JP5295161B2 - Method for producing thermoplastic resin film - Google Patents

Description

  The present invention relates to a method for producing a thermoplastic resin film.

  Conventionally, biaxially stretched films of polyester films, particularly polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) have mechanical strength, heat resistance, chemical resistance, etc., magnetic tape, ferromagnetic thin film tape, It is widely used as a material for photographic films, packaging films, films for electronic members, electrical insulation films, films for metal laminates, films to be attached to glass surfaces such as glass display films, and protective films for various members.

  When producing a polyester film, for example, a melt of a thermoplastic resin is extruded from an extrusion die and applied onto a casting roll to form a sheet, and the thermoplastic resin sheet is further passed through a heating roll, a cooling roll, and the like in a vertical direction. The film is formed into a film having a predetermined thickness by performing stretching and transverse stretching (biaxial stretching).

  When a biaxially stretched film is produced by such a method, the film (base) in the middle is in contact with various rolls, so that scratches may occur on the surface of the film due to contact with the rolls. As a countermeasure against scratches on the film surface, for example, there is a method of improving the holding force of the film by reducing the roughness of the roll surface. However, when entering the base roll, the holding force decreases at the time of peeling, so that the film slips on the roll and is easily damaged.

  Further, in order to prevent fine scratches from entering into the roll and the film from being scratched due to that, it has been proposed to use a roll having a high surface hardness as a cooling roll for the stretched portion (for example, Patent Document 1). reference).

  In addition, in order to suppress the generation of scratches on the film due to foreign matter attached to the roll, use a roll of a material that suppresses charging due to friction between the roll and the film (for example, see Patent Document 2), or It has been proposed to remove dirt on the roll surface by intermittently irradiating the roll with laser light (see, for example, Patent Document 3).

  In addition, it has been proposed that the temperature of the preheating roll before stretching is set to be equal to or lower than the glass transition temperature of the thermoplastic resin sheet, and the thermoplastic resin sheet is heated and stretched using a radiation heating source (see Patent Document 4). .

  On the other hand, in recent years, photovoltaic power generation that converts sunlight into electricity has attracted attention from the viewpoint of protecting the global environment. The solar cell module used for this photovoltaic power generation has a structure in which (sealing material) / solar cell element / sealing material / back sheet are laminated in this order on glass on which sunlight is incident. .

  Solar cell modules must have high weather resistance so that they can maintain battery performance such as power generation efficiency over a long period of several decades even in harsh usage environments exposed to wind and rain and direct sunlight. It is said. In order to provide such weather resistance, weather resistance is also required for various materials such as a back sheet constituting the solar cell module and a sealing material for sealing the element. In addition, strong weather resistance is also required between these various materials, for example, adhesion between a back sheet and a sealing material (for example, ethylene-vinyl acetate copolymer (EVA)). As the back sheet, a polyester film such as PET or PEN having weather resistance is generally used.

Japanese Patent No. 3287602 JP 2004-322571 A JP 2009-40036 A JP 2009-233918 A

When weather resistance is required, such as a back sheet (back surface protective film) of a solar cell module, a thick polyester film is usually used, but when a thick film is produced by biaxial stretching, the film becomes a roll. A difference in temperature change is likely to occur between the contacting surface and the opposite surface. Therefore, in the step of longitudinally stretching the film, resistance is applied to the force contracted by linear expansion and the film becomes slippery, and as a result, the surface of the film is easily scratched. If the film surface is scratched, the weather resistance will be reduced.
In addition, a film for optical use such as a display film has a severe demand for scratches, and if the film surface is scratched in the stretching process, the optical properties are deteriorated or defective.

  An object of this invention is to provide the manufacturing method of the thick biaxially-oriented thermoplastic resin film by which generation | occurrence | production of a crack on a film surface is suppressed by a longitudinal stretch process.

In order to achieve the above object, the following invention is provided.
<1> An unstretched thermoplastic resin sheet having a glass transition temperature of Tg (° C.) is transported from the heating roll to the first cooling roll and stretched in the transporting direction between the heating roll and the first cooling roll. A longitudinal stretching step for forming a film having a thickness of 500 μm or more and 2000 μm or less, and transporting the film after stretching in the transport direction from the first cooling roll to the second cooling roll, By immediately cooling at a cooling rate of 30 ° C./s or more and 100 ° C./s or less in a section immediately after contact with the second cooling roll, the film is brought into contact with the second cooling roll. A cooling step for setting the average temperature in the thickness direction to (Tg-5) ° C. or less, and lateral stretching for stretching the film after passing through the second cooling roll in the width direction Method for producing a thermoplastic resin film comprising the steps, a.
<2> In the cooling step, the temperature change amount of the average temperature in the thickness direction of the film while the film passes through the second cooling roll is set to 20 ° C. or less and is in contact with the second cooling roll. The method for producing a thermoplastic resin film according to <1>, wherein the difference between the temperature change amount of the surface and the temperature change amount of the surface not in contact with the second cooling roll is controlled to 20 ° C. or less.
<3> The heat according to <1> or <2>, in which the shrinkage rate in at least one direction of the transport direction and the width direction of the film is 0.2% or less while the film passes through the second cooling roll. A method for producing a plastic resin film.
<4> The film according to any one of <1> to <3>, in which the film that is not in contact with the first cooling roll is forcibly cooled with respect to the film that is in contact with the first cooling roll. A method for producing a thermoplastic resin film.
<5> The method for producing a thermoplastic resin film according to any one of <1> to <4>, wherein the film between the first cooling roll and the second cooling roll is forcibly cooled.
<6> The film according to any one of <1> to <5>, wherein the film on the side not in contact with the second cooling roll is forcibly cooled with respect to the film in contact with the second cooling roll. A method for producing a thermoplastic resin film.
<7> As means for cooling the film other than the first cooling roll and the second cooling roll, a means for cooling by blowing a gas, a means for cooling via a liquid, and a solid are brought into contact with each other The method for producing a thermoplastic resin film according to any one of <4> to <6>, wherein at least one kind selected from means for cooling is used.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the biaxially-oriented thick thermoplastic resin film by which generation | occurrence | production of a crack on a film surface is suppressed at a longitudinal stretch process is provided.

It is the schematic which shows the structural example of the apparatus which enforces the manufacturing method of the thermoplastic resin film which concerns on this invention. It is the schematic which shows the structural example of the horizontal extending machine which implements a horizontal extending process. It is a schematic sectional drawing which shows the structural example of a solar cell module. It is a figure which shows the temperature variation | change_quantity (DELTA) T2 (degreeC) of the side which a film does not contact with the temperature variation | change_quantity (DELTA) T1 (degreeC) on the side which contacts a cooling roll.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
The inventors of the present invention have repeated research on scratches caused by rubbing with a roll when manufacturing a thick thermoplastic resin film. If the thickness of the film after longitudinal stretching is large, as shown in FIG. 4, there is a difference between the temperature change amount ΔT1 (° C.) on the side in contact with the cooling roll 6 and the temperature change amount ΔT2 (° C.) on the non-contact side. The film 8 is resistant to the force of contraction due to linear expansion and becomes slippery, and the contact surface with the roll 6 is easily scratched. Further, when the temperature of the film after longitudinal stretching is equal to or higher than the glass transition temperature Tg (° C.), shrinkage due to residual strain occurs on the second cooling roll 6, and the surface is crystallized, so there is a scratch. In this case, scratches are likely to remain after the transverse stretching step. On the other hand, in the first cooling roll immediately after the longitudinal stretching, since the film surface is a low crystal region, the scratch is shallow and can be improved in the transverse stretching step.

  As a result of further research based on these findings, the melt-extruded unstretched sheet was longitudinally stretched so as to be within a predetermined thickness range between the heating roll and the first cooling roll, and rapidly If cooling is performed and the temperature of the film is set to (Tg-5) ° C. or lower before being wound on the next second cooling roll, the shrinkage on the second roll is suppressed and the occurrence of scratches is suppressed. Furthermore, the shallow scratches generated on the first cooling roll can be almost removed in the subsequent transverse stretching process, and as a result, a thick biaxially stretched thermoplastic resin film with suppressed surface scratches is produced. I found out that I can.

The method for producing a thermoplastic resin film according to the present invention is as follows.
By conveying an unstretched thermoplastic resin sheet having a glass transition temperature of Tg (° C.) from the heating roll to the first cooling roll and stretching in the transport direction between the heating roll and the first cooling roll, A longitudinal stretching step for forming a film having a thickness of 500 μm or more and 2000 μm or less;
The film after being stretched in the transport direction is transported from the first cooling roll to the second cooling roll, and immediately after contacting the first cooling roll until it contacts the second cooling roll at 30 ° C. / a cooling step of bringing the average temperature in the thickness direction of the film to (Tg-5) ° C. or less until the film comes into contact with the second cooling roll by quenching at a cooling rate of s or more and 100 ° C./s or less; ,
A transverse stretching step of stretching the film after passing through the second cooling roll in the width direction;
including.

