TW201726415A - White reflective film - Google Patents

Abstract

A white reflective film having a reflective layer (A), and a surface layer (B) comprising a resin composition containing particles, the white reflective film having projections formed by the particles on a surface of the surface layer (B) on the reverse side thereof from the reflective layer (A), the number of projections having a height of at least 5 [mu]m in the surface being 104 to 1010/m2, and the particles being non-spherical particles having an average particle diameter of 3-100 [mu]m and a 10% compressive strength of 0.1-15 MPa. In this film, adhesion to a light guide plate can be adequately suppressed, and at the same time, scratching of the light guide plate can be adequately suppressed.

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) is a direct type having a light source on a back surface of a liquid crystal display panel and a reflective film on the back surface, and a light guide plate having a reflector on the back surface of the liquid crystal display panel; The side surface of such a light guide plate is provided with a side light type of a light source. In the past, the backlight unit used in a large LCD was mainly used in a direct type (mainly a direct type CCFL) from the viewpoint of the brightness of the screen and the uniformity of the brightness in the screen, and the side light type was mostly used in a notebook computer or the like. Compared with the development of the light source or the light guide plate, the brightness of the backlight unit and the uniformity of brightness in the screen are improved, so that it is adopted not only in a relatively small size but also in a large LCD. Sidelight type backlight unit. This is because of the advantage of being able to thin the LCD.

The edge type backlight unit is configured to directly contact the light guide plate and the reflective film. Therefore, in such a configuration, when the light guide plate and the reflective film are stuck together, the problem is that the brightness of the portion to be stuck together is abnormal, and the brightness is generated. In-plane differences. Thus, there is a gap between the light guide plate and the reflective film, and it is necessary to keep such an interval constant. For example, it is possible to prevent the interval between the light guide plate and the reflection film from being constant by having beads on the surface of the reflective film. However, at this time, when the light guide plate composed of the relatively soft material is in contact with the reflection film, there is a problem that the light guide plate is damaged by the reflection film or the beads on the surface. In this case, for example, Patent Documents 1 to 3 report on the surface of the reflective film by coating to form a damage preventing layer containing synthetic rubber-based beads.

However, in the damage prevention layer such as Patent Documents 1 to 3, the effect of suppressing the damage of the light guide plate is somewhat suppressed, but there is a tendency that the original purpose of ensuring the interval (suppression of adhesion) is deteriorated. In addition, according to the review by the inventors of the present invention, it can be understood that only the number of protrusions is focused on only the former method, and it is the satisfaction of the suppression of the light guide plate and the suppression of the light guide plate in recent years. There are occasions that are insufficient.

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

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

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

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

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

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 by the particles. The number of protrusions having a height of 5 μm or more on the surface is 10 ⁴ to 10 ¹⁰ /m ² ; and the particles are non-spherical particles having an average particle diameter of 3 to 100 μm and a 10% compression 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 the above 1 to 3, wherein the average aspect ratio (long diameter/short diameter) of the particles is 1.31 or more and 1.80 or less, and the standard deviation of the aspect ratio is 0.15. 0.50 non-spherical particles.

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

7. The white reflective film according to any one of the above 1 to 3, wherein the reflective layer A contains a void having a void volume ratio of 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 fraction 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 the above 1 to 3, wherein It is used as a surface light source reflector with a light guide plate.

1 and 2 are examples of electron micrographs of protrusions formed by non-spherical particles of the present invention.

Fig. 3 is a schematic view showing a method of evaluating the damage of the light guide plate of the present invention and a method of evaluating the particle shedding.

Fig. 4 is a schematic view showing a constitution employed in the evaluation of the adhesion spot of the present invention.

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

Hereinafter, each constituent 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 pore-forming agent, and contains a void in the layer by a pore-forming agent to form a white layer. Such a pore-forming agent can be, for example, an inorganic particle or a resin which is incompatible with the thermoplastic resin constituting the reflective layer A (hereinafter, abbreviated as a non-coherent resin). Further, the reflectance of the reflection layer A at a wavelength of 550 nm is preferably 95% or more, more preferably 96% or more, and particularly preferably 97% or more. Thereby, the reflectance of the white reflective film can be easily set in a preferable range.

The reflective layer A, as described above, is a layer having voids in the layer, and thus The ratio of the volume of the pores to the volume of the reflective layer A (void volume ratio) is preferably 15% by volume or more and 70% by volume or less. By setting such a range, the effect of improving the reflectance can be improved, and the above-described reflectance can be easily obtained. In addition, the effect of improving the film stretchability can be improved. When the void volume ratio is too low, there is a tendency that it is difficult to obtain a preferable reflectance. From such a viewpoint, the porosity of the reflective layer A is preferably 30% by volume or more, and more preferably 40% by volume or more. On the other hand, in the case where it is too high, there is a tendency that the effect of improving the film stretchability is lowered. From such a viewpoint, the porosity of the reflective layer A is preferably 65 vol% or less, more preferably 60 vol% or less.

The void volume ratio can be achieved by adjusting the type, size, and amount of the pore former of the reflective layer A.

(thermoplastic resin)

The thermoplastic resin constituting the reflective layer A may, for example, be a thermoplastic resin composed of, for example, polyester, polyolefin, polystyrene or acrylate. Among them, from the viewpoint of obtaining a white reflective film having excellent mechanical properties and thermal stability, polyester is also preferred.

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 terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, adipic acid, and sebacic acid. The ingredients. The diol component may be a component obtained from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol or the like. Among these polyesters, aromatic polyesters are also preferred, in pairs. Ethylene phthalate is particularly preferred. The polyethylene terephthalate may be a homopolymer. However, from the viewpoint of suppressing crystallization and improving the film stretchability when the film is stretched on one or two axes, It is preferred to copolymerize the polymer. The dicarboxylic acid component or the diol component is exemplified as the copolymerization component. However, from the viewpoint of high heat resistance and high effect of improving film formation elongation, the isophthalic acid component and 2,6- The naphthalene dicarboxylic acid component is preferred. The proportion of the copolymerized component is based on 100% by mole of the total dicarboxylic acid component of the polyester, for example, in the range of 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 15 mol%. , with 7 to 11 moles of extra good. By setting the ratio of the copolymerization component within this range, the effect of improving the film stretchability can be excellent. In addition, the thermal dimensional stability is excellent.

(emptor forming agent)

In the case where the inorganic layer is used as the pore 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 oxide, cerium oxide, and calcium carbonate. These inorganic particles are not particularly limited as long as the white reflective film has an appropriate reflectance to select an average particle diameter or a content. Preferably, the reflectance of the reflective layer A or the white reflective film is preferably in the preferred range of the present invention. Further, the void volume ratio of the reflective layer A may be in the preferred range of the present invention. In view of such circumstances, the average particle diameter of the inorganic particles is, for example, 0.2 to 3.0 μm, preferably 0.3 to 2.5 μm, more preferably 0.4 to 2.0 μm. Further, the content thereof is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, and most preferably 31 to 53% by mass based on the mass of the reflective layer A. good. Further, by adopting the particle form described above, the particles can be appropriately dispersed in the polyester, and aggregation of the particles can be prevented from occurring, and a film having no coarse protrusions can be obtained. In addition, the starting point at which the coarse particles break when they are extended can also be suppressed. The inorganic particles may be in the form of particles of any type, such as a plate shape or a spherical shape. The inorganic particles may also be subjected to a surface treatment for improving the dispersibility.

