JP5496024B2 - Foam diffuse reflector - Google Patents

Description

  The present invention relates to a foamed diffuse reflector. In detail, it is related with the novel foaming diffused reflection body which can express the outstanding diffuse reflection performance with the special foam surface structure formed by including specific resin.

  The diffuse reflector is provided in a lighting device such as a backlight device of a liquid crystal display device, a fluorescent lamp, an incandescent lamp, and an LED, thereby exhibiting diffuse reflection performance.

  Usually, the diffuse reflector is required to have high diffuse reflection performance.

  As a diffuse reflector with high diffuse reflection performance, the film contains a diffuse reflector formed by depositing a metal vapor-deposited film on the surface of a substrate such as metal to form a metal mirror surface, or a pigment or fine particles that enhance light scattering. Diffuse reflectors are known. However, the diffuse reflector formed with the metal mirror surface has a problem that the light scattering performance is low although the light reflecting performance is high. In addition, a diffuse reflector in which a film containing pigments and fine particles that enhance light scattering properties needs to increase the amount of pigments and fine particles added in order to suppress the leakage of light to the back side, There is a problem in that the loss due to light absorption cannot be ignored and the light reflection performance decreases as the amount of pigment or fine particles added increases.

  Recently, a polyester foam containing fine bubbles has been reported as a new diffuse reflector (see, for example, Patent Documents 1 and 2). This diffuse reflector utilizes the property that light is diffusely reflected by a large number of fine bubbles.

  However, the polyester foam reported in Patent Document 1 has fine bubbles arranged inside the polyester foam and has an unfoamed skin layer near both surfaces. For this reason, there is a problem that fine bubbles do not exist in the vicinity of both surfaces, and sufficient diffuse reflection performance cannot be exhibited.

  Moreover, also about the polyester foam reported by patent document 2, the polyester foam which has an unfoamed skin layer in the surface vicinity of both surfaces is obtained first in the manufacture stage. In Patent Document 2, in order to obtain a polyester foam in which fine bubbles are present near the surface, a cut surface perpendicular to the thickness direction is formed on the polyester foam having an unfoamed skin layer near both surfaces. So that it is cut. By this operation, a polyester foam in which fine bubbles are present in the vicinity of one of the two surfaces is obtained. However, in Patent Document 2, in order to obtain a polyester foam in which fine bubbles are present in the vicinity of the surface, a post-treatment called cutting for forming a cut surface is essential. In addition, since the polyester foam having an unfoamed skin layer in the vicinity of both surfaces is cut so that a cut surface perpendicular to the thickness direction is formed, the resulting polyester foam is still on one surface. There is a problem that an unfoamed skin layer remains. Furthermore, Patent Document 2 uses a supercritical fluid foaming method under high pressure in order to form fine bubbles inside the polyester foam, and there is a problem that the cell structure cannot be precisely controlled. There is a problem that the bubble rate is not sufficient, and a problem that the capital investment of the foaming method is large. In addition, there is a problem that the diffuse reflection performance is not sufficient.

Japanese Patent Application Laid-Open No. 9-1117 JP 2009-244749

  An object of the present invention is a foamed diffuse reflector having a cell structure, the cell structure is precisely controlled, the cell rate is high, and has a large number of finely controlled surface openings. Mechanical post-processing such as supercritical fluid foaming method and difficult to control during manufacturing, such as supercritical fluid foaming method, which can express very good diffuse reflection performance, has excellent flexibility and heat resistance It is an object of the present invention to provide a novel foaming diffused reflector that does not require the above.

The foamed diffuse reflector of the present invention is
Including a foam containing a hydrophilic polyurethane-based polymer;
The surface of the foam has a surface opening having an average pore diameter of 20 μm or less,
The diffuse reflectance in the wavelength region of 400 nm to 500 nm is 90% or more.

  In a preferred embodiment, the foamed diffuse reflector of the present invention has a diffuse reflectance of 90% or more in a wavelength region of 400 nm to 700 nm.

  In a preferred embodiment, the foamed diffuse reflector of the present invention has an open cell structure having through holes between adjacent spherical cells.

  In a preferred embodiment, the average pore diameter of the spherical bubbles is less than 20 μm.

  In preferable embodiment, the average hole diameter of the said through-hole is 5 micrometers or less.

In a preferred embodiment, the foam has a density in the ^{0.15g / cm 3 ~0.5g / cm 3} .

In a preferred embodiment, the foamed diffuse reflector of the present invention has a 50% compression load of 300 N / cm ² or less.

  In a preferred embodiment, the foamed diffuse reflector of the present invention has a dimensional change rate of less than ± 5% when stored at 125 ° C. for 22 hours.

  In a preferred embodiment, the foam ratio of the foam is 30% or more.

  According to the present invention, the foam diffuse reflector having a cell structure, the cell structure is precisely controlled, the cell rate is high, and has a number of fine surface openings that are precisely controlled, Mechanical post-processing such as supercritical fluid foaming method and difficult to control during manufacturing, such as supercritical fluid foaming method, which can express very good diffuse reflection performance, has excellent flexibility and heat resistance Thus, it is possible to provide a novel foaming diffused reflector that does not require the above.

It is a schematic sectional drawing which shows preferable embodiment of the foaming diffused reflection body of this invention. It is a schematic sectional drawing which shows another preferable embodiment of the foaming diffused reflection body of this invention. It is a photograph figure of the surface / cross-section SEM photograph which image | photographed the foaming diffused reflection body produced in Example 1 from diagonally. It is a photograph figure of a section SEM photograph of a foaming diffused reflector of the present invention, and is a photograph figure clearly showing open cell structure which has a penetration hole between adjacent spherical bubbles. It is a chart figure which shows the measurement result of the diffuse reflectance of the foaming diffused reflection body of this invention.

≪ << A. Foam diffuse reflector >>>>
The foaming diffused reflection body of this invention contains the foam containing a hydrophilic polyurethane type polymer, and has a surface opening part with an average hole diameter of 20 micrometers or less on the surface of this foam. The foam contained in the foamed diffuse reflector of the present invention preferably has an open cell structure having through holes between adjacent spherical cells. Typical structures include a foam diffuse reflector 100 (FIG. 1) made of the foam 10, and a foam diffuse reflector 100 (FIG. 2) including a base material 20 (described later) between the foam 10a and the foam 10b. ). In FIG. 1 and FIG. 2, the release film 30 is provided for protecting the surface of the foaming diffuse reflector, but the release film may not be provided.

  In the present specification, the “spherical bubble” does not have to be a strict true spherical bubble, and may be, for example, a substantially spherical bubble having a partial strain or a bubble composed of a space having a large strain. .

  The average pore diameter of the spherical bubbles that the foam contained in the foamed diffuse reflector of the present invention may have is preferably less than 20 μm, more preferably 15 μm or less, and even more preferably 10 μm or less. The lower limit value of the average pore diameter of the spherical bubbles of the foam contained in the foamed diffuse reflector of the present invention is not particularly limited. For example, it is preferably 0.01 μm, more preferably 0.1 μm, and still more preferably. 1 μm. When the average pore diameter of the spherical bubbles contained in the foamed diffuse reflector of the present invention falls within the above range, the average pore diameter of the spherical bubbles of the foam contained in the foamed diffuse reflector of the present invention is precisely reduced. A novel foamed diffuse reflector that can be controlled and is excellent in flexibility and heat resistance can be provided.

