WO2014157109A1 - ポリエステルフィルム及びその製造方法 - Google Patents
ポリエステルフィルム及びその製造方法 Download PDFInfo
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- WO2014157109A1 WO2014157109A1 PCT/JP2014/058129 JP2014058129W WO2014157109A1 WO 2014157109 A1 WO2014157109 A1 WO 2014157109A1 JP 2014058129 W JP2014058129 W JP 2014058129W WO 2014157109 A1 WO2014157109 A1 WO 2014157109A1
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- polyester film
- film
- polyester
- width direction
- heat
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
- B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
- B29C55/14—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial successively
- B29C55/143—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial successively firstly parallel to the direction of feed and then transversely thereto
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
- B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
- B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
- B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
Definitions
- the present invention relates to a polyester film and a method for producing the same.
- Polyester is applied to various applications such as electrical insulation and optical applications.
- solar cell applications such as a sheet for protecting the back surface of a solar cell (so-called back sheet) have attracted attention as electrical insulation applications in recent years.
- a polyester film obtained by biaxial stretching after melt extrusion may be used as a functional film by applying or pasting a functional material on the film. At this time, if the polyester film is manufactured while being conveyed by a roller or the like, the polyester film may be wrinkled or scratched or the film may meander due to various causes during heating and conveyance.
- the heat fixing temperature of the polyester film is fixed at Tm-35 to 65 ° C. and heat relaxation treatment is performed at 140 to 175 ° C. It has been disclosed to improve failures such as wrinkles in the process (for example, see JP 2012-094699 A).
- the heat shrinkage rate in the film transport direction (MD) and the direction perpendicular to the MD (TD; Transverse Direction) and the specific MD / TD heat shrinkage rate the film is heated and transported. It has been disclosed to impart properties (see, for example, JP-A-2001-191406).
- Japanese Patent Application Laid-Open No. 2012-094699 and Japanese Patent Application Laid-Open No. 2001-191406 both show that the reduction of heat shrinkage and uniformity of the film are effective in improving wrinkles, but the wrinkles and scratches Insufficient suppression.
- the present invention has been made in view of the above, and an object of the present invention is to provide a polyester film in which wrinkles and flaws are less likely to occur during heating and conveyance and a method for producing the same, and to achieve the object.
- the present invention when heated and conveyed polyester film, the knowledge that the polyester film is locally long and slack, etc., and that the wrinkles and scratches are likely to occur, and the curvature of the end in the film width direction
- the heat shrinkage rate in the longitudinal direction in the width direction is within a predetermined range, and it has been found that local length unevenness is suppressed even during heating and conveyance, and that wrinkles and scratches are less likely to occur. It was achieved based on knowledge. Specific means for achieving the above object are as follows.
- a polyester film satisfying the following formulas (1) to (4).
- W / 1000 ⁇ [(S s1 ⁇ S s2 ) / C S1 / 100] ⁇ 2W (1) 0 ⁇ (S s1 -S s2 ) ⁇ 0.5 (2) ⁇ 1 ⁇ (S s1 + S s2 + S CT ) / 3 ⁇ 3 (3) 0 ⁇ C s1 ⁇ 0.2 (4)
- S s1 is orthogonal to the polyester film width direction at the end of the polyester film width direction at the end portion having a large thermal shrinkage at 150 ° C. and 30 minutes in the direction orthogonal to the polyester film width direction.
- S s2 is orthogonal to the polyester film width direction at the end of the polyester film width direction at the end of the side having a small heat shrinkage rate at 150 ° C. for 30 minutes in the direction orthogonal to the polyester film width direction.
- SCT represents the thermal shrinkage [%] at 30 ° C.
- C S1 is the maximum value of the magnitude of the curve at the end on the side where the thermal shrinkage rate is large at 150 ° C. and 30 minutes in the direction orthogonal to the polyester film width direction among the ends in the polyester film width direction [ m].
- W represents the film width [m] of the polyester film.
- S s1 is synonymous with S s1 in the formula (1) or the like, of the ends of the polyester film width direction, 0.99 ° C. in a direction orthogonal to the polyester film width direction, the side heat shrinkage ratio is large at 30 minutes
- S s2 has the same meaning as S s2 in the formula (1) or the like, of the ends of the polyester film width direction, 0.99 ° C. in a direction orthogonal to the polyester film width direction, the side heat shrinkage ratio is large at 30 minutes
- S CT has the same meaning as S CT in the formula (3) represents the polyester film at the central portion in the width direction, the direction of 0.99 ° C. perpendicular to the polyester film width direction, the thermal shrinkage at 30 min [%] .
- C CT is the maximum value of the curvature at the end in the width direction of the half-cut polyester film obtained by cutting the polyester film along a straight line connecting the centers in the film width direction at both ends in the polyester film longitudinal direction. It represents the value [m] that is added and divided by 2.
- W is synonymous with W in Formula (1), and represents the film width [m] of the polyester film.
- ⁇ 3> The polyester film according to ⁇ 1> or ⁇ 2>, in which a film width (W) is 0.3 m or more and 8 m or less.
- ⁇ 4> The polyester according to any one of ⁇ 1> to ⁇ 3>, wherein the pre-peak temperature unevenness measured by differential scanning calorimetry (DSC) in the film width direction is 0.5 ° C. or more and 10 ° C. or less. It is a film.
- DSC differential scanning calorimetry
- ⁇ 5> The polyester film according to any one of ⁇ 1> to ⁇ 4>, wherein the intrinsic viscosity of the polyester film is 0.55 dL / g or more and 0.90 dL / g or less.
- ⁇ 6> The polyester film according to any one of ⁇ 1> to ⁇ 5>, wherein the amount of terminal carboxy groups of the polyester film is 5 eq / ton or more and 35 eq / ton or less.
- the content ratio of structural units derived from a trifunctional or higher polyfunctional monomer is 0.005 mol% or more and 2.5 mol% or less with respect to all the structural units of the polyester in the polyester film ⁇ 1>.
- Heat-fixing part that heats and crystallizes the polyester film, heat-fixes the heat-fixed polyester film, relaxes the tension of the polyester film and removes residual distortion of the film, and heat-relaxation
- Radiant heating is the method for producing a polyester film according to ⁇ 8>, which is performed with a ceramic heater.
- the transverse stretching step includes a preheating portion, a stretching portion, a heat fixing portion, a heat relaxation portion, and a cooling portion, and at least two gripping members per one end portion of each end portion in the width direction of the polyester film in the preheating portion.
- a biaxial stretching device that conveys the polyester film from the preheating part to the cooling part.
- the temperature of the surface of the polyester film when the polyester film is detached from the gripping member is that of the polyester film at a position 200 mm away from the gripping member in the width direction with respect to the surface temperature at the center in the width direction of the polyester film.
- S s1, S s2, S CT according to the present invention, a polyester film schematic diagram for explaining the definition of C S1, and W. It is cut in half polyester film schematic view for explaining the definition of C C1, C C2, and C CT in the present invention. It is a top view which shows an example of a biaxial stretching machine from the upper surface.
- the polyester film may be highly functionalized or compounded by laminating a plurality of polyester films or laminating a functional layer on the polyester film.
- the film In processing such a polyester film, the film is usually heated or stretched while being conveyed by a roll or the like. Wrinkles and scratches that occur when the polyester film is heated and conveyed tend to be caused by the presence of unevenness in the flatness (slack or shrinkage) in the film. Locally slack spots on the film slip on the roll and become scratches, or the slack breaks during transportation and wrinkles.
- the unevenness of the flatness of the polyester film may exist from an unheated film before heating the film, or the heat shrinkage unevenness at the time of heating (some parts are relatively less shrunk than other parts and are not loose). For example). There were attempts to individually improve the flatness of the unheated film and the heat shrinkage rate unevenness during heating, but this was insufficient.
- the polyester film by making the polyester film satisfy the formulas (1) to (4) described later, specifically, the heat shrinkage ratio of the unheated film is large and the shrinkage of the shrinkage is shown.
- the thermal shrinkage rate By reducing the thermal shrinkage rate, it is possible to obtain a film in which scratches and creases are suppressed during heating and conveyance.
- the flatness of the film refers to the state of looseness and shrinkage of the polyester film, and is said to be good when there is no partial looseness or partial shrinkage in the form. Further, when the film is partially loosened or shrunk or both in the TD direction of the film, it is also referred to as “difference in flatness” or “unevenness in flatness”.
- difference in flatness or “unevenness in flatness”.
- the polyester film of the present invention satisfies the following formulas (1) to (4).
- W / 1000 ⁇ [(S s1 ⁇ S s2 ) / C S1 / 100] ⁇ 2W (1) 0 ⁇ (S s1 -S s2 ) ⁇ 0.5 (2) ⁇ 1 ⁇ (S s1 + S s2 + S CT ) / 3 ⁇ 3 (3) 0 ⁇ C s1 ⁇ 0.2 (4)
- S s1 is the thermal shrinkage rate in the direction perpendicular to the film width direction of the polyester film on the side having the larger thermal shrinkage rate (150 ° C., 30 minutes) in the direction perpendicular to the film width direction among the ends in the film width direction [ %]
- S s2 is the direction perpendicular to the film width direction of the polyester film on the side where the thermal contraction rate (150 ° C., 30 minutes) in the direction perpendicular to the film width direction is small among the ends in the film width direction.
- SCT represents the thermal shrinkage rate (150 ° C., 30 minutes) [%] in the direction perpendicular to the film width direction of the polyester film in the film center in the film width direction.
- C S1 is the maximum value [m] of the curvature at the end of the film end in the film width direction on the side where the thermal contraction rate (150 ° C., 30 minutes) in the direction orthogonal to the film width direction is large.
- W represents the film width [m] of the polyester film.
- the “end in the film width direction” means not only the edge in the width direction of the polyester film but also the region from the edge to 10% of the total length in the width direction of the polyester film (that is, the width).
- the film conveyance direction is also referred to as MD (Machine Direction) direction.
- the MD direction of the film is also referred to as the longitudinal direction of the film.
- the film width direction is a direction orthogonal to the longitudinal direction.
- the film width direction is also called a TD (Transverse Direction) direction in a film manufactured while transporting the film.
- the film width direction is referred to as TD or TD direction
- the direction orthogonal to the film width direction is referred to as MD or MD direction.
- the heat shrinkage in the MD direction is also referred to as MD heat shrinkage, and the ratio is referred to as MD heat shrinkage rate. Therefore, the thermal contraction rate in the direction orthogonal to the film width direction is also expressed as MD thermal contraction rate.
- the heat shrinkage rate (150 ° C., 30 minutes) is defined as follows. Two reference lines are put in advance in a sample piece M of a polyester film cut in 30 mm in the TD direction and 120 mm in the MD direction so as to have an interval of 100 mm in the MD direction in advance. After the sample piece M is left in a heating oven at 150 ° C. for 30 minutes under no tension, the sample piece M is cooled to room temperature, and the interval between the two reference lines is measured. The interval after processing measured at this time is A [mm]. The numerical value [%] calculated by using the formula “100 ⁇ (100 ⁇ A) / 100” from the interval 100 mm before the processing and the interval Amm after the processing is used as the MD thermal contraction rate (S ).
- the heat shrinkage rate (150 ° C., 30 minutes) is also simply referred to as the heat shrinkage rate.
- the type of polyester is not particularly limited, and the type of polyester that can be used in the present invention will be described later.
- polyethylene terephthalate PET
- PET polyethylene terephthalate
- S s1 , S s2 , and S CT are as follows.
- S s1 and S s2 are both MD thermal contraction rates of the end portions in the TD direction of the polyester film
- S s1 represents MD thermal contraction rate [%] on the side where the MD thermal contraction rate is large
- S s2 is MD MD thermal contraction rate [%] of the side with a small thermal contraction rate is represented
- S CT represents the MD heat shrinkage [%] at the center in the TD direction of the polyester film.
- FIGS. 1A and 1B show curved polyester films, respectively.
- a polyester film obtained by melting and kneading a polyester raw material resin and stretching and recovering one end of the end of the film in the MD direction is fixed at a high place and suspended. The edges tend to be curved.
- FIG. 1 schematically shows a polyester film suspended from a high place and stretched so that the film is not slack.
- FIG. 1A shows a film in which the S1 side (high MD heat shrinkage rate side) swells in an arc shape when the polyester film is hung from a high place
- FIG. 1B shows the S2 side (low MD heat shrinkage). (Rate side) shows a film expanding in an arc shape.
- the polyester film shown in FIGS. 1A and 1B shows W as the film width (total film length in the TD direction) at the MD direction end of the film. Further, in FIG. 1, the center position of the film width W in the MD direction end portion of the film and C W, of the MD direction end portion of the film, C Wu and C W in a fixed side to a high place, the other end C W is indicated as C Wd .
- the total length in the MD direction of the polyester film is L.
- L is not the length of the edge of the TD direction end part of the polyester film, but the distance from one end part in the MD direction to the other end part of the polyester film suspended from a high place.
- the distance from C Wu to C Wd of the straight line Y1 obtained by connecting C Wu and C Wd (the straight line indicated by the dotted line in the vertical direction in FIG. 1) is L.
- a straight line (straight line Y1) connecting C Wu and C Wd is aligned with the direction of gravity.
- C Wu sides in FIG. 1, a straight line represented by a dashed line
- straight Z1 parallel to the direction of gravity on the polyester film Pull on.
- L / 2 the position of half of the straight line Y1 (L / 2), draw a straight line C L which perpendicular to a straight line Y1.
- C S1 is a distance on the straight line C L, the side S1 of the TD direction end portion of the polyester film, to the straight line Z1 Expressed as distance.
- C S1 that is the maximum value of the curvature of the polyester film having the width W is also referred to as a “full width arc”.
- the arc is called a plus arc, and when the S1 side is retracted (the straight line Z1 is The arc in the case of being pulled outward is called a minus arc.
- FIG. 2 shows a half-cut polyester film obtained by cutting the polyester film shown in FIG. 1 along a straight line Y1 obtained by connecting C Wu and C Wd .
- FIG. 2A shows a fragment on the S1 side of the half-cut polyester film of the polyester film shown in FIG.
- FIG. 2B shows a fragment on the S2 side of the half-cut polyester film of the polyester film shown in FIG.
- C Wd located at the center in the film TD direction is located at an end portion in the TD direction in FIG. 2 by cutting the film.
- the position of C Wd is referred to as C1 in FIG. 2A and C2 in FIG.
- FIG. 2 also schematically shows a state in which a half-cut polyester film is hung with one end of the end in the MD direction of the film being fixed at a high place like the polyester film of FIG. Yes.
