JP2010191113A - Reflecting sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflecting sheet, having high reflectance, obtaining a bright and clear reflected image, thin, light and having favorable processing characteristics such as folding. <P>SOLUTION: The reflecting sheet is formed by stacking a cavity-containing resin layer formed of polymer having crystallinity and a base material whose transmittance at a wavelength of 550 nm is 30% or less. In the reflecting sheet, when the average thickness of a cavity in a section vertical to the surface of the cavity-containing resin and right-angled to a first drawing direction is r(μm) and the average length of the cavity in a section vertical to the cavity-containing resin layer and parallel to the first drawing direction is L(μm), the ratio L/r is 10 or more, and a projecting and recessed part with 0.15 μm<Ra<0.5 μm is provided on the surface opposite to the surface where the base material is stacked in the cavity-containing resin layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflection sheet that can be suitably used for a light reflection type screen or the like.

  In recent years, with the spread of computers, it is frequently used to project materials and data on a screen using a projector in classes and meetings, and it is suitable for a light reflective screen used in combination with a small projector. There is a need for a reflective sheet that exhibits reflectivity.

For example, Patent Document 1 proposes a method of manufacturing a reflective screen in which the average surface roughness Ra of the matte surface is 0.15 to 0.25 μm by rolling two aluminum foils. Yes. However, the reflection type screen obtained by this method has a low reflectance of 20 to 40%, and is not suitable for small projector applications in that a clear projection image cannot be obtained.
On the other hand, as a technique for obtaining a reflective sheet having a high reflectance, a technique for forming a cavity layer by containing a large amount of fine cavities inside a resin (for example, a polyester-based resin) has been proposed. This is because when the hollow layer is formed in the polyester resin, the presence of the hollow layer increases the reflectance of the polyester resin.

For example, in Patent Document 2, a polyester-based resin film containing a large number of fine cavities, the total light transmittance of which is 10% or more and less than 40%, a metallic glossy surface is disposed on the back surface of the film. A reflected light diffusing film for liquid crystal monitors has been proposed in which the reflectance of the film is improved by utilizing the high reflectance of the surface. In this technique, the difference between the average reflectance of the film at a wavelength of 400 to 700 nm and the average reflectance when the metallic glossy surface is disposed on the back surface of the film is 5% or more. The rate is as high as 10% or more, and there is still room for improvement. In addition, when the metallic glossy surface is provided on the film, since the entire thickness is large, it is difficult to bend and use as it is, and there is a problem that workability is inferior. If it is provided with a small thickness, there is a problem that it is difficult to obtain characteristics required for the reflector application.
Patent Document 3 proposes a void-containing polyester resin film obtained by adding an incompatible thermoplastic resin to a polyester resin. Although this film has a high reflectivity of 91% or more, it is rigid, so when it is bent, it has a crease and is unsuitable for a rollable screen application corresponding to a general projector.

  Therefore, the present situation is that a reflection sheet having a high reflectance, a bright and clear reflection image, and good processing characteristics such as bending has not been provided yet.

Japanese Unexamined Patent Publication No. Hei 4-296968 JP 2002-148415 A JP 2005-281396 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a reflective sheet having a high reflectance, a bright and clear reflected image, and good processing characteristics such as bending.

Means for solving the problems are as follows. That is,
<1> A void-containing resin layer made of a crystalline polymer and a base material having a transmittance of 30% or less at a wavelength of 550 nm are laminated,
The average thickness of cavities in a cross section perpendicular to the surface of the void-containing resin layer and perpendicular to the first stretching direction is r (μm), perpendicular to the surface of the void-containing resin layer, and the first L / r ratio when the average length of cavities in a cross section parallel to the stretching direction is L (μm) is 10 or more,
And it is a reflective sheet | seat characterized by having an unevenness | corrugation of 0.15 micrometer <Ra <0.5 micrometer on the surface on the opposite side to the surface where the said base material was laminated | stacked in the said void containing resin layer.
<2> The reflective sheet according to <1>, wherein the unevenness in the void-containing resin layer is formed by at least one of application of a mat material-containing coating solution, embossing, and optical imprinting.
<3> The surface having irregularities in the void-containing resin layer is composed of two or more kinds selected from the surface of the mat material-containing coating layer, the surface subjected to embossing, and the surface subjected to optical imprinting. The reflective sheet according to any one of <1> to <2>.
<4> The reflective sheet according to any one of <1> to <3>, wherein the base material has a thickness of 0.001 μm to 140 μm.
<5> A substrate containing a cavity-containing film made of a thermoplastic resin, a layer formed by metal vapor deposition, a layer made of a thermoplastic resin containing a pigment, a metal plating layer, a resin layer with a metal plate attached thereto, and The reflective sheet according to any one of <1> to <4>, wherein the reflective sheet is at least one of metal plates.
<6> The reflective sheet according to any one of <1> to <5>, wherein the polymer having crystallinity is at least one selected from polyolefins, polyamides, and polyesters.
<7> The transmittance of the void-containing resin layer is M (%), and the polymer has the same thickness as the void-containing resin layer and the same crystallinity as the crystalline polymer constituting the void-containing resin layer. From the above <1>, the M / N ratio when the transmittance of the polymer layer not containing voids is N (%) is 0.2 or less, and the glossiness of the void-containing resin layer is 50 or more <6> A reflection sheet according to any one of the above.
<8> P is the average number of cavities in the layer thickness direction in the cross section perpendicular to the surface of the void-containing resin layer and perpendicular to the first stretching direction, and the refractive index of the polymer layer having crystallinity is N1, The refractive index of the hollow layer is N2, and the difference between N1 and N2 is ΔN (= N1−N2), the product of ΔN and P is 3 or more, and any one of <1> to <7> This is a reflection sheet.
<9> The reflective sheet according to any one of <1> to <8>, wherein the polymer having at least one kind of crystallinity includes a plurality of kinds of crystal states.
<10> The reflective sheet according to any one of <1> to <9>, wherein the void-containing resin layer is composed of only one type of polymer having crystallinity.
<11> A polymer molded body in which the void-containing resin layer is made of a polymer having crystallinity at a speed of 10 to 36,000 mm / min, and
When the stretching temperature is T (° C) and the glass transition temperature of the polymer having crystallinity is Tg (° C),
(Tg-30) (° C.) ≦ T (° C.) ≦ (Tg + 50) (° C.)
The reflective sheet according to any one of <1> to <10>, including a cavity formed by stretching at a stretching temperature T (° C.) in a range indicated by.

  According to the present invention, it is possible to solve the conventional problems, provide a reflective sheet with high reflectivity, a bright and clear reflected image, and excellent processing characteristics such as bending.

