JP5771064B2 - 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

  Since the edge light type backlight unit has a structure in which the light guide plate and the reflection plate are in direct contact as described above, a gap is formed between the light guide plate and the reflection plate in order to suppress in-plane variation in luminance. It is necessary to keep this gap constant. And since a reflecting plate has a bead on the surface, the gap between a light-guide plate and a reflecting plate can be kept constant, and these sticking can be prevented. However, if the beads are too soft as in Patent Documents 1 and 2, it is difficult to keep the gap between the light guide plate and the reflection plate constant, for example, when an excessive external force is applied due to the weight of the optical sheet. Thus, the light guide plate and the reflection plate are easily attached, and if a part of the light guide plate is attached, there is a problem that a so-called adhesion spot is generated in which the brightness of the part in close contact is seen high. In recent years, in order to reduce the cost of the LCD, there is a tendency to reduce the optical sheet provided on the light guide plate. Specifically, the conventional four-sheet configuration (eg, two diffusion films, one prism, DBEF (1 sheet) tends to become a 3 sheet configuration (eg, 2 diffusion films, 1 prism), so that the above adhesion spots tend to be more visible, and a better sticking suppression function is required. Yes.

Further, 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 point defects are likely to occur. Moreover, it becomes difficult to keep the gap between the light guide plate and the reflection plate constant, and adhesion spots are generated as described above. Further, the present inventors only have to adjust the average particle diameter and burial rate of beads as described in Patent Document 3 above, so that the removal of beads and the suppression of white spot defects generated on the LCD screen by the dropped beads can be suppressed. We focused on the fact that it may be insufficient.
Accordingly, an object of the present invention is to provide a reflective film that can suppress damage to the light guide plate, and at the same time, suppress the dropout of particles and highly suppress sticking to the light guide plate.

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 sticking to a light guide plate, scratching of the light guide plate, and dropout of particles 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 coating film, a bead layer containing spherical particles A and particles B on the surface of a white film, the S10 intensity of the spherical particles A being 5.8 to 18.6 N / mm ² , and the S10 intensity of the particles B Is in a range exceeding 18.6 N / mm ² , the particle B is an organic particle, the average particle size of the particle B is smaller than the average particle size of the spherical particle A, and the spherical particle A and the particle B in the bead layer The volume ratio (total volume A of spherical particles A / total volume B of particles B) is 0.2 to 9, and the coverage by the spherical particles A and particles B on the white film surface is 2 to 100%. A reflective film in which the average exposure rate of particles A and the average exposure rate of particles B are 5 to 80%, respectively.
2 . 2. The reflective film as described in 1 above, wherein the spherical particles A have an average particle diameter of 1 to 100 μm.
3 . 3. The reflective film as described in 1 or 2 above, wherein the total content of spherical particles A and particles B in the bead layer is 5 to 80% by mass with respect to 100% by mass of the bead layer.
4 . The reflection film according to any one of 1 to 3 above, wherein the hardness of the coating film determined by a microhardness meter is 96.0 to 225.4 N / mm ² .
5 . 5. The reflective film as described in 4 above, wherein the coating film is formed from a composition containing a binder and a crosslinking agent.
6 . 6. The reflective film as described in 5 above, wherein the binder has a glass transition temperature Tg of 40 ° C. or higher.
7 . In the coating, the binder has a reactive group, the cross-linking agent has a crosslinking group, the molar ratio of the such reactive group crosslinkable group (crosslinking group / reactive group) is described in the above 5 or 6 is 18 Reflective film.
8 . 8. The reflection film as described in any one of 1 to 7 above, which is for a liquid crystal display device.
9 . 9. The reflective film as described in any one of 1 to 8 above, which is for an edge light type backlight unit.

  According to the present invention, in a reflective film having a bead layer containing particles, the reflection that can suppress damage to the light guide plate, and at the same time, suppress the dropout of particles and also highly suppress sticking to the light guide plate. A film can be provided. As a result, when the reflective film of the present invention is used as a reflective plate of a liquid crystal display device, even if a load is applied, or even if the number of optical sheets provided on the front surface of the light guide plate is reduced, adhesion spots are not generated. Can be suppressed. Moreover, the black spot defect resulting from the damage | wound of a light-guide plate can be suppressed. Furthermore, the occurrence of white spot defects due to the falling particles can be suppressed.

  Further, according to another preferable aspect of the present invention, it is possible to provide a reflective film capable of simultaneously suppressing adhesion to a light guide plate, scratching of the light guide plate, and dropout of particles 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 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.

