WO2015020223A1 - White reflective film - Google Patents

Abstract

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

Description

White reflective film

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

A backlight unit of a liquid crystal display device (LCD) includes a direct type having a light source on the back of the liquid crystal display panel and a reflective film on the back, and a light guide plate having a 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 of the light guide plate. Conventionally, as a backlight unit used for a large LCD, a direct type (mainly direct type CCFL) is mainly used from the viewpoint of excellent brightness of a screen and uniformity of brightness in the screen. The type was often used for relatively small LCDs such as notebook PCs, but 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. As a result, edge-light type backlight units have been used not only in relatively small but large LCDs. This is because there is a merit that the LCD can be thinned.
In the edge light type backlight unit, the light guide plate and the reflective film are in direct contact with each other. Therefore, if the light guide plate and the reflective film are attached in such a structure, there is a problem that the luminance of the attached portion becomes abnormal and in-plane variation in luminance occurs. Therefore, it is necessary to have a gap between the light guide plate and the reflective film and keep this gap constant. For example, by having beads on the surface of the reflective film, the gap between the light guide plate and the reflective film can be kept constant, and sticking of these can be prevented. However, at this time, when the light guide plate made of a relatively soft material comes into contact with the reflective film, there is a problem that the light guide plate is damaged by the reflective film or the beads on the surface. As countermeasures, for example, as in Patent Documents 1 to 3, there is a report of forming a scratch-preventing layer containing elastomeric beads on the surface of a reflective film by coating.
However, the scratch-preventing layers as described in Patent Documents 1 to 3 tend to be inferior in securing the gap (inhibiting sticking), which is the original purpose, although there is a certain degree of scratch-suppressing effect on the light guide plate. In addition, according to the study by the present inventors, only focusing on the number of protrusions as in the prior art satisfies both the suppression of sticking to the light guide plate and the suppression of scratches on the light guide plate that are required in recent years. It was found that there are cases where it is insufficient.
JP 2003-92018 A Special table 2008-512719 gazette JP 2009-244509 A

The objective of this invention is providing the white reflective film which can fully suppress sticking with a light-guide plate, and can fully suppress the damage | wound of a light-guide plate simultaneously.
The present invention adopts the following configuration in order to solve the above problems.
1. A white reflective film having a reflective layer A and a surface layer B made of a resin composition containing particles,
The surface layer B has protrusions formed of the particles on the surface opposite to the reflective layer A, and the number of protrusions having a height of 5 μm or more on the surface is 10 ⁴ to 10 ¹⁰ / m ² ;
The white reflective film, wherein the particles are non-spherical particles having an average particle diameter of 3 to 100 μm and a 10% compressive strength of 0.1 to 15 MPa.
2. 2. The white reflective film as described in 1 above, wherein the particles are ground polymer particles obtained by grinding a polymer.
3. 3. The white reflective film as described in 2 above, wherein the polymer is polyester.
4). The particles are non-spherical particles having an average aspect ratio (major axis / minor axis) of 1.31 or more and 1.80 or less, and a standard deviation of the aspect ratio of 0.15 to 0.50. 4. The white reflective film as described in any one of 1 to 3 above.
5. 4. The white reflective film as described in any one of 1 to 3 above, wherein the content of the particles in the surface layer B is 1 to 70% by mass based on the mass of the surface layer B.
6). 4. The white reflective film as described in any one of 1 to 3 above, wherein the volatile organic solvent amount is 10 ppm or less.
7). 4. The white reflective film as described in any one of 1 to 3 above, wherein the reflective layer A contains voids, and the void volume ratio is 15% by volume or more and 70% by volume or less.
8). Furthermore, the white reflective film of said 7 which has the support layer C whose void volume ratio is 0 volume% or more and less than 15 volume%.
9. 8. The white reflective film as described in 7 above, wherein the surface layer B is a layer formed by applying a coating liquid.
10. 4. The white reflective film as described in any one of 1 to 3 above, which is used as a surface light source reflector provided with a light guide plate.

1 and 2 are examples of electron micrographs of protrusions formed by non-spherical particles in the present invention.
FIG. 3 is a schematic diagram showing a method for evaluating damage of the light guide plate and evaluation of particle dropout according to the present invention.
FIG. 4 is a schematic diagram showing a structure used for adhesion spot evaluation in the present invention.

