WO2013121907A1

WO2013121907A1 - Foam diffuser-reflector

Info

Publication number: WO2013121907A1
Application number: PCT/JP2013/052465
Authority: WO
Inventors: 平尾　昭; 智紀兵藤
Original assignee: 日東電工株式会社
Priority date: 2012-02-15
Filing date: 2013-02-04
Publication date: 2013-08-22
Also published as: JP2013167721A; TW201337341A

Abstract

The purpose of the present invention is to provide a foam diffuser-reflector having a bubble structure, the bubble structure being precisely controlled, the bubble fraction being high, the foam diffuser-reflector having numerous fine surface openings that are precisely controlled, and the foam diffuser-reflector being capable of demonstrating extremely good diffusion and reflection performance. This foam diffuser-reflector includes a foam body having a continuous bubble structure having through holes between adjacent spherical bubbles, and has a plurality of projections 0.05 mm-0.5 mm high on one or both sides of the foam body, the foam diffuser-reflector is held between flat plates from upper and lower sides thereof, the average value (Ly) of the shortest distance (y) between top ends of lateral surfaces of adjacent projections is at least 0.5 mm when the foam diffuser-reflector is compressed 5% in the thickness direction, the average pore diameter of the spherical bubbles is less than 20 µm, the average pore diameter of the through holes is 5 µm or less, and the surface of the foam body has surface openings having an average pore diameter of 20 µm or less.

Description

Foam diffuse reflector

The present invention relates to a foamed diffuse reflector.

The reflector exhibits reflection performance by being 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.

In particular, reflectors introduced in edge light type backlight units used in small liquid crystals, notebook computers and LCD monitors, LED lighting, lighting advertising panels, etc., have high diffuse reflection performance (that is, high light Both a reflection performance and a high light diffusion performance are required. Note that the edge light type backlight generally includes a light source such as a cold cathode tube or an LED, a reflector, and a light guide plate. The light guide plate is a silk printing method in which reflective dots are printed with white ink on an acrylic plate, a molding method in which the acrylic surface is made uneven with a stamper or injection, and an adhesive dot method in which the acrylic plate and reflector are attached with a dot-like adhesive. And groove processing methods.

As a diffuse reflector having high diffuse reflection performance, the film contains a diffuse reflector formed by depositing a metal vapor deposition 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 diffusibility. Diffuse reflectors are known. However, the diffuse reflector formed with the metal mirror surface has a problem that the light diffusion performance is low although the light reflection performance is high. In addition, a diffuse reflector in which pigment or fine particles that enhance light diffusibility are contained in a film needs to increase the amount of pigment or fine particles added in order to suppress leakage of light to the back surface, 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 (for example, Patent Document 1). 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 light diffusion performance cannot be expressed. Furthermore, when such a foam is used as a diffuse reflector in, for example, a backlight device, the in-plane luminance uniformity may be insufficient.

Also, in recent years, in the edge-light type backlight unit that combines the mainstream silk printing type light guide plate and reflector, the printed dots wear due to the contact between the light guide plate and the reflector, and the in-plane brightness uniformity is It may be insufficient.

Japanese Patent Publication No. 97/1117

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. An object of the present invention is to provide a foamed diffuse reflector capable of exhibiting very excellent diffuse reflection performance.

The foaming diffused reflection body of this invention is a foaming diffused reflection body containing the foam which has an open-cell structure which has a through-hole between adjacent spherical bubbles, Comprising: Height is set to 0. at least on one side of this foam. There are a plurality of convex portions of 05 mm to 0.5 mm, the foam diffuse reflector is sandwiched between smooth plates from the upper and lower surfaces, and the side surfaces of adjacent convex portions when the foam diffuse reflector is compressed 5% in the thickness direction. The average value Ly of the shortest distance y between the upper end and the upper end of the side surface is 0.5 mm or more, the average pore diameter of the spherical bubbles is less than 20 μm, the average pore diameter of the through holes is 5 μm or less, The surface has a surface opening having an average pore diameter of 20 μm or less.

In a preferred embodiment, the foaming diffused reflector of the present invention is a foamed diffused reflector including a foam having an open-cell structure having a through-hole between adjacent spherical bubbles, on at least one surface of the foam. , Having a plurality of convex portions having a height of 0.05 mm to 0.5 mm, sandwiching the foamed diffuse reflector from upper and lower surfaces with a smooth plate, and adjacent to the foamed diffuse reflector when compressed by 5% in the thickness direction. The shortest distance y between the upper end of the side surface and the upper end of the side of the convex portion is 0.2 mm or more, the average pore diameter of the spherical bubbles is less than 20 μm, the average pore diameter of the through holes is 5 μm or less, and the foaming The surface of the body has a surface opening having an average pore diameter of 20 μm or less.

