TWI575192B - White reflective film - Google Patents

Description

White reflective film

The present invention relates to a white reflective film. In particular, it relates to a white reflective film used in a liquid crystal display device.

The backlight unit of the liquid crystal display (LCD) has a direct light type including a light source on the back surface of the liquid crystal display panel and a reflective film on the back surface thereof, and a light guide plate having a reflector on the back surface of the liquid crystal display panel. And having an edge illumination type of the light source on the side of the light guide plate. In the conventional backlight unit used for a large-sized LCD, from the viewpoint of the brightness of the screen and the uniformity of the brightness in the screen, the direct type (mainly direct type CCFL) is mainly used, and the edge type is often used. Notebook PCs and other relatively small LCDs, but in recent years, due to the development of light sources or light guides, even edge-lit backlight units have improved brightness and uniformity of brightness in the screen, not only in smaller cases, even It is a large LCD, and it has also become a backlight unit using an edge illumination type. This is because LCD has the advantage of being thin and thin.

In the edge-lit backlight unit, the light guide plate is in direct contact with the reflective film. Therefore, once the structure is attached to the light guide plate and the reflection thin In the film, the brightness of the attached portion becomes abnormal, causing unevenness in the in-plane brightness. Here, there is a gap between the light guide plate and the reflective film, and it is necessary to keep the gap constant. For example, since the surface of the reflective film has beads, the gap between the light guide plate and the reflective film can be kept constant, and the adhesion can be prevented. However, at this time, when the light guide plate composed of the relatively soft material is in contact with the reflective film, there is a problem that the light guide plate is scratched due to the reflective film or the beads on the surface. As a countermeasure against this, for example, Patent Documents 1 to 3 report that the surface of the reflective film is coated with a bead containing an elastic system to form a scratch-resistant layer.

Further, according to the study of the present inventors, even in the scratch-resistant layer as disclosed in Patent Documents 1 to 3, by the relationship between the hardness of the beads and the hardness of the surface layer protrusion of the beads (hardness of the surface layer), It is judged that the gap between the reflector and the light guide plate is ensured, and that the scratch of the light guide plate due to the reflector is prevented.

In addition, in the formation of the scratch-resistant layer coated as in Patent Documents 1 to 3, it is necessary to provide a coating step or the like to increase the cost. Therefore, it is considered that the beads are added to the reflective film to ensure a gap between the light guide plate and the reflective film. However, according to studies by the present inventors, it has been found that the film forming property of the reflective film is lowered by the beads, and cracking easily occurs in the film formation of the reflective film.

(Patent Document 1) Japanese Patent Laid-Open Publication No. 2003-92018

(Patent Document 2) Japanese Patent Publication No. 2008-512719

(Patent Document 3) Japanese Patent Laid-Open Publication No. 2009-244509

Therefore, the first object of the present invention is to provide a white reflective film which can sufficiently suppress the adhesion to the light guide plate and can sufficiently suppress the scratch of the light guide plate.

In addition, the second object of the present invention is to provide a white reflective film which is excellent in film formability of a film while sufficiently suppressing adhesion to a light guide plate and sufficiently suppressing scratching of the light guide plate.

In order to achieve the above problems, the present invention employs the following constituents.

A white reflective film having a surface layer B composed of a reflective layer A and a thermoplastic resin composition containing particles, on a surface of the surface layer B opposite to the reflective layer A, having a white reflective film having protrusions formed by the particles and having a number of protrusions having a height of 5 μm or more on the surface of 10 ⁴ to 10 ¹⁰ /m ² , characterized in that the surface layer B is an aligned layer. The white reflective film a having a compression ratio of 40% or more when compressed at a load of 0.3 gf of the above particles, or b. is 10% compressive strength when compressed at a load of 3 gf of the particles is 0.1 to 10 MPa, and the Vickers hardness of the protrusions (Vickers hardness) is a white reflective film b of 5~30.

2. The white reflective film according to the above 1, wherein the particles are agglomerated particles.

3. The white reflective film according to the above 2, wherein the agglomerated particles are organic agglomerated particles of polyester agglomerated particles, acrylic-based agglomerated particles, polyurethane-condensed particles, and polyethylene agglomerated particles, and by oxidation At least one selected from the group consisting of condensed particles, alumina agglomerated particles, and inorganic agglomerated particles of ceramic agglomerated particles.

4. The white reflective film according to the above 1, wherein the particles have an average particle diameter d of 5 μm or more and 100 μm or less.

5. The white reflective film according to the above 2, wherein the secondary particle diameter ds of the aggregated particles is 5 μm or more and 100 μm or less.

6. The white reflective film according to any one of the above 1 to 5, wherein the content of the particles in the surface layer B is 30% by volume or less based on the volume of the surface layer B.

7. The white reflective film according to any one of the above 1 to 5, wherein the white reflective film a is based on the volume of the surface layer B, and the content of the particles in the surface layer B is 1% by volume or more. 30% by volume or less.

8. The white reflective film according to any one of the above 1 to 5, wherein the white reflective film is the white reflective film b.

9. The white reflective film according to any one of the above 1 to 5, wherein the content of the particles in the surface layer B is 50% by volume or less based on the volume of the surface layer B.

The white reflective film according to any one of the above-mentioned items 1 to 5, wherein the content of the particles in the surface layer B is 1% by volume or more based on the volume of the surface layer B, and 50% by volume or less.

The white reflective film according to any one of the above 1 to 5, wherein the reflective layer A has a pore volume ratio of 15% by volume or more and 70% by volume. %the following.

The white reflective film according to any one of the above 1 to 5, wherein the surface layer B has a void volume ratio of 0% by volume or more and less than 15% by volume.

The white reflective film according to any one of the above 1 to 5, wherein the amount of the volatile organic solvent is 10 ppm or less.

14. The white reflective film according to any one of the above 1 to 5, which is used as a surface light source reflector having a light guide plate.

15. The white reflective film according to any one of the above 1 to 5, which is used as a reflector for an edge illumination type backlight unit.

1‧‧‧Handle section

2‧‧‧ iron plate

3‧‧‧Reflective film

4‧‧‧Light guide plate

Load of 5‧‧500g

6‧‧‧Chassis

7‧‧‧3 optical sheets (2 diffusion films and 1 prism)

401‧‧‧ dots

801‧‧‧A triangular-shaped platform

Load of 802‧‧15kg

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a method of scratch evaluation and particle fall-off evaluation of a light guide plate of the present invention.

Fig. 2 is a schematic view showing a constitution used in the evaluation of the adhesion spot of the present invention.

The white reflective film of the present invention is also a white reflective film a or a white reflective film b having a reflective layer A and a surface layer B.

Hereinafter, each constituent component constituting the present invention will be described in detail.

[Reflective layer A]

In the white reflective film a and the white reflective film b of the present invention (represented In these cases, the reflective layer A of the white reflective film may be composed of a thermoplastic resin and a pore-forming agent, and thus contains a pore-forming agent, and contains pores in the layer, such as white. Layer. Although the details of the pore-forming agent are described later, for example, inorganic particles may be used, and a resin which is incompatible with the thermoplastic resin constituting the reflective layer A (hereinafter sometimes referred to as a non-compatible resin) may be used. Further, the reflectance at a wavelength of 550 nm of the reflective layer A is preferably 95% or more, more preferably 96% or more, and particularly preferably 97% or more. Thereby, the reflectance of the white reflective film is more easily changed into a preferable range.

The reflective layer A has pores in the layer as described above, but the ratio of the volume of the pores to the volume of the reflective layer A (pore volume ratio) is preferably 15% by volume or more and 70% by volume or less. By being such a range, the effect of improving the reflectance can be improved, and the reflectance as described above can be easily obtained. Moreover, the effect of improving the film forming property can be improved. When the pore volume ratio is too low, it tends to be difficult to obtain a preferable reflectance. From such a viewpoint, the void volume ratio of the reflective layer A is more preferably 30% by volume or more, and particularly preferably 40% by volume or more. Moreover, when it is too high, the film-forming property improvement effect tends to fall. From such a viewpoint, the void volume ratio of the reflective layer A is more preferably 65 vol% or less, particularly preferably 60 vol% or less.

The void volume ratio can be achieved by adjusting the kind, size, and amount of the pore former in the reflective layer A.

(thermoplastic resin)

As the thermoplastic resin constituting the reflective layer A, for example, a poly A thermoplastic resin composed of an ester, a polyolefin, a polystyrene, or an acrylic group. Among them, polyester is preferred from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As the polyester, a polyester composed of a dicarboxylic acid component and a diol component is preferably used. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, and sebacic acid. ingredient. Examples of the diol component include components derived from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol. Among these polyesters, aromatic polyesters are preferred, especially polyethylene terephthalate. Although the polyethylene terephthalate may be a homopolymer, when the film is stretched to the first or second axis, the crystallization is suppressed to improve the stretchability and the film-forming property. Copolymers are preferred. The above-mentioned dicarboxylic acid component or diol component is mentioned as a copolymerization component, but isophthalic acid and 2,6-naphthalene are used from the viewpoint of the high heat resistance and the high film-forming improvement effect. Carboxylic acid is preferred. The ratio of the copolymerization component is, based on 100 mol% of the total dicarboxylic acid component of the polyester, for example, 1 to 20 mol%, preferably 2 to 18 mol%, and more preferably 3 to 15 mol%. %, especially good for 7~11 mole%. By setting the ratio of the copolymerization component to this range, the effect of improving the film formability is excellent. Moreover, the thermal size method is excellent in stability.

