KR102051724B1 - Polyester film, process for producing same, back-protective sheet for solar cell, and solar cell module - Google Patents

Abstract

One embodiment of the present invention includes the white particles, satisfies Expressions 1 and 2, and is the maximum value and the minimum value of 10I + T values respectively obtained in two or more regions in the width direction perpendicular to the longitudinal direction. The polyester film which shows the fluctuation | variation range which is represented by the absolute value of the difference of 2.0 or less, its manufacturing method, a solar cell back surface protective sheet, and a solar cell module are provided.
2 mass% ≤ T ≤ 20 mass% ...
0.6dL / g≤I≤0.8dL / g
In formula, T shows the content rate of the white particle with respect to the film mass per unit volume, and I shows the intrinsic viscosity in the area | region where T was measured.

Description

Polyester film and its manufacturing method, solar cell back protective sheet and solar cell module {POLYESTER FILM, PROCESS FOR PRODUCING SAME, BACK-PROTECTIVE SHEET FOR SOLAR CELL, AND SOLAR CELL MODULE}

The present disclosure relates to a polyester film, a method for producing the same, a back protective sheet for a solar cell, and a solar cell module.

Polyester films are widely used as various optical films in view of excellent strength, dimensional stability, chemical resistance, and the like, and the use of colored polyester films has also been expanded in accordance with applications. For example, a white polyester film colored in white has recently been used as a support for a rear protective sheet (so-called back sheet) disposed on the rear surface of a solar cell module for the purpose of improving the power generation efficiency.

In order to make a polyester film suitable for a back sheet, in addition to durability to heat | fever, light, etc., it is calculated | required to be provided with the performance according to a use. Specifically, for example, in the case of coating the adjacent layer with a polyester film, for example, it is required that coating unevenness, for example, in which the thickness variation occurs in the coating layer, is unlikely to occur. Moreover, when bonding a polyester film to the sealing material of a solar cell element, wrinkles hardly arise at the time of bonding, and adhesiveness which does not peel easily after bonding is calculated | required.

As a technique related to the above circumstances, if the polyester film used for the liquid crystal display has a thickness variation, color irregularity or luminance nonuniformity tends to occur, so that the thickness of the lip in the width direction of the clasp is adjusted, and the film thickness, and By reducing the standard deviation of the thickness of the film width direction with respect to the average film thickness, the laminated polyester film which suppresses the thickness variation of the film width direction is proposed (for example, refer Unexamined-Japanese-Patent No. 2010-52329). Moreover, in the magnetic recording medium use, the technique which suppresses the coarsening of the film surface is proposed by making the number of spherical coarse particle | grains below a specific value (for example, refer Unexamined-Japanese-Patent No. 2000-80258). ).

The polyester film is applied to various various uses, and the method used differs according to a use, etc., for example, a functional layer may be laminated | stacked on a polyester film by application | coating etc., or affixed to another member. When a polyester film is colored white, it is usual that white particle | grains, such as titanium oxide, are contained in a film. When the presence state of the white particle in a film is uniform, comparatively, film thickness also tends to become uniform, and surface unevenness tends to become small. By the way, when forming a polyester film through a die using a melt extruder, the flow system of the molten resin which distribute | circulates the inside of an extruder, a die, etc., in other words, the flow system of the white particle in a molten resin is not constant, distribution Is easy to occur. Moreover, distribution tends to appear also in the intrinsic viscosity of resin itself. The occurrence of such a distribution is one of the factors of the thickness variation of the film itself.

Moreover, in order to improve the dispersion | distribution state of the white particle in polyester, the method of controlling the particle size or particle size distribution of a particle | grain, or surface friction, etc., or changing the kneading conditions at the time of extrusion is known, and it is known to disperse | distribute Even if the generation pitch of the thickness variation is effective in the range of several μm to several mm, the improvement effect of the thickness variation cannot be expected when the generation pitch of the thickness variation of the dispersion is in the range of several tens of mm or more.

In the invention described in Japanese Unexamined Patent Application Publication No. 2010-52329, a technique of suppressing the thickness variation in the film width direction by considering the film thickness and the standard deviation of the film thickness, but it is influenced by the unevenness of the content of white particles and the intrinsic viscosity. Since this is not eliminated, the improvement effect on the thickness variation of the film is also small.

In the invention described in JP-A-2000-80258, by reducing the coarse particles, protrusions smaller than a few mm due to coarse protrusions are reduced, but the thickness variation that appears in pitches of several tens of mm or more cannot be eliminated.

The present disclosure has been made in view of the above, and has a polyester film having excellent thickness uniformity in a width direction perpendicular to the film longitudinal direction, a method for producing the same, and a solar cell back protective sheet and a solar cell module excellent in long-term durability. It aims to provide.

Specific means for solving the problem include the following aspects.

The difference between the maximum value and the minimum value among 10I + T values including <1> white particles and satisfying the following formulas 1 and 2 and obtained in two or more regions in the width direction perpendicular to the longitudinal direction: It is a polyester film whose range of fluctuations represented by an absolute value is 2.0 or less.

2 mass% ≤ T ≤ 20 mass% ...

0.6dL / g≤I≤0.8dL / g

In formula, T shows the content rate of the white particle with respect to the film mass per unit volume, and I shows the intrinsic viscosity of the polyester in the area | region where T was measured.

<2> white particle | grains are the polyester films as described in <1> which are titanium oxide particles.

It is a polyester film as described in <1> or <2> whose variation width (DELTA) T of the content rate T of white particle in the width direction orthogonal to a <3> longitudinal direction is 1.5 mass% or less.

It is a polyester film in any one of <1>-<3> whose fluctuation range (DELTA) I of intrinsic viscosity I in the width direction orthogonal to a <4> longitudinal direction is 0.1 dL / g or less.

<5> Moreover, the elasticity modulus YT of the width direction orthogonal to a longitudinal direction satisfy | fills following Formula 3, and is an absolute value of the difference of the maximum value and minimum value among YT measured in two or more areas in the width direction orthogonal to a longitudinal direction, respectively. The fluctuation range (DELTA) YT shown is a polyester film in any one of <1>-<4> which satisfy | fills following formula 4.

3500 MPa ≤ YT ≤ 5000 MPa ...

0 MPa <ΔYT≤500MPa

It is a polyester film in any one of <1>-<5> which is a <6> white polyethylene terephthalate film.

It is the polyester film in any one of <1>-<6> whose fluctuation range of the thickness in the width direction orthogonal to a <7> longitudinal direction is 5% or less.

<8> Thickness is a polyester film in any one of <1>-<7> whose thickness is 200 micrometers or more and 350 micrometers or less.

<9> It is a back protective sheet for solar cells which has the polyester film in any one of <1>-<8>.

<10> It is a solar cell module provided with the back protective sheet for solar cells as described in <9>.

<11> Melting step of mixing white particles in polyester to melt with an extruder, conveying step of conveying polyester melted with extruder to a die through a pipe, and polyester conveyed to the die under conditions A and conditions It is a manufacturing method of the polyester film including the film forming process of shape | molding in a sheet form on at least one condition of B, and forming a polyester sheet, and the cooling process of cooling the formed polyester sheet.

 Condition A: The following formulas 5 and 6 are satisfied.

 C0 <C1 ... Expression 5

C2 <C1

 Condition B: All the following formulas 7 to 11 are satisfied.

T0 <T1 ...

T2 <T1 ...

270 ° C≤T0≤320 ° C

270 ° C≤T1≤320 ° C

270 ° C≤T2≤320 ° C

In formulas 5 to 6, C0 represents a lip clearance in the center portion in the width direction of the die, and C1 represents the lip clearance in each center portion between the center portion and one end or the other end in the width direction of the die. An average value is shown, and C2 represents an average value of each lip clearance at both ends in the width direction of the die. All values in C0, C1, or C2 are in millimeters.

In Formulas 7-11, T0 represents the sheet temperature of the center part in the width direction of the polyester sheet at the time of a point away from die, and T2 represents the average value of each sheet temperature of the both ends in the width direction of a polyester sheet. , T1 represents the average value of the sheet temperature of each center portion between the center portion and one end or the other end in the width direction of the polyester sheet.

The <12> conveyance process is a manufacturing method of the polyester film as described in <11> which conveys a polyester to die on condition which satisfy | fills following formula 12.

0 ° C <T11-T10≤20 ° C ...

In formula, T10 represents the resin temperature of the center part in the radial direction of the at least 1 area | region in the longitudinal direction of a piping, and T11 is 5 mm in radial direction from the inner wall surface of the area | region where the resin temperature of the piping was measured. The resin temperature at the position is shown.

According to this disclosure, the polyester film excellent in the thickness uniformity in the width direction orthogonal to a film longitudinal direction, and its manufacturing method are provided.

Moreover, according to this indication, the solar cell back surface protection sheet which is excellent in long-term durability, and a solar cell module are provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a graph which shows the relationship between the intrinsic viscosity I and the content rate T of a white particle for demonstrating the range of the polyester film which concerns on embodiment of this invention.
It is a figure for demonstrating the measuring method of content rate T and intrinsic viscosity I of a white particle.
It is a schematic diagram which shows the structural example of the polyester manufacturing apparatus which concerns on embodiment of this invention.
It is a schematic sectional drawing which shows the structural example of the twin screw extruder which comprises the polyester manufacturing apparatus of FIG.
It is a conceptual diagram explaining the state in which the flow in the center part has many in the flow of resin and white particle in a die | dye.
It is a conceptual diagram explaining the state which flows the resin and white particle which flow through the center part to both end sides in the flow of resin and white particle in a die | dye.
6 is a schematic diagram for explaining each lip clearance in the die.
7 is a schematic view for explaining the sheet temperature of the sheet discharged from the die.
It is a schematic diagram for demonstrating the method of measuring the temperature of resin which flows in the piping connected to die | dye.

Hereinafter, the polyester film of this indication, the manufacturing method of a polyester film, the back surface protective sheet for solar cells, and a solar cell module are demonstrated in detail.

<Polyester film and its manufacturing method>

The polyester film of one embodiment of the present invention contains white particles, satisfies Equations 1 and 2 below, and is further obtained in two or more regions in the width direction perpendicular to the longitudinal direction, respectively. The fluctuation range represented by the absolute value of the difference between the maximum value and the minimum value of is set to 2.0 or less. By satisfy | filling Formula 1-Formula 2 and making the fluctuation range of the value of 10I + T into 2.0 or less (that is, (DELTA) (10I + T) <= 2.0), the width direction orthogonal to a film longitudinal direction (henceforth a film width direction Thickness variation in the remarks) is remarkably improved.

In the present disclosure, the "width direction" refers to the transverse direction (TD) orthogonal to the longitudinal direction (Machine Direction, MD) of the polyester film.

Moreover, the polyester film of one Embodiment of this invention becomes a white polyester film colored by achromatic white by containing white particle | grains.

2≤T≤20

0.6≤I≤0.8 Equation 2

In Formula 1-Formula 2, T represents content rate [mass%] of the white particle with respect to film mass per unit volume, and I represents the intrinsic viscosity [dL / g] in the area | region where content rate T of titanium oxide was measured. Indicates.

In addition, said (DELTA) (10I + T) is the fluctuation range (unbalance) of the value of "10I + T" calculated | required from T and I in the at least 2 area | region measured in the width direction orthogonal to a longitudinal direction.

