WO2017010471A1

WO2017010471A1 - White-reflecting film for large-scale display

Info

Publication number: WO2017010471A1
Application number: PCT/JP2016/070505
Authority: WO
Inventors: 浅井　真人; 倉垣　雅弘; 真一郎岡田; 利洋大澤
Original assignee: 帝人フィルムソリューション株式会社
Priority date: 2015-07-16
Filing date: 2016-07-12
Publication date: 2017-01-19
Also published as: TWI772267B; CN107710032B; KR20180030855A; TW201708338A; CN107710032A

Abstract

The present invention addresses the problem of providing a white-reflecting film that resists deflecting under heat while having exceptional reflection characteristics. The problem is overcome by a white-reflecting film that has a reflective layer A, wherein the white-reflecting film satisfies either condition (a) or condition (b) that the reflective layer A (a) comprises a thermoplastic resin composition A1 containing calcium carbonate particles in a thermoplastic resin A, the content of the calcium carbonate particles being 10─70% by mass with respect to the mass of the thermoplastic resin composition A1, or (b) comprises a thermoplastic resin composition A2 containing calcium carbonate particles in the thermoplastic resin A, and a resin that is incompatible with the thermoplastic resin A, the content of the calcium carbonate particles being 5─69% by mass with respect to the mass of the thermoplastic resin composition A2, the content of the incompatible resin being 1─40% by mass with respect to the mass of the thermoplastic resin composition A2, and the combined content of the calcium carbonate particles and the incompatible resin being 10─70% by mass with respect to the mass of the thermoplastic resin composition A2. The calcium carbonate particles have an average grain size of 0.1─1.2 μm. The relationship (D90 ‒ D10)/D50 ≤ 1.6 is satisfied, where D10, D50, and D90 are the 10%-, 50%-, and 90%-volume grain sizes, respectively, integrated from the small grain size side. The white-reflecting film has a reflectivity of at least 60%.

Description

White reflective film for large displays

The present invention relates to a white reflective film for large displays that can be suitably used as a reflector.

The surface light source is provided with a reflector on the back, and the light from the light source is reflected to the front by the reflector to improve the light extraction efficiency and improve the brightness.

For example, in a backlight unit of a liquid crystal display device (hereinafter sometimes referred to as LCD), a direct type including a light source and a reflective film on the back surface of the liquid crystal display panel, and a reflective plate on the back surface of the liquid crystal display panel. There is an edge light type in which a light guide plate is provided and a light source is provided on a side surface of the light guide plate. As a light source, a CCFL has been often used in the past, but in recent years, a light emitting diode (hereinafter sometimes referred to as an LED) is used to reduce power consumption and thickness, and an edge light type LED backlight or a direct light source is used. Type LED backlights are the mainstream. The edge light type backlight has an advantage that the LCD can be made thinner, while the direct type LED backlight is low in cost because it does not use a light guide plate.

Surface light sources are also used for lighting to brighten indoors and outdoors.

As the reflector, for example, a void-containing film in which voids are formed inside by adding inorganic particles or an incompatible resin to a thermoplastic resin such as polyester and stretching it (Patent Literature). 1-5).

However, such a reflector may be deformed and bent due to heat or humidity from the light source or the external environment (hereinafter, such a bend may be referred to as “heat bend”). If the reflector is bent, it becomes a luminance spot of a surface light source, and for example, an LCD brightness spot.

Therefore, in order to solve the problem of such thermal deflection, Patent Document 6 proposes a concept of making a reflective surface in which a metal layer is formed on an uneven surface made of particles, so that it does not easily become a luminance spot even if it is bent. In addition, a protrusion is formed on the bottom surface member of the LCD to support the reflector (Patent Document 7), or a slit that absorbs the deflection is inserted into the reflector (Patent Document 8), thereby bending the reflector. Consideration for improvement has been made. However, both of these processes are expensive.
JP 2004-330727 A JP 2011-11370 A JP 2011-232369 A JP 2013-88715 A JP2013-88716A JP 2002-100227 A JP 2013-229185 A Japanese Unexamined Patent Publication No. 2014-22060

A large display has a recess to provide a circuit board or the like on the back chassis. The present inventors have found out that heat tends to stay in such a depression, and the heat deflection problem becomes more noticeable due to such heat, and have focused on this.

In view of the above-described background art, an object of the present invention is to provide a white reflective film that has excellent reflection characteristics and is difficult to bend even when used in a large display.

The inventors of the present invention have focused on the fact that the presence of voids in the void-containing film makes it easier for heat deflection to occur. However, simply reducing the void is not preferable because it is in the direction of reducing the reflection characteristics. In addition, the inventors focused on the fact that heat distortion tends to occur when the inorganic particles as the void forming agent are heavy.

That is, the present invention employs the following configuration in order to achieve the above-described problems.
1. A white reflective film having a reflective layer A,
The reflective layer A is
a. The thermoplastic resin A is composed of a thermoplastic resin composition A1 containing calcium carbonate particles, and the content of the calcium carbonate particles is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A1. is there,
Or
b. The thermoplastic resin A comprises a thermoplastic resin composition A2 containing calcium carbonate particles and a resin incompatible with the thermoplastic resin A, and the content of the calcium carbonate particles is in the mass of the thermoplastic resin composition A2. The content of the incompatible resin is 5% by mass to 69% by mass with respect to the mass of the thermoplastic resin composition A2, and the calcium carbonate is 1% by mass to 40% by mass. Satisfying either a or b in which the total content of the particles and the incompatible resin is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A2,
The calcium carbonate particles have an average particle diameter of 0.1 μm or more and 1.2 μm or less, and 10% volume particle diameter D10, 50% volume particle diameter D50 and 90% volume particle diameter D90 accumulated from the small particle diameter side are (D90−D10) /D50≦1.6 is satisfied,
A white reflective film for large displays, wherein the reflectance of the film is 60% or more.
2. The reflective layer A has a. The thermoplastic resin A is composed of a thermoplastic resin composition A1 containing calcium carbonate particles, and the content of the calcium carbonate particles is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A1. The white reflective film as described in 1 above.
3. The reflective layer A is b. The thermoplastic resin A comprises a thermoplastic resin composition A2 containing calcium carbonate particles and a resin incompatible with the thermoplastic resin A, and the content of the calcium carbonate particles is in the mass of the thermoplastic resin composition A2. The content of the incompatible resin is 5% by mass to 69% by mass with respect to the mass of the thermoplastic resin composition A2, and the calcium carbonate is 1% by mass to 40% by mass. 2. The white reflective film as described in 1 above, wherein the total content of the particles and the incompatible resin is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A2.
4). The reflective layer A, and further has a surface layer C on at least one surface,
The surface layer C is composed of a thermoplastic resin composition C containing surface layer particles, and the surface layer particles have an average particle size of 2.0 μm or more and 50.0 μm or less, and the content thereof is the thermoplastic resin. 4. The white reflective film for large displays according to any one of 1 to 3 above, which is 3% by volume to 50% by volume with respect to the volume of the composition C.
5). 5. The white reflective film as described in any one of 1 to 4 above, wherein the thermoplastic resin A is copolymerized polyethylene terephthalate.
6). 6. The white reflective film as described in 5 above, wherein the copolymerized polyethylene terephthalate has a copolymerization amount of 1 mol% or more and 20 mol% or less with respect to 100 mol% of the total acid component of the copolymer polyethylene terephthalate.
7). 7. The white reflective film as described in any one of 1 to 6 above, wherein the thickness ratio of the reflective layer A with respect to 100% of the thickness of the white reflective film is 50% or more.
8). 8. The white reflective film as described in any one of 1 to 7 above, further comprising a support layer B made of the thermoplastic resin B or the thermoplastic resin composition B.
9. A surface light source using the white reflective film described in any one of 1 to 8 above.

On the other hand, Patent Document 1 uses barium sulfate having a small standard deviation of the particle size distribution, and barium sulfate has a heavy specific gravity and thus is susceptible to thermal deflection. Patent Documents 2 to 5 use calcium carbonate particles and disclose the ratio D90 / D10 between the 90% volume particle diameter D90 and the 10% volume particle diameter D10, but in fact, as narrow as the present invention. No investigation has been made up to the region of particle size distribution. Furthermore, none of them recognizes the problem of heat deflection, and no examination is made from such a viewpoint.

According to the present invention, it is possible to provide a white reflective film that has excellent reflection characteristics and is difficult to bend even when used in a large display.

It is a schematic diagram which shows the structure used for sticking evaluation in this invention.

Drawing reference

DESCRIPTION OF SYMBOLS 1 Chassis 2 White reflection film, light-guide plate, optical sheet laminate 3 Equilateral triangle type base 4 Weight

The white reflective film of the present invention is
(Aspect a) The thermoplastic resin A has a reflective layer A composed of a thermoplastic resin composition A1 containing calcium carbonate particles of a specific aspect, or
(Aspect b) A thermoplastic resin composition containing the calcium carbonate particles of a specific aspect in the thermoplastic resin A and a resin incompatible with the thermoplastic resin A (hereinafter sometimes referred to as incompatible resin). The reflective layer A made of the object A2 is included.

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

[Reflection layer A]
The reflective layer A in the present invention is composed of a thermoplastic resin composition A1 containing calcium carbonate particles in the thermoplastic resin A, or a thermoplastic resin composition containing calcium carbonate particles and an incompatible resin in the thermoplastic resin A. This is a layer made of the product A2, in which the calcium carbonate particles and / or the incompatible resin function as a void forming agent, contain voids in the layer, and exhibit a white color. In addition, the thermoplastic resin composition A1 and the thermoplastic resin composition A2 may be collectively referred to as the thermoplastic resin composition A. The reflective layer A exhibits a reflective function due to such voids. The reflectance of the reflective layer A at a wavelength of 550 nm is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more. Thereby, it becomes easy to make the reflectance of a white reflective film into a preferable range.

The reflection layer A has voids in the layer as described above, but the ratio of the void volume to the volume of the reflection layer A, that is, the void volume ratio is 15 volume% or more and 70 volume% or less. It is preferable that By setting it as such a range, the improvement effect of a reflectance can be made high and it becomes easy to obtain the above reflectances. Moreover, the improvement effect of stretch film forming property can be made high. When the void volume ratio is too low, a preferable reflectance tends to be difficult to obtain. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 30% by volume or more, and particularly preferably 40% by volume or more. On the other hand, when too high, there exists a tendency for the improvement effect of extending | stretching film forming property to become low. From such a viewpoint, the void volume ratio in the reflective layer A is more preferably 65% by volume or less, and particularly preferably 60% by volume or less.

