technically, wherein the average size of the pores 210 of the light diffusion sheet 200 disposed close to the light source is smaller than the average size of the pores 210 of the light diffusion layer 200 disposed far from the light source.
[81] It will be apparent to those skilled in the art that such a simple change is made without departing from the scope of the invention as defined in the following claims.

Claims

Claims
[1] A light diffusion sheet provided with a light diffusion layer formed in a same sheet, comprising: a light diffusion sheet made of a light transmitting material and including a plurality of layers; a light diffusion layer to constitute at least one layer of the plurality of layers of the light diffusion sheet in which a plurality of pores are distributed by foaming; and a light transmitting layer as a layer different from the light diffusion layer of the plurality of layers of the light diffusion sheet in which any pore is not distributed, wherein each of the plurality of layers of the light diffusion sheet is divided from each other in the same sheet by foaming; and when the light diffusion layer is plural, the average size of the pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of the pores in the light diffusion layers disposed far from the light source; and the average density of pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.
[2] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein if the light diffusion sheet includes three layers, a first layer disposed closest to the light source and a third layer disposed farthest from the light source are formed of light diffusion layers; and a central second layer is formed of a light transmitting layer.
[3] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein if the light diffusion sheet includes three layers, a first layer disposed closest to the light source; and a third layer disposed farthest from the light source are formed of light transmitting layers and a central second layer is formed of a light diffusion layer.
[4] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein if the light diffusion sheet includes five layers, a first layer disposed closest to the light source, a central third layer and a fifth layer disposed farthest from the light source are formed of light diffusion layers; and a second layer and a fourth layer disposed in the center are formed of light transmitting layers.
[5] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein if the light diffusion sheet includes five layers, a first layer disposed closest to the light source, a central third layer and a fifth layer disposed farthest from the light source are formed of light transmitting layers; and a second layer and a fourth layer disposed in the center are formed of light diffusion layers.
[6] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein the average size of the pores in the light diffusion layers is in the range of 5/M to 150/M.
[7] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein a transmissivity of a whole light ray of the light diffusion sheet is in the range of 40% to 80%.
[8] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein a transmissibity of a parallel light ray is less than 6.5%.
[9] The light diffusion sheet provided with the light diffusion layer formed in the same sheet as recited in claim 1, wherein the light diffusion sheet is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
[10] A method for manufacturing a light diffusion sheet provided with a light diffusion layer formed in a same sheet, the method comprising the steps of: a saturation process for saturating a part or the whole of the light diffusion sheet by inputting the light diffusion sheet formed of the same sheet in a high pressure chamber and injecting a high pressure gas; and a foaming process for forming pores by the gas infiltrated into the light diffusion sheet by heat treating the saturated light diffusion sheet, wherein the light diffusion layer in which the pores are distributed is formed in the foaming process; and when the light diffusion layer is plural, the average size of pores in the light diffusion layers disposed close to a light source is equal to or larger than the average size of pores in the light diffusion layers disposed far from the light source; and the average density of the pores in the light diffusion layers disposed close to the light source is equal to or lower than the average density of the pores in the light diffusion layers disposed far from the light source.
[11] The method as recited in claim 10, wherein the injected gas is more than any one selected from a group consisting of a CO gas, an N gas and a combination gas
2 2 thereof as an inert gas.
[12] The method as recited in claim 11, wherein if the injected gas is the CO gas or the N gas, each of the injected gas is not a supercritical state.
[13] The method as recited in claim 11, wherein if the injected gas is the gas combined with the CO gas and the N gas, only the CO gas of the combined gas
2 2 2 is not a supercritical state.
[14] The method as recited in claim 11, wherein if the injected gas is the CO gas or the N gas, each of the injected gas is injected in order.
[15] The method as recited in claim 10, wherein the heat treatment in the foaming process is performed by any one selected from a group consisting of a heat plate, an infrared ray heater, a heat blast device and a liquid heat source.
[16] The method as recited in claim 10, wherein the foaming process is performed in an incomplete saturated condition.
[17] The method as recited in claim 10, wherein the light diffusion sheet is made of more than any one selected from a group consisting of polycarbonates, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polystyrene polyester-based resin and polyolefin based resin.
[18] The method as recited in claim 10, wherein if the light diffusion sheet includes three layers with a first layer to a third layer, in the saturation process, a region corresponding to the first layer and the third layer of the light diffusion sheet is saturated in the high pressure chamber with the injected gas, and in the foaming process, pores in the fist layer and the third layer are formed to have same or different average size and average density by heat treating the light diffusion sheet, when the average size and the average density of the pores are different, the average size of the pores in the first layer disposed close to the light source is larger than the average size of the pores in the third layer disposed far from the light source and the average density of the pores in the first layer disposed close to the light source is lower than the average density of the pores in the third layer disposed far from the light source.
[19] The method as recited in claim 10, wherein if the light diffusion sheet includes three layers with a first layer to a third layer, in the saturation process, the gas saturated in the first layer and the third layer except for a central second layer is discharged in the air after the whole light diffusion sheet is saturated in the high pressure chamber with the injected gas, and in the foaming process, pores in the second layer are formed by heat treating the light diffusion sheet.
[20] The method as recited in claim 10, wherein the light diffusion sheet includes five layers with a first layer to a fifth layer, in the saturation process, a whole of the light diffusion sheet is saturated with the injected gas in the high pressure chamber, the gas saturated in the other layers except for a central third layer is discharged in the air and a region corresponding to the first layer and the fifth layer of the light diffusion sheet is saturated with the injected gas in the high pressure chamber again, and in the foaming process, pores in the fist layer, the third layer and the fifth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet, when the average size and the average density of the pores are different, the average size of the pores in the layer disposed close to the light source is larger than the average size of the pores in the disposed far from the light source and the average density of the pores in the layer disposed close to the light source is lower than the average density of the pores in the layer disposed far from the light source.
[21] The method as recited in claim 10, wherein if the light diffusion sheet includes five layers with a first layer to a fifth layer, in the saturation process, a region corresponding to the other layers except for a central third layer is saturated with the injected gas in the high pressure chamber and the gas saturated in the external first and fifth layers is discharged in the air, and in the foaming process, pores in a second layer and the fourth layer are formed to have same or different average size and average density by heat treating the light diffusion sheet, when the average size and the average density of the pores are different, the average size of the pores in the second layer disposed close to the light source is larger than the average size of the pores in the fourth layer disposed far from the light source and the average density of the pores in the second layer disposed close to the light source is lower than the average density of the pores in the fourth layer disposed far from the light source.
PCT/KR2008/000946 2007-12-12 2008-02-18 Light diffusion sheet comprising light diffusion layer formed in same sheet, and manufacturing method for the sheet WO2009075408A1 (en)

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WO2022222175A1 (en) * 2021-04-22 2022-10-27 苏州三鑫时代新材料股份有限公司 Light diffusion plate containing nitrogen ball or carbon dioxide gas ball
CN115128716A (en) * 2022-05-25 2022-09-30 广东瑞捷光电股份有限公司 Novel foaming diffusion plate structure
CN115128716B (en) * 2022-05-25 2024-01-02 广东瑞捷新材料股份有限公司 Novel foaming diffusion plate structure

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