JP4608977B2 - Light reflector - Google Patents

Description

The present invention relates to a light reflector having a foamed structure (including a porous structure) in which a plurality of independent microbubbles and / or a plurality of continuous microbubbles are formed.
The light reflector of the present invention includes a backlight unit of a liquid crystal display device, an internally illuminating fixture, an internally illuminated signboard, a light box, a projection screen, a shakasten, a copying machine, a projector-type display, a facsimile, and an electronic blackboard. It is suitably used as a light reflecting member of a light source built-in device selected from the group consisting of

Applications of light reflectors In recent years, light reflectors have been used in various fields. For example, backlight units for liquid crystal display devices, internally illuminated lighting fixtures, internally illuminated signboards, light boxes, and projection screens. It is used as a light-reflecting member in Schaukasten, copiers, projector-type displays, facsimiles, and electronic blackboards. In particular, liquid crystal display devices are widely used as display devices for electronic devices such as televisions, personal computers, word processors, mobile phones, PDAs, digital cameras, video cameras, and various game machines. There is a need to save power and improve display quality. In particular, in order to meet the demand for thinning, it is essential to supply as much light as possible to the liquid crystal unit of the backlight used in the liquid crystal display device.

There are two types of backlight units for light reflector liquid crystal display devices for liquid crystal backlights: a direct light system in which the light source is placed directly under the liquid crystal part and an edge light system in which the light source is placed on the side of the transparent light guide plate. The latter method is suitable for conversion. In that case, the light reflectors are mainly disposed at two locations, the lamp holder portion and the lower portion of the light guide plate. The light quantity from the light source is transmitted from the lamp holder part to the liquid crystal part via the light guide plate, but a part of it is reflected on the light reflecting film under the lamp holder part and the light guide plate and then on the liquid crystal part. Reportedly. Therefore, in order to efficiently transmit the amount of light supplied from the backlight unit to the liquid crystal unit, it is necessary to increase the light reflection efficiency of the light reflection film. However, as the liquid crystal display device is made thinner, there is a demand for thinner light reflectors, which tends to reduce the light reflection efficiency. In addition, the diameter of the lamps installed on the side has been reduced, and in addition to thinning of the light reflector, workability, productivity, and molding processability incorporated in the apparatus are also important.

As a conventional light reflector , an aluminum plate (Patent Document 1), a metal plate such as aluminum having a thin film layer mainly composed of silver (Patent Document 2), a metal plate coated with a white pigment (Patent Document 3) has been used in the past. However, since these light reflectors have a low electrical resistance, a leakage current due to an induced current from the light source is generated, so that a current used for light emission is reduced and the light emission efficiency is lowered. In order to prevent this leakage current, a foamed resin sheet having a high insulating property has been used in recent years. Further, since the foamed resin contains air layers having different refractive indexes in the resin, the light scattering efficiency is good and the light reflectance is improved. For example, there are polyester sheets (Patent Documents 4 to 6) containing fine foam, and light is diffusely reflected by pores (stretched foam) formed by stretching the resin sheet. Currently, a white foamed polyester film (product name: E60, manufactured by Toray Industries, Inc.) with a thickness of 188 μm is used as the light reflector of the backlight unit, but this thickness can be used to reduce the thickness of the backlight unit. Can not. Further, there is a demand for a next-generation thin light reflecting sheet having a thickness of 100 μm or less. However, if the thickness is further reduced, it becomes difficult to reduce the pore diameter, and light reflection at the interface between the PET and the pores becomes difficult. There was a problem that the light reflectance was not sufficient. Therefore, like a polyester resin and polyolefin thermoplastic resin sheet containing an inorganic filler (Patent Documents 7 to 8), a light reflecting film provided with light reflecting efficiency by adding a pigment having a refractive index higher than that of the resin is used. It has been. However, since the specific gravity of the pigment is higher than that of the resin, there is a problem that the weight reduction is impaired by adding the pigment. Further, the mechanical strength and the stretchability of the resin deteriorated (lowered the elongational viscosity) due to the addition of the pigment, and the film was cut at the time of stretch foaming, resulting in poor moldability and productivity. Further, these films are incorporated into the backlight unit, but the rigidity is high and the workability is poor when the film is incorporated into the lamp holder. On the other hand, in order to improve workability, a method of creating a thin light reflector by a coating method has been reported, and a paint in which hollow particles are mixed with a (meth) acrylic ester copolymer resin (Patent Document 9). The light reflector which apply | coated to the support body corresponds. However, if the amount of hollow particles, which are pore elements, is increased in order to suppress the reduction of light reflectance due to thin objects, the coating layer is cracked, resulting in poor film formability and a very brittle film. It was. As a result, it is difficult to obtain a high light reflectance with a thin object.

JP-A-62-286019 Japanese Utility Model Publication No. 4-22755 JP-A-2-13925 JP-A-4-239540 JP 2002-98811 A JP 2002-71913 A JP 7-287110 A JP 2002-333511 A JP-A-9-63329

  An object of the present invention is to obtain a light reflector that has fine bubbles, is thin, has high light reflectance, and has good workability, productivity, and moldability.

In order to solve the above problems, the present invention employs the following configurations (1) to (10).
(1) Contains an acid generator that generates an acid by the action of active energy rays or a base generator that generates a base, and further decomposes and desorbs one or more low-boiling volatile substances by reacting with the acid or base. A light reflector produced by foaming a foamable composition containing a decomposable foamable compound having a decomposable foamable functional group.
(2) In the invention of (1), the light reflector has fine bubbles, and the average bubble diameter is 0.005 to 10 μm.
(3) In the invention of (1) or (2), the light reflector has fine bubbles, and the bubble ratio is 5% to 90%.
(4) In the invention of (1) to (3), the light reflector has a thickness of 10 to 500 μm.
(5) In the invention of (1) to (4), the light reflector is characterized in that the average light reflectance for incident light in the wavelength range of 320 to 800 nm is 80% or more.
(6) In the inventions of the above (1) to (5), the light reflector is produced from a coating layer in which a foamable composition is coated on a planar and / or curved support. Light reflector.
(7) In the inventions of the above (1) to (6), the backlight unit of the liquid crystal display device, the internally illuminated lighting device, the internally illuminated signboard, the light box, the projection screen, the Schaukasten, the copying machine, and the projector system A light reflector that can be used as a light reflecting member of a light source built-in device selected from the group consisting of displays, facsimiles, and electronic blackboards.
(8) In the inventions of (1) to (6), a light reflector that can be used as a light reflector that forms a lamp holder constituting a backlight unit of a liquid crystal display device.
(9) The light reflector that can be used as the light reflector under the light guide plate constituting the backlight unit of the liquid crystal display device in the inventions of (1) to (6).
(10) The light reflecting sheet is incorporated on one side of the light guide plate, the light diffusing sheet is incorporated on the other surface, and the light source 1 is incorporated on at least one side surface of the laminate in which the lens sheet is incorporated on the surface of the light diffusing sheet. In the light reflection device in which the light source 1 is covered with a curved lamp holder, the light reflection according to any one of the above (1) to (6) as a light reflection sheet on one side of the lamp holder and the light guide plate A light reflecting device characterized by using a body.

  Decomposing and foaming that includes an acid generator that generates an acid by the action of active energy rays or a base generator that generates a base, and further decomposes and desorbs one or more low-boiling volatile substances by reacting with the acid or base. A light reflector manufactured from a foamable composition containing a decomposable foamable compound having a functional group has a plurality of independent and / or continuous fine bubbles, and can be thinned while maintaining a high light reflectance. It was. The light reflector of the present invention includes a backlight unit of a liquid crystal display device, an internally illuminated lighting fixture, an internally illuminated electric signboard, a light box, a projection screen, a shakasten, a copying machine, a projector-type display, a facsimile, and an electronic blackboard. It can be suitably used as a thin light reflecting member of a light source built-in device selected from the group consisting of.

