MXPA98001509A - Reflection sheet to back for liquid crystal - Google Patents

Abstract

A reflection sheet is provided, using a thinner, thinner film, to be used to surround a fluorescent lamp of the straight tube type in a liquid crystal display panel backlight device, of the edge type, whose Reflection can perform a higher brightness of the backlight device. A reflection sheet comprising: a film support having a thickness of 25 to 50æm and, applying on a support surface, a coating of reflective paint comprising a mixture of a resin binder of a (meth) acrylate copolymer with a small particle balloon having a particle diameter of 0.05 to 10æm and a ratio of the empty internal diameter to the particle diameter of 0.2 to 0

Description

REFLECTION SHEET TO BACK FOR LIQUID CRYSTAL FIELD OF THE INVENTION The present invention relates to a reflective sheet, particularly a reflective sheet placed to surround a fluorescent lamp of the straight tube type, provided along the edge of a light guide plate in a flange-type backlight device between the backlight devices of the liquid crystal display panels, and a reflection sheet placed on the back side of the light guide plate.

BACKGROUND OF THE INVENTION In a flange type backlight device, between the backlighting devices of the liquid crystal display panels, a fluorescent lamp of the straight tube type is placed along the edge of a light guide plate. Part of the light emitted from the fluorescent lamp on the light guide plate is directly guided to the light guide plate. The light reflection is reflected by a reflection sheet placed to surround the fluorescent lamp, REF: 26875 and then enters the light guide plate. The light guided towards the light guide plate is reflected by a diffusing layer of light, which has been printed in a dotted form on the back side of the light guide plate, and then leaves the surface of the light guide plate (lighting surface). On the other hand, the light directed to the back or back side of the light guide plate, through the light diffusing layers, is reflected by the reflection sheet placed on the back side of the light guide plate. The light diffusing layer is generally formed of a white pigment ink with glass spheres optionally dispersed therein.

Many proposals on the light diffusing layer have been made up to date as means to increase the brightness of the illumination surface. Japanese Examined Patent Publication (Ko oku) No. 4-66519 discloses a light diffusing layer having thin cells formed by foaming or a light diffusing layer formed by screen printing a powder of plastic spheres. Japanese Unexamined Patent Publication (Kokai) No. 4-76593 discloses a light diffusing layer formed by screen printing of a polymer in spheres, having a diameter of 0.1 to 20 μm, of an acrylic resin. Japanese Unexamined Patent Publication (Kokai) No. 5-273552 discloses a light diffusing layer formed by screen printing of thin transparent spheres or reflecting spheres including a white pigment. Japanese Unexamined Patent Publication (Kokai) No. 5-303017 discloses a light diffusing layer formed by mixing an acrylic binder with ultrathin particulate titanium oxide coated with an organic fluorescent material to prepare an ink and form an ink. a graduation pattern by points using ink, by screen printing. Japanese Unexamined Patent Publication (Kokai) No. 6-94923 discloses a light diffusing layer formed by the printing of a foamable coating and the formation of thin cells.

All the aforementioned means for improving brightness use a light diffusing layer provided on the back side of the light guide plate, by screen printing or the like, and attempts have been made to improve the brightness, by improving the components that they constitute the backlight device. In order to improve the brightness, a polyester film with silver deposited on it, is in some cases used as the reflection sheet placed to surround the fluorescent lamp. This type of reflection sheet, however, involves problems that include a high frequency current leaking from the fluorescent lamp, resulting in increased current consumption. In recent years, a white polyester film of 75 μm thickness or similar has been used, as the reflection sheet. In addition, a foamed, white polyester film, 188 μm thick, has been used on the back side of the light guide plate. The inventions described in the above patent documents use too much the white foamed polyester film. The foamed or foamed polyester film, white, has a lower reflectance than the polyester film with the silver deposited thereon, resulting in approximately 10 ° or more decrease in brightness, when the foamed polyester film white is constituted in the backlight device.

For this reason, when shown in Figure 2, a reflection sheet comprising a white, 75 μm thick, polyester film 5 of the type described above, a white ink coating layer 6 provided on the back side of the polyester film, and a reflective layer 7, formed of barium sulfate and an acrylic binder, provided on the side of the reflecting surface, has been developed and used as an improved reflection sheet having improved brilliance (R 75C manufactured by Kimoto Co., Ltd.). For this reflection sheet, however, the improvement in brightness over the brightness of the conventional reflection sheet is not satisfactory, for example, only 3 to 5%.