Generally, a polyester film is manufactured as a white polyester film by adding white particle | grains, such as a titanium oxide, into a polyester film, melt-extruding, and also extending | stretching, and extending | stretching. By the way, compared with the transparent polyester film which does not contain white particle | grains, a white polyester film tends to generate thickness deviation easily in the film width direction. When thickness variation occurs, coating unevenness occurs when the coating liquid is applied in a later step, or when a polyester film is bonded to a solar cell element and modularized, an ethylene vinyl acetate copolymer (ethylene-) sealing the solar cell element Bonding failure may occur between vinylacetate copolymer (EVA).

Although it is not necessarily clear about the cause which thickness deviation tends to generate | occur | produce in the film width direction of a polyester film, it is presumed that the following two developments contribute, and two developments combine and generate thickness variation. Hereinafter, the case where titanium oxide particles are used as the white particles will be described mainly.

(1) In the film width direction, there is a distribution of the content of the titanium oxide particles, and a portion having a large content of the titanium oxide particles has a high stretching stress, and a portion having a small content of the titanium oxide has a low stress. That is, it is presumed that the crystallization of the polyester is selectively promoted at the point where the titanium oxide particles are present, and the stress tends to be large.

(2) In the film width direction, there are also distributions of intrinsic viscosity (hereinafter sometimes abbreviated as IV), where a high IV has a high stretching stress, and a low IV has a low stretch stress. That is, in the place where IV is high, since molecular chain is long and entanglement also increases, it is estimated that extending | stretching stress becomes easy to selectively increase.

For this reason, in order to make thickness of a polyester film uniform, it is ideal to make all distribution of content rate in the film width direction of a titanium oxide particle, and distribution in the film width direction of IV uniform. However, in practice, the distribution of the above (1) and (2) in the film width direction tends to occur in the die during the film forming step of forming the molten resin into a sheet form via the die.

That is, in the widthwise center portion of the die, titanium oxide particles having a higher density than the polyester tend to flow with respect to the widthwise end portion of the die, and the content rate of the titanium oxide particles increases. Moreover, in the width direction center part of die | dye, since residence time of the polyester in die | dye is short, IV becomes high compared with periphery of a center part. On the other hand, in the width direction edge part of die | dye, the content rate of a titanium oxide particle on the contrary becomes low and IV also becomes low. For this reason, in the width direction center part of die | dye, the film inevitably high drawing stress is formed compared with the width direction edge part of die | dye.

Moreover, although the cause which the distribution generate | occur | produced in the width direction of the die | dye was shown above, not only die but also the ease of flow in extrusion piping etc. at the time of extruding molten resin to die | dye from an extruder, the content rate of titanium oxide particle also oxidizes It is estimated that it causes the distribution of the titanium particles and the IV, and causes the thickness variation in the film width direction.

Therefore, the thickness variation in the film width direction is caused by a complex phenomenon as described above, uniformizes the distribution in the film width direction of the content ratio of the titanium oxide particles and the resin and the intrinsic viscosity, and furthermore, the film width. It is difficult to improve the thickness deviation in the direction.

On the other hand, in view of the above (1), in order to improve dispersion of the titanium oxide particles in the polyester, it is known to control the particle size and particle size distribution of the titanium oxide particles or the surface friction, or to improve the kneading conditions. . By the way, even if the generation pitch of thickness deviation is effective in the range of several micrometers-several mm, when the generation pitch of thickness deviation occurs in tens of mm or more, the improvement effect of thickness variation cannot be expected.

In view of the above, in the present disclosure, in view of the content rate T and the intrinsic viscosity I of the white particles, a region in which the content rate T of the white particles such as titanium oxide is high in terms of T and I lowers the intrinsic viscosity I and is white. The region where the content rate T of the particles is low increases the intrinsic viscosity I and also suppresses the variation (unbalance) of "10I + T" represented by T and I within a specific range. In other words, T and I are selected to satisfy Equations 1 and 2 in the ridge region shown in FIG. 1. In Fig. 1, the whole of the ridge region cannot be said to satisfy the relationship of Δ (10I + T) ≤ 2.0, and the relationship of Δ (10I + T) ≤ 2.0 in accordance with the range of Expressions 1 to 2 is shown in FIG. Part of is to satisfy selectively.

By adjusting the relationship between T and I in this manner, the thickness variation in the film width direction can be made uniform.

(DELTA) (10I + T) represents n points (n≥2) in the transverse direction (TD; also called "film width direction") orthogonal to the longitudinal direction (Machine Direction, MD) of a polyester film. In the case of a measurement, the fluctuation range of n "10I + T" values is shown. The fluctuation range of the values of n "10I + T" is subtracted from the maximum value "max (10I + T)" from the maximum value "max (10I + T)" out of n values of "10I + T" as shown in the following formula. Appears as a difference. A concrete calculation method is mentioned later.

Δ (10I + T) = max (10I + T) -min (10I + T)

In embodiment of this invention, (DELTA) (10I + T) is made into 2.0 or less range. Since the fluctuation range of the value of "10I + T" is 2.0 or less, it becomes excellent in the thickness variation in the width direction of a polyester film.

For Δ (10I + T), the smaller the value is, the more preferable is the range of 1.5 or less, more preferably 1.0 or less, for the same reason as described above.

The content rate T [mass%] of the white particle with respect to the film mass per unit volume of 2 or more area | regions measured in the width direction orthogonal to a longitudinal direction shall be a range which satisfy | fills Formula (1).

T is the amount of white particles contained in the film per unit volume. When T is 2 mass% or more, the reflectance of a polyester film improves and when generating the polyester film which is embodiment of this invention as a back protection sheet of a solar cell module, power generation efficiency can be improved. Moreover, since T is 20 mass% or less, even if it satisfy | fills the relationship of (DELTA) (10I + T) <= 2.0, the phenomenon which causes deterioration of thickness deviation is suppressed.

As T, 2 mass%-12 mass% are more preferable, and 3 mass%-8 mass% are more preferable.

The calculation method of T value is mentioned later.

It is preferable that the fluctuation range ((DELTA) T) of the content rate T of the white particle in the film width direction of a polyester film is 1.5 mass% or less. When (DELTA) T is 1.5 mass% or less, thickness deviation improves more.

(DELTA) T is so preferable that it is small in the point which shows the grade of the fluctuation range, More specifically, 1.0 mass% or less is more preferable, 0.5 mass% or less is more preferable.

(DELTA) T is represented by the difference calculated | required by subtracting the minimum value Tmin from the maximum value Tmax among the measured T. ΔT can be obtained by the following formula.

ΔT = Tmax-Tmin

Intrinsic viscosity I in the at least 2 area | region where the content rate of titanium oxide was measured in the width direction orthogonal to a longitudinal direction is taken as the range which satisfy | fills said formula (2).

When I is 0.6 dL / g or more, since a polymerization degree does not become low too much, when a polyester film is arrange | positioned as a back protection sheet of a solar cell module, generation | occurrence | production of the cracks in a film is suppressed. Moreover, when I is 0.8 dL / g or less, even if it satisfy | fills the relationship of (DELTA) (10I + T) <= 2.0, the phenomenon which causes deterioration of thickness deviation is suppressed.

As I, 0.65 dL / g-0.75 dL / g are more preferable.

The calculation method of an I value is mentioned later.

It is preferable that the fluctuation range (ΔI) of the intrinsic viscosity I in the film width direction of the polyester film is 0.1 dL / g or less. When ΔI is 0.1 dL / g or less, the thickness deviation is further improved.

(DELTA) I is so preferable that it is small in the point which shows the grade of a fluctuation range, More specifically, 0.05 dL / g or less is more preferable, 0.03 dL / g or less is more preferable.

ΔI is represented by the difference obtained by subtracting the minimum value Imin from the maximum value Imax among the measured I. A concrete calculation method is mentioned later.

ΔI = Imax-Imin

T, I, and (DELTA) (10I + T) in said Formula 1-Formula 2 can be calculated | required with the following method with reference to FIG.

First, as shown in FIG. 2, ten square test pieces S of one side length A = 50mm are equally spaced D in the width direction TD orthogonal to the longitudinal direction MD of a polyester film. The content rate (T; mass%) and the intrinsic viscosity (I; dL / g) of a white particle are measured about each of the 10 test pieces S cut out and cut out.

The measurement of T and I is performed by the method shown below.

Using "T and I" measured for each test piece S, "10I + T" of each test piece S is calculated.

Then, the maximum value [max (10I + T)] and minimum value [min (10I + T)] are selected from the calculated value of "10I + T", and the fluctuation range of the value of "10I + T" is obtained from the following equation ( Δ (10I + T) representing an imbalance) is obtained.

Δ (10I + T) = max (10I + T) -min (10I + T)

T is a value measured as follows.

Using a fluorescence X-ray analyzer (model: XRF-1500, manufactured by Shimadzu Corporation), under the following conditions (Ti represents a titanium element), the amount of elements in the polyester film was measured by single-stage measurement. For example, in the case of titanium oxide, the amount of titanium element) is obtained to calculate the amount of white particles. In the case of a laminated polyester film, it is measured as content with respect to the whole polyester film by melt | dissolving a polyester film, shape | molding to a single layer in disk shape, and measuring it.

TABLE 1

I is a value measured as follows.

I is the value obtained by dividing the specific viscosity (η _sp = η _r −1) by subtracting 1 from the ratio η _r (= η / η ₀ ; relative viscosity) of the solution viscosity (η) and the solvent viscosity (η ₀ ). Is a value obtained by extrapolation in a state of zero concentration, and the solid state polymerization reaction after polymerization by melt-kneading and extruding the raw material resin (melting temperature, kneading speed, screw rotation speed, etc.), and esterification reaction. By adjusting the conditions, etc., it can adjust to the range which satisfy | fills Formula 2.

Specifically, I is a mixed solvent of 1,1,2,2-tetrachloroethane and phenol (1,1,2,2-tetrachloroethane / phenol = 2 / using a Uberode-type viscometer. 3, mass ratio), and is determined from the viscosity of the solution temperature-controlled at 25 ° C. In addition, when measuring I, a measurement is performed after white particle is removed by filtration.

It is preferable that the polyester film of one Embodiment of this invention satisfy | fills following formula 3 and formula 4 further.

3500 ≤ YT ≤ 5000

0 <ΔYT≤500 Equation 4

In Formulas 3 to 4, YT represents an elastic modulus [MPa] in the width direction orthogonal to the longitudinal direction of the polyester film, and ΔYT is at least 2 measured in the width direction orthogonal to the longitudinal direction of the polyester film. The fluctuation range [MPa] of the elasticity modulus YT of the width direction of a location is shown.

In addition, the elasticity modulus of the width direction of a polyester film measures by the measuring method of JISK7127. Sample piece E1 is cut out to a size of 10 mm in length (MD) in length and 150 mm in length in width direction (TD) orthogonal to MD, and with respect to sample piece E1, Strograph R2 manufactured by Toyo Seiki Seisakusho Co., Ltd. The tensile test is carried out using. The tensile test performs a tensile test in the width direction of sample piece E1 with the distance between chucks being 100 mm, and the tensile velocity being 10 mm / min. In the longitudinal direction passing through a specific point in the width direction, five specimen pieces E1 were cut out, the tensile test was repeated five times using five specimen pieces, and the average value of the five tensile modulus obtained was YT. do.

In Formula 3, when YT is 3500 Mpa or more, handling, such as a process and application | coating in a post process becomes favorable. Moreover, even when YT is 5000 Mpa or less, handling, such as a process and application | coating in a post process becomes favorable. Moreover, since YT is 5000 Mpa or less, the thickness variation (thickness fluctuation range) of a film can be suppressed small.

As YT, the range which satisfy | fills following formula 3a is more preferable for the same reason as the above.