The void volume ratio can be achieved by adjusting the size and amount of calcium carbonate particles in the reflective layer A and the type and amount of incompatible resin.

(Thermoplastic resin A)
Examples of the thermoplastic resin A constituting the reflective layer A include thermoplastic resins made of polyester, polyolefin, polystyrene, and acrylic. Among these, polyester is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As such a polyester, it is preferable to use a polyester comprising a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include a terephthalic acid component, an isophthalic acid component, a 2,6-naphthalenedicarboxylic acid component, a 4,4'-diphenyldicarboxylic acid component, an adipic acid component, and a sebacic acid component. Examples of the diol component include an ethylene glycol component, a 1,4-butanediol component, a 1,4-cyclohexanedimethanol component, and a 1,6-hexanediol component. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable. Polyester and preferably polyethylene terephthalate may be a homopolymer. However, when the film is stretched uniaxially or biaxially, crystallization is suppressed and the effect of improving the stretched film-forming property is enhanced. And more preferably copolymerized polyethylene terephthalate. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above. From the viewpoint of high heat resistance and a high effect of improving the stretched film forming property, an isophthalic acid component and a 2,6-naphthalenedicarboxylic acid component are used. preferable. The content of the copolymerization component is, for example, 1 mol% or more, preferably 2 mol% or more, more preferably 3 mol% or more, particularly preferably 7 mol% or more, based on 100 mol% of all dicarboxylic acid components of the polyester. For example, it is 20 mol% or less, preferably 18 mol% or less, more preferably 15 mol% or less, and particularly preferably 11 mol% or less. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of stretch film forming property. Moreover, it is excellent in thermal dimensional stability. Furthermore, the effect of suppressing thermal deflection can be further improved.

The thermoplastic resin A has a melting point of preferably 200 ° C. or higher and 280 ° C. or lower. This makes it easier to suppress thermal deflection. If it is too low, the effect of suppressing heat deflection tends to be low, and if it is too high, handling tends to be difficult. From this viewpoint, it is more preferably 205 ° C or higher, further preferably 210 ° C or higher, more preferably 275 ° C or lower, and further preferably 265 ° C or lower.

In addition, as the thermoplastic resin A which comprises the reflection layer A in this invention, the mixture of polyester which is a preferable thermoplastic resin, and another thermoplastic resin different from this polyester may be sufficient.

(Calcium carbonate particles)
In this invention, the reflection layer A contains the calcium carbonate particle which comprises a specific aspect as a void formation agent.

In the present invention, the calcium carbonate particles have an average particle size of 0.1 μm or more and 1.2 μm or less, and (D90-D10) / D50 is 1.6 or less. Here, D10, D50, and D90 are a 10% volume particle diameter, a 50% volume particle diameter, and a 90% volume particle diameter, respectively, integrated from the small particle diameter side of the calcium carbonate particles. By adopting the calcium carbonate particles of such an aspect, thermal deflection can be suppressed while having a high reflectance. In other words, when there are coarse voids, heat deflection is likely to occur, but by using calcium carbonate particles having a small average particle size and a sharp particle size distribution, there may be relatively small voids (hereinafter referred to as micro voids). .) Is present in the form of a film in which many exist, and thermal deflection due to coarse voids is suppressed. When the particle size distribution is broad, coarse particles are present, whereby coarse voids are easily formed. At the same time, the reduction in the amount of the interface between the void and the thermoplastic resin can be suppressed, and a high reflectance can be obtained. Furthermore, since the calcium carbonate particles have a relatively small specific gravity, the mass difference or density difference between the particles and the thermoplastic resin is small, so that local density differences are unlikely to occur in portions other than the voids. This also suppresses thermal deflection.

If the average particle diameter of the calcium carbonate particles is too large, coarse voids tend to be formed, and thermal deflection cannot be suppressed. Therefore, the average particle diameter is preferably 1.1 μm or less, more preferably 1.0 μm or less, still more preferably 0.95 μm or less, and particularly preferably 0.9 μm or less. On the other hand, if the particle size is too small, the particles are aggregated to form coarse voids, and it is very difficult to obtain such calcium carbonate particles. From this viewpoint, the average particle diameter is preferably 0.3 μm or more, more preferably 0.5 μm or more, and further preferably 0.6 μm or more.

In another aspect, if the average particle size of the calcium carbonate particles is too large, it becomes difficult to suppress thermal deflection, but if it is too small, coarse voids are easily formed due to aggregation, and thermal deflection is difficult to suppress. In some cases, there is a point of balance between suppression of thermal deflection and improvement of reflectance, and a point of cost. From such a viewpoint, the average particle diameter of the calcium carbonate particles is preferably 1.2 μm or less, more preferably 1.18 μm or less, still more preferably 1.15 μm or less, and preferably 0.6 μm or more, More preferably, it is 0.8 μm or more, more preferably 1.01 μm or more, particularly preferably 1.02 μm or more, and most preferably 1.05 μm or more.

(D90-D10) / D50 is preferably smaller from the above viewpoint, more preferably 1.5 or less, and still more preferably 1.4 or less. The lower limit is theoretically 0, and is preferably 0.1 or more in practice.

In order to satisfy the above aspects, it is particularly preferable in the present invention to employ particles made of synthetic calcium carbonate (hereinafter sometimes referred to as synthetic calcium carbonate particles) as the calcium carbonate particles. As the calcium carbonate particles, there are particles made of natural calcium carbonate (hereinafter sometimes referred to as natural calcium carbonate particles) and synthetic calcium carbonate particles, and natural calcium carbonate particles are usually used. However, with natural calcium carbonate particles, it tends to be difficult to satisfy the above aspect, and it is difficult to achieve the object of the present invention.

As a method for incorporating the calcium carbonate particles into the polyester resin, various conventionally known methods can be used. Typical methods include the following methods.
(A) A method of adding after the esterification stage or the transesterification reaction at the time of synthesizing the polyester resin.
(A) A method of adding to the obtained polyester resin and melt-kneading.
(C) A master pellet obtained by adding a large amount of calcium carbonate particles to a polyester resin in the method (a) or (b) above is manufactured, and this is mixed with a polyester resin as a diluting polymer, and a predetermined amount of carbonic acid is added to the polyester resin. A method of containing calcium particles.
(D) A method of using the master pellet of (c) as it is.

(Surface treatment of calcium carbonate particles)
The calcium carbonate particles in the present invention are preferably subjected to a surface treatment with a surface treatment agent. Thereby, Ca activity on the surface of calcium carbonate particles can be deactivated, and calcium carbonate particles with deactivated surface Ca activity can be obtained, and generation of gas marks can be further suppressed. Examples of such surface treatment agents include phosphorous compounds such as phosphoric acid, phosphorous acid, phosphonic acid, or derivatives thereof, fatty acids such as stearic acid, silane coupling agents, and the like. In the present invention, surface treatment with a phosphorus compound is particularly preferable. Specific examples of such phosphorus compounds include phosphoric acid, phosphorous acid, phosphoric acid trimethyl ester, phosphoric acid tributyl ester, phosphoric acid triphenyl ester, and phosphoric acid. Preferable examples include mono- or dimethyl ester, trimethyl phosphite, methylphosphonic acid, methylsulfonic acid diethylester, phenylphosphonic acid dimethylester, and phenylphosphonic acid diethylester. Of these, phosphoric acid, phosphorous acid, and ester molding derivatives thereof are preferable. In the present invention, the surface treatment with trimethyl phosphate is most preferred. These phosphorus compounds can be used alone or in combination of two or more.

The surface treatment method of the calcium carbonate particles is not particularly limited, and a conventionally known method can be employed. For example, when the surface treatment is performed with a phosphorus compound, it is preferable to employ a method (physical mixing method) in which the phosphorus compound and calcium carbonate particles are physically mixed. The physical mixing method is not particularly limited. For example, various types of pulverizers such as a roll rolling mill, a high-speed rotary pulverizer, a ball mill, and a jet mill can be used to pulverize calcium carbonate while using a phosphorus compound. Examples include a surface treatment method, or a container rotation type mixer in which the container itself rotates, a surface treatment method using a container fixed type mixer that has a rotating blade in a fixed container or blows an air flow, etc. it can. Specifically, a mixer such as a nauta mixer, a ribbon mixer, or a Henschel mixer is preferable.

Further, the treatment conditions at that time are not particularly limited, and the treatment temperature is preferably 30 ° C. or higher, from the viewpoint of dispersibility of the calcium carbonate particles with respect to the polyester, generation of foreign matters during high-temperature residence of the polyester, and foaming, and further 50 C. or higher, particularly 90.degree. C. or higher is preferable. The treatment time is preferably within 5 hours, more preferably within 3 hours, particularly preferably within 2 hours. Further, the phosphorus compound may be mixed simultaneously with the calcium carbonate particles, or the phosphorus compound may be added after the calcium carbonate particles are previously charged. At that time, the phosphorus compound may be dropped or sprayed, or may be dissolved or dispersed in water or alcohol.

In the present invention, the surface treatment of calcium carbonate can be performed by adding and blending a surface treatment agent for calcium carbonate particles to the polyester, and then adding calcium carbonate particles thereto. For example, the surface treatment agent can be added at any stage until the polyester is produced, that is, until the polymerization reaction is completed, or at the stage after the completion of the polymerization reaction until melt kneading.

The addition amount of the surface treatment agent in the surface treatment step may be an amount that sufficiently deactivates the Ca activity on the surface of the calcium carbonate particles. For example, the amount of the phosphorus element is 0.00 with respect to the mass of the calcium carbonate particles. The amount is 1% by mass or more. On the other hand, if too much is added, a large amount of phosphorus compound remains in the film, which is not preferable from the viewpoint of the environment, and from the viewpoint that the calcium carbonate particles can be prevented from aggregating in the extruder or the like. 5 mass% or less is preferable, 2 mass% or less is more preferable, 1 mass% or less is more preferable, 0.5 mass% or less is especially preferable.

(Incompatible resin)
In the embodiment b in the present invention, the reflective layer A contains an incompatible resin as a void forming agent.

