TWI632403B - White reflective film - Google Patents

Abstract

The present invention provides a white reflective film comprising a reflective layer A and a support layer B composed of a thermoplastic resin composition containing aggregated particles in a thermoplastic resin, wherein the aggregated particles have a primary particle diameter (dp) of 3 μm. Hereinafter, the secondary particle diameter (ds) is 8 μm or less, and the content in the support layer B is 1% by volume or more and 50% by volume or less based on the volume of the support layer B, and the support layer B forms at least a white reflective film. An outermost layer, the ten-point average roughness (Rz) on the surface of the outermost support layer B opposite to the reflective layer A satisfies the following formula (1), and the agglomerated particles in the support layer B The secondary particle diameter (ds) and the thickness (t) of the support layer B satisfy the following formula (2), and the secondary particle diameter (ds) of the aggregated particles in the support layer B and the thickness (t) of the support layer B satisfy the following Formula (2), 0.1 × ds (μm) ≦ Rz (μm) ≦ 0.7 × ds (μm) ‧ ‧ (1)

0.07≦ds(μm)/t(μm)≦20‧‧‧(2).

This film can sufficiently suppress the damage of the light guide plate, and when the film is recovered and used as a raw material for recycling, the film is excellent in film formability.

Description

White reflective film

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

The backlight unit of the liquid crystal display device (LCD) has a direct light type having 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 The side of the light guide plate is provided with an edge-emitting type of the light source. In the past, the backlight unit used in large LCDs mainly uses a direct type (mainly a direct type CCFL) from the viewpoint of excellent brightness and uniform brightness in the screen, and the edge type is attached to a notebook PC (PC). It is used in smaller LCDs, etc. However, in recent years, due to the development of light sources or light guide plates, even the edge-emitting type backlight unit has improved brightness and brightness uniformity in the screen, becoming not only a smaller type. An edge-lit backlight unit can also be used in a large LCD. According to this, there is also an advantage that the LCD is thinned.

In the edge-lit backlight unit, the light guide plate and the reflective film are in direct contact with each other. Therefore, in this configuration, the light guide plate and the reflective film are attached At the time, the brightness of the attached portion becomes abnormal, and there is a problem that unevenness in brightness occurs. Therefore, it is necessary to have a gap between the light guide plate and the reflective film, and to keep the gap constant. For example, since the surface of the reflective film has beads to keep the gap between the light guide plate and the reflective film constant, the attachment can be prevented.

However, at this time, if the light guide plate made of a soft material is attached to 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 a countermeasure, a reflective sheet having a flaw preventing layer using beads of an elastic system is reported in JP-A-2003-92018 and JP-A-2008-512719.

However, when soft beads are used as described in the above-mentioned JP-A-2003-92018 and JP-A-2008-512719, the damage of the light guide plate can be suppressed, but the gap required for securing the recent requirements cannot be achieved. Large stresses do not ensure clearance and do not inhibit attachment. In order to ensure the problem of the gap, it is considered that beads having high hardness such as inorganic particles such as true spherical cerium oxide or organic particles having a crosslinked structure are used as the beads, but such damage of the light guide plate cannot be suppressed. Further, the inventors of the present invention have found that when such a high-hardness bead is used and a bead having a sufficient degree of clearance can be sufficiently obtained, a film which does not become a product is recovered, and it is remanufactured as a raw material for recycling itself. In the case of a film, the beads remaining in the recovered raw material are mixed into the film, especially in the reflective layer, so that film rupture often occurs, and the film forming property of the film is lowered, and the problem of substantially failing to be recovered by itself is considered. problem.

In view of the above, it is an object of the present invention to provide a recyclable white reflective film which is excellent in film formability when a film is produced by using a film which is sufficiently recovered as a material for recycling the film. .

Other objects and advantages of the invention will be apparent from the description which follows.

According to the present invention, the above objects and advantages of the present invention can be attained by a white reflective film which is formed of a reflective layer A and a thermoplastic resin and inert particles dispersed therein and which form at least one of the most a support layer B of the outer layer, and a white reflective film having a protrusion formed by the inert particles on the surface opposite to the reflective layer A of the outermost support layer B, and a. the above thermoplastic resin is condensed In the ester resin, the average particle diameter (d) of the inert particles is 2 to 100 μm, and the frequency of the protrusions having a 10-point average roughness (Rz) of 5 to 100 μm and a height of 5 μm or more on the surface on the opposite side is 10 ⁶ to 10 ¹⁰ pieces/m ² , wherein the above-mentioned inorganic particles are formed by coating the surface of the polyester resin with a coating thickness of 50 nm to 10 μm, or b. the secondary particle diameter (ds) of the inert particles is more than 10 μm and 100 μm or less. The aggregated particles are contained in the support layer B in an amount of 1 to 50% based on the volume of the support layer B, and the ten-point average roughness (Rz) on the surface of the opposite side satisfies the following formula (1): 0.1 × ds (μ m) ≦ Rz (μ m) ≦ 0.7 × ds (μ m) ‧‧ (1).

According to the white reflective film (hereinafter referred to as white reflective film a) having the characteristics of a above, the above first object of the present invention can be achieved smoothly. According to the white reflective film of the present invention (hereinafter referred to as the white reflective film b) having the characteristics of b described above, the above second object of the present invention can be attained.

In particular, the present invention has a white reflective film having a reflective layer A and a support layer B made of a thermoplastic resin composition containing agglomerated particles in a thermoplastic resin, wherein the primary particle diameter (dp) of the aggregated particles is 3 μm or less, the secondary particle diameter (ds) is 8 μm or less, and the content in the support layer B is 1% by volume or more and 50% by volume or less based on the volume of the support layer B, and the support layer B is formed into a white reflective film. At least one outermost layer, the ten-point average roughness (Rz) on the surface of the outermost support layer B opposite to the reflective layer A satisfies the following formula (1), and the agglomerated particles in the support layer B The secondary particle diameter (ds) and the thickness (t) of the support layer B satisfy the following formula (2), 0.1 × ds (μm) ≦ Rz (μm) ≦ 0.7 × ds (μm) ‧ ‧ (1)

0.07≦ds(μm)/t(μm)≦20‧‧‧(2).

According to the white reflective film of the present invention having the above-described characteristics, it is possible to sufficiently suppress the damage of the light guide plate, and to recover the film, and to use the film as a raw material to recover the film, the film formation property of the film is excellent. Recycled white reflective film.

1‧‧‧Handle part

2‧‧‧ iron plate

3‧‧‧Reflective film

4‧‧‧Light guide plate

401‧‧ points

5‧‧‧ weight

6‧‧‧Chassis

7‧‧‧Optical sheets

801‧‧‧French triangle

802‧‧ ‧ weight

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

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

Fig. 3 is a photograph showing an example of a profile of a projection of the present invention.

The white reflective film of the present invention has a reflective layer A and a support layer B on both the white reflective film a and the white reflective film b.

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

First, the white reflective film a will be described.

[Reflective layer A]

The reflective layer A of the present invention is composed of a thermoplastic resin and a pore-forming agent, and contains a pore-forming agent to form a white layer by containing pores in the layer. Although the pore-forming agent is described in detail later, a resin which is incompatible with, for example, inorganic particles and a thermoplastic resin constituting the reflective layer A (hereinafter sometimes referred to as an incompatible resin) can be used. Further, the reflectance of the reflective layer A at a wavelength of 550 nm is preferably 95% or more, more preferably 96% or more, and most preferably 97% or more, whereby the reflectance of the white reflective film a is easily in 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 in the range of 15 to 70% by volume. By being in this range, the effect of improving the reflectance can be improved, and the reflectance as described above can be easily obtained. In addition, the effect of improving film formability can be improved. When the pore volume ratio is too low, there is a tendency that it is difficult to obtain a preferable reflectance. From these viewpoints, the lower limit of the void volume ratio in the reflective layer A is more preferably 30% by volume, and most preferably 40% by volume. On the other hand, over When it is high, there is a tendency that the effect of improving the film forming property is lowered. From these points of view, the upper limit of the void volume ratio in the reflective layer A is more preferably 65 vol%, and most preferably 60 vol%.

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

(thermoplastic resin)

The thermoplastic resin constituting the reflective layer A may, for example, be a thermoplastic resin made of polyester, polyolefin, polystyrene or acrylic. Among them, polyester is preferred from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

The polyester preferably uses a polyester composed of a dicarboxylic acid component and a diol component. The dicarboxylic acid component may be derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid or the like. ingredient. The diol component may be a component derived from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol or the like. Among the polyesters, aromatic polyesters are preferred, and polyethylene terephthalate is preferred. The polyethylene terephthalate may be a homopolymer, but a copolymerized polymer is preferred from the viewpoint that the crystallization of the film is inhibited by stretching in one or two axes, and the elongation and film forming properties are improved. . The copolymerization component is exemplified by the above dicarboxylic acid component or diol component, but isophthalic acid and 2,6-naphthalene dicarboxylic acid are preferred from the viewpoint of heat resistance and film formability. The ratio of the copolymerization component is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 15 mol%, based on 100 mol% of the total dicarboxylic acid component of the polyester. Best 7~11 moles %. By setting the copolymerization component within this range, the effect of improving the film formability is excellent. Moreover, the thermal size stability is excellent.

