KR101937007B1 - 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, wherein the surface layer (B) has a projection formed on the surface opposite to the reflective layer (A) Wherein the number of projections having a height of 5 占 퐉 or more on the surface is 10 ⁴ to 10 ¹⁰ per square meter and the particles are non-spherical particles having an average particle size of 3 to 100 占 퐉 and a 10% compressive strength of 0.1 to 15 MPa; . This film is capable of sufficiently restraining the attachment to the light guide plate and sufficiently restraining the light guide plate from being damaged.

Description

WHITE REFLECTIVE FILM

The present invention relates to a white reflective film. And more particularly to a white reflective film used in a liquid crystal display device.

In the backlight unit of the liquid crystal display (LCD), a direct light type having a light source on the back side of the liquid crystal display panel and a reflection film on the back side thereof, and a light guide plate having a reflection plate on the back side of the liquid crystal display panel And an edge light type having a light source on the side surface of such a light guide plate. Conventionally, as a backlight unit used in a large-sized LCD, a direct-type (mainly direct-type CCFL) is mainly used, and an edge light type is a relatively small In recent years, even in the back light unit of the edge light type, uniformity of the brightness and the brightness in the screen is improved due to the development of the light source or the light guide plate, and in addition to the relatively small size, the edge light type backlight unit Has been used. This is because it has the advantage of thinning the LCD.

In the edge light type backlight unit, the light guide plate and the reflective film are in direct contact with each other. Therefore, in such a structure, when the light guide plate and the reflective film are pasted (adhered), there is a problem that the brightness of the pasted portion becomes unstable, and the in-plane deviation of brightness occurs. Therefore, it is necessary to have a gap between the light guide plate and the reflective film, and to maintain such a gap constant. For example, by providing the beads on the surface of the reflective film, the gap between the light guide plate and the reflective film can be kept constant, and these attachments can be prevented. However, at this time, when the light guide plate made of a relatively flexible material contacts the reflective film, there is a problem that the light guide plate is damaged by the reflective film or beads on the surface. As a countermeasure therefor, for example, there is a report to form a damage prevention layer containing elastomeric beads by coating on the surface of a reflection film as in Patent Documents 1 to 3.

However, in the damage preventive layer as in Patent Documents 1 to 3, the effect of suppressing the damage of the light guide plate is to some extent, but there is a tendency that the gap for ensuring the original purpose (adhesive restraint) is inferior. According to the examination by the inventors of the present invention, it has been found that merely paying attention to the number of protrusions as in the prior art is insufficient for satisfying both of the suppression of the adhesion to the light guide plate and the suppression of damage to the light guide plate, which are recently required .

Japanese Patent Application Laid-Open No. 2003-92018 Japanese Patent Publication No. 2008-512719 Japanese Patent Application Laid-Open No. 2009-244509

An object of the present invention is to provide a white reflective film capable of sufficiently restraining the attachment to the light guide plate and sufficiently restraining the damage of the light guide plate.

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

1. A white reflective film having a reflective layer (A) and a surface layer (B) comprising a resin composition containing particles,

The surface layer (B) has protrusions formed by the particles on the surface opposite to the reflective layer (A), the number of protrusions having a height of 5 占 퐉 or more on the surface is 10 ⁴ to 10 ¹⁰ /

Wherein the particles are non-spherical particles having an average particle size of 3 to 100 占 퐉 and a 10% compressive strength of 0.1 to 15 MPa.

2. The white reflecting film according to 1 above, wherein the particles are ground polymer particles obtained by pulverizing the polymer.

3. The white reflective film of claim 2, wherein the polymer is a polyester.

4. The non-spherical particle according to any one of 1 to 3 above, wherein the particles are non-spherical particles having an aspect ratio (long diameter / short diameter) of not less than 1.31 and not more than 1.80 and a standard deviation of aspect ratio of 0.15 to 0.50 Reflective film.

5. The white reflecting 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 reflecting 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 not less than 15% by volume and not more than 70% by volume.

8. The white reflective film according to 7 above, further comprising a support layer (C) having a void volume ratio of not less than 0 volume% and less than 15 volume%.

9. The white reflecting film according to 7 above, wherein the surface layer (B) is a layer formed by applying a coating liquid.

10. The white reflective film according to any one of 1 to 3 above, which is used as a planar light source reflector having a light guide plate.

1 and 2 are electron micrographs of protrusions formed by non-spherical particles in the present invention.
Fig. 3 is a schematic view showing a method of evaluating damage of a light guide plate and dropout evaluation of particles in the present invention. Fig.
Fig. 4 is a schematic view showing a constituent used in the adhesion spot evaluation in the present invention. Fig.

The white reflecting film of the present invention has 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) in the present invention is a layer composed of a thermoplastic resin and a void-forming agent, containing voids in the layer by containing a void-forming agent and having a white color. Examples of such a void-forming agent include an inorganic particle and a resin that is incompatible with the thermoplastic resin constituting the reflective layer (A) (hereinafter sometimes referred to as a nonreinforced resin). Can be used. The reflectance of the reflective layer (A) at a wavelength of 550 nm is preferably 95% or more, more preferably 96% or more, particularly preferably 97% or more. This makes it easy to set the reflectance of the white reflecting film within a preferable range.

The reflective layer (A) has voids in the layer as described above, but it is preferable that the volume (void volume ratio) of the volume of the void with respect to the volume of the reflective layer (A) is not less than 15% by volume and not more than 70% by volume Do. By setting this range, the effect of improving the reflectance can be enhanced, and the reflectance as described above can be easily obtained. In addition, the effect of improving film-forming stretchability can be enhanced. When the void volume ratio is too low, it tends to make it difficult to obtain a desirable reflectance. From this point of view, the void volume ratio in the reflection layer (A) is more preferably not less than 30% by volume, particularly preferably not less than 40% by volume. On the other hand, if it is excessively high, the effect of improving the film stretchability tends to be lowered. From this point of view, the void volume ratio in the reflective layer (A) is more preferably 65% by volume or less, 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 a thermoplastic resin composed of polyester, polyolefin, polystyrene and acrylic. Among them, a polyester is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As such a polyester, it is preferable to use a polyester comprising a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include those derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, have. Examples of the diol component include components derived from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. The polyethylene terephthalate may be a homopolymer, but a copolymer polymer is preferable from the viewpoint that crystallization is suppressed when the film is uniaxially or biaxially stretched and the effect of improving the film stretchability is enhanced. As the copolymerization component, there may be mentioned the dicarboxylic acid component and the diol component, but an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component are preferable from the viewpoint of high heat resistance and high effect of improving film stretchability. The proportion of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 15 mol%, based on 100 mol% of the total dicarboxylic acid component of the polyester, And particularly preferably 7 to 11 mol%. When the ratio of the copolymerization component is within this range, the effect of improving the film stretchability is excellent. Also, the thermal dimensional stability is excellent.

(Void-forming agent)

When inorganic particles are used as the void-forming agent in the reflective layer (A), white inorganic particles are preferable as the inorganic particles. As the white inorganic particles, particles of barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate can be exemplified. The average particle diameter and the content of the inorganic particles may be selected so that the white reflecting film has an appropriate reflectance, and these are not particularly limited. Preferably, the reflectance of the reflective layer (A) or the white reflective film is within a preferable range in the present invention. In addition, the void volume ratio in the reflective layer (A) may be within a preferable range in the present invention. Taking these points into consideration, the average particle diameter of the inorganic particles is, for example, 0.2 to 3.0 占 퐉, preferably 0.3 to 2.5 占 퐉, more preferably 0.4 to 2.0 占 퐉. The content thereof is preferably 20 to 60 mass%, more preferably 25 to 55 mass%, and most preferably 31 to 53 mass%, based on the mass of the reflective layer (A). In addition, by adopting the above-described aspect of the particles, the particles can be appropriately dispersed in the polyester, aggregation of the particles does not occur well, and a film free of coarse protrusions can be obtained. Further, fracture at the time of stretching where the coarse particles originate is also suppressed. The inorganic particles may be in the form of any particles, for example, in the form of a plate or a sphere. The inorganic particles may be subjected to a surface treatment for improving dispersibility.

