JP5739178B2 - Reflective film - Google Patents

Description

  The present invention relates to a reflective film. In particular, it is related with the 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 reflector on the back of the liquid crystal display panel, and a light guide plate provided with the reflector on the back 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 conventionally used for relatively small LCDs such as notebook PCs. However, since the light guide plate and the reflection plate are in direct contact with each other, the light guide plate made of a relatively soft material is used. Is damaged by the reflector. As a countermeasure, for example, as disclosed in Patent Documents 1 and 2, there is a report of a reflective sheet having 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

However, the present inventors only have to adjust the average particle diameter and burial rate of beads as described in Patent Document 3 above, and it is possible to suppress the dropping of beads and white spot defects generated on the LCD screen by the dropped beads. We focused on the fact that it may be insufficient.
Accordingly, an object of the present invention is to provide a reflective film having a bead layer containing particles, which suppresses sticking to a light guide plate by the bead layer and at the same time suppresses dropout of particles.

  Furthermore, the present inventors have newly discovered that if the beads are made too soft as in Patent Documents 1 and 2, the beads are likely to fall off and white spot defects are likely to occur. In addition, since the reflective plate has beads on the surface, the gap between the light guide plate and the reflective plate can be kept constant, and sticking of these can be prevented. There is a problem that it is difficult to keep the gap between the plates constant, the light guide plate and the reflection plate are easily attached, and luminance spots are generated when part of them is attached.

Then, this invention makes it a desirable objective to provide the reflective film which can further suppress the damage to a light-guide plate simultaneously.
For example, in the case of a large LCD such as 30 type or more, the mass of the light guide plate and the reflective film becomes heavy, and the force applied between them increases, so the above problem becomes more severe.
Accordingly, it is a further desirable object of the present invention to provide a reflective film that can simultaneously suppress all of particle dropout, scratching of the light guide plate, and sticking to the light guide plate even in a large LCD.

The present invention adopts the following configuration in order to achieve the above-described problems.
1. A reflective film having a bead layer formed of the coating and the spherical particles to the surface of the white film, S10 strength of the spherical particles are 11.37~23.6N / mm ^2, the microhardness tester of the coating The liquid crystal whose hardness is calculated by 112.7 to 225.4 N / mm ² , the coverage with spherical particles on the white film surface is ² to 45%, and the average exposure rate of spherical particles is 5 to 80%. A reflective film used as a reflective plate on the back surface of a light guide plate in an edge light type backlight unit of a display device .
2. 2. The reflective film as described in 1 above, wherein the coating film is formed from a composition containing a binder and a crosslinking agent.
3. 3. The reflective film as described in 2 above, wherein the binder has a glass transition temperature Tg of 40 ° C. or higher.
4). In the coating film, the binder has a reactive group, the crosslinking agent has a crosslinking group, and the molar ratio of the reactive group to the crosslinking group (crosslinking group / reactive group) is 1 to 18, Reflective film .
5 . 5. The reflective film as described in any one of 1 to 4 above, wherein the content of spherical particles in the bead layer is 10 to 50% by mass with respect to 100% by mass of the bead layer .

  According to the present invention, in a reflective film having a bead layer containing particles, it is possible to provide a reflective film in which the bead layer suppresses sticking to the light guide plate and at the same time, the particles are prevented from falling off. As a result, when the reflective film of the present invention is used as a reflector of a liquid crystal display device, it is possible to suppress the occurrence of white spot defects due to falling particles, and to suppress the occurrence of black spot defects due to scratches on the light guide plate. It is possible to suppress the occurrence of adhesion spots due to.

Moreover, according to the preferable aspect of this invention, the damage of a light-guide plate can be suppressed further.
Furthermore, according to another preferable aspect of the present invention, it is possible to provide a reflective film capable of simultaneously suppressing particle dropping, scratching of the light guide plate, and sticking to the light guide plate even in a large LCD. it can.

It is a schematic diagram which shows an example of the cross section of the reflective film of this invention. It is a schematic diagram which shows the structure used for sticking 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.

Hereinafter, the present invention will be described in detail.
[White film]
The white film in the present invention is a film made of a thermoplastic resin and having a white color by containing a white colorant or void forming agent in the film. As the colorant or void forming agent, for example, inorganic particles, organic particles, and a resin that is incompatible with the thermoplastic resin constituting the film (hereinafter, sometimes referred to as incompatible resin) are used. Can do.

  The reflectance of the white film at a wavelength of 550 nm is preferably 95% or more, more preferably 96% or more, and particularly preferably 97% or more. The white film may be a single layer film or a laminated film. Laminated film composed of a layer containing a relatively large amount of voids (reflective layer) and a layer containing a relatively small amount of voids or a layer containing no voids (support layer) from the viewpoint of obtaining high reflectivity and mechanical strength Is preferred. Moreover, as a thermoplastic resin which comprises a film, polyester, polyolefin, a polystyrene, and an acryl can be mentioned, for example, Polyester is preferable from a viewpoint of obtaining the white film excellent in a mechanical characteristic and thermal stability.

(polyester)
When using polyester as a thermoplastic resin of a white film, it is preferable to use polyester which consists of a dicarboxylic acid component and a diol component as polyester. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, and sebacic acid. Examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol.

  Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. Polyethylene terephthalate may be a homopolymer, but a copolymer is preferred. In particular, when a laminated white film composed of a layer containing a relatively large amount of voids and a layer containing a relatively small amount of voids or a layer containing no voids is used as the white film, a layer containing a relatively large amount of voids The polyester used for is preferably a copolymer. In this case, the ratio of the copolymerization component is, for example, 3 to 20 mol%, preferably 4 to 15 mol%, more preferably 5 to 13 mol%, based on 100 mol% of all dicarboxylic acid components. By setting the proportion of the copolymer component within this range, excellent film forming properties can be obtained even for a layer containing a relatively large amount of voids. Moreover, the laminated film excellent in thermal dimensional stability can be obtained.

(Coloring agent, void forming agent)
When inorganic particles are used as the colorant or 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 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 is preferably 25 to 55% by mass, more preferably 30 to 50% by mass based on the mass of the white film. By using such inorganic particles, it becomes easy to achieve a preferable reflectance. In addition, it can be dispersed moderately in the polyester, making it difficult for particles to aggregate and producing a film without coarse protrusions. At the same time, the surface of the film is not too rough and the gloss level is controlled within an appropriate range. can do. 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.

  When organic particles are used as the colorant or void forming agent, resin particles that are incompatible with polyester are used as the organic particles. As the organic particles, silicone resin particles, polystyrene resin particles, and polytetrafluoroethylene particles are preferable. The average particle diameter of the organic particles is, for example, 0.2 to 10 μm, preferably 0.3 to 8.0 μm, and more preferably 0.4 to 6.0 μm. The content is preferably 25 to 55% by mass, more preferably 30 to 50% by mass based on the mass of the white film. By using such organic particles, it becomes easy to achieve a preferable reflectance. In addition, it can be dispersed moderately in the polyester, making it difficult for particles to aggregate and producing a film without coarse protrusions. At the same time, the surface of the film is not too rough and the gloss level is controlled within an appropriate range. can do. The organic particles may have any particle shape, for example, a plate shape or a spherical shape.

  Further, when an incompatible resin is used as the colorant or void forming agent, the incompatible resin is preferably polyolefin or polystyrene. The content is preferably 25 to 55% by mass, more preferably 30 to 50% by mass based on the mass of the white film. By using such an incompatible resin, it becomes easy to achieve a preferable reflectance. In the case of an incompatible resin, if the content is too large, the bending moment tends to be too low.

[Bead layer]
The reflective film of the present invention has a bead layer comprising a coating film and spherical particles on the surface of a white film. Then, the spherical particles are held by the coating film, and the white film surface is covered.

<Spherical particles>
Here, the spherical particles refer to particles having a major axis / minor axis of 1.3 or less. The spherical particles in the present invention are preferably nonporous. By being nonporous, it is possible to enhance the effect of suppressing breakage of particles and dropout of some of them. Moreover, the improvement effect of a reflectance can be made high.

(S10 strength)
The spherical particles in the present invention preferably have an S10 strength of 5.8 to 23.6 N / mm ² (0.6 to 2.4 kgf / mm ² ). When S10 intensity | strength exists in the said numerical range, the damage to a light-guide plate can be suppressed. At the same time, the effect of suppressing particle dropout can be increased. Moreover, the improvement effect of sticking suppression with a light-guide plate can be heightened. When S10 intensity | strength is too low, it exists in the tendency for the inhibitory effect of particle fall-off to become low. Moreover, it exists in the tendency for sticking to a light-guide plate to produce easily. On the other hand, when it is too high, the light guide plate is scraped and damaged when it comes into contact with the light guide plate. From such a viewpoint, the S10 strength is preferably 7.8 to 19.6 N / mm ² (0.8 to 2.0 kgf / mm ² ), more preferably 8.8 to 17.7 N / mm ² (0 .9 to 1.8 kgf / mm ² ). The S10 strength of the spherical particles can be achieved by adjusting the degree of polymerization and the degree of crosslinking of the particles. For example, in the same type of particles, the S10 strength tends to increase when the degree of polymerization or the degree of crosslinking is increased.

  As the type of spherical particles, for example, organic spherical particles such as crosslinked acrylic particles, crosslinked silicone particles, crosslinked styrene particles, and crosslinked nylon particles can be used, and crosslinked nylon particles are particularly preferable. These are preferable because the S10 strength can be appropriately increased by using a highly crosslinked product. Inorganic particles have too high S10 strength, and elastomers have too low S10 strength. The spherical particles preferably have a light transmittance of 50% or more, preferably 60% or more, more preferably 70% or more, and preferably have no light absorption in the visible region. . By setting it as such an aspect, it will reduce that the reflectance of a white film will become low, and the improvement effect of the reflectance of a reflective film can be made high.

(Average particle size)
The lower limit of the average particle diameter of the spherical particles is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 4 μm or more, and particularly preferably 5 μm or more. Thereby, aggregation of the spherical particles in the bead layer can be suppressed, generation of streaky coating defects during coating can be suppressed, and the effect of suppressing particle dropout can be enhanced. Further, by increasing the average particle diameter, it is easy to maintain a gap between the light guide plate and the effect of suppressing sticking to the light guide plate can be increased. On the other hand, the upper limit of the average particle diameter is preferably 100 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, and particularly preferably 20 μm or less. Thereby, the inhibitory effect of particle omission can be made high. Further, when the gap becomes too large, the luminance tends to decrease.