Density of the foam contained in the foam diffuse reflector of the present invention is preferably ^{0.15g / cm 3 ~0.6g / cm 3} , more preferably 0.15g ^/ cm ³ ~0.5g ^/ cm 3 , and still more preferably from ^{0.15g / cm 3 ~0.45g / cm 3} , particularly preferably from ^{0.15g / cm 3 ~0.4g / cm 3} . When the density of the foam contained in the foamed diffuse reflector of the present invention falls within the above range, the density range of the foam contained in the foamed diffused reflector of the present invention is widely controlled, and the flexibility and heat resistance It is possible to provide a novel foaming diffused reflector having excellent properties.

  The foam contained in the foamed diffuse reflector of the present invention preferably has an open cell structure having through holes between adjacent spherical bubbles. This open cell structure may be an open cell structure having through holes between most or all adjacent spherical cells, or may be a semi-independent semi-open cell structure having a relatively small number of through holes. .

  The through-hole which has between adjacent spherical bubbles influences the physical property of a foaming diffused reflection body. For example, the strength of the foamed diffuse reflector tends to increase as the average hole diameter of the through holes decreases. FIG. 4 is a photographic view of a cross-sectional SEM photograph of the foamed diffuse reflector of the present invention, and a photographic view clearly showing an open cell structure having through holes between adjacent spherical bubbles.

  The average pore diameter of the through holes between adjacent spherical bubbles is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. The lower limit value of the average pore diameter of the through holes between adjacent spherical bubbles is not particularly limited, and is preferably 0.001 μm, and more preferably 0.01 μm, for example. When the average pore diameter of the through holes between adjacent spherical bubbles is within the above range, a novel foamed diffuse reflector having excellent flexibility and heat resistance can be provided.

  The foamed diffuse reflector of the present invention has a surface opening on the surface. The average pore diameter of the surface opening is 20 μm or less, preferably less than 20 μm, more preferably 15 μm or less, further preferably 10 μm or less, further preferably 5 μm or less, and particularly preferably 4 μm or less. And most preferably 3 μm or less. The lower limit of the average pore diameter of the surface opening is not particularly limited, and is preferably 0.001 μm, and more preferably 0.01 μm, for example. When the foamed diffuse reflector of the present invention has a surface opening and the average pore diameter of the surface opening is within the above range, very excellent diffuse reflection performance can be exhibited.

The foamed diffuse reflector of the present invention has a 50% compression load of preferably 300 N / cm ² or less, more preferably 200 N / cm ² or less, still more preferably 150 N / cm ² or less, and particularly preferably. 100 N / cm ² or less, and most preferably 50 N / cm ² or less. When the 50% compressive load of the foamed diffuse reflector of the present invention falls within the above range, the foamed diffuse reflector of the present invention can exhibit excellent flexibility.

  In the foamed diffuse reflector of the present invention, the dimensional change rate when stored at 125 ° C. for 22 hours is preferably less than ± 5%, more preferably ± 3% or less, and further preferably ± 1% or less. is there. In the foamed diffuse reflector of the present invention, the dimensional change rate when stored at 125 ° C. for 22 hours is within the above range, whereby the foamed diffuse reflector of the present invention can have excellent heat resistance.

  The foam contained in the foamed diffuse reflector of the present invention has a cell ratio of preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. In the foamed diffuse reflector of the present invention, the foam ratio falls within the above range, so that the foam diffuse reflector of the present invention can exhibit very excellent diffuse reflective performance, and has excellent flexibility and excellent heat resistance. be able to.

  The foamed diffuse reflector of the present invention can exhibit very excellent diffuse reflection performance.

  The foaming diffuse reflector of the present invention has a diffuse reflectance of 90% or more in the wavelength region of 400 nm to 500 nm, preferably 95% or more, more preferably 400 nm to 500 nm. The diffuse reflectance in the wavelength region of 500 nm is 98% or more, particularly preferably the diffuse reflectance in the wavelength region of 400 nm to 500 nm is 99% or more, and most preferably the diffuse reflectance in the wavelength region of 400 nm to 500 nm is 99%. .5% or more.

  The foamed diffuse reflector of the present invention has a diffuse reflectance of 90% or more in the wavelength range of 400 nm to 700 nm, preferably 95% or more in the wavelength range of 400 nm to 700 nm, more preferably 400 nm to The diffuse reflectance in the wavelength region of 700 nm is 98% or more, particularly preferably the diffuse reflectance in the wavelength region of 400 nm to 700 nm is 99% or more, and most preferably the diffuse reflectance in the wavelength region of 400 nm to 700 nm is 99%. .5% or more.

  The foam contained in the foamed diffuse reflector of the present invention contains a hydrophilic polyurethane polymer. Since the foam contained in the foamed diffuse reflector of the present invention contains a hydrophilic polyurethane polymer, the cell structure is precisely controlled, the cell rate is high, and a large number of fine surface openings controlled precisely. It is possible to provide a novel foamed diffuse reflector that has a portion, can exhibit very excellent diffuse reflection performance, and has excellent flexibility and excellent heat resistance.

  The details of the foam contained in the foamed diffuse reflector of the present invention and the details of the hydrophilic polyurethane polymer contained therein will be mentioned in the description of the production method described later.

  The foaming diffuse reflector of this invention can take arbitrary appropriate shapes. In the foamed diffuse reflector of the present invention, the thickness, the long side, the short side and the like can take any appropriate value.

  The foaming diffused reflection body of this invention may contain arbitrary appropriate base materials in the range which does not impair the effect of this invention. Examples of the form in which the base material is contained in the foamed diffuse reflector of the present invention include a form in which a base layer is provided inside the foamed diffuse reflector. Examples of such a substrate include fiber woven fabric, fiber nonwoven fabric, fiber laminated fabric, fiber knitted fabric, resin sheet, metal foil film sheet, and inorganic fiber.

  As the fiber woven fabric, a woven fabric formed of any appropriate fiber can be adopted. Examples of such fibers include natural fibers such as plant fibers, animal fibers, and mineral fibers; artificial fibers such as regenerated fibers, synthetic fibers, semi-synthetic fibers, and artificial inorganic fibers. Examples of synthetic fibers include fibers obtained by melt spinning thermoplastic fibers. Further, the fiber woven fabric may be metallic processed by plating or sputtering.

  As a fiber nonwoven fabric, the nonwoven fabric formed from arbitrary appropriate fibers can be employ | adopted. Examples of such fibers include natural fibers such as plant fibers, animal fibers, and mineral fibers; artificial fibers such as regenerated fibers, synthetic fibers, semi-synthetic fibers, and artificial inorganic fibers. Examples of synthetic fibers include fibers obtained by melt spinning thermoplastic fibers. Moreover, the fiber nonwoven fabric may be metallic-processed by plating, sputtering, etc. More specifically, for example, a spunbond nonwoven fabric can be mentioned.

  As the fiber laminated fabric, a laminated fabric formed of any appropriate fiber can be adopted. Examples of such fibers include natural fibers such as plant fibers, animal fibers, and mineral fibers; artificial fibers such as regenerated fibers, synthetic fibers, semi-synthetic fibers, and artificial inorganic fibers. Examples of synthetic fibers include fibers obtained by melt spinning thermoplastic fibers. In addition, the fiber laminated fabric may be metallic processed by plating, sputtering, or the like. More specifically, for example, a polyester fiber laminated fabric can be mentioned.

