JP2016004978A - White laminate polyester film for solar battery backsheet, manufacturing method thereof, solar battery backsheet, and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a white laminate polyester film for a solar battery backsheet, which has both of weather resistance (hydrolysis resistance) and visible light concealability (reflectance); a method for manufacturing such a white laminate polyester film; a solar battery backsheet; and a solar battery module which has superior durability even under such an environment that it is exposed to heat or light over a long period of time.SOLUTION: A white laminate polyester film for a solar battery backsheet comprises: a first layer including a polyester resin and white inorganic particles of which the content is 5-15 mass% to the total mass of the layer, and having a terminal carboxy group concentration of 10-40 eq./ton; and a second layer including a polyester resin and white inorganic particles of which the content is 5 mass% or less to the total mass of the layer, and having a terminal carboxy group concentration of 5-25 eq./ton. The first layer is thinner than the second layer in thickness.

Description

  The present invention relates to a white laminated polyester film for a solar battery back sheet and a method for producing the same, a solar battery back sheet, and a solar battery module.

  Polyester films are used in various fields because they are inexpensive and have excellent characteristics. The performance required for polyester films is diverse. For example, when a polyester film is used for a long-term outdoor use such as solar cell protection, it has high hydrolysis resistance to maintain the strength over a long period of time, and is visible from the viewpoint of design. It is required that the light concealment is high.

For this reason, for example, in Patent Document 1, as a laminated polyester film for protecting the back surface of a solar cell having weather resistance and hydrolysis resistance, a polyester composition comprising 10 to 30% by weight of rutile titanium oxide particles and 70 to 90% by weight of polyester. And a base layer (B) composed of a polyester composition comprising 0.1 to 4% by weight of rutile-type titanium oxide particles and 96 to 99.9% by weight of polyester. A laminated polyester film for protecting the back surface of a solar cell having a COOH terminal group concentration of 6 to 25 equivalents / ton of polyester in the laminated film has been proposed.
For example, in patent document 2, as a manufacturing method of the polyester film for solar cell back surface protection which has durability under high temperature and high humidity, while putting polyethylene terephthalate and particles dried beforehand into an extruder, deaeration, A method for producing a polyester film for protecting the back surface of a solar cell, characterized in that a master batch is produced by extrusion, has been proposed. According to this method, a solar cell having whiteness of 50 or more, 3 to 50% by mass of fine particles having an average particle size of 0.1 to 3 μm, and an acid value of the film of 1 (eq / ton) or less. It is said that a polyester film for protecting the back surface is obtained.

Japanese Patent No. 5102392 Japanese Patent No. 5114681

The visible light hiding property of the polyester film can be improved by adding white inorganic particles to the polyester film. However, in the step of kneading the white inorganic particles into the polyester during the production of the polyester film, the hydrolysis of the polyester may occur due to the water contained in the white inorganic particles, and the terminal carboxy group concentration may increase. In addition, when a resin containing white inorganic particles is melt-kneaded, frictional heat is likely to be generated due to shear generated during kneading, and thermal decomposition of the polyester may occur due to frictional heat, resulting in an increase in the terminal carboxy group concentration.
For this reason, there exists a problem that the terminal carboxyl group density | concentration of polyester increases and the hydrolysis resistance falls, so that the density | concentration of the white inorganic particle in a film is made high in order to improve visible light concealment property.
For these reasons, it is difficult to produce a polyester film having both hydrolysis resistance and visible light hiding properties with conventional techniques.

The polyester film described in Patent Document 1 achieves both the hydrolysis resistance and the visible light hiding property by increasing the visible light hiding property by the surface layer and enhancing the hydrolysis resistance by the base material layer. However, the titanium oxide concentration contained in the surface layer is as high as 10 to 30% by weight, and the terminal carboxy group concentration increases in the step of kneading titanium oxide into the surface layer. As a result, the hydrolysis resistance of the entire polyester film is not sufficient.
The polyester film of Patent Document 2 is produced under the conditions of light reflection efficiency and high temperature and high humidity by producing a master batch while degassing and by setting the average particle size and content of particles contained in the film within a specific range. To achieve both excellent durability. However, the content of fine particles is as high as 3 to 50% by weight, and the terminal carboxy group concentration increases in the step of kneading the fine particles into the polyester layer. As a result, the hydrolysis resistance is not sufficient.

  The present invention has been made in view of the circumstances as described above, and is a white laminated polyester film for a solar battery backsheet having both weather resistance (hydrolysis resistance) and visible light hiding properties (reflectance), It is an object to provide a manufacturing method thereof, a solar battery back sheet, and a solar battery module having excellent durability under an environment exposed to heat and light over a long period of time. To do.

  Specific means for achieving the object are as follows.

<1> The polyester resin is included, the content of the white inorganic particles is 5% by mass to 15% by mass with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalents / ton to 40 equivalents / ton. A certain first layer and a polyester resin, the content of white inorganic particles is 5% by mass or less based on the total mass of the layer, and the terminal carboxy group concentration of the layer is 5 eq / ton to 25 eq / ton A white laminated polyester film for a solar battery backsheet, comprising: a second layer, wherein the thickness of the first layer is thinner than the thickness of the second layer.

<2> The solar battery back according to <1>, having a void inside the first layer, wherein the surface area A of the void and the content C relative to the total mass of the layer of the white inorganic particles satisfy the following relational expression 1. White laminated polyester film for sheet.
1 <A / C <100 Relational expression 1
<3> The white laminated polyester film for solar battery backsheet according to <1> or <2>, wherein the terminal carboxy group concentration of the first layer is 12 equivalent / ton to 35 equivalent / ton.
<4> The thickness of the first layer is 20 μm to 100 μm, and the thickness of the second layer is 50 μm to 300 μm. The white laminate for a solar battery backsheet according to any one of <1> to <3> Polyester film.
<5> The solar cell backsheet white according to any one of <1> to <4>, wherein the ratio of the thickness of the first layer to the thickness of the second layer is 1: 2 to 1:10. Laminated polyester film.
<6> The white laminated polyester film for solar battery backsheet according to any one of <1> to <5>, wherein the white inorganic particles are titanium oxide.

<7> White inorganic particles whose water content has been reduced to 2000 ppm or less are introduced into the extruder into which the polyester resin is introduced by the side feed method, and deaeration is performed downstream from the position where the white inorganic particles are introduced in the extruder. , Co-extrusion of a masterbatch production step for producing a masterbatch, a first raw material resin containing a masterbatch produced in the masterbatch production step and a polyester resin, and a second raw material resin containing at least a polyester resin Thus, the content of the white inorganic particles is 5% by mass or more and 15% by mass or less with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalent / ton to 40 equivalent / ton. Second, the content of the layer and the white inorganic particles is 5% by mass or less with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 5 equivalent / ton to 25 equivalent / ton. A white laminate for a solar battery backsheet, comprising: forming a white laminated polyester film for a solar battery backsheet having a thickness of the first layer thinner than a thickness of the second layer. A method for producing a polyester film.
<8> The method for producing a white laminated polyester film for a solar battery backsheet according to <7>, wherein the white inorganic particles introduced by the side feed method in the master batch production step are titanium oxide.
<9> The white laminated polyester film for a solar battery backsheet according to <7> or <8>, wherein the polyester resin charged in the masterbatch production step has an intrinsic viscosity of 0.70 dl / g to 0.80 dl / g. Manufacturing method.
The <10> first layer has voids inside the layer, and the surface area A of the voids and the content C relative to the total mass of the layer of white inorganic particles satisfy the following relational expression 1 <7> to <9 The manufacturing method of the white laminated polyester film for solar cell backsheets as described in any one of>.
1 <A / C <100 Relational expression 1
<11> The white inorganic particles introduced in the masterbatch production step are white inorganic particles whose water content is reduced to 1000 ppm or less, for the solar battery backsheet according to any one of <7> to <10>. A method for producing a white laminated polyester film.

<12> A solar cell backsheet having the white laminated polyester film for solar cell backsheet according to any one of <1> to <6>.
<13> A solar battery backsheet having a white laminated polyester film for a solar battery backsheet produced by the production method according to any one of <7> to <11>.
<14> A solar cell module comprising the solar cell back sheet according to <12> or <13>.
<15> A transparent substrate on which sunlight is incident, an element structure portion provided on the substrate and having a solar cell element and a sealing material for sealing the solar cell element, and a substrate of the element structure portion The solar cell module provided with the solar cell backsheet as described in <12> or <13> arrange | positioned on the opposite side to the located side.

  According to the present invention, a white laminated polyester film for a solar battery backsheet having both weather resistance (hydrolysis resistance) and visible light hiding properties (reflectance), a method for producing the same, a solar battery backsheet, and Provided is a solar cell module that is excellent in durability under an environment where it is exposed to heat and light for a long period of time.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.
In the present specification, the numerical range may be indicated by using the notation “to”, which means a range including the numerical values described before and after “to” as the minimum value and the maximum value lower limit, respectively.

<White laminated polyester film>
The white laminated polyester film for solar cells of the present invention (hereinafter also referred to as a laminated film as appropriate) contains a polyester resin, and the content of white inorganic particles is 5% by mass or more and 15% by mass or less with respect to the total mass of the layer. The terminal layer has a terminal carboxy group concentration of 10 equivalents / ton to 40 equivalents / ton and includes a polyester resin, and the content of white inorganic particles is the total mass of the layer. And a second layer (hereinafter, also referred to as a base material layer as appropriate) having a terminal carboxy group concentration of 5 equivalent / ton to 25 equivalent / ton. Yes. “Ton” means “1000 kg”.
In the laminated film of the present invention, the thickness of the first layer is thinner than the thickness of the second layer.
In the laminated film of the present invention, the first layer and the second layer are preferably laminated in contact with each other.

Although the action mechanism of the present invention is not clear, the present inventor presumes as follows.
That is, when it is configured to have a laminated structure in order to effectively increase the reflectance of the polyester film, while including a predetermined amount of white inorganic particle content in the first layer (skin layer) located on the surface layer, By controlling the terminal carboxy group concentration within a specific range, it is possible to achieve both hydrolysis resistance and reflectance in the skin layer. Thus, it is considered that the hydrolysis resistance of the skin layer, which has conventionally been apt to be inferior in hydrolysis resistance, can be improved instead of obtaining sufficient reflectance. As a result, it is considered that the laminated film as a whole is more excellent in hydrolysis resistance and reflectance.

In the present invention, when forming the skin layer, the master batch method is used, and when the master batch is produced, the dehydrated white inorganic particles are introduced into the extruder by the side feed method, so that the same amount as compared with the conventional manufacturing method. Even when white inorganic particles are added, it is considered that an increase in the terminal carboxy group concentration can be suppressed.
Moreover, it is thought that the increase in a terminal carboxy group density | concentration can be suppressed more effectively by performing deaeration downstream from the position into which the white inorganic particle was thrown in in an extruder at the time of masterbatch preparation.
Thereby, a skin layer containing white inorganic particles with low terminal carboxy group concentration and sufficient reflectivity is obtained, and by laminating with a base layer having good hydrolysis resistance, the laminated film is It is considered that both hydrolysis resistance and reflectance can be achieved at a high level.
Below, each layer of the laminated | multilayer film of this invention is demonstrated in detail.