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 composed of a coating film, spherical particles A and particles B on the surface of a white film. And the spherical particle A and particle | grains B are hold | maintained by this coating film, and it becomes the aspect which coat | covers the white film surface.

<Spherical particle A>
The spherical particle A is a particle having a major axis / minor axis = 1.3 or less. The spherical particles A 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 A in the present invention have an S10 strength of 5.8 to 18.6 N / mm ² (0.6 to 1.89 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 the drop-out of the spherical particles A 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. From such a viewpoint, the S10 strength of the spherical particles A is preferably 7.8 N / mm ² or more (0.8 kgf / mm ² or more), more preferably 8.8 N / mm ² or more (0.9 kgf / mm ^2). Above). On the other hand, if it is too high, the light guide plate will be scraped off and easily damaged when it comes into contact with the light guide plate. From such a viewpoint, the S10 strength is preferably 17.7 N / mm ² or less (1.8 kgf / mm ² or less), more preferably 15.7 N / mm ² or less (1.6 kgf / mm ² or less). . The S10 strength of the spherical particles A can be achieved, for example, by adopting organic spherical particles as described below and 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 the spherical particles A, 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. In general, inorganic particles tend to have too high S10 strength, and elastomers tend to have too low S10 strength. As the spherical particles A, organic-inorganic composite spherical particles can also be used. In addition, the spherical particles A may have a light transmittance of 50% or more, preferably 60% or more, more preferably 70% or more, and no absorption of light in the visible region. preferable. 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 A 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 A in the bead layer can be suppressed, the occurrence of streaky coating defects can be suppressed during coating, and the effect of suppressing particle dropout can be increased. 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 of the spherical particles A 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. In addition, the gap between the light guide plate and the reflective film tends to increase, but if it becomes too large, the luminance tends to decrease.

<Particle B>
If the particle | grains B in this invention satisfy | fill the aspect of S10 intensity | strength and average particle diameter which are mentioned later, the kind and shape will not be specifically limited. The particle B may be an organic particle, an inorganic particle, an organic-inorganic composite particle (for example, a surface of an inorganic particle coated with an organic material, a surface of an organic particle coated with an inorganic material, etc. ). Moreover, a spherical shape may be sufficient and a non-spherical shape (lump shape or flat shape) may be sufficient. In order to enhance the effect of suppressing sticking, the shape is preferably spherical, and the degree of the spherical shape is preferably the major axis / minor axis of the particle = 1.3 or less.

(S10 strength)
S10 strength of the particles B in the present invention (greater than 1.90kgf / mm ²⁾ of greater than 18.6N / mm ² range. When S10 intensity | strength exists in the said numerical range, sticking with a reflective film and a light-guide plate can be suppressed, and the adhesion spot by it can be suppressed. When S10 intensity | strength is too low, the effect of sticking suppression will become low and sticking will arise easily when an excessive load is applied. From this point of view, S10 strength of the particles B is preferably 19.6 N / mm ² or more (2.0 kgf / mm ² or higher), more preferably, 21.5N / mm ² or more (2.2 kgf / mm ² Above). Thus, from the viewpoint of sticking suppression, but preferably as S10 strength high particle B, on the other hand, from the viewpoint of the particle to obtain, in reality 98.0N / mm ² or less (10.0 kgf / mm ² or less ). Moreover, when S10 intensity | strength of particle | grains B is low, the improvement effect of the damage suppression of a light-guide plate can further be heightened. Moreover, the improvement effect of drop-off suppression of the particle | grains B can be made high. From such a viewpoint, it is preferably 78.4 N / mm ² or less (8.0 kgf / mm ² or less), more preferably 58.8 N / mm ² or less (6.0 kgf / mm ² or less), and particularly preferably 39. 2 N / mm ² or less (4.0 kgf / mm ² or less). In order to satisfy the S10 strength of the particle B, particles having such an S10 strength may be selected. For example, when organic particles are employed as the particle B, this is achieved by adjusting the degree of polymerization and the degree of crosslinking. can do. 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 the particles B, for example, organic spherical particles such as crosslinked acrylic particles, crosslinked silicone particles, crosslinked styrene particles, and crosslinked nylon particles, and inorganic particles such as barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate are used. it can. Among these, since it is easy to achieve the S10 strength, crosslinked styrene and crosslinked nylon are preferred, and crosslinked acrylic particles are particularly preferred. In addition, the particle B may have a light transmittance of 50% or more, preferably 60% or more, and more preferably 70% or more, and preferably has 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 particle B needs to have an average particle size smaller than the average particle size of the spherical particles A. By setting it as such an aspect, the probability of the particle | grains B which contact a light guide plate in a normal state can be made low, and, thereby, the damage of a light guide plate can be suppressed. From such a viewpoint, the average particle diameter of the particles B is preferably smaller than the average particle diameter of the spherical particles A by, for example, 0.5 μm or more, preferably 1.0 μm or more, and preferably 1.5 μm or more. More preferably, it is further preferably smaller than 2.0 μm.