  As a fiber knitted fabric, the knitted fabric formed from arbitrary appropriate fibers can be employ | adopted, for example. Examples of such fibers include natural fibers such as plant fibers, animal fibers, and mineral fibers; artificial fibers such as regenerated fibers, synthetic fibers, semi-synthetic fibers, and artificial inorganic fibers. Examples of synthetic fibers include fibers obtained by melt spinning thermoplastic fibers. Further, the fiber knitted fabric may be metallically processed by plating or sputtering.

  As the resin sheet, a sheet formed of any appropriate resin can be adopted. An example of such a resin is a thermoplastic resin. The resin sheet may be metallic processed by plating or sputtering.

  As the metal foil film sheet, a sheet formed from any appropriate metal foil film can be adopted.

  Any appropriate inorganic fiber can be adopted as the inorganic fiber. Specific examples of such inorganic fibers include glass fibers, metal fibers, and carbon fibers.

  In the foamed diffuse reflector of the present invention, when voids are present in the substrate, the same material as the foamed diffuse reflector may be present in part or all of the voids.

  Only 1 type may be used for a base material and it may use 2 or more types together.

≪≪B. Manufacturing method of foamed diffuse reflector >>>>
The foaming diffuse reflector of this invention can be manufactured by arbitrary appropriate methods. The foamed diffuse reflector of the present invention can be preferably produced by shaping and polymerizing a W / O emulsion.

  As a method for producing the foamed diffuse reflector of the present invention, for example, a W / O type that can be used to continuously supply a continuous oil phase component and an aqueous phase component to an emulsifier to obtain the foamed diffuse reflector of the present invention. There is a “continuous method” in which an emulsion is prepared, and then the obtained W / O emulsion is polymerized to produce a water-containing polymer, and then the obtained water-containing polymer is dehydrated. As a method for producing the foamed diffuse reflector of the present invention, for example, an appropriate amount of an aqueous phase component is charged into an emulsifier with respect to the continuous oil phase component, and the aqueous phase component is continuously supplied while stirring. A W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention is prepared, and the resulting W / O emulsion is polymerized to produce a hydrous polymer, followed by the hydrous weight obtained. A “batch method” in which the coalescence is dehydrated can be mentioned.

  The continuous polymerization method in which the W / O emulsion is continuously polymerized is a preferable method because the production efficiency is high and the effect of shortening the polymerization time and the shortening of the polymerization apparatus can be most effectively utilized.

More specifically, the foamed diffuse reflector of the present invention is preferably
Step (I) of preparing a W / O type emulsion that can be used to obtain the foamed diffuse reflector of the present invention;
Step (II) of shaping the obtained W / O emulsion,
Polymerizing the shaped W / O emulsion (III);
Step (IV) of dehydrating the obtained hydrous polymer;
It can manufacture with the manufacturing method containing. Here, at least a part of the step (II) for shaping the obtained W / O emulsion and the step (III) for polymerizing the shaped W / O emulsion may be performed simultaneously.

<< B-1. Step for preparing W / O type emulsion (I) >>
The W / O type emulsion that can be used to obtain the foamed diffuse reflector of the present invention is a W / O type emulsion containing a continuous oil phase component and an aqueous phase component immiscible with the continuous oil phase component. More specifically, the W / O type emulsion is obtained by dispersing an aqueous phase component in a continuous oil phase component.

  The ratio of the water phase component to the continuous oil phase component in the W / O type emulsion that can be used to obtain the foamed diffuse reflector of the present invention is any suitable ratio within a range in which the W / O type emulsion can be formed. It can be taken. The ratio of the water phase component and the continuous oil phase component in the W / O type emulsion that can be used to obtain the foamed diffuse reflector of the present invention is the structural ratio of the foam obtained by polymerization of the W / O type emulsion. It can be an important factor in determining mechanical and performance characteristics. Specifically, the ratio of the water phase component to the continuous oil phase component in the W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention is the foam obtained by polymerization of the W / O emulsion. It can be an important factor in determining the body density, bubble size, bubble structure, and dimensions of the wall forming the porous structure.

  The ratio of the aqueous phase component in the W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention is preferably 30% by weight, more preferably 40% by weight, and still more preferably as the lower limit. Is 50% by weight, particularly preferably 55% by weight, and the upper limit is preferably 95% by weight, more preferably 90% by weight, still more preferably 85% by weight, and particularly preferably 80% by weight. % By weight. If the ratio of the aqueous phase component in the W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention is within the above range, the effects of the present invention can be sufficiently exhibited.

  The W / O emulsion that can be used for obtaining the foamed diffuse reflector of the present invention may contain any appropriate additive as long as the effects of the present invention are not impaired. Examples of such additives include tackifying resins; talc; calcium carbonate, magnesium carbonate, silicic acid and salts thereof, clay, mica powder, aluminum hydroxide, magnesium hydroxide, zinc white, bentonine, carbon black, Examples thereof include fillers such as silica, alumina, aluminum silicate, acetylene black, and aluminum powder; pigments; dyes; Only one kind of such an additive may be contained, or two or more kinds thereof may be contained.

  Any appropriate method can be adopted as a method for producing a W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention. As a method for producing a W / O type emulsion that can be used for obtaining the foamed diffuse reflector of the present invention, for example, a continuous oil phase component and an aqueous phase component are continuously supplied to an emulsifier to obtain a W / O type. A W / O type emulsion can be obtained by adding an appropriate amount of aqueous phase component to the continuous oil phase component in an emulsion machine and supplying the aqueous phase component continuously with stirring. Examples include “batch method” to be formed.

  When producing a W / O type emulsion that can be used to obtain the foamed diffuse reflector of the present invention, as a shearing means for obtaining an emulsion state, for example, a rotor stator mixer, a homogenizer, a microfluidizer or the like was used. Application of high shear conditions. In addition, as another shearing means for obtaining an emulsion state, for example, gentle mixing of continuous and dispersed phases by application of low shear conditions using a moving blade mixer or a pin mixer, low stirring conditions using a magnetic stir bar, etc. Can be mentioned.

  Examples of the apparatus for preparing the W / O emulsion by the “continuous method” include a static mixer, a rotor stator mixer, and a pin mixer. More intense agitation may be achieved by increasing the agitation speed or by using an apparatus designed to finely disperse the aqueous phase component in the W / O emulsion by a mixing method.

  Examples of the apparatus for preparing the W / O type emulsion by the “batch method” include manual mixing and shaking, a driven blade mixer, and three propeller mixing blades.

  Arbitrary appropriate methods can be employ | adopted as a method of preparing a continuous oil phase component. As a method for preparing the continuous oil phase component, typically, for example, a mixed syrup containing a hydrophilic polyurethane-based polymer and an ethylenically unsaturated monomer is prepared, and subsequently, a polymerization initiator, It is preferable to prepare a continuous oil phase component by blending a crosslinking agent and any other appropriate components.

  Any appropriate method can be adopted as a method of preparing the hydrophilic polyurethane-based polymer. A typical method for preparing a hydrophilic polyurethane-based polymer is, for example, by reacting polyoxyethylene polyoxypropylene glycol and a diisocyanate compound in the presence of a urethane reaction catalyst.