  FIG. 1 schematically shows an example of the configuration of an apparatus for carrying out the method for producing a thermoplastic resin film according to the present invention. The apparatus 100 mainly forms a polyester sheet by casting a polyester molten resin, and the polyester sheet formed by the film forming process unit 10 is stretched in the transport direction to form a polyester film. The longitudinal stretching process section 12, the cooling process section 14 for rapidly cooling the polyester film longitudinally stretched in the longitudinal stretching process section 12, and the transverse stretching process section 16 for stretching the polyester film cooled in the cooling process section 14 in the width direction. The winding process unit 18 winds up the polyester film stretched in the lateral stretching process unit 16.

<Film forming process>
First, a film forming process for obtaining an unstretched thermoplastic resin sheet having a glass transition temperature of Tg (° C.) will be described.
In the film forming process part 10, the die 20 and the casting drum 22 are provided in the film forming process part 10, and the molten resin used as a raw material is pressed and formed into a sheet shape.
Although the thermoplastic resin used as a raw material is not particularly limited, for example, in the case of producing a solar cell back surface protective film, it is preferable to use a polyester resin polycondensed using a titanium-based catalyst. This polyester resin will be described later.
After sufficiently drying the polyester resin, the polyester resin is melt-extruded into a sheet shape through an extruder, a filter and a die controlled in a temperature range of, for example, a melting point +10 to 50 ° C., and cast onto a rotating casting drum 22 to be rapidly cooled and solidified. Thereby, the polyester resin sheet 11 is obtained.

Although the thickness of the polyester resin sheet 11 depends on the thickness of the target biaxially stretched film, the polyester resin sheet 11 has a thickness of 500 μm or more and 2000 μm or less after the polyester resin sheet 11 is longitudinally stretched. The thickness of the sheet 11 is preferably 1500 mm or more and 8000 mm, for example.
The thickness of the polyester resin sheet 11 can be controlled by adjusting the discharge amount of the extruder, the width and height of the slit of the die 20, and the like.

<Vertical stretching process>
The unstretched polyester resin sheet 11 obtained in the film forming process is sent to the longitudinal stretching process section 12 and longitudinally stretched.
In the longitudinal stretching process section 12, there are nip rolls 25 and 27 for sandwiching the sheet 11 (film 13) between the heating roll 24 and the first cooling roll 26, which rotate at a predetermined speed, and the rolls 24 and 26, respectively. Is provided. Preheating rolls 23 and 23N for heating the sheet 11 without stretching are provided in front of the heating roll 24. In FIG. 1, the space between the two preheating rolls 23 and 23N is omitted. A free roll (not shown) may be provided between the heating roll 24 and the first cooling roll 26. The number of preheating rolls 23, 23N and free rolls is not limited, and may be appropriately provided according to the line speed and the film thickness.
Moreover, between the heating roll 24 and the 1st cooling roll 26, you may provide the heating means 15, such as an infrared heater for heating the polyester resin sheet 11 stretched longitudinally. The heating means 15 may be provided on one side of the sheet 11 conveyed between the rolls 24 and 26, or may be provided on both sides. For example, a far infrared heater is provided near the heating roll 24 to heat the unstretched polyester resin sheet 11 to 80 ° C. or higher and 110 ° C. or lower.

  The unstretched polyester resin sheet 11 is sent to the first cooling roll 26 from the heating roll 24 that rotates at a predetermined speed after being preheated. The first cooling roll 26 on the outlet side conveys the polyester resin sheet 11 at a faster conveying speed than the heating roll 24 on the inlet side, so that the conveying direction (vertical direction) is between the heating roll 24 and the first cooling roll 26. ) To be processed into a film 13A having a thickness smaller than that of the sheet 11. In this invention, it is set as the film 13A which has thickness of 500 micrometers or more and 2000 micrometers or less by this longitudinal stretch. If the thickness of the film after longitudinal stretching is less than 500 μm, the transverse stretching ratio is kept small, and it is difficult to remove scratches generated before lateral stretching by lateral stretching. On the other hand, when the thickness of the film 13A after longitudinal stretching exceeds 2000 μm, temperature unevenness in the thickness direction is large, and scratches are easily generated in the cooling process. From such a viewpoint, the thickness of the film 13A after longitudinal stretching is preferably 700 μm or more and 1500 μm or less, and more preferably 900 μm or more and 1200 μm or less.

The thickness of the film 13A can be controlled by adjusting the thickness of the unstretched polyester resin sheet 11, the rotational speeds of the heating roll 24 and the first cooling roll 26, and the like.
The longitudinal stretching ratio depends on the thickness of the unstretched polyester resin sheet 11 introduced into the heating roll 24, but is preferably 2.0 times or more and 4.0 times or less in order to suppress the occurrence of uneven thickness in the longitudinal stretching. It is more preferably 8 times or more and 3.5 times or less.

<Cooling process>
Next, the film 13A having a thickness of 500 μm or more and 2000 μm or less in the longitudinal stretching process is rapidly cooled in the cooling process unit 14.
In the cooling process section 14, the film 13 </ b> A after being stretched in the transport direction (longitudinal direction) is transported from the first cooling roll 26 to the second cooling roll 28 and immediately after coming into contact with the first cooling roll 26, the second cooling roll 28. By rapidly cooling at a cooling rate of 30 ° C./s or more and 100 ° C./s or less in the interval until contact with the film 13A, the average temperature in the thickness direction of the film 13A (Tg) until the film 13A contacts the second cooling roll 28 is obtained. -5) Set at or below ° C.
Here, when the cooling rate of the film 13A in the above section is less than 30 ° C./s, it is difficult to make the average temperature in the thickness direction of the film 13A be (Tg−5) ° C. or less, while from 100 ° C./s. If it is large, wrinkles are likely to occur.
Further, if the average temperature in the thickness direction of the film 13A is larger than (Tg-5) ° C. before the film 13A comes into contact with the second cooling roll 28, shrinkage due to residual strain occurs on the second cooling roll 28, Since the surface is crystallized, scratches remain even after the transverse stretching process when scratches occur.

In order to quench the longitudinally stretched film 13 </ b> A in a section immediately after contact with the first cooling roll 26 until contact with the second cooling roll 28, for example, try to quench with only the first cooling roll 26. However, the longitudinally stretched film 13A has a high temperature, and it is difficult to achieve both the cooling rate and the average temperature in the thickness direction with only the first cooling roll 26. Therefore, a means 17 for forcibly cooling the film 13A is provided in addition to the first cooling roll 26 and the second cooling roll 28, and the first cooling roll 26 is provided for the film 13A in contact with the first cooling roll 26. It is preferable to forcibly cool the surface that does not come into contact with the surface.
Further, the film 13A between the first cooling roll 26 and the second cooling roll 28 may be forcibly cooled.

  As the forced cooling means 17, at least one means selected from a means for cooling by blowing a gas, a means for cooling via a liquid, and a means for cooling by contacting a solid can be used. . Two or more types of cooling means may be combined for more efficient cooling.

Regardless of which type of cooling means 17 is used, the second cooling roll can be obtained by setting the average temperature in the thickness direction of the film 13A to (Tg-5) ° C. or less before the film 13A reaches the second cooling roll 28. The generation | occurrence | production of the damage resulting from shrinkage | contraction of the film 13A on 28 can be suppressed.
From the viewpoint of more reliably suppressing the occurrence of such scratches, the cooling rate of the film 13A in the section immediately after contacting the first cooling roll 26 until contacting the second cooling roll 28 is 35 ° C./s. The average temperature in the thickness direction of the film 13A until the film 13A comes into contact with the second cooling roll 28 is preferably (Tg-10) ° C. or less. In addition, from the viewpoint of the flaw depth, the average temperature in the thickness direction of the film 13A until the film 13A comes into contact with the second cooling roll 28 is preferably 32 ° C. or higher.

  The film 13 </ b> A sent to the second cooling roll 28 is also cooled on the second cooling roll 28. Since the average temperature in the thickness direction of the film 13A until the film 13A comes into contact with the second cooling roll 28 is (Tg-5) ° C. or less, the amount of shrinkage is small even if it is cooled on the second cooling roll 28. The shrinkage rate in at least one direction in the transport direction (longitudinal direction) and the width direction (transverse direction) of the film 13A while the film passes through the second cooling roll 28 can be 0.2% or less. Therefore, the generation of scratches on the film surface due to contact with the second cooling roll 28 is suppressed.

