JP2011159508A - Backlight system for image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction of a backlight system for an image display device in which LEDs are used as a light source of a direct type and capable of emitting light efficiently and provide a polymer to be used in the backlight system having an excellent heat resistance with no foaming phenomenon even if it is used directly for the LED light source, and provide a backlight system capable of contributing to energy saving and long life and the polymer to be used for the backlight system. <P>SOLUTION: In the backlight system for an image display device, with LEDs 20 as a light source of a direct type, a base plate 10 on which the LED 20 light source is arranged and an optical film 40 are laminated with a polymer 30 having a refractive index 1.4 or more and a total light transmittance 85% or more interposed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a configuration of a backlight system that efficiently emits light using an LED as a direct light source in an image display device, and a polymer used in the backlight system. By using the backlight system and polymer of the present invention, there is less total reflection of light at the interface with the optical member, it is possible to emit light efficiently, and further contribute to energy saving and long life. It will be.

  In optical devices such as TVs, monitors, game consoles, and mobile phones, the light emitted from the surface directly affects the brightness of the screen, and improving the brightness greatly affects the appearance of brightness and contrast. is there. In addition, high brightness has an energy-saving advantage such as a reduced current value.

  Under such circumstances, there are roughly two types of backlights for image display devices represented by liquid crystal display. There are two types of light sources used for edge light types, cold cathode fluorescent lamps and LEDs, and they are classified into three types as a whole (direct light sources are light sources directly under the liquid crystal panel. In the arrangement method, the light source is arranged on the frame side with the edge light). Size and application are also related to this classification. Generally, large-sized 20-inch or larger liquid crystal televisions are directly under type, and medium to small-sized liquid crystal televisions are of edge light type.

On the other hand, in the case of large-sized LCD TVs, in addition to energy saving, from the viewpoint of improving the image quality of the liquid crystal display, a method has been proposed in which the backlight emission section is divided into blocks and the block brightness is controlled according to the video signal. ing. This is because the contrast is improved and the power consumption of the backlight can be reduced by appropriately controlling the luminance of each block. For this reason, it is expected that direct-type LEDs will be increasingly used as light sources for large televisions. (For example, Non-Patent Document 1)
Up to now, as a method for efficiently emitting light from such a light source and improving luminance, there have been devised designs such as optical film design and shape and arrangement of light emitters such as cold cathode tubes and LEDs. Therefore, a device for emitting light with as low power as possible has been devised (for example, see Patent Documents 1 to 3).

  However, even in a commercially available monitor or the like, the edge light type has been devised in various ways for improving the luminance, but a light source using an LED as a direct light source has not been sufficiently studied. In addition, from the viewpoint of heat dissipation, there is an air layer between the base plate on which the LED light sources are arranged and the optical film (for example, a diffusion plate) even if various documents are viewed, various liquid crystal monitors, liquid crystal TVs, etc. are disassembled. There is no example of direct lamination with a polymer. (Non-Patent Document 1).

  Patent Document 3 shows that in an edge light type, an optical film is bonded to a light guide plate using an adhesive to improve loss due to reflection of light at the interface with the optical film. No device has been devised to eliminate the loss of the type LED. Also, the design of the polymer required for direct contact with the light source has not been shown.

JP 2006-179494 A JP-A-11-288614 JP 2008-243803 A

"LED and backlight performance improvement technology for each light source -Technical issues and higher brightness, higher efficiency, lower cost, etc.", Information Organization Co., Ltd.

  An object of the present invention is to provide a backlight system for an image display device using an LED as a direct light source, and a structure of the backlight system that efficiently emits light, and a foaming phenomenon is observed even when the LED light source is used directly. The polymer used for the backlight system having excellent heat resistance is provided. Furthermore, the present invention provides a backlight system that is a technology that contributes to energy saving and long life, and a polymer used in the backlight system.

  As a result of intensive studies to solve the above problems, the present invention has been completed.

  That is, according to the present invention, an LED is used as a direct light source, and the base plate and the optical film on which the LED light sources are arranged have a refractive index of 1.4 or more, a total light transmittance of 85% or more, and JIS K6253. It is related with the backlight system for image display apparatuses characterized by laminating | stacking with the polymer whose hardness in a type A durometer measured according to 1 is 30 or less.

  The polymer has a weight average molecular weight (Mw) measured by gel permeation chromatography of 5000 or more, and a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.0. The following is preferable.

  The polymer is preferably obtained by controlled polymerization.

  The optical film is preferably a diffusion plate.

  The gel fraction of the polymer is preferably 50 to 100% or more.

  The polymer is preferably composed of a (meth) acrylic polymer.

  The (meth) acrylic polymer is preferably an acrylic block copolymer (A) comprising a methacrylic polymer block (a) and an acrylic polymer block (b).

  The acrylic block copolymer (A) has a number average molecular weight measured by gel permeation chromatography of 30,000 to 150,000, and a methacrylic polymer block mainly composed of a methacrylic polymer ( a) 5 to 30% by weight and acrylic polymer block (b) containing 95 to 70% by weight of an acrylic polymer as a main component are preferable.

  The optical film is preferably a laminate of a plurality of optical films.