Such an incompatible resin is not particularly limited as long as it is incompatible with the thermoplastic resin A constituting the reflective layer A. For example, when the thermoplastic resin A is polyester, polyolefin resin such as polyethylene, polypropylene, polymethylpentene, cycloolefin resin, polystyrene resin, polyacrylate resin, polycarbonate resin, polyacrylonitrile resin, polyphenylene sulfide resin, fluorine resin Etc. are preferable. These may be used alone or in combination of two or more. Further, it may be a homopolymer or a copolymer. In particular, it is preferable that the difference in critical surface tension between the thermoplastic resin A and the thermoplastic resin A is preferably polyester. Further, a resin that is not easily deformed by heat treatment after stretching is preferred. Specifically, polyolefin resin is preferable. Examples of the polyolefin resin include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene, and copolymers thereof. Among these, a copolymer of ethylene and bicycloalkene, which is a cycloolefin copolymer, is particularly preferable.

The glass transition temperature of the incompatible resin is preferably 180 ° C. or higher and 220 ° C. or lower, more preferably 190 ° C. or higher and 220 ° C. or lower. In the region where the glass transition temperature is lower than 180 ° C., voids developed during stretching are deformed in the heat treatment step in the film production process, causing void size non-uniformity, and coarse voids tend to be easily formed. There exists a tendency for the improvement effect of bending suppression to become low. In the region higher than 220 ° C., when melt kneading with the thermoplastic resin A constituting the reflective layer A, the incompatible resin is not sufficiently melted, and it tends to be difficult to promote fine dispersion. Also, the effect of suppressing thermal deflection tends to be low. The method for controlling the glass transition temperature of the incompatible resin is, for example, a linear olefin part, such an olefin part is, for example, an ethylene part, and a cycloolefin part, such a cycloolefin part is, for example, a methylene-norbornene part. It can be arbitrarily changed by controlling the copolymerization ratio of, for example, to increase the glass transition temperature, it can be achieved by increasing the copolymerization ratio of the cycloolefin part.

Preferably used incompatible resins include TOPAS (registered trademark) COC series of Polyplastics, for example, grade 6017S-04.

(Content of calcium carbonate particles in embodiment a)
In the aspect a, the reflective layer A is made of the thermoplastic resin composition A1 containing calcium carbonate particles. The content of the calcium carbonate particles in the thermoplastic resin composition A1 is such a thermoplastic resin composition A1. 10 mass% or more and 70 mass% or less based on the mass of Thereby, it becomes easy to set it as the preferable void volume ratio mentioned above, and it can be set as a high reflectance by it. Further, thermal deflection is suppressed. Furthermore, the effect of improving the stretch film forming property can be increased. If the content is too small, the reflectance will be low. On the other hand, when there is too much content rate, a void will increase too much and heat deflection cannot be suppressed. From these viewpoints, the content is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less.

(Content of calcium carbonate particles and incompatible resin in embodiment b)
In aspect b, the content of calcium carbonate particles in the thermoplastic resin composition A2 constituting the reflective layer A is 5% by mass or more and 69% by mass or less based on the mass of the thermoplastic resin composition A2. Thereby, it becomes easy to set it as the preferable void volume ratio mentioned above, and it can be set as a high reflectance by it. Further, thermal deflection is suppressed. Furthermore, the effect of improving the stretch film forming property can be increased. If the content is too small, the reflectance will be low. On the other hand, when there is too much content rate, a void will increase too much and heat deflection cannot be suppressed. From these viewpoints, the content is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less.

In embodiment b, the content of the incompatible resin in the thermoplastic resin composition A2 constituting the reflective layer A is 1% by mass or more and 40% by mass or less based on the mass of the thermoplastic resin composition A2. As a result, the preferred void volume ratio described above can be easily obtained while suppressing thermal deflection, thereby achieving a high reflectance. Furthermore, the effect of improving the stretch film forming property can be increased. If the content is too small, the reflectance will be low. On the other hand, when there is too much content rate, a void will increase too much and heat deflection cannot be suppressed. In addition, many incompatible resins having relatively low heat resistance are present in the film, which also tends to make it difficult to suppress thermal deflection. From these viewpoints, the content is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less.

In aspect b, the total content of the calcium carbonate particles and the incompatible resin in the thermoplastic resin composition A2 constituting the reflective layer A is 10% by mass or more based on the mass of the thermoplastic resin composition A2, 70% by mass or less. Thereby, it becomes easy to set it as the preferable void volume ratio mentioned above, suppressing heat deflection, and it can be set as a high reflectance by it. Furthermore, the effect of improving the stretch film forming property can be increased. If the total content is too small, the reflectance will be low. On the other hand, if the total content is too high, thermal deflection cannot be suppressed for the same reason as the case where the content of the calcium carbonate particles described above is too high or the content of the incompatible resin is too high. From these viewpoints, the content is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably 65% by mass or less, more preferably 60% by mass or less.

(Other ingredients)
The reflective layer A, which can be the thermoplastic resin composition A constituting the reflective layer A, is a component that does not impair the object of the present invention, such as an ultraviolet absorber, an antioxidant, and an antistatic agent. Agents, fluorescent brighteners, and waxes. Moreover, as long as the objective of this invention is not inhibited, void forming agents, such as particle | grains and resin different from the calcium carbonate particle | grains mentioned above or incompatible resin, can be contained.

[Support layer B]
The white reflective film of this invention can have the support layer B which consists of the thermoplastic resin composition B which adds the particle | grains etc. to the thermoplastic resin B or the thermoplastic resin B further to the reflective layer A mentioned above. . Such support layer B can improve the stretch film-forming property and further suppress the thermal deflection. Preferably, local deformation due to heat can be further suppressed by providing a support layer B having a composition with less voids or higher heat resistance as much as possible on the reflective layer A, and thermal deformation can be further suppressed. Can be further suppressed.

Hereinafter, the support layer B in the present invention will be described in detail.

(Thermoplastic resin B)
As the thermoplastic resin B constituting the support layer B in the present invention, the same thermoplastic resin as the thermoplastic resin A constituting the reflective layer A described above can be used. Among these, polyester is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

As such polyester, the same polyester as the polyester in the reflection layer A described above can be used. Among these polyesters, aromatic polyesters are preferable, and polyethylene terephthalate is particularly preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability. Polyester and preferably polyethylene terephthalate may be a homopolymer. However, when the film is stretched uniaxially or biaxially, crystallization is suppressed, and the copolyester and Furthermore, copolymerized polyethylene terephthalate is preferable. Examples of the copolymer component include the dicarboxylic acid component and the diol component described above in the section of the reflective layer A. From the viewpoint of high heat resistance and a high effect of improving the stretched film forming property, the isophthalic acid component, 2, A 6-naphthalenedicarboxylic acid component is preferred. The content of the copolymerization component is, for example, 1 mol% or more, preferably 2 mol% or more, more preferably 3 mol% or more, particularly preferably 12 mol% or more, based on 100 mol% of all dicarboxylic acid components of the polyester. For example, it is 20 mol% or less, preferably 18 mol% or less, more preferably 17 mol% or less, and particularly preferably 16 mol% or less. By making the ratio of a copolymerization component into this range, it is excellent in the improvement effect of stretch film forming property. Moreover, it is excellent in thermal dimensional stability. Furthermore, the effect of suppressing thermal deflection can be further improved.

Such thermoplastic resin B preferably has a melting point of 190 ° C. or higher and 280 ° C. or lower. This makes it easier to suppress thermal deflection. If it is too low, the effect of suppressing heat deflection tends to be low, and if it is too high, handling tends to be difficult. From this viewpoint, it is more preferably 195 ° C. or higher, further preferably 200 ° C. or higher, more preferably 275 ° C. or lower, further preferably 270 ° C. or lower.

In addition, as the thermoplastic resin B which comprises the support layer B in this invention, the mixture of polyester which is a preferable thermoplastic resin, and another thermoplastic resin different from this polyester may be sufficient.

(Other ingredients)
The support layer B may be composed of the thermoplastic resin composition B containing the optional component in the above-described thermoplastic resin B within a range not impairing the object of the present invention. Examples of such optional components include ultraviolet absorbers, antioxidants, antistatic agents, fluorescent brighteners, and waxes.

Further, the support layer B may contain the void forming agent mentioned in the reflective layer A as an optional component as long as the object of the present invention is not impaired. Can be high. On the other hand, if the content of the void forming agent in the support layer B is reduced or if no void forming agent is contained, the effect of improving the stretch film forming property can be increased. From these viewpoints, the void volume ratio in the support layer B, which is the ratio of the void volume in the support layer B to the volume of the support layer B, is 0% by volume or more and less than 15% by volume. Is preferable, more preferably 5% by volume or less, and particularly preferably 3% by volume or less. In particular, in the present invention, since the effect of improving the reflection characteristics and stretched film forming properties can be enhanced at the same time, the preferred void volume ratio in the reflective layer A and the preferred void volume ratio in the support layer B are simultaneously employed. It is particularly preferred.

[Surface layer C]
The white reflective film of the present invention can have a surface layer C made of a thermoplastic resin composition C containing surface layer particles on at least one surface of the film. Such a surface layer C can provide a function of imparting diffusibility to the reflected light, ensuring a gap with the light guide plate when in contact with the light guide plate, and suppressing damage to the light guide plate. In order to achieve such an effect, the surface layer C is on the reflective surface side in the film, and is on the light source side or the light guide plate side in the backlight unit. In order to achieve such an effect, the average particle diameter of the surface layer particles is 2.0 μm or more and 50.0 μm or less, and the content is 3 volumes with respect to the volume of the thermoplastic resin composition C. % Or more and 50% by volume or less.

Further, in order to achieve the above effect, it is preferable that protrusions are formed by the surface layer particles on the surface of the surface layer C and on the surface opposite to the reflective layer A. The center line average roughness Ra is preferably in the range of 0.1 μm to 6.0 μm, and the ten-point average roughness Rz is preferably in the range of 3.0 μm to 40.0 μm. Both Ra and Rz are preferably within such a range.

Hereinafter, the surface layer C in the present invention will be described in detail.