  The light reflector of the present invention is a foam produced from a foamable composition containing the following two components. One of them is an acid generator that generates an acid by the action of an active energy ray, or a base generator that generates a base, and the other is one or more types that react with the generated acid or base. It is a decomposition foamable compound that decomposes and desorbs low boiling point volatile compounds. Thermal energy can be applied in the process of generating an acid or base, or in the process of decomposition and elimination.

Acid generators and base generators Acid generators or base generators used in foamable compositions include photo-amplifiers and photo-base generators that are used in chemically amplified photoresists and photocationic polymerization. What is called can be used.

As a photoacid generator suitable for the present invention,
(1) Diazonium salt compounds (2) Ammonium salt compounds (3) Iodonium salt compounds (4) Sulfonium salt compounds (5) Oxonium salt compounds (6) Phosphonium salt compounds Mention may be made of PF _6- , AsF _6- , SbF ₆ -and CF ₃ SO ₃ -salts of aliphatic onium compounds. Although the specific example is enumerated below, it is not limited to what was illustrated.

Bis (phenylsulfonyl) diazomethane,
Bis (cyclohexylsulfonyl) diazomethane,
Bis (tert-butylsulfonyl) diazomethane,
Bis (p-methylphenylsulfonyl) diazomethane,
Bis (4-chlorophenylsulfonyl) diazomethane,
Bis (p-tolylsulfonyl) diazomethane,
Bis (4-tert-butylphenylsulfonyl) diazomethane,
Bis (2,4-xylylsulfonyl) diazomethane,
Bis (cyclohexylsulfonyl) diazomethane,
Benzoylphenylsulfonyldiazomethane,

Trifluoromethanesulfonate,
Trimethylsulfonium trifluoromethanesulfonate,
Triphenylsulfonium trifluoromethanesulfonate,
Triphenylsulfonium hexafluoroantimonate,
2,4,6-trimethylphenyldiphenylsulfonium trifluoromethanesulfonate,
p-tolyldiphenylsulfonium trifluoromethanesulfonate,
4-phenylthiophenyldiphenylsulfonium hexafluorophosphate,
4-phenylthiophenyldiphenylsulfonium hexafluoroantimonate,
1- (2-naphthoylmethyl) thiolanium hexafluoroantimonate,
1- (2-naphthoylmethyl) thiolanium trifluoromethanesulfonate,
4-hydroxy-1-naphthyldimethylsulfonium hexafluoroantimonate,
4-hydroxy-1-naphthyldimethylsulfonium trifluoromethanesulfonate,
(2-oxo-1-cyclohexyl) (cyclohexyl) methylsulfonium trifluoromethanesulfonate,
(2-oxo-1-cyclohexyl) (2-norbornyl) methylsulfonium trifluoromethanesulfonate,
Diphenyl-4-methylphenylsulfonium perfluoromethanesulfonate,
Diphenyl-4-tert-butylphenylsulfonium perfluorooctanesulfonate,
Diphenyl-4-methoxyphenylsulfonium perfluorobutanesulfonate,

Diphenyl-4-methylphenylsulfonium tosylate,
Diphenyl-4-methoxyphenylsulfonium tosylate,
Diphenyl-4-isopropylphenylsulfonium tosylate

Diphenyliodonium,
Diphenyliodonium tosylate,
Diphenyliodonium chloride,
Diphenyliodonium hexafluoroarsenate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium nitrate,
Diphenyliodonium perchlorate,
Diphenyliodonium trifluoromethanesulfonate,

Bis (methylphenyl) iodonium trifluoromethanesulfonate,
Bis (methylphenyl) iodonium tetrafluoroborate,
Bis (methylphenyl) iodonium hexafluorophosphate,
Bis (methylphenyl) iodonium hexafluoroantimonate,
Bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate,
Bis (4-tert-butylphenyl) iodonium hexafluorophosphate,
Bis (4-tert-butylphenyl) iodonium hexafluoroantimonate,
Bis (4-tert-butylphenyl) iodonium perfluorobutanesulfonate,

2-methyl-4,6-bis (trichloromethyl) -1,3,5-triazine,
2,4,6-tri (trichloromethyl) -1,3,5-triazine,
2-phenyl-4,6-ditrichloromethyl-1,3,5-triazine,
2- (p-methoxyphenyl) -4,6-ditrichloromethyl-1,3,5-triazine,
2-naphthyl-4,6-ditrichloromethyl-1,3,5-triazine,
2-biphenyl-4,6-ditrichloromethyl-1,3,5-triazine,
2- (4′-hydroxy-4-biphenyl) -4,6-ditrichloromethyl-1,3,5-triazine,
2- (4′-methyl-4-biphenyl) -4,6-ditrichloromethyl-1,3,5-triazine,
2- (p-methoxyphenylvinyl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-chlorophenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-methoxy-1-naphthyl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (benzo [d] [1,3] dioxolan-5-yl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-methoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (3,4,5-trimethoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (3,4-dimethoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (2,4-dimethoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (2-methoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-butoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,
2- (4-pentyloxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine,

2,6-di-tert-butyl-4-methylpyrylium trifluoromethanesulfonate,
Trimethyloxynium tetrafluoroborate,
Triethyloxynium tetrafluoroborate,
N-hydroxyphthalimide trifluoromethanesulfonate,
N-hydroxynaphthalimide trifluoromethanesulfonate,
(Α-benzoylbenzyl) p-toluenesulfonate,
(Β-benzoyl-β-hydroxyphenethyl) p-toluenesulfonate,
1,2,3-benzenetriyltrismethanesulfonate,
(2,6-dinitrobenzyl) p-toluenesulfonate,
(2-nitrobenzyl) p-toluenesulfonate,
(4-nitrobenzyl) p-toluenesulfonate,
Etc. Of these, iodonium salt compounds and sulfonium salt compounds are preferred.

  In addition to the onium compounds, sulfonates that generate sulfonic acid upon irradiation with active energy rays, for example, 2-phenylsulfonylacetophenone, halides that generate hydrogen halide upon irradiation with active energy rays, such as phenyl trisone. Bromomethylsulfone, 1,1-bis (4-chlorophenyl) -2,2,2-trichloroethane, and ferrocenium compounds that photogenerate phosphoric acid upon irradiation with active energy rays, such as bis (cyclopentadienyl) ferrocenium Hexafluorophosphate, bis (benzyl) ferrocenium hexafluorophosphate, and the like can be used.

Furthermore, the following imide compound derivatives having acid generating ability can also be used.
N- (phenylsulfonyloxy) succinimide,
N- (trifluoromethylsulfonyloxy) succinimide,
N- (10-camphorsulfonyloxy) succinimide,
N- (trifluoromethylsulfonyloxy) phthalimide,
N- (trifluoromethylsulfonyloxy) -5-norbornene-2,3-dicarboximide,
N- (trifluoromethylsulfonyloxy) naphthalimide,
N- (10-camphorsulfonyloxy) naphthalimide.

As a photobase generator suitable for the present invention,
(1) Oxime ester compounds (2) Ammonium compounds (3) Benzoin compounds (4) Dimethoxybenzyl urethane compounds (5) Orthonitrobenzyl urethane compounds, etc. As an amine. In addition, a base generator that generates ammonia or hydroxy ions by the action of light may be used. These include, for example, N- (2-nitrobenzyloxycarbonyl) piperidine, 1,3-bis [N- (2-nitrobenzyloxycarbonyl) -4-piperidyl] propane, N, N′-bis (2-nitrobenzyl). It can be selected from oxycarbonyl) dihexylamine, O-benzylcarbonyl-N- (1-phenylethylidene) hydroxylamine, and the like. Further, a compound that generates a base by heating may be used in combination with the photobase generator.

  In order to expand the wavelength region of the active energy ray of the photoacid generator or photobase generator, a photosensitizer may be used in combination as appropriate. For example, examples of photosensitizers for onium salt compounds include acridine yellow, benzoflavin, and acridine orange.