In recent years, a reduction in the thickness of the liquid crystal panels has been desired in the art, leading to a reduction in the diameter of the fluorescent lamp. The polyester film in the form of a foam, 75 μm thick, which has been used up to now, has a problem that, when the film is built in a backlight device to surround the fluorescent lamp, due to the excessive rigidity high, the work efficiency is so low that productivity can not be increased. In addition, the polyester film in the form of foam often imposes a problem of pushing out the joints or welds in the body of the liquid crystal panel, creating an empty space through which the light leaks. This results in decreased brilliance. On the other hand, reducing the thickness of the polyester film in the form of foam, white, for purposes of decreasing rigidity, causes a problem because the brightness decreases with a reduction in the thickness of the film.

Problems to be solved by the Invention For the above reason, in order to provide a screen that has higher brightness, it has been desired in the art to develop a reflection sheet, low stiffness, high reflectance. An object of the present invention is to provide such a reflective sheet.

Means to solve problems The present invention provides a reflection sheet comprising: a film backing, such as polyester, and, applied on one side of the backing, a reflective paint coating comprised of a mixture of a resin binder of a (met) acrylate (the term "methacrylate" refers to acrylate or methacrylate, the same applies hereinafter) in copolymeric form with a globe or sphere of small particles.

The particle diameter of the small balloon or balloon may be in the range of about 0.05 to 10 μm. When the particle diameter is less than about 0.05 μm, it is difficult to prepare such a balloon or small balloon by emulsion polymerization. Although the small balloon could be prepared successfully, the ability to scatter light is low, resulting in diminished brightness. When the particle diameter is greater than about 10 μm, the light scattering capacity is decreased, except for the case where a number of small empty spaces are present within the particle, for example, where the empty space is not of a simple spherical type. The ratio of the empty internal diameter to the diameter of the particle is preferably in the range of 0.2 to 0.9. When this ratio is less than 0.2, the ratio of the empty space within the particle balloon after the formation of a reflective coating layer (from here onwards often referred to as a "reflective layer") becomes very small, resulting in decreased brilliance. On the other hand, when the ratio exceeds 0.90, the resistance of the small particle balloon becomes so low that the particle balloon, when it dries, can not maintain its spherical shape and is crushed or collapsed, resulting here again the diminished brilliance .

The balloon of small particles can be formed of an organic material or an inorganic material. With respect to the small particle balloon formed of an inorganic material, there is a glass globe. However, the small particle balloon is preferably formed of an organic material, because it is difficult to provide balloons of particles having the aforementioned particle diameter, from the inorganic material. The small organic balloon can be prepared by the emulsion polymerization or the suspension polymerization of an acrylic monomer or a styrene monomer. Details regarding the production of the balloon of organic particles are known and described, for example, in Japanese Unexamined Patent Publication (Kokai) No. 62-127336 and Japanese Examined Patent Publication (Kokoku) No. 3-9124 .

The mixing ratio or velocity of the balloon of small particles to the binder comprised of a (meth) acrylate copolymer also influences the brilliance. The amount of the small particle balloon added is preferably 20 to 800 parts by weight, more preferably 100 to 300 parts by weight, based on 100 parts by weight of the binder. When this is less than 20 parts by weight, the brilliance is decreased, whereas when it exceeds 800 parts by weight, the layer-forming property of the reflective paint becomes so poor that the resultant reflective paint coating is very brittle.

Preferably, the binder used in the present invention is highly transparent and can maintain the optical properties even after use for a prolonged period of time, and a (meth) acrylate copolymer is desirable. Specific examples of the (meth) acrylate copolymer include the (meth) acrylate / ester (me) copolymer copolymer, copolymer of (meth) acrylate / (meth) acrylic ester / styrene and the ester copolymer (me) acrylic 1 grafted with silicone. Among these resins, a resin having an average light transmittance of not less than 80 ° in the wavelength range from 400 to 800 nm is preferred, as measured in a 50 μm thick film form at 23 ° C. When the transmittance is less than 80%, the brightness becomes unfavorably small. The glass transition temperature (Tg) of the resin is preferably in the range of -75 to 30 ° C. When the (meth) acrylate copolymer has a Tg less than -75 ° C, the cohesive force is unsatisfactory. As a result, the surface of the reflective layer becomes thick, causing the reflective layer to be probably fouled. On the other hand, when the Tg exceeds 30 ° C, the adhesion of the reflective layer is lost, causing the reflective layer to be easily cracked or delaminated when the reflective sheet is curved.