(Thermoplastic resin C)
As the thermoplastic resin C constituting the surface layer C in the present invention, the same thermoplastic resin as the thermoplastic resin A constituting the reflective layer A described above can be used. Among these, polyester is preferable from the viewpoint of obtaining a white reflective film excellent in mechanical properties and thermal stability.

The thermoplastic resin C preferably has a melting point of 225 ° C. or higher and 260 ° C. or lower. This makes it easier to suppress thermal deflection. If it is too low, the effect of suppressing heat deflection tends to be low, and if it is too high, handling tends to be difficult. From this viewpoint, it is more preferably 230 ° C. or higher, further preferably 235 ° C. or higher, more preferably 258 ° C. or lower, and further preferably 256 ° C. or lower.

In addition, as the thermoplastic resin C which comprises the surface layer C in this invention, the mixture of polyester which is a preferable thermoplastic resin, and another thermoplastic resin different from this polyester may be sufficient.

(Surface layer particles)
In the present invention, by having the surface layer C, it is possible to impart diffusibility to the reflected light. Moreover, when using it in contact with a light guide plate, the effect of ensuring the gap with a light guide plate or suppressing the damage | wound of a light guide plate can be provided.

First, a preferable aspect of the surface layer particles in the case of imparting diffusibility to the reflected light will be described. This aspect is suitable for a direct type backlight unit, and particularly suitable for a direct type backlight unit having a light source including a lens cap, and such a light source is preferably an LED light source.

In this case, in order to achieve the above effect better, the outer surface of the surface layer C preferably has an Ra of 0.1 μm or more, more preferably 0.2 μm or more, and 3.0 μm or less. It is preferable that the thickness is 2.7 μm or less. Rz is preferably 3.0 μm or more, more preferably 4.0 μm or more, and preferably 15.0 μm or less, more preferably 13.0 μm or less. Such a surface mode can be achieved by appropriately adjusting the surface particle diameter and content of the surface layer particles described later.

At this time, the surface layer particles used for the surface layer C preferably have an average particle size of 2.0 μm or more and 40.0 μm or less. By setting it as such an aspect, the diffusibility of reflected light becomes easy to improve. If the average particle size is too small, it tends to be difficult to form protrusions, and the diffusibility of reflected light tends to be small. From this viewpoint, the average particle diameter of the surface layer particles is more preferably 2.5 μm or more, further preferably 3.0 μm or more, further preferably 3.5 μm or more, and particularly preferably 4.0 μm or more. On the other hand, if the surface layer particles used are too large, the filter or the like tends to be clogged when producing a film, and the surface layer particles tend to drop off from the surface layer C. From this viewpoint, it is more preferably 35.0 μm or less, further preferably 30.0 μm or less, further preferably 25.0 μm or less, and particularly preferably 20.0 μm or less.

Further, in order to make the above-mentioned function of the surface layer C easier to perform, the content of the surface layer particles in the surface layer C is the surface layer C, that is, the thermoplastic resin composition C constituting the surface layer C. It is preferable that it is 3 volume% or more and 50 volume% or less on the basis of the volume of obtained. When the content is too small, the diffusibility of reflected light tends to be small. On the other hand, if the amount is too large, the filter tends to be clogged, and the surface layer particles tend to fall off. From this point of view, the content is more preferably 5% by volume or more, further preferably 6% by volume or more, particularly preferably 10% by volume or more, more preferably 45% by volume or less, still more preferably 40% by volume. Hereinafter, it is more preferably 35% by volume or less, particularly preferably 30% by volume or less.

The surface layer particles used for the surface layer C in the present invention may be organic particles, inorganic particles, or organic-inorganic composite particles regardless of the type. More specifically, a particularly preferred embodiment will be described. Preferred organic particles include, for example, fluorine-containing resin particles such as polytetrafluoroethylene, high heat-resistant nylon particles, and high heat-resistant acrylic particles. Preferred inorganic particles include titanium oxide particles, barium sulfate, calcium carbonate, zinc oxide particles, zirconium oxide particles, aluminum oxide particles, silica particles, and the like.

Among these, aggregated particles are preferable, aggregated inorganic particles are preferable, and aggregated silica particles are particularly preferable. By adopting such preferable surface layer particles, more preferable diffusibility can be obtained. This is because, in the present invention, by employing aggregated particles as the surface layer particles of the surface layer C, light diffusion can be expected even in the aggregated particles, so that the diffusibility of reflected light can be further improved. Conceivable and preferred. In addition, the use of aggregated particles also has the effect of further suppressing breakage failure at the time of film-forming stretching, and suppressing breakage failure during film production using self-collecting raw materials and influence on optical properties.

Also, the above inorganic particles, high heat resistant nylon particles, and high heat resistant acrylic particles have an effect that they are hardly melted or gas generated even if they are heated. Furthermore, it is preferable from the viewpoint that the particle size distribution and the shape hardly change when the surface layer C is formed.

Next, a preferable aspect of the surface layer particles in the case of providing a function of ensuring a gap with the light guide plate and suppressing damage to the light guide plate will be described. This aspect is particularly suitable for an edge light type backlight unit including a light guide plate.

In this case, in order to achieve the above effect better, the outer surface of the surface layer C preferably has an Ra of 1.0 μm or more, more preferably 1.5 μm or more, and 6.0 μm or less. It is preferable that it is 5.5 μm or less. Rz is preferably 6.0 μm or more, more preferably 6.5 μm or more, and preferably 40.0 μm or less, more preferably 35.0 μm or less. Such a surface mode can be achieved by appropriately adjusting the surface particle diameter and content of the surface layer particles described later.

At this time, the surface layer particles used for the surface layer C preferably have an average particle size of 3.0 μm or more and 50.0 μm or less. By setting it as such an aspect, it is easy to secure a gap with the light guide plate and to suppress damage to the light guide plate. If the average particle size is too small, it tends to be difficult to form protrusions, and it is difficult to secure a gap with the light guide plate. Further, the light guide plate tends to be easily damaged. From this viewpoint, the average particle diameter of the surface layer particles is more preferably 3.5 μm or more, further preferably 4.0 μm or more, further preferably 4.5 μm or more, and particularly preferably 5.0 μm or more. On the other hand, if the surface layer particles to be used are too large, the filter tends to be clogged when the film is produced, and the surface layer particles are liable to fall off and the light guide plate is easily damaged. From this viewpoint, it is more preferably 48.0 μm or less, further preferably 46.0 μm or less, further preferably 44.0 μm or less, and particularly preferably 42.0 μm or less.

Moreover, in order to make the surface aspect of the surface layer C more satisfactory, the content of the surface layer particles in the surface layer C is the surface layer C, that is, the thermoplastic resin composition constituting the surface layer C. It is preferably 3% by volume or more and 50% by volume or less based on the volume of C. When the content is too small, it tends to be difficult to ensure a gap with the light guide plate and to suppress damage to the light guide plate. On the other hand, if the amount is too large, the filter tends to be clogged, and the surface layer particles tend to fall off. From this point of view, the content is more preferably 5% by volume or more, further preferably 6% by volume or more, particularly preferably 10% by volume or more, more preferably 45% by volume or less, still more preferably 40% by volume. Hereinafter, it is more preferably 35% by volume or less, particularly preferably 30% by volume or less.

The surface layer particles used for the surface layer C in the present invention may be organic particles, inorganic particles, or organic-inorganic composite particles regardless of the type. More specifically, a particularly preferred embodiment will be described. Preferred organic particles include, for example, fluorine-containing resin particles such as polytetrafluoroethylene, high heat-resistant nylon particles, and high heat-resistant acrylic particles. Moreover, as a preferable inorganic particle, an aggregated inorganic particle is preferable. Examples of the aggregated inorganic particles include aggregated titanium oxide particles, aggregated barium sulfate particles, aggregated calcium carbonate particles, aggregated zinc oxide particles, aggregated zirconium oxide particles, aggregated aluminum oxide particles, and aggregated silica particles. Among these, agglomerated silica particles are preferable.

By adopting such preferable surface layer particles, the effect of securing a gap with the light guide plate and suppressing damage to the light guide plate is excellent. In the present invention, by adopting aggregated particles as inorganic particles, the surface layer particles become moderately soft, and the effect of suppressing damage to the light guide plate is further improved while ensuring a gap with the light guide plate. It is thought that it can be possible and is preferable. In addition, the use of aggregated particles also has the effect of further suppressing breakage failure at the time of film-forming stretching, and suppressing breakage failure during film production using self-collecting raw materials and influence on optical properties.

(Other ingredients)
The surface layer C may be composed of the thermoplastic resin composition C containing the optional components in the above-described thermoplastic resin C within a range not impairing the object of the present invention. Examples of such optional components include ultraviolet absorbers, antioxidants, antistatic agents, fluorescent brighteners, and waxes.

Further, the surface layer C may contain the void forming agent mentioned in the reflective layer A as an optional component as long as the object of the present invention is not hindered. Can be high. On the other hand, if the content of the void forming agent in the surface layer C is reduced or if no void forming agent is contained, the effect of improving the stretch film forming property can be increased. From these viewpoints, the void volume ratio in the surface layer C, which is the ratio of the void volume in the surface layer C to the volume of the surface layer C, is 0% by volume or more and less than 15% by volume. Is preferable, more preferably 5% by volume or less, and particularly preferably 3% by volume or less. In particular, in the present invention, since the effect of improving the reflection characteristics and stretched film forming properties can be enhanced at the same time, the preferred void volume ratio in the reflective layer A and the preferred void volume ratio in the surface layer C are simultaneously employed. It is particularly preferred.

[Layer structure]
In the present invention, the thickness of the white reflective film is preferably 155 μm or more and 350 μm or less. Here, the thickness is the thickness of the reflective layer A when the white reflective film is composed of only the reflective layer A. Thereby, the improvement effect of a reflectance can be made high. Moreover, the improvement effect of heat deflection suppression can be made high. If it is too thin, the effect of improving the reflectivity is low, and the effect of suppressing thermal deflection is low, while if it is too thick, it is inefficient. From such a viewpoint, it is more preferably 160 μm or more, further preferably 170 μm or more, particularly preferably 180 μm or more, more preferably 340 μm or less, still more preferably 330 μm or less, particularly preferably 320 μm or less.

