WO2005012958A1 - Light diffusion plate for lcd backlight with improved masking effect of lamp and light transmittance - Google Patents
Light diffusion plate for lcd backlight with improved masking effect of lamp and light transmittance Download PDFInfo
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- WO2005012958A1 WO2005012958A1 PCT/KR2004/001953 KR2004001953W WO2005012958A1 WO 2005012958 A1 WO2005012958 A1 WO 2005012958A1 KR 2004001953 W KR2004001953 W KR 2004001953W WO 2005012958 A1 WO2005012958 A1 WO 2005012958A1
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- Prior art keywords
- light diffusion
- light
- diffusion plate
- beads
- lamp
- Prior art date
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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
- G02B5/0205—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
- G02B5/0268—Diffusing elements; Afocal elements characterized by the fabrication or manufacturing method
-
- 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
- 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
Definitions
- the present invention relates to a light diffusion plate with improved masking effect of lamp and light transmittance that is useful for a lighting fixture cover, an advertisement panel, and especially a direct backlight type LCD.
- the backlight in the conventional LCD device includes an edge lighting system, and a direct lighting system.
- a fluorescent lamp is disposed at the edge of a light guide plate that has a downward slope to the bottom end under which a reflecting plate of sheet is installed. If necessary, a pattern may be printed on the bottom end of the light guide plate.
- This system which inevitably provides a low brightness, is mainly applied to small-sized display devices.
- the direct lighting system does not employ, a light guide plate but includes a reflecting plate, a plurality of lamps installed on the reflecting plate, and a light diffusion plate disposed on the lamps at a predetermined distance.
- the core of this system is a uniform brightness because of the lamps concealed completely.
- the light diffusion should be high resulting in lower light transmittance. This causes an inevitable reduction of the brightness.
- Another method is arranging the light diffusion plate farther away from the lamps, making it difficult to realize a thin display device.
- An improved method is using a geometric light guide plate and a light diffusion plate at once, as disclosed in Korean Patent Laid-open Publication No. 2002-71358.
- this system has problems regarding to complicated structure, increased complexity of the process, high production cost, and heavy weight.
- a light diffusion plate for an LCD backlight that is fabricated by coextrusion or multi-layer extrusion of at least two. light diffusion layers including a binder resin with or without light diffusion beads.
- the light diffusion plate has a structure that the light diffusion rate of the respective light diffusion layers gradually increases from the bottom of the light diffusion plate with an incident light of a lamp striking thereon to the top of the light diffusion plate.
- the light diffusion plate is fabricated by extrusion of light diffusion layers comprising a binder resin and light diffusion beads.
- the present invention is directed to a light diffusion plate fabricated by coextrusion or multi-layer extrusion of a plurality of light diffusion layers.
- the first light diffusion layer with an incident light of a lamp striking thereon may not include light diffusion beads.
- the light diffusion plate for a LCD backlight according to the present invention, particularly the light diffusion plate useful for a direct backlight LCD display is obtained by coextrusion or multi-layer extrusion of at least two light diffusion layers each having a different light diffusion rate gradient. The coextrusion or multi-layer extrusion of the multiple light diffusion layers to increase the light diffusion rate from the bottom of the light diffusion plate with an
- incident light( ⁇ ) of a lamp striking thereon to the top of the light diffusion plate may
- FIG. 1 This case of light diffusion is illustrated in FIG. 1.
- density distribution the term "density distribution” as used herein is defined as a number density expressed as the number of the light diffusion beads per volume
- the extrusion rate of the light diffusion beads in the light diffusion layers to have a different thickness and a different light transmittance in coextrusion or multilayer extrusion of multiple light diffusion layers
- a method of forming light diffusion layers comprising light diffusion beads each having a different refractive index
- the number of the light diffusion beads is controlled to have a density distribution increasing from the bottom of the light diffusion plate with an incident light of the lamp striking thereon to the top of the light diffusion plate.