The influence of the transmittance of the binder on the brightness is greater than the influence of the refractive index of the binder on the brightness, and the transmittance after aging is particularly important. When the binder is such that the transmittance is decreased after hot aging even if the high brightness is initially achieved, the brightness is unfavorably decreased after use for a prolonged period of time. With respect to the properties of the binder other than the gloss, the layer-forming property and the adhesion to the substrate are also important. When these properties are not satisfactory, there is a possibility that a serious delamination problem of the layer will occur after use for a prolonged period of time. The results of the evaluation of the binder are given in Table 1. The data shown in Table 1 are simple point data.

Table 1 15 Name Transmittance (Í) Commercial after the Transmittance Aging index in Binder Manufacturer Initial refraction type (ji) Hot E-1054K Soken Acrylic 1.470 94.6 91.5 Chemical Engineering Co., Ltd.

Table 1 (continued) Name Transmittance (%) Commercial after the Transmittance Aging index in Binder Manufacturer Initial refraction type () Hot AN-49B Soken Acrylic 1.468 95.6 93.4 Chemical Engineering Co., Ltd. E-2150 Soken Acrylic 1.472 93.6 89.0 Chemical Engineering Co., Ltd. SX-3307A04 Japan Acrylic / 1.476 100.0 96.2 Synthetic silicone Rubber Co., Ltd. S-O211 Toho Poly- 1.503 97.5 50.0 Chemical Ethylene Industry Co., Ltd. RW75C Kimoto Co., Ltd.

Brightness Name after clei Adhesion of the Comercial del Brillantez Envej ecimiento Capa Aglutinan .te Initial (:%) in Calierite Reflectora E-1054K 106.7 98.0 Good AN-49B 106.8 102.0 Good E-2150 104.3 98.8 Good SX-8307A04 102.0 100.0 De-laminated after aging S-6211 103.5 79.2 Delaminated after aging RW75C * 100.0 - Good Note. Refractive index: This was measured with an Abbe refractometer. Transmittance: This was measured using an autographic spectrophotometer type U-4000 (manufactured by Hitachi, Ltd.). 50 μm thick films were prepared from the above binders, and the transmittance was measured at a wavelength of 400 nra. In the wavelength range of 400 to 800 nm, the 0 transmittance is minimum at 400 nm for all binder films.

Hot aging conditions: 100 ° C, 180 hours Brilliance: The reflection sheets composed of the reflective layer, the support layer and the white ink layer were prepared in the same manner as in Example 14 below, except that the previous binders and a small particle balloon (MH5055; manufactured by Nippon Zeon Co., Ltd.) were mixed together in a ratio of 100: 200 (weight ratio). The reflection sheets were then used to measure the brilliance. The brilliance was expressed in terms of the value (%) of the brightness in relation to that of R 75C (initial) manufactured by Kimoto Co. , Ltd. The brightness of a heat-aged sample of RW75C was not measured. Adhesion of the reflective layer: For a reflection sheet made from the same sheet for which the brightness was measured, the adhesion of the reflective layer was observed. *: Reflection sheet but without binder.

In the previous test, the reflection sheet prepared using SX-8307A04 gave rise to delamination after hot aging.

This problem can be overcome by treatment with aprester or the like.