On the second cooling roll 28, the film 13A is gradually cooled to prevent scratches on the film surface due to linear expansion. Specifically, the temperature change amount ΔT of the average temperature in the thickness direction of the film while the film 13A passes the second cooling roll 28 is 20 ° C. or less, and the temperature of the surface in contact with the second cooling roll 28 It is preferable to control the difference between the change amount ΔT1 and the temperature change amount ΔT2 of the surface not in contact with the second cooling roll 28 to 20 ° C. or less. Here, the temperature change amount ΔT of the average temperature in the thickness direction of the film while passing through the second cooling roll 28 is the thickness when the film 13A that has passed through the first cooling roll 26 enters the second cooling roll 28. It means the difference between the average temperature in the vertical direction and the average temperature in the thickness direction when moving away from the second cooling roll 28.
That is, by suppressing the temperature change amount of the film 13A while passing through the second cooling roll 28, the surface of the film 13A (contact surface with the roll) is scratched by linear expansion on the second cooling roll 28. Can be more reliably suppressed.

The film 13A sent to the second cooling roll 28 is substantially maintained in the thickness adjusted in the longitudinal stretching step. In such a thick film 13A, the surface that does not contact the surface that contacts the second cooling roll 28; And the temperature change amount is different, and the difference in temperature change amount between both surfaces of the film 13A tends to be large. If the difference between the temperature changes on both sides is large, there is a risk of causing scratching. Therefore, it is preferable that the forced cooling means 19 is also provided here to forcibly cool the surface of the film 13A that is in contact with the second cooling roll 28 that is not in contact with the second cooling roll 28. As the forced cooling means 19 here, at least one means selected from a means for cooling by blowing a gas, a means for cooling through a liquid, and a means for cooling by contacting a solid is used. be able to.
In FIG. 1, cooling rolls 29 and 29N are provided after the second cooling roll 28 to further cool the longitudinally stretched film 13A before lateral stretching. The number of the cooling rolls 29 and 29N is not limited, and may be appropriately provided according to the line speed and the film thickness.

<Horizontal stretching process>
Next, the film 13A (longitudinal stretched polyester film) after passing through the second cooling roll 28 is stretched in the width direction (lateral direction) orthogonal to the transport direction (vertical direction).
In the transverse stretching step, the longitudinally stretched polyester film 13A is heated and stretched in the width direction by applying tension in the film width direction. A tenter is used as the transverse stretching machine. As shown in FIG. 2, the tenter is composed of a number of zones that can be individually controlled by hot air or the like and divided by a windshield curtain 30, and from the entrance, preheating zones T ₁ , T ₂ , transverse stretching zones T ₃ , T ₄ , T ₅ , T ₆ , heat fixing zones T ₇ , T ₈ , thermal relaxation zones T _{9 to} T _n-3 and cooling zones T _{n-2 to} T _n are preferably arranged. The thermal relaxation zone _T 9 _{~T n-3} and cooling zones _{T n-2} ~T _n is not necessarily required, may be provided if necessary.

This way the transverse stretching in the transverse stretching section 16 configured is performed, the transverse stretching section 16, through a longitudinally stretched polyester film 13A in the tenter 32, the transverse stretching zone _{T 3, T 4, T 5} , glass transition temperature (Tg) of more than T _6, after transverse stretching in the range of the glass transition temperature (Tg) of + 70 ° C. or less, in the heat setting zone _T 7, _{T 8} mp (Tm) -30 ° C. or higher and a melting point (Tm) of A heat setting process is performed in a range of −5 ° C. or lower.

In the lateral stretching step section 16, for example, the lateral stretching zones T _3, T ₄ , T ₅ , T ₆ are laterally stretched in the range of the glass transition temperature (Tg) or higher and the glass transition temperature (Tg) + 70 ° C. or lower, preferably Stretches in the range of glass transition temperature (Tg) + 25 ° C. or higher and glass transition temperature (Tg) + 60 ° C. When the transverse stretching temperature is less than the glass transition temperature (Tg), the polyester film 13A during transverse stretching may be broken. On the other hand, when it exceeds the glass transition temperature (Tg) + 70 ° C., in the width direction of the polyester film 13A. There is a risk of uneven elongation.

Further, the transverse stretching ratio in the transverse stretching zones T _3, T ₄ , T ₅ and T ₆ is preferably 3.0 times or more and 4.6 times or less. If the transverse draw ratio is less than 3.0 times, the thickness unevenness may be increased, and if it exceeds 4.6 times, tearing may occur.

After the transverse stretching in this way, a biaxially stretched polyester film 13B can be obtained, and the obtained biaxially stretched polyester film 13B is wound up by the winding process section 18.
Through the above steps, a polyester film in which scratches due to rubbing with the cooling roll are suppressed can be produced.

  Next, polyester suitably used as a thermoplastic resin when producing a thermoplastic resin sheet according to the present invention will be described.

-Esterification reaction-
In the esterification reaction when polymerizing polyester, a titanium (Ti) compound is used as a catalyst, and the amount of Ti added is 1 ppm or more and 30 ppm or less, more preferably 2 ppm or more and 20 ppm or less, more preferably 3 ppm or more and 15 ppm, in terms of element. Polymerization is preferably performed within the following range. In this case, the polyester film produced according to the present invention contains 1 ppm or more and 30 ppm or less of titanium.
When the amount of the Ti compound is 1 ppm or more, the polymerization rate is increased, and a preferable intrinsic viscosity IV is obtained. Further, when the amount of the Ti-based compound is 30 ppm or less, the terminal COOH can be adjusted to satisfy the above range, and a good color tone can be obtained.

  For the synthesis of Ti-based polyester using such a Ti-based compound, for example, Japanese Patent Publication No. 8-30119, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3897756, Japanese Patent No. 396226 No. 3, Patent No. 3997866, Patent No. 39996871, Patent No. 40000867, Patent No. 4053837, Patent No. 4127119, Patent No. 4134710, Patent No. 4159154, Patent No. 4269704, Patent No. 431538, JP-A-2005 The methods described in JP-A No. 340616, JP-A No. 2005-239940, JP-A No. 2004-319444, JP-A No. 2007-204538, Japanese Patent No. 3436268, and Japanese Patent No. 3780137 can be applied.

  The polyester used as a raw material for producing a polyester film in the present invention is (A) malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelin. Aliphatic dicarboxylic acids such as acids, azelaic acid, methylmalonic acid and ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic 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′- Diphenyl ether dicarboxylic acid, A dicarboxylic acid or an ester derivative thereof such as an aromatic dicarboxylic acid such as sodium sulfoisophthalic acid, phenylendanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9′-bis (4-carboxyphenyl) fluorenic acid; ) Aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, cyclohexanedimethanol, spiro Arocyclic diols such as glycol and isosorbide, aromatic diols such as bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9′-bis (4-hydroxyphenyl) fluorene A diol compound such as It can be obtained by esterification reaction and / or transesterification in known manner.

It is preferable that at least one aromatic dicarboxylic acid is used as the dicarboxylic acid component. More preferably, the dicarboxylic acid component contains an aromatic dicarboxylic acid as a main component. The “main component” means that the proportion of aromatic dicarboxylic acid in the dicarboxylic acid component is 80% by mass or more. A dicarboxylic acid component other than the aromatic dicarboxylic acid may be included. Examples of such a dicarboxylic acid component include ester derivatives such as aromatic dicarboxylic acids.
Further, it is preferable that at least one aliphatic diol is used as the diol component. The aliphatic diol can contain ethylene glycol, and preferably contains ethylene glycol as a main component. The main component means that the proportion of ethylene glycol in the diol component is 80% by mass or more.

  The amount of the aliphatic diol (for example, ethylene glycol) used is in the range of 1.015 to 1.50 mol with respect to 1 mol of the aromatic dicarboxylic acid (for example, terephthalic acid) and, if necessary, its ester derivative. Is preferred. The amount used is more preferably in the range of 1.02 to 1.30 mol, and still more preferably in the range of 1.025 to 1.10 mol. If the amount used is in the range of 1.015 or more, the esterification reaction proceeds favorably, and if it is in the range of 1.50 mol or less, for example, by-production of diethylene glycol due to dimerization of ethylene glycol is suppressed, Many characteristics such as melting point, glass transition temperature, crystallinity, heat resistance, hydrolysis resistance, and weather resistance can be kept good.

  Conventionally known reaction catalysts can be used for the esterification reaction and / or the transesterification reaction. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. Usually, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

Among these, more preferable polyesters are polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), and still more preferable is PET.
The PET is polymerized using one or more selected from a germanium (Ge) -based catalyst, an antimony (Sb) -based catalyst, an aluminum (Al) -based catalyst, and a titanium (Ti) -based catalyst. PET is preferable, and a Ti-based catalyst is more preferably used.