<B-1-1. Water phase component>
The aqueous phase component can be any aqueous fluid that is substantially immiscible with the continuous oil phase component. From the viewpoint of ease of handling and low cost, water such as ion-exchanged water is preferable.

  Any appropriate additive may be contained in the aqueous phase component as long as the effects of the present invention are not impaired. Examples of such additives include polymerization initiators and water-soluble salts. The water-soluble salt can be an effective additive for further stabilizing the W / O emulsion. Examples of such water-soluble salts include sodium carbonate, calcium carbonate, potassium carbonate, sodium phosphate, calcium phosphate, potassium phosphate, sodium chloride, potassium chloride and the like. Only one kind of such an additive may be contained, or two or more kinds thereof may be contained. The additive that can be contained in the aqueous phase component may be only one kind or two or more kinds.

<B-1-2. Continuous oil phase component>
The continuous oil phase component preferably contains a hydrophilic polyurethane polymer and an ethylenically unsaturated monomer. The content ratio of the hydrophilic polyurethane polymer and the ethylenically unsaturated monomer in the continuous oil phase component can take any appropriate content ratio as long as the effects of the present invention are not impaired.

  The hydrophilic polyurethane-based polymer depends on the polyoxyethylene ratio in the polyoxyethylene polyoxypropylene glycol unit constituting the hydrophilic polyurethane-based polymer or the amount of the aqueous phase component to be blended. The hydrophilic polyurethane polymer is in the range of 10 to 30 parts by weight with respect to 70 to 90 parts by weight of the ethylenically unsaturated monomer, and more preferably hydrophilic to 75 to 90 parts by weight of the ethylenically unsaturated monomer. The polyurethane polymer is in the range of 10 to 25 parts by weight. Further, for example, the hydrophilic polyurethane polymer is preferably in the range of 1 to 30 parts by weight, more preferably 1 to 25 parts by weight of the hydrophilic polyurethane polymer with respect to 100 parts by weight of the aqueous phase component. It is a range. If the content ratio of the hydrophilic polyurethane polymer is within the above range, the effects of the present invention can be sufficiently exhibited.

(B-1-2-1. Hydrophilic polyurethane polymer)
The hydrophilic polyurethane-based polymer preferably contains a polyoxyethylene polyoxypropylene unit derived from polyoxyethylene polyoxypropylene glycol, and 5 wt% to 25 wt% in the polyoxyethylene polyoxypropylene unit is polyoxyethylene. Ethylene.

  The content ratio of polyoxyethylene in the polyoxyethylene polyoxypropylene unit is preferably 5% by weight to 25% by weight as described above, and is more preferably 10% by weight as the lower limit, and the upper limit. More preferably, it is 25% by weight, and more preferably 20% by weight. The polyoxyethylene in the polyoxyethylene polyoxypropylene unit exhibits an effect of stably dispersing the aqueous phase component in the continuous oil phase component. When the content of polyoxyethylene in the polyoxyethylene polyoxypropylene unit is less than 5% by weight, it may be difficult to stably disperse the water phase component in the continuous oil phase component. If the polyoxyethylene content in the polyoxyethylene polyoxypropylene unit exceeds 25% by weight, there is a risk of phase inversion from a W / O type emulsion to an O / W type (oil-in-water type) emulsion as it approaches the HIPE condition. There is.

  A conventional hydrophilic polyurethane polymer can be obtained by reacting a diisocyanate compound with a hydrophobic long-chain diol, polyoxyethylene glycol and derivatives thereof, and a low molecular active hydrogen compound (chain extender). Since the number of polyoxyethylene groups contained in the hydrophilic polyurethane polymer obtained in 1) is uneven, the emulsion stability of such a W / O emulsion containing such a hydrophilic polyurethane polymer may be reduced. There is. On the other hand, the hydrophilic polyurethane-based polymer contained in the continuous oil phase component of the W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention has a characteristic structure as described above. When included in the continuous oil phase component of the / O type emulsion, excellent emulsifiability and excellent stationary storage stability can be expressed without positively adding an emulsifier or the like.

  The hydrophilic polyurethane-based polymer is preferably obtained by reacting polyoxyethylene polyoxypropylene glycol and a diisocyanate compound. In this case, the ratio between the polyoxyethylene polyoxypropylene glycol and the diisocyanate compound is NCO / OH (equivalent ratio), and the lower limit is preferably 1, more preferably 1.2, and still more preferably 1. .4, particularly preferably 1.6, and the upper limit is preferably 3, more preferably 2.5, and even more preferably 2. When NCO / OH (equivalent ratio) is less than 1, a gelled product may be easily formed when a hydrophilic polyurethane polymer is produced. When NCO / OH (equivalent ratio) exceeds 3, the residual diisocyanate compound increases, and the W / O emulsion that can be used to obtain the foamed diffuse reflector of the present invention may become unstable.

  As polyoxyethylene polyoxypropylene glycol, for example, polyether polyol (ADEKA (registered trademark) Pluronic L-31, L-61, L-71, L-101, L-121, L-42 manufactured by ADEKA Corporation) , L-62, L-72, L-122, 25R-1, 25R-2, 17R-2) and polyoxyethylene polyoxypropylene glycol (Pronon (registered trademark) 052, 102, manufactured by NOF Corporation. 202). As for polyoxyethylene polyoxypropylene glycol, only 1 type may be used and 2 or more types may be used together.

  Examples of the diisocyanate compound include aromatic, aliphatic, and alicyclic diisocyanates, dimers and trimers of these diisocyanates, polyphenylmethane polyisocyanate, and the like. Aromatic, aliphatic, and alicyclic diisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate. 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, butane-1,4-diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4 -Diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, methyl Cyclohexane diisocyanate, m- tetramethylxylylene diisocyanate. Examples of the diisocyanate trimer include isocyanurate type, burette type, and allophanate type. Only 1 type may be used for a diisocyanate compound and it may use 2 or more types together.

  The diisocyanate compound may be selected as appropriate from the viewpoint of urethane reactivity with the polyol and the like, as well as the type and combination thereof. From the viewpoint of rapid urethane reactivity with polyol and suppression of reaction with water, it is preferable to use alicyclic diisocyanate.

  The weight average molecular weight of the hydrophilic polyurethane polymer is preferably 5000 as a lower limit, more preferably 7000, still more preferably 8000, particularly preferably 10,000, and preferably 50,000 as an upper limit. More preferably, it is 40000, more preferably 30000, and particularly preferably 20000.

  The hydrophilic polyurethane polymer may have an unsaturated double bond capable of radical polymerization at the terminal. By having an unsaturated double bond capable of radical polymerization at the terminal of the hydrophilic polyurethane-based polymer, the effects of the present invention can be further exhibited.

(B-1-2-2. Ethylenically unsaturated monomer)
As the ethylenically unsaturated monomer, any appropriate monomer can be adopted as long as it is a monomer having an ethylenically unsaturated double bond. Only one type of ethylenically unsaturated monomer may be used, or two or more types may be used.

  The ethylenically unsaturated monomer preferably comprises a (meth) acrylic ester. The content ratio of the (meth) acrylic acid ester in the ethylenically unsaturated monomer is preferably 80% by weight, more preferably 85% by weight as the lower limit, and preferably 100% by weight as the upper limit. More preferably, it is 98% by weight. Only one (meth) acrylic acid ester may be used, or two or more may be used.