(pore forming agent)

When inorganic particles are used as the pore former in the reflective layer A, the inorganic particles are preferably white inorganic particles. The white inorganic particles can be exemplified by particles of barium sulfate, titanium oxide, cerium oxide, and calcium carbonate. The inorganic particles are not particularly limited as long as the average particle diameter or content is selected so that the white reflective film has an appropriate reflectance. Preferably, the reflectance of the reflective layer A or the white reflective film falls within the preferred range of the present invention. Further, the void volume ratio in the reflective layer A may be within the preferred range of the present invention. In view 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 from 20 to 60% by mass, more preferably from 25 to 55% by mass, most preferably from 31 to 53% by mass based on the mass of the reflective layer A. Further, by using the particle form as described above, it can be appropriately dispersed in the polyester, and it is difficult to cause aggregation of the particles, and a film having no coarse protrusions can be obtained, and at the same time, it is possible to suppress the extension of the coarse particles 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 also be subjected to a surface treatment for improving dispersibility.

When a non-compatible resin is used as the pore-forming agent, the non-compatible 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 also be the form of particles. And its content and the feeling of inorganic particles In the same manner, the average particle diameter or content is selected so that the white reflective film has a moderate reflectance, and is not particularly limited. Preferably, the reflectance of the reflective layer A or the white reflective film is preferably in the preferred range of the present invention. Further, the void volume ratio in the reflective layer A may be within the preferred range of the present invention. In view of the above, the content is preferably from 10 to 50% by mass, more preferably from 12 to 40% by mass, most preferably from 13 to 35% by mass based on the mass of the reflective layer A.

(other ingredients)

The reflective layer A may contain other components such as an ultraviolet absorber, an antioxidant, an antistatic agent, a fluorescent whitening agent, a wax, a particle or a resin different from the pore former, or the like, within a range not impairing the object of the present invention.

[support layer B]

The support layer B of the present invention contains inert particles made of a polyester resin.

(polyester resin)

The polyester used as the polyester resin of the support layer B can be exemplified by the same polyester as the polyester in the above-mentioned reflective layer A. 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 preferred. The polyethylene terephthalate may be a homopolymer, but it is preferably a copolymerized polymer from the viewpoint of improving the effect of improving the damage inhibition of the light guide plate. The copolymerization component is exemplified by the above dicarboxylic acid component or diol component, but the damage suppression is similarly From the viewpoint, isophthalic acid and 2,6-naphthalene dicarboxylic acid are preferred. The ratio of the copolymerization component is preferably 1 mol% or more, more preferably 1.5 mol% or more, and more preferably 2 mol% or more, based on 100 mol% of the total dicarboxylic acid component of the polyester. Good for more than 3 moles. Further, it is preferably 20 mol% or less, more preferably 18 mol% or less, still more preferably 15 mol% or less, and most preferably 12 mol% or less. When the ratio of the copolymerization component is at least the lower limit, the effect of improving the damage of the light guide plate can be particularly improved. On the other hand, by setting it as an upper limit or less, it is easy to have moderate hardness by crystal orientation, etc., and the improvement effect of a sticking suppression can be improved.

(inert particles)

The inert particles in the support layer B may be organic inert particles, inorganic inert particles, or organic-inorganic composite inert particles.

The organic inert particles are exemplified by, for example, polystyrene resin particles, polyoxyxylene resin particles, acrylic resin particles, styrene-acrylic resin particles, divinylbenzene-acrylic resin particles, polyester resin particles, polyimine resin, melamine. Polymer resin particles such as resin particles. Among them, from the viewpoint of easily forming a protrusion having a particularly appropriate hardness for securing a gap, it is preferably a polysiloxane resin particle or an acrylic resin particle.

Further, the inorganic inert particles are exemplified by (1) cerium oxide (including hydrate, cerium, quartz, etc.); (2) alumina in various crystal forms; and (3) citric acid containing 30% by mass or more of SiO ₂ component. a salt (for example, an amorphous or crystalline clay mineral, an aluminosilicate (including a burnt or a hydrate), a chrysotile, a zircon, a fly ash, etc.; (4) Mg, Oxides of Zn, Zr and Ti; (5) sulfates of Ca and Ba; (6) phosphates of Li, Ba and Ca (including 1 or 2 hydrogen salts); (7) Li, Na and K Benzoate; (8) terephthalate of Ca, Ba, Zn and Mn; (9) titanic acid of Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co and Ni a salt; (10) a chromate of Ba and Pb; (11) a carbon (for example, carbon black, graphite, etc.); (12) a glass (for example, a glass frit, a glass bead, etc.); (13) a carbonate of Ca and Mg; (14) fluorite (fluorite); (15) spinel oxide. Among them, from the viewpoint of easily forming protrusions having a particularly appropriate hardness for ensuring a gap, it is preferably cerium oxide particles, preferably condensed cerium oxide particles.

Further, as the inert particles of the present invention, organic inorganic composite inert particles such as inorganic particles coated with an organic substance or organic particles coated with an inorganic substance may be used. Specifically, the organic-inorganic composite particles are, for example, organic-inorganic hybrids in which a polymer having an organometallic compound such as a mercaptoalkyl group at a side chain or a terminal and an inorganic compound such as ceria are covalently bonded. a particle formed by a material, or a particle obtained by fusing an organic polymer microparticle such as crosslinked polystyrene onto a surface of an inert inorganic particle, or an inert inorganic microparticle such as alumina fixed to an inert organic polymer particle Particles formed on the surface.

In the present invention, the inert particles are preferably inorganic particles from the viewpoint that the more excellent effects are easily exhibited. In particular, when inorganic inert particles are used as the inert particles, the present invention is particularly useful because the inorganic inorganic particles are generally hard and easily damage the light guide plate.

The average particle diameter and content of the inert particles in the support layer B are such as to satisfy the ten-point average roughness Rz or the protrusion frequency described later in order to suppress the attachment. The range can be selected.

For example, the average particle diameter is preferably from 2 μm to 100 μm from the viewpoint of keeping the distance between the light guide plate and the film constant and suppressing the adhesion. When the average particle diameter is too small, Rz tends to be small, and there is a tendency that a part of the white reflective film is closely adhered to the light guide plate. From these viewpoints, the lower limit of the average particle diameter is preferably 5 μm, more preferably 10 μm, still more preferably 15 μm. On the other hand, when the average particle diameter is too large, the particles tend to fall off, and when they fall off, they become white spot defects in the backlight unit. From these viewpoints, the upper limit of the average particle diameter is preferably 80 μm, more preferably 75 μm, still more preferably 70 μm, still more preferably 65 μm.

Further, the content is preferably from 0.1% by volume to 20% by volume based on the volume of the support layer B, for example. When there is too little, there is a tendency to ensure that the effect of improving the gap is lowered. Therefore, the lower limit is preferably 0.2% by volume, preferably 0.3% by volume. On the other hand, when the amount is too large, there is a tendency that the effect of suppressing the fall of the particles is lowered. Therefore, the upper limit is more preferably 15% by volume, and most preferably 12% by volume.

(other ingredients)

The support layer B may contain components other than the above constituent components within the range not impairing the object of the present invention. The component may, for example, be an ultraviolet absorber, an antioxidant, an antistatic agent, a fluorescent whitening agent, a wax, or a particle or a resin different from the above inert particles.

Further, the support layer B may also contain a pore-forming agent as exemplified in the reflective layer A, and by this state, the effect of improving the reflectance can be improved. Conversely, When the content of the pore former in the support layer B is reduced, or when the pore former is not contained, the effect of improving the film formability can be improved. From such a viewpoint, the pore volume ratio in the support layer B (the ratio of the pore volume in the support layer B to the volume of the support layer B) is preferably from 0% by volume to less than 15% by volume, more preferably 0%. ~5 vol%, preferably 0 to 3% by volume. In particular, in the present invention, it is preferable to simultaneously adopt a preferred void volume ratio in the reflective layer A and a preferred void volume ratio in the support layer B based on the effect of simultaneously improving the reflection characteristics and the elongation.

(the form of support layer B)

In the present invention, the support layer B composed of the above-mentioned polyester resin and containing the above-mentioned inert particles forms at least one outermost layer of the white reflective film. Therefore, the surface on the side opposite to the reflective layer A on which the outermost support layer B is formed has protrusions formed of the above-described inert particles. Further, the projections are formed by coating the inert particles with a polyester resin constituting the support layer B.

When the polyester resin is coated with the inert particles, the coating thickness is in the range of 50 nm to 10 μm. The coating thickness herein means the thickness of the polyester resin at the apex of the protrusion. By setting the thickness of the coating to fall within the above range, damage to the light guide plate can be suppressed. Further, the projections have moderate hardness, whereby the gap can be secured and the attachment can be suppressed. When the coating thickness is too thin, the damage of the light guide plate cannot be suppressed, and there is a possibility that the particles are detached due to rubbing. Moreover, it is difficult to ensure a gap. On the other hand, when the thickness of the coating is too thick, the particles forming the protrusions exist deep inside the support layer B, and thus the shape of the protrusions becomes a "smoothness" of the curvature. The possibility is that it is not easy to prevent adhesion to the light guide plate. From these viewpoints, the lower limit of the thickness of the protruding inert particles by the polyester resin is preferably 200 nm, more preferably 1 μm, and the upper limit is preferably 8 μm, more preferably 7.5 μm.