When an emulsion resin is used as the void-forming agent, the emulsion resin is not particularly limited as long as it is non-emissive to the thermoplastic resin constituting the layer. For example, when such thermoplastic resin is polyester, polyolefin, polystyrene and the like are preferable. These may be particle shapes. As in the case of the inorganic particles, the content thereof is not particularly limited, and the average particle size or the content may be selected so that the white reflecting film has an appropriate reflectance. Preferably, the reflectance of the reflective layer (A) or the white reflective film is within a preferable range in the present invention. In addition, the void volume ratio in the reflective layer (A) may be within a preferable range in the present invention. In consideration of these points, the content is preferably 10 to 50 mass%, more preferably 12 to 40 mass%, and most preferably 13 to 35 mass%, based on the mass of the reflective layer (A).

(Other components)

The reflective layer (A) may contain other components, such as ultraviolet absorbers, antioxidants, antistatic agents, fluorescent brighteners, waxes, and particles or resins different from the void-forming agent can do.

[Surface layer (B)]

The surface layer (B) in the present invention is a layer formed of a resin composition containing particles in a resin and having protrusions formed on the surface thereof. As such a resin, a thermoplastic resin is preferable. The crosslinking agent may have a crosslinking structure. In this case, a thermoplastic resin having a functional group capable of reacting with the reactive group of the crosslinking agent may be used to form a crosslinking structure of the crosslinking agent and the thermoplastic resin, or a thermoplastic resin having no functional group capable of reacting with the reactive group of the crosslinking agent And a matrix of a thermoplastic resin and a matrix of a cross-linked structure in which a cross-linking agent is cross-linked may be used. If it has a crosslinked structure, the strength of the surface layer B tends to be improved. On the other hand, when the cross-linking structure is excessively large, the recoverability of the film tends to be inferior, for example, when the film is recovered and regenerated, the amount of unmelted material increases, and from this viewpoint, it is preferable not to make the cross-linking structure excessively large.

The surface layer (B) may be formed by applying a coating liquid during or after the production of the film, and may be formed simultaneously with the reflective layer (A) by employing, for example, coextrusion. As described above, in order for the surface layer (B) to have a crosslinked structure, it is preferable that the surface layer (B) is formed by applying a coating liquid. The content of the crosslinking agent is preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, particularly preferably 20% by mass or less based on the solid content constituting the coating liquid, By mass is 20% by mass or less. Further, it is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, particularly preferably 5% by mass or more.

(Thermoplastic resin)

As the thermoplastic resin constituting the surface layer (B), the same thermoplastic resin as the thermoplastic resin constituting the above-mentioned reflective layer (A) can be used. Of these, acrylic and polyester are preferable, and polyester is particularly preferable from the viewpoint of obtaining a white reflecting film having excellent mechanical properties and thermal stability.

As such a polyester, the same polyester as the polyester in the above-described reflective layer (A) can be used. Of these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability. Polyethylene terephthalate may be a homopolymer, but a copolymerized polymer is preferable, and a copolymerized polyethylene terephthalate is particularly preferable in that the surface layer (B) is suitably softened and an effect of suppressing particle dropping is obtained. Thereby, even if an external force is applied to cause friction with the light guide plate, the particles do not drop off well. Examples of such a copolymerization component include the dicarboxylic acid component and the diol component, but an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component are preferable from the viewpoints of high heat resistance and high effect of improving film stretchability . The proportion of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 17 mol%, based on 100 mol% of the entire dicarboxylic acid component of the polyester, , Particularly preferably 12 to 16 mol%. When the ratio of the copolymerization component is within this range, the effect of improving the film stretchability is excellent. Also, the thermal dimensional stability is excellent.

In the case of forming the surface layer (B) by coating the coating liquid during or after the production of the film, for the purpose of obtaining the above effect and for improving the stability of the coating liquid, Or a group having a function of improving the affinity for the hydrophilic group in the main chain. The group having a function of improving hydrophilicity is preferably a sulfonic acid metal salt group (preferably a sulfonic acid sodium salt), a hydroxyl group, an alkyl ether group, or a carboxylate group. In the present invention, the isophthalic acid component having a sulfonic acid metal salt group is preferably contained in an amount of preferably 3 to 30 mol%, more preferably 5 to 20 mol%, and still more preferably 5 to 20 mol%, based on 100 mol% Is 5 to 15 mol%. The content of the diethylene glycol component is also preferably from the same viewpoint. The amount of the component is preferably 3 to 30 mol%, more preferably 5 to 20 mol%, more preferably 5 to 20 mol% based on 100 mol% And more preferably 5 to 15 mol%.

(Non-spherical particles)

In the present invention, it is necessary that the particles in the surface layer (B) are non-spherical particles having an average particle size of 3 to 100 mu m. When the average particle size falls within the above-mentioned range, it is easy to form a mode of the number of projections to be described later, thereby making it easier to secure the gap. If the average particle diameter is too large, the particles may easily fall off, which may cause defects on the screen. On the other hand, if the average particle size is too small, it is difficult to secure a gap with the light guide plate as the original purpose. From this viewpoint, it is more preferably at least 5 mu m, more preferably at least 7 mu m, particularly preferably at least 8 mu m, even more preferably at most 80 mu m, even more preferably at most 70 mu m, 50 탆 or less.

In addition, since the particles forming the projections on the outermost layer surface are non-spherical particles, it is possible to secure the gap with the light guide plate and to enhance the damage suppressing effect of the light guide plate. In the present invention, the non-spherical particle means a particle having a maximum diameter Dx (in the x direction) and a direction perpendicular to the x direction (in the y direction and z direction and z direction is the direction perpendicular to the y direction) (Dx-Dy, Dx-Dz, Dy-Dz) of the maximum diameters in these directions is 20% of Dx Shall be said to exceed.

It is considered that the reason why the above-mentioned effects are obtained by such non-spherical particles is due to the following mechanism. That is, by making the shape of the particles non-spherical, it is considered that the contact area with the light guide plate is widened, and the pressure dispersion is less likely to cause damage. If the shape of the particles is an aspherical shape determined as described above, the particles have a maximum diameter in either direction. If they are contained in the surface layer (B), the maximum diameter direction is probabilistically similar to the surface direction of the surface layer It is likely to be in a parallel direction. Therefore, the contact area between the light guide plate and the protrusion formed from such particles 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 narrowed, so that pressure is liable to be concentrated and damage is likely to occur. Therefore, even if flexible particles are used, the light guide plate is likely to be damaged due to the structure.

The present invention is characterized in that the surface layer (B) is provided with a specific particle as described above, so that the contact area between the projection and the light guide plate is increased while maintaining the projection number rather than contacting the light guide plate with a narrow range of the projection peak And it is suitable as the number of contact points with the light guide plate. Therefore, it is possible to suppress the occurrence of damage of the light guide plate by reducing the pressure to the light guide plate by each projection while achieving the gap. If it is not within the above-mentioned range, for example, the light guide plate comes into contact with a narrow range of the projecting apex, and the pressure applied to the light guide plate increases, which makes it easier to cut.

In the present invention, it is preferable that the average of the aspect ratio (long diameter / short diameter) of the particles is not less than 1.31 and not more than 1.80 in order to further improve the damage suppressing effect of the light guide plate and the effect of suppressing the attachment to the light guide plate. This aspect ratio is more preferably 1.35 or more, and still more preferably 1.75 or less. For this effect, it is preferable that the aspect ratio is large. However, if it is too large, it tends to be difficult to maintain the number of protrusions having a height of 5 占 퐉 or more on the outermost layer surface. Here, the aspect ratio is obtained by observation using an electron microscope described later. The maximum diameter of the particles in such an observation is taken as the long diameter, and the maximum diameter in the direction orthogonal to the maximum diameter is taken as the short diameter.