In a preferred embodiment, when the foam diffuse reflector is compressed by 5% in the thickness direction, the shape of the top surface of the convex portion is substantially circular, and when the foam diffuse reflector is compressed by 5% in the thickness direction. The ratio (Ly / La) of the average value La of the convex portion upper surface diameter to the average value Ly of the shortest distance y between the side surface upper ends of the adjacent convex portions is 1 or more.

In a preferred embodiment, when the foam diffuse reflector is compressed by 5% in the thickness direction, the shape of the top surface of the convex portion is a polygon, and when the foam diffuse reflector is compressed by 5% in the thickness direction. The ratio (Ly / Lb) between the average value Lb of the diameter b of the circle inscribed in the upper surface of the convex portion and the average value Ly of the shortest distance y between the side surface upper ends of the adjacent convex portions is 1.2 or more is there.

In a preferred embodiment, the foam contains a hydrophilic polyurethane polymer.

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 600 nm.

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 800 nm.

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, It is possible to provide a foamed diffuse reflector that can exhibit very excellent diffuse reflection performance. In addition to having the above-mentioned cell structure, the foamed diffuse reflector of the present invention can exhibit excellent diffuse reflection performance by providing a plurality of convex portions on at least one surface. Moreover, when the foaming diffused reflection body of this invention is used for an edge light type backlight apparatus, an air layer can be formed between a light-guide plate and this foaming diffused reflection body by the said convex part. As a result, the diffuse reflector of the present invention can promote diffuse reflection of light in the edge light type backlight device, and can contribute to high brightness and uniform in-plane brightness. Furthermore, when the foaming diffused reflection body of this invention has a convex part as mentioned above, when used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

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 schematic sectional drawing which shows another preferable embodiment of the foaming diffused reflection body of this invention. It is a photograph figure of the reflective surface side of the foaming diffused reflection body of this invention, Comprising: It is a photograph figure showing a mode that it has a some convex part on the surface. It is a schematic sectional drawing of the convex part which the foaming diffused reflection body of this invention has. (A) is a schematic sectional drawing when the foaming diffused reflection body of this invention is pinched | interposed by the smooth plate from the upper and lower surfaces, and the said foaming diffused reflection body is compressed 5% in the thickness direction. (B) is a schematic plan view when the foamed diffuse reflector of the present invention is sandwiched between upper and lower surfaces by a smooth plate and the foamed diffuse reflector is compressed by 5% in the thickness direction. It is a photograph figure of the section SEM photograph of the foaming diffused reflector of the present invention, and is a photograph figure clearly showing the open-cell structure which has a penetration hole between adjacent spherical bubbles. It is a schematic sectional drawing showing the structure of the backlight unit used by the measurement of the in-plane brightness | luminance in an Example and a comparative example. It is a schematic plan view showing the measurement point in a light emission surface in the measurement of the in-plane brightness | luminance of an Example and a comparative example. It is a chart figure showing the average brightness | luminance of each measuring point column of the in-plane brightness | luminance measured in the Example and the comparative example. It is a chart figure which shows the measurement result of the diffuse reflectance of the foaming diffused reflection body produced in Example 1. FIG. It is a photograph figure of digital microscope observation of the convex part cross section of the foaming diffused reflection body produced in Example 1. FIG. It is a photograph figure of the surface / cross-section SEM photograph which image | photographed the plane part of the foaming diffused reflection body produced in Example 1 from diagonally. It is a photograph figure of the surface / cross-section SEM photograph which image | photographed the convex part of the foaming diffused reflection body produced in Example 1 from diagonally. It is a chart figure which shows the measurement result of the diffuse reflectance of the foaming diffused reflection body produced in Example 2. FIG. It is a photograph figure of digital microscope observation of the convex part cross section of the foaming diffused reflection body produced in Example 2. FIG. It is a chart figure which shows the measurement result of the diffuse reflectance of the foaming diffused reflection body produced in the comparative example 1.

≪ << A. Foam diffuse reflector >>>>
The foaming diffused reflection body of this invention contains the foam which has a spherical cell. The foam contained in the foamed diffuse reflector of the present invention has an open cell structure having through holes between adjacent spherical bubbles. Typical structures include a foam diffuse reflector 100 (FIG. 1) made of the foam 10, a foam diffuse reflector 100 (FIG. 2) including a base material 20 (described later) on one side of the foam 10, and a foam 10a. And a foam diffuse reflector 100 (FIG. 3) including the base material 20 between the foam 10b and the foam 10b. In FIGS. 1 and 3, the release film 30 is provided for protecting the surface of the foamed diffuse reflector, but the release film may not be provided.

The foamed diffuse reflector of the present invention has a plurality of convex portions on at least one surface (reflecting surface) of the foam (FIG. 4). The convex portions are preferably provided in a substantially matrix shape.