Drawing 1 is a figure showing an example of a manufacturing method of a void content resin layer, and is a flow figure of a biaxially stretched film manufacturing device. FIG. 2A is a diagram for explaining the aspect ratio, and is a perspective view of the void-containing resin layer. FIG. 2B is a view for explaining the aspect ratio, and is a cross-sectional view taken along the line A-A ′ of the void-containing resin layer in FIG. 2A. FIG. 2C is a diagram for explaining the aspect ratio, and is a B-B ′ sectional view of the void-containing resin layer in FIG. 2A. FIG. 3A is a view (No. 1) for describing a method for evaluating the bendability of the reflective sheets of Examples and Comparative Examples. FIG. 3B is a diagram (No. 2) for describing a method for evaluating the bendability of the reflective sheets of Examples and Comparative Examples. FIG. 3C is a diagram (No. 3) for explaining a method for evaluating the bendability of the reflective sheets of Examples and Comparative Examples. FIG. 4A is a diagram for explaining a method for evaluating the visibility of the reflected image of the reflective sheet of the example and the comparative example, and is a side view showing the positional relationship between the reflective sheet and the projector. FIG. 4B is a diagram for explaining a method for evaluating the visibility of the reflected image of the reflective sheet of the example and the comparative example, and is a top view illustrating the arrangement relationship between the reflective sheet and the projector.

(Reflective sheet)
The reflective sheet of the present invention comprises at least a void-containing resin layer and a base material, and further comprises other layers appropriately selected as necessary.
Further, in the reflection sheet of the present invention, the void-containing resin layer and the base material are laminated, and on the surface of the void-containing resin layer opposite to the surface on which the base material is laminated, 0. It has irregularities of 15 μm <Ra <0.5 μm.

The size (surface roughness) Ra of the unevenness is not particularly limited as long as it is 0.15 μm to 0.5 μm, and can be appropriately selected according to the purpose, but is preferably 0.2 μm to 0.45 μm. . When the Ra is in the range of 0.15 μm to 0.5 μm, the reflectance is high and the generation of moire is suppressed. When the reflective sheet is used as a reflective screen, a clear image can be obtained.
The surface roughness Ra can be measured using, for example, an optical interference type three-dimensional shape analyzer (“New View 5022”; manufactured by Zygo).

The method for forming irregularities in the void-containing resin layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, at least one of application of a matting material-containing coating solution, embossing, and optical imprinting may be used. It is preferable to carry out.
The formation of the unevenness may be performed by any one of the application of the matting material-containing coating solution, the embossing, and the optical imprinting. For example, after forming the unevenness by the embossing, Different types of unevenness may be formed by applying the mat material-containing coating liquid to a part of the unevenness forming surface.

The mat material-containing coating solution can be prepared, for example, by adding a mat material to a resin.
The resin is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably a crystalline polymer that is a component of the void-containing resin layer. For example, polyesters described below are suitable. Can be mentioned.
There is no restriction | limiting in particular as said mat | matte material, Although it can select suitably according to the objective, For example, a silica, titanium oxide, etc. are mentioned suitably.

  The embossing method is not particularly limited and may be appropriately selected depending on the purpose.For example, a method of placing a file on one side of the void-containing resin layer and performing hot pressing in this state Can be mentioned. Thereby, the surface shape of the file is transferred to the surface of the void-containing resin layer, and irregularities are formed.

There is no restriction | limiting in particular as said optical imprint processing method, According to the objective, it can select suitably.
In addition to these, the unevenness can be formed using, for example, a method of pressure-bonding a metal plate or the like with a dedicated transfer pattern, laser ablation, nanoimprinting, or the like.

The surface having unevenness in the void-containing resin layer may have the same unevenness (surface roughness) or different in the surface, but the occurrence of moire is suppressed, and It is preferable that the unevenness is different in that the brightness is improved as compared with the case where the size of the unevenness is uniform in the plane. Therefore, the surface having irregularities in the void-containing resin layer is composed of two or more types selected from the surface of the mat material-containing coating layer, the surface subjected to embossing, and the surface subjected to optical imprinting. Is preferred.
The mat material-containing coating layer can be formed, for example, by applying the mat material-containing coating liquid to the surface of the cavity-containing resin layer opposite to the surface on which the base material is laminated.

-Resin layer containing voids-
The void-containing resin layer is made of at least a polymer having crystallinity, and further contains other components as necessary.
There is no restriction | limiting in particular as a shape of the said cavity containing resin layer, According to the objective, it can select suitably, For example, a film form and a sheet form are mentioned.

-Polymer with crystallinity-
In general, polymers are classified into polymers having crystallinity (hereinafter sometimes simply referred to as “crystalline polymers”) and amorphous (amorphous) polymers, but even crystalline polymers are 100% crystalline. It is not in a state, and includes a crystalline region in which long chain molecules are regularly arranged in a molecular structure and an amorphous region that is not regularly arranged.
Therefore, the polymer having crystallinity in the void-containing resin layer only needs to include at least the crystalline region in the molecular structure, and the crystalline region and the amorphous region may be mixed.

  There is no restriction | limiting in particular as said crystalline polymer, According to the objective, it can select suitably, For example, high-density polyethylene, polyolefins (for example, polypropylene etc.), polyamides (PA) (for example, nylon-6 etc.) ), Polyacetals (POM), polyesters (eg, PET, PEN, PTT, PBT, PBN, PLA, PBS, PHT, PHN, etc.), syndiotactic polystyrene (SPS), polyphenylene sulfides (PPS), poly Examples include ether ether ketones (PEEK), liquid crystal polymers (LCP), and fluororesins. Among these, polyolefins, polyamides, polyesters, syndiotactic polystyrene (SPS), and liquid crystal polymers (LCP) are preferable in terms of high mechanical strength and easy production, and polyesters and polyolefins are preferred. More preferred. Two or more of these polymers may be blended or copolymerized.

There is no restriction | limiting in particular as melt viscosity of the said crystalline polymer, Although it can select suitably according to the objective, 50-700 Pa.s is preferable, 70-500 Pa.s is more preferable, 80-300 Pa.s is Further preferred.
When the melt viscosity is 50 Pa · s or more, it is preferable in that the sagging film at the time of melt film formation is stable and uniform film formation is facilitated. In addition, when the melt viscosity is 700 Pa · s or less, the viscosity at the time of melt film formation becomes appropriate and it is easy to extrude, or the melt film at the time of film formation is leveled so that unevenness can be reduced. preferable.
Here, the melt viscosity can be measured by a plate type rheometer or a capillary rheometer.

There is no restriction | limiting in particular as intrinsic viscosity (IV) of the said crystalline polymer, Although it can select suitably according to the objective, 0.4-1.2 are preferable and 0.6-1.0 are more preferable. 0.7 to 0.9 is more preferable.
When the IV is 0.4 or more, it is preferable in that the strength of the formed film is increased. Further, when the IV is 1.2 or less, the strength of the film is not excessively high, and it is preferable in that the film can be appropriately stretched.
Here, the IV can be measured by an Ubbelohde viscometer.

There is no restriction | limiting in particular as melting | fusing point (Tm) of the said crystalline polymer, Although it can select suitably according to the objective, 40-350 degreeC is preferable, 100-300 degreeC is more preferable, 150-260 degreeC is still more preferable.
It is preferable that the melting point is 40 ° C. or higher because the shape can be easily maintained in a temperature range expected for normal use. Moreover, it is preferable that the melting point is 350 ° C. or less because a uniform film can be formed without using a special technique required for processing at a high temperature.
Here, the melting point can be measured by a differential thermal analyzer (DSC).

