TWI619607B - White reflective film - Google Patents

Abstract

The present invention is a white reflective film having a reflective layer A and a surface layer B composed of a resin composition containing particles, and is characterized in that the surface of the surface layer B opposite to the reflective layer A is formed of the particles The number of protrusions on the surface with a height of 5 μm or more is 10 ⁴ to 10 ¹⁰ / m ² ; the particles are non-spherical particles with an average particle size of 3 to 100 μm and a 10% compressive strength of 0.1 to 15 MPa. This film can sufficiently suppress adhesion to the light guide plate, and at the same time, sufficiently prevent damage to the light guide plate.

Description

White reflective film

The present invention relates to a white reflective film. In particular, it relates to a white reflective film used in a liquid crystal display device.

A backlight unit of a liquid crystal display device (LCD) includes a direct type having a light source on the back of the liquid crystal display panel and a reflective film on the back, a light guide plate provided with a reflective plate on the back of the liquid crystal display panel, A side light type of a light source is provided on the side of such a light guide plate. In the past, the backlight unit used in large LCDs mainly used direct-type (mainly direct-type CCFL) from the standpoint of the brightness of the screen and the uniformity of the brightness within the screen, and the side-light type was mostly used in notebook computers, etc. Smaller LCDs. However, with the development of light sources or light guide plates, the brightness of the side-light type backlight unit and the uniformity of the brightness in the screen have also improved. Therefore, it is gradually adopted not only in the smaller ones but also in large LCDs Edge-lit backlight unit. This is because there is an advantage that the LCD can be thinned.

The edge-light type backlight unit has a structure in which the light guide plate and the reflective film are in direct contact. Therefore, in such a structure, when the light guide plate and the reflective film are pasted together, the problem is that the brightness of the pasted portion is abnormal and the brightness is generated. In-plane difference. Therefore, there is a gap between the light guide plate and the reflective film, and it is necessary to maintain such a gap at a constant value. For example, by having beads on the surface of the reflective film, the distance between the light guide plate and the reflective film can be kept at a constant value, and such sticking can be prevented. However, at this time, when the light guide plate composed of a relatively soft material is in contact with the reflective film, there is a problem that the light guide plate is damaged due to the reflective film or the beads on the surface. As a countermeasure for this, for example, Patent Documents 1 to 3 have reported that a surface of a reflective film is coated with a coating to form a damage prevention layer containing synthetic rubber-based beads.

However, the damage prevention layers such as Patent Documents 1 to 3 have an effect of suppressing damage to the light guide plate to a certain extent, but tend to degrade the intended interval (suppression of adhesion). In addition, according to the review by the inventors, it can be understood that focusing only on the number of protrusions in the previous manner is necessary for satisfying the requirements for suppressing sticking with the light guide plate and suppressing damage to the light guide plate in recent years. There are deficiencies.

(Patent Document 1) Japanese Patent Laid-Open No. 2003-92018

(Patent Document 2) Japanese Patent Publication No. 2008-512719

(Patent Document 3) Japanese Patent Laid-Open No. 2009-244509

An object of the present invention is to provide a white reflective film capable of sufficiently suppressing adhesion to a light guide plate and at the same time sufficiently suppressing damage to the light guide plate.

In order to solve the above problems, the present invention adopts the following configuration.

1. A white reflective film having a reflective layer A and a surface layer B composed of a resin composition containing particles, characterized in that the surface of the surface layer B opposite to the reflective layer A has a surface formed of the particles The number of protrusions on the surface of which is 5 μm or more is 10 ⁴ to 10 ¹⁰ / m ² ; the particles are non-spherical particles having an average particle diameter of 3 to 100 μm and a 10% compressive strength of 0.1 to 15 MPa.

2. The white reflective film according to the above 1, wherein the particles are pulverized polymer particles obtained by pulverizing a polymer.

3. The white reflective film according to the above 2, wherein the polymer is a polyester.

4. The white reflective film according to any one of 1 to 3 above, wherein the particles have an average aspect ratio (long diameter / short diameter) of 1.31 to 1.80, and the standard deviation of the aspect ratio is 0.15 to Non-spherical particles of 0.50.

5. The white reflective film according to any one of 1 to 3 above, wherein the content of the particles in the surface layer B is 1 to 70% by mass based on the mass of the surface layer B.

6. The white reflective film according to any one of 1 to 3 above, wherein the amount of the volatile organic solvent is 10 ppm or less.

7. The white reflective film according to any one of 1 to 3 above, wherein the reflective layer A contains voids, and the void volume ratio is 15% by volume or more and 70% by volume or less.

8. The white reflective film according to the above 7, further comprising a support layer C having a void volume ratio of 0% by volume or more and 15% by volume or less.

9. The white reflective film according to the above 7, wherein the surface layer B is a layer formed by coating with a coating liquid.

10. The white reflective film according to any one of 1 to 3 above, wherein Used as a surface light source reflector with a light guide plate.

1 and 2 are examples of electron microscope photographs of protrusions formed by aspherical particles according to the present invention.

FIG. 3 is a schematic diagram showing a method for evaluating damage to a light guide plate and evaluating particles falling off according to the present invention.

FIG. 4 is a schematic diagram showing a structure used in the evaluation of a close spot according to the present invention.

The white reflective film of the present invention includes a reflective layer A and a surface layer B.

Hereinafter, each component constituting the present invention will be described in detail.

[Reflective layer A]

The reflective layer A of the present invention is composed of a thermoplastic resin and a void-forming agent. The void-forming agent is used to contain voids in the layer to form a white layer. Such a pore-forming agent will be described in detail later. For example, inorganic particles and a thermoplastic resin constituting the reflective layer A can be used as a non-compatible resin (hereinafter, referred to as a non-compatible resin). In addition, the reflectance of the reflective layer A at a wavelength of 550 nm is preferably 95% or more, more preferably 96% or more, and particularly preferably 97% or more. This makes it easy to set the reflectance of the white reflective film in a better range.

Reflective layer A is a layer having holes in the layer as described above, and The ratio of the volume of the voids to the volume of the reflective layer A (void volume ratio) is preferably 15% by volume or more and 70% by volume or less. In such a range, the effect of increasing the reflectance can be improved, and the above-mentioned reflectance can be easily obtained. In addition, the effect of improving the stretchability of the film can be improved. When the void volume ratio is too low, it tends to be difficult to obtain a better reflectance. From such a viewpoint, the void volume ratio of the reflective layer A is more preferably 30% by volume or more, and particularly preferably 40% by volume or more. On the other hand, when it is too high, there is a tendency that the effect of improving the stretchability of the film formation is reduced. From such a viewpoint, the void volume ratio of the reflective layer A is more preferably 65% by volume or less, and particularly preferably 60% by volume or less.

The void volume ratio can be achieved by adjusting the type, size, and amount of the void-forming agent in the reflective layer A.

(Thermoplastic resin)

Examples of the thermoplastic resin constituting the reflective layer A include thermoplastic resins made of, for example, polyester, polyolefin, polystyrene, and acrylate. Among these, polyester is also preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As such a polyester, a polyester composed of a dicarboxylic acid component and a diol component is preferably used. Examples of the dicarboxylic acid component include those obtained from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, adipic acid, and sebacic acid. Of ingredients. Examples of the diol component include components obtained from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol. Among these polyesters, aromatic polyesters are also preferred. Ethylene phthalate is particularly preferred. Polyethylene terephthalate may be a homopolymer. However, from the standpoint of suppressing crystallization and improving the film elongation improvement effect when the film is stretched uniaxially or biaxially, Copolymers are preferred. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component or diol component. However, from the standpoint of high heat resistance and high film extensibility improvement effect, the isophthalic acid component, 2,6- A naphthalenedicarboxylic acid component is preferred. The proportion of the copolymerization component is based on 100 mol% of the total dicarboxylic acid content of the polyester, for example, 1 to 20 mol%, preferably 2 to 18 mol%, and more preferably 3 to 15 mol%. It is particularly good at 7 to 11 mole%. By setting the ratio of the copolymerization component in this range, the effect of improving the film-forming extensibility can be excellent. In addition, it has excellent thermal dimensional stability.

