JP5926512B2 - White reflective film - Google Patents

Description

  The present invention relates to a white reflective film. In particular, it is related with the white reflective film used for a liquid crystal display device.

  A backlight unit of a liquid crystal display device (LCD) includes a direct type provided with a light source and a reflective film on the back surface of the liquid crystal display panel, and a light guide plate provided with a reflective plate on the back surface of the liquid crystal display panel. There is an edge light type provided with a light source on the side surface. Conventionally, as a backlight unit used in a large-sized LCD, a direct type (mainly direct type CCFL) has been mainstream from the viewpoint of excellent screen brightness and uniformity of brightness within the screen.

  On the other hand, the edge light type is often used for a comparatively small LCD such as a conventional notebook PC, but the light guide plate made of a relatively soft material because the light guide plate and the reflection film are in direct contact with each other. Is damaged by the reflective film. As a countermeasure, for example, as disclosed in Patent Documents 1 and 2, there is a report of a reflective sheet including a scratch-preventing layer using elastomeric beads. Furthermore, there is a report that adjusts the average particle diameter and burial rate of beads to suppress the dropping of beads and suppress the occurrence of white spot defects (Patent Document 3).

  In recent years, with the development of light sources and light guide plates, the brightness and uniformity of brightness within the screen have been improved even in edge-light type backlight units, and the LCD can be made thinner. In addition, edge-light type backlight units have come to be used even in large LCDs.

JP 2003-92018 A Special table 2008-512719 gazette JP 2009-244509 A

  Since the edge light type backlight unit has a structure in which the light guide plate and the reflection film are in direct contact as described above, a gap is formed between the light guide plate and the reflection film in order to suppress in-plane variation in luminance. It is necessary to keep this gap constant. And since a reflective film has a bead on the surface, the gap between a light-guide plate and a reflective film can be kept constant, and these sticking can be prevented.

However, as described in Patent Documents 1 to 3, the present inventor collects a film that does not become a product by applying a coating containing a binder resin, beads, and an organic solvent to form a scratch prevention layer. When a new film is produced again using as a self-collecting raw material, if the beads remaining in the recovered raw material are present in the film and in particular in the reflective layer without being melted, voids per film thickness The problem was that the number decreased, it became difficult to obtain a high reflectance, and the self-collection was practically impossible.
Accordingly, an object of the present invention is to provide a recoverable white reflective film in which the film is excellent in reflection characteristics even if the film is recovered and used as a self-collecting raw material to produce the film.

In addition, at the time of recovery, residual organic solvent in the film, beads or binder resin cross-linked in the recovery process of the film, resulting in gas mark defects, or increased foreign matter such as unmelted material, We also focused on the point that the film-forming stability is inferior.
Therefore, the present invention further provides a recoverable white reflective film in which the obtained film is excellent in film-forming stability (also referred to as stretchability or film-forming property) even when a self-collecting raw material is used. , With a desirable purpose.

The present invention adopts the following configuration in order to achieve the above-described problems.
1. A white reflective film having a reflective layer A and a bead layer B,
The reflective layer A is composed of a thermoplastic resin composition and a void forming agent, contains voids,
The bead layer B is composed of organic particles having an average particle diameter of 1 to 50 μm and a thermoplastic resin, and the coverage of the organic particles on the surface of the white reflective film is 10 to 100%.
The melting point Tm1 of the organic particles, the melting point Tm2 of the thermoplastic resin constituting the bead layer B, and the melting point Tm3 of the thermoplastic resin composition constituting the reflective layer A satisfy the following formula:
White reflective film.
Tm1 ≧ Tm2 + 10
| Tm1-Tm3 | ≦ 13
2. 2. The white reflective film as described in 1 above, wherein the amount of the volatile organic solvent in the white reflective film is 10 ppm or less based on the mass of the white reflective film.
3. 3. The white reflective film as described in 1 or 2 above, wherein the void volume ratio of the reflective layer A is 15% by volume or more and 70% by volume or less.
4). The white reflective film according to any one of 1 to 3, wherein the void volume ratio of the bead layer B is 0% by volume or more and less than 15% by volume.
5. It is a manufacturing method of the white reflective film of any one of said 1-4,
A production method in which the bead layer B is laminated by any one of a molten resin coating method, an extrusion resin coating method, a coextrusion method, and a lamination method .

Moreover, this invention includes the following manufacturing methods.
6). It is a manufacturing method of the white reflective film of said 1, Comprising:
The thermoplastic resin composition and the void forming agent are melted at a temperature of (Tm3) ° C. or higher and (Tm1) ° C. or higher to form the reflective layer A,
A manufacturing method in which organic particles and a thermoplastic resin are heated at a temperature of (Tm2) ° C. or higher and lower than (Tm1) ° C. to melt the thermoplastic resin, form a bead layer B, and laminate them.

According to the present invention, a recoverable white reflective film in which the obtained film is excellent in reflection characteristics even if the film is recovered and used again as a self-collecting raw material to produce the film can be provided.
Moreover, according to the preferable aspect of this invention, even if it uses a self-recovery raw material, the recoverable white reflective film whose film obtained is excellent also in film forming stability can be provided.

It is a schematic diagram which shows an example of the reflective film cross section of this invention. It is a schematic diagram which shows the structure used for the adhesion spot evaluation in this invention. It is a schematic diagram which shows the method of the damage evaluation of the light-guide plate in this invention, and the drop-off evaluation of particle | grains.

Hereafter, each structural component which comprises this invention is demonstrated in detail.
[Reflection layer A]
The reflective layer A in the present invention is a layer composed of a thermoplastic resin composition and a void forming agent, containing a void by containing the void forming agent, and exhibiting a white color. The void forming agent will be described in detail later. For example, inorganic particles and a resin that is incompatible with the thermoplastic resin composition constituting the layer (hereinafter, may be referred to as an incompatible resin). Can be used. The reflectance of the reflective layer A at a wavelength of 550 nm is preferably 95% or higher, more preferably 96% or higher, and particularly preferably 97% or higher. Thereby, it becomes easy to make the reflectance of a white reflective film into a preferable range.

  The reflection layer A has voids in the layer as described above, and the ratio of the volume of the voids to the volume of the reflection layer A (void volume ratio) is preferably 15 to 70% by volume. . By setting it as such a range, the improvement effect of a reflectance can be made high and it becomes easy to obtain the above reflectances. Moreover, the improvement effect of film forming property can be made high. When the void volume ratio is too low, a preferable reflectance tends to be difficult to obtain. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 30% by volume or more, and particularly preferably 40% by volume or more. On the other hand, if it is too high, the effect of improving the film forming property tends to be low. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 65% by volume or less, and particularly preferably 60% by volume or less. The void volume ratio can be achieved by adjusting the type, size, and amount of the void forming agent in the reflective layer A.

(Thermoplastic resin composition)
The thermoplastic resin composition constituting the reflective layer A is not particularly limited as long as it satisfies the aspect of the melting point described later, and examples thereof include a thermoplastic resin composition made of polyester, polyolefin, polystyrene, and acrylic. Among these, 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 terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid and the like. Examples of the diol component include 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. Polyethylene terephthalate may be a homopolymer, but a copolymer is preferable from the viewpoint that crystallization is suppressed when the film is stretched uniaxially or biaxially and stretchability and film-forming property are improved. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above, and isophthalic acid and 2,6-naphthalenedicarboxylic acid are preferable from the viewpoint of achieving both heat resistance and film forming properties. The proportion of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 15 mol%, particularly preferably 7 to 11 based on 100 mol% of the total dicarboxylic acid component of the polyester. Mol%. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of film forming property. Moreover, it is excellent in thermal dimensional stability. Furthermore, it becomes easy to achieve the aspect of the melting point described later.