(Coverage)
The reflective film of this invention has the bead layer which consists of a coating film and a spherical particle on the surface of a white film, and becomes a mode by which the spherical particle has coat | covered the white film surface by this. The coating with the spherical particles has a coverage of 2 to 45%, preferably 5 to 40%, more preferably 10 to 35%, still more preferably 10 to 30%, and particularly preferably 10 to 20%, as defined later. It means that the surface of the white film is coated at a rate. When the coverage is within such a range, the effect of the bead layer can be obtained without significantly reducing the reflectance and luminance. If the coverage is less than 2%, the gap between the light guide plate and the reflective film cannot be maintained, and there is a possibility that luminance unevenness occurs due to contact or sticking between the light guide plate and the reflective film. Further, the friction between the light guide plate and the reflective film tends to increase, and the light guide plate is easily scratched. On the other hand, when the coverage is 45% or more, the presence of too many spherical particles on the surface of the reflective film may reduce the reflectivity of the reflective film, which may reduce the brightness of the display device. The coverage can be adjusted by adjusting the size and content of the spherical particles in the bead layer, and the coverage tends to increase when the size is increased or the content is increased.

  In the present invention, the coverage ratio is obtained by observing a cross section of a measurement area having a total length of 6 mm in a measurement area having a length of 3 mm in each of two orthogonal directions within the film plane, and the spherical film covers the surface of the white film in the measurement area. Is defined as the percentage of

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 perpendicular to the one direction randomly selected in 1 and the thickness direction is a cut surface, and the bead layer surface has a length of 3 mm in the section of section sample 1; In the cross section of the slice sample 2, the measurement area of 6 mm in total with the 3 mm length of the bead layer surface was observed at a magnification of 3000 times using a Hitachi S-4700 field emission scanning electron microscope. In the measurement region in the cut surface of the sample, the lengths of the portions of the film surface not covered with the spherical particles (reference numeral 201 in FIG. 1) are integrated and obtained by the following formula ( Reference 1).
Coverage ratio = (6 mm− (integrated length of the portion not coated with spherical particles (mm))) / 6 mm × 100 (%)

  In addition, when the maximum diameter portion of the spherical particles is outside the coating film surface (reference numeral 203 in FIG. 1) on the cut surface, the portion covered with the maximum diameter of the spherical particles is covered with the spherical particles. Considering (for example, reference numerals 103 and 105 in FIG. 1), when the maximum diameter portion of the spherical particles is inside the coating film surface, that is, when the spherical particles are sinking in the coating film, out of the spherical particles from the coating film surface. It is assumed that the maximum diameter of the dome-shaped protrusion formed by the portion protruding in the region is covered with particles (for example, reference numeral 102 in FIG. 1). At this time, spherical particles satisfying the exposure rate described later are considered to be coated, and even if there are spherical particles not satisfying the exposure rate, they are regarded as uncoated (for example, reference numeral 101 in FIG. 1). 104).

(Exposure rate)
In the calculation of the coverage in the present invention, the spherical particles treated as covering the surface of the white film are those in which part or all of the spherical particles are exposed on the surface of the reflective film. This exposure refers to exposure at an exposure rate of 1% or more as defined by the present invention. Thus, spherical particles with an exposure rate of less than 1% are not treated as coated particles.

  The spherical particles are supported by a coating film provided on the surface of the white film in order to support the spherical particles on the surface of the white film. For this reason, some spherical particles are in contact with the coating film or sinking. The exposure rate of 100% corresponds to the situation where the white film surface and the spherical particle surface are in contact with each other on the cut surface, and the surface of the white film is supported by the coating film. The exposure rate of 0% is the white film on the cut surface. The spherical particles are completely submerged in the coating film provided on the surface, and the exposure rate of 50% is that at the cut surface, half of the spherical particles are present in the coating film provided on the white film surface. It is buried and the other half is protruding from the coating film.

  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 spherical particle in the cut surface of the slice sample and perpendicular to the coating surface of the film. Of the two points that intersect the surface of the spherical particle in the cut surface, S is the point on the exposed surface, T is the point on the unexposed surface, and the straight line intersects the coating surface. When the point is B, it is expressed 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 spherical 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, similarly to the above-described coverage, when the measurement area is 3 mm in length in each of the two orthogonal directions in the film plane and the measurement area is 6 mm in total, the exposure of each spherical particle in the measurement area The average value of the rate (average exposure rate, when calculating the average value does not include exposure rate of 0% or less) is 5 to 80%. When in this range, a gap with the light guide plate can be ensured, and at the same time, dropout of particles can be suppressed. When the average exposure rate is too low, it is difficult to secure a gap, while when it is too high, it is difficult to suppress particle dropout. From such a viewpoint, the average exposure rate is preferably 20 to 80%, more preferably 50 to 80%, still more preferably 60 to 80%.

<Coating film>
(Coating hardness)
The coating film in the present invention has a hardness of 96.0 to 225.4 N / mm ² (9.8 to 23 mgf / μm ² ) determined by a micro hardness tester. When the hardness of the coating film is in the above numerical range, the falling off of the spherical particles can be suppressed. When the hardness of the coating film is too low, the dropping of the particles cannot be suppressed. From such a viewpoint, the hardness of the coating film is preferably 112.7 N / mm ² or more (11.5 mgf / μm ² or more), more preferably 137.2 N / mm ² or more (14 mgf / μm ² or more). . On the other hand, when the hardness is too high, it is not possible to prevent the particles from falling off. Moreover, the improvement effect of suppression of the damage of a light-guide plate will become low. From such a viewpoint, the hardness of the coating film is preferably 196.0 N / mm ² or less (20 mgf / μm ² or less), more preferably 186.2 N / mm ² or less (19 mgf / μm ² or less).

  The method for achieving the hardness of the coating film as described above is not particularly limited, but can be achieved by adjusting the glass transition temperature Tg of the binder constituting the coating film and the crosslinking agent. For example, increasing the Tg of the binder tends to increase the hardness of the coating film. Moreover, hardness can be hardened by adding a crosslinking agent to a coating film and forming a crosslinked structure in a coating film. In that case, by adjusting the content ratio of the binder and the crosslinking agent in the coating film, that is, the ratio of the reactive group in the binder and the crosslinking group in the crosslinking agent, a more preferable hardness of the coating film can be easily obtained.