4000≤YT≤4800 Equation 3a

YT can be adjusted by controlling the content rate of white particle | grains, the intrinsic viscosity of a polyester film, the draw ratio in MD and TD, extending | stretching temperature, etc.

In Equation 4, since ΔYT is 500 MPa or less, there is no significant difference in the degree of elongation, so that the thickness variation is further improved. In addition, in order to make ΔYT to 0 MPa, it is necessary to make the film properties such as the content rate of the white particles or the intrinsic viscosity of the polyester film very uniform, and in actuality, a huge installation cost is required for realization. Therefore, an embodiment that satisfies 0 MPa < DELTA YT is preferred.

As ΔYT, 10 MPa to 300 MPa are more preferable for the same reason as described above.

As for the polyester film of one Embodiment of this invention, it is preferable that the fluctuation range (unbalance; below, also called thickness deviation) of the thickness in a film width direction is 5% or less.

If the thickness imbalance is 5% or less, in the subsequent step, coating unevenness is unlikely to occur in the coating film when the desired coating liquid is applied onto the polyester film. Moreover, when bonding a polyester film to a solar cell element and making it modular, bonding defects (for example, wrinkles etc.) which are easy to generate | occur | produce between ethylene vinyl acetate (EVA) which seals a solar cell element are also suppressed.

Especially, 3% or less is more preferable, and, as for the fluctuation range (thickness variation) of the thickness in a film width direction, 2% or less is more preferable.

The range of 200 micrometers or more and 350 micrometers or less is preferable, and, as for the thickness of the polyester film of one Embodiment of this invention, the range of 220 micrometers or more and 320 micrometers or less is more preferable. When thickness is 200 micrometers or more, the improvement effect with respect to the fluctuation range (thickness variation) of the thickness in a film width direction is large. Moreover, when thickness is ensured, when a polyester film is arrange | positioned as a back surface protection sheet of a solar cell module, problems, such as an electric leak, can be suppressed. On the other hand, when thickness is 350 micrometers or less, it is preferable from a cost point of view.

It is preferable that the density | concentration (Acid value, AV) of the terminal carboxy group of a polyester film is 1 eq / ton (equivalent / ton; same or less)-25 eq / ton. As for the density | concentration of terminal carboxy group, it is more preferable that it is 3eq / ton or more, and it is more preferable that it is 5eq / ton or more. Moreover, it is preferable that the density | concentration of terminal carboxy group is 25 eq / ton or less, It is more preferable that it is 20 eq / ton or less, It is more preferable that it is 15 eq / ton or less.

In addition, "equivalent / ton" represents molar equivalents per ton.

By adjusting the density | concentration of the terminal carboxy group of a polyester film in the said range, white particle can be disperse | distributed to the surface layer area | region of a film, and partial discharge voltage can be raised. Moreover, since the viscosity of polyester can be made into an appropriate range by adjusting the density | concentration of terminal carboxyl group in said range, adhesiveness with respect to the sealing material (for example, ethylene-vinyl acetate copolymer) of an adjacent layer or a solar cell element. Can increase.

Next, the agent component in a polyester film is demonstrated.

The polyester film of one Embodiment of this invention contains polyester and white particle | grains at least, and may contain other components, such as a terminal sealing material of a polyester, a catalyst, as needed.

-polyester-

The polyester is not particularly limited as long as it is a material containing polyester, and may contain a metal element (for example, titanium element, magnesium element, etc.) derived from a catalyst. There is no restriction | limiting in particular in the kind of polyester, For example, what was synthesize | combined using the dicarboxylic acid component and the diol component may be sufficient, and a commercially available polyester may be used.

When synthesize | combining polyester, it can synthesize | combine by performing at least one of an esterification reaction and an ester exchange reaction, for example with a dicarboxylic acid component and a diol component conventionally well-known methods.

As for the specific examples of the dicarboxylic acid component and the diol component, preferred embodiments, the amount of use, and the like, descriptions of paragraphs [0036] to [0039] of JP2012-197432A can be referred to.

Specifically, the following examples are mentioned, for example.

As esters of dicarboxylic acids or dicarboxylic acids, for example, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecaneionic acid, dimer acid, eicoceinionic acid, pimelic acid, Aliphatic dicarboxylic acids, such as azelaic acid, methyl malonic acid, and ethyl malonic acid, alicyclic dicarboxylic acid, norbornene dicarboxylic acid, alicyclic dicarboxylic acid, such as isosorbide, cyclohexane dicarboxylic acid, and decalindamic acid, terephthalic acid, iso Phthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4 ' Aromatics such as diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, phenyl indeni carboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, and 9,9'-bis (4-carboxyphenyl) fluorene acid Dicarboxylic acid, such as dicarboxylic acid, or its ester derivative is mentioned.

As the diol compound, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol and 1,2-butanediol Alicyclic diols such as aliphatic diols, such as 1,3-butanediol, cyclohexanedimethanol, spiroglycol and isosorbide, bisphenol A, 1,3-benzenedimethanol, 1, Aromatic diols, such as 4-benzenedimethanol and 9,9'-bis (4-hydroxyphenyl) fluorene, etc. are mentioned.

At the time of esterification reaction and transesterification reaction, a conventionally well-known reaction catalyst can be used. For the specific examples of the reaction catalyst and the details of the esterification step, the descriptions of paragraphs [0040] to [0042] of JP2012-197432A can be referred to.

Preferred polyesters are polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), more preferably polyethylene terephthalate, and even more preferably white polyethylene terephthalate containing white particles. As polyethylene terephthalate, polymerization is carried out using a catalyst selected from a germanium (Ge) catalyst, an antimony (Sb) catalyst, an aluminum (Al) catalyst, a magnesium (Mg) catalyst, and a titanium (Ti) catalyst. Preferred polyethylene terephthalate is preferred, and more preferably polyethylene terephthalate polymerized using a Ti-based catalyst.

The Ti-based catalyst has high reaction activity and can lower the polymerization temperature. For this reason, it is possible to suppress that PET decomposes and carboxyl group generate | occur | produces during a polymerization reaction, and it is suitable for adjusting the density | concentration (AV) of the terminal carboxyl group of a polyester film to the range of 30 eq / ton or less.

When using a reaction catalyst, it is preferable to add a phosphorus compound, a magnesium compound, etc. at the time of superposition | polymerization of polyester. As a specific example, addition rate, etc. of a phosphorus compound and a magnesium compound, description of Unexamined-Japanese-Patent No. 2012-197432 can be referred to description of Paragraph [0071]-[0077].

In the polymerization of polyester, description of Paragraph [0078]-[0085] of Unexamined-Japanese-Patent No. 2012-197432 can be referred for the conditions of an esterification reaction, an ester exchange reaction, an additive, etc.

After superposing | polymerizing to polyester through an esterification reaction and an ester exchange reaction, it is preferable to perform a solid state polymerization reaction. By performing the solid state polymerization reaction, the water content of the polyester, the crystallinity, the acid value of the polyester (that is, the concentration of the terminal carboxyl group of the polyester), and the intrinsic viscosity can be adjusted.

If the time of the solid phase polymerization reaction is extended, the concentration of the terminal carboxyl group decreases, and if the time of the solid phase polymerization reaction is shortened, the concentration of the terminal carboxyl group tends to increase.

The ethylene glycol (EG) gas concentration at the start of the solid phase polymerization reaction is preferably higher than the EG gas concentration at the end of the solid phase polymerization reaction in the range of 200 ppm to 1000 ppm, and is 250 ppm to 800 ppm. It is more preferable that it is high in a range, More preferably, it is a case where it is high in the range of 300 ppm-700 ppm.

By adjusting the average concentration of the EG gas (the average of the gas concentrations at the start and end of the solid phase polymerization reaction), the concentration of the terminal carboxy group can be adjusted. That is, the concentration of the terminal carboxyl group can be reduced by reacting EG with the terminal carboxyl group by the addition of EG.

100 ppm-500 ppm are preferable, as for EG gas concentration, 150 ppm-450 ppm are more preferable, More preferably, they are 200 ppm-400 ppm.

180 degreeC-230 degreeC is preferable, as for the temperature of solid state polymerization reaction, More preferably, it is 190 degreeC-215 degreeC, More preferably, it is 195 degreeC-209 degreeC.

10 hours-40 hours are preferable, as for the time of solid state polymerization reaction, More preferably, they are 14 hours-35 hours, More preferably, they are 18 hours-30 hours.

White particles

The polyester film contains at least one of the white particles.

As white particle | grains, a white inorganic particle (henceforth a white inorganic particle) is preferable from a viewpoint of suppressing the thickness variation in the width direction orthogonal to a film longitudinal direction.

Examples of the white inorganic particles include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, alumina, aluminum hydroxide, hydroxyapatite, silica and mica. You may use at least 1 sort (s) of particle | grains of the inorganic powder chosen from talc, kaolin, clay, glass powder, asbestos powder, zeolite, and clay silicate. Especially, as white inorganic particle, a titanium oxide particle and a barium sulfate particle are preferable, and a titanium oxide particle is more preferable.

As white particles, organic particles may be used in combination with white inorganic particles.

Moreover, as an example of organic particle | grains, polystyrene, polymethylmethacrylate, polymethacrylate, silicone resin, fluororesin, benzoguanamine resin, phenol resin, nylon resin etc. which have a crosslinked structure are mentioned.

It is preferable that a white particle has a big refractive index difference with a film from a viewpoint of improving the improvement effect of the reflectance of the light of a polyester film. That is, inorganic powder with a large refractive index is preferable. Specifically, as the particles having a refractive index of 1.6 or more, at least one particle selected from the group consisting of calcium carbonate, barium sulfate, titanium oxide, and zinc oxide is more preferable. Especially, a titanium oxide particle is especially preferable. By containing titanium oxide particles, high light reflection performance can be imparted to the polyester film with a small filling amount. In addition, the titanium oxide particles can obtain high light reflection performance even in a thin polyester film.

As titanium oxide, crystalline titanium oxide, such as anatase type titanium oxide and rutile type titanium oxide, is mentioned, for example. From the viewpoint of increasing the refractive index difference with the polyester, titanium oxide having a refractive index of 2.7 or more is preferable, and titanium oxide in the form of a crystal of rutile titanium oxide is particularly suitable.

Among titanium oxides, titanium oxide with high purity is preferable. Titanium oxide with high purity is titanium oxide having a small light absorption ability to visible light, and has a small content of colored elements such as vanadium, iron, niobium, copper, and manganese (titanium oxide having a content of colored elements of 5 ppm or less). Point to. It is preferable that titanium oxide also has few coloring elements, such as iron, niobium, copper, and manganese, contained in a titanium oxide from a viewpoint of making light absorption capacity small.

The white particles may be surface-treated with a silicone compound, a polyhydric alcohol compound, an amine compound, a fatty acid, a fatty acid ester, or the like. For example, in order to improve the dispersibility of titanium oxide to polyester and to suppress photocatalytic activity of titanium oxide, you may surface-treat the surface of titanium oxide. As a surface treating agent used for surface treatment, the at least 1 sort (s) of organic compound chosen from the group which consists of a siloxane compound, a silane coupling agent, a polyol compound, and polyethylene glycol, etc. are mentioned, for example.

Moreover, a white particle may use multiple types together, for example, may use titanium oxide and another filler together, and may use titanium oxide and other particle with high purity together.

0.1 micrometer-3 micrometers are preferable, as for the average particle diameter of a white particle, 0.15 micrometer-2 micrometers are more preferable, and 0.2 micrometer-1 micrometer are more preferable. An average particle diameter is a value measured using microtrack FRA (made by Honeywell).