- the light diffusion layer at the bottom of the light diffusion plate with an incident light of the lamp striking thereon contains light diffusion beads having a relatively low refractive index difference from the binder resin, while the light diffusion layer at the top of the light diffusion plate contains light diffusion beads having a relatively high refractive index difference from the binder resin.
- the coextrusion or multi-layer extrusion of multiple light diffusion layers using the density distribution difference of the light diffusion beads or the refractive index gradient of the light diffusion beads results in a light diffusion plate having multiple light diffusion layers with a light diffusion rate gradient.
- a light diffusion plate having a thickness of 1 to 3 mm and a light transmittance of 20 to 75 % can be produced by controlling the light diffusion layer at the bottom of the light diffusion plate with an incident light of the lamp striking thereon to have a light transmittance of 70 to 93 % (light diffusion rate: 98 ⁇ 6%) and a thickness of 0.5 to 1.5 mm, and the light diffusion layer at the top of the light diffusion plate to have a light transmittance of 30 to 80 % (light diffusion rate: 99 - 96%) and a thickness of 0.5 to 1.5 mm.
- the light diffusion plate of the present invention Compared with a single-layer light diffusion plate having the same light transmittance, the light diffusion plate of the present invention thus obtained is excellent in masking effect of lamp to maintain high brightness uniformity, achieving a desired brightness without increasing the distance from the lamp to the light diffusion plate, so it can be used for a direct backlight system necessary to a thin display system.
- the number of light diffusion layers coextruded or multilayer extruded and the thickness of the respective light diffusion layers can be controlled.
- the variety of the binder resin and the light diffusion beads in the light diffusion layers are generally given and specifically described as follows.
- binder resin examples include acryl-, urethane-, or epoxy melamine-based polymer or copolymer or ternary copolymer of unsarurated polyester, methylmethacrylate, ethylmethacrylate, isobutylmethacrylate, n- butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyethylacrylate, acrylamide, methylolacrylamide, glycidylmethacrylate, ethylacrylate, isobutylacrylate, n-butylacrylate, or 2-ethylhexylacrylate.
- a variety of organic or inorganic beads are used as the light diffusion beads so as to enhance the light transmittance and the light diffusion rate with a refractive index difference from the general binder resin.
- the specific examples of the light diffusion beads as used herein include organic beads such as acryl-based polymer, copolymer or ternary copolymer beads of methylmethacrylate, ethylmethacrylate, isobutylmethacrylate, n- butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxy ethylacrylate, acrylamide, methylolacrylate, glycidylmethacrylate, ethylacrylate, isobutylacrylate, n-butylacrylate, or 2-ethylhexylacrylate, olefinic beads of polyethylene, polystyrene or polyprop
- FIG. 1 is an illustration of a light diffusion state of light on a light diffusion plate having multiple light diffusion layers according to an embodiment of the present invention.
- Example 1 Control of Light diffusion Rate of Light diffusion layers by Density Distribution Difference of Light diffusion Beads.
- a light diffusion plate was fabricated by coextrusion of a light diffusion layer having a light transmittance of 90 % (light diffusion rate: 30%) and a thickness of 1.5 mm, and a light diffusion layer having a light transmittance of 70 % (light diffusion rate: 98%) and a thickness of 0.5 mm.
- the transmittance and the light diffusion rate were measured for sheets obtained by a single extrusion to the corresponding thickness with an NDH 2000 (Denshoku in Japan) as measurement equipment according to the standard method of ASTM D 1003.
- the h-ansmittance of the light diffusion layers was regulated by controlling the density distribution of light diffusion beads, while the thickness of the light diffusion layers was regulated by controlling the extrusion rate of the extruder.
- the light diffusion layers were prepared using polymethylmethacrylate (VH-001 supplied by Mitsubishi Rayon in Japan) as a binder resin, and cross-linked polystyrene ⁇ >. beads (Diasphere supplied by Kolon in Korea) as light diffusion beads. The details are '-, presented in Table 1.
- the light diffusion plate thus obtained had a total thickness of 2 mm, and a light transmittance of 63 %.