- a C Wu -C Wd straight line straight line Y1
- the tension is lost and the film tends to be bent in the same manner as the original film.
- the film width (the total length in the TD direction) at the end portion in the MD direction of the half-cut polyester film shown in FIGS. 2A and 2B is W / 2.
- CW2 a half position of W / 2 at the MD end portion of the film
- the C W2U the C W2 in a fixed side to a high place
- C W2d the C W2d
- the distance from C W2U linear obtained by connecting the C W2U and C W2d Y2 (straight line indicated by a dotted line in the vertical direction in FIG. 2) to C W2d is L.
- a straight line (straight line Y2) connecting C W2u and C W2d is aligned with the direction of gravity. Further, on the C1 side of the half-finished polyester film, a straight line Z2 (a straight line represented by a one-dot chain line in FIG. 2) passing through C1 and parallel to the direction of gravity is drawn on the half-cut polyester film. Then, at the position of half of the straight line Y2 (L / 2), draw a straight line C L of the straight line Y2 vertical.
- a polyester film in which an end portion in the TD direction of the film is curved in an arc shape has the largest curvature of half the distance in the MD direction of the film (position where the straight line CL is drawn).
- “Ends in the width direction of two half-cut polyester films obtained by cutting the polyester film along a straight line connecting the centers in the width direction of the polyester film at both ends in the length direction of the polyester film in the formulas (5) and (7)” The value [m] "obtained by adding the maximum value of the curvature of the curve and dividing by 2 [m]” is "(C C1 + C C2 ) / 2" from C C1 and C C2 in FIGS.
- the numerical value C CT obtained as follows.
- the half-finished polyester film will be further described.
- the two half-cut polyester films are obtained by cutting the polyester film along two straight lines connecting the midpoints of the sides along the film width direction at two ends in the longitudinal direction of the polyester film. Obtained.
- C CT representing the degree of curvature of a half-cut polyester film having a width of W / 2 is also referred to as “half-cut arc”. Further, an arc when the C1 side of the polyester film swells in an arc shape is called a plus arc, and an arc when the C2 side swells is called a minus arc.
- Formula (1) is represented by the following inequality sign. W / 1000 ⁇ [(S s1 ⁇ S s2 ) / C S1 / 100] ⁇ 2W (1)
- the MD thermal contraction rate difference “S s1 ⁇ S s2 ” is also expressed as ⁇ S.
- Formula (1) is the ratio of the MD thermal shrinkage difference ⁇ S to the full width arc C S1 of the polyester film having a film width W at the end in the MD direction [(S s1 ⁇ S s2 ) / C S1 / 100 [%]. ] Is larger than 1/1000 of the film width W and smaller than twice the film width W.
- the polyester film it is usually difficult to set the MD heat shrinkage difference ⁇ S to 0.
- the problem of the present invention easily occurs.
- the effect of the present invention is increased with respect to a polyester film in which the ratio of the MD thermal contraction rate difference ⁇ S to the full width arc C S1 is greater than W / 1000.
- the limit is a value exceeding W / 1000.
- an increase in the ratio of the MD thermal contraction rate difference ⁇ S to the full-width arc C S1 means that the degree of bending is small and ⁇ S is large. That is, even if the full-width arc CS1 is small, if ⁇ S is large, MD heat shrinkage in the TD direction varies during heating and conveyance, resulting in a difference in film flatness and looseness. Wrinkles and scratches during transportation cannot be prevented. If the ratio of the MD heat shrinkage rate difference ⁇ S to the full width arc C S1 exceeds twice the film width W, it becomes impossible to prevent wrinkles and scratches during heating and conveyance.
- the ratio [MD (S s1 ⁇ S s2 ) / C S1 / 100] of the MD heat shrinkage ratio difference ⁇ S to the full width arc C S1 is more than W / 700, preferably less than W / 2, and more than W / 500. More preferably, it is less than W / 4, more preferably more than W / 400 and less than W / 8.
- Formula (2) is represented by the following inequality sign. 0 ⁇ (S s1 -S s2 ) ⁇ 0.5 (2) That is, ⁇ S is greater than 0 and less than 0.5.
- ⁇ S is greater than 0 and less than 0.5.
- ⁇ S is preferably 0.02 ⁇ S ⁇ 0.4, and more preferably 0.03 ⁇ S ⁇ 0.3.
- Formula (3) is represented by the following inequality sign. ⁇ 1 ⁇ (S s1 + S s2 + S CT ) / 3 ⁇ 3 (3) “(S s1 + S s2 + S CT ) / 3” is an average of S s1 , S s2 and S CT, and hereinafter, “(S s1 + S s2 + S CT ) / 3” is also expressed as S AV .
- the MD heat shrinkage rate in the TD direction of the polyester film is important not only in the balance between the S1 side and the S2 side, but also in the balance between S s1 and S s2 and the MD heat shrinkage rate S CT in the center of the film in the TD direction. is there.
- the film central portion in the film width direction means that the center position of one end and the other end in the TD direction of the polyester film is CT, and the center of CT is the TD direction.
- CT the center position of one end and the other end in the TD direction of the polyester film
- CT the center of CT
- the MD direction it means a region that is ⁇ 10% of the total length of the polyester film in the TD direction.
- S AV is preferably ⁇ 0.5 ⁇ S AV ⁇ 2, more preferably ⁇ 0.2 ⁇ S AV ⁇ 1.5.
- Formula (4) is represented by the following inequality sign. 0 ⁇ C s1 ⁇ 0.2 (4)
- Formula (4) defines the range of the maximum value (full width arc) of the curvature of the polyester film whose width is W.
- a polyester film obtained by melt-kneading and stretching a polyester raw material resin has a curved edge in the film TD direction, and it is difficult to set the full width arc to zero.
- the full width arc C s1 is preferably 0.001 ⁇ C s1 ⁇ 0.1, and more preferably 0.002 ⁇ C s1 ⁇ 0.05.
- the polyester film of the present invention preferably satisfies the formulas (5) to (7) in addition to the formulas (1) to (4).
- Formulas (5) to (7) are rules for a semi-cut polyester film obtained by cutting a polyester film having a film width W along the C Wu -C Wd straight line (straight line Y1) shown in FIG. is there.
- the film looseness (sagging at the end in the TD direction) and medium slacking (sagging at the center in the TD direction) are controlled. By doing so, it becomes easy to suppress wrinkles and scratches during heating and conveyance.
- C CT is more preferably ⁇ 0.1 ⁇ C CT ⁇ 0.1, and further preferably ⁇ 0.05 ⁇ C CT ⁇ 0.05.
- the polyester film to which the formulas (1) to (7) are applied is not particularly limited as long as it is a polyester film obtained by melt-kneading a polyester raw material resin and performing longitudinal stretching, lateral stretching, or both.
- the formulas (1) to (7) may be applied to a film wound after stretching, or a polyester film that has been semi-processed after winding, a film that has been subjected to a thermal relaxation process offline, and a film that has undergone an undercoating process. You may apply to the film etc. in which the coating layer was formed.
- the end in the TD direction of the film may be cut for trimming, and may be applied to the polyester film before cutting or applied to the polyester film after cutting. May be.
- the film width (full length in the TD direction of the film) W of the polyester film of the present invention is preferably 0.3 m or more and 8 m or less. That is, it is preferable that 0.3 m ⁇ W ⁇ 8 m.
- productivity is difficult to decrease.
- a film having a film width of 8 m or less is easy to handle, and the control of the MD heat shrinkage rate and the size of the full width arc easily suppresses the generation of wrinkles and scratches during heating and conveyance.
- the film width W of the polyester film is more preferably from 0.5 m to 5 m, further preferably from 0.7 m to 3 m, and most preferably from 0.8 m to 2 m.
- the polyester film further reduces wrinkles and scratches during heating and conveyance by setting the pre-peak temperature unevenness measured by differential scanning calorimetry (DSC) in the TD direction to 0.5 ° C. or more and 10 ° C. or less. Can be suppressed.
- DSC differential scanning calorimetry
- the “pre-peak temperature” of DSC is the temperature of the peak that appears first when the polyester film is subjected to DSC measurement.
- the pre-peak temperature of DSC generally corresponds to the maximum film surface temperature (heat setting temperature) of the polyester film at the time of heat setting during the transverse stretching process performed by biaxial stretching of the polyester film.
- the DSC pre-peak temperature is a value obtained by a conventional method in differential scanning calorimetry (DSC).
- unevenness of the pre-peak temperature film pieces at 11 positions P1 to P11 arranged at equal intervals in the TD direction of the polyester film are sampled. DSC measurement is performed on the film pieces in P1 to P11, the pre-peak temperatures Tpp1 to Tpp11 are measured, and the difference between the maximum value and the minimum value in Tpp1 to Tpp11 is defined as unevenness in the pre-peak temperature of the DSC in the TD direction.
- unevenness in the pre-peak temperature of the DSC in the TD direction is also referred to as ⁇ Tpp.
- the DSC pre-peak temperature unevenness ( ⁇ Tpp) in the TD direction of the polyester film is 0.5 ° C. to 10 ° C., and the polyester film easily satisfies the formulas (1) to (7) described above.
- ⁇ Tpp is more preferably 0.5 ° C. or higher and 7 ° C. or lower, further preferably 0.5 ° C. or higher and 5 ° C. or lower, and most preferably 0.5 ° C. or higher and 4 ° C. or lower.
- the intrinsic viscosity (IV; Intrinsic Viscosity) of the polyester film is preferably 0.55 dL / g or more and 0.90 dL / g or less from the viewpoint of improving the hydrolysis resistance of the polyester film and improving the weather resistance. More preferably, it is 0.60 dL / g or more and 0.80 dL / g or less, More preferably, it is 0.62 dL / g or more and 0.78 dL / g or less, 0.63 dL / g or more and 0.75 dL / g or less Most preferably it is.
- the amount of terminal carboxy group of the polyester film [terminal COOH amount (also referred to as acid value), AV; Acid Value] is preferably 5 eq / ton or more and 35 eq / ton or less.
- the amount of terminal COOH is more preferably 6 eq / ton to 30 eq / ton, and still more preferably 7 eq / ton to 28 eq / ton.
- “eq / ton” represents a molar equivalent per ton.
- the polyester film is synthesized by copolymerizing a dicarboxylic acid component and a diol component. Details of the dicarboxylic acid component and the diol component will be described later.
- the polyester film of the present invention is a polyfunctional monomer having a total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) of 3 or more (hereinafter referred to as “a trifunctional or more polyfunctional monomer”). Or it is preferable that it is what contains the structural unit derived only from a "polyfunctional monomer”.
- the polyester film of the present invention can be obtained, for example, by subjecting (A) a dicarboxylic acid component and (B) a diol component to an esterification reaction and / or transesterification reaction by a well-known method. Is obtained by copolymerizing a trifunctional or higher polyfunctional monomer. Details such as examples and preferred embodiments of the dicarboxylic acid component, the diol component, and the polyfunctional monomer are as described later.
- the number of carboxylic acid groups (a) Is a carboxylic acid having 3 or more and a polyfunctional monomer having a hydroxyl number (b) of 3 or more, such as an ester derivative or an acid anhydride thereof, and “a carboxylic acid group having both a hydroxyl group and a carboxylic acid group in one molecule.
- Oxyacids in which the total (a + b) of the number (a) of hydroxyl groups and the number (b) of hydroxyl groups is 3 or more. Details of these examples and preferred embodiments are as described later. Also, oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid and derivatives thereof at the carboxy terminus of carboxylic acid or at the carboxy terminus of “polyfunctional monomer having both hydroxyl group and carboxylic acid group in one molecule” Further, a product obtained by adding a plurality of such oxyacids connected to each other is also suitable. These may be used individually by 1 type, or may use multiple types together as needed.
- the content ratio of structural units derived from a trifunctional or higher polyfunctional monomer is 0.005 mol% or more and 2.5 mol% or less with respect to all the structural units of the polyester in the polyester film.
- the content ratio of the structural unit derived from the polyfunctional monomer is more preferably 0.020 mol% to 1 mol%, still more preferably 0.025 mol% to 1 mol%, still more preferably 0.8. It is 035 mol% or more and 0.5 mol% or less, Especially preferably, it is 0.05 mol% or more and 0.5 mol% or less, Most preferably, it is 0.1 mol% or more and 0.25 mol% or less.
- a structure in which a polyester molecular chain is branched from a structural unit derived from a trifunctional or higher polyfunctional monomer is obtained by the presence of a structural unit derived from a trifunctional or higher polyfunctional monomer in the polyester film.
- entanglement is formed between the polyester molecules, so that the embrittlement of the polyester film is suppressed and more excellent. Weather resistance is obtained.
- entanglement is also effective in suppressing heat shrinkage. This is presumably because the motility of the polyester molecules decreases due to the entanglement of the polyester molecules, so that even if the molecules try to contract due to heat, they cannot contract and the thermal contraction of the polyester film is suppressed.
- polyester film used for the back sheet for solar cell is in close contact with a sealing agent such as EVA after an application layer such as an easy-adhesion layer is applied and formed, but in an environment where it is exposed to wind and rain such as outdoors. Even when left for a long time, good adhesion that hardly peels off can be obtained.
- the content ratio of the structural unit derived from the trifunctional or higher polyfunctional monomer is 0.005 mol% or more, the weather resistance, low heat shrinkage, and adhesion with the coating layer formed on the polyester film are adhered. The power is likely to improve further.
- the content ratio of the structural unit derived from the trifunctional or higher polyfunctional monomer is 2.5 mol% or less, the structural unit derived from the trifunctional or higher polyfunctional monomer is bulky, so that it is difficult to form a crystal. It is suppressed. As a result, it is possible to promote the formation of a low migration component formed through the crystal and suppress the decrease in hydrolyzability.
- the amount of fine irregularities on the film surface increases, so that an anchor effect is easily manifested, and the polyester film and the coating layer formed on the film Adhesion improves.
- the increase in free volume is suppressed by the bulkiness, and heat shrinkage that occurs when polyester molecules slip through the large free volume can be suppressed.
- a decrease in glass transition temperature (Tg) due to excessive addition of structural units derived from a trifunctional or higher polyfunctional monomer is also suppressed, which is effective in preventing a decrease in weather resistance.
- the polyester film of the present invention preferably further has a structural portion derived from an end-capping agent selected from an oxazoline-based compound, a carbodiimide compound, and an epoxy compound.
- the “structural portion derived from the end-capping agent” refers to a structure in which the end-capping agent reacts with the carboxylic acid at the polyester end and is bonded to the end.