  The lower limit of the average particle diameter of the particles B is preferably 0.1 μm or more, more preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 2 μm or more, and particularly preferably 4 μm or more. Thereby, sticking with a light guide plate can be suppressed and sticking with a light guide plate can be suppressed, for example, even when an excessive external force is applied. Furthermore, the aggregation of the particles B in the bead layer can be suppressed, and the occurrence of streaky coating defects can be suppressed during coating.

  The upper limit of the average particle size of the particles B is determined by the difference in average particle size from the spherical particles A, but is preferably 100 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, and particularly preferably 20 μm or less. is there. Thereby, as described above, the improvement effect of suppressing damage to the light guide plate can be increased, and the effect of suppressing particle dropout can be increased.

<Coverage>
The reflective film of the present invention has a bead layer composed of a coating film, spherical particles A and particles B on the surface of a white film, whereby the spherical particles A and particles B cover the white film surface. The coverage with the spherical particles A and the particles B is 2 to 100%, preferably 5 to 95%, more preferably 10 to 90%, still more preferably 10 to 80%, and particularly preferably 10 to 50 in terms of coverage defined later. The aspect which coat | covers the white film surface with the coverage of% is preferable. When the coverage is within such a range, the effect of the bead layer can be suitably achieved. 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 risk that contact spots between the light guide plate and the reflective film will be caused by sticking. Further, the friction between the light guide plate and the reflective film tends to increase, and the light guide plate is easily scratched. In addition, the coverage is preferably higher from the viewpoint of securing a gap and suppressing sticking, but if it is too high, the reflectance of the white film tends to decrease, thereby reducing the luminance in the display device. There is a tendency. The coverage can be adjusted by adjusting the size and content of the spherical particles A and particles B in the bead layer, and the coverage tends to increase when the size is increased or the content is increased. is there.

  In the present invention, the covering ratio is obtained by observing a cross section of a measurement area having a total length of 6 mm in each measurement area having a length of 3 mm in two orthogonal directions in the film plane. B (hereinafter, these may be collectively referred to as “particles”) is defined as the ratio of coating.

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 within the cut surface of the sample, the lengths of the portions of the film surface not covered with particles (reference numeral 201 in FIG. 1) are integrated and determined by the following equation (FIG. 1). Irradiation).
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 particle | grains has come out outside the coating-film surface (code | symbol 203 of FIG. 1) in a cut surface, it considers that the part covered with the largest particle diameter is covered with particle | grains (for example, 1, when the maximum diameter portion of the particle is inside the coating film surface, that is, when the particle is sinking in the coating film, the portion of the particle that protrudes outside the coating film surface 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 covering the surface of the white film are partly or entirely 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, particles with an exposure rate of less than 1% are not treated as coated particles.

  Spherical particles A and particles B are supported by a coating film provided on the surface of the white film in order to hold these particles on the surface of the white film. For this reason, some of the particles are in contact with the coating film or sink. The exposure rate of 100% corresponds to the situation where the white film surface and the particle surface are exposed in contact with each other on the cut surface, and the exposure rate is 0%. The particles are completely submerged in the coating film provided on the white film surface, and the exposure rate of 50% is such that half of the particles are present in the coating film provided on the white film surface at the cut 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 that passes through the center of the cross section of the particle in the cut surface of the slice sample and goes perpendicular to the coating surface of the film. Of the two points that intersect the surface of the particle in the plane, S is the point on the exposed surface, T is the point on the unexposed surface, and the point where the straight line intersects the coating surface. When 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 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 has a total length of 6 mm, the spherical particles A are exposed in the measurement area. The average value of the rate (referred to as the average exposure rate. When calculating the average value, the exposure rate of 0% or less is not included) is 5 to 80%. When in this range, a gap with the light guide plate can be secured, and the effect of suppressing sticking is excellent. At the same time, dropping of the spherical particles A can be suppressed. When the average exposure rate is too low, it is difficult to secure a 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 spherical particles A is preferably 20 to 80%, more preferably 50 to 80%, still more preferably 60 to 80%.