Other Ingredients

The polyester of one embodiment of the present invention may further contain other components such as a terminal sealant or an additive, in addition to the material containing the polyester and the white particles.

(Terminal sealant)

The terminal sealant may be supplied to a polyester serving as a raw material during melt kneading. Specifically, the polyester raw material to which the terminal sealing material is added may be melt-kneaded, for example, by supplying the terminal sealing material of a solid state from the same supply port according to supply of the cylinder of polyester. After melt-kneading, the polyester raw material which reacted with the terminal sealing material at the time of melt-kneading is melt-extruded from the extrusion opening of a cylinder as mentioned later, and can form into a film in the downstream die | dye.

By adding the terminal sealer in the solid state to the polyester raw material, the hydrolysis resistance of the polyester resin is improved, and in addition, by adjusting the ratio of the terminal sealant, the temperature and water content of the polyester, and the suction side pressure of the gear pump. The variation in hydrolysis resistance (in other words, AV) and physical properties of the polyester film can be reduced.

In one embodiment of the present invention, the terminal sealant can be incorporated into the polyester resin in a solid state. The form of the terminal sealant may be in any form such as powder form, granule form or particle form.

As a terminal sealing material, a carbodiimide compound, an oxazoline compound, a ketene imine compound, an epoxy compound, a carbonate compound, etc. are mentioned. Terminal sealant may be used individually by 1 type, and may be used in combination of 2 or more type.

The carbodiimide compound and the ketene imine compound react with the terminal carboxyl group and the hydroxyl group of the polyester, and function as a terminal sealant. Thereby, the fall of partial discharge is suppressed. In particular, after the thermal treatment in which the partial discharge voltage tends to be lowered, a high partial discharge voltage can be maintained and insulation can be exhibited.

0.1 mass%-10 mass% are preferable with respect to polyester, and, as for content in the polyester of a carbodiimide compound and a ketene imine compound, 0.1 mass%-4 mass% are more preferable, 0.1 mass%-2 Mass% is more preferable. When the content rate of a carbodiimide compound and a ketene imine compound is in the said range, adhesiveness with respect to the surface of a polyester film and heat resistance of a polyester film can be improved.

In addition, when using a carbodiimide compound and a ketene imine compound together, it is preferable that the sum total of the content rate of two types of compounds exists in said range.

1.Carbodiimide Compound

As a carbodiimide compound, the compound (including the polycarbodiimide compound) which has one or more carbodiimide groups in a molecule | numerator is mentioned, Specifically, as a monocarbodiimide compound, dicyclohexyl carbodiimide and dia Isopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, die -(beta) -naphthyl carbodiimide, N, N'-di-2,6- diisopropylphenyl carbodiimide, etc. are illustrated. As a polycarbodiimide compound, a thing with a polymerization degree of 2 or more (preferably 4 or more) 40 or less (preferably 30 or less) is suitable.

Carbodiimide compounds are disclosed in US Patent Publication No. 2941956, Japanese Patent Application Publication No. 47-33279, J. Org. Chem. 28, p 2069-2075 (1963), and Chemical Review 1981, Vol. 81, No. 4, p. The thing manufactured by the method of 619-621 etc. is mentioned.

Examples of industrially available polycarbodiimide include carbodilite (registered trademark) HMV-8CA (manufactured by Nisshinbo Corporation), carbohydrate (registered trademark) LA-1 (manufactured by Nisshinbo Corporation), and starbacsol (registered trademark) P (Made by Rheinchem Co., Ltd.), Starbacsol (registered trademark) P100 (made by Rheinchem Co., Ltd.), Starbacsol (registered trademark) P400 (Made by Rheinchem Co., Ltd.), Stabilizer 9000 (made by Rashi-Hikemi Co., Ltd.), etc. are illustrated.

Although a carbodiimide compound may be used individually by 1 type, you may use it in mixture of several compounds.

2. Cyclic Carbodiimide Compound

The cyclic carbodiimide compound contains one carbodiimide group in the ring skeleton and has at least one cyclic carbodiimide compound in the molecule in which the first nitrogen and the second nitrogen of the carbodiimide group are bonded by a bonding group. Etc., and functions as an annular sealing material. A cyclic carbodiimide compound can be prepared by the method of international publication 2011/093478.

Hereinafter, the specific example of a cyclic carbodiimide compound is shown. However, embodiment of this invention is not limited by the following specific example.

[Formula 1]

[Formula 2]

3. Keteneimine Compounds

The ketene imine compound is a compound having at least one ketene imine group, for example, J. Am. Chem. Soc., 1953, 75 (3), and the method described in pp 657-660 and the like.

Hereinafter, the specific example of a ketene imine compound is shown. However, embodiment of this invention is not limited by the following specific example.

[Formula 3]

[Formula 4]

[Formula 5]

(Additives, etc.)

A polyester film is a light stabilizer, antioxidant, a releasing agent, a ultraviolet absorber, a coloring agent, a nucleating agent (crystallizing agent), a flame retardant, etc. in the range which does not significantly inhibit the effect in one Embodiment of this invention. It may further contain an additive.

<Method for producing polyester film>

The polyester film of one embodiment of the present invention may be produced by any method as long as it is a method that satisfies the above-described equations 1 to 2 and Δ (10I + T) ≦ 2.0. For example, you may manufacture by using the polyester manufacturing apparatus shown in FIG. 3 schematically shows an example of the configuration of a polyester manufacturing apparatus according to an embodiment of the present invention.

The polyester manufacturing apparatus shown in FIG. 3 is a gear pump arranged in the molten resin extrusion direction downstream of the twin screw extruder 100 and the extrusion port (the extruder outlet 14 of FIG. 4) of the twin screw extruder 100 ( 44, the filter 42 which filters the molten resin sent out from the gear pump 44, and the die 40 which is a polyester film forming machine which forms the molten resin which passed the filter 42 are provided. The twin screw extruder 100, the gear pump 44, the filter 42, and the die 40 are connected via a pipe, respectively. Moreover, the raw material supply apparatus 46 is connected to the twin screw extruder 100. As shown in FIG. 4, the raw material supply apparatus 46 is equipped with the PET fixed-quantity feeder 32 and the sealing material fixed-quantity feeder 34 for quantitatively supplying polyester raw material to the raw material feed port of a twin screw extruder.

It is preferable that the piping is provided with the temperature detector for measuring resin temperature in arbitrary positions of a resin flow direction. As a temperature detector, a thermometer and a temperature detection sensor (for example, a thermocouple etc.) are mentioned suitably. For example, in the piping 41 directly connected to the die 40, as shown in FIG. 3, in order to measure the temperature of resin which distribute | circulates the axial center part or wall surface vicinity of a piping as shown in FIG. It can be comprised in the aspect which attached (2, 3).

As shown in FIG. 4, the twin screw extruder 100 may be a twin screw extruder provided with two screws in a cylinder. FIG. 4 schematically shows a structural example of a twin screw extruder constituting the polyester manufacturing apparatus of FIG. 3 by a cross section along the resin extrusion direction. The twin screw extruder 100 is connected to a PET metered feeder 32 and a sealing material metered feeder 34 for metering a polyester raw material into the raw material feed port 12. The extruder is not limited to a twin screw extruder, and various kneaders such as a single screw extruder, a Banbury mixer, and a brabender can be used. Especially, the aspect using a twin screw extruder is preferable.

In FIG. 4, the twin screw extruder 100 includes the cylinder 10 (barrel) which has the raw material supply port 12 which supplies raw material resin, and the extrusion port (extruder outlet) 14 which extrudes molten resin, Screws rotating in the cylinder 10, each having a diameter of 140 mm or more, the screw 20A and the screw 20B, and a temperature control means arranged around the cylinder 10 to control the temperature in the cylinder 10. 30 is provided.

The cylinder 10 has a raw material supply port 12 for supplying a raw material resin, and an extruder outlet 14 through which the hot melted resin is extruded.

As for the inner wall surface of the cylinder 10, it is necessary to use the raw material which is excellent in heat resistance, abrasion resistance, and corrosion resistance, and can ensure friction with resin. In general, nitrided steel with a nitrided inner surface is used, and chromium molybdenum steel, nickel chromium molybdenum steel, and stainless steel may be nitrided and used. In particular, in applications where wear resistance and corrosion resistance are required, bimetallic cylinders in which corrosion-resistant, wear-resistant material alloys such as nickel, cobalt, chromium and tungsten are lined on the inner wall surface of the cylinder 10 by centrifugal injection, and ceramics It is effective to form a thermal sprayed coating.

The cylinder 10 is provided with vent 16A, 16B for evacuating. By evacuating through the vents 16A and 16B, volatile components such as moisture in the resin in the cylinder 10 can be efficiently removed. By arrange | positioning vent 16A, 16B appropriately, the raw material (pellet, powder, flakes, etc.) of undried state, the crushed debris (fluff) of the film which came out in the middle of film forming, etc. can be used as raw material resin as it is.

In the present embodiment, two vents 16A and 16B are provided, but with respect to the arrangement of the vents, it is required to appropriate the opening area and the number thereof from the relationship with the degassing efficiency. It is preferable that the twin screw extruder 100 has one or more vents. In addition, when the number of the vents is too large, there is a fear that the molten resin will overflow from the vents and the deterioration of retention foreign matter may increase. Therefore, it is preferable that a vent is one place or two places.

In addition, the resin and precipitated volatile components retained on the wall near the vent may fall inside the extruder 100 (cylinder 10), and if dropped, the product may be surfaced as a foreign material. It is important not to fall. As for the retention, the shape of the vent cover and the proper selection of the upper vent and the side vent are effective. As the precipitation of the volatile component, a method of preventing precipitation by heating such as piping is generally used.

The screw segment of various shapes is used for the twin screw extruder which can be used in this indication. As the shape of the screws 20A and 20B, for example, a full flight screw provided with a set of spiral pitches 22 of equal pitch is suitably used.

Moreover, it is preferable that at least 1 resin kneading | mixing member is arrange | positioned downstream of the resin extrusion direction of the raw material supply port 12 in the longitudinal direction of the cylinder 10. As shown in FIG. The resin kneading member is, for example, a kneading segment for providing shear such as a kneading disc or a rotor. In this embodiment, the kneading discs 24A and 24B are provided as shown in FIG. By providing the kneading segment, the raw material resin can be melted and kneaded more reliably. The kneading segment is disposed in a heating zone (heating zones C1 to C7 shown in FIG. 4 in this embodiment) allocated in the cylinder longitudinal direction, and a kneading portion for promoting melting and kneading of the raw material resin is formed in the heating zone. have.

Moreover, by using a reverse screw and a seal ring in this heating zone, a melt seal can be formed when a resin is prevented and it vacuums through a vent. In this embodiment, a reverse screw may be provided in the vicinity of the vents 16A and 16B of FIG., For example (not shown).

It is effective that a cooling zone (temperature controller) for cooling the molten resin and adjusting the temperature is provided downstream of the resin extrusion direction of the longitudinal center portion of the cylinder 10 constituting the twin screw extruder 100. When the heat transfer efficiency of the cylinder 10 is higher than the shear heat generation, as shown in FIG. 4, by providing a screw 28 having a short pitch in the cooling zone (temperature control unit), the resin movement speed of the cylinder 10 wall surface becomes high. The temperature control efficiency can be improved. From the viewpoint of enhancing the cooling effect, the pitch of the screws 28 located in the cooling zone (temperature control unit) is preferably 0.5D to 0.8D (D: diameter of the screw).