(pore forming agent)

When inorganic particles are used as the pore former in the reflective layer A, white inorganic particles are preferred as the inorganic particles. Examples of the white inorganic particles include particles of barium sulfate, titanium oxide, cerium oxide, and calcium carbonate. this When the inorganic particles are selected such that the white reflective film has an average particle diameter or content such as an appropriate reflectance, it is not particularly limited. Preferably, the reflectance of the reflective layer A or the white reflective film is as long as it is within the preferred range of the present invention. Further, the void volume ratio of the reflective layer A may be in the preferred range of the present invention. In consideration of these, the average particle diameter of the inorganic particles is, for example, 0.2 to 3.0 μm, preferably 0.3 to 2.5 μm, more preferably 0.4 to 2.0 μm. Further, the content thereof is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, most preferably 31 to 53% by mass based on the mass of the reflective layer A. Further, by using the particle state as described above, it is possible to appropriately disperse in the polyester, and it is difficult to cause aggregation of the particles, thereby obtaining a film having no coarse protrusions, and at the same time suppressing stretching when the coarse particles are used as a starting point. rupture. The inorganic particles may be in any particle shape, and may be, for example, a plate shape or a spherical shape. The inorganic particles can be subjected to a surface treatment for enhancing the dispersibility.

When a non-compatible resin is used as the pore-forming agent, the non-coherent 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 a polyester, polyolefin, polystyrene or the like is preferred. These can be the characteristics of the particles. Further, the content thereof is the same as in the case of the inorganic particles, and if the white reflective film is selected to have an average particle diameter or content such as an appropriate reflectance, it is not particularly limited. Preferably, the reflectance of the reflective layer A or the white reflective film is as long as it is within the preferred range of the present invention. Further, the void volume ratio of the reflective layer A may be in the preferred range of the present invention. In consideration of the content, the content of the reflective layer A is preferably 10 to 50% by mass, more preferably 12 to 40% by mass, most preferably 13 to 35% by mass.

(other ingredients)

The reflective layer A may contain other components such as particles or resins different from ultraviolet absorbers, antioxidants, antistatic agents, fluorescent whitening agents, waxes, and pore formers, within a range not inhibiting the object of the present invention.

[Surface Layer B]

In the white reflective film of the present invention, the surface layer B composed of the thermoplastic resin composition containing particles forms the outermost layer of at least one side of the white reflective film. Further, a surface (hereinafter sometimes referred to as an outermost surface) on the side opposite to the reflective layer A of the surface layer B on which the outermost layer is formed has protrusions formed of the above particles.

Further, from the viewpoint of ensuring the gap between the light guide plate and the film, the protrusion must have a protrusion of an appropriate height at an appropriate frequency in the outermost surface. Therefore, in the present invention, the number of protrusions (protrusion frequency) of usually 5 μm or more on the outermost surface must be 10 ⁴ to 10 ¹⁰ / m ² . Thereby, the gap between the light guide plate and the film can be sufficiently ensured, so that the adhesion suppressing effect is excellent. When the frequency of the protrusion is too small, the adhesion suppressing effect is deteriorated. Further, when the frequency of the protrusion is too large, there is a tendency to increase the rate of falling off the particles or lower the reflectance.

Further, in the present invention, the ten-point average roughness (Rz) on the outermost surface and the average particle diameter d of the particles constituting the surface layer B (the secondary particle diameter is ds when the particles are agglomerated particles) satisfy the following The style is better.

0.1 × d (μm) ≦ Rz (μm) ≦ 0.7 × d (μm)

By satisfying the above formula, the particles in the outermost surface are suitably covered by the surface layer B. When it is embedded and becomes a more appropriate protrusion, it becomes easy to have a surface unevenness with an appropriate height, and the lifting effect can be ensured by the gap. In the above formula, the value of Rz is smaller than the value on the left side, and the particles are more embedded in the surface layer B, so that there is a tendency to reduce the effect of ensuring the gap. From this viewpoint, it is more preferable to satisfy 0.2 × d (μm) ≦ Rz (μm), and more preferably to satisfy 0.3 × d (μm) ≦ Rz (μm). Further, when the value of Rz is larger than the value on the right side, the particles excessively protrude from the surface layer B, and the effect of suppressing the fall of the particles when coming into contact with the light guide plate tends to be lowered. From this viewpoint, it is more preferable to satisfy Rz (μm) ≦ 0.6 × d (μm), and more preferably to satisfy Rz (μm) ≦ 0.5 × d (μm).

In order to achieve the above-described aspect, the average particle diameter d of the particles to be used (when the particles are agglomerated particles to be described later, the secondary particle diameter is ds), the thickness of the surface layer B may be adjusted. For example, in the particles having a certain average particle diameter, when the thickness of the surface layer B is thin, the value of Rz tends to increase, and when the thickness of the surface layer B is increased, the value of Rz tends to decrease. You can consider this tendency to make adjustments. The relationship between the average particle diameter of the particles and the thickness of the surface layer B will be described later.

The particle of the surface layer B of the present invention means a soft particle having a high compression ratio or a low compressive strength (S10 intensity) of 10%, and is formed as a layer of the alignment surface layer B or becomes a hard protrusion to suppress At the same time as the light guide plate is attached, the scratcher of the light guide plate is suppressed.

Hereinafter, the white reflective film a having the particles having a high compressibility and the aligned surface layer B, and the white reflective film b having the particles having a low S10 intensity and the hard protrusions are in the state of the surface layer B of various aspects. The sample is explained.

[Surface layer B of white reflective film a]

The surface layer B of the white reflective film a of the present invention is a layer of a thermoplastic resin composition containing particles and is oriented. The term "aligned layer" as used herein does not mean a layer formed by coating a film which has been stretched, but is formed by a preferred manufacturing method as described later, for example, by coextrusion. The method of drawing, etc., followed by the layer formed by stretching. Regarding the method of forming the surface layer B, the surface layer B is preferably a aligning polyester film layer, and the aligning polyethylene terephthalate film layer is more preferable. More preferably, it is a biaxially oriented polyester film layer, particularly preferably a biaxially oriented polyethylene terephthalate film layer. Thereby, the effect of improving the film forming property can be improved.

(thermoplastic resin)

The aspect of the thermoplastic resin for the white reflective film a will be described later.

(particle)

In the present invention, the particles of the surface layer B containing the white reflective film a are obtained by a measurement method described later to obtain a particle having a compression ratio of 40% or more at a load of 0.3 gf. In the present invention, as the particles for forming the surface unevenness for ensuring the gap and suppressing the adhesion of the light guide plate, by using the particles as described above, the scratch of the light guide plate can be suppressed. Further, the film has excellent film formability. This is considered to be due to the following mechanism. That is, as described above by particles The compression ratio is 40% or more. In the film forming step, particularly the stretching step of the film, the particles can be appropriately deformed following the deformation of the film, and it is considered that the film is broken in order to suppress the deformation of the film which does not follow the film. In particular, in the present invention, in order to secure the gap, the surface layer B has a specific protrusion in the surface thereof, and in order to obtain such a protrusion, it is preferable to use a particle having a relatively large particle diameter, but such a film When a particle having a relatively large particle diameter is contained, a film having the particle as a starting point is usually easily broken, and the present invention is suppressed by using a particle having a specific compression ratio as described above.

From such a viewpoint, the compression ratio when the particle weight is 0.3 gf is preferably 42% or more, more preferably 44% or more, still more preferably 45% or more.

In addition, when the compression ratio is too high, the surface of the surface layer B tends to be less likely to be formed, and it tends to be easily adhered to the light guide plate. From this viewpoint, the compression ratio at the time of compression of the particle load of 0.3 gf is preferably 95% or less, more preferably 90% or less, and still more preferably 85% or less.

In the present invention, the particles of the surface layer B of the white reflective film a satisfy the aspect of the protrusion of the surface layer B of the present invention, and the shape of the compression ratio is not particularly limited, and may be The organic particles may be inorganic particles or organic-inorganic composite particles. Further, the shape of the particles is not particularly limited, and examples thereof include spherical particles, plate-like particles, aggregated particles, and hollow particles. Among them, agglomerated particles are preferred, and the preferred agglomerated particles of the white reflective film a will be described later.

[Surface layer B of white reflective film b]

The surface layer B of the white reflective film b of the present invention is composed of a thermoplastic resin composition containing particles.