  Furthermore, the present invention relates to an image display device including the backlight system for the image display device described above.

  It is preferable that the polymer contains light transmissive uncolored particles in a dispersed manner and exhibits light diffusibility.

  The thickness of the polymer is preferably 5 to 100 μm.

  Furthermore, the present invention relates to a method for improving the luminance of emitted light, characterized by using the backlight system described above.

  As described above, the backlight system for an image display device of the present invention has a refractive index of 1.4 or more, using an LED as a direct light source, a base plate on which the LED light sources are arranged, and an optical film. It has been found that the luminance is greatly improved by laminating with a polymer having a light transmittance of 85% or more. Furthermore, this technology will contribute to energy saving and long life.

It is sectional drawing which shows the one aspect | mode of the backlight system of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1 as an example, the backlight system for an image display device of the present invention includes an LED light source and an optical film 40 (for example, a diffusion plate) arranged immediately below the image display device from which light is emitted. Are bonded via a polymer 30. At this time, it is desirable that the polymer 30 follows the unevenness of the LED light source so that no gap is generated and no light loss occurs. The LED light source referred to here represents an LED lamp 20 (a package in which an LED chip is mounted), and depending on the package shape, a chip LED type (a package in which an LED chip is mounted on a general resin substrate and resin molded), a PLCC type (Package in which an LED chip is mounted on a base in which the lamp house and frame are integrated by insert molding and resin molded), CLCC type (package in which an LED is bonded to a ceramic package in which the substrate and lamp house are integrated, and resin molded), etc. Is exemplified.

  Usually, when an optical film such as a diffusion plate is provided on a direct type LED light source, an air layer having a refractive index of 1.0 exists between the LED light source and the optical film, so that light at the interface is present. The loss of light was caused by the reflection of the light, but this loss was reduced by providing an optical sheet through the polymer, and further, by providing a polymer layer approximating the refractive index of the optical film, It is assumed that the loss of light is almost eliminated and light can be emitted efficiently.

  As the above-mentioned optical film, those used for forming a backlight unit of an image display device are used, and the type thereof is not particularly limited, and specifically, a microlens, a light diffusion plate, a prism sheet, a light guide plate, etc. can give. In the present invention in which the LED light sources are arranged directly below, a microlens and / or a light diffusing plate are preferable, and a light diffusing plate is more preferable, from the viewpoint of simplifying the configuration of the image display device.

  Examples of the microlens include those having a surface that has been subjected to a uniform bullet-like, spherical, or pyramidal processing of 1 to 100 μm. Since such a microlens has a uniform structure, uniform light can be emitted to the air layer. In addition, the above-mentioned light diffusion plate is coated with a polymer solution in which diffusion particles are dispersed with a dry thickness smaller than the particle size of the fine particles, so that fine particles are added to the polymer melt. Examples thereof include a diffusion plate having a light diffusing function on the surface by kneading and extrusion molding.

  Specific materials for the optical film can be used as long as they are transparent, such as acrylic resin, polyester resin, epoxy resin, polystyrene resin, polycarbonate resin, urethane resin, styrene-acrylonitrile copolymer, styrene. -A methyl methacrylate copolymer etc. are mention | raise | lifted. The optical film may be a laminate of a plurality of optical films.

  The refractive index of the polymer used in the present invention is preferably approximate to the refractive index of the optical film to be used. From the viewpoint of reducing loss, the refractive index is preferably 1.4 or more. 45 or more is more preferable, and 1.5 or more is particularly preferable. Further, from the viewpoint of improving luminance, the polymer needs to be transparent, and the total light transmittance is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. preferable.

  In addition, each layer of the polymer or optical film of the present invention is treated with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may be one having an ultraviolet absorbing ability by such a method.

  The polymer of the present invention can be preferably used for forming backlights for various image display devices such as liquid crystal display devices.

  The image display device of the present invention is a liquid crystal display device using the above backlight system, and can emit light efficiently, and further contributes to energy saving and long life.

  On the other hand, the backlight system of the present invention is characterized in that an LED light source and an optical film are joined via a polymer layer.

  The polymer for forming the polymer layer is not particularly limited, but is a vinyl polymer such as a (meth) acrylic polymer, a polystyrene polymer or a polyolefin polymer, a polyoxyalkylene polymer, or a polyorganosiloxane. A polymer or the like can be used. Of these, vinyl polymers are preferable from the viewpoint of easy heat resistance deterioration characteristics, transparency and refractive index adjustment, and (meth) acrylic polymers are more preferable.

  Since the polymer of the present invention is directly laminated with an LED light source, heat resistance is required. In addition, if a low molecular weight component or a low volatile content is contained, it may cause bubbles due to foaming. Therefore, the weight average molecular weight (Mw) measured by GPC is preferably 2,000 or more, more preferably 5,000 or more, and 10,000. The above is particularly preferable. When the weight average molecular weight (Mw) is small, bubbles tend to be generated. Further, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably 2.0 or less, more preferably 1.8 or less, and 1.5 or less. More preferably it is. When Mw / Mn is small, it is preferable in terms of suppressing a decrease in luminance due to bubble generation or the like.