FIG. 5 is a schematic cross-sectional view of the protrusion 11 included in the foamed diffuse reflector of the present invention. The height x of the convex portion 11 is 0.05 mm to 0.5 mm, preferably 0.05 mm to 0.3 mm, and more preferably 0.1 mm to 0.3 mm. By having such a convex part, the foaming diffused reflection body of this invention can express the very outstanding light-diffusion performance. Moreover, when the foaming diffused reflection body of this invention is used for an edge light type backlight device, the diffuse reflection of light can be promoted, and it can contribute to high brightness and uniform in-plane brightness. Furthermore, when the foaming diffused reflection body of this invention has a convex part as mentioned above, when used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

FIG. 6A is a schematic cross-sectional view when the foamed diffuse reflector of the present invention is sandwiched between the smooth plate 1 from the upper and lower surfaces and the foamed diffuse reflector is compressed by 5% in the thickness direction. The foaming diffused reflector of the present invention is sandwiched between the smooth plate 1 from the upper and lower surfaces, and the foamed diffused reflector is compressed by 5% in the thickness direction. The average value Ly is preferably 0.5 mm or more, more preferably 0.5 mm to 2 mm, and particularly preferably 0.8 mm to 1.5 mm. By having such a convex part, the foaming diffused reflection body of this invention can express the very outstanding light-diffusion performance. Moreover, when the foaming diffused reflection body of this invention is used for an edge light type backlight device, the diffuse reflection of light can be promoted, and it can contribute to high brightness and uniform in-plane brightness. Furthermore, when the foaming diffused reflection body of this invention has a convex part as mentioned above, when used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate. The average value Ly is calculated, for example, by randomly extracting five or more sets (preferably five sets) of the adjacent convex portions.

When the foamed diffuse reflector of the present invention is sandwiched between the smooth plates 1 from the upper and lower surfaces and the foamed diffuse reflector is compressed by 5% in the thickness direction, the shortest distance y between the upper side surface and the upper side surface of the adjacent convex portion 11 is The thickness is preferably 0.2 mm or more, more preferably 0.2 mm to 2.3 mm, particularly preferably 0.5 mm to 2 mm, and most preferably 0.8 mm to 1.8 mm. By having such a convex part, the foaming diffused reflection body of this invention can express the very outstanding light-diffusion performance. Moreover, when the foaming diffused reflection body of this invention is used for an edge light type backlight device, the diffuse reflection of light can be promoted, and it can contribute to high brightness and uniform in-plane brightness. Furthermore, when the foaming diffused reflection body of this invention has a convex part as mentioned above, when used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

The plan view shape of the convex portion may take any appropriate shape. The plan view shape of the bottom surface of the convex portion is preferably a polygon, a circle or an ellipse, more preferably a circle or an ellipse, and still more preferably a circle. Any appropriate shape may be adopted as the cross-sectional shape of the convex portion. The sectional shape of the convex portion is preferably a split circle, a split ellipse or a polygon. The upper surface of the convex portion may be a flat surface. When the upper surface of the convex portion is a plane, the planar view shape of the upper surface of the convex portion is preferably a polygon, a circle or an ellipse, more preferably a circle or an ellipse, and still more preferably a circle. . In addition, the area of a convex part bottom face and an upper surface can be set to arbitrary appropriate areas according to the use (specifically size in the time of use of a foaming diffused reflection body) of the foaming diffused reflection body of this invention.

FIG. 6 (b) is a schematic plan view when the foamed diffuse reflector of the present invention is sandwiched between upper and lower surfaces by a smooth plate and the foamed diffuse reflector is compressed by 5% in the thickness direction. In FIG.6 (b), some convex parts 11 in a foaming diffused reflection body are shown. FIG. 6B shows a foamed diffuse reflector in which the shape of the top surface of the convex portion 11 is substantially circular when compressed by 5% in the thickness direction. When the foamed diffuse reflector of the present invention is compressed by 5% in the thickness direction and the shape of the top surface of the convex portion 11 is substantially circular, the “convex portion when the foamed diffuse reflector is compressed by 5% in the thickness direction” The ratio (Ly / La) of “the average value La of 11 upper surface diameters a” and “the average value Ly of the shortest distance y between the upper end surfaces of adjacent convex portions 11” is preferably 1 or more, more preferably 1 .2 or more, particularly preferably 1.5 to 3. By having such a convex part, the foaming diffused reflection body of this invention can express the very outstanding light-diffusion performance. Moreover, when the foaming diffused reflection body of this invention is used for an edge light type backlight device, the diffuse reflection of light can be promoted, and it can contribute to high brightness and uniform in-plane brightness. Furthermore, when the foaming diffused reflection body of this invention has a convex part as mentioned above, when used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate. The “average value La of the diameter a of the upper surface of the convex portion 11” is calculated, for example, by randomly extracting five or more (preferably ten) convex portions.