(thermoplastic resin)

The aspect of the thermoplastic resin for the white reflective film b will be described later.

(particles and protrusions)

In the present invention, as described above, the surface layer B containing the particles forms the outermost layer of at least one side of the white reflective film, and the surface of the outermost layer opposite to the reflective layer A of the surface layer B is formed by the particles. Protrusion.

In the present invention, the 10% compressive strength (S10 intensity) at a load of 3 gf, which is obtained by the measurement method described later by the particle, is 0.1 MPa or more and 10 MPa or less, and is determined by the measurement method described later by the protrusion. It is necessary to have a Vickers hardness of 5 or more and 30 or less when measured by weighting 500N. In the present invention, as the particles for forming the surface unevenness of the light-shielding plate for suppressing the adhesion, the relatively soft particles as described above are used, and the hardness of the protrusions is made harder as described above, and can be simultaneously achieved. The adhesion suppressing effect with the light guide plate and the scratch suppressing effect of the light guide plate. This is considered to be due to the following mechanism. That is, first, the attachment of the reflector and the light guide plate is considered to be an action such as attaching the light guide plate and the reflection plate, whereby the protrusion is parallel to the height direction of the protrusion. The relationship to the stress (in a direction perpendicular to the film surface) can be suppressed by setting the Vickers hardness in the height direction of the protrusion to a relatively hard region as in the above numerical range. In addition, for the scratch of the light guide plate, it is considered that the light guide plate and the reflection plate act as a rubbing action, whereby the protrusion is associated with the stress in a direction perpendicular to the height direction of the protrusion (a direction parallel to the film surface). The protrusion may be deformed and skewed in a direction perpendicular to the height direction, or may be suppressed by making the S10 intensity of the particles forming the protrusion into a relatively soft region as in the above numerical range.

When the S10 intensity of the particles is too high, when stress is applied in a direction perpendicular to the height direction of the protrusions, deformation of the particles tends to be less likely to occur, and since the scratch suppression effect of the light guide plate is deteriorated, it is preferably 5.0 MPa or less, more preferably It is 2.0 MPa or less, more preferably 1.0 MPa or less, and particularly preferably 0.8 MPa or less. Further, when the S10 strength of the particles is too high, the Vickers hardness of the protrusions may become too high. Further, when the S10 strength of the particles is too low, the Vickers hardness of the protrusions tends to be difficult to increase, and therefore it is preferably 0.12 MPa or more, more preferably 0.13 MPa or more, still more preferably 0.14 MPa or more, and particularly preferably 0.15 MPa. the above.

Further, when the Vickers hardness of the protrusion is too low, the adhesion suppressing effect with the light guide plate is deteriorated, so it is preferably 8 or more, more preferably 10 or more, still more preferably 12 or more. In addition, when it is too high, it is difficult to form a very hard protrusion by the particles which are relatively soft as described above, and even if the particles are easily deformed into relatively soft protrusions, the hard protrusions are overcome, and the scratch suppression effect of the light guide plate is deteriorated. . From this viewpoint, the Vickers hardness of the protrusions is preferably 25 or less, more preferably 20 or less, still more preferably 15 or less.

In the present invention, the particles of the surface layer B of the white reflective film b satisfy the protrusions on the surface of the surface layer B of the present invention, and the S10 strength is not particularly limited, and may be The organic particles may be inorganic particles or organic-inorganic composite particles. Further, the shape of the particles is not particularly limited, and examples thereof include spherical particles, plate-like particles, aggregated particles, and hollow particles. Among them, agglomerated particles are preferred, and the preferred agglomerated particles of the white reflective film b will be described later.

The surface layer B of the white reflective film b of the present invention is formed regardless of the range of the above requirements. For example, it can be melted simultaneously with the material of the reflective layer A, and can also be stretched by a sheet formed by extruding the same or adjacent metal cap. The method of crystallization (melt coextrusion method) may be provided by a method (coating method) in which a thermoplastic resin and a particle are coated and dissolved in a coating liquid of a suitable solvent or water, followed by drying. Among them, from the viewpoint of efficiently forming the surface layer B simultaneously with the formation of the reflective layer A, it is preferred to form the coating liquid by a melt coextrusion method and water. By analyzing the amount of the organic solvent when the film formed by heating, it was confirmed that the coating liquid was not applied by the organic solvent, but was formed by a co-extrusion method or a coating liquid using water as a solvent. In the present invention, the resin of the added particle and the material of the reflective layer A are simultaneously melted and stretched from the viewpoint of easily using the S10 low-strength particles while making the protrusion of the surface layer B suitable. The method of crystallization from a sheet formed by extrusion of the same or adjacent metal cap is preferred.

Regarding the preferred formation method of the surface layer B, the surface layer B of the white reflective film b is preferably a aligning polyester film layer to align the polyterephthalic acid. The ethylene glycol ester film layer is more preferable. More preferably, it is a biaxially oriented polyester film layer, particularly preferably a biaxially oriented polyethylene terephthalate film layer. Thereby, it becomes easy to obtain the Vickers hardness of a suitable protrusion.

[Component of Surface Layer B]

Hereinafter, components constituting the above-described white reflective film a and white reflective film b will be described.

(thermoplastic resin)

As the thermoplastic resin constituting the thermoplastic resin composition of the surface layer B, the same thermoplastic resin as the thermoplastic resin constituting the above-mentioned reflective layer A can be used. Among them, from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability, it is preferable to obtain a surface layer B which is easily aligned, or a Vickers hardness which is easy to obtain a suitable protrusion. .

As the polyester, the same polyester as the polyester of the above-mentioned reflective layer A can be used. Among these polyesters, from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability, an aromatic polyester is preferred, and polyethylene terephthalate is particularly preferred. Although polyethylene terephthalate can be a homopolymer, when the film is stretched on one axis or two axes, the crystallization is suppressed to improve the stretchability and the film-forming property. Copolymers are preferred. The above-mentioned dicarboxylic acid component or diol component is mentioned as the copolymerization component, but isophthalic acid and 2,6-naphthalene are used from the viewpoint of high heat resistance and high film forming property improvement effect. Carboxylic acid is preferred. Ratio of copolymerized components The example is based on 100% by mole of the total dicarboxylic acid component of the polyester, and is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, and more preferably 3 to 17 mol%, particularly preferably It is 12~16% by mole. By setting the ratio of the copolymerization component to this range, the effect of improving the film formability is excellent. Moreover, it is easy to achieve the Vickers hardness of the protrusion. Further, the thermal size method is excellent in stability.

(condensed particles)

In the present invention, as the particles which are suitably used for the surface layer B of the white reflective film a and the surface layer B of the white reflective film b, aggregated particles are preferred. Thereby, it is easier to form an appropriate protrusion by having appropriate heat resistance, and the above-described compression ratio or S10 intensity can be easily achieved. When the particles having non-agglomerated particles are to achieve the above-described compression ratio or S10 intensity, that is, generally, soft resin particles are used, and thus the resin particles are low in heat resistance, and a film production step such as an extrusion step is employed. In the middle, the particles tend to be difficult to maintain the shape of the particles, and there is a tendency that it is difficult to obtain a proper surface protrusion.

The aggregated particles may be organic aggregated particles and may be inorganic aggregated particles. The organic agglomerated particles preferably include polyester agglomerated particles, acrylic-based agglomerated particles, and polyurethane condensate from the viewpoint of easily obtaining an appropriate compression ratio or S10 strength and the above-described heat resistance and surface protrusion formation. Condensed particles, polyethylene agglomerated particles. Among them, the polyester agglomerated particles are preferred because they have a good compatibility with the polyester as the main raw material and have little influence on the film formability. Further, as the inorganic agglomerated particles, from the viewpoint of easily obtaining an appropriate compression ratio or S10 strength, preferred are cerium oxide agglomerated particles and oxygen. Aluminum condensed particles, ceramic agglomerated particles. Among them, in particular, it is preferable to obtain an appropriate compression ratio or S10 strength, and it is preferable to use a cerium oxide agglomerated particle.

In the present invention, as the particles of the surface layer B, from the viewpoint of easily obtaining an appropriate compression ratio or S10 strength, and excellent heat resistance, and easy formation of surface protrusions, it is preferable to use inorganic agglomerated particles, that is, to oxidize.矽 Condensed particles are particularly good.

(particle size)

The aggregated particles in the surface layer B preferably have a secondary particle diameter (ds) of 5 μm or more and 100 μm or less. As a result, it is easy to satisfy the protrusion of the surface layer B of the present invention, and the distance between the light guide plate and the film is kept constant, and the adhesion of the film can be further suppressed and the film formation property of the film can be improved. Improvement effect. When the secondary particle diameter is too small, a part of the white reflective film tends to adhere to the light guide plate. From such a viewpoint, the secondary particle diameter is more preferably 6 μm or more, still more preferably 8 μm or more, and particularly preferably 10 μm or more. Further, when it is too large, there is a tendency to lower the film forming property. Further, the particles tend to fall off easily, and the backlight unit becomes a white point defect when it falls off. From such a viewpoint, the secondary reflective particle a has a secondary particle diameter of preferably 90 μm or less, more preferably 80 μm or less, still more preferably 70 μm or less, particularly preferably 60 μm or less, and most preferably 50 μm or less. Further, the white reflective film b preferably has a secondary particle diameter of 95 μm or less, more preferably 90 μm or less, still more preferably 80 μm or less, particularly preferably 30 μm or less, and most preferably 25 μm or less.