The temperature control means 30 is provided around the cylinder 10. In the twin screw extruder 100 of this embodiment, as shown in FIG. 4, the cylinder 10 is divided into nine regions in the longitudinal direction from the raw material supply port 12 toward the extruder outlet 14. In the cylinder 10, heating apparatuses C1 to C7 are arranged in seven regions from the resin extrusion direction upstream, and cooling apparatuses C8 to C9 are arranged in two regions from the resin extrusion direction downstream. The control means 30 is provided. Thus, the circumference | surroundings of the cylinder 10 are divided into heating zones C1-C7 and cooling zones C8-C9 by the heating apparatus C1-C7 and cooling apparatus C8-C9 arrange | positioned dividedly. . As a result, the inside of the cylinder 10 can be controlled at a desired temperature for each region (zone). In addition, in FIG. 4, although the structure which can divide a cylinder into 9 zones in the longitudinal direction and can control temperature for each zone was shown as the example, the number of zones (zones) is not limited to this, A zone (zone) is arbitrarily according to the objective etc. You can select the number of).

Generally as a heating, a band heater or a sheath wire aluminum casting heater is used. However, a heater is not limited to these, For example, a heat circulation heating method can also be applied. On the other hand, the cooling is usually performed by air blower, but the cooling pipe for circulating the refrigerant around the cylinder 10 is wound up or provided inside, and the cooling is circulated through the cooling pipe. It may be. As the refrigerant, water or oil is generally used.

In the present disclosure, from the viewpoint of suitably producing a polyester film that satisfies all of the above-described formulas 1 to 2 and Δ (10I + T) ≦ 2.0, preferably, the production method shown below (poly of the present disclosure Manufacturing method of the ester film).

That is, the polyester film of the present disclosure is preferably a melting step of mixing white particles with polyester to melt with an extruder, a conveying step of conveying polyester melted with an extruder to a die through a pipe, and polyester It is manufactured by the method including the film forming process of shape | molding in a sheet form on at least one of conditions A and B shown below, and forming a polyester sheet, and the cooling process of cooling the formed polyester sheet. In manufacturing the polyester of this indication, you may also have the extending process of extending | stretching the polyester sheet after a cooling process to at least one direction. When the extending process is performed, thickness variation tends to occur, and the effect in one Embodiment of this invention appears more notably in the aspect which provided the extending process.

In addition, the detail of condition A and the condition B is mentioned later.

Melting Process

In the melting step, white particles are mixed with polyester and melted with an extruder.

In this process, polyester which is raw material resin for forming a polyester film at least, and white particle are thrown into the raw material supply port 12 of the twin screw extruder 100 shown, for example in FIG. In addition to the polyester and the white particles, the terminal sealant may be further added.

When the polyester, the white particles, and the terminal sealant are added, the polyester and the PET metering feeder 32 and the sealant metering feeder 34 attached to the raw material supply port 12 are used as shown in FIG. 4. The white particles may be introduced by the PET metering feeder 32, and the terminal sealant may be added by the sealant metering feeder 34. Thus, although the terminal sealing material, such as a carbodiimide compound or a ketene imine compound, may be directly injected into an extruder, the method of forming a master batch with polyester previously and injecting into an extruder is preferable from a viewpoint of performing extrusion stably. Do.

The PET metering feeder 32 and the sealant metering feeder 34 are apparatuses for metering the polyester raw material and the terminal sealer, respectively.

It is preferable to prepare the master pellet which specifically mixed the additives, such as polyester, a white particle, and terminal sealing material as needed. The polyester used for preparation of a master pellet can polycondense a dicarboxylic acid component and a diol component according to a conventional method, and can process and use it in a pellet shape.

When preparing a master pellet, it is preferable to provide a drying process. It is preferable to dry the composition containing the additives, such as polyester and a white particle, and a terminal sealing material in vacuum or hot air. In a drying process, it is preferable to make water content in a composition 100 ppm or less, More preferably, it is 80 ppm or less, More preferably, it is 60 ppm or less. 80 degreeC-200 degreeC is preferable, as for the drying temperature at the time of drying, More preferably, it is 100 degreeC-180 degreeC, More preferably, it is 110 degreeC-170 degreeC. Moreover, what is necessary is just to adjust a drying time suitably so that it may become a desired water content.

Subsequently, it is preferable to melt-knead the composition containing the additives, such as dry polyester, white particle | grains, and an end sealing material, and to produce the master pellet which the white particle disperse | distributed to high concentration. As for the content density | concentration of the white particle or terminal sealing material in a master pellet, 1.5 times-20 times of the density | concentration in the case of using a film are preferable, 2 times-15 times are more preferable, More preferably, they are 3 times-10 times.

As for the temperature at the time of melt-kneading, the crystal melting temperature (Tm) or more of polyester (Tm + 80 degreeC) or less is preferable, (Tm + 10 degreeC)-(Tm + 70 degreeC) are more preferable, More preferably, (Tm + 20 degreeC)-(Tm + 60 degreeC).

In addition, Tm was measured on condition of the following using the differential scanning calorimeter (DSC-60, the Shimadzu Corporation make).

<Condition>

Atmosphere in the measuring room: nitrogen (50 mL / min)

Heating rate: 5 ℃ / min

Measurement start temperature: 25 ° C

Measurement end temperature: 300 ℃

Mass of measurement sample: 5 mg

The kneading atmosphere may be any of air, vacuum, and inert air, and more preferably in vacuum or inert air.

1 minute-20 minutes are preferable, as for the time of melt-kneading, 2 minutes-18 minutes are more preferable, More preferably, they are 3 minutes-15 minutes.

In addition, the master pellet is heated and melted so that the maximum achieved temperature of the temperature of polyester may be about 300 degreeC.

Return process

The polyester melt | dissolved with the extruder in a melting process conveys the melted polyester to die | dye through piping in a next conveyance process.

As shown in FIG. 3, the gear pump 44 and the filter 42 are connected to the extruder exit of the twin screw extruder 100 by piping, and the gear pump 44 is arrange | positioned further downstream through piping. It is connected with the die 40. The molten polyester having passed through the filter 42 flows into the pipe and is sent to the next die 40.

The gear pump 44 provided in the molten resin extrusion direction downstream of the extruder exit 14 of the twin screw extruder 100 adjusts the flow volume of molten polyester by a drive gear and a driven gear. Both gears may be driven. Since the gear pump 44 is provided between the twin screw extruder 100 and the die 40 which is a polyester film making machine, the fluctuation of the extrusion amount of the molten polyester is reduced, and a certain amount of resin is supplied to the die 40. By doing so, thickness precision is improved. In particular, when using a twin screw extruder, since the pressure raising ability of the extruder itself is low, the aspect by which extrusion stabilization by the gear pump 44 is aimed at is preferable.

By using the gear pump 44, the pressure fluctuation (outlet pressure fluctuation) on the discharge side of the gear pump 44 can be made 1/5 or less of the pressure fluctuation (inlet pressure fluctuation) on the suction side, and the resin pressure fluctuation range is ± 1. Can be reduced to within%.

When the polyester extruded through melt kneading in the twin screw extruder passes through the piping and flows to the die 40, the polyester is sent to the die 40 under the condition that the following expression 12 is satisfied. desirable.

0 <T11-T10≤20 ... Expression 12

In Equation 12, T10 represents a resin temperature [° C.] of at least one central portion in the radial direction in the longitudinal direction of the pipe, and T11 is from an inner wall surface in the radial direction passing through the measurement point at which the resin temperature T10 is measured. The resin temperature [° C.] in the pipe 5 mm apart is shown.

As shown in FIG. 5A, white particles flowing near the wall surface of the pipe tend to flow in the end direction of the die connected downstream of the pipe. Resin which distribute | circulates the center part of piping tends to flow in a center part in a downstream die. Resin or white particles hardly flow in the vicinity of the wall surface of the pipe, and the viscosity of the resin near the wall surface of the pipe can be lowered by making the temperature near the wall surface of the pipe higher than the temperature of the central portion in the radial direction of the pipe. Thereby, white particle | grains tend to flow also in the vicinity of the wall surface of piping, and more white particle | grains which flow to the edge part of a die | dye also increase. As a result, the thickness variation in the film width direction becomes good.

Therefore, in Formula 12, the thickness variation in the film width direction is alleviated by satisfying that T11-T10 exceeds 0, that is, T11> T10. Moreover, by suppressing "T11-T10" to 20 degrees C or less, deterioration of resin near the wall surface of a piping becomes difficult to progress remarkably, and the fall of the intrinsic viscosity of resin which flows to the edge part of a die is suppressed. Therefore, the thickness variation in the film width direction can be kept better.

For the same reasons as described above, "T11-T10" more preferably satisfies Expression 12a, and even more preferably satisfies Expression 12b.

2 <T11-T10≤15 ... Expression 12a

5≤T11-T10≤13 ... Expression 12b

When the difference between the discharge side pressure (inlet pressure) and the suction side pressure (outlet pressure) (differential pressure) becomes too large, the gear pump 44 has a large load on the gear pump 44, resulting in large shear heat generation. For this reason, from the viewpoint of preventing deterioration of the resin, that is, lowering of the intrinsic viscosity I, the differential pressure during operation is preferably within 20 MPa, more preferably within 15 MPa, even more preferably within 10 MPa. In addition, in order to make the primary pressure of the gear pump 44 constant from the viewpoint of film thickness uniformity, it is effective to control the screw rotation of the extruder or to use a pressure regulating valve.

In addition, a filter 42 is provided between the gear pump 44 and the die 40 to prevent unmelted resin and foreign matter from mixing in the polyester used for film formation. A metal fiber filter etc. can be used for a filter. The filter hole diameter can be suitably selected in the range of 1 micrometer-100 micrometers.

Production Process

Downstream of the gear pump 44 and the filter 42 disposed in the pipe leading to the extruder outlet 14 of the cylinder 10, as shown in FIGS. 3 to 4, the extruder outlet 14 is a polyester film making machine. Die 40 for molding the molten resin extruded from the sheet into a sheet shape, and a cooling roll (chill roll) (not shown) for cooling the molded sheet. Molten resin is formed into a sheet form from the die 40, sent to a cooling roll, and formed into a sheet by cooling. In this way, an unstretched polyester sheet is obtained.

In this process, the molten resin (polyester) extruded from the extruder outlet 14 is shape | molded by the die 40 in sheet form on at least one of condition A and condition B below, and a polyester sheet is formed into a film. . In the die 40, any one of condition A, condition B, or three conditions of condition A and condition B is selected, and it shape | molds in sheet form. By selecting any one of three conditions and forming a film under each condition, the thickness variation in the film width direction is suppressed little.

(1) Condition A: The following Expressions 5 and 6 are satisfied.

C0 <C1 ... Expression 5

C2 <C1

In addition, C0, C1, and C2 in Formula 5-Formula 6 are as follows. All values in C0, C1 or C2 are in millimeters [mm].

C0 [mm]: Lip clearance of the center part in the width direction of the die

C1 [mm]: average value of the lip clearance of each center portion between the center portion and one end or the other end in the width direction of the die

C2 [mm]: average value of each lip clearance at both ends in the width direction of the die

(2) Condition B: All the following formulas 7 to 11 are satisfied.

T0 <T1 ...

T2 <T1 ...

270 ° C≤T0≤320 ° C

270 ° C≤T1≤320 ° C

270 ° C≤T2≤320 ° C

In addition, T0, T1, and T2 in Formulas 7-11 are as follows.

T0 [° C.]: The sheet temperature of the center portion in the sheet width direction of the polyester sheet at the point of time away from the die

T1 [° C.]: the average value of the sheet temperatures of the central portion between the central portion and one end or the other end in the width direction of the polyester sheet

T2 [° C.]: Average value of each sheet temperature at both ends in the width direction of the polyester sheet

In condition A, it forms into a film so that Formula 5 and Formula 6 may be satisfied.