  The Ti-based catalyst has high reaction activity and can lower the polymerization temperature. Therefore, in particular, it is possible to suppress the thermal decomposition of PET and the generation of COOH during the polymerization reaction, which is suitable for adjusting the amount of terminal COOH to a predetermined range in the polyester film produced according to the present invention. is there.

Examples of the Ti-based catalyst include oxides, hydroxides, alkoxides, carboxylates, carbonates, oxalates, organic chelate titanium complexes, and halides. The Ti-based catalyst may be used in combination of two or more titanium compounds as long as the effects of the present invention are not impaired.
Examples of Ti-based catalysts include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl Titanium alkoxide such as titanate and tetrabenzyl titanate, titanium oxide obtained by hydrolysis of titanium alkoxide, titanium-silicon or zirconium composite oxide obtained by hydrolysis of a mixture of titanium alkoxide and silicon alkoxide or zirconium alkoxide, titanium acetate , Titanium oxalate, potassium potassium oxalate, sodium oxalate, potassium titanate, sodium titanate, titanium titanate-aluminum hydroxide mixture, titanium chloride, titanium chloride-aluminum chloride Miniumu mixture, titanium acetylacetonate, an organic chelate titanium complex having an organic acid as a ligand, and the like.

  Among the Ti-based catalysts, at least one organic chelate titanium complex having an organic acid as a ligand can be suitably used. Examples of the organic acid include citric acid, lactic acid, trimellitic acid, malic acid and the like. Among them, an organic chelate complex having citric acid or citrate as a ligand is preferable.

For example, when a chelate titanium complex having citric acid as a ligand is used, there is little generation of foreign matters such as fine particles, and a polyester resin having better polymerization activity and color tone than other titanium compounds can be obtained. Furthermore, even when using a citric acid chelate titanium complex, by adding it at the stage of the esterification reaction, a polyester resin having better polymerization activity and color tone and less terminal carboxyl groups can be obtained compared to the case where it is added after the esterification reaction. It is done. In this regard, the titanium catalyst also has a catalytic effect of the esterification reaction. By adding it at the esterification stage, the oligomer acid value at the end of the esterification reaction is lowered, and the subsequent polycondensation reaction is performed more efficiently. In addition, complexes with citric acid as a ligand are more resistant to hydrolysis than titanium alkoxides, etc., and do not hydrolyze in the esterification reaction process, while maintaining the original activity and catalyzing the esterification and polycondensation reactions It is estimated to function effectively as
In general, it is known that the greater the amount of terminal carboxyl groups, the worse the hydrolysis resistance. By reducing the amount of terminal carboxyl groups by the addition method of the present invention, improvement in hydrolysis resistance is expected. The
Examples of the citric acid chelate titanium complex are readily available as commercial products such as VERTEC AC-420 manufactured by Johnson Matthey.

  The aromatic dicarboxylic acid and the aliphatic diol can be introduced by preparing a slurry containing them and continuously supplying it to the esterification reaction step.

  In the present invention, an aromatic dicarboxylic acid and an aliphatic diol are polymerized in the presence of a catalyst containing a titanium compound, and at least one of the titanium compounds is an organic chelate titanium complex having an organic acid as a ligand. An esterification reaction step including at least a step of adding an organic chelate titanium complex, a magnesium compound, and a pentavalent phosphate ester having no aromatic ring as a substituent in this order, and an ester formed in the esterification reaction step And a polycondensation step in which a polycondensation product is produced by a polycondensation reaction of the polymerization reaction product, and is preferably produced by a method for producing a polyester resin.

In this case, in the course of the esterification reaction, the addition of a magnesium compound to the presence of an organic chelate titanium complex as a titanium compound, followed by the addition order of adding a specific pentavalent phosphorus compound, thereby providing a titanium catalyst. As the result, the coloring reaction is less and the electrostatic application property is high. At the same time, a polyester resin with improved yellowing when exposed to high temperatures is obtained.
As a result, coloring during polymerization and subsequent coloring during melt film formation are reduced, and yellowishness is reduced compared to conventional antimony (Sb) catalyst-based polyester resins, and germanium catalysts having a relatively high transparency are also obtained. It is possible to provide a polyester resin having a color tone and transparency comparable to a polyester resin and having excellent heat resistance. Further, a polyester resin having high transparency and less yellowness can be obtained without using a color tone adjusting material such as a cobalt compound or a pigment.

  This polyester resin can be used for applications requiring high transparency (for example, optical film, industrial squirrel, etc.), and it is not necessary to use an expensive germanium-based catalyst, so that the cost can be greatly reduced. In addition, since foreign matters caused by the catalyst that are likely to occur in the Sb catalyst system are also avoided, the occurrence of failures and quality defects in the film forming process can be reduced, and the cost can be reduced by improving the yield.

  In the above, when the aromatic dicarboxylic acid and the aliphatic diol are mixed with a catalyst containing an organic chelate titanium complex that is a titanium compound prior to the addition of the magnesium compound and the phosphorus compound, the organic chelate titanium complex or the like is subjected to an esterification reaction. Therefore, the esterification reaction can be carried out satisfactorily. At this time, you may add a titanium compound in mixing the dicarboxylic acid component and the diol component. Moreover, after mixing a dicarboxylic acid component (or diol component) and a titanium compound, you may mix a diol component (or dicarboxylic acid component). Further, the dicarboxylic acid component, the diol component, and the titanium compound may be mixed at the same time. The mixing is not particularly limited, and can be performed by a conventionally known method.

  In the esterification reaction, it is preferable to provide a process in which an organic chelate titanium complex which is a titanium compound and a magnesium compound and a pentavalent phosphorus compound as additives are added in this order. At this time, the esterification reaction proceeds in the presence of the organic chelate titanium complex, and thereafter, the addition of the magnesium compound can be started before the addition of the phosphorus compound.

(Phosphorus compound)
As the pentavalent phosphorus compound, at least one pentavalent phosphate having no aromatic ring as a substituent can be used. Examples of the pentavalent phosphate ester in the present invention include trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, tris phosphate (triethylene glycol), methyl acid phosphate, and phosphoric acid. Examples include ethyl acid, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol acid phosphate.

Among pentavalent phosphates, phosphates having a lower alkyl group having 2 or less carbon atoms as a substituent [(OR) ₃ —P═O; R = an alkyl group having 1 or 2 carbon atoms] are preferable, Specifically, trimethyl phosphate and triethyl phosphate are particularly preferable.

  In particular, when a chelate titanium complex coordinated with citric acid or a salt thereof is used as the catalyst as the titanium compound, the pentavalent phosphate ester has better polymerization activity and color tone than the trivalent phosphate ester. Furthermore, in the case of adding a pentavalent phosphate having 2 or less carbon atoms, the balance of polymerization activity, color tone, and heat resistance can be particularly improved.

  The addition amount of the phosphorus compound is preferably such that the P element conversion value is in the range of 50 ppm to 90 ppm. The amount of the phosphorus compound is more preferably 60 ppm to 80 ppm, and still more preferably 65 ppm to 75 ppm.

(Magnesium compound)
Inclusion of the magnesium compound improves electrostatic applicability. In this case, although it is easy to color, in this invention, coloring is suppressed and the outstanding color tone and heat resistance are obtained.

  Examples of the magnesium compound include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among these, magnesium acetate is most preferable from the viewpoint of solubility in ethylene glycol.

  The amount of magnesium compound added is preferably such that the Mg element conversion value is 50 ppm or more, more preferably 50 ppm or more and 100 ppm or less in order to impart high electrostatic applicability. The addition amount of the magnesium compound is preferably an amount that is in the range of 60 ppm to 90 ppm, more preferably 70 ppm to 80 ppm in terms of imparting electrostatic applicability.

In the esterification reaction step in the present invention, the value Z calculated from the following formula (i) is calculated from the following relational expression (ii) for the titanium compound as the catalyst component and the magnesium compound and phosphorus compound as the additive. ) Is preferably added and melt polymerized so as to satisfy. Here, the P content is the amount of phosphorus derived from the entire phosphorus compound including the pentavalent phosphate ester having no aromatic ring, and the Ti content is the amount of titanium derived from the entire Ti compound including the organic chelate titanium complex. It is. As described above, by selecting the combined use of the magnesium compound and the phosphorus compound in the catalyst system containing the titanium compound and controlling the addition timing and the addition ratio, while maintaining the catalyst activity of the titanium compound moderately high, yellow A color tone with less taste can be obtained, and heat resistance that hardly causes yellowing can be imparted even when exposed to high temperatures during polymerization reaction or subsequent film formation (during melting).
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0
This is an index for quantitatively expressing the balance between the three because the phosphorus compound not only acts on titanium but also interacts with the magnesium compound.
The formula (i) expresses the amount of phosphorus that can act on titanium by excluding the phosphorus content that acts on magnesium from the total amount of phosphorus that can be reacted. When the value Z is positive, it can be said that there is an excess of phosphorus that inhibits titanium, and conversely, when it is negative, there is a shortage of phosphorus necessary to inhibit titanium. In the reaction, since each atom of Ti, Mg, and P is not equivalent, each mole number in the formula is weighted by multiplying by a valence.