  Moreover, the thermoplastic resin composition can contain the self-collecting raw material which collect | recovered the edge part etc. which were not grasped | ascertained in the white reflective film of this invention, or were formed by the clip in film forming. In the present invention, since each component constituting the reflective layer A and the bead layer B is in a specific melting point range, even if the reflective layer A contains a self-collecting raw material in this way, white reflection with excellent reflectivity is achieved. A film can be obtained.

  Examples of such a self-recovery raw material include a pulverized recovered film, a pulverized film made into a chip shape by pressure or the like, and a pulverized film melt-extruded into a chip shape.

  The content of the self-recovery raw material in the reflective layer A is not particularly limited as long as the object of the present invention is not impaired, but is, for example, 10 to 50% by mass, preferably 30 to 40% by mass based on the mass of the reflective layer A. . Within such a range, it is difficult to adversely affect the reflectance. Moreover, it is excellent in productivity.

(Void forming agent)
In the reflective layer A, when inorganic particles are used as the void forming agent, the inorganic particles are preferably white inorganic particles. Examples of the white inorganic particles include barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate particles. The average particle diameter and content of these inorganic particles may be selected so that the white reflective film has a certain degree of reflectance, and these are not particularly limited. Preferably, the reflectance of the reflective layer A or the white reflective film may be within a preferable range in the present invention. Moreover, what is necessary is just to make it the void volume ratio in the reflection layer A become the preferable range in this invention. Taking this into consideration, the average particle size of the inorganic particles is, for example, 0.2 to 3.0 μm, preferably 0.3 to 2.5 μm, and more preferably 0.4 to 2.0 μm. 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. By using inorganic particles in this range, it becomes easy to achieve a preferable reflectance and void volume ratio. Further, by adopting the particle mode as described above, it is possible to appropriately disperse in the polyester, it is difficult for the particles to aggregate, and a film without coarse protrusions can be obtained. Breaking during stretching starting from is also suppressed. The inorganic particles may have any particle shape, for example, a plate shape or a spherical shape. The inorganic particles may be subjected to a surface treatment for improving dispersibility.

  Moreover, when using incompatible resin as a void formation agent, as incompatible resin, polyolefin, polystyrene, etc. are preferable. These may be in the form of particles. Moreover, the content should just select an average particle diameter and content so that a white reflective film may have a certain reflectance similarly to the case of an inorganic particle, These are not specifically limited. Preferably, the reflectance of the reflective layer A or the white reflective film may be within a preferable range in the present invention. Moreover, what is necessary is just to make it the void volume ratio in the reflection layer A become the preferable range in this invention. Taking this into consideration, 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 mass of the reflective layer A. By using an incompatible resin in such a range, it becomes easy to achieve a preferable reflectance and void volume ratio.

(Other ingredients)
As long as the purpose of the present invention is not hindered, the reflective layer A is made of other components such as UV absorbers, antioxidants, antistatic agents, fluorescent brighteners, waxes, particles and resins different from the void forming agents. Can be contained.

[Bead layer B]
The bead layer B of the present invention comprises organic particles and a thermoplastic resin. In the present invention, an embodiment in which these organic particles and thermoplastic resin are not crosslinked is preferable. Moreover, the aspect in which bead layer B does not contain a crosslinking agent is preferable. This is because in the film formation using the self-recovery raw material, a foreign material such as an unmelted material is easily generated and the effect of improving the stretchability is reduced when the crosslinking system is used. Further, when the organic particles are a crosslinked system, the particles tend to be hard, and the effect of improving the suppression of damage to the light guide plate tends to be low. In addition, whether it is a bridge | crosslinking system here can judge that what does not have melting | fusing point is a bridge | crosslinking system, for example. Most preferably, the organic particles and the thermoplastic resin do not have a crosslinking group (crosslinkable functional group), and the bead layer B does not have a crosslinking agent.

(Thermoplastic resin)
The thermoplastic resin constituting the bead layer B in the present invention is not particularly limited as long as the melting point described below is satisfied, and examples thereof include thermoplastic resins such as polyester, polyolefin, polystyrene, and acrylic. From the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability, polyester is preferred. In addition, when the reflective layer A and the bead layer B are laminated in contact with each other, adhesion between the layers is improved by using a similar resin.

  When polyester is used as the thermoplastic resin of the bead layer B, examples of the polyester include the same polyester as the polyester in the reflective layer A described above. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. Polyethylene terephthalate may be a homopolymer, but a copolymer is preferred from the viewpoint that crystallization is suppressed when the film is stretched uniaxially or biaxially and stretchability is improved. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above, and isophthalic acid and 2,6-naphthalenedicarboxylic acid are preferable from the viewpoint of achieving both heat resistance and film forming properties. The proportion of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 17 mol%, and particularly preferably 12 to 16 mol%, based on 100 mol% of the total dicarboxylic acid component of the polyester. Mol%. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of film forming property. Moreover, it is excellent in thermal dimensional stability. Furthermore, it becomes easy to achieve the aspect of the melting point described later.

(Organic particles)
The organic particles of the bead layer in the present invention are thermoplastic resin particles, and examples thereof include polyester particles, acrylic particles, polystyrene particles, nylon particles, silicone particles, polyolefin particles, etc. From the standpoint that the film is recovered and easy to handle when used as a self-collecting raw material, the resulting film has excellent reflectivity, and foreign substances such as gas marks and unmelted materials are less likely to be produced. Polyester particles are preferred and particularly preferred.

  The average particle diameter of the organic particles is 1 to 50 μm from the viewpoint that the distance between the light guide plate and the film can be kept constant, and that they can be satisfactorily suppressed and the organic particles are prevented from falling off. If the average particle size is too small, the possibility that the white reflective film partially adheres to the light guide plate tends to increase. From such a viewpoint, the average particle diameter is preferably 2 μm or more, more preferably 3 μm or more, and particularly preferably 5 μm or more. On the other hand, when it is too large, the organic particles tend to drop off, and when the dropping occurs, a white spot defect occurs in the backlight unit. From such a viewpoint, the average particle size is preferably 45 μm or less, more preferably 40 μm or less, particularly preferably 35 μm or less, and most preferably 30 μm or less.

The organic particles are preferably spherical, and particles having a minor axis / major axis = 0.7 or more are preferred. By making it close to a sphere, it becomes easy to keep the distance between the light guide plate and the film constant, which is advantageous in that it has excellent luminance uniformity. From such a viewpoint, the ratio of the minor axis / major axis is more preferably 0.8 or more, and still more preferably 0.9 or more.
In addition, what is necessary is just to select the range which satisfies the coverage mentioned later, considering the average particle diameter of an organic particle, etc. for content of the organic particle in a bead layer. For example, it is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and particularly preferably 10 to 35% by mass based on the mass of the bead layer.

Here, an example is shown below about the manufacturing method in the case of a polyester particle.
It can be obtained by preparing a polyester emulsion by dispersing an ionic group-containing polyester resin in water, and slowly aggregating the water-dispersed polyester microparticles in a plasticized state. As a method of aggregating, there are a method of reducing the surface potential of dispersed particles, a method of adding an electrolyte into the dispersion system, and a method of reducing the thickness of the electric double layer. In this way, when microparticles are slowly aggregated in a plasticized state, the particles are plasticized, so when a plurality of particles are aggregated, they are spheroidized due to surface tension, and particles having a larger particle diameter Grain grows up. The particles thus obtained are substantially spherical.