- the end-capping agent reacts with the carboxylic acid at the end of the polyester and is bonded to the end of the polyester, so that the amount of terminal COOH (AV value) is preferably as described above. It becomes easy to stably maintain a desired value such as a range. That is, the hydrolysis of the polyester promoted by the terminal carboxylic acid is suppressed, and the weather resistance can be kept high.
- the end portion of the molecular chain becomes bulky by binding to the polyester terminal, and the amount of fine irregularities on the film surface increases, so that the anchor effect is easily developed, and the polyester film and a coating layer formed on the film by coating Improved adhesion.
- the end-capping agent is bulky and the polyester molecules are prevented from moving through the free volume. As a result, it also has an effect of suppressing heat shrinkage accompanied by molecular movement.
- the end-capping agent is an additive that reacts with the carboxyl group at the end of the polyester to reduce the amount of carboxyl end of the polyester.
- a terminal blocker may be used individually by 1 type, and may be used in combination of 2 or more type.
- the end-capping agent is preferably contained in the range of 0.1% by mass to 5% by mass, more preferably 0.3% by mass to 4% by mass with respect to the mass of the polyester film. More preferably, it is 0.5 mass% or more and 2 mass% or less.
- the content ratio of the end-capping agent in the polyester film is 0.1% by mass or more, the adhesion with the coating layer is improved and the weather resistance can be improved due to the AV lowering effect, and the low heat shrinkage is also achieved. Can be granted.
- the content ratio of the terminal sealing agent in the polyester film is 5% by mass or less, the adhesion with the coating layer is improved and the glass transition temperature (Tg) of the polyester is decreased by the addition of the terminal sealing agent. Is suppressed, and a decrease in weather resistance and an increase in heat shrinkage due to this can be suppressed. This is due to the fact that the increase in hydrolyzability caused by the relatively increased polyester reactivity is suppressed by the decrease in Tg, or the mobility of polyester molecules that increase due to a decrease in Tg is likely to increase. This is because heat shrinkage is suppressed.
- terminal blocking agent in the present invention a compound having a carbodiimide group, an epoxy group, or an oxazoline group is preferable.
- Specific examples of the terminal blocking agent include carbodiimide compounds, epoxy compounds, oxazoline compounds, and the like.
- the carbodiimide compound having a carbodiimide group includes a monofunctional carbodiimide and a polyfunctional carbodiimide.
- monofunctional carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide and di- ⁇ -naphthylcarbodiimide. Of these, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferable.
- the polyfunctional carbodiimide is preferably a polycarbodiimide having a polymerization degree of 3 to 15.
- the polycarbodiimide generally has a repeating unit represented by “—R—N ⁇ C ⁇ N—” or the like, and R represents a divalent linking group such as alkylene or arylene.
- repeating units examples include 1,5-naphthalene carbodiimide, 4,4′-diphenylmethane carbodiimide, 4,4′-diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide, 2,4-tolylene carbodiimide, 2,6-tolylenecarbodiimide, a mixture of 2,4-tolylenecarbodiimide and 2,6-tolylenecarbodiimide, hexamethylenecarbodiimide, cyclohexane-1,4-carbodiimide, xylylenecarbodiimide, isophoronecarbodiimide, dicyclohexylmethane-4, 4'-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimide, 2,6-diisopropylphenylcarbodiimide and 1,3,5-triisopropylbenzene-2 Such as
- the carbodiimide compound is preferably a carbodiimide compound having high heat resistance in that generation of isocyanate gas due to thermal decomposition is suppressed.
- the molecular weight degree of polymerization
- the terminal of the carbodiimide compound has a structure having high heat resistance.
- the polyester film using the carbodiimide compound preferably has an isocyanate gas generation amount of 0 mass% to 0.02 mass% when held at a temperature of 300 ° C. for 30 minutes. If the amount of isocyanate-based gas generated is 0.02% by mass or less, bubbles (voids) are not easily generated in the polyester film, and therefore stress-concentrated sites are not easily formed. Can be prevented. Thereby, the close_contact
- the isocyanate-based gas is a gas having an isocyanate group, such as diisopropylphenyl isocyanate, 1,3,5-triisopropylphenyl diisocyanate, 2-amino-1,3,5-triisopropylphenyl-6-isocyanate. 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and cyclohexyl isocyanate.
- an isocyanate group such as diisopropylphenyl isocyanate, 1,3,5-triisopropylphenyl diisocyanate, 2-amino-1,3,5-triisopropylphenyl-6-isocyanate.
- 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and cyclohexyl isocyanate such as diisopropylphenyl isocyanate, 1,3,5
- Preferred examples of the epoxy compound having an epoxy group include glycidyl ester compounds and glycidyl ether compounds.
- glycidyl ester compounds include benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, P-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, lauric acid glycidyl ester , Glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolein, glycidyl behenol, glycidyl stearol, diglycidyl terephthalate, isophthalic acid Diglycidyl ester, diglycidyl phthalate, diglycidyl naphthalene dicar
- the glycidyl ether compound examples include phenyl glycidyl ether, O-phenyl glycidyl ether, 1,4-bis ( ⁇ , ⁇ -epoxypropoxy) butane, 1,6-bis ( ⁇ , ⁇ - Epoxypropoxy) hexane, 1,4-bis ( ⁇ , ⁇ -epoxypropoxy) benzene, 1- ( ⁇ , ⁇ -epoxypropoxy) -2-ethoxyethane, 1- ( ⁇ , ⁇ -epoxypropoxy) -2-benzyl Oxyethane, 2,2-bis- [ politician- ( ⁇ , ⁇ -epoxypropoxy) phenyl] propane, 2,2-bis- (4-hydroxyphenyl) propane and 2,2-bis- (4-hydroxyphenyl) Examples thereof include bisglycidyl polyether obtained by the reaction of bisphenol such as methane and epichlorohydrin.
- the oxazoline compound it can be appropriately selected from compounds having an oxazoline group, and among them, a bisoxazoline compound is preferable.
- the bisoxazoline compound include 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), and 2,2′-bis (4,4-dimethyl-2).
- 2,2′-bis (2-oxazoline) is most preferable from the viewpoint of good reactivity with polyester and high weather resistance improvement effect.
- Bisoxazoline compounds may be used singly or in combination of two or more unless the effects of the present invention are impaired.
- the above-mentioned or later-described trifunctional or higher polyfunctional monomer and end-capping agent may be used singly or in combination.
- the polyester film of the present invention may be produced by any method as long as it can produce a polyester film satisfying the formulas (1) to (4).
- it can be most suitably produced by the method for producing a polyester film of the present invention shown below.
- the manufacturing method of the polyester film of this invention is demonstrated concretely.
- the method for producing the polyester film of the present invention comprises: A film forming process in which a polyester raw material resin is melt-extruded into a sheet and cooled on a casting drum to form a polyester film; A longitudinal stretching step of longitudinally stretching the molded polyester film in the longitudinal direction; Preheated part for preheating the stretched polyester film to a temperature at which it can be stretched, stretched part for transversely stretching the preheated polyester film in the width direction perpendicular to the longitudinal direction, after longitudinal stretching and transverse stretching Heat-fixing part that heats and crystallizes the polyester film, heat-fixes the heat-fixed polyester film, relaxes the tension of the polyester film and removes residual distortion of the film, and heat-relaxation
- a transverse stretching step in which the polyester film is transported in this order to a cooling section that cools the subsequent polyester film, and the polyester film after longitudinal stretching is laterally stretched in the width direction orthogonal to the longitudinal direction, and includes a heat fixing section and heat In at least one of the
- the production method of the polyester film of the present invention mainly includes a film forming step, a longitudinal stretching step, and a transverse stretching step.
- Longitudinal stretching means stretching in the longitudinal direction (MD direction) of the polyester film
- lateral stretching refers to stretching in the width direction (TD direction) of the polyester film.
- the transverse stretching step is divided into a preheating part, a stretching part, a heat fixing part, a heat relaxation part, and a cooling part, and conveys the polyester film to each part.
- the TD direction end of the polyester film is specified from the film surface in the heat fixing part or the heat relaxation part in the transverse stretching step, or in both the heat fixing part and the heat relaxation part. Radiant heating is selectively performed by a heater separated by a distance.
- the polyester film production method As described above, it is easy to produce a polyester film satisfying the above-mentioned formulas (1) to (4), and a polyester film that is less likely to be wrinkled and scratched even when heated and conveyed. Easy to manufacture.
- the MD heat shrinkage of a polyester film is generally determined by the degree of crystallinity of the polyester constituting the film and the degree of relaxation of the polyester molecules in the MD direction. MD thermal shrinkage tends to decrease as the degree of crystallization of polyester and the degree of relaxation of polyester molecules progress.
- the degree of crystallinity of PET and the degree of relaxation of PET molecules are determined by the temperature of the heat fixing part of the stretching apparatus. The higher the heat setting temperature of the film, the higher the crystallinity of the polyester and the lower the MD heat shrinkage of the polyester film.
- the film When performing transverse stretching and heat setting with a stretching device, the film is gripped with a gripping member such as a clip.
- This gripping member is connected to the outlet (when the polyester film enters the preheating portion) of the stretching device (the polyester film is
- the temperature is about 100 ° C. to 150 ° C. through the cooling unit.
- the heat fixing temperature of the film In the case of PET, the heat fixing temperature of the film is usually around 200 ° C.
- the temperature of the gripping member itself is lower than the heat fixing temperature, the heat escapes to the gripping member side, and the film inevitably The heat setting temperature on the end side tends to be low. For this reason, the MD heat shrinkage rate of the film is also likely to be distributed such that the film edge becomes large.
- MD length distribution The length distribution in the MD direction of the polyester film tends to depend on the mode of cooling in the vicinity of the exit of the stretching apparatus that performs transverse stretching. In general, the length of the film in the MD direction tends to be longer at a rapidly cooled portion and shorter at a gradually cooled portion. This is thought to be due to the following reason. Although the film shrinks by cooling (a phenomenon opposite to thermal expansion), the film does not shrink sufficiently when cooled rapidly, and as a result, the film length in the MD direction is considered to be long. On the contrary, it is considered that the film length in the MD direction is shortened because the film sufficiently contracts when cooled slowly.
- the temperature of the gripping member of the stretching apparatus is about 100 ° C. to 150 ° C., which is relatively high compared to the cooling temperature of the stretching apparatus (generally, about room temperature to about 100 ° C.). For this reason, in the cooling unit of the stretching device, the temperature of the film end is increased due to the high temperature of the gripping member, and the film end is gradually cooled compared to the cooling state in the center of the film. Tend to be. Thereby, the film length in the MD direction tends to be shorter at the film end than at the center of the film.
- the central portion of the film tends to be a film having a small MD heat shrinkage and a large film length in the MD direction compared to the film end. Then, since the film length in the original MD direction before unheating is long and the film central portion is more difficult to shrink during heating and conveyance, the film becomes longer and loosens easily, so that scratches and wrinkles are likely to occur.
- the thermal relaxation treatment is further performed off-line.
- scratches and wrinkles are likely to occur in the film due to the thermal relaxation treatment, and the film after the thermal relaxation treatment also has a smaller MD thermal shrinkage in the TD direction central portion than the end portion in the TD direction.
- the shape is likely to remain long. Therefore, the polyester film obtained by the technique disclosed in JP-A-2001-191406 does not satisfy the requirements of the formulas (1) to (7) in the present invention.
- the polyester film manufacturing method of the present invention at least one of the heat fixing portion and the heat relaxation portion, the end portion of the polyester film in the width direction (TD direction) is selectively radiantly heated by the heater.
- the shortest distance between the surface of the heater and the surface of the polyester film is 10 mm or more and 300 mm or less.
- the MD heat shrinkage rate is increased at a location where the film length in the TD direction before heating and conveyance is long (location where the arc is large), and conversely, the heat shrinkage rate is reduced at a short location. This is a technique for eliminating unevenness in the local length by selectively shrinking the originally long portion.
- a polyester raw material resin is melt-extruded into a sheet and cooled on a casting drum to form a polyester film.
- the method of melt-extruding the polyester raw material resin and the polyester raw material resin are not particularly limited, but the intrinsic viscosity can be set to a desired intrinsic viscosity by a catalyst used for synthesis of the polyester raw material resin, a polymerization method, or the like. First, the polyester raw material resin will be described.
- the polyester raw material resin is not particularly limited as long as it is a raw material for the polyester film and contains polyester, and may contain a slurry of inorganic particles or organic particles in addition to the polyester. Moreover, the polyester raw material resin may contain a titanium element derived from a catalyst.
- the kind of polyester contained in the polyester raw material resin is not particularly limited. It may be synthesized using a dicarboxylic acid component and a diol component, or a commercially available polyester may be used.
- the polyester when the polyester is synthesized, for example, it can be obtained by subjecting (A) a dicarboxylic acid component and (B) a diol component to an esterification reaction and / or a transesterification reaction by a known method.
- the dicarboxylic acid component include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid Aliphatic dicarboxylic acids such as ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, and the like, terephthalic acid, isophthalic acid, phthalic acid, 1,4- Naphthalene dicarboxylic
- diol component examples include fats such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol.
- Diols cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl)
- Diol compounds such as aromatic diols such as fluorene.
- the dicarboxylic acid component contains an aromatic dicarboxylic acid as a main component.
- 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.
- the “main component” means that the proportion of aromatic dicarboxylic acid in the dicarboxylic acid component is 80% by mass or more.
- it is preferable that at least one aliphatic diol is used as the (B) 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 diol component (for example, ethylene glycol) is 1.015 to 1.50 mol per 1 mol of the dicarboxylic acid component (especially aromatic dicarboxylic acid (for example, terephthalic acid)) and, if necessary, its ester derivative.
- a range 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.
- 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.
- a polyfunctional monomer in which the total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) is 3 or more is used as a copolymerization component (a trifunctional or more functional component). It is preferable to include. "Containing a polyfunctional monomer as a copolymerization component (a trifunctional or higher functional component)" means containing a structural unit derived from a polyfunctional monomer.
- Examples of the structural unit derived from the polyfunctional monomer having the sum (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) of 3 or more include the structural units derived from carboxylic acids shown below. .
- examples of the trifunctional aromatic carboxylic acid include trimesic acid, trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, Anthracentricarboxylic acid and the like are trifunctional aliphatic carboxylic acids such as methanetricarboxylic acid, ethanetricarboxylic acid, propanetricarboxylic acid, and butanetricarboxylic acid, and tetrafunctional aromatic carboxylic acids are exemplified by benzenetetracarboxylic acid.