As described above, the white reflective film of the present invention can be suppressed by the protrusion when the outermost layer of the white reflective film has a protrusion composed of a polyester resin coated with inert particles at a specific coating thickness and used in contact with the light guide plate. Scratch of the light guide plate. In addition, it is possible to suppress particle shedding. Also, the gap can be ensured. Moreover, at this time, the surface provided on the side of the protrusion is the side of the light guide plate.

Further, from the viewpoint of ensuring the gap between the light guide plate and the reflective film, on the surface of the support layer B forming the outermost layer opposite to the reflective layer A, the protrusions must have a moderate height and exist at a moderate frequency.

On the surface of the support layer B which forms the outermost layer on the side opposite to the reflection layer A, the height of the protrusions is a ten-point average roughness (Rz) of 5 to 100 μm. Thereby, the gap with the light guide plate can be sufficiently ensured by the protrusion frequency described later, and the adhesion suppression effect is excellent. Rz is too small to attach a small suppression effect. On the other hand, when Rz is too large, the particle fall suppression effect is inferior. From these viewpoints, the lower limit of Rz is preferably 7 μm, more preferably 10 μm, and the upper limit is preferably 75 μm, more preferably 50 μm. Moreover, the state of Rz is mainly obtained by the above-mentioned protrusions. The reason for this is that if a protrusion having a projection which is not provided with the above-described protrusion-like state is formed, the damage suppression effect of the light guide plate cannot be obtained.

Further, the frequency of the protrusions having a height of 5 μm or more is 10 ⁶ to 10 ¹⁰ / m ² per unit area on the surface of the support layer B forming the outermost layer opposite to the reflection layer A. Thereby, the gap with the light guide plate can be sufficiently ensured by the above Rz, and the adhesion suppressing effect is excellent. When the frequency of the protrusion is too small, the adhesion suppression effect is poor. On the other hand, when the frequency of the protrusion is too large, the probability of falling off the particles increases, and the reflectance tends to decrease. From these viewpoints, the lower limit of the protrusion frequency is preferably 10 ⁷ / m ² , more preferably 5 × 10 ⁷ / m ² , and the upper limit is preferably 2 × 10 ⁹ / m ² , more Good is 5 × 10 ⁸ / m ² .

Further, based on further suppressing the damage of the light guide plate, it is easy to ensure a sufficient gap when the light guide plate and the reflective film are pressed, and further prevent the particles from falling off from the surface of the film into foreign matter, and the above-mentioned protrusions are caused by the deterioration of the display quality due to the image defect. The hardness is preferably from 10 ⁰ to 10 ³ .

When the hardness is too hard, there is a tendency that the light guide plate is easily damaged. On the other hand, when it is too soft, the effect of securing a gap tends to be low, and the effect of suppressing the particle fall tends to be low. From this point of view, the lower limit of the protrusion hardness is preferably 5, more preferably 10, and the upper limit is preferably 500, more preferably 200.

The protrusion hardness can be expressed by a value measured by a micro hardness meter (for example, ENT-1100a manufactured by ELIONIX Co., Ltd.) based on JIS Z2244. Using a triangular cone indenter (corner angle = 115° positive triangular tapered tip), the pressing load (P) is set to 500 mgf (about 4.9 mN), and the maximum indentation depth (h [μm]) measured from the measurement. The value is calculated by the following formula (H).

H=0.038×P/h ²

The measurement is preferably performed on a sample randomly sampled from a sample (one of the preferred measurement methods is selected at a height of 5 μm or more), for example, for a majority of 30 points or more, and the average value of these is used as the protrusion hardness. And the height of the protrusion can be Confirmed with a laser microscope.

[layer composition]

The thickness of the reflective layer A of the present invention is preferably from 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 low, and when it is too thick, there is no efficiency. From these points of view, it is preferably 150 to 250 μm.

Further, the thickness of the support layer B (having a thickness of one layer which is the outermost layer on the side of the light guide plate when it has a plurality of layers) is preferably from 10 to 70 μm. Thereby, in combination with the above-described preferred inert particles, it is easy to obtain a preferred Rz and protrusion frequency, and it is easy to ensure a gap with the light guide plate. Moreover, the effect of improving the reflectance and the effect of improving the elongation can be improved. When it is too thin, it is difficult to achieve a preferable Rz, and there is a tendency that the particle fall suppressing effect is lowered. And there is a tendency for the enhancement effect of the extension to become lower. On the other hand, when it is too thick, there is a tendency that the effect of improving the reflectance becomes low, and it is difficult to obtain a preferable Rz and the frequency of protrusion. From this point of view, the lower limit of the thickness is more preferably 20 μm, and the upper limit is more preferably 60 μm.

In the present invention, in order to make the coating thickness of the inert particles and the protrusion height represented by Rz easily within the range specified by the present invention, the average particle diameter (d) of the inert particles in the support layer B and the thickness (t) of the support layer B are It is better to satisfy the following formula (2)-1: 0.05≦d( μ m)/t( μ m)≦20‧‧‧(2)-1

It is better to satisfy the following formula (2)-2: 0.1≦d( μ m)/t( μ m)≦10‧‧‧(2)-2

It is better to satisfy the following formula (2)-3: 0.2≦d( μ m)/t( μ m)≦2.5‧‧‧(2)-3

When the value of d/t is too small, it is difficult to generate a sufficiently high protrusion, and there is a tendency to ensure that the effect of improving the gap with the light guide plate is lowered. On the other hand, when it is too large, there is a tendency that the coating thickness is insufficient, and particle falling off is suppressed. The tendency to improve the effect is lower. From these points of view, the lower limit of the above ratio is preferably 0.5, more preferably 0.6, and the upper limit is preferably 2.0, and more preferably 1.8.

When the reflective layer A is represented by A and the support layer B is represented by B, the two layers of B/A are formed, and the B/A/B is composed of three layers, B/A. A four-layer structure of /B/A and a multilayer of five or more layers in which B is disposed on the outermost layer of at least one surface. It is preferably composed of two layers of B/A and three layers of B/A/B. It is preferably composed of three layers of B/A/B, and it is difficult to cause curling.

In the state of the reflective layer A and the support layer B, when the thickness of the entire white reflective film is 100%, the thickness ratio of the reflective layer A is 50 to 90%, and the thickness ratio of the support layer B is 5 to 50%. It is preferably 5 to 25%, which makes the balance of the characteristics better. The thickness ratio of each layer herein, when having a plurality of layers, refers to the ratio of the cumulative thicknesses of the layers.

In the present invention, in addition to the reflective layer A and the support layer B, other layers may be provided without departing from the object of the present invention. For example, it may have a layer for imparting functions such as antistatic property, electrical conductivity, and ultraviolet durability.

[Characteristics of reflective film] (reflectance, brightness)

The reflectance of the white reflective film of the present invention measured on the side of the self-supporting layer B is preferably 96% or more, more preferably 97% or more, still more preferably 97.5% or more. When the reflectance is 96% or more, high luminance can be obtained when used in a liquid crystal display device, illumination, or the like. The reflectance can be set to a preferred state by increasing the pore volume ratio of the reflective layer A, increasing the thickness of the reflective layer A, and thinning the thickness of the support layer B. And reached.

The brightness measured from the support layer B side is preferably 5400 cd/m ² or more, more preferably 5450 cd/m ² or more, and most preferably 5500 cd/m ² or more.

The reflectance and the brightness are in the white reflective film, and are used as the value 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, for example, in the edge-emitting liquid crystal display, the advantage of improving the durability and the like of the light guide plate in direct contact with the reflective film can be exemplified. From this point of view, it is more preferably 5 ppm or less, still more preferably 3 ppm or less, and desirably 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, when the support layer B is formed, it is preferred not to use a solution coating method using an organic solvent, and a method described later is employed.

Next, the white reflective film b will be described.

[Reflective layer A]

For the description of the reflective layer A, the foregoing description in the white reflective film a is directly applied. That is, the above description of the white reflective film a also includes descriptions of (thermoplastic resin), (pore former), and (other components), and is applied directly to the white reflective film b.

[support layer B]

The support layer B of the present invention contains agglomerated particles made of a thermoplastic resin.

(thermoplastic resin)

As the thermoplastic resin constituting the support layer B, the same thermoplastic resin as the thermoplastic resin constituting the above-mentioned reflective layer A can be used. Among them, a polyester resin is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As the polyester resin, 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 preferred. The polyethylene terephthalate may be a homopolymer, but a copolymerized polymer is preferred from the viewpoint of suppressing crystallization and extending the film when the film is extended by one or two axes. The copolymerization component is exemplified by the above dicarboxylic acid component or diol component, but isophthalic acid and 2,6-naphthalene dicarboxylic acid are preferred from the viewpoint of heat resistance and film formability. Ratio of copolymerized components The example is, for example, 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 3 to 17 mol%, and most preferably 12, based on 100 mol% of all dicarboxylic acid components of the polyester. ~16 moles %. By making the ratio of the copolymerization component fall within this range, the effect of improving the film formability is excellent. Moreover, the thermal dimensional stability is also excellent.

(condensed particles)

In the present invention, by using the agglomerated particles specified in the present invention as particles for forming surface irregularities for securing the gap and suppressing adhesion to the light guide plate, it is possible to recover the film itself, and even if the film is produced using the self-recovered material, The film is also excellent in film formability. It is considered that if it is agglomerated particles, the particles are appropriately pulverized at the time of production of the self-recovered raw material.