(Void forming agent)

When the inorganic particles are used as the void-forming agent in the reflective layer A, the inorganic particles are preferably white inorganic particles. Examples of the white inorganic particles include particles of barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate. These inorganic particles are not particularly limited as long as the average particle size or content is selected so that the white reflective film has a suitable reflectance. It is preferable that the reflectance of the reflective layer A or the white reflective film is within the preferred range of the present invention. In addition, the pore volume ratio of the reflective layer A may be in a preferred range of the present invention. In consideration of such matters, the average particle diameter of the inorganic particles is, for example, 0.2 to 3.0 μm, preferably 0.3 to 2.5 μm, and more preferably 0.4 to 2.0 μm. In addition, its content is based on the quality of the reflective layer A, and is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, and most preferably 31 to 53% by mass. good. In addition, by adopting such a particle type as described above, the particles can be appropriately dispersed in the polyester, it is not easy to cause aggregation of the particles, and a film without coarse protrusions can be obtained. In addition, the origin of breakage of coarse particles during extension can be suppressed. The inorganic particles may have any type of particle shape, such as a plate shape and a spherical shape. The inorganic particles may be subjected to a surface treatment for improving dispersibility.

When an immiscible resin is used as the void-forming agent, the immiscible resin is not particularly limited as long as it is immiscible with the thermoplastic resin constituting the layer. For example, when the thermoplastic resin is polyester, polyolefin and polystyrene are preferred. These can also be in the form of particles. In addition, the content may be the same as in the case of the inorganic particles, and the average particle diameter or content may be selected so that the white reflective film has an appropriate reflectance, and these are not particularly limited. It is preferable that the reflectance of the reflective layer A or the white reflective film is within the preferred range of the present invention. In addition, the pore volume ratio of the reflective layer A may be in a preferred range of the present invention. In consideration of such matters, the content is based on the quality of the reflective layer A, and is preferably 10 to 50% by mass, more preferably 12 to 40% by mass, and most preferably 13 to 35% by mass.

(Other ingredients)

The reflective layer A may preferably contain other components such as an ultraviolet absorber, an oxidation inhibitor, an antistatic agent, a fluorescent whitening agent, a wax, and particles different from the void-forming agent, as long as the object of the present invention is not hindered. Or resin.

[Surface Layer B]

The surface layer B of the present invention is composed of a resin composition containing particles in the resin, and a layer of protrusions is formed on the surface by the particles. As such a resin, a thermoplastic resin is preferable. In addition, a bridging structure may be used by using a bridging agent. In this case, a thermoplastic resin having a functional group capable of reacting with the reactive group of the bridging agent may be used, and a bridging structure may be formed by the bridging agent and the thermoplastic resin, or a resin having no functional group may be used to follow the bridging agent. The reactive resin reacts with a thermoplastic resin, and has a matrix of a thermoplastic resin and a matrix of a bridging structure that bridges with a bridging agent. When the bridge structure is provided, the strength of the surface layer B tends to increase. On the other hand, when there are too many bridge structures, the recovery of the membrane tends to deteriorate when more membranes are recovered when the membrane is recovered and regenerated. From this viewpoint, it is better not to have too many bridge structures.

The surface layer B may be formed by coating with a coating liquid during or after the film is produced, or may be formed simultaneously with the reflection layer A by, for example, a co-extrusion method. In the above-mentioned method, the surface layer B has a bridge structure, and is preferably formed by coating with a coating liquid. The content of the bridging agent is, from the above-mentioned viewpoint, based on the solid content of the coating liquid, preferably 35 mass% or less, more preferably 30 mass% or less, more preferably 25 mass% or less, and 20 mass% or less Extraordinary. In addition, it is preferably at least 1 mass%, more preferably at least 2 mass%, more preferably at least 3 mass%, and particularly preferably at least 5 mass%.

(Thermoplastic resin)

As the thermoplastic resin constituting the surface layer B, a thermoplastic resin similar to the thermoplastic resin constituting the above-mentioned reflective layer A can be used. Among them, acrylates and polyesters are preferred, and in particular, polyesters are preferred from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As such a polyester, the same polyester as the polyester of the reflective layer A can be used. Among these polyesters, in terms of obtaining a white reflective film excellent in mechanical properties and thermal stability, aromatic polyesters are preferred, and polyethylene terephthalate is particularly preferred. Polyethylene terephthalate can be a homopolymer. However, from the point that the surface layer B is moderately softened and the effect of suppressing particle shedding is obtained, a copolymerized polymer is preferred, and polyethylene terephthalate is preferred. Ethylene formate is particularly preferred. Thereby, even if an external force such as friction with the light guide plate is applied, the particles are not easily detached. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component or diol component. However, from the standpoint of high heat resistance and high film extensibility improvement effect, the isophthalic acid component, 2,6- A naphthalenedicarboxylic acid component is preferred. The proportion of the copolymerization component is based on 100 mol% of the total dicarboxylic acid content of the polyester, for example, 1 to 20 mol%, preferably 2 to 18 mol%, and more preferably 3 to 17 mol%. It is especially good with 12 ~ 16 mole%. By setting the ratio of the copolymerization component in this range, the effect of improving the film-forming extensibility can be excellent. In addition, it has excellent thermal dimensional stability.

In addition, when the surface layer B is formed by coating with a coating liquid during or after the production of the film, it is preferable to achieve the above-mentioned effects and also to improve the stability of the coating liquid. The polyester has a base having a function of improving lyophilicity in a side chain or a main chain of the polyester. Here, for Examples of the group having a function of improving the lyophilic property include a metal sulfonate group (preferably sodium chloride sulfonate), a hydroxyl group, an alkyl ether group, and a carboxylate group. Wait. In the present invention, a particularly preferable form is that it contains a phthalic acid component with a sulfonic acid metal salt base, which is 100 mol% relative to the total acid content of the polyester, preferably 3 to 30 mol%. 20 mol% is preferred, and 5 to 15 mol% is more preferred. In addition, from the point of view of containing the diethylene glycol component, it is preferable to contain a related component type. It is preferably 3 to 30 mol% relative to the total acid content of the polyester. 5 ~ 20 mole% is preferred, and 5 ~ 15 mole% is more preferred.

(Non-spherical particles)

In the present invention, it is necessary that the particles of the surface layer B are non-spherical particles having an average particle diameter of 3 to 100 μm. When the average particle diameter is in the above range, the pattern of the number of protrusions described later is easily formed, and it is easier to ensure the interval. When the average particle diameter is too large, particles are likely to fall off, which is the cause of defects on the screen. On the other hand, if the average particle diameter is too small, it becomes difficult to ensure the distance between the original purpose and the light guide plate. From such a viewpoint, 5 μm or more is preferable, 7 μm or more is more preferable, 8 μm or more is particularly preferable, and 80 μm or less is more preferable, 70 μm or less is more preferable, and 50 μm or less is particularly preferable.

In addition, by making the particles forming the protrusions non-spherical particles on the surface of the outermost layer, it is possible to secure a distance from the light guide plate and improve the damage suppression effect of the light guide plate. Here, the non-spherical particles of the present invention set the maximum diameter Dx of the particles (set to the x direction) and the direction perpendicular to the x direction (set to the y direction and the z direction, and the z direction is also the direction perpendicular to the y direction) Maximum diameter Dy and Dz (however, Dy ≧ Dz is set), and at least any one of the maximum diameter differences (Dx-Dy, Dx-Dz, Dy-Dz) in these directions is set to exceed 20% of Dx.

The above-mentioned effect can be obtained by using such non-spherical particles, and it is considered based on the following mechanism. That is, it is considered that by making the shape of the particles non-spherical, the contact area with the light guide plate is enlarged, and the pressure is dispersed to prevent damage easily. When the shape of the particle is non-spherical as determined above, the particle will have the largest diameter in a certain direction, and if it is contained in the surface layer B, the probability of the largest diameter direction is likely to be the same as that of the surface layer B. The plane direction is substantially parallel. Therefore, the contact area between the protrusions formed by such particles and the light guide plate is widened, and the pressure is dispersed. On the other hand, when the particles are spherical, the area of the portion in contact with the light guide plate is narrow, so that the pressure concentration is liable to cause damage. In this way, even if soft particles are used, the light guide plate is likely to be damaged due to the spherical shape.

In the present invention, the surface layer B is provided with a specific particle shape as described above, so that the contact of the light guide plate is concentrated in a narrow range of the apex of the protrusion, and it is better to make it to maintain the number of protrusions on one side. Increasing the contact area between the protrusions and the light guide plate to disperse the pressure, while making the number of contact points with the light guide plate appropriate to ensure the interval, each protrusion reduces the pressure on the light guide plate and suppresses the damage of the light guide plate. When the specifications are out of the above range, for example, the light guide plate is brought into contact with each other, and only a narrow range focused on the apex of the protrusion is caused. This causes an increase in the pressure applied to the portion or is easily scratched.