(binder)
The coating film in the present invention is formed from a composition containing a binder. Then, the spherical particles are supported on the white polyester film by such a coating film and cover the surface of the white film. By setting it as such an aspect, it becomes easy to make a covering rate and an exposure rate into an appropriate range, and can also suppress the omission of spherical particles.

  As this binder, an acrylic resin, a polyester resin, a polyurethane resin, a polyesteramide resin, a polyolefin resin, a copolymer or a blend thereof can be used. Such a binder preferably has a reactive group. Such a reactive group is not particularly limited as long as it can react with a crosslinking group possessed by a crosslinking agent described later, and examples thereof include a hydroxyl group, an amide group, and a methylol group. Among these, from the viewpoint of being able to improve the effect of suppressing particle dropout, and excellent in long-term adhesion with the reflective film surface, and optical properties, an acrylic resin is preferable as a binder, and a hydroxyl group is preferable as a reactive group, In particular, an acrylic resin having a hydroxyl group is preferably used as the binder.

  Moreover, it is preferable that the glass transition temperature Tg of this binder is 40 degreeC or more. In such an embodiment, the coating film tends to be hard, the coating film hardness specified by the present invention is easily achieved, and the effect of suppressing particle dropout can be increased. From such a viewpoint, the Tg of the binder is more preferably 45 ° C. or higher, and further preferably 50 ° C. or higher.

  The content of the binder in the coating film is preferably 40 to 100% by mass or more, more preferably 40 to 85% by mass, and particularly preferably 50 to 80% by mass or more with respect to the mass of the coating film.

(Crosslinking agent)
The coating film is preferably formed from a composition obtained by further blending a crosslinking agent in addition to the binder described above. That is, the coating film is preferably blended with a crosslinking agent to form a crosslinked structure, which makes it easier to achieve the hardness of the coating film defined by the present invention and improves the effect of suppressing particle dropout. be able to. As such a crosslinking agent, an isocyanate-based, melamine-based, or epoxy-based crosslinking agent is preferable, and among them, an isocyanate-based one is preferable from the viewpoint that a crosslinking reaction can be rapidly performed even at a relatively low temperature.

  Such a crosslinking agent has a crosslinking group. The crosslinking group is not particularly limited as long as it can react with the reactive group of the binder. For example, when the reactive group of the binder is a hydroxyl group, an isocyanate-based crosslinking agent (in this case, the crosslinking group is an isocyanate group) can be preferably employed as the crosslinking agent.

When the crosslinking agent is blended, the blending amount of the molar ratio of the reactive group of the binder to the crosslinking group of the crosslinking agent (crosslinking group / reactive group) is preferably 1-18. If the molar ratio is too low, the crosslinking group in the crosslinking agent may self-react, so that the crosslinking group tends to be insufficient in the crosslinking system, whereby the crosslinking effect is not reduced and the hardness of the coating film is not soft. This tends to reduce the effect of suppressing particle dropout. From such a viewpoint, the molar ratio of the reactive group to the crosslinking group (crosslinking group / reactive group) is more preferably 1.2 or more, further preferably 1.3 or more, and particularly preferably 1.5 or more. What is necessary is just to select the compounding ratio of a binder and a crosslinking agent. On the other hand, if the molar ratio is too high, reactive groups tend to be insufficient in the crosslinking system, and the formation of a crosslinked structure in the coating film becomes central to the self-reaction of the crosslinking agent, thereby sufficiently crosslinking the coating film. Tends to be difficult, the hardness of the coating film tends to be soft, and the effect of suppressing particle dropout is reduced. From such a viewpoint, the molar ratio of the reactive group to the crosslinking group (crosslinking group / reactive group) is more preferably 10 or less, further preferably 8 or less, and particularly preferably 6 or less. What is necessary is just to select the compounding ratio.
The content of the crosslinking agent in the coating film is, for example, preferably 60 to 0% by mass, more preferably 60 to 15% by mass, and particularly preferably 50 to 20% by mass with respect to the mass of the coating film.

(Bead layer configuration)
The content ratio of the spherical particles in the bead layer is preferably 10 to 50% by mass with respect to 100% by mass of the bead layer. Moreover, it is preferable that the content rate of the coating film in a bead layer is 90-50 mass% with respect to 100 mass% of mass of a bead layer. When the content ratio of the spherical particles exceeds 50% by mass, the coating film supporting the spherical particles decreases and the effect of suppressing particle drop tends to be low. On the other hand, when the content is less than 10% by mass, it is difficult to achieve the coverage. There is a tendency, and it tends to be difficult to maintain a gap between the light guide plate and the reflective film. From such a viewpoint, the content ratio of the spherical particles is more preferably 10 to 30% by mass, particularly preferably 10 to 20% by mass, and the content ratio of the coating film is further preferably 90 to 70% by mass, particularly Preferably it is 90-80 mass%.

Moreover, it is preferable that the thickness of the coating film in a bead layer is 20 to 100% of the average particle diameter of spherical particles. With such an aspect, it becomes easy to achieve the exposure rate specified by the present invention. And the inhibitory effect of particle drop-off can be enhanced. From such a viewpoint, the coating film thickness is more preferably 20 to 50%, more preferably 20 to 35%, and particularly preferably 20 to 30% of the average particle diameter of the spherical particles.
Further, in the bead layer or coating film of the present invention, other additives such as particles other than spherical particles, dyes, pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, silane coupling agents, etc. It may be added within a range that does not impede the purpose.