  The polyesters (hereinafter referred to as “polyester resins”) mean a general term for polymer compounds having an ester bond as a main bond chain. Therefore, as the polyester resin suitable as the polymer having the crystallinity, the exemplified PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PTT (polytrimethylene terephthalate), PBT (polybutylene terephthalate), Not only PBN (polybutylene naphthalate), PLA (polylactic acid), PBS (polybutylene succinate), PHN (polyhexamethylene naphthalate), PHT (polyhexamethylene terephthalate), but also dicarboxylic acid component and diol component All polymer compounds obtained by polycondensation reaction are included.

  The dicarboxylic acid component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, oxycarboxylic acids, and polyfunctional acids. Can be mentioned. Among these, aromatic dicarboxylic acids are preferable because they have high mechanical strength and excellent heat resistance.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfoisophthalic acid. Among these, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are preferable, and terephthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are more preferable because they are relatively inexpensive and easily available.

Examples of the aliphatic dicarboxylic acid include oxalic acid, succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, and fumaric acid.
Examples of the alicyclic dicarboxylic acid include cyclohexyne dicarboxylic acid.
Examples of the oxycarboxylic acid include p-oxybenzoic acid.
Examples of the polyfunctional acid include trimellitic acid and pyromellitic acid.

  There is no restriction | limiting in particular as said diol component, According to the objective, it can select suitably, For example, aliphatic diol, alicyclic diol, aromatic diol, diethylene glycol, polyalkylene glycol etc. are mentioned. Among these, aliphatic diols are preferable in terms of good crystallinity and stretchability.

Examples of the aliphatic diol include ethylene glycol, propane diol, butane diol, pentane diol, hexane diol, neopentyl glycol, and triethylene glycol. Among these, propanediol, butanediol, pentanediol, and hexanediol are particularly preferable.
Examples of the alicyclic diol include cyclohexanedimethanol.
Examples of the aromatic diol include bisphenol A and bisphenol S.

There is no restriction | limiting in particular as melt viscosity of the said polyester resin, Although it can select suitably according to the objective, 50-700 Pa.s is preferable, 70-500 Pa.s is more preferable, 80-300 Pa.s is further preferable.
When the melt viscosity is higher, voids are more likely to occur during stretching, but when the melt viscosity is 700 Pa · s or less, extrusion becomes easier during film formation, and the resin flow becomes stable and retention is less likely to occur. , Which is preferable in terms of stable quality. Furthermore, when the melt viscosity is 700 Pa · s or less, the stretching tension is appropriately maintained at the time of stretching, so that it is easy to stretch uniformly and it is difficult to break.
Further, when the melt viscosity is 50 Pa · s or more, it is easy to maintain the form of the melt film discharged from the die head at the time of film formation, and it can be stably molded or the product is hardly damaged. It is preferable in terms of improving physical properties.

There is no restriction | limiting in particular as intrinsic viscosity (IV) of the said polyester resin, Although it can select suitably according to the objective, 0.4-1.2 are preferable, 0.6-1.0 are more preferable, More preferred is 0.7 to 0.9.
When the IV is larger, voids are more likely to be generated during stretching. However, when the IV is 1.2 or less, extrusion becomes easier during film formation, and the resin flow becomes stable and retention is less likely to occur. Is preferable in terms of stability. Furthermore, when the IV is 1.2 or less, even when a molten resin filter is installed at the time of film formation, it is difficult to apply a load to the filter, and the resin flow is stable and stagnation hardly occurs. Is preferable.
Further, when the IV is 1.2 or less, the stretching tension is appropriately maintained at the time of stretching, so that it is easy to stretch uniformly and it is preferable in that a load is not easily applied to the apparatus. Further, when the IV is 0.4 or more, it is preferable in that the product is hardly damaged and the physical properties are increased.

  There is no restriction | limiting in particular as melting | fusing point (Tm) of the said polyester resin, Although it can select suitably according to the objective, 150-300 degreeC is preferable at the point which is excellent in heat resistance and film forming property, 180-270 degreeC. Is more preferable.

  In addition, as said polyester resin, the said dicarboxylic acid component and the said diol component may each superpose | polymerize, and the polymer may be formed, and at least any one of the said dicarboxylic acid component and the said diol component is 2 types. A polymer may be formed by copolymerization as described above. Further, as the polyester resin, two or more kinds of polymers may be blended and used.

  In the blend of two or more kinds of polymers, the polymer added to the main polymer has a melt viscosity and an intrinsic viscosity that are close to those of the main polymer, and the addition amount is smaller when the film is formed or melted. It is preferable in that the physical properties are enhanced during extrusion and the extrusion is easy.

  In addition, for the purpose of improving the flow characteristics of the polyester resin, controlling light transmittance, and improving the adhesion with the coating solution, a resin other than polyester may be added to the polyester resin.

  As described above, the void-containing resin layer can form voids in a simple process even without adding a void forming agent such as inorganic fine particles and incompatible resins added in the prior art. . Further, special equipment for dissolving the inert gas in the resin in advance is not required. In addition, the manufacturing method of the said void containing resin layer is mentioned later.

Here, as long as the said cavity containing resin layer is a component which does not contribute to expression of a cavity, it may contain the other component as needed.
Examples of the other components include a heat resistance stabilizer, an antioxidant, an organic lubricant, a nucleating agent, a dye, a pigment, a dispersant, and a coupling agent. Whether or not the other component contributed to the development of the cavity is determined by whether or not a component other than the crystalline polymer (for example, each component described later) is detected in the cavity or at the interface portion of the cavity. Can do.

There is no restriction | limiting in particular as said antioxidant, According to the objective, it can select suitably, For example, well-known hindered phenols are mentioned.
Examples of the hindered phenols include antioxidants commercially available under trade names such as Irganox 1010, Similarizer BHT, and Similarizer GA-80.
Further, the antioxidant can be used as a primary antioxidant and further combined with a secondary antioxidant.
Examples of the secondary antioxidant include antioxidants commercially available under trade names such as Sumilizer TPL-R, Sumilizer TPM, Sumilizer TP-D, and the like.

--Cavity--
The void-containing resin layer contains voids and is characterized by the aspect ratio of the voids.
The cavity means a vacuum domain or a gas phase domain existing in the resin layer.

The aspect ratio of the cavity will be described below with reference to FIGS.
2A is a perspective view of the void-containing resin layer, FIG. 2B is an AA ′ cross-sectional view of the void-containing resin layer in FIG. 2A, and FIG. 2C is a cross-sectional view of the void-containing resin layer in FIG. 'Cross section.

The aspect ratio is the average thickness of the cavities 100 in a section perpendicular to the surface 1a of the cavity-containing resin layer 1 and perpendicular to the first stretching direction (AA ′ section in FIG. 2A), r (μm). (See FIG. 2B), and the average length of the cavities 100 in a cross section (BB ′ cross section in FIG. 2A) perpendicular to the surface of the void-containing resin layer and parallel to the first stretching direction is L ( μm) (refer to FIG. 2C).
The aspect ratio is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. However, the aspect ratio is 10 or more in that the ratio of light reflection and scattering is preferable. Is required, preferably 15 or more, and more preferably 20 or more.