  The (meth) acrylic acid ester is preferably an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms (a concept including a cycloalkyl group, an alkyl (cycloalkyl) group, and a (cycloalkyl) alkyl group). It is. Preferably the carbon number of the said alkyl group is 4-18. In addition, (meth) acryl means acryl and / or methacryl, and (meth) acrylate means acrylate and / or methacrylate.

  Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and s-butyl. (Meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) Acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isode Ru (meth) acrylate, n-dodecyl (meth) acrylate, isomyristyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, pentadecyl Examples include (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and isostearyl (meth) acrylate. Among these, n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable. Only 1 type may be sufficient as the alkyl (meth) acrylate which has a C1-C20 alkyl group, and 2 or more types may be sufficient as it.

  The ethylenically unsaturated monomer preferably further comprises a polar monomer copolymerizable with the (meth) acrylic acid ester. The content of the polar monomer in the ethylenically unsaturated monomer is preferably 0% by weight, more preferably 2% by weight as the lower limit, and preferably 20% by weight, more preferably as the upper limit. 15% by weight. Only one type of polar monomer may be used, or two or more types may be used.

  Examples of polar monomers include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, ω-carboxy-polycaprolactone monoacrylate, phthalic acid monohydroxyethyl acrylate, itaconic acid, maleic acid, fumaric acid Carboxyl group-containing monomers such as acid and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 4-hydroxybutyl, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethyl Shi And hydroxyl group-containing monomers such as chlorohexyl) methyl (meth) acrylate; amide group-containing monomers such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide;

(B-1-2-3. Polymerization initiator)
The continuous oil phase component preferably contains a polymerization initiator.

  Examples of the polymerization initiator include radical polymerization initiators and redox polymerization initiators. Examples of the radical polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator.

  Examples of the thermal polymerization initiator include azo compounds, peroxides, peroxycarbonic acid, peroxycarboxylic acid, potassium persulfate, t-butylperoxyisobutyrate, and 2,2′-azobisisobutyronitrile. .

  Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (for example, Ciba Japan, trade name: Darocur-2959), α-hydroxy- α, α'-dimethylacetophenone (for example, Ciba Japan, trade name: Darocur-1173), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone (for example, Ciba Japan, trade name) Acetophenone photopolymerization initiators such as Irgacure-651) and 2-hydroxy-2-cyclohexylacetophenone (for example, Ciba Japan, trade name; Irgacure-184); Ketal photopolymerization initiator such as benzyldimethyl ketal Agents; Other halogenated ketones; Acylphosphine oxides (As an example, Ciba Japan Co., Ltd., trade name: Irgacure -819); and the like.

  The polymerization initiator may contain only 1 type and may contain 2 or more types.

  The content of the polymerization initiator is preferably 0.05% by weight, more preferably 0.1% by weight, more preferably 0.1%, and preferably 5.0% as a lower limit with respect to the entire continuous oil phase component. % By weight, more preferably 1.0% by weight. When the content of the polymerization initiator is less than 0.05% by weight based on the entire continuous oil phase component, the amount of unreacted monomer components increases, and the amount of residual monomer in the resulting foamed diffuse reflector may increase. There is. When the content of the polymerization initiator exceeds 5.0% by weight with respect to the entire continuous oil phase component, the mechanical properties of the obtained foamed diffuse reflector may be lowered.

  Note that the amount of radicals generated by the photopolymerization initiator varies depending on the type and intensity of light to be irradiated, irradiation time, the amount of dissolved oxygen in the monomer and solvent mixture, and the like. And when there is much dissolved oxygen, the radical generation amount by a photoinitiator is suppressed, superposition | polymerization does not fully advance and an unreacted substance may increase. Therefore, it is preferable to blow an inert gas such as nitrogen into the reaction system and replace oxygen with the inert gas before the light irradiation.

(B-1-2-4. Crosslinking agent)
The continuous oil phase component preferably includes a cross-linking agent.

  Crosslinking agents are typically used to link polymer chains together to build a more three-dimensional molecular structure. The selection of the type and content of the cross-linking agent depends on the structural, mechanical and fluid treatment characteristics desired for the resulting foam diffuse reflector. Selection of the specific type and content of the cross-linking agent is important in achieving a desirable combination of structural properties, mechanical properties, and fluid treatment properties of the foamed diffuse reflector.

  In producing the foamed diffuse reflector of the present invention, preferably, at least two kinds of crosslinking agents having different weight average molecular weights are used as the crosslinking agent.

  In producing the foamed diffuse reflector of the present invention, more preferably, as a crosslinking agent, "from a polyfunctional (meth) acrylate having a weight average molecular weight of 800 or more, a polyfunctional (meth) acrylamide, and a polymerization reactive oligomer. “One or more selected” and “one or more selected from polyfunctional (meth) acrylate and polyfunctional (meth) acrylamide having a weight average molecular weight of 500 or less” are used in combination. Here, the polyfunctional (meth) acrylate is specifically a polyfunctional (meth) acrylate having at least two ethylenically unsaturated groups in one molecule, and the polyfunctional (meth) acrylamide is Specifically, it is polyfunctional (meth) acrylamide having at least two ethylenically unsaturated groups in one molecule.

  Examples of the polyfunctional (meth) acrylate include diacrylates, triacrylates, tetraacrylates, dimethacrylates, trimethacrylates, and tetramethacrylates.

  Examples of the polyfunctional (meth) acrylamide include diacrylamides, triacrylamides, tetraacrylamides, dimethacrylamides, trimethacrylamides, tetramethacrylamides and the like.

  The polyfunctional (meth) acrylate can be derived from, for example, diols, triols, tetraols, bisphenol A and the like. Specifically, for example, 1,10-decanediol, 1,8-octanediol, 1,6 hexane-diol, 1,4-butanediol, 1,3-butanediol, 1,4 butane-2-enedi It can be derived from all, ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, polyethylene glycol, sorbitol, polypropylene glycol, polytetramethylene glycol, bisphenol A propylene oxide modified product, and the like.

  The polyfunctional (meth) acrylamide can be derived from, for example, corresponding diamines, triamines, tetraamines and the like.

  Examples of the polymerization reactive oligomer include urethane (meth) acrylate, epoxy (meth) acrylate, copolyester (meth) acrylate, oligomer di (meth) acrylate and the like. Preferably, it is hydrophobic urethane (meth) acrylate.

  The weight average molecular weight of the polymerization reactive oligomer is preferably 1500 or more, more preferably 2000 or more. Although the upper limit of the weight average molecular weight of a polymerization reactive oligomer is not specifically limited, For example, Preferably it is 10,000 or less.