- Carboxylic acid benzophenone tetracarboxylic acid, naphthalene tetracarboxylic acid, anthracene tetracarboxylic acid, perylene tetracarboxylic acid and the like are tetrafunctional aliphatic carboxylic acids such as ethane tetracarboxylic acid, ethylene tetracarboxylic acid, butane tetracarboxylic acid.
- Cyclopen Tetracarboxylic acid, cyclohexanetetracarboxylic acid, adamantanetetracarboxylic acid and the like are pentafunctional or higher functional aromatic carboxylic acids such as benzenepentacarboxylic acid, benzenehexacarboxylic acid, naphthalenepentacarboxylic acid, naphthalenehexacarboxylic acid, naphthalene.
- Heptacarboxylic acid, naphthalene octacarboxylic acid, anthracene pentacarboxylic acid, anthracene hexacarboxylic acid, anthracene heptacarboxylic acid, anthracene octacarboxylic acid and the like are pentafunctional or higher aliphatic carboxylic acids such as ethanepentacarboxylic acid, ethanehepta Carboxylic acid, butanepentacarboxylic acid, butaneheptacarboxylic acid, cyclopentanepentacarboxylic acid, cyclohexanepentacarboxylic acid, cyclohexanehexacarboxylic acid, adamanta Penta carboxylic acid, and adamantane hexa acid.
- these ester derivatives, acid anhydrides and the like are mentioned as examples, but are not limited
- those obtained by adding oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid, and derivatives thereof, a combination of a plurality of such oxyacids to the carboxy terminus of the carboxylic acid described above are also preferably used. . These may be used individually by 1 type, or may use multiple types together as needed.
- polyfunctional monomers having a hydroxyl number (b) of 3 or more include trifunctional aromatic compounds such as trihydroxybenzene, trihydroxynaphthalene, trihydroxyanthracene, trihydroxychalcone, trihydroxyflavone, and trihydroxycoumarin.
- trifunctional aromatic compounds such as trihydroxybenzene, trihydroxynaphthalene, trihydroxyanthracene, trihydroxychalcone, trihydroxyflavone, and trihydroxycoumarin.
- examples of the trifunctional aliphatic alcohol include glycerin, trimethylolpropane, and propanetriol
- examples of the tetrafunctional aliphatic alcohol include pentaerythritol.
- a compound obtained by adding a diol to the hydroxyl terminal of the above compound is also preferably used. These may be used individually by 1 type, or may use multiple types together as needed.
- one molecule has both a hydroxyl group and a carboxylic acid group, and the total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) is 3
- the oxyacids which are the above are also mentioned. Examples of such oxyacids include hydroxyisophthalic acid, hydroxyterephthalic acid, dihydroxyterephthalic acid, and trihydroxyterephthalic acid.
- those obtained by adding oxyacids and derivatives thereof such as l-lactide, d-lactide, hydroxybenzoic acid, or a combination of a plurality of such oxyacids to the carboxy terminus of these polyfunctional monomers are also preferably used. It is done. These may be used individually by 1 type, or may use multiple types together as needed.
- the content ratio of the structural unit derived from the polyfunctional monomer in the polyester raw material resin is 0.005 mol% to 2.5% with respect to all the structural units of the polyester in the polyester raw material resin. It is preferable that it is below mol%.
- the content ratio of the structural unit derived from the polyfunctional monomer is more preferably 0.020 mol% to 1 mol%, still more preferably 0.025 mol% to 1 mol%, still more preferably 0.8. It is 035 mol% or more and 0.5 mol% or less, Especially preferably, it is 0.05 mol% or more and 0.5 mol% or less, Most preferably, it is 0.1 mol% or more and 0.25 mol% or less.
- the functional group that is not used for polycondensation is polyester.
- the adhesion between the coating layer and the polyester film can be kept better, and the occurrence of peeling can be effectively prevented.
- a structure in which a polyester molecular chain is branched from a structural unit derived from a trifunctional or higher polyfunctional monomer can be obtained, and entanglement between polyester molecules can be promoted.
- a conventionally known reaction catalyst can be used for the esterification reaction and / or transesterification reaction.
- 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.
- 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.
- a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.
- an aromatic dicarboxylic acid and an aliphatic diol are polymerized in the presence of a catalyst containing a titanium compound.
- an organic chelate titanium complex having an organic acid as a ligand is used as a catalyst titanium compound, and at least an organic chelate titanium complex, a magnesium compound, and an aromatic ring as a substituent in the step.
- a process of adding a pentavalent phosphate ester having no sulfite in this order is
- an aromatic dicarboxylic acid and an aliphatic diol are mixed with a catalyst containing an organic chelate titanium complex, which is a titanium compound, prior to addition of a magnesium compound and a phosphorus compound.
- Titanium compounds such as organic chelate titanium complexes have high catalytic activity for esterification reactions, so that esterification reactions can be performed satisfactorily.
- the titanium compound may be added to the mixture of the dicarboxylic acid component and the diol component, or after mixing the dicarboxylic acid component (or diol component) and the titanium compound, the diol component (or dicarboxylic acid component) is mixed. May be. 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.
- PET polyethylene terephthalate
- PEN polyethylene-2,6-naphthalate
- 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.
- Ge germanium
- Sb antimony
- Al aluminum
- Ti titanium
- Ti-based catalyst has high reaction activity and can lower the polymerization temperature. Therefore, it is possible to suppress the polyester from being thermally decomposed during the polymerization reaction and generating COOH. That is, by using a Ti-based catalyst, it is possible to reduce the amount of terminal carboxylic acid of polyester that causes thermal decomposition, and it is possible to suppress foreign matter formation. By reducing the amount of the terminal carboxylic acid of the polyester, it is possible to suppress thermal decomposition of the polyester film after the production of the polyester film.
- Ti-based catalyst examples 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.
- 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
- the polymerization is performed using a titanium (Ti) compound as a catalyst in the range of 1 ppm to 50 ppm, more preferably 2 ppm to 30 ppm, more preferably 3 ppm to 15 ppm in terms of titanium element. Is preferred.
- the polyester raw material resin contains 1 ppm or more and 50 ppm or less of titanium element.
- Mw weight average molecular weight
- the amount of the titanium element contained in the polyester raw material resin is 1 ppm or more, the weight average molecular weight (Mw) of the polyester is increased, and thermal decomposition is difficult. For this reason, foreign matters are reduced in the extruder.
- the amount of titanium element contained in the polyester raw material resin is 50 ppm or less, the Ti-based catalyst is unlikely to become a foreign substance, and stretching unevenness is reduced when the polyester film is stretched.
- titanium compounds As the titanium compound as the catalyst component, at least one organic chelate titanium complex having an organic acid as a ligand is preferably used.
- 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.
- the method of adding at the stage of esterification reaction gives a polyester having better polymerization activity and color tone and less terminal carboxy groups than when added after the esterification reaction.
- 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.
- 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 carboxy groups, the worse the hydrolysis resistance. By reducing the amount of terminal carboxy groups by the above addition method, improvement in hydrolysis resistance is expected. .
- citric acid chelate titanium complex examples are easily 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.
- titanium compounds In addition to the organic chelate titanium complex, titanium compounds generally include oxides, hydroxides, alkoxides, carboxylates, carbonates, oxalates, and halides. Other titanium compounds may be used in combination with the organic chelate titanium complex as long as the effects of the present invention are not impaired.
- titanium compounds examples include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, Titanium alkoxide such as tetraphenyl titanate, 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 titanium oxalate, potassium titanate, sodium titanate, titanium titanate-aluminum hydroxide mixture, titanium chloride, titanium chloride Down - aluminum chloride mixture, and titanium acetylacetonate.
- Titanium alkoxide such
- 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
- a polycondensation step in which a polycondensation product is produced by a polycondensation reaction of the chemical reaction product, and is preferably produced by a polyester production method.
- This polyester 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.
- 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.
- 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.
- pentavalent phosphorus compound at least one pentavalent phosphate having no aromatic ring as a substituent is used.
- pentavalent phosphate having no aromatic ring as a substituent
- phosphoric acid esters 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]
- phosphoric acid Trimethyl and triethyl phosphate are particularly preferable.
- the amount of phosphorus compound added 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 or more and 80 ppm or less, and still more preferably 60 ppm or more and 75 ppm or less.
- magnesium compound By including a magnesium compound in the polyester, the electrostatic applicability of the polyester is improved. 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.
- 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 Mg element conversion value is preferably 50 ppm or more, and more preferably 50 ppm or more and 100 ppm or less.
- 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.
- the titanium compound as the catalyst component and the magnesium compound and the phosphorus compound as the additive are set so that the value Z calculated from the following formula (i) satisfies the following relational expression (ii): Particularly preferred is the case of adding and melt polymerizing.
- the P content is the amount of phosphorus derived from the entire phosphorus compound including the pentavalent phosphate ester having no aromatic ring
- the Ti content is the amount of titanium derived from the entire Ti compound including the organic chelate titanium complex. It is.
- chelating titanium having aromatic dicarboxylic acid and aliphatic diol as a ligand with citric acid or citrate of 1 ppm or more and 30 ppm or less in terms of Ti element.
- 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) in terms of Mg element is added.
- the chelate titanium complex organic chelate titanium complex
- the magnesium salt magnesium compound
- the pentavalent phosphate pentavalent phosphate
- 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.
- the esterification reaction temperature is preferably 230 to 260 ° C, more preferably 240 to 250 ° C.
- 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.
- the temperature of the esterification reaction in the second reaction tank is preferably 230 to 260 ° C., more preferably 245 to 255 ° C., and the pressure is 0.5 to 5.0 kg / 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.
- a polycondensation product is produced by polycondensation reaction of the esterification reaction product produced by the esterification 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.
- the polycondensation reaction conditions in a three-stage reaction tank are as follows: the first reaction tank has a reaction temperature of 255 to 280 ° C., more preferably 265 to 275 ° C., and a pressure of 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). 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.
- 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), aspect is preferably more preferably 5 ⁇ 0.5torr (6.67 ⁇ 10 -4 ⁇ 6.67 ⁇ 10 -5 MPa) .
- Polyester raw materials synthesized as described above include light stabilizers, antioxidants, ultraviolet absorbers, flame retardants, lubricants (fine particles), nucleating agents (crystallization agents), crystallization inhibitors, etc. An additive may be further contained.
- the intrinsic viscosity (IV) of the polyester raw material resin is preferably 0.55 dL / g or more and 0.90 dL / g or less.
- 0.60 dL / g or more and 0.80 dL / g or less is more preferable
- 0.62 dL / g or more and 0.78 dL / g or less is further preferable
- it is g or less.
- the polyester raw material resin obtained as described above is melt-extruded and further cooled to form a polyester film.
- the melt extrusion of the polyester raw material resin is performed, for example, using an extruder provided with one or two or more screws, heated to a temperature equal to or higher than the melting point of the polyester raw resin, rotating the screw, and melt-kneading.
- the polyester raw material resin is melted into a melt in the extruder by heating and kneading with a screw.
- the extruder is preferably a twin screw extruder because the kneading temperature can be kept low.
- the molten polyester raw material resin (melt) is extruded from an extrusion die through a gear pump, a filter or the like.
- the extrusion die is also simply referred to as “die” (see JIS B 8650: 2006, a) extrusion molding machine, number 134). At this time, the melt may be extruded as a single layer or may be extruded as a multilayer.
- the polyester raw material resin preferably contains an end-capping agent selected from an oxazoline-based compound, a carbodiimide compound, and an epoxy compound.
- an end-capping agent selected from an oxazoline-based compound, a carbodiimide compound, and an epoxy compound.
- the polyester raw material resin to which the end-capping agent is added is melt-kneaded, and the polyester raw material resin that has reacted with the end-capping agent during melt-kneading is melt-extruded.
- the end-capping agent is not particularly limited as long as it is melt-kneaded with the polyester raw material resin in the process from the raw material charging to the extrusion. It is preferably added until it is fed to the vent port and is used for melt kneading together with the raw material resin.
- a supply port for supplying the end sealant can be provided between the raw material charging port and the vent port of the cylinder for performing melt kneading, and can be directly added to the raw material resin in the cylinder.
- the end-capping agent may be added to the polyester raw material resin that has been heated and kneaded but has not completely reached the molten state, or may be added to the molten polyester raw material resin (melt). Good.
- 0.1 to 5 mass% is preferable with respect to the total mass of the polyester raw resin.
- a preferable amount of the terminal blocking agent with respect to the polyester raw material resin is 0.3% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 2% by mass or less.
- the content ratio of the end-capping agent is 0.1% by mass or more, weather resistance can be improved due to the AV lowering effect, and low heat shrinkability and adhesion can be imparted.
- the content ratio of the end-capping agent is 5% by mass or less, the adhesion is improved, and the decrease in the glass transition temperature (Tg) of the polyester due to the addition of the end-capping agent is suppressed.
- Tg glass transition temperature
- Decrease and increase in heat shrinkage can be suppressed. This is due to the fact that the increase in hydrolyzability caused by the relatively increased polyester reactivity is suppressed by the decrease in Tg, or the mobility of polyester molecules that increase due to a decrease in Tg is likely to increase. This is because heat shrinkage is suppressed.
- the compound which has a carbodiimide group, an epoxy group, or an oxazoline group is preferable.
- Specific examples of the terminal blocking agent include carbodiimide compounds, epoxy compounds, oxazoline compounds, and the like. Details of the carbodiimide compound, the epoxy compound, and the oxazoline-based compound, such as examples and preferred embodiments thereof, are as described above in the section “Polyester film”.
- the melt (polyester) can be extruded from a die onto a casting drum to be formed into a film (cast process).
- the thickness of the film-like polyester molded body obtained by the cast treatment is preferably 0.1 mm to 5 mm, more preferably 0.2 mm to 4.7 mm, and 0.3 mm to 4.6 mm. Is more preferable.
- the means for cooling the melt extruded from the extrusion die is not particularly limited, and it is sufficient to apply cold air to the melt, bring it into contact with a cast drum (cooled cast drum), or spray water. Only one cooling means may be performed, or two or more cooling means may be combined. Among the above, the cooling means is preferably at least one of cooling by cold air and cooling using a cast drum from the viewpoint of preventing oligomer adhesion to the film surface during continuous operation. Further, it is particularly preferable that the melt extruded from the extruder is cooled with cold air and the melt is brought into contact with the cast drum and cooled.
- the polyester molded body cooled using a cast drum or the like is peeled off from a cooling member such as a cast drum using a peeling member such as a peeling roll.
- the polyester film molded in the film molding process is longitudinally stretched in the longitudinal direction.
- the longitudinal stretching of the film is performed, for example, by applying tension between two or more pairs of nip rolls arranged in the film conveyance direction while passing the film through a pair of nip rolls sandwiching the film and conveying the film in the longitudinal direction of the film.