- the light diffusion plate was cut in 17-inch long units, which were placed 13 mm above a device with 8 cold cathode fluorescent lamps arranged at predetermined intervals to measure the brightness right over the lamps and in the middle between the lamps. The average ratio of the brightness right over the lamps to the brightness in the middle of the lamps was 1.02 on average. Table 1
- Example 2 Control of Light diffusion Rate of Light diffusion layers by Refractive Index Gradient of Light diffusion Beads.
- a light diffusion plate was fabricated by coextrusion of a light diffusion layer having a light transmittance of 90 % (light diffusion rate: 30 %) and a thickness of 1.5 mm, and a light diffusion layer having a light transmittance of 70 % (light diffusion rate: 98 %) and a thickness of 0.5 mm in the same manner as described in Example 1.
- the transmittance and the light diffusion rate were measured for sheets obtained by a single extrusion to the corresponding thickness with an NDH 2000 (Denshoku in Japan) as measurement equipment according to the standard method of ASTM D 1003.
- the transmittance of the light diffusion layers was regulated by controlling the refractive index difference between the light diffusion beads and the binder resin, while the thickness of the light diffusion layers was regulated by controlling the extrusion rate of the extruder.
- the light diffusion layers were prepared using polymethylmethacrylate (VH-001 (refractive index: 1.49 %) supplied by Mitsubishi Rayon in Japan) as the binder resin, and polystyrene-methylmethacrylate copolymer beads (Diasphere MSP-X10) and polystyrene beads (Diasphere SPB-XIO) as the light diffusion beads for the respective layers.
- the refractive index of the light diffusion beads can be regulated depending on the content of monomers used in the preparation of the light diffusion beads.
- the lower styrene content may result in a lower refractive index and a higher transmittance.
- the details are presented in Table 2.
- the light diffusion plate thus obtained- had a total thickness of 2 mm, and a light transmittance of 63 %.
- the light diffusion plate was cut in 17-inch long units, which were placed 13 mm above a device with 8 cold cathode fluorescent lamps arranged at predetermined intervals to measure the brightness right over.the lamps and in the middle between the lamps. The ratio of the brightness right over the lamps to the brightness in the middle of the lamps was 1.02 on average.
- Table 2 Table 2
- Example 1 and 2 and Comparative Example 1 the distance between the lamps and the light diffusion plate to acquire the defined brightness ratio was about 13 mm in the Examples 1 and 2, but 18 mm for the light diffusion plate produced by extrusion of a single light diffusion layer in the Comparative Example 1.
- the use of the light diffusion plate of the present invention decreases the thickness of the backlight by about 5 mm.
- the light diffusion plate manufactured by coextrusion or multi-layer extrusion of multiple light diffusion layers each having a different light diffusion rate gradient can reduce the thickness of the backlight unit without a loss of light transmittance and haze relative to the light diffusion plate produced by extrusion of a single light diffusion layer having a same light
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Optical Elements Other Than Lenses (AREA)
Abstract
The present invention relates to a light diffusion plate for an LCD backlight with enhanced masking effect of lamp and light transmittance, which light diffusion plate is manufactured by coextrusion or multi-layer extrusion of at least two light diffusion layers each having a different light diffusion rate gradient, to weaken light diffusion at the inlet portion of an incident light and gradually intensifies light diffusion with the progress of light, thereby enhancing both the masking effect of lamp and the light transmittance. Accordingly, the light diffusion plate of the present invention is useful for a lighting fixture cover required to have uniform brightness and advertisement panels, particularly direct backlight type LCD devices required to have a thin structure.
Description
LIGHT DIFFUSION PLATE FOR LCD BACKLIGHT WITH IMPROVED MASKING EFFECT OF LAMP AND LIGHT TRANSMITTANCE
Technical Field The present invention relates to a light diffusion plate with improved masking effect of lamp and light transmittance that is useful for a lighting fixture cover, an advertisement panel, and especially a direct backlight type LCD.