At the same time, if there is an appropriate deviation in the shape of the particles, that is, the shapes of the particles are not properly matched, it is difficult to apply pressure to the specific particles, and it is presumed that it is difficult to damage the light guide plate.

Therefore, it is preferable that the standard deviation of the aspect ratio of these particles is 0.15 to 0.50. That is, it indicates that there is a suitable deviation in each particle shape. Since the shape of the protrusions is appropriately varied, the effect of suppressing the damage of the light guide plate can be further enhanced while securing a gap with the light guide plate. When the deviation is small, the effect of improving the gap ensuring and damaging suppressing is lowered. On the other hand, even if the deviation is excessively large, a problem tends to occur when it is added to the surface layer (B), and the expected projecting frequency tends to be hardly obtained. As a result, . From this viewpoint, the standard deviation of the aspect ratio of the particles is more preferably 0.16 or more, still more preferably 0.17 or more, still more preferably 0.45 or less, still more preferably 0.43 or less.

In the present invention, it is necessary that the 10% compression strength of the particles is 0.1 to 15 MPa. As a result, the gap can be ensured and the damage to the light guide plate can be suppressed. If the compressive strength is too low, it will be excessively deformed with respect to the stress, so that it is difficult to secure a gap with the light guide plate, which is originally intended. On the other hand, if the compressive strength is excessively high, damage to the light guide plate tends to occur even if it is non-spherical particles. From this viewpoint, the 10% compressive strength is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, further preferably 3 MPa or more, particularly preferably 8 MPa or more, and more preferably 14 MPa or less Preferably not more than 13 MPa, more preferably not more than 12 MPa.

The content of the non-spherical particles in the surface layer (B) in the present invention can be suitably adjusted so as to satisfy the aspect of the number of projections to be described later by using particles having an average particle size as described above. For example, when the thickness of the surface layer (B) tends to be thinner than the average particle size of the particles, since the projections tend to be formed, the content may be relatively small, and conversely, Is preferable, and it can be appropriately adjusted in view of such a tendency. Specifically, the amount is preferably 1 to 70 mass%, more preferably 5 mass% or more, further preferably 10 mass% or more, and particularly preferably 20 mass% or more, based on the mass of the surface layer (B) , More preferably not more than 60 mass%, further preferably not more than 50 mass%, particularly preferably not more than 30 mass%.

In the present invention, the particles contained in the surface layer (B) may be organic particles of any kind, inorganic particles, or organic-inorganic composite particles. From the viewpoint of satisfying the aspect of the particle as described above, polymer particles composed of polymers such as acrylic, polyester, polyurethane, nylon, polyolefin, polyether and the like are preferable. More preferably, it is polyester or nylon, and more suitable 10% compression strength is easily obtained. Particularly preferred is a polyester (particularly polyethylene terephthalate), which is advantageous in that it has excellent recovered film formability.

In the present invention, the method for achieving the above-described shape of the particles is not particularly limited. However, from the viewpoints of obtaining particles having particularly preferable shapes and from the viewpoint of production cost and productivity, the solid polymer is pulverized A method of obtaining particles is preferred. The particles obtained by such a process are referred to as pulverized polymer particles. Such a process is more particularly preferably a method of crystallizing pelletized polymer pieces after polymerization, preferably by heat treatment, and pulverizing at a temperature lower than room temperature to room temperature. From the viewpoint of easier crushing, it is preferable to crush at a temperature lower than room temperature. As a method for obtaining such a low temperature, a method of cooling with liquid nitrogen is preferable.

In addition to the above-described pelletized polymer pieces, intended polymer particles can also be produced by pulverizing molded polymer compositions, film-formed polymer films, and fabricated polymer fibers. By selecting the mode of the polymer to be pulverized in this manner (for example, the size of the pellet, the thickness of the film, and the diameter of the fiber are changed), particles having various aspect ratios (aspect ratios) And the deviation (standard deviation) of the particle shape can also be adjusted.

The polymer of the pulverized polymer particles may be a copolymer or a blend of two kinds of polymers, and the pulverized polymer particles may contain inorganic particles or organic particles smaller in diameter than the pulverized polymer particles, or may contain an ultraviolet absorber or lubricant.

(Mode of the surface layer (B)) [

In the present invention, the surface layer (B) made of the resin composition containing the particles described above forms at least one outermost layer of the white reflective film. A surface of the surface layer B forming the outermost layer opposite to the reflection layer A (hereinafter sometimes referred to as an outermost layer surface) has projections formed by the particles. Such protrusions are required to have protrusions of an appropriate height at an appropriate frequency on the outermost layer surface from the viewpoint of securing a gap between the light guide plate and the film.

Therefore, in the present invention, it is usually necessary that the number of protrusions (protrusion frequency) of 5 탆 or more in height on the outermost layer surface is 10 ⁴ to 10 ¹⁰ pieces / m 2. As a result, the gap between the light guide plate and the film can be sufficiently secured, and the effect of suppressing the adhesive can be secured. If the protrusion frequency is too low, the effect of suppressing the adhesive is inferior. On the other hand, if the projecting frequency is too high, the probability of particle dropout tends to be improved and the reflectance tends to decrease.

(Other components)

The surface layer (B) may contain components other than the above-described components within a range not hindering the object of the present invention. Examples of such components include ultraviolet absorbers, antioxidants, antistatic agents, fluorescent whitening agents, waxes, surfactants, and particles and resins different from the above-mentioned particles.

[Floor composition]

The thickness of the reflective layer (A) in the present invention is preferably 80 to 350 mu m. As a result, the effect of improving the reflectance can be enhanced. If the thickness is too thin, the effect of improving the reflectance is low, and if it is too thick, it is inefficient. From such a viewpoint, it is more preferably 80 to 300 占 퐉, more preferably 100 to 320 占 퐉, and particularly preferably 150 to 250 占 퐉.

The thickness of the surface layer (B) in the present invention is preferably 5 to 100 mu m. More preferably 5 to 80 탆. In this case, the thickness of the surface layer (B) is the sum of the particle diameter of the particles and the thickness of the resin portion covering the surface.

The thickness of the resin portion holding the particles of the surface layer (B) is preferably 0.2 to 50 mu m. As a result, the projecting frequency can be easily made into a preferable mode, and a gap with the light guide plate can be easily ensured. If the thickness of the resin portion of the surface layer B is too thin, particles in the surface layer B tend to fall off from the protrusions formed on the surface. On the other hand, if the thickness is excessively large, a preferable projection frequency tends to be hard to obtain. From this viewpoint, it is more preferably not less than 0.3 mu m, more preferably not less than 0.5 mu m, particularly preferably not less than 1 mu m, most preferably not less than 2 mu m, and more preferably not more than 40 mu m. Further, in consideration of the decolorability, it is preferably 1 占 퐉 or more, more preferably 2 占 퐉 or more.

When the reflective layer (A) is represented by A and the surface layer (B) is represented by B, the laminated structure of the white reflective film is composed of two layers of B / A, three layers of B / A / B, Layer structure of four or more layers arranged on the outermost layer of the substrate. Particularly preferably, it has a support layer C (indicated by C) for further stabilizing the film forming property and has a three-layer structure of B / C / A or B / A / C and a four-layer structure of B / C / A / C to be. Most preferably, a four-layer structure of B / C / A / C, and is superior in film extensibility. In addition, problems such as curls do not occur well. In the present invention, an embodiment having such a support layer (C) is preferable. The support layer (C) is preferably made of the same polyester as the reflection layer (A), and has a relatively low void volume ratio (preferably 0 volume% or more, less than 15 volume%, more preferably 5 volume% Or less, particularly preferably 3 vol% or less). The thickness of the support layer (C in total) is preferably 5 to 140 占 퐉, more preferably 20 to 140 占 퐉.