  As the cross-linking agent, “one or more selected from polyfunctional (meth) acrylates having a weight average molecular weight of 800 or more, polyfunctional (meth) acrylamides, and polymerization reactive oligomers” and “a weight average molecular weight of 500 or less. When using together with “one or more selected from functional (meth) acrylate and polyfunctional (meth) acrylamide” ”,“ polyfunctional (meth) acrylate having a weight average molecular weight of 800 or more, polyfunctional (meth) acrylamide, and polymerization ” The amount of “one or more selected from reactive oligomers” is preferably 40% by weight as a lower limit with respect to the total amount of the hydrophilic polyurethane polymer and the ethylenically unsaturated monomer in the continuous oil phase component. The upper limit is preferably 100% by weight, and more preferably 80% by weight. The amount of use of “one or more selected from a polyfunctional (meth) acrylate having a weight average molecular weight of 800 or more, a polyfunctional (meth) acrylamide, and a polymerization reactive oligomer” is a hydrophilic polyurethane-based heavy in the continuous oil phase component When the amount is less than 40% by weight based on the total amount of the coalesced monomer and the ethylenically unsaturated monomer, the cohesive force of the resulting foamed diffuse reflector may be lowered, and it may be difficult to achieve both toughness and flexibility. There is. The amount of use of “one or more selected from a polyfunctional (meth) acrylate having a weight average molecular weight of 800 or more, a polyfunctional (meth) acrylamide, and a polymerization reactive oligomer” is a hydrophilic polyurethane-based heavy in the continuous oil phase component When it exceeds 100 weight% with respect to the total amount of a coalescence and an ethylenically unsaturated monomer, the emulsion stability of a W / O type emulsion will fall and there exists a possibility that a desired foaming diffused reflection body may not be obtained.

  As the cross-linking agent, “one or more selected from polyfunctional (meth) acrylates having a weight average molecular weight of 800 or more, polyfunctional (meth) acrylamides, and polymerization reactive oligomers” and “a weight average molecular weight of 500 or less. When using together with “one or more selected from functional (meth) acrylate and polyfunctional (meth) acrylamide” ”,“ selected from polyfunctional (meth) acrylate and polyfunctional (meth) acrylamide having a weight average molecular weight of 500 or less ” The amount of “one or more” used is preferably 1% by weight, more preferably 5% as a lower limit with respect to the total amount of the hydrophilic polyurethane polymer and the ethylenically unsaturated monomer in the continuous oil phase component. The upper limit is preferably 30% by weight, and more preferably 20% by weight. Use amount of “one or more selected from polyfunctional (meth) acrylate having a weight average molecular weight of 500 or less and polyfunctional (meth) acrylamide” is a hydrophilic polyurethane polymer and ethylenic unsaturated in a continuous oil phase component When the amount is less than 1% by weight based on the total amount of monomers, the heat resistance is lowered, and the cell structure may be crushed by contraction in the step (IV) of dehydrating the water-containing polymer. Use amount of “one or more selected from polyfunctional (meth) acrylate having a weight average molecular weight of 500 or less and polyfunctional (meth) acrylamide” is a hydrophilic polyurethane polymer and ethylenic unsaturated in a continuous oil phase component When it exceeds 30% by weight with respect to the total amount of the monomers, the toughness of the foamed diffuse reflector to be obtained is lowered, and there is a possibility that brittleness is exhibited.

  The crosslinking agent may contain only 1 type and may contain 2 or more types.

(B-1-2-5. Other components in the continuous oil phase component)
The continuous oil phase component may contain any appropriate other component as long as the effects of the present invention are not impaired. Typically, such other components preferably include a catalyst, an antioxidant, an organic solvent, and the like. Such other components may be only one type or two or more types.

  Examples of the catalyst include a urethane reaction catalyst. Any appropriate catalyst can be adopted as the urethane reaction catalyst. Specific examples include dibutyltin dilaurate.

  Arbitrary appropriate content rates can be employ | adopted for the content rate of a catalyst according to the target catalytic reaction.

  The catalyst may contain only 1 type and may contain 2 or more types.

  Examples of the antioxidant include a phenol-based antioxidant, a thioether-based antioxidant, and a phosphorus-based antioxidant.

  Arbitrary appropriate content rates can be employ | adopted for the content rate of antioxidant in the range which does not impair the effect of this invention.

  Antioxidant may contain only 1 type and may contain 2 or more types.

  Any appropriate organic solvent can be adopted as the organic solvent as long as the effects of the present invention are not impaired.

  Arbitrary appropriate content rates can be employ | adopted for the content rate of an organic solvent in the range which does not impair the effect of this invention.

  The organic solvent may contain only 1 type and may contain 2 or more types.

<< B-2. Step of shaping W / O type emulsion (II) >>
In the step (II), any appropriate shaping method can be adopted as a method for shaping the W / O type emulsion. For example, there is a method in which a W / O emulsion is continuously supplied onto a traveling belt and shaped into a smooth sheet on the belt. Moreover, the method of apply | coating to one surface of a thermoplastic resin film, and shaping is mentioned.

  In the step (II), as a method of shaping the W / O type emulsion, when adopting a method of coating and shaping on one surface of a thermoplastic resin film, as a method of coating, for example, a roll coater, Examples include a method using a die coater, a knife coater, or the like.

<< B-3. Step of polymerizing shaped W / O emulsion (III) >>
In the step (III), any appropriate polymerization method can be adopted as a method for polymerizing the shaped W / O emulsion. For example, the belt surface of a belt conveyor is heated by a heating device, and a W / O type emulsion is continuously supplied onto a traveling belt and shaped into a smooth sheet on the belt by heating. A W / O emulsion is continuously supplied onto the running belt, with a method of polymerization and a structure in which the belt surface of the belt conveyor is heated by irradiation of active energy rays, and a smooth sheet is formed on the belt. The method of superposing | polymerizing by irradiation of an active energy ray is mentioned, shaping.

  In the case of polymerization by heating, the polymerization temperature (heating temperature) is preferably 23 ° C., more preferably 50 ° C., still more preferably 70 ° C., particularly preferably 80 ° C. as the lower limit. The upper limit is preferably 90 ° C, and is preferably 150 ° C, more preferably 130 ° C, and even more preferably 110 ° C. When the polymerization temperature is less than 23 ° C., the polymerization takes a long time, and industrial productivity may be reduced. When the polymerization temperature exceeds 150 ° C., the pore diameter of the foamed diffuse reflector obtained may be non-uniform or the strength of the foamed diffuse reflector may be reduced. The polymerization temperature need not be constant. For example, the polymerization temperature may be varied in two stages or multiple stages during the polymerization.

  In the case of polymerization by irradiation with active energy rays, examples of the active energy rays include ultraviolet rays, visible rays, and electron beams. The active energy ray is preferably ultraviolet light or visible light, and more preferably visible to ultraviolet light having a wavelength of 200 nm to 800 nm. Since the W / O type emulsion has a strong tendency to scatter light, it is possible to penetrate the W / O type emulsion by using visible to ultraviolet light having a wavelength of 200 nm to 800 nm. Moreover, the photoinitiator which can be activated with a wavelength of 200 nm-800 nm is easy to obtain, and a light source is easy to obtain.

  The wavelength of the active energy ray is preferably 200 nm, more preferably 300 nm as the lower limit value, and preferably 800 nm, more preferably 450 nm as the upper limit value.

  As a typical apparatus used for irradiation of active energy rays, for example, an ultraviolet lamp capable of performing ultraviolet irradiation includes an apparatus having a spectral distribution in a wavelength region of 300 to 400 nm. , Black light (trade name manufactured by Toshiba Lighting & Technology Co., Ltd.), metal halide lamp and the like.

  The illuminance at the time of irradiation with active energy rays can be set to any appropriate illuminance by adjusting the distance from the irradiation device to the irradiation object and the voltage. For example, by the method disclosed in Japanese Patent Application Laid-Open No. 2003-13015, the ultraviolet irradiation in each step is performed in a plurality of stages, thereby making it possible to precisely adjust the adhesive performance.