Further, when the particles of the surface layer B of the present invention are not agglomerated particles, From the same viewpoint as described above, the average particle diameter d of the particles is preferably in the same range as the above-described secondary particle diameter ds.

The primary particle diameter (dp) of the aggregated particles is preferably 0.01 μm or more, and more preferably 5 μm or less. By simultaneously satisfying the above-described secondary particle size range, it is easy to obtain a suitable surface protrusion state, and it becomes easy to achieve a suitable particle compression ratio or S10 intensity. Further, the effect of improving the film formability can be further improved. When the primary particle diameter is too small, it tends to be difficult to obtain a secondary particle diameter of a sufficient size, and there is a tendency that it is difficult to obtain a suitable surface protrusion. From this viewpoint, the primary particle diameter is more preferably 0.02 μm or more, still more preferably 0.03 μm or more, and particularly preferably 0.05 μm or more. Further, when it is too large, it tends to be difficult to obtain a proper surface protrusion, and it is difficult to obtain an appropriate compression ratio or S10 strength. Further, there is a tendency to reduce the effect of improving the film forming property. From this viewpoint, it is more preferably 4 μm or less, still more preferably 3 μm or less, particularly preferably 2 μm or less, and most preferably 1 μm or less.

(content of particles)

In the white reflective film a, the content of the surface layer B is preferably 30% by volume or less based on the volume of the surface layer B. By setting it as this range, it is excellent in film-formability. Further, it is preferably 1% by volume or more and 30% by volume or less, and in the present invention, it is easy to form a surface of the surface layer B. When the amount is too small, the surface unevenness tends to decrease, and it is difficult to keep the interval between the light guide plate and the light guide plate constant. Accordingly, it is more preferably 2% by volume or more, and particularly preferably 3% by volume or more. In addition, when the amount is too large, the strength of the surface layer B tends to deteriorate, and there is a tendency to lower the film forming property, and there is a tendency to decrease. The tendency of the mechanical strength of the resulting film to be low. Accordingly, it is more preferably 25% by volume or less, still more preferably 20% by volume or less, and particularly preferably 15% by volume or less.

In the white reflective film b, the content of the particles in the surface layer B is preferably 1% by volume or more and 50% by volume or less based on the volume of the surface layer B. By being in this range, in the present invention, it is easy to become the Vickers hardness of the appropriate protrusion, and it is easy to become the surface of the surface layer B. When the amount is too small, the surface unevenness tends to be small, and it becomes difficult to keep the interval with the light guide plate constant. Accordingly, it is more preferably 2% by volume or more, and particularly preferably 3% by volume or more. Further, when the amount is too large, the Vickers hardness of the desired protrusion is hard to be obtained, and the strength of the surface layer B tends to be deteriorated, which tends to lower the film forming property. Further, there is a tendency to lower the mechanical strength of the obtained film. Accordingly, it is more preferably 45% by volume or less, still more preferably 40% by volume or less, and particularly preferably 30% by volume or less.

Further, the volume fraction of the particles can be determined from the mass fraction and density of the thermoplastic resin constituting the surface layer B, and the mass fraction and density of the particles.

(other ingredients)

The surface layer B may contain components other than the above constituent components insofar as it does not inhibit the object of the present invention. Examples of the component include particles, resins, and the like which are different from the ultraviolet absorber, the antioxidant, the antistatic agent, the fluorescent whitening agent, the wax, and the agglomerated particles.

Further, the surface layer B may contain a range which does not inhibit the object of the present invention. The pore-forming agent listed in the reflective layer A can improve the reflectance by such a phenomenon. On the other hand, when the content of the pore former in the surface layer B is reduced or the pore former is not contained, the effect of improving the film formability can be improved. From such a viewpoint, the pore volume ratio of the surface layer B (the volume ratio of the volume of the surface layer B to the pores of the surface layer B) is 0% by volume or more, and preferably less than 15% by volume, and more preferably It is preferably 5% by volume or less, and particularly preferably 3% by volume or less. In particular, in the present invention, since the effect of improving the reflection property and the film forming property can be simultaneously improved, it is particularly preferable to use the above-mentioned preferred pore volume ratio in the reflective layer A and the preferred pore volume ratio in the surface layer B.

[layer composition]

The thickness of the reflective layer A of the present invention is preferably 80 to 300 μm. Thereby, the effect of improving the reflectance can be improved. When the thickness is too thin, the effect of improving the reflectance is lowered, and when it is too thick, there is no efficiency. From this point of view, it is more preferably 150 to 250 μm.

Further, the thickness of the surface layer B (when the number of layers is plural, the thickness of one layer which is the outermost layer on the side of the light guide plate) is preferably 10 to 70 μm. Thereby, the relationship between the average particle diameter d of the particles or the secondary particle diameter ds of the aggregated particles and the ten-point average roughness Rz together with the above-described preferred particle form is preferable as described above. The gap between the light plates is ensured to be easy. Moreover, the aspect of Rz and the frequency of the protrusions tends to be the preferred aspect described above. Further, the effect of improving the reflectance and the effect of improving the film forming property can be improved. When it is too thin, it becomes difficult to achieve a preferable Rz, and there exists a tendency for the particle fall suppression effect to fall. also There is a tendency to reduce the film-forming effect. Further, when it is too thick, there is a tendency to lower the effect of improving the reflectance, and it becomes difficult to obtain a preferable Rz and a frequency of protrusion. From this viewpoint, it is more preferably 20 μm or more, and still more preferably 60 μm or less.

In the white reflective film a of the present invention, the average particle diameter d of the particles in the surface layer B (the secondary particle diameter ds when the particles are agglomerated) and the thickness t of the surface layer B satisfy the following formula.

0.05≦d(μm)/t(μm)≦20

By satisfying the above formula, it is easy to have surface unevenness having an appropriate height on the outermost surface, whereby the effect of ensuring the gap can be improved. In the above formula, the value of d/t is smaller than the value on the left side, and the particles tend to be easily embedded in the surface layer B, and tend to reduce the effect of ensuring the gap. From this viewpoint, it is preferable to satisfy 0.07 ≦d (μm) / t (μm), more preferably 0.09 ≦ d (μm) / t (μm), and even more preferably 0.3 ≦ d (μm) / t (μm), particularly preferably in the form of 0.4 ≦d (μm) / t (μm). Further, when the value of d/t is larger than the value on the right side, the particles tend to protrude from the surface layer B, and there is a tendency to lower the effect of suppressing the fall-off when the contact with the light guide plate is reduced. From this point of view, it is preferable to satisfy d (μm) / t (μm) ≦ 19, more preferably satisfies d (μm) / t (μm) ≦ 18, and even more preferably satisfies d (μm) / t ( Μm) ≦10, particularly preferably satisfies the condition of d(μm)/t(μm) ≦2.

Further, in the white reflective film b, the average particle diameter d of the particles added to the surface layer B (the secondary particle diameter ds when the particles are agglomerated particles) and the surface layer B are from the viewpoint of easily achieving the hardness of the appropriate protrusions. Thickness (the particle does not have a thickness protruding from the surface portion in the surface layer B) t The relationship between 1.5d≦t≦5.0d is better. More preferably, it is 2.0d≦t≦4.0d, and the best is 2.5d≦t≦3.5d.

The laminated structure of the white reflective film includes a reflection layer A for A, a surface layer B for B, a B/A layer structure, a B/A/B layer structure, and a B/A/B'/A layer. The four-layer structure (herein, B' indicates the inner layer B' having the same configuration as the surface layer B), and B is disposed in a plurality of layers of five or more layers on the outermost layer of at least one side. It is particularly preferably composed of a two-layer structure of B/A and three layers of B/A/B. It is preferably composed of three layers of B/A/B, and is more excellent in film formability. Moreover, it is difficult to cause problems such as curling.

When the thickness of the entire white reflective film is set to 100%, the thickness ratio of the reflective layer A is 50 to 90%, and the thickness ratio of the surface layer B is 5 to 50%, and further 5 to 25%. The aspect is preferable, and the balance of various characteristics such as reflection characteristics and film forming properties can be made better. Where the thickness ratio of each layer has a plurality of layers, it means the ratio of the integrated thicknesses of the layers.

In the present invention, in addition to the reflective layer A and the surface layer B, other layers may be provided within a range not impairing the object of the present invention. For example, it may have a layer for imparting functions such as antistatic property or electrical conductivity, ultraviolet durability, and the like. Further, in order to improve the film forming property of the film, the void volume ratio may be relatively low (preferably 0% by volume or more, 15% by volume or less, more preferably 5% by volume or less, and particularly preferably 3% by volume or less). Support layer C.