  In the present invention, no special synthesis or the like is required, and the titanium compound, phosphorus compound, and magnesium compound, which are inexpensive and easily available, are used for color tone and heat while having the reaction activity required for the reaction. A polyester resin excellent in coloring resistance can be obtained.

  In the formula (ii), from the viewpoint of further enhancing the color tone and the coloration resistance to heat while maintaining the polymerization reactivity, it is preferable to satisfy + 1.0 ≦ Z ≦ + 4.0, and + 1.5 ≦ Z ≦ + 3 Is more preferable.

  As a preferred embodiment in the present invention, before the esterification reaction is completed, after adding a chelate titanium complex having 1 ppm or more and 30 ppm or less of citric acid or citrate as a ligand to the aromatic dicarboxylic acid and the aliphatic diol, In the presence of the chelate titanium complex, a magnesium salt of weak acid of 60 ppm or more and 90 ppm or less (more preferably 70 ppm or more and 80 ppm or less) is added, and after the addition, 60 ppm or more and 80 ppm or less (more preferably 65 ppm or more and 75 ppm or less). And an embodiment in which a pentavalent phosphate having no aromatic ring as a substituent is added.

  The esterification reaction may be carried out using a multistage apparatus in which at least two reactors are connected in series under conditions where ethylene glycol is refluxed while removing water or alcohol produced by the reaction from the system. it can.

The esterification reaction described above may be performed in one stage or may be performed in multiple stages.
When the esterification reaction is performed in one step, the esterification reaction temperature is preferably 230 to 260 ° C, more preferably 240 to 250 ° C.
When the esterification reaction is performed in multiple stages, the temperature of the esterification reaction in the first reaction tank is preferably 230 to 260 ° C, more preferably 240 to 250 ° C, and the pressure is 1.0 to 5.0 kg / cm ² is preferable, and 2.0 to 3.0 kg / cm ² is more preferable. Temperature of the esterification reaction of the second reaction vessel is preferably from 230 to 260 ° C., more preferably from 245 to 255 ° C., the pressure is 0.5~5.0kg / cm ^2, more preferably 1.0 to 3. 0 kg / cm ² . Furthermore, when carrying out by dividing into three or more stages, it is preferable to set the conditions for the esterification reaction in the intermediate stage to the conditions between the first reaction tank and the final reaction tank.

-Polycondensation-
In polycondensation, a polycondensation product is produced by subjecting an esterification reaction product produced by the esterification reaction to a polycondensation reaction. The polycondensation reaction may be performed in one stage or may be performed in multiple stages.

  The esterification reaction product such as an oligomer generated by the esterification reaction is subsequently subjected to a polycondensation reaction. This polycondensation reaction can be suitably performed by supplying it to a multistage polycondensation reaction tank.

For example, as for the polycondensation reaction conditions in the case of carrying out in a three-stage reaction vessel, the reaction temperature of the first reaction vessel is 255 to 280 ° C., more preferably 265 to 275 ° C., and the pressure is 100 to 10 torr (13.3). × 10 ^{−3 to} 1.3 × 10 ⁻³ MPa), more preferably 50 to 20 torr (6.67 × 10 ^{−3 to} 2.67 × 10 ⁻³ MPa), and the second reaction tank is a reaction The temperature is 265 to 285 ° C., more preferably 270 to 280 ° C., and the pressure is 20 to 1 torr (2.67 × 10 ^{−3 to} 1.33 × 10 ⁻⁴ MPa), more preferably 10 to ³ torr (1. 33 × 10 ^{−3 to} 4.0 × 10 ⁻⁴ MPa), and the third reaction vessel in the final reaction vessel has a reaction temperature of 270 to 290 ° C., more preferably 275 to 285 ° C., and a pressure of 10-0.1tor ^{(1.33 × 10 -3 ~1.33 × 10} -5 MPa), is a preferred embodiment more preferably ^{5~0.5torr (6.67 × 10 -4 ~6.67 ×} 10 -5 MPa) .

In the present invention, by providing the esterification reaction step and the polycondensation step described above, the titanium atom (Ti), the magnesium atom (Mg), and the phosphorus atom (P) are included and calculated from the following formula (i). Value Z can produce a polyester resin composition satisfying the following relational expression (ii).
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) + 0 ≦ Z ≦ + 5.0

  The polyester resin composition satisfies + 0 ≦ Z ≦ + 5.0, and the balance of the three elements of Ti, P, and Mg is appropriately adjusted, so that the polymerization reactivity is maintained, It is excellent in color tone and heat resistance (reduction of yellow coloring under high temperature) and can maintain high electrostatic applicability. Moreover, in this invention, it has high transparency, without using color tone adjusting materials, such as a cobalt compound and a pigment | dye, and can obtain polyester resin with little yellowishness.

As described above, the formula (i) is a quantitative expression of the balance between the phosphorus compound, the magnesium compound, and the phosphorus compound, and the phosphorus content acting on the magnesium from the total amount of phosphorus that can be reacted. This represents the amount of phosphorus that can act on titanium. When the value Z is +0 or more, that is, the amount of phosphorus acting on titanium is not too small, better heat resistance can be obtained while keeping the catalytic activity (polymerization reactivity) of titanium high. A yellow tone is also suppressed in the color tone, and coloring is suppressed even at the time of film formation (melting time) after polymerization, and a better color tone is obtained. Moreover, when the value Z is +5.0 or less, that is, within a range where the amount of phosphorus acting on titanium is not too much, the resulting polyester has better heat resistance and color tone and is more excellent in catalytic activity and productivity.
In the present invention, for the same reason as described above, the formula (ii) preferably satisfies 1.0 ≦ Z ≦ 4.0, and more preferably satisfies 1.5 ≦ Z ≦ 3.0.

  Measurement of each element of Ti, Mg, and P is obtained by quantifying each element in PET using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology). It can carry out by calculating content [ppm] from the obtained result.

Moreover, it is preferable that the produced | generated polyester resin composition satisfy | fills the relationship represented by the following relational expression (iii) further.
B value when pelletized after polycondensation ≦ 4.0 (iii)
When the polyester resin obtained by polycondensation is pelletized and the b value of the pellet is 4.0 or less, yellowness is small and the transparency is excellent. When the b value is 3.0 or less, the color tone is comparable to that of a polyester resin polymerized with a Ge catalyst.

  The b value is an index representing the color and is a value measured using ND-101D (manufactured by Nippon Denshoku Industries Co., Ltd.).

Furthermore, the polyester resin composition preferably satisfies the relationship represented by the following relational expression (iv).
Color tone change rate [Δb / min] ≦ 0.15 (iv)
When the polyester resin pellets obtained by polycondensation are melt-held at 300 ° C., the color change rate [Δb / min] is 0.15 or less, so that yellow coloring when exposed to heating is low. Can be suppressed. Thereby, when extruding with an extruder, for example, to form a film, a film with little yellow coloring and excellent color tone can be obtained.

  The color change rate is preferably as small as possible, and is particularly preferably 0.10 or less.

The color tone change rate is an index representing a color change due to heat, and is a value obtained by the following method. That is,
The pellets of the polyester resin composition are put into a hopper of an injection molding machine (for example, EC100NII manufactured by Toshiba Machine Co., Ltd.) and melted and held in a cylinder (300 ° C.). The plate b value at this time is measured by ND-101D (manufactured by Nippon Denshoku Industries Co., Ltd.). The rate of change [Δb / min] is calculated based on the change in the b value.

(Additive)
The polyester in the present invention can further contain additives such as a light stabilizer and an antioxidant.

  It is preferable that the light stabilizer is added to the polyester film manufactured by this invention. By containing the light stabilizer, it is possible to prevent ultraviolet degradation. Examples of the light stabilizer include a compound that absorbs light such as ultraviolet rays and converts it into thermal energy, a material that absorbs light and decomposes when the film or the like absorbs light, and a material that suppresses the decomposition chain reaction. .

  The light stabilizer is preferably a compound that absorbs light such as ultraviolet rays and converts it into heat energy. By including such a light stabilizer in the film, it becomes possible to keep the effect of improving the partial discharge voltage by the film high for a long time even if the film is irradiated with ultraviolet rays continuously for a long time. Changes in color tone, strength deterioration, and the like due to UV rays.