In the present invention, in addition to the reflective layer (A), the surface layer (B), and the support layer (C), other layers may be provided as long as the object of the present invention is not impaired. For example, it may have a layer for imparting functions such as ease of adhesion, windability (slipperiness), antistatic property, conductivity, ultraviolet durability, etc., or a layer for adjusting optical performance.

[Production method of film]

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

When the white reflecting film of the present invention is produced, it is preferable that the reflective layer (A) obtained by the melt extrusion method or the like is subjected to a melt resin coating method (including a melt extrusion resin coating method), a coarse extrusion method and a lamination method, The surface layer (B) can be formed by a coating liquid coating method using a coating liquid for forming the surface layer (B). Among them, a method of laminating the surface layer (B) by a coating liquid coating method is particularly preferable for a laminate obtained by laminating the reflective layer (A) and the support layer (C) by a co-extrusion method. By laminating the surface layer (B) by the coating solution 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 the predetermined projections can be mass-produced inexpensively and easily. It is also easy to handle particles having a relatively low 10% compression strength. In addition, the shape of the specific particles in the present invention can be easily maintained, and the aspect of the projections can be easily made into a preferable aspect.

A coextrusion method is employed as a method of laminating the reflective layer (A) and the support layer (C), employing polyester as the thermoplastic resin constituting the thermoplastic resin and the support layer (C) constituting the reflective layer (A) (B) will be described. However, the present invention is not limited to such a production method, and other aspects can be similarly produced by referring to the following. At that time, when the extrusion step is not included, the following "melt extrusion temperature" can be read by, for example, "melting temperature". Here, the melting point of the polyester used is Tm (unit: 占 폚) and the glass transition temperature is Tg (unit: 占 폚).

First, as a polyester composition for forming the reflective layer (A), a mixture of a polyester and a void-forming agent and other optional components is prepared. As the polyester composition for forming the support layer (C), a mixture of polyester and optionally a void-forming agent and other optional components is prepared. These polyester compositions are used by drying and sufficiently removing moisture.

Next, the dried polyester composition is put into different extruders and melt-extruded. The melt extrusion temperature needs to be not less than Tm and may be set to about Tm + 40 占 폚.

At this time, the polyester composition used in the production of the film, particularly the polyester composition used for the reflection layer (A), is preferably a non-woven fabric filter having an average scale interval of 10 to 100 mu m and made of stainless steel fine wire having a line diameter of 15 mu m or less It is preferable to carry out filtration by using the filtration method. By carrying out this filtration, it is possible to obtain a film with less coarse foreign matters by suppressing coagulation of particles, which are usually coagulated to become coarse aggregated particles. The average scale interval of the nonwoven fabric is preferably 20 to 50 占 퐉, more preferably 15 to 40 占 퐉. The filtered polyester composition is extruded from a die in a multilayer state by a simultaneous multilayer extrusion method (coextrusion method) using a feed block in a molten state to produce an unoriented laminated sheet. The unstretched laminated sheet extruded from the die is cooled and solidified with a casting drum to obtain an unstretched laminated film.

Then, the unstretched laminated film is heated by roll heating, infrared heating, or the like, and stretched in the machine direction of the film-forming machine (hereinafter sometimes referred to as longitudinal or longitudinal direction or MD) to obtain a longitudinally stretched film. This stretching is preferably carried out using the main speed difference of two or more rolls. The film after the longitudinal stretching is continuously stretched in the tenter in the longitudinal direction and in the direction perpendicular to the thickness direction (hereinafter sometimes referred to as the transverse direction or the width direction or TD) to form a biaxially oriented film.

The stretching temperature is preferably Tg of not less than Tg and not more than Tg + 30 占 폚 of polyester (preferably polyester constituting the reflective layer (A)), and is excellent in film forming properties and voids are preferably formed . The stretching ratio is preferably 2.5 to 4.3 times, more preferably 2.7 to 4.2 times in both the longitudinal direction and the transverse direction. If the stretching ratio is too low, the thickness of the film tends to be uneven, and voids tend to be hardly formed. On the other hand, if the stretching ratio is too high, the film tends to be easily broken during film formation. It is preferable that the second stage (in this case, the transverse stretching) is higher than the first stage stretching temperature by about 10 to 50 ° C during the sequential biaxial stretching in which the longitudinal stretching is performed and then the transverse stretching is performed. This is attributed to the fact that the Tg as the uniaxial film is increased by orienting in the first-stage stretching.

It is also preferable to preheat the film before each stretching. For example, the preheating treatment of the transverse stretching may be started at a temperature higher than Tg + 5 占 폚 of the polyester (preferably the polyester constituting the reflective layer (A)) and gradually elevated. The temperature rise in the transverse stretching process may be continuous or stepwise (sequential), but usually the temperature is raised in a sequential manner. For example, the transversely stretched zone of the tenter is divided into plural pieces along the film running direction, and the temperature is raised by flowing a heating medium at a predetermined temperature for each zone.

The biaxially stretched film is successively subjected to heat fixation and heat relaxation treatment successively to form a biaxially oriented film, but these processes can be carried out while the film is running, following the melt extrusion.

The film after the biaxial stretching is stretched (Tm-20 ° C) to (Tm-100 ° C) with the melting point of the polyester (preferably the polyester constituting the reflective layer (A) , And it is preferable that heat treatment is performed by heat treatment at a constant width or a width reduction of not more than 10% to fix the heat and lower the heat shrinkage rate. If the heat treatment temperature is too high, the flatness of the film tends to deteriorate and the thickness variation tends to increase. On the other hand, if it is too low, the heat shrinkage tends to increase.

Further, in order to adjust the amount of heat shrinkage, both ends of the gripping film can be cut off, and the pulling speed in the longitudinal direction of the film can be adjusted to relax in the longitudinal direction. As the means for relaxing, the speed of the roll group on the tenter outlet side is adjusted. As the rate of relaxation, the speed of the roll group is lowered with respect to the film line speed of the tenter, and the speed reduction is preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3 to 2.0% (This value is referred to as " relaxation rate ") to adjust the heat shrinkage rate in the longitudinal direction by controlling the relaxation rate. Further, the width of the film in the transverse direction is reduced in the course of cutting until both ends are cut, and a desired heat shrinkage ratio can be obtained.

In addition, in the biaxial stretching, a transverse-longitudinal biaxial stretching method may be used in addition to the longitudinal-transverse biaxial stretching method as described above. It is also possible to form the film by the simultaneous biaxial stretching method. In the case of the simultaneous biaxial stretching method, the stretching magnification is, for example, 2.7 to 4.3 times, preferably 2.8 to 4.2 times in both the longitudinal direction and the transverse direction.

The surface layer (B) is obtained by applying the coating liquid for forming the surface layer (B) to the longitudinally stretched film after the longitudinally stretching of the above-mentioned process and drying and drying the surface layer (B) by such heat in the preheating step, the transverse stretching step, It can be formed by the so-called in-line coating method, in which curing is carried out. The coating liquid can be obtained by mixing components constituting the surface layer (B) and optionally diluting with a solvent so as to be easy to apply. At this time, water is preferable as the solvent, and the amount of the volatile organic solvent to be described later can be reduced. The coating method of the coating liquid is not particularly limited, and preferred examples include a reverse roll coating method, a gravure coating method, a die coating method and a spray coating method. The surface layer (B) may be formed by a so-called off-line coating method in a biaxially oriented film obtained by biaxial orientation and heat fixation. Further, in the case of the off-line coating method, it is difficult to apply high heat for drying due to the reason that the film is deformed. Therefore, an organic solvent which is ordinarily easy to dry is used as the solvent. However, in this case, since the amount of the volatile organic solvent to be described later tends to increase, the inline coating method is particularly preferable in the present invention.