The reflection sheet can be produced by a process comprising the steps of applying a support with a flowable reflective paint, comprising a mixture of an aqueous dispersion of a small balloon with an aqueous acrylic binder; and the drying of the resulting coating. Said application of a support with a reflective paint capable of flowing, includes coating and spraying. The temperatures at the drying time are preferably from 90 ° C or higher to below the melting or softening point of the support. The reflective paint can be prepared by dispersing a balloon of small particles, commercially available in a powder form, in a solvent, and incorporating a binder in the dispersion. The mixing of an aqueous dispersion with an aqueous acrylic binder from the viewpoint of productivity is preferred, because a reflective film can be easily prepared at low cost. The thickness of the reflective paint after drying is preferably in the range of 10 to 100 μm. When this is less than 10 μm, the brightness is low. On the other hand, when it exceeds 100 μm, problems associated with the coating occur, such as cracking of the surface of the resulting paint coating and decreased coating speed. When an aqueous reflective paint is used, the drying temperature must be 100 ° C or higher and, at the same time, dimensional stability must be ensured. For this reason, in this case, the use of a polyester film or a white polyester film, in the form of a foam, is preferred as the support.

Examples of films usable as the substrate include oriented polypropylene, polyester, nylon, polycarbonate, polysulfone, polyethersulfone, polyetheretherketone, polyphenyl sulfide, polyallylate, polyethylene naphthalate, polyester ether and polyvinyl chloride films, an acrylic film and an polymethylterpene resin film. As described above, the thickness of these films is preferably less than 75 μm. When the thickness of the film is not less than 75 μm, the operability of the film for its incorporation in a backlight device to surround a fluorescent lamp, is so low that productivity can not be increased. Furthermore, in this case, an additional problem often occurs such that the reflection sheet surrounding the fluorescent lamp in a backlight device becomes incomplete in the surroundings, and the light leaks, resulting in decreased brightness. On the other hand, in the case of an excessively thin film, the elasticity of the film is so low that the reflection sheet is corrugated or folded when the reflection sheet is constituted in a backlight device, making it possible to place the reflection sheet in an exact arc shape when the backlight device is constituted to surround the fluorescent lamp. This results in decreased brilliance. For this reason, the thickness of the polyester film is preferably in the range of 25 to 50 μm. The working efficiency in incorporating the reflection sheets with varied polyester film thicknesses is given in Table 2.

Table 2 Spesor Handle of the film for the state of the leaf peel incorporation in a reflection after Leak of (μm) backlight device incorporating light 12 Good Wrinkle S in Fuga Good Not Wrinkled S in Fuga 38 Good Not Wrinkled S in Fuga 50 Difficult to incorporate Not wrinkled S in leakage due to high elasticity 75 Difficult to incorporate Large curvature To guna due to high arch leakage elasticity A white paint, containing titanium oxide, having high opacifying power can be coated on the reflection sheet away from the reflecting layer, or between the support and the reflecting layer. The provision of such a white opacifying layer prevents the transmission of light, contributing to an improvement in brightness. In Figure 1, a cross-sectional view of one embodiment of the present invention is shown. In this figure, 1 is a support layer, 2 is a reflective paint coating layer and 3 is a white ink layer.

The brilliance can also be improved by incorporating an inorganic white pigment or a relatively large diameter glass globe (to date it is technically difficult to make a glass globe having a diameter smaller than 10 μm) as a third component within the reflective paint. Examples of the white inorganic pigment include titanium oxide, zinc sulphide, barium sulfate, aluminum silicate and acrylic spheres containing titanium oxide. The incorporation of titanium oxide, zinc oxide or the like between the above inorganic white pigments into the reflective paint can provide high gloss even when the opacifying layer is not formed.

It is also possible to additionally coat, on the reflector layer of the reflection sheet, a reflective paint comprising a copolymer of , met) acrylate and a white inorganic pigment incorporated in it. In such a case, the surface resistance can be increased without detriment to the brightness, by coating the reflective layer with a reflective paint prepared by mixing 100 parts by weight of an acrylic resin having a good layering property and a high transmittance, with approximately 100 parts by weight of a white inorganic pigment, to form a layer with a thickness of 1 to 10 μm (referred to as "top coat").