  As a method for minimizing the addition amount of the acid generator or base generator and the light irradiation energy while generating the necessary acid, an acid proliferator or base proliferator (K. Ichimura et al., Chemistry Letters, 551) -552 (1995), JP-A-8-248561, and JP-A-2000-330270) can be used together with an acid generator or a base generator. The acid proliferator is thermodynamically stable at around room temperature, but decomposes with acid and generates a strong acid by itself to greatly accelerate the acid-catalyzed reaction. By utilizing this reaction, it is possible to improve the generation efficiency of acid or base, and to control the foam generation rate and the foam structure.

Decomposable foamable compound The decomposable foamable compound (hereinafter abbreviated as a decomposable compound) used in the foamable composition used in the present invention reacts with an acid or a base to produce one or more low boiling volatile substances (low boiling point). Volatile compounds are decomposed and desorbed. That is, this decomposable compound must be previously introduced with a degradable functional group capable of generating a low boiling point volatile substance. The low boiling point is the upper limit of the temperature at which gasification occurs during foaming. Usually, it is preferably 100 ° C. or lower and room temperature or lower. Examples of the low boiling point volatile substance include isobutene (boiling point −7 ° C.), carbon dioxide (boiling point −79 ° C.), nitrogen (boiling point −196 ° C.), and the like. Examples of the decomposable functional group include tert-butyl group, tert-butyloxycarbonyl group, keto acid and keto ester group as those that react with acid, and urethane group and carbonate group as those that react with base. Can be mentioned. As for those that react with acid, tert-butyl group represents isobutene gas, tert-butyloxycarbonyl group represents isobutene gas and carbon dioxide, keto acid site represents carbon dioxide, keto acid ester such as tert-butyl keto acid group Generates carbon dioxide and isobutene. As those that react with the base, urethane groups and carbonate groups generate carbon dioxide gas. In this way, each gas is released from the decomposable compound. As examples of the acid (or base) decomposable compound, monomers, oligomers, polymer compounds (polymers) and the like can be used. For example, the compounds can be classified into the following compound groups.
(1) Non-curable low molecular weight degradable compound group (2) Curable monomer based degradable compound group (3) Polymeric degradable compound group Examples of curable monomer based degradable compounds In the case of an active energy ray-curable compound containing a vinyl group that causes a polymerization reaction when irradiated with active energy rays, it is easy to form uniform microbubbles, that is, a foam having excellent strength, It is possible to obtain a light reflector. Specific examples of the decomposable compound are shown below, but are not limited thereto.

(1) -a, non-curing low molecular weight decomposable compound group <acid decomposable compound>
1-tert-butoxy-2-ethoxyethane,
2- (tert-butoxycarbonyloxy) naphthalene,
N- (tert-butoxycarbonyloxy) phthalimide,
2,2-bis [p- (tert-butoxycarbonyloxy) phenyl] propane

(1) -b, non-curing low molecular weight decomposable compound group <base decomposable compound>
N- (9-fluorenylmethoxycarbonyl) piperidine,
Since the low molecular weight non-curable compound itself has no moldability, it is preferably used together with a moldable compound such as a resin or a curable monomer.

(2) -a, curable monomer-based decomposable compound group <acid-decomposable compound>
tert-butyl acrylate,
tert-butyl methacrylate,
tert-butoxycarbonylmethyl acrylate,
2- (tert-butoxycarbonyl) ethyl acrylate,
p- (tert-butoxycarbonyl) phenyl acrylate,
p- (tert-butoxycarbonylethyl) phenyl acrylate,
1- (tert-butoxycarbonylmethyl) cyclohexyl acrylate,
4-tert-butoxycarbonyl-8-vinylcarbonyloxy-tricyclo [5.2.1.02,6] decane,
2- (tert-butoxycarbonyloxy) ethyl acrylate,
p- (tert-butoxycarbonyloxy) phenyl acrylate,
p- (tert-butoxycarbonyloxy) benzyl acrylate,
2- (tert-butoxycarbonylamino) ethyl acrylate,
6- (tert-butoxycarbonylamino) hexyl acrylate,
p- (tert-butoxycarbonylamino) phenyl acrylate,
p- (tert-butoxycarbonylamino) benzyl acrylate,
p- (tert-butoxycarbonylaminomethyl) benzyl acrylate,
(2-tert-butoxyethyl) acrylate,
(3-tert-butoxypropyl) acrylate,
(1-tert-butyldioxy-1-methyl) ethyl acrylate,
3,3-bis (tert-butyloxycarbonyl) propyl acrylate,
4,4-bis (tert-butyloxycarbonyl) butyl acrylate,
p- (tert-butoxy) styrene,
m- (tert-butoxy) styrene,
p- (tert-butoxycarbonyloxy) styrene,
m- (tert-butoxycarbonyloxy) styrene,
Acryloyl acetate, methacryloyl acetate tert-butyl acryloyl acetate,
tert-butyl methacryloyl acetate,
N- (tert-butoxycarbonyloxy) maleimide.
The curable monomer is polymerized by irradiation with active energy rays, and when the polymer comes into contact with an acid, the acid-decomposable group is decomposed to generate a bubble forming gas. Although it has moldability by itself, it can also be used in combination with a resin or other curable monomer.

(2) -b, curable monomer group decomposable compound group <base decomposable compound>
4-[(1,1-dimethyl-2-cyano) ethoxycarbonyloxy] styrene,
4-[(1,1-dimethyl-2-phenylsulfonyl) ethoxycarbonyloxy] styrene,
4-[(1,1-dimethyl-2-methoxycarbonyl) ethoxycarbonyloxy] styrene,
4- (2-cyanoethoxycarbonyloxy) styrene,
(1,1-dimethyl-2-phenylsulfonyl) ethyl methacrylate,
(1,1-dimethyl-2-cyano) ethyl methacrylate,
The monomer is polymerized by irradiation with active energy rays. When this polymer reacts with a base, the base-decomposable group is decomposed to generate a bubble-forming gas. Although it has moldability by itself, it can also be used in combination with a resin or other curable monomer.

(3) -a, decomposable compound group of polymer system <acid-decomposable compound>
Poly (tert-butyl acrylate),
Poly (tert-butyl methacrylate),
Poly (tert-butoxycarbonylmethyl acrylate),
Poly [2- (tert-butoxycarbonyl) ethyl acrylate],
Poly [p- (tert-butoxycarbonyl) phenyl acrylate],
Poly [p- (tert-butoxycarbonylethyl) phenyl acrylate],
Poly [1- (tert-butoxycarbonylmethyl) cyclohexyl acrylate],
Poly {4-tert-butoxycarbonyl-8-vinylcarbonyloxy-tricyclo [5.2.1.02,6] decane},
Poly [2- (tert-butoxycarbonyloxy) ethyl acrylate],
Poly [p- (tert-butoxycarbonyloxy) phenyl acrylate],
Poly [p- (tert-butoxycarbonyloxy) benzyl acrylate],
Poly [2- (tert-butoxycarbonylamino) ethyl acrylate],
Poly [6- (tert-butoxycarbonylamino) hexyl acrylate],
Poly [p- (tert-butoxycarbonylamino) phenyl acrylate],
Poly [p- (tert-butoxycarbonylamino) benzyl acrylate],
Poly [p- (tert-butoxycarbonylaminomethyl) benzyl acrylate],
Poly (2-tert-butoxyethyl acrylate),
Poly (3-tert-butoxypropyl acrylate),
Poly [(1-tert-butyldioxy-1-methyl) ethyl acrylate],
Poly [3,3-bis (tert-butyloxycarbonyl) propyl acrylate],
Poly [4,4-bis (tert-butyloxycarbonyl) butyl acrylate],
Poly [p- (tert-butoxy) styrene],
Poly [m- (tert-butoxy) styrene],
Poly [p- (tert-butoxycarbonyloxy) styrene],
Poly [m- (tert-butoxycarbonyloxy) styrene],
Polyacryloyl acetic acid, polymethacryloyl acetic acid,
Poly [tert-butyl acroyl acetate],
Poly [tert-butylmethacryloyl acetate],
N- (tert-butoxycarbonyloxy) maleimide / styrene copolymer and the like.
When the polymer-based compound comes into contact with an acid, the acid-decomposable group is decomposed to form a bubble forming gas. Although it has moldability by itself, it can also be used in combination with a resin or other curable monomer.