The white reflective film of the present invention has a reflective layer A and a surface layer B.
Hereafter, each structural component which comprises this invention is demonstrated in detail.
[Reflection layer A]
The reflective layer A in the present invention is a layer that is composed of a thermoplastic resin and a void forming agent and contains a void forming agent so as to exhibit a white color. The void forming agent will be described in detail later. For example, inorganic particles and a resin that is incompatible with the thermoplastic resin that constitutes the reflective layer A (hereinafter may be referred to as an incompatible resin). Can be used. The reflectance of the reflective layer A at a wavelength of 550 nm is preferably 95% or higher, more preferably 96% or higher, and particularly preferably 97% or higher. Thereby, it becomes easy to make the reflectance of a white reflective film into a preferable range.
The reflection layer A has voids in the layer as described above, and the proportion of the void volume to the volume of the reflection layer A (void volume ratio) is 15% by volume or more and 70% by volume or less. Preferably there is. By setting it as such a range, the improvement effect of a reflectance can be made high and it becomes easy to obtain the above reflectances. Moreover, the improvement effect of film forming stretchability can be heightened. When the void volume ratio is too low, a preferable reflectance tends to be difficult to obtain. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 30% by volume or more, and particularly preferably 40% by volume or more. On the other hand, if it is too high, the effect of improving the film-forming stretchability tends to be low. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 65% by volume or less, and particularly preferably 60% by volume or less.
The void volume ratio can be achieved by adjusting the type, size, and amount of the void forming agent in the reflective layer A.
(Thermoplastic resin)
Examples of the thermoplastic resin constituting the reflective layer A include thermoplastic resins made of polyester, polyolefin, polystyrene, and acrylic. Among these, polyester is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.
As such a polyester, it is preferable to use a polyester comprising a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include components derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, sebacic acid, and the like. Examples of the diol component include components derived from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. The polyethylene terephthalate may be a homopolymer, but is preferably a copolymer from the viewpoint of suppressing the crystallization when the film is stretched uniaxially or biaxially and improving the film-forming stretchability. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above. From the viewpoint of high heat resistance and a high effect of improving film-forming stretchability, an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component are used. preferable. The proportion of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 15 mol%, particularly preferably 7 to 11 based on 100 mol% of the total dicarboxylic acid component of the polyester. Mol%. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of film forming stretchability. Moreover, it is excellent in thermal dimensional stability.
(Void forming agent)
In the reflective layer A, when inorganic particles are used as the void forming agent, white inorganic particles are preferable as the inorganic particles. Examples of the white inorganic particles include barium sulfate, titanium dioxide, silicon dioxide, and calcium carbonate particles. These inorganic particles should just select an average particle diameter and content so that a white reflective film may have an appropriate reflectance, and these are not specifically limited. Preferably, the reflectance of the reflective layer A or the white reflective film may be within a preferable range in the present invention. Moreover, what is necessary is just to make it the void volume ratio in the reflection layer A become the preferable range in this invention. Considering these facts, 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 thereof is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, and most preferably 31 to 53% by mass based on the mass of the reflective layer A. In addition, by adopting the above-described particle mode, it is possible to appropriately disperse the particles in the polyester, and it is difficult for the particles to aggregate and a film without coarse protrusions can be obtained. Moreover, the fracture | rupture at the time of extending | stretching from which a coarse particle starts is also suppressed. The inorganic particles may have any particle shape, for example, a plate shape or a spherical shape. The inorganic particles may be subjected to a surface treatment for improving dispersibility.
When an incompatible resin is used as the void forming agent, the incompatible resin is not particularly limited as long as it is incompatible with the thermoplastic resin constituting the layer. For example, when the thermoplastic resin is polyester, polyolefin, polystyrene, or the like is preferable. These may be in the form of particles. Moreover, the content should just select an average particle diameter and content so that a white reflective film may have a suitable reflectance similarly to the case of an inorganic particle, These are not specifically limited. Preferably, the reflectance of the reflective layer A or the white reflective film may be within a preferable range in the present invention. Moreover, what is necessary is just to make it the void volume ratio in the reflection layer A become the preferable range in this invention. Considering these facts, the content is preferably 10 to 50% by mass, more preferably 12 to 40% by mass, and most preferably 13 to 35% by mass based on the mass of the reflective layer A.
(Other ingredients)
As long as the purpose of the present invention is not hindered, the reflective layer A is made of other components such as UV absorbers, antioxidants, antistatic agents, fluorescent brighteners, waxes, particles and resins different from the void forming agents. Can be contained.
[Surface layer B]
The surface layer B in the present invention is a layer made of a resin composition containing particles in a resin and having protrusions formed on the surface by the particles. As such a resin, a thermoplastic resin is preferable. Moreover, you may have a crosslinked structure with a crosslinking agent. In that case, using a thermoplastic resin having a functional group capable of reacting with the reactive group of the crosslinking agent, a crosslinked structure of the crosslinking agent and the thermoplastic resin may be formed, or the reactive group of the crosslinking agent and An embodiment having a thermoplastic resin matrix and a crosslinked structure matrix in which a crosslinking agent is crosslinked may be used by using a thermoplastic resin having no functional group capable of reacting. When it has a crosslinked structure, the strength of the surface layer B tends to be improved. On the other hand, when there are too many cross-linked structures, there is a tendency that the film recoverability tends to be inferior, for example, the amount of unmelted material increases when the film is recovered and regenerated. .
The surface layer B can be formed by applying a coating solution during or after the production of the film. For example, the surface layer B may be formed simultaneously with the reflective layer A by employing a coextrusion method or the like. As described above, in order for the surface layer B to have a crosslinked structure, it is preferably formed by applying a coating liquid. The content of the crosslinking agent is preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 25% by mass or less, in particular, based on the solid content constituting the coating liquid from the above viewpoint. Preferably it is 20 mass% or less. Moreover, it is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, and particularly preferably 5% by mass or more.
(Thermoplastic resin)
As the thermoplastic resin constituting the surface layer B, the same thermoplastic resin as the thermoplastic resin constituting the reflective layer A described above can be used. Among these, acrylic and polyester are preferable, and polyester is particularly preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.
As this polyester, the same polyester as the polyester in the reflective layer A described above can be used. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability. Polyethylene terephthalate may be a homopolymer, but a copolymer is preferable from the viewpoint that the surface layer B is appropriately softened and an effect of suppressing particle dropout is obtained, and copolymerized polyethylene terephthalate is particularly preferable. As a result, even if an external force such as rubbing against the light guide plate is applied, the particles are difficult to drop off. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above. From the viewpoint of high heat resistance and a high effect of improving the film-forming stretchability, the isophthalic acid component and the 2,6-naphthalenedicarboxylic acid component. Is preferred. The ratio of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 17 mol%, particularly preferably 12 to 16 mol% based on 100 mol% of the total dicarboxylic acid component of the polyester. Mol%. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of film forming stretchability. Moreover, it is excellent in thermal dimensional stability.
In the case of forming the surface layer B during the production of the film or by the application of the coating liquid after the production, the side chains of these polyesters are used for the purpose of obtaining the above effects and for improving the stability of the coating liquid. Alternatively, the main chain preferably has a group having a function of improving solvophilicity. Examples of the group having a function of improving the solvophilicity include a sulfonic acid metal salt group (preferably sulfonic acid sodium salt), a hydroxyl group, an alkyl ether group, and a carboxylate group. In the present invention, the isophthalic acid component having a sulfonic acid metal salt group is particularly preferably 3 to 30 mol%, more preferably 5 to 20 mol%, based on 100 mol% of the total acid component of the polyester. Preferably, the content is 5 to 15 mol%. It is also preferable to contain a diethylene glycol component from the same viewpoint, and such a component is preferably 3 to 30 mol%, more preferably 5 to 20 mol%, still more preferably based on 100 mol% of the total acid component of the polyester. Is preferably 5 to 15 mol%.
(Non-spherical particles)
In the present invention, the particles in the surface layer B are required to be non-spherical particles having an average particle diameter of 3 to 100 μm. When the average particle diameter is in the above range, it becomes easy to form an aspect of the number of protrusions described later, and it becomes easier to secure a gap. If the average particle size is too large, the particles are likely to fall off, causing a defect on the screen. On the other hand, if the average particle size is too small, it is difficult to secure a gap with the light guide plate, which is the original purpose. From this viewpoint, it is more preferably 5 μm or more, further preferably 7 μm or more, particularly preferably 8 μm or more, more preferably 80 μm or less, still more preferably 70 μm or less, and particularly preferably 50 μm or less.
Moreover, the particle | grains which form a processus | protrusion in the outermost layer surface can increase the damage suppression effect of a light-guide plate, ensuring a gap with a light-guide plate. Here, in the present invention, the non-spherical particles are the maximum particle diameter Dx (assumed to be the x direction) and directions perpendicular to the x direction (the y direction and the z direction. The z direction is also a direction perpendicular to the y direction). As the maximum diameters Dy and Dz (where Dy ≧ Dz), at least one of the maximum diameter differences in these directions (Dx−Dy, Dx−Dz, Dy−Dz) is Dx It shall mean more than 20%.