In the present invention, in order to further improve the effect of suppressing damage to the light guide plate and the effect of suppressing adhesion to the light guide plate, the average of the aspect ratio (long diameter / short diameter) of the particles is best. It is 1.31 or more and 1.80 or less. Such an aspect ratio is more preferably 1.35 or more and 1.75 or less. Although it is better to have a large aspect ratio for the above-mentioned effects, when it is too large, it may be difficult to maintain the number of protrusions with a surface height of 5 μm or more. Here, the aspect ratio is obtained by observation with an electron microscope described later. In addition, the largest diameter of the particles observed in this way is set as the major diameter, and the largest diameter in a direction orthogonal to such a largest diameter is set as the minor diameter.

In addition, when there is a moderate difference in particle shapes at the same time, even if the particle shapes are moderately irregular, it is presumed that it is not easy to apply pressure to specific particles and make the light guide plate difficult to damage.

Therefore, the standard deviation of such particles is preferably 0.15 to 0.50. That is, this means that the shape of each particle has a moderate difference. By appropriately differentizing the shape of the particles forming the protrusions, it is possible to improve the effect of suppressing damage to the light guide plate while ensuring a distance from the light guide plate. When the difference is small, the improvement effect of the interval securing and the damage suppression is reduced. On the other hand, if the difference is too large, it is easy to cause a defect when it is added to the surface layer B, and it is difficult to obtain the expected protrusion frequency. As a result, it is difficult to exert the effect of ensuring the interval or suppressing the damage. From such a viewpoint, the standard deviation of the aspect ratio of the particles is preferably 0.16 or more, more preferably 0.17 or more, and more preferably 0.45 or less, and more preferably 0.43 or less.

In the present invention, it is necessary that the 10% compressive strength of the particles is 0.1 to 15 MPa. This makes it possible to secure the gap and to suppress damage to the light guide plate. When the compressive strength is too low, it will cause excessive deformation due to the stress, making it difficult to ensure the distance from the light guide plate. On the other hand, when the compressive strength is too high, even non-spherical particles can be easily applied to the light guide plate. Cause damage. From such a point of view, 10% compressive strength is preferably 0.2 MPa or more, 0.3 MPa or more, 3 MPa or more, particularly 8 MPa or more, and 14 MPa or less, 13 MPa or less, and It is more preferably 12 MPa or less.

In the present invention, the content of the non-spherical particles in the surface layer B can be adjusted as appropriate by using the above-mentioned particles having an average particle diameter to satisfy the type of the number of protrusions described later. For example, the average particle size of the particles tends to form protrusions when the thickness of the surface layer B tends to be thin, so the content can be relatively small. On the other hand, it is preferable to have a large content. These tendencies can be adjusted as appropriate. Specifically, based on the mass of the surface layer B, 1 to 70% by mass is preferred, 5% by mass or more is preferred, 10% by mass or more is preferred, 20% by mass or more is particularly preferred, and 60% by mass or less is preferred. Preferably, 50 mass% or less is more preferable, and 30 mass% or less is particularly preferable.

The particles contained in the surface layer B of the present invention may be either organic particles, inorganic particles, or organic-inorganic composite particles, regardless of the type. From the viewpoint of easily satisfying the particle types described above, polymer particles composed of polymers such as acrylate, polyester, polyurethane, nylon, polyolefin, and polyether are preferred. Polyester and nylon are preferred, and a more suitable 10% compressive strength is easily obtained. Particularly preferred is polyester (of which, polyethylene terephthalate), which is advantageous in that it has excellent film recovery properties.

In addition, in the present invention, the method for achieving the particle shape is not particularly limited. However, from the viewpoint of easily obtaining particles having a particularly good shape, and from the viewpoint of manufacturing cost or productivity, pulverized solid particles are used. The method of obtaining particles from a bulk polymer is preferred. The particles obtained by the relevant steps are made into pulverized polymer particles. Relevant steps, more specifically, it is preferable to crystallize the polymer sheet, such as a pelletized polymer sheet, by heat treatment, and then pulverize it at normal temperature to a lower temperature than normal temperature. From the viewpoint of making it easier to pulverize, it is preferable to perform pulverization at a lower temperature than normal temperature, and as a method for obtaining such a low temperature, a method using liquid nitrogen for cooling is preferable.

In addition to the above pelletized polymer sheet, crushing the polymer composition to be molded, the polymer film to be formed, the polymer fiber to be formed, and the like can also be used as a pulverized polymer for the purpose. particle. By selecting the shape of the polymer to be pulverized in this way (including changing, for example, the size of the testicle, the thickness of the film, and the diameter of the fiber), particles having various non-spherical shapes (aspect ratio) can be obtained. It is also possible to adjust the difference (standard deviation) of the particle shape.

The polymer of the pulverized polymer particles may be a copolymer or a mixture of two polymers. In addition, the pulverized polymer particles may contain inorganic particles or organic particles having a diameter smaller than this, or may include an ultraviolet absorber. Or lubricants.

(Type of surface layer B)

In the present invention, the surface layer B made of a resin composition containing particles such as those described above forms at least one of the outermost layers of the white reflective film. Next, the surface on the opposite side of the reflective layer A from the surface layer B forming such an outermost layer (hereinafter referred to as the outermost surface) is useful The protrusions formed by the particles. Next, from the viewpoint of ensuring the distance between the light guide plate and the film, such protrusions are necessary to have protrusions having a moderate height on the outermost surface at a moderate frequency.

Therefore, in the present invention, it is usually necessary to set the number of protrusions (protrusion frequency) of 10 ⁴ to 10 ¹⁰ / m ² on the outermost surface. Thereby, the space between a light guide plate and a film can be fully ensured, and the adhesion suppression effect can be ensured. If the frequency of protrusions is too small, the adhesion suppression effect is deteriorated. On the other hand, when the frequency of protrusions is excessive, there is a possibility that particles may fall off or reflectance tends to decrease.

(Other ingredients)

The surface layer B may contain components other than the above-mentioned constituent components so long as the object of the present invention is not hindered. Examples of such a component include an ultraviolet absorber, an oxidation inhibitor, an antistatic agent, a fluorescent whitening agent, a wax, a surfactant, and particles or resins different from the above-mentioned particles.

[Layer Structure]

The thickness of the reflective layer A of the present invention is preferably 80 to 350 μm. This can increase the effect of improving the reflectance. Too thin will reduce the improvement of reflectivity, while too thick will not be effective. From such a viewpoint, the thickness is preferably 80 to 300 μm, more preferably 100 to 320 μm, and particularly preferably 150 to 250 μm.

The thickness of the surface layer B of the present invention is preferably 5 to 100 m. It is preferably 5 to 80 μm. In this case, the particle size of the thickness-based particles of the surface layer B is The sum of the thicknesses of the resin portions covering this surface.

The thickness of the resin portion holding the particles of the surface layer B is preferably 0.2 to 50 μm. Thereby, it is easy to make the protrusion frequency into a better shape, and it is easy to make it possible to secure a distance from the light guide plate. When the thickness of the resin portion of the surface layer B is too thin, particles tend to fall out of the protrusions formed on the surface of the surface layer B. On the other hand, if it is too thick, it is difficult to obtain a good protrusion frequency. From such a viewpoint, the thickness is preferably 0.3 μm or more, more preferably 0.5 μm or more, particularly preferably 1 μm or more, most preferably 2 μm or more, and more preferably 40 μm or less. When the detachability is also considered, it is preferably 1 μm or more, and more preferably 2 μm or more.

The laminated structure of the white reflective film. When A represents the reflective layer A, and B represents the surface layer B, the two-layer structure of B / A, the three-layer structure of B / A / B, or the arrangement of B at least The outermost layer on either side is composed of more than 4 layers. It is particularly preferable to have a support layer C (indicated by C) for film formation stability, a three-layer structure of B / C / A or B / A / C, and a four-layer structure of B / C / A / C. A four-layer structure of B / C / A / C is preferred, and film extensibility is more excellent. In addition, problems such as curling are unlikely to occur. The present invention is preferably a form having such a supporting layer C. The supporting layer C is preferably made of the same polyester as the reflective layer A, and preferably has a relatively low void volume ratio (more than 0% by volume, less than 15% by volume, and less than 5% by volume). More preferred, particularly preferably less than 3% by volume). In addition, the thickness of the support layer C (total thickness when there are multiple layers) is preferably 5 to 140 μm, and more preferably 20 to 140 μm.