  For the production of the polymer of the present invention, any known production method such as solution polymerization, bulk polymerization, emulsion polymerization and the like can be adopted, but a polymer having an arbitrary molecular weight can be obtained and Mw / Mn can be reduced. From the viewpoint, it is preferable that the polymer is produced by controlled polymerization using an initiator. Examples of the controlled polymerization method include a living anion polymerization method, a radical polymerization method using a chain transfer agent, and a recently developed living radical polymerization method. Of these, the living radical polymerization method is preferable from the viewpoint of control of molecular weight and structure.

  The living radical polymerization method is a radical polymerization method in which the activity at the polymerization terminal is maintained without being lost. In the narrow sense, the living polymerization method refers to a polymerization method in which the terminal always has activity, but in general, the pseudo-living polymerization method in which the terminal inactivated and the terminal are in an equilibrium state. Is also included. The definition here is also the latter. The living radical polymerization method has been actively researched by various groups in recent years.

  Examples thereof include those using a chain transfer agent such as polysulfide, cobalt porphyrin complex (J. Am. Chem. Soc., 1994, 116, 7943), Those using radical scavengers such as nitroxide compounds (Macromolecules, 1994, 27, 7228), atom transfer radical polymerization method using organic halide as initiator and transition metal complex as catalyst (Atom Transfer Radical Polymerization: ATRP). In the present invention, any of these methods is not particularly limited, but the atom transfer radical polymerization method is preferred from the viewpoint of easy control.

  Specific examples of the atom transfer radical polymerization method include the method described in JP-A-2004-107447.

  Further, the polymer of the present invention preferably has a measured hardness of 40 or less, more preferably 30 or less, and particularly preferably 20 or less in accordance with JIS K6253 according to JIS K6253. When the hardness is higher than 40, when the polymer and the LED light source are laminated, the unevenness of the LED lamps arranged on the base plate cannot be followed and an air layer tends to be formed.

  Furthermore, the polymer of the present invention is preferable from the viewpoint of heat resistance, because the cohesive force and durability are improved by crosslinking. The polymer of the present invention preferably has at least one crosslinkable functional group in the molecule in order to crosslink the polymer. The crosslinkable functional group is at least one crosslinkable functional group selected from the group consisting of a crosslinkable silyl group, an alkenyl group, a hydroxyl group, an amino group, a polymerizable carbon-carbon double bond and an epoxy group. It is preferable. Among these, an alkenyl group, a polymerizable carbon-carbon double bond and an epoxy group are preferable from the viewpoint of being capable of crosslinking with light or heat and easily increasing the gel fraction.

  Some polymers of the present invention require a crosslinking catalyst or a crosslinking agent depending on each crosslinkable functional group. Moreover, you may add various compounding agents according to the target physical property. Specific examples of the crosslinking catalyst and the crosslinking agent according to each crosslinkable functional group include those described in JP-A-2004-315608.

  The blending amount of the crosslinking agent varies depending on the material used, but is usually 0.03 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the polymer. Is preferred. If the blending amount of the crosslinking agent is too small, the gel fraction is low, the cohesive force is insufficient, and if it is too much, there is a tendency to cause coloring or volatile matter.

  Furthermore, when the polymer of the present invention is crosslinked, the gel fraction is preferably 50 to 100% by weight and more preferably 80 to 100% by weight from the viewpoint of heat resistance. When the gel fraction is less than 50% by weight, the heat from the LED light source tends to cause deformation or foaming of the polymer. The gel fraction mentioned here means that when various compounding agents that are not incorporated into the crosslinked structure are used, the compounding agent dissolves in the solvent together with the uncrosslinked polymer, so the amount of the compounding agent is corrected. It shows the amount of cross-linked polymer relative to the initial polymer.

  Regarding the crosslinking of the polymer, it may be laminated on a light source after crosslinking or may be crosslinked after lamination on a light source.

  Furthermore, the polymer of the present invention is a graft polymer comprising a polymer block having a glass transition temperature of 50 ° C. or higher and a polymer block having a glass transition temperature of 0 ° C. or higher from the viewpoints of flexibility and heat resistance. Or it is preferable that it is a block copolymer. In the case of a graft polymer or a block copolymer, it has sufficient heat resistance even if it is not cross-linked, and it is preferable from the viewpoint that it can give further heat resistance by adding a cross-linkable functional group and cross-linking. . Among the graft polymers or block copolymers, a block copolymer is more preferable from the viewpoint of a balance between heat resistance and flexibility.

  Block copolymers include styrene-butadiene-styrene block copolymers and their hydrogenated products, styrene block copolymers such as styrene-isoprene-styrene block copolymers and their hydrogenated products, and olefinic blocks. A copolymer, an acrylic block copolymer, and the like can be mentioned, and an acrylic block copolymer is preferable from the viewpoint of transparency, flexibility, and easy refractive index control.

  The acrylic block copolymer is an acrylic block copolymer (a) composed of a methacrylic polymer block (a) mainly composed of a methacrylic ester and an acrylic polymer block (b) mainly composed of an acrylate ester ( A) is preferred. The structure of the acrylic block copolymer (A) may be either a linear block copolymer, a branched (star) block copolymer, or a mixture thereof. The structure of such a block copolymer is appropriately selected according to the required physical properties of the acrylic block copolymer (A). However, in terms of cost and ease of polymerization, linear block copolymer Coalescence is preferred.