(Coverage)
The white reflective film of the present invention has organic particles (beads) on the surface, and the organic particles cover the white reflective film surface. The coating with organic particles means that the surface of the white reflective film is coated so as to be 10 to 100% at a coverage defined later. When the coverage is in such a range, the effect of maintaining the gap between the light guide plate and the reflective film can be obtained. If the coverage is less than 10%, the gap may not be maintained, and adhesion spots due to sticking between the light guide plate and the reflective film (a defect in which the sticking part appears white) may occur. Further, the friction between the light guide plate and the reflective film tends to increase, and the light guide plate is easily scratched. The coverage is preferably higher from the viewpoint of securing a gap and suppressing sticking, but if it is too high, the effect of improving the reflectivity is lowered, and thus the effect of improving the brightness tends to be lowered in the display device. . From such a viewpoint, the coverage is preferably 12% or more, more preferably 15% or more, further preferably 20% or more, preferably 95% or less, more preferably 90% or less, and still more preferably 85%. Hereinafter, it is particularly preferably 50% or less. The coverage can be adjusted by adjusting the size and content of the organic particles. If the size is increased or the content is increased, the coverage can be adjusted to be high.

  In the present invention, the coverage ratio is obtained by observing a cross section of a measurement region having a total length of 6 mm in each of measurement regions having a length of 3 mm in two orthogonal directions within the film plane. , Sometimes simply referred to as “particles”).

Specifically, using a microtome, the section sample 1 is cut out so that the plane formed by one direction randomly selected in the film plane and the thickness direction of the film is a cut plane. Section sample 2 is cut out so that the surface formed by the direction orthogonal to the one direction randomly selected in 1 and the thickness direction is a cut surface, and the length of the surface covered with organic particles in the section of the slice sample 1 S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd. with respect to a measurement area of 6 mm in total including a 3 mm-long area and a 3 mm-long area covered with organic particles in the cross section of the slice sample 2 , And the length of the part of the film surface not covered with particles in the measurement region in the cut surface of the section sample (reference numeral in FIG. 1). 01) by integrating the obtained by the following equation (see FIG. 1).
Coverage rate = (6 mm− (integrated length of the portion not covered with particles (mm))) / 6 mm × 100 (%)

  In addition, when the largest diameter part of a particle has come out outside the bead layer surface (code | symbol 203 of FIG. 1) in a cut surface, it is considered that the part covered with the largest particle diameter is covered with the particle (for example, 1 and 103), when the maximum diameter portion of the particle is inside the surface of the bead layer, that is, when it is sinking in the coating film, the portion of the particle that protrudes from the surface of the bead layer. Is considered to be covered with particles (for example, reference numeral 102 in FIG. 1). At this time, it is considered that particles satisfying the exposure rate described later are covered, and even if there are particles that do not satisfy the exposure rate, they are not covered (for example, reference numerals 101 and 104 in FIG. 1). ).

(Exposure rate)
In the calculation of the coverage in the present invention, the particles treated as coating the film surface are those in which part or all of the particles are exposed on the bead layer surface. This exposure refers to exposure at an exposure rate of 1% or more as defined by the present invention. Thus, particles with an exposure rate of less than 1% are not treated as coated particles. Here, “exposed” does not necessarily mean that the particles are in contact with the air outside the film, even if the particles are covered with a thin film such as a thermoplastic resin on the surface of the bead layer. A case where a convex shape is formed with respect to the surface of the bead layer and has an exposure rate is defined as “exposed”.

  For example, an exposure rate of 100% corresponds to a situation where particles are in contact with the film surface at the cut surface, and the exposure rate is 0%. The exposure rate of 50% is a state in which half of the particles are buried and the other half protrudes outside the film surface on the cut surface.

  To define the exposure rate more precisely, the exposure rate is calculated by drawing a straight line passing through the center of the cross section of the particle in the cut surface of the slice sample and perpendicular to the film surface of the film. Of the two points that intersect the particle surface, S is the point on the exposed surface, T is the point on the unexposed surface, and B is the point where the straight line intersects the film surface. Is represented by (distance between S and B) / (distance between S and T) (see FIG. 1).

That is, the exposure rate (%) is defined by the following formula.
Exposure rate = (distance between S and B) / (distance between S and T) × 100 (%)
The center of the cross section of the particle in the cut surface is the center of the circle of the cross section when the particle is spherical, and the center of gravity of the cross section when the particle is non-spherical.

  In the present invention, as in the case of the above-described coverage, when the measurement area is 6 mm in total length of the measurement areas each having a length of 3 mm in two orthogonal directions in the film plane, the exposure rate of the particles in the measurement area The average value (average exposure rate, when calculating the average value does not include those with an exposure rate of 0% or less) is preferably 5 to 90%. Within such a range, it is easy to ensure a gap with the light guide plate, and the effect of improving sticking suppression is enhanced. At the same time, dropping of particles can be suppressed. When the average exposure rate is too low, it is difficult to secure the gap, and sticking tends to occur. On the other hand, if it is too high, it will be difficult to suppress particle dropout. From such a viewpoint, the average exposure rate of the particles is preferably 10 to 85%, more preferably 15 to 80%, still more preferably 20 to 75%.

(Other ingredients)
The bead layer B may contain components other than the above-described constituent components as long as the object of the present invention is not impaired. Examples of such components include ultraviolet absorbers, antioxidants, antistatic agents, fluorescent brighteners, waxes, particles and resins different from the above organic particles, and the like.

  Moreover, the bead layer B may contain the void formation agent in the reflection layer A, and the effect of improving the reflectance can be enhanced by adopting such a mode. On the other hand, if the content of the void forming agent in the bead layer B is reduced or no void forming agent is contained, the effect of improving the film forming property can be increased. From these viewpoints, the void volume ratio in the bead layer B (ratio of the volume of the void in the bead layer B to the volume of the bead layer B) is preferably 0% by volume or more and less than 15% by volume, and more preferably 5%. It is not more than volume%, particularly preferably not more than 3 volume%.

[Melting point of each component]
In the present invention, the melting point of the organic particles in the bead layer B is Tm1 (unit: ° C), the melting point of the thermoplastic resin constituting the bead layer B is Tm2 (unit: ° C), and the thermoplastic resin composition constituting the reflective layer A When the melting point of the product is Tm3 (unit: ° C.), it is necessary to satisfy the following formula.
Tm1 ≧ Tm2 + 10
| Tm1-Tm3 | ≦ 40

  By adopting such a melting point mode, the white reflective film can maintain a gap with the light guide plate, and at the same time, the white reflective film of the present invention can be recovered to produce the film again as a self-collecting raw material. Even when the white reflective film of the present invention is produced by using the film for forming a reflective layer, the obtained white reflective film is excellent in reflectance. In other words, organic particles are present as particles in the bead layer, and a gap can be secured. At the same time, when the particles are collected, the organic particles are sufficiently melted in the film, particularly in the reflective layer. As a result, voids are easily formed, and an excellent reflectance can be obtained.

When Tm1 is less than (Tm2 + 10), when forming a bead layer by melt extrusion, the organic particles are likely to be deformed and melted, so that they do not serve as beads and cannot maintain a gap with the light guide plate. From this perspective,
Tm1 ≧ Tm2 + 20
It is preferable that
Tm1 ≧ Tm2 + 30
More preferably.