[First layer]
The laminated film of the present invention contains a polyester resin, the content of white inorganic particles is 5% by mass to 15% by mass with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalents / ton to 40%. It has a first layer that is equivalent / ton.
Conventionally, the reflectance and hydrolysis resistance of polyester films were contradictory physical properties. However, the first layer of the present invention contains white inorganic particles in order to obtain high reflectance, but the terminal carboxyl of the layer is also included. By controlling the group concentration within the above range, both the reflectance and the hydrolysis resistance can be achieved. As a result, both the reflectance and the hydrolysis resistance of the laminated film can be achieved.

When the content of the white inorganic particles is less than 5% by mass, the first layer is inferior in reflectance, and when it exceeds 15% by mass, the first layer is inferior in hydrolysis resistance.
The content of the white inorganic particles in the first layer is preferably 8% by mass or more and 14% by mass or less, and more preferably 10% by mass or more and 13% by mass or less from the viewpoint of achieving both reflectance and hydrolysis resistance.

When the terminal carboxy group concentration is less than 10 equivalent / ton, the first layer has poor adhesion between the layers of the laminated film, and when it exceeds 40 equivalent / ton, the first layer has poor hydrolysis resistance.
From the above viewpoint, the terminal carboxy group concentration of the first layer is preferably 12 equivalent / ton to 35 equivalent / ton, and more preferably 13 equivalent / ton to 25 equivalent / ton.
The unit “equivalent / ton” of the terminal carboxy group concentration represents the molar equivalent per ton.

  The terminal carboxy group concentration (AV) is a value measured by the following method. That is, 0.1 g of the first layer was scraped and dissolved in 5 ml of benzyl alcohol, and then a phenol red indicator was dropped into a mixed solution containing 5 ml of chloroform, and this was added as a reference solution (0.01 N KOH-benzyl alcohol mixed solution). Titrate. The concentration (equivalent / ton) of the terminal carboxy group is calculated from the dripping amount.

The thickness of the first layer is thinner than the thickness of the second layer described later. When the thickness of the first layer is thicker than the thickness of the second layer, compatibility between hydrolysis resistance and reflectance when a laminated film is formed cannot be achieved.
The first layer is preferably 100 μm or less, more preferably 20 μm to 100 μm, further preferably 20 μm to 80 μm, and most preferably 30 μm to 70 μm from the viewpoint of production cost.

The first layer may have voids inside the layer, and the smaller the void surface area in the first layer, the smaller the area where the first layer is in contact with air. Become advantageous. The void surface area is preferably 3000 m ² / g or less, more preferably 1500 m ² / g or less, and still more preferably 100 m ² / g or less.

Further, from the viewpoint of achieving both hydrolysis resistance and reflectance of the laminated film, the void surface area A (m ² / g) and the white inorganic particle content C (mass%) in the first layer are expressed by the following relational expression. 1 is preferably satisfied.
1 <A / C <100 Relational expression 1

When A / C satisfies the relational expression 1, both hydrolysis resistance and reflectance can be achieved at a higher level.
Furthermore, from the same viewpoint, A / C more preferably satisfies the following relational expression (2), and further preferably satisfies the following relational expression (3).
5 <A / C <50 Relational expression (2)
10 <A / C <30 Relational expression (3)

In this specification, “void” means bubbles in the layer, and the surface area A of the void can be determined by the following method.
The cross section of the film is observed with a scanning electron microscope, the magnification is appropriately changed according to the size of the void, and the photographed image is enlarged and copied. Next, the lengths in the thickness direction and the normal direction are measured for at least 200 voids selected at random. The calculated surface area is calculated by assuming a circle whose diameter is the average length of the obtained voids, and calculating the surface area of the voids.

[Second layer]
The laminated film of the present invention contains a polyester resin, the content of white inorganic particles is 5% by mass or less based on the total mass of the layer, and the terminal carboxy group concentration of the layer is 5 equivalents / ton to 25 equivalents / ton. Having a second layer.

When the content of the white inorganic particles exceeds 5% by mass, the second layer is inferior in hydrolysis resistance.
The content of the white inorganic particles in the second layer is preferably 3% by mass or less, more preferably 1% by mass or less, and still more preferably 0% by mass from the viewpoint of achieving both reflectivity and hydrolysis resistance. .

When the second layer has a terminal carboxy group concentration of less than 5 equivalents / ton, it is inferior in adhesion between layers when used as a back sheet, and when it exceeds 25 equivalents / ton, it has poor hydrolysis resistance.
From the above viewpoint, the terminal carboxy group concentration of the second layer is preferably 8 equivalent / ton to 20 equivalent / ton, and more preferably 10 equivalent / ton to 15 equivalent / ton.
The measurement method is as described above.

The thickness of the second layer is larger than the thickness of the first layer described above. If the thickness of the second layer is thinner than the thickness of the first layer, compatibility between hydrolysis resistance and reflectance when a laminated film is formed cannot be achieved.
From the viewpoint of production cost, the second layer is preferably 350 μm or less, more preferably 50 μm to 300 μm, and even more preferably 100 μm to 250 μm.

(Polyester resin)
The polyester resin used in the first layer and the second layer is not particularly limited. For example, a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Is mentioned.
Specific examples of the polyester resin include polyethylene terephthalate (PET), polyethylene isophthalate, polybutylene terephthalate (PBT), poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate and the like. it can. Of these, polyethylene terephthalate or polyethylene-2,6-naphthalate is more preferable, and polyethylene terephthalate is particularly preferable in terms of the balance between mechanical properties and cost.

  The polyester resin may be a homopolymer or a copolymer. Further, polyester may be blended with a small amount of other types of resins such as polyimide.

  When the polyester resin is polymerized, it is preferable to use an Sb-based, Ge-based, or Ti-based compound as a catalyst from the viewpoint of keeping the terminal carboxy group concentration below a predetermined range, and among these, a Ti-based compound is particularly preferable. In the case of using a Ti-based compound, an embodiment in which polymerization is performed by using the Ti-based compound as a catalyst in a range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm is preferable. When the proportion of the Ti-based compound is within the above range, the terminal carboxy group concentration can be adjusted to the range described later, and the hydrolysis resistance of the laminated film can be improved.

  For synthesis of a polyester resin using a Ti-based compound, for example, Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3897756, Japanese Patent No. 396226, Patent No. The methods described in Japanese Patent No. 3997866, Japanese Patent No. 3996871, Japanese Patent No. 40000867, Japanese Patent No. 4053837, Japanese Patent No. 4127119, Japanese Patent No. 4134710, Japanese Patent No. 4159154, Japanese Patent No. 4269704, Japanese Patent No. 431538, and the like can be applied. .

The terminal carboxy group concentration of each polyester resin used in the first layer and the second layer is preferably 20 equivalent / ton or less, more preferably 17 equivalent / ton or less, and particularly preferably 15 equivalent / ton. It is as follows.
When the terminal carboxy group concentration of the polyester resin is 20 equivalents / ton or less, it is easy to adjust the terminal carboxy group concentrations of the first layer and the second layer in the predetermined range when the laminated film is formed. The lower limit of the terminal carboxy group concentration is preferably 2 equivalents / ton in that the adhesiveness with the sealing material when the laminated film is used as a solar battery back sheet is maintained.

  The terminal carboxy group concentration of the polyester resin can be adjusted by polymerization catalyst species and film forming conditions (film forming temperature and time).

  The polyester resin constituting the first layer or the second layer is preferably solid-phase polymerized after polymerization. Thereby, it can adjust to the preferable terminal carboxyl group density | concentration. Solid-phase polymerization may be a continuous method (a method in which a tower is filled with a resin, which is slowly heated for a predetermined time and then sent out), or a batch method (a resin is charged into a container). , A method of heating for a predetermined time). Specifically, for solid phase polymerization, Japanese Patent No. 2621563, Japanese Patent No. 3121876, Japanese Patent No. 3136774, Japanese Patent No. 3603585, Japanese Patent No. 3616522, Japanese Patent No. 3617340, Japanese Patent No. 3680523, Japanese Patent No. 3717392 are disclosed. The method described in Japanese Patent No. 4167159 can be applied.

  The temperature of the solid phase polymerization is preferably 170 ° C. or higher and 240 ° C. or lower, more preferably 180 ° C. or higher and 230 ° C. or lower, and further preferably 190 ° C. or higher and 220 ° C. or lower. The solid phase polymerization time is preferably 5 hours to 100 hours, more preferably 10 hours to 75 hours, and still more preferably 15 hours to 50 hours. The solid phase polymerization is preferably performed in a vacuum or in a nitrogen atmosphere.

(White inorganic particles)
The white inorganic particles are selected from those capable of reflecting visible light and imparting concealability to the laminated film. White inorganic particles may be used alone or in combination of two or more.

  The average primary particle diameter of the white inorganic particles is not particularly limited, but is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm, and further preferably 0.15 μm to 1 μm from the viewpoint of reflectance.

In addition, the average primary particle diameter of the white inorganic particles can be obtained by an electron microscope method, and specifically, can be obtained by the following method.
The particles are observed with a scanning electron microscope, the magnification is appropriately changed according to the size of the particles, and the photographed image is enlarged and copied. Next, the circumference of each particle is traced for at least 200 particles selected at random. The equivalent circle diameter of the particles is measured from these trace images with an image analyzer, and the average value of these is taken as the average primary particle diameter.

The shape of the white inorganic particles is not particularly limited, but the aspect ratio is preferably 2 to 20 and more preferably 5 to 10 from the viewpoint of controlling the surface area of voids generated when the laminated film is stretched. 6 to 8 is more preferable.
Note that the larger the aspect ratio, the smaller the void surface area. Further, when the aspect ratio is 20 or less, cleavage of the laminated film (delamination of the laminated film) can be further suppressed.

The aspect ratio of the white inorganic particles can be obtained by an electron microscope method, and specifically, can be obtained by the following method.
The particles are observed with a scanning electron microscope, the magnification is appropriately changed according to the size of the particles, and the photographed image is enlarged and copied. Next, for at least 200 or more randomly selected particles, the length of the long side and the short side of each particle is measured with an image analyzer, and the average value of the ratio of the long side to the short side is defined as the aspect ratio. .

Examples of white inorganic particles include titanium oxide, wet and dry silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, zinc oxide (zinc white), antimony oxide, cerium oxide, and zirconium oxide. , Tin oxide, lanthanum oxide, magnesium oxide, barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, mica titanium, talc, clay, kaolin, fluoride Lithium and calcium fluoride can be used, and titanium oxide and barium sulfate are particularly preferable.
The titanium oxide may be either anatase type or rutile type. The particle surface may be subjected to inorganic treatment such as alumina or silica, or may be subjected to organic treatment such as silicon or alcohol.

  Among these white inorganic particles, titanium oxide is preferable, and thereby excellent durability can be achieved even under light irradiation. Thus, since light decomposition and degradation are suppressed by light irradiation, polyester is more suitable as a use of a solar battery back sheet used outdoors.