The thickness ratio of the reflective layer A when the thickness of the entire white reflective film is 100% is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. More preferably it is 95% or less, and still more preferably 90% or less. Here, the thickness ratio is the ratio of the total thickness when a plurality of reflective layers A are provided. Moreover, when it has the support layer B, the thickness ratio is preferably 5% or more, more preferably 10% or more, preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. It is. Here, the thickness ratio is the ratio of the total thickness when a plurality of support layers B are provided. Thereby, the balance of each characteristic, such as a reflection characteristic and extending | stretching film forming property, can be improved. Moreover, the improvement effect of thermal deflection suppression can be made higher while improving these balances.

The thickness of the support layer B in the present invention is preferably 2 μm or more and 80 μm or less. Here, this thickness is the total thickness when the film has a plurality of support layers B. Thereby, the improvement effect of extending | stretching film forming property can be made high, and the suppression effect of heat deflection can be made high. Furthermore, thermal shrinkage can be reduced. When the support layer B is too thin, the effect of improving the stretch film forming property tends to be low. In addition, the effect of suppressing thermal deflection tends to be low. On the other hand, even if it is too thick, the above effect does not change so much and is inefficient. From these viewpoints, the thickness (total thickness) of the support layer B is more preferably 5 μm or more, further preferably 10 μm or more, more preferably 70 μm or less, and further preferably 65 μm or less.

Further, when the support layer B is provided on the reflection surface side of the reflection layer A, the thickness of the support layer B affects the reflectance. That is, when the thickness of the support layer B on the reflective surface side of the reflective layer A is too thick, the effect of improving the reflectance tends to be low. On the other hand, if it is too thin, the effect of suppressing the falling of calcium carbonate particles in the reflective layer A and the effect of suppressing the damage of the device and other members due to the calcium carbonate of the reflective layer A tend to be low. From these viewpoints, the thickness of the support layer B is preferably 1 μm or more and 40 μm or less, more preferably 2.5 μm or more, further preferably 5 μm or more, more preferably 35 μm or less, and further preferably 32. 5 μm or less. Here, the thickness is the thickness of one layer of the support layer B.

When the white reflective film has the reflective layer A and the support layer B, the laminated structure is a two-layer structure of B / A when the reflective layer A is represented by A and the support layer B is represented by B, A / B / A three-layer structure of A and B / A / B, a four-layer structure of B / A / B / A and B / A / B ′ / A, and a multilayer structure of five or more layers having A and B similarly. be able to. In the above, B ′ has the same configuration as that of the support layer B and represents a support layer B ′ having a different configuration. Particularly preferred are a two-layer structure of B / A and a three-layer structure of A / B / A and B / A / B. Most preferably, it has a three-layer structure of B / A / B, and is excellent in stretch film forming properties. Moreover, when the support layers B on the front and back sides are in the close thickness range, problems such as curling are unlikely to occur.

In the present invention, in addition to the reflective layer A and the support layer B, other layers may be provided as long as the object of the present invention is not impaired. For example, you may have the layer for providing functions, such as antistatic property, electroconductivity, and ultraviolet durability. Such a layer is preferably a coating layer. Further, a bead layer containing beads for imparting diffusibility to the reflected light or securing a gap with the light guide plate can be provided on at least one outermost surface on the reflective surface side. The surface layer C is a preferred embodiment of the bead layer.

In the case of having the surface layer C, the thickness of the surface layer C in the present invention is preferably 5 μm or more and 70 μm or less. Here, the thickness is a thickness of one layer on the light source side or the light guide plate side when a plurality of surface layers C are included in the film. Thereby, the above-described effects of the surface layer C can be easily achieved. If it is too thin, the surface layer particles are likely to fall off. On the other hand, if it is too thick, it tends to be difficult to form protrusions, and it tends to be difficult to achieve the above effects. It is also economically inefficient. From such a viewpoint, it is more preferably 10 μm or more and 60 μm or less.

When the white reflective film has the reflective layer A and the surface layer C, the laminated structure is a two-layer structure of C / A when the reflective layer A is represented by A and the surface layer C is represented by C, C / A / Examples thereof include a three-layer structure of C, a four-layer structure of C / A / C / A and C / A / C ′ / A, and a multilayer structure of five or more layers having A and C. In the above, C not on the surface represents an inner surface layer C having the same configuration as the surface layer C. C ′ has the same configuration as the surface layer C and represents a surface layer C ′ having a different configuration. Particularly preferred are a two-layer structure of C / A and a three-layer structure of C / A / C. Most preferably, it has a three-layer structure of C / A / C, and is excellent in stretch film formation. Further, when the front and back surface layers C are in the close thickness range, problems such as curling hardly occur.

Further, when the white reflective film has the reflective layer A, the support layer B, and the surface layer C, when the support layer B is represented as B, the laminated structure is C / B / A or C / A / B 3 Layer structure, 4 layer structure of C / A / B / A and C / B / A / B, 5 layer structure of C / B / A / B / A and C / B / A / B '/ A, and the like And a multilayer structure having a surface layer C on at least one surface of a multilayer structure of 6 or more layers having A and B. In the above, B ′ has the same configuration as that of the support layer B and represents a support layer B ′ having a different configuration. Particularly preferred are a three-layer structure of C / B / A and C / A / B, and a four-layer structure of C / A / B / A and C / B / A / B. Most preferably, it has a four-layer structure of C / B / A / B, and is excellent in stretch film forming properties. Moreover, when the support layers B on the front and back sides are in the close thickness range, problems such as curling are unlikely to occur.

[Film Production Method]
Hereinafter, an example of the method for producing the white reflective film of the present invention will be described.

In producing the white reflective film of the present invention, the reflective layer A is preferably formed by a melt extrusion method. Further, when the white reflective film has a laminated structure of the reflective layer A and the support layer B, or a laminated structure of the reflective layer A and the surface layer C, or the reflective layer A, the support layer B, and the surface layer C. In the case of the laminated structure, it is preferable that these layers are laminated by a coextrusion method. Thereby, the improvement effect of extending | stretching film forming property can be heightened. The reflective layer A and the support layer B, or the reflective layer A and the surface layer C, or the reflective layer A, the support layer B, and the surface layer C are preferably directly laminated by a coextrusion method. By laminating in this way by coextrusion, the interfacial adhesion of each layer can be increased, and the films are bonded together or the support layer B and the surface layer C are formed again after the film is formed. Since it is not necessary to go through this process, it can be easily mass-produced at low cost.

Hereinafter, an example of a more specific production method of the white reflective film of the present invention will be described. However, the present invention is not limited to this production method, and other embodiments can be similarly produced with reference to the following. . At that time, when the extrusion step is not included, the following “melt extrusion temperature” may be read as, for example, “melt temperature”. Here, the melting point of the polyester used is Tm (unit: ° C), and the glass transition temperature is Tg (unit: ° C).

In the case of having a reflective layer A and a support layer B, polyester is adopted as the thermoplastic resin A constituting the reflective layer A and the thermoplastic resin B constituting the support layer B, and a coextrusion method is adopted as the laminating method. In this case, first, the thermoplastic resin composition A for forming the reflective layer A, which is also referred to as the polyester composition A when the polyester is used as the thermoplastic resin A, the polyester and calcium carbonate particles And when it contains incompatible resin, what mixed cycloolefin and another arbitrary component as incompatible resin is prepared. Further, a thermoplastic resin composition B for forming the support layer B, which is also referred to as a polyester composition B when a polyester is employed as the thermoplastic resin B, is mixed with polyester and other optional components. Prepare things. Here, for the support layer B, the thermoplastic resin B may be used without adding other optional components, and the thermoplastic resin B may be polyester, for example. These polyester compositions are used after drying to sufficiently remove moisture.

Further, in the case of having a reflective layer A and a surface layer C, a polyester is adopted as the thermoplastic resin A constituting the reflective layer A and the thermoplastic resin C constituting the surface layer C, and a coextrusion method is used as a laminating method. First, a thermoplastic resin composition A for forming the reflective layer A, which is also referred to as a polyester composition A when a polyester is used as the thermoplastic resin A, is polyester and carbonic acid. Prepare a mixture of calcium particles and other optional ingredients. Also, a thermoplastic resin composition C for forming the surface layer C, which is also referred to as a polyester composition C when polyester is used as the thermoplastic resin C, polyester, surface layer particles, and other Prepare a mixture of optional ingredients. These polyester compositions are used after drying to sufficiently remove moisture.

Next, the dried polyester composition is put into separate extruders and melt-extruded. The melt extrusion temperature needs to be Tm or higher, and may be about Tm + 40 ° C.

At this time, the polyester composition used for the production of the film, particularly the polyester composition A used for the reflective layer A, uses a nonwoven fabric type filter having an average opening of 10 μm or more and 100 μm or less made of stainless steel fine wires having a wire diameter of 15 μm or less. It is preferable to perform filtration. By performing this filtration, it is possible to suppress aggregation of particles that normally tend to aggregate into coarse aggregated particles, and to obtain a film with few coarse foreign matters. And by suppressing the aggregated particles, it becomes easier to form microvoids, and thermal deflection is further suppressed. The average opening of the nonwoven fabric is preferably 15 μm or more, more preferably 20 μm or more, and preferably 50 μm or less, more preferably 40 μm or less. In addition, the thermoplastic resin composition C is preferably 35 μm or more, more preferably 40 μm or more, and preferably 70 μm or less, more preferably 60 μm or less. The filtered polyester composition is extruded in a multilayer state from a die by a simultaneous multilayer extrusion method using a feed block in a molten state, that is, a co-extrusion method, to produce an unstretched laminated sheet. The unstretched laminated sheet extruded from the die is cooled and solidified with a casting drum to obtain an unstretched laminated film.

Next, this unstretched laminated film is heated by roll heating, infrared heating or the like, and stretched in the film forming machine axial direction (hereinafter sometimes referred to as the longitudinal direction or the longitudinal direction or MD) to obtain a longitudinally stretched film. . This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The film after the longitudinal stretching is then guided to a tenter and stretched in a direction perpendicular to the longitudinal direction and the thickness direction (hereinafter sometimes referred to as a transverse direction or a width direction or TD) to be biaxially stretched. A film.