If | Tm1-Tm3 | exceeds 40, that is, if the temperature difference between Tm1 and Tm3 is too large, organic particles tend to remain in the film, particularly in the reflective layer, when the film is used as a self-collecting raw material. As a result, void formation is likely to be hindered, making it difficult to obtain a preferable void form, and as a result, excellent reflectivity cannot be obtained, and deteriorated products are likely to be generated, resulting in foreign matter. It becomes easy to generate | occur | produce and a drawability becomes low. From this perspective,
| Tm1-Tm3 | ≦ 30
It is preferable that
| Tm1-Tm3 | ≦ 25
More preferably.

  Furthermore, it is preferable that Tm3 ≧ Tm2, and it is easy to obtain a preferable void mode in the reflective layer A, and the effect of improving the reflectance can be enhanced. From this viewpoint, Tm3 ≧ Tm2 + 10 is more preferable, and Tm3 ≧ Tm2 + 15 is particularly preferable.

[Layer structure]
The thickness of the reflective layer A in the present invention is preferably 80 to 300 μm. Thereby, the improvement effect of a reflectance can be made high. If it is too thin, the effect of improving the reflectance is low, while if it is too thick, it is inefficient. From such a viewpoint, it is more preferably 150 to 250 μm.

  Moreover, it is preferable that the thickness of the bead layer B (the thickness of one layer on the surface on the light guide plate side when there are a plurality of bead layers) is 10 to 70 μm. Thereby, it becomes easy to set it as the aspect of a preferable coverage and exposure rate, and it becomes easy to ensure the gap with a light-guide plate. Moreover, the improvement effect of a reflectance and the improvement effect of stretchability can be made high. If it is too thin, it tends to be difficult to achieve both coverage and particle dropout suppression, and the effect of improving stretchability is low. On the other hand, if it is too thick, the effect of improving reflectivity is low, and a preferable exposure rate is obtained. It tends to be difficult to obtain. From this viewpoint, it is more preferably 20 to 60 μm.

  When the reflective layer A is represented as A and the bead layer B is represented as B, the laminated structure is a two-layer structure of B / A, a three-layer structure of B / A / B, and a four-layer structure of B / A / B / A. In addition, a multi-layer configuration of five or more layers in which B is disposed on at least one of the surfaces can be given. Particularly preferred are a B / A two-layer structure, a B / A / B three-layer structure, and most preferably a B / A / B three-layer structure, and problems such as curling are unlikely to occur.

  The reflective layer A and the bead layer B have a thickness ratio of the reflective layer A of 50 to 90% and a thickness ratio of the bead layer B of 5 to 50% when the thickness of the entire white reflective film is 100%. Furthermore, the aspect which is 5 to 25% is preferable, and the balance of each characteristic can be improved. Here, the thickness ratio of each layer refers to the ratio between the integrated thicknesses when there are a plurality of layers.

  In the present invention, in addition to the reflective layer A and the bead layer B, other layers may be provided as long as the object of the present invention is not impaired. For example, you may have the layer for providing functions, such as antistatic property, electroconductivity, and ultraviolet durability. Moreover, the improvement effect of a mechanical characteristic, heat resistance, and a drawability can be made high by having a support layer. Such a support layer is a layer containing relatively few voids or no voids. Such a support layer can be a layer made of the same resin composition as that of the reflective layer A, and polyester is preferred from the viewpoint of excellent mechanical properties and thermal stability. As the polyester, the same polyester as the reflective layer A can be used. Moreover, although the support layer may contain the void using the void formation agent in the reflection layer A, it is preferable that the void volume ratio is less than 0-15 volume%, and it is excellent in film forming property by this. If the void volume ratio is too high, the stretchability is inferior and the role as a support layer is not achieved. From such a viewpoint, the void volume ratio of the support layer is more preferably 0 to 12% by volume, and particularly preferably 0 to 10% by volume. The thickness of the support layer is, for example, about 10 to 70 μm. In addition, as a layer structure in the case of having a support layer, when the support layer is expressed as C, a three-layer structure of B / A / C, B / A / C / B, B / A / B / C, etc. A layer structure in which B is arranged on at least one surface, such as a four-layer structure, preferably a B / A structure, such as a layer structure in which B is arranged on at least one surface so that it becomes a surface layer.

[Production method]
Hereinafter, an example of the method for producing the white reflective film of the present invention will be described. The melting point of the organic particles in the bead layer B is Tm1 (unit: ° C), the glass transition temperature is Tg1 (unit: ° C), the melting point of the thermoplastic resin constituting the bead layer B is Tm2 (unit: ° C), and the glass transition. The temperature is Tg2 (unit: ° C), the melting point of the thermoplastic resin composition constituting the reflective layer A is Tm3 (unit: ° C), and the glass transition temperature is Tg3 (unit: ° C).

  First, when producing the white reflective film of the present invention, the reflective layer A obtained by a melt extrusion method or the like is subjected to beads by a melt resin coating method (including a melt extrusion resin coating method), a co-extrusion method, a lamination method, or the like. It is preferable to form the layer B by forming the layer B. At this time, in the present invention, the composition for forming the reflective layer A containing at least the thermoplastic resin composition and the void forming agent is (Tm3) ° C. or higher and (Tm1) ° C. or higher. A composition for forming the bead layer B, which is melted at a temperature to form a reflective layer A and contains at least organic particles and a thermoplastic resin, is not lower than (Tm2) ° C. and lower than (Tm1) ° C. It is important to heat at a temperature to melt the thermoplastic resin to form the bead layer B and to laminate them.

  In the present invention, it is particularly preferred that it is produced by a coextrusion method. Moreover, it is preferable that the reflective layer A and the bead layer B are directly laminated by a coextrusion method. By laminating in this way by coextrusion, the interfacial adhesion between the reflective layer A and the bead layer B can be increased, and the bead layer B is formed again after the films are bonded or after film formation. Since it is not necessary to go through a process for making a product, it can be easily mass-produced.

  Hereinafter, a case where a polyester is employed as the thermoplastic resin composition constituting the reflective layer A and the thermoplastic resin constituting the bead layer B, and a coextrusion method is adopted as a laminating method thereof will be described. The production method is not limited, and other embodiments of the present invention can be similarly produced with reference to the following. At that time, when the extrusion step is not included, the following “melt extrusion temperature” may be read as “melting temperature”.

  First, a polyester composition for forming the reflective layer A is prepared by mixing polyester as a thermoplastic resin composition, a void forming agent, and other optional components. Moreover, as the polyester composition for forming the bead layer B, a mixture of polyester as a thermoplastic resin, organic particles, and other optional components is prepared. These polyester compositions are used after drying to sufficiently remove moisture.

  Next, the dried polyester composition is put into separate extruders and melt-extruded. The melt extrusion temperature on the reflective layer A side is (Tm3) ° C. or higher and (Tm1) ° C. or higher, preferably (Tm3 + 5) ° C. or higher and (Tm1 + 5) ° C. or higher. And it is sufficient. As a result, even when the reflective layer A contains a self-collecting raw material, the organic particles derived from the self-collecting raw material are sufficiently melted to form a suitable void in the reflective layer A, thereby improving the reflectance. The effect can be increased. From this viewpoint, the range is more preferably (Tm3 + 10) ° C. or more and (Tm1 + 10) ° C. or more. The upper limit is not particularly limited as long as a problem due to deterioration of the resin, a problem due to a decrease in the melt viscosity of the resin, or the like does not occur. For example, (Tm3 + 100) ° C. or lower or (Tm1 + 100) ° C. or lower, preferably (Tm3 + 50) ° C. or lower or (Tm1 + 50) ° C. or lower.