  For example, if an ultraviolet absorber is a range in which other properties of the polyester are not impaired, any of organic ultraviolet absorbers, inorganic ultraviolet absorbers, and combinations thereof are preferably used without particular limitation. Can do. On the other hand, it is desired that the ultraviolet absorber has excellent heat and humidity resistance and can be uniformly dispersed in the film.

Examples of ultraviolet absorbers include, for example, salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, and the like as organic ultraviolet absorbers. Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, benzotriazole 2- (2'-hydroxy-5) '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 (2H benzotriazol-2-yl) phenol], a cyanoacrylate Ethyl-2-cyano-3,3′-diphenylacrylate), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol as triazine system Hindered amine-based bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethyl Piperidine polycondensate, in addition, nickel bis (octylphenyl) sulfide, 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, and the like .
Of these ultraviolet absorbers, triazine-based ultraviolet absorbers are more preferable in that they have high resistance to repeated ultraviolet absorption. In addition, these ultraviolet absorbers may be added to the above-mentioned ultraviolet absorber alone, or a form in which an organic conductive material or a water-insoluble resin is copolymerized with a monomer having an ultraviolet absorber ability. May be introduced.

  The content of the light stabilizer in the polyester film is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.3% by mass or more and 7% by mass or less with respect to the total mass of the polyester film. More preferably, it is 0.7 mass% or more and 4 mass% or less. Thereby, the molecular weight fall of the polyester by the photodegradation over a long time can be suppressed, and the adhesive force fall resulting from the cohesive failure in the film which arises as a result can be suppressed.

  In addition to the light stabilizer, the polyester film produced according to the present invention includes, for example, a lubricant (fine particles), an ultraviolet absorber, a colorant, a heat stabilizer, a nucleating agent (crystallization agent), a flame retardant. An agent or the like can be contained as an additive.

  In addition, the method for producing a polyester film of the present invention further includes a synthesis step in which a polyester used in the solid phase polymerization step is synthesized by esterifying a dicarboxylic acid or an ester derivative thereof and a diol compound in the presence of a titanium catalyst. It is preferable to have. The details of the dicarboxylic acid and its ester derivative, the diol compound, and the titanium catalyst are as described above, and the preferred embodiments are also the same.

-Solid phase polymerization process-
In the solid phase polymerization step in the present invention, polyester is solid phase polymerized. The solid-phase polymerization can be suitably performed using the polyester polymerized by the esterification reaction described above or a commercially available polyester in the form of small pieces such as pellets. The solid phase polymerization is performed at 150 ° C. or higher and 250 ° C. or lower, more preferably 170 ° C. or higher and 240 ° C. or lower, more preferably 190 ° C. or higher and 230 ° C. or lower for 1 hour or longer and 50 hours or shorter, more preferably 5 hours or longer and 40 hours or shorter, It is preferable to carry out under conditions of 10 hours or more and 30 hours or less. The solid phase polymerization is preferably performed in a vacuum or a nitrogen stream.

  Solid-phase polymerization may be carried out in a batch mode (a method in which a resin is placed in a container and stirred while applying heat for a predetermined time), or a continuous mode (a resin is placed in a heated cylinder and this is stirred). It may be carried out by a system in which the gas is passed through the cylinder while being kept flowing for a predetermined time while being heated, and sequentially fed out.

  The polyester after the solid phase polymerization step is melt-kneaded, the polyester sheet 11 is formed by the above-described film forming step, and the longitudinal stretching step, the cooling step, and the transverse stretching step are sequentially performed.

(Polyester film for solar cell backside sealing)
The polyester film produced by the method of the present invention is thick and has a suppressed surface scratch, and is therefore suitable as a polyester film for sealing the back surface of a solar cell.

(Solar cell back surface protective film)
The polyester film produced according to the present invention can be constituted by providing at least one functional layer such as an easy-adhesive layer, an ultraviolet-absorbing layer, and a light-reflecting white layer that are easily adhesive to the adherend. . For example, the following functional layer may be applied to a polyester film after uniaxial stretching and / or biaxial stretching. For coating, a known coating technique such as a roll coating method, a knife edge coating method, a gravure coating method, or a curtain coating method can be used.
Further, surface treatment (flame treatment, corona treatment, plasma treatment, ultraviolet treatment, etc.) may be performed before the coating. Furthermore, it is also preferable to bond together using an adhesive.

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

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

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

(3) Crosslinking agent The easy-adhesion layer in this invention can contain at least 1 sort (s) of a crosslinking agent.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent is particularly preferable from the viewpoint of securing adhesiveness after wet heat aging.
Specific examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- ( 2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline) 2,2′-hexamethylene-bis- (2-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (4,4′- Methyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be mentioned. Furthermore, (co) polymers of these compounds can also be preferably used.
Further, as a compound having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS500, WS700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used.
The preferable addition amount of the crosslinking agent in the easy-adhesive layer is preferably 5 to 50% by mass, more preferably 20 to 40% by mass per binder of the easy-adhesive layer. When the addition amount of the crosslinking agent is 5% by mass or more, a good crosslinking effect is obtained, and the strength of the reflective layer is not reduced and adhesion failure hardly occurs, and when it is 50% by mass or less, the pot life of the coating liquid is further increased. I can keep it long.

(4) Additives In the easy-adhesive layer in the present invention, a known matting agent such as polystyrene, polymethyl methacrylate, or silica, or a known surfactant such as an anionic or nonionic surfactant is added as necessary. May be.

(5) Method for forming an easy-adhesive layer As a method for forming an easy-adhesive layer in the present invention, there are a method for pasting a polymer sheet having easy adhesion to a polyester film and a method for coating. It is preferable in that it can be formed with a simple and highly uniform thin film. As a coating method, for example, a known method such as a gravure coater or a bar coater can be used. The solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

(6) Physical property Although there is no restriction | limiting in particular in the thickness of the easily-adhesive layer in this invention, Usually, 0.05-8 micrometers is preferable, More preferably, it is the range of 0.1-5 micrometers. When the thickness of the easy-adhesive layer is 0.05 μm or more, the required easy adhesion can be easily obtained, and when the thickness is 8 μm or less, the planar shape can be maintained better.
In addition, the easy-adhesion layer in the present invention may have transparency from the viewpoint of not impairing the effect of the colored layer when a colored layer (particularly a reflective layer) is disposed between the polyester film. preferable.

-UV absorbing layer-
The polyester film produced according to the present invention may be provided with an ultraviolet absorbing layer containing the above ultraviolet absorber. An ultraviolet absorption layer can be arrange | positioned in the arbitrary positions on a polyester film.
The ultraviolet absorber is preferably dissolved and dispersed together with an ionomer resin, polyester resin, urethane resin, acrylic resin, polyethylene resin, polypropylene resin, polyamide resin, vinyl acetate resin, cellulose ester resin, and the like. The transmittance is preferably 20% or less.

-Colored layer-
The polyester film produced according to the present invention can be provided with a colored layer. The colored layer is a layer arranged in contact with the surface of the polyester film or through another layer, and can be constituted using a pigment or a binder.

  The first function of the colored layer is to increase the power generation efficiency of the solar cell module by reflecting the light that has reached the back sheet without being used for power generation in the solar cell out of the incident light and returning it to the solar cell. is there. The second function is to improve the decorativeness of the appearance when the solar cell module is viewed from the front side. In general, when a solar cell module is viewed from the front side, a back sheet can be seen around the solar cell, and the decorativeness can be improved by providing a colored layer on the back sheet.

(1) Pigment The colored layer in the present invention can contain at least one pigment.
The pigment is preferably contained in the range of 2.5 to 8.5 g / m ² . The more preferable content of the pigment in the colored layer is in the range of 4.5 to 7.5 g / m ² . When the pigment content is 2.5 g / m ² or more, necessary coloring can be easily obtained, and the light reflectance and decorativeness can be adjusted to be more excellent. When the pigment content is 8.5 g / m ² or less, the planar shape of the colored layer can be maintained better.

  Examples of the pigment include inorganic pigments such as titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, ultramarine blue, bitumen, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. It is done. Among these pigments, a white pigment is preferable from the viewpoint of constituting a colored layer as a reflective layer that reflects incident sunlight. As the white pigment, for example, titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and the like are preferable.

As an average particle diameter of a pigment, 0.03-0.8 micrometer is preferable, More preferably, about 0.15-0.5 micrometer is preferable. If the average particle size is within the above range, the light reflection efficiency may be reduced.
When a colored layer is configured as a reflective layer that reflects incident sunlight, the preferred addition amount of the pigment in the reflective layer varies depending on the type of pigment used and the average particle size, but cannot be generally stated. preferably to 15 g / ^{m 2,} more preferably about 3 to 10 g / ^{m 2.} When the addition amount is 1.5 g / m ² or more, the required reflectance is easily obtained, and when the addition amount is 15 g / m ² or less, the strength of the reflection layer can be kept higher.