When a non-compatible resin is used as the pore-forming agent, the non-compatible resin is not particularly limited as long as it is incompatible with the thermoplastic resin constituting the layer. For example, in the case where the related thermoplastic resin is a polyester, polyolefin, polystyrene or the like is preferred. These may also be the form of the particles. In addition, the content of the white reflective film is selected to have an appropriate average particle diameter or content in the same manner as in the case of the inorganic particles, and the content thereof is not particularly limited. Preferably, the reflectance of the reflective layer A or the white reflective film is preferably in the preferred range of the present invention. Further, the void volume ratio of the reflective layer A may be in the preferred range of the present invention. Considering these circumstances, the content is preferably 10 to 50% by mass, more preferably 12 to 40% by mass, and most preferably 13 to 35% by mass based on the quality of the reflective layer A.

(other ingredients)

The reflective layer A may preferably contain, for example, an ultraviolet absorber, an oxidation preventive agent, a charge preventive agent, a fluorescent whitening agent, a wax, and a pore-forming agent, for the purpose of preferably not impeding the object of the present invention. Or resin, etc.

[surface layer B]

The surface layer B of the present invention is composed of a resin composition containing particles in a resin, and a layer in which protrusions are formed on the surface by the particles. As such a resin, a thermoplastic resin is preferable. In addition, it is also possible to have a bridging structure by using a bridging agent. In this case, a thermoplastic resin having a functional group reactive with a bridging agent may be used, and the bridging agent may form a bridging structure with the thermoplastic resin, or may be a carrier having no functional group. The reactive group reacts with a thermoplastic resin, and has a matrix of thermoplastic resin and a matrix of a bridging structure of a bridging agent bridge. When the bridge structure is provided, the strength of the surface layer B tends to increase. On the other hand, when the bridge structure is too large, it is found that the recovery of the film tends to be deteriorated when the film is recovered and regenerated, and it is preferable that the bridging structure is not excessive in such a viewpoint.

The surface layer B may be formed by coating with a coating liquid during or after the production of the film, or may be formed simultaneously with the reflective layer A by, for example, co-extrusion. In the above manner, the surface layer B has a bridging structure, and is preferably formed by coating with a coating liquid. From the above viewpoints, the content of the bridging agent is preferably 35 mass% or less, more preferably 30 mass% or less, more preferably 25% by mass or less, and even more preferably 20 mass% or less based on the solid content of the coating liquid. Very good. Further, it is preferably 1% by mass or more, 2% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more.

(thermoplastic resin)

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

As such a polyester, the same polyester as the polyester of the above-mentioned reflective layer A can be used. Among these polyesters, from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability, an aromatic polyester is preferred, and polyethylene terephthalate is particularly preferred. The polyethylene terephthalate may be a homopolymer, but from the point of moderately softening the surface layer B to obtain an effect of suppressing particle shedding, it is preferred to use a copolymerized polymer to form a polyparaphenylene. Ethylene formate is particularly preferred. Thereby, even if an external force such as friction with the light guide plate is applied, the particles are less likely to fall off. The dicarboxylic acid component or the diol component is exemplified as the copolymerization component. However, from the viewpoint of high heat resistance and high effect of improving film formation elongation, the isophthalic acid component and 2,6- The naphthalene dicarboxylic acid component is preferred. The ratio of the copolymerization component is based on 100 mol% of the total dicarboxylic acid component of the polyester, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 17 mol%. , with 12~16 moles is especially good. By setting the ratio of the copolymerization component within this range, the effect of improving the film stretchability can be excellent. In addition, the thermal dimensional stability is excellent.

Further, in the case where 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-described effects and to improve the stability of the coating liquid. It has a function of improving the lyophilic property in the side chain or main chain of the polyester. Here, In order to have a function of improving lyophilicity, a base of a sulfonic acid metal salt (preferably sodium sulfonate), a hydroxyl group, an alkyl ether group, or a carboxylate group may be mentioned. Wait. In the present invention, the preferred form is a phthalic acid component having a base having a sulfonic acid metal salt, preferably 100% by mole based on the total acid component of the polyester, preferably 3 to 30 mol%, 5~ 20 mol% is better, and 5 to 15 mol% is more preferable. Further, from the viewpoint of the same content of the diethylene glycol-containing component, it is preferable to contain a form of the relevant component, preferably 100 to 30 mol%, and preferably 3 to 30 mol%, based on the total acid component of the polyester, 5 ~20% by mole is better, preferably 5 to 15% by mole.

(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. By setting the average particle diameter within the above range, the pattern of the number of protrusions described later can be easily formed, and the interval can be ensured more easily. When the average particle diameter is too large, the particles are likely to fall off, which is a cause of defects on the screen. On the other hand, if the average particle diameter is too small, it is difficult to ensure the interval between the original purpose and the light guide plate. From such a viewpoint, it is preferably 5 μm or more, more preferably 7 μm or more, and particularly preferably 8 μm or more, and more preferably 80 μm or less, more preferably 70 μm or less, and particularly preferably 50 μm or less.

Further, by forming the particles forming the protrusions on the outermost surface as non-spherical particles, it is possible to secure the space between the light guide plates and the effect of suppressing the damage of the light guide plate. Here, the non-spherical particles of the present invention set the maximum diameter Dx of the particles (in the x direction) and the direction in the vertical x direction (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 one of the maximum diameter differences (Dx-Dy, Dx-Dz, Dy-Dz) in the respective directions is set to exceed 20% of Dx.

The above effects can be obtained by using such non-spherical particles, and are considered to be based on the following mechanism. In other words, it is considered that the contact area of the light guide plate is enlarged by making the shape of the particles non-spherical, and the pressure dispersion is not easy to cause damage. When the shape of the particles is aspherical as determined as described above, the particles have the largest diameter in a certain direction, and in the case of being contained in the surface layer B, the probability of the largest diameter is likely to be the surface layer B. The direction of the face is substantially parallel. Therefore, the contact area between the protrusion formed by such particles and the light guide plate becomes wide, 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 pressure concentration is liable to cause damage. As a result, even if soft particles are used, for example, it is easy to damage the light guide plate due to the spherical shape.

The present invention is not limited to the fact that the surface layer B has the specific particle pattern as described above, so that the contact of the light guide plate is concentrated in the narrow range of the apex of the protrusion, and the number of protrusions is maintained by one side. The contact area between the protrusion and the light guide plate is increased to allow the pressure to be dispersed, and the number of contact points with the light guide plate is appropriately set to ensure a space, and the pressure on the light guide plate is reduced by the protrusions, thereby suppressing damage of the light guide plate. When the specification is out of the above range, for example, the light guide plate is brought into contact and concentrated only in a narrow range of the apex of the projection, and the pressure applied to the portion is increased or the shaving is easily performed.

In the present invention, in order to further improve the effect of suppressing the damage of the light guide plate and suppressing the adhesion of the light guide plate, the average aspect ratio (long diameter/short diameter) of the particles is preferably the best. It is 1.31 or more and 1.80 or less. Such an aspect ratio is more preferably 1.35 or more and is 1.75 or less. Although the aspect ratio is large in order to achieve the above effect, when it is too large, there is a tendency that it is difficult to maintain the number of protrusions having a height of the outermost surface of 5 μm or more. Here, the aspect ratio is obtained by observation by an electron microscope described later. Further, the maximum diameter of the particles thus observed is set to be the long diameter, and the maximum diameter in the direction in which the maximum diameter is orthogonal is the short diameter.