The agglomerated particles in the support layer B may be organic agglomerated particles or inorganic agglomerated particles. The organic agglomerated particles are exemplified by, for example, polyester agglomerated particles, acrylic acid agglomerated particles, polyurethane agglomerated particles, and polyethylene agglomerated particles. Among them, the polyester agglomerated particles are considered to have good compatibility with the polyester of the main raw material even if they are insufficiently broken in the self-recovering step, and are preferable because they have a limited effect on film forming properties and the like. The inorganic agglomerated particles are exemplified by, for example, ceria condensed particles, alumina agglomerated particles, and ceramic agglomerated particles. When the particles are too hard, the film is easily broken when the film is stretched, and the film forming property is poor. Therefore, it is preferable to cohere the particles with cerium oxide from this viewpoint.

The secondary particle diameter (ds) of the aggregated particles in the support layer B as the average particle diameter of the aggregated particles must be more than 10 μm and 100 μm or less. Thereby, the gap between the light guide plate and the film can be kept constant, and the attachment can be satisfactorily suppressed. Further, when the self-recovered raw material is used, the elongation at the time of film formation is improved. When the secondary particle diameter is too small, the white reflective film tends to be partially adhered to the light guide plate. From these viewpoints, the lower limit of the secondary particle diameter is preferably 12 μm, more preferably 14 μm, still more preferably 15 μm, and most preferably 16 μm. On the other hand, when it is too large, there is a tendency that the elongation is poor, and there is a tendency that the recyclability is poor, that is, the film forming property of the film after self-recovery tends to be poor. Further, the particles tend to fall off easily, and if they fall off, the backlight unit becomes a white defect. From these viewpoints, the upper limit of the secondary particle diameter is preferably 95 μm, more preferably 90 μm, still more preferably 85 μm, still more preferably 80 μm, still more preferably 30 μm.

Further, the primary particle diameter (dp) of the primary particles constituting the aggregated particles is preferably 0.01 μm or more, and preferably 5 μm or less. By simultaneously satisfying the above-described secondary particle size range, the effect of improving the film forming property when the self-recovered raw material is used can be further improved. When the primary particle diameter is too small, the strength of the agglomerated particles tends to be too weak, so that it is difficult to obtain a sufficiently large secondary particle diameter. From this point of view, the lower limit of the primary particle is more preferably 0.02 μm, still more preferably 0.03 μm, and most preferably 0.05 μm. On the other hand, when it is too large, even if the secondary particles are destroyed during the production of the self-recovered raw material, particles having a large particle diameter remain, and the effect of improving the film forming property after recovery tends to be low. From this point of view, the upper limit value is more preferably 4 μm, more preferably 3 μm, still more preferably 2 μm, still more preferably 1 μm.

Further, the content of the aggregated particles in the support layer B is from 1 to 50% by volume based on the volume of the support layer B. When the amount is too small, the surface of the white reflective film has few irregularities, and the distance from the light guide plate cannot be kept constant. Therefore, under The limit is more preferably 2% by volume, and most preferably 3% by volume. On the other hand, when the strength of the support layer B is too large, the productivity at the time of film formation deteriorates, and the mechanical strength of the obtained film tends to be insufficient. Moreover, the amount of particles in self-recovery increases, and it is difficult to increase the recovery rate, which is a problem. Therefore, the upper limit is more preferably 45% by volume, and most preferably 40% by volume.

(other ingredients)

In the description of the above (other components) of the white reflective film a, the inert particles in the description are read as agglomerated particles.

(the form of support layer B)

In the present invention, the support layer B made of the above-mentioned thermoplastic resin and containing the agglomerated particles as described above forms at least one outermost layer of the white reflective film. Further, the surface of the outermost support layer B on the side opposite to the reflective layer A (hereinafter sometimes referred to as the outermost surface) has protrusions formed by the agglomerated particles. Further, the protrusion must have a moderate height on the outermost surface from the viewpoint of ensuring the gap between the light guide plate and the reflective film.

Therefore, in the present invention, the ten-point average roughness (Rz) of the outermost surface and the secondary particle diameter (ds) of the aggregated particles constituting the support layer B must satisfy the following formula (1).

0.1×ds( μ m)≦Rz( μ m)≦0.7×ds( μ m)‧‧‧(1)

By satisfying the above formula (1), the agglomerated particles on the outermost surface are appropriately buried in the support layer, and are appropriately protruded, so that the surface unevenness having an appropriate height is obtained, whereby the effect of securing the gap is excellent. on In the above formula, the value of Rz is smaller than the value on the left side, indicating that the aggregated particles are excessively buried in the support layer B, so that the effect of ensuring the gap is poor. From this point of view, it is preferable to satisfy 0.2 × ds (μm) ≦ Rz (μm), and more preferably 0.3 × ds (μm) ≦ Rz (μm). On the other hand, when the value of Rz is larger than the value on the right side, it means that the aggregated particles protrude from the support layer B, and the peeling property of the particles when it comes into contact with the light guide plate tends to be inferior. From this point of view, it is preferable to satisfy Rz (μm) ≦ 0.6 × ds (μm), and more preferably to satisfy Rz (μm) ≦ 0.5 × ds (μm).

In order to achieve the above state, the thickness of the support layer B may be adjusted in consideration of the secondary particle diameter of the aggregated particles used. For example, in the aggregated particles having a certain secondary particle diameter, when the thickness of the support layer B is made thin, the value of Rz becomes a value closer to the right side, and when it is too thin, it exceeds the value of the right side. On the other hand, when the thickness of the support layer B is thickened, the value of Rz becomes a direction approaching the value of the left side, and when it is too thick, it is lower than the value of the left side. This tendency can be adjusted in consideration of this.

The aspect of the surface unevenness in the outermost surface is preferably a moderate protrusion frequency from the viewpoint of ensuring the gap between the light guide plate and the reflective film.

The protrusion frequency of the protrusions having a height of 5 μm or more is in the outermost surface, and the number per unit area is preferably from 10 ⁶ to 10 ¹⁰ / m ² . Thereby, the gap with the light guide plate can be more sufficiently ensured by the above-described Rz, and the effect of improving the adhesion suppression is excellent. When the frequency of the protrusion is too small, the effect of the adhesion suppression is poor. On the other hand, when the frequency of the protrusion is too large, the probability that the particles fall off will increase, and the reflectance tends to decrease.

[layer composition]

The thickness of the reflective layer A of the present invention is preferably from 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 on the other hand, when it is too thick, it is inefficient. From these points of view, it is preferably 150 to 250 μm.

Further, the thickness of the support 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 from 10 to 70 μm. Thereby, in combination with the above-described preferred agglomerated particles, the relationship between the secondary particle diameter ds of the aggregated particles and the ten-point average roughness Rz is easily obtained as described above, and the gap with the light guide plate is easily secured. Further, it is easy to make the state of Rz and the frequency of the protrusions into the above-described preferred state. In addition, the effect of improving the reflectance and the effect of the extension can be improved. When it is too thin, it is difficult to achieve a preferable Rz, and there is a tendency that the particle fall suppressing effect is lowered. And there is a tendency for the enhancement effect of the extension to become lower. On the other hand, when it is too thick, there is a tendency that the effect of improving the reflectance is lowered, and it is difficult to obtain a preferable Rz and the frequency of protrusion. From this point of view, the lower limit value is more preferably 20 μm, and the upper limit value is more preferably 60 μm.

In the present invention, the secondary particle diameter (ds) of the aggregated particles in the support layer B and the thickness (t) of the support layer B preferably satisfy the following formula (2)-1': 0.05 ≦ ds ( μ m) / t ( μ m)≦20‧‧‧(2)-1'

It is better to satisfy the following formula (2)-2': 0.1≦ds( μ m)/t( μ m)≦10‧‧‧(2)-2'

It is better to satisfy the following formula (2)-3': 0.2≦ds( μ m)/t( μ m)≦2.5‧‧‧(2)-3'

By satisfying the above formula, it is easy to have a surface unevenness having a moderate height on the outermost surface, and it is possible to improve the effect of ensuring the clearance. In the above formula (2)-1', when the value of ds/t is smaller than the value on the left side, the aggregated particles tend to be buried in the support layer B, and the effect of ensuring the improvement of the gap tends to be poor. From this point of view, the lower limit value preferably satisfies 0.07 ≦ ds (μm) / t (μm), more preferably satisfies 0.09 ≦ ds (μm) / t (μm), and more preferably satisfies 0.3 ≦ ds ( Μm) / t (μm), and more preferably to satisfy the state of 0.4 ≦ ds (μm) / t (μm). On the other hand, when the value of ds/t is larger than the value on the right side of the above formula (2)-1', the aggregated particles tend to protrude from the support layer B, and there is a tendency to suppress the fall-off when contact with the light guide plate. Poor tendency. From this point of view, the upper limit should preferably satisfy ds(μm)/t(μm) ≦19, more preferably ds(μm)/t(μm) ≦18, and better satisfy ds(μm)/ t (μm) ≦ 2.