(2) Binder The colored layer in the present invention can contain at least one binder.
As a quantity in the colored layer in the case of containing a binder, the range of 15-200 mass% is preferable with respect to the pigment, and the range of 17-100 mass% is more preferable. When the amount of the binder is 15% by mass or more, the strength of the colored layer can be more favorably maintained, and when it is 200% by mass or less, the reflectance and the decorativeness are lowered.
As a binder suitable for the colored layer, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. From the viewpoint of durability, the binder is preferably an acrylic resin or a polyolefin. As the acrylic resin, a composite resin of acrylic and silicone is also preferable. Examples of preferred binders include the following.
Examples of the polyolefin include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals). Examples of the acrylic resin include Julimer ET-410 and SEK-301 (both manufactured by Nippon Pure Chemical Industries, Ltd.). Examples of the composite resin of acrylic and silicone include Ceranate WSA1060, WSA1070 (both manufactured by DIC Corporation), H7620, H7630, H7650 (both manufactured by Asahi Kasei Chemicals Corporation) and the like.

(3) Additive In addition to the binder and the pigment, a cross-linking agent, a surfactant, a filler, and the like may be further added to the colored layer in the present invention as necessary.

  Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. The addition amount of the crosslinking agent in the colorant is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, per binder of the colored layer. When the addition amount of the crosslinking agent is 5% by mass or more, a good crosslinking effect can be obtained, the strength and adhesiveness of the colored layer can be maintained high, and when it is 50% by mass or less, the coating solution The pot life can be maintained longer.

As the surfactant, a known surfactant such as an anionic or nonionic surfactant can be used. 0.1-15 mg / m < ² > is preferable and, as for the addition amount of surfactant, 0.5-5 mg / m < ² > is more preferable. The amount of the surfactant added is 0.1 mg / m ² or more to effectively suppress the occurrence of repelling, and the amount added is 15 mg / m ² or less to provide excellent adhesion.

  Furthermore, a filler such as silica may be added to the colored layer in addition to the above pigment. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less per binder of the colored layer. By including the filler, the strength of the colored layer can be increased. Moreover, since the ratio of a pigment can be maintained because the addition amount of a filler is 20 mass% or less, favorable light reflectivity (reflectance) and decorativeness are obtained.

(4) Forming method of colored layer As a forming method of the colored layer, there are a method of pasting a polymer sheet containing a pigment on a polyester film, a method of co-extruding a colored layer at the time of forming a polyester film, a method by coating, and the like. Among these, the method by coating is preferable in that it can be formed with a simple and highly uniform thin film. As a coating method, for example, a known method such as a gravure coater or a bar coater can be used. The solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. However, from the viewpoint of environmental burden, it is preferable to use water as a solvent.
A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

(5) Physical property It is preferable that a colored layer contains a white pigment and is comprised as a white layer (light reflection layer). The light reflectance at 550 nm in the case of the reflective layer is preferably 75% or more. When the reflectance is 75% or more, sunlight that has passed through the solar battery cell and has not been used for power generation can be returned to the cell, and the effect of increasing power generation efficiency is high.

  1-20 micrometers is preferable, as for the thickness of a white layer (light reflection layer), 1-10 micrometers is more preferable, More preferably, it is about 1.5-10 micrometers. When the film thickness is 1 μm or more, necessary decoration and reflectance are easily obtained, and when it is 20 μm or less, the surface shape may be deteriorated.

-Undercoat layer-
The polyester film produced according to the present invention can be provided with an undercoat layer. For example, when a colored layer is provided, the undercoat layer can be provided between the colored layer and the polyester film. The undercoat layer can be formed using a binder, a crosslinking agent, a surfactant, and the like.

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

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

The application may be applied to the polyester film after biaxial stretching or may be applied to the polyester film after uniaxial stretching. In this case, the film may be further stretched in a direction different from the initial stretching after coating. Furthermore, you may extend | stretch in 2 directions, after apply | coating to the polyester film before extending | stretching.
The thickness of the undercoat layer is preferably 0.05 μm to 2 μm, more preferably about 0.1 μm to 1.5 μm. When the film thickness is 0.05 μm or more, the necessary adhesiveness is easily obtained, and when it is 2 μm or less, the surface shape can be favorably maintained.

-Fluorine resin layer / silicon resin layer-
The polyester film produced according to the present invention is preferably provided with at least one of a fluorine-based resin layer and a silicon-based (Si-based) resin layer. By providing the fluorine-based resin layer or the Si-based resin layer, it is possible to prevent contamination of the polyester surface and improve weather resistance. Specifically, it is preferable to have the fluororesin-based coating layer described in JP2007-35694A, JP2008-28294A, and WO2007 / 063698.
Moreover, it is also preferable to stick together fluorine resin films such as Tedlar (manufactured by DuPont).

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

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

Water vapor permeability of the inorganic layer as the (moisture ^{permeability), 10 0 g / m 2} · d~10 -6 g / m 2 · d , more preferably ^{10 1 g / m 2 · d~10} -5 g / ^m is ² · d, more preferably from ^{10 2 g / m 2 · d~10} -4 g / m 2 · d.
In order to form an inorganic layer having such moisture permeability, the following dry method is suitable.

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

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

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

(Solar cell module)
The solar cell module is provided with the polyester film (including the back sheet) manufactured according to the present invention described above, and more preferably a transparent substrate on the side on which sunlight is incident, the light energy of sunlight It is comprised using the solar cell element which converts into electrical energy, the sealing material which seals a solar cell element, etc.

  For example, as shown in FIG. 3, the solar cell module is composed of a power generation element (solar cell element) 3 connected by metal wiring (not shown) for taking out electricity, an ethylene / vinyl acetate copolymer (EVA) resin, etc. The sealing material 2 may be sealed, and this may be sandwiched between a transparent substrate 4 such as glass and a back sheet 1 provided with a polyester film manufactured according to the present invention, and bonded together.

  The transparent substrate only needs to have a light-transmitting property through which sunlight can pass, and can be appropriately selected from base materials that transmit light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

  Solar cell elements include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, III-V groups such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenide, and II Various known solar cell elements such as -VI group compound semiconductor systems can be applied.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

-Synthesis of polyester resin-
(1) PET: Ti catalyst A PET sample was obtained according to the method described below.
-Esterification reaction-
4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed over 90 minutes to form a slurry, and continuously fed to the first esterification reactor at a flow rate of 3800 kg / h. Furthermore, an ethylene glycol solution of a citrate chelate titanium complex (VERTEC AC-420, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal was continuously supplied, and the average temperature was 250 ° C. with stirring in the reaction vessel. The reaction was carried out with a residence time of about 4.3 hours. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of element. At this time, the acid value of the obtained oligomer was 600 eq / ton.

  This reaction product was transferred to a second esterification reaction vessel and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 200 eq / ton. The inside of the second esterification reaction tank is partitioned into three zones. Among the three zones, the ethylene glycol solution of magnesium acetate is continuously added from the second zone so that the added amount of Mg is 75 ppm in terms of element. The ethylene glycol solution of trimethyl phosphate was continuously supplied from the third zone so that the amount of P added was 65 ppm in terms of element.

-Polycondensation reaction-
The obtained esterification reaction product was continuously supplied to the first polycondensation reaction tank, and with stirring, the reaction temperature was 270 ° C., the reaction tank internal pressure was 20 torr (2.67 × 10 ⁻³ MPa), and the average residence time. The polycondensation was performed in about 1.8 hours. Further, it was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions. Subsequently, it was further transferred to the third triple condensation reaction tank, in which the temperature in the reaction tank was 278 ° C., the pressure in the reaction tank was 1.5 torr (2.0 × 10 ⁻⁴ MPa), and the residence time was 1.5 hours. The reaction (polycondensation) was carried out to obtain polyethylene terephthalate.

(2) PEN: Sb catalyst Polymerization was performed according to the conditions described in “Comparative Experimental Example 6” in Table 3 of Japanese Patent No. 3119067, and a PEN sample was obtained using an Sb catalyst.

-Solid state polymerization-
The PET sample and PEN sample polymerized above were pelletized (diameter 3 mm, length 7 mm), and solid phase polymerization was carried out by the batch method and the continuous method using the obtained resin pellets.