  The linear block copolymer may have any structure. From the viewpoint of the physical properties of the linear block copolymer and the composition, the methacrylic polymer block (a) is a, acrylic When the polymer block (b) is expressed as b, (ab) n type, b- (ab) n type, and (ab) na type (n is an integer of 1 or more, for example, 1 It is preferable that it consists of an at least 1 sort (s) of acrylic block copolymer selected from the group which consists of -3. Among these, an ab type diblock copolymer, an abb type triblock copolymer, or a mixture thereof is preferable from the viewpoint of easy handling during processing and physical properties of the composition.

  The number average molecular weight (Mn) of the acrylic block copolymer (A) can be appropriately set according to the properties required for the polymer layer, but is preferably 10,000 to 300,000, 000 to 150,000 is more preferable. When the number average molecular weight is less than 10,000, the heat resistance tends to decrease, and when the number average molecular weight is greater than 300,000, the melt viscosity is too high and the workability and fluidity tend to decrease. In addition, the said number average molecular weight shows the value measured by polystyrene conversion by the gel permeation chromatography (GPC) which uses chloroform as a mobile phase and uses a polystyrene gel column.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic block copolymer (A) measured by GPC is not particularly limited, but is preferably 2.0 or less. It is more preferably 1.8 or less, and further preferably 1.5 or less. It is preferable that Mw / Mn is small in that problems such as bubble generation due to a low molecular weight component, problems such as deterioration in workability and poor appearance due to a high molecular weight component can be reduced.

  In the acrylic block copolymer (A), the proportion of the methacrylic polymer block (a) is 5 to 30% by weight, and the proportion of the acrylic polymer block (b) is 95 to 70% by weight. It is preferable. If the proportion of the methacrylic polymer block (a) is less than 5% by weight, the cohesive force tends to be insufficient and the heat resistance and the like tend to decrease, and the shape tends to be difficult to be retained. When the proportion of the methacrylic polymer block (a) is more than 30% by weight, the flexibility is insufficient and the unevenness of the light source tends not to be followed.

<Methacrylic polymer block (a)>
The methacrylic polymer block (a) is a block formed by polymerizing a monomer having a methacrylic acid ester as a main component. Here, the main component means that 50% by weight or more of the monomers constituting the methacrylic polymer block (a) is methacrylic acid and / or methacrylic acid ester.

  The glass transition temperature of the methacrylic polymer block (a) is more preferably 50 ° C. or higher. If it is less than 50 ° C., the cohesive force is insufficient and the heat resistance is lowered.

  Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, Methacrylic acid aliphatic hydrocarbons such as n-heptyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl methacrylate (for example, alkyl having 1 to 18 carbon atoms) ) Ester; Methacrylic acid alicyclic hydrocarbon ester such as cyclohexyl methacrylate and isobornyl methacrylate; Aralkyl methacrylate such as benzyl methacrylate; Phenyl methacrylate, Tolu methacrylate Methacrylic acid aromatic hydrocarbon esters such as dimethyl ether; esters of methacrylic acid such as 2-methoxyethyl methacrylate and 3-methoxybutyl methacrylate with functional group-containing alcohols having etheric oxygen; trifluoromethyl methacrylate, methacrylic acid Trifluoromethyl methyl, 2-trifluoromethyl ethyl methacrylate, 2-trifluoroethyl methacrylate, 2-perfluoroethyl ethyl methacrylate, 2-perfluoroethyl-2-perfluorobutyl ethyl methacrylate, 2-methacrylic acid 2- Perfluoroethyl, perfluoromethyl methacrylate, diperfluoromethyl methyl methacrylate, 2-perfluoromethyl 2-perfluoroethyl methyl methacrylate, 2-perfluorohexyl ethyl methacrylate, methacrylate Acid 2-perfluorodecyl ethyl, methacrylic acid fluorinated alkyl esters such as methacrylic acid 2-perfluoroalkyl-hexadecyl ethyl. Among these, methyl methacrylate and / or methacrylic acid aromatic hydrocarbon ester are preferable from the viewpoints of transparency and availability, and adjustment to a high refractive index. These may be used alone or in combination of two or more.

  The methacrylic polymer block (a) contains a methacrylic acid ester as a main component, but may contain 50 to 0% by weight of a vinyl monomer other than the methacrylic acid ester copolymerizable therewith. Examples of the copolymerizable vinyl monomer include acrylic acid esters, aromatic alkenyl compounds, vinyl cyanide compounds, conjugated diene compounds, halogen-containing unsaturated compounds, silicon-containing unsaturated compounds, vinyl ester compounds, and maleimides. Compound etc. can be mentioned.

  Examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, Acrylic aliphatic hydrocarbons such as n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, etc. (eg, alkyl having 1 to 18 carbon atoms) ) Esters; Acrylic alicyclic hydrocarbon esters such as cyclohexyl acrylate and isobornyl acrylate; Aromatic aromatic hydrocarbon esters such as phenyl acrylate and toluyl acrylate; Aralkyl acrylates such as benzyl acrylate; Esters of acrylic acid and functional group-containing alcohols having etheric oxygen such as 2-methoxyethyl acrylate and 3-methoxybutyl acrylate; trifluoromethyl methyl acrylate, 2-trifluoromethyl ethyl acrylate, acrylic acid 2 -Perfluoroethylethyl, 2-perfluoroethyl-2-perfluorobutylethyl acrylate, 2-perfluoroethyl acrylate, perfluoromethyl acrylate, diperfluoromethyl methyl acrylate, 2-perfluoromethyl acrylate Examples thereof include fluorinated alkyl acrylates such as 2-perfluoroethylmethyl, 2-perfluorohexylethyl acrylate, 2-perfluorodecylethyl acrylate, and 2-perfluorohexadecylethyl acrylate.

  Examples of the aromatic alkenyl compound include styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, and the like.

  Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.

  Examples of the conjugated diene compound include butadiene and isoprene.

  Examples of the halogen-containing unsaturated compound include vinyl chloride, vinylidene chloride, perfluoroethylene, perfluoropropylene, and vinylidene fluoride.

Examples of the vinyl ester compound include vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, vinyl cinnamate, and the like.
Examples of the maleimide compound include maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, cyclohexylmaleimide and the like.

<Acrylic polymer block (b)>
The acrylic polymer block (b) is a block formed by polymerizing a monomer mainly composed of an acrylate ester. The main component means that 50% by weight or more of the monomers constituting the acrylic polymer block (b) is an acrylate ester.

  The glass transition temperature of the acrylic polymer block (b) is preferably 0 ° C. or lower, and more preferably −20 ° C. or lower. When the temperature is 0 ° C. or higher, the flexibility is inferior and the unevenness of the light source tends not to be followed.

  As the acrylic ester, the same acrylic ester used in the methacrylic polymer block (a) can be used. Among these, n-butyl acrylate, ethyl acrylate, 2-methoxyethyl acrylate, and 2-ethylhexyl acrylate are preferable. These may be used alone or in combination of two or more.

  The acrylic polymer block (b) contains an acrylate ester as a main component, but may contain 50 to 0% by weight of a vinyl monomer other than the acrylate ester copolymerizable therewith. Examples of the different types of copolymerizable vinyl monomers include methacrylic acid esters, aromatic alkenyl compounds, vinyl cyanide compounds, conjugated diene compounds, halogen-containing unsaturated compounds, silicon-containing unsaturated compounds, and vinyl esters. Examples thereof include a compound and a maleimide compound.

  The acrylic block copolymer (A) can have a functional group in at least one polymer block. Examples of the functional group may include the crosslinkable functional group, and may be one or more.

  These functional groups may be contained in either the methacrylic polymer block (a) or the acrylic polymer block (b), and can be selected according to required characteristics. For example, it is preferably contained in the methacrylic polymer block (a) when heat resistance is required, and the acrylic polymer block (b) when elasticity or adhesive strength to a polar adherend is required. It is preferable that it is contained in.

  The method for introducing a functional group into the acrylic block copolymer (A) is not particularly limited, and a method of copolymerizing a monomer having the functional group, a single unit having a functional group serving as a precursor of the functional group. There is a method in which the functional group is generated by a known chemical reaction after copolymerization of the monomer.

Furthermore, as the polymer, it is preferable to disperse and contain light-transmitting non-colored particles to impart light diffusibility.
As the light-transmitting non-colored particles dispersed and contained in the polymer, appropriate colorless and transparent particles can be used. As light-transmitting non-colored particles, for example, inorganic particles that may be conductive such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, various crosslinked or uncrosslinked polymers, etc. Organic particles made of By forming the diffusion polymer layer exhibiting light diffusibility, the visibility of the image display device can be improved. In addition, the number of diffusion sheets laminated on the polymer can be reduced.

  The light-transmitting uncolored particles have an average particle diameter of 1 to 10 μm, preferably 9 μm or less, particularly 2 to 8 μm. In addition, when the refractive index of the non-colored particles is n1 and the refractive index of the polymer layer is n2 in terms of suppressing backscattering and providing good diffusibility in the transmission direction, the formula: 0.01 <| n1- A combination satisfying n2 | <0.1, preferably | n1-n2 | <0.09, particularly -0.08 <n1-n2 <-0.01 is preferable. The amount of light-transmitting non-colored particles to be dispersed and contained in the diffusion adhesive layer is appropriately determined based on the above-described light diffusivity and the like, but is generally 5 to 200 weights per 100 parts by weight of the polymer. Parts, preferably 10 to 150 parts by weight, more preferably 15 to 100 parts by weight of uncolored particles are used.

  Further, when the polymer of the present invention is laminated between an LED light source and an optical film, a tackifier resin or a silane coupling agent may be blended in order to improve the adhesion between the LED light source and the optical film. good.

  The polymer may contain other known additives, such as colorants, dyes, surfactants, plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents. An agent, a light stabilizer, an ultraviolet absorber, a polymerization inhibitor, an inorganic or organic filler, a metal powder, and the like can be appropriately added depending on the use.

  The polymer may be laminated by forming a sheet after extrusion or solvent coating, laminating it, dissolving it in an appropriate solvent, applying it and then drying the solvent, or liquefying the polymer. Crosslinking may be performed after direct potting.