In the present invention, in addition to the reflection layer A, the surface layer B, and the support layer C, There may be other layers without impairing the object of the present invention. For example, it may have a layer for imparting functions such as easy adhesion, winding property (lubricity), antistatic property, conductivity, and ultraviolet durability, or a layer for adjusting optical characteristics.

[Method for Manufacturing Film]

Hereinafter, an example of a method for manufacturing the white reflective film of the present invention will be described.

In the production of the white reflective film of the present invention, in the reflective layer A obtained by the melt extrusion method or the like, a melt resin coating method (including a melt extrusion resin coating method), a co-extrusion method, a lamination method, or a supply method can be used. The coating liquid for forming the surface layer B is formed by the coating liquid coating method. Among them, a method in which the reflective layer A and the support layer C are laminated by a coextrusion method and the surface layer B is laminated by a coating liquid coating method is particularly preferred. By laminating the surface layer B by a coating liquid coating method, it is easy to control the distribution state of particles by changing the drying conditions, etc., and the specified number of protrusions can be mass-produced at a low price and easily. In addition, even particles with a relatively small 10% compressive strength can be handled easily. Furthermore, the specific particle shape of the present invention can be easily maintained, and the shape of the protrusions can be easily made into a preferable shape.

Hereinafter, it will be described that polyester is used as the thermoplastic resin constituting the reflective layer A and the thermoplastic resin that constitutes the support layer C, and the coextrusion method is adopted as the method of laminating the reflective layer A and the support layer C, and the surface layer B is laminated As the method, a production method in the case of a coating liquid coating method is used. However, the present invention is not limited to such a production method, or it can be produced similarly for other types by referring to the following. In this case, if the extrusion step is not included, "Melting Extrusion Temperature" can be read as "Melting Temperature". Here, the melting point of the polyester used is Tm (unit: ° C), and the glass transition temperature is Tg (unit: ° C).

First, as a polyester composition for forming the reflective layer A, a composition in which polyester, a void-forming agent, and other optional components are mixed is prepared. In addition, as the polyester composition for forming the support layer C, a composition in which polyester, a pore-forming agent, and other optional components are mixed is prepared. These polyester compositions are used after drying and sufficiently removing moisture.

Next, the dried polyester composition was put into different extruders and melt-extruded. The melt extrusion temperature must be above Tm, which can be about Tm + 40 ° C.

In addition, at this time, the polyester composition used in the production of the film, especially the polyester composition used in the reflective layer A, is a non-woven filter sheet with an average pore diameter of 10 to 100 μm made of stainless steel thin wires having a diameter of 15 μm or less. It's better to filter. By performing this filtration, the aggregation of particles that tend to form coarse aggregated particles after aggregation can be suppressed, and a membrane with few coarse foreign matters can be obtained. The average pore diameter of the nonwoven fabric is preferably 20 to 50 μm, and more preferably 15 to 40 μm. The filtered polyester composition is extruded from a die in a multilayer state by using a simultaneous multi-layer extrusion method (co-extrusion method) using a supply block (supply block) in a molten state to produce an unstretched laminated sheet. The unstretched laminated sheet extruded from the die is cooled and solidified under a casting drum to form an unstretched laminated film.

Next, the unstretched laminated film is heated by drum heating, infrared heating, or the like in the direction of the film forming machine axis (hereinafter, referred to as the vertical direction or the long side). (Or in the case of MD) to obtain a longitudinally stretched film. This stretching is preferably performed using a difference in the rotation speed of two or more rollers. The longitudinally stretched film is then guided to a tenter, and stretched in a direction perpendicular to the longitudinal direction and the thickness direction (hereinafter referred to as a horizontal direction or a width direction or TD) to form a biaxially stretched film.

As the elongation temperature, it is preferably performed at a temperature of Tg or higher and Tg + 30 ° C or lower of the polyester (preferably the polyester constituting the reflective layer A), the film extensibility is better, and the voids are easily made better. form. In addition, in terms of stretching magnification, 2.5 to 4.3 times is preferable in the longitudinal and horizontal directions, and 2.7 to 4.2 times is more preferable. When the stretching ratio is too low, the thickness deviation of the film tends to be worse, and there is a tendency that voids are not easily formed. On the other hand, when it is too high, the film tends to be easily broken. When performing successive biaxial stretching such as horizontal stretching after longitudinal stretching, the stretching temperature in the second stage (horizontal stretching in this case) is preferably about 10 to 50 ° C higher than that in the first stage. This is because the Tg as a uniaxial film is increased by performing alignment in the first stage.

In addition, it is preferable to preheat the film before each stretching. For example, the laterally-stretched pre-heat treatment can be started at a temperature higher than Tg + 5 ° C of the polyester (preferably the polyester constituting the reflective layer A), and then gradually raised in temperature. The temperature rise in the transverse extension process may be continuous or stepwise (sequential), but usually the temperature is gradually increased. For example, the horizontal extension zone of the tenter is divided into a plurality of zones along the film advance direction, and a heating medium of a specified temperature is flowed to each zone to raise the temperature.

The biaxially stretched film is then sequentially subjected to heat fixation and thermal relaxation treatments to form a biaxially oriented film, but it can also be stretched immediately after melt extrusion. These processes were allowed to proceed together while advancing the film.

The biaxially stretched film can be directly held under both ends with a paper clip, and the melting point of polyester (preferably the polyester constituting the reflective layer A) is set to Tm, and (Tm-20 ° C) At ~ (Tm-100 ℃), heat treatment is performed at a fixed width or 10% or less to reduce heat shrinkage. When such a heat treatment temperature is too high, there is a tendency that the planarity of the film is deteriorated and a thickness deviation is increased. On the other hand, when it is too low, there is a tendency that the thermal shrinkage rate becomes large.

In addition, to adjust the amount of heat shrinkage, both ends of the film being held can be cut off, and the pull-back speed in the longitudinal direction of the film can be adjusted to relax the longitudinal direction. As a means to relax, the speed of the roller group on the tenter side is adjusted. The proportion of relaxation is reduced by reducing the speed of the roller group to the film forming line speed of the tenter, and the implementation speed is preferably lowered by 0.1 to 2.5%, more preferably 0.2 to 2.3%, and lowered by 0.3 to 2.0%. The film (referred to as the "relaxation rate" for short), the thermal shrinkage rate in the longitudinal direction is adjusted by controlling the relaxation rate. In addition, the width of the film can be reduced in the process until the both ends of the film are cut and the desired heat shrinkage can be obtained.

In the biaxial stretching, in addition to the longitudinal-horizontal sequential biaxial stretching method described above, a lateral-vertical sequential biaxial stretching method may be used. In addition, a simultaneous biaxial stretching method can also be used for film formation. In the case of the biaxial stretching method, the stretching ratio in the longitudinal direction and the transverse direction is, for example, 2.7 to 4.3 times, and preferably 2.8 to 4.2 times.

The surface layer B is preferably formed by applying a coating liquid for forming the surface layer B on the longitudinally-stretched film after the longitudinal stretching in the above-mentioned steps. The step, the horizontal stretching step, and the heat-fixing step are formed by such heat to dry and harden by a so-called in-line coating method. The coating liquid can be obtained by mixing the components constituting the surface layer B and arbitrarily diluting the solvent in a manner that allows easy application. In this case, the solvent is preferably water, which can reduce the amount of volatile organic solvents described later. The coating method of the coating liquid is not particularly limited, and preferred methods include a reverse roll coating method, a gravure coating method, a mold coating method, and a spray coating method. The surface layer B may be formed by a so-called off-line coating method, which is a biaxially oriented film obtained after biaxially extending and thermally fixing. In the external coating method, it is not easy to apply drying and high heat for reasons such as film deformation. Therefore, an organic solvent that is easy to dry is generally used as a solvent. However, in this case, there is a tendency that the amount of the volatile organic solvent to be described later increases. Therefore, the present invention is particularly preferred by the in-line coating method.

In this way, the white reflective film of the present invention can be obtained.