(3) -b, decomposable compound group of polymer system <base decomposable compound>
Poly {p-[(1,1-dimethyl-2-cyano) ethoxycarbonyloxy] styrene},
Poly {p-[(1,1-dimethyl-2-phenylsulfonyl) ethoxycarbonyloxy] styrene},
Poly {p-[(1,1-dimethyl-2-methoxycarbonyl) ethoxycarbonyloxy] styrene},
Poly [p- (2-cyanoethoxycarbonyloxy) styrene],
Poly [(1,1-dimethyl-2-phenylsulfonyl) ethyl methacrylate],
Poly [(1,1-dimethyl-2-cyano) ethyl methacrylate],
And so on.
When the polymer reacts with a base, the base-decomposable group is decomposed to generate a bubble forming gas. Although it has moldability by itself, it can also be used in combination with a resin or other curable monomer.

Organic polymer compounds such as polyethers, polyamides, polyesters, polyimides, polyvinyl alcohols and dendrimers into which degradable functional groups are introduced can be used as acid-decomposable or base-decomposable polymer compounds. Furthermore, an acid-decomposable or base-decomposable polymer compound in which a decomposable functional group is introduced into an inorganic compound such as silica is also included. Especially, it is preferable that a decomposable functional group is introduce | transduced into the compound group which has a functional group chosen from the group which consists of a carboxylic acid group or a hydroxyl group, and an amine group.
The decomposable compound group may be used alone, or two or more different types may be used in combination.
Moreover, the decomposable compound can be used by mixing with other resins. When mixed, the decomposable compound and the other resin may be either compatible or incompatible. Other resins include ABS resins, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, unsaturated polyester resins, polycarbonate resins, polyolefin resins such as polyethylene and polypropylene, polyolefin composite resins, polystyrene resins, polybutadiene resins, acrylic resins, Methacrylic resin, fluororesin, polyimide resin, polyacetal resin, polysulfone resin, vinyl chloride resin, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, starch, polyvinyl alcohol, polyamide resin, phenol resin, melamine resin, urea resin, urethane resin, epoxy resin, The resin can be appropriately selected from commonly used resins such as silicone resins. A gas barrier resin can also be used for the purpose of incorporating a low-boiling volatile substance that decomposes and gasifies from the decomposable compound into the system. The gas barrier resin may be mixed or laminated. For example, in the case of a sheet-like light reflector, it is preferable to stack a gas barrier resin on the sheet surface in order to make the low boiling point volatile substance more contained in the sheet.
Among the decomposable foaming compounds, the curable monomer-based decomposable compound group and the polymer-based decomposable compound group may be used singly or in combination with the generally used resins.
On the other hand, the non-curable low molecular weight decomposable compound group does not form a layer by itself, so it is mixed with the above-mentioned generally used resin or “other active energy ray-curable unsaturated organic compound” described later. It is necessary to use it.

  In order to maintain a foam structure even when left under high temperature and high humidity, and to obtain a light-reflecting body having water resistance, the decomposable compound is decomposed into a compound containing at least one hydrophobic functional group. It is preferable that the compound is a compound in which a decomposable and foaming functional group is introduced into a low-hygroscopic compound.

The hydrophobic functional group is preferably selected from the group consisting mainly of an aliphatic group, an alicyclic group, an aromatic group, a halogen group, and a nitrile group. The decomposable and foamable functional group is easily introduced into a hydrophilic functional group selected from the group consisting mainly of a carboxylic acid group, a hydroxyl group and an amine group. Therefore, the decomposable compound of the present invention is preferably a composite compound comprising a decomposable unit in which a decomposable and foamable functional group is introduced into the hydrophilic functional group and a hydrophobic unit containing a hydrophobic functional group. In the more preferable composite compound, the decomposable unit and the hydrophobic unit are vinyl polymers. Hydrophobic units include aliphatic (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate, aromatic vinyl compounds such as styrene, methylstyrene and vinylnaphthalene, (meth) acrylonitrile compounds, vinyl acetate A compound group, a vinyl chloride compound group, etc. are mentioned. As a representative example of the decomposable compound, the decomposable unit is tert-butyl acrylate in which a tert-butyl group which is a decomposable functional group is introduced into acrylic acid having a carboxylic acid group of a hydrophilic functional group, and Examples thereof include vinyl copolymers comprising a combination in which the hydrophobic unit is methyl acrylate having a hydrophobic functional group methyl group. Specific examples of the decomposable compound comprising a combination of degradable unit / hydrophobic unit are shown below.
tert-butyl acrylate / methyl methacrylate copolymer tert-butyl methacrylate / methyl acrylate copolymer tert-butyl methacrylate / methyl methacrylate copolymer tert-butyl acrylate / ethyl acrylate copolymer tert-butyl acrylate / ethyl methacrylate copolymer Tert-butyl methacrylate / ethyl acrylate copolymer tert-butyl methacrylate / ethyl methacrylate copolymer tert-butyl acrylate / styrene copolymer tert-butyl acrylate / vinyl chloride copolymer tert-butyl acrylate / acrylonitrile copolymer p -(Tert-Butoxycarbonyloxy) styrene / styrene copolymer In addition, a degradable unit in the decomposable compound and The hydrophobic unit can be used alone or in combination of two or more. The form of copolymerization can be performed arbitrarily such as random copolymerization, block copolymerization, and graft copolymerization. Further, the copolymerization ratio of the hydrophobic unit is preferably 5 to 95% by weight based on the total amount of the decomposable compound, and considering the decomposable foamability of the decomposable compound and the environmental preservation of the foam structure, 20 to 80%. % Is more preferable.
The decomposable compounds may be used alone or in combination of two or more different types.

  More preferably, the low hygroscopic compound has an equilibrium water absorption of less than 10% when measured by the JIS K-7209D method in an environmental atmosphere at a temperature of 30 ° C. and a relative humidity of 60%. Examples of the low hygroscopic compound having a structure in which a decomposable and foamable functional group can be easily introduced include p-hydroxystyrene and m-hydroxystyrene. Accordingly, examples of the decomposable compound include p- (tert-butoxy) styrene, m- (tert-butoxy) styrene, p- (tert-butoxycarbonyloxy) styrene, and m- (tert-butoxycarbonyloxy) styrene. These may be a curable monomer or a polymer in which one or more kinds are mixed.

Further, a decomposable and foamable functional group may be introduced into a composite compound comprising a combination of a highly hygroscopic compound having a water absorption rate of 10% or more and a low hygroscopic compound having a water absorption rate of less than 10%. However, the composite compound must have a water absorption of less than 10% with the appropriate combination. For example, a copolymer (composite compound) of acrylic acid, which is a highly hygroscopic compound, and p-hydroxystyrene, which is a low hygroscopic compound, has a copolymerization ratio of acrylic acid / p-hydroxystyrene = 90 / 10-0 / 100 is preferred. Specific examples of degradable compounds include
tert-butyl acrylate / p- (tert-butoxy) styrene copolymer tert-butyl acrylate / m- (tert-butoxy) styrene copolymer tert-butyl acrylate / p- (tert-butoxycarbonyloxy) styrene copolymer tert-butyl acrylate / m- (tert-butoxycarbonyloxy) styrene copolymer tert-butyl methacrylate / p- (tert-butoxycarbonyloxy) styrene copolymer Further polyester, polyimide, polyvinyl acetate, polyvinyl chloride Further, a decomposable and foamable functional group may be introduced into a low-hygroscopic polymer material selected from the group consisting of polyacrylonitrile, phenol resin, and dendrimer.
The decomposable compounds may be used alone or in combination of two or more different types.
The decomposable compound is a compound containing at least one hydrophobic functional group after the decomposable and foamable functional group is decomposed and eliminated to generate a bubble-forming gas, and has a foamed structure even when left under high temperature and high humidity. Can be held.