It is considered that the above-described effects can be obtained by such non-spherical particles due to the following mechanism. That is, by making the shape of the particles non-spherical, it is considered that the contact area with the light guide plate is widened, and pressure dispersion occurs, so that scratches are less likely to occur. If the shape of the particles is non-spherical as defined above, the particles will have a maximum diameter in a certain direction, but when contained in the surface layer B, the maximum diameter direction stochastically takes place on the surface. It tends to be a direction substantially parallel to the surface direction of the layer B. Therefore, the contact area between the protrusions formed from the particles and the light guide plate is widened, and the pressure is dispersed. On the other hand, when the particles are spherical, the area of the portion that comes into contact with the light guide plate is narrowed, so that pressure is concentrated and scratches are likely to occur. Then, even if soft particles are used, the light guide plate is easily damaged due to the spherical shape.
In the surface layer B, the present invention has the specific particle mode as described above, so that the light guide plate is brought into contact with the light guide plate while maintaining the number of protrusions rather than concentrating on a narrow range of the apexes of the protrusions. By increasing the contact area between the light guide plate and the light guide plate, the pressure distribution is achieved, and the number of contact points with the light guide plate is suitable. By doing so, the light guide plate is prevented from being damaged. If it is not in the above range, for example, the light guide plate is brought into contact with only a narrow range of the apexes of the protrusions, and the pressure applied to that portion becomes high, and it becomes easy to scrape.
In the present invention, in order to further enhance the effect of suppressing damage to the light guide plate and the effect of suppressing adhesion to the light guide plate, the average aspect ratio (major axis / minor axis) of the particles is 1.31 or more and 1.80 or less. Preferably there is. The aspect ratio is more preferably 1.35 or more, and more preferably 1.75 or less. A larger aspect ratio is preferable for the above effect, but if it is too large, it tends to be difficult to maintain the number of protrusions having a height of 5 μm or more on the outermost layer surface. In addition, an aspect ratio is calculated | required by observation using the electron microscope mentioned later here. In addition, the maximum diameter of the particles in such observation is the major axis, and the maximum diameter in the direction orthogonal to the maximum diameter is the minor axis.
At the same time, if there are moderate variations in the shape of the particles, that is, the shapes of the particles are moderately irregular, it is assumed that it is difficult to apply pressure to the specific particles, and it is difficult to damage the light guide plate. .
Therefore, such particles preferably have a standard deviation of aspect ratio of 0.15 to 0.50. That is, this indicates that there is a moderate variation in the shape of each particle. By appropriately varying the shape of the particles forming the protrusions, it is possible to further enhance the effect of suppressing damage to the light guide plate while ensuring a gap with the light guide plate. If the variation is small, the effect of improving the gap securing and the suppression of scratches becomes low. On the other hand, even if the variation is too large, defects are likely to occur when added to the surface layer B, and it is difficult to obtain the expected projection frequency, and as a result, it is difficult to achieve the effect of securing gaps and suppressing scratches. Become. From such a viewpoint, the standard deviation of the aspect ratio of the particles is more preferably 0.16 or more, further preferably 0.17 or more, more preferably 0.45 or less, and further preferably 0.43 or less. .
In the present invention, the 10% compressive strength of the particles is required to be 0.1 to 15 MPa. As a result, a gap can be secured, and damage to the light guide plate can be suppressed. If the compressive strength is too low, it will be deformed too much against stress, making it difficult to ensure the gap with the light guide plate, which is the original purpose. On the other hand, if the compressive strength is too high, the light guide plate is likely to be damaged even with non-spherical particles. From this viewpoint, the 10% compressive strength is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, further preferably 3 MPa or more, particularly preferably 8 MPa or more, and preferably 14 MPa or less, more preferably 13 MPa. Hereinafter, it is more preferably 12 MPa or less.
In the present invention, the content of the non-spherical particles in the surface layer B can be appropriately adjusted using the particles having the average particle diameter as described above so as to satisfy the aspect of the number of protrusions described later. For example, when the thickness of the surface layer B tends to be thin with respect to the average particle diameter of the particles, the protrusion may tend to be formed, so the content may be relatively low, and vice versa. The content is preferably larger, and can be appropriately adjusted in consideration of such a tendency. Specifically, 1 to 70% by mass is preferable based on the mass of the surface layer B, more preferably 5% by mass or more, still more preferably 10% by mass or more, and particularly preferably 20% by mass or more. More preferably, it is 60 mass% or less, More preferably, it is 50 mass% or less, Most preferably, it is 30 mass% or less.
In the present invention, the particles contained in the surface layer B may be organic particles, inorganic particles, or organic-inorganic composite particles regardless of their types. From the viewpoint of easily satisfying the above-described particle mode, polymer particles made of a polymer such as acrylic, polyester, polyurethane, nylon, polyolefin, and polyether are preferable. More preferred are polyester and nylon, and a more suitable 10% compressive strength is easily obtained. Particularly preferred is polyester (especially polyethylene terephthalate), which has an advantage of excellent recovery film-forming properties.
Further, in the present invention, the method for achieving the above-mentioned particle shape is not particularly limited, but from the viewpoint of easily obtaining particles having a particularly preferable shape, and from the viewpoint of production cost and productivity, A method of pulverizing the polymer to obtain particles is preferred. The particles obtained by this process are referred to as pulverized polymer particles. More specifically, such a step is preferably a method in which, after polymerization, for example, the pelletized polymer piece is crystallized, preferably by heat treatment, and pulverized at normal temperature or lower than normal temperature. From the viewpoint of easier pulverization, pulverization is preferably performed at a temperature lower than normal temperature, and a method of cooling with liquid nitrogen is preferable as a method for obtaining such a low temperature.
In addition to the above-described pelletized polymer pieces, the desired pulverized polymer particles can also be produced by pulverizing a molded polymer composition, a formed polymer film, a formed polymer fiber, and the like. By selecting the mode of the polymer to be pulverized in this way (including changing the size in the pellet, the thickness in the film, and the diameter in the fiber), various non-spherical modes (aspect ratios) can be obtained. The particles can be obtained, and the variation (standard deviation) in the shape of the particles can be adjusted.
The polymer of the pulverized polymer particles may be a copolymer or a blend of two kinds of polymers, and the pulverized polymer particles contain inorganic or organic particles having a smaller diameter, UV absorbers or slip agents. Etc. may be included.
(Aspect of surface layer B)
In the present invention, the surface layer B made of the resin composition containing the particles as described above forms at least one outermost layer of the white reflective film. The surface layer B that forms the outermost layer has protrusions formed of the particles on the surface opposite to the reflective layer A (hereinafter sometimes referred to as the outermost layer surface). Such protrusions need to have protrusions with an appropriate height at an appropriate frequency on the outermost layer surface from the viewpoint of securing a gap between the light guide plate and the film.
Therefore, in the present invention, the number of protrusions having a height of 5 μm or more (protrusion frequency) is 10 on the outermost layer surface. ⁴ ~ 10 ¹⁰ Pieces / m ² Usually it is necessary. Thereby, the gap between the light guide plate and the film can be sufficiently secured, and the sticking suppression effect can be secured. If the projection frequency is too low, the sticking suppression effect is poor. On the other hand, if the protrusion frequency is too high, the probability of particle dropout tends to improve and the reflectance tends to decrease.
(Other ingredients)
The surface layer B may contain components other than the above-described constituent components as long as the object of the present invention is not impaired. Examples of such components include ultraviolet absorbers, antioxidants, antistatic agents, fluorescent brighteners, waxes, surfactants, particles and resins different from the above particles.
[Layer structure]
The thickness of the reflective layer A in the present invention is preferably 80 to 350 μm. Thereby, the improvement effect of a reflectance can be made high. If it is too thin, the effect of improving the reflectance is low, while if it is too thick, it is inefficient. From such a viewpoint, the thickness is more preferably 80 to 300 μm, still more preferably 100 to 320 μm, and particularly preferably 150 to 250 μm.
The thickness of the surface layer B in the present invention is preferably 5 to 100 μm. More preferably, it is 5 to 80 μm. In this case, the thickness of the surface layer B is the sum of the particle diameter of the particles and the thickness of the resin portion covering the surface.
Further, the thickness of the resin part holding the particles of the surface layer B is preferably 0.2 to 50 μm. Thereby, it becomes easy to make a protrusion frequency into a preferable aspect, and it becomes easy to ensure a gap with a light-guide plate. If the thickness of the resin portion of the surface layer B is too thin, the particles in the protrusions formed on the surface of the surface layer B tend to fall off. On the other hand, if it is too thick, it tends to be difficult to obtain a preferable projection frequency. From this viewpoint, it is more preferably 0.3 μm or more, further preferably 0.5 μm or more, particularly preferably 1 μm or more, most preferably 2 μm or more, and more preferably 40 μm or less. Furthermore, when considering drop-off property, 1 μm or more is preferable, and 2 μm or more is preferable.
When the reflective layer A is represented as A and the surface layer B is represented as B, the laminated structure of the white reflective film is a two-layer structure of B / A, a three-layer structure of B / A / B, and at least one of B A multilayer configuration of four or more layers arranged in the outermost layer can be exemplified. Particularly preferably, it further has a support layer C (denoted as C) for stabilizing the film-forming property, and has a three-layer structure of B / C / A and B / A / C, and 4 of B / C / A / C. It is a layer structure. Most preferably, it has a four-layer structure of B / C / A / C, and is excellent in film-forming stretchability. Further, problems such as curling are unlikely to occur. In this invention, the aspect which has such a support layer C is preferable. The support layer C is preferably made of the same polyester as the reflective layer A, and has a relatively low void volume ratio (preferably not less than 0% by volume and less than 15% by volume, more preferably not more than 5% by volume, particularly preferably 3) or less) is preferred. In addition, the thickness of the support layer C (the total thickness when there are a plurality of the support layers C) is preferably 5 to 140 μm, and more preferably 20 to 140 μm.