[Production method]
Hereinafter, an example of the method for producing the reflective film of the present invention will be described. In this example, a laminated film is used as the white film. In addition, as a white film, the film marketed with the name of Teijin Tetron UXSP-225 (made by Teijin DuPont Film) can also be used, for example.

The polyester used for the laminated white film is preferably filtered using a nonwoven fabric type filter having an average opening of 10 to 100 μm, preferably an average opening of 20 to 50 μm, and made of stainless steel fine wires having a wire diameter of 15 μm or less. By performing this filtration, it is possible to suppress agglomeration of particles that are usually agglomerated and become coarse agglomerated particles, and to obtain a laminated film with few coarse foreign matters.
The filtered polyester composition is extruded in a multilayer state from a die by a simultaneous multilayer extrusion method using a feed block in a molten state to produce a laminated unstretched sheet.

  The laminated unstretched sheet extruded from the die is cooled and solidified by a casting drum to form a laminated unstretched film. This laminated unstretched film is heated by roll heating, infrared heating or the like, and stretched in the longitudinal direction to obtain a laminated longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The stretching is preferably performed at a temperature equal to or higher than the glass transition point (Tg) of the polyester. The draw ratio in the machine direction (machine axis direction) is preferably 2.2 to 4.0 times, more preferably 2.3 to 3.9 times. If it is less than 2.2 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.0 times, breakage tends to occur during film formation, which is not preferable.

  Subsequently, the laminated film after the longitudinal stretching is sequentially subjected to lateral stretching, heat setting, and thermal relaxation to form a laminated biaxially oriented film. These processes are performed while the film is running. The transverse stretching process starts from a temperature higher than Tg. 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 stretching ratio in the transverse direction (direction perpendicular to the longitudinal direction) is preferably 2.5 to 4.5 times, more preferably 2.8 to 3.9 times, although it depends on the required characteristics of this application. If it is less than 2.5 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.5 times, breakage tends to occur during film formation. Hereinafter, the melting point of polyester is abbreviated as Tm.

  The film after transverse stretching is heat-treated at a temperature of (Tm-100 ° C.) to (Tm-20 ° C.) with a constant width or a decrease in width of 10% or less while lowering both ends to reduce the heat shrinkage rate. Good. When the heat treatment temperature is higher than (Tm−20 ° C.), the flatness of the film is deteriorated, and the thickness unevenness is increased. If it is lower than (Tm-100) ° C., the heat shrinkage rate may increase, which is not preferable. 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.

  As a coating solution for forming a bead layer on the surface of the laminated white film thus prepared, spherical particles, a binder, an optional crosslinking agent and other components are dispersed or dissolved in a solvent. The reflective film of the present invention is obtained by applying a predetermined amount of the liquid using a coating apparatus and drying it in an oven set at a temperature of 70 to 120 ° C., preferably stepwise to form a bead layer. Can do. As the coating apparatus, for example, a die coating apparatus or a gravure roll coating apparatus can be used. As the solvent, methyl ethyl ketone (MEK), ethyl acetate, toluene, or the like can be used. The solid content concentration of the coating liquid is preferably 20 to 50% by mass, which makes it easy to suppress aggregation of spherical particles and increase the effect of suppressing particle dropout.

[Characteristics of reflective film]
(Reflectance)
The reflectance of the 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 reflectance can be achieved, for example, by using a white film as described above and setting the coverage of spherical particles within the range specified by the present invention.

(Bending moment)
The reflective film of the present invention preferably has a bending moment of 176 mN · cm (18 gf · cm) or more. When the bending moment is in the above numerical range, even if the bending moment is used for a large-screen LCD such as a 30-inch type, it is possible to suppress the reflection film from being bent by its own weight. Thereby, the suppression effect of particle drop-off and the suppression effect of damage to the light guide plate can be enhanced. From such a viewpoint, the bending moment is preferably 196 mN · cm (20 gf · cm) or more, more preferably 245 mN · cm (25 gf · cm) or more, and particularly preferably 294 mN · cm (30 gf · cm) or more.
Such a bending moment can be achieved by increasing the thickness of the reflective film or increasing the Young's modulus.

  Hereinafter, the present invention will be 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.

(2) Average particle size of organic particles and inorganic particles of white film The particle size distribution of the particles was obtained 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 spherical 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) Hardness of the coating film The hardness (H) of the coating film was determined by using a micro hardness tester (manufactured by Elionix, ultra-fine indentation hardness tester ENT-1100), and there was no spherical particle in the coating film, only the coating film. When a constant load P (mgf) is applied, the maximum displacement h (μm) of the indenter is measured.
Hardness (H, mgf / μm ² ) = 37.926 × 10 ⁻³ × P / h ²
It was calculated as a value obtained by calculation. In addition, it calculated | required as 1 kgf = 9.8N.
Test temperature: 28 ° C
・ Indenter for testing: Triangular pyramid indenter (ridge interval 115 degrees)
・ Test load: 300mgf
・ Number of divisions: 1000
・ Step interval: 10msec
The said operation was performed with respect to eight different places, and those average values were calculated | required.
In addition, when the maximum displacement amount became more than the thickness of the coating film, the test load was lowered (for example, 100 to 200 mgf) and the measurement was performed so that the maximum displacement amount was less than the thickness of the coating film.