Background Art In general, the backlight in the conventional LCD device includes an edge lighting system, and a direct lighting system. In the edge lighting system, a fluorescent lamp is disposed at the edge of a light guide plate that has a downward slope to the bottom end under which a reflecting plate of sheet is installed. If necessary, a pattern may be printed on the bottom end of the light guide plate. This system, which inevitably provides a low brightness, is mainly applied to small-sized display devices. The direct lighting system does not employ, a light guide plate but includes a reflecting plate, a plurality of lamps installed on the reflecting plate, and a light diffusion plate disposed on the lamps at a predetermined distance. The core of this system is a uniform brightness because of the lamps concealed completely. For this purpose, the light diffusion should be high resulting in lower light transmittance. This causes an inevitable reduction of the brightness. Another method is arranging the light diffusion plate farther away from the lamps, making it difficult to realize a thin display device. An improved method is using a geometric light guide plate and a light diffusion plate at once, as disclosed in Korean Patent Laid-open Publication No. 2002-71358. However, this system
, has problems regarding to complicated structure, increased complexity of the process, high production cost, and heavy weight.
Disclosure of Invention It is an object of the present invention to provide a light diffusion plate with excellent masking effect of lamp and high light transmittance to maintain high brightness uniformity, thereby enabling realization of a thin backlight with enhanced performance. To achieve the object of the present invention, there is provided a light diffusion plate for an LCD backlight that is fabricated by coextrusion or multi-layer extrusion of at least two. light diffusion layers including a binder resin with or without light diffusion beads. The light diffusion plate has a structure that the light diffusion rate of the respective light diffusion layers gradually increases from the bottom of the light diffusion plate with an incident light of a lamp striking thereon to the top of the light diffusion plate. Hereinafter, the present invention will be described in detail as follows. Generally, the light diffusion plate is fabricated by extrusion of light diffusion layers comprising a binder resin and light diffusion beads. The present invention is directed to a light diffusion plate fabricated by coextrusion or multi-layer extrusion of a plurality of light diffusion layers. In the light diffusion plate of the present invention, the first light diffusion layer with an incident light of a lamp striking thereon may not include light diffusion beads. The light diffusion plate for a LCD backlight according to the present invention, particularly the light diffusion plate useful for a direct backlight LCD display is obtained by coextrusion or multi-layer extrusion of at least two light diffusion layers each having a different light diffusion rate gradient. The coextrusion or multi-layer extrusion of the multiple light diffusion layers to
increase the light diffusion rate from the bottom of the light diffusion plate with an
incident light(λ) of a lamp striking thereon to the top of the light diffusion plate may
prevent a re-expulsion of light by reflection at the bottom of the light diffusion plate to avoid a leak of light and maximize light diffusion from bottom to top of the light diffusion plate. This case of light diffusion is illustrated in FIG. 1. This can be realized by different methods that specifically include, for example, a method of regulating the density distribution (the term "density distribution" as used herein is defined as a number density expressed as the number of the light diffusion beads per volume) and the extrusion rate of the light diffusion beads in the light diffusion layers to have a different thickness and a different light transmittance in coextrusion or multilayer extrusion of multiple light diffusion layers, and a method of forming light diffusion layers comprising light diffusion beads each having a different refractive index difference from the binder resin. In case of using the density distribution of the light diffusion beads, for example, the number of the light diffusion beads is controlled to have a density distribution increasing from the bottom of the light diffusion plate with an incident light of the lamp striking thereon to the top of the light diffusion plate. The light diffusion layer at the bottom of the light diffusion plate with an incident light of the lamp striking thereon contains light diffusion beads having a relatively low refractive index difference from the binder resin, while the light diffusion layer at the top of the light diffusion plate contains light diffusion beads having a relatively high refractive index difference from the binder resin. Namely, the coextrusion or multi-layer extrusion of multiple light diffusion layers using the density distribution difference of the light diffusion beads or the refractive index gradient of the light diffusion beads results in a light diffusion plate having multiple light