In addition, said 1st extending | stretching direction shows the extending direction of 1 axis | shaft, when extending | stretching is only 1 axis | shaft. Usually, since longitudinal stretching is performed along the flow direction of a polymer molded body, which will be described later, at the time of production, this longitudinal stretching direction corresponds to the first stretching direction.
Moreover, when extending | stretching is biaxial or more, at least 1 direction is shown among the extending directions aiming at cavity formation. Usually, even in stretching with two or more axes, longitudinal stretching is performed along the flow direction of the polymer molded body, which will be described later, during manufacture, and a cavity can be formed by this longitudinal stretching. Corresponds to the first stretching direction.

The void-containing resin layer is characterized by an average number P of voids in the layer thickness direction, a refractive index difference ΔN between the polymer layer having crystallinity and the void layer, and a product of the ΔN and the P. Have.
The number of cavities in the layer thickness direction is included in the layer thickness direction in a cross section (AA ′ cross section in FIG. 2A) perpendicular to the surface 1a of the void-containing resin layer 1 and perpendicular to the first stretching direction. Means the number of cavities 100 to be removed.
The average number P of cavities in the layer thickness direction is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. However, the ratio of reflection and transmission of light is preferable. In this respect, 5 or more are preferable, 10 or more are more preferable, and 15 or more are more preferable.
Here, the number of cavities in the layer thickness direction can be measured by an image of an optical microscope or an electron microscope.

Specifically, the refractive index difference ΔN between the crystalline polymer layer and the cavity layer is N1 when the refractive index of the crystalline polymer layer is N1 and the refractive index of the cavity layer is N2. And the value of ΔN (= N1−N2) which is the difference between N2 and N2.
Here, the refractive index N1 of the polymer layer having crystallinity and the refractive index N2 of the cavity layer can be measured by an Abbe refractometer or the like.
The product of the ΔN and the P is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose. In view of good gloss, 3 or more is preferable, 5 or more is more preferable, and 7 or more is more preferable.

  As described above, since the void-containing resin layer contains the voids, the void-containing resin layer has various excellent characteristics, for example, in reflectance and glossiness. In other words, characteristics such as reflectivity and glossiness can be adjusted by changing the mode of the voids contained in the void-containing resin layer.

[Glossiness]
The glossiness of the void-containing resin layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 50 or more from the viewpoint of obtaining a clear image by increasing the amount of light by reflection, 70 or more is more preferable, and 80 or more is still more preferable.
Here, the glossiness can be measured by a variable glossmeter.
At this time, the transmittance of the void-containing resin layer is M (%), the same thickness as the void-containing resin layer, and the same crystallinity as the crystalline polymer constituting the void-containing resin layer. The M / N ratio is preferably 0.2 or less, more preferably 0.15 or less, where N (%) is the transmittance of a polymer layer made of a polymer and containing no voids.
When the M / N ratio is 0.2 or less, the regular reflectance is preferable from the viewpoint of gloss.
Here, the said transmittance | permeability can be measured with a spectrophotometer ("U-4100"; Hitachi Ltd. make), for example.

  Furthermore, since the void-containing resin layer contains the voids but is added in the prior art, inorganic fine particles for expressing the voids, incompatible resins, and inert gases are not added, Excellent surface smoothness.

The method for producing the void-containing resin layer is not particularly limited and may be appropriately selected depending on the intended purpose, but includes at least a stretching step for stretching the polymer molded body, and further includes a film-forming step as necessary. It is preferable to include other steps.
In addition, the said polymer molded object means the thing which consists of said crystalline polymer, and does not contain a cavity especially, for example, a polymer film, a polymer sheet, etc. are mentioned.

<Extension process>
In the stretching step, the polymer molded body is stretched at least uniaxially. And by the said extending process, while the said polymer molded object is extended | stretched, the said cavity containing resin layer is obtained by forming the cavity which made the 1st extending | stretching direction a long axis in the inside.

The reason why the voids are formed by the stretching is that at least one of fine crystal nuclei and crystals are present in at least one kind of crystalline polymer constituting the polymer molded body. It is considered that a cavity is formed by being peeled and stretched in such a manner that the resin is torn off at the interface between the hard phase and the amorphous part.
Note that such void formation by stretching is possible not only when the crystalline polymer is one type, but also when two or more types of crystalline polymers are blended or copolymerized.

  The stretching method is not particularly limited, and includes, for example, uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching. In any stretching method, the polymer molded body flows along the direction of production. It is preferable that longitudinal stretching is performed.

Generally, in the longitudinal stretching, the number of longitudinal stretching stages and the stretching speed can be adjusted by the combination of rolls and the speed difference between the rolls.
The number of stages of the longitudinal stretching is not particularly limited as long as it is 1 or more, but it is preferably longitudinally stretched to 2 or more stages in that it can be more stably stretched at a high speed. Further, longitudinal stretching in two or more stages is advantageous in that a cavity can be formed by stretching in the second stage after confirming the occurrence of necking in the first stage.

There is no restriction | limiting in particular as the extending | stretching speed | rate of the said longitudinal stretch, Although it can select suitably according to the objective, 10-36,000 mm / min is preferable, 800-24,000 mm / min is more preferable, 1,200 More preferably, 12,000 mm / min.
When the stretching speed is 10 mm / min or more, it is preferable in that sufficient necking can be easily expressed. Further, when the stretching speed is 36,000 mm / min or less, uniform stretching is facilitated, and the resin is not easily broken. In particular, a large stretching apparatus for high-speed stretching is not required, and the cost is reduced. Is preferable in that it can be reduced.

Examples of the stretching method include one-stage stretching and two-stage stretching, both of which can be suitably used. However, two-stage stretching is more preferable in terms of production yield and machine constraints. preferable.
More specifically, the stretching speed in the case of one-stage stretching is preferably 1,000 to 36,000 mm / min, more preferably 1,100 to 24,000 mm / min, and 1,200 to 12,000 mm / min. Min is more preferable.

In the case of two-stage stretching, it is preferable that the first-stage stretching is a preliminary stretching whose main purpose is to develop necking.
The stretching speed of the preliminary stretching is preferably 10 to 300 mm / min, more preferably 40 to 220 mm / min, and still more preferably 70 to 150 mm / min.

In the two-stage stretching, it is preferable that the second-stage stretching speed after the necking is expressed by the preliminary stretching (first-stage stretching) is changed from the preliminary stretching speed.
The stretching speed of the second stage after causing necking by the preliminary stretching is preferably 600 to 36,000 mm / min, more preferably 800 to 24,000 mm / min, and 1,200 to 15,000 mm. / Min is more preferable.