  What is necessary is just to set the thickness of a polymer suitably, and it should just be set so that it may become 5-100 micrometers from viewpoints, such as 2-5000 micrometers and economical efficiency.

  Furthermore, the backlight system of the present invention can be devised to improve the luminance as appropriate by applying a reflective agent to the base plate or using a reflective sheet.

  EXAMPLES Although this invention is demonstrated further in detail based on an Example, this invention is not limited only to these Examples.

<Molecular weight measurement method>
The molecular weight shown in this example was measured by the GPC analyzer shown below, and the molecular weight in terms of polystyrene was determined using chloroform as the mobile phase. As a system, a GPC system manufactured by Waters was used, and Shodex K-804 (polystyrene gel) manufactured by Showa Denko Co., Ltd. was used for the column.

<Method for measuring conversion rate of polymerization reaction>
The conversion rate of the polymerization reaction shown in this example was measured using the following analyzer and conditions.
Equipment used: Gas chromatography GC-14B manufactured by Shimadzu Corporation
Separation column: J & W SCIENTIFIC INC, capillary column DB-17, 0.35 mmφ × 30 m
Separation conditions: Initial temperature 50 ° C., hold for 3.5 minutes
Temperature increase rate 40 ° C / min
Final temperature 140 ° C, hold for 1.5 minutes
Injection temperature 250 ° C
Detector temperature 250 ° C
Sample preparation: The sample was diluted about 10 times with ethyl acetate, and acetonitrile was used as an internal standard substance.

<Measurement of refractive index>
The refractive indexes shown in the examples and comparative examples were measured by the following methods. Under an atmosphere of 25 ° C., sodium D line (589 nm) was irradiated, and the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, DR = M4).

<Measurement of hardness>
The hardness shown in the examples and comparative examples was measured by the following method. According to JIS K6253, the hardness at 23 ° C. (immediately after, JIS A) was measured.

<Measurement of total light transmittance (%)>
Transparency shown in the examples and comparative examples was measured under the following conditions.
The total light transmittance (TT) (%) of the 2 mm-thick polymer sheets obtained in Examples and Comparative Examples was measured.
For the measurement, a turbidimeter NDH-300A (manufactured by Nippon Denshoku Industries Co., Ltd.) was used.

<Measurement of gel fraction (% by weight)>
The gel fraction (% by weight) shown in the examples and comparative examples was measured by the following method. 1 g of the polymer is wrapped in a 350 mesh wire mesh and immersed in toluene at 80 ° C. for 24 hours, and then the toluene soluble fraction is separated, the residual solid content is vacuum dried at 80 ° C., and the weight g of the residual solid content after drying is determined. Measured and represents the weight percent of residual solids relative to the polymer.

<Foaming / heat resistance test>
The polymer sheet having a thickness of 1 mm obtained in Examples and Comparative Examples was sandwiched between two 2 mm-thick polycarbonate plates, and then placed in a dryer at 120 ° C., and the presence or absence of foaming after 24 hours and the polymer sheet The presence or absence of thermal deformation was evaluated visually. Evaluation was made as ◯ when neither foaming nor thermal deformation was observed, Δ when slightly heat-deforming but not foaming, and X when both foaming and thermal deformation were observed.

<Evaluation of followability to LED light source>
A polymer sheet of 2 mm thickness obtained in Examples and Comparative Examples is laminated on a template in which LED lamps of REGZA 46ZX8000, which is a 46V type LCD TV manufactured by Toshiba, are arranged, and an acrylic plate (Sumitomo Chemical Co., Sumipex E00, thickness) Then, the followability to the LED lamp was visually observed. The case where there was no gap between the LED lamp and the polymer was evaluated as ◯, and the case where there was no gap between the LED lamp and the polymer was evaluated as x.

<Evaluation of brightness>
The 1 mm-thick polymer sheets obtained in the examples and comparative examples are laminated on a template in which LED lamps of REGZA 46ZX8000, which is a 46V type liquid crystal television made by Toshiba, are arranged, and the brightness is visually observed after being sandwiched between diffusion plates. Evaluated. The case where it was bright compared with the case where a polymer was not pinched | interposed was evaluated as (circle), and the case where it became a little bright was evaluated as (triangle | delta).

(Production Example 1) Production of acrylic block copolymer 1 In a 500-liter reactor purged with nitrogen, 81 kg of BA was charged as a monomer constituting the acrylic polymer block, followed by 474 g of cuprous bromide. Agitation was started. Thereafter, a solution prepared by dissolving 476 g of diethyl 2,5-dibromoadipate in 7 kg of acetonitrile and 7 kg of toluene was charged, and the jacket was heated and held at an internal temperature of 75 ° C. for 30 minutes. Thereafter, 57 g of pentamethyldiethylenetriamine was added to initiate polymerization of the acrylic polymer block. About 100 g of the polymerization solution was sampled for sampling from the polymerization solution at regular intervals from the start of polymerization, and the conversion rate of BA was determined by gas chromatogram analysis of the sampling solution. The polymerization rate was controlled by adding pentamethyldiethylenetriamine as needed.