Further, when the particle shape is appropriately changed at the same time, even if the particle shape is moderately irregular, it is presumed that it is not easy to apply pressure to the specific particles and the light guide plate is not easily damaged.

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

Further, in the present invention, it is necessary that the above particles have a 10% compressive strength of 0.1 to 15 MPa. Thereby, the interval can be ensured, and the light guide plate can be suppressed from being damaged. When the compressive strength is too low, the surface stress causes excessive deformation, so that the original purpose of ensuring the interval with the light guide plate becomes difficult. On the other hand, when the compressive strength is too high, even the non-spherical particles are easy to be used for the light guide plate. Cause damage. From such a viewpoint, the 10% compressive strength is preferably 0.2 MPa or more, preferably 0.3 MPa or more, more preferably 3 MPa or more, and particularly preferably 8 MPa or more, and more preferably 14 MPa or less, and preferably 13 MPa or less. 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 particles having the above average particle diameter to satisfy the pattern of the number of protrusions described later. For example, when the average particle diameter of the particles tends to be thinner than the thickness of the surface layer B, the protrusion tends to be easily formed, so that the content is relatively small, and in the opposite case, the content is preferably large. It can be adjusted as appropriate, taking into account such trends. Specifically, the mass of the surface layer B is preferably 1 to 70% by mass, preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 60% by mass or less. More preferably, it is 50% by mass or less, and more preferably 30% by mass or less.

The particles contained in the surface layer B of the present invention may be any organic particles, inorganic particles or organic-inorganic composite particles, regardless of the type thereof. From the viewpoint of easily satisfying the particle form described above, it is preferably a polymer particle composed of a polymer such as acrylate, polyester, polyurethane, nylon, polyolefin, or polyether. It is preferably polyester or nylon, and it is easy to obtain a suitable 10% compressive strength. Particularly preferred is a polyester (including polyethylene terephthalate), which is advantageous in that it is excellent in film formability for recovery.

Further, in the present invention, the method for achieving the particle shape is not particularly limited, but from the viewpoint of easily obtaining particles having a particularly good shape, and from the viewpoint of production cost or productivity, pulverization is solid. A method in which a bulk polymer obtains particles is preferred. The particles obtained by the relevant steps are made into pulverized polymer particles. The relevant step, more specifically, the polymer sheet after the polymerization, for example, shot peening, is preferably crystallization by heat treatment, and is preferably pulverized at a normal temperature to a temperature lower than normal temperature. From the viewpoint of being more easily pulverized, pulverization is preferably carried out at a lower temperature than normal temperature, and as a method for obtaining such a low temperature, a method of cooling with liquid nitrogen is preferred.

Further, in addition to the above-mentioned shot-formed polymer sheet, it is also possible to pulverize the polymer composition to be formed, the polymer film to be formed, the fiber-formed polymer fiber, and the like. particle. By selecting the type of the polymer to be pulverized in this manner (including, for example, changing the size of the testicle, the thickness of the film, and the diameter of the fiber), it is possible to obtain particles having various types of non-spherical shapes (aspect ratio). Also, the difference in particle shape (standard deviation) can be adjusted.

The polymer which pulverizes the polymer particles may be a copolymer or a mixture of two kinds of polymers, or may contain inorganic particles or organic particles having a smaller diameter than the inside of the pulverized polymer particles, or may contain an ultraviolet absorber. Or a lubricant, etc.

(Type of surface layer B)

In the present invention, the surface layer B composed of the resin composition containing the particles described above forms the outermost layer of at least one of the white reflecting films. Next, on the surface of the surface layer B on which the outermost layer is formed on the opposite side to the reflective layer A (hereinafter, there is a case called the outermost surface), A protrusion formed by particles. Next, such protrusions are necessary to have a moderate height of protrusions at an appropriate frequency on the outermost surface from the viewpoint of ensuring the distance between the light guide plate and the film.

Therefore, in the present invention, it is usually necessary to set the number of protrusions (protrusion frequency) of 5 μm or more in height on the outermost surface to 10 ⁴ to 10 ¹⁰ /m ² . Thereby, the gap between the light guide plate and the film can be sufficiently ensured, and the adhesion suppressing effect can be ensured. When the frequency of the protrusion is too small, the adhesion suppressing effect is deteriorated. On the other hand, when the frequency of the protrusion is too large, there is a possibility that the particles may fall off or the reflectance may decrease.

(other ingredients)

The surface layer B may contain components other than the above-described constituent components within a range that does not inhibit the object of the present invention. Examples of such a component include an ultraviolet absorber, an oxidation preventive agent, a charge preventive agent, a fluorescent whitening agent, a wax, a surfactant, particles different from the above particles, and a resin.

[layer composition]

The thickness of the reflective layer A of the present invention is preferably 80 to 350 μm. Thereby, the effect of improving the reflectance can be improved. Too thin will reduce the effect of improving the reflectivity. On the other hand, if it is too thick, it will be inefficient. From such a viewpoint, the thickness is preferably from 80 to 300 μm, more preferably from 100 to 320 μm, and particularly preferably from 150 to 250 μm.

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

Further, it is preferable that the thickness of the resin portion of the surface layer B particles is 0.2 to 50 μm. Thereby, the frequency of the projections can be easily made into a preferable shape, and it is easy to ensure the distance from the light guide plate. When the thickness of the resin portion of the surface layer B is too thin, there is a tendency that particles which are formed in the protrusions on the surface of the surface layer B tend to fall off. On the other hand, if it is too thick, it tends to be difficult to obtain a preferable protrusion frequency. From such a viewpoint, the thickness is preferably 0.3 μm or more, more preferably 0.5 μm or more, more preferably 1 μm or more, and most preferably 2 μm or more, and further preferably 40 μm or less. Further, in consideration of the peeling property, 1 μm or more is preferable, and 2 μm or more is preferable.

The laminated structure of the white reflective film, when A indicates that the reflective layer A and B represent the surface layer B, a two-layer structure of B/A, a three-layer structure of B/A/B, or a B layer is provided. It is composed of a plurality of layers of four or more layers of the outermost layer of either side. 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. It is preferably composed of four layers of B/C/A/C, and the film-forming extensibility is more excellent. In addition, problems such as curling are less likely to occur. The invention is preferably of the type having such a support layer C. Such a support layer C is preferably composed of the same polyester as the reflective layer A, and preferably has a relatively low void volume ratio (0% by volume or more, preferably less than 15% by volume, and preferably 5% by volume or less). More preferably, the type is preferably 3% by volume or less. Further, the thickness of such a support layer C (the total thickness in the case of a plurality of layers) is preferably 5 to 140 μm, more preferably 20 to 140 μm.

The present invention, in addition to the reflective layer A, the surface layer B, and the support layer C, Other layers may also be provided without damaging the purpose of the invention. For example, a layer for imparting functions such as easy adhesion, winding property (lubricity), charge prevention, conductivity, ultraviolet durability, or the like, or a layer for adjusting optical characteristics may be provided.