Example 1
A sample of the PET-Ti catalyst system was dried to a water content of 20 ppm or less, then charged into a hopper of a single-screw kneading extruder having a diameter of 50 mm, melted at 270 ° C. and extruded. The melt (melt) was passed through a gear pump and a filter (pore diameter 20 μm), and then extruded from a die to a cooling (chill) roll under the following conditions. The extruded melt was brought into close contact with the cooling roll using an electrostatic application method.
Adjust the discharge rate of the extruder and the slit height of the die. This adjusted to the melt thickness (thickness at the time of extrusion) described in Table 1 below. The melt thickness was measured by photographing with a camera installed at the die exit.
(E) Temperature unevenness in the cooling roll A hollow chill roll is used, and the temperature is controlled by passing a heating medium (for example, water) through the hollow chill roll. At this time, a baffle plate is installed in the chill roll to generate temperature unevenness. For temperature unevenness, the baffle plate is adjusted while measuring the temperature of the chill roll surface with a non-contact thermometer (thermoviewer).

-Stretching-
The unstretched polyester resin sheet extruded and solidified on the cooling roll by the above method was successively biaxially stretched by the following method to obtain films described in Tables 1 and 2 below.

(A) Longitudinal Stretching Step An unstretched resin sheet (thickness at the time of extrusion: 3000 μm) is conveyed from the heating roll 24 equipped with nip rolls 25 and 27 to the first cooling roll 26 in the configuration as shown in FIG. Stretching was performed in the transport direction (longitudinal direction), and a PET film having a thickness of 1000 μm after longitudinal stretching was obtained. The longitudinal stretching conditions are as follows.
・ Preheating temperature: 82 ℃
・ Heating roll temperature: 82 ℃
-Longitudinal draw ratio: 3 times-First cooling roll temperature: 30 ° C

  The thickness of the polyester film was measured with a non-contact on-line thickness gauge.

(B) Cooling process The film after longitudinal stretching was conveyed from the 1st cooling roll to the 2nd cooling roll, and rapid cooling was performed. The cooling conditions are as follows.
・ Line speed: 30m / min
Cooling rate: 30 ° C / s
-Second cooling roll temperature: 26 ° C
・ Auxiliary cooling means: Air blowing

The film temperature (° C.) when entering the second cooling roll was calculated as follows.
The surface temperature of the film on the second cooling roll is measured with a radiation thermometer from the first cooling roll, and the heat transfer of the first cooling roll and the second cooling roll is matched with the actual film surface temperature in the heat transfer simulation. The coefficient was calculated, and the average temperature in the film thickness direction when entering the second cooling roll was estimated from the simulation.

The temperature change amount ΔT (° C.) on the second cooling roll was calculated as follows.
Similarly to the above, the average temperature in the film thickness direction when entering and exiting the second cooling roll was determined from the heat transfer simulation, and the temperature change ΔT (° C.) was estimated.

The difference (ΔT1−ΔT2) between the temperature change amount ΔT1 (° C.) of the contact surface on the second cooling roll and the temperature change amount ΔT2 (° C.) of the non-contact surface was calculated as follows.
Similarly to the above, from the heat transfer simulation, when entering the second cooling roll for each of the 100 μm thick layer closest to the surface in contact with the second cooling roll and the 100 μm thick layer closest to the non-contact surface, The amount of temperature change ΔT1 (° C.) and ΔT2 (° C.) when exiting was estimated, and ΔT1-ΔT2 was calculated.

The shrinkage rate (%) of the film on the second cooling roll was measured as follows.
Three markings of 15 cm square are put in the width direction with a laser marker on the non-contact surface of the first cooling roll, and the marking size near the second cooling roll inlet and outlet is photographed with a high speed camera for the three markings, and the flow direction And the amount of size change in the width direction was determined. An average was taken with respect to the size change amount at three places in the width direction, and the shrinkage rate (%) in the flow direction and the width direction was calculated.

(C) Transverse stretching step The film after the cooling step was stretched horizontally under the following conditions using a tenter.
<Condition>
-Preheating temperature: 110 ° C
-Stretching temperature: 120 ° C
-Stretch ratio: 3.9 times-Stretch speed: 70% / second

-Heat fixation / thermal relaxation-
Then, the biaxially stretched film after finishing longitudinal stretching and lateral stretching was heat-set under the following conditions. Further, after heat setting, the tenter width was reduced and heat relaxation was performed under the following conditions.
<Thermal process conditions>
・ Heat setting temperature: 215 ℃
・ Heat setting time: 2 seconds
<Heat relaxation conditions>
-Thermal relaxation temperature: 210 ° C
-Thermal relaxation rate: 2%

-Winding-
After heat setting and heat relaxation, both ends were trimmed by 10 cm. Then, after extruding (knurling) with a width of 10 mm at both ends, it was wound up with a tension of 25 kg / m. The width was 1.5 m and the winding length was 2000 m.
A polyester film was produced as described above.

(Evaluation)
-Scratches-
The presence or absence of scratches on the produced film surface was evaluated by a laser microscope. The evaluation criteria are as follows.
A: Scratch length is less than 0.05% of film width and depth is less than 0.05 μm B: Scratch length is less than 0.1% of film width and depth is less than 0.1 μm Δ: Scratch length Is less than 0.15% of the film width and the depth is less than 0.1 μm ×: the scratch length is 0.15% or more of the film width or the depth is 0.1 μm or more

(Examples 2 to 10 and Comparative Examples 1 to 4)
The polyester film was manufactured by changing the conditions as shown in Tables 1 and 2 with respect to Example 1, and the generation of scratches was evaluated.

  The production conditions and evaluation of the polyester film are shown in Table 1 and Table 2, respectively.

  As shown in Table 2, the polyester films of Examples 1 to 10 had fewer scratches than the polyester films of Comparative Examples 1 to 4.

The method for producing a thermoplastic resin film according to the present invention is, for example, used for a back sheet (a sheet disposed on the side opposite to the sunlight incident side of a solar cell element; a so-called back sheet) constituting a solar cell module. It is suitable for producing a thick polyester film to be used.
Moreover, the manufacturing method of the thermoplastic resin film which concerns on this invention is suitable also for manufacture of films for optical uses, such as a film for displays.

1 Back sheet (back protective film)
2 Sealant 3 Solar Cell Element 11 Unstretched Polyester Resin Sheet 12 Longitudinal Stretching Process Section 13A Longitudinal Stretched Polyester Film 13B Biaxially Stretched Polyester Film 14 Cooling Process Section 15 Heating Means 16 Horizontal Stretching Process Section 17 Forced Cooling Means 18 Winding Process Unit 19 Forced cooling means 20 Die 22 Casting drum 23, 23N Preheating roll 24 Heating roll 25, 27 Nip roll 26 First cooling roll 28 Second cooling roll 29, 29N Cooling roll 30 Windshield curtain 32 Tenter

Claims (7)

By conveying an unstretched thermoplastic resin sheet having a glass transition temperature of Tg (° C.) from the heating roll to the first cooling roll and stretching in the transport direction between the heating roll and the first cooling roll, A longitudinal stretching step for forming a film having a thickness of 500 μm or more and 2000 μm or less;
The film after being stretched in the transport direction is transported from the first cooling roll to the second cooling roll, and immediately after contacting the first cooling roll until it contacts the second cooling roll at 30 ° C. / a cooling step of bringing the average temperature in the thickness direction of the film to (Tg-5) ° C. or less until the film comes into contact with the second cooling roll by quenching at a cooling rate of s or more and 100 ° C./s or less; ,
A transverse stretching step of stretching the film after passing through the second cooling roll in the width direction;
A method for producing a thermoplastic resin film.   In the cooling step, the temperature change of the average temperature in the thickness direction of the film while the film passes through the second cooling roll is 20 ° C. or less, and the temperature of the surface in contact with the second cooling roll The method for producing a thermoplastic resin film according to claim 1, wherein the difference between the amount of change and the amount of temperature change on the surface not in contact with the second cooling roll is controlled to 20 ° C. or less.   3. The thermoplastic resin film according to claim 1, wherein a shrinkage ratio in at least one direction of the transport direction and the width direction of the film while the film passes through the second cooling roll is 0.2% or less. 4. Manufacturing method.   The heat according to any one of claims 1 to 3, wherein a surface of the film that is not in contact with the first cooling roll is forcibly cooled with respect to the film that is in contact with the first cooling roll. A method for producing a plastic resin film.   The manufacturing method of the thermoplastic resin film as described in any one of Claims 1-4 which forcibly cools the said film between a said 1st cooling roll and a said 2nd cooling roll.   The heat according to any one of claims 1 to 5, wherein a surface of the film that is not in contact with the second cooling roll is forcibly cooled with respect to the film that is in contact with the second cooling roll. A method for producing a plastic resin film.   As means for cooling the film other than the first cooling roll and the second cooling roll, cooling is performed by blowing a gas, means for cooling through a liquid, and cooling by bringing a solid into contact with the film. The method for producing a thermoplastic resin film according to any one of claims 4 to 6, wherein at least one means selected from the means is used.

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