- tension between two or more pairs of nip rolls arranged in the film conveyance direction while passing the film through a pair of nip rolls sandwiching the film and conveying the film in the longitudinal direction of the film.
- the longitudinal stretching ratio of the polyester film is preferably 2 to 5 times, more preferably 2.5 to 4.5 times, and even more preferably 2.8 to 4 times.
- the area stretch ratio represented by the product of the longitudinal and lateral stretch ratios is preferably 6 to 18 times, more preferably 8 to 17.5 times the area of the polyester film before stretching, more preferably 10 to More preferably, it is 17 times.
- the temperature during the longitudinal stretching of the polyester film (hereinafter also referred to as “longitudinal stretching temperature”) is preferably Tg ⁇ 20 ° C. or more and Tg + 50 ° C. or less, more preferably Tg as the glass transition temperature of the polyester film. Tg ⁇ 10 ° C. or higher and Tg + 40 ° C. or lower, more preferably Tg ° C. or higher and Tg + 30 ° C. or lower.
- the polyester film when extending
- a heat source such as a heater
- the horizontal stretch process mentioned later is included separately from a vertical stretch process. Therefore, in the manufacturing method of the polyester film of this invention, a polyester film is extended
- the stretching in the MD direction and the TD direction may be performed at least once each.
- the direction (TD) orthogonal to the longitudinal direction (conveyance direction, MD) of a polyester film intends the direction which makes a perpendicular
- a direction in which the angle with respect to the longitudinal direction (that is, the conveyance direction) can be regarded as 90 ° due to mechanical error or the like (for example, a direction of 90 ° ⁇ 5 ° with respect to the MD direction) is included.
- the biaxial stretching method may be any of a sequential biaxial stretching method in which longitudinal stretching and lateral stretching are separated and a simultaneous biaxial stretching method in which longitudinal stretching and lateral stretching are simultaneously performed.
- the longitudinal stretching and the lateral stretching may be independently performed twice or more, and the order of the longitudinal stretching and the lateral stretching is not limited.
- stretching modes such as longitudinal stretching ⁇ transverse stretching, longitudinal stretching ⁇ transverse stretching ⁇ longitudinal stretching, longitudinal stretching ⁇ longitudinal stretching ⁇ transverse stretching, transverse stretching ⁇ longitudinal stretching can be mentioned. Of these, longitudinal stretching ⁇ transverse stretching is preferred.
- the transverse stretching step in the present invention is a step of transversely stretching the polyester film after longitudinal stretching in the width direction perpendicular to the longitudinal direction.
- A a preheating portion for preheating the polyester film after longitudinal stretching to a temperature at which it can be stretched;
- B a stretched portion that stretches the preheated polyester film in a transverse direction by applying tension to the width direction orthogonal to the longitudinal direction;
- C a heat setting part for heating and crystallizing the heat-fixed polyester film after longitudinal stretching and transverse stretching;
- D a heat relaxation part that heats the heat-fixed polyester film, relaxes the tension of the polyester film and removes the residual distortion of the film, and
- E Conveying the polyester film in this order to the cooling part for cooling the polyester film after heat relaxation,
- C) In at least one of the heat fixing part and (d) the heat relaxation part, the TD direction end part of the polyester film is selectively radiant
- the specific means is not limited as long as the polyester film is transversely stretched in the above configuration, but a lateral stretching apparatus or biaxial stretching capable of processing each step constituting the above configuration. It is preferable to use a machine.
- the biaxial stretching machine 100 includes a pair of annular rails 60a and 60b, and gripping members 2a to 2l attached to the annular rails and movable along the rails.
- the annular rails 60a and 60b are arranged symmetrically with respect to the polyester film 200.
- the annular rails 60a and 60b can be stretched in the film width direction by gripping the polyester film 200 with the gripping members 2a to 21 and moving along the rail. It has become.
- FIG. 3 is a top view showing an example of a biaxial stretching machine from the top.
- the biaxial stretching machine 100 includes a preheating unit 10 that preheats the polyester film 200, a stretching unit 20 that stretches the polyester film 200 in an arrow TD direction that is a direction orthogonal to the arrow MD direction, and applies tension to the polyester film,
- the heat fixing part 30 that heats the polyester film to which the tension is applied is heated
- the heat relaxation part 40 that relaxes the tension of the polyester film that is heat-fixed by heating the heat-fixed polyester film, and the heat relaxation part. It is comprised in the area
- Gripping members 2a, 2b, 2e, 2f, 2i, and 2j that are movable along the annular rail 60a are attached to the annular rail 60a, and the annular rail 60b is movable along the annular rail 60b.
- Gripping members 2c, 2d, 2g, 2h, 2k, and 2l are attached.
- the gripping members 2a, 2b, 2e, 2f, 2i, and 2j grip one end of the polyester film 200 in the TD direction, and the gripping members 2c, 2d, 2g, 2h, 2k, and 2l are the polyester film 200. The other end in the TD direction is gripped.
- the gripping members 2a to 2l are generally called chucks, clips, and the like.
- the gripping members 2a, 2b, 2e, 2f, 2i, and 2j move counterclockwise along the annular rail 60a, and the gripping members 2c, 2d, 2g, 2h, 2k, and 2l move along the annular rail 60b. Move clockwise.
- the gripping members 2a to 2d grip the end portion of the polyester film 200 in the preheating unit 10 and move along the annular rail 60a or 60b while gripping, so that the heat at which the extending unit 20 and the gripping members 2e to 2h are located
- the process proceeds through the relaxation part 40 to the cooling part 50 where the gripping members 2i to 2l are located.
- the gripping members 2a and 2b and the gripping members 2c and 2d are separated from the end of the polyester film 200 at the end of the cooling unit 50 on the downstream side in the MD direction in the transport direction, and then the annular rail 60a or 60b. , And return to the preheating unit 10.
- the polyester film 200 moves in the direction of the arrow MD, and sequentially preheats in the preheating unit 10, stretches in the stretching unit 20, heat fixes in the heat fixing unit 30, heat relaxation in the heat relaxation unit 40, and cooling. Cooling at the part 50 is performed and transverse stretching is performed.
- the moving speed of the gripping members 2a to 2l in each region such as the preheating portion becomes the conveying speed of the polyester film 200.
- the gripping members 2a to 2l can change the moving speed independently of each other.
- the biaxial stretching machine 100 enables transverse stretching in which the polyester film 200 is stretched in the TD direction in the stretching unit 20, but the polyester film 200 is removed by changing the moving speed of the gripping members 2a to 2l. It can also extend in the MD direction. That is, simultaneous biaxial stretching can be performed using the biaxial stretching machine 100.
- gripping members 2a to 21 may be collectively referred to as “grip member 2”.
- the polyester film after being longitudinally stretched in the longitudinal stretching step is preheated to a temperature at which it can be stretched.
- the polyester film 200 is preheated in the preheating unit 10.
- the polyester film 200 is preheated before being stretched so that the polyester film 200 can be easily stretched in the transverse direction.
- the film surface temperature at the end point of the preheating part (hereinafter also referred to as “preheating temperature”) is preferably Tg ⁇ 10 ° C. to Tg + 60 ° C. when the glass transition temperature of the polyester film 200 is Tg, It is more preferable that it is Tg + 50 degreeC.
- the end point of the preheating portion refers to a time point when the preheating of the polyester film 200 is finished, that is, a position where the polyester film 200 is separated from the region of the preheating portion 10.
- the polyester film preheated in the preheating section is stretched in the transverse direction with tension in the width direction (TD direction) perpendicular to the longitudinal direction (MD direction).
- the preheated polyester film 200 is laterally stretched at least in the TD direction orthogonal to the longitudinal direction of the polyester film 200 to give tension to the polyester film 200.
- Stretching (transverse stretching) in the direction (TD) perpendicular to the longitudinal direction (conveying direction, MD) of the polyester film 200 is an angle direction perpendicular (90 °) to the longitudinal direction (conveying direction, MD) of the polyester film 200.
- the range of the mechanical error is a direction at an angle (90 ° ⁇ 5 °) that can be regarded as perpendicular to the longitudinal direction (conveying direction, MD) of the polyester.
- the area stretch ratio (product of each stretch ratio) of the polyester film 200 is preferably 6 to 18 times, more preferably 8 to 17.5 times the area of the polyester film 200 before stretching. More preferably, it is from 1 to 17 times.
- the film surface temperature (hereinafter also referred to as “lateral stretching temperature”) of the polyester film 200 during transverse stretching is Tg ⁇ 10 ° C. or higher and Tg + 100 ° C. or lower when the glass transition temperature of the polyester film 200 is Tg. It is preferably Tg ° C. or more and Tg + 90 ° C. or less, and more preferably Tg + 10 ° C. or more and Tg + 80 ° C. or less.
- the movement speeds of the gripping members 2a to 2l can be changed independently of each other. Therefore, for example, the polyester film 200 is transported by increasing the moving speed of the gripping member 2 on the downstream side in the extending portion 20MD direction of the extending portion 20 and the heat fixing portion 30 rather than the moving speed of the holding member 2 in the preheating portion 10. It is also possible to perform longitudinal stretching that stretches in the direction (MD direction).
- the longitudinal stretching of the polyester film 200 in the transverse stretching step may be performed only by the stretching unit 20 or may be performed by the heat fixing unit 30, the heat relaxation unit 40, or the cooling unit 50 described later. You may longitudinally stretch in several places.
- Heat fixing part In the heat setting section, the polyester film that has already been subjected to longitudinal stretching and lateral stretching is heated and crystallized to be heat-set. Heat setting means heating the polyester film 200 while applying tension to the stretched portion 20 to crystallize the polyester.
- the maximum reachable film surface temperature of the surface of the polyester film 200 with respect to the tensioned polyester film 200 (in this specification, “heat fixing temperature”, “T heat fixing ”). Is also preferably controlled in the range of 160 ° C. to 240 ° C. to heat the film.
- the heat setting temperature is 160 ° C. or higher, the polyester is easily crystallized, the polyester molecules can be fixed in an extended state, and the hydrolysis resistance of the polyester film can be improved.
- the heat setting temperature is 240 ° C. or lower, slippage hardly occurs at a portion where the polyester molecules are entangled with each other, and the polyester molecules are not easily contracted, so that a decrease in hydrolysis resistance of the polyester film can be suppressed.
- the heat setting temperature is 160 ° C. to 240 ° C., it is possible to orient the polyester molecule crystals and improve the hydrolysis resistance of the polyester film.
- the heat setting temperature is preferably in the range of 170 ° C. to 230 ° C., more preferably in the range of 175 ° C. to 225 ° C.
- the maximum film surface temperature is a value measured by bringing a thermocouple into contact with the surface of the polyester film 200.
- the variation of the maximum film surface temperature in the film width direction is 0.5 ° C. or higher and 10.0 ° C. or lower.
- the variation in the maximum film surface temperature of the film is 0.5 ° C. or more, which is advantageous in terms of wrinkles during conveyance in the subsequent process, and the variation is 10.0 ° C. or less.
- the variation in the maximum reached film surface temperature is more preferably 0.5 ° C. or more and 7.0 ° C. or less, further preferably 0.5 ° C. or more and 5.0 ° C. or less, for the same reason as described above. It is particularly preferably from 5 ° C. to 4.0 ° C.
- the heating of the film during heat setting may be performed from only one side of the film or from both sides.
- the molded polyester film is different in how it is cooled on one side and the opposite side, so the film is likely to curl. ing. Therefore, it is preferable to perform the heating in the heat setting step on the surface brought into contact with the casting drum in the film forming step. Curling can be eliminated by setting the heating surface in the heat setting step to the surface in contact with the casting drum, that is, the cooling surface. At this time, the heating is high in the range of 0.5 ° C. or more and 5.0 ° C.
- the surface temperature immediately after heating on the heating surface in the heat setting step is higher than the surface temperature of the non-heating surface opposite to the heating surface. It is preferable to be performed as follows.
- the temperature difference between the heated surface and the non-heated surface on the opposite side is more preferably in the range of 0.7 to 3.0 ° C., and 0.8 to 2.0 ° C. The following is more preferable.
- the curl eliminating effect is great.
- the film thickness is thick, if a temperature change is applied to the film from one side of the film, a temperature distribution is easily formed in the film thickness direction, and curling is likely to occur.
- polyester melt-extruded in the film forming process is cooled from one side when it comes into contact with the cast drum, while the opposite side is in contact with the atmosphere, for example, and there is heat dissipation, but one side and the opposite side Since different cooling advances, temperature differences are likely to occur. Therefore, if the thickness of the polyester film is 180 ⁇ m or more, a temperature difference is likely to occur, so that a curling elimination effect is expected, and if it is 350 ⁇ m or less, the hydrolysis resistance is favorably maintained.
- the TD direction edge part of a polyester film is selectively radiatively heated with a heater in at least one of the heat fixing part 30 and the heat relaxation part 40.
- the MD thermal contraction rate in the TD direction of the produced polyester film does not decrease, and the distribution of MD thermal contraction rate and unevenness in flatness do not become small. Therefore, the formulas (1) to ( A film satisfying 4) cannot be produced.
- the radiant heating in the heat fixing unit 30 may be omitted, or may be performed in both the heat fixing unit 30 and the heat relaxation unit 40. .
- the heating of the end portion in the TD direction of the polyester film is performed using a heater capable of radiation heating, and at least one end portion in the TD direction of the polyester film is selectively heated. From the viewpoint of suppressing local MD heat shrinkage, it is preferable to heat both ends of the polyester film in the TD direction.
- “selectively heating” means that the entire film including the end of the polyester film is not heated but the end of the film is locally heated.
- a heater capable of radiation heating for example, an infrared heater can be mentioned, and it is particularly preferable to use a ceramic heater (ceramic heater). Only one heater capable of radiant heating may be used, or two or more heaters may be used.
- the heating of the end portion in the TD direction of the polyester film is performed by setting the shortest distance between the polyester film surface and the heater to 10 mm or more and 300 mm or less. If the shortest distance between the polyester film surface and the heater is less than 10 mm, temperature unevenness is likely to occur at the heater pitch, and if it exceeds 300 mm, the radiant heat is not sufficiently transmitted to the film.
- the shortest distance between the heater surface and the film surface is preferably 50 mm or more and 250 mm or less, and more preferably 80 mm or more and 200 mm or less.
- the film In addition to the distance between the film surface and the heater surface, it is preferable to heat the film by adjusting the surface temperature of the heater as required. It is preferable that at least one surface temperature of the ceramic heater is 300 ° C. or higher and 700 ° C. or lower. When the surface temperature is 300 ° C. or higher, radiant heat is easily transmitted to the film, and when the surface temperature is 700 ° C. or lower, overheating of the film can be suppressed.