diffusion layers with a light diffusion rate gradient. In the case of fabricating a light diffusion plate by coextrusion or multi-layer extrusion of two light diffusion layers, for example, a light diffusion plate having a thickness of 1 to 3 mm and a light transmittance of 20 to 75 % (light diffusion rate: 99 ~ 98%) can be produced by controlling the light diffusion layer at the bottom of the light diffusion plate with an incident light of the lamp striking thereon to have a light transmittance of 70 to 93 % (light diffusion rate: 98 ~ 6%) and a thickness of 0.5 to 1.5 mm, and the light diffusion layer at the top of the light diffusion plate to have a light transmittance of 30 to 80 % (light diffusion rate: 99 - 96%) and a thickness of 0.5 to 1.5 mm. Compared with a single-layer light diffusion plate having the same light transmittance, the light diffusion plate of the present invention thus obtained is excellent in masking effect of lamp to maintain high brightness uniformity, achieving a desired brightness without increasing the distance from the lamp to the light diffusion plate, so it can be used for a direct backlight system necessary to a thin display system. In the present invention, the number of light diffusion layers coextruded or multilayer extruded and the thickness of the respective light diffusion layers can be controlled. In the fabrication of the light diffusion plate according to the present invention, the variety of the binder resin and the light diffusion beads in the light diffusion layers are generally given and specifically described as follows. The specific examples of the binder resin as used herein include acryl-, urethane-, or epoxy melamine-based polymer or copolymer or ternary copolymer of unsarurated polyester, methylmethacrylate, ethylmethacrylate, isobutylmethacrylate, n- butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyethylacrylate, acrylamide,
methylolacrylamide, glycidylmethacrylate, ethylacrylate, isobutylacrylate, n-butylacrylate, or 2-ethylhexylacrylate. A variety of organic or inorganic beads are used as the light diffusion beads so as to enhance the light transmittance and the light diffusion rate with a refractive index difference from the general binder resin. The specific examples of the light diffusion beads as used herein include organic beads such as acryl-based polymer, copolymer or ternary copolymer beads of methylmethacrylate, ethylmethacrylate, isobutylmethacrylate, n- butylmethacrylate, n-butylmethylmethacrylate, acrylic acid, methacrylic acid, hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxy ethylacrylate, acrylamide, methylolacrylate, glycidylmethacrylate, ethylacrylate, isobutylacrylate, n-butylacrylate, or 2-ethylhexylacrylate, olefinic beads of polyethylene, polystyrene or polypropylene, acryl- olefin copolymer beads, or multi-layer multi-component beads prepared by forming single polmer beads, and then coating the beads with a different monomer; or inorganic beads such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, magnesium fluoride, etc.. Generally, the organic beads are superior in light diffusibility to inorganic beads.
Brief Description of the Drawings FIG. 1 is an illustration of a light diffusion state of light on a light diffusion plate having multiple light diffusion layers according to an embodiment of the present invention.
Best Mode for Carrying out the Invention Hereinafter, ■ the present invention will be described in detail by way of the following examples, which are not intended to limit the scope of the present invention. Example 1: Control of Light diffusion Rate of Light diffusion layers by Density
Distribution Difference of Light diffusion Beads. In this example, a light diffusion plate was fabricated by coextrusion of a light diffusion layer having a light transmittance of 90 % (light diffusion rate: 30%) and a thickness of 1.5 mm, and a light diffusion layer having a light transmittance of 70 % (light diffusion rate: 98%) and a thickness of 0.5 mm. Here, the transmittance and the light diffusion rate were measured for sheets obtained by a single extrusion to the corresponding thickness with an NDH 2000 (Denshoku in Japan) as measurement equipment according to the standard method of ASTM D 1003. In this example, the h-ansmittance of the light diffusion layers was regulated by controlling the density distribution of light diffusion beads, while the thickness of the light diffusion layers was regulated by controlling the extrusion rate of the extruder. The light diffusion layers were prepared using polymethylmethacrylate (VH-001 supplied by Mitsubishi Rayon in Japan) as a binder resin, and cross-linked polystyrene ■>. beads (Diasphere supplied by Kolon in Korea) as light diffusion beads. The details are '-, presented in Table 1. The light diffusion plate thus obtained had a total thickness of 2 mm, and a light transmittance of 63 %.. The light diffusion plate was cut in 17-inch long units, which were placed 13 mm above a device with 8 cold cathode fluorescent lamps arranged at predetermined intervals to measure the brightness right over the lamps and in the middle between the lamps. The average ratio of the brightness right over the lamps to the brightness in the middle of the lamps was 1.02 on average.