The temperature during stretching is not particularly limited and can be appropriately selected according to the purpose.
When the stretching temperature is T (° C) and the glass transition temperature is Tg (° C),
(Tg-30) (° C.) ≦ T (° C.) ≦ (Tg + 50) (° C.)
It is preferable to stretch at a stretching temperature T (° C.) in the range indicated by
(Tg-25) (° C.) ≦ T (° C.) ≦ (Tg + 45) (° C.)
It is more preferable to stretch at a stretching temperature T (° C.) in the range indicated by
(Tg-20) (° C.) ≦ T (° C.) ≦ (Tg + 40) (° C.)
More preferably, the film is stretched at a stretching temperature T (° C.) in the range indicated by

  In general, the higher the stretching temperature (° C.), the lower the stretching tension, and the easier the stretching, but when the stretching temperature (° C.) is {glass transition temperature (Tg) +50} ° C. or less, the void content And the aspect ratio is preferably 10 or more. Moreover, it is preferable that the stretching temperature (° C.) is {glass transition temperature (Tg) −30} ° C. or higher in that a cavity is sufficiently developed.

  Here, the stretching temperature T (° C.) can be measured with a non-contact thermometer. The glass transition temperature Tg (° C.) can be measured by a differential thermal analyzer (DSC).

In the stretching step, lateral stretching may or may not be performed within a range that does not hinder the development of the cavity. Moreover, when performing the said horizontal extending | stretching, a film may be relieve | moderated using a horizontal extending process, or heat processing may be performed.
Further, for the purpose of stabilizing the shape, the void-containing resin layer after stretching may be further subjected to treatment such as heat shrinkage or tension.

The method for producing the polymer molded body is not particularly limited and may be appropriately selected depending on the intended purpose. For example, when the crystalline polymer is the polyester resin, it is more preferable to use a melt film forming method. Can be manufactured.
Moreover, the polymer molded body may be produced independently of the stretching step or continuously.

FIG. 1 is a diagram illustrating an example of a method for producing the void-containing resin layer, and is a flow diagram of a biaxially stretched film production apparatus.
As shown in FIG. 1, the raw material resin 11 is melted and kneaded inside an extruder 12 (a twin screw extruder or a single screw extruder is used depending on the raw material shape and production scale), and then T It is discharged from the die 13 into a soft plate (film or sheet).
Next, the discharged film or sheet F is cooled and solidified by the casting roll 14 to form a film. The formed film or sheet F (corresponding to “polymer molded body”) is sent to the longitudinal stretching machine 15.
And the film or sheet | seat F formed into a film is again heated within the longitudinal stretch machine 15, and is stretched | stretched longitudinally between the rolls 15a from which speed differs. By this longitudinal stretching, a cavity is formed in the film or sheet F along the stretching direction. Then, the film or sheet F in which the cavity is formed is gripped at both ends by the left and right clips 16a of the transverse stretching machine 16, and is stretched laterally while being sent to the winder side (not shown). Resin layer 1 is formed. In addition, in the said process, you may use the film or sheet | seat F which performed only the longitudinal stretch as the cavity containing resin layer 1 without using for the horizontal stretcher 16. FIG.

-Base material-
The shape, structure, color, thickness, material and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. However, the transmittance at a wavelength of 550 nm is 30% or less. is required.

[Transmissivity]
The transmittance needs to be 30% or less and preferably 20% or less at a wavelength of 550 nm. When the transmittance is 30% or less, the reflectance as a material is excellent.
The transmittance can be measured using, for example, a spectrophotometer (“U-4100”; manufactured by Hitachi, Ltd.).

There is no restriction | limiting in particular as a shape of the said base material, According to the objective, it can select suitably, For example, a sheet form, a film form, plate shape, etc. are mentioned. Among these, a film shape is preferable in that it is thin and lightweight and has good workability such as bending.
There is no restriction | limiting in particular as a structure of the said base material, According to the objective, it can select suitably, A single layer structure may be sufficient and a laminated structure may be sufficient.
There is no restriction | limiting in particular as a color of the said base material, Although it can select suitably according to the objective, White and silver are preferable at the point which can improve a reflectance.

The material for the substrate is not particularly limited and may be appropriately selected depending on the intended purpose. Preferred examples include thermoplastic resins, thermoplastic resins containing pigments, and metals.
As the base material made of the thermoplastic resin, it is preferable to contain a cavity inside, for example, the same void-containing film as the above-mentioned void-containing resin layer may be used as the base material, Commercially available void-containing films in which there is present may be applied.
There is no restriction | limiting in particular as said pigment in the thermoplastic resin containing the said pigment, According to the objective, it can select suitably, For example, a white pigment, a colored pigment, an inorganic pigment, an organic pigment etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, white and silver pigments are preferable in that the reflectance can be improved. In addition, when the said colored pigment is used, reflected light can be changed and an unexpected effect is exhibited in terms of aesthetics.
Specific examples of the substrate include, for example, PET in which carbon black is kneaded.
Specific examples of the pigment include, for example, carbon black in the case of black, and other colors include PR254 (red), PY155 (yellow), PB15 (blue), and the like. .

There is no restriction | limiting in particular as said metal, Although it can select suitably according to the objective, For example, silver, aluminum, etc. are mentioned suitably.
The base material made of metal may be formed by metal vapor deposition, may be formed by metal plating, or a metal plate may be applied.
As the metal in the case of the metal vapor deposition and the metal plating, silver and aluminum are preferably mentioned.
As said metal plate, an aluminum foil, an aluminum plate, etc. are mentioned suitably, for example.
Moreover, you may affix the said metal plate to resin and use it.

There is no restriction | limiting in particular as thickness of the said base material, Although it can select suitably according to the objective, It is preferable that it is thin, 0.001-140 micrometers is more preferable, and 0.005-70 micrometers is more preferable.
If the thickness is less than 0.001 μm, vapor deposition or the like may be insufficient, and the reflectivity may not be sufficiently increased. If the thickness exceeds 140 μm, the total thickness of the reflective sheet increases, and bending or the like may occur. It may be inferior in workability and handleability.

The total thickness of the reflective sheet of the present invention can be appropriately determined according to the thickness of the void-containing resin layer and the substrate, but is preferably 30 to 150 μm, and more preferably 40 to 120 μm.
When the total thickness is in the range of 30 to 150 μm, it can be easily folded, wound on a roll with a small curvature, and is excellent in workability and handleability.

  The reflective sheet of the present invention shows a high reflectance because the void-containing resin layer contains the void, and is further laminated with the base material, and on the opposite side of the laminated surface of the base material By forming irregularities on the surface, the reflectance is further improved, and a bright and clear image can be obtained. Further, since the thickness of the reflection sheet is thin, the processing characteristics such as bending and handling are good, and the weight is light. For this reason, it can be rolled up and stored, is easy to carry, and can be suitably used for light reflecting screens for small projectors, portable small screens used in homes and small conference rooms, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example at all.

(Production Example 1)
-Production of void-containing film A-
PBT with intrinsic viscosity (IV) = 0.72 (100% polybutylene terephthalate resin polymerized by FUJIFILM Corporation; polyester) is extruded from a T-die at 245 ° C. using a melt extruder, and a casting drum The polymer molded body (polymer film) having a thickness of about 210 μm was obtained. Subsequently, this polymer film was uniaxially stretched (longitudinal stretching).
Specifically, in a heated atmosphere of 48 ° C., uniaxially stretching at a speed of 120 mm / min and confirming that necking has occurred, and then in the same direction as the beginning at a speed of 7,000 mm / min. The film was further uniaxially stretched to obtain a cavity-containing film (cavity-containing resin layer) A having a thickness of about 42 μm.