  Titanium oxide includes rutile type and anatase type, and it is preferable to add titanium oxide particles mainly composed of rutile type to polyester. The anatase type has a very high spectral reflectance of ultraviolet rays, whereas the rutile type has a characteristic that the absorption rate of ultraviolet rays is large (spectral reflectance is small). The inventor paid attention to such a difference in spectral characteristics in the crystal form of titanium oxide, and found that weather resistance can be improved in the solar cell backsheet by utilizing the rutile-type ultraviolet absorption performance. Thereby, even if other ultraviolet absorbers are not substantially added, the durability of the laminated film under light irradiation is excellent. For this reason, it is difficult for the ultraviolet absorber to bleed out and to reduce contamination and adhesion.

As described above, the titanium oxide is preferably mainly composed of a rutile type. However, the term “main body” as used herein means that the amount of rutile titanium oxide in the total titanium oxide exceeds 50% by mass. Means that.
Moreover, it is preferable that the amount of anatase-type titanium oxide in the total titanium oxide is 10% by mass or less. More preferably, it is 5 mass% or less, Most preferably, it is 0 mass%. If the content of anatase-type titanium oxide exceeds the above upper limit, the amount of rutile-type titanium oxide in the total titanium oxide will decrease, resulting in insufficient UV absorption performance. Anatase-type titanium oxide is a photocatalyst. Since the action is strong, the weather resistance also tends to be lowered by this action. Rutile titanium oxide and anatase titanium oxide can be distinguished by X-ray structural diffraction and spectral absorption characteristics.

  The rutile titanium oxide may be subjected to an inorganic treatment such as alumina or silica on the particle surface, or an organic treatment such as silicon or alcohol. The rutile titanium oxide may be subjected to primary particle size adjustment and coarse particle removal using a purification process before blending into the polyester composition. As industrial means of the purification process, for example, a jet mill or a ball mill can be applied as a pulverizing means, and as a classification means, for example, dry or wet centrifugation can be applied.

(Other materials)
The first layer and the second layer may contain a terminal blocking agent. Hydrolysis resistance can be further improved by the first layer and the second layer containing a terminal blocking agent. Furthermore, various additives such as compatibilizers, plasticizers, weathering agents, antioxidants, heat, and the like may be added to the first layer and / or the second layer as long as the effects of the present invention are not impaired. Stabilizers, lubricants, antistatic agents, brighteners, colorants, conductive agents, ultraviolet absorbers, flame retardants, flame retardant aids and dyes may be added.

-End sealant-
The 1st layer and / or the 2nd layer may contain 0.1 mass%-10 mass% terminal blocker with respect to the total mass of a polyester resin. As for content of the terminal blocker in a 1st layer and a 2nd layer, 0.2 mass%-5 mass% are more preferable with respect to the total mass of a polyester resin, and 0.3 mass%-2 mass% are Further preferred.

Since the hydrolysis of the polyester resin is accelerated by the catalytic effect of H ⁺ (proton) generated from the terminal carboxylic acid or the like, an end-capping agent that reacts with the terminal carboxylic acid is added to improve the hydrolysis resistance. Is effective.
If the addition amount of the end-capping agent is 0.1% by mass or more with respect to the total mass of the polyester resin, the effect of improving hydrolysis resistance is easily exhibited. Acting as a plasticizer is suppressed, and a decrease in mechanical strength and heat resistance is suppressed.

  Examples of the end capping agent include an epoxy compound, a carbodiimide compound, an oxazoline compound, and a carbonate compound, and carbodiimide having high affinity with polyethylene terephthalate (PET) and high end capping ability is preferable.

It is preferable that terminal blocker (especially carbodiimide terminal blocker) is high molecular weight. This can reduce volatilization during melt film formation. The molecular weight is preferably 200 to 100,000, more preferably 2000 to 80,000, and still more preferably 10,000 to 50,000. If the molecular weight of the end-capping agent (particularly carbodiimide end-capping agent) is within the above range, it is easy to uniformly disperse in the polyester, and the hydrolysis resistance improving effect can be sufficiently expressed, and during extrusion and film formation. It is difficult to volatilize and it becomes easy to express the hydrolysis resistance improving effect.
In addition, the molecular weight of terminal blocker means a weight average molecular weight.

-Carbodiimide-based end-capping agent-
The carbodiimide compound having a carbodiimide group includes a monofunctional carbodiimide and a polyfunctional carbodiimide. Examples of the monofunctional carbodiimide include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, and diphenylcarbodiimide. , Di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and the like. Particularly preferred are dicyclohexylcarbodiimide and diisopropylcarbodiimide.

  As the polyfunctional carbodiimide, carbodiimide having a polymerization degree of 3 to 15 is preferably used. Specifically, 1,5-naphthalene carbodiimide, 4,4′-diphenylmethane carbodiimide, 4,4′-diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide, 1,4-phenylene diisocyanate, 2,4-tolylene Carbodiimide, 2,6-tolylene carbodiimide, mixture of 2,4-tolylene carbodiimide and 2,6-tolylene carbodiimide, hexamethylene carbodiimide, cyclohexane-1,4-carbodiimide, xylylene carbodiimide, isophorone carbodiimide, isophorone carbodiimide, Dicyclohexylmethane-4,4′-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimide, 2,6-diisopropylphenylcarbodiimide and , And the like can be exemplified 3,5-triisopropyl-2,4-carbodiimide.

  The carbodiimide compound is preferably a carbodiimide compound having high heat resistance because an isocyanate gas is generated by thermal decomposition. In order to improve heat resistance, it is preferable that the molecular weight (degree of polymerization) is high, and it is more preferable that the terminal of the carbodiimide compound has a structure with high heat resistance. Further, once thermal decomposition occurs, further thermal decomposition is likely to occur. Therefore, it is necessary to devise measures such as setting the extrusion temperature of the polyester as low as possible.

  A carbodiimide as a terminal blocking agent preferably has a cyclic structure (for example, those described in JP2011-153209A). These exhibit the same effect as the above high molecular weight carbodiimide even at low molecular weight. This is because the terminal carboxylic acid of the polyester and the cyclic carbodiimide undergo a ring-opening reaction, one reacts with this polyester, and the other with the ring-opening reacts with another polyester to increase the molecular weight, thus suppressing the generation of isocyanate gas. It is to do.

Among those having a cyclic structure, in the present invention, the terminal blocking agent is a carbodiimide compound having a carbodiimide group and a cyclic structure in which the first nitrogen and the second nitrogen are bonded by a bonding group. It is preferable. Further, the end capping agent has a cyclic structure in which at least one carbodiimide group adjacent to the aromatic ring is present, and the first nitrogen and the second nitrogen of the carbodiimide group adjacent to the aromatic ring are bonded by a bonding group. More preferred is carbodiimide (also referred to as aromatic cyclic carbodiimide).
The aromatic cyclic carbodiimide may have a plurality of cyclic structures.
The aromatic cyclic carbodiimide is preferably an aromatic carbodiimide having no ring structure in which the first nitrogen and the second nitrogen of two or more carbodiimide groups are bonded by a linking group in the molecule, that is, a monocyclic ring. Can be used.

  The cyclic structure has one carbodiimide group (—N═C═N—), and the first nitrogen and the second nitrogen are bonded by a bonding group. One cyclic structure has only one carbodiimide group. For example, when there are a plurality of cyclic structures in the molecule, such as a spiro ring, one cyclic structure bonded to a spiro atom is included in each cyclic structure. Needless to say, the compound may have a plurality of carbodiimide groups as long as it has a carbodiimide group. The number of atoms in the cyclic structure is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15.

  Here, the number of atoms in the cyclic structure means the number of atoms that directly constitute the cyclic structure. For example, it is 8 for an 8-membered ring and 50 for a 50-membered ring. This is because if the number of atoms in the cyclic structure is smaller than 8, the stability of the cyclic carbodiimide compound is lowered, and it may be difficult to store and use. From the standpoint of reactivity, the upper limit of the number of ring members is not particularly limited, but a cyclic carbodiimide compound having 50 or less atoms is less difficult to synthesize, and the cost can be kept low. From this viewpoint, the number of atoms in the cyclic structure is preferably 10-30, more preferably 10-20, and particularly preferably 10-15.

  Specific examples of the carbodiimide-based end capping agent having a cyclic structure include the following compounds. However, the present invention is not limited to the following specific examples.

-Epoxy terminal blocker-
Preferable examples of the epoxy compound include glycidyl ester compounds and glycidyl ether compounds.

  Specific examples of the glycidyl ester compound include benzoic acid glycidyl ester, t-butyl-benzoic acid glycidyl ester, P-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, and lauric acid glycidyl ester. , Glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolein, glycidyl behenol, glycidyl stearol, diglycidyl terephthalate, isophthalic acid Diglycidyl ester, diglycidyl phthalate, diglycidyl naphthalene dicarboxylate Stell, methyl terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecane Examples thereof include diglycidyl diacid, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester. These may be used alone or in combination of two or more.

  Specific examples of the glycidyl ether compound include phenyl glycidyl ether, O-phenyl glycidyl ether, 1,4-bis (β, γ-epoxypropoxy) butane, 1,6-bis (β, γ- Epoxypropoxy) hexane, 1,4-bis (β, γ-epoxypropoxy) benzene, 1- (β, γ-epoxypropoxy) -2-ethoxyethane, 1- (β, γ-epoxypropoxy) -2-benzyl Oxyethane, 2,2-bis- [р- (β, γ-epoxypropoxy) phenyl] propane and 2,2-bis- (4-hydroxyphenyl) propane and 2,2-bis- (4-hydroxyphenyl) Examples include bisglycidyl polyether obtained by reaction of bisphenol such as methane and epichlorohydrin, and these include one or more. It can be used.

-Oxazoline-based end-capping agent-
As the oxazoline compound, a bisoxazoline compound is preferable, and specifically, 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), and 2,2′-bis. (4,4-dimethyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4,4′-diethyl-2-oxazoline), 2,2 '-Bis (4-propyl-2-oxazoline), 2,2'-bis (4-butyl-2-oxazoline), 2,2'-bis (4-hexyl-2-oxazoline), 2,2'- Bis (4-phenyl-2-oxazoline), 2,2'-bis (4-cyclohexyl-2-oxazoline), 2,2'-bis (4-benzyl-2-oxazoline), 2,2'-p- Phenylenebis (2-oxazoline), 2,2'-m- Enylene bis (2-oxazoline), 2,2'-o-phenylene bis (2-oxazoline), 2,2'-p-phenylene bis (4-methyl-2-oxazoline), 2,2'-p-phenylene bis (4,4-dimethyl-2-oxazoline), 2,2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4,4-dimethyl-2-oxazoline) ), 2,2′-ethylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-decamethylenebis (2-oxazoline), 2,2′-ethylenebis (4-methyl-2-oxazoline), 2,2′-tetramethylenebis (4,4 - Methyl-2-oxazoline), 2,2′-9,9′-diphenoxyethanebis (2-oxazoline), 2,2′-cyclohexylenebis (2-oxazoline) and 2,2′-diphenylenebis ( 2-oxazoline) and the like. Among these, 2,2′-bis (2-oxazoline) is most preferably used from the viewpoint of reactivity with polyester. Furthermore, as long as the objective of this invention is achieved, the bisoxazoline compound mentioned above may be used individually by 1 type, or may use 2 or more types together.