- the surface temperature of the ceramic heater is more preferably 400 ° C. or higher and 650 ° C. or lower, and further preferably 450 ° C. or higher and 650 ° C. or lower.
- the ceramic heater is preferably covered with a grid-like metal cover. Since the heater is covered with the grid-like metal cover, it is possible to prevent the torn film from colliding with the heater and damaging the heater.
- the metal constituting the cover is not particularly limited, and examples thereof include stainless steel such as SUS304.
- the temperature variation in the film TD direction when radiant heating is performed, it is preferable to narrow the temperature variation in the film TD direction to a range of 0.7 ° C. or more and 3.0 ° C. or less, and thereby the variation in crystallinity in the film width direction is 0.5% or more. It can be reduced to a range of up to 3.0%. If it does in this way, the slack difference in the width direction will reduce, generation
- the residence time in the heat setting part is 5 seconds or more and 50 seconds or less.
- the residence time is the time during which the state in which the film is heated in the heat fixing part is continued.
- the residence time is 5 seconds or longer, the change in crystallinity with respect to the heating time is small, and therefore, it is advantageous in that unevenness of crystallinity in the width direction is relatively less likely to occur. This is advantageous in terms of productivity because it is not necessary to extremely reduce the line speed.
- the residence time is preferably 8 seconds or longer and 40 seconds or shorter, and more preferably 10 seconds or longer and 30 seconds or shorter for the same reason as described above.
- At least one of the heat fixing part and the heat relaxation part is radiantly heated at the end of the polyester film. Further, at the preheating part or the stretching part, or at both the preheating part and the stretching part, Selective radiant heating may be performed.
- the heat-fixed polyester film is heated to relieve the tension of the polyester film and remove the residual distortion of the film.
- the end portion in the TD direction of the polyester film is selectively radiantly heated by the heater.
- the selective radiant heating at the end of the polyester film in the TD direction at the heat relaxation portion may be performed in the same manner as the selective radiant heating at the end of the polyester film in the TD direction at the heat fixing portion.
- the preferred embodiments are also the same.
- heat relaxation heats the heat-fixed polyester film and relieves tension of the polyester film
- heating of the polyester film in the heat relaxation portion is preferably performed as follows.
- the maximum ultimate film surface temperature of the surface of the polyester film 200 is 5 ° C. or more lower than the maximum ultimate film surface temperature (T heat fixation ) of the polyester film 200 in the heat fixing part 30.
- T heat fixation maximum ultimate film surface temperature
- the highest reached film surface temperature of the surface of the polyester film 200 at the time of thermal relaxation is also referred to as “thermal relaxation temperature (T thermal relaxation )”.
- the thermal relaxation temperature (T thermal relaxation ) is heated at a temperature 5 ° C. lower than the thermal fixing temperature (T thermal fixing ) (T thermal relaxation ⁇ T thermal fixing ⁇ 5 ° C.) to release the tension.
- T thermal fixing the thermal fixing temperature
- T thermal relaxation ⁇ T thermal fixing ⁇ 5 ° C. the thermal fixing temperature
- T heat relaxation ⁇ T heat--15 ° C.
- 110 ° C. or higher and more preferably than T heat setting temperature is lower region 25 ° C. or higher (110 ° C. ⁇ T heat relaxation ⁇ T heat--25 ° C.), at 120 ° C. or higher, and lower 30 ° C. or higher than T heat set
- a temperature range 120 ° C. ⁇ T thermal relaxation ⁇ T heat setting ⁇ 30 ° C. is particularly preferable.
- the T heat relaxation is a value measured by bringing a thermocouple into contact with the surface of the polyester film 200.
- Cooling part In a cooling part, the polyester film after heat-relaxing in a heat relaxation part is cooled. As shown in FIG. 3, in the cooling unit 50, the polyester film 200 that has passed through the thermal relaxation unit 40 is cooled. By cooling the polyester film 200 heated by the heat fixing part 30 or the heat relaxation part 40, the shape of the polyester film 200 is fixed.
- the temperature (hereinafter also referred to as “cooling temperature”) of the polyester surface (film surface) at the cooling unit outlet of the polyester 200 in the cooling unit 50 is preferably lower than the glass transition temperature Tg + 50 ° C. of the polyester film 200.
- the temperature is preferably 25 ° C to 110 ° C, more preferably 25 ° C to 95 ° C, and further preferably 25 ° C to 80 ° C.
- the cooling unit outlet refers to an end portion of the cooling unit 50 when the polyester 200 separates from the cooling unit 50, and the gripping member 2 that grips the polyester film 200 (the gripping members 2j and 2l in FIG. 3). The position when releasing the polyester film 200 is said.
- leaves from a holding member shall be 40 degreeC or more and 140 degrees C or less. This means that the temperature of the surface (film surface) of the polyester 200 located at the end of the cooling unit 50 when the polyester 200 moves away from the cooling unit 50 in FIG. 3 is 40 ° C. to 140 ° C. .
- the temperature of the surface of the polyester film when the polyester film is detached from the gripping member is the surface of the polyester film at a position 200 mm away from the gripping member in the TD direction with respect to the surface temperature at the center of the polyester film in the TD direction. It is preferable to lower the temperature by 1 to 20 ° C.
- the film length in the MD direction of the polyester film is the film length in the MD direction at the end portion (S1 side in FIG. 1) on the side having a large MD heat shrinkage among the film end portions in the TD direction.
- the temperature at the end portion in the TD direction of the film when the polyester film is detached from the gripping member is lower by 1 ° C. to 20 ° C. than the central portion in the TD direction. Even when the polyester film is gripped by the gripping member with the stretching device, it tends to shrink in the MD direction. It is in.
- the central part of the film in the TD direction is selectively shrunk, and the TD
- the film length in the direction is preferably set so that the central part in the TD direction is smaller than the end part in the TD direction. From this viewpoint, it is preferable to control the temperature of the surface of the polyester film when the polyester film is detached from the gripping member in the range of 40 to 140 ° C.
- the temperature of the surface of the polyester film when the polyester film is detached from the gripping member is 40 ° C. or higher, the end of the film in the TD direction is less likely to be longer than the center of the film in the TD direction. CT tends to be larger than ⁇ 0.2.
- C CT of the resulting polyester film is likely to be less than 0.2. That is, it becomes easy to obtain polyester satisfying the formula (7).
- the temperature of the surface of the polyester film when the polyester film is detached from the holding member is more preferably 50 ° C. or higher and 120 ° C. or lower, and further preferably 60 ° C. or higher and 100 ° C. or lower.
- the temperature of the surface of the polyester film when the polyester film is detached from the gripping member is such that the polyester film at a position 200 mm away from the gripping member in the width direction with respect to the surface temperature at the center in the width direction of the polyester film.
- the surface temperature is lowered by 1 ° C. to 20 ° C.
- thermocontrol means for heating or cooling the polyester film 200 in preheating, stretching, heat setting, heat relaxation, and cooling in the transverse stretching step hot or cold air is blown on the polyester film 200, or the polyester film 200 is Contact with the surface of a metal plate capable of temperature control, or pass through the vicinity of the metal plate.
- the polyester film 200 cooled in the cooling step cuts the gripped portion held by the clips at both ends in the TD direction, and is wound up in a roll shape.
- the stretched polyester film is preferably relaxed by the following method in order to further improve the hydrolysis resistance and dimensional stability of the produced polyester film.
- the both ends of the width direction (TD) of the polyester film 200 are hold
- one end of the polyester film 200 in the width direction (TD) is held by the holding members 2a and 2b, and the other is held by the holding members 2c and 2d.
- the polyester film 200 is conveyed from the preheating unit 10 to the cooling unit 50 by moving the gripping members 2a to 2d.
- a gripping member 2a (2c) that grips one end of the polyester film 200 in the width direction (TD direction) in the preheating unit 10 and another gripping member 2b (2d) adjacent to the gripping member 2a (2c)
- the distance between the gripping member 2a (2c) that grips one end of the polyester film 200 in the width direction in the cooling unit 50 and the other gripping member 2b (2d) adjacent to the gripping member 2a (2c) By narrowing, the conveyance speed of the polyester film 200 is reduced. With this method, the cooling unit 50 can relax the MD direction.
- the relaxation of the polyester film 200 in the MD direction can be performed in at least a part of the heat fixing unit 30, the heat relaxation unit 40, and the cooling unit 50.
- the polyester film 200 can be relaxed in the MD direction by narrowing the gap between the gripping members 2a-2b and the gap between the gripping members 2c-2d more downstream than the upstream side in the MD direction. it can.
- the conveyance speed of the polyester film and the width of the polyester film (the total length in the TD direction of the film) satisfy the following relationship. That is, the width W1 of the polyester film when the width of the polyester film in the transverse stretching step is maximized and the width W2 of the polyester film at the end of the cooling portion where the polyester film is separated from the cooling portion are expressed by the following formula (I). It is preferable that the polyester film transport speed Sp1 in the preheating section and the polyester film transport speed Sp2 in the end of the cooling section satisfy the following formula (II).
- the width W1 of the polyester film when the width of the polyester film in the transverse stretching step is maximized is the maximum length in the TD direction of the polyester film after the polyester film is widened in the TD direction at the stretched portion. That's it.
- the width W0 of the polyester film 200 before stretching in the preheating portion 10 is widened in the TD direction by the stretching portion 20 to become the width W1, and the tension is released in the heat relaxation portion 40, and the polyester film 200 is stretched. It is shown that when the film 200 leaves the cooling unit 50, the width W2 is obtained.
- the width increases in the order of W0 ⁇ W2 ⁇ W1.
- W1 is the maximum width of the polyester film 200 in the transverse stretching process from the preheating part 10 to the cooling part 50.
- the width W ⁇ b> 1 is usually the polyester in the heat fixing portion 30. It can also be said to be the width of the film 200 (length in the TD direction).
- the width W2 of the polyester film at the end of the cooling part where the polyester film is separated is positioned in the cooling part, and the gripping members (the gripping members 2j and 2l in FIG. 3) grip the polyester film. It is the width
- the gripping member that grips the polyester film releases the polyester film, the polyester film leaves the region of the cooling unit.
- the gripping member 2j shown in FIG. 3 is at point P and the gripping member 21 is at point Q
- the polyester film 200 is released, the end of the cooling unit 50 (end in the MD direction) It is represented by a straight line connecting the point Q and the point Q.
- the “conveying speed Sp1 of the polyester film in the preheating portion” corresponds to the moving speed of the gripping member (2a to 2d in FIG. 3) that grips the polyester film and moves the edge of the annular rail. Further, “the conveyance speed Sp2 of the polyester film at the end of the cooling unit” is located when the gripping members (the gripping members 2j and 2l in FIG. 3) that are positioned in the cooling unit and grip the polyester film release the polyester film. It is the conveyance speed of the polyester film in.
- the polyester film 200 at the end of the cooling unit 50 corresponds to the transport speed when the polyester film 200 exceeds the straight line connecting the P point and the Q point.
- the “conveying speed Sp2 of the polyester film 200 at the end of the cooling unit 50” corresponds to the moving speed of the gripping members 2j and 2l immediately before the gripping members 2j and 2l release the polyester film 200.
- the maximum width (length in the TD direction) W1 of the polyester film 200 is reduced by 2% to 15% in the cooling unit 50. It is preferable to relax.
- the transport speed Sp1 in the preheating portion 10 of the polyester film 200 is relaxed so as to be reduced by 2% to 15% in the cooling portion 50. Means.
- ⁇ W indicates the relaxation rate in the TD direction (lateral direction) of the polyester film, so ⁇ W is also referred to as “TD relaxation rate”.
- ⁇ Sp indicates the relaxation rate in the MD direction (longitudinal direction) of the polyester film, ⁇ Sp is also referred to as “MD relaxation rate”.
- both ⁇ W and ⁇ Sp are preferably 2% to 15% (2% ⁇ ⁇ W ⁇ 15%, 2% ⁇ ⁇ Sp ⁇ 15%).
- both ⁇ W and ⁇ Sp are 2% or more, the polyester film easily satisfies the formulas (1) to (7), and wrinkles and scratches during heating and conveyance are easily suppressed.
- both ⁇ W and ⁇ Sp are 15% or less, the polyester film can be easily shrunk by a stretching device, and slack can be suppressed.
- ⁇ W is more preferably 2% to 10% (2% ⁇ ⁇ W ⁇ 10%), and further preferably 3% to 8% (3% ⁇ ⁇ W ⁇ 8%).
- ⁇ Sp is preferably 2% to 10% (2% ⁇ ⁇ Sp ⁇ 10%), more preferably 3% to 8% (3% ⁇ ⁇ Sp ⁇ 8%).
- the polyester film of the present invention is less likely to be wrinkled and scratched even when heated and conveyed, and even when a coating liquid or a functional member sheet is pasted on the film, there are problems such as coating unevenness and air bubble mixing during sheet bonding. Hard to occur. Therefore, it can be used for various applications that are processed by heating and conveyed. For example, it can be suitably used for an optical film and an electrical insulating film.
- a solar cell module generally includes a solar cell element that converts light energy of sunlight into electric energy, a transparent substrate on which sunlight is incident, and the polyester film of the present invention described above (back sheet for solar cell). It is arranged between them.
- a power generating element (solar cell element) connected by a lead wiring (not shown) for extracting electricity is sealed with a sealing agent such as ethylene / vinyl acetate copolymer system (EVA system) resin, You may comprise in the aspect comprised by sticking together this between transparent substrates, such as glass, and the polyester film (back sheet
- a sealing agent such as ethylene / vinyl acetate copolymer system (EVA system) resin
- solar cell elements examples include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic.
- group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic.
- group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic.
- group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic.
- II-VI group compound semiconductor systems can be applied.
- the substrate and the polyester film can be formed by sealing with a
- polyester raw resin 1 polyester raw resin 1
- polyester raw resin 1 polyester raw resin 1
- terephthalic acid and ethylene glycol by directly reacting terephthalic acid and ethylene glycol to distill off water, esterify, and then use a direct esterification method in which polycondensation is performed under reduced pressure, polyester (Ti catalyst) by a continuous polymerization apparatus. System PET) was obtained.
- the 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 equivalents / ton.
- the inside of the second esterification reaction tank is partitioned into three zones, and an ethylene glycol solution of magnesium acetate is continuously supplied from the second zone so that the amount of Mg added is 75 ppm in terms of element, From the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the added amount of P was 65 ppm in terms of element.