  Further, the melt extrusion temperature on the bead layer B side is (Tm2) ° C. or more and less than (Tm1) ° C., preferably (Tm2 + 5) ° C. or more, (Tm1-5) ° C. or less, more preferably (Tm2 + 10) ° C. or more, ( Tm1-10) It should just be made into ° C or less. As a result, the organic particles can sufficiently retain the shape in the bead layer B, and the coverage rate and the exposure rate can be easily changed to a preferable mode, and effects as a bead layer such as sticking to the light guide plate and securing a gap can be achieved. Can do. If the melt extrusion temperature is too high, it becomes difficult for the organic particles to retain their shape, and the coverage and exposure rate tend to be less favorable.

  At this time, the polyester composition used for the production of the film, particularly the polyester composition used for the reflective layer A, is filtered using a nonwoven fabric type filter having an average opening of 10 to 100 μm made of stainless steel fine wires having a wire diameter of 15 μm or less. It is preferable. By performing this filtration, it is possible to suppress aggregation of particles that normally tend to aggregate into coarse aggregated particles, and to obtain a film with few coarse foreign matters. In addition, the average opening of a nonwoven fabric becomes like this. Preferably it is 20-50 micrometers, More preferably, it is 15-40 micrometers. The filtered polyester composition is extruded in a multilayer state from a die by a simultaneous multilayer extrusion method (coextrusion method) using a feed block in a molten state to produce an unstretched laminated sheet. The unstretched laminated sheet extruded from the die is cooled and solidified with a casting drum to obtain an unstretched laminated film.

Next, this unstretched laminated film is heated by roll heating, infrared heating, or the like, and stretched in the machine axis direction (hereinafter, sometimes referred to as the longitudinal direction or the longitudinal direction or MD) to obtain a longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls.
The film after the longitudinal stretching is then guided to a tenter and stretched in a direction perpendicular to the mechanical axis direction and the thickness direction (hereinafter sometimes referred to as a transverse direction or a width direction or TD) to be biaxial. Let it be a stretched film.

  These stretches are performed at a temperature of Tg + 30 ° C. or higher, where Tg of polyester is higher than Tg3 of polyester in the reflective layer or Tg2 of polyester in the bead layer. It is preferable, and it is excellent in film forming property, and a void is preferably formed easily. 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 draw ratio is too low, uneven thickness of the film tends to be worsened, and voids tend not to be formed. On the other hand, if it is too high, breakage tends to occur during film formation. In the case of sequential biaxial stretching in which longitudinal stretching is performed and then lateral stretching is performed, the second stage (in this case, lateral stretching) should be about 10 to 50 ° C. higher than the first stage stretching temperature. Is preferred. This is due to the fact that the Tg as a uniaxial film is increased due to the orientation in the first stage of stretching.

  Moreover, it is preferable to preheat a film before each extending | stretching. For example, the pre-heat treatment for transverse stretching starts from a temperature higher than Tg + 5 ° C. of polyester (herein, Tg of polyester is Tg3 of polyester in the reflective layer or Tg2 of polyester in the bead layer). It is better to raise the temperature. Although the temperature rise in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually raised sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone.

The film after biaxial stretching is subsequently subjected to heat-fixing and heat-relaxing treatments in order to obtain a biaxially oriented film. However, following melt-extrusion to stretching, these treatments can also be performed while the film is running. it can.
The film after biaxial stretching is held at both ends with clips (Tm-20 ° C.) to (Tm-100 ° C.) (where Tm is higher of Tm3 of the polyester of the reflective layer or Tm2 of the polyester of the bead layer) It is preferable that the heat shrinkage is performed by heat treatment under a constant width or a width decrease of 10% or less, and heat shrinkage is reduced. When the heat treatment temperature is too high, the flatness of the film tends to deteriorate, and the thickness unevenness tends to increase. On the other hand, if it is too low, the thermal shrinkage tends to increase.

  Further, in order to adjust the heat shrinkage, both ends of the film being held can be cut off, the take-up speed in the film vertical direction can be adjusted, and the film can be relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3. The film is relaxed by performing a speed reduction of ˜2.0% (this value is referred to as “relaxation rate”), and the longitudinal heat shrinkage rate is adjusted by controlling the relaxation rate. Further, the width of the film in the horizontal direction can be reduced in the process until both ends are cut off, and a desired heat shrinkage rate can be obtained.

  In the biaxial stretching, a lateral-longitudinal sequential biaxial stretching method may be used in addition to the longitudinal-lateral sequential biaxial stretching method as described above. Moreover, it can form into a film using a simultaneous biaxial stretching method. In the case of the simultaneous biaxial stretching method, the stretching ratio 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.

Thus, the white reflective film of the present invention can be obtained.
Further, the obtained white reflective film, which has been made into chips by pulverization or melt extrusion, is used as a self-collecting raw material, and is added to the film, preferably added to the reflective layer A. A film can be produced.

[Characteristics of reflective film]
(Reflectance, brightness)
The reflectance of the white reflective film of the present invention is preferably 96% or more, more preferably 97% or more, and further preferably 97.5% or more. When the reflectance is 96% or more, high luminance can be obtained when used in a liquid crystal display device or illumination. Such reflectivity is a preferable mode such as increasing the void volume ratio of the reflective layer A, the thickness of the reflective layer A is increased, the thickness of the bead layer B is decreased, and the mode of each layer is set as a preferable mode. Can be achieved.
Moreover, although a brightness | luminance is calculated | required with the measuring method mentioned later, 5400 cd / m < ² > or more is preferable, 5450 cd / m < ² > or more is more preferable, and 5500 cd / m < ² > or more is especially preferable.

(Amount of volatile organic solvent)
In the white reflective film of the present invention, the amount of volatile organic solvent measured by the method described later is preferably 10 ppm or less. Thereby, when a self-recovery raw material is obtained and a film is formed using the raw material, a gas mark is hardly generated and stretchability is improved. From this viewpoint, it is more preferably 5 ppm or less, further 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 in forming the bead layer B without adopting the solution coating method using the organic solvent.

Hereinafter, the present invention is described in detail by way of examples. Each characteristic value was measured by the following method.
(1) Light reflectance The integrating sphere was attached to a spectrophotometer (Shimadzu Corporation UV-3101PC), the reflectance when the BaSO ₄ white plate was 100% was measured at a wavelength of 550 nm, and this value was defined as the reflectance. The measurement was performed on the surface on the bead layer B side. When different bead layers B are provided on the front and back sides, the measurement may be performed on the bead layer surface on the light guide plate side.

(2) Average particle size of inorganic particles The particle size distribution of the particles was determined with a particle size distribution meter (LA-950, manufactured by Horiba, Ltd.), and the particle size at d50 was defined as the average particle size.

(3) Average particle diameter of organic particles Using an S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd., 100 particles were arbitrarily measured at a magnification of 1000 times to obtain an average particle diameter. In addition, in the case of other than spherical shape, it was determined by (major axis + minor axis) / 2.

(4) Amount of Volatile Organic Solvent At room temperature (23 ° C.), 1 g of a film sample was placed in a 10 L fluororesin bag, which was purged with pure nitrogen and sealed. Next, immediately from the nitrogen in the bag, 0.2 L and 1.0 L of nitrogen were collected in two analytical TENAX-TA collection tubes at a flow rate of 0.2 L / min. The mass of the organic solvent component contained in the collected nitrogen was quantified by HPLC, GCMS. The obtained value is converted into the amount in 10 L of nitrogen, and the mass of the organic solvent volatilized in 10 L of nitrogen is obtained from 1 g of the film sample, and the amount of volatile organic solvent (unit: ppm, based on the mass of the film sample) did. The aldehydes were quantified by HPLC by eluting the aldehyde derivatized product from the collection tube with acetonitrile. Moreover, when the value was different between HPLC and GCMS, the value of the more detected one was adopted.