[Characteristics of white reflective film]

(Reflectivity, brightness)

The reflectance (reflectance at a wavelength of 550 nm) of the white reflective film of the present invention measured from the surface layer B side is preferably 95% or more, 96% or more, 97% or more, or 97.5% or more Above 98% is particularly good. With a reflectance of 95% or more or 96% or more, when used in a liquid crystal display device, lighting, or the like, high brightness can be obtained. Such reflectivity can be achieved by forming a preferred type such as increasing the void volume ratio of the reflective layer A, or increasing the thickness of the reflective layer A or reducing the thickness of the surface layer B. To achieve a better form and so on.

Further, the luminance measured from the surface of the layer B-side can be determined using the measurement methods described below, to 5400cd / m ² or more preferably, 5450cd / m ² or more better, 5500cd / m ² or more particularly preferred.

The above-mentioned reflectance and brightness are numerical values of the surface on the light guide plate side when the white reflective film is used as a light guide plate.

(Amount of volatile organic solvents)

In the white reflective film of the present invention, the amount of the volatile organic solvent measured by the method described later is preferably 10 ppm or less. Thereby, it can be shown that the surface layer B is not formed by a coating method using an organic solvent. In addition, when the raw material can be recovered by itself and a film is formed therefrom, gas marks are less likely to occur, and the film extensibility (recovery film formation) is improved. From such a viewpoint, the dose is preferably 5 ppm or less, more preferably 3 ppm or less, and ideally 0 ppm. In the present invention, in order to reduce the amount of volatile organic solvents, a solution coating method using an organic solvent is not used in the formation of the surface layer B, and the above-mentioned method is preferably used.

Examples

Hereinafter, the present invention will be described in detail using examples. In addition, each characteristic value is measured by the following method.

(1) Light reflectivity

An integrating sphere was attached to a spectrophotometer (UV-3101PC, manufactured by Shimadzu Corporation), and the reflectance at a BaSO ₄ whiteboard of 100% was measured at a wavelength of 550 nm, and this value was used as the reflectance. The measurement was performed on the surface on the surface layer B side. When the surface layer B is different from the front and back surfaces, the measurement is performed on the surface of the surface layer B on the light guide plate side.

(2) average particle diameter

Using a laser scattering type particle size distribution measuring machine (SALD-7000, manufactured by Shimadzu Corporation), the particle size distribution (standard deviation of the particle size) was determined, and the particle size of d50 (50% of Particle size) is set to the average particle size.

(3) Particle shape

(3-1) Particle shape 1

The particle powder was fixed to a measurement platform with a conductive tape, and the S-4700 field emission scanning electron microscope manufactured by Hitachi was observed at a magnification of 1000 times to observe the shape of the particles. For the 30 randomly selected particles, find the maximum of the maximum diameter Dx of the particles (set as the x direction) and the direction perpendicular to the x direction (set as the y direction and the z direction, and the z direction is also the direction perpendicular to the y direction). Diameters Dy and Dz (where DyZDz), calculate the average, set Dxave, Dyave, Dzave, and find Dxave-Dyave, Dxave-Dzave, Dyave-Dzave, at least one of which is more than 20% of Dx It is judged as non-spherical, otherwise it is judged as spherical.

(3-2) Particle shape 2 (standard deviation of aspect ratio and aspect ratio)

Use a glass rod to lightly adhere the particles to the conductive tape and fix this On the measurement platform, an S-4700 field-emission scanning electron microscope manufactured by Hitachi, Ltd. was used to observe from the directly opposite side (without an inclination angle) at a magnification of 100 times. For 30 randomly selected particles, the maximum diameter of the particles was used as the The major axis was taken as the major axis, and the major axis in a direction orthogonal to such a major axis was defined as a minor axis. The major axis / minor axis (aspect ratio) was calculated for each particle, and the average value was taken as the average of the aspect ratio. In addition, the standard deviation of the aspect ratio is calculated from the numerical value of each aspect ratio.

In addition, when the average particle diameter is small (for example, 3 μm or less is assumed), observation is performed by increasing the magnification (for example, 1000 times).

(4) Frequency of protrusions on the film surface (number of protrusions)

The protrusion cross section of the film surface was cut with a three-dimensional roughness measuring device SE-3CKT (made by Kosaka Laboratories, Ltd.), 0.25 mm, measured 1 mm in length, 2 μm in scanning pitch, and 100 scanning lines. Strip measurement was performed, and the protrusion cross section was recorded with a magnification of 1000 times in the height and a magnification of 200 in the scanning direction. From the obtained projection cross section (horizontal axis: projection height, vertical axis: projection cross section number of projections), the number of projections (height / m ² ) having a height of 5 μm or more was determined as the projection frequency. For analysis, a three-dimensional roughness analysis device SPA-11 (manufactured by Kosaka Research Institute) was used.

(5) 10% compressive strength

The micro-hardness tester ENT-1100a made by ELIONIX was used to measure the compressive strength of each particle under a weight of 3 gf, and the compressive strength (MPa) at the time of 10% deformation was used. An average of 5 measurements was used.

(6) Volatile organic solvent

At room temperature (23 ° C), 1 g of the film sample was put into a 10 L fluororesin bag, which was purged with pure nitrogen and sealed. Next, directly from the nitrogen in such a bag, 0.2 L and 1.0 L of nitrogen were taken at a flow rate of 0.2 L / min to 2 TENAX-TA trap tubes for analysis. Using these, HPLC and GCMS will be used. The mass of the organic solvent component contained in the nitrogen was quantified. The obtained numerical value was converted into the amount in 10 L of nitrogen, and the mass of the organic solvent evaporated from 1 g of the film sample to 10 L of nitrogen was determined, and it was set as the amount of the volatile organic solvent (unit: ppm, the mass standard of the film sample). In addition, acetaldehydes were obtained by dissolving acetaldehyde-inducible compounds from the collection tube with acetonitrile and quantifying them by HPLC. In addition, when the values under HPLC and GCMS are different, more values are detected.

(7) Film thickness and layer structure

A white reflective film was sliced with a microtome to expose a cross section. Such a cross section was observed at a magnification of 500 times using an S-4700 field emission scanning electron microscope manufactured by Hitachi, and the entire film and the reflective layer were determined. A, the thickness of the surface layer B, the support layer C. For the surface layer B, the thickness of the portion where the particles are present was arbitrarily taken at 10 points, and the average value of these was taken as the thickness.

(8) Calculation of void volume ratio

From the layer and polymer for determining the void volume ratio, the added particles, and other Calculate the calculated density by the proportion of the density of the components. At the same time, the layer is peeled off and separated to measure mass and volume, and the real density is calculated from these. The calculated density and the real density are calculated from the following formula.

Void volume ratio = 100 × (1- (real density / calculated density))

The density of the isophthalic acid copolymerized polyethylene terephthalate (after biaxial stretching) was 1.39 g / cm ³ , and the density of barium sulfate was 4.5 g / cm ³ .

In addition, only the layer for measuring the void volume ratio was separated, and the mass per unit volume was determined to obtain the real density. The volume refers to a sample cut out of an area of 3 cm ² , and the thickness of the sample was measured by an electric micrometer (K-402B manufactured by Anritsu) at 10 points as the thickness to calculate the area × thickness. Quality is measured with an electronic balance.

The specific gravity of the particles (including agglomerated particles) is the value of the volume specific gravity determined by the following measuring cylinder method. After filling a dry cylinder with a volume of 1000 ml, the entire weight is measured, and the weight of the cylinder is subtracted from the total weight to determine the weight of the particle. The volume of the cylinder is measured, and the weight (g) of the particle is divided by the volume. (cm ³ ).

(9) Melting point, glass transition temperature

The measurement was performed using a differential scanning calorimeter (TA Instruments 2100 DSC) at a temperature increase rate of 20 ° C / min.

(10) Brightness

Take out the reflective film from the LG LCD TV (LG42LE5310AKR), set the surface layer B side of the various reflective films described in the examples on the screen side (connected to the light guide plate side), and use brightness in the state of the backlight unit A meter (Model MC-940 manufactured by Otsuka Electronics) measures the brightness of the center of the backlight from a front side at a measurement distance of 500 mm.