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

[Characteristics of white reflective film]

(Reflectance, luminance)

The reflectance (reflectance at a wavelength of 550 nm) measured from the side of the surface layer (B) of the white reflecting film of the present invention is preferably 95% or more, more preferably 96% or more, further preferably 97% , Still more preferably 97.5% or more, and particularly preferably 98% or more. Since the reflectance is 95% or more, but 96% or more, high luminance can be obtained when used in a liquid crystal display device or an illumination. Such a reflectance may be set to a preferable mode such as increasing the void volume ratio of the reflective layer (A), or the aspect of each layer may be made to be a preferable mode, for example, the thickness of the reflective layer (A) may be increased or the thickness of the surface layer Can be achieved.

The luminance measured from the side of the surface layer (B) is determined by a measurement method described later, but is preferably 5400 cd / m 2 or more, more preferably 5450 cd / m 2 or more, and particularly preferably 5500 cd / .

The reflectance and the luminance are values on the side of the white reflective film that becomes the light guide plate side when used with the light guide plate.

(Amount of volatile organic solvent)

In the white reflecting film of the present invention, the amount of volatile organic solvent measured by a method described later is preferably 10 ppm or less. Thus, it can be shown that the surface layer (B) is not formed by a coating method using an organic solvent. In addition, when a film is formed by using a self-recovering raw material and using it, gas marks are not generated well, and the film extensibility (recovered film formability) is improved. From this viewpoint, it is more preferably 5 ppm or less, still more preferably 3 ppm or less, and ideally 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, it is preferable to employ the above-described method without adopting the solution coating method using the organic solvent in the formation of the surface layer (B).

Example

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

(1) Light reflectance

The reflectance was measured at a wavelength of 550 nm when an integrating sphere was attached to a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation) and the BaSO ₄ white plate was taken as 100%, and this value was regarded as the reflectance. The measurement was carried out on the surface on the side of the surface layer (B). In the case of having a different surface layer (B) on the front and back sides, it was measured on the surface of the surface layer (B) which is the side of the light guide plate.

(2) average particle diameter of the particles

The particle size distribution (particle size standard deviation) of the particles was determined with a laser scattering particle size analyzer (SALD-7000 manufactured by Shimadzu Corporation), and the particle size at d50 (the particle size distribution having a distribution of 50% Respectively.

(3) Particle shape

(3-1) Particle shape 1

The particle powder was fixed on a measuring stage with a conductive tape and observed at a magnification of 1000 times using a S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd., and the shape of the particles was observed. For 30 randomly selected particles, the maximum diameter Dx (in the x direction) and the direction perpendicular to the x direction (in the y direction and the z direction, and the z direction is the direction perpendicular to the y direction) Dxave-Dzave, and Dyave-Dzave are obtained by obtaining the maximum diameters Dy and Dz (where Dy ≥ Dz) One of them exceeding 20% of Dx was judged to be non-spherical, and those not so judged to be spherical.

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

The particles were lightly adhered to a conductive tape using a glass rod, fixed on a measurement stage, and magnified at a magnification of 100 (no inclination angle) using the S-4700 field emission scanning electron microscope manufactured by Hitachi, And the maximum diameter of the particles in the direction orthogonal to the maximum diameter is taken as the short diameter, and the long diameter / short diameter (aspect ratio) And the average value was taken as the average value of the aspect ratio. The standard deviation of the aspect ratio was calculated from the values of the respective aspect ratios.

Further, with respect to those having a small average particle size (for example, those having a size of 3 mu m or less), the magnification was increased (for example, 1000 times).

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

The projection profile of the film surface was measured with a cut-off of 0.25 mm, a measuring length of 1 mm, a scanning pitch of 2 占 퐉 and a scanning number of 100 with a three-dimensional roughness measuring device SE-3CKT (manufactured by Kosaka Laboratory Co., Ltd.) The ridge profile was recorded at a magnification of 200 times. The number of protrusions having a height of 5 탆 or more (number of protrusions / ㎡) was obtained from the obtained protrusion profile (transverse axis: protrusion height, vertical axis: protrusion profile number of protrusions) A three-dimensional roughness analyzer SPA-11 (manufactured by Kosaka Laboratory Co., Ltd.) was used for the analysis.

(5) 10% Compressive Strength

The compressive strength of each particle at a weight of 3 gf was measured using a microhardness tester ENT-1100a manufactured by Elyonics, and the compressive strength (MPa) at 10% strain was adopted. The mean value of 5 measurements was used.

(6) Amount of volatile organic solvent

At room temperature (23 DEG C), 1 g of the film sample was put into a 10 L fluororesin bag, and the inside thereof was purged with pure nitrogen and sealed. Subsequently, 0.2 L and 1.0 L of nitrogen were collected from these bag tissues at a flow rate of 0.2 L / min into two analytical TENAX-TA collecting tubes, respectively, and these were used to collect nitrogen in the nitrogen collected by HPLC and GCMS The mass of the organic solvent component contained therein was quantified. The mass of the organic solvent volatilized into 10 L of nitrogen was determined from 1 g of the film sample in terms of the amount in 10 L of nitrogen, and the amount of the volatile organic solvent (unit: ppm, based on the mass of the film sample) was determined. The aldehydes were determined by eluting the aldehyde derivatives with acetonitrile from a collection tube and measuring by HPLC. Further, when the values were different in HPLC and GCMS, the value of the much detected one was adopted.

(7) Film thickness and layer composition

The white reflective film was sliced with a microtome and a cross-section was formed. The cross section was observed at a magnification of 500 times by using a S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd. The entire film, the reflective layer (A), the surface layer (B) , And the thickness of the support layer (C), respectively. With respect to the surface layer (B), the thickness of the portion where the particles exist is arbitrarily taken at 10 points, and the average value thereof is taken as the thickness.

(8) Calculation of void volume ratio

Calculated densities were obtained from the density and mixing ratio of polymer, additive particles, and other components of the void volume ratio layer. At the same time, the layer was peeled off or separated, the mass and the volume were measured, and the actual density was calculated from the mass and the volume, and the following formulas were obtained from the calculated density and the actual density.

Void volume ratio = 100 x (1- (true density / calculated density))

The density of isophthalic acid copolymerized polyethylene terephthalate (after biaxially stretching) was 1.39 g / cm3, and the density of barium sulfate was 4.5 g / cm3.

Further, only the layer for measuring the void volume ratio was isolated, and the mass per unit volume was determined to obtain the actual density. The volume was calculated by cutting out the sample to an area of 3 cm 2 and measuring the thickness at that size at 10 points on an electric micrometer (K-402B manufactured by Anritsu Co., Ltd.) as the thickness as an area × thickness. The mass was weighed in an electronic balance.

As the specific gravity of the particles (including agglomerated particles), the volume specific gravity value obtained by the following mass cylinder method was used. The weight of the entire cylinder was measured by measuring the weight of the entire cylinder by filling the cylinder with a volume of 1000 ml in absolute dry state and subtracting the weight of the cylinder from the weight of the entire cylinder, And dividing the weight (g) of the particle by the volume (cm 3) thereof.

(9) Melting point, glass transition temperature

And measured by a differential scanning calorimeter (TA Instruments 2100 DSC) at a heating rate of 20 캜 / min.

(10) Luminance

A reflective film was taken out from an LED liquid crystal television (LG42LE5310AKR) manufactured by LG, and the side of the surface layer (B) of the various reflective films described in the examples was provided on the screen side (surface contacting the light guide plate) Manufactured by Otsuka Electronics Co., Ltd., Model MC-940), the luminance was measured at the measurement distance of 500 mm from the front face at the center of the backlight.