  Such an end-capping agent needs to be kneaded into the polyester film. That is, the above effects cannot be obtained unless the polyester molecules are directly reacted. This is because even when added to the coating layer on the polyester film, the polyester and the end-capping agent do not react.

[Physical properties of laminated film]
Each physical property value of the whole film when the above layers are laminated to form a laminated film will be described below.

(Average concentration of terminal carboxy groups in the entire film)
In the laminated film of the present invention, the average concentration of terminal carboxy groups in the entire film is preferably 30 equivalents / ton or less.
When the average concentration of the terminal carboxy group is 30 equivalents / ton or less, the laminated film is excellent in hydrolysis resistance. Therefore, good weather resistance can be maintained.
The average concentration of the terminal carboxy group is preferably 5 equivalents / ton to 28 equivalents / ton, more preferably 10 equivalents / ton to 24 equivalents / ton, from the viewpoint of further improving the hydrolysis resistance.

(Thickness)
The total thickness of the laminated film of the present invention is preferably 75 μm to 400 μm, more preferably 150 μm to 300 μm, and even more preferably 200 μm to 275 μm.
Regarding the thickness of the first layer and the thickness of the second layer in the laminated film, the thickness of the first layer is small. Since the thickness of the first layer is thin, the hydrolysis resistance and reflectance of the laminated film can be compatible.
The ratio of the thickness of the first layer to the thickness of the second layer in the laminated film (first layer: second layer) is preferably 1: 2 to 1:10, and is preferably 1: 2 to 1: 8. Is more preferable. When the (first layer: second layer) is within the above range, the hydrolysis resistance and reflectance of the laminated film can be made compatible at a higher level.

(Intrinsic viscosity IV)
The laminated film of the present invention preferably has an intrinsic viscosity (IV) of 0.6 dl / g to 1.5 dl / g, more preferably 0.65 dl / g to 1.2 dl / g, and 0.7 dl / g. -0.9 dl / g is more preferable. “Dl” means “10 ⁻⁴ m ³ ”.
When the intrinsic viscosity (IV) is in the above range, the hydrolysis resistance of the laminated film is further improved.

<Method for producing laminated film>
The method for producing a white laminated polyester film for a solar cell according to the present invention is such that white inorganic particles whose water content is reduced to 2000 ppm or less are introduced into an extruder into which a polyester resin is introduced by a side feed method, A masterbatch production process for producing a masterbatch by performing deaeration downstream from the position where the particles are charged, a first raw material resin including the masterbatch and a polyester resin produced in the masterbatch production process, and at least a polyester resin The content of white inorganic particles is 5% by mass to 15% by mass with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalents The content of white inorganic particles is 5% by mass or less with respect to the total mass of the first layer of / 40 to 40 equivalents / ton, And a second layer having a boxy group concentration of 5 equivalents / ton to 25 equivalents / ton, and forming a white laminated polyester film for solar cells in which the thickness of the first layer is thinner than the thickness of the second layer Forming a film.

[Master batch production process]
In the master batch production process, by using white inorganic particles whose water content is reduced to 2000 ppm or less, when the polyester resin and the white inorganic particles are melt-kneaded, the polyester resin caused by the moisture contained in the white inorganic particles Hydrolysis can be suppressed and an increase in the terminal carboxy group concentration of the polyester resin can be suppressed.
From the above viewpoint, it is preferable to use white inorganic particles whose water content is reduced to 1000 ppm or less in the masterbatch preparation step, more preferably white inorganic particles reduced to 500 ppm or less, and 100 ppm or less. More preferably, white inorganic particles are used.

  The water content of the white inorganic particles can be measured with a Karl Fischer moisture meter (MKC-520, manufactured by Kyoto Electronics Industry Co., Ltd.). Specifically, 1 g of white inorganic particles can be heated at 300 ° C., and the amount of water can be determined by mass change before and after heating.

In the masterbatch production process, white carboxyl particles are introduced into the extruder by the side feed method, which is generated when the polyester resin and white inorganic particles are melted and kneaded. An increase in concentration can be suppressed.
When the polyester resin and the white inorganic particles are introduced simultaneously from the inlet of the extruder, the time affected by frictional heat and hydrolysis generated by melt kneading is long, and the terminal carboxy group concentration of the polyester resin tends to increase.
On the other hand, by introducing white inorganic particles into the extruder by the side feed method, the influence of frictional heat and hydrolysis generated by melt kneading can be reduced, and the increase in the terminal carboxyl group concentration of the polyester resin can be suppressed. Can do.

  The charging method of the white inorganic particles in the side feed method is not particularly limited, but it is preferable to use a quantitative feeder and a screw-type charging method from the viewpoint of stable supply of white inorganic particles.

  The input amount of the white inorganic particles is preferably 30% by mass to 70% by mass, and more preferably 40% by mass to 60% by mass with respect to the total mass of the master batch. When the input amount of the white inorganic particles is within the above range, the content of the white inorganic particles in the master batch can be easily controlled, and the first layer can be formed when the first layer is formed using the master batch. It is easy to control the content of white inorganic particles.

  The polyester resin in the master batch production step can be selected from the polyester resins described above. From the point that the terminal carboxyl group concentration of the masterbatch can be kept low, the intrinsic viscosity of the polyester resin is preferably 0.70 dl / g to 0.80 dl / g, more preferably 0.71 dl / g to 0.76 dl / g. Preferably, 0.72 dl / g to 0.74 dl / g is more preferable.

The intrinsic viscosity (IV) of the polyester resin can be calculated from the following formula from the solution viscosity measured at 25 ° C. by dissolving the polyester resin in orthochlorophenol.
ηsp / C = [η] + K [η] 2 · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the dissolved polymer weight per 100 ml of solvent (in this measurement, 1 g / 100 ml), and K is the Huggins constant (0.343). The solution viscosity and the solvent viscosity can be measured using an Ostwald viscometer.

In the master batch production process, deaeration is performed downstream from the position where the white inorganic particles are introduced in the extruder, so that moisture contained in the white inorganic particles can be further reduced, and the terminal carboxy group of the master batch by melt kneading can be reduced. An increase in concentration can be suppressed.
The extruder preferably uses an extruder having a vent structure, and may be a single-screw extruder having a vent structure or a twin-screw extruder having a vent structure. From the viewpoint of dispersibility of the white inorganic particles in the master batch, a twin screw extruder having a vent structure is preferable.
The temperature of the melt kneading is preferably 260 ° C. to 300 ° C., more preferably 265 ° C. to 290 ° C., and further preferably 270 ° C. to 280 ° C. from the viewpoints of suppression of increase in terminal carboxy group concentration and dispersibility of white inorganic particles.
The atmosphere of the melt-kneading is preferably in a vacuum from the viewpoint of discharging water volatilized from the polyester resin or white inorganic particles during melt-kneading. The vacuum pressure by the vent is preferably 0.1 Torr to 50 Torr, more preferably 1 Torr to 10 Torr. When the vacuum pressure is in the above range, both high dehydration effect and equipment cost can be achieved.
The melt kneading time is preferably from 1 minute to 15 minutes, more preferably from 2 minutes to 10 minutes, and further preferably from 3 minutes to 7 minutes.

  The master batch obtained in the master batch production step can be cooled and solidified in air or water and then cut and pelletized to obtain a master pellet.

[Film forming process]
The method for producing a laminated film of the present invention comprises coextruding a first raw material resin containing a masterbatch produced in the masterbatch production step and a polyester resin, and a second raw material resin containing at least a polyester resin, A first layer in which the content of inorganic particles is 5% by mass to 15% by mass with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalent / ton to 40 equivalent / ton; A second layer having a particle content of 5% by mass or less based on the total mass of the layer, and a terminal carboxy group concentration of the layer of 5 to 25 equivalents / ton, and the first layer A film forming step of forming a white laminated polyester film in which the thickness of the layer is thinner than the thickness of the second layer;

(First raw resin)
1st raw material resin contains the masterbatch produced by the masterbatch manufacturing process, and polyester resin. The polyester resin can be selected from the polyester resins described above.

  As the raw material resin for the first layer, the above-described master batch in which white inorganic particles are dispersed in advance is used, and by using the first raw material resin to which the above-described polyester resin is added, the dispersion of white inorganic particles is performed. Therefore, it is easy to control the content of the white inorganic particles. Moreover, the terminal carboxy group density | concentration of a 1st layer can be adjusted to 10 equivalent / tons-40 equivalent / tons by including the already-mentioned masterbatch.

(Second raw resin)
The second raw material resin contains at least a polyester resin. The polyester resin can be selected and used from the polyesters described above, and the same or different polyester resin as that contained in the first raw material resin may be used.
Moreover, pellets, fluffs, mixtures thereof, and the like can be used as the second raw material resin, and those obtained by mixing the fluff with a mass ratio of 60% or less and pellets are preferable.

  By using a mixture of pellets and fluffs in this way, the melting method and heat history of the raw resin can be adjusted. The fluff is, for example, a pulverized product obtained by pulverizing an unnecessary film into small pieces (so-called chips), scrap pieces, or the like, that is, a recycled chip obtained by trimming and crushing the end portion in the width direction of the laminated film. Increasing the fluff ratio has a high recycling ratio and can reduce the cost of raw materials. On the other hand, an increase in the fluff ratio gives a bulkiness, and the bulk specific gravity can be lowered as compared with, for example, a pellet alone. As the resin film for obtaining the fluff, a polyester film is preferable, and a polyester film of the same type as the polyester resin in the raw resin is preferable. By setting the fluff ratio to 60% by mass or less, the fluctuation range of the terminal carboxy group concentration of the obtained polyester film can be kept low. Among these, for the same reason, the mass ratio of the fluff is preferably 60% by mass or less, more preferably 10% by mass to 50% by mass, and further preferably 20% by mass to 40% by mass.

  The fluff size is not limited as long as the bulk change is given, but a fluff thickness of 20 μm to 5000 μm is preferable. Among these, from the viewpoint of preventing the bulk density from becoming too small and reducing the filling rate too much and avoiding insufficient melting, the thickness of the fluff is preferably in the range of 100 μm to 1000 μm, more preferably in the range of 100 μm to 500 μm.

  Further, in terms of further reducing the terminal carboxy group concentration of the second layer to be formed, it is preferable that the variation in the size of the fluff is smaller, for example, the variation in the thickness of the fluff is preferably within ± 100%, More preferably, it is within ± 50%, and further within ± 10%. When a fluff is used, variation in the terminal carboxy group concentration of the obtained second layer can be suppressed low by suppressing size variation such as thickness.