(5) Glass transition temperature Tg of binder
Put 5 ml of the agent (solution) containing the binder in a glass, let it air dry at room temperature, blow off the solvent, and use the solid content of the resulting binder under the following measurement conditions by DSC according to JIS K-7121. It was measured.
[Measurement conditions for glass transition temperature Tg]
・ Sample amount: 10 mg ± 0.2 mg
・ Starting temperature: 20 ℃
・ Limit temperature: 200 ℃
・ Temperature increase speed: 20 ℃ / min
The resulting DSC curve (the differential scanning calorimetry results, the heat flow on the vertical axis and the temperature on the horizontal axis), the straight line with the low temperature side base line extended to the high temperature side, and the step change of the glass transition The temperature at the point of intersection with the tangent drawn at the point where the gradient of the partial curve is maximum was taken as Tg.

(6) S10 Strength The S10 strength of the spherical particles is the amount of deformation of the resin particles when a load of 1 gf is applied to one spherical particle at a constant load speed using a micro compression tester MCTM2000 manufactured by Shimadzu Corporation. The load when the particle diameter is deformed by 10% and the particle radius before compression are expressed by the following formula:
Compressive strength (kgf / mm ² ) = 2.8 × load (kgf) / {π × (particle radius (mm)) ² }
It was calculated as a value obtained by calculation. In addition, it calculated | required as 1 kgf = 9.8N.
[Measurement conditions of compressive strength (S10 strength)]
Sample preparation: Each spherical particle obtained in the following Examples and Comparative Examples was dispersed in ethanol, and then applied to a sample stage and dried to prepare a measurement sample.
Test temperature: Room temperature Test indenter: Flat 50 (flat indenter with a diameter of 50 μm)
・ Test type: Compression test (MODE1)
Test load: 1.00 (gf)
・ Loading speed: 0.072500 (gf / sec)
・ Displacement full scale: 10 (μm)
The above operation was performed on 8 different spherical particles, and the average value thereof was obtained.

(7) Exposure rate of spherical particles (7-1) Preparation of sample Section sample 1 and section sample 2 were cut out from an epoxy-embedded film using a microtome. 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.

(7-2) Measurement About the measurement area of the total length of 6 mm of the area of 3 mm in length of the coating film surface of the binder of the section sample 1 and the area of 3 mm in length of the coating film surface of the binder of the section sample 2 Observation was performed at a magnification of 3000 times using a S-4700 field emission scanning electron microscope manufactured by Seisakusho.
The exposure rate is determined by drawing a straight line passing through the center of the cross section of the spherical particle in the cut surface of the slice sample and perpendicular to the coating surface of the film. Of the two intersecting points, when the point on the exposed side surface is S, the point on the unexposed side surface is T, and the point where the straight line intersects the coating surface of the binder is B, It is expressed 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 spherical 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 6 mm measurement area | region, and the average value was made into the average exposure rate.

(8) Coverage ratio of film surface with spherical particles (8-1) Preparation of sample The sample obtained in the above (7-1) was evaluated.

(8-2) Measurement About a measurement area of a total length of 6 mm including a 3 mm long area of the coating film surface of the binder of the slice sample 1 and a 3 mm long area of the coating film surface of the binder of the slice sample 2, Hitachi Using a scanning electron microscope Schottky emission electron beam system S-4300SE / N, observation was performed at a magnification of 3000 times.
The coverage was obtained from the following formula by integrating the lengths of the film surface portions not covered with the spherical particles in the measurement region in the cut surface of the section sample (see FIG. 1).
Coverage ratio = (6 mm− (integrated length of the portion not coated with spherical particles (mm))) / 6 mm × 100 (%)

(9) Coating thickness A cross section in the thickness direction of a film sample was observed and photographed at a magnification of 3000 times using a Hitachi scanning electron microscope Schottky emission electron beam system S-4300SE / N. The thickness of the coating film was measured in (for example, reference numeral 204 in FIG. 1), and 10 points were arbitrarily measured to obtain an average value thereof.

(10) Evaluation of scratches on light guide plate (evaluation of shaving property) and evaluation of dropout of particles As shown in FIG. 3, a ruler is used as a handle portion (reference numeral 7 in FIG. 3), and the length is 200 mm × width 200 mm × A steel plate having a thickness of 3 mm (reference numeral 8 in FIG. 3, weight of about 200 g) is firmly attached, and a reflective film (reference numeral 9 in FIG. 3) having a width of 250 mm × length of 200 mm is placed on the evaluation surface. Each piece was pasted so that each 25 mm portion 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. Reduced as much as possible.
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 shown, place the reflective film side face down on the light guide plate and place a 1 kg weight (reference numeral 10 in FIG. 3) on it, and fix it 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 spherical particles dropped 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, it was defined as “cannot be scraped” (scratch evaluation ○) if there was no scratch that could be observed with a loupe. On the other hand, when there was a flaw that could be observed, it was defined as “scraping” (scraping evaluation ×).
Further, in the entire range of 400 mm × 200 mm rubbed on the light guide plate, if there was no white foreign matter that could be observed with a magnifying glass, “spherical particles did not drop” (dropping evaluation o). Further, 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 a spherical particle contained in the bead layer. “Particles hardly fall off” (dropping evaluation Δ), and if the number is 6 or more, “spherical particles drop off” (dropping 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.
In the above evaluation, the reflective film was placed in an environment of at least a temperature of 23 ° C. and a relative humidity of 55 RH% for 3 days, and the evaluation was performed after the bead layer was sufficiently stabilized.

(11) White spot evaluation Using the reflective film and light guide plate used in the evaluation of (10) above, place the reflective film on the desk so that the bead layer faces upward, and the dot surface faces downward on it. A light guide plate is placed on each of the four sides of the light guide plate, 200 g weights are placed and fixed, and light is incident from the side of the light guide plate using the backlight light source of LG LED liquid crystal television (LG42LE5310AKR). If there are bright spots other than the light guide plate dots that can be visually observed, 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 ○).