The white reflective film is laminated, and when the reflective layer A is represented by A and the support layer B is represented by B, it may be a two-layer structure of B/A, a three-layer structure of B/A/B, and a B/A. The four-layer structure of /B/A and the multilayer structure in which B is provided in five or more layers of the outermost layer of at least one surface. It is preferably composed of two layers of B/A and three layers of B/A/B. It is preferably composed of three layers of B/A/B, and it is difficult to cause problems such as curling.

In the reflective layer A and the support layer B, when the thickness of the entire white reflective film is 100%, the thickness ratio of the reflective layer A is 50 to 90%, and the thickness ratio of the support layer B is 5 to 50%, and further preferably For a 5 to 25% pattern, the balance of the characteristics is better. The ratio of the thicknesses of the layers herein to the plural layers refers to the ratio of the cumulative thicknesses of the layers.

In the present invention, in addition to the reflective layer A and the support layer B, other layers may be provided without departing from the object of the present invention. For example, it may have a layer for imparting functions such as antistatic property, electrical conductivity, and ultraviolet durability. Further, in particular, when the support layer B is provided by a coating method or a lamination method, a layer for improving the film formability of the film having the reflective layer A may be provided.

[Characteristics of reflective film] (reflectance, brightness)

The relevant description directly relates to the description relating to the white reflective film a.

(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. Therefore, when the self-recovered raw material is obtained and the film is formed by using the film, it is difficult to generate a gas trace, and the elongation is improved. From this point of view, it is more preferably 5 ppm or less, still more preferably 3 ppm or less, and desirably 0 ppm. In the present invention, in order to reduce the amount of the volatile organic solvent, when the support layer B is formed, it is preferred not to use a solution coating method using an organic solvent, and a method described later is employed.

Next, a method of producing the white reflective films a and b will be described.

[Manufacturing method of film]

An example of a method of producing the white reflective film a or b of the present invention will be described below.

When the white reflective film of the present invention is produced, it is preferably a molten resin coating method (including a melt extrusion resin coating method), a coextrusion method, a lamination method, or the like, and a reflective layer A obtained by a melt extrusion method or the like. The support layer B is formed thereon to form a laminated structure. Among them, the white reflective film of the present invention is preferably produced by laminating the reflective layer A and the support layer B by a co-extrusion method. Further, the reflective layer A and the support layer B are preferably directly laminated by a co-extrusion method. By laminating by the co-extrusion method, the interface adhesion between the reflective layer A and the support layer B can be improved, and since the step of forming the support layer B after the film formation is not required, the step of re-forming the support layer B after film formation is not required. It can be mass-produced cheaply and easily.

Hereinafter, the case where polyester is used as the thermoplastic resin constituting the reflective layer A and the thermoplastic resin constituting the support layer B and the coextrusion method is used as the lamination method will be described, but the present invention is not limited to this method, and The same can be applied to other aspects as described below. In this case, when the extrusion step is not included, the following "melt extrusion temperature" may be changed to "melting 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, a pore former, and other optional components are prepared as a polyester composition for forming the reflective layer A. Further, a polyester composition, an inert particle, and other optional components are prepared as a polyester composition for forming the support layer B. The polyester compositions were dried to completely remove the water and used.

Next, the dried polyester composition was placed in an individual extruder and melt extruded. The melt extrusion temperature must be Tm or more, and it is only required to be about Tm + 40 °C.

In this case, the polyester composition used for the production of the film, in particular, the polyester composition used in the reflective layer A is preferably a non-woven filter having an average mesh size of 10 to 100 μm made of a stainless steel fine wire having a wire diameter of 15 μm or less. filter. By carrying out this filtration, aggregation of particles which are easily aggregated into coarse aggregated particles can be generally suppressed, and a film having a small number of coarse particles can be obtained. Further, the average mesh of the non-woven fabric is preferably from 20 to 50 μm, more preferably from 15 to 40 μm. The filtered polyester composition is extruded in a molten state by a multi-layer extrusion method (co-extrusion method) using a feed block, and extruded from a die in a multi-layered state to produce an unstretched laminate. Sheet. The unstretched laminated sheet extruded from the nozzle was cooled and solidified by a casting roll to form an unstretched laminated film.

Then, the unstretched laminated film is heated by roll heating, infrared heating, or the like, and is stretched in the film forming machine axis direction (hereinafter sometimes referred to as a longitudinal direction or a longitudinal direction or MD) to obtain a longitudinally stretched film. This extension is preferably carried out by using the peripheral speed difference of two or more rolls. The longitudinally stretched film 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 a TD direction) to form a biaxially stretched film.

The stretching temperature is preferably at least Tg of the polyester (preferably the polyester constituting the reflective layer A) and at a temperature of Tg + 30 ° C or less, and it is easy to form excellent in film formability and to form pores. Further, as for the stretching ratio, it is preferably 2.5 to 4.3 times, more preferably 2.7 to 4.2 times in the longitudinal direction and the transverse direction. When the stretching ratio is too low, the thickness of the film tends to be poor, and the tendency of the pores is less likely to occur. On the other hand, when the stretching ratio is too high, the film tends to be easily broken during film formation.

Here, in the production of the white reflective film a of the present invention, in order to form a suitable inert particle coating, it is preferred to employ a high alignment extending condition. The term "high alignment extension" means an extension condition which tends to form a high molecular alignment, for example, lowering the extension temperature, increasing the stretching ratio, or combining the stretching conditions. Therefore, the low stretching ratio is set to a low stretching temperature condition, and conversely, the high stretching ratio is set to a high stretching ratio, and it is preferable to set it in such a combination.

In addition, it is also preferable to adopt a moderate extension speed. This is because the resin tends to be moderated when the stretching speed is too slow, so that it is difficult to form a protrusion, and the coating thickness tends to be thin, and when the stretching speed is too fast, the elongation stress tends to increase. There is a tendency that the inert particles are easily pushed into the support layer B, and the thickness of the coating tends to be thick. Specifically, the stretching speed in the longitudinal direction is preferably from 5 to 1000%/second, more preferably from 200 to 500%/second. Further, the stretching speed in the transverse direction is preferably from 0.2 to 100%/second, preferably from 3 to 10%/second.

Therefore, when the method of manufacturing the white reflective film a or b of the present invention is successively described, the second stage (in this case, the lateral extension) is better than the first stage when the longitudinal extension is performed and the lateral extension is successively performed in the two-axis extension. The extension temperature is about 10~50 °C. The reason for this is that the Tg as a 1-axis film rises due to the alignment in the first stage.

Moreover, it is preferred to preheat the film before each extension. For example, the pre-heat treatment in the lateral direction starts from a temperature higher than Tg + 5 ° C of the polyester (preferably the polyester constituting the reflective layer A), and the temperature is gradually increased. The temperature rise during the lateral extension may be continuous or periodic (sequential), but is usually a sequential heating. For example, the tenter When the lateral extension of the machine is divided into a plurality of zones in the traveling direction of the film, the temperature is raised by flowing a heating medium of a specific temperature to each zone.

The film after the biaxial stretching is then subjected to heat fixation and thermal relaxation to form a biaxial alignment film, but it is also possible to carry out the treatment while continuing to extend from the melt extrusion.

After the biaxially stretched film, the melting point of the polyester sandwiched between the two ends of the polyester (preferably the polyester constituting the reflective layer A) is set to Tm, preferably (Tm-20 ° C) to (Tm - 100 ° C). The heat treatment is performed by fixing the width or reducing the width by 10% or less, and heat-fixing to lower the heat shrinkage rate. When the heat treatment temperature is too high, the planarity of the film tends to be deteriorated, and the thickness of the film tends to become large. On the other hand, when it is too low, there is a tendency that the heat shrinkage rate becomes large.

Further, in order to adjust the amount of heat shrinkage, both ends of the film to be sandwiched can be cut off, and the stretching speed in the longitudinal direction of the film can be adjusted to relax the longitudinal direction. The means of relaxation is to adjust the speed of the roller group on the pull-out side of the tenter. As for the relaxation ratio, the roll speed of the tenter is reduced with respect to the linear speed of the film, and it is preferably carried out by 0.1 to 2.5%, more preferably 0.2 to 2.3%, and most preferably 0.3 to 2.0%. This value is called "relaxation rate"), and the thermal contraction rate in the longitudinal direction is adjusted by controlling the relaxation rate. In addition, the transverse direction of the film can be reduced in width during the process of cutting off the ends to obtain the desired heat shrinkage.

Further, in the case of biaxial stretching, in addition to the above-described longitudinal-transverse secondary biaxial stretching method, a lateral-longitudinal biaxial stretching method may be employed. Moreover, the film can be formed 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.

According to this, the white reflective film of the present invention can be obtained.

Finally, the recovery of the film which is strongly associated with the manufacture of the white reflective film b of the present invention is explained in particular.

[Manufacture of self-recovered raw materials]

In the present invention, the obtained white reflective film can be granulated by pulverization or melt extrusion, and used as a self-recovering raw material, added to the film, preferably added to the reflective layer A, and can be produced in the same manner as described above. White reflective film. In this case, when the film which is the raw material of the self-recovery material is a white reflective film having the aspect of the present invention, the step of producing the self-recovered raw material or the step of forming the film by using the film is performed to cause the cohesion in the support layer B. When the particles are pulverized, even if they are contained in a newly produced film, optical properties such as film forming properties and reflectance are not lowered, and good film forming properties can be obtained. Therefore, the step of preparing the granules is not particularly limited, but it is preferable to have a pulverizing mechanism capable of disintegrating the contained condensed particles as much as possible in consideration of the above mechanism. In this way, when the self-recovered raw material is used as a film raw material and used again, the effect of containing aggregated particles can be made smaller, and a white reflective film which is more excellent in film formability and the like can be obtained.