In Formula 5, C1 is lip clearance C1a [mm] of the center part between the center part and one end in the width direction of die 40, and the center part in the width direction of die 40 as shown in FIG. It is the average value of the lip clearance C1b [mm] between the center and the other end.

In Formula 6, C2 is lip clearance C2a [mm] of one end in the width direction of the die 40, and lip clearance C2b [of the other end in the width direction of the die 40, as shown in FIG. mm].

In addition, the arrow in FIG. 6 shows the flow direction of molten resin. The molten resin (polyester) extruded from the extruder exit is shape | molded by the die 40 in the sheet form like FIG. 6, and the polyester sheet 50 is formed into a film.

"C0 <C1" represented by Formula 5 is the lip clearance C0 of the center part in the width direction of the die 40, and the average value of the lip clearance of each center part between the center part and both ends in the width direction of the die 40 It is smaller than (ie, the lip clearance obtained by (C1a + C1b) / 2).

Moreover, "C2 <C1" represented by Formula 6 is a lip clearance at the width direction edge part of the die 40 (specifically, the average lip clearance calculated | required by (C2a + C2b) / 2), and die 40 It is smaller than the average value of the lip clearance of each center part between the center part and both ends in the width direction of (namely, the lip clearance calculated | required by (C1a + C1b) / 2).

Lip clearance refers to the length [mm] of the direction parallel to the thickness direction of the sheet | seat to be shape | molded of the slit-shaped clearance gap (discharge port) for ejecting and shape | molding melt from a die | sheet, and shape | molds and regulates the thickness of the sheet | seat formed do. Lip clearance is 0.1 mm or more normally, Preferably it becomes the range of 0.2 mm-5.0 mm.

Generally, as shown in FIG. 5A, the flow of molten resin in a die is the best in the width direction center part of a die. In the width direction of the die, the center portion of the die has a wider flow path than both ends, so that the white particles having a higher density than the polyester tend to be deflected and flow in the center portion in the width direction of the die. For this reason, in the width direction center part of die | dye, the content rate of white particle becomes high, and the residence time of polyester is short compared with the width direction end part of die | dye in the width direction center part of die | dye, and it is hard to produce polyester deterioration (that is, extreme Viscosity I is high). As a result, the stretching stress tends to be high. On the other hand, since the flow path is narrow in the widthwise end portion of the die, white particles having a higher density than polyester are difficult to flow. For this reason, the content ratio of white particle | grains becomes low at the width direction edge part of a die, and the residence time of polyester is longer at the width direction edge part of a die compared with the width direction center part of die | dye, and it is easy to deteriorate polyester (that is, Intrinsic viscosity I is low). As a result, the stretching stress tends to be low.

Therefore, in a die | dye, white particle | grains tend to flow to the center part of the width direction of a die | dye, the content rate of the white particle | grains of a center part rises compared with an edge part, and the stress of a center part rises easily. As a result, in the case of using a polyester film, thickness variation is likely to occur in the film width direction.

On the other hand, since the polyester sheet formed into a film at a place close to both ends of the die in the width direction does not become a product by edge cutting, the flow of white particles in both ends of the die in the width direction is suppressed so as not to be too good. It is preferable.

In view of the above, in the present disclosure, the lip clearance in the center portion in the width direction of the die is narrower than the lip clearance in each center portion between the center portion and both ends in the width direction of the die, and is adjusted in the relationship of C0 <C1. do. Thereby, as shown to FIG. 5B, the polyester distribute | circulated abundantly in the center part is sent to both ends of a die, and it is made to disperse | distribute. Moreover, it adjusts so that the relationship of C2 <C1 may be satisfy | filled so that the flow of the white particle in the vicinity of the both ends which will not become a product finally becomes so good.

By doing in this way, the content rate of a white particle becomes uniform in the width direction of a die | dye, and also the intrinsic viscosity I of polyester is also uniformized. Thereby, in the die area | region which can be a product, thickness variation in the film width direction at the time of film-forming can be effectively reduced.

In condition A, as the relationship between C0 and C1, it is more preferable that the ratio of C1 to C0 (= C1 / C0) is within a range that satisfies 1.0 <C1 / C0 ≦ 2.0.

Next, condition B will be described.

In condition B, a film is formed so as to satisfy all of Expressions 7 to 11.

In Formula 7, T1 shows the sheet temperature T1a [degreeC] in the center part between the center part and one end in the width direction of a polyester sheet, and the center part and the other end in the width direction of a polyester sheet. It is the average value of the sheet temperature T1b [degreeC] in the center part between.

In Formula 8, as shown in FIG. 7, T2 is the sheet temperature T2a [degreeC] of one end in the width direction of a polyester sheet, and the sheet temperature T2b [degreeC] at the other end in the width direction of a polyester sheet. ] Is the average value.

In addition, the arrow in FIG. 7 shows the flow direction of molten resin. The molten resin (polyester) extruded from the extruder exit is shape | molded in die | dye 40 in the sheet form like FIG. 7, and the polyester sheet 50 is formed into a film.

"T0 <T1" represented by Formula 7 is a sheet temperature T0 of the center part in the width direction of a polyester sheet, and the average value of the sheet temperature of each center part between the center part and both ends in the width direction of a polyester sheet (that is, , Sheet temperature determined by (T1a + T1b) / 2).

Moreover, "T2 <T1" represented by Formula 8 is a sheet temperature (specifically, the sheet temperature calculated | required by (T2a + T2b) / 2) at the width direction edge part of a polyester sheet, and the width of a polyester sheet. It is shown that it is smaller than the average value (namely, the sheet temperature calculated | required by (T1a + T1b) / 2) of the sheet temperature of each center part between the center part and both ends in a direction.

In general, when the flow of molten resin in the die is T0 ≧ T1, the flow of the center portion in the width direction of the die is the best as shown in FIG. 5A due to the decrease in viscosity. Therefore, in the width direction center part where a flow path is wider than the both ends of die | dye, the white particle which is higher in density than polyester is deflected and flows easily in the width direction center part of die | dye. For this reason, similarly to the above, the content rate of the white particle of the width direction center part of polyester becomes high, and intrinsic viscosity I also becomes high. As a result, the stress also tends to be high.

Therefore, in a die | dye, white particle | grains tend to flow in the center part of the width direction of a die | dye, the content rate of the white particle | grains of a center part rises compared with the edge part, and the stress of a center part rises. As a result, thickness variation tends to occur in the film width direction when a polyester film is used.

On the other hand, since both ends of the width direction of a polyester sheet do not become a product finally by edge cutting, it is preferable that the temperature in the width direction both ends of a polyester sheet does not become too high.

In view of the above, in the present disclosure, as shown in b in the width direction of the polyester sheet, the polyester, which has been widely distributed in the center portion, can be flowed to both ends of the die to be dispersed. Moreover, it adjusts so that the relationship of T2 <T1 may be satisfy | filled so that the flow of the white particle in the vicinity of the both ends which will not become a product finally becomes so good.

By doing in this way, the content rate of a white particle becomes uniform in the width direction of a polyester sheet, and also the intrinsic viscosity I of a polyester is also uniformized. Thereby, in the die area | region which can be a product, thickness variation in the film width direction at the time of film forming can be reduced more effectively.

In the relationship shown by said Formula 7-8, T0, T1, and T2 are adjusted to the temperature range of 270 degreeC-320 degreeC, respectively (Formula 9-Formula 11). When the temperatures of T0, T1, and T2 are 270 DEG C or higher, the viscosity of the polyester rises remarkably, so that poor discharge or cracking accompanied with promotion of crystallization tends to occur. . Moreover, when each temperature of T0, T1, and T2 is 320 degrees C or less, it is suitable for preventing deterioration of polyester.

The preferable range of each temperature of T0, T1, and T2 is 280 degreeC-310 degreeC for the same reason as the above.

The temperature (sheet temperature) of a polyester sheet is measured by the method of measuring a thermocouple by making it contact a surface of a porous base material, or the method of non-contact measurement by an infrared temperature measuring apparatus etc. using infrared rays.

In this indication, the aspect shape | molded in sheet form combining said condition A and condition B is more preferable.

Extrusion of molten resin is preferably performed by applying an extrusion pressure of 0.5 MPa to 30 MPa. 2 MPa or more is more preferable, and 5 Mpa or more of an extrusion pressure is more preferable. Moreover, 30 MPa or less is preferable, 25 MPa or less is more preferable, and, as for extrusion pressure, 15 MPa or less is more preferable. The extrusion pressure of 0.5 MPa or more is effective in that the particles can be localized on the surface of the polyester sheet. Moreover, when extrusion pressure is 30 Mpa or less, generation | occurrence | production of the scratch by molten resin contacting a die lip can be prevented. By extruding in the range of said extrusion pressure, particle | grains can also be localized in the surface layer of a polyester sheet.

Moreover, in the case of extrusion of molten resin, it is preferable to give 1%-10% of fluctuations to extrusion pressure. The fluctuation | variation of extrusion pressure refers to the value which measured the pressure applied to molten resin for 1 minute, when passing through a die lip, divides the difference of the maximum value and minimum value by the average value, and shows it as the percentage. If the fluctuation | variation of extrusion pressure is in the said range, molten resin will expand too much at a die | dye exit, and a molten resin will adhere to a die lip, and it can prevent that a scratch or unevenness | corrugation arises on a film surface.

Cooling process

The cooling step cools the polyester sheet formed into a film in the film forming step.

In the film forming process, the molten resin extruded through the die is formed into a sheet, and is supplied to a cooling roll (also called a casting drum) that is not shown and cooled. Molten resin is solidified on a cooling roll and is obtained as a cast film (unstretched film).

0 to 60 degreeC is preferable, as for the surface temperature of a cooling roll, 5 to 55 degreeC is more preferable, More preferably, it is 10 to 50 degreeC. Cooling by the cooling roll is preferably performed by an electrostatic application method, an air knife method, water coating on the cooling roll or the like from the viewpoint of enhancing the adhesion of the molten resin to the cooling roll to improve the planarity of the cast film.

Drawing process

In the manufacturing method of the polyester sheet of one Embodiment of this invention, you may have the extending process of extending | stretching a polyester sheet to at least one direction.

The unstretched film formed into a film by the film forming process may be extended | stretched. It is preferable to perform extending | stretching to at least one of the longitudinal direction (Machine Direction, MD) and the transverse direction (Transverse Direction, TD) orthogonal to MD, More preferably, it is biaxially stretched by MD and TD. Biaxial stretching may be performed in order by MD and TD, and may be performed simultaneously by MD and TD.

It is preferable to perform extending | stretching in the range of glass transition temperature (Tg) degreeC-(Tg + 60) degreeC of a polyester sheet, The range of (Tg + 3 degreeC)-(Tg + 40 degreeC) is more preferable, More Preferably it is the range of (Tg + 5 degreeC)-(Tg + 30 degreeC).

There is no restriction | limiting in particular in draw ratio, 280%-500% are preferable, More preferably, it is 300%-480%. A draw ratio is calculated | required by the following formula.

Stretch ratio (%) = 100 × {(length after stretching) / (length before stretching)}

Stretching to MD can be performed by speeding up the drive speed of the downstream nip roll using the some nip roll arrange | positioned at MD, and conveying it. Moreover, you may perform extending | stretching to MD by holding the width direction with a chuck and widening the space | interval of the longitudinal direction between chucks.

Extending | stretching to TD can be performed by holding the width direction both ends of a polyester sheet by a chuck, and extending it in the direction orthogonal to MD.