(12) Sticking evaluation Take out the chassis from LG's LED liquid crystal television (LG42LE5310AKR) 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 the same size as the chassis is placed on the bead layer. Was placed upward, and further, a light guide plate and four optical sheets (two diffusion films, one prism, and one DBEF) originally provided in the television were placed thereon. Next, in the plane, place four weights of 500g as shown in FIG. 2 on the area including the most uneven part of the chassis, and visually observe the area surrounded by the four weights. If there was no bright part, it was set as "no sticking" (sticking evaluation (circle)). In addition, if there is an abnormally bright part, place the diffusion sheet originally provided on the TV on the four optical sheets and observe it with the same eye. If there is still an abnormally bright part, “There was sticking” (evaluation ×), and when there was no abnormally bright part, “no sticking” (evaluation Δ). The region surrounded by the four weights was a substantially square of about 15 cm × about 15 cm.

(13) Rigidity (bending moment)
Using a taber type stiffness tester manufactured by Toyo Seiki Seisakusho, hold one end of the short side of the test piece of the size shown below to form a cantilever, then apply a constant load to the opposite end, The bending moment required to bend up to ° was calculated by the following formula: M = 38 × n × K / W. Such measurement was carried out in the longitudinal direction and the transverse direction of the film, and the average value thereof was defined as the rigidity (bending moment) of the film. In addition, it calculated | required as 1 gf = 9,8mN.
Specimen size: length 70mm, width 38mm
M: Bending moment (gf · cm)
n: Scale reading (left and right average)
K: Moment per scale (gf · cm)
W: Specimen width (mm)
Regarding the load, a load of 10 g was applied when the film thickness was 300 μm or less, and a load of 50 g was applied when the thickness was 300 μm or more. When the indicated load scale did not fall within 15 to 85, the load was changed so as to fall within the range.
The K value is as follows depending on the load used. That is, when the load used was 10 g, the K value was 1 gf · cm, when the load was 50 g, the K value was 5 gf · cm, and when the load was 100 g, the K value was 10 gf · cm.

[ Reference Example 1]
A white film with a total thickness of 225 μm (Teijin) composed of two layers, a reflective layer made of a polyester composition containing 47% by mass of barium sulfate particles having an average particle size of 1.37 μm as a void forming agent, and a support layer made of polyester On the reflective layer (reflectance 98.6%) of DuPont Films Teijin Tetron UXSP-225), a coating solution having the composition shown in the following preparation recipe 1 is applied to a wet thickness of 9 g / m. After coating with a coating amount of ² , it was dried in an oven at 80 ° C. to obtain a reflective film.
(Preparation recipe 1, solid concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 (nylon beads, non-porous particles, powder) ... 5.3% by mass
-Acrylic binder: DIC ACRYDIC WBU-305 (Tg 50 ° C., solid content concentration 55% by mass)... 40.1% by mass
-Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL (isocyanate-based crosslinking agent, solid content concentration: 75% by mass) ... 10.3% by mass
Organic solvent: butyl acetate 44.4% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
・ Binder: 63% by mass
・ Crosslinking agent: 22% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 1.2.

[Example 2]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 2, solid concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
-Acrylic binder: DIC Acrydic WBU-305 41.4% by mass
-Cross-linking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HX (isocyanate-based cross-linking agent, solid content concentration: 100% by mass) ... 6.9% by mass
Organic solvent: butyl acetate 46.4% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
・ Binder: 65% by mass
・ Crosslinking agent: 20% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 1.6.

[Example 3]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Liquid preparation recipe 3, solid concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
-Acrylic binder: DIC Acrydic A-817BA (Tg 95 ° C., solid content concentration 50 mass%) 30.1 mass%
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 19.5 mass%
Organic solvent: butyl acetate 45.1% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 43% by mass
・ Crosslinking agent: 42% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[ Reference Example 2 ]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 4, solid concentration 36.0% by mass)
・ Spherical particles: Sekisui Plastics Industry ABX-8 (highly crosslinked acrylic beads, nonporous particles, powder)
... 5.4% by mass
-Acrylic binder: DIC Acrydic A-817BA ... 31% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 20.1% by mass
Organic solvent: butyl acetate 43.5% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 43% by mass
・ Crosslinking agent: 42% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[ Reference Example 3 ]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a wet thickness of 15 g / m ² .
(Preparation recipe 5, solid content concentration 36.0% by mass)
-Spherical particles: Sekisui Plastics Industry ABX-12 (highly crosslinked acrylic beads, non-porous particles, powder) 5.4% by mass
-Acrylic binder: DIC Acrydic A-817BA ... 31% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 20.1% by mass
Organic solvent: butyl acetate 43.5% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 43% by mass
・ Crosslinking agent: 42% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[Example 6]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 6, solid content concentration 36.0% by mass)
-Spherical particles: Sekisui Plastics Industry BM30X-8 (highly crosslinked acrylic beads, non-porous particles, powder) 5.4% by mass
-Acrylic binder: DIC Acrydic A-817BA ... 31% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 20.1% by mass
Organic solvent: butyl acetate 43.5% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 43% by mass
・ Crosslinking agent: 42% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[Example 7]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Liquid preparation recipe 7, solid content concentration 35.0% by mass)
・ Spherical particles: Sumika Enviro Science MW-330 ... 3.5% by mass
-Acrylic binder: DIC Acrydic A-817BA 31.5% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL 21.0% by mass
Organic solvent: butyl acetate 44.0% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 10% by mass
・ Binder: 45% by mass
・ Crosslinking agent: 45% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[Example 8]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 8, solid content concentration 35.0% by mass)
・ Spherical particles: Sumika Enviro Science MW-330 ... 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
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 25% by mass
・ Binder: 38% by mass
・ Crosslinking agent: 37% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[Example 9]
A reflective film was obtained in the same manner as in Example 3 except that the wet thickness was 17 g / m ² .
The physical properties of the obtained reflection film are as shown in Tables 1 and 2.