Since the reflection sheet is arranged to surround the fluorescent lamp, the sheet deteriorates under the influence of an infrared radiation and the heat emitted from the fluorescent lamp, which according to the conditions of use of the sheet, decreases the characteristics optical, mainly brightness. In order to prevent these problems, it is preferable to add from 0.01 to 5% by weight of an antioxidant, an ultraviolet light absorber or an ultraviolet light stabilizer to the reflection sheet. Examples of the antioxidant include 2,4-bis [(octylthio) methyl] -o-cresol, iso-octyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, etc. Examples of the ultraviolet light absorber include methyl-3- [3-t-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] -propionate-polyethylene glycol, hydroxydiphenyl-benzotriazole derivatives, etc. Examples of the ultraviolet light stabilizer are bis (2, 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-pentamethyl-4-pi? Eridyl) sebacate, etc. These can be used alone or as a mixture. It is also effective to increase the resistance to the environmental conditions of the reflection sheet to add an ultraviolet light absorber or an inorganic filler that has a protective effect against ultraviolet light. Since a major cause of deterioration by ultraviolet light is the small particle balloon that includes styrene, it is also effective to increase the resistance to environmental conditions of the reflection sheet by replacing an inorganic filler with the small particle balloon.

EXAMPLES The details of the small particle balloons used in the reflective paints in the following examples and comparative examples are as follows according to the reports of each manufacturer.

Table 3 Diameter Diameter of internal Empty particle symbol / diameter identification Manufacturer Material (μm) particle OP-62 Rohm & Hass Styrene / acrylic 0.45 0.69 Japan. . OP-84J Rohm & Hass Styrene / acrylic 0.55 0.64 Japan. . HP-91 Rohm & Hass Styrene / acrylic 1.00 0.80 Japan k. k. AE-863A Synthetic Styrene / Acrylic 0.35 0.80 Rubber, Co., Ltd. MH5055 Nippon Zeon Styrene / Acrylic 0.50 0.82 Co., Ltd.

The binder used in the reflective paint was SKDYNE (trade name) AN-49B, which is an acrylic ester copolymer, manufactured by Soken Chemical Engineering Co. , Ltd. This had a Tg of -43 ° C and an average light transmittance of 97% in the wavelength range of 400 to 800 nm.

The details of the fillers used in the reflective paint or top coat are as follows.

Table 4 Trade name Abbreviation or symbol in the Manufacturer identification Material Table 5 Dainichiseika EP 677 White TiO? 677 White Color & Chemicals Manufacturing Co., Ltd. SACHTLEBEN Sachtolith ^ HD-S ZnS HD-s CHEMIE GMBH Toshiba- Toshiba Glass Glass bubble HSC110 Ballotini Co. , Bubble HSC110 Ltd. Degussa Japan Aluminum Silicate P-820 Silicate P-820 Mere Japan Aluminum Iriodin! R103W2 Pearl Pigment 103W2 Examples 1 to 7 A white ink (a mixture of an acrylic binder / urethane with 50% by weight of White Lamic ™ F-220HC manufactured by Dainichiseika Color &Chemicals Manufacturing Co., Ltd. (titanium oxide)) was coated on a surface of a film of polyester in the form of foam, white, 36 μm thick (MELINEXMR337, manufactured by ICI Company, Ltd.) (Examples 1 and 2 and 4 to 7) or a transparent polyester film, not in the form of foam, of 36 μm thickness (example 3), which has been subjected to a treatment to facilitate the joining, up to a thickness on a dry base of 20 μm, and the resulting coating was then dried, whereby a white sheet is prepared. A reflective paint prepared according to a formulation specified in Table 3, was coated on the white ink layer of the white layer to a thickness on a dry basis of 50 μm, and the resulting coating was then dried to prepare a reflection sheet. The reflection sheet obtained in this way was divided into a strip having a width of 20 mm and a length of 219 mm. The strip was fixed with a tape coated with double pressure sensitive adhesive, having a width of 2 mm (# 531, manufactured by Nitto Denko Corp.) to a light guide plate (width 164 mm, length 219 mm, thickness on the side of the fluorescent tube 3.2 mm, thickness on the opposite side 1.2 mm) to surround a fluorescent tube, having a diameter of 2.6 mm, placed on one end of the light guide plate, and then constitute a backlight device , and the brightness was measured with a luminance meter LS-110 manufactured by Minolta KK Similarly, the brightness was measured for R 75C manufactured by Kimoto Company, Ltd. (Comparative Example 1). The value (%) of the brightness of the sample in relation to the brightness for RW75C are given in Table 5.