(11) Evaluation of light guide plate damage (scratchability evaluation)

(11-1) Damage evaluation 1

As shown in FIG. 3, an iron plate (width: 200 mm) with a width of 200 mm × a length of 200 mm × a thickness of 3 mm is fixed to the end of the handle portion (1), and the width of the evaluation side facing up is 250 mm × The reflection film (3) with a length of 200mm is made to stick out 25mm portions from the iron plate from both ends in the width direction (the 200mm × 200mm portion made in the center overlaps the iron plate). At this time, the evaluation surface (surface layer) of the reflective film is made outside. In addition, the extra 25mm portions at the two ends in the width direction of the reflective film are folded back to the inner side of the iron plate, and the end of the reflective film (the portion where the blade is cut in by a knife or the like when sampling) is excluded from the effect of scraping the light guide plate.

Next, fix the light guide plate (4, with a size of at least 400mm × 200mm) with the point (401) facing upward on a horizontal table, and fix the reflective film on the iron plate made above to evaluate the surface and light guide plate. The contact method is to place the reflective film side face down on the light guide plate, and then load 500g (5) on it, at a distance of 200mm (actuate the reflective film fixed on the iron plate in the area of 400mm × 200mm) 15 round trips at a speed of about 5 to 10 seconds per round trip. Then, on the surface of the light guide plate, according to the scraping situation, and The presence or absence of particles falling off the reflective film was observed with a 20-times magnifying glass and evaluated based on the following criteria.

The full range of 400mm × 200mm that was rubbed on the light guide plate was set to "No Scratching" when there were no scratches that could be observed with a magnifying glass after 20 times of reciprocating motion (scratch evaluation ○); no observation was possible after 10 reciprocating motions If there are scars that can be observed after 20 times of reciprocating action, it is set as "not easy to scrape" (scratch evaluation △); when there are visible scars after 10 times of reciprocating action, it is set as "scratched" "(Scrape evaluation ×).

In the above evaluation, it should be possible to minimize the influence of the dot size. In the light guide plate, as far as possible, a region with a larger dot size is selected so that each evaluation sample is evaluated uniformly.

(11-2) Damage evaluation 2

In the above (11-1), except that the size of the iron plate (2) is set to 400mm × 200mm (with the use of a reflective film of 400mm × 250mm and a light guide plate of at least 400mm × 400mm in size, it is transferred in the area of 400mm × 400mm The reflection film fixed on the iron plate moves, and the observation range is also in the relevant range). The weight of the weight (5) is set to 1000g (the pressure system is the same as the above (11-1)). .

(12) White review price

(12-1) White review price 1

Using the reflective film and light guide plate used in the above evaluation (11-1), A reflective film is placed on the surface in an upward direction, and a light guide plate is placed on it with the dots facing downward. A weight of 300g is fixed on each of the four sides of the light guide plate. The LED LCD TV (LG42LE5310AKR) made by LG is used. Backlight light source, the light is incident from the side of the light guide plate, and if bright points other than the light guide plate can be visually observed, a white point is considered to have occurred (evaluation △). On the other hand, if abnormal bright spots were not observed visually, it was considered that no white spots occurred (evaluation ○).

(12-2) White review price 2

The reflective film and light guide plate used in the evaluation of the above (11-2) are evaluated based on the assumption that white spots (evaluation x) occur if bright spots other than the light guide plate spots are visually observed, and abnormalities are not observed visually. For bright spots, it is considered that no white spots have occurred (evaluation ○). If the bright spots other than the light guide plate spots that can be visually observed are not obvious, the same as (12-1) above, except that some white spots (evaluation △) are considered to occur. Evaluation.

(13) Evaluation of adhesion spots (adhesion evaluation)

(13-1) Sticking evaluation 1

As shown in Figure 4, take out the chassis (6) from the LG LCD TV (47 inches), and place it on a horizontal table with the TV's interior side up. On it, the size is about the same as the chassis The reflective film is placed with the surface layer facing upward, and then 3 light guide plates and optical sheets (7, 2 diffuser films, and 1) are provided on the original television. Secondly, as shown in FIG. 4, the area including the most rugged part of the chassis is placed in the surface, as shown in FIG. 4. Three equilateral triangle-shaped tables (801) with a cylindrical foot of 5mm diameter are loaded with a 10kg weight (802) on it, and the area surrounded by these three feet is visually observed. If there is no abnormal brightness A part was regarded as "no close spot" (close spot evaluation ○). In addition, when there are abnormally bright parts, place the original DBEF film on the TV on top of three optical sheets, and observe the same visually. If the abnormally bright parts have not been corrected, it will be regarded as "closed spots" (evaluation ×), if there is no abnormally bright part, it is regarded as "almost no tight spots" (evaluation △). In addition, the area surrounded by the three feet is made into a regular triangle with a length of 10 cm on each side.

(13-2) Sticking Evaluation 2

In the above (13-1), evaluation was performed in the same manner except that the weight of the heavy object (802) was 15 kg.

(14) Evaluation of recovery film formation

The biaxially stretched film obtained in the example was pulverized, melted, extruded, and fragmented to prepare a self-recovered raw material. Using such self-recovered raw materials, using the mass of the reflective layer A as a reference, add 35% by mass to the reflective layer A, and the mass ratio of the remaining polyester to the void-forming agent is made the same as the original film and the original film The same method was used to make a biaxially stretched film containing its own recovered materials, and evaluated according to the following criteria.

：: Films can be formed stably up to a length of 2000 m or more.

○: Films can be formed stably up to a length of 1,000 m or more and less than 2000 m.

Δ: Once the length is less than 1000 m, a break occurs once.

×: Two or more fractures occurred before the length was less than 1000 m.

<Manufacturing Example 1: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 1>

136.5 mass parts of dimethyl terephthalate, 13.5 mass parts of dimethyl isophthalate (9 mol% based on 100 mol% of the total acid content of the obtained polyester), and 98 mass of ethylene glycol Parts, 1.0 parts by mass of diethylene glycol, 0.05 parts by mass of manganese acetate, and 0.012 parts by mass of lithium acetate were placed in a flask equipped with a distillation column and a distillation condenser, and heated to 150-240 ° C while stirring to evaporate methanol for esterification. Exchange reaction. After the methanol was distilled off, 0.03 mass parts of trimethyl phosphate and 0.04 mass parts of germanium dioxide were added, and the reactants were transferred to a reactor. Next, the inside of the reactor was gradually depressurized to 0.3 mmHg while stirring, and the temperature was raised to 292 ° C to perform a polycondensation reaction to obtain isophthalic acid copolymerized polyethylene terephthalate 1. These polymers have a melting point of 235 ° C.

<Manufacturing Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2>

Except changing to 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (100 mol% to 14 mol% of the total acid content of the obtained polyester) In the same manner as in Example 1, isophthalic acid copolymerized polyethylene terephthalate 2 was obtained. These polymers have a melting point of 215 ° C.

<Manufacturing Example 3: Preparation of Particle Master Wafer 1>

Using a part of the isophthalic acid copolymerized polyethylene terephthalate 1 obtained above and barium sulfate particles (averaged as BaSO _{4 in the} table) with an average particle diameter of 1.0 μm of pore-forming agent, use The NEX-T60 tandem extruder made by Kobe Steel Co., Ltd. of Japan mixed the content of barium sulfate particles so that the mass of the obtained main wafer became 60% by mass, and extruded it at a resin temperature of 260 ° C. A particle master wafer 1 containing barium sulfate particles is prepared.

<Manufacturing Example 4: Preparation of Particle Master Wafer 2>

Using a part of the isophthalic acid copolymerized polyethylene terephthalate 2 and the barium sulfate particles with an average particle diameter of 1.0 μm of the pore-forming agent, NEX- The T60 tandem extruder mixes the content of barium sulfate particles so that the mass of the obtained main wafer becomes 60% by mass. It is extruded at a resin temperature of 260 ° C to make a particle main wafer containing barium sulfate particles 2.

<Manufacturing Example 5: Preparation of Particle 1 for Surface Layer B>

Put 150 mass parts of dimethyl terephthalate, 98 mass parts of ethylene glycol, 1.0 mass parts of diethylene glycol, 0.05 mass parts of manganese acetate, and 0.012 mass parts of lithium acetate into a flask equipped with a distillation column and a distillation condenser. While stirring, it was heated to 150 to 240 ° C to distill off methanol for transesterification reaction. After the methanol was distilled off, 0.03 mass parts of trimethyl phosphate and 0.04 mass parts of germanium dioxide were added, and the reactants were transferred to a reactor. Then, one The inside of the reactor was gradually depressurized to 0.3 mmHg while being stirred while being heated to 292 ° C., and a polycondensation reaction was performed to obtain isophthalic acid copolymerized polyethylene terephthalate 3. The obtained isophthalic acid copolymerized polyethylene terephthalate 3 was extruded from a strand die, and after being cooled, it was cut into pellets. Next, the obtained pellets were dried and crystallized by heating in an oven at 170 ° C. for 3 hours, and then liquidized with an atomizer mill TAP-1 made by Japan Matsuo Corporation. The nitrogen was pulverized while cooling, and polyester particles having an average particle diameter of 60 μm were obtained. The polyester particles were subjected to wind classification to obtain particles 1 (aspherical particles) having an average particle diameter of 40 μm.