When the foamed diffuse reflector of the present invention is compressed by 5% in the thickness direction and the shape of the top surface of the convex portion 11 is substantially circular, the adjacent convex portions when the foamed diffuse reflector is compressed by 5% in the thickness direction. 11, the ratio (y / La ′) between the average value La ′ of the upper surface diameters a and a (that is, the average of the upper surface diameters of two adjacent convex portions) and the shortest distance y between the upper ends of the side surfaces is preferably It is 1 or more, more preferably 1.2 or more, and particularly preferably 1.5 to 3. By having such a convex part, the foaming diffuse reflector of the present invention can express a very excellent light diffusion performance, for example, when used in an edge light type backlight device, a very excellent in-plane brightness. The uniformity can be expressed. Moreover, when the foaming diffused reflection body of this invention is used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

When the planar view shape of the upper surface of the convex portion becomes a polygon when compressed by 5% in the thickness direction, the “diameter b of the circle inscribed in the upper surface of the convex portion when the foamed diffuse reflector is compressed by 5% in the thickness direction” The ratio (Ly / Lb) between the “average value Lb” and “the average value Ly of the shortest distance y between the side surface upper ends of the adjacent convex portions 11” is preferably 1.2 or more, more preferably 1.4 or more. It is particularly preferably 1.7 to 3.2. By having such a convex part, the foaming diffuse reflector of the present invention can express a very excellent light diffusion performance, for example, when used in an edge light type backlight device, a very excellent in-plane brightness. The uniformity can be expressed. Moreover, when the foaming diffused reflection body of this invention is used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate. The “average value Lb of the diameters b of the circles inscribed on the upper surface of the convex portion” is calculated, for example, by randomly extracting five or more (preferably ten) convex portions.

When the planar view shape of the upper surface of the convex portion becomes a polygon when compressed by 5% in the thickness direction, the diameter of the circle inscribed in the upper surface of the adjacent convex portion when the foamed diffuse reflector is compressed by 5% in the thickness direction The ratio (y / Lb ′) between the average value Lb ′ of b and b (that is, the average of the diameters of the circles inscribed in the upper surfaces of two adjacent convex portions) and the shortest distance y between the upper ends of the side surfaces is preferably It is 1.2 or more, more preferably 1.4 or more, and particularly preferably 1.7 to 3.2. By having such a convex part, the foaming diffuse reflector of the present invention can express a very excellent light diffusion performance, for example, when used in an edge light type backlight device, a very excellent in-plane brightness. The uniformity can be expressed. Moreover, when the foaming diffused reflection body of this invention is used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

The ratio of the total area of the upper surface of the convex portion when the foamed diffuse reflector of the present invention is sandwiched between smooth plates from the upper and lower surfaces and the foamed diffuse reflector is compressed by 5% in the thickness direction is the projected area of the upper surface of the foam diffuse reflector On the other hand, it is preferably 10% to 70%, more preferably 20% to 50%. By having such a convex part, the foaming diffuse reflector of the present invention can express a very excellent light diffusion performance, for example, when used in an edge light type backlight device, a very excellent in-plane brightness. The uniformity can be expressed. Moreover, when the foaming diffused reflection body of this invention is used in combination with a light guide plate, it can prevent deterioration of the printed dot pattern of a light guide plate.

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 less than 20 μm, preferably 15 μm or less, 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.

The foam contained in the foamed diffuse reflector of the present invention has an open cell structure having through holes between adjacent spherical cells. 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. . By using a foam having such an open cell structure, the foamed diffuse reflector of the present invention can exhibit very excellent diffuse reflection performance.

The through hole between adjacent spherical bubbles affects the physical properties of the foam diffuse reflector. For example, the strength of the foamed diffuse reflector tends to increase as the average hole diameter of the through holes decreases. FIG. 7 is a photographic view of a cross-sectional SEM photograph of the foamed diffuse reflector of the present invention, and shows 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 5 μm or less, preferably 4 μm or less, 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 foam contained in 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. By using the foam having such a surface opening continuous cell structure, the foamed diffuse reflector of the present invention can exhibit a very excellent diffuse reflection performance and can have sufficient adhesion. Since the foaming diffused reflection body of this invention has sufficient adhesive force in this way, it can stick without providing an adhesive bond layer or an adhesive layer separately.

The density of the foam contained in the foamed diffuse reflector of the present invention is preferably 0.15 g / cm ³ to 0.6 g / cm ³ , more preferably 0.15 g / cm ³ to 0.5 g / 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 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. In the present specification, the “bubble ratio” is obtained by polymerizing the apparent density of the foam, only the resin component constituting the foam (the oil phase component (described later) when producing the emulsion). The value calculated by the following formula using the relative density obtained by dividing by the density of the polymer).
Bubble ratio = (1−relative density) × 100

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.

In the foamed diffuse reflector of the present invention, the diffuse reflectance in the wavelength region of 400 nm to 600 nm is preferably 90% or more, more preferably 95% or more, still more preferably 98% or more, and particularly preferably. It is 99% or more, and most preferably 99.5% or more.