  Moreover, the average exposure rate of the particle | grains B calculated | required similarly is 5 to 80%. By being in this range, it is excellent in the effect of suppressing sticking to the light guide plate. For example, even when an excessive load is applied, sticking to the light guide plate can be suppressed. And thereby, adhesion spots can be suppressed. Further, the falling off of the particles B can be suppressed. When the average exposure rate is too low, the effect of suppressing sticking tends to be low. 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 B 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 preferably 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 a coating film exists in the said numerical range, the inhibitory effect of particle drop-off can be made high. When the hardness of the coating film is too low, the effect of suppressing particle dropout is reduced. From such a viewpoint, the hardness of the coating film is more preferably 112.7 N / mm ² or more (11.5 mgf / μm ² or more), and still more preferably 137.2 N / mm ² or more (14 mgf / μm ² or more). is there. On the other hand, when the hardness is too high, the effect of suppressing particle dropout is also reduced. 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 more preferably 196.0 N / mm ² or less (20 mgf / μm ² or less), and still 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 described later 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 A and the particles B are supported on the white polyester film with such a coating to cover the surface of the white film. By setting it as such an aspect, it becomes easy to make a coverage and an exposure rate into an appropriate range, and omission of spherical particle A and particle B can be controlled.

  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 as defined by the present invention, and the effect of suppressing particle dropout. Can be improved. 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 (total content ratio) of spherical particles A and particles B in the bead layer is preferably 5 to 80% 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 95-20 mass% with respect to 100 mass% of mass of a bead layer. When the content ratio of the spherical particles A and the particles B exceeds 80% by mass, the coating film that supports the spherical particles A and the particles B tends to decrease, and the effect of suppressing the drop-off of particles tends to be low. If the content ratio is less than 5% by mass, the coverage tends to be difficult to achieve, and it tends to be difficult to maintain the gap between the light guide plate and the reflective film. From such a viewpoint, the content ratio of the spherical particles A and the particles B is more preferably 10 to 70% by mass, particularly preferably 10 to 60% by mass, and the content ratio of the coating film is more preferably 90 to 30%. It is 90 mass%, Most preferably, it is 90-40 mass%.

  Further, the volume ratio of the spherical particles A and the particles B in the bead layer (the total volume A of the spherical particles A / the total volume B of the particles B) is preferably 0.1 to 9. When the volume ratio is in the above range, the improvement effect of suppressing damage to the light guide plate can be increased, and the improvement effect of suppressing sticking can be increased. If the volume ratio is smaller than 0.1, the effect of improving the suppression of damage to the light guide plate tends to be low. On the other hand, when it is higher than 9, the effect of improving sticking suppression tends to be low. From such a viewpoint, the volume ratio is more preferably 0.2 to 8, still more preferably 0.3 to 7, and particularly preferably 0.4 to 6.

  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 the spherical particles A. 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 60% of the average particle diameter of the spherical particles A, more preferably 20 to 50%, still more preferably 20 to 35%, and particularly preferably 20 to 30%. preferable.

  The aspect that the thickness of the coating film in the bead layer is in the range of 20 to 95% with respect to the average particle diameter of both the spherical particles A and the particles B is preferable. With such an embodiment, it becomes easier to achieve the exposure rate defined by the present invention. And the inhibitory effect of particle dropout can be further enhanced. From such a viewpoint, the coating film thickness is more preferably in the range of 20 to 50% with respect to any average particle diameter of the spherical particles A and the particles B, and is in the range of 20 to 45%. Is more preferable, and the aspect which is 20 to 40% of range is especially preferable.

  Further, in the bead layer or coating film in the present invention, other additives such as particles other than spherical particles A and particles B, dyes, pigments, fluorescent brighteners, ultraviolet absorbers, antioxidants, silane coupling agents, etc. May be added as long as the object of the present invention is not impaired.

[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 liquid for forming a bead layer on the surface of the laminated white film thus prepared, spherical particles A, particles B, a binder, an optional cross-linking agent and other components are dispersed in a solvent or By applying a predetermined amount of the dissolved coating solution using a coating apparatus and drying it in an oven set at a temperature of 70 to 120 ° C., preferably stepwise, a bead layer is formed. A film can be obtained. 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, and it becomes easy to suppress the aggregation of the spherical particles A and the particles B, so that the effect of suppressing the particle dropout can be enhanced.