[Manufacturing method of film]

Hereinafter, one of the methods for producing the white reflective film of the present invention will be described. example.

When the white reflective film of the present invention is produced, the surface of the reflective layer A obtained by a melt extrusion method or the like is formed by a molten resin coating method (including a melt extrusion resin coating method), a coextrusion method, and a lamination method. The layer B has a laminated structure and is preferable from the viewpoint of film forming properties. Thereby, the surface layer B is easily used as the aligned layer, and the Vickers hardness of the desired protrusion is easily obtained. Among them, the white reflective film of the present invention is particularly preferable in that the reflective layer A and the surface layer B are laminated by a co-extrusion method. Further, it is preferable that the reflective layer A and the surface layer B are directly laminated by a co-extrusion method. By laminating by the co-extrusion method, in addition to improving the interface adhesion between the reflective layer A and the surface layer B, the surface layer B is formed after the film is formed without being subjected to film formation or film formation. The steps are therefore cheap and easy to mass produce.

Hereinafter, a description will be given of a method of using a polyester as a thermoplastic resin constituting the reflective layer A and a thermoplastic resin constituting the surface layer B by a coextrusion method as a lamination method, but the present invention is not limited thereto. The manufacturing method is also referred to the following, and can be manufactured in the same manner even in other aspects. In this case, when the extrusion step is not included, the following "melt extrusion temperature" can be changed, for example, to "melting temperature". Further, the melting point of the polyester used was defined as Tm (unit: ° C), and the glass transition temperature was determined to be Tg (unit: ° C).

First, as the polyester composition for forming the reflective layer A, it is prepared to mix a polyester, a pore former, and other optional components. Moreover, as a polyester composition for forming the surface layer B, it is prepared to mix a polyester, a particle, and other arbitrary components. These polyester compositions are dried and used to remove moisture.

Next, the dried polyester composition was separately introduced into another extruder to carry out melt extrusion. The melt extrusion temperature is preferably Tm or more and may be about Tm + 40 °C.

Further, at this time, the polyester composition used for the production of the film, in particular, the polyester composition used for the reflective layer A, is a non-woven fabric having an average screen width of 10 to 100 μm composed of stainless steel fine wires having a wire diameter of 15 μm or less. It is better to filter the filter. By performing this filtration, aggregation of particles which are easily aggregated to become coarse aggregated particles is generally suppressed, and a film having a small amount of foreign matter can be obtained. Further, the average screen spacing of the non-woven fabric is preferably 20 to 50 μm, and more preferably 15 to 40 μm. The filtered polyester composition is extruded in a molten state using a co-extrusion die while being extruded from a die in a multilayer state by a multilayer extrusion method (co-extrusion method) to produce an unstretched product. Laminated sheets. The unstretched laminated sheet extruded from the mold is cooled and solidified by a casting drum to form an unstretched laminated film.

Then, the unstretched laminated film is heated by roll heating, infrared heating, or the like, and stretched in the film forming machine axis direction (hereinafter sometimes referred to as a longitudinal direction or a long-hand direction or MD) to obtain a longitudinally stretched film. This stretching is excellent in the behavior of the circumferential speed difference using two or more rolls. The film after the longitudinal stretching is continuously guided to a tenter, and is stretched in a direction perpendicular to the longitudinal direction (hereinafter sometimes referred to as a lateral direction or a width direction or TD) to form a biaxially stretched film.

The stretching temperature is preferably a Tg or more of a polyester (preferably a polyester constituting the reflective layer A) and a temperature of Tg + 30 ° C or less, and the film forming property is more excellent, and the pores are easily formed. Also, as the stretching ratio, the vertical The direction in the horizontal direction is preferably 2.5 to 4.3 times, and more preferably 2.7 to 4.2 times. When the draw ratio is too low, the thickness of the film tends to be deteriorated, and it is difficult to form voids. When the draw ratio is too high, cracking tends to occur in the film formation. In addition, when the longitudinal stretching is performed and the horizontal stretching is followed by the two-axis stretching, the second stage (in this case, the horizontal stretching) is higher than the stretching temperature of the first stage by about 10 to 50 ° C. good. This is due to the fact that the Tg as a 1-axis film is lifted by the stretching in the first step.

Further, it is preferred to use a preheated film before each stretching. For example, the pre-heat treatment of the transverse stretching is preferably carried out slowly from a temperature higher than the polyester (preferably the polyester constituting the reflective layer A) by a temperature of Tg + 5 °C. The temperature rise in the transverse stretching process can be stepwise (sequential), usually a sequential heating. For example, the transverse stretching zone of the tenter is divided into a plurality of sections along the traveling direction of the film, and the temperature is raised in each zone by a heating medium that flows at a predetermined temperature.

The film after the biaxial stretching is continuously applied in the order of heat fixation and thermal relaxation to form a biaxial alignment film, but the stretching is continued from the melt extrusion, and the treatment can be carried out while the film is being operated.

After the biaxial stretching, the film is directly grasped by the clip, and the melting point of the polyester (preferably the polyester constituting the reflective layer A) is set to be fixed by Tm (Tm-20 ° C) to (Tm - 100 ° C). The heat treatment is carried out at a reduced amplitude of 10% or less, and heat-fixing is performed to lower the heat shrinkage rate. When the heat treatment temperature is too high, the planarity of the film tends to deteriorate, and the thickness spot tends to increase. When it is too low, there is a tendency that the heat shrinkage rate increases.

Also, in order to adjust the amount of heat shrinkage, two of the films that are being held by the cut are held At the end, the rolling speed of the film in the longitudinal direction is adjusted to relax in the longitudinal direction. As a means for relaxing, the speed of the roller group on the exit side of the tenter is adjusted. As the ratio of the slack, the deceleration of the roll group is performed with respect to the film linear velocity of the tenter, and it is preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, and particularly preferably 0.3 to 2.0%. The relaxed film (this value is referred to as "relaxation rate") is adjusted in the longitudinal direction by controlling the relaxation rate. Further, the film is reduced in the lateral direction by the process of cutting both ends, and the desired heat shrinkage rate can be obtained.

Further, in the case of biaxial stretching, in addition to the above-described vertical-horizontal sequential biaxial stretching method, a lateral-longitudinal biaxial stretching method may be employed. Further, it is possible to form a film by simultaneous biaxial stretching. 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 the longitudinal direction and the transverse direction.

Further, as a method of forming the surface layer B of the white reflective film b, after longitudinal stretching, a solution in which a layer forming material is dissolved or dispersed in water is applied, and after drying, it may be formed by lateral stretching. Drying can also take into account the preliminary heating of the transverse stretching.

A white reflective film of the present invention as such can be obtained.

[Characteristics of White Reflective Film] (reflectance, brightness)

The reflectance of the white reflective film of the present invention measured from the surface layer B side is preferably 96% or more, more preferably 97% or more, still more preferably 97.5% or more. With a reflectance of 96% or more, it is used in liquid crystal display devices, illumination, etc. When you get a higher brightness. The reflectance can be a preferred aspect by increasing the pore volume ratio of the reflective layer A or the like, or thickening the thickness of the reflective layer A, or thinning the thickness of the surface layer B to obtain a preferred aspect. To be reached.

Further, the measured luminance from the layer B-side surface is determined from the measured although the method described below, but 5400cd / m ² or more preferably, 5450cd / m ² or more better, 5500cd / m ² or more particularly preferred.

The reflectance and brightness of the white reflective film are the values of the surface on the side of the light guide plate when used with the light guide plate.

(amount of volatile organic solvent)

The amount of the volatile organic solvent measured by the method described later in the white reflective film of the present invention is preferably 10 ppm or less. Thereby, the surface layer B can be represented by a coating method which is not formed by using an organic solvent. In addition, when a film for forming a self-recovering material is used, it is difficult to generate a gas mark and the film forming property is improved (recovery film-forming property). From this viewpoint, it is more preferably 5 ppm or less, still more preferably 3 ppm or less, and is preferably 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, the surface layer B is formed by a solution coating method without using an organic solvent, and the above method is preferably employed. Moreover, the amount of volatile organic solvent tends to increase by the use of organic particles.

Example

Hereinafter, the present invention will be described in detail by way of examples. Also, each characteristic value is as follows Method of determination.

(1) Light reflectance

The integrating sphere was attached to a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and the reflectance at a wavelength of 550 nm when the BaSO ₄ whiteboard was set to 100% was used as a reflectance. Further, the measurement was performed on the surface of the surface layer B side. When the surface layer B has a different surface layer B, it is measured on the surface of the surface layer B which becomes the light guide plate side.

(2) Average particle diameter of particles (d)

The particle size distribution of the particles was determined by a particle size distribution meter (LA-950, manufactured by Horiba, Ltd.), and the particle diameter at d50 was taken as the average particle diameter.