In the foamed diffuse reflector of the present invention, the diffuse reflectance in the wavelength region of 400 nm to 800 nm is preferably 90% or more, more preferably 95% or more, still more preferably 98% or more, and particularly preferably. It is 99% or more, and most preferably 99.5% or more.

Foam diffuse reflectors of the present invention, 50% compression load, is preferably 100 N / cm ² or less, more preferably 70N / cm ² or less, still more preferably 50 N / cm ² or less, particularly preferably 40 N / cm ² or less, and most preferably 30 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 and adhesion.

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.

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 foamed diffuse reflector of the present invention may contain any appropriate base material as long as the effects of the present invention are not impaired. 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. In one embodiment, the substrate is a light shielding layer. In this embodiment, as the base material (light shielding layer), for example, a metallic processed resin sheet, a metal foil film sheet, or the like is used, and the base material (light shielding layer) is opposite to the reflecting surface of the foaming diffuse reflector. On the side surface.

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 the fiber nonwoven fabric, a nonwoven 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. 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 the fiber knitted fabric, for example, a knitted 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 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. When the resin sheet is subjected to metallic processing, the resin sheet functions as a light shielding layer.

As the metal foil film sheet, a sheet formed of 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 there are voids in the substrate, the same material as the foamed diffuse reflector may be present in part or all of the voids.

The substrate may be used alone or in combination of two or more.

≪≪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.

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

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 to obtain 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 type emulsion that can be used for obtaining 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 emulsion by the “batch method” include manual mixing and shaking, a driven blade mixer, and a three-propeller mixing blade. Specifically, “TK Ajihomomica (trade name)” and “TK Combimix (trade name)” manufactured by Primix Co., Ltd. produce the target W / O emulsion under reduced pressure. This is possible, and the resulting W / O emulsion greatly reduces the incorporation of bubbles.

Any appropriate method can be adopted as a method for preparing the 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 for 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.

The water phase component may contain any appropriate additive 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 with respect 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 to 25% by weight of the polyoxyethylene polyoxypropylene unit is polyoxyethylene polyoxypropylene unit. Ethylene.

As described above, the content of polyoxyethylene in the polyoxyethylene polyoxypropylene unit is preferably 5% by weight to 25% by weight, and the lower limit is more preferably 10% by weight. 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 polymer is preferably obtained by reacting polyoxyethylene polyoxypropylene glycol with 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, 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 (isocyanatomethyl) 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 a polyol, and the like. 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-based 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. 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 contains a (meth) acrylic acid 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 (concept including a cycloalkyl group, an alkyl (cycloalkyl) group, and a (cycloalkyl) alkyl group). It is. The number of carbon atoms of the alkyl group is preferably 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, iso Sil (meth) acrylate, n-dodecyl (meth) acrylate, isomyristyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, pentadecyl (Meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, etc. It is done. Among these, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isobornyl (meth) acrylate are preferable. Alkyl (meth) acrylate having an alkyl group of 1 to 20 carbon atoms, may be only one kind, or may be two or more.

The ethylenically unsaturated monomer preferably further contains a polar monomer copolymerizable with (meth) acrylic acid ester. By including the polar monomer, the effects of the present invention can be further exhibited. 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, (meth) acrylic acid 4-hydroxybutyl, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethyl Hydroxyl group-containing monomers such as cyclohexyl) methyl (meth) acrylate; Amide group-containing monomers such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, and hydroxyethyl (meth) acrylamide; It is done.

(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, 2,2′-azobisisobutyronitrile and the like. .

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-based photopolymerization initiators such as Irgacure-651) and 2-hydroxy-2-cyclohexylacetophenone (for example, product name; Irgacure-184 manufactured by Ciba Japan); Ketal-based photopolymerization initiators such as benzyldimethyl ketal Agents; Other halogenated ketones; Acylphosphine oxa (As an example, Ciba Japan Co., Ltd., trade name: Irgacure -819); de 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 also varies depending on the type and intensity of irradiated light, the 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 that an inert gas such as nitrogen is blown into the reaction system before the light irradiation, and oxygen is replaced with an inert gas or deaerated by a reduced pressure treatment.

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

The cross-linking agent is typically used for linking polymer chains 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 types 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 polyfunctional (meth) acrylates 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 hexanediol, 1,4-butanediol, 1,3-butanediol, 1,4 butane-2-enediol , Ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, polyethylene glycol, sorbitol, polypropylene glycol, polytetramethylene glycol, modified bisphenol A propylene oxide, and the like.

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, and oligomer di (meth) acrylate. 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. Examples of such other components typically include a catalyst, an antioxidant, a light stabilizer, and an organic solvent. 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.

As the catalyst content ratio, any appropriate content ratio can be adopted depending on the target catalytic reaction.

The catalyst may contain only one type or two or more types.

Examples of the antioxidant include phenolic antioxidants, thioether antioxidants, and phosphorus antioxidants.

As the content ratio of the antioxidant, any appropriate content ratio can be adopted as long as the effects of the present invention are not impaired.