[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 A and particles B Using a 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, about the particle | grains A, when it was other than spherical shape, it calculated | required by (long diameter + short diameter) / 2. In addition, for the particles B, when the particles were not spherical, the area B equivalent diameter was obtained.

(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 A and B is a resin 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 deformation amount and load of the particles are measured, and 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 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 particles, and the average value was obtained.

(7) Particle exposure rate (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 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 coating surface of the film. Of the two points, S is the point on the exposed surface, T is the point on the unexposed surface, and B is the point where the previous straight line intersects the coating surface of the binder (S (Distance between 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.

(8) Coverage ratio of film surface with 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 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 (%)

(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, 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 ×).
Moreover, after 15 reciprocating movements, if there was no white foreign matter that could be observed with a magnifying glass in the entire range of 400 mm × 200 mm rubbed on the light guide plate, it was defined as “spherical particles do not fall off” (dropout evaluation ○). 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, and 200 g weights are placed and fixed. Using a backlight light source of LG LED liquid crystal television (LG42LE5310AKR), light is incident from the side of the light guide plate, If there were bright spots other than light guide plate dots that could be observed visually, white spots were 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) Adhesion spots evaluation (adhesion evaluation)
Take out the chassis from the LG 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 it, a reflective film of approximately the same size as the chassis, with the bead layer facing upward Furthermore, a light guide plate and three optical sheets (two diffusing films and one prism) originally provided in the television were placed thereon. Next, an equilateral triangular base (reference numeral 601 in FIG. 2) having three circular legs with a diameter of 5 mm as shown in FIG. 2 is placed in the area including the most severe part of the unevenness of the chassis in the plane. An additional 20 kg weight (reference numeral 602 in FIG. 2) is placed on the top, and the region surrounded by the three legs is visually observed. If there is no abnormally bright part, “no adhesion spots” (adhesion spots evaluation) ○). 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.

(13) Volume ratio of spherical particles A and particles B A reflective film of 3 cm × 3 cm was cut out, and the bead layer coated on the surface of the reflective film was completely dissolved with 1000 cc of methyl ethyl ketone (MEK). Next, 10 cc was collected from the obtained MEK solution, diluted 100 times to 1000 cc, and further 10 cc was collected therefrom. In this operation, a sample was taken from a state in which particles derived from the bead layer were uniformly dispersed in the MEK solution. The obtained MEK solution of the bead layer was applied and dried on the sample stage of the micro compression tester MCTM2000 used in the above (6) to prepare a measurement sample. Subsequently, S10 intensity | strength is measured by the method of said (6) about all the particles in a sample stand, and what has S10 intensity | strength in the range of 5.8-18.6 N / mm < ² > is determined as the spherical particle A, Particles having an S10 intensity exceeding 18.6 N / mm ² were determined as particles B. In addition, even if S10 intensity | strength was in the range of 5.8-18.6 N / mm < ² >, what did not satisfy | fill spherical requirements was not set as the spherical particle A. FIG. When measuring the S10 intensity, the particle diameter of each particle read by the above apparatus is recorded, and the total particle diameter (total particle diameter) of each of the spherical particles A and the particles B is obtained from the particle diameters of the obtained particles. ) And the ratio of the cube of the total particle diameter of the spherical particles A to the cube of the total particle diameter of the particles B (the cube of the total particle diameter of the spherical particles A / the cube of the total particle diameter of the particles B) The volume ratio of the spherical particles A and the particles B was obtained.

(14) 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.