[Method for Producing Film]

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

When the white reflective film of the present invention is produced, the reflective layer A obtained by a melt extrusion method or the like can be coated by a molten resin (including a method of coating a molten extruded resin), a co-extrusion method, a laminate method, or a supply. The coating liquid for the surface layer B is formed, and the surface layer B is formed by a coating liquid coating method. Among them, in the case where the reflective layer A and the support layer C are laminated by a co-extrusion method, the method of laminating the surface layer B by the coating liquid coating method is particularly preferable. By laminating the surface layer B by the coating liquid coating method, it is easy to control the distribution state of the particles by changing the drying conditions and the like, and the number of designated projections can be mass-produced at a low price. In addition, even with particles having a relatively small compressive strength of 10%, the handling becomes easy. Further, the specific particle shape of the present invention can be easily maintained, and the shape of the protrusion can be easily made into a preferable form.

Hereinafter, the thermoplastic resin constituting the reflective layer A and the thermoplastic resin constituting the support layer C will be described as polyester, and as a method of laminating the reflective layer A and the support layer C, a co-extrusion method is employed as a laminate of the surface layer B. Although the method of the coating liquid coating method is employed, the present invention is not limited to such a production method, or may be produced in the same manner for other types as described below. At this time, if there is no extrusion step, the following "dissolving" The melt extrusion temperature can be interpreted as, for example, "melting temperature". Here, the melting point of the polyester to be 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 of a mixed polyester, a pore-forming agent, and other optional components is prepared. Further, as a polyester composition for forming the support layer C, a composition in which a polyester, a pore former is optionally mixed, and other optional components is prepared. These polyester compositions are used after being dried and sufficiently removing water.

Next, the dried polyester composition was placed in a separate extruder and subjected to melt extrusion. The melting temperature must be above Tm, and it can be around Tm + 40 °C.

Further, in this case, the polyester composition used for the production of the film, particularly the polyester composition used for the reflective layer A, is a non-woven filter having an average pore diameter of 10 to 100 μm made of a stainless steel fine wire having a wire diameter of 15 μm or less. It is better to filter. By performing this filtration, it is generally possible to suppress aggregation of particles in which coarse aggregated particles are easily formed after aggregation, and to obtain a film having less coarse foreign matter. Further, the average pore diameter of the nonwoven fabric is preferably 20 to 50 μm, more preferably 15 to 40 μm. The filtered polyester composition was extruded in a multi-layered state from a mold by a multilayer extrusion method (coextrusion method) while using a supply block (supply block) in a molten state to produce an unstretched laminate. The unstretched laminated sheets extruded from the mold are cooled and solidified under a casting drum to form an unextended laminate 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, the longitudinal direction or the long side is referred to as a film) The longitudinally stretched film is extended to or to the MD. This extension is preferably carried out by using a difference in rotational speed between 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 lateral direction or a web direction or TD) to form a biaxially stretched film.

The elongation temperature is preferably at a temperature of Tg or more and Tg + 30 ° C or less of the polyester (preferably the polyester constituting the reflective layer A), and the film-forming extensibility is more excellent, and the void is preferably made easy. form. Further, in terms of the stretching ratio, it is preferably 2.5 to 4.3 times in the longitudinal direction and the lateral direction, and more preferably 2.7 to 4.2 times. When the stretching ratio is too low, the thickness deviation of the film tends to be deteriorated, and there is a tendency that the pores are less likely to be formed. On the other hand, when the stretching ratio is too high, the film tends to be broken during the film formation. Further, in the case of performing the two-axis stretching such as the lateral extension after the longitudinal stretching, the extension temperature of the second stage (in this case, the lateral extension) is preferably about 10 to 50 ° C higher than that of the first stage. This is because the Tg is increased as a uniaxial film by the alignment in the first step.

In addition, it is preferred to preheat the film prior to each extension. For example, the pre-heat treatment of the transverse stretching may start from a temperature higher than Tg + 5 ° C of the polyester (preferably the polyester constituting the reflective layer A), and then gradually increase the temperature. The temperature rise during the transverse extension process can be continuous or phased (sequential), but is usually a sequential increase in temperature. For example, by dividing the lateral extent of the tenter into a plurality of zones in the film advancing direction, a heating medium of a specified temperature is allowed to flow to each zone to raise the temperature.

The biaxially stretched film is then subjected to heat fixation and thermal relaxation to form a biaxial alignment film, but it may be extended from the melt extrusion. These treatments are carried out together while advancing the film.

The film after the biaxial stretching can directly set the melting point of the polyester (preferably the polyester constituting the reflective layer A) to Tm and (Tm-20 ° C) under the holding of both ends by the reticle. ~(Tm-100 ° C), heat treatment, heat setting, and reduction of heat shrinkage rate are performed at a reduced amplitude or a range of 10% or less. When such a heat treatment temperature is too high, the planarity of the film tends to be deteriorated, and the thickness variation tends to increase. On the other hand, when it is too low, the heat shrinkage rate tends to become large.

Further, in order to adjust the amount of heat shrinkage, both ends of the film to be held can be cut, and the pulling speed in the longitudinal direction of the film can be adjusted to relax in the longitudinal direction. As a means of relaxing, the speed of the roller group on the exit side of the tenter is adjusted. In terms of the ratio of slackening, the speed of the roller group is reduced to the film forming linear velocity of the tenter, and the speed of the reduction is preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, and 0.3 to 2.0% lower to relax. The film (referred to as "the relaxation rate" for short) adjusts the thermal contraction rate in the longitudinal direction by controlling the relaxation rate. Further, the width direction of the film can be reduced in the process up to the end of the cutting, and the desired heat shrinkage rate can be obtained.

Further, in the case of biaxial stretching, in addition to the vertical-transverse secondary biaxial stretching method described above, the horizontal-longitudinal secondary axial stretching method may be employed. In addition, simultaneous biaxial stretching can also be used to form the film. In the case of the two-axis stretching method, the stretching ratio is, for example, 2.7 to 4.3 times, preferably 2.8 to 4.2 times, in the longitudinal direction and the lateral direction.

The surface layer B, preferably after the longitudinal extension of the above steps, is coated with a coating liquid for forming the surface layer B in the longitudinally stretched film, in the preheating step. The step, the lateral stretching step, the heat setting step, and the like are formed by drying, hardening, and so-called in-line coating. The coating liquid can be obtained by mixing the components constituting the surface layer B and diluting it by any solvent so as to be easily applied. In this case, the solvent is preferably water, and the amount of the volatile organic solvent described later can be reduced. The coating method of the coating liquid is not particularly limited, and preferred methods include a reverse roll coating method, a concave plate coating method, a die coating method, and a spray coating method. Further, the surface layer B may be formed by a so-called off-line coating method by a biaxial alignment film obtained after biaxial stretching and heat setting. Further, in the case of the off-line coating method, it is not easy to apply dryness or high heat for reasons such as film deformation, and therefore, an organic solvent which is easily dried is usually used as a solvent. However, in this case, the amount of the volatile organic solvent to be described later tends to increase, and therefore, the present invention is particularly preferable by the in-line coating method.

Thus, the white reflective film of the present invention can be obtained.