(3) Primary particle size (dp) of agglomerated particles

When the particles are aggregated particles, the following primary particle diameter (dp) measurement method is employed.

In the film containing the aggregated particles, the resin component was dissolved in a solvent, and the particles (secondary particles) thus recovered were observed using a S-4700 electric field emission type scanning electron microscope manufactured by Hitachi, Ltd. at a magnification of 10,000 times. The aggregation state of the primary particles on the surface of the secondary particles, the particle diameter of 100 arbitrary primary particles, and the primary particle diameter (dp) was obtained from the average value.

In the above method, when the resin component is dissolved in a solvent, when the agglomerated particles are also dissolved (for example, in the case of organic particles), the agglomerated particles before blending are used. The S-4700 electric field emission type scanning electron microscope manufactured by Hitachi, Ltd. was observed at a magnification of 10,000 times, and the aggregation state of the primary particles on the surface of the secondary particles was observed, and the particle diameter of 100 arbitrary primary particles was measured. The average value of the primary particle diameter (dp) was obtained.

The case of 1 μm or more and less than 3 μm is set to "<3", and the case of less than 1 μm is set to "<1".

(4) Secondary particle size of aggregated particles (ds)

When the particles are aggregated particles, the following secondary particle diameter (ds) measurement method is employed.

In the film containing the agglomerated particles, the resin component was dissolved in a solvent, and the particles (secondary particles) thus recovered were observed using a S-4700 electric field emission type scanning electron microscope manufactured by Hitachi, Ltd., at a magnification of 1,000 times, and 100 samples were observed. The particle diameter was measured for any particles, and the secondary particle diameter (ds) was determined from the average value thereof. In addition, the case other than the spherical shape is obtained by (long diameter + short diameter)/2. The short diameter refers to the largest diameter perpendicular to the long diameter.

In the above method, when the resin component is dissolved in a solvent, the aggregated particles are also dissolved (for example, in the case of organic particles), and the agglomerated particles before blending are used, and an electric field emission type scanning electron microscope (S-4700) manufactured by Hitachi, Ltd. is used at a magnification of 1000. The number of particles was measured by 100 arbitrary particles, and the secondary particle diameter (ds) was determined from the average value. In addition, the case other than the spherical shape is obtained by (long diameter + short diameter)/2. The short diameter refers to the largest diameter perpendicular to the long diameter.

(5) Compressibility of particles (%)

Using a micro-compression tester MCTM-200 manufactured by Shimadzu Corporation, a compression test was performed on each of the particles at a load of 0.3 gf and a load rate of 0.0725 gf/sec, and the average value of the 10-point measurement was determined as a compression ratio.

(6) 10% compressive strength (S10 intensity)

The compressive strength of each of the particles of 3 gf was measured using a micro hardness tester ENT-1100a manufactured by Elionix Co., Ltd., and the compressive strength (MPa) at 10% deformation was used. The average of 5 measurements was used.

(7) Vickers hardness of the protrusion

In the same manner as the measurement of the 10% compressive strength described above, a tiny hardness tester ENT-1100a manufactured by Elionix Co., Ltd. was used, and the pressure was extruded into the projections of the respective surface layers at a weight of 500 N to calculate the Vickers hardness. The average of 5 measurements was used.

(8) Film thickness and layer composition

The white reflective film was cut into a cross section by a microtome, and the cross section was observed using a S-4700 electric field radiation type scanning electron microscope manufactured by Hitachi, Ltd., and observed at a magnification of 500 times to obtain a film overall and reflection. Layer A, the thickness of the surface layer B. Further, the thickness of the entire film and the surface layer B is a thickness at which a portion which is more prominent than the surface of the surface layer B is removed. The thickness ratio of each layer was calculated in addition to the thickness (μm) of each layer.

(9) Calculation of pore volume ratio

The calculated density was determined from the density and blending ratio of the polymer, the added particles, and other components of the layer in which the void volume ratio was determined. At the same time, the layer or the like is peeled off to measure the mass and the volume, and the solid density is calculated, and the calculated density and the solid density are obtained by the following formula.

Pore volume ratio = 100 × (1 - (solid density / calculated density))

Further, the density of the isophthalic acid copolymerized polyethylene terephthalate (after 2-axis stretching) was set to 1.39 g/cm ³ , and the density of barium sulfate was set to 4.5 g/cm ³ .

Further, the solid density was determined by determining the mass per unit volume only by the layer which measured the pore volume ratio. In the volume system, the sample was cut out to have an area of 3 cm ² , and the thickness of the sample was measured by an electric micrometer (K-402B manufactured by Anritsu K.) at an average value of 10 points as a thickness, and was calculated as an area×thickness. The quality is measured in an electronic balance.

Further, as the specific gravity of the particles (including the aggregated particles), the value of the specific gravity of the bulk is used in the following cylinder method. The cylinder having a volume of 1000 ml was filled with particles in an absolute state, and the total weight was measured. The weight of the cylinder was determined by subtracting the weight of the cylinder from the weight of the whole cylinder, and the volume of the cylinder was measured by the weight of the pellet (g). ) is obtained by dividing the volume (cm ³ ).

(10) Melting point, glass transition temperature

Use a differential scanning calorimeter (TA Instruments 2100) DSC) was measured at a temperature increase rate of 20 ° C / min.

(11) Ten point average roughness (Rz) and protrusion frequency

The shape of the protrusion on the surface of the film was measured by a three-dimensional roughness measuring device SE-3CKT (manufactured by Otaru Research Co., Ltd.), and the measurement was performed at a height of 0.25 mm, a measurement length of 1 mm, a scanning pitch of 2 μm, and a scanning frequency of 100 times. The shape of the protrusion is recorded at 1000 times and the scanning direction magnification is 200 times. In the obtained protrusion shape, 5 points from the point where the peak (Hp) was high and 5 points from the valley (Hv) were taken out, and the 10-point average roughness (Rz, unit: nm) was obtained by the following formula. In addition, the analysis system uses a three-dimensional roughness analysis device SPA-11 (manufactured by Otaru Research Co., Ltd.).

Moreover, the number of protrusions (number/m ² ) having a height of 5 μm or more was obtained from the obtained protrusion shape (horizontal axis: protrusion height, vertical axis: projection shape of the number of protrusions) as the protrusion frequency.

(12) Brightness

The reflective film was taken out from the LED liquid crystal television (LG42LE5310AKR) manufactured by LG, and the surface layer B side of each of the reflective films described in the examples was placed on the screen side (the side in contact with the light guide plate), and the brightness meter was used in the state of the backlight unit. (Dayu Electronics Model MC-940), will be backlit The center was measured by the front side at a measuring distance of 500 mm.

(13) Close spot assessment (attachment evaluation)

As shown in Fig. 2, the chassis (6) is taken out from the LED LCD TV (LG42LE5310AKR) made by LG, and the inner side of the TV is placed on the water platform in an upward direction, on which the chassis will be almost the same size as the chassis. The reflective film is placed such that the surface layer is upward, and three light guide plates and two optical sheets (one diffusion film and one prism) (7) of the original television are placed thereon. Next, in the plane, in the region containing the most intense portion of the concave and convex portion of the chassis, as shown in Fig. 2, a triangular-shaped table (801) having three cylindrical legs with a diameter of 5 mm is placed, on which the weight is multiplied. The load of 15kg (802), the area surrounded by the three legs is visually observed, and if there is no abnormal bright part, it is recorded as "no close spot" (close spot evaluation ○). In the case of an abnormally bright portion, the DBEF sheet of the original television is placed on the optical sheet, and the DBEF sheet of the original television is also visually observed. If the abnormally bright portion cannot be corrected, it is marked as "closed spot" (evaluation ×). When the abnormally bright part disappears, it is recorded as "almost no dense spot" (evaluation △). Moreover, the length of each side of the area surrounded by the three legs becomes a slightly equilateral triangle of 10 cm.

(14) Film forming properties

The film described in the examples was observed for film formation stability at the time of film formation by a continuous film forming method using a tenter, and was evaluated on the basis of the following criteria.

◎: The film can be stably formed for 8 hours or more.

○: It is stable for 3 hours or more for 8 hours.

△: The cut was not performed for 3 hours and 1 degree.

X: The film was cut for a period of less than 3 hours, and the film formation was not stable.

(15) Amount of volatile organic solvent

At room temperature (23 ° C), 1 g of the film sample was placed in a 10 L fluororesin bag in which it was rinsed with pure nitrogen and sealed. Next, immediately take nitrogen from the bag at a flow rate of 0.2 L/min, and take 0.2 L and 1.0 L of nitrogen in two tubes of the TENAX-TA trap for analysis. Using this method, quantify by HPLC and GCMS. The quality of the organic solvent component contained in the nitrogen. The obtained value was converted into an amount of 10 L of nitrogen, and the mass of the organic solvent volatilized in 10 L of nitrogen was determined from 1 g of the film sample as the amount of the volatile organic solvent (unit: ppm, mass basis of the film sample). Further, the aldehyde was eluted from the trap tube in acetonitrile and quantified by HPLC. Further, when the values of HPLC and GCMS are different, the values of most of the detected persons are used.