  When the conversion rate of BA reached 95%, 55 kg of toluene, 327 g of cuprous chloride, 57 g of pentamethyldiethylenetriamine, and 20 kg of MMA were added as monomers constituting the methacrylic polymer block. Polymerization of the combined block was started. When the MMA conversion rate reached 90%, 115 kg of toluene was added to dilute the reaction solution, and the reactor was cooled to stop the polymerization.

  Toluene was added to the resulting acrylic block copolymer solution to make the polymer concentration 25% by weight. To this solution, 1.3 kg of p-toluenesulfonic acid monohydrate was added, the inside of the reactor was purged with nitrogen, and the mixture was stirred at 30 ° C. for 3 hours. The reaction solution was sampled to confirm that the solution was colorless and transparent, and 5 kg of Radiolite # 3000 manufactured by Showa Chemical Industry was added. Thereafter, pressure filtration was performed at 0.1 to 0.4 MPaG using a pressure filter equipped with polyester felt as a filter medium to separate a solid content.

  To the obtained acidic solution, 1.5 kg of Kyowa Chemical Kyodo 500SH was added as a solid base and stirred at 30 ° C. for 1 hour. Thereafter, the solid content was separated by pressure filtration at 0.1 to 0.4 MPaG using a pressure filter equipped with polyester felt as a filter medium. The obtained polymer solution was vacuum-dried to remove the solvent and unreacted monomers to obtain the target acrylic block copolymer 1.

  When the GPC analysis of the obtained acrylic block copolymer 1 was conducted, the number average molecular weight (Mn) was 109,000 and the molecular weight distribution (Mw / Mn) was 1.34. The weight ratio of the methacrylic polymer block to the acrylic polymer block was 20/80.

(Production Example 2) Production of acrylic block copolymer 2 As the monomer constituting the acrylic polymer block, BA 89 kg is used, and as the monomer constituting the methacrylic polymer block, MMA 46 kg is used. Polymerization was carried out in the same manner as in Production Example 1 except that 658 g of cuprous bromide, 661 g of diethyl 2,5-dibromoadipate, 8 kg of acetonitrile, 80 g of pentamethyldiethylenetriamine, 107 kg of toluene and 454 g of cuprous chloride were used. It was.

  Production Example except that 1.6 kg of p-toluenesulfonic acid monohydrate, 6.5 kg of Radiolite # 3000, and 1.9 kg of Kyoward 500SH were used for the resulting acrylic block copolymer solution. 1 to obtain the desired acrylic block copolymer 2. When the GPC analysis of the obtained acrylic block copolymer 2 was conducted, the number average molecular weight (Mn) was 113,000 and the molecular weight distribution (Mw / Mn) was 1.32. The weight ratio of the methacrylic polymer block to the acrylic polymer block was 35/65.

(Production Example 3) Production of acrylic block copolymer 3 Using a 500 L reactor, 83.0 kg of BA is used as a monomer constituting the acrylic polymer block, and a single amount constituting the methacrylic polymer block Polymerization was carried out in the same manner as in Production Example 1 except that 35.6 kg of MMA was used as the body.

  Production Example 1 except that 1.6 kg of p-toluenesulfonic acid monohydrate, 2.3 kg of Radiolite # 3000, and 1.7 kg of Kyoward 500SH were used for the resulting acrylic block copolymer solution. And the target acrylic block copolymer 3 was obtained. When the GPC analysis of the obtained acrylic block copolymer 3 was conducted, the number average molecular weight (Mn) was 109,000 and the molecular weight distribution (Mw / Mn) was 1.31. The weight ratio of the methacrylic polymer block to the acrylic polymer block was 30/70.

(Production Example 4) Production of acrylic copolymer 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 98 parts by weight of butyl acrylate, acrylic acid 1.0 part by weight, 1.0 part by weight of 4-hydroxybutyl acrylate, 0.1 part by weight of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. The polymerization reaction was performed for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 970,000 was obtained. The molecular weight distribution (Mw / Mn) was 4.10.

Production Example 5 Production of Acrylic Block Copolymer 4 In a nitrogen-substituted 5 L pressure-resistant reactor, 4.98 g of copper bromide, 694.18 g of BA, 60.88 g of acetonitrile, and 5.0 g of diethyl 2,5-dibromoadipate The mixture was stirred and heated to 75 ° C. Thereafter, 0.602 g of pentamethyldiethylenetriamine (hereinafter referred to as triamine) was added to initiate polymerization. The polymerization solution was sampled as appropriate, and the conversion was measured by gas chromatography analysis. When the conversion rate of BA was 97%, 793 g of toluene, 3.44 g of copper chloride, 275 g of MMA, and 12.08 g of GMA were added. Triamine was added as appropriate to adjust the reaction rate. When the conversion rate of MMA was 90%, 1190 g of toluene was added and the reaction was stopped by cooling.

  To the acrylic block copolymer solution after polymerization, 76 g of activated alumina and 38 g of Kyoward 700 SEN (manufactured by Kyowa Chemical) were added, and an adsorption treatment was performed at 100 ° C. for 3 hours. The adsorbent was filtered off by filtering the solution after cooling using a pressure filter equipped with a polyester felt. The purified solution of the obtained acrylic block copolymer is vacuum-dried to obtain the desired acrylic block copolymer 4 (crosslinkable functional group (epoxy group) -containing acrylic block copolymer (P (MMA)). / GMA) -b-PBA-b-P (MMA / GMA)).