In the present invention, in addition to the reflective layer A, the surface layer B, and the support layer C, other layers may be included as long as the object of the present invention is not impaired. For example, it may have a layer for imparting functions such as easy adhesion, winding property (sliding property), antistatic property, electrical conductivity, ultraviolet durability, and a layer for adjusting optical properties. Good.
[Film Production Method]
Hereinafter, an example of the method for producing the white reflective film of the present invention will be described.
In producing the white reflective film of the present invention, the reflective layer A obtained by a melt extrusion method or the like is applied to a melt resin coating method (including a melt extrusion resin coating method), a co-extrusion method and a lamination method, or a surface layer B. The surface layer B can be formed by a coating liquid coating method using the coating liquid for forming the film. Among these, the method of laminating the surface layer B by the coating liquid coating method on the one produced by laminating the reflective layer A and the support layer C by the coextrusion method is particularly preferable. By laminating the surface layer B by the coating liquid coating method, the distribution state of the particles can be easily controlled by changing the drying conditions and the like, and the predetermined number of protrusions can be easily mass-produced at low cost. Further, even particles having a relatively small 10% compressive strength can be easily handled. Furthermore, the shape of the specific particle in the present invention is easily maintained, and the aspect of the protrusion is easily made a preferable aspect.
Below, polyester is adopted as the thermoplastic resin constituting the reflective layer A and the thermoplastic resin constituting the support layer C, a coextrusion method is adopted as a method of laminating the reflective layer A and the support layer C, and the surface layer B Although the manufacturing method at the time of employ | adopting the coating liquid coating method as a lamination | stacking method is demonstrated, this invention is not limited to this manufacturing method, Moreover, it can manufacture similarly about another aspect with reference to the following. At that time, when the extrusion step is not included, the following “melt extrusion temperature” may be read as, for example, “melt temperature”. Here, the melting point of the polyester used is Tm (unit: ° C), and the glass transition temperature is Tg (unit: ° C).
First, a polyester composition for forming the reflective layer A is prepared by mixing polyester, a void forming agent, and other optional components. In addition, as the polyester composition for forming the support layer C, a mixture of polyester, optionally a void forming agent, and other optional components is prepared. These polyester compositions are used after drying to sufficiently remove moisture.
Next, the dried polyester composition is put into separate extruders and melt-extruded. The melt extrusion temperature needs to be Tm or higher, and may be about Tm + 40 ° C.
At this time, the polyester composition used for the production of the film, particularly the polyester composition used for the reflective layer A, is filtered using a nonwoven fabric type filter having an average aperture of 10 to 100 μm made of stainless steel fine wires having a wire diameter of 15 μm or less. It is preferable. By performing this filtration, it is possible to suppress aggregation of particles that normally tend to aggregate into coarse aggregated particles, and to obtain a film with few coarse foreign matters. The average opening of the nonwoven fabric is preferably 20 to 50 μm, more preferably 15 to 40 μm. The filtered polyester composition is extruded in a multilayer state from a die by a simultaneous multilayer extrusion method (coextrusion method) using a feed block in a molten state to produce an unstretched laminated sheet. The unstretched laminated sheet extruded from the die is cooled and solidified with a casting drum to obtain an unstretched laminated film.
Next, this unstretched laminated film is heated by roll heating, infrared heating or the like, and stretched in the film forming machine axial direction (hereinafter sometimes referred to as the longitudinal direction or the longitudinal direction or MD) to obtain a longitudinally stretched film. . This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The film after the longitudinal stretching is then guided to a tenter and stretched in a direction perpendicular to the longitudinal direction and the thickness direction (hereinafter sometimes referred to as a transverse direction or a width direction or TD) to be biaxially stretched. A film.
The stretching temperature is preferably a temperature of Tg or more and preferably Tg + 30 ° C. or less of the polyester (preferably the polyester constituting the reflective layer A), excellent in film-forming stretchability, and voids are preferably formed. The stretching ratio is preferably 2.5 to 4.3 times, more preferably 2.7 to 4.2 times in both the vertical direction and the horizontal direction. If the draw ratio is too low, uneven thickness of the film tends to be worsened, and voids tend not to be formed. On the other hand, if it is too high, breakage tends to occur during film formation. In the case of sequential biaxial stretching in which longitudinal stretching is performed and then lateral stretching is performed, the second stage (in this case, lateral stretching) is made about 10 to 50 ° C. higher than the first stage stretching temperature. Things are preferable. This is due to the fact that the Tg as a uniaxial film is increased due to the orientation in the first stage of stretching.
Moreover, it is preferable to preheat a film before each extending | stretching. For example, the pre-heat treatment for transverse stretching may start from a temperature higher than Tg + 5 ° C. of the polyester (preferably the polyester constituting the reflective layer A) and gradually increase the temperature. Although the temperature rise in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually raised sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone.
The film after biaxial stretching is subsequently subjected to heat-fixing and heat-relaxing treatments in order to obtain a biaxially oriented film. However, following melt-extrusion to stretching, these treatments can also be performed while the film is running. it can.
The biaxially stretched film has a constant width or a Tm-20 ° C. to (Tm−100 ° C.) melting point of the polyester (preferably the polyester constituting the reflective layer A) while holding both ends with clips. It is preferable to heat-treat under a width reduction of 10% or less and heat-set to lower the heat shrinkage rate. When the heat treatment temperature is too high, the flatness of the film tends to deteriorate, and the thickness unevenness tends to increase. On the other hand, if it is too low, the thermal shrinkage tends to increase.
Further, in order to adjust the heat shrinkage, both ends of the film being held can be cut off, the take-up speed in the film vertical direction can be adjusted, and the film can be relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3. The film is relaxed by carrying out a speed reduction of ˜2.0% (this value is referred to as “relaxation rate”), and the longitudinal heat shrinkage rate is adjusted by controlling the relaxation rate. Further, the width of the film in the horizontal direction can be reduced in the process until both ends are cut off, and a desired heat shrinkage rate can be obtained.
In the biaxial stretching, a lateral-longitudinal sequential biaxial stretching method may be used in addition to the longitudinal-lateral sequential biaxial stretching method as described above. Moreover, it can also form into a film using a simultaneous biaxial stretching method. In the case of the simultaneous biaxial stretching method, the stretching ratio is, for example, 2.7 to 4.3 times, preferably 2.8 to 4.2 times in both the longitudinal direction and the transverse direction.
The surface layer B is coated with a coating liquid for forming the surface layer B on the longitudinally stretched film after the longitudinal stretching in the above-described process, and is dried and cured by heat applied in the preheating process, the lateral stretching process, the heat setting process, and the like. It can be formed by the so-called in-line coating method. The coating liquid can be obtained by mixing the components constituting the surface layer B and optionally diluting with a solvent so as to be easily applied. In this case, water is preferable as the solvent, and the amount of the volatile organic solvent described later can be reduced. The method for applying the coating liquid is not particularly limited, but preferred methods include reverse roll coating, gravure coating, die coating, and spray coating. Further, the surface layer B may be formed on a biaxially oriented film obtained by biaxial stretching and heat setting by a so-called offline coating method. In the off-line coating method, it is difficult to apply high heat to drying because the film is deformed, and therefore, an organic solvent that is usually easily dried is used as the solvent. However, in this case, since the amount of the volatile organic solvent described later tends to increase, the in-line coating method is particularly preferable in the present invention.
Thus, the white reflective film of the present invention can be obtained.
[Characteristics of white reflective film]
(Reflectance, brightness)
The reflectance (reflectance at a wavelength of 550 nm) of the white reflective film of the present invention measured from the surface layer B side is preferably 95% or more, more preferably 96% or more, still more preferably 97% or more, and still more preferably 97. .5% or more, particularly preferably 98% or more. When the reflectance is 95% or more or 96% or more, high luminance can be obtained when used in a liquid crystal display device, illumination, or the like. Such reflectivity is set to a preferable mode such as increasing the void volume ratio of the reflective layer A, the thickness of the reflective layer A is increased, the thickness of the surface layer B is decreased, and the like is set as a preferable mode. Etc. can be achieved.
Moreover, although the brightness | luminance measured from the surface layer B side is calculated | required by the measuring method mentioned later, it is 5400 cd / m. ² Or more, preferably 5450 cd / m ² More preferably, 5500 cd / m ² The above is particularly preferable.
The reflectance and brightness are values on the surface on the side of the light guide plate when used with the light guide plate in the white reflective film.
(Amount of volatile organic solvent)
In the white reflective film of the present invention, the amount of volatile organic solvent measured by the method described later is preferably 10 ppm or less. Thereby, it can be shown that the surface layer B is not formed by a coating method using an organic solvent. Further, when a self-recovery raw material is obtained and a film is formed using the self-recovery raw material, a gas mark is less likely to be generated, and film-forming stretchability (recovery film-forming property) is improved. From this viewpoint, it is more preferably 5 ppm or less, further preferably 3 ppm or less, and ideally 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, it is preferable to employ the above-described method in forming the surface layer B without adopting the solution coating method using the organic solvent.