(A) For Examples 1 to 10 and Comparative Examples 1 to 2 (16) Scratch evaluation of the light guide plate (grinding evaluation) and evaluation of particle shedding (1)

As shown in Fig. 1, an iron plate (2, weight about 200 g) having a length of 200 mm, a width 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 placed on the upper width of 250 mm × length 200 mm. The reflective film (3) is attached from the both ends of the width direction by 25 mm so as to protrude from the iron plate (central 200 mm × 200 mm) The part is carried out in an overlapping manner with the iron plate). At this time, the evaluation surface (surface level) of the reflective film has become the outer side. Further, a portion of 25 mm remaining at both ends in the width direction of the reflective film is folded back to the end portion of the reflective film on the back side of the iron plate (the portion where the blade is opened by a knife or the like during sampling), and the light guide plate is shaved to eliminate the influence.

Next, the dot surface having the dot (401) is fixed on the water guiding plate (4, at least 400 mm × 200 mm), and is fixed on the reflective film of the iron plate prepared as described above. The evaluation surface is in contact with the light guide plate such that the side of the reflective film faces downward and is placed on the light guide plate, and then carries a load of 500 g (5) thereon, and is fixed at a distance of 200 mm (in a region of 400 mm × 200 mm). The reflective film on the iron plate is moved back and forth 15 times at a speed of about 5 to 10 seconds. Then, on the surface of the light guide plate, the presence or absence of the particles which were peeled off from the reflective film and the presence or absence of the reflection film were observed using a 20-fold magnifying glass (Loupe) and evaluated by the following criteria.

The full range of 400mm × 200mm wiped on the light guide plate can be observed by a magnifying glass after moving back and forth 15 times. When there is no scar, it is recorded as "no grinding" (grinding evaluation ○), and there is no observable scar after 10 round-trip movement. However, when there are observable scars after moving back and forth 15 times, it is marked as "difficult to be ground" (grinding evaluation △). When there are observable scars after moving back and forth 10, it is recorded as "sharpable" (grinding evaluation ×).

Further, after the movement of 15 is repeated, the entire range of 400 mm × 200 mm wiped on the light guide plate is referred to as "the particles are not detached" (the detachment evaluation ○) unless there is no white foreign matter observed by the magnifying glass. Observable white When the foreign matter is colored, the white foreign matter is observed by a microscope, and the particles of the surface layer B (agglomerated particles) are observed. If the particles are separated by 5 or less, the particles are almost not peeled off (the peeling evaluation Δ), and if it is 6 More than one is described as "particle falling off" (falling evaluation ×).

Further, by the above evaluation, in order to suppress the influence of the dot size as much as possible, a large area of the spot size of the light guide plate is selected, and each evaluation sample is collected.

(17) White point evaluation (1)

Using the reflective film and the light guide plate used in the evaluation of the above (16), the reflective film is placed on the stage with the surface layer facing upward, and the light guide plate is placed thereon with the dot surface facing downward. The weight of each of the four sides of the light board is fixed to 200g, and the backlight source of the LED LCD TV (LG42LE5310AKR) made by LG makes light from the side of the light guide plate. If there is a bright spot other than the dot of the light guide plate that can be visually observed, it is generated. White point (evaluation ×). In addition, if there is an abnormally bright spot that can be visually observed, it is recorded that no white spot is generated (evaluation ○).

(B) For Examples 11 to 13, Comparative Examples 3 to 5 (18) Scratch evaluation of the light guide plate (grinding evaluation) and evaluation of particle shedding (2)

In the above (16), the evaluation was carried out in the same manner except that 1 kg of the weight (5) was used.

(19) White point evaluation (2)

Except for the reflective film and the light guide plate used for the evaluation of the above (18), the evaluation was performed in the same manner as (17) above.

[Manufacturing 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% based on 100 mol% of the total acid component of the obtained polyester), and 98 parts by mass of ethylene glycol. 1.0 parts by mass of diethylene glycol, 0.05 parts by mass of manganese acetate, and 0.012 parts by mass of lithium acetate were injected into a flask equipped with a distillation column and a distillation condenser, and heated at 150 to 240 ° C while stirring to distill off methanol. The transesterification reaction is carried out. After distilling off methanol, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of cerium oxide were added, and the reactant was transferred to a reactor. Next, the inside of the reactor was gradually reduced to 0.3 mmHg while stirring, and the temperature was raised to 292 ° C to carry out a polycondensation reaction to obtain an isophthalic acid copolymerized polyethylene terephthalate 1. This polymer has a melting point of 235 °C.

[Production Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2]

In addition to being changed to 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (14 mol% relative to 100 mol% of the total acid component of the obtained polyester), In the same manner as in the above Production Example 1, the isophthalic acid copolymerized polyethylene terephthalate was obtained. Ester 2. This polymer has a melting point of 215 °C.

[Manufacturing Example 3: Preparation of Particle Master Wafer 1]

A part of the above-mentioned obtained phthalic acid copolymerized polyethylene terephthalate 1, and a barium sulfate particle having an average particle diameter of 1.0 μm as a pore-forming agent (abbreviated as BaSO ₄ in the table), in the god The NEX-T60 tandem extruder manufactured by the Steel Co., Ltd. was mixed with the content of the barium sulfate particles in an amount of 63% by mass based on the mass of the obtained main wafer, and extruded at a resin temperature of 260 ° C to prepare barium sulfate. Particle particle master wafer 1.

[Manufacturing Example 4: Preparation of Particle Master Wafer 2]

The above-obtained phthalic acid copolymerized polyethylene terephthalate 2, as agglomerated particles A, will be Dongcao. GO105 (coagulated cerium oxide) manufactured by Sebacillus Oxide Co., Ltd. was subjected to air classification to obtain particles having an average particle diameter (secondary particle diameter) of 15 μm so as to be mixed at 8% by mass, and extruded at a melting temperature of 235 ° C to prepare. Particle main wafer 2.

[Example 1] (Manufacture of white reflective film)

Using the above-mentioned obtained phthalic acid copolymerized polyethylene terephthalate 1 and the particle main wafer 1 as a raw material of the reflective layer (layer A), the isophthalic acid copolymerized polyethylene terephthalate The alcohol ester 2 and the particle main wafer 2 are used as raw materials of the surface layer (layer B), and the respective layers are as shown in Table 1. The composition is mixed and put into an extruder. The layer A is melted at a temperature of 255 ° C, and the layer B is at a melt extrusion temperature of 230 ° C. As shown in Table 1, it is a layer B/layer A/B. In the manner of layer formation, a three-layer co-extrusion die device is used to join the cells, and the lamination is formed from the crystal grains directly while maintaining the lamination state. At this time, the thickness of the B layer/A layer/B layer was adjusted so that the amount of discharge of each extruder was 10/80/10 after stretching in two directions. Further, the sheet was cooled to a temperature of 25 ° C to form a cooled and solidified unstretched film. The unstretched film was passed through a preheating zone at 73 ° C, followed by a preheating zone of 75 ° C, guided to a longitudinal stretching zone maintained at 92 ° C, stretched 2.9 times in the longitudinal direction, and cooled at 25 ° C. Next, both ends of the film were held by a clip, and were held at a cross-sectional stretching zone of 130 ° C by a preheating zone of 115 ° C, and stretched 3.6 times in the transverse direction. Then, it was heat-fixed at 185 ° C in a tenter to reduce the width ratio by 2%, the width at 130 ° C to reduce the width in the transverse direction, and then cut off both ends of the film to thermally relax at a longitudinal relaxation rate of 2%. At room temperature, a film having a thickness of 250 μm as shown in Table 1 was obtained. The evaluation results of the obtained film are shown in Table 2.

[Examples 2 to 10, Comparative Examples 1 to 2]

A white reflective film was obtained in the same manner as in Example 1 except that the appearance of the particles used in the surface layer was as shown in Table 1. The evaluation results of the obtained film are shown in Table 2.

Further, the types of particles used individually are as follows.

Condensed Particle B: Will Dongcao. AY-601 (coagulated cerium oxide) manufactured by cerium oxide co., Ltd. as the average particle diameter by wind grading (2 The secondary particle size) is 15 μm.

Aggregated particle C: C812 (coagulated cerium oxide) manufactured by Grace Japan Co., Ltd. was used as an average particle diameter (secondary particle diameter) of 15 μm by air classification.

Aggregated particle D: CARiACT P-10 (coagulated ceria) manufactured by Fuji Silicia Chemical Co., Ltd. was used as an average particle diameter (secondary particle diameter) of 15 μm by air classification.

Aggregated particle E: C622 (coagulated cerium oxide) manufactured by Grace Japan Co., Ltd. as an average particle diameter (secondary particle diameter) of 15 μm by air classification.