Mixtures / additives with foamable compositions In addition to acid generators or base generators and decomposable foamable compounds, other active energy ray-curable unsaturated organic compounds may be used in combination with foamable compositions. Good. Examples of combination compounds include
(1) Aliphatic, alicyclic, aromatic 1-6 valent alcohols and polyalkylene glycol (meth) acrylates (2) Aliphatic, alicyclic, aromatic 1-6 valent alcohols with alkylene (Meth) acrylates of compounds obtained by adding oxides (3) poly (meth) acryloylalkylphosphate esters (4) reaction products of polybasic acids, polyols and (meth) acrylic acid (5) Reaction product of isocyanate, polyol, (meth) acrylic acid (6) Reaction product of epoxy compound and (meth) acrylic acid (7) Reaction product of epoxy compound, polyol, (meth) acrylic acid (8) Melamine and A reaction product of (meth) acrylic acid can be mentioned.

Among the compounds that can be used in combination, the curable monomer and resin can be expected to improve the physical properties of the coating film such as the strength and heat resistance of the coating film and to control the foaming property. Additives such as fillers can be expected to improve foamability and light reflection characteristics (particularly in the case of white pigments). Moreover, if a curable monomer is used for the decomposable compound and the combination compound, it can be coated and cured on a support without using a solvent, and a production method with less environmental load can be provided.
As a specific example of a combination compound,
Methyl acrylate, ethyl acrylate, lauryl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxy Butyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, caprolactone modified tetrahydrofurfuryl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, dicyclohexyl acrylate, isobornyl acrylate, isobornyl methacrylate, benzyl acrylate, benzyl methacrylate, ethoxydiethylene Glycol acrylate, methoxytriethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxy polyethylene glycol acrylate, phenoxy polypropylene glycol acrylate, ethylene oxide modified phenoxy acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, 2-ethylhexyl Carbitol acrylate, ω-carboxypolycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, acrylic acid dimer, 2-hydroxy-3-phenoxypropyl acrylate, acrylic acid-9,10-epoxidized oleyl, ethylene glycol monoacrylate maleate Dicyclopentenyloxyethylene Acrylate, acrylate of caprolactone adduct of 4,4-dimethyl-1,3-dioxolane, acrylate of caprolactone adduct of 3-methyl-5,5-dimethyl-1,3-dioxolane, polybutadiene acrylate, ethylene oxide modified phenoxylated phosphorus Acid acrylate, ethanediol diacrylate, ethanediol dimethacrylate, 1,3-propanediol diacrylate, 1,3-propanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1 , 6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, diethylene glycol diacrylate Polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, neopentyl glycol diacrylate, 2-butyl-2-ethylpropanediol diacrylate, ethylene oxide modified bisphenol A diacrylate, polyethylene oxide modified Bisphenol A diacrylate, polyethylene oxide modified hydrogenated bisphenol A diacrylate, propylene oxide modified bisphenol A diacrylate, polypropylene oxide modified bisphenol A diacrylate, ethylene oxide modified isocyanuric acid diacrylate, pentaerythritol diacrylate monostearate, 1,6- Hexanediol jig Sidyl ether acrylic acid adduct, polyoxyethylene epichlorohydrin modified bisphenol A diacrylate, trimethylolpropane triacrylate, ethylene oxide modified trimethylolpropane triacrylate, polyethylene oxide modified trimethylolpropane triacrylate, propylene oxide modified trimethylolpropane tri Acrylate, polypropylene oxide modified trimethylolpropane triacrylate, pentaerythritol triacrylate, ethylene oxide modified isocyanuric acid triacrylate, ethylene oxide modified glycerol triacrylate, polyethylene oxide modified glycerol triacrylate, propylene oxide modified glycerol triacrylate, polypropylene oxide Glycerol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, caprolactone modified dipentaerythritol hexaacrylate, polycaprolactone modified dipentaerythritol hexaacrylate However, it is not limited to these.

  Further, as part or all of the combined active energy ray-curable unsaturated organic compound, an active energy ray-curable resin having a (meth) acryloyl group at the molecular chain terminal and having a molecular weight of about 400 to 5000 can be combined. . As such a curable resin, for example, polyurethane poly (meth) acrylate polymers such as polyurethane-modified polyether poly (meth) acrylate and polyurethane-modified polyester poly (meth) acrylate are preferably used.

  The foamable composition used in the present invention includes, if necessary, inorganic or organic fillers, dispersants such as various surfactants, reactive compounds such as polyvalent isocyanate compounds, epoxy compounds, and organometallic compounds, silicone oils. And processing aids, organic fillers as softeners, UV absorbers, fluorescent brighteners, antioxidants, light stabilizers, antifogging agents, antiblocking agents, lubricants, antistatic agents, antislip agents, colored dyes One or more kinds of other stabilizers may be added. The addition amount can be determined within a range that does not hinder the high light reflectance that is the object of the present invention.

Specific examples of the inorganic compound filler include pigments such as titanium oxide, magnesium oxide, aluminum oxide, calcium carbonate, calcium silicate, calcium sulfate, magnesium sulfate, barium sulfate, magnesium carbonate, aluminum hydroxide, clay, talc and silica. , Metal soap like zinc stearate, kaolin, silicate clay, diatomaceous earth, zinc oxide, silicon oxide, magnesium hydroxide, calcium oxide, magnesium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite etc. It is done. Among them, calcium carbonate, barium sulfate, titanium oxide, magnesium carbonate, alumina, magnesium hydroxide and the like are preferable as an auxiliary agent for further improving the light reflectance.
Examples of the organic compound filler include cellulose powder such as wood powder and pulp powder, and polymer beads. As the polymer beads, for example, those produced from acrylic resin, styrene resin or cellulose derivative, polyvinyl resin, polyvinyl chloride, polyester, polyurethane and polycarbonate, monomers for crosslinking, and the like can be used.
These fillers may be a mixture of two or more.

  Specific examples of the ultraviolet absorber are selected from salicylic acid-based, benzophenone-based, or benzotriazole-based ultraviolet absorbers. Examples of salicylic acid-based ultraviolet absorbers include phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate, and the like. Examples of the benzophenone ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone. Examples of the benzotriazole ultraviolet absorber include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-5'-t-butylphenyl) benzotriazole and the like.

  Specific examples of the antioxidant include monophenol-based, bisphenol-based, polymer-type phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.

  A typical example of the light stabilizer is a hindered amine compound.

Softeners can be used for the purpose of improving processability and moldability. Specifically, ester compounds, amide compounds, hydrocarbon polymers having side chains, mineral oils, liquid paraffins, waxes, etc. Is mentioned.
The ester compound is not particularly limited as long as it is a mono- or polyester having a structure comprising an alcohol and a carboxylic acid, and may be a compound in which the hydroxyl group and carbonyl group ends are left in the molecule, or a compound blocked in the form of an ester group. . Specifically, stearyl stearate, sorbitan tristearate, epoxy soybean oil, refined castor oil, hydrogenated castor oil, dehydrated castor oil, epoxy soybean oil, extremely hardened oil, trioctyl trimellitic acid, ethylene glycol dioctanoate, pentaerythritol tetra Examples include octanoate.
The amide compound is not particularly limited as long as it is a mono- or polyamide compound having a structure composed of an amine and a carboxylic acid, and may be a compound in which the amino group and carbonyl group ends are left in the molecule, or a compound blocked in the form of an amide group. Good. Specifically, stearic acid amide, behenic acid amide, hexamethylene bis stearic acid amide, trimethylene bisoctylic acid amide, hexamethylene bishydroxy stearic acid amide, triocta trimellitic acid amide, distearyl urea, butylene bis stearic acid Amides, xylylene bis stearic acid amides, distearyl adipic acid amides, distearyl phthalic acid amides, distearyl octadecadioic acid amides, epsilon caprolactam, and derivatives thereof.
The hydrocarbon polymer having a side chain is preferably a poly α-olefin and classified into a normal oligomer having a side chain having 4 or more carbon atoms. Specifically, ethylene-propylene copolymer and its maleic acid derivative, isobutylene polymer, butadiene, isoprene oligomer and hydrogenated product thereof, 1-hexene polymer, polystyrene polymer and the like are derived from these. Derivatives thereof, hydroxypolybutadiene and hydrogenated products thereof, and terminal hydroxypolybutadiene hydrogenated products.