When the self-recovered raw material is added to the film, it is preferably from 5 to 50% by mass based on the total mass of the film, and the effect of improving the film forming property can be improved. Moreover, a better state is the state of being added to both the support layer B and the reflective layer A, or substantially not added to the support layer B, but added to the reflective layer A. In this case, the content of the self-recovered raw material in the reflective layer A is preferably from 10 to 70% by mass based on the mass of the reflective layer A, and the effect of improving the film forming property is further improved. Also, in support layer B It is also possible to add the self-recovering raw material, but it is preferable to use the self-recovering raw material in the reflective layer A, and the support layer B is not substantially used. When the film forming property and the reflectance are maintained in this state, it is preferable to suppress the adhesion to the light guide plate and to obtain excellent productivity.

Example

The invention is described in detail below by way of examples. Further, each characteristic value was measured by the following method.

(A) Measurement methods of Reference Examples 1 to 9, Examples 2, 3, and 10 to 17, and Comparative Examples 1, 4, and 5 to 11. (1) Light reflectance

The integrating sphere was attached to a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and the reflectance when the reflectance of the BaSO ₄ white plate was set to 100% was measured at a wavelength of 550 nm, and this value was defined as a reflectance. Further, the measurement was performed on the surface of the support layer B side. When the back of the watch has different support layers B, the surface of the support layer on the side of the light guide plate is measured.

(2) Average particle size of pore former (inorganic particles)

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 of d ₅₀ was taken as the average particle diameter.

(3) Amount of volatile organic solvent

1 g of film sample was placed in 10 L of fluororesin at room temperature (23 ° C) In the bag, it was blown in with pure nitrogen and sealed. Then, immediately take nitrogen from the bag at a flow rate of 0.2 L/min, and use two TEAX-TA traps for analysis to sample 0.2 L and 1.0 L of nitrogen, and use these to sample by HPLC and GCMS. The mass of the organic solvent component contained in the nitrogen gas. The obtained value was converted into an amount of 10 L of nitrogen gas, and the mass of the organic solvent volatilized from 1 g of the film sample in 10 L of nitrogen gas was determined as the amount of the volatile organic solvent (unit: ppm, mass basis of the film sample). Further, the aldehyde was eluted from the collecting tube by acetonitrile and quantified by HPLC. Further, when the values of HPLC and GCMS are different, a larger number of values are detected.

Further, in Examples 10 to 17 and Comparative Examples 5 to 11, the case where the amount of the volatile organic solvent was 10 ppm or less was evaluated as ○, and the case where it exceeded 10 ppm was evaluated as ×.

(4) Film thickness and layer composition

The white reflective film was sliced by a microtome and the cross section was exposed. The S-4700 field emission type scanning electron microscope manufactured by Hitachi, Ltd. was used to observe the cross section at a magnification of 500 times, and the whole film and reflection were obtained. The thickness of layer A and support layer B. Further, the thickness of the entire film and the support layer B is the thickness of a portion where the agglomerated particles or the inert particles are protruded from the surface of the support layer. The thickness (μm) of each layer was determined, and the thickness ratio of each layer was calculated.

(5) Calculation of pore volume ratio

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

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

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

Further, only the layer to be measured for the void volume ratio was separated, and the mass per unit volume was determined to determine the solid density. The volume was cut into an area of 3 cm ² , and the thickness of 10 points of the size was measured with an electronic micrometer (K-402B manufactured by Anritsu), and the average value was used as the thickness, and the area was calculated by area×thickness. The quality is weighed with an electronic balance.

Further, the specific gravity of the agglomerated particles is obtained by using the following scale cylinder method to obtain the value of the bulk specific gravity. The aggregated particles in an absolute dry state are filled in a graduated cylinder having a volume of 1000 ml, and the weight of the whole is measured, and the weight of the condensed particles is obtained by subtracting the weight of the graduated cylinder from the weight of the whole, and the volume of the graduated cylinder is measured. The weight (g) of the aggregated particles was determined by dividing the volume (cm ³ ).

(6) Melting point, glass transition temperature

The measurement was carried out using a differential scanning calorimeter (TA Instruments 2100 DSC) at a temperature increase rate of 20 ° C/min.

(7) Ten point average roughness (Rz)

The three-dimensional roughness measuring device SE-3CKT (manufactured by Otaru Research Laboratory Co., Ltd.) was used to measure the protrusion profile of the film surface with an intercept of 0.25 mm, a measurement length of 1 mm, a scanning pitch of 2 μm, and a number of scanning strips, with a height magnification of 1000. The projection angle is recorded at a magnification of 200 times in the scanning direction. Among the obtained protrusion profiles, 5 points were taken from the peak of the peak (Hp), and 5 points were taken from the bottom of the valley bottom (Hv), and the 10-point average roughness (Rz, unit: nm) was obtained from the following formula. Further, 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 projection contour (horizontal axis: projection height, vertical axis: projection number of projections) as the projection frequency.

(8) Damage assessment of the light guide plate (scraping evaluation) and evaluation of particle shedding

As shown in Fig. 1, an iron plate (2, a weight of about 200 g) having a length of 200 mm, a width of 200 mm, and a thickness of 3 mm is fixedly attached to the end portion of the handle portion (1), and the evaluation surface is upwardly oriented in the width direction. The two ends are exposed to a portion of 25 mm from the iron plate (the portion of the center of 200 mm × 200 mm overlaps with the iron plate), and a reflective film (3) having a width of 250 mm and a length of 200 mm is attached. At this time, the evaluation surface (support layer) of the reflective film becomes the outer side. And, the 25 mm portion remaining at both ends of the width direction of the reflective film is folded back to the back of the iron plate On the side, the effect of scraping the light guide plate is eliminated by the end portion of the reflective film (the portion cut into the blade by a cutter or the like during sampling).

Next, the light guide plate (4, at least 400 mm × 200 mm) is fixed on the horizontal table with the dots (401) facing upward, and the reflective film fixed to the iron plate prepared as described above is used for evaluation. The surface is placed in contact with the light guide plate, and the surface of the reflective film is placed face down on the light guide plate, and then a 500 g weight (5) is placed thereon at a distance of 200 mm (fixed to iron in a region of 400 mm × 200 mm). The reflective film on the board moves back and forth 15 times at a speed of about 5 to 10 seconds. Subsequently, on the surface of the light guide plate, the degree of scraping and the presence or absence of particles peeled off from the reflective film were observed using a magnifying glass of 20 times, and evaluated by the following criteria.

In the entire range of 400 mm × 200 mm of friction on the light guide plate, after 15 reciprocating movements, there is no scratch that can be observed by the magnifying glass, and it is recorded as "no scraping" (scraping evaluation ○), after 10 reciprocating movements Observable scratches, but when there are observable scratches after 15 reciprocating movements, it is marked as "not easy to scrape" (scraping evaluation △), and there are observable scratches after 10 reciprocating movements. It is "will scrape" (scraping evaluation ×).

Further, after 15 reciprocating movements, if there is no white foreign matter observed by the magnifying glass in the entire range of 400 mm × 200 mm rubbed on the light guide plate, it is referred to as "particles not falling off" (falling evaluation ○). In addition, when the white foreign matter was observed, the white foreign matter was observed under a microscope, and it was confirmed that it was an inert particle (aggregated particle), and if the particle which fell off was five or less, it was described as "the particle hardly fell off" (falling evaluation △ If it is six or more, it will be described as "particles will fall off" (falling evaluation ×).

Further, in the above evaluation, the influence of the spot size should be suppressed as much as possible, and a large area of the spot size is strongly selected in the light guide plate, and the evaluation samples are uniformly performed.

(9) Close spot assessment (attachment evaluation)

The LED LCD TV (LG42LE5310AKR) made by LG Company takes out the chassis (6) and places it on the horizontal table so that the inner side of the TV is facing upwards, on which the support surface is placed upwards. The reflective film of the same size is used for the casing, and then the light guide plate and the optical sheet (2 pieces of the diffusion film and 1 piece of the film) (7) of the original television are placed thereon. Next, in its surface, on the area containing the most severe portion of the concave and convex portion of the casing, a triangular triangular table (801) having three cylindrical legs of 5 mm in diameter as shown in Fig. 2 is placed, and 15 kg is placed thereon. The weight (802) is used to visually observe the area surrounded by the three legs, and if there is no abnormally bright part, it is recorded as "no close spot" (close spot evaluation ○). In addition, when there is an abnormally bright portion, the DBEF sheet of the original television is placed on the optical sheet 3, and the DBEF sheet of the original television is also visually observed. If the abnormally bright portion is not corrected, it is recorded as "closed spot" (evaluation) ×), if the abnormally bright portion disappears, it is recorded as "almost no dense spot" (evaluation △). Moreover, the area surrounded by the three legs is a slightly equilateral triangle having a length of 10 cm on each side.