(Production Example 2)
-Production of void-containing film B-
Polypropylene (100% polypropylene resin; polyolefin, manufactured by Aldrich, number average molecular weight = 50,000, MFI: 35 g / 10 min (ASTM D1238, 230 ° C., 2.16 kg), Tm = 173 ° C.) using a melt extruder The polymer was extruded from a T die at 220 ° C. and solidified with a casting drum to obtain a polymer molded body (polymer film) having a thickness of about 290 μm. Subsequently, this polymer film was uniaxially stretched (longitudinal stretching).
Specifically, uniaxial stretching was performed in one step at a rate of 13,000 mm / min in a heated atmosphere at 35 ° C. to obtain a cavity-containing film (cavity-containing resin layer) B having a thickness of 47 μm.

(Production Example 3)
-Production of void-containing film C-
Nylon (polyamides, “MXD6 nylon”; manufactured by Mitsubishi Gas Chemical Co., MI = 2) was extruded from a T-die at 270 ° C. using a melt extruder and solidified with a casting drum to give a polymer molded body having a thickness of about 120 μm ( Polymer film) was obtained. Next, this polymer film was uniaxially stretched.
Specifically, uniaxial stretching was performed at a speed of 100 mm / min in a heated atmosphere at 95 ° C., and it was confirmed that necking occurred, and then at the speed of 6,000 mm / min in the same direction as the beginning. The film was further uniaxially stretched to obtain a cavity-containing film (cavity-containing resin layer) C having a thickness of about 28 μm.

(Comparative Production Example 1)
-Production of reflective film D-
Based on the description of Japanese Patent No. 3013551, a reflective film D was produced.
That is, 60 parts by mass of ultra-low density polyethylene (density 0.90) having a refractive index of 1.54 and 40 parts by mass of polystyrene having a refractive index of 1.59 (molecular weight 95,000) are kneaded, using polyethylene as a matrix, polystyrene Was prepared as a spherical dispersion (island part of sea-island structure). This phase-separated resin composition was supplied to a T-die type extruder with a discharge port clearance of 0.7 mm and extruded at a melting temperature of 240 ° C. The extruded sheet-like molten resin was cooled at 15 m / min in the extrusion direction while being strongly drawn and stretched to obtain a film of anisotropic light scattering material having a thickness of 50 μm.
Next, an aluminum vapor-deposited film having a film thickness of 100 μm was bonded to this film with an adhesive to obtain a reflective film D having a thickness of 150 μm.

(Comparative Production Example 2)
-Production of void-containing film E-
A void-containing film E was produced based on the description of Example 1 in JP-A No. 2002-71915.
That is, polyethylene terephthalate resin (manufactured by Toyobo Co., Ltd., intrinsic viscosity: 0.62 dl / g) 74% by mass), general-purpose polystyrene resin (PS) (“T575-57U”; manufactured by Mitsui Toatsu Chemical Co., Ltd.) 25 mass %, And 1% by mass of maleimide-modified polystyrene resin (M-PS) (“NH1200”; manufactured by Mitsui Toatsu Chemical Co., Ltd.) were vacuum dried at 180 ° C. for 4 hours, and then charged into a twin screw extruder. After melt extrusion at 295 ° C. from a T-die, an unstretched sheet was obtained by electrostatically adhering and solidifying to a cooling rotating roll. Next, the unstretched sheet was passed through a roll stretching machine and longitudinally stretched 3.2 times at 82 ° C., and then stretched 2.5 times at 125 ° C. with a tenter and further 220 ° C. with a tenter. Was stretched 1.4 times. Thereafter, a 4% relaxation heat treatment was performed at 230 ° C. to obtain a 185 μm-thick polyester film (cavity-containing film E) having many cavities inside the film.

  In addition to these films A to E, a reflected light diffusion film F (“E60L”; manufactured by Toray) and a reflected light diffusion film G (“MCPET”; manufactured by Furukawa Electric) were prepared.

  For the above films A to G, transmittance, glossiness, thickness, surface smoothness, aspect ratio, average number P of cavities in the layer thickness direction, and refractive index difference ΔN between the crystalline polymer layer and the cavity layer are as follows: Measured by the method. The results are shown in Table 1.

(1) Measurement of transmittance The transmittance was measured using a spectrophotometer ("U-4100"; manufactured by Hitachi, Ltd.). Light was incident on the surface of the film from a direction perpendicular to it, and the intensity of the light transmitted through the film was compared with the value of a blank where no film was placed. A wavelength of 550 nm was used.

(2) Measurement of Glossiness Glossiness was obtained by measuring using a variable angle glossimeter (“VG-1001DP”; manufactured by Nippon Denshoku Industries Co., Ltd.) under conditions of 60 ° incidence and 60 ° light reception.

(3) Measurement of thickness It measured using the long range contact-type displacement meter ("AF030 (measurement part)", "AF350 (indication part)"; Keyence Corporation make).

(4) Measurement of surface smoothness Using an optical interference type three-dimensional shape analyzer (“New View 5022”; manufactured by Zygo), the surface smoothness was measured at a magnification of 50 times.

(5) Measurement of aspect ratio A cross section perpendicular to the surface of the film and perpendicular to the longitudinal stretching direction (see FIG. 2B), and a cross section perpendicular to the surface of the film and parallel to the longitudinal stretching direction (see FIG. 2C). ) With a scanning electron microscope at an appropriate magnification of 300 to 3,000 times, and a measurement frame was set in each cross-sectional photograph. This measurement frame was set so that 50 to 100 cavities were included in the measurement frame.
Next, the number of cavities included in the measurement frame is measured, and the number of cavities included in the measurement frame having a cross section perpendicular to the longitudinal stretching direction (see FIG. 2B) is m and the cross section parallel to the longitudinal stretching direction. The number of cavities included in the measurement frame (see FIG. 2C) was n.
Then, the longitudinal stretching direction perpendicular cross section of the measurement frame measured one by one in the thickness of the cavity (r _i) included in (see FIG. 2B), and the thickness of the average and r. Further, the length (L _i ) of each cavity included in the measurement frame (see FIG. 2C) having a cross section parallel to the longitudinal stretching direction was measured, and the average length was defined as L.
That is, r and L can be represented by the following formulas (1) and (2), respectively.
r = (Σr _i ) / m (1)
L = (ΣL _i ) / n (2)
Then, L / r was calculated as an aspect ratio.

(6) Average number P of cavities in the layer thickness direction
First, a cross section perpendicular to the surface of the film and perpendicular to the longitudinal stretching direction was photographed with a scanning electron microscope.
In the cross-sectional photograph, a straight line was drawn in the layer thickness direction (from the bottom surface to the top surface of the film), and the number of cavities in contact with the straight line was measured. This operation was performed for 20 straight lines, and the average was obtained.