  The foamable composition used in the present invention can be prepared using a general kneader. For example, two rolls, three rolls, cowless resolver, homomixer, sand grinder, planetary mixer, ball mill, kneader, high speed mixer, homogenizer, and the like. An ultrasonic disperser or the like can also be used.

Production of Light Reflector The shape / molding method of the light reflector containing the foamable composition of the present invention is not particularly limited, and may be any of a square block shape, a spherical shape, a rod shape, a curved surface shape, a sheet shape, and the like.
As a production example of a sheet / film-like light reflector, a method of coating a coating liquid containing a foamable composition on a support or a method of melt-molding into a film is useful. In these methods described below, a method of heating and foaming after irradiating active energy rays is exemplified, but if necessary, after heating in advance, the active energy rays may be irradiated and foamed. Irradiation may be performed simultaneously.
The method for coating on the support will be described in more detail. The support may be in the form of a rod, a plane, and / or a curved surface, and a coating solution containing a foamable composition is coated on the support to form a coating layer. Then, the coating layer is irradiated with active energy rays and further subjected to a heat treatment to form a foam structure in the coating layer. Thereby, a foamed resin layer is formed on the support. When the foamable composition does not have a film-forming property, a coating liquid containing a film-forming resin is used. When the decomposable foamable compound contained in the coating solution is a polymer compound, in the method of the present invention, this decomposable polymer compound reacts with an acid or base generated by irradiation with active energy rays in the heat treatment step. Then, the acid or base-decomposable group is decomposed to generate a bubble forming gas and form bubbles. In the coating solution, when the decomposable polymer compound is dissolved in the solvent, the solvent is removed from the coating solution layer by volatilization before irradiation with the active energy ray to solidify the coating solution layer. As the solvent at this time, for example, alcohols such as ethyl acetate, toluene, methyl ethyl ketone, ethanol, and / or water are preferably used. Further, the solid content concentration of the solvent-containing coating solution is preferably 10 to 50% by mass, and more preferably 20 to 30% by mass. When the concentration is 20 to 30% by mass, the viscosity of the coating solution is preferably 0.5 to 1 Pa · s (500 to 1000 cPs). When the decomposable foamable compound is a curable monomer compound for active energy ray irradiation, it is polymerized in the active energy ray irradiation step to form a polymer, and in the heating step, it reacts with an acid or base to react with the acid. Alternatively, the base decomposable group is decomposed to generate a bubble forming gas. At this time, the above solvent may be used in combination, if necessary, but generally, the use of a solvent is unnecessary because the curable monomer is a liquid.
Further, when the decomposable foamable compound is a monomer that is not polymerized and cured by irradiation with active energy rays, the decomposable foamable compound and a film-forming resin are mixed to form a foamable composition, and if necessary, the above solvent After the solvent is removed by volatilization and the film-forming resin is solidified, the coating liquid layer is irradiated with active energy rays to generate an acid or base, and further heated. Then, a non-polymer curable monomer is reacted with an acid or a base to generate a bubble forming gas, thereby forming a foamed structure therein.

  Moreover, the method of apply | coating a foaming composition containing coating liquid on a support body can use the casting method, a spin coat method, a direct coating method, etc. In addition, a method used for plastic molding such as a melt extrusion method or an injection method may be used. The former method is preferable in order to satisfy the demand for foam thinning. The thickness of the foamed resin layer is not particularly limited, but it can be reduced to 50 μm or less. It is preferable that it is more than a desired bubble diameter.

  Examples of the support include paper, synthetic paper, plastic resin, and metal. The shape of the support is not particularly limited, and examples thereof include a plate shape, a sheet shape, a film shape, and a spherical shape. These may be used alone, or more than these steps may be laminated together. Specific examples of the sheet-like support are made of plastic resin, polystyrene resin sheet, polyolefin resin sheet such as polyethylene, polypropylene and stretched polypropylene, polyester resin sheet such as polyethylene terephthalate, acrylic film, and polymethylpentene resin sheet. , Polyvinyl chloride resin sheet, polysulfone resin sheet, nylon sheet and the like. Moreover, aluminum, copper, etc. are mentioned as a metal which comprises a metal sheet. Furthermore, a component in the backlight unit may be used as a support, and can be provided as a light reflecting layer having a foam structure on the surface of the lamp holder.

  The foam may be used with the foamed resin layer formed on the support, or the foamed resin layer may be peeled from the support and used as a single foam sheet.

Active energy rays Examples of the active energy rays used in the present invention include ionizing radiation such as electron beams, ultraviolet rays, and γ rays. In these, it is preferable to use an electron beam and an ultraviolet-ray.

Electron beam irradiation When using electron beam irradiation, in order to obtain a sufficient transmission power, the acceleration voltage is 30 to 1000 kV, more preferably an electron beam accelerator of 30 to 300 kV, and the one-pass absorbed dose is 0.5 to 20 Mrad. Is preferably controlled (1 rad = 0.001 Gy). If the accelerating voltage or the electron beam irradiation dose is lower than the above range, the transmission power of the electron beam will be insufficient, and the inside of the coating liquid layer cannot be sufficiently transmitted. Not only is the efficiency deteriorated, the strength of the resulting cured coating layer may be insufficient, resulting in decomposition of the resin and additives contained therein, and the resulting foam quality may be unsatisfactory. As the electron beam accelerator, for example, any of an electro curtain system, a scanning type, a double scanning type, or the like may be used, but a curtain beam type electron beam accelerator that can obtain a large output at a relatively low cost is used. preferable. In this curtain beam type electron beam accelerator, the acceleration voltage is preferably 100 to 300 kV, and the absorbed dose is preferably controlled to 0.5 to 10 Mrad. Furthermore, in order to produce the foam stably and continuously, it is more preferable that the acceleration voltage is 120 to 250 kV and the absorbed dose is controlled to 2 to 9 Mrad.
In addition, when the oxygen concentration in the irradiation atmosphere is high during electron beam irradiation, generation of acid or base and / or hardening of the curable decomposable compound may be hindered. Substitution with an inert gas such as carbon dioxide is preferred. The oxygen concentration in the irradiation atmosphere is preferably 1000 ppm or less, and more preferably 500 ppm or less in order to obtain more stable electron beam energy.