The stretching temperature is preferably Tg or higher of the polyester, preferably Tg of the polyester constituting the reflective layer A and Tg + 30 ° C. or lower, and is excellent in stretch film-forming properties, and voids are preferably formed. The stretching ratio is preferably 2.5 to 4.3 times, more preferably 2.7 to 4.2 times in both the longitudinal direction and the transverse direction. If the draw ratio is too low, uneven thickness of the film tends to be worsened, and voids tend not to be formed. On the other hand, if it is too high, breakage tends to occur during film formation. In the case of sequential biaxial stretching in which longitudinal stretching is performed and then lateral stretching is performed, the second stage, that is, in this case, transverse stretching, is about 10 to 50 ° C. than the first stage stretching temperature. Higher is preferable. This is due to the fact that the Tg as a uniaxial film is increased due to the orientation in the first stage of stretching.

Also, it is preferable to preheat the film before each stretching. For example, the pre-heat treatment for transverse stretching is preferably started from a temperature higher than Tg + 5 ° C. of polyester, which is preferably the polyester constituting the reflective layer A, and gradually raised. The temperature increase in the transverse stretching process may be continuous or stepwise (also referred to as sequential), but the temperature is generally increased sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone.

The film after biaxial stretching is subsequently subjected to heat-fixing and heat-relaxing treatments in order to obtain a biaxially oriented film. However, following melt-extrusion to stretching, these treatments can also be performed while the film is running. it can.

The film after biaxial stretching is 0.01% with a constant width or a decrease in width of 10% or less with the melting point of the polyester being Tm (Tm-10 ° C) to (Tm-100 ° C) while holding both ends with clips. It is preferable to heat-fix for ˜100 seconds to reduce heat shrinkage. The melting point is preferably the melting point of the polyester constituting the reflective layer A. When the heat treatment temperature is too high, the flatness of the film tends to deteriorate, and the thickness unevenness tends to increase. On the other hand, if it is too low, the thermal shrinkage tends to increase. Moreover, this can further improve the effect of suppressing thermal deflection.

Also, in order to adjust the amount of heat shrinkage, both ends of the film being gripped can be cut off, the film take-up speed in the vertical direction can be adjusted, and the film can be relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3. Adjust the thermal shrinkage in the longitudinal direction by controlling the relaxation rate by relaxing the film by reducing the speed by ~ 2.0% (hereinafter this value may be referred to as "relaxation rate"). . Moreover, this can further improve the effect of suppressing thermal deflection. In the film transverse direction, the width can be reduced in the process until both ends are cut off, and a desired heat shrinkage rate can be obtained.

In addition, in biaxial stretching, in addition to the above-described longitudinal-lateral sequential biaxial stretching method, a lateral-longitudinal sequential biaxial stretching method may be used. Moreover, it can form into a film using a simultaneous biaxial stretching method. In the case of the simultaneous biaxial stretching method, the stretching ratio is, for example, 2.7 to 4.3 times, preferably 2.8 to 4.2 times in both the longitudinal direction and the transverse direction.

Thus, the white reflective film of the present invention can be obtained.

[Characteristics of white reflective film]
(Reflectance, front brightness)
The reflectance of the white reflective film of the present invention is 60% or more. Preferably it is 70% or more, more preferably 80% or more, still more preferably 90% or more, particularly preferably 95% or more, and most preferably 97% or more. When the reflectance is within the above range, high luminance can be obtained when used in a liquid crystal display device, illumination, or the like. Such reflectivity is preferably a mode in which the void volume ratio of the reflective layer A is increased, the thickness of the reflective layer A is increased, or when the support layer B and the surface layer C are provided, voids are formed in these layers. This can be achieved by adding an agent, or by reducing the thickness of the support layer B or the surface layer C closer to the reflective surface than the reflective layer A, or by making the mode of each layer a preferred mode.

Further, the front luminance is determined by a measuring method described below is preferably 2000 cd / ^{m 2} or more, more preferably 3000 cd / ^{m 2} or more, more preferably 4000 cd / ^{m 2} or more, 4400cd / ^{m 2} or more is particularly preferable.

In addition, a reflectance and front luminance here are the values about the surface used as a reflective surface of a white reflective film.

(Heat deflection)
The object of the present invention is to suppress thermal deflection. For example, in a product such as a television or a monitor, heat deflection is caused by an electric circuit for driving a display device such as a liquid crystal display, heat generated from a backlight unit or a light source, or heat and humidity from a use environment. This is a phenomenon in which the white reflective film is bent or distorted. When heat deflection occurs in the white reflective film, it causes brightness spots, which directly leads to a decrease in image quality.

[Usage]
The white reflective film of the present invention is for a large display. Here, the large display means a liquid crystal display of 30 inches or more, preferably 32 inches or more, more preferably 40 inches or more, and further preferably 42 inches or more. Such a large display is provided with a recess or partition for incorporating an electric circuit or the like into the back chassis. For this reason, the heat generated by the above-described causes or the like is locally retained in the depression, and thermal deflection is more likely to occur. As the size of the display increases, the number of light sources necessary to ensure the luminance increases, so that the circuit and the like are complicated, so that the accumulated heat increases and thermal deflection tends to occur more easily. For this reason, it has been difficult for the conventional technology to suppress thermal deflection in such a large display. On the other hand, the present invention can satisfactorily suppress thermal deflection even in such a large display.

Hereinafter, the present invention will be described in detail by way of examples. Each characteristic value was measured by the following method.

(1) Light reflectivity An integrating sphere was attached to a spectrophotometer (Shimadzu UV-3101PC), and the reflectivity was measured at a wavelength of 550 nm when the BaSO ₄ white plate was taken as 100%, and this value was taken as the reflectivity. In addition, the measurement was performed on the surface to be used as the reflecting surface, that is, the light source side.

(2) Average particle size of particles The particle size was measured using a laser scattering particle size distribution analyzer SALD-7000 manufactured by Shimadzu Corporation. Before the measurement, the dispersion in ethylene glycol was measured such that the particle powder was equivalent to a 5% by mass slurry concentration, stirred with a mixer for 10 minutes, cooled to room temperature, and then supplied to a flow cell type supply device. Here, as the mixer, for example, National MXV253 type cooking mixer is used. Then, the sample was subjected to ultrasonic treatment for 30 seconds for defoaming in the supply device and then subjected to measurement. In addition, the intensity | strength of the ultrasonic wave in this ultrasonic processing set the knob of the ultrasonic processing apparatus to the position of 60% from the position which shows a MAX value. The 50% volume particle size (D50) was determined from the particle size distribution measurement result, and this was used as the average particle size. Similarly, 10% volume particle size (D10) and 90% volume particle size (D90) were determined.

(3) Content of particles and incompatible resin (3-1) Content of particles Incinerate the film for 6 hours at a temperature of 500 ° C., measure the weight before and after that, and determine the weight of residual ash as particles Content. In addition, content of the particle | grains of each layer in a laminated body was calculated | required by performing the said operation after isolate | separating each layer.

(3-2) Content of Incompatible Resin After weighing the film, it is dissolved in a mixed solvent of hexafluoroisopropanol (HFIP) / chloroform at a mass ratio of 50/50. After separation by centrifugation, the mass is measured, and the structure and mass fraction of the component are measured by elemental analysis, FT-IR, and NMR methods. If the supernatant component is analyzed in the same manner, the mass fraction and structure of the polyester component and other components can be specified. After the solvent is distilled off from the supernatant component, it is dissolved in a mixed solvent having a mass ratio of HFIP / deuterochloroform of 50/50, and then a ¹ H-NMR spectrum is measured.

From the obtained spectrum, the peak area intensity of absorption peculiar to each component is obtained, and the molar ratio of the blend is calculated from the ratio and the number of protons. Further, the mass ratio is calculated from the formula amount corresponding to the unit unit of the polymer. Thus, the mass fraction and structure of each component were specified.

In addition, the content of the particles in each layer in the laminate was determined by performing the above operation after separating each layer.

(4) Film thickness and layer structure A white reflective film was sliced with a microtome to obtain a cross section, and this cross section was observed at a magnification of 500 times using a Hitachi S-4700 field emission scanning electron microscope. The thickness of the whole film, the reflective layer A, the support layer B, and the surface layer C was determined. The thickness was measured as an average value by measuring an arbitrary position at n = 7. After determining the thickness (μm) of each layer, the thickness ratio of each layer was calculated.

(5) Calculation of Void Volume Ratio Calculated density was determined from the density and blending ratio of the polymer, additive particles, and other components of the layer for which void volume ratio was determined. At the same time, it was isolated by peeling off the layer, and the mass and volume were measured. The actual density was calculated from these, and the following formula was obtained from the calculated density and the actual density.

Void volume fraction = 100 × (1− (actual density / calculated density))
The density of isophthalic acid copolymerized polyethylene terephthalate after biaxial stretching is 1.39 g / cm ³ , the density of calcium carbonate particles is 2.7 g / cm ³ , the density of barium sulfate particles is 4.5 g / cm ³ , non- The density of the cycloolefin copolymer, which is a compatible resin, was 1.02 g / cm ³ .

Moreover, only the layer which measures a void volume ratio was isolated, the mass per unit volume was calculated | required, and the real density was calculated | required. The volume was calculated as an area × thickness by taking an average value obtained by cutting a sample into an area of 3 cm ² and measuring the thickness at that point with an electric micrometer (K-402B manufactured by Anritsu) at 10 points. The mass was weighed with an electronic balance.

In addition, as the specific gravity of other particles including aggregated particles, the value of bulk specific gravity obtained by the following graduated cylinder method was used. Fill a 1000 ml measuring cylinder with completely dry particles, measure the total weight, subtract the weight of the measuring cylinder from the total weight to obtain the weight of the particle, and measure the volume of the measuring cylinder. , By dividing the weight (g) of the particles by the volume (cm ³ ).

(6) Melting point, glass transition temperature Using a differential scanning calorimeter (TA Instruments 2100 DSC), the measurement was performed at a heating rate of 20 ° C./min.

(7) Front brightness (7-1) Front brightness 1
The reflective film was taken out from the edge light type LED liquid crystal television (LG42LE5310AKR) (42 inches) manufactured by LG, and instead the various reflective films obtained in the examples were installed so that the reflective surface side was the screen side. The luminance was measured using a luminance meter (Model MC-940 manufactured by Otsuka Electronics Co., Ltd.) in the state of the backlight unit with the diffusion film and prism sheet provided.