In the case of simultaneous stretching by MD and TD, the gripping can be performed by combining the operation of widening the chuck spacing with MD and the operation of widening the chuck spacing with TD.

In an extending process, you may heat-process a polyester sheet before and behind an extending process (preferably after an extending process). By carrying out the heat treatment, microcrystals can be generated to improve mechanical properties and durability. As for the temperature of heat processing, 1 second-60 second is suitable at 180 degreeC-225 degreeC.

In an extending process, you may heat-process after heat processing. The thermal relaxation treatment refers to a treatment in which heat for stress relaxation is applied to the polyester sheet to shrink the sheet. It is preferable to perform heat relaxation treatment to both MD and TD. It is preferable to perform heat relaxation treatment at the temperature lower than heat processing, and 130 degreeC-220 degreeC is specifically, preferable.

As thermal contraction rate (150 degreeC) by a heat relaxation process, it is preferable that MD and TD are 1%-12%.

<Backside protective sheet for solar cell>

The solar cell backside protective sheet of one Embodiment of this invention has the polyester film of one Embodiment of this invention demonstrated above. Since the thickness variation is suppressed in the polyester film of one embodiment of the present invention, the polyester film is easily adhered to a sealing material in a solar cell element, and peeling due to long-term use is unlikely to occur. Moreover, peeling of an adjacent layer hardly arises even when an adjacent layer is laid.

As thickness of the back surface protective sheet for solar cells of one Embodiment of this invention, 100 micrometers-500 micrometers are preferable.

<Solar cell module>

The solar cell module of one Embodiment of this invention is equipped with the solar cell back surface protection sheet of one Embodiment of this invention demonstrated above. That is, the solar cell module includes one embodiment of the present invention described above disposed on a side opposite to the side on which the transparent substrate to which sunlight is incident, the solar cell element disposed on one side of the substrate, and the substrate on which the solar cell element is disposed. The solar cell back surface protection sheet is provided. Since the solar cell module provided with the solar cell back surface protection sheet of one Embodiment of this invention has the polyester film of one Embodiment of this invention demonstrated above, adhesiveness with a solar cell element becomes favorable and an adjacent layer In the structure having a structure, since the peeling of the adjacent layer provided by application | coating etc. does not occur easily, the stable power generation performance is acquired over a long term.

Specifically, the solar cell module of one embodiment of the present invention is provided on a transparent substrate (front substrate such as a glass substrate) on which solar light is incident, and a sealing material for sealing the solar cell element and the solar cell element. And a back protective sheet for solar cells (back sheet) disposed on the side opposite to the side where the substrate of the device structural portion is located, and having a lamination of "transparent front base material / element structure part / back sheet". It has a structure. Specifically, the transparent front base material and the back surface for solar cells of one embodiment of the present invention in which the element structure portion in which the solar cell element for converting light energy of solar light into electrical energy is arranged is arranged on the side where sunlight directly enters. It arrange | positions between protective sheets, and uses the sealing material, such as an ethylene vinyl acetate (EVA) system, as an element structure part (for example, a solar cell) containing a solar cell element between a front base material and a back protection sheet. To be sealed and bonded.

Members other than a solar cell module, a solar cell, and a back seat | sheet are described in detail in "photovoltaic power generation system component material" (Shimoto Eichi supervision, Kosago Co., Ltd., 2008 issue). .

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

Examples of the solar cell element include group III-V and group II-VI such as silicon-based such as monocrystalline silicon, polycrystalline silicon, amorphous silicon, copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenic, and the like. Various well-known solar cell elements, such as a group compound semiconductor type, can be applied. Between a board | substrate and a polyester film, it can be comprised by sealing with resin (so-called sealing material), such as ethylene-vinyl acetate copolymer, for example.

Example

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described further more concretely by an Example. However, embodiments of the present invention are not limited to the following examples unless departing from the spirit thereof. In addition, "part" is a mass reference | standard unless there is particular notice.

(Example 1)

<Production of Polyester Film>

Synthesis of polyester

Approximately 123 kg of bis (hydroxyethyl) terephthalate was added to a slurry prepared by mixing 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemical Co., Ltd.) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.). The esterification reactor maintained at 250 degreeC and the pressure of 1.2 * 10 <^5> Pa was sequentially supplied for 4 hours. After the end of the supply, an esterification reaction was further performed for 1 hour. Thereafter, 123 kg of the obtained esterification product was transferred to a polycondensation reactor.

Subsequently, 0.3 mass% of ethylene glycol was added to the polymer obtained to the polycondensation reaction tank to which the esterification reaction product was transferred. After stirring for 5 minutes, the ethylene glycol solution of cobalt acetate and manganese acetate was added to the polycondensation reaction tank so that the cobalt atom conversion amount and the manganese atom conversion amount with respect to the polymer obtained are 30 ppm and 15 ppm, respectively. After stirring for 5 minutes, the 2 mass% ethylene glycol solution of a titanium alkoxide compound was added so that the titanium atom conversion amount with respect to the polymer obtained may be 5 ppm. After 5 minutes of addition, 10 mass% ethylene glycol solution of ethyl diethylphosphono acetate was added so that the phosphorus atom conversion amount with respect to the polymer obtained may be 5 ppm.

Thereafter, the reaction solution was gradually heated from 250 ° C to 285 ° C while stirring the reaction solution in the polycondensation reactor at a rotation speed of 30 rpm, and the pressure in the system was lowered to 40 Pa. The time until reaching the final temperature and the final pressure was all 60 minutes.

At the time of the predetermined stirring torque, the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped.

And it discharged to cold water in strand shape, and cut immediately after discharge, and produced the pellet of polyethylene terephthalate (diameter: about 3 mm, length: about 7 mm; hereafter called "PET pellet"). In addition, the time from the depressurization start until the predetermined stirring torque was reached was 3 hours.

In addition, as a titanium alkoxide compound, the titanium alkoxide compound (Ti content = 4.44 mass%) synthesize | combined in Example 1 of Paragraph No. 0083 of Unexamined-Japanese-Patent No. 2005-340616 was used.

Solid State Polymerization

The PET pellet obtained above was hold | maintained at the temperature of 220 degreeC for 30 hours in the vacuum container hold | maintained at the pressure of 40 Pa, and the solid state polymerization reaction was performed and the intrinsic viscosity (I; dL / g) was adjusted.

PET pellet 1 was manufactured as mentioned above.

Intrinsic viscosity (I) of PET pellet 1 which had undergone the solid state polymerization reaction was measured by the following method.

[Measurement of Intrinsic Viscosity (I)]

Using a Uberode viscometer, PET pellet 1 was mixed with 1,1,2,2-tetrachloroethane and phenol in a mixed solvent (1,1,2,2-tetrachloroethane / phenol = 2/3, mass ratio). It melt | dissolved and calculated | required I (dL / g) from the viscosity of the solution which was temperature-controlled at 25 degreeC.

The unit of intrinsic viscosity in following Table 2 is "dL / g".

Production of Film

PET pellet 1 (polyester) and titanium oxide (average particle size: 0.3 μm, manufactured by Ishihara Sangyo Co., Ltd.) in an amount necessary to achieve the addition rate (unit: mass%) shown in Table 2 using PET pellet 1 that had undergone a solid phase polymerization reaction; Particle | grains [PET pellet 1: titanium oxide = 95.5: 4.5 [mass%]] was thrown into the raw material supply port 12 equipped with the twin screw extruder of the following polyester manufacturing apparatus. After the addition, the mixture was melt kneaded at 280 ° C. and cast on a cooling roll to prepare an unstretched polyethylene terephthalate sheet having a thickness of about 3.5 mm.

In addition, the average particle diameter of titanium oxide was measured using the microtrack FRA (made by Honeywell).

In forming a polyethylene terephthalate sheet, the lip clearance of the resin discharge port (lip) of the die 40 was set as shown in Table 2. Moreover, the heater 40 (not shown) for heating resin which distribute | circulates the die inside is attached to the die 40, and the preset temperature was changed so that it might be adjusted to the sheet temperature shown in following Table 2.

In addition, in the piping 41 directly connected to the die 40, as shown in FIG. 8, measuring the temperature T10 (degreeC) of the polyester resin which flows through the radial center part (axial center part) of a piping toward die | dye. And a temperature sensor 3 for measuring the temperature T11 (° C) of the polyester resin flowing at a position 5 mm away from the inner wall surface of the pipe.

[Polyester manufacturing apparatus]

As shown in FIG. 4, the polyester manufacturing apparatus shown in FIG. 3 was prepared, and as shown in FIG. 4, the raw material supply port 12 with which the PET fixed-quantity feeder 32 and the sealing material fixed-quantity feeder 34 were equipped, and two vents ( In the cylinder 10 provided with 16A, 16B, the screw 20A, 20B of the following structure is provided, and around the cylinder 10 is divided into nine zones in the cylinder longitudinal direction (screw axis direction), and temperature control is performed. A double vent type co-rotating interlocking type biaxial extruder 100 having a heater (temperature control means) 30 that can be performed was prepared.

<Configuration of Twin Screw Extruder>

(a) screw

Screw diameter D: 180mm

Length L [mm] / screw diameter D [mm]: 31.5 (width of one cylinder (screw axial length): 3.5D)

Screw shape:

Plasticizing kneading unit just before the first vent (neutral kneading 2D, reverse screw 1D)

Degassing promotion kneading unit just before the second vent (neutral kneading 2D)

Screw speed: 90 rpm

(b) discharge rate: 3000kg / h

(c) cylinder temperature

Zone C1: 60 ° C, Zone C2: 200 ° C, Zone C3: 250 ° C, Zone C4: 270 ° C, Zone C5: 270 ° C, Zone C6: 280 ° C, Zone C7: 280 ° C, Zone C8: 270 ° C, Zone C9 : 270 ℃

Here, the C1 zone is the first zone on the raw material supply port 12 side.

(d) PET feeder, sealing material feeder: screw type

(e) Hopper: Y-shaped (two kinds of raw materials are fed to the same feed port)

In this polyester manufacturing apparatus, as shown in FIG. 3, the downstream side of the extruder exit in the melt resin extrusion direction of a twin screw extruder, The gear pump 44, the metal fiber filter 42 which have the following structures, and The die 40 is connected. The average residence time of the resin in the die 40 was uniformly 10 minutes.

<Configuration other than twin screw extruder>

(f) Gear pump: 2 gear type

(g) Filter: Metal fiber sintered filter (pore diameter: 20 μm)

(h) Lip clearance of the die (lip clearance): see table 2

Thereafter, the obtained unoriented polyethylene terephthalate sheet was stretched 3.4 times in MD at 90 ° C., and then stretched 4.5 times in TD at 105 ° C. to obtain a biaxially stretched film. The film after extending | stretching was heat-processed for 15 second by making the temperature of the film surface into 200 degreeC, and also thermally relaxed MD and TD at 190 degreeC by MD relaxation rate 5% and TD relaxation rate 10%.

Thus, a biaxially stretched polyethylene terephthalate film (polyester film) having a thickness of 250 µm was obtained.

Titanium oxide content (T) and an elastic modulus of a biaxially stretched polyethylene terephthalate film were measured with the following method.

Measurement of T

Using a biaxially stretched polyethylene terephthalate film, using a fluorescent X-ray analyzer (XRF-1500, manufactured by Shimadzu Seisakusho Co., Ltd.), the amount of titanium element in the polyester film was determined by single-measurement under the conditions shown in Table 1 above. And the content rate (T; mass%) of titanium oxide with respect to the film mass per unit volume was computed.