In the case of ultraviolet irradiation, an ultraviolet lamp generally used in the semiconductor / photoresist field or the ultraviolet curing field can be used. Typical UV lamps include, for example, halogen lamps, halogen heater lamps, xenon short arc lamps, xenon flash lamps, ultra high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, medium pressure mercury lamps, deep UV lamps, metal halide lamps. There are noble gas fluorescent lamps, krypton arc lamps, excimer lamps, etc., and in recent years, there are also Y-ray lamps that emit an extremely short wavelength (peak at 214 nm). Some of these lamps are ozone-less types that generate less ozone. These ultraviolet rays may be scattered light or parallel light with high straightness.
For ultraviolet irradiation, various lasers such as ArF excimer laser, KrF excimer laser, YAG laser via a harmonic unit including a nonlinear optical crystal, and ultraviolet light emitting diodes can be used. The emission wavelength of the ultraviolet lamp, laser, or ultraviolet light emitting diode is not limited as long as it does not interfere with the foamability of the foamable composition. Preferably, the photoacid generator or the photobase generator is more efficient in acid or base efficiency. The emission wavelength that is often generated is good. That is, an emission wavelength that overlaps with the photosensitive wavelength region of the photoacid generator or photobase generator to be used is preferable. Furthermore, the light emission wavelength which overlaps the maximum absorption wavelength or the maximum absorption wavelength in the photosensitive wavelength region of these generators is more preferable, and the generation efficiency tends to increase. The energy irradiation intensity of ultraviolet rays is appropriately determined depending on the foamable composition. When using UV lamps with high irradiation intensity, such as various mercury lamps and metal halide lamps, productivity can be improved, and the irradiation intensity (lamp output) is 30 W / cm or more for long arc lamps. Is preferred. The integrated irradiation light quantity (J / cm ² ) of ultraviolet rays is obtained by adding the irradiation time to the energy irradiation intensity, and is appropriately determined depending on the foam composition and the desired bubble distribution. It may be set according to the extinction coefficient of the acid generator or base generator. For stable and continuous production, a range of 1.0 mJ / cm ^{2 to 20} J / cm ² is preferable. When using an ultraviolet lamp, the irradiation time can be shortened because the irradiation intensity is high. When using an excimer lamp or excimer laser, the irradiation intensity is weak, but it is close to a single light, so if the emission wavelength is optimized for the photosensitive wavelength of the generator, higher generation efficiency and foamability Is possible. When the amount of irradiation light is increased, heat generation may interfere with foaming properties depending on the ultraviolet lamp. At that time, a cooling treatment such as a cold mirror can be performed. As the irradiation method, any one of contact irradiation and projection irradiation can be adopted.

  Although there is no restriction | limiting in particular as a heater which can be used by heating foaming, What can be heated by induction heating, resistance heating, dielectric heating (and microwave heating), infrared heating, etc. can be illustrated. Examples include an electric or gas type infrared dryer using radiant heat, a roll heater using electromagnetic induction, an oil heater using an oil medium, an electric heater, and a hot air dryer using these hot air. In the case of dielectric heating and infrared heating, since the internal heating method directly heats the inside of the material, it is preferable to perform uniform heating instantaneously compared to an external heating method such as a hot air dryer. In the case of dielectric heating, high frequency energy with a frequency of 1 MHz to 300 MHz (wavelength 30 m to 1 m) is used. A frequency of 6 MHz to 40 MHz is often used. Among the dielectric heating, especially microwave heating uses microwaves with a frequency of 300 MHz to 300 GHz (wavelength 1 m to 1 mm), but 2450 MHz and 915 MHz (same as a microwave oven) are often used. In the case of infrared heating, an electromagnetic wave having a wavelength in the infrared region of 0.76 to 1000 μm is used. Although the optimum band of the wavelength selected varies depending on the situation from the surface temperature of the heater and the infrared absorption spectrum of the material to be heated, a wavelength band of preferably 1.5 to 25 μm, more preferably 2 to 15 μm can be used. Moreover, it can also heat, pressurizing like the heating press used at the time of press molding. The temperature used in the heating and foaming step can be appropriately determined depending on the desired foaming. In order to refine the bubbles, 50 to 200 ° C. is preferable.

The foam manufactured from the foam structure foamable composition has fine bubbles. There is no restriction on the internal structure characteristics such as the thickness of the foam, the average cell diameter, and the porosity (foaming ratio), and it can be controlled by the foaming conditions such as the irradiation energy amount of the active energy ray and the heat treatment temperature. The average cell diameter is generally preferably 0.005 to 10 μm in order to obtain a thin foam.
When the average cell diameter is smaller than 0.005 μm, the function as a foam may be difficult to be exhibited, and when it is larger than 10 μm, the smoothness of the surface of the foam may be insufficient.
Furthermore, in order to sufficiently exhibit the light reflection function in the visible light region, it is preferable that the average bubble diameter is 0.01 to 10 μm.
Furthermore, in order to obtain a foam having improved functions such as strength and heat insulation in a well-balanced manner, the average cell diameter is more preferably 0.01 to 5 μm.
The porosity is preferably 5% to 90%. If it is lower than 5%, sufficient light reflectance cannot be obtained, and if it is higher than 90%, the foam is greatly deformed, resulting in uneven light reflectance. In order to achieve a good balance between high light reflectivity and foam smoothness, 25% to 70% is more preferable.
The thickness of the light reflector is preferably 10 to 500 μm. If it is less than 10 μm, foaming may be insufficient, and if it exceeds 500 μm, the foamed internal structure may be uneven. In particular, the light reflector of the present invention can be thinned to 100 μm or less.

Light reflectivity The light reflectivity of the light reflector of the present invention is preferably 80% or more of the average light reflectivity for incident light in the wavelength range of 320 to 800 nm when used in a backlight unit of a liquid crystal display device or the like. .

Applications of the light reflector The light reflector of the present invention is used for backlight units of liquid crystal display devices, internally illuminated lighting fixtures, internally illuminated signboards, light boxes, projection screens, schaukasten, copying machines, projectors. It can be used as a light reflecting member of a device with a built-in light source selected from the group consisting of a type display, a facsimile, and an electronic blackboard. In particular, a backlight unit of a liquid crystal display device can be used as a light reflector that encloses a lamp holder in the backlight unit or a light reflector under a light guide plate.
Furthermore, it is possible to create a light reflection device using a light reflector. For example, the light reflection sheet of the present invention is incorporated in the lower part of the light guide plate, the light diffusion sheet is incorporated in the upper part, and the light source is incorporated in at least one side surface of the laminate in which the lens sheet is incorporated on the surface of the light diffusion sheet. A light reflecting device in which a light source is covered with a curved lamp holder can be manufactured.

Surface Treatment of Light Reflector The light reflector of the present invention can be surface treated or laminated. For example,
1. The light reflector of the present invention may be subjected to a surface treatment for eliminating the harmful effects of bright lines where the linear light source is locally bright. For example, black ink may be printed where bright lines are generated. Moreover, you may provide the easily bonding layer for making it easy to print in the light reflector surface.
2. The light reflector of the present invention may be subjected to surface treatment for preventing discoloration and deterioration due to the influence of heat and ultraviolet rays generated from the light source on the reflection surface. For example, a transparent resin layer containing an ultraviolet absorber may be provided. The light reflector of the present invention can be provided with a regular reflection layer such as a silver mirror or a white ink layer on the surface. Thereby, the light which may leak through the light reflector can be reflected by the regular reflection layer or the white ink, and the light reflection efficiency can be further increased.
3. The light reflector of the present invention can be provided with minute protrusions on the reflecting surface in order to reflect light uniformly.

  The present invention will be described in detail by the following examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” in the examples represent “parts by mass” and “mass%”, respectively.

<Example 1>
<Production of foam sheet>
(1) Formation of coating layer Bis (4-tert-butylphenyl) iodonium perfluorobutanesulfonate (trademark) as an iodonium salt-based acid generator with respect to 100 parts of poly (tert-butyl acrylate) used as a decomposable compound : BBI-109, manufactured by Midori Chemical Co., Ltd.) was mixed and dissolved in ethyl acetate to prepare a solution with a solid content of 25%, which was used as a coating solution. This coating solution was coated on one side of a support made of transparent polyethylene terephthalate (trademark: Lumirror 75-T60, manufactured by Panac) having a thickness of 75 μm using an applicator bar having a coating gap width of 300 μm. Immediately thereafter, the solvent was evaporated and removed by leaving it in a constant temperature dryer at a temperature of 80 ° C. for 10 minutes. A thin, colorless and transparent coating layer was formed on a polyethylene terephthalate support. The thickness of the coating layer was adjusted within the range of 40 to 50 μm.

(2) Electron beam irradiation The coating layer formed in the step (1) was irradiated with an electron beam under the conditions of an acceleration voltage of 175 kV, an absorbed dose of 16 Mrad, and an oxygen concentration of 500 ppm or less. The obtained coating layer remained colorless and transparent similarly to the coating layer after the step (1).

(3) Foaming by heat treatment The coating layer obtained by the step (2) could be foamed by leaving it in a thermostat kept at a temperature of 100 ° C. for 2 minutes and subjecting it to a heat treatment. At this time, the coating layer changed from colorless and transparent to white, and a foamed resin layer was formed. That is, a thin foamed resin layer having fine bubbles could be formed. The foamed resin layer had a thickness of 50 μm and was peeled from the support to obtain a single foam sheet.