  In order to prevent the adverse effect of oxygen having an inhibitory action on the ultraviolet rays, for example, a W / O emulsion is applied to one surface of a substrate such as a thermoplastic resin film and then shaped under an inert gas atmosphere. UV rays such as polyethylene terephthalate coated with a release agent such as silicone after passing through a W / O emulsion on one surface of a substrate such as a thermoplastic resin film and shaping, but blocking oxygen It is preferable to carry out by covering the film.

  As the thermoplastic resin film, any appropriate thermoplastic resin film can be adopted as long as it can be formed by coating a W / O emulsion on one surface. Examples of the thermoplastic resin film include plastic films and sheets such as polyester, olefin resin, and polyvinyl chloride.

  The inert gas atmosphere refers to an atmosphere in which oxygen in the light irradiation zone is replaced with an inert gas. Therefore, in the inert gas atmosphere, it is necessary that oxygen is not present as much as possible, and the oxygen concentration is preferably 5000 ppm or less.

<< B-4. Step of dehydrating the obtained water-containing polymer (IV) >>
In step (IV), the obtained water-containing polymer is dehydrated. In the water-containing polymer obtained in step (III), the aqueous phase component is present in a dispersed state. By removing the aqueous phase component by dehydration and drying, a foam contained in the foamed diffuse reflector of the present invention is obtained. The obtained foam can be directly used as the foamed diffuse reflector of the present invention. Further, as described later, by combining with a base material, the foamed diffuse reflector of the present invention can be obtained.

  Arbitrary appropriate drying methods can be employ | adopted as a dehydration method in process (IV). Examples of such a drying method include vacuum drying, freeze drying, press drying, microwave drying, drying in a heat oven, drying with infrared rays, or a combination of these techniques.

<< B-5. When the foamed diffuse reflector of the present invention contains a base material >>
When the foamed diffuse reflector of the present invention contains a substrate, as one preferred embodiment of the method for producing the foamed diffuse reflector of the present invention, a W / O emulsion is applied to one surface of the substrate, W / O emulsion is polymerized by heating or irradiation with active energy rays in an active gas atmosphere or in a state where oxygen is blocked by coating with a UV transparent film coated with a release agent such as silicone. Examples of the water-containing polymer include dehydrating the obtained water-containing polymer to form a foamed diffuse reflector having a substrate / foamed layer laminate structure.

  As another preferred embodiment of the method for producing a foamed diffuse reflector of the present invention, two sheets of W / O type emulsions coated on one surface of an ultraviolet transmissive film coated with a release agent such as silicone are prepared. Then, a base material is laminated on the application surface of one of the two W / O emulsion application sheets, and another W / O emulsion application sheet is provided on the other surface of the laminated base material. In a state where the coating surfaces are laminated so as to match, the W / O emulsion is polymerized by heating or irradiation with active energy rays to form a water-containing polymer, and the resulting water-containing polymer is dehydrated to produce foam. The form made into the foaming diffused reflection body which has the laminated structure of a layer / base material / foaming layer is mentioned.

  Examples of the method of coating the W / O type emulsion on one side of the base material or one surface of the ultraviolet ray transmissive film coated with a release agent such as silicone include a roll coater, a die coater, and a knife coater.

  Hereinafter, although the present invention is explained based on an example, the present invention is not limited to these. The normal temperature means 23 ° C.

(Molecular weight measurement)
The weight average molecular weight was determined by GPC (gel permeation chromatography).
Equipment: “HLC-8020” manufactured by Tosoh Corporation
Column: “TSKgel GMH _HR- H (20)” manufactured by Tosoh Corporation
Solvent: Tetrahydrofuran Standard: Polystyrene

(Measurement of average pore diameter)
A sample for measurement was prepared by cutting the prepared composite sheet with a microtome cutter in the thickness direction. The cut surface of the sample for measurement was photographed with a scanning electron microscope (Hitachi, S-3400N) at 800 to 5000 times. Using the photographed image, measure the pore diameter of an arbitrary range of spherical bubbles, the diameter of a through-hole penetrating between the spherical bubbles of an arbitrary range, and the pore diameter of the surface opening of an arbitrary range. The average hole diameter, the average hole diameter of the through holes, and the average hole diameter of the surface openings were calculated.

(Diffuse reflectance)
Using a spectrophotometer UV-2250 manufactured by Shimadzu Corporation equipped with an integrating sphere device, the diffuse reflectance in a wavelength region of 190 nm to 800 nm was measured every 1 nm. At this time, the measuring apparatus was adjusted by setting the diffuse reflectance of the barium sulfate powder to 100%.

(Measurement of 50% compression load)
After laminating 10 sheets of the obtained foamed diffuse reflector, it was cut into 20 mm × 20 mm to obtain a measurement sample. Tensilon was used for the measurement. The sample for measurement was compressed in the thickness direction to 50% of the initial thickness at a speed of 10 mm / min, and the maximum value when the thickness was compressed by 50% was measured. Samples were measured at n = 2, and the average value was 50% compression load.

(Dimensional change rate when stored at 125 ° C for 22 hours)
The heating dimensional change of the obtained foaming diffused reflector was measured based on the dimensional stability evaluation at high temperature of JIS-K-6767. That is, the produced foam was cut out to a size of 100 mm × 100 mm to form a test piece, stored in an oven at 125 ° C. for 22 hours, and then in accordance with the dimensional stability evaluation at high temperature of JIS-K-6767, The dimensional change rate before and after the heat storage treatment was determined.

(Measurement of density of foam diffuse reflector)
Five foam diffuse reflectors obtained were cut into a size of 100 mm × 100 mm to form test pieces, and the apparent density was determined by dividing the weight by the volume. The average value of the apparent density obtained was taken as the density of the foamed diffuse reflector.

(Measurement of bubble rate)
Only the oil phase component at the time of producing the emulsion was polymerized, and the obtained polymer sheet was cut into five pieces of 100 mm × 100 mm to obtain test pieces, and the apparent density was obtained by dividing the weight by the volume. The average value of the apparent density obtained was taken as the density of the resin component constituting the foamed diffuse reflector. The cell ratio of the foamed diffuse reflector was calculated by the following equation using the relative density obtained by dividing the density of the foamed diffuse reflector by the density of the resin component.
Bubble ratio = (1−relative density) × 100

[Production Example 1]: Preparation of mixed syrup 1 In a reaction vessel equipped with a condenser, a thermometer, and a stirrer, 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd., hereinafter "2EHA") as an ethylenically unsaturated monomer A monomer solution consisting of 173.2 parts by weight, and 100 parts by weight of Adeka (registered trademark) Pluronic L-62 (molecular weight 2500, manufactured by ADEKA Corporation, polyether polyol) as polyoxyethylene polyoxypropylene glycol, As a urethane reaction catalyst, 0.014 part by weight of dibutyltin dilaurate (manufactured by Kishida Chemical Co., Ltd., hereinafter abbreviated as “DBTL”) is added and stirred, and hydrogenated xylylene diisocyanate (manufactured by Takeda Pharmaceutical Co., Ltd., Takenate). 600, hereinafter abbreviated as “HXDI”) 12.4 parts by weight were added dropwise and reacted at 65 ° C. for 4 hours. Let In addition, the usage-amount of the polyisocyanate component and the polyol component was NCO / OH (equivalent ratio) = 1.6. Thereafter, 5.6 parts by weight of 2-hydroxyethyl acrylate (manufactured by Kishida Chemical Co., Ltd., hereinafter abbreviated as “HEA”) is dropped and reacted at 65 ° C. for 2 hours, and a hydrophilic polyurethane system having acryloyl groups at both ends. A polymer / ethylenically unsaturated monomer mixed syrup was obtained. The weight average molecular weight of the obtained hydrophilic polyurethane polymer was 15,000. 48 parts by weight of 2EHA with respect to 100 parts by weight of the obtained hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup, acrylic acid (manufactured by Toa Gosei Co., Ltd., hereinafter abbreviated as “AA”) 12 parts by weight A hydrophilic polyurethane-based polymer / ethylenically unsaturated monomer mixed syrup 1 was added.