An antioxidant may contain only 1 type and may contain 2 or more types.

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

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

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

As the light stabilizer, any appropriate light stabilizer can be adopted as long as the effects of the present invention are not impaired.

Any appropriate content ratio can be adopted as the content ratio of the light stabilizer as long as the effects of the present invention are not impaired.

The light stabilizer 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 sheet on the belt. Moreover, the method of apply | coating to one surface of a thermoplastic resin film, and shaping is mentioned. Preferably, the belt and the thermoplastic resin film have a concave portion corresponding to a desired shape of the convex portion on the surface of the foamed diffuse reflector. The surface of the belt and the thermoplastic resin film may be embossed into a concavo-convex shape corresponding to the desired shape of the convex portion on the surface of the foamed diffuse reflector. By forming using such a belt and a thermoplastic resin film, a foamed diffuse reflector having convex portions on the surface can be obtained.

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 emulsion is continuously supplied onto a traveling belt and polymerized by heating while being shaped into a sheet on the belt. With the method and the structure where the belt surface of the belt conveyor is heated by irradiation with active energy rays, the W / O emulsion is continuously supplied onto the traveling belt and shaped into a sheet on the belt. The method of superposing | polymerizing by irradiation of an active energy ray is mentioned.

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, preferably ultraviolet light, a visible light, more preferably, a wavelength of light outside the visible-violet 200 nm - 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. In addition, a photopolymerization initiator that can be activated at a wavelength of 200 nm to 800 nm is easily available and a light source is easily available.

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

As a typical apparatus used for irradiation of active energy rays, for example, as an ultraviolet lamp capable of performing ultraviolet irradiation, an apparatus having a spectral distribution in a wavelength region of 300 to 400 nm can be mentioned. , 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 irradiated 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. If a film having a concave portion is used as the oxygen-blocking film, a foamed diffuse reflector surface having a convex portion can be obtained. Moreover, if the film which has a recessed part is used as a film which interrupts oxygen, and the film which has a recessed part is used as base materials, such as a thermoplastic resin film, the foaming diffused reflection body which has a convex part on both surfaces can be obtained.

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. Further, the film may be subjected to a peeling treatment on one side or both sides thereof.

The inert gas atmosphere is 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.

Any appropriate drying method can be adopted as the dehydration method in step (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. The ultraviolet ray transmissive film has a concave portion corresponding to a desired shape of the convex portion on the surface of the foamed diffuse reflector. By forming using such a belt and a thermoplastic resin film, a foamed diffuse reflector having convex portions on the surface can be obtained.

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. The ultraviolet ray transmissive film may have a concave portion corresponding to a desired shape of the convex portion on the surface of the foamed diffuse reflector. By forming using such a belt and a thermoplastic resin film, a foamed diffuse reflector having convex portions on the surface can be obtained.

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

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto. 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)
The obtained foam was cut in the thickness direction with a microtome cutter as a measurement sample. The cut surface of the measurement sample 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 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

(Measurement of in-plane brightness)
The obtained foamed diffuse reflector was cut into a size of 190 mm × 140 mm, and a backlight unit as shown in FIG. 8 (manufactured by Fujita Sangyo Co., Ltd., trade name “SOLEITA D Ecolight Kit”, light emitting surface size: 150 mm × 100 mm) The thickness of the light guide plate 2 is 5 mm, the thickness of the face plate 3 is 2 mm, the semi-transparent acrylic plate single-sided mat, the LED light source 4 is 7 high-luminance chip LEDs (white) manufactured by Nichia Corporation, and the width of the LED substrate 5 is 8 mm. In the aluminum frame 6), the surface having the convex portion is placed on the lower side of the light guide plate 2 to make a measurement panel.
In-plane luminance was measured from above the light emitting surface (vertical height: 680 mm) using a luminance distribution measurement system (I System Co., CCD camera: Sony Corporation, trade name “DXC-390”). . As shown in FIG. 9, a total of 121 measurement points were set at 11 points at regular intervals in the column direction and 11 points at regular intervals in the row direction.
Table 1 shows the average value of luminance at all measurement points as overall average luminance. In addition, FIG. 10 shows a value obtained by averaging the luminance of 11 points for each column as the average luminance of each column. Furthermore, Table 1 shows the standard deviation calculated as the average brightness of each column as an individual value as uniformity of in-plane brightness. 9 and 10, the column number of the column closest to the light source is 1 and the column number of the farthest column is 11.