<Evaluation of foam structure>
From the cross-sectional structure, the foam thickness and the average cell diameter were determined, and the foaming ratio was determined by measuring the density. The foam thickness was measured from cross-sectional images (magnification: 2500 times) before and after heating and foaming observed with the electron microscope (trademark: S-510, manufactured by Hitachi, Ltd.). The one obtained by freezing and cleaving and performing a gold vapor deposition treatment on the cross section of the obtained resin foam layer was used. For the bubble diameter, 100 bubbles were randomly selected from the observation image (magnification: 5000 times) of the cross section of the foamed resin layer, and the average of the diameters was selected. The foaming ratio is measured by the Archimedes method at room temperature, the density of foam (A), and the density (B) when the foam is dissolved in a solvent and re-formed to form an unfoamed state. Asked. Table 1 shows the obtained foam thickness, cell diameter, and expansion ratio.

<Evaluation of physical properties>
(1) Evaluation of reflection spectrum The light reflectance of the obtained foam was measured. Using a integrating sphere jig of spectrophotometer UV-3100PC manufactured by Shimadzu Corporation, the spectral reflectance at a wavelength of 550 nm was measured according to JIS-K7105 measurement method B, and a standard plate (barium sulfate plate) The relative reflectance% with respect to was determined. The results are shown in FIG. The unfoamed product was transparent and had a reflectance of zero, but it was whitened by fine foaming, and even a thin film of about 50 μm showed a high reflectance of 80% or more.
(2) Film forming strength The case where the folded portion of the foam was bent 90 degrees was evaluated as “◯” when the fold was not formed, and “X” when the fold was broken or fragile.

<Example 2>
In the same manner as in Example 1, a thin-film foam sheet having fine bubbles was produced. However, a copolymer of tert-butyl acrylate (60% by mass) and methyl methacrylate (40% by mass) instead of poly (tert-butyl acrylate) used as the decomposable compound in the step (1) of Example 1. Was used. In step (3), heating was performed at 110 ° C. for 2 minutes instead of heating at 100 ° C. for 2 minutes. The test results are shown in Table 1. It was whitened by fine foaming, and even a thin film showed high reflectance.

<Example 3>
In the same manner as in Example 2, a thin-film foam sheet having fine bubbles was produced. However, in the process (2) of Example 1, ultraviolet rays were used instead of the electron beams used as active energy rays. This ultraviolet ray was irradiated using an ultraviolet curing device (manufactured by Eye Graphics) having a 120 W / cm long arc lamp type high-pressure mercury lamp so that the irradiation dose was 1100 mJ / cm ² . The test results are shown in Table 1. It was whitened by fine foaming, and even a thin film showed high reflectance.

<Example 4>
In the same manner as in Example 1, a thin-film foam sheet having fine bubbles was produced. However, tert-butyl acrylate (20% by mass), tert-butyl methacrylate (37% by mass) and methyl instead of poly (tert-butyl acrylate) used as the decomposable compound in step (1) of Example 1 A copolymer of methacrylate (43% by mass) was used. Moreover, in the process (2) of Example 1, ultraviolet rays were used instead of the electron beams used as active energy rays. This ultraviolet ray was irradiated using an ultraviolet ray irradiation apparatus (manufactured by USHIO INC.) Having a Y-ray lamp (peak wavelength: 214 nm) so that the irradiation dose was 3000 mJ / cm ² . The test results are shown in Table 1. It was whitened by fine foaming, and even a thin film showed high reflectance.

<Comparative Example 1>
The same operation as in Example 1 was performed. However, instead of poly (tert-butyl acrylate) used as the decomposable compound in the step (1) of Example 1, polyethylene that is not a decomposable compound was used, and 100 parts of this polyethylene was subjected to an iodonium salt acid. A kneaded mixture of 3 parts of bis (4-tert-butylphenyl) iodonium perfluorobutanesulfonate (trademark: BBI-109, manufactured by Midori Chemical) was used as a coating solution. However, no foam sheet was obtained, and no light reflectance was obtained. The test results are shown in Table 1.

<Comparative Example 2>
100 parts of a PET-based resin was impregnated with 10 parts of carbon dioxide as a foaming agent under a pressure of 5.5 MPa for 10 hours and extruded into a sheet shape so as to have a thickness of 50 μm. Thereafter, heating was performed at 150 ° C. under normal pressure for 0.5 minutes, but a foam sheet could not be prepared, and there was almost no reflectivity. The test results are shown in Table 1.

<Comparative Example 3>
70 parts of precipitated barium sulfate and 3 parts of hardened castor oil were mixed with 30 parts of PP resin and uniaxially stretched and foamed so that the thickness of the foam sheet was 50 μm. Foaming was insufficient and sufficient light reflectance could not be obtained. The reflectance is shown in Table 1 as a test result.

<Comparative example 4>
A foamed film was prepared by applying a coating material in which 50 parts of hollow particles and 10 parts of polyvinyl alcohol were mixed with 100 parts of an acrylate copolymer on one side of a support made of transparent polyethylene terephthalate to a thickness of 50 μm. Obtained. However, the film formability was poor and the reflectivity was not sufficient. The test results are shown in Table 1.

In Examples 1 to 3 using a combination of an acid generator and an acrylate-based decomposable compound having a tert-butyl group, even when the thickness is reduced to 50 μm, the light reflectance is as high as 80% or more. I was able to create a body.
On the other hand, in Comparative Example 1 using polyethylene which is not a degradable compound and in Comparative Example 2 in which an inert gas was impregnated and saturated in a PET resin, a foam was not obtained and the light reflectance was not obtained. Moreover, although the comparative example 3 and the foam which extended | stretched the polypropylene containing an inorganic pigment were obtained, the film-forming intensity | strength was bad and the light reflectivity was not enough in the comparative example 4 which contained the hollow particle in resin.

Claims (10)

Decomposing foam that contains an acid generator that generates an acid by the action of active energy rays or a base generator that generates a base, and further decomposes and desorbs one or more low-boiling volatile substances by reacting with the acid or base. A light reflector produced by foaming a foamable composition containing a decomposable foamable compound having a functional functional group. The light reflector according to claim 1, wherein the light reflector has fine bubbles, and the average bubble diameter is 0.005 to 10 μm. The light reflector according to claim 1 or 2, wherein the light reflector has fine bubbles, and the bubble ratio is 5% to 90%. The light reflector according to any one of claims 1 to 3, wherein the thickness of the light reflector is 10 to 500 µm. The light reflector according to any one of claims 1 to 4, wherein an average light reflectance with respect to incident light in a wavelength range of 320 to 800 nm is 80% or more. The light reflector according to any one of claims 1 to 5, wherein the light reflector is produced from a coating layer in which a foamable composition is coated on a planar and / or curved support. . Light source selected from the group consisting of a backlight unit of a liquid crystal display device, an internally illuminated lighting fixture, an internally illuminated electric signboard, a light box, a projection screen, a Schaukasten, a copying machine, a projector-type display, a facsimile, and an electronic blackboard The light reflector according to claim 1, which can be used as a light reflecting member of a built-in device. The light reflector according to claim 1, which can be used as a light reflector forming a lamp holder constituting a backlight unit of a liquid crystal display device. The light reflector in any one of Claims 1-6 which can be used as a light reflector under the light-guide plate which comprises the backlight unit of a liquid crystal display device. A light source 1 is incorporated into at least one side of a laminate in which a light reflecting sheet is incorporated on one side of the light guide plate, a light diffusion sheet is incorporated on the other side, and a lens sheet is incorporated on the surface of the light diffusion sheet. In a light reflecting device covered with a curved lamp holder, the light reflector according to any one of claims 1 to 6 is used as a light reflecting sheet on one side of the lamp holder and the light guide plate. Characteristic light reflecting device.