- reaction tank temperature was 276 ° C.
- reaction tank pressure was 5 torr (6.67 ⁇ 10 ⁇ 4 MPa)
- residence time was about 1.2 hours.
- the reaction (polycondensation) was performed under the conditions.
- the reaction product (polyethylene terephthalate (PET)) was obtained by reaction (polycondensation) under the following conditions.
- polyester pellets cross section: major axis: about 4 mm, minor axis: about 2 mm, length: about 3 mm).
- Polyester raw material resin 1 was subjected to solid phase polymerization by a batch method. That is, polyester pellets were put into a container, preliminarily crystallized at 150 ° C. while stirring under vacuum, and then a solid-state polymerization reaction was performed at 190 ° C. for 30 hours. Polyester raw resin 2 was synthesized as described above.
- the reaction was terminated when the stirring torque reached the target value, and the resulting polymer was taken out in water as a strand having a diameter of 2.5 mm.
- the obtained strand polymer was cut into chips with a chip cutter.
- the obtained polymer had an intrinsic viscosity (IV) of 0.60.
- PEN polyethylene-2,6-naphthalate
- PET polyester raw material resin 4 having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.65 was prepared.
- polyester raw resin 1 was dried to a moisture content of 20 ppm or less, and then charged into a hopper of a single-screw kneading extruder having a diameter of 50 mm.
- Polyester raw resin 1 was melted at 300 ° C. and extruded from a die through a gear pump and a filter (pore diameter: 20 ⁇ m) under the following extrusion conditions.
- the dimension of the die slit was adjusted so that the thickness of the polyester sheet was 3 mm.
- the thickness of the polyester sheet was measured by an automatic thickness meter installed at the exit of the cast drum.
- the extrusion of the molten resin was performed under the condition that the pressure fluctuation was 1% and the temperature distribution of the molten resin was 2%. Specifically, the back pressure in the barrel of the extruder is 1% higher than the average pressure in the barrel of the extruder, and the piping temperature of the extruder is 2% higher than the average temperature in the barrel of the extruder. Heated as temperature.
- the molten resin was extruded onto a cooling cast drum and brought into close contact with the cast drum using an electrostatic application method. For cooling the molten resin, the temperature of the cast drum was set to 25 ° C., and cold air of 25 ° C.
- An unstretched polyester film (unstretched polyester film 1) having a thickness of 3 mm and a film width of 0.9 m was peeled off from the cast drum by a peeling roll disposed opposite to the cast drum.
- the preheating temperature was 110 ° C., and heating was performed so that stretching was possible.
- heat fixing part the highest reachable film surface temperature (heat setting temperature) of the polyester film was controlled within the following range to heat and crystallize.
- heat setting temperature T heat fixation in is the pre-peak temperature of DSC [°C].
- both ends in the film width direction were radiantly heated with a ceramic infrared heater (heater surface temperature: 650 ° C.) from the cast surface side in contact with the cast drum in the film forming process. At this time, the distance between the heater and the polyester film was 170 mm.
- Heat relaxation part The polyester film after heat setting was heated to the following temperature to relax the tension of the film. At this time, both ends in the film width direction were radiantly heated from the cast surface side with an infrared heater (heater surface temperature: 350 ° C.) in the same manner as the heat setting.
- PET film biaxially stretched polyester film having a thickness of 250 ⁇ m was produced.
- the MD thermal contraction rate obtained by measuring the sample piece M located at the end in the TD direction on the film F was S S1 with a large numerical value, and S S2 with a small numerical value. Further, the MD thermal shrinkage rate obtained by measuring a test piece M located in central TD direction in the film F was S CT. The results are shown in Table 2.
- the thickness of the obtained biaxially stretched polyester film was determined as follows. For biaxially stretched polyester film, using a contact-type film thickness meter (manufactured by Anritsu), 50 points were sampled at equal intervals over 0.5 m in the longitudinally stretched direction (longitudinal direction), and the film width direction ( After sampling 50 points at equal intervals (50 equal parts in the width direction) over the entire width of the film in the direction perpendicular to the longitudinal direction, the thicknesses of these 100 points were measured. The average thickness of these 100 points was determined and used as the thickness of the polyester film.
- DSC pre-peak temperature unevenness The film F, in the position where the on the straight line C L of FIG. 1, with respect to the total width of the other end from one end of the TD direction, was sampled at regular intervals at 11 points to obtain a sample piece M2.
- the DSC pre-peak temperature (Tpp) was measured for the sample piece M2 at each position.
- the difference ( ⁇ Tpp) between the maximum value and the minimum value of the plurality of measured Tpp values was determined as the unevenness of the DSC pre-peak temperature.
- the DSC pre-peak temperature was increased to 300 ° C. at a heating rate of 10 ° C./min by setting a predetermined amount (2 to 10 mg) of the sampled sample M2 film on DSC-60 manufactured by Shimadzu Corporation. Measured by warming.
- the peak temperature of the endothermic peak that appears before the melting peak of polyester (PET) was read as the DSC pre-peak temperature (Tpp).
- Example 2 to 15 and Comparative Examples 1 to 5 Biaxially stretched polyester films of Examples 2 to 15 and Comparative Examples 1 to 5 were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. Moreover, about the obtained biaxially stretched polyester film, it evaluated by the method similar to the biaxially stretched polyester film of Example 1, and the physical property evaluation of a biaxially stretched polyester film, and the presence or absence of a wrinkle and a damage
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Abstract
Description
また、フィルムの搬送方向(MD;Machine Direction)の熱収縮率とMDに直交する方向(TD;Transverse Direction)の熱収縮率と比MD/TD熱収縮率を低くすることで、フィルムの加熱搬送性を付与することが開示されている(例えば、特開2001-191406号公報参照)。
前記課題を達成するための具体的手段は以下の通りである。
W/1000<〔(Ss1-Ss2)/CS1/100〕<2W ・・・(1)
0<(Ss1-Ss2)<0.5 ・・・(2)
-1<(Ss1+Ss2+SCT)/3<3 ・・・(3)
0<Cs1<0.2 ・・・(4)
Ss1は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表し、
Ss2は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が小さい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表す。
SCTは、ポリエステルフィルム幅方向の中央部における、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率 [%]を表す。
CS1は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、湾曲の大きさの最大値[m]を表す。
Wは、ポリエステルフィルムのフィルム幅[m]を表す。
W/2000<〔{SCT-(Ss1+Ss2)/2}/CCT/100〕<W ・・・(5)
-0.5<{SCT-(Ss1+Ss2)/2}<0.5 ・・・(6)
-0.2<CCT<0.2 ・・・(7)
Ss1は、式(1)等におけるSs1と同義であり、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表す。
Ss2は、式(1)等におけるSs2と同義であり、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表す。
SCTは、式(3)におけるSCTと同義であり、ポリエステルフィルム幅方向の中央部における、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率 [%]を表す。
CCTは、ポリエステルフィルム長手方向の両端部におけるフィルム幅方向の中央を結んだ直線に沿ってポリエステルフィルムを裁断して得られる半裁ポリエステルフィルムの幅方向の端部における湾曲の大きさの最大値を足して2で割った値[m]を表す。
Wは、式(1)におけるWと同義であり、ポリエステルフィルムのフィルム幅[m]を表す。
成形されたポリエステルフィルムを長手方向に縦延伸する縦延伸工程と、
縦延伸後のポリエステルフィルムを延伸可能な温度に予熱する予熱部、予熱されたポリエステルフィルムを長手方向と直交する幅方向に緊張を与えて横延伸する延伸部、縦延伸及び横延伸を行なった後のポリエステルフィルムを加熱し結晶化させて熱固定する熱固定部、熱固定されたポリエステルフィルムを加熱し、ポリエステルフィルムの緊張を緩和してフィルムの残留歪みを除去する熱緩和部、並びに、熱緩和後のポリエステルフィルムを冷却する冷却部に、ポリエステルフィルムをこの順に搬送して、縦延伸後のポリエステルフィルムを長手方向に直交する幅方向に横延伸する横延伸工程と、を含み
熱固定部および熱緩和部の少なくとも一方において、幅方向のポリエステルフィルムの端部をヒーターにより選択的に輻射加熱し、ヒーターの表面とポリエステルフィルムの表面との最短距離を10mm以上300mm以下とするポリエステルフィルムの製造方法である。
ポリエステルフィルムが把持部材から離脱するときのポリエステルフィルムの表面の温度を、40℃~140℃とする<8>~<11>のいずれか1つに記載のポリエステルフィルムの製造方法である。
ポリエステルフィルムは、複数のポリエステルフィルムを積層したり、ポリエステルフィルム上に機能層を積層して、高機能化または複合化することがある。このようなポリエステルフィルムの加工に当たっては、通常、ロール等により搬送されながら、フィルムの加熱や延伸等がなされる。
ポリエステルフィルムが加熱搬送されるときに生じるシワや傷は、フィルムに平面性のムラ(弛みや縮み)が存在することで起きる傾向にある。フィルム上、局所的に弛んだ箇所がロール上でスリップして傷になったり、弛みが搬送中に折れて、シワになったりする。