[Characteristics of White Reflective Film]

(reflectance, brightness)

The reflectance (reflectance at a wavelength of 550 nm) measured from the surface layer B side of the white reflective film of the present invention is preferably 95% or more, preferably 96% or more, 97% or more, and more preferably 97.5% or more. More than 98% is especially good. When the reflectance is 95% or more or 96% or more, high luminance can be obtained when used in a liquid crystal display device, illumination, or the like. Such a reflectance can be made by a preferred form such as increasing the porosity of the reflective layer A, or by thickening the thickness of the reflective layer A or by thinning the thickness of the surface layer B. It is achieved by a better type.

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

(amount of volatile organic solvent)

The white reflective film of the present invention preferably has a volatile organic solvent content of 10 ppm or less as measured by a method described later. Thereby, it can be shown that the surface layer B is not formed by a coating method using an organic solvent. Further, when the raw material can be recovered by itself and the film is formed by this, gas marks are less likely to occur, and film forming elongation (recovery film forming property) is improved. From such a viewpoint, the dose is preferably 5 ppm or less, more preferably 3 ppm or less, and desirably 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, a solution coating method using an organic solvent is not employed in the formation of the surface layer B, and it is preferable to employ the above method.

Example

Hereinafter, the present invention will be described in detail by way of examples. Further, each characteristic value was measured by the following method.

(1) Light reflectance

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

(2) Average particle size of particles

Using a laser scattering type particle size distribution measuring machine (SALD-7000 manufactured by Shimadzu Corporation), the particle size distribution (standard deviation of particle diameter) of the particles was determined, and the particle diameter of d50 (50% distribution from the small side under the volume distribution standard) was determined. The particle size) is set to an average particle diameter.

(3) particle shape

(3-1) Particle shape 1

The particle powder was fixed on a measurement platform with a conductive tape, and observed by a S-4700 field-type scanning electron microscope manufactured by Hitachi, Ltd. at a magnification of 1,000 times, and the shape of the particles was observed. For the 30 randomly selected particles, the maximum diameter Dx of the particles (in the x direction) and the direction perpendicular to the x direction (the y direction and the z direction, and the z direction is also perpendicular to the y direction) are obtained. The diameters Dy and Dz (where DyZDz) are respectively calculated as average values, set to Dxave, Dyave, and Dzave, and Dxave-Dyave, Dxave-Dzave, and Dyave-Dzave are obtained, and at least one of them is more than 20% of Dx. It is judged to be non-spherical, otherwise it is determined to be spherical.

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

Gently stick the particles to the conductive tape with a glass rod and fix this In the measurement platform, the S-4700 field-type scanning electron microscope made by Hitachi, Ltd. was observed from the front side (without the tilt angle) at a magnification of 100 times. For the randomly selected 30 particles, the maximum diameter of the particles was used. The longest diameter and the largest diameter in the direction orthogonal to such a maximum diameter are regarded as the short diameter, and the long diameter/short diameter (aspect ratio) is obtained for each particle, and the average value is taken as the average value of the aspect ratio. Further, the standard deviation of the aspect ratio is calculated from the values of the respective aspect ratios.

Moreover, when the average particle diameter is small (it is assumed to be, for example, 3 μm or less), the magnification is increased (for example, 1000 times).

(4) The frequency of protrusion on the surface of the film (the number of protrusions)

The projection cross section of the film surface was measured by a three-dimensional roughness measuring device SE-3CKT (manufactured by Otaru Research Laboratory Co., Ltd.), cutoff 0.25 mm, measurement length 1 mm, scanning pitch 2 μm, and scanning line number 100. For the measurement, the protrusion profile was recorded with a height magnification of 1000 times and a scanning direction magnification of 200 times. The number of protrusions (number/m ² ) having a height of 5 μm or more was obtained from the obtained projection cross section (horizontal axis: projection height, vertical axis: projection cross section), and the projection frequency was obtained. Further, in the analysis, a three-dimensional roughness analysis device SPA-11 (manufactured by Otaru Research Institute Co., Ltd.) was used.

(5) 10% compressive strength

The compression strength of each particle at a weight of 3 gf was measured by using a small hardness tester ENT-1100a manufactured by ELIONIX, and the compressive strength (MPa) at the time of 10% deformation was used. The average value of the five measurements was used.

(6) Amount of volatile organic solvent

At room temperature (23 ° C), 1 g of the film sample was placed in a 10 L fluororesin bag, which was cleaned with pure nitrogen and sealed. Next, directly take nitrogen from the bag at 0.2 L/min, and take 0.2 L and 1.0 L of nitrogen to two TENAX-TA traps for analysis. These are used and taken by HPLC and GCMS. The mass of the organic solvent component contained in the nitrogen is quantified. The obtained numerical value was converted into an amount of 10 L of nitrogen, and the mass of the organic solvent volatilized from 1 g of the film sample to 10 L of nitrogen was determined, and the amount of the volatile organic solvent (unit: ppm, mass basis of the film sample) was determined. Further, in the acetaldehyde, the acetaldehyde-inducing compound was eluted from the collecting tube with acetonitrile, and quantified by HPLC. In addition, when the values are different between HPLC and GCMS, a large number of values are detected.

(7) Film thickness and layer composition

The white reflective film was cut into a sheet by a microtome to expose the cross section, and the S-4700 field-type scanning electron microscope manufactured by Hitachi, Ltd. was used to observe the cross-section at 500 magnifications, and the entire film and the reflection layer were obtained. A, the thickness of the surface layer B and the support layer C. Further, with respect to the surface layer B, the thickness of the portion where the particles are present is arbitrarily taken at 10 points, and the average value of the particles is used as the thickness.

(8) Calculation of void volume ratio

From the layer and the polymer, the added particles, and the other The calculated density is determined by the ratio of the density of the components. At the same time, the layer was separated by peeling or the like, and the mass and the volume were measured. The solid density was calculated from these, and the calculated density and the solid density were obtained by the following formula.

Empty volume ratio = 100 × (1 - (solid density / calculated density))

Further, the density of the isophthalic acid copolymerized polyethylene terephthalate (after the 2-axis stretching) was 1.39 g/cm ³ , and the density of the barium sulfate was 4.5 g/cm ³ .

Further, only the layer in which the void volume ratio was measured was separated, and the mass per unit volume was determined to determine the solid density. In the volume, the sample was cut out to have an area of 3 cm ² , and the thickness of the sample was measured by an average value of 10 points measured by an electric micrometer (K-402B manufactured by Anritsu) as a thickness, and the area × thickness was calculated. The quality is measured by an electronic balance.

Further, the specific gravity of the particles (including agglomerated particles) is a numerical value obtained by the following cylinder method. After the pellet of the volume of 1000 ml was filled with the particles in the dry state, the total weight was measured, and the weight of the pellet was determined by subtracting the weight of the cylinder from the total weight, and the volume of the cylinder was measured, and the weight (g) of the pellet was divided by the volume. Determined by (cm ³ ).

(9) melting point, glass transition temperature

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

(10) Brightness

The reflective film is taken out from the LG (LED) LED liquid crystal television (LG42LE5310AKR), and the surface layer B side of each of the various reflective films described in the examples is placed on the screen side (on the side of the light guide plate), and the brightness is used in the state of the backlight unit. The brightness of the center of the backlight was measured by measuring the distance of 500 mm from the front side (Model MC-940 of Otsuka Electronics Co., Ltd.).