(7-2) Front brightness 2
The reflective film is taken out from the LG LED liquid crystal television (LG LN5400) (42 inches) manufactured by LG, and instead the various reflective films obtained in the examples are installed so that the reflective surface side is the screen side, Luminance was measured using a luminance meter (Model MC-940, manufactured by Otsuka Electronics Co., Ltd.) in the state of a backlight unit with the diffusion film and prism sheet originally provided.

(8) Stretching film forming property The film forming stability when the film described in the example was formed by a continuous film forming method using a tenter was observed and evaluated according to the following criteria.
A: The film can be stably formed for 8 hours or more.
○: The film can be stably formed for 3 hours or more and less than 8 hours.
Δ: Cutting occurred once in less than 3 hours.
X: Cutting occurs multiple times in less than 3 hours, and stable film formation is not possible.

(9) Evaluation of heat deflection An edge-light type LED liquid crystal television (LG42LE5310AKR) (42 inches) manufactured by LG was disassembled, and the reflective film provided on the original was taken out. In this state, the television was stored in a white display for 72 hours in an environment with a temperature of 50 ° C. and a humidity of 80% RH, and brightness spots before and after the evaluation were evaluated.

(9-1) Luminance spot evaluation 1
Luminance spots were visually determined and evaluated according to the following criteria: ○: No brightness spots were observed.
Δ: Luminance spots are barely recognized.
X: A remarkable brightness spot is seen.

(9-2) Luminance spot evaluation 2
Luminance meter (CA-2000 manufactured by Konica Minolta Co., Ltd.) averaged the luminance of 10 arbitrary points in the screen, and evaluated the value of [(maximum luminance−lowest luminance) / average luminance] in the screen. When the above-mentioned value is 5% or less, it can be determined that there is little luminance unevenness due to thermal deflection and that the state is good. Preferably it is 4% or less, More preferably, it is 3% or less.

(10) Evaluation with light guide plate pasting The chassis is taken out from an LED liquid crystal television (LG42LE5310AKR) manufactured by LG, placed on a horizontal desk so that the inside of the television is facing upward, and a reflective film of approximately the same size as the chassis is placed thereon. Is placed so that the surface layer surface is facing upward, and further on that, the light guide plate and three optical sheets originally provided in the television, the three optical sheets are two diffusion films and one prism, Placed. Next, an equilateral triangular base having three columnar legs with a diameter of 5 mm as shown in FIG. 1 is placed in the area including the most severely uneven portion of the chassis in the plane, and a weight of 15 kg is further placed thereon. The region surrounded by the three legs was visually observed, and if there was no abnormally bright part, “no adhesion spots”, that is, evaluation “◯” was given. If there is an abnormally bright part, place the DBEF sheet originally provided on the television on top of the three optical sheets and observe it in the same manner. “Spots”, ie, evaluation ×, and when there were no abnormally bright parts, “there was almost no adhesion spots”, ie, evaluation Δ. In addition, the area surrounded by the three legs was a substantially equilateral triangle having a side length of 10 cm.

<Production Example 1: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 1>
136.5 parts by mass of dimethyl terephthalate and 13.5 parts by mass of dimethyl isophthalate, that is, the isophthalic acid component is 9 mol% with respect to 100 mol% of the total acid component of the obtained polyester, 98 parts by mass of ethylene glycol, diethylene glycol 1 0.0 part by mass, 0.05 part by mass of manganese acetate, and 0.012 part by mass of lithium acetate were charged into a flask equipped with a rectifying column and a distillation condenser, and heated to 150 to 240 ° C. with stirring to distill methanol. A transesterification reaction was performed. After methanol was distilled, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Next, while stirring, the pressure in the reactor was gradually reduced to 0.3 mmHg and the temperature was raised to 292 ° C. to carry out a polycondensation reaction to obtain isophthalic acid copolymerized polyethylene terephthalate 1. The melting point of this polymer was 235 ° C.

<Production Example 2: Synthesis of isophthalic acid copolymerized polyethylene terephthalate 2>
Except for the change to 129.0 parts by weight of dimethyl terephthalate and 21.0 parts by weight of dimethyl isophthalate, that is, the isophthalic acid component is 14 mole% with respect to 100 mole% of the total acid component of the polyester obtained, In the same manner as in Example 1, isophthalic acid copolymerized polyethylene terephthalate 2 was obtained. The melting point of this polymer was 215 ° C.

<Production Example 3: Preparation of particle master chip 1>
Using a part of the isophthalic acid copolymerized polyethylene terephthalate 1 obtained above and synthetic calcium carbonate particles having an average particle size of 0.9 μm and (D90-D10) / D50 of 1.4 as a void forming agent, Kobe Steel In a NEX-T60 tandem type extruder manufactured by the company, mixing is performed so that the content of the synthetic calcium carbonate particles is 60% by mass with respect to the mass of the obtained master chip, and the mixture is extruded at a resin temperature of 260 ° C. A particle-containing particle master chip 1 was prepared. The synthetic calcium carbonate particles are surface-treated with phosphoric acid trimethyl ester.

<Production Example 4: Preparation of particle master chip 2>
A particle master chip 2 containing synthetic calcium carbonate particles was prepared in the same manner as in Production Example 3 except that the isophthalic acid copolymerized polyethylene terephthalate 2 obtained above was used instead of the isophthalic acid copolymerized polyethylene terephthalate 1.

<Production Example 5: Creation of particle master chip 3>
To the isophthalic acid copolymerized polyethylene terephthalate 2 obtained above, as particles A, AY-601 manufactured by Tosoh Silica Co., Ltd., which is an agglomerated silica, was subjected to air classification to obtain particles having an average particle size of 6.5 μm. The mixture was mixed by a twin screw extruder so that the concentration in the obtained particle master chip was 8% by mass, and extruded at a melting temperature of 250 ° C. to prepare a particle master chip 3.

<Production Example 6: Creation of particle 1 used for bead layer>
150 parts by mass of dimethyl terephthalate, 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, 0.05 part by mass of manganese acetate, 0.012 part by mass of lithium acetate were charged into a rectifying column and a flask equipped with a distillation condenser. While stirring, the mixture was heated to 150 to 240 ° C. to distill methanol to conduct a transesterification reaction. After methanol was distilled, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Next, the pressure in 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, whereby polyethylene terephthalate 3 was obtained. The obtained polyethylene terephthalate 3 was extruded from a strand die and cut after cooling to form a pellet. As a result of adjusting the shape of the strand, the shape of the pellet was substantially a rectangular parallelepiped shape, and the average shape was 4 mm × 3 mm × 2 mm. Next, the obtained pellets were dried and crystallized by heating in an oven at 170 ° C. for 3 hours, and pulverized while cooling with liquid nitrogen using an atomizer mill TAP-1 manufactured by Matsubo Co., Ltd. Polyester particles having a particle size of 60 μm were obtained. Further, the polyester particles were subjected to air classification to obtain particles 1 having an average particle size of 43 μm, which are non-spherical particles.

[Example 1-1]
(Manufacture of white reflective film)
The isophthalic acid copolymerized polyethylene terephthalate 1 and the particle master chip 1 obtained above were used as the raw material for the reflective layer (A layer), and the isophthalic acid copolymerized polyethylene terephthalate 2 and the particle master chip 2 were used as the support layer (B layer). )) And mixed so that each layer has the structure described in Table 1, and put into an extruder. Layer A is melt-extruded at a temperature of 255 ° C. through a nonwoven fabric type filter having an average opening of 30 μm. Using a three-layer feed block device, the layer B has a layer constitution of layer B / layer A / layer B as shown in Table 1 at a melt extrusion temperature of 230 ° C. through a nonwoven fabric type filter having an average opening of 30 μm. The sheet was merged and formed into a sheet from a die while maintaining the laminated state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of B layer / A layer / B layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 3.0 times in the longitudinal direction, and cooled by a roll group at 25 ° C. did. Subsequently, while holding both ends of the film with clips, the film was led to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. and stretched 3.6 times in the transverse direction. Then, heat treatment at 155 ° C. for 10 seconds, heat setting at 200 ° C. for 10 seconds, and heat treatment at 155 ° C. for 10 seconds are carried out continuously in the tenter, and then the width ratio is 2% and the width is 130 ° C. The width of the film was then cut, and both ends of the film were cut off, heat relaxed at a longitudinal relaxation rate of 2.5%, and cooled to room temperature to obtain a film having a thickness of 300 μm. The evaluation results of the obtained film are shown in Table 1.

[Examples 1-2 to 1-9, 1-11, Comparative Examples 1-1 to 1-6]
A white reflective film was obtained in the same manner as in Example 1-1 except that the form of the particles and the composition of the film were as shown in Table 1. The evaluation results of the obtained film are shown in Table 1. The used synthetic calcium carbonate particles are surface-treated with trimethyl phosphate.

In Example 1-11, the total thickness of the film was 188 μm.

[Comparative Example 1-7]
A particle master chip was prepared in the same manner as in Production Examples 3 and 4 except that barium sulfate particles having an average particle size of 0.9 μm and (D90-D10) / D50 of 1.4 were used instead of calcium carbonate particles as a void forming agent. A white reflective film was obtained in the same manner as in Example 1-1 except that the film configuration was as shown in Table 1. The evaluation results of the obtained film are shown in Table 1. Such barium sulfate particles were obtained by repeating air classification.

[Example 1-10]
On one side of the biaxially stretched film obtained in the same manner as in Example 1-1, a coating liquid having the composition shown in Coating liquid 1 for forming the following bead layer with a direct gravure coating apparatus, After apply | coating with the application quantity of 15 g / m < ² > of wet thickness, it dried at 100 degreeC in oven, and obtained the white reflective film which has a bead layer. The evaluation results of the obtained film are shown in Table 1. In the evaluation, the bead layer side was used as the reflecting surface.