(5) Film thickness A white reflective film is sliced with a microtome to obtain a cross section, and the cross section is observed at a magnification of 500 times using a S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd. The thicknesses of the reflective layer A and the bead layer B were determined. In addition, the thickness of the whole film and bead layer B was made into the thickness of the part except the part which the organic particle protruded from the bead layer surface. After determining the thickness (μm) of each layer, the thickness ratio of each layer was calculated.

(6) Calculation of void volume ratio Calculated density was calculated from the density and blending ratio of the polymer, additive particles, and other components of the layer for which the void volume ratio was determined. At the same time, it was isolated by peeling off the layer, and the mass and volume were measured. The actual density was calculated from these, and the following formula was obtained from the calculated density and the actual density.
Void volume fraction = 100 × (1− (actual density / calculated density))
An example of how to obtain the void volume ratio is shown below.
For example, the component constituting the reflective layer A is polyethylene terephthalate (biaxial), the density is 1.39 g / cm ³ , the content is 48% by mass, the additive particles are barium sulfate, and the density is 4. When the content is 5 g / cm ³ and the content ratio is 52 mass%, the calculated density is as follows.
1.39 × 0.48 + 4.5 × 0.52 = 3.01 g / cm ³ (calculated)
Moreover, only the reflective layer A was isolated, the mass per unit volume was calculated | required, and the real density was calculated | required.
Actual density = mass of isolated reflective layer / volume of isolated reflective layer The volume of the reflective layer was obtained by cutting a sample into an area of 3 cm ² and measuring the thickness at the size with an electric micrometer (K-402B manufactured by Anritsu). The average value measured at 10 points was taken as the thickness and calculated as area × thickness.
Moreover, the mass of the isolated reflective layer was weighed with an electronic balance.
If the actual density is 1.29 g / cm ³ Void volume fraction = 100 × (1− (1.29 (actual density) /3.01 (calculated))
= 57%

(7) Melting point, crow transition temperature Using a differential scanning calorimeter (TA Instruments 2100 DSC), the measurement was performed at a heating rate of 20 m / min.

(8) Particle exposure rate (8-1) Preparation of sample Using a microtome, section sample 1 and section sample 2 were cut out from an epoxy-embedded film. The section sample 1 is a section sample cut out so that the surface formed by one direction randomly selected in the film plane and the thickness direction of the film is a cut surface, and the section sample 2 is selected by the section sample 1 This is a slice sample cut out so that the surface formed by the direction perpendicular to one random direction and the thickness direction is a cut surface.
(8-2) Measurement S-4700 manufactured by Hitachi, Ltd. with respect to a measurement area having a total length of 6 mm including an area of 3 mm on the film surface in the section sample 1 and an area of 3 mm on the film surface in the section sample 2 Observation was performed at a magnification of 3000 times using a field emission scanning electron microscope.
The exposure rate is the two points where the straight line intersects the surface of the particle in the cut surface of the film slice when a straight line passing through the center of the cross section of the particle in the cut surface of the slice sample and perpendicular to the surface of the film is drawn. Where S is the point on the exposed surface, T is the point on the unexposed surface, and B is the point where the straight line intersects the film surface (the distance between S and B). ) / (Distance between S and T) (see FIG. 1).
That is, the exposure rate (%) is defined by the following formula.
Exposure rate = (distance between S and B) / (distance between S and T) × 100 (%)
The center of the cross section of the particle in the cut surface is the center of the circle of the cross section when the particle is spherical, and the center of gravity of the cross section when the particle is non-spherical.
Moreover, this measurement was implemented about all the particles observed in the said measurement area | region of 6 mm, and made the average value the average exposure rate.

(9) Film surface coverage with particles (9-1) Preparation of sample The sample obtained in (8-1) above was evaluated.
(9-2) Measurement Hitachi Scanning Electron Microscope Schottky Emission for a measurement area of 6 mm in total including an area of 3 mm on the film surface in the section sample 1 and an area of 3 mm in the film surface on the section sample 2 The observation was performed at a magnification of 3000 times using a shaped electron beam system S-4300SE / N.
The coverage was obtained from the following formula by integrating the lengths of the film surface portions not covered with the particles in the measurement region in the cut surface of the section sample (see FIG. 1).
Coverage rate = (6 mm− (integrated length of the portion not covered with particles (mm))) / 6 mm × 100 (%)

(10) Brightness Take out the reflective film from the LED liquid crystal television (LG42LE5310AKR) manufactured by LG, and install the various reflective films (if there are organic particles, the side with the organic particles on the screen side (the surface in contact with the light guide plate). Using a luminance meter (Model MC-940 manufactured by Otsuka Electronics Co., Ltd.) in the state of the light unit, the luminance was measured at a measurement distance of 500 mm from the front of the center of the backlight.

(11) Evaluation of scratches on light guide plate (evaluation of shaving property) and evaluation of dropout of particles As shown in FIG. 3, an iron plate (length 200 mm × width 200 mm × thickness 3 mm) at the end of the handle portion (reference numeral 7 in FIG. 3) 3 is affixed firmly, and a reflective film having a width of 250 mm × a length of 200 mm (reference numeral 9 in FIG. 3) is 25 mm from both ends in the width direction. Was pasted so that the part of the plate protruded from the iron plate (so that the central 200 mm × 200 mm portion overlapped the iron plate). At this time, the evaluation surface (bead layer surface) of the reflective film was placed outside. In addition, the 25 mm portion remaining at both ends in the width direction of the reflective film is folded back to the back side of the iron plate, and the end portion of the reflective film (the portion where the blade is inserted with a knife or the like at the time of sampling) has the effect of scraping the light guide plate. Eliminated.
Next, the light guide plate (with a size of at least 400 mm × 200 mm) with the dot surface up is fixed on a horizontal desk, and the evaluation film and the light guide plate are in contact with the reflection film fixed on the iron plate created above. As described above, the reflective film side is placed on the light guide plate with the surface facing downward, and a 500 g weight (reference numeral 10 in FIG. 3) is placed thereon, and fixed to the iron plate at a distance of 200 mm (400 mm × 200 mm region). The reciprocating film was moved 15 times at a speed of about 5 to 10 seconds. Then, on the surface of the light guide plate, the degree of shaving and the presence or absence of organic particles dropped off from the reflective film were observed with a 20-fold magnifier and evaluated according to the following criteria.
In the entire range of 400 mm × 200 mm rubbed on the light guide plate, if there are no scratches that can be observed with a loupe after 15 reciprocating movements, it is determined that “cannot be scraped” (scraping evaluation ○), and scratches that can be observed after 10 reciprocating movements. Although there were no scratches that could be observed after 15 reciprocating movements, “scratch was difficult” (shave evaluation Δ), and when there were scratches that could be observed after 10 reciprocations, “scraped” (scraping evaluation ×).
Further, after 15 reciprocating movements, if there was no white foreign matter that could be observed with a loupe over the entire rubbed area of 400 mm × 200 mm on the light guide plate, it was determined that “the organic particles would not drop” (dropping evaluation o). In addition, when there is a white foreign matter that can be observed, the white foreign matter is observed with a microscope to confirm that it is an organic particle. ”(Dropout evaluation Δ), and if 6 or more,“ particles dropped out ”(dropout evaluation ×).
In the evaluation, in order to suppress the influence of the dot size as much as possible, an area having a large dot size was selected as much as possible on the light guide plate, and the evaluation samples were aligned.