(11) Light guide plate damage evaluation (scraping evaluation)

(11-1) Damage Evaluation 1

As shown in Fig. 3, at the end of the handle portion (1), an iron plate having a width of 200 mm, a length of 200 mm, and a thickness of 3 mm (2 g of about 200 g) is fixedly attached, and the width of the evaluation face up is 250 mm × The reflection film (3) having a length of 200 mm was formed by peeling a portion of 25 mm from the both ends in the width direction from the iron plate (the portion of the center of 200 mm × 200 mm overlapped with the iron plate). At this time, the evaluation surface (surface layer) of the reflective film was made to be outside. Further, the excess 25 mm portion at both ends in the width direction of the reflecting film is folded back to the back side of the iron plate, and the end portion of the reflecting film (the portion where the blade is cut by a knife or the like during sampling) is excluded to cause the effect of scraping the light guiding plate.

Next, a light guide plate (4, size at least 400 mm × 200 mm) having a dot (401) facing upward is fixed on a horizontal table, and is fixed on the reflective film of the prepared iron plate to evaluate the surface and the light guide plate. The contact method is such that the reflective film side faces down on the light guide plate, and further, 500 g (5) is loaded thereon, and the reflective film fixed to the iron plate is operated at a distance of 200 mm (in the field of 400 mm × 200 mm) It is 15 round trips at a speed of about 5 to 10 seconds. After that, on the surface of the light guide plate, for the scraping situation, The presence or absence of the particles which were detached from the reflection film was observed with a 20-times magnifying glass, and evaluated according to the following criteria.

The entire range of 400 mm × 200 mm that was rubbed on the light guide plate was set to "no shaving" (scraping evaluation ○) when there was no scratch that could be observed with the magnifying glass after 20 reciprocating operations; it was not observed after 10 reciprocating motions. In the case of a flaw that has been observed, it is "not easy to scrape" (scratch evaluation △) when there is a scratch that can be observed after 20 reciprocating movements; and it is "scraped" when there is a flaw that can be observed after 10 reciprocating movements. (Scratch evaluation ×).

Further, in the above evaluation, it is possible to suppress the influence of the dot size as much as possible, and to select the areas where the dot size is large as much as possible in the light guide plate, and to evaluate each evaluation sample in unison.

(11-2) Damage Evaluation 2

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

(12) White rating

(12-1) White Rating 1

The reflection film and the light guide plate used for the evaluation of the above (11-1) are used at the table. The reflective film is placed on the surface layer upwards, and the light guide plate is placed on the bottom side of the light guide plate, and the weight of each 300 g is fixedly placed on the four sides of the light guide plate, and the LED liquid crystal television (LG42LE5310AKR) made of LG (share) is used. The backlight source emits light from the side of the light guide plate, and if a bright spot other than the light guide plate point is visually observed, it is considered that a white point (evaluation Δ) occurs. On the other hand, if the highlight is not observed by visual observation, it is considered that no white spot has occurred (evaluation ○).

(12-2) White Rating 2

In the reflection film and the light guide plate used for the evaluation of the above (11-2), the evaluation criteria are that if a bright spot other than the light guide plate point is observed by visual observation, white spots (evaluation ×) are considered, and if abnormality is not observed by visual observation, It is considered that the white point (evaluation ○) does not occur, and it is not obvious that the bright spot other than the light guide plate point that can be observed is visually observed, and the same as (12-1) above, except that several white spots (evaluation △) are considered to occur. Evaluation.

(13) Evaluation of adhesion spots (adhesion evaluation)

(13-1) Paste evaluation 1

As shown in Figure 4, the chassis (6) is taken out from the LG LED TV (47吋), placed on a horizontal table with the TV inside up, on which the size is roughly the same as the chassis. The reflective film is placed in such a manner that the surface layer is upward, and three light guide plates and optical sheets (seven, two diffusion films and one cymbal) of the original television are placed thereon. Next, in this area, in the field including the most bulging portion of the chassis, the placement is as shown in FIG. 3 sets of symmetrical triangles (801) with a diameter of 5 mm cylindrical feet, and 10 kg of weights (802) loaded thereon, to visually observe the fields surrounded by such 3 feet, if there is no abnormal brightness Some of them are treated as "no dense spots" (closed spot evaluation ○). In addition, when there is an abnormally bright portion, the DBEF sheet of the original TV is placed on the optical sheet three, and the same observation is made visually. If the abnormally bright portion is not corrected, it is referred to as "closed spot" (evaluation) ×) If there is no abnormal bright portion, it is "almost no dense spot" (evaluation △). In addition, the area surrounded by the three feet is a slightly equilateral triangle with a length of 10 cm on each side.

(13-2) Paste evaluation 2

The above (13-1) was evaluated in the same manner except that the weight of the weight (802) was set to 15 kg.

(14) Recycling filming evaluation

The biaxially stretched film obtained in the examples was pulverized, melted and extruded, and fragmented to prepare a raw material for recycling. The self-recovered raw material was added to the reflective layer A by a mass ratio of 35% by mass based on the mass of the reflective layer A, and the mass ratio of the remaining polyester to the pore-forming agent was made the same as the original film. In the same manner, a biaxially stretched film containing its own recycled raw material was prepared and evaluated according to the following criteria.

◎: The film can be stably formed to a length of 2000 m or more.

○: The film can be stably formed to have a length of 1000 m or more and less than 2000 m.

△: One break occurred when the length was less than 1000 m.

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

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

136.5 parts by mass of dimethyl terephthalate, 13.5 parts by mass of dimethyl isophthalate (100 mol% relative to the total acid component of the obtained polyester, 9 mol%), ethylene glycol 98 mass a portion, a diethylene glycol 1.0 mass portion, a manganese acetate 0.05 mass portion, and a lithium acetate 0.012 mass portion are placed in a flask equipped with a rectification column and a distillation condenser, and heated to 150 to 240 ° C while stirring to distill off methanol to carry out esterification. Exchange reactions. After the methanol was distilled off, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of cerium oxide were added, and the reactant was transferred to a reactor. Next, the inside of the reactor was gradually reduced to 0.3 mmHg while stirring, and the temperature was raised to 292 ° C to carry out a polycondensation reaction to obtain an isophthalic acid copolymerized polyethylene terephthalate 1. These polymers have a melting point of 235 °C.

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

In addition to the change of 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (the molar content of 100% of the total acid component of the obtained polyester is 14 mol%), Example 1 was carried out in the same manner to obtain an isophthalic acid copolymerized polyethylene terephthalate 2. These polymers have a melting point of 215 °C.

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

Using one of the above-mentioned isophthalic acid copolymerized polyethylene terephthalate 1 and a pore-forming agent having an average particle diameter of 1.0 μm of barium sulfate particles (hereinafter referred to as BaSO ₄ ), NEX-T60 tandem extruder manufactured by Kobe Steel Co., Ltd. in Japan, and the content of barium sulfate particles is mixed so that the mass of the obtained main wafer becomes 60% by mass, and extruded at a resin temperature of 260 ° C. A particle master wafer 1 containing barium sulfate particles was prepared.