[Production Example 2]: Preparation of mixed syrup 2 In Production Example 1, isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., hereinafter abbreviated as “IBXA”) is used in place of 2EHA as the ethylenically unsaturated monomer. Was carried out in the same manner as in Production Example 1 to obtain a hydrophilic polyurethane-based polymer / ethylenically unsaturated monomer mixed syrup having acryloyl groups at both ends. The weight average molecular weight of the obtained hydrophilic polyurethane polymer was 15,000. 7.9 parts by weight of 2EHA, 114 parts by weight of IBXA, and 16.2 parts by weight of AA as a polar monomer were added to 100 parts by weight of the obtained hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup. A hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup 2 was obtained.

[Example 1]
To 100 parts by weight of the hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup 1 obtained in Production Example 1, 1,6-hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “NK Ester A” -HD-N ") (molecular weight 226) 10 parts by weight, a reactive oligomer of polyurethane synthesized from polytetramethylene glycol (hereinafter abbreviated as" PTMG ") and isophorone diisocyanate (hereinafter abbreviated as" IPDI ") Both ends treated with HEA, urethane acrylate having ethylenically unsaturated groups at both ends (hereinafter abbreviated as “UA”) (molecular weight 3720), 56 parts by weight, diphenyl (2,4,6-trimethylbenzoyl) phos Fin oxide (BASF, trade name "Lucirin TPO") 0.5 parts by weight, hindered pheno Le-based antioxidant (manufactured by Ciba Japan, trade name "Irganox 1010") 1.0 part by weight were uniformly mixed, continuous oil phase component (hereinafter, referred to as "oil phase") was. On the other hand, 300 parts by weight of ion-exchanged water as an aqueous phase component (hereinafter referred to as “aqueous phase”) with respect to 100 parts by weight of the oil phase is continuously introduced into a stirring mixer that is an emulsifier charged with the oil phase at room temperature. Were added dropwise to prepare a stable W / O emulsion. The weight ratio of the water phase to the oil phase was 75/25.
The obtained W / O emulsion was stored at room temperature for 1 hour, and then applied onto a substrate that had been subjected to a release treatment so that the thickness after light irradiation was 0.5 mm, and was continuously molded. Further, a polyethylene terephthalate film having a thickness of 38 μm and subjected to a release treatment was placed thereon. This sheet was irradiated with ultraviolet light with a light intensity of 5 mW / cm ² (measured with Topcon UVR-T1 having a peak sensitivity maximum wave of 350 nm) using black light (15 W / cm), and a highly hydrous crosslinked polymer having a thickness of 0.5 mm was obtained. Obtained. Next, the top film was peeled off, and the high water content crosslinked polymer was heated at 130 ° C. for 20 minutes to obtain a foamed diffuse reflector (1) having a thickness of about 0.5 mm.
The results are shown in Table 1 and FIG.
Moreover, the photograph figure of the surface / cross-section SEM photograph which image | photographed the obtained foaming diffused reflection body (1) from diagonally was shown in FIG.

[Example 2]
In Example 1, instead of the hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup 1 obtained in Production Example 1, the hydrophilic polyurethane polymer / ethylenically unsaturated monomer obtained in Production Example 2 was used. An oil phase was prepared in the same manner as in Example 1 except that the mixed syrup 2 was used, 15 parts by weight of NK ester A-HD-N and 70 parts by weight of UA were used. Further, 186 parts by weight of ion-exchanged water as an aqueous phase with respect to 100 parts by weight of the oil phase was continuously dropped into a stirring mixer which is an emulsifier charged with the oil phase at room temperature, and stable W / O A mold emulsion was prepared. The weight ratio of the water phase to the oil phase was 65/35.
About the obtained W / O type | mold emulsion, it carried out similarly to Example 1 and the foaming diffused reflection body (2) of thickness about 0.5 mm was obtained.
The results are shown in Table 1 and FIG.

  From FIG. 5, it can be seen that the foamed diffuse reflector of the present invention has a very high diffuse reflectance in the wavelength region of 400 nm to 700 nm, and particularly has a very high diffuse reflectance in the wavelength region of 400 nm to 500 nm. In the chart of FIG. 5, there is a region where the diffuse reflectance exceeds 100%. This is because the measurement apparatus was adjusted with the diffuse reflectance of the barium sulfate powder being 100%. Guessed. However, the region where the measurement result of the diffuse reflectance when the barium sulfate powder that theoretically shows 100% diffuse reflectance is used as a comparative material exceeds 100% is almost the same as or more than the diffuse reflectance of the barium sulfate powder. It is thought that it shows. Therefore, in the chart of FIG. 5, the diffuse reflectance in the wavelength region of 400 nm to 700 nm is considered to be almost 100% in both Examples 1 and 2.

  The foamed diffuse reflector of the present invention is useful as a diffuse reflector provided in a backlight device of a liquid crystal display device, a lighting device such as a fluorescent lamp, an incandescent lamp, and an LED.

100 Foam Diffuse Reflector 10 Foam 10a Foam 10b Foam 20 Base Material 30 Release Film

Claims (9)

Including a foam containing a hydrophilic polyurethane-based polymer;
The surface of the foam has a surface opening having an average pore diameter of 20 μm or less,
Having an open cell structure with through-holes between adjacent spherical cells;
The diffuse reflectance in the wavelength region of 400 nm to 500 nm is 90% or more,
Foam diffuse reflector.   The foaming diffused reflection body of Claim 1 whose diffuse reflectance in the wavelength range of 400 nm-700 nm is 90% or more. The foaming diffuse reflector of Claim 1 or 2 whose average hole diameter of the said spherical bubble is less than 20 micrometers. The foaming diffused reflection body in any one of Claim 1 to 3 whose average hole diameter of the said through-hole is 5 micrometers or less. Wherein the foam has a density in the ^{0.15g / cm 3 ~0.6g / cm 3} , the foamed diffuse reflector according to any one of claims 1 to 4. The foaming diffused reflection body in any one of Claim 1-5 whose 50% compressive load is 300 N / cm < ² > or less. The foaming diffused reflection body in any one of Claim 1-6 whose dimensional change rate when preserve | saved at 125 degreeC for 22 hours is less than +/- 5%. The foam cell ratio of not less than 30%, foam diffuse reflector according to any one of claims 1 to 7. Step (I) for preparing a W / O emulsion, Step (II) for shaping the obtained W / O emulsion, Step (III) for polymerizing the shaped W / O emulsion, The foaming diffused reflection body in any one of Claim 1-8 obtained by the manufacturing method including process (IV) which spin-dry | dehydrates the obtained water-containing polymer.