Table 1
Example 2: Control of Light diffusion Rate of Light diffusion layers by Refractive Index Gradient of Light diffusion Beads. In this example, a light diffusion plate was fabricated by coextrusion of a light diffusion layer having a light transmittance of 90 % (light diffusion rate: 30 %) and a thickness of 1.5 mm, and a light diffusion layer having a light transmittance of 70 % (light diffusion rate: 98 %) and a thickness of 0.5 mm in the same manner as described in Example 1. Here, the transmittance and the light diffusion rate were measured for sheets obtained by a single extrusion to the corresponding thickness with an NDH 2000 (Denshoku in Japan) as measurement equipment according to the standard method of ASTM D 1003. In this example, the transmittance of the light diffusion layers was regulated by controlling the refractive index difference between the light diffusion beads and the binder resin, while the thickness of the light diffusion layers was regulated by controlling the extrusion rate of the extruder. The light diffusion layers were prepared using polymethylmethacrylate (VH-001 (refractive index: 1.49 %) supplied by Mitsubishi Rayon in Japan) as the binder resin, and polystyrene-methylmethacrylate copolymer beads (Diasphere MSP-X10) and polystyrene
beads (Diasphere SPB-XIO) as the light diffusion beads for the respective layers. The refractive index of the light diffusion beads can be regulated depending on the content of monomers used in the preparation of the light diffusion beads. For example, the lower styrene content may result in a lower refractive index and a higher transmittance. The details are presented in Table 2. The light diffusion plate thus obtained- had a total thickness of 2 mm, and a light transmittance of 63 %. The light diffusion plate was cut in 17-inch long units, which were placed 13 mm above a device with 8 cold cathode fluorescent lamps arranged at predetermined intervals to measure the brightness right over.the lamps and in the middle between the lamps. The ratio of the brightness right over the lamps to the brightness in the middle of the lamps was 1.02 on average. Table 2
According to the results of Example 1 and 2 and Comparative Example 1, the distance between the lamps and the light diffusion plate to acquire the defined brightness ratio was about 13 mm in the Examples 1 and 2, but 18 mm for the light diffusion plate produced by extrusion of a single light diffusion layer in the Comparative Example 1. Hence, the use of the light diffusion plate of the present invention decreases the thickness of the backlight by about 5 mm.
Industrial Applicability As described above, the light diffusion plate manufactured by coextrusion or multi-layer extrusion of multiple light diffusion layers each having a different light diffusion rate gradient according to the present invention can reduce the thickness of the
backlight unit without a loss of light transmittance and haze relative to the light diffusion plate produced by extrusion of a single light diffusion layer having a same light
transmittance.
Claims
1. A light diffusion plate for an LCD (Liquid Crystal Display) backlight, being fabricated by coextrusion or multi-layer extrusion of at least two light diffusion layers comprising a binder resin with or without light diffusion beads, the respective light diffusion layers having a light diffusion rate gradually increasing from the bottom of the light diffusion plate with an incident light of a lamp striking thereon to the top of the light diffusion plate.
2. The light diffusion plate for an LCD backlight as claimed in claim 1, wherein each of the at least two light diffusion layers has a different density gradient of the light diffusion bead to have a density distribution of the light diffusion beads gradually increasing from the bottom of the light diffusion plate with an incident light of the lamp, striking thereon to the top of the light diffusion plate, the density distribution being- defined as the number of the light diffusion beads per volume.