(7) Refractive index difference ΔN between the crystalline polymer layer and the cavity layer
The refractive index N1 of the crystalline polymer layer and the refractive index N2 of the cavity layer were measured with an Abbe refractometer, and the difference ΔN (= N1−N2) was calculated.

From Table 1, it was found that the void-containing films (void-containing resin layers) A to C effectively block light and exhibit good reflection characteristics and gloss.

Example 1
-Production of reflective sheet-
Ag vapor deposition was directly performed on one side of the 42 μm-thick void-containing film A prepared in Production Example 1 to produce an Ag vapor deposition layer as the substrate having a thickness of 0.01 μm.
The transmittance of this Ag vapor deposition layer was measured using a spectrophotometer (“U-4100”; manufactured by Hitachi, Ltd.) after forming the vapor deposition layer on a commercially available PET film having a transmittance of 99%. Light was incident from a direction perpendicular to the surface of the Ag vapor deposition layer, and the intensity of the light transmitted through the Ag vapor deposition layer was compared with the value of the blank without the Ag vapor deposition layer. A wavelength of 550 nm was used. As a result, the transmittance was 0%.
Here, both of the Ag vapor-deposited layer and the vapor-deposited layer formed on the PET film were subjected to a current value of 12 mA under high vacuum for 3 minutes using an ion sputtering apparatus (“E-1030 type”; manufactured by Hitachi, Ltd.). It was formed by vapor deposition.

  Next, 10 parts by mass of a polyester resin (“Byron 200”; manufactured by TOYOBO), 1 part by mass of a fluorescent brightening agent (“Uvitex”; manufactured by Ciba Geigy), and 30 parts by mass of titanium oxide were mixed with a solvent (methyl ethyl ketone / toluene = 1: 1). ) Dissolved in 80 parts by mass to prepare a coating material containing a mat material. Using this coating solution, a mat material-containing coating layer having a thickness of 10 μm was formed on the surface of the cavity-containing film A opposite to the surface on which the Ag vapor deposition layer was laminated using a bar coater to obtain a reflective sheet.

(Example 2)
-Production of reflective sheet-
A cloth file (# 2,000) was placed on one side of the cavity-containing film A having a thickness of 42 μm prepared in Production Example 1. In this state, hot pressing was performed under the conditions of a pressing surface temperature of 150 ° C., a pressing pressure of 0.2 MPa, and a pressing time of 10 minutes, and the surface shape of the cloth file was transferred to the cavity-containing film A to form irregularities (the embossing) processing). The cloth file was changed and pressed twice.
Next, an Ag vapor deposition layer was formed by vapor deposition on the surface of the cavity-containing film A opposite to the embossed surface in the same manner as in Example 1 to obtain a reflective sheet.

(Example 3)
-Production of reflective sheet-
A cloth file (# 2,000) is placed on the cavity-containing film A having a thickness of 42 μm produced in Production Example 1, and hot pressing is performed in the same manner as in Example 1 to change the surface shape of the cloth file to the cavity-containing film A. To form irregularities (the embossing). In addition, the cloth file was replaced and further pressed twice.
Next, an Ag vapor deposition layer was formed on the surface opposite to the embossed surface by vapor deposition in the same manner as in Example 1.
Furthermore, the mat material-containing coating solution prepared in the same manner as in Example 1 was stamped on the embossed surface using an aluminum stamp in which a checkered pattern of 0.5 mm square was formed by unevenness, and the thickness was about 2 μm. A discontinuous layer mat material-containing coating layer was formed to obtain a reflective sheet.

Example 4
-Production of reflective sheet-
An Al (aluminum) vapor-deposited layer having a thickness of 0.01 μm was directly produced on one side of the cavity-containing film A in the same manner as in Example 1. When the transmittance of this Al vapor deposition layer was measured in the same manner as in Example 1, it was 0.4%.
Next, a roll-to-roll photocuring imprint was performed on the surface of the cavity-containing film A opposite to the Al vapor deposition surface using the method described in JP-A-2007-83447. Specifically, as a resin liquid, trimethylolpropane triacrylate (“Aronix M309”; manufactured by Toagosei Co., Ltd.) 98% by mass and a photopolymerization initiator (TPO-L) (“Lucirin TPO-L”; BASF A product prepared by mixing 2% by mass) was used.
A transparent resin mold separately prepared with a photo-curing resin engraved with a pattern of 5 μm × 5 μm × 3 μm in advance is pasted on an embossing roller without grooves, and the above-mentioned Al deposited layer is formed. Film A was conveyed as a sheet. The resin liquid was applied using a die coater so as not to be dried and to have a thickness of 5 μm. Further, a metal halide lamp was used as a resin curing means, and irradiation was performed with an energy of 1,000 mJ / cm ² . And the reflective sheet in which the uneven | corrugated pattern was formed was obtained.

(Example 5)
-Production of reflective sheet-
The same cavity-containing film B as the cavity-containing resin layer was laminated on the cavity-containing film B having a thickness of 47 μm prepared as the base material, and an adhesive (“E-4105”; manufactured by Soken Chemical Co., Ltd.). ) Was applied and dried, and then laminated to form a laminate.
Next, in the same manner as in Example 3, the surface shape of the cloth file (# 200) was transferred to the surface of the void-containing film B as the void-containing resin layer to form irregularities (the embossing). Further, a discontinuous mat material-containing coating layer having a thickness of about 2 μm was formed on the embossed surface in the same manner as in Example 1 to obtain a reflective sheet having a thickness of 96 μm.

(Example 6)
-Production of reflective sheet-
As the substrate, an aluminum foil having a thickness of 12 μm (“Mitsubishi foil”; manufactured by Mitsubishi Aluminum Co., Ltd.) was used. The transmittance of this aluminum foil was measured in the same manner as in Example 1. As a result, it was 0%.
Next, a cavity-containing film C as the cavity-containing resin layer produced in Production Example 3 was laminated on the aluminum foil, and bonded with the adhesive to form a laminate.
Further, in the same manner as in Example 4, irregularities were formed on the surface of the cavity-containing film C by imprinting to obtain a reflective sheet having a thickness of 43 μm.

(Example 7)
-Production of reflective sheet-
As the void-containing resin layer and the substrate, the void-containing film A produced in Production Example 1 was used.
The cavity-containing film A prepared as the base material was laminated with the same cavity-containing film A as the cavity-containing resin layer and bonded with the adhesive.
Next, in the same manner as in Example 1, a mat material-containing coating layer having a thickness of 10 μm was formed on the surface of the cavity-containing film A as the cavity-containing resin layer, thereby obtaining a reflective sheet having a thickness of 94 μm.

(Comparative Example 1)
In Example 1, a base material was not laminated | stacked and the mat | matte material containing coating layer was not formed, but the cavity containing film A itself was made into the reflective sheet.

(Comparative Example 2)
The reflective film D produced in Comparative Production Example 2 (a laminate of an anisotropic light scattering material film having a thickness of 50 μm and an aluminum vapor deposition film having a thickness of 100 μm) itself was used as a reflective sheet having a thickness of 150 μm.