(B) Examples 2, 3, Reference Examples 1 to 9 and Comparative Example 1 (10) Primary particle size (dp) of agglomerated particles

For the film containing aggregated particles and the recovered raw material, the solvent is used to dissolve the resin component, and the S-4700 field emission type scan manufactured by Hitachi, Ltd. is used. Electron microscopy, the particles recovered from the particles (secondary particles) were observed at a magnification of 10,000 times, and the aggregation state of the primary particles in the surface of the secondary particles was observed, and the particle diameter was measured for any 100 primary particles from the average value thereof. The primary particle diameter (dp) was determined.

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

When it is 1 μm or more and less than 3 μm, it is referred to as "<3", and when it is less than 1 μm, it is referred to as "<1".

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

For the film containing the aggregated particles and the recovered raw material, the resin component was dissolved using a solvent, and the particles recovered from the particles (secondary particles) were observed at a magnification of 1000 times using a S-4700 field emission type scanning electron microscope manufactured by Hitachi, Ltd. The particle diameter was measured for any 100 particles, and the secondary particle diameter (ds) was determined from the average value. Further, the case other than the spherical shape is obtained by (long diameter + short diameter)/2. Here, the short diameter refers to the largest diameter perpendicular to the long diameter.

In the above method, when agglomerated particles are dissolved in a solvent (for example, in the case of organic particles), agglomerated particles before blending are used, and a S-4700 field emission type scanning electron microscope manufactured by Hitachi, Ltd. is used. 1000 times observation, and measuring the particle size of 100 particles, from the flat The average particle diameter (ds) was obtained from the mean value. Further, when having a long diameter and a short diameter, it is obtained by (long diameter + short diameter)/2. Here, the short diameter refers to the largest diameter perpendicular to the long diameter.

(12) Brightness

The reflective film is taken out from the LED LCD TV (LG42LE5310AKR) manufactured by LG, and the support layer of various reflective films is placed on the screen side (the surface in contact with the light guide plate), and the brightness meter is used in the state of the backlight unit (made by Otsuka Electronics Co., Ltd.). Model MC-940), the center brightness of the backlight was measured from the front side at a measuring distance of 500 mm.

(13) White point assessment

Using the reflective film and the light guide plate used in the evaluation of (8) above, the reflective film is placed on the table in such a manner that the support layer faces upward, and the light guide plate is placed on the four sides of the light guide plate with the dots facing downward. Place a weight of 200g on each side and fix it. Use the backlight source of LED LCD TV (LG42LE5310AKR) made by LG to make the light incident on the side of the light guide. If there is any bright spot other than the light guide point that can be observed by visual observation. Then it is recorded as white point occurrence (evaluation ×). In addition, no abnormal white spots observed by visual observation are recorded as white spots (evaluation ○).

(14) Film extension

The film-forming stability at the time of film formation of the film described in the Example by the continuous film forming method using a tenter was observed and evaluated based on the following criteria.

◎: The film can be stably formed for 3 hours or more.

○: Film formation can be stably performed for 1 hour or more.

△: 1 degree interruption occurred in 1 hour.

×: Several interruptions occurred within one hour, and it was impossible to form a film stably.

(C) About Examples 10 to 17 and Comparative Examples 5 to 11 (15) Coating thickness of inert particles

A sliced sample was cut from the epoxy-embedded film using a microtome. At this time, the direction of cutting into the blade or the like is noted so as not to break the projection. The section of the sliced sample was observed using a S-4700 field emission type scanning electron microscope manufactured by Hitachi, Ltd. at a magnification of 3000 times.

Photographing the 100 particle profiles, as shown in Figure 3, drawing the horizontal line (a) of the film surface in parallel with (a) parallel to the apex of the protrusion (b), and parallel with (a) The thickness of the resin coating portion at the apex portion of the projection is measured by the straight line (c) at the uppermost portion of the particles in the projection, and the average value of the resin coating portion at the apex portion of the projection is used as the coating thickness of the particle.

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% based on 100 mol% of all acid components of the obtained polyester), 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, 0.05 parts by mass of manganese acetate, and 0.012 parts by mass of lithium acetate are fed into a flask equipped with a rectification column and a distillation condenser, and heated to 150 to 240 ° C while stirring to distill off methanol for transesterification reaction. . After methanol is distilled off, trimethyl phosphate is added. 0.03 parts by mass, 0.04 parts by mass of cerium oxide, and the reactants were transferred to the reactor. Subsequently, 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. The polymer had a melting point of 235 °C.

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

Except for the change to 129.0 parts by mass of dimethyl terephthalate and 21.0 parts by mass of dimethyl isophthalate (14 mol% based on 100 mol% of the total acid component of the obtained polyester), In the same manner as in Example 1, the isophthalic acid copolymerized polyethylene terephthalate 2 was obtained. The polymer had a melting point of 215 °C.

Production Example 3: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 3

Except for the change to 142.5 parts by mass of dimethyl terephthalate and 7.5 parts by mass of dimethyl isophthalate (5 mol% based on 100 mol% of the total acid component of the obtained polyester), In the same manner as in Example 1, ethylene terephthalate copolymerized polyethylene terephthalate 3 was obtained. The polymer had a melting point of 245 °C.

Production Example 4: Preparation of Organic Cohesive Particles

The raw materials described below were fed into an autoclave, and heated at 180 to 240 ° C for 120 minutes to carry out a transesterification reaction. The reaction system is then heated to 245 ° C and The internal pressure was changed to 1 to 10 mmHg, and the reaction was continued for 60 minutes, and as a result, a copolymerized polyester was obtained.

The obtained resin was slowly agglomerated to obtain organic agglomerated particles (agglomerated polyester particles).

Production Example 5: Preparation of Particle Parent Particles 1

Using the above-mentioned portion of the terephthalic acid copolymerized polyethylene terephthalate 1 and the pore-forming agent having an average particle diameter of 1.0 μm of barium sulfate particles (hereinafter referred to as BaSO ₄ ) to Kobe Steel Co., Ltd. The NEX-T60 tandem extruder was prepared by mixing the content of barium sulfate particles with the mass of the obtained mother particles of 63% by mass, and extruding at a resin temperature of 260 ° C to prepare inorganic particles containing barium sulfate particles. Mother particle 1.

Production Example 6: Preparation of Particle Parent Particles 2

Will be used as agglomerated cerium oxide particle A of TOSOH. AY-603 manufactured by SILICA Co., Ltd. was mixed with the above-mentioned phthalic acid copolymerized polyethylene terephthalate 2 in an amount of 8 mass%, and extruded at a melting temperature of 235 ° C to prepare an inorganic solution. Particle mother particle 2.

Manufacture of granules 7 to 14: preparation of particle mother particles 3 to 10

The inert particles shown in Table 1 were added to the above-mentioned obtained terephthalic acid copolymerized polyterephthalate 3, mixed so as to have the contents shown in Table 1, and extruded at a melting temperature of 235 ° C to prepare. The particle mother particles are 3~10.

In addition, the KMP series manufactured by Shin-Etsu SILICONE Co., Ltd. was used as the polysiloxane particles, and the MBX series manufactured by Sekisui Seisakusho Co., Ltd. was used as the acrylic particles.

Production Example 15: Preparation of particle mother particles 11

The agglomerated polyester particles obtained in Production Example 4 were added to the above-mentioned obtained phthalic acid copolymerized polyethylene terephthalate 2, and the content thereof was 15% by mass, and the melting temperature was 235 ° C. Extrusion is carried out to prepare the particle mother particles 11.

Reference example 1 (Manufacture of white reflective film)

Using the above-mentioned phthalic acid copolymerized polyethylene terephthalate 1 and the particle mother particle 1 as a raw material of the reflective layer (layer A), using isophthalic acid copolymerized polyethylene terephthalate 2 The particle mother particle 2 was used as a raw material of the support layer (layer B), and each layer was mixed so as to have the structure described in Table 2, and was put into an extruder, and the melt extrusion temperature of the layer A was 255 ° C, and the layer B was The melt extrusion temperature was 230 ° C, and the three-layer feed sleeve device which was formed as a layer of the B layer/A layer/B layer was combined as shown in Table 2, and the lamination was formed from the nozzle while being laminated. Flaky. At this time, the discharge amount of each extruder was adjusted so that the thickness of the B layer/A layer/B layer was 10/80/10 after the 2-axis extension. The sheet was then cooled and solidified by a cooling drum having a surface temperature of 25 ° C to form an unstretched film. The unstretched film was passed through a preheating zone at 73 ° C, followed by a preheating zone of 75 ° C, directed to a longitudinal extension maintained at 92 ° C, extended 2.9 times in the machine direction, and cooled at 25 ° C. Next, the both ends of the film were held by a jig to pass through a preheating zone of 115 ° C to be guided to a laterally extending region maintained at 130 ° C, extending 3.6 times in the lateral direction. Subsequently, heat-fixing was carried out at 185 ° C in a tenter, and the transverse direction was narrowed at a shrinkage ratio of 2% and a shrinkage temperature of 130 ° C. Then, both ends of the film were cut off, and thermal relaxation was performed at a longitudinal relaxation rate of 2%. After cooling to room temperature, a biaxially stretched film having a thickness of 250 μm as shown in Table 2 was obtained.