(11) Damage Evaluation of Light Guide Plate (Sharpness Evaluation)

(11-1) Damage assessment 1

As shown in Fig. 3, an iron plate (2, weight: about 200 g) having a width of 200 mm, a length of 200 mm and a thickness of 3 mm was firmly attached to an end of the grip portion 1, A reflective film 3 of 200 mm was pasted from both ends in the width direction such that a portion of 25 mm was projected out of the steel plate (a portion of 200 mm x 200 mm at the center overlapped with the steel plate). At this time, the evaluation surface (surface layer surface) of the reflection film was made to be outside. The remaining 25 mm portions of the reflective film at both ends in the width direction were folded back to the side of the steel plate to eliminate the influence of the end portion of the reflective film (the portion where the sheath was formed with a knife or the like at the time of sampling) shaved the light guide plate .

Next, a light guide plate 4 (having a size of at least 400 mm x 200 mm) having a dot surface with the dot 401 facing up is fixed on a horizontal table, and a reflective film, which is fixed to the above- And a weight 5 of 500 g was placed thereon. The weight 5 was placed on the light guide plate so that the distance between the weight plate 5 and the light guide plate was 200 mm (fixed to the steel plate in an area of 400 mm x 200 mm) It moved 15 round trips at a speed of about 5 ~ 10 seconds per round trip. Thereafter, on the surface of the light guide plate, the degree of the cut-off and the presence or absence of the particles dropped off from the reflective film were observed using a 20-fold magnification, and evaluated according to the following criteria.

In the entire range of 400 mm x 200 mm rubbed on the light guide plate, when there is no scratch that can be observed with a loupe after 20 reciprocating movements, it is determined that it is not "shaved" When there is a scratch that can be observed after 20 reciprocating movements, it is judged that there is no scratch that can be observed, but when there is a scratch that can be observed after 20 round trips, Quot; (subtraction evaluation x).

In the above evaluation, in order to suppress the influence of the dot size as much as possible, a region having a maximum dot size as large as possible in the light guide plate was selected and sorted by each evaluation sample.

(11-2) Damage assessment 2

In the above (11-1), the size of the steel plate 2 is set to 400 mm x 200 mm (correspondingly, the reflective film is made to be 400 mm x 250 mm and the light guide plate having a size of at least 400 mm x 400 mm is used (The reflective film fixed on the steel plate is moved in the area of 400 mm x 400 mm, and the observation range is also in this range), and the weight of the weight 5 is 1000 g The same as above).

(12) White point evaluation

(12-1) white point evaluation 1

Using a reflection film and a light guide plate used in the evaluation of the above (11-1), a reflective film was placed so as to face the surface layer surface on the table, a light guide plate was placed thereon such that the dot surface was downward, Light having a weight of 300 g was fixed thereon, light was incident from the side of the light guide plate using a backlight light source of an LED liquid crystal television (LG42LE5310AKR) manufactured by LG, and a light spot other than a light guide plate dot, (Evaluation?). On the other hand, when there were no abnormal bright spots that can be observed with the naked eye, it was determined that no white spots were generated (evaluation ◯)

(12-2) white point evaluation 2

Using a reflection film and a light guide plate used in the evaluation of the above (11-2), if there is a bright spot other than a light guide plate dot on which evaluation criteria can be visually observed, white spot generation (evaluation X) (12-2), except that a white spot was slightly observed (evaluation?), But a white spot was not observed (evaluation?) And a light spot other than a light guide plate dot observable with the naked eye was observed, 1).

(13) Adhesion spot evaluation (appraisal)

(13-1) Appraisal Evaluation 1

As shown in Fig. 4, the chassis 6 is taken out from an LED liquid crystal television (47 inch size) manufactured by LG, a horizontal table is placed so that the inside of the TV is upward, and a reflection film (7, two diffusion films and one prism) provided on the original television, and a light guide plate and three optical sheets, which were provided on the television, were placed on the top surface of the light guide plate. Next, in the area including the most severe portion of the concavo-convexity of the chassis in the plane, as shown in Fig. 4, a quadrangular frame 801 having three circumferential legs each having a diameter of 5 mm is placed, A weight 802 of 10 kg was put on the top of the three legs, and the area surrounded by these three legs was visually observed. When there was no abnormally bright portion, "no close contact spot" (close contact spot evaluation O) was made. If there is an unusually bright area, a DBEF sheet originally provided on the television is placed on top of the three optical sheets, and the same observation is made with the naked eye. If the oddly bright area is not recovered, the " Evaluation x), and when an oddly bright portion was lost, " almost no adhesion spot was observed " (evaluation?). The area surrounded by the three legs was a substantially regular triangle having a length of 10 cm.

(13-2) Attachment evaluation 2

In the above (13-1), evaluation was made in the same manner, except that the weight 802 was changed to 15 kg.

(14) Recovery of film formability

The biaxially stretched film obtained in the examples was pulverized, melted and extruded into chips, thereby preparing a self-recovering raw material. This magnetic recovery material is added to the reflective layer (A) in an amount of 35 mass% based on the mass of the reflective layer (A), and the mass ratio of the remaining polyester to the void-forming agent is made to be the same as that of the original film, The biaxially oriented film containing the self-recovering raw material was produced in the same manner as the original film, and evaluated according to the following criteria.

◎: The film can be stably formed over 2000 m in length.

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

?: Cutting occurred at a length of less than 1000 m.

X: Cutting occurred more than twice at a length of less than 1000 m.

≪ Preparation Example 1: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 1 >

136.5 parts by mass of dimethyl terephthalate and 13.5 parts by mass of dimethyl isophthalate (9% by mole based on 100% by mole of the total acid component of the resulting polyester), 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, And 0.012 parts by mass of lithium acetate were introduced into a flask equipped with a rectification tower and a distillation condenser and heated at 150 to 240 ° C with stirring to distill methanol and carry out an ester exchange reaction. After methanol was spilled out, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Subsequently, the inside of the reactor was gradually reduced to 0.3 mmHg while stirring, and the temperature was raised to 292 ° C, and polycondensation reaction was carried out to obtain isophthalic acid copolymerized polyethylene terephthalate 1. The melting point of this polymer was 235 ° C.

≪ Preparation Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2 >

, 129.0 parts by mass of dimethyl terephthalate, and 21.0 parts by mass of dimethyl isophthalate (14% by mole based on 100% by mol of the total acid component of the polyester obtained) was changed to isophthalic acid copolymerized polyethylene terephthalate Phthalate 2 was obtained. The melting point of this polymer was 215 ° C.

≪ Preparation Example 3: Production of particle master chip 1 >

A part of the obtained isophthalic acid copolymerized polyethylene terephthalate 1 and barium sulfate particles having an average particle size of 1.0 占 퐉 (represented by BaSO ₄ in the table) were used as a void-forming agent, and a NEX-T60 tandem extruder manufactured by Kobe Steel Corporation , The mixture was mixed so that the content of barium sulfate particles was 60% by mass with respect to the mass of the obtained master chip, and the mixture was extruded at a resin temperature of 260 캜 to prepare a particle master chip 1 containing barium sulfate particles.

≪ Preparation Example 4: Production of particle master chip 2 >

A part of the isophthalic acid copolymerized polyethylene terephthalate 2 obtained above and barium sulfate particles having an average particle size of 1.0 mu m as a void-forming agent were used in a NEX-T60 bending type extruder manufactured by Kobe Steel Corporation to obtain barium sulfate particles By mass to 60% by mass, and extruded at a resin temperature of 260 占 폚 to prepare a particle master chip 2 containing barium sulfate particles.