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
An integrating sphere was attached to a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and BaSO ₄ The reflectance when the white plate was 100% was measured at a wavelength of 550 nm, and this value was taken as the reflectance. The measurement was performed on the surface on the surface layer B side. In the case where the front and back surfaces have different surface layers B, the measurement was performed on the surface layer B surface on the light guide plate side.
(2) Average particle diameter of particles
The particle size distribution (standard deviation of particle size) of the particles is obtained with a laser scattering type particle size distribution analyzer (SALD-7000 manufactured by Shimadzu Corporation), and the particle size at d50 (50% distribution from the smaller side on the basis of volume distribution) Particle diameter) was defined as the average particle diameter.
(3) Particle shape
(3-1) Particle shape 1
The particle powder was fixed to the measurement stage with a conductive tape, and observed with a magnification of 1000 using an S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd., and the shape of the particles was observed. For 30 randomly selected particles, the maximum particle diameter Dx (referred to as x direction) and the direction perpendicular to the x direction (referred to as y direction and z direction. The z direction is also perpendicular to the y direction) The maximum diameters Dy and Dz (where Dy ≧ Dz) are calculated, and average values are calculated for each, and Dxave, Dave, Dzave, and Dxave-Dave, Dxave-Dzave, Dyave-Dzave are obtained. When at least one of these exceeded 20% of Dx, it was determined as non-spherical, and when it was not, it was determined as spherical.
(3-2) Particle shape 2 (aspect ratio and standard deviation of aspect ratio)
Lightly affix the particles to the conductive tape using a glass rod, fix it to the measurement stage, and use the S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd. from the front (without the tilt angle). For 30 particles randomly selected and observed at a magnification of 100, the maximum diameter in the direction perpendicular to the maximum diameter is defined as the major axis, and the major axis / minor axis ( (Aspect ratio) was determined and the average value was taken as the average aspect ratio. In addition, the standard deviation of the aspect ratio was calculated from each aspect ratio value.
In addition, about what has a small average particle diameter (for example, what is assumed to be 3 micrometers or less), the magnification was made high (for example, 1000 times), and it observed.
(4) Projection frequency on the film surface (number of protrusions)
The projection profile on the film surface was measured with a three-dimensional roughness measuring device SE-3CKT (manufactured by Kosaka Laboratory Ltd.) with a cutoff of 0.25 mm, a measurement length of 1 mm, a scanning pitch of 2 μm, and a scanning number of 100. The projection profile was recorded at a height magnification of 1000 times and a scanning direction magnification of 200 times. From the obtained projection profile (horizontal axis: projection height, vertical axis: projection profile of the number of projections), the number of projections having a height of 5 μm or more (pieces / m ² ) Was calculated as the protrusion frequency. For the analysis, a three-dimensional roughness analyzer SPA-11 (manufactured by Kosaka Laboratory Ltd.) was used.
(5) 10% compressive strength
Using a micro hardness tester ENT-1100a manufactured by Elionix, the compressive strength of each particle at a load of 3 gf was measured, and the compressive strength (MPa) at 10% deformation was adopted. The average value of 5 measurements was used.
(6) Volatile organic solvent amount
At room temperature (23 ° C.), 1 g of a film sample was placed in a 10 L fluororesin bag, which was purged with pure nitrogen and sealed. Next, immediately from the nitrogen in the bag, 0.2 L and 1.0 L of nitrogen were collected in two analytical TENAX-TA collection tubes at a flow rate of 0.2 L / min. The mass of the organic solvent component contained in the collected nitrogen was quantified by HPLC, GCMS. The obtained value is converted into the amount in 10 L of nitrogen, and the mass of the organic solvent volatilized in 10 L of nitrogen is obtained from 1 g of the film sample, and the amount of volatile organic solvent (unit: ppm, based on the mass of the film sample) did. The aldehydes were quantified by HPLC by eluting the aldehyde derivatized product from the collection tube with acetonitrile. Moreover, when the value was different between HPLC and GCMS, the value of the more detected one was adopted.
(7) Film thickness and layer structure
A white reflective film is sliced with a microtome to obtain a cross section, and this cross section is observed at a magnification of 500 times using a S-4700 field emission scanning electron microscope manufactured by Hitachi, Ltd. The thicknesses of the surface layer B and the support layer C were determined. In addition, about the surface layer B, the thickness of the part in which particle | grains exist was arbitrarily extract | collected 10 points | pieces, and those average values were made into thickness.
(8) Calculation of void volume ratio
The calculated density was determined from the density and blending ratio of the polymer, additive particles, and other components of the layer for which the void volume ratio was determined. At the same time, it was isolated by peeling off the layer, and the mass and volume were measured. The actual density was calculated from these, and the following formula was obtained from the calculated density and the actual density.
Void volume fraction = 100 × (1− (actual density / calculated density))
The density of isophthalic acid copolymerized polyethylene terephthalate (after biaxial stretching) is 1.39 g / cm. ³ The density of barium sulfate is 4.5 g / cm ³ It was.
Moreover, only the layer which measures a void volume ratio was isolated, the mass per unit volume was calculated | required, and the real density was calculated | required. Volume is 3cm in area of sample ² Then, the thickness at that size was measured at 10 points with an electric micrometer (K-402B manufactured by Anritsu), and the average value was calculated as area × thickness. The mass was weighed with an electronic balance.
In addition, as the specific gravity of the particles (including aggregated particles), the value of bulk specific gravity obtained by the following graduated cylinder method was used. Fill a 1000 ml measuring cylinder with completely dry particles, measure the total weight, subtract the weight of the measuring cylinder from the total weight to obtain the weight of the particle, and measure the volume of the measuring cylinder. , The weight (g) of the particles to the volume (cm ³ ).
(9) Melting point, crow transition temperature
Using a differential scanning calorimeter (TA Instruments 2100 DSC), the temperature was measured at a heating rate of 20 ° C./min.
(10) Brightness
The reflective film is taken out from the LED liquid crystal television (LG42LE5310AKR) manufactured by LG, and the surface layer B side of the various reflective films described in the examples is installed on the screen side (side in contact with the light guide plate), in the state of the backlight unit. Using a luminance meter (Model MC-940, manufactured by Otsuka Electronics Co., Ltd.), the luminance was measured at a measurement distance of 500 mm from the front of the center of the backlight.
(11) Evaluation of scratches on light guide plate (Evaluation of shaving)
(11-1) Scratch evaluation 1
As shown in FIG. 3, an iron plate (2, 200 g in weight) having a width of 200 mm, a length of 200 mm, and a thickness of 3 mm is firmly attached to the end of the handle portion (1), and the evaluation surface is on the top, and the width is 250 mm. X A reflective film (3) having a length of 200 mm was pasted so that each 25 mm portion protruded from the iron plate from both ends in the width direction (so that the central 200 mm × 200 mm portion overlapped the iron plate). At this time, the evaluation surface (surface layer surface) of the reflective film was placed outside. In addition, the 25 mm portion remaining at both ends in the width direction of the reflective film is folded back to the back side of the iron plate, and the end portion of the reflective film (the portion where the blade is inserted with a knife or the like at the time of sampling) has the effect of scraping the light guide plate. Eliminated.
Next, a light guide plate (4, having a size of at least 400 mm × 200 mm) with a dot surface having dots (401) is fixed on a horizontal desk, and the reflection film fixed on the iron plate created above is evaluated. Place the reflective film side face down on the light guide plate so that the surface and the light guide plate are in contact with each other, and place a 500 g weight (5) on it, at a distance of 200 mm (in the region of 400 mm × 200 mm) The reflective film fixed to the iron plate is moved.) 15 reciprocations were performed at a speed of about 5 to 10 seconds per reciprocation. Then, on the surface of the light guide plate, the degree of shaving and the presence or absence of particles dropped from the reflective film were observed using a 20-fold magnifier and evaluated according to the following criteria.
If there are no scratches that can be observed with a loupe after 20 reciprocating movements in the entire range of 400 mm × 200 mm rubbed on the light guide plate, it is determined that “cannot be scraped” (scratch evaluation ○), and there are scratches that can be observed after 10 reciprocating movements Although there were no scratches that could be observed after 20 reciprocating movements, “scratch was difficult” (shave evaluation Δ), and when there were scratches that could be observed after 10 reciprocations, “scraped” (scraping 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.
(11-2) Scratch evaluation 2
In the above (11-1), the size of the iron plate (2) is 400 mm × 200 mm (in accordance with this, the reflective film is 400 mm × 250 mm, and the light guide plate is at least 400 mm × 400 mm in size. 400 mm × 400 mm). In this region, the reflective film fixed to the iron plate is moved, and the observation range is also within this range.) The weight of the weight (5) is 1000 g (the pressure is the same as (11-1) above.) The evaluation was performed in the same manner except that.
(12) White spot evaluation
(12-1) White spot evaluation 1
Using the reflective film and the light guide plate used in the evaluation of (11-1) above, place the reflective film on the desk so that the surface layer surface faces upward, and place the light guide plate so that the dot surface faces downward. Place and fix each 300 g weight on each of the four sides of the light guide plate, and use a backlight light source of an LED liquid crystal television (LG42LE5310AKR) manufactured by LG to make light incident from the side of the light guide plate and observe visually If there are bright spots other than light guide plate dots that can be formed, white spots are generated (evaluation Δ). On the other hand, if there were no abnormal bright spots that could be observed visually, no white spots were generated (evaluation ○).
(12-2) White spot evaluation 2
Using the reflective film and the light guide plate used in the evaluation of (11-2) above, if there is a bright point other than the light guide plate dot that can be observed visually, white spots are generated (evaluation x) and observed visually If there is no abnormal bright point that can be produced, white spots will not occur (evaluation ○), and there are bright spots other than light guide plate dots that can be visually observed, but thin ones will generate white spots (evaluation Δ), Evaluation was performed in the same manner as in (12-1) above.
(13) Adhesion spot evaluation (adhesion evaluation)
(13-1) Sticking evaluation 1
As shown in FIG. 4, take out the chassis (6) from the LED liquid crystal television (47 inch size) manufactured by LG and place it on a horizontal desk so that the inside of the television is facing upward. The reflective film was placed with the surface layer surface facing upward, and further, the light guide plate and three optical sheets (7, two diffusion films, one prism) originally provided in the television were placed thereon. Next, an equilateral triangular base (801) having three columnar legs with a diameter of 5 mm as shown in FIG. 4 is placed in the area including the most severely uneven portion of the chassis within the plane, and a further 10 kg is placed thereon. A region surrounded by the three legs was visually observed, and if there was no abnormally bright part, “no adhesion spots” (adhesion spots evaluation ○) was obtained. 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.
(13-2) Sticking evaluation 2
In the above (13-1), evaluation was made in the same manner except that the weight of the weight (802) was 15 kg.
(14) Evaluation of recovered film-forming properties
The biaxially stretched film obtained in the examples was pulverized, melt-extruded, and formed into chips to prepare a self-recovery raw material. Such a self-recovered raw material is added to the reflective layer A in an amount of 35% by mass based on the mass of the reflective layer A, and the mass ratio of the remaining polyester to the void forming agent is the same as that of the original film. A biaxially stretched film containing a self-recovery raw material was prepared in the same manner as the above film and evaluated according to the following criteria.
A: The film can be stably formed with a length of 2000 m or more.