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

Using one of the above-mentioned isophthalic acid copolymerized polyethylene terephthalate 2 and a pore-forming agent having an average particle diameter of 1.0 μm of barium sulfate particles, NEX-made by Kobe Steel Co., Ltd. In a T60 tandem extruder, the content of the barium sulfate particles was mixed so that the mass of the obtained main wafer became 60% by mass, and the resin was extruded at a resin temperature of 260 ° C to prepare a particle master wafer containing barium sulfate particles. 2.

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

The dimethyl terephthalate 150 mass part, the ethylene glycol 98 mass part, the diethylene glycol 1.0 mass part, the manganese acetate 0.05 mass part, and the lithium acetate 0.012 mass part are placed in a flask equipped with a rectification column and a distillation condenser. While stirring, the mixture was heated to 150 to 240 ° C to distill off methanol for transesterification. After the methanol was distilled off, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of cerium oxide were added, and the reactant was transferred to a reactor. Next, one While slowly stirring the inside of the reactor to 0.3 mmHg while stirring, the temperature was raised to 292 ° C to carry out a polycondensation reaction to obtain an isophthalic acid copolymerized polyethylene terephthalate 3. The obtained isophthalic acid copolymerized polyethylene terephthalate 3 was extruded from a strand die, cooled, and cut into pellets. Next, the obtained pellets were dried and crystallized by heating at 170 ° C for 3 hours in an oven, and then a liquidizer TAP-1 made of Japan Matsubo Co., Ltd. was used as a liquid. The particles were pulverized while cooling with nitrogen to obtain polyester particles having an average particle diameter of 60 μm. Further, by subjecting the polyester particles to wind classification, particles 1 (non-spherical particles) having an average particle diameter of 40 μm were obtained.

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

Particle 3: Non-spherical particles having an average particle diameter of 10 μm obtained by pulverization and classification were obtained in the same manner as in Production Example 5 except that a pellet of nylon 66 resin CM3006 manufactured by Toray Co., Ltd. was used.

Particles 4: Non-spherical particles having an average particle diameter of 10 μm obtained by pulverization and classification were obtained in the same manner as in Production Example 5 except that pellets of nylon 6 resin CM1017 manufactured by Toray Co., Ltd., were used.

Particle 5: MBX-40 (true spherical acrylate particles, average particle diameter: 40 μm) manufactured by Nippon Sekisui Chemicals Co., Ltd.

Particle 6: An average particle diameter of 10 μm obtained by pulverization and classification in the same manner as in Production Example 5 except that a pellet of poly(methyl methacrylate) (PMMA) resin SUMIPEX MGSS manufactured by Sumitomo Chemical Co., Ltd. was used. Non-spherical particles.

Particle 7: SP-10 (true spherical nylon particles, average particle diameter: 10 μm) manufactured by Toray Co., Ltd., Japan.

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

In the same manner as in the above Production Example 5, polyethylene terephthalate 3 was extruded from a strand die, cooled, and cut into pellets. As a result of adjusting the shape of the strand, the shape of the pellet was substantially a rectangular parallelepiped shape and the average shape was 4 mm × 3 mm × 2 mm. Then, in the same manner as in the above Production Example 5, polyester particles having an average particle diameter of 60 μm were obtained. Further, by subjecting the polyester particles to wind classification, particles 8 (non-spherical particles) having an average particle diameter of 43 μm were obtained.

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

The pellet obtained by the above Production Example 6 was subjected to the conditions generally employed for the biaxially stretched film of polyethylene terephthalate (the longitudinal stretching ratio was 3.0 times, the lateral stretching ratio was 4.0, and the heat setting temperature was set at 220 ° C). A transparent 2-axis-extending polyethylene terephthalate film (thickness: 50 μm) obtained by alignment crystallization was obtained. This was pulverized by cooling with liquid nitrogen in the same manner as in the above Production Example 6, and then subjected to air classification to obtain particles 9 (non-spherical particles) having an average particle diameter of 52 μm.

<Manufacturing Example 8: Preparation of Particles 10 for Surface Layer B>

The pellet obtained in the above Production Example 6 was prepared by a conventional method. The polyester fiber having a diameter of 35 μm was pulverized by liquid nitrogen while cooling in the same manner as in Production Example 6 to obtain particles 10 (non-spherical particles) having an average particle diameter of 40 μm.

<Production Examples 9 and 10: Preparation of Particles 11, 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. Further, the film obtained in Production Example 7 was similarly pulverized and subjected to wind classification to obtain particles 12 (non-spherical particles) having an average particle diameter of 50 μm. In the above, the conditions of the wind classification are adjusted so that the obtained particles are in the form shown in Table 3.

Particle 13: An average particle diameter of 40 μm obtained by pulverization and classification was carried out in the same manner as in Production Example 6 except that a pellet of poly(methyl methacrylate) (PMMA) resin SUMIPEX MGSS manufactured by Sumitomo Chemical Co., Ltd. was used. Non-spherical particles.

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

The film thickness of the above-mentioned Production Example 7 was changed to 75 μm, and pulverization and air classification were carried out in the same manner as in Production Example 7, to obtain particles 14 (non-spherical particles). Further, the film thickness was 100 μm, and the same procedure was carried out to obtain particles 15 (non-spherical particles). In the above, the conditions of the wind classification are adjusted so that the obtained particles 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 subjected to wind classification to obtain particles 16 to 23 (non-spherical particles or spherical particles) each having the configuration shown in Table 3. In the above, the conditions of the wind classification are adjusted so that the obtained particles 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 main wafer 1 obtained as the raw material of the reflective layer (layer A) and the isophthalic acid copolymerized polyethylene terephthalate 2 were respectively used. With the particle main wafer 2 as a raw material of the support layer (C layer), the reflective layer A is mixed such that the content of the pore-forming agent is 49% by mass of the mass of the reflective layer A, and the support layer C is formed with a pore-forming agent. The content is mixed in such a manner that the mass of the support layer C is 3% by mass, and is put into an extruder. The layer A is at a melt extrusion temperature of 255 ° C, and the layer C is at a melt extrusion temperature of 230 ° C to form a layer C/layer A. The layer structure of the /C layer is formed by a three-layer supply block device, and is formed into a sheet shape by molding in a state of being stacked. At this time, the thickness ratio of the C layer/A layer/C layer was adjusted by the discharge amount of each extruder so as to be 10/80/10 after extending in two directions. Further, an unstretched film in which the sheet was cooled and solidified by a cooling cylinder having a surface temperature of 25 ° C was prepared. The unstretched film was passed through a preheating zone of 73 ° C and then a preheating zone of 75 ° C to a longitudinal extension maintained at 92 ° C, extended 2.9 times in the longitudinal direction, and cooled by a roller group of 25 ° C to obtain a one-axis stretch film. . Next, a single surface of the obtained one-axis stretched film was coated by a reverse roll coating method to form a surface layer (layer B) shown below. Liquid 1.

<coating liquid 1>

Z-465, which is a resin of Japan Mutual Chemical Co., Ltd. (made polyethylene terephthalate containing a sulfonic acid sodium benzoate component to a total acid component of 100 mol% of 10 mol%, diethylene glycol It is the same as 10 mol% of the copolymerized polyester resin (such a copolymerized polyester is made into the resin 1), and the particle 1 obtained by the above-mentioned manufacturing example 5 as particle|grains The ion-exchanged water of the solvent was mixed, and the resin and the particles were mixed in a ratio of the content shown in Table 1, and the solid content of the coating liquid was 20% by mass to prepare a coating liquid 1.