Particle 2: Non-spherical particles having an average particle diameter of 40 μm, which were obtained by pulverizing and classifying in the same manner as in Production Example 5 except that the pellets of nylon 66 resin CM3006 made by Japan Toray Co., Ltd. were used.

Particle 3: Non-spherical particles having an average particle diameter of 10 μm, which were obtained by pulverizing and classifying in the same manner as in Production Example 5 except that the pellets of nylon 66 resin CM3006 made by Japan Toray Co.

Particle 4: Non-spherical particles with an average particle diameter of 10 μm were obtained by pulverizing and classifying in the same manner as in Production Example 5 except that the pellets of nylon 6 resin CM1017 made by Japan Toray Co., Ltd. were used.

Particle 5: MBX-40 (True spherical acrylate particles, average particle diameter: 40 μm) manufactured by Sekisui Chemicals Industries, Ltd., Japan.

Particle 6: An average particle diameter of 10 μm was obtained by pulverizing and classifying in the same manner as in Production Example 5 except that the pellets of poly (methyl methacrylate) (PMMA) resin SUMIPEX MGSS made by Sumitomo Chemical Co., Ltd. were used. Of non-spherical particles.

Particle 7: SP-10 (true spherical nylon particles, average particle size: 10 μm) made by Toray, Japan.

<Manufacturing Example 6: Preparation of Particle 8 for Surface Layer B>

In the same manner as in Production Example 5, polyethylene terephthalate 3 was extruded from a strand die, and after cooling, it was cut into pellets. As a result of adjusting the shape of the strands, the shape of the pellet was approximately a rectangular parallelepiped, and the average shape was 4 mm × 3 mm × 2 mm. Next, in the same manner as in Production Example 5, polyester particles having an average particle diameter of 60 μm were obtained. The polyester particles were subjected to wind classification to obtain particles 8 (aspherical particles) having an average particle diameter of 43 μm.

<Manufacturing Example 7: Preparation of Particle 9 for Surface Layer B>

The conditions for the biaxially stretched film of polyethylene terephthalate were generally used for the pellets obtained in Production Example 6 described above (the longitudinal stretching ratio is 3.0 times, the lateral stretching ratio is 4.0, and the heat fixing temperature is set to 220 ° C). To obtain a crystallized transparent biaxially stretched polyethylene terephthalate film (thickness: 50 μm). This was crushed in the same manner as in Production Example 6 above while cooling with liquid nitrogen, followed by wind classification to obtain particles 9 (non-spherical particles) having an average particle diameter of 52 μm.

<Manufacturing Example 8: Preparation of particles 10 used in surface layer B>

The pellets obtained in Production Example 6 were used to make straight Polyester fibers having a diameter of 35 μm were pulverized by cooling with liquid nitrogen in the same manner as in Production Example 6 above to obtain particles 10 (aspherical particles) having an average particle diameter of 40 μm.

<Production Examples 9 and 10: Preparation of Particles 11 and 12 for Surface Layer B>

The pellets obtained in Production Example 6 were dried and crystallized, pulverized in the same manner, and subjected to wind classification to obtain particles 11 (non-spherical particles) having an average particle diameter of 35 μm. In addition, the film obtained in Production Example 7 was similarly pulverized and subjected to wind classification to obtain particles 12 (aspherical particles) having an average particle diameter of 50 μm. The above is to adjust the conditions of the wind classification so that the particles obtained are in the form shown in Table 3.

Particle 13: Pellets obtained from Sumitomo Chemical Co., Ltd.'s poly (methyl methacrylate) (PMMA) resin SUMIPEX MGSS were crushed and classified in the same manner as in Production Example 6 above to obtain an average particle size of 40 μm. Of non-spherical particles.

<Manufacturing Examples 11, 12: Preparation of Particles 14 and 15 for Surface Layer B>

Particles 14 (aspherical particles) were obtained by changing the film thickness of Production Example 7 to 75 μm, and performing pulverization and wind classification in the same manner as in Production Example 7. In addition, a film thickness of 100 μm was used in the same manner to obtain particles 15 (non-spherical particles). The above is to adjust the conditions of the wind classification so that the particles obtained are in the form shown in Table 3.

<Production Examples 13 to 20: Preparation of Particles 16 to 23 for Surface Layer B>

The pellets obtained in Production Example 6 were dried and crystallized, and similarly pulverized and classified by wind, to obtain particles 16 to 23 (aspherical particles or spherical particles) each having a structure shown in Table 3. The above is to adjust the conditions of the wind classification so that the particles obtained are in the form shown in Table 3.

[Example 1-1]

(Manufacture of white reflective film)

The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master wafer 1 obtained as the raw materials of the reflective layer (layer A) and the isophthalic acid copolymerized polyethylene terephthalate 2 were respectively used. The particle main wafer 2 is used as a raw material for the support layer (layer C). The reflection layer A is mixed so that the content of the void-forming agent is 49% by mass of the reflection layer A, and the support layer C is a void-forming agent. The content is mixed so that the mass of the support layer C is 3% by mass. The mixture is put into an extruder, and the layer A is melt-extruded at a temperature of 255 ° C, and the layer C is melt-extruded at a temperature of 230 ° C to form a layer C / A. The layer structure of the / C layer uses a three-layer supply block device to converge, and the mold is formed into a sheet shape while maintaining the layered state. At this time, the thickness ratio of the C layer / A layer / C layer is adjusted by the discharge amount of each extruder so that the biaxial extension becomes 10/80/10. An unstretched film was prepared by cooling and solidifying the sheet with a cooling cylinder having a surface temperature of 25 ° C. The unstretched film was passed through a preheating zone at 73 ° C, and then a preheating zone at 75 ° C, was guided to a longitudinally stretched zone maintained at 92 ° C, and extended 2.9 times in the longitudinal direction, and was cooled with a roller group at 25 ° C to obtain a uniaxially stretched film . Next, one side of the obtained uniaxially stretched film was coated by a reverse roll coating method to form a surface layer (layer B) shown below. 液 1。 Liquid 1.

<Coating liquid 1>

Resin Z-465 (made by Nippon Kogyo Chemical Co., Ltd. (so that polyethylene terephthalate contains sodium sulfoisophthalate component to total acid component 100 mol% to 10 mol%, diethylene glycol The same 10 mol% of the copolymerized polyester resin (using such a copolymerized polyester as the resin 1) an aqueous solution having a solid content concentration of 15% by mass), the particles 1 obtained in the above Production Example 5 as particles, and The ion-exchanged water of the diluted solvent was mixed so that the resin and particles had the content ratios shown in Table 1, and the solid content concentration of the coating liquid was 20% by mass, thereby preparing coating liquid 1.

After coating, the two ends of the film were held by clips while passing through a preheating zone at 115 ° C and guided to a horizontal extension zone maintained at 130 ° C, extending 3.6 times in the horizontal direction. After that, it is heat-fixed in a tenter at 185 ° C, and the width is narrowed in the widthwise direction at a wide width narrowing rate of 2% and a wide width narrowing temperature of 130 ° C. Then, the two ends of the falling film are cut to achieve a longitudinal relaxation rate. 2% thermal relaxation and cooling to room temperature to obtain a biaxially stretched film. The evaluation results of the obtained film are shown in Table 2.

[Examples 1-2, 1-3, 1-5, Comparative Examples 1-1 to 1-3]

A biaxially stretched film was obtained in the same manner as in Example 1-1 except that the particle types used to form the surface layer (layer B) were as shown in Table 1. The evaluation results of the obtained film are shown in Table 2.

[Example 1-4]

In addition to changing the pore-forming agent of the reflective layer A to a resin that is not compatible with polyester (cycloolefin, "TOPAS 6017S-04" manufactured by POLYPLASTICS (Japan)), the quality of the reflection layer A was reduced to that of the pore-forming agent. A biaxially stretched film was prepared and evaluated in the same manner as in Example 1-1 except that the content was 20% by mass. The evaluation results are shown in Table 2.