  The bulk specific gravity of the fluff is preferably in the range of 0.3 to 0.7 as long as the bulk specific gravity of the raw material resin satisfies the range. The bulk specific gravity of the raw material resin refers to the specific gravity (per unit volume) obtained by dividing the mass of the powder into a predetermined shape by dividing the powder into a predetermined volume in a constant volume container. Mass), the smaller the bulk specific gravity, the larger the bulk.

  In addition, it is preferable that 1st raw material resin does not contain a recycling chip substantially. “Substantially not contained” means that it is not contained within a range that does not affect the effects of the present invention, and represents, for example, 0.1% by mass or less.

(Extrusion / Filming)
In the film forming step in the present invention, the first raw material resin and the second raw material resin are coextruded to form a laminated film having the first layer and the second layer.
It is preferable that the first raw material resin and the second raw material resin are dried and then charged into the extruder.

The drying of the first raw resin and the second raw resin is preferably performed at a drying temperature of 100 ° C to 200 ° C, and more preferably 150 ° C to 180 ° C.
The drying time is preferably 30 minutes to 1440 minutes, more preferably 60 minutes to 300 minutes.
The preferable water content of the first raw material tree and the second raw material resin after drying is 10 ppm to 300 ppm, more preferably 20 ppm to 150 ppm.

It is preferable that the first raw material resin and the second raw material resin are melt-kneaded, respectively, and then the melt (melt) is coextruded on a cast drum through a multilayer die. The melt is solidified on a cast, formed into a film, and obtained as a cast film (unstretched film).
As the multi-layer die system, either a multi-manifold die or a feed block die can be suitably used. The shape of the die can be a T-die, a hanger coat die, a fish tail, or the like. The molten resin (melt) is preferably passed through a melt pipe, a gear pump, and a filter.
The opening of the filter is preferably 1 μm to 50 μm, more preferably 5 μm to 40 μm, and even more preferably 10 μm to 30 μm. It is also preferable to provide a static mixer in the melt pipe to promote mixing of the resin and the additive.

  The temperature of the cast drum is preferably 0 ° C to 60 ° C, more preferably 5 ° C to 55 ° C, and further preferably 10 ° C to 50 ° C. At this time, in order to improve the adhesion between the molten resin and the cast drum and improve the flatness, it is also preferable to use an electrostatic application method, an air knife method, water coating on the cast drum, or the like. Furthermore, in order to perform cooling efficiently, cold air may be blown from the cast drum.

Extrusion is preferably performed under vacuum exhaust or an inert gas atmosphere. Thereby, the increase in the terminal carboxy group concentration can be suppressed. The temperature of the extruder is preferably in the temperature range from the melting point of the polyester used to the melting point + 80 ° C or less, more preferably in the range of melting point + 10 ° C or more, melting point + 70 ° C or less, more preferably melting point + 20 ° C or more. , Melting point + 60 ° C. or less.
When the temperature of the extruder is equal to or higher than the melting point of the polyester, the resin melts well, and conversely, when the temperature of the extruder is “melting point + 80 ° C.” or lower, an increase in the terminal carboxy group concentration is suppressed.

[Stretching process]
In the production method of the laminated film of the present invention, the unstretched film obtained in the film-forming process is biaxial in the longitudinal direction (hereinafter, also referred to as longitudinal direction, MD) and the width direction (hereinafter, also referred to as lateral direction, TD). It is preferable to provide the process of extending | stretching.

As the stretching method, a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction, a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched using a simultaneous biaxial tenter, etc. A method combining a sequential biaxial stretching method and a simultaneous biaxial stretching method is included.
The method for producing the laminated film of the present invention is preferably a sequential biaxial stretching method in which stretching in the width direction is performed after stretching in the longitudinal direction from the viewpoint of controlling the surface area of the voids of the first layer.

  As an example of the sequential stretching biaxial method, an unstretched film is stretched in the longitudinal direction using a difference in peripheral speed of the rolls using a longitudinal stretching machine in which several rolls are arranged (MD stretching, longitudinal stretching). Subsequently, a biaxial stretching method in which stretching is performed in the transverse direction with a tenter (TD stretching, transverse stretching) can be mentioned.

First, it is preferable to MD-stretch an unstretched film. Further, it is preferable to sufficiently preheat the unstretched film prior to MD stretching. The preheating temperature is preferably 40 ° C. or higher and 90 ° C. or lower, more preferably 50 ° C. or higher and 85 ° C. or lower, and further preferably 60 ° C. or higher and 80 ° C. or lower. Such preheating is performed by passing the unstretched film through a heating (temperature-controlling) roll. A preferable preheating time is 1 second to 120 seconds, more preferably 5 seconds to 60 seconds, and further preferably 10 seconds to 40 seconds. Less than a second.
MD stretching may be performed in one stage or in multiple stages. When performed in one stage, the glass transition temperature is Tg to Tg + 15 ° C. (more preferably Tg + 10 ° C.), and the preferred draw ratio is 3.0 times to 5.0 times, more preferably 3.3 times to 4.5 times, more preferably 3.5 times to 4.2 times. It is preferable to cool with a cooling roll group having a temperature of 20 ° C to 50 ° C after stretching. If it is equal to or greater than the lower limit value of this magnification, the orientation of the amorphous part generated with this can be sufficiently formed, and peeling failure is unlikely to occur. On the other hand, if it is below the upper limit of this range, the longitudinal orientation does not become too strong, cleavage (delamination of laminated films) hardly occurs, and peeling failure does not easily occur, which is preferable.
When performing longitudinal stretching in multiple stages, the first low-temperature stretching (MD stretching 1) is in the range of (Tg-20) ° C. to (Tg + 10) ° C., more preferably (Tg−10) ° C. to (Tg + 5) ° C. Heated with a heating roll group in the range, preferably 1.1 times to 3.0 times, more preferably 1.2 times to 2.5 times, more preferably 1.5 times to 2.0 times in the longitudinal direction. Next, MD stretching 2 is performed at a temperature higher than MD stretching 1 temperature (Tg + 10) ° C. to (Tg + 50) ° C. A more preferable temperature is (Tg + 15) ° C. to (Tg + 30) ° C. The preferable draw ratio of MD stretch 2 is 1.2 times to 4.0 times, and more preferably 1.5 times to 3.0 times. The MD stretching ratio of MD stretching 1 and MD stretching 2 is preferably 2.0 times to 6.0 times, more preferably 3.0 times to 5.5 times, and even more preferably 3.5 times. Times to 5.0 times. The ratio of the draw ratio of the first stage and the second stage (second stage / first stage = multistage ratio) is preferably 1.1 or more and 3 or less, more preferably 1.15 or more and 2 or less, Preferably they are 1.2 times or more and 1.8 times or less. If the multistage stretching ratio is equal to or greater than the lower limit of this range, it is preferable that peeling failure hardly occurs as in the case of single-stage stretching.

  Next, it is preferable to perform stretching in the width direction using a tenter (sometimes referred to as a stenter). The draw ratio is preferably 3.0 times to 5.0 times, more preferably 3.3 times to 4.5 times, and even more preferably 3.5 times to 4.2 times. The temperature is preferably in the range of (Tg) ° C. to (Tg + 50) ° C., more preferably in the range of (Tg) ° C. to (Tg + 30) ° C.

  The surface area of the void of the first layer in the laminated film can be adjusted by the stretching temperature and the stretching speed in the stretching step.

(Heat fixing)
After stretching in two directions, the film may be heat-set (heat treated). The heat setting can be performed by any conventionally known method such as in a tenter, a heating oven, or on a heated roll.
In the method for producing a laminated film of the present invention, the heat setting temperature is preferably 196 ° C. or higher and 215 ° C. or lower.
By setting the heat setting temperature to 196 ° C. or more and 215 ° C. or less, more preferably 198 ° C. or more and 210 ° C. or less, and more preferably 200 ° C. or more and 208 ° C. or less, the tension of molecules due to stretching can be appropriately released and heat shrinkage can be reduced ( Thermal contraction is manifested by the release of molecular tension generated by orientation).
This heat setting is generally performed at a temperature lower than the melting point of the polyester, but in the present invention, heat setting is preferably performed at the temperature as described above. At this time, it is also preferable to relax as described above in at least one of the vertical and horizontal directions.

[Winding process]
It is preferable that the manufacturing method of a laminated | multilayer film includes the process of winding up the film obtained in this way.

<Solar cell back sheet>
The solar cell backsheet of the present invention is configured by providing the above-described laminated film of the present invention, and for an adherend, if necessary, an easy-adhesive easily-adhesive layer, an ultraviolet absorbing layer, etc. The functional layer may be provided with at least one layer. Since the laminated film of the present invention is provided, stable durability performance is exhibited during long-term use.

In the solar cell backsheet of the present invention, for example, the following functional layer may be applied to the laminated film after uniaxial stretching and / or biaxial stretching. For coating, a known coating technique such as a roll coating method, a knife edge coating method, a gravure coating method, or a curtain coating method can be used.
Further, surface treatment (flame treatment, corona treatment, plasma treatment, ultraviolet treatment, etc.) may be performed before the coating. Furthermore, it is also preferable to bond together using an adhesive.

[Adhesive layer]
When the laminated film of the present invention constitutes a solar cell module, the solar cell element may have an easy-adhesive layer on the side facing the sealing material of the battery side substrate sealed with the sealing material. preferable. Easy adhesion showing adhesion to an adherend containing a sealing material (especially ethylene-vinyl acetate copolymer) (for example, the surface of the sealing material of the battery-side substrate in which the solar cell element is sealed with the sealing material). By providing the conductive layer, the back sheet and the sealing material can be firmly bonded. Specifically, it is preferable that the easy-adhesive layer has an adhesive force of 10 N / cm or more, preferably 20 N / cm or more, particularly with EVA (ethylene-vinyl acetate copolymer) used as a sealing material.
Further, the easy-adhesive layer needs to prevent the backsheet from peeling off during use of the solar cell module, and therefore, the easy-adhesive layer desirably has high moisture and heat resistance.

(binder)
The easy-adhesion layer can contain at least one binder. As the binder, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. Among these, acrylic resins and polyolefins are preferable from the viewpoint of durability. As the acrylic resin, a composite resin of acrylic and silicone is also preferable. The following can be mentioned as an example of a preferable binder.
Examples of polyolefins include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals, Inc.). Examples of acrylic resins include Julimer ET-410 and SEK-301 (both manufactured by Nippon Pure Chemical Industries, Ltd.). Examples of the composite resin of acrylic and silicone include Ceranate WSA 1060 and WSA 1070 (both manufactured by DIC Corporation), and H7620, H7630, and H7650 (both manufactured by Asahi Kasei Chemicals Corporation).
The amount of the binder is preferably in the range of ^{0.05g / m 2 ~5g / m 2} , the range of 0.08g ^{/ m 2} ~3g ^/ m 2 is particularly preferred. The binder amount is more good adhesion is obtained by at 0.05 g / m ² or more, a better surface is obtained by at 5 g / m ² or less.