After coating, both ends of the film were held by a clip while passing through a preheating zone of 115 ° C and guided to a transverse extension maintained at 130 ° C, extending 3.6 times in the transverse direction. Then, it was heat-fixed at 185 ° C in a tenter, and the width was narrowed in the width direction at a wide narrowing ratio of 2% and a wide narrowing temperature of 130 ° C. Then, the film was cut at both ends to obtain a longitudinal relaxation rate. 2% heat relaxes and cools 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 type used for the surface layer (layer B) was prepared as shown in Table 1. The evaluation results of the obtained film are shown in Table 2.

[Examples 1-4]

In addition to changing the pore-forming agent of the reflective layer A to a polyester-incompatible resin (cycloolefin, "TOPAS 6017S-04" manufactured by Japan POLYPLASTICS Co., Ltd.), the quality of the reflective layer A was compared with the pore former. The biaxially stretched film was prepared in the same manner as in Example 1-1 except that the content was 20% by mass, and the evaluation was carried out. The evaluation results are shown in Table 2.

[Example 1-6]

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

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

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

‧Acrylate resin (thermoplastic resin): ACRYDIC A-817BA manufactured by DIC Co., Ltd. (solid content concentration: 50% by mass, and resin 2 in the table)... 30% by mass

‧Briging agent: CORONATE HL (isocyanate-based bridging agent, solid content concentration: 75 mass%, and the bridge agent 1 in the table) of Japan Polyurethane Industry Co., Ltd....10% by mass

‧Diluted solvent: butyl acetate...52.5 mass%

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

‧ Particles: 25% by mass

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

‧Bridge carrier: 25% by mass

[Example 2-1]

(Manufacture of white reflective film)

The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle main wafer 1 obtained as the raw material of the reflective layer (layer A) and the isophthalic acid copolymerized polyethylene terephthalate 2 were respectively used. With the particle main wafer 2 as a raw material of the support layer (C layer), the reflective layer A is mixed such that the content of the pore-forming agent is 49% by mass of the mass of the reflective layer A, and the support layer C is formed with a pore-forming agent. The content is mixed in such a manner that the mass of the support layer C is 3% by mass, and is put into an extruder. The layer A is at a melt extrusion temperature of 265 ° C, and the layer C is at a melt extrusion temperature of 240 ° C to form a layer C/layer A. The layer structure of the /C layer is formed by a three-layer supply block device, and is formed into a sheet shape by molding in a state of being stacked. At this time, the thickness ratio of the C layer/A layer/C layer was adjusted by the discharge amount of each extruder so as to be 10/80/10 after extending in two directions. Further, an unstretched film in which the sheet was cooled and solidified by a cooling cylinder having a surface temperature of 25 ° C was prepared. The unstretched film was passed through a preheating zone of 73 ° C and then a preheating zone of 75 ° C to a longitudinal extension maintained at 92 ° C, extended 2.9 times in the longitudinal direction, and cooled by a roller group of 25 ° C to obtain a one-axis stretch film. . Next, a coating liquid 3 for forming a surface layer (layer B) shown below was applied to one side of the obtained one-axis stretched film by a reverse roll coating method.

<coating liquid 3>

Z-465 (resin 1) manufactured by Nippon Mutual Chemical Co., Ltd. as a resin, and particles 8 obtained as the above-mentioned Production Example 6 as particles, as a diluent solvent The ion-exchanged water is mixed so that the ratio of the solid content of the resin to the particles is such that the resin: particles are 75:25 (% by mass), and the solid content of the coating liquid is 20% by mass. 3.

After coating, both ends of the film were held by a clip while passing through a preheating zone of 115 ° C and guided to a transverse extension maintained at 130 ° C, extending 3.6 times in the transverse direction. After that, it was heat-fixed at 185 ° C in a tenter, and the width was narrowed at a wide narrowing ratio of 2% and a wide narrowing temperature of 130 ° C, and then the film was cut at both ends to obtain a longitudinal relaxation rate. 2% heat relaxes and cools 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, and 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 the layer constitution used for the surface layer (layer B) were prepared as 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 polyester-incompatible resin (cycloolefin, "TOPAS 6017S-04" manufactured by Japan POLYPLASTICS Co., Ltd.), the quality of the reflective layer A was compared with the pore former. The biaxially stretched film was prepared in the same manner as in Example 2-1 except that the content was 20% by mass, and the evaluation was carried out. The evaluation results are shown in Table 4.

[Examples 2-7]

The biaxially stretched film was obtained in the same manner as in Example 2-1 except that the coating liquid was not applied after the one-axis stretching and the two-axis stretching, and the direct gravure coating apparatus was used to form the following surface layer (layer). B) The coating liquid composed of the composition shown by the coating liquid 4 was applied at a coating amount of a wet thickness of 15 g/m ² , and then dried at 80 ° C in an oven 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 mass%

‧Acrylate resin (thermoplastic resin): ACRYDIC A-817BA (resin 2) made by Japan DIC Co., Ltd....30% by mass

‧Briging agent: CORONATE HL (bridge agent 1) made by Japan Polyurethane Industry...10% by mass

‧Diluted solvent: butyl acetate...52.5 mass%

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

‧ Particles: 25% by mass

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

‧Bridge carrier: 25% by mass

[Effects of the Invention]

According to the present invention, it is possible to provide a white reflective film which can sufficiently suppress adhesion to the light guide plate and at the same time sufficiently suppress damage of the light guide plate.

Industrial use possibility

The white reflective film of the present invention can sufficiently suppress the adhesion to the light guide plate and sufficiently suppress the damage of the light guide plate, and can be suitably used as a surface light source reflector having a light guide plate, for example, for use in a liquid crystal display device or the like. A reflective film for an edge type 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 having a surface height of 5 μm or more is 10 ⁴ to 10 ¹⁰ /m ² ; and the particles are pulverized polymer particles composed of polyethylene terephthalate having an average particle diameter of 3 to 100 μm. The white reflective film according to the first aspect of the invention, wherein the particles have an aspect ratio (long diameter/short diameter) of 1.31 or more and 1.80 or less, and a standard deviation of an aspect ratio of 0.15 to 0.50. The white reflective film according to the first or second aspect of the invention, 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. The white reflective film according to claim 1 or 2, wherein the amount of the volatile organic solvent is 10 ppm or less. The white reflective film according to claim 1 or 2, wherein the reflective layer A contains voids having a void volume ratio of 15% by volume or more and 70% by volume or less. The white reflective film according to claim 1 or 2, further comprising a void volume fraction of 0% by volume or more and 15% by volume or less. Support layer C. The white reflective film according to claim 1 or 2, wherein the surface layer B is a layer formed by coating with a coating liquid. A white reflective film according to claim 1 or 2, which is used as a surface light source reflector having a light guide plate. A method for producing a white reflective film having a reflective layer A and a surface layer B composed of a resin composition containing particles, characterized by a white reflective film having a surface on the opposite side of the surface layer B from the reflective layer A the projection of the particles formed, the number of projections on the surface height of 5μm or more is 10 ⁴ to 10 ¹⁰ / m ^2; the above-described particles, based average particle diameter of 3 ~ 100μm pulverized by pulverizing a polymer obtained by polymerizing Particles, the polymer is polyethylene terephthalate.