未加熱のフィルムの平面性と加熱時の熱収縮率ムラを、それぞれ個別に改良する試みはあったが、不十分であった。
なお、本発明において、フィルムの平面性とは、ポリエステルフィルムの弛み及び縮みの状態をいい、フォルム中に部分的な弛みまたは部分的な縮みがないときに平面性が良いという。また、フィルムのTD方向において、部分的にフィルムに弛み若しくは縮みまたはその両方がある場合、「平面性に差がある」または「平面性にムラがある」ともいう。
以下、本発明のポリエステルの詳細について説明する。
W/1000<〔(Ss1-Ss2)/CS1/100〕<2W ・・・(1)
0<(Ss1-Ss2)<0.5 ・・・(2)
-1<(Ss1+Ss2+SCT)/3<3 ・・・(3)
0<Cs1<0.2 ・・・(4)
Ss1は、フィルム幅方向の端部のうち、フィルム幅方向と直交する方向の熱収縮率(150℃、30分)が大きい側のポリエステルフィルムのフィルム幅方向と直交する方向の熱収縮率[%]を表し、Ss2は、フィルム幅方向の端部のうち、フィルム幅方向と直交する方向の熱収縮率(150℃、30分)が小さい側のポリエステルフィルムのフィルム幅方向と直交する方向の熱収縮率[%]を表す。
SCTは、フィルム幅方向のフィルム中央部におけるポリエステルフィルムのフィルム幅方向と直交する方向の熱収縮率(150℃、30分)[%]を表す。
CS1は、フィルム幅方向のフィルム端部のうち、フィルム幅方向と直交する方向の熱収縮率(150℃、30分)が大きい側の端部における湾曲の大きさの最大値[m]を表す。
Wは、ポリエステルフィルムのフィルム幅[m]を表す。
本発明においては、フィルム幅方向を、TDまたはTD方向と称し、フィルム幅方向と直交する方向を、MDまたはMD方向と称する。また、MD方向の熱収縮を、MD熱収縮ともいい、その割合をMD熱収縮率という。従って、フィルム幅方向と直交する方向の熱収縮率は、MD熱収縮率とも表現する。
TD方向30mm、MD方向120mmに裁断したポリエステルフィルムの試料片Mに、予めMD方向で100mmの間隔となるように2本の基準線を入れる。試料片Mを、無張力下で150℃の加熱オーブン中に30分間放置した後、試料片Mを室温まで冷却する処理を行い、2本の基準線の間隔を測定する。このときに測定される処理後の間隔をA〔mm〕とする。処理前の間隔100mmと、処理後の間隔Ammとから、「100×(100-A)/100」の式を用いて算出される数値〔%〕を、試料片MのMD熱収縮率(S)とする。
以下、熱収縮率(150℃、30分)を、単に熱収縮率とも称する。
Ss1及びSs2は、いずれもポリエステルフィルムのTD方向の端部のMD熱収縮率であり、Ss1はMD熱収縮率が大きい側のMD熱収縮率[%]を表し、Ss2はMD熱収縮率が小さい側のMD熱収縮率[%]を表す。
SCTは、ポリエステルフィルムのTD方向の中央部におけるMD熱収縮率 [%]を表す。
図1(A)および(B)には、それぞれ、湾曲したポリエステルフィルムが示されている。
一般に、ポリエステル原料樹脂を溶融混練し、延伸して回収されるポリエステルフィルムは、フィルムのMD方向の端部のうち一方の端部を、高所に固定して吊るすと、TD方向の端部の縁が湾曲している傾向にある。
図1には、このように、高所から吊るし、フィルムに弛みが無いように張ったポリエステルフィルムの様子を模式的に示してある。
図1(A)には、ポリエステルフィルムを高所から吊るしたとき、S1側(高MD熱収縮率側)が円弧状に膨らむフィルムを示し、(B)には、S2側(低MD熱収縮率側)が円弧状に膨らむフィルムを示している。
また、図1では、ポリエステルフィルムのMD方向の全長をLとしている。ただし、Lは、ポリエステルフィルムのTD方向端部の縁の長さではなく、高所から吊るしたポリエステルフィルムのMD方向の一方の端部から他方の端部までの距離である。CWuとCWdとを結んで得られる直線Y1(図1において垂直方向に点線で示される直線)のCWuからCWdまでの距離がLとなる。
また、ポリエステルフィルムのS1側で、かつ、CWuがある辺のフィルムTD方向の端部を通り、重力方向と平行する直線Z1(図1において、一点鎖線で表される直線)をポリエステルフィルム上に引く。次いで、直線Y1の半分(L/2)の位置で、直線Y1に垂直する直線CLを引く。
一般に、フィルムのTD方向端部が円弧状に湾曲したポリエステルフィルムは、フィルムのMD方向の距離の半分(直線CLが引かれる位置)の湾曲の大きさが最も大きい。式(1)および(4)における「フィルム幅方向のフィルム端部のうち、フィルム幅方向と直交する方向の熱収縮率(150℃、30分)が大きい側の端部における湾曲の大きさの最大値[m]」は、図1(A)、(B)のCS1として得られる数値である。
以下、幅がWであるポリエステルフィルムの湾曲の大きさの最大値であるCS1を「全幅円弧」ともいう。
なお、ポリエステルフィルムのS1側が円弧状に膨らんでいる場合(直線Z1が、ポリエステルフィルムの内側に引かれる場合)の円弧をプラス円弧といい、S1側が引っ込んでいる場合(直線Z1が、ポリエステルフィルムの外側に引かれる場合)の円弧をマイナス円弧という。
図2は、図1に示されるポリエステルフィルムを、CWuとCWdとを結んで得られる直線Y1に沿って裁断した半裁ポリエステルフィルムが示されている。図2(A)には、図1(B)に示されるポリエステルフィルムの半裁ポリエステルフィルムのうち、S1側の断片が示されている。図2(B)には、図1(A)に示されるポリエステルフィルムの半裁ポリエステルフィルムのうち、S2側の断片が示されている。
図1(A)に示されるフィルムでは、フィルムTD方向の中央に位置したCWdは、フィルムの裁断により、図2では、TD方向の端部に位置する。
CWdの位置を、図2(A)ではC1と称し、図2(B)ではC2と称する。
一般に、湾曲しているフィルムにおいてCWu-CWd直線(直線Y1)を裁断すると、張力を失って、元のフィルムと同様に湾曲する傾向にある。
図2において、CW2uとCW2dとを結んで得られる直線Y2(図2において垂直方向に点線で示される直線)のCW2uからCW2dまでの距離はLである。
また、半裁ポリエステルフィルムのC1側で、C1を通り、重力方向と平行する直線Z2(図2において、一点鎖線で表される直線)を半裁ポリエステルフィルム上に引く。次いで、直線Y2の半分(L/2)の位置で、直線Y2垂直する直線CLを引く。
半裁ポリエステルフィルムのC2側が膨らんでいる図2(B)に示す半裁ポリエステルフィルムにおいては、直線CL上の距離であって、半裁ポリエステルフィルムのC2側のTD方向端部から、直線Z2までの距離を、CC2という。
半裁ポリエステルフィルムについて更に説明すると、2つの半裁ポリエステルフィルムは、ポリエステルフィルムの長手方向の2つの端部において、フィルム幅方向に沿った辺の中点どうしを結んだ直線に沿ってポリエステルフィルムを裁断して得られる。
〔式(1)〕
式(1)は、下記不等号で表される。
W/1000<〔(Ss1-Ss2)/CS1/100〕<2W ・・・(1)
以下、MD熱収縮率差「Ss1-Ss2」をΔSとも表す。
式(1)は、MD方向の端部のフィルム幅がWであるポリエステルフィルムの全幅円弧CS1に対するMD熱収縮率差ΔSの割合〔(Ss1-Ss2)/CS1/100[%]〕がフィルム幅Wの1000分の1より大きく、フィルム幅Wの2倍よりも小さいことを表している。
ただし、ポリエステルフィルムにおいて、湾曲の程度が酷く、全幅円弧CS1が大きいと、MD熱収縮率差ΔSを小さくしても、加熱搬送時のシワや傷を防ぐことはできない。その限度がW/1000を超える値である。
式(2)は、下記不等号で表される。
0<(Ss1-Ss2)<0.5 ・・・(2)
つまり、ΔSは0を超え0.5未満であることを表す。式(1)で説明したように、通常、ポリエステルフィルムのMD熱収縮率差ΔSを0とすることは困難であり、フィルムのTD方向の一端と他端とでMD熱収縮率は異なる傾向にある。また、式(1)においては、全幅円弧CS1に対するMD熱収縮率差ΔSの割合を2W未満とすることを規定しているが、CS1が小さくても、ΔSが大きくなりすぎると、フィルムの加熱搬送時の平面性を良くすることができなくなる。
ΔSは、0.02<ΔS<0.4であることが好ましく、0.03<ΔS<0.3であることがより好ましい。
式(3)は、下記不等号で表される。
-1<(Ss1+Ss2+SCT)/3<3 ・・・(3)
「(Ss1+Ss2+SCT)/3」は、つまり、Ss1とSs2とSCTとの平均であり、以下、「(Ss1+Ss2+SCT)/3」をSAVとも表す。
ポリエステルフィルムのTD方向におけるMD熱収縮率は、S1側とS2側とのバランスのみならず、Ss1及びSs2と、TD方向のフィルム中央部におけるMD熱収縮率SCTとのバランスも重要である。
ここで、「フィルム幅方向(TD方向)のフィルム中央部」とは、ポリエステルフィルムのTD方向の一方の末端と他方の末端との中心の位置をCTとしたとき、CTを中心として、TD方向およびMD方向に、各々ポリエステルフィルムのTD方向の全長の±10%となる領域をいう。
SAVは、-0.5<SAV<2であることが好ましく、-0.2<SAV<1.5であることがより好ましい。
式(4)は、下記不等号で表される。
0<Cs1<0.2 ・・・(4)
式(4)は、幅がWであるポリエステルフィルムの湾曲の大きさの最大値(全幅円弧)の範囲を規定したものである。ポリエステル原料樹脂を溶融混練し、延伸して得られるポリエステルフィルムは、一般に、フィルムTD方向の縁が湾曲してしまい、全幅円弧を0とすることが難しい。全幅円弧が0.2以上となると、フィルムの加熱搬送前から既に、フィルムに大きな弛みが生じており、フィルムを加熱搬送した時に、シワおよび傷の発生を抑制することができない。
全幅円弧Cs1は、0.001<Cs1<0.1であることが好ましく、0.002<Cs1<0.05であることがより好ましい。
本発明のポリエステルフィルムは、式(1)~(4)に加え、さらに、式(5)~(7)を満たすことが好ましい。
式(5)~式(7)は、フィルム幅がWであるポリエステルフィルムを、図1に示すCWu-CWd直線(直線Y1)に沿って裁断して得られる半裁ポリエステルフィルムについての規定である。
フィルム幅がW/2である半裁ポリエステルフィルムについても、フィルム幅がWであるポリエステルフィルムと同様に、フィルムの端弛み(TD方向端部における弛み)および中弛み(TD方向中央部における弛み)を制御することで、加熱搬送時のシワ及び傷を抑制し易くなる。
式(5)は、下記不等号で表される。
W/2000<〔{SCT-(Ss1+Ss2)/2}/CCT/100〕<W ・・・(5)
「{SCT-(Ss1+Ss2)/2}/CCT/100」が上記範囲内であることで、加熱搬送時に中央と端部で平面性に差が生じにくく、弛み等の発生が抑制されるので、シワ及び傷が生じにくい。
「{SCT-(Ss1+Ss2)/2}/CCT/100」は、-0.4を超え、0.4未満であることがより好ましく、-0.3を超え、0.3未満であることが更に好ましい。
式(6)は、下記不等号で表される。
-0.5<{SCT-(Ss1+Ss2)/2}<0.5 ・・・(6)
「{SCT-(Ss1+Ss2)/2}」が上記範囲内であることで、加熱搬送時に中央と端部で平面性に差が生じにくく、弛み等の発生が抑制されるので、シワ及び傷が生じにくい。
「{SCT-(Ss1+Ss2)/2}」は、-0.4を超え、0.4未満であることがより好ましく、-0.3を超え、0.3未満であることが更に好ましい。
式(7)は、下記不等号で表される。
-0.2<CCT<0.2 ・・・(7)
CCTが上記範囲内であることで、加熱搬送前の段階での弛み等が発生しにくく、シワ及び傷の発生が抑制される。
CCTは、-0.1<CCT<0.1であることがより好ましく、-0.05<CCT<0.05であることが更に好ましい。
ポリエステルフィルムのフィルム幅Wは、0.5m以上5m以下がより好ましく、0.7m以上3m以下が更に好ましく、0.8m以上2m以下が最も好ましい。
ここで、DSCとは、示差走査熱量測定 (Differential scanning calorimetry)であり、DSCの「プレピーク温度」とは、ポリエステルフィルムをDSC測定したときに最初に現れるピークの温度である。
DSCのプレピーク温度は、一般に、ポリエステルフィルムの二軸延伸で行われる横延伸工程中の熱固定時におけるポリエステルフィルムの最高到達膜面温度(熱固定温度)に相当する。
なお、DSCのプレピーク温度は、示差走査熱量測定(DSC)で常法により求められる値である。
ΔTppは、0.5℃以上7℃以下がより好ましく、0.5℃以上5℃以下が更に好ましく、0.5℃以上4℃以下が最も好ましい。
なお、本明細書中において、「eq/トン」は1トンあたりのモル当量を表す。
AVは、ポリエステルをベンジルアルコール/クロロホルム(=2/3;体積比)の混合溶液に完全溶解させ、指示薬としてフェノールレッドを用い、基準液(0.025N KOH-メタノール混合溶液)で滴定し、その適定量から算出される値である。
本発明のポリエステルフィルムは、後述のように、例えば(A)ジカルボン酸成分と(B)ジオール成分とを周知の方法でエステル化反応及び/又はエステル交換反応させることによって得ることができ、更に好ましくは、これに3官能以上の多官能モノマーを共重合させて得られる。ジカルボン酸成分、ジオール成分、及び多官能モノマー等の例示や好ましい態様などの詳細については、後述する通りである。
カルボン酸基の数(a)と水酸基の数(b)との合計(a+b)が3以上である多官能モノマーに由来の構成単位としては、後述するように、カルボン酸基の数(a)が3以上のカルボン酸並びにこれらのエステル誘導体や酸無水物等、水酸基数(b)が3以上の多官能モノマー、並びに「一分子中に水酸基とカルボン酸基の両方を有し、カルボン酸基の数(a)と水酸基の数(b)との合計(a+b)が3以上であるオキシ酸類」などを挙げることができる。これらの例示及び好ましい態様などの詳細については、後述する通りである。
また、カルボン酸のカルボキシ末端、又は「一分子中に水酸基とカルボン酸基の両方を有する多官能モノマー」のカルボキシ末端に、l-ラクチド、d-ラクチド、ヒドロキシ安息香酸などのオキシ酸類及びその誘導体、そのオキシ酸類が複数個連なったもの等を付加させたものも好適である。
これらは、一種単独で用いても、必要に応じて、複数種を併用してもよい。
本発明のポリエステルフィルムは、更に、オキサゾリン系化合物、カルボジイミド化合物、及びエポキシ化合物から選ばれる末端封止剤に由来する構造部分を有していることが好ましい。なお、「末端封止剤に由来する構造部分」とは、末端封止剤がポリエステル末端のカルボン酸と反応して末端に結合している構造をさす。
末端封止剤は、ポリエステルフィルムの質量に対して、0.1質量%以上5質量%以下の範囲で含有されていることが好ましく、より好ましくは0.3質量%以上4質量%以下であり、さらに好ましくは0.5質量%以上2質量%以下である。
ポリエステルフィルム中における末端封止剤の含有比率が0.1質量%以上であることで、塗布層との密着が良好になると共に、AV低下効果による耐候性向上を達成できる上、低熱収縮性も付与することができる。また、ポリエステルフィルム中における末端封止剤の含有比率が5質量%以下であると、塗布層との密着が良好になると共に、末端封止剤の添加によるポリエステルのガラス転移温度(Tg)の低下が抑制され、これによる耐候性の低下や熱収縮の増加を抑制することができる。これは、Tgが低下した分、相対的にポリエステルの反応性が増加することで生じる加水分解性の増加を抑制したり、Tg低下で増加するポリエステル分子の運動性が増加し易くなることで生じる熱収縮が抑制されるためである。
ここで、イソシアネート系ガスは、イソシアネート基をもつガスであり、例えば、ジイソプロピルフェニルイソシアネート、1,3,5-トリイソプロピルフェニルジイソシアネート、2-アミノ-1,3,5-トリイソプロピルフェニル-6-イソシアネート、4,4’-ジシクロヘキシルメタンジイソシアネート、イソホロンジイソシアネート、及びシクロヘキシルイソシアネートなどが挙げられる。
ビスオキサゾリン化合物としては、例えば、2,2'-ビス(2-オキサゾリン)、2,2'-ビス(4-メチル-2-オキサゾリン)、2,2'-ビス(4,4-ジメチル-2-オキサゾリン)、2,2'-ビス(4-エチル-2-オキサゾリン)、2,2'-ビス(4,4'-ジエチル-2-オキサゾリン)、2,2'-ビス(4-プロピル-2-オキサゾリン)、2,2'-ビス(4-ブチル-2-オキサゾリン)、2,2'-ビス(4-ヘキシル-2-オキサゾリン)、2,2'-ビス(4-フェニル-2-オキサゾリン)、2,2'-ビス(4-シクロヘキシル-2-オキサゾリン)、2,2'-ビス(4-ベンジル-2-オキサゾリン)、2,2'-p-フェニレンビス(2-オキサゾリン)、2,2'-m-フェニレンビス(2-オキサゾリン)、2,2'-o-フェニレンビス(2-オキサゾリン)、2,2'-p-フェニレンビス(4-メチル-2-オキサゾリン)、2,2'-p-フェニレンビス(4,4-ジメチル-2-オキサゾリン)、2,2'-m-フェニレンビス(4-メチル-2-オキサゾリン)、2,2'-m-フェニレンビス(4,4-ジメチル-2-オキサゾリン)、2,2'-エチレンビス(2-オキサゾリン)、2,2'-テトラメチレンビス(2-オキサゾリン)、2,2'-ヘキサメチレンビス(2-オキサゾリン)、2,2'-オクタメチレンビス(2-オキサゾリン)、2,2'-デカメチレンビス(2-オキサゾリン)、2,2'-エチレンビス(4-メチル-2-オキサゾリン)、2,2'-テトラメチレンビス(4,4-ジメチル-2-オキサゾリン)、2,2'-9,9'-ジフェノキシエタンビス(2-オキサゾリン)、2,2'-シクロヘキシレンビス(2-オキサゾリン)及び2,2'-ジフェニレンビス(2-オキサゾリン)等を例示することができる。これらの中では、ポリエステルとの反応性が良好で耐候性の向上効果が高い観点から、2,2'-ビス(2-オキサゾリン)が最も好ましい。
ビスオキサゾリン化合物は、本発明の効果を損なわない限り、1種単独で用いてもよいし、2種以上を組み合わせて用いてもよい。
以下、本発明のポリエステルフィルムの製造方法について具体的に説明する。
本発明のポリエステルフィルムの製造方法は、
ポリエステル原料樹脂をシート状に溶融押出し、キャスティングドラム上で冷却してポリエステルフィルムを成形するフィルム成形工程と、
成形されたポリエステルフィルムを長手方向に縦延伸する縦延伸工程と、
縦延伸後のポリエステルフィルムを延伸可能な温度に予熱する予熱部、予熱されたポリエステルフィルムを長手方向と直交する幅方向に緊張を与えて横延伸する延伸部、縦延伸及び横延伸を行なった後のポリエステルフィルムを加熱し結晶化させて熱固定する熱固定部、熱固定されたポリエステルフィルムを加熱し、ポリエステルフィルムの緊張を緩和してフィルムの残留歪みを除去する熱緩和部、並びに、熱緩和後のポリエステルフィルムを冷却する