Examples 8 to 19 Each of the reflective paints listed in Table 5 was coated on the surface of the same white sheet as used in Example 1 (Examples 8 and 10 to 19) or the same transparent sheet as used in Example 3 (Example 9) away from the white ink layer, at a dry base thickness of 50 μm, and the resulting coating was then dried, whereby the reflection sheets are prepared. For the reflection sheets obtained in this way, the brightness was measured in the same manner as in Example 1. The values of relative brightness are given in Table 5.

Examples 20 to 22 Each of the reflective paintings (binder: an acrylic ester copolymer of the grafted type with silicone (trade name: Silicone-Acrylic Emulsion SX-8307 (A) 04), Tg = 5 ° C, average light transmittance at the wavelength of 400 to 800 nm = 100%) containing the fillers listed in Table 5, were coated on the reflective coating layer of the reflection sheet prepared in Example 8, to a thickness on a dry basis of 5 μm, and the resulting coating was then dried to form a layer (called a "topcoat"), whereby reflection sheets are prepared. For the reflection sheets obtained in this way, the brightness was measured in the same manner as in Example 1. The values of relative brightness are given in Table 5.

Comparative Example 1 For a reflection sheet R 75C manufactured by Kimoto Co. , Ltd., the brightness was measured in the same manner as in Example 1. The results are given in Table 5. This reflection sheet is one that is formed from a white, foam-like polyester film that has a thickness of 75 μm, the back side of which is coated with an ink layer formed by mixing Ti0 and a urethane binder having a thickness of 30 μm and the side of the reflection surface of which is coated with a reflection layer formed of barium sulfate and an acrylic binder with a thickness of μm.

Comparative Example 2 A white ink (The icR F-220HC hite, manufactured by Dainichiseika Color &Chemicals Manufacturing Col., Ltd.) (titanium oxide) was coated on the surface of a 36 μm thick white polyester film (MELINEXMR337, manufactured by ICI Co., Ltd.), which has been subjected to a treatment to facilitate the bonding, to a thickness on a dry base of 20 μm, and the resulting coating was then dried, whereby a white sheet was prepared. The brightness was measured in the same manner as in Example 1, in the case where the white sheet was placed so that the white ink face of the white sheet was facing the fluorescent tube. The results are given in Table 5.

Comparative Examples 3 and 4 Each of the reflective paints listed in Table 5 was coated on the white sheet prepared in Comparative Example 2, away from the white ink layer to a thickness on a dry basis of 50 μm, and the resulting coating was then dried, with which a reflection sheet is prepared. For this reflection sheet, the brightness was measured in the same way as in Example 1. The results are given in Table 5.

Table 5 Formulation (or construction) or reflective layer Mixing ratio (weight ratio) Construction Balloon Globe: Binding Particle Sheet: Brilliance Ex. C cmp. Small reflection Binder Filler Filler 111 Ex. 1 RBW OP-62 AN-49B - 200: 100 113 Ex. 2 RBW OP-62 AN-49B - 400: 100 121 Ex. 3 RBW OP-62 AN-49B - 200: 100 115 Ex. 4 RBW OP-62 AN-49B White677 150: 100: 50 115 Ex. 5 RBW OP-62 AN-49B HD-S 160: 100: 40 117 Ex. 6 RBW OP-62 AN-49B HSC110 160: 100: 40 116 ? j. RBW OP-62 AN-49B P-820 160: 100: 40 115 ? j • 3 RBW OP-62 AN-49B - 200: 100 121 £. j. 9 R3W OP-62 AN-49B - 200: 100 118 Ex. 10 RB OP-62 AN-49B - 200: 100 117 Ex. 11 RBW OP-84J AN-49B - 200: 100 117 Ex. 12 RBW HP-91 AN-49B - 200: 100 120 j • 13 RBW AE-863A AN-49B - 200: 100 117 Ex. 14 RBW MH5055 AN-49B - 200: 100 117 ? j. 15 RBW CP-62 AN-49B BIanco677 150: 100: 50 1 3 Ex. 16 RB OP-62 AN-493 White677 150: 100: 50 115 Table 5 (continued) Formulation (or construction) or reflective layer Mixing ratio (weight ratio) Construction Balloon Balloon: binder particle sheet: Brilliance Ex. Comp. small reflection Binder Filler filler ÜL ? j. 17 RBW OP-62 AN-49B HD-S 160: 100: 40 121 Ex. 18 RBW OP-62 AN-49B HSC110 160: 100: 40 120 ? j. 19 RBW OP-62 AN-49B P-820 160: 100: 40 117 Ex. 20 TRBW1 OP-62 AN-49B - 200: 100 117 Ex. 21 TRBW2 OP-62 AN-49B - 200: 100 117 ? j. 22 TRBW3 OP-62 AN-49B - 200: 100 115 Ex. RBW RW75C from Kimoto i Co,. , Ltd - 100 Comp. 1 Ex. B MELINEX 337 36 μm White PET - 107 Ccpp. 2? J. RBW AN-49B 103W2 0: 100: 200 90 Comp. 3? J. RBW A -49B HSC110 0: 100: 200 103 C or IT.D. 4 Note R: Reflective layer W: White ink layer B: Support layer T: Top coating layer TRBW1: Barium sulfate was used as a filler for the top coating. TRBW2: Toshiba Glass Bubble HSC-110 (trademark) manufactured by Toshiba-Ballotini Co., Ltd., was used as a filler for the top coating. TRBW3: Aluminum Silicate P-820 manufactured from Degussa Japan Company, Ltd., was used as a filler for the top coating.