(Fine particles)
The easily adhesive layer can contain at least one kind of fine particles. The easy-adhesive layer preferably contains 5% by mass or more of fine particles with respect to the mass of the entire layer.
As the fine particles, inorganic fine particles such as silica, calcium carbonate, magnesium oxide, magnesium carbonate, tin oxide and the like are preferably exemplified. Among these, fine particles of tin oxide and silica are preferable in that the decrease in adhesiveness when exposed to a humid heat atmosphere is small.
The primary particle diameter of the fine particles is preferably about 10 nm to 700 nm, more preferably about 20 nm to 300 nm. By using fine particles having a primary particle size in a range, good easy adhesion can be obtained. The shape of the fine particles is not particularly limited, and those having a spherical shape, an indefinite shape, a needle shape or the like can be used.
The addition amount of the fine particles in the easy-adhesive layer is preferably 5% by mass to 400% by mass, more preferably 50% by mass to 300% by mass, per binder in the easy-adhesive layer. When the addition amount of the fine particles is 5% by mass or more, the adhesiveness when exposed to a moist heat atmosphere is excellent, and when it is 1000% by mass or less, the surface state of the easy-adhesive layer is better.

(Crosslinking agent)
The easy-adhesion layer can contain at least one crosslinking agent.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent is particularly preferable from the viewpoint of securing adhesiveness after wet heat aging.
Specific examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- (2 -Oxazoline), 2,2'-ethylene-bis- (2-oxazoline), 2,2'-trimethylene-bis- (2-oxazoline), 2,2'-tetramethylene-bis- (2-oxazoline), 2,2'-hexamethylene-bis- (2-oxazoline), 2,2'-octamethylene-bis- (2-oxazoline), 2,2'-ethylene-bis- (4,4'-dimethyl) -2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be mentioned. Furthermore, (co) polymers of these compounds can also be preferably used.

Further, as a compound having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS500, WS700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used.
A preferable addition amount of the crosslinking agent in the easy-adhesive layer is preferably 5% by mass to 50% by mass, more preferably 20% by mass to 40% by mass, per binder of the easy-adhesive layer. When the addition amount of the crosslinking agent is 5% by mass or more, a good crosslinking effect is obtained, and the strength of the reflective layer is not reduced and adhesion failure hardly occurs, and when it is 50% by mass or less, the pot life of the coating liquid is further increased. I can keep it long.

(Additive)
If necessary, the easily adhesive layer may further contain a known matting agent such as polystyrene, polymethyl methacrylate, silica, or the like, or a known surfactant such as an anionic or nonionic surfactant.

(Method for forming easy-adhesive layer)
As a method for forming the easy-adhesive layer, there are a method of pasting a polymer sheet having easy adhesion to a polyester film and a method by coating, but the method by coating is simple and highly uniform. This is preferable because it is possible. As a coating method, for example, a known method such as a gravure coater or a bar coater can be used. The solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.
When forming an easily bonding layer by application | coating, it is preferable to form on a back sheet in the following procedures.
In the above-described laminated film manufacturing method, the easy-adhesion layer is formed by applying an in-stretch film to the first direction, and then applying (in-line application) a coating liquid that constitutes the easy-adhesion layer. The film is preferably formed by drying and further stretching in a second direction (a direction orthogonal to the first direction).
Moreover, as another aspect, after the unstretched film is extended | stretched in the 1st and 2nd direction, the coating liquid which comprises an easily bonding layer is apply | coated, and the coating film apply | coated after that is an easily bonding layer. It is preferably formed by drying.

(Physical properties of easy adhesion layer)
Although there is no restriction | limiting in particular in the thickness of an easily-adhesive layer, Usually, 0.05 micrometer-8 micrometers are preferable, More preferably, it is the range of 0.1 micrometer-5 micrometers. When the thickness of the easy-adhesive layer is 0.05 μm or more, the required easy adhesion can be easily obtained, and when the thickness is 8 μm or less, the planar shape can be maintained better.
The easy-adhesive layer preferably has transparency from the viewpoint of not impairing the reflective performance of the white laminated polyester film.

[UV absorbing layer]
The laminated film of the present invention may be provided with an ultraviolet absorbing layer containing an ultraviolet absorber. The ultraviolet absorbing layer can be disposed at any position on the laminated film.
The UV absorber is preferably dissolved and dispersed together with an ionomer resin, polyester resin, urethane resin, acrylic resin, polyethylene resin, polypropylene resin, polyamide resin, vinyl acetate resin, cellulose ester resin, etc. The transmittance is preferably 20% or less.

[Undercoat layer]
An undercoat layer can be provided in the laminated film of the present invention. The undercoat layer can be formed using a binder, a crosslinking agent, a surfactant, and the like.

  Examples of the binder contained in the undercoat layer include polyester, polyurethane, acrylic resin, and polyolefin. In addition to the binder, an epoxy, isocyanate, melamine, carbodiimide, oxazoline, or other crosslinking agent, anionic or nonionic surfactant, silica or other filler may be added to the undercoat layer.

There are no particular restrictions on the method for coating the undercoat layer and the solvent of the coating solution used.
As a coating method, for example, a gravure coater or a bar coater can be used. The solvent may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

[Fluorine resin layer / silicon resin layer]
The laminated film of the present invention is preferably provided with at least one of a fluorine-based resin (also referred to as fluorocarbon-based resin) layer and a silicon-based (Si-based) resin layer. By providing the fluorine-based resin layer or the Si-based resin layer, it is possible to prevent contamination of the polyester surface and improve weather resistance. Specifically, it is preferable to have the fluororesin-based coating layer described in JP 2007-35694 A, JP 2008-28294 A, and International Publication No. 2007/063698 pamphlet.
Moreover, it is also preferable to stick together fluorine resin films such as Tedlar (manufactured by DuPont).

  The thicknesses of the fluorine-based resin layer and the Si-based resin layer are each preferably in the range of 1 μm to 50 μm, more preferably in the range of 1 μm to 40 μm, and still more preferably in the range of 1 μm to 10 μm.

[Inorganic layer]
The laminated film of the present invention preferably further has a form in which an inorganic layer is provided. By providing the inorganic layer, it is possible to provide a moisture-proof and gas barrier function to prevent water and gas from entering the polyester. The inorganic layer may be provided on either the front or back side of the polyester film, but from the viewpoint of waterproofing, moisture proofing, etc., it is preferably on the opposite side of the polyester film facing the battery side substrate (the surface on which the easy adhesion layer is formed). Provided.

Water vapor permeability of the inorganic layer as the (moisture ^{permeability),} 100 g / m is preferably ^{2 · d~10 -6 g / m 2} · d, more preferably ^{10 -1 g / m 2 · d~10} -5 g / m is ² · d, more preferably ^{10 -2 g / m 2 · d~10} -4 g / m 2 · d.
The moisture permeability can be measured based on JIS Z0208.
In order to form an inorganic layer having such moisture permeability, the following dry method is suitable.

  As a method of forming a gas barrier inorganic layer (hereinafter also referred to as a gas barrier layer) by a dry method, resistance heating vapor deposition, electron beam vapor deposition, induction heat vapor deposition, and vacuum vapor deposition such as an assist method using plasma or ion beam for these. , Reactive sputtering method, ion beam sputtering method, sputtering method such as ECR (electron cyclotron) sputtering method, physical vapor deposition method such as ion plating method (PVD method), heat, light, plasma, etc. Examples include chemical vapor deposition (CVD). Among these, a vacuum vapor deposition method in which a film is formed by a vapor deposition method under vacuum is preferable.

Here, when the material forming the gas barrier layer is mainly composed of inorganic oxide, inorganic nitride, inorganic oxynitride, inorganic halide, inorganic sulfide, etc., it is the same as the composition of the gas barrier layer to be formed. It is possible to directly volatilize the material and deposit it on a substrate or the like. However, when this method is used, the composition changes during volatilization, and as a result, the formed film does not exhibit uniform characteristics. There is a case. Therefore, 1) As a volatilization source, a material having the same composition as the barrier layer to be formed is used. In the case of inorganic oxide, oxygen gas, in the case of inorganic nitride, nitrogen gas, in the case of inorganic oxynitride, oxygen gas A method of volatilizing a mixed gas of nitrogen gas, halogen gas in the case of inorganic halide, and sulfur gas in the case of inorganic sulfide while being introduced into the system, and 2) inorganic substance group as a volatile source And volatilizing this, oxygen gas in the case of inorganic oxide, nitrogen gas in the case of inorganic nitride, mixed gas of oxygen gas and nitrogen gas in the case of inorganic oxynitride, and inorganic halide In the case of halogen-based gas, in the case of inorganic sulfide, sulfur-based gas is introduced into the system, and the inorganic substance and the introduced gas are reacted and deposited on the surface of the substrate. Use this To form an inorganic group layer, and in the case of inorganic oxide, it is in an oxygen gas atmosphere, in the case of inorganic nitride, in a nitrogen gas atmosphere, in the case of inorganic oxynitride, oxygen gas and nitrogen gas In a mixed gas atmosphere, in the case of an inorganic halide, a method of reacting an introduced gas with an inorganic layer by holding in a halogen-based gas atmosphere, and in the case of an inorganic sulfide, a sulfur-based gas atmosphere, and the like.
Among these, 2) or 3) is more preferably used because it is easy to volatilize from a volatile source. Furthermore, the method 2) is more preferably used because the film quality can be easily controlled. When the barrier layer is an inorganic oxide, the inorganic group is used as a volatilization source, volatilized to form an inorganic group layer, and then left in the air to naturally oxidize the inorganic group. The method is also preferable because it is easy to form.

  It is also preferable to use an aluminum foil as a barrier layer by bonding. The thickness is preferably 1 μm or more and 30 μm or less. When the thickness is 1 μm or more, water hardly penetrates into the polyester film during the lapse of time (thermo) and hardly causes hydrolysis, and when it is 30 μm or less, the thickness of the barrier layer does not become too thick, and the barrier layer The stress does not cause the film to bend.

<Solar cell module>
The solar cell module of the present invention is configured by providing the above-described white laminated polyester film of the present invention as a solar cell backsheet.
The solar cell module of the present invention is provided for the solar cell module of the present invention. The white laminated polyester film of the present invention described above has excellent long-term adhesion to the adjacent layer. Stable power generation performance can be maintained.

  Specifically, the solar cell module of the present invention is provided on a transparent base material (a front base material such as a glass substrate) on which sunlight enters and the base material, and seals the solar cell element and the solar cell element. An element structure portion having a sealing material to be stopped, and a white laminated polyester film (solar cell backsheet) disposed on the side opposite to the side where the substrate such as a glass substrate of the element structure portion is located, and transparent It has a laminated structure of a front substrate / element structure portion / back sheet. Specifically, an element structure portion in which a solar cell element that converts light energy of sunlight into electric energy is disposed on a transparent front base material disposed on a side where sunlight directly enters, and An element structure portion (for example, a solar cell) including a solar cell element is sealed with an ethylene-vinyl acetate (EVA) system between the front substrate and the white laminated polyester film. It is configured to be sealed and bonded using a stopper. The white laminated polyester film of the present invention is particularly excellent in adhesiveness with EVA and can improve long-term durability.