[Production Example 1]: Preparation of mixed syrup 1 In a reaction vessel equipped with a cooling tube, a thermometer, and a stirrer, 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd., hereinafter "2EHA") as an ethylenically unsaturated monomer And 173.2 parts by weight of a monomer solution consisting 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 added dropwise 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 having acryloyl groups at both ends was 15,000. 27.3 parts by weight of 2EHA, n-butyl acrylate (manufactured by Toa Gosei Co., Ltd., hereinafter abbreviated as “BA”) with respect to 100 parts by weight of the resulting hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup 51. 8 parts by weight, 17.4 parts by weight of isobornyl acrylate (for example, Osaka Organic Chemical Industries, Ltd., hereinafter abbreviated as “IBXA”), acrylic acid (for example, manufactured by Toa Gosei Co., Ltd.) as a polar monomer, 10.5 parts by weight of "AA") was added to obtain a hydrophilic polyurethane polymer / ethylenically unsaturated monomer mixed syrup 1.

[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) 11.9 parts by weight, synthesized as a reactive oligomer from polytetramethylene glycol (hereinafter abbreviated as" PTMG ") and isophorone diisocyanate (hereinafter abbreviated as" IPDI "). 47.7 parts by weight of urethane acrylate having both ends of polyurethane treated with HEA and having ethylenically unsaturated groups at both ends (hereinafter abbreviated as “UA”) (molecular weight 3720) as a photoinitiator, 2,4,6-trimethylbenzoyl) phosphine oxide (manufactured by BASF, trade name “Lucirin TPO”) 8 parts by weight, 0.95 parts by weight of hindered phenol antioxidant (Ciba Japan, trade name “Irganox 1010”), 2 parts by weight of light stabilizer (for example, BASF, trade name: TINUVIN 123) The parts were uniformly mixed to obtain a continuous oil phase component (hereinafter referred to as “oil phase”). 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 type emulsion was allowed to stand at room temperature for 1 hour, and then embossed PET film (released jointly) with a silicon spray so that the thickness of the planar part after light irradiation was 0.7 mm. Application was made on Resin Kogyo Co., Ltd., trade name “PG-62”, thickness: 50 μm). Further, a polyethylene terephthalate film was covered on the coated surface. This sheet was irradiated with ultraviolet light having a light illuminance of 5 mW / cm ² (measured by Topcon, trade name “UVR-T1” having a peak sensitivity maximum wave of 350 nm) using black light (15 W / cm), and a highly hydrous crosslinked polymer. Got. Next, the embossed PET film is peeled off, and the high water content cross-linked polymer is heated at 130 ° C. for 20 minutes, thereby having a plane portion thickness of about 0.7 mm and a plurality of convex portions on the entire upper surface. A foamed diffuse reflector (1) was obtained.
The results are shown in Table 1, FIG. 10 and FIG.
The obtained foamed diffuse reflector (1) was cut in the thickness direction with a microtome cutter, and the cross-sectional shape of the convex portion was a digital microscope (manufactured by KEYENCE, trade name “VHX-100F”, lens: VH-Z100, magnification: When observed 100 times, it was trapezoidal as shown in FIG. Moreover, the convex part height was about 0.3 mm.
Further, when the foamed diffuse reflector is sandwiched between the upper and lower surfaces by a slide glass and the foamed diffuse reflector is compressed by 5% in the thickness direction, the shortest distance y between the upper side surface and the upper side surface of the adjacent convex portion is 1.2 mm. The average value Ly of the shortest distance y between the upper end of the side surface and the upper end of the side surface of the adjacent convex portions randomly selected from 5 sets was 1.4 mm.
When the foamed diffuse reflector is compressed by 5% in the thickness direction, the “average value La ′ of the upper surface (substantially circular) diameters of adjacent convex portions (that is, the average upper surface diameter of two adjacent convex portions)” is The average value La of the diameters a of the upper surfaces of the convex portions selected at random from 10 to 0.9 mm was 1.1 mm.
The ratio (y / La ′) between the average value La ′ of the upper surface diameters and the shortest distance y between the upper ends of the side surfaces of adjacent convex portions when the foaming diffused reflector is compressed 5% in the thickness direction is 1.22. It was ˜1.32.
Moreover, the photograph figure of the surface / cross-section SEM photograph which image | photographed the plane part of the obtained foaming diffused reflection body (1) from diagonally was shown in FIG. In FIG. 13, the convex portion is not photographed.
Moreover, the photograph figure of the surface / cross-section SEM photograph which image | photographed the convex part of the obtained foaming diffused reflection body (1) from diagonally was shown in FIG.

[Example 2]
In Example 1, the same procedure as in Example 1 was used except that the embossed PET film (trade name “PG-62”, thickness: 50 μm, manufactured by Godo Plastics Co., Ltd.) was used. 2) was obtained.
The results are shown in Table 1, FIG. 10 and FIG.
When the cross-sectional view shape of the convex portion was observed in the same manner as in Example 1, it was a half circle shape as shown in FIG. The height of the convex portion was about 0.25 mm.
Further, when the foamed diffuse reflector is sandwiched between the upper and lower surfaces by a slide glass and the foamed diffuse reflector is compressed by 5% in the thickness direction, the shortest distance y between the side upper end and the side upper end of the adjacent convex portion is 1 mm-1 The average value Ly of the shortest distance y between the upper end of the side surface and the upper end of the side surface of the adjacent convex portions randomly selected from 5 sets was 1.2 mm.
When the foamed diffuse reflector is compressed by 5% in the thickness direction, the “average value La ′ of the upper surface (substantially circular) diameters of adjacent convex portions (that is, the average upper surface diameter of two adjacent convex portions)” is The average value La of the diameters a of the upper surfaces of the convex portions selected at random from 10 to 0.6 mm was 0.8 mm.
The ratio (y / La ′) between the average value La ′ of the upper surface diameter and the shortest distance y between the upper ends of the side surfaces of adjacent convex portions when the foamed diffuse reflector is compressed 5% in the thickness direction is 1.45. It was ˜1.55.