Example 23 A reflection sheet was obtained by a method similar to Example 8, except that, as the ultraviolet light stabilizer, 2.0 parts by weight of TINUVIN (registered trademark) 765 manufactured by Nihon Ciba Geigy K.K. When it was accommodated in a backlight unit and measured in brightness, it showed a brightness 15% higher than RW75C manufactured by Kimoto Co. , Ltd. In addition, the reflection sheet obtained as described above and PW75C manufactured by Kimoto Co. , Ltd., were each accommodated in a backlight unit and left in an oven at a temperature of 80 ° C for 230 hours. Then only the reflection sheets were removed and accommodated in new backlight units, respectively. The brilliance of the leaves was measured. The reflective sheet obtained as described above decreased the brightness by 3%. However, it showed brightness values 12% higher than RW75C manufactured by Kimoto Co. , Ltd.

Effect of the Invention The present invention can provide a reflection sheet which, in comparison with a conventional, 75 μm thick, white foam-shaped polyester film, used to surround a straight tube fluorescent lamp, in a backlight type device edge between backlighting devices? The liquid crystal display panels, can realize higher brightness of the backlight device using a less rigid, thinner film.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (9)

1. A reflection sheet, characterized in that it comprises: a film support and, applied on a surface of the support, a coating of reflective paint comprised of a mixture of a resin binder of a (meth) acrylate copolymer (the term "(meth) acrylate "refers to acrylate or methacrylate, the same will apply hereafter) with a small particle balloon having a particle diameter of 0.05 to 10 μm.

2. A reflection sheet according to claim 1, characterized in that the small particle balloon has a ratio of the empty internal diameter to the diameter of the particle from 0.2 to 0.9.

3. The reflection sheet according to claim 1 or 2, characterized in that the reflective paint coating has a thickness of 10 to 100 μm.

4. The reflection sheet according to any of claims 1 to 3, characterized in that the amount of the small particle balloon incorporated is from 20 to 800 parts by weight, based on 100 parts by weight on a solid base of the resin binder. .

5. The reflection sheet according to any of claims 1 to 4, characterized in that the (meth) acrylate copolymer has an average light transmittance of not less than 80% in the wavelength range of 400 to 800 nm, and a glass transition temperature of -75 to 30 ° C.

6. The reflection sheet according to any of claims 1 to 5, characterized in that a white paint coating containing titanium oxide is applied on the surface of the support, away from the reflective paint coating, or between the reflective paint coating and the support.

7. The reflection sheet according to any of claims 1 to 6, characterized in that the reflective paint coating contains an inorganic white pigment.

8. The reflection sheet according to any of claims 1 to 7, characterized in that a white inorganic pigment is coated on the surface of the support away from the reflective paint coating.

9. A process for producing a reflection sheet according to any of claims 1 to 8, characterized in that it comprises the steps of: applying a support with a reflective paint capable of flowing, comprising a mixture of an aqueous dispersion of a balloon of small particles with an aqueous acrylic binder; and drying the resulting coating at a temperature of 90 ° C or higher, and below the melting or softening point of the support.