  The members other than the solar cell module, the solar cell, and the back sheet are described in detail in, for example, “Photovoltaic power generation system constituent material” (supervised by Eiichi Sugimoto, Kogyo Kenkyukai, published in 2008).

  The transparent base material should just have the light transmittance which sunlight can permeate | transmit, and can be suitably selected from the base materials which permeate | transmit light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

  Examples of solar cell elements include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic. Various known solar cell elements such as II-VI group compound semiconductor systems can be applied. A space between the substrate and the polyester film can be configured by sealing with a resin (so-called sealing material) such as an ethylene-vinyl acetate copolymer.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

(Example 1)
<Synthesis of polyester>
(Esterification)
In the first esterification reactor, 4.7 tons (4700 kg) of high-purity terephthalic acid and 1.8 tons (1800 kg) of ethylene glycol are mixed over 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. To the first esterification reactor. Further, an ethylene glycol solution of a citric acid chelate titanium complex (VERTEC AC-420, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied, and the average residence time is maintained at 250 ° C. in the reaction vessel with stirring. The reaction was carried out for about 4.3 hours. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of Ti element. At this time, the acid value of the obtained oligomer was 600 equivalent / ton.
This reaction product was transferred to a second esterification reaction vessel, and reacted under stirring at a reaction vessel temperature of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 200 equivalents / ton. The inside of the second esterification reaction tank is partitioned into three zones, and an ethylene glycol solution of magnesium acetate is continuously supplied from the second zone so that the amount of Mg added is 67 ppm in terms of element, From the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the added amount of P was 65 ppm in terms of element.

(Polycondensation reaction)
The esterification reaction product obtained above was continuously supplied to the first polycondensation reaction tank, and with stirring, the reaction temperature was 270 ° C., the reaction tank internal pressure was 2.67 × 10 ⁻³ MPa (20 Torr), and the average The polycondensation was carried out with a residence time of about 1.8 hours.
Further, the mixture was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 6.67 × 10 ⁻⁴ MPa (5 Torr), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.

Subsequently, it was further transferred to the third triple condensation reaction tank, in which the temperature in the reaction tank was 278 ° C., the pressure in the reaction tank was 2.0 × 10 ⁻⁴ MPa (1.5 Torr), and the residence time was 1.5 hours. The reaction product (polyethylene terephthalate; hereinafter abbreviated as PET) was obtained by reaction (polycondensation) under the following conditions.
The obtained PET (reaction product) was measured using high resolution high frequency inductively coupled plasma mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology). As a result, Ti = 9 ppm, Mg = 67 ppm, and P = 58 ppm. P is slightly reduced with respect to the initial addition amount, but is estimated to have volatilized during the polymerization process.

(Solid phase polymerization)
The above polymerized PET was pelletized (diameter 3 mm, length 7 mm), and the resulting resin pellet (inherent viscosity IV = 0.60 dl / g, terminal carboxy group concentration = 16 equivalents / ton) was obtained as follows. The solid phase polymerization was carried out.

In the solid phase polymerization, the polyester polymerized by the above-described esterification reaction was heated at 140 ° C. for 7 minutes with nitrogen having a dew point temperature of −30 ° C., and pre-crystallization was performed for the purpose of preventing sticking during the solid phase polymerization.
Next, it was dried at 160 ° C. for 4 hours using heated nitrogen having a dew point temperature of −30 ° C., and the moisture content in the resin was adjusted to 50 ppm or less.

Next, after the dried polyester resin was preheated to 210 ° C., solid-state polymerization was advanced by circulating nitrogen at 210 ° C. for 38 hours. As nitrogen circulation conditions, the gas ratio (the amount of nitrogen gas circulated with respect to the amount of discharged resin) is 1.5 m ³ / kg, the superficial velocity is 0.08 m / sec, the ethylene glycol concentration is 240 ppm, the water concentration is 12 ppm, the ethylene glycol and water The solid phase polymerization was allowed to proceed by using nitrogen having a molar partial pressure ratio of 20 (methylene partial pressure of ethylene glycol / molar partial pressure of water) of 20. In order to obtain the above mixed gas composition, high purity ethylene glycol having a water content of 100 ppm was used for the ethylene glycol scrubber, and the scrubber temperature was set to 35 ° C. The pressure in the scrubber was in the range of 0.1 MPa to 0.11 MPa.
Next, the resin (500 kg / h) discharged from the reaction step was cooled to 60 ° C.

<Preparation of master batch>
Titanium oxide (white inorganic particles) (PF-739, average primary particle size: 250 nm, surface polyol treatment, manufactured by Ishihara Sangyo Co., Ltd.) was vacuum-dried at 160 ° C. for 24 hours to adjust the water content of titanium oxide to 2000 ppm.
PET pellets (polyester resin) (intrinsic viscosity: 0.78 dl / g, terminal carboxy group concentration: 11 equivalents / ton) after solid phase polymerization was put into a vented twin screw extruder and kneaded at 285 ° C. Thereafter, titanium oxide having a water content of 2000 ppm by a side feed method was put into a twin screw extruder with a vent to knead PET pellets and titanium oxide.
Deaeration was performed at a vacuum pressure of 300 Pa downstream from the position where the titanium oxide was charged in the vented twin-screw extruder.
In this way, a master batch (MB) was produced.
Here, the ratio of PET pellets to titanium oxide was such that titanium oxide was 50% by mass with respect to the total mass of the masterbatch.
The master batch was pelletized into a master pellet.

<Film forming process>
(Extrusion / Filming)
In the first layer, the PET and the master pellet are mixed so that the concentration of titanium oxide (white inorganic particles) is 12% by mass, dried to a water content of 100 ppm or less, and then supplied to the extruder 1. And melt extruded at 285 ° C. As the extruder 1, a double vent type co-rotating and meshing twin screw extruder having two vents was used. The vacuum pressure of the vent part was 300 Pa.
The second layer was prepared by mixing the PET and the recycled chip so that the titanium oxide concentration was 1% by mass. This was dried to a water content of 100 ppm or less, then supplied to the extruder 2 and melt extruded at 285 ° C. As the extruder 2, a double vent type co-rotating mesh type twin screw extruder provided with two vents was used like the extruder 1. The vacuum pressure of the vent part was 300 Pa.
Here, the recycled chip is a chip produced by trimming and crushing the end portion in the width direction of the laminated film already formed, and contains several mass% of titanium oxide.
The melt (melt) extruded from the exit of each extruder is passed through a gear pump and a filter (pore diameter 20 μm), and then merged using a two-layer feed block device, and the chill roll from the die while maintaining the laminated state. Extruded. The extruded melt was brought into close contact with the cooling roll using an electrostatic application method. As the cooling roll, a hollow cast roll is used, and the temperature can be adjusted by passing water as a heating medium.

(Extension / winding)
The unstretched film extruded and solidified by the above method was successively biaxially stretched by the following method to obtain a laminated film having a thickness of 250 μm.
The stretching was performed in the order of longitudinal stretching at 95 ° C. and transverse stretching at 140 ° C. in the order of longitudinal stretching and transverse stretching. Thereafter, the film was heat-fixed at 210 ° C. for 12 seconds and then relaxed by 3% in the lateral direction at 205 ° C. After stretching, both ends were trimmed by 10 cm, and after thicknessing was applied to both ends, 3000 m was wound around a resin core having a diameter of 30 cm. The width was 1.5 m. The thickness of the first layer was 50 μm, and the thickness of the second layer was 200 μm.
The void in the first layer generated by the longitudinal stretching had a surface area of 2400 m ² / g after completion of biaxial stretching.

-Longitudinal stretching-
The unstretched film was passed between two pairs of nip rolls having different peripheral speeds, and stretched in the longitudinal direction (conveying direction) under the following conditions.
・ Preheating temperature: 95 ℃
-Stretching temperature: 95 ° C
-Stretching ratio: 3.5 times-Stretching speed: 3000% / second

-Horizontal stretching-
The longitudinally stretched film was stretched transversely using the tenter under the following conditions.
-Preheating temperature: 110 ° C
-Stretching temperature: 120 ° C
-Stretch ratio: 3.9 times-Stretch speed: 70% / second

<Measurement / Evaluation>
The laminated film obtained above was subjected to the following measurements and evaluations.

[Concentration of terminal carboxy group (AV; unit: equivalent / ton)]
The terminal carboxy group concentration was measured for the first layer and the second layer of the obtained laminated film. For measurement, the first layer and the second layer are scraped, the first layer or the second layer is completely dissolved in a mixed solution of benzyl alcohol / chloroform (= 2/3 [volume ratio]), and phenol is used as an indicator. Using red, the solution was titrated with a standard solution (0.025N KOH-methanol mixed solution) and calculated from the appropriate amount.
The evaluation results are shown in Table 1.

[Thickness]
The thickness of the obtained laminated film is measured using a contact-type film thickness meter (manufactured by Anritsu), 10 points are sampled at equal intervals over 0.2 m in the longitudinal direction, and the thicknesses of these 10 points are measured. . The average thickness of these 10 points is obtained and set as the average thickness of the film.
The thickness of the 1st layer and the 2nd layer was measured by measuring each layer thickness of film cutting.

[Weatherability]
About the hydrolysis resistance of the obtained laminated | multilayer film, it can evaluate by breaking elongation retention time. This is calculated | required from the fall of the breaking elongation at the time of promoting hydrolysis by heat-processing (thermo process) forcibly. A specific measuring method is shown below.

(Hydrolysis resistance)
The hydrolysis resistance of the laminated film was evaluated by the following method.
The film was aged in an atmosphere of 120 ° C. and 100% RH, and the elongation at break was measured as the mechanical properties of the film. Specifically, after performing heat treatment (thermo treatment) at 120 ° C. and 100% RH for 10 hours to 300 hours [hr] at intervals of 10 hours, the elongation at break of each thermo-treated sample was measured and obtained. The measured value is divided by the breaking elongation before the thermo treatment to obtain the breaking elongation retention ratio at each thermo treatment time. Then, the horizontal axis represents the thermo time, and the vertical axis represents the breaking elongation retention rate, and the results are plotted, and the processing time until the breaking elongation retention rate reaches 50% (breaking elongation retention time) [hr] Ask for.

Breaking elongation retention rate = breaking elongation after treatment ÷ breaking elongation before treatment × 100

The elongation at break is set to a tensile tester and the elongation until it breaks by pulling at 20 mm / min in an environment of 25 ° C. and 60% RH. At each divided point, the measurement is repeated 5 times while shifting the position to MD (Machine Direction) at intervals of 20 cm, a total of 50 points are measured, and the obtained values are averaged.
Hydrolysis resistance was evaluated according to the following evaluation criteria.

Evaluation criteria are shown below.
A: Breaking elongation retention time is 105 hours or more.
B: Break elongation retention time is 95 hours or more and less than 105 hours.
C: Break elongation retention time is 85 hours or more and less than 95 hours.
D: Break elongation retention time is 85 hours or more and less than 75 hours.
E: Breaking elongation retention time is less than 75 hours.