(Comparative Example 3)
-Production of reflective sheet-
In Example 6, the cavity-containing film C was replaced with the reflected light diffusing film E produced in Comparative Production Example 2, and the surface of the reflected light diffusing film E was not formed with irregularities. In the same manner as described above, a reflective sheet having a thickness of 197 μm was produced.

(Comparative Example 4)
-Production of reflective sheet-
In Example 6, the cavity-containing film C was replaced with a reflected light diffusing film F (“E60L”; manufactured by Toray, thickness 170 μm), and the surface of the reflected light diffusing film F was not formed with irregularities. In the same manner as in Example 6, a reflective sheet having a thickness of 182 μm was produced.

(Comparative Example 5)
-Production of reflective sheet-
In Example 6, the void-containing film C is replaced with a reflected light diffusing film G (“MCPET”; manufactured by Furukawa Electric Co., Ltd., thickness: 1,000 μm), and no irregularities are formed on the surface of the reflected light diffusing film G. A reflective sheet having a thickness of 1,012 μm was produced in the same manner as in Example 6 except that.

(Comparative Example 6)
-Production of reflective sheet-
In Example 2, the cavity-containing film A is replaced with a reflected light diffusing film G (“MCPET”; manufactured by Furukawa Electric, thickness: 1,000 μm), and instead of forming the Ag vapor deposition layer, the base material is used. A reflective sheet was produced in the same manner as in Example 2, except that an aluminum foil having a thickness of 12 μm (“Mitsubishi foil”; manufactured by Mitsubishi Aluminum Co., Ltd.) was bonded to the cavity-containing film A with the adhesive. .

  The reflective sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 6 were each backed with a polyester felt (black) having a thickness of about 1 mm, and then the surface roughness and reflective properties (reflectance and reflection) of these reflective sheets. Rate difference), workability (foldability), and visibility of the reflected image were evaluated as follows. The results are shown in Table 2.

(1) Surface Roughness In each reflection sheet, the unevenness (surface roughness) on the surface opposite to the surface on which the base material is laminated in the films A to G is measured with an optical interference type three-dimensional shape analyzer (“NewView 5022”). "; Manufactured by Zygo Co., Ltd.) and measured with an objective lens 50 times.

(2) Reflection characteristics [Reflectance]
The reflectance was obtained by attaching an integrating sphere to a spectrophotometer (“V-570”; manufactured by JASCO Corporation), measuring the reflectance at a wavelength of 400 nm to 700 nm for each wavelength of 1 nm, and obtaining the reflectance at 550 nm. Here, as a reference value, the reflectance of the standard white board attached to the apparatus was set to 100%.
[Reflectance difference]
The average reflectance of film A to film G alone was measured. And the difference with the average reflectance of the said reflection sheet produced by laminating | stacking each film and the said base material was calculated | required.

(3) Workability [Bendability]
First, as shown in FIG. 3A, a stainless ruler 20 having a thickness of about 2 mm was placed at 90 ° with respect to the longitudinal direction of the reflection sheet 30, and a straight line was drawn with the oil marker 22 as it was.
Next, as shown in FIG. 3B, the stainless ruler 20 was removed after being bent at 90 ° along a straight line described by the oil marker 22.
Furthermore, as shown in FIG. 3C, after the reflecting sheet 30 is bent and pressed at 180 °, the reflecting sheet 30 is again spread on a flat table, and the bent portion is visually observed. Evaluation was made based on the following criteria.
-Evaluation criteria-
○: A crease is formed in a straight line along a straight line drawn with an oil marker, and no cracks are observed in the crease part when observing from both the front and back sides of the reflection sheet. Can be bent.
X: The crease does not follow the straight line drawn by the oil marker, and meanders or discontinuous portions are observed. Further, when observed from both the front and back surfaces of the reflective sheet, fine wrinkles are observed at the crease portion.

[Visibility of reflected images]
Next, as shown in FIG. 4A and FIG. 4B, each reflection sheet 30 and a small projector (“PRO920”; manufactured by Oculon Optics Inc.) 40 are placed on a table whose surface illuminance is 840-850 Lx. It was arranged to face each other at an interval of 8 m.
Next, the visual acuity test table (Landolt ring) is projected onto the reflective sheet 30 in a size of 30 cm in length by the projector 40, and the reflected image is visually observed at points A and B, based on the following criteria: evaluated. The results are also shown in Table 2.
Here, FIG. 4A is a side view showing the arrangement of the reflection sheet 20 and the projector 40, and FIG. 4B is a top view thereof.
-Evaluation criteria-
A: The reflected image was bright and clear, and a Landolt ring of 1.5 could be recognized.
○: A Landolt ring of 1.0 could be recognized.
Δ: A Landolt ring of 0.8 could be recognized.
X: The reflection image was unclear and a 0.6 Landolt ring could not be recognized.

  From Table 2, the reflection sheets of Examples 1 to 7 have high reflectivity and good visibility, and in particular, the reflections of Examples 3 and 5 in which different uneven patterns were formed in the same plane. The sheet was found to show excellent visibility. Moreover, it turned out that the reflective sheet of this invention has favorable bendability. For this reason, winding up is easy and it can be conveniently used as a screen corresponding to a general projector.

  The reflecting sheet of the present invention is suitable for a light reflecting screen for a small projector, a portable small screen and the like.

DESCRIPTION OF SYMBOLS 1 Cavity containing resin layer 1a Surface 20 Stainless steel ruler 22 Oily marker 30 Reflective sheet 40 Projector 100 Cavity L Cavity length in aspect ratio r Cavity thickness in aspect ratio

Claims (6)

A void-containing resin layer made of a polymer having crystallinity and a base material having a transmittance of 30% or less at a wavelength of 550 nm are laminated,
The average thickness of cavities in a cross section perpendicular to the surface of the void-containing resin layer and perpendicular to the first stretching direction is r (μm), perpendicular to the surface of the void-containing resin layer, and the first L / r ratio when the average length of cavities in a cross section parallel to the stretching direction is L (μm) is 10 or more,
And the reflective sheet | seat which has an unevenness | corrugation of 0.15 micrometer <Ra <0.5 micrometer on the surface on the opposite side to the surface where the said base material was laminated | stacked in the said cavity containing resin layer.   The reflection sheet according to claim 1, wherein the unevenness in the void-containing resin layer is formed by at least one of application of a mat material-containing coating solution, embossing, and optical imprinting.   The surface having irregularities in the void-containing resin layer is composed of two or more kinds selected from the surface of the mat material-containing coating layer, the surface subjected to embossing, and the surface subjected to optical imprinting. The reflection sheet according to any one of 2 above.   The thickness of a base material is 0.001 micrometer-140 micrometers, The reflection sheet in any one of Claim 1 to 3.   A substrate containing a cavity-containing film made of a thermoplastic resin, a layer formed by metal vapor deposition, a layer made of a thermoplastic resin containing a pigment, a metal plating layer, a resin layer with a metal plate attached thereto, and a metal plate The reflection sheet according to any one of claims 1 to 4, which is at least one of them.   The reflective sheet according to claim 1, wherein the polymer having crystallinity is at least one selected from polyolefins, polyamides, and polyesters.