[Examples 1-6]

A biaxially stretched film was obtained in the same manner as in Example 1-1 except that the coating solution was not applied after the uniaxial stretching and before the biaxial stretching. The direct gravure coating device was used to form the following surface layer (layer B) The coating liquid consisting of the composition shown in Coating liquid 2 was applied at a coating thickness of 15 g / m ² with a wet thickness, and then dried in an oven at 80 ° C. to obtain a film.

<Coating liquid 2, solid content concentration 30% by mass>

‧ Particles: Particles 1 (non-spherical particles) obtained in the above Production Example 5 ... 7.5% by mass

‧Acrylic Resin (Thermoplastic Resin): ACRYDIC A-817BA (solid content concentration: 50% by mass, described as Resin 2 in the table) made by DIC (Japan) ... 30% by mass

‧Crosslinking agent: CORONATE HL (isocyanate-based bridging agent, solid content concentration 75% by mass, described in table as bridging agent 1) ... 10% by mass

‧Dilution solvent: Butyl acetate ... 52.5 mass%

The evaluation results of the obtained film are shown in Table 2. The solid content ratio of each component of the coating liquid 2 is as follows.

‧Particles: 25% by mass

‧Acrylic resin (thermoplastic resin): 50% by mass

‧Bridge agent: 25% by mass

[Example 2-1]

(Manufacture of white reflective film)

The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master wafer 1 obtained as the raw materials of the reflective layer (layer A) and the isophthalic acid copolymerized polyethylene terephthalate 2 were respectively used. The particle main wafer 2 is used as a raw material for the support layer (layer C). The reflection layer A is mixed so that the content of the void-forming agent is 49% by mass of the reflection layer A, and the support layer C is a void-forming agent. The content is mixed with the mass of the support layer C to be 3% by mass, and the mixture is put into an extruder, and the layer A is melt-extruded at a temperature of 265 ° C, and the layer C is melt-extruded at a temperature of 240 ° C to form a layer C / A The layer structure of the / C layer uses a three-layer supply block device to converge, and the mold is formed into a sheet shape while maintaining the layered state. At this time, the thickness ratio of the C layer / A layer / C layer is adjusted by the discharge amount of each extruder so that the biaxial extension becomes 10/80/10. An unstretched film was prepared by cooling and solidifying the sheet with a cooling cylinder having a surface temperature of 25 ° C. The unstretched film was passed through a preheating zone at 73 ° C, and then a preheating zone at 75 ° C, was guided to a longitudinally stretched zone maintained at 92 ° C, and extended 2.9 times in the longitudinal direction, and was cooled with a roller group at 25 ° C to obtain a uniaxially stretched film . Next, on one side of the obtained uniaxially stretched film, a coating liquid 3 for applying a surface layer (layer B) shown below was applied by a reverse roll coating method.

<Coating liquid 3>

As a resin, Z-465 (resin 1) manufactured by Nippon Kayaku Chemical Co., Ltd., as particles 8 obtained in the above-mentioned Production Example 6, and as a dilution solvent Ion-exchanged water is mixed so that the solid content content ratio of the resin and the particles becomes resin: particles = 75: 25 (mass%), and the solid content concentration of the coating liquid is mixed to make a coating liquid. 3.

After coating, the two ends of the film were held by clips while passing through a preheating zone at 115 ° C and guided to a horizontal extension zone maintained at 130 ° C, extending 3.6 times in the horizontal direction. After that, it is heat-fixed in a tenter at 185 ° C, and the width is narrowed in the horizontal direction at a wide width narrowing rate of 2% and a wide width narrowing temperature of 130 ° C. Then, the two ends of the falling film are cut to achieve a longitudinal relaxation rate. 2% thermal relaxation and cooling to room temperature to obtain a biaxially stretched film. The evaluation results of the obtained film are shown in Table 4.

[Examples 2-2 to 2-5, 2-8 to 2-15, Comparative Examples 2-1 to 2-5]

A biaxially stretched film was obtained in the same manner as in Example 2-1 except that the particle type and layer structure used to prepare the surface layer (layer B) were shown in Tables 3 and 4, respectively. The evaluation results of the obtained film are shown in Table 4.

[Example 2-6]

In addition to changing the pore-forming agent of the reflective layer A to a resin that is not compatible with polyester (cycloolefin, "TOPAS 6017S-04" manufactured by POLYPLASTICS (Japan)), the quality of the reflection layer A was reduced to that of the pore-forming agent. A biaxially stretched film was prepared and evaluated in the same manner as in Example 2-1 except that the content was set to 20% by mass. The evaluation results are shown in Table 4.

[Example 2-7]

A biaxially stretched film was obtained in the same manner as in Example 2-1 except that the coating liquid was not applied after the uniaxial stretching and before the biaxial stretching. The direct gravure coating device was then used to form the following surface layer (layer The coating liquid consisting of the composition shown in coating liquid 4 was applied at a coating thickness of 15 g / m ² with a wet thickness, and then dried in an oven at 80 ° C. to obtain a film.

<Coating liquid 4, solid content concentration 30% by mass>

‧ Particles: Particles 8 (non-spherical particles) obtained in the above Production Example 6 ... 7.5% by mass

‧Acrylic Resin (Thermoplastic Resin): ACRYDIC A-817BA (Resin 2) manufactured by Japan DIC (Resin) ... 30% by mass

‧Cross-linking agent: CORONATE HL (Cross-linking agent 1) made by Japan Polyurethane Industry (Stock) ... 10% by mass

‧Dilution solvent: Butyl acetate ... 52.5 mass%

The evaluation results of the obtained film are shown in Table 4. The solid content ratio of each component of the coating liquid 4 is as follows.

‧Particles: 25% by mass

‧Acrylic resin (thermoplastic resin): 50% by mass

‧Bridge agent: 25% by mass

[Effect of the invention]

According to the present invention, it is possible to provide a white reflective film capable of sufficiently suppressing adhesion to the light guide plate and sufficiently suppressing damage to the light guide plate.

Industrial use possibility

The white reflective film of the present invention can sufficiently suppress adhesion to the light guide plate and sufficiently suppress damage to the light guide plate. In particular, it can be suitably used as a surface light source reflection plate having a light guide plate. Among them, it is used in, for example, liquid crystal display devices. Reflective film for edge-lit backlight unit.

Claims (9)

A white reflective film having a reflective layer A and a surface layer B composed of a resin composition containing particles, characterized in that the surface of the surface layer B opposite to the reflective layer A has protrusions formed by the particles, The number of protrusions at a surface height of 5 μm or more is 10 ⁴ to 10 ¹⁰ / m ² ; the particles are pulverized polymer particles composed of polyethylene terephthalate having an average particle diameter of 3 to 100 μm. For example, the white reflective film described in the first item of the patent application range, wherein the above-mentioned particles have an average aspect ratio (long / short diameter) of 1.31 or more and 1.80 or less, and the standard deviation of the aspect ratio is 0.15 to 0.50. For example, the white reflective film described in item 1 or 2 of the scope of patent application, wherein the content of the particles in the surface layer B is 1 to 70% by mass based on the mass of the surface layer B. For example, the white reflective film described in item 1 or 2 of the scope of patent application, wherein the amount of volatile organic solvents is 10 ppm or less. For example, the white reflective film described in item 1 or 2 of the patent application scope, wherein the reflective layer A contains voids, and the void volume ratio is 15% by volume or more and 70% by volume or less. The white reflective film as described in item 1 or 2 of the scope of patent application, which further has a void volume ratio of 0% by volume or more and 15% by volume or less. The support layer C. The white reflective film according to item 1 or 2 of the patent application scope, wherein the surface layer B is a layer formed by coating with a coating liquid. The white reflective film as described in item 1 or 2 of the scope of patent application, which is used as a surface light source reflective plate having a light guide plate. A method for manufacturing a white reflective film having a reflective layer A and a surface layer B composed of a resin composition containing particles, which is characterized in that the white reflective film has a surface on the opposite side of the surface layer B to the reflective layer A The number of projections formed by the particles above the surface height of 5 μm or more is 10 ⁴ to 10 ¹⁰ / m ² ; the particles are pulverized polymerization obtained by pulverizing the polymer with an average particle diameter of 3 to 100 μm. Particles, the polymer is polyethylene terephthalate.