PREPARATION EXAMPLE 5: Preparation of Particle 1 for use in the surface layer (B)

150 parts by mass of dimethyl terephthalate, 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, 0.05 part by mass of manganese acetate and 0.012 parts by mass of lithium acetate were fed into a flask equipped with a rectifying column and an outlet condenser, And the ester exchange reaction was carried out by heating. After methanol was spilled out, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Subsequently, the inside of the reactor was gradually reduced to 0.3 mmHg while stirring, and the temperature was raised to 292 ° C, and polycondensation reaction was carried out to obtain polyethylene terephthalate 3. The obtained polyethylene terephthalate 3 was extruded from a strand die, cut after cooling, and made into a pellet shape. Then, the obtained pellets were dried and crystallized by heating at 170 DEG C for 3 hours in an oven, followed by pulverization while cooling with liquid nitrogen using an atomizer mill TAP-1 manufactured by Matsubo Corporation to obtain a polyester having an average particle size of 60 mu m Particles were obtained. The polyester particles were classified by wind force to obtain particles 1 (non-spherical particles) having an average particle diameter of 40 탆.

Particle 2: Nona-particle having an average particle size of 40 占 퐉 obtained by pulverization and classification in the same manner as in Production Example 5, except that pellets of nylon 66 resin CM3006 manufactured by Toray Industries, Inc. were used.

Particle 3: Nona-particle having an average particle size of 10 占 퐉 obtained by pulverization and classification in the same manner as in Production Example 5, except that pellets of nylon 66 resin CM3006 manufactured by Toray Industries, Inc. were used.

Particle 4: Nona-particle having an average particle size of 10 占 퐉 obtained by pulverization and classification in the same manner as in Production Example 5, except that pellets of nylon 6 resin CM1017 manufactured by Toray Industries, Inc. were used.

Particle 5: MBX-40 (spherical acrylic particles, average particle diameter 40 占 퐉) manufactured by Sekisui Chemical Co.,

Particle 6: Polytetrafluoroethylene (PMMA) resin, manufactured by Sumitomo Chemical Co., Ltd. [0156] The same procedure as in Production Example 5 was carried out except that pellets of SumiPEX MGSS were used, .

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

≪ Preparation Example 6: Preparation of particle 8 for use in surface layer (B) >

In the same manner as in 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 strands, the shape of the pellets was almost rectangular parallelepiped and the average shape was 4 mm x 3 mm x 2 mm. Then, polyester particles having an average particle size of 60 占 퐉 were obtained in the same manner as in Production Example 5. These polyester particles were classified by wind power to obtain particles 8 (non-spherical particles) having an average particle size of 43 탆.

PREPARATION EXAMPLE 7: Preparation of Particle 9 for use in the surface layer (B)

Using the pellets obtained in Production Example 6, the biaxially oriented film of polyethylene terephthalate was oriented and crystallized under the usual conditions (longitudinal stretching magnification: 3.0 times, transverse stretching magnification: 4.0 times, heat setting temperature: 220 占 폚) To obtain a transparent biaxially stretched polyethylene terephthalate film (thickness 50 탆). This was pulverized while cooling with liquid nitrogen in the same manner as in Production Example 6, and then subjected to wind power classification to obtain Particles 9 (non-spherical particles) having an average particle size of 52 mu m.

≪ Preparation Example 8: Preparation of particle 10 used for surface layer (B) >

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

Production Examples 9 and 10: Preparation of Particles 11 and 12 used in the surface layer (B)

The pellets obtained in Production Example 6 were dry-crystallized, pulverized in the same manner, and classified by wind power to obtain particles 11 (non-spherical particles) having an average particle diameter of 35 mu m. The film obtained in Production Example 7 was pulverized in the same manner and subjected to wind power classification to obtain particles 12 (non-spherical particles) having an average particle diameter of 50 mu m. In the above, conditions for classifying wind power were adjusted so that the obtained particles had the form shown in Table 3. [

Particle 13: Polymer (methyl methacrylate) (PMMA) resin, manufactured by Sumitomo Chemical Co., Ltd. [0154] The same procedure as in Production Example 6 was carried out except that pellets of SumiPEX MGSS were used, .

PREPARATION EXAMPLES 11 AND 12 Preparation of Particles 14 and 15 Used for the Surface Layer (B)

The film thickness was changed to 75 占 퐉 in Production Example 7 and pulverization and wind classification were carried out in the same manner as in Production Example 7 to obtain particles 14 (non-spherical particles). In addition, particles 15 (non-spherical particles) were similarly obtained with a film thickness of 100 mu m. In the above, conditions for classifying wind power were adjusted so that the obtained particles had the form shown in Table 3. [

PREPARATION EXAMPLES 13 TO 20 Preparation of particles 16 to 23 used in the surface layer (B)

The pellets obtained in Production Example 6 were dry-crystallized, pulverized in the same manner, and subjected to wind power classification to obtain particles 16 to 23 (non-spherical particles or spherical particles) having the composition shown in Table 3, respectively. In the above, conditions for classifying wind power were adjusted so that the obtained particles had the form shown in Table 3. [

[Example 1-1]

(Preparation of white reflective film)

The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master chip 1 obtained above were used as a raw material for the reflection layer (A layer), the isophthalic acid copolymerized polyethylene terephthalate 2 and the particle master chip 2 were used as raw materials for the support layer (C layer) The reflective layer A is formed such that the content of the voiding agent with respect to the mass of the reflective layer A is 49 mass% and the content of the voiding agent with respect to the mass of the supporting layer C is 3 mass% And the resulting mixture was put in an extruder. The A layer was melt-extruded at a temperature of 255 DEG C and the C layer at a melt extrusion temperature of 230 DEG C using a three-layer feed block device so as to have a layer structure of C layer / A layer / And they were molded into a sheet form from the dies while maintaining the laminated state. At this time, the thickness ratio of the C layer / A layer / C layer was adjusted to be 10/80/10 after the biaxial stretching by the discharge amount of each extruder. Further, this sheet was cooled and solidified with a cooling drum having a surface temperature of 25 占 폚 to form an unstretched film. The unstretched film was passed through a preheating zone at 73 DEG C and then a preheating zone at 75 DEG C and was led to a longitudinal stretching zone maintained at 92 DEG C and stretched to 2.9 times in the longitudinal direction and cooled in a roll group at 25 DEG C, A stretched film was obtained. Subsequently, a coating liquid 1 for forming a surface layer (layer B) shown below was applied to one side of the obtained monoaxially stretched film by a reverse roll coating method.

<Coating liquid 1>

Z-465 (manufactured by KAO KOGYO KABUSHIKI KOGYO CO., LTD.) Containing 10 mol% of sodium sulfoisophthalic acid component relative to 100 mol% of the total acid component and 10 mol% of diethylene glycol component of polyethylene terephthalate (This copolymerized polyester is referred to as Resin 1), an aqueous solution having a solid content concentration of 15 mass%), particles 1 obtained in Production Example 5 as particles, and ion exchanged water as a diluting solvent, 1 and the solid content concentration of the coating liquid was 20% by mass to prepare a coating liquid 1.

Following application, both ends of the film were passed through a preheating zone at 115 占 폚 while being held in a clip, led to a transverse stretching zone maintained at 130 占 폚, and stretched 3.6 times in the transverse direction. Thereafter, heat fixation was carried out at 185 ° C in a tenter, widthwise shrinkage in the transverse direction was carried out at a width shrinkage rate of 2% and a width shrinkage temperature of 130 ° C. Then, both ends of the film were cut out to relax the film with a longitudinal relaxation rate of 2% Followed by cooling to room temperature to obtain a biaxially oriented film. Table 2 shows the evaluation results of the obtained film.

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

A biaxially oriented film was obtained in the same manner as in Example 1-1 except that the mode of particles used for the surface layer (B layer) was changed as shown in Table 1, respectively. Table 2 shows the evaluation results of the obtained film.