[Comparative Example 1]
Evaluation was performed without providing a coating layer on the white film in Reference Example 1.

[Comparative Example 2]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a wet thickness of 20 g / m ² .
(Preparation recipe 9, solid concentration 35% by mass)
-Spherical particles: None-Acrylic binder: DIC Acridic A-817BA 35% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 23.3 mass%
・ Organic solvent: butyl acetate 41.7% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 0% by mass
・ Binder: 50% by mass
・ Crosslinking agent: 50% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 5.7.

[Comparative Example 3]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to the coating liquid having the composition shown in the following preparation recipe and the coating liquid was applied at a wet thickness of 20 g / m ² .
(Preparation recipe 10, solid content concentration 35% by mass)
-Spherical particles: None-Acrylic binder: DIC Acrydic WBU-305 ... 47.1 mass%
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 12.1% by mass
Organic solvent: butyl acetate ... 40.8% by mass
The physical properties of the obtained reflection film are as shown in Tables 1 and 2. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 0% by mass
-Binder: 74% by mass
・ Crosslinking agent: 26% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 1.2.

[Comparative Example 4]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 11, solid concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
Acrylic binder: Nippon Shokubai U-Double S2740 (Tg 35 ° C., solid content concentration 50 mass%) ... 59.4 mass%
・ Organic solvent: methyl ethyl ketone: 35.3 mass%
The physical properties of the obtained reflective film are shown in Table 1. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
・ Binder: 85% by mass
・ Crosslinking agent: 0% by mass
Further, the molar ratio (crosslinking group / reactive group) between the reactive group in the binder and the crosslinking group in the crosslinking agent is 0.

[Comparative Example 5]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Preparation recipe 12, solid concentration 35.0% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
Acrylic binder: Nippon Shokubai U Double S2740 ... 51.8% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 5.1% by mass
Organic solvent: methyl ethyl ketone 37.8% by mass
The physical properties of the obtained reflective film are shown in Table 1. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 74% by mass
・ Crosslinking agent: 11% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 0.9.

[Comparative Example 6]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Liquid preparation recipe 13, solid content concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
Acrylic binder: Nippon Shokubai U Double S2740 ... 51.8% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HX ... 3.8% by mass
Organic solvent: methyl ethyl ketone 39.1% by mass
The physical properties of the obtained reflective film are shown in Table 1. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 74% by mass
・ Crosslinking agent: 11% by mass
Moreover, the molar ratio (crosslinking group / reactive group) of the reactive group in the binder and the crosslinking group in the crosslinking agent is 1.4.

[Comparative Example 7]
A reflective film was obtained in the same manner as in Reference Example 1 except that the coating liquid was changed to a coating liquid having the composition shown in the following preparation recipe.
(Liquid preparation recipe 14, solid concentration 35% by mass)
-Spherical particles: Sumika Enviro Science MW-330 ... 5.3 mass%
-Acrylic binder: DIC Acrydic A-817BA 21.7% by mass
・ Crosslinking agent: Nippon Polyurethane Industry Co., Ltd. Coronate HL ... 25.2 mass%
Organic solvent: butyl acetate 47.9% by mass
The physical properties of the obtained reflective film are shown in Table 1. In addition, the solid content ratio of each component in the bead layer obtained from the above recipe is as follows.
・ Spherical particles: 15% by mass
-Binder: 31% by mass
・ Crosslinking agent: 54% by mass
Further, the molar ratio (crosslinking group / reactive group) between the reactive group in the binder and the crosslinking group in the crosslinking agent is 10.

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

101-105 Spherical particle 2 Coating film 201 Portion not covered with spherical particle 202 Portion covered with spherical particle 203 Coating surface 204 Coating thickness 3 White film 4 Chassis 5 Reflective film, light guide plate, lamination of optical sheet Object 6 Weight 7 Handle part 8 Iron plate 9 Reflective film 10 Weight 11 Light guide plate 1101 dots

Claims (5)

A reflective film having a bead layer formed of the coating and the spherical particles to the surface of the white film, S10 strength of the spherical particles are 11.37~23.6N / mm ^2, the microhardness tester of the coating The liquid crystal whose hardness is calculated by 112.7 to 225.4 N / mm ² , the coverage with spherical particles on the white film surface is ² to 45%, and the average exposure rate of spherical particles is 5 to 80%. A reflective film used as a reflective plate on the back surface of a light guide plate in an edge light type backlight unit of a display device .   The reflective film according to claim 1, wherein the coating film is formed from a composition containing a binder and a crosslinking agent.   The reflective film according to claim 2, wherein the binder has a glass transition temperature Tg of 40 ° C. or higher.   In the coating film, the binder has a reactive group, the crosslinking agent has a crosslinking group, and the molar ratio of the reactive group to the crosslinking group (crosslinking group / reactive group) is 1 to 18. The reflective film as described. The reflective film according to any one of claims 1 to 4 , wherein the content of spherical particles in the bead layer is 10 to 50% by mass with respect to 100% by mass of the bead layer.

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