○: The film can be stably formed with a length of 1000 m or more and less than 2000 m.
(Triangle | delta): The cutting | disconnection produced once in less than 1000 m in length.
X: The cutting | disconnection produced twice or more in length less than 1000 m.
<Production Example 1: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 1>
136.5 parts by mass of dimethyl terephthalate, 13.5 parts by mass of dimethyl isophthalate (9 mol% with respect to 100 mol% of total acid components of the obtained polyester), 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol Then, 0.05 part by mass of manganese acetate and 0.012 part by mass of lithium acetate were charged into a rectification column and a flask equipped with a distillation condenser, and heated to 150 to 240 ° C. with stirring to distill methanol to conduct a transesterification reaction. went. After methanol was distilled, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Next, while stirring, the pressure in the reactor was gradually reduced to 0.3 mmHg and the temperature was raised to 292 ° C. to carry out a polycondensation reaction to obtain isophthalic acid copolymerized polyethylene terephthalate 1. The melting point of this polymer was 235 ° C.
<Production Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2>
Except for changing to 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (14 mol% with respect to 100 mol% of the total acid component of the resulting polyester), the same as in Production Example 1 above. Thus, isophthalic acid copolymerized polyethylene terephthalate 2 was obtained. The melting point of this polymer was 215 ° C.
<Production Example 3: Preparation of particle master chip 1>
Part of the isophthalic acid copolymerized polyethylene terephthalate 1 obtained above and barium sulfate particles having an average particle diameter of 1.0 μm as a void forming agent (in the table, BaSO ₄ Is written. ) Using a NEX-T60 tandem extruder manufactured by Kobe Steel, so that the content of barium sulfate particles is 60% by mass with respect to the mass of the obtained master chip, and the resin temperature is set to 260 ° C. To produce a particle master chip 1 containing barium sulfate particles.
<Production Example 4: Preparation of particle master chip 2>
Using a part of the isophthalic acid copolymerized polyethylene terephthalate 2 obtained above and barium sulfate particles having an average particle size of 1.0 μm as a void forming agent, a NEX-T60 tandem extruder manufactured by Kobe Steel was used. The mixture was mixed so that the content of barium sulfate particles was 60% by mass with respect to the mass of the master chip, and extruded at a resin temperature of 260 ° C. to prepare particle master chip 2 containing barium sulfate particles.
<Production Example 5: Creation of particles 1 used for surface layer B>
150 parts by mass of dimethyl terephthalate, 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, 0.05 part by mass of manganese acetate, 0.012 part by mass of lithium acetate were charged into a rectifying column and a flask equipped with a distillation condenser. While stirring, the mixture was heated to 150 to 240 ° C. to distill off methanol and conduct transesterification. After methanol was distilled, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Next, while stirring, the pressure in the reactor was gradually reduced to 0.3 mmHg and the temperature was raised to 292 ° C. to conduct a polycondensation reaction to obtain polyethylene terephthalate 3. The obtained polyethylene terephthalate 3 was extruded from a strand die and cut after cooling to form a pellet. Next, the obtained pellets were dried and crystallized by heating at 170 ° C. for 3 hours in an oven, and then pulverized while being cooled with liquid nitrogen using Matsubo Co., Ltd. atomizer mill TAP-1. Polyester particles having an average particle diameter of 60 μm were obtained. Furthermore, particles 1 (non-spherical particles) having an average particle diameter of 40 μm were obtained by air classification of the polyester particles.
Particle 2: Non-spherical particles having an average particle size of 40 μm obtained by pulverization and classification in the same manner as in Production Example 5 except that pellets of nylon 66 resin CM3006 manufactured by Toray Industries, Inc. are used.
Particle 3: Non-spherical particles having an average particle diameter of 10 μm obtained by pulverization and classification in the same manner as in Production Example 5 except that pellets of nylon 66 resin CM3006 manufactured by Toray Industries, Inc. are used.
Particle 4: Non-spherical particles having an average particle diameter of 10 μm obtained by pulverization and classification in the same manner as in Production Example 5 except that pellets of nylon 6 resin CM1017 manufactured by Toray Industries, Inc. are used.
Particle 5: MBX-40 manufactured by Sekisui Plastics Co., Ltd. (true spherical acrylic particles, average particle size 40 μm)
Particle 6: Non-spherical particle having an average particle diameter of 10 μm obtained by pulverization and classification in the same manner as in Production Example 5 except that a pellet of poly (methyl methacrylate) (PMMA) resin Sumipex MGSS manufactured by Sumitomo Chemical Co., Ltd. is used. .
Particle 7: SP-10 manufactured by Toray Industries, Inc. (true spherical nylon particles, average particle diameter 10 μm)
<Production Example 6: Creation of particles 8 used for surface layer B>
In the same manner as in Production Example 5, polyethylene terephthalate 3 was extruded from a strand die and cut after cooling to form a pellet. As a result of adjusting the shape of the strand, the shape of the pellet was almost a rectangular parallelepiped shape, and the average shape was 4 mm × 3 mm × 2 mm. Next, polyester particles having an average particle diameter of 60 μm were obtained in the same manner as in Production Example 5. Furthermore, particles 8 (non-spherical particles) having an average particle diameter of 43 μm were obtained by air classification of the polyester particles.
<Production Example 7: Creation of particles 9 used for surface layer B>
Using the pellets obtained in Production Example 6 above, the conditions normally used for a biaxially stretched film of polyethylene terephthalate (longitudinal stretch ratio: 3.0 times, transverse stretch ratio: 4.0 times, heat setting temperature set at 220 ° C.) Thus, a transparent biaxially stretched polyethylene terephthalate film (thickness: 50 μm) was obtained. This was pulverized while cooling with liquid nitrogen in the same manner as in Production Example 6 above, followed by air classification to obtain particles 9 (non-spherical particles) having an average particle diameter of 52 μm.
<Production Example 8: Creation of particles 10 used for surface layer B>
Using the pellets obtained in Production Example 6 above, polyester fibers having a diameter of 35 μm were prepared by a conventional method, and this was crushed while cooling with liquid nitrogen in the same manner as in Production Example 6 to obtain particles 10 having an average particle diameter of 40 μm. (Non-spherical particles) were obtained.
<Production Examples 9 and 10: Creation of particles 11 and 12 used for surface layer B>
The pellets obtained in Production Example 6 were dried and crystallized, similarly pulverized, and subjected to air classification to obtain particles 11 (non-spherical particles) having an average particle diameter of 35 μm. Further, the film obtained in Production Example 7 was similarly crushed and subjected to air classification to obtain particles 12 (non-spherical particles) having an average particle diameter of 50 μm. In the above, the air classification conditions were adjusted so that the particles obtained would be in the form shown in Table 3.
Particle 13: Non-spherical particle having an average particle diameter of 40 μm obtained by pulverization and classification in the same manner as in Production Example 6 except that pellets of poly (methyl methacrylate) (PMMA) resin Sumipex MGSS manufactured by Sumitomo Chemical Co., Ltd. are used. .
<Production Examples 11 and 12: Creation of particles 14 and 15 used for the surface layer B>
In Production Example 7, the film thickness was changed to 75 μm, and pulverization and air classification were performed in the same manner as in Production Example 7 to obtain particles 14 (non-spherical particles). Moreover, the film thickness was set to 100 μm, and similarly, particles 15 (non-spherical particles) were obtained. In the above, the air classification conditions were adjusted so that the particles obtained would be in the form shown in Table 3.
<Production Examples 13 to 20: Creation of particles 16 to 23 used for the surface layer B>
The pellets obtained in Production Example 6 were dried and crystallized, similarly crushed, and subjected to air classification to obtain particles 16 to 23 (non-spherical particles or spherical particles) each having the structure shown in Table 3. In the above, the air classification conditions were adjusted so that the particles obtained would be in the form shown in Table 3.
[Example 1-1]
(Manufacture of white reflective film)
The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master chip 1 obtained above as raw materials for the reflective layer (A layer), and the isophthalic acid copolymerized polyethylene terephthalate 2 and the particle master chip 2 as raw materials for the support layer (C layer), respectively. The reflective layer A is used so that the content of the void forming agent is 49% by mass with respect to the mass of the reflective layer A, and the supporting layer C is 3% by mass of the void forming agent with respect to the mass of the supporting layer C. The layer A is melt extruded at a temperature of 255 ° C., the layer C is melt extruded at a temperature of 230 ° C., and the layer configuration is C layer / A layer / C layer. And a three-layer feed block device, and the sheet was formed into a sheet from a die while maintaining the laminated state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of C layer / A layer / C layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 2.9 times in the longitudinal direction, and cooled by a roll group at 25 ° C. A uniaxially stretched film was obtained. Subsequently, the coating liquid 1 for forming the surface layer (B layer) shown below was apply | coated to the single side | surface of the obtained uniaxially stretched film using the reverse roll coating method.
<Coating liquid 1>
Z-465 manufactured by Kyodo Chemical Co., Ltd. as a resin (a copolymerized polyester resin containing 10 mol% of sodium sulfoisophthalic acid component and 100 mol% of total acid component and 10 mol% of diethylene glycol component in polyethylene terephthalate) Polymerized polyester is resin 1.) An aqueous solution having a solid content concentration of 15% by mass.), Particles 1 obtained in Production Example 5 as particles, and ion-exchanged water as a diluting solvent, resin and particles; Was mixed so that the solid content concentration of the coating liquid was 20% by mass so that the content ratio shown in Table 1 was obtained.
Following application, the film was guided to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. while holding both ends with clips, and stretched 3.6 times in the transverse direction. Then, heat setting is performed at 185 ° C. in the tenter, the width is set to 2%, the width is set in the horizontal direction at a temperature of 130 ° C., then both ends of the film are cut off, and the film is thermally relaxed at a longitudinal relaxation rate of 2%. It cooled and the biaxially stretched film was obtained. The evaluation results of the obtained film are shown in Table 2.
[Examples 1-2, 1-3, 1-5, Comparative Examples 1-1 to 1-3]
A biaxially stretched film was obtained in the same manner as in Example 1-1 except that the aspect of the particles used for the surface layer (B layer) was as shown in Table 1. The evaluation results of the obtained film are shown in Table 2.
[Example 1-4]
The void forming agent of the reflective layer A was changed to a resin incompatible with polyester (cycloolefin, “TOPAS 6017S-04” manufactured by Polyplastics Co., Ltd.), and the content of the void forming agent with respect to the mass of the reflective layer A was 20 A biaxially stretched film was prepared and evaluated in the same manner as in Example 1-1 except that the mass% was used. The evaluation results are shown in Table 2.
[Example 1-6]
After the uniaxial stretching, the following surface layer (layer) was formed on the biaxially stretched film obtained in the same manner as in Example 1-1 except that the coating solution was not applied before the biaxial stretching. A coating liquid having the composition shown in the coating liquid 2 for forming B) is applied with a wet thickness of 15 g / m. ² Then, the film was dried in an oven at 80 ° C. to obtain a film.
<Coating liquid 2, solid content concentration 30% by mass>
Particle: Particle 1 (non-spherical particle) obtained in Production Example 5 7.5 mass%
Acrylic resin (thermoplastic resin): DIC ACRICID A-817BA (solid content concentration 50% by mass, described as resin 2 in the table) ... 30% by mass
-Crosslinking agent: Coronate HL manufactured by Nippon Polyurethane Industry Co., Ltd. (isocyanate-based crosslinking agent, solid content concentration 75% by mass, described as crosslinking agent 1 in the table) ... 10% by mass
Diluting solvent: butyl acetate 52.5% by mass
The evaluation results of the obtained film were as shown in Table 2. In addition, the solid content ratio of each component in the coating liquid 2 is as follows.
・ Particles: 25% by mass
-Acrylic resin (thermoplastic resin): 50% by mass
・ Crosslinking agent: 25% by mass