[Example 1-4]

The void-forming agent of the reflection layer (A) was changed to a resin for non-use in polyester (cycloolefin, TOPAS 6017S-04 manufactured by Polyplastics Co., Ltd.), and the content of the voiding agent with respect to the mass of the reflection layer (A) By mass in terms of mass%, a biaxially stretched film was produced and evaluated. The evaluation results are shown in Table 2.

[Example 1-6]

(B) for forming a surface layer (layer B) in a direct gravure coating apparatus on a biaxially stretched film obtained in the same manner as in Example 1-1, except that the coating liquid was not applied before uniaxial stretching after biaxial stretching The coating liquid having the composition shown in the coating liquid 2 was applied at a coating amount of a wet thickness of 15 g / m &lt; 2 &gt;, followed by drying at 80 DEG C in an oven to obtain a film.

&Lt; Coating liquid 2, solid concentration 30 mass% &gt;

Particle: Particle 1 (non-spherical particle) obtained in Preparation Example 5 7.5 mass%

Acrylic resin (thermoplastic resin): Acrydic A-817BA (solid content concentration: 50% by mass, manufactured by DIC Corporation, represented by resin 2 in the table) 30 mass%

Crosslinking agent: Colonate HL manufactured by Nippon Polyurethane Industry Co., Ltd. (isocyanate crosslinking agent, solid content concentration: 75 mass%, crosslinking agent 1 in the table) 10 mass%

ㆍ diluting solvent: butyl acetate ... 52.5 mass%

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

ㆍ Particles: 25 mass%

Acrylic resin (thermoplastic resin): 50 mass%

Crosslinking agent: 25 mass%

[Table 1]

[Table 2]

[Example 2-1]

(Preparation of white reflective film)

The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master chip 1 obtained above were used as a raw material for the reflection layer (A layer), the isophthalic acid copolymerized polyethylene terephthalate 2 and the particle master chip 2 were used as raw materials for the support layer (C layer) The reflective layer A is formed such that the content of the voiding agent with respect to the mass of the reflective layer A is 49 mass% and the content of the voiding agent with respect to the mass of the supporting layer C is 3 mass% Layer feed block device so as to have a C layer / A layer / C layer composition at a melt extrusion temperature of 265 deg. C and a C layer at a melt extrusion temperature of 240 deg. C And they were molded into a sheet form from the dies while maintaining the laminated state. At this time, the thickness ratio of the C layer / A layer / C layer was adjusted to be 10/80/10 after the biaxial stretching by the discharge amount of each extruder. Further, this sheet was cooled and solidified with a cooling drum having a surface temperature of 25 占 폚 to form an unstretched film. The unstretched film was passed through a preheating zone at 73 DEG C and then a preheating zone at 75 DEG C and was led to a longitudinal stretching zone maintained at 92 DEG C and stretched to 2.9 times in the longitudinal direction and cooled in a roll group at 25 DEG C, A stretched film was obtained. Subsequently, a coating liquid 3 for forming a surface layer (layer B) shown below was applied to one side of the obtained monoaxially stretched film by a reverse roll coating method.

&Lt; Coating liquid 3 &

(Resin 1) manufactured by Ko Ko Chemical Co., Ltd. as a resin, the particles 8 obtained in Production Example 6 as particles, and ion-exchanged water as a diluting solvent were mixed so that the solid content ratio between the resin and the particles was resin: (Mass%), and the solid content concentration of the coating liquid was 20 mass%.

Subsequent to the application, the film was passed through a preheating zone at 115 ° C while keeping both ends of the film in a clip, and was led to a transverse stretching zone maintained at 130 ° C and stretched 3.6 times in the transverse direction. Thereafter, heat fixation was carried out at 185 ° C in a tenter, widthwise shrinkage in the transverse direction was carried out at a width shrinkage rate of 2% and a width shrinkage temperature of 130 ° C. Then, both ends of the film were cut out to relax the film with a longitudinal relaxation rate of 2% Followed by cooling to room temperature to obtain a biaxially oriented film. Table 4 shows the evaluation results of the obtained film.

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

A biaxially oriented film was obtained in the same manner as in Example 2-1 except that the mode of the particles used in the surface layer (layer B) and the layer structure were changed as shown in Tables 3 and 4, respectively. Table 4 shows the evaluation results of the obtained film.

[Example 2-6]

The void-forming agent of the reflection layer (A) was changed to a resin for non-use in polyester (cycloolefin, TOPAS 6017S-04 manufactured by Polyplastics Co., Ltd.), and the content of the voiding agent with respect to the mass of the reflection layer (A) The biaxially stretched film was produced in the same manner as in Example 2-1 except that the amount of the biaxially oriented film was changed to the mass%. The evaluation results are shown in Table 4.

[Example 2-7]

The following surface layer (layer B) was formed on the biaxially stretched film obtained in the same manner as in Example 2-1, except that the coating liquid was not applied after uniaxial stretching and before the biaxial stretching was carried out using a direct gravure coating apparatus Was applied at a coating amount of a wet thickness of 15 g / m &lt; 2 &gt;, followed by drying at 80 DEG C in an oven to obtain a film.

&Lt; Coating liquid 4, solid concentration 30 mass% &gt;

Particles: Particles 8 (non-spherical particles) obtained in Preparation Example 6 7.5 mass%

Acrylic resin (thermoplastic resin): Acridic A-817BA (resin 2) manufactured by DIC Co., Ltd. 30 mass%

Crosslinking agent: Colonate HL (Crosslinking agent 1) manufactured by Nippon Polyurethane Industry Co., Ltd. 10 mass%

ㆍ diluting solvent: butyl acetate ... 52.5 mass%

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

ㆍ Particles: 25 mass%

Acrylic resin (thermoplastic resin): 50 mass%

Crosslinking agent: 25 mass%

[Table 3]

[Table 3] (Continued)

[Table 4]

[Table 4] (Continued)

Effects of the Invention

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a white reflective film capable of sufficiently restraining adherence to a light guide plate and sufficiently restricting damage to the light guide plate.

Industrial availability

The white reflecting film of the present invention can sufficiently suppress the adhesion of the light guide plate to the light guide plate and can sufficiently prevent the damage of the light guide plate. Therefore, the white light reflecting plate of the present invention can be used as a surface light source reflector, And can be preferably used as a reflective film used in a light type backlight unit.

Claims (9)

A method for producing a white reflective film having a reflective layer (A) and a surface layer (B) comprising a resin composition containing particles,
The white reflecting film has a projection formed by the particles on the surface of the surface layer (B) opposite to the reflection layer (A), and the number of projections having a height of 5 탆 or more on the surface is 10 ⁴ to 10 ¹⁰ / ,
Wherein the pulverized polymer particles obtained by pulverizing a polymer having an average particle size of 3 to 100 占 퐉 and a 10% compressive strength of 0.1 to 15 MPa are used as the particles. The method according to claim 1,
Wherein the polymer is a polyester. 3. The method according to claim 1 or 2,
Wherein said particles have an average aspect ratio (long diameter / short diameter) of not less than 1.31 and not more than 1.80, and a standard deviation of an aspect ratio of 0.15 to 0.50. 3. The method according to claim 1 or 2,
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). 3. The method according to claim 1 or 2,
Wherein the amount of the volatile organic solvent in the white reflecting film is 10 ppm or less. 3. The method according to claim 1 or 2,
Wherein the reflective layer (A) contains voids and the void volume ratio is not less than 15% by volume and not more than 70% by volume. 3. The method according to claim 1 or 2,
Wherein the white reflecting film further has a support layer (C) having a void volume ratio of not less than 0 volume% and less than 15 volume%. 3. The method according to claim 1 or 2,
Wherein the surface layer (B) is formed by application of a coating liquid. 3. The method according to claim 1 or 2,
Wherein the white reflecting film is used as a surface light source reflecting plate having a light guide plate.

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