3. The light diffusion plate for an LCD backlight as claimed in claim 1 or 2, the at least two light diffusion layers include the light diffusion beads having a refractive index difference from the binder resin gradually increasing from the bottom of the light diffusion plate with an incident light of the lamp striking thereon to the top of the light diffusion plate.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2003-0053972 | 2003-08-05 | ||
| KR20030053972 | 2003-08-05 | ||
| KR1020040056645A KR20050016008A (en) | 2003-08-05 | 2004-07-21 | Diffusion plate for LCD back-light |
| KR10-2004-0056645 | 2004-07-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2005012958A1 true WO2005012958A1 (en) | 2005-02-10 |
Family
ID=34118006
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/KR2004/001953 WO2005012958A1 (en) | 2003-08-05 | 2004-08-04 | Light diffusion plate for lcd backlight with improved masking effect of lamp and light transmittance |
Country Status (2)
| Country | Link |
|---|---|
| TW (1) | TWI288844B (en) |
| WO (1) | WO2005012958A1 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2021838A4 (en) * | 2006-05-30 | 2011-08-17 | Lg Chemical Ltd | Multi-layered light diffusion plate and liquid crystal display device comprising the same |
| US20110317096A1 (en) * | 2009-04-27 | 2011-12-29 | Masahiro Yokota | Planar lighting device and liquid-crystal display device with the same |
| JP2016133579A (en) * | 2015-01-19 | 2016-07-25 | 東洋インキＳｃホールディングス株式会社 | Resin composition for light scattering layer, light scattering layer, and organic electroluminescence device |
| CN109856714A (en) * | 2018-10-23 | 2019-06-07 | 友达光电股份有限公司 | The display of light leakage prevention film assembly and application the light leakage prevention film assembly |
| WO2024203123A1 (en) * | 2023-03-31 | 2024-10-03 | 日東電工株式会社 | Diffusion film, light diffusion device, and method for manufacturing diffusion film |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0695107A (en) * | 1991-08-02 | 1994-04-08 | Tosoh Corp | Backlight |
| JPH11194204A (en) * | 1997-09-19 | 1999-07-21 | Sekisui Chem Co Ltd | Light-diffusing sheet and its production |
| US6556347B1 (en) * | 1998-12-18 | 2003-04-29 | Mitsubisi Rayon Co., Ltd. | Rear projection screen |
-
2004
- 2004-08-03 TW TW93123179A patent/TWI288844B/en not_active IP Right Cessation
- 2004-08-04 WO PCT/KR2004/001953 patent/WO2005012958A1/en active Application Filing
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0695107A (en) * | 1991-08-02 | 1994-04-08 | Tosoh Corp | Backlight |
| JPH11194204A (en) * | 1997-09-19 | 1999-07-21 | Sekisui Chem Co Ltd | Light-diffusing sheet and its production |
| US6556347B1 (en) * | 1998-12-18 | 2003-04-29 | Mitsubisi Rayon Co., Ltd. | Rear projection screen |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2021838A4 (en) * | 2006-05-30 | 2011-08-17 | Lg Chemical Ltd | Multi-layered light diffusion plate and liquid crystal display device comprising the same |
| US8508850B2 (en) | 2006-05-30 | 2013-08-13 | Lg Chem, Ltd. | Multi-layered light diffusion plate and liquid crystal display device comprising the same |
| US20110317096A1 (en) * | 2009-04-27 | 2011-12-29 | Masahiro Yokota | Planar lighting device and liquid-crystal display device with the same |
| JP2016133579A (en) * | 2015-01-19 | 2016-07-25 | 東洋インキＳｃホールディングス株式会社 | Resin composition for light scattering layer, light scattering layer, and organic electroluminescence device |
| CN109856714A (en) * | 2018-10-23 | 2019-06-07 | 友达光电股份有限公司 | The display of light leakage prevention film assembly and application the light leakage prevention film assembly |
| WO2024203123A1 (en) * | 2023-03-31 | 2024-10-03 | 日東電工株式会社 | Diffusion film, light diffusion device, and method for manufacturing diffusion film |
Also Published As
| Publication number | Publication date |
|---|---|
| TWI288844B (en) | 2007-10-21 |
| TW200508718A (en) | 2005-03-01 |
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