[Reflectance]
An integrating sphere is attached to a spectrophotometer (manufactured by Shimadzu Corporation, self-recording spectrophotometer “UV-3150”), and the reflectance of a standard white plate (manufactured by SphereOptics, white standard plate “ZRS-99-010-W”). Was calibrated as 100%, and light was incident on the white laminated polyester film from the second layer side to measure the spectral reflectance (%). The measurement was performed in 1 nm increments in a wavelength region of 400 nm to 800 nm, an average value was obtained, and evaluation was performed according to the following evaluation criteria.

Evaluation criteria are shown below.
A: The reflectance is 88% or more.
B: The reflectance is 84% or more and less than 88%.
C: The reflectance is 80% or more and less than 84%.
D: The reflectance is 75% or more and less than 80%.
E: Reflectance is less than 75%.

[PVBS suitability]
Evaluation was performed according to the following criteria based on the evaluation results of hydrolysis resistance and reflectance. In addition, if an evaluation result is A, B, or C, it can be judged that there exists suitability for a solar cell backsheet (Photovoltaic Back Sheet; PVBS).

Evaluation criteria are shown below.
A: Both hydrolysis resistance and reflectance are A.
B: Hydrolysis resistance or reflectance is A, or hydrolysis resistance and reflectance are both B.
C: Either hydrolysis resistance or reflectance is C, or hydrolysis resistance and reflectance are both C.
D: Either hydrolysis resistance or reflectance is D.
E: Either hydrolysis resistance or reflectance is E.

(Example 2 to Example 9, Comparative Example 1 to Comparative Example 5)
In Examples 2 to 9 and Comparative Examples 1 to 5, the titanium oxide concentrations of the first layer and the second layer in Example 1 were changed to the values shown in Table 1, or A laminated film was obtained in the same manner as in Example 1 except that the terminal carboxy group concentrations of the first layer and the second layer were changed to the values shown in Table 1, and the same evaluation as in Example 1 was performed. went. The evaluation results are shown in Table 1.

(Example 10 to Example 11)
Examples 10 to 11 are the same as those in Example 1 except that the surface area A (A / C) of the void with respect to the titanium oxide content C of the first layer in Example 1 was changed to the value shown in Table 1. In the same manner as in Example 1, a laminated film was obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Example 12 to Example 13)
Examples 12 to 13 were the same as in Example 1 except that the water content of titanium oxide was changed to the value shown in Table 1 in the production of the masterbatch in Example 1, and the laminated film was prepared in the same manner as in Example 1. The same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

(Example 14)
Example 14 is the production of a master batch in Example 1, and a laminated film was obtained in the same manner as in Example 1 except that the intrinsic viscosity of the PET pellet was changed to 0.78 dl / g. Similar evaluations were made. The evaluation results are shown in Table 1.

(Example 15)
Example 15 is the production of the masterbatch in Example 1, and the intrinsic viscosity of the PET pellet is changed to 0.78 dl / g, and the void surface area A (A / C) with respect to the titanium oxide content C of the first layer. A laminated film was obtained in the same manner as in Example 1 except that the value was changed to the value shown in Table 1, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

(Comparative Example 6 to Comparative Example 7)
Comparative Example 6 to Comparative Example 7 were the same as in Example 1 except that the thicknesses of the first layer and the second layer in Example 1 were changed to the values shown in Table 1, respectively. And the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

(Comparative Example 8 to Comparative Example 9)
Comparative Example 8 to Comparative Example 9 are films in which the first layer in Example 1 is not provided and only the second layer is formed as a single layer, or the first layer is not provided and the second layer is provided. Evaluation was made in the same manner as in Example 1 for a film in which only a single layer was extruded and the content of titanium oxide in the second layer was changed to the values shown in Table 1. The evaluation results are shown in Table 1.

(Comparative Example 10)
Comparative Example 10 is a production of a masterbatch in Example 1, and a laminated film was obtained in the same manner as in Example 1 except that titanium oxide was added together with the PET pellets from the inlet, and the same evaluation as in Example 1 was performed. It was. The evaluation results are shown in Table 1.

(Comparative Example 11)
Comparative Example 11 was a production of a masterbatch in Example 1, and a laminated film was obtained in the same manner as in Example 1 except that degassing was not performed during melt kneading, and the same evaluation as in Example 1 was performed. . The evaluation results are shown in Table 1.

(Comparative Example 12)
Comparative Example 12 is a production of a masterbatch in Example 1, and a laminated film was obtained in the same manner as in Example 1 except that titanium oxide was added together with PET pellets from the inlet and degassing was not performed during melt kneading. The same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

  From Table 1, it can be seen that the Examples are excellent in hydrolysis resistance and reflectance, and have PVBS suitability.

(Example 16 to Example 30)
<Preparation of solar cell back sheet>
On the surface of the second layer of each laminated film of Examples 1 to 15, an easy-adhesion layer composed of coating layer A and coating layer B was formed as follows, and the suns of Examples 16 to 30 were formed. A battery back sheet was prepared.

(Formation of coating layer A)
A coating layer A-forming composition having the following composition is applied to the surface of the second layer side of the laminated film so that the film thickness after drying is 1.0 μm, and dried at 170 ° C. for 2 minutes to form a laminated film. Coating layer A was formed.

(Composition for forming coating layer A)
Epocros WS700 (manufactured by Nippon Shokubai Co., Ltd.) 29.0 parts by mass Ponlon XPS002 (manufactured by Mitsui Chemicals) 144.7 parts by mass Sodium-1.2- {Bis (3, 3, 4, 4, 5, 5 , 6,6,6-nanofluorohexylcarbonyl)} ethanesulfonate (solid content 2% by mass) 3.6 parts by mass Distilled water 822.6 parts by mass

(Formation of coating layer B)
A composition for forming a coating layer B having the following composition is applied to the surface of the coating layer A of the laminated film on which the coating layer A is formed so that the film thickness after drying is 0.3 μm, and the composition is formed at 170 ° C. for 2 minutes. The coating layer B was formed by drying.

(Composition for forming coating layer B)
Arrow Base SE-1013N (manufactured by Unitika Ltd.) 86.4 parts by mass AS-563A (manufactured by Daicel Finechem Co., Ltd.) 15.6 parts by mass Epocros WS700 (manufactured by Nippon Shokubai Co., Ltd.) 11.1 parts by mass SI- 3 (compound having the following structure) 64.7 parts by mass Distilled water 822.2 parts by mass

(Example 31 to Example 45)
<Production of solar cell module>
Using the solar cell backsheets of Examples 16 to 30, solar cell modules of Examples 31 to 45 were produced by the following method.

  3.2 mm thick tempered glass (transparent substrate), EVA sheet (encapsulant) (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell (solar cell element), EVA Sheets (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.) and any one of the solar cell backsheets of Examples 16 to 30 were superposed in this order, and a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminating machine) was laminated. Each member and the EVA sheet were bonded to each other by hot pressing. A solar cell module was produced as described above.

(Evaluation)
About each solar cell module of Example 31-Example 45 produced above, when the electric power generation operation test was done, in any Example, favorable electric power generation performance was shown as a solar cell.

Claims (15)

A first resin containing a polyester resin, wherein the content of white inorganic particles is 5% by mass or more and 15% by mass or less with respect to the total mass of the layer, and the terminal carboxy group concentration of the layer is 10 equivalent / ton to 40 equivalent / ton. Layer of
A second layer containing a polyester resin, wherein the content of white inorganic particles is 5% by mass or less based on the total mass of the layer, and the terminal carboxy group concentration of the layer is 5 equivalents / ton to 25 equivalents / ton; Have
The thickness of the first layer is thinner than the thickness of the second layer;
White laminated polyester film for solar battery backsheet. The solar battery back according to claim 1, wherein the first layer has voids, and the surface area A of the voids and the content C with respect to the total mass of the layer of the white inorganic particles satisfy the following relational expression 1. White laminated polyester film for sheet.
1 <A / C <100 Relational expression 1   The white laminated polyester film for a solar battery backsheet according to claim 1 or 2, wherein the terminal carboxy group concentration of the first layer is 12 equivalent / ton to 35 equivalent / ton.   The thickness of the said 1st layer is 20 micrometers-100 micrometers, and the thickness of the said 2nd layer is 50 micrometers-300 micrometers, The white laminated polyester for solar cell backsheets of any one of Claims 1-3. the film.   The ratio of the thickness of the said 1st layer and the thickness of the said 2nd layer is 1: 2-1: 10, The white lamination | stacking for solar cell backsheets of any one of Claims 1-4. Polyester film.   The said white inorganic particle is a titanium oxide, The white laminated polyester film for solar cell backsheets of any one of Claims 1-5. Into the extruder charged with the polyester resin, white inorganic particles whose water content is reduced to 2000 ppm or less are charged by the side feed method, and deaeration is performed downstream from the position where the white inorganic particles are charged in the extruder. A master batch production process for producing a master batch;
By co-extruding the first raw material resin containing the master batch and the polyester resin produced in the master batch production step, and the second raw material resin containing at least the polyester resin, the content of the white inorganic particles is The first layer having a terminal carboxy group concentration of 10 to 40 equivalents / ton and a content of white inorganic particles of 5 to 15% by weight with respect to the total weight of the layer And a second layer having a terminal carboxy group concentration of 5 eq / ton to 25 eq / ton with respect to the total mass of the first layer, and the thickness of the first layer is A film forming step of forming a white laminated polyester film for solar battery backsheet thinner than the thickness of the second layer;
The manufacturing method of the white laminated polyester film for solar cell backsheets which has this.   The method for producing a white laminated polyester film for a solar battery backsheet according to claim 7, wherein the white inorganic particles introduced by the side feed method in the masterbatch production step is titanium oxide.   9. The production of a white laminated polyester film for a solar battery backsheet according to claim 7, wherein the polyester resin charged in the master batch production step has an intrinsic viscosity of 0.70 dl / g to 0.80 dl / g. Method. The first layer has a void inside the layer, and the surface area A of the void and the content C with respect to the total mass of the layer of the white inorganic particles satisfy the following relational expression 1. The manufacturing method of the white laminated polyester film for solar cell backsheets of any one of 9.
1 <A / C <100 Relational expression 1   The white lamination | stacking for solar cell backsheets of any one of Claims 7-10 in which the white inorganic particle thrown in by the said masterbatch preparation process is a white inorganic particle by which the water content was reduced to 1000 ppm or less. A method for producing a polyester film.   The solar cell backsheet which has a white laminated polyester film for solar cell backsheets of any one of Claims 1-6.   The solar cell backsheet which has a white laminated polyester film for solar cell backsheets manufactured by the manufacturing method of any one of Claims 7-11.   The solar cell module provided with the solar cell backsheet of Claim 12 or Claim 13.   A transparent base material on which sunlight is incident, an element structure portion provided on the base material and having a solar cell element and a sealing material for sealing the solar cell element, and the base material of the element structure portion The solar cell module provided with the solar cell backsheet of Claim 12 or Claim 13 arrange | positioned on the opposite side to the side in which this is located.