Condensed Particle F: Tosoh. AY-601 manufactured by Semantic Oxide Co., Ltd. has an average particle diameter (secondary particle diameter) of 20 μm by air classification.

Condensed Particles G: Dong Cao. AY-601 manufactured by Semantic Oxide Co., Ltd. has an average particle diameter (secondary particle diameter) of 10 μm by air classification.

Crosslinked Acrylic Particles A: Water-Contained Finished Industrial BMX-30 (True Spherical Particles)

[Manufacturing Example 5: Preparation of Particle Master Wafer 3]

The above-obtained phthalic acid copolymerized polyethylene terephthalate 2 was used as the aggregated particle H, and the CARiACT P-10 manufactured by Fuji Silicia Chemical Co., Ltd. was mixed at a mass concentration of 8 mass%, at the melting temperature. The pellet main wafer 3 was produced by extrusion at 235 °C.

[Example 11] (Manufacture of white reflective film)

Using the above-mentioned obtained phthalic acid copolymerized polyethylene terephthalate 1 and the particle main wafer 1 as a raw material of the reflective layer (layer A), isophthalic acid copolymerized polyethylene terephthalate The ester 2 and the particle main wafer 3 were used as raw materials of the surface layer (layer B), and the respective layers were mixed so as to have the configuration shown in Table 3, and were put into an extruder, and the layer A was melted at a temperature of 255 ° C. The B layer is formed at a melt extrusion temperature of 230 ° C in a manner of forming a layer of the B layer / the A layer / the B layer, using a three-layer co-extrusion die device to join the flow, directly maintaining the laminated state by the crystal grains. Formed in a flake shape. At this time, the thickness of the B layer/A layer/B layer was adjusted so that the amount of discharge of each extruder was 10/80/10 after stretching in two directions. Further, the sheet was cooled to a temperature of 25 ° C to form a cooled and solidified unstretched film. The unstretched film was passed through a preheating zone at 73 ° C, followed by a preheating zone of 75 ° C, guided to a longitudinal stretching zone maintained at 92 ° C, stretched 2.9 times in the longitudinal direction, and cooled at 25 ° C. Then, both ends of the film were held by a clip, and were held at a cross-sectional stretching zone of 130 ° C by a preheating zone of 115 ° C, and stretched 3.8 times in the transverse direction. Then heat-set at 185 ° C in a tenter The width was reduced by 2%, the width was reduced by 130 ° C, and the width was reduced in the transverse direction. Secondly, both ends of the film were cut and thermally relaxed at a longitudinal relaxation rate of 2%, and cooled to room temperature to obtain a temperature as shown in Table 3. A white reflective film having a thickness of 250 μm. The evaluation results of the obtained film are shown in Table 4.

[Embodiment 12]

The white reflective film was obtained in the same manner as in Example 11 except that AY-603 manufactured by Tosoh Sebacillus Co., Ltd. was used as the particles of the surface layer B. The evaluation results of the obtained film are shown in Table 4.

[Example 13]

The white reflective film was obtained in the same manner as in Example 11 except that G0105 manufactured by Tosoh Chrysan Co., Ltd. was used as the particles of the surface layer B, and the lateral stretching ratio was changed to 4.0. The evaluation results of the obtained film are shown in Table 4.

[Comparative Example 3]

A white reflective film was obtained in the same manner as in Example 11 except that the crosslinked poly(methyl methacrylate) (PMMA) particles of Imade Chemical Co., Ltd. were used as the particles of the surface layer B.

[Comparative Example 4] (Adjustment of coating solution)

Contains water-soluble polyester binder Z565 made by Mutual Chemical Co., Ltd. (solid content: 30%), as a solid component, 60% by mass of CARiACT P-10, manufactured by Fuji Silicia Chemical Co., Ltd. as a solid component, and 5 mass% of EMULGEN420 manufactured by Kao Co., Ltd. as a solid component. The solid solid concentration of the liquid was diluted with water to 30% by mass to prepare a coating liquid for forming the surface layer B.

(Manufacture of white reflective film)

Using the above-mentioned obtained phthalic acid copolymerized polyethylene terephthalate 1 and the particle main wafer 1 as a raw material of the reflective layer (layer A), isophthalic acid copolymerized polyethylene terephthalate The ester 2 was used as a raw material of the support layer (C layer), and the respective layers were mixed so as to have the configuration shown in Table 3, and were put into an extruder. The layer A was melt-extruded at a temperature of 255 ° C, and the layer C was melt-extruded. The temperature was 230 ° C, and the two layers of the co-extrusion die apparatus were used to form a layer of the C layer/A layer, and the laminate was directly formed into a sheet shape by the crystal grains while maintaining the lamination state. At this time, the thickness of the C layer/A layer was adjusted so that the amount of discharge of each extruder was 20/80 after stretching in two directions. Further, the sheet was cooled to a temperature of 25 ° C to form a cooled and solidified unstretched film. The coating liquid of the above composition was applied to the layer A side of the unstretched film, and after drying, the coating layer was applied to a thickness of 3 μm by a roll coater, and the unstretched film was passed through a preheating zone of 73 ° C, followed by Through a preheating zone of 75 ° C, the guide was held at a longitudinal stretching zone of 92 ° C, stretched 2.9 times in the longitudinal direction, and cooled at 25 ° C. Then, both ends of the film were held by a clip, and were held at a cross-sectional stretching zone of 130 ° C by a preheating zone of 115 ° C, and stretched 3.8 times in the transverse direction. Can be simultaneously shaped by this step Form the surface layer B. Then, it was heat-fixed at 185 ° C in a tenter to reduce the width ratio by 2%, the width at 130 ° C to reduce the width in the transverse direction, and then cut off both ends of the film to thermally relax at a longitudinal relaxation rate of 2%. To the room temperature, a substrate (layer A + C layer) having a thickness of 250 μm as shown in Table 3 was obtained to form a white reflective film of the coating layer B having a thickness of 3 μm as the surface layer B. The evaluation results of the obtained film are shown in Table 4.

[Comparative Example 5]

A white reflective film was obtained in the same manner as in Comparative Example 4 except that the particles added to the coating liquid for forming the surface layer B were changed to AY-603 manufactured by Tosoh Sebacillus Co., Ltd. The evaluation results of the obtained film are shown in Table 4.

Effect of the invention

According to the present invention, it is possible to provide a white reflective film which can sufficiently suppress the adhesion to the light guide plate and can sufficiently suppress the scratch of the light guide plate.

Moreover, according to a preferred aspect of the present invention, it is possible to provide a white reflective film which can sufficiently suppress adhesion to a light guide plate and can sufficiently suppress scratching of the light guide plate, and can also be excellent in film formability of the film.

Industrial availability

The white reflective film of the present invention can sufficiently suppress the adhesion to the light guide plate, and can sufficiently suppress the scratch of the light guide plate, and is particularly useful as a surface light source reflector having a light guide plate, for example, as used in a liquid crystal display device. It can be suitably used as a reflective film used as a backlight unit of an edge illumination type.

1‧‧‧Handle section

2‧‧‧ iron plate

3‧‧‧Reflective film

4‧‧‧Light guide plate

Load of 5‧‧500g

401‧‧‧ dots

Claims (7)

A white reflective film having a reflective layer A and a white reflective film composed of a surface layer B composed of a thermoplastic resin composition containing particles, wherein the white reflective film has the surface layer B as a layer of alignment a surface formed on the surface of the surface layer B opposite to the reflective layer A has protrusions formed by the particles, and the number of protrusions having a height of 5 μm or more on the surface is 4 × 10 ⁷ to 10 ¹⁰ / m ² The content of the particles of the surface layer B is 30% by volume or less based on the volume of the surface layer B. The particles of the surface layer B are aggregated particles, and the compression ratio of the particles at a load of 0.3 gf is 40%. the above. A white reflective film having a reflective layer A and a white reflective film composed of a surface layer B composed of a thermoplastic resin composition containing particles, wherein the white reflective film is formed on the surface layer B and the reflection The surface on the opposite side of the layer A has protrusions formed by the above particles, and the number of protrusions having a height of 5 μm or more on the surface is 10 ⁴ to 10 ¹⁰ /m ² , and the particles are 10% compressed at a load of 3 gf. The strength is 0.1 to 1.0 MPa, and the Vickers hardness of the above protrusions is 10 to 30. The white reflective film of claim 1, wherein the reflective layer A has a void volume ratio of 15% by volume or more and 70% by volume or less. The white reflective film of claim 2, wherein the reflective layer A has a void volume ratio of 15% by volume or more and 70% by volume or less, and the surface layer B has a pore volume ratio of 0% by volume or more and less than 15% by volume. The white reflective film of claim 1, wherein the amount of the volatile organic solvent is 10 ppm or less. The white reflective film according to any one of claims 1 to 5, which is used as a surface light source reflector having a light guide plate. A white reflective film according to claim 2 or 4, which is used as a reflector for an edge illumination type backlight unit.