  When the GPC analysis of the obtained acrylic block copolymer 4 was conducted, the number average molecular weight Mn was 11,3475 and the molecular weight distribution Mw / Mn was 1.35. The weight ratio of the methacrylic polymer block to the acrylic polymer block was 30/70.

Example 1
The acrylic block copolymer 1 obtained in Production Example 1 was hot-pressed at a set temperature of 200 ° C. for 5 minutes (compression molding machine NSF-50, manufactured by Kondo Metal Industry Co., Ltd.), and the thickness was 1 mm and 2 mm. A polymer sheet for evaluation was obtained. About these molded objects, refractive index, hardness, total light transmittance, and gel fraction were measured, and foaming / heat resistance test, followability to LED light source, and luminance were evaluated. The results are shown in Table 1.

(Example 2)
Evaluation was performed in the same manner as in Example 1 except that the acrylic block copolymer 1 of Example 1 was changed to the acrylic block copolymer 3. The results are shown in Table 1.

(Example 3)
The acrylic block copolymer 4 of Production Example 5 was dissolved in toluene to make a 30% solution. 1 part by weight of Adekaoptomer SP-172 (manufactured by ADEKA), which is a cationic photoinitiator, was added to the obtained solution in a solution state to obtain a curable liquid formulation 1. The blend was applied and devolatilized so that the dry thickness was 1 mm and 2 mm, and then crosslinked by irradiating with ultraviolet rays so as to obtain 20000 mJ / cm ² to obtain a polymer sheet. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 1 except that the acrylic block copolymer 1 of Example 1 was changed to the acrylic block copolymer 2. The results are shown in Table 1.

(Comparative Example 2)
Evaluation was performed in the same manner as in Example 1 except that the acrylic block copolymer 1 of Example 1 was changed to the acrylic copolymer 1. The results are shown in Table 1.

(Comparative Example 3)
To 100 parts by weight of the solid content of the (meth) acrylic polymer of Production Example 4, 0.5 parts by weight of isocyanurate trimer of hexamethylene diisocyanate (Mitsui Chemical Polyurethane, Takenate D-170N) was further added. Then, it apply | coated so that dry thickness might be 1 mm and 2 mm, and it dried and bridge | crosslinked at 120 degreeC for 3 minutes, and obtained the polymer sheet. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

  From Examples 1 and 2 and Comparative Example 1, it can be seen that if the hardness is high, the followability of the polymer to the LED light source is insufficient and the luminance is adversely affected.

  Moreover, it turns out that it becomes a cause of foaming from Comparative Examples 2-3 so that molecular weight distribution is large. Moreover, although heat resistance improves by bridge | crosslinking, it turns out that the followable | trackability to a LED light source is insufficient and it has a bad influence also on a brightness | luminance.

  From Example 3 and Comparative Example 3, it can be seen that maintaining low hardness even after cross-linking can improve foaming and heat resistance, have good followability to the LED light source, and contribute to luminance improvement.

10: Base plate 20: LED lamp 30: Polymer 40: Optical film

Claims (13)

A type plate having a refractive index of 1.4 or more and a total light transmittance of 85% or more, measured according to JIS K6253, using an LED as a direct light source and a base plate on which the LED light source is arranged and an optical film. A backlight system for an image display device, characterized by being laminated with a polymer having a durometer hardness of 30 or less. The polymer has a weight average molecular weight (Mw) measured by gel permeation chromatography of 5000 or more, and a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.0. The backlight system for an image display device according to claim 1, wherein: The backlight system for an image display device according to claim 1, wherein the polymer is obtained by controlled polymerization. 4. The backlight system for an image display device according to claim 1, wherein the optical film is a diffusion plate. The backlight system for an image display device according to any one of claims 1 to 4, wherein the polymer has a gel fraction of 50 to 100% by weight. The backlight system for an image display device according to claim 1, wherein the polymer is a (meth) acrylic polymer. 7. The (meth) acrylic polymer is an acrylic block copolymer (A) comprising a methacrylic polymer block (a) and an acrylic polymer block (b). Backlight system for image display devices. The acrylic block copolymer (A) has a number average molecular weight measured by gel permeation chromatography of 30,000 to 150,000, and a methacrylic polymer block mainly composed of a methacrylic polymer ( The backlight system for an image display device according to claim 7, comprising: a) 5 to 30% by weight and an acrylic polymer block (b) 95 to 70% by weight mainly composed of an acrylic polymer. The backlight system for an image display device according to claim 1, wherein the optical film is a laminate of a plurality of optical films. The image display apparatus containing the backlight system for image display apparatuses in any one of Claims 1-9. The backlight system according to claim 1, wherein the polymer exhibits light diffusibility by dispersing and containing light-transmitting non-colored particles. The backlight system according to claim 1, wherein the polymer has a thickness of 5 to 100 μm. A method for improving the brightness of emitted light, comprising using the backlight system according to claim 1.

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