(12) White spot evaluation Using the reflective film and light guide plate used in the evaluation of (11) above, a reflective film is placed on a desk so that the surface on which the organic particles are exposed faces upward, and dots are formed thereon. Place the light guide plate so that the surface is facing down, place 200g weights on each of the four sides of the light guide plate, and fix the side surface of the light guide plate using the backlight light source of LED liquid crystal television (LG42LE5310AKR) manufactured by LG. If a bright spot other than light guide plate dots that can be visually observed is incident, white spots are generated (evaluation x). On the other hand, if there were no abnormal bright spots that could be observed visually, no white spots were generated (evaluation ○).

(13) Adhesion spot evaluation (adhesion evaluation)
Take out the chassis from the LED liquid crystal television (LG42LE5310AKR) manufactured by LG and place it on a horizontal desk so that the inside of the television is facing upward. On top of that, a reflective film of approximately the same size as the chassis is placed, with the bead layer facing upward Further, a light guide plate and three optical sheets (two diffusion films and one prism) originally provided in the television were placed thereon. Next, an equilateral triangular base having three circular feet with a diameter of 5 mm as shown in FIG. 2 is placed in the area including the most severely uneven portion of the chassis within the plane, and a weight of 15 kg is further provided thereon. The area surrounded by these three legs was visually observed, and if there was no abnormally bright part, “no adhesion spots” (adhesion spots evaluation ○) was designated. If there is an abnormally bright part, place the DBEF sheet originally provided on the television on top of the three optical sheets and observe it in the same manner. When there was a spot (evaluation x), and when there was no abnormally bright part, it was set as "there was almost no adhesion spot" (evaluation (triangle | delta)). In addition, the area surrounded by the three legs was a substantially equilateral triangle having a side length of 10 cm.

(14) Stretchability The film formation stability when the films described in the Examples were formed by a continuous film formation method using a tenter was observed and evaluated according to the following criteria.
○: A film can be stably formed for 1 hour or more.
Δ: Cutting occurred once in 1 hour.
X: Cutting occurs multiple times within 1 hour, and stable film formation is not possible.

[Example 1]
(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 (9 mol% with respect to 100 mol% of total acid components of the obtained polyester), 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol , 0.05 parts by mass of manganese acetate and 0.012 parts by mass of lithium acetate were charged into a rectification column and a flask equipped with a distillation condenser, and heated to 150 to 240 ° C. with stirring to distill methanol to conduct a transesterification reaction. went. After methanol was distilled, 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. Next, while stirring, the pressure in the reactor was gradually reduced to 0.3 mmHg and the temperature was raised to 292 ° C. to carry out a polycondensation reaction to obtain isophthalic acid copolymerized polyethylene terephthalate 1. The melting point of this polymer was 235 ° C.

(Production Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2)
Except for changing to 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (14 mol% with respect to 100 mol% of the total acid component of the resulting polyester), the same as in Production Example 1 above. Thus, isophthalic acid copolymerized polyethylene terephthalate 2 was obtained. The melting point of this polymer was 215 ° C.

(Production Example 3: Organic particles)
The raw materials described below were charged into an autoclave and heated at 180 to 240 ° C. for 120 minutes to conduct a transesterification reaction. Next, the temperature of the reaction system was raised to 245 ° C., and the reaction was continued for 60 minutes at an internal pressure of 1-10 mmHg. As a result, a copolyester was obtained.
134 parts by weight of dimethyl terephthalate 5 parts by weight of dimethyl isophthalate 3 parts by weight of 5-sodium sulfodimethylisophthalate 5 parts by weight of methyl paraterbutyl benzoate Ethylene glycol 136 parts by weight Tetrabutoxy titanate 0.1 parts by weight The organic particles (polyester particles A) shown in the table were obtained by flocculation.

(Production Example 4: Preparation of inorganic particle master chip 1)
Using part of the isophthalic acid copolymerized polyethylene terephthalate 1 obtained above and barium sulfate particles having an average particle diameter of 1.0 μm as a void forming agent (indicated in the table as BaSO4), NEX manufactured by Kobe Steel -In a T60 tandem extruder, mixed so that the content of barium sulfate particles is 63% by mass with respect to the mass of the obtained master chip, extruded at a resin temperature of 260 ° C, and inorganic particles containing barium sulfate particles Master chip 1 was created.

(Production Example 5: Creation of organic particle master chip 2)
The polyester particles A obtained above are added to the isophthalic acid copolymerized polyethylene terephthalate 2 obtained above, mixed so that the content is 15% by mass, extruded at a melting temperature of 235 ° C., and an organic particle master chip 2 was created.

(Manufacture of white reflective film)
The isophthalic acid copolymerized polyethylene terephthalate 1 and inorganic particle master chip 1 obtained above are used as the raw material for the reflective layer (A layer), and the isophthalic acid copolymerized polyethylene terephthalate 2 and organic particle master chip 2 are used as the raw material for the bead layer (B layer). As shown in Table 1, each layer is mixed so that each layer has the structure described in Table 1, and then fed into an extruder. As shown in Table 1, a three-layer feedblock device is formed so as to be B layer / A layer / B layer. They were used and merged, and formed into a sheet from a die while maintaining the laminated state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of B layer / A layer / B layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 2.9 times in the longitudinal direction, and cooled by a roll group at 25 ° C. did. Subsequently, while holding both ends of the film with clips, the film was led to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. and stretched 3.6 times in the transverse direction. Then, heat setting is performed at 185 ° C. in the tenter, the width is set to 2%, the width is set in the horizontal direction at a temperature of 130 ° C., then both ends of the film are cut off, and the film is thermally relaxed at a longitudinal relaxation rate of 2%. As shown in Table 1, a biaxially stretched film having a thickness of 250 μm was obtained. Here, the melting point of the thermoplastic resin composition constituting the reflective layer A was defined as a self-collecting raw material-free melting point Tm3.
The film is recovered, pulverized, melt-extruded to form a chip by making a self-collecting raw material, and 35% by mass of the self-collecting raw material is added to the reflective layer A based on the mass of the reflective layer A. Similarly, as shown in Table 1, a biaxially stretched film having a thickness of 250 μm was obtained to obtain a white reflective film. The evaluation results of the obtained film are shown in Table 2. Here, the melting point of the thermoplastic resin composition constituting the reflective layer A was defined as a self-collecting raw material-containing melting point Tm3.

[Example 2]
A self-recovery raw material was prepared in the same manner as in Example 1 except that polyester particles B in which the average particle diameter of polyester particles A was changed as shown in Table 1 were used as organic particles, and a white reflective film was prepared using the same. And evaluated. The evaluation results are shown in Table 2.

[Example 3]
As the organic particles, polyester particles C in which the addition amount of dimethyl isophthalate was changed from 5 parts by mass to 12 parts by mass in the production of organic particles with respect to the polyester particles A, and the average particle diameter was changed as shown in Table 1. A self-recovery raw material was prepared in the same manner as in Example 1 except that was used, and a white reflective film was prepared using the self-recovery raw material. The evaluation results are shown in Table 2.

[Example 4]
Except for using nylon fine particles “TR-2” (nylon 6 particles, average particle diameter 20 μm) manufactured by Toray Industries, Inc. as organic particles, and carrying out the melting temperature at 220 ° C. when preparing organic particle master chips. A self-recovery raw material was prepared in the same manner as in No. 1, a white reflective film using the raw material was prepared and evaluated. The evaluation results are shown in Table 2.