<Coating liquid 1, solid content concentration 30% by mass>
-Particles: Particles 1 (non-spherical particles) obtained in Production Example 6 7.5 mass%
Acrylic resin (thermoplastic resin): DIC's ACRICID A-817BA (solid content concentration 50% by mass) ... 30% by mass
・ Crosslinking agent: Coronate HL (isocyanate-based crosslinking agent, solid content concentration: 75% by mass) manufactured by Nippon Polyurethane Industry Co., Ltd .: 10% by mass
Diluting solvent: butyl acetate 52.5% by mass
In addition, the solid content ratio of each component in the coating liquid 1 is as follows.
・ Particles: 25% by mass
-Acrylic resin (thermoplastic resin): 50% by mass
・ Crosslinking agent: 25% by mass

[Example 2-1]
(Manufacture of white reflective film)
The above-obtained isophthalic acid copolymerized polyethylene terephthalate 1, particle master chip 1 and incompatible resin (cycloolefin copolymer, Tg = 210 ° C., “TOPAS” manufactured by Polyplastics Co., Ltd.) are used as a reflective layer (referred to as layer A). As raw materials, isophthalic acid copolymerized polyethylene terephthalate 2 and particle master chip 2 were used as raw materials for the support layer (referred to as layer B), mixed so that each layer had the structure described in Table 2, and extruded. As shown in Table 2, the A layer is melt-extruded through a non-woven filter having an average opening of 30 μm at a melt extrusion temperature of 255 ° C., and the B layer is passed through a non-woven filter having an average opening of 30 μm at a melt-extruding temperature of 230 ° C. Combined using a three-layer feed block device so as to have a layer structure of B layer / A layer / B layer, The sheet was formed into a sheet from a die while maintaining the state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of B layer / A layer / B layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 3.0 times in the longitudinal direction, and cooled by a roll group at 25 ° C. did. Subsequently, while holding both ends of the film with clips, the film was led to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. and stretched 3.6 times in the transverse direction. Then, heat treatment at 155 ° C. for 10 seconds, heat setting at 200 ° C. for 10 seconds, and heat treatment at 155 ° C. for 10 seconds are carried out continuously in the tenter, and then the width ratio is 2% and the width is 130 ° C. The width of the film was then cut, and both ends of the film were cut off, heat relaxed at a longitudinal relaxation rate of 2.5%, and cooled to room temperature to obtain a film having a thickness of 300 μm. The evaluation results of the obtained film are shown in Table 2.

[Examples 2-2 to 2-17, Comparative examples 2-1 to 2-6]
A white reflective film was obtained in the same manner as in Example 2-1, except that the aspect of the particles and the incompatible resin and the configuration of the film were as shown in Table 2. The evaluation results of the obtained film are shown in Table 2. The used synthetic calcium carbonate particles are surface-treated with trimethyl phosphate.

In Example 2-17, the total thickness of the film was 188 μm.

[Example 2-18]
On one side of the biaxially stretched film obtained in the same manner as in Example 2-1, a coating liquid having the composition shown in the coating liquid 1 for forming the above-described bead layer was formed using a direct gravure coating apparatus. After apply | coating with the application quantity of 15 g / m < ² > of wet thickness, it dried at 100 degreeC in oven, and obtained the white reflective film which has a bead layer. The evaluation results of the obtained film are shown in Table 2. In the evaluation, the bead layer side was used as the reflecting surface.

[Comparative Example 2-7]
A particle master chip was prepared in the same manner as in Production Examples 3 and 4 except that barium sulfate particles having an average particle size of 0.9 μm and (D90-D10) / D50 of 1.4 were used instead of calcium carbonate particles as a void forming agent. A white reflective film was obtained in the same manner as in Example 2-1, except that the composition of the film was as shown in Table 2. The evaluation results of the obtained film are shown in Table 2. Such barium sulfate particles were obtained by repeating air classification.

[Example 3-1]
(Manufacture of white reflective film)
The isophthalic acid copolymerized polyethylene terephthalate 1 and particle master chip 1 obtained above were used as the raw material for the reflective layer (A layer), and the isophthalic acid copolymerized polyethylene terephthalate 2 and particle master chip 3 were used as the surface layer (C layer). )) And mixed so that each layer has the structure described in Table 3, and put into an extruder. Layer A is melt extruded through a nonwoven fabric type filter having an average aperture of 30 μm at a temperature of 255 ° C. The C layer is passed through a nonwoven fabric type filter having an average opening of 50 μm at a melt extrusion temperature of 230 ° C., using a three layer feed block device so as to have a layer configuration of C layer / A layer / C layer as shown in Table 3. The sheet was merged and formed into a sheet from a die while maintaining the laminated state. At this time, it adjusted with the discharge amount of each extruder so that the thickness ratio of C layer / A layer / C layer might become 10/80/10 after biaxial stretching. Further, this sheet was an unstretched film cooled and solidified with a cooling drum having a surface temperature of 25 ° C. This unstretched film is led to a longitudinal stretching zone maintained at 92 ° C. through a preheating zone at 73 ° C., followed by a preheating zone at 75 ° C., stretched 3.0 times in the longitudinal direction, and cooled by a roll group at 25 ° C. did. Subsequently, while holding both ends of the film with clips, the film was led to a transverse stretching zone maintained at 130 ° C. through a preheating zone at 115 ° C. and stretched 3.6 times in the transverse direction. Then, heat treatment at 155 ° C. for 10 seconds, heat setting at 200 ° C. for 10 seconds, and heat treatment at 155 ° C. for 10 seconds are carried out continuously in the tenter, and then the width ratio is 2% and the width is 130 ° C. The width of the film was then cut, and both ends of the film were cut off, heat relaxed at a longitudinal relaxation rate of 2.5%, and cooled to room temperature to obtain a film having a thickness of 300 μm. The evaluation results of the obtained film are shown in Table 3.

[Examples 3-2 to 3-15, Comparative examples 3-1 to 3-10]
A white reflective film was obtained in the same manner as in Example 3-1, except that the form of the particles and the composition of the film were as shown in Table 3. The evaluation results of the obtained film are shown in Table 3. The used synthetic calcium carbonate particles are surface-treated with trimethyl phosphate.

In Example 3-10, the total thickness of the film was 188 μm.

In addition, each surface layer particle | grain used for the surface layer C is shown below. It was used as a particle master chip in the same manner as in Production Example 5.
Particle B: AY-601 manufactured by Tosoh Silica Co., Ltd., which is agglomerated silica, was classified by wind classification to have an average particle size of 5.0 μm Particle C: AY-601 manufactured by Tosoh Silica Co., Ltd., which was agglomerated silica Is a particle particle D: AY-601 manufactured by Tosoh Silica Co., Ltd., which is agglomerated silica, and is a particle particle having an average particle size of 35.3 μm. E: AY-601 manufactured by Tosoh Silica Co., Ltd., which is an agglomerated silica, and classified by wind classification to obtain an average particle size of 1.0 μm F: AY-601 manufactured by Tosoh Silica Co., Ltd. Particles classified by wind force to have an average particle size of 52.0 μm [Comparative Example 3-11]
A particle master chip was prepared in the same manner as in Production Example 3 except that barium sulfate particles having an average particle size of 0.9 μm and (D90-D10) / D50 of 1.4 were used instead of calcium carbonate particles as a void forming agent. A white reflective film was obtained in the same manner as in Example 3-1, except that the composition of the film was as shown in Table 3. The evaluation results of the obtained film are shown in Table 3. Such barium sulfate particles were obtained by repeating air classification.

The white reflective film of the present invention suppresses heat deflection caused by heat generated from an electric circuit or a light source, heat from the use environment, or humidity even when used in a large display while having excellent reflection characteristics. be able to. Thereby, since the brightness spot which arises when a white reflective film bends can be suppressed, industrial applicability is high.

Claims

A white reflective film having a reflective layer A,
The reflective layer A is
a. The thermoplastic resin A is composed of a thermoplastic resin composition A1 containing calcium carbonate particles, and the content of the calcium carbonate particles is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A1. is there,
Or
b. The thermoplastic resin A comprises a thermoplastic resin composition A2 containing calcium carbonate particles and a resin incompatible with the thermoplastic resin A, and the content of the calcium carbonate particles is in the mass of the thermoplastic resin composition A2. The content of the incompatible resin is 5% by mass to 69% by mass with respect to the mass of the thermoplastic resin composition A2, and the calcium carbonate is 1% by mass to 40% by mass. Satisfying either a or b in which the total content of the particles and the incompatible resin is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A2,
The calcium carbonate particles have an average particle diameter of 0.1 μm or more and 1.2 μm or less, and 10% volume particle diameter D10, 50% volume particle diameter D50 and 90% volume particle diameter D90 accumulated from the small particle diameter side are (D90−D10) /D50≦1.6 is satisfied,
A white reflective film for large displays, wherein the reflectance of the film is 60% or more.
The reflection layer A is a. The thermoplastic resin A is composed of a thermoplastic resin composition A1 containing calcium carbonate particles, and the content of the calcium carbonate particles is 10% by mass or more and 70% by mass or less with respect to the mass of the thermoplastic resin composition A1. The white reflective film according to claim 1, wherein
The reflection layer A is b. The thermoplastic resin A comprises a thermoplastic resin composition A2 containing calcium carbonate particles and a resin incompatible with the thermoplastic resin A, and the content of the calcium carbonate particles is in the mass of the thermoplastic resin composition A2. The content of the incompatible resin is 5% by mass to 69% by mass with respect to the mass of the thermoplastic resin composition A2, and the calcium carbonate is 1% by mass to 40% by mass. The white reflective film of Claim 1 whose sum total of content of particle | grains and the said incompatible resin is 10 mass% or more and 70 mass% or less with respect to the mass of the said thermoplastic resin composition A2.
The reflective layer A, and further has a surface layer C on at least one surface,
The surface layer C is composed of a thermoplastic resin composition C containing surface layer particles, and the surface layer particles have an average particle size of 2.0 μm or more and 50.0 μm or less, and the content thereof is the thermoplastic resin. The white reflective film for a large display according to any one of claims 1 to 3, which is 3 to 50% by volume with respect to the volume of the composition C.
The white reflective film according to any one of claims 1 to 4, wherein the thermoplastic resin A is copolymerized polyethylene terephthalate.
The white reflective film according to claim 5, wherein the copolymerization amount of the copolymerized polyethylene terephthalate is 1 mol% or more and 20 mol% or less with respect to 100 mol% of the total acid component of the copolymerized polyethylene terephthalate.
The white reflective film according to any one of claims 1 to 6, wherein a thickness ratio of the reflective layer A to a thickness of 100% of the white reflective film is 50% or more.
The white reflective film according to any one of claims 1 to 7, further comprising a support layer B made of the thermoplastic resin B or the thermoplastic resin composition B.
A surface light source using the white reflective film according to any one of claims 1 to 8.