[Example 2-1]
(Manufacture of white reflective film)
The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master chip 1 obtained above as raw materials for the reflective layer (A layer), and the isophthalic acid copolymerized polyethylene terephthalate 2 and the particle master chip 2 as raw materials for the support layer (C layer), respectively. The reflective layer A is used so that the content of the void forming agent is 49% by mass with respect to the mass of the reflective layer A, and the supporting layer C is 3% by mass of the void forming agent with respect to the mass of the supporting layer C. The layer A is melt extruded at a temperature of 265 ° C., the layer C is melt extruded at a temperature of 240 ° C., and the layer configuration is C layer / A layer / C layer. And a three-layer feed block device, and the sheet was formed into a sheet from a die while maintaining the laminated state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of C layer / A layer / C layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 2.9 times in the longitudinal direction, and cooled by a roll group at 25 ° C. A uniaxially stretched film was obtained. Subsequently, the coating liquid 3 for forming the surface layer (B layer) shown below was apply | coated to the single side | surface of the obtained uniaxially stretched film using the reverse roll coating method.
<Coating liquid 3>
Z-465 (Resin 1) manufactured by Kyodo Chemical Co., Ltd. as a resin, particles 8 obtained in Production Example 6 as particles, and ion-exchanged water as a diluting solvent, the solid content of the resin and particles The coating liquid 3 was prepared by mixing so that the ratio was resin: particles = 75: 25 (mass%) and the solid content concentration of the coating liquid was 20 mass%.
Following application, the film was guided to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. while holding both ends with clips, and stretched 3.6 times in the transverse direction. Then, heat setting is performed at 185 ° C. in the tenter, the width is set to 2%, the width is set in the horizontal direction at a temperature of 130 ° C., then both ends of the film are cut off, and the film is thermally relaxed at a longitudinal relaxation rate of 2%. It cooled and the biaxially stretched film was obtained. Table 4 shows the evaluation results of the obtained film.
[Examples 2-2 to 2-5, 2-8 to 2-15, Comparative Examples 2-1 to 2-5]
A biaxially stretched film was obtained in the same manner as in Example 2-1, except that the aspect and layer structure of the particles used for the surface layer (B layer) were as shown in Table 3 and Table 4, respectively. Table 4 shows the evaluation results of the obtained film.
[Example 2-6]
The void forming agent of the reflective layer A was changed to a resin incompatible with polyester (cycloolefin, “TOPAS 6017S-04” manufactured by Polyplastics Co., Ltd.), and the content of the void forming agent with respect to the mass of the reflective layer A was 20 A biaxially stretched film was prepared and evaluated in the same manner as in Example 2-1, except that the mass% was used. The evaluation results are shown in Table 4.
[Example 2-7]
After the uniaxial stretching, the following surface layer (layer) was formed on the biaxially stretched film obtained in the same manner as in Example 2-1, except that the coating solution was not applied before the biaxial stretching. A coating liquid having the composition shown in the coating liquid 4 for forming B) is applied with a wet thickness of 15 g / m. ² Then, the film was dried in an oven at 80 ° C. to obtain a film.
<Coating liquid 4, solid content concentration 30% by mass>
Particles: Particles 8 (non-spherical particles) obtained in Production Example 6 7.5% by mass
Acrylic resin (thermoplastic resin): DIC's Acridic A-817BA (resin 2) ... 30% by mass
Crosslinking agent: Coronate HL (crosslinking agent 1) manufactured by Nippon Polyurethane Industry Co., Ltd. 10% by mass
Diluting solvent: butyl acetate 52.5% by mass
The evaluation results of the obtained film were as shown in Table 4. In addition, the solid content ratio of each component in the coating liquid 4 is as follows.
・ Particles: 25% by mass
-Acrylic resin (thermoplastic resin): 50% by mass
・ Crosslinking agent: 25% by mass