[Bead layer components]
Spherical particles A1: Sumika Enviro Science MW-330 (nylon beads, non-porous particles, powder)
Spherical particle A2: Sekisui Plastics Industry BM30X-8 (cross-linked acrylic beads, nonporous particles, powder)
Spherical particles A3: Sekisui Plastics ABX-15 (cross-linked acrylic beads, nonporous particles, powder)
Spherical particles A4: Sekisui Plastics ARX-15 (cross-linked acrylic beads, nonporous particles, powder)
Spherical particle A5: Ganz Kasei Co., Ltd. GPA-550 (nylon 12 beads, non-porous particles, powder)
Spherical particle A6: Sekisui Plastics ARX-806 (cross-linked acrylic beads, nonporous particles, powder)
Particle B1: Sekisui Plastics Industry MBX-5 (cross-linked acrylic beads, nonporous particles, powder)
Particle B2: Gantz Kasei Co., Ltd. GS0605 (crosslinked polystyrene, nonporous particles, powder)
Particle B3: Nippon Shokubai Co., Ltd. MA-1010 (cross-linked acrylic beads, nonporous particles, powder)
Particle B4: Sekisui Plastics Industry EXM-12 (cross-linked acrylic beads, nonporous particles, powder)
Particle B5: Sekisui Plastics Industry BM30X-5 (cross-linked acrylic beads, nonporous particles, powder)
Binder C1: DIC ACRYDIC A-817BA (acrylic binder, Tg 95 ° C., solid content concentration 50 mass%)
Binder C2: DIC ACRYDIC WBU-305 (acrylic binder, Tg 50 ° C., solid content concentration 55% by mass)
Binder C3: Nippon Shokubai U Double S2740 (acrylic binder, Tg 35 ° C., solid content concentration 50 mass%)
Binder C4: DIC Acrydic A-807BA (acrylic binder, Tg 65 ° C., solid content concentration 50 mass%)
Cross-linking agent D1: Nippon Polyurethane Industry Co., Ltd. Coronate HL (isocyanate-based cross-linking agent, solid concentration 75% by mass)
Cross-linking agent D2: Nippon Polyurethane Industry Co., Ltd. Coronate HX (isocyanate-based cross-linking agent, solid concentration 100% by mass)

[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 with a wet thickness of 8 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 A1 ... 1.1% by mass
-Particle B1 ... 1.1 mass%
-Acrylic binder C1 32.9% by mass
・ Crosslinking agent D1 21.9% by mass
Organic solvent: butyl acetate 43.1% 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 A1: 3% by mass
-Particle B1: 3% by mass
-Binder C1: 47% by mass
・ Crosslinking agent D1: 47% 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 2 to 4, Comparative Examples 2-10, Reference Example 1]
A reflective film was obtained in the same manner as in Example 1 except that the preparation recipe and the wet coating thickness were changed so that the composition of the bead layer and the coating thickness of the bead layer were as shown in Tables 1 and 2. The physical properties of the obtained reflection film are shown in Tables 1 and 2.

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

  In Comparative Example 6, each measurement value was obtained with Sekisui Plastics Industry BM30X-5 as particle B.

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

101-105 Spherical particle A or particle B
DESCRIPTION OF SYMBOLS 2 Coating film 201 The part which is not coat | covered with particle | grains 202 The part which is coat | covered with particle | grain 203 Coating film surface 204 Coating film thickness 3 White film 4 Chassis 5 Laminated film of reflective film, light guide plate, optical sheet 601 Equilateral triangle type base 602 Weight 7 Handle part 8 Iron plate 9 Reflective film 10 Weight 11 Light guide plate 1101 dots

Claims (9)

A reflective film having a coating film, a bead layer containing spherical particles A and particles B on the surface of a white film, the S10 intensity of the spherical particles A being 5.8 to 18.6 N / mm ² , and the S10 intensity of the particles B Is in a range exceeding 18.6 N / mm ² , the particle B is an organic particle, the average particle size of the particle B is smaller than the average particle size of the spherical particle A, and the spherical particle A and the particle B in the bead layer The volume ratio (total volume A of spherical particles A / total volume B of particles B) is 0.2 to 9, and the coverage by the spherical particles A and particles B on the white film surface is 2 to 100%. A reflective film in which the average exposure rate of particles A and the average exposure rate of particles B are 5 to 80%, respectively. The reflective film according to claim 1, wherein the spherical particles A have an average particle diameter of 1 to 100 μm. The reflective film according to claim 1 or 2 , wherein the total content of the spherical particles A and the particles B in the bead layer is 5 to 80% by mass with respect to 100% by mass of the bead layer. Reflective film according to any one of claims 1 to 3 hardness obtained by microhardness meter coating is 96.0~225.4N / mm ^2. The reflective film according to claim 4 , wherein the coating film is formed from a composition containing a binder and a crosslinking agent. The reflective film according to claim 5 , wherein the binder has a glass transition temperature Tg of 40 ° C. or higher. In the coating, the binder has a reactive group, the cross-linking agent has a crosslinking group, the molar ratio of the such reactive group crosslinkable group (crosslinking group / reactive group) in claim 5 or 6 is 18 The reflective film as described. Reflective film according to any one of claims 1 to 7 which is a liquid crystal display device. The reflective film according to any one of claims 1 to 8 , which is used for an edge light type backlight unit.