Measurement of modulus of elasticity

The elasticity modulus in the width direction (TD) of the obtained biaxially stretched polyethylene terephthalate film was measured in accordance with the measuring method of JISK7127. Specifically, the sample piece E1 is cut out to a size of 10 mm in length in the longitudinal direction (MD) and 150 mm in length in the width direction (TD) orthogonal to MD, and manufactured by Toyo Seiki Seisakusho Co., Ltd. The tensile test was done using the strograph R2 of. The tensile test performs a tensile test in the width direction of sample piece E1 with the distance between chucks being 100 mm, and the tensile velocity being 10 mm / min. In the longitudinal direction passing through the specific point in the width direction, five pieces of sample piece E1 were cut out, the tensile test was repeated five times using five pieces of samples, and the average value of the five tensile modulus obtained was YT. .

-evaluation-

The following evaluation was performed about the obtained biaxially stretched polyethylene terephthalate film. Table 3 shows the results of the evaluation.

(1) fluctuation range (deviation) of film thickness

In the width direction orthogonal to the longitudinal direction of the biaxially stretched polyethylene terephthalate film, measuring points were determined at intervals of 1 mm, and the film thickness in the width direction was measured by FILM THICKNESS TESTER KG601B (Anritsu Corporation). The value which subtracted the minimum value was calculated | required from the maximum value of the obtained measured value, and it was set as the index which shows the deviation of film thickness.

<Evaluation Criteria>

A: The variation in thickness is 2% or less.

B: The variation in thickness is more than 2% and 3% or less.

C: The variation in thickness is more than 3% and 5% or less.

D: The variation in thickness exceeds 5%.

(2) uneven coating

On the biaxially stretched polyethylene terephthalate film, the coating liquid for polymer layer formation prepared as follows was apply | coated with the bar coater, it dried at 170 degreeC for 2 minutes, and the polymer layer with a dry thickness of 0.2 micrometer was formed. About the formed polymer layer, application | coating was apply | coated thickly by visual inspection, and the number of the places which are not apply | coated was counted as application | coating nonuniformity, and it evaluated according to the following evaluation criteria.

<Evaluation Criteria>

A: The coating nonuniformity is one per 1 m ² .

B: The coating nonuniformity is ^two per 1 m ² .

C: Coating nonuniformity is three pieces per 1m <^2> .

D: The coating nonuniformity exceeds 3 pieces per 1m < ² >.

Preparation of ... coating liquid for polymer layer formation

Each following component was mixed and the coating liquid for forming a polymer layer was prepared so that it might become the following composition.

<Composition>

Olefin-based binder 213.8 parts

(Arobase (registered trademark) SE-1013N, made by Unitica Co., Ltd., solid content: 20.2% by mass)

Carbodiimide compound (crosslinking agent) 73.5 parts

(Kaibolite (registered trademark) V-02-L2, manufactured by Nisshin Boseki Co., Ltd., solid content: 10% by mass)

Oxazoline compound (crosslinking agent) 45.0 parts

(Epocross (registered trademark) WS700, Nippon Shokubai Co., Ltd., solid content: 5% by mass)

Titanium dioxide dispersions as follows

Surfactants45.0 parts

(Naroacti (registered trademark) CL95, Sanyo Kasei Kogyo Co., Ltd., solid content: 1% by mass)

Distilled water

Titanium Dioxide Dispersion

The titanium dioxide dispersion liquid was prepared by mixing the component in the following composition, and disperse | distributing so that the average particle diameter of titanium dioxide might be 0.42 micrometer using the dino mill disperser. In addition, the average particle diameter of titanium dioxide was measured using the microtrack FRA (made by Honeywell).

<Composition>

Titanium Dioxide

(Tai park (registered trademark) CR-95, Ishihara Sangyo Co., Ltd. powder)

Polyvinyl alcohol (PVA) aqueous solution 227.9 parts

(PVA-105, Gureray Co., Ltd., concentration: 10% by mass)

Dispersant 5.5 parts

(DEMO (registered trademark) EP, manufactured by Kao Corporation, concentration: 25 mass%)

Distilled water310.8parts

(3) power generation efficiency

By forming the said polymer layer on a biaxially stretched polyethylene terephthalate film, it was set as the back sheet, after bonding a back sheet with ethylene vinyl acetate copolymer (EVA), it attached to the solar cell module and measured power generation efficiency. Based on the measured value, it evaluated according to the following evaluation criteria.

<Evaluation Criteria>

A: The power generation efficiency of the module is 15% or more.

B: The power generation efficiency of the module is 12% or more and less than 15%.

C: The power generation efficiency of the module is 10% or more but less than 12%.

D: The power generation efficiency of the module is less than 10%.

(Examples 2-5, Example 8, Comparative Examples 1-3)

In Example 1, PET pellet 1 was replaced with any one of the following PET pellets 2-3 or PEN pellets, except that the conditions for producing the white polyester film were changed as shown in Table 2, In the same manner, a biaxially stretched polyethylene terephthalate film was produced and evaluated. The evaluation results are shown in Table 3.

Preparation of PET Pellets 2-3 and PEN Pellets

(1) Preparation of PET Pellets 2

In the production of PET pellet 1, PET pellet 2 was produced in the same manner as in the production of PET pellet 1, except that the temperature and time of the solid phase polymerization reaction were changed from 220 ° C and 30 hours to 230 ° C and 60 hours. .

(2) Preparation of PET Pellet 3

In the production of PET pellet 1, PET pellet 3 was produced in the same manner as in the production of PET pellet 1, except that the temperature and time of the solid phase polymerization reaction were changed from 220 ° C and 30 hours to 210 ° C and 10 hours. .

(3) Preparation of PEN Pellets

2,6-naphthalenedicarboxylic acid and ethylene glycol were polymerized as a raw material to prepare PEN pellets.

(Example 6, Comparative Example 4)

In Example 1, the biaxially stretched polyethylene terephthalate film was changed in the same manner as in Example 1 except that the amount of titanium oxide was changed, and the production conditions of the white polyester film were changed as shown in Table 2. It produced and evaluated. The evaluation results are shown in Table 3.

(Example 7, Comparative Example 5)

In Example 4, the biaxially stretched polyethylene terephthalate film was changed in the same manner as in Example 4 except that the amount of titanium oxide was changed and the manufacturing conditions of the white polyester film were changed as shown in Table 2. It produced and evaluated. The evaluation results are shown in Table 3.

TABLE 2

TABLE 3

As shown in Table 3, in Example, generation | occurrence | production of thickness variation was suppressed compared with the comparative example, and when the coating film was formed in the next process, generation | occurrence | production of a coating nonuniformity was suppressed little. Moreover, when the solar cell module was produced by being in close contact with the sealing material (EVA) of the solar cell element, the decrease in power generation efficiency, which is thought to be caused by poor bonding between EVA, was also suppressed.

As for the indication of the Japanese patent application 2015-063013, the whole is taken in into this specification by reference.

All documents, patent applications, and technical specifications described herein are incorporated by reference in the present specification to the same extent as if each document, patent application, and technical specification were specifically incorporated by reference and also recorded in each of them. .

Claims (16)

10 test pieces each having a white particle and satisfying the following Equations 1 and 2, and having a width of orthogonal to the longitudinal direction and having a length of 50 mm in one side at equal intervals, The variation range represented by the absolute value of the difference between the maximum value and the minimum value among the values of 10I + T obtained for each is 2.0 or less, and the tensile modulus YT in the width direction perpendicular to the longitudinal direction satisfies Equation 3 below, and is perpendicular to the longitudinal direction. The polyester film in which the fluctuation range (DELTA) YT represented by the absolute value of the difference of the maximum value and minimum value among the YTs measured in two or more areas in the width direction to satisfy | fills following formula 4 is satisfied.
2 mass% ≤ T ≤ 20 mass% ...
0.6dL / g≤I≤0.8dL / g
3500 MPa ≤ YT ≤ 5000 MPa ...
0 MPa <ΔYT≤500MPa
(In formula, T shows the content rate of the white particle with respect to the film mass per unit volume, I shows the intrinsic viscosity of the polyester in the area | region where said T was measured, and tensile elasticity modulus of the width direction orthogonal to a longitudinal direction. YT is measured by the measuring method of JIS K 7127) The method according to claim 1,
Polyester film, wherein the white particles are titanium oxide particles. The method according to claim 1,
The polyester film whose fluctuation range (DELTA) T of the content rate T of the said white particle in the width direction orthogonal to a longitudinal direction is 1.5 mass% or less. The method according to claim 1,
The polyester film whose fluctuation range (DELTA) I of the said intrinsic viscosity I in the width direction orthogonal to a longitudinal direction is 0.1 dL / g or less. delete The method according to claim 1,
The fluctuation range (DELTA) T of the content rate T of the said white particle in the width direction orthogonal to a longitudinal direction is 1.5 mass% or less, and the fluctuation range (DELTA) I of the said ultimate viscosity I in the width direction orthogonal to a longitudinal direction is 0.1 dL / g or less And the white particles are titanium oxide particles. The method according to any one of claims 1 to 4 and 6,
Polyester film which is a white polyethylene terephthalate film. The method according to any one of claims 1 to 4 and 6,
The polyester film whose fluctuation range of the thickness in the width direction orthogonal to a longitudinal direction is 5% or less. The method according to any one of claims 1 to 4 and 6,
Polyester film whose thickness is 200 micrometers or more and 350 micrometers or less. The method according to claim 8,
The polyester film whose thickness is 200 micrometers or more and 350 micrometers or less, and is a white polyethylene terephthalate film. The back protective sheet for solar cells which has the polyester film in any one of Claims 1-4. The back protective sheet for solar cells which has the polyester film of Claim 10. The solar cell module provided with the back surface protection sheet for solar cells of Claim 11. The solar cell module provided with the back surface protection sheet for solar cells of Claim 12. A melting process of mixing white particles with polyester and melting them with an extruder;
A conveying step of conveying the molten polyester to the die through a pipe,
The film-forming process of shape | molding the polyester conveyed to die in the sheet form on at least one of the following conditions A and B, and forming a polyester sheet,
A cooling process for cooling the film-formed polyester sheet,
The manufacturing method of the polyester film in any one of Claims 1-4.
Condition A: The following formulas 5 and 6 are satisfied.
C0 <C1 ... Expression 5
C2 <C1 ... Equation 6
Condition B: All the following formulas 7 to 11 are satisfied.
T0 <T1 ...
T2 <T1 ...
270 ° C≤T0≤320 ° C
270 ° C≤T1≤320 ° C
270 ° C≤T2≤320 ° C
In formulas 5-6, C0 represents the lip clearance of the center part in the width direction of the said die, and C1 represents the average value of the lip clearance of each center part between the center part and one end or the other end in the width direction of the said die | dye. C2 represents the average value of each lip clearance at both ends in the width direction of the die.
In Formulas 7-11, T0 represents the sheet temperature of the center part in the width direction of the polyester sheet at the time of a point away from die, and T2 represents the average value of each sheet temperature of the both ends in the width direction of a polyester sheet. , T1 represents the average value of the sheet temperature of each center portion between the center portion and one end or the other end in the width direction of the polyester sheet. The method according to claim 15,
The said conveyance process is a manufacturing method of the polyester film which conveys a polyester to die on condition which satisfy | fills following formula 12.
0 ° C <T11-T10≤20 ° C ...
In formula, T10 represents the resin temperature of the center part in the radial direction of the at least 1 area | region in the longitudinal direction of the said pipe | tube, and T11 is 5 mm in the radial direction from the inner wall surface of the area | region where the said resin temperature of the said pipe | tube was measured. The resin temperature at the position in the separated pipe is shown.

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