[Comparative Example 1]
In Example 1, a foamed diffuse reflector (3) having a plane part thickness of about 1 mm was obtained in the same manner as in Example 1 except that an unembossed PET film was used instead of the embossed PET film. . The obtained foaming diffused reflection body (3) did not have a convex part.
The results are shown in Table 1, FIG. 10 and FIG.

As is clear from Table 1 and FIG. 10, the foamed diffuse reflector of the present invention has a specific shape of the convex portion, so that it has excellent diffuse reflectance and contributes to the improvement of the brightness and uniformity of the backlight device. obtain. In Table 1, FIGS. 11 and 15, there are examples in which the diffuse reflectance exceeds 100%, which is due to the adjustment of the measuring apparatus with the diffuse reflectance of the barium sulfate powder being 100%. Presumed to be. However, an example in which the measurement result of the diffuse reflectance when the barium sulfate powder that theoretically exhibits 100% diffuse reflectance is used as a comparative material exceeds 100% is equivalent to or higher than that of the barium sulfate powder. It is thought that it shows.

The foamed diffuse reflector of the present invention is useful as a diffuse reflector provided in LED substrates, backlight devices of liquid crystal display devices, lighting fixtures such as fluorescent lamps and incandescent lamps.

DESCRIPTION OF SYMBOLS 100 Foam diffuse reflector 10 Foam 10a Foam 10b Foam 11 Convex part 20 Base material 30 Release film

Claims

A foamed diffuse reflector comprising a foam having an open cell structure with through-holes between adjacent spherical cells,
A plurality of protrusions having a height of 0.05 mm to 0.5 mm on at least one surface of the foam;
An average value Ly of the shortest distance y between the side upper end and the side upper end of the adjacent convex portion when the foam diffuse reflector is sandwiched between smooth plates from the upper and lower surfaces and the foam diffuse reflector is compressed 5% in the thickness direction is , 0.5 mm or more,
The average pore size of the spherical bubbles is less than 20 μm,
The average pore diameter of the through holes is 5 μm or less,
The surface of the foam has a surface opening having an average pore diameter of 20 μm or less.
Foam diffuse reflector.
A foamed diffuse reflector comprising a foam having an open cell structure with through-holes between adjacent spherical cells,
A plurality of protrusions having a height of 0.05 mm to 0.5 mm on at least one surface of the foam;
When the foamed diffuse reflector is sandwiched between smooth plates from the upper and lower surfaces, and the foam diffuse reflector is compressed by 5% in the thickness direction, the shortest distance y between the side upper end and the side upper end of the adjacent convex portion is 0.2 mm. That's it,
The average pore size of the spherical bubbles is less than 20 μm,
The average pore diameter of the through holes is 5 μm or less,
The surface of the foam has a surface opening having an average pore diameter of 20 μm or less.
Foam diffuse reflector.
The shape of the upper surface of the convex portion when the foamed diffuse reflector is compressed 5% in the thickness direction is substantially circular, and the upper surface of the convex portion when the foamed diffuse reflector is compressed 5% in the thickness direction. 3. The foamed diffuse reflector according to claim 1, wherein a ratio (Ly / La) between an average value La of diameters and an average value Ly of the shortest distance y between the upper ends of side surfaces of adjacent convex portions is 1 or more. .
The shape of the top surface of the convex portion when the foamed diffuse reflector is compressed 5% in the thickness direction is a polygon, and the top surface of the convex portion when the foamed diffuse reflector is compressed 5% in the thickness direction. The ratio (Ly / Lb) between the average value Lb of the diameter b of the circle inscribed in the circle and the average value Ly of the shortest distance y between the side surface upper ends of the adjacent convex portions is 1.2 or more. 2. A foamed diffuse reflector according to 2.
The foamed diffuse reflector according to any one of claims 1 to 4, wherein the foam comprises a hydrophilic polyurethane-based polymer.
The foamed diffuse reflector according to any one of claims 1 to 5, wherein the diffuse reflectance in a wavelength region of 400 nm to 600 nm is 90% or more.
The foamed diffuse reflector according to any one of claims 1 to 5, wherein the diffuse reflectance in a wavelength region of 400 nm to 800 nm is 90% or more.