The invention's effect
ADVANTAGE OF THE INVENTION According to this invention, the white reflective film which can fully suppress sticking with a light-guide plate, and can fully suppress the damage | wound of a light-guide plate simultaneously can be provided.

Since the white reflective film of the present invention can sufficiently suppress sticking to the light guide plate and sufficiently suppress scratches on the light guide plate, in particular, as a surface light source reflector including the light guide plate, for example, It can be suitably used as a reflective film used in an edge light type backlight unit used in a liquid crystal display device or the like.

Claims (10)

1. A white reflective film having a reflective layer A and a surface layer B made of a resin composition containing particles,
   The surface layer B has protrusions formed of the particles on the surface opposite to the reflective layer A, and the number of protrusions having a height of 5 μm or more on the surface is 10 ⁴ to 10 ¹⁰ / m ² ;
   The white reflective film, wherein the particles are non-spherical particles having an average particle diameter of 3 to 100 μm and a 10% compressive strength of 0.1 to 15 MPa.
2. The white reflective film according to claim 1, wherein the particles are pulverized polymer particles obtained by pulverizing a polymer.
3. The white reflective film according to claim 2, wherein the polymer is polyester.
4. The particles are non-spherical particles having an average aspect ratio (major axis / minor axis) of 1.31 or more and 1.80 or less, and a standard deviation of the aspect ratio of 0.15 to 0.50. The white reflective film according to any one of claims 1 to 3.
5. The white reflective film according to any one of claims 1 to 3, wherein the content of the particles in the surface layer B is 1 to 70% by mass based on the mass of the surface layer B.
6. The white reflective film according to any one of claims 1 to 3, wherein the amount of volatile organic solvent is 10 ppm or less.
7. The white reflective film according to any one of claims 1 to 3, wherein the reflective layer A contains voids, and the void volume ratio thereof is 15% by volume or more and 70% by volume or less.
8. Furthermore, the white reflective film of Claim 7 which has the support layer C whose void volume fraction is 0 volume% or more and less than 15 volume%.
9. The white reflective film according to claim 7, wherein the surface layer B is a layer formed by application of a coating liquid.
10. The white reflective film according to any one of claims 1 to 3, which is used as a surface light source reflective plate provided with a light guide plate.

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