[Example 5]
As shown in Table 1, the void forming agent of the reflective layer A was changed to a resin incompatible with polyester (cycloolefin, “TOPAS 6017S-04” manufactured by Polyplastics Co., Ltd.), and polyester as an organic particle in the bead layer. A self-recovery raw material is prepared in the same manner as in Example 1 except that the polyester particle D whose average particle diameter is changed as shown in Table 1 is used from the particle A, and a white reflective film is prepared using the raw material. Carried out. The evaluation results are shown in Table 2.

[Example 6]
A self-recovery raw material was prepared in the same manner as in Example 1 except that the production conditions, layer structure and organic particle mode were changed as shown in Table 1, and a white reflective film was prepared and evaluated using the same. did. The evaluation results are shown in Table 2.

[Comparative Example 1]
Biaxial stretching with a thickness of 250 μm as in Example 1 except that no organic particles are added to the bead layer B of Example 1 (isophthalic acid copolymerized polyethylene terephthalate 2 is used instead of the organic particle master chip 2). After creating the film, a coating liquid having the composition shown in the following liquid preparation recipe 1 was applied to one side of the film with a die coating apparatus in an application amount with a wet thickness of 8 g / m ² , and then in an oven. A film was obtained by drying at 80 ° C. to form a bead layer. Next, the film is recovered, pulverized, melt-extruded to form a chip, and a self-recovery raw material is prepared, and this is added to the reflective layer A by using 35% by mass based on the mass of the reflective layer A, and the same as above Attempts were made to form a film. However, a large amount of unmelted material, gas marks and other foreign matters were generated during film formation, and the stretchability was greatly reduced, so that a sample could not be collected.
(Preparation recipe 1, solid concentration 35% by mass)
・ Particles: Sekisui Plastics Industry BM30X-8 (cross-linked acrylic particles A, non-porous particles, powder, no cross-linking because of a cross-linking system) ... 17.6% by mass
-Acrylic binder: DIC Acrydic A-817BA ... 17.5% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 11.7% by mass
・ Organic solvent: butyl acetate 53.3 mass%
In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Particles: 50% by mass
・ Binder: 25% by mass
・ Crosslinking agent: 25% by mass
Here, the molar ratio of the reactive group in the binder to the crosslinking group in the crosslinking agent (crosslinking group / reactive group) is 5.7. Further, the resin component composed of the binder and the crosslinking agent did not exhibit a melting point because of the crosslinking system.

[Comparative Example 2]
A self-recovery raw material was prepared in the same manner as in Comparative Example 1 except that the coating liquid was changed to the following liquid preparation recipe 2, and a white reflective film was prepared using it.
(Preparation recipe 2, solid concentration 35% by mass)
-Particles: Sekisui Plastics Industry ARX-806 (cross-linked acrylic particles B, non-porous particles, powder, no melting point due to cross-linking system) ... 8.8% by mass
-Acrylic binder: DIC Acridic A-817BA 26.6% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 17.3 mass%
-Organic solvent: butyl acetate 47.4% by mass
When a film was formed using a self-collecting raw material, a white reflective film could be obtained although a decrease in stretchability was observed. Table 2 shows the evaluation results of the obtained white reflective film. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Particles: 25% by mass
・ Binder: 38% by mass
・ Crosslinking agent: 37% by mass
Here, the molar ratio of the reactive group in the binder to the crosslinking group in the crosslinking agent (crosslinking group / reactive group) is 5.7. Further, the resin component composed of the binder and the crosslinking agent did not exhibit a melting point because of the crosslinking system.

[Comparative Example 3]
As the organic particles, the same procedure as in Example 1 was performed except that the polyester particles E were used in which the addition amount of dimethyl isophthalate was changed from 5 parts by mass to 45 parts by mass in the synthesis of the organic particles. Was made and evaluated. The evaluation results are shown in Table 2.

[Comparative Example 4]
As shown in Table 1, a self-recovery raw material was prepared in the same manner as in Example 1 except that polyester particles F in which the average particle diameter of polyester particles A was changed were used as organic particles, and a white reflective film was prepared using the same. And evaluated. The evaluation results are shown in Table 2.

[Comparative Examples 5 and 6]
As shown in Table 1, nylon fine particles “TR-2” (nylon 6 particles, average particle size 20 μm) and “SP-10” (nylon 12 particles, average particle size 10 μm) manufactured by Toray Industries, Inc. were used. Made a self-recovery raw material in the same manner as in Example 1, and made a white reflective film using it, and evaluated it. The evaluation results are shown in Table 2. In preparing the master chip, referring to Production Example 5, the melting temperature was adjusted by the melting point of the particles.

[Comparative Example 7]
As shown in Table 1, a self-recovery raw material was prepared in the same manner as in Example 1 except that the polyester particle A was replaced with the crosslinked acrylic particle A used in Comparative Example 1, and a white reflective film was prepared using it. . The evaluation results are shown in Table 2.

[Comparative Example 8]
As shown in Table 1, a self-recovery raw material was prepared in the same manner as in Comparative Example 2 except that the crosslinked acrylic particles B were replaced with the polyester particles B used in Example 2, and a white reflective film was formed using them. However, a large amount of foreign matter such as unmelted material and gas marks was generated, the stretchability was low, the fracture occurred frequently, and a sample was not obtained.

  The white reflective film of the present invention is an edge light type used in LCDs including large LCDs, particularly as reflective films used in liquid crystal display devices, lighting fixtures and the like, particularly as reflective films used in display devices such as LCDs. It can be suitably used as a reflective film of the backlight unit.

101-105 Organic particles 2 Bead layer 201 Part not covered with particle 202 Part covered with particle 203 Bead layer surface 204 Bead layer thickness 3 Reflective layer 4 Chassis 5 Reflective film, light guide plate, optical sheet laminate 6 Weight 7 Handle part 8 Iron plate 9 Reflective film 10 Weight 11 Light guide plate 1101 dots

Claims (6)

A white reflective film having a reflective layer A and a bead layer B,
The reflective layer A is composed of a thermoplastic resin composition and a void forming agent, contains voids,
The bead layer B is composed of organic particles having an average particle diameter of 1 to 50 μm and a thermoplastic resin, and the coverage of the organic particles on the surface of the white reflective film is 10 to 100%.
The melting point Tm1 of the organic particles, the melting point Tm2 of the thermoplastic resin constituting the bead layer B, and the melting point Tm3 of the thermoplastic resin composition constituting the reflective layer A satisfy the following formula:
White reflective film.
Tm1 ≧ Tm2 + 10
| Tm1-Tm3 | ≦ 13 The white reflective film of Claim 1 whose amount of volatile organic solvents in a white reflective film is 10 ppm or less on the basis of the mass of a white reflective film.   The white reflective film of Claim 1 or 2 whose void volume ratio of the reflection layer A is 15 volume% or more and 70 volume% or less.   The white reflective film of any one of Claims 1-3 whose void volume ratio of the bead layer B is 0 volume% or more and less than 15 volume%. It is a manufacturing method of the white reflective film according to any one of claims 1 to 4,
A production method in which the bead layer B is laminated by any one of a molten resin coating method (including a melt extrusion resin coating method), a coextrusion method, and a lamination method . It is a manufacturing method of the white reflective film according to claim 1,
The thermoplastic resin composition and the void forming agent are melted at a temperature of (Tm3) ° C. or higher and (Tm1) ° C. or higher to form the reflective layer A,
A manufacturing method in which organic particles and a thermoplastic resin are heated at a temperature of (Tm2) ° C. or higher and lower than (Tm1) ° C. to melt the thermoplastic resin, form a bead layer B, and laminate them.