The film is recovered, pulverized, melt extruded, and pelletized to form a self-recovering raw material, which is in the reflective layer A based on the mass of the reflective layer A. 35 % by mass of the self-recovered raw material was added, and a biaxially stretched film having a thickness of 250 μm was obtained in the same manner as above to obtain a white reflective film. The evaluation results of the obtained film are shown in Table 3.

Reference example 2

In the same manner as in Reference Example 1, except that the condensed cerium oxide particles A were changed to condensed cerium oxide particles B (C812 manufactured by GRACE Co., Ltd., Japan), a biaxially stretched film and a self-recovered raw material were used, and a white reflective film was used. And evaluate. The evaluation results are shown in Table 3.

Reference example 3

In the same manner as in Reference Example 1, except that the condensed cerium oxide particles A were changed to the condensed cerium oxide particles C (the powder of 30 μm or more of CARiACT P-10 manufactured by Fuji Silysia Chemical Co., Ltd. was removed by an air classifier). The biaxially stretched film and the self-recovered material were used as a white reflective film and evaluated. The evaluation results are shown in Table 3.

Reference example 4

In the same manner as in Reference Example 1, except that the condensed cerium oxide particles A were changed to the condensed cerium oxide particles D (CARiACT P-10 manufactured by Fuji Silysia Chemical Co., Ltd.), the same was used as the biaxially stretched film and the self-recovered raw material. A white reflective film was prepared and evaluated. The evaluation results are shown in Table 3.

Reference example 5 (Manufacture of white reflective film)

In the same manner as in Reference Example 1, except that the particle mother particles 2 were changed to the particle mother particles 11, a biaxially stretched film and a self-recovered material were prepared, and a white reflective film was used for evaluation. The evaluation results are shown in Table 3.

Reference example 6

In the same manner as in Reference Example 1, except that the pore-forming agent of the reflective layer A was changed to the resin (cycloolefin, "TOPAS 6017S-04" manufactured by Polyplastic Co., Ltd.) which is incompatible with the polyester shown in Table 2, The raw materials were recovered, used as a white reflective film, and evaluated. The evaluation results are shown in Table 3.

Reference example 7, 8

The addition amount of the condensed cerium oxide particles A was as shown in Table 2, and a biaxially stretched film and a self-recovered raw material were prepared in the same manner as in Reference Example 1, and a white reflective film was used for evaluation. The evaluation results are shown in Table 3.

Reference Example 9

In the same manner as in Reference Example 1, except that the production conditions and the layer constitution were changed to those shown in Table 2, a biaxially stretched film and a self-recovered material were prepared, and a white reflective film was used for evaluation. Evaluation result In Table 3.

Comparative example 1

Except that the agglomerated particles were not added to the support layer B of Reference Example 1 (the use of isophthalic acid copolymerized polyethylene terephthalate 2 in place of the particle mother particles 2, and the layer was the surface layer C), the remainder and the reference examples 1 A 2-axis stretch film having a thickness of 250 μm was also formed, and a coating liquid composed of the composition shown in the following liquid preparation formula 1 was applied to one surface of the film by a nozzle coating apparatus, and dried at 80 ° C in an oven. A support layer B is formed to obtain a film. The support layer B has a dry thickness of 2 μm. Then, the film was collected, pulverized, melt-extruded, and pelletized to prepare a self-recovered material, which was added to the reflective layer A at a mass of 35 mass% based on the mass of the reflective layer A, and the film was again produced in the same manner as described above. However, when a film is formed, a large amount of foreign matter such as unmelted material or gas traces is generated, and the elongation is drastically lowered, so that sampling is impossible.

(Liquid formulation 1, solid content concentration 35 mass%)

. Particle: hydrated finished product industry BM30X-8 (crosslinked acrylic particles, non-porous particles, powder)... 17.6% by mass

. Acrylic adhesive: DIC ACRYDICA-817BA...17.5 mass%

. Crosslinking agent: Japan Polyurethane Industrial Co., Ltd. CORONATE HL...11.7 mass%

. Organic solvent: butyl acetate... 53.2% by mass

Further, the solid content ratio of each component in the support layer B obtained from the above formulation was as follows.

. Particle: 50% by mass

. Adhesive: 25% by mass

. Crosslinking agent: 25% by mass

Example 2

In the same manner as in Reference Example 1, except that the condensed cerium oxide particles A were changed to condensed cerium oxide particles A (BY601 manufactured by TOSO. SILICA Co., Ltd.), a biaxially stretched film and a self-recovered raw material were used, and white reflection was used. The film was evaluated. The evaluation results are shown in Table 3.

Example 3

In the same manner as in Reference Example 1, except that the condensed cerium oxide particles A were changed to the condensed cerium oxide particles F (SYLYSIA 350 manufactured by Fuji Silysia Chemical Co., Ltd.), the same was used as the biaxially stretched film and the self-recovered raw material, and white color was used. Reflective film was evaluated. The evaluation results are shown in Table 3.

Comparative example 4

In the same manner as in Example 1, except that the condensed cerium oxide particles A were changed to spherical cerium oxide particles (SHILTON JC manufactured by Mizusawa Chemical Co., Ltd.), the same was used as the biaxially stretched film and the self-recovered raw material, and white color was used. Reflective film was evaluated. The evaluation results are shown in Table 3.

According to the above-mentioned Embodiments 2 and 3, according to the present invention, it is possible to sufficiently suppress the damage of the light guide plate, and to provide a film having excellent film formability and recyclable when the film is recovered and used as a self-recovering material. White reflective film.

Example 10 (Manufacture of white reflective film)

On the other hand, the above-mentioned polyethylene terephthalate 1 and the mother particle 1 are used as a raw material of the reflective layer (layer A), and the content of barium sulfate is 45% by weight. Using isophthalic acid The polyethylene terephthalate 3 and the mother particle 3 were used as a raw material of the support layer (layer B), and they were mixed and used as the content shown in Table 4, and they were put into an extruder to become B layer/A. The layer/B layer layer structure is joined by a three-layer feed sleeve device, and the laminated state is maintained from the nozzle into a sheet shape. At this time, the discharge amount of each extruder was adjusted so that the thickness of the B layer/A layer/B layer became 10/80/10 after the biaxial stretching. The sheet was then cooled and solidified by a cooling drum having a surface temperature of 25 ° C to form an unstretched film. The unstretched film was guided to the induction heating roller group and preheated to 73 ° C, and then between the two sets of nip rollers, so that the surface temperature of the film became 95 ° C. The extension speed of %/sec was extended by 2.9 times in the longitudinal direction using the circumferential speed difference of the front and rear rolls, and was cooled by a roll group of 25 °C. Then, the both ends of the film were sandwiched by a jig and passed through a preheating roll of 95 ° C and guided to a laterally extending region maintained at 110 ° C, and extended in the lateral direction at an interval of 5.8% / sec. 3.6 times. Then, it was heat-fixed at 185 ° C in a tenter, and the width direction was narrowed at a shrinkage ratio of 2% and a shrinkage temperature of 130 ° C, and then both ends of the film were cut off, and then thermally relaxed at a longitudinal relaxation rate of 2%. After cooling to room temperature, a biaxially stretched film having a thickness of 250 μm was obtained. The evaluation results of the obtained film are shown in Table 4.

Examples 11 to 17, and Comparative Examples 5 to 11

A film was obtained in the same manner as in Example 10 except that the state of the inert particles added to the layer B (particle mother particles), the layer constitution of the film, and the stretching conditions were as shown in Tables 4 and 5. The evaluation results of the obtained film are shown in Tables 4 and 5.

As is apparent from the above-described Examples 10 to 17, according to the present invention, it is possible to provide a white reflective film which can sufficiently suppress adhesion to a light guide plate, suppress damage of the light guide plate, and suppress particle separation.

[Industrial availability]

The white reflective film of the present invention can sufficiently suppress the damage of the light guide plate, and it is difficult to reduce the film formability of the film even if the self-recovering raw material is used. Therefore, it can be preferably used as a surface light source reflector having a light guide plate, among which A reflective film used in, for example, an edge-emitting type backlight unit used for a liquid crystal display device or the like can be preferably used.

Claims (4)

A white reflective film comprising a reflective layer A and a support layer B made of a thermoplastic resin composition containing agglomerated particles in a thermoplastic resin, wherein the aggregated particle system has a primary particle diameter (dp) of 3 μm or less, 2 The secondary particle diameter (ds) is 8 μm or less, and the content of the aggregated particles in the support layer B is 1% by volume or more and 50% by volume or less based on the volume of the support layer B, and the support layer B is formed into a white reflective film. At least one outermost layer, the ten-point average roughness (Rz) on the surface of the outermost support layer B opposite to the reflective layer A satisfies the following formula (1), and the agglomerated particles in the support layer B The secondary particle diameter (ds) and the thickness (t) of the support layer B satisfy the following formula (2), 0.1 × ds (μm) ≦ Rz (μm) ≦ 0.7 × ds (μm) ‧ ‧ (1) 0.07 ≦ Ds (μm) / t (μm) ≦ 20‧‧‧(2). The white reflective film of claim 1, wherein the amount of the volatile organic solvent is 10 ppm or less. The white reflective film of claim 1 or 2, wherein the pore volume ratio of the reflective layer A is 15 to 70% by volume, and the pore volume ratio of the support layer B is 0 to less than 15% by volume. A white reflective film according to claim 1 or 2, which is used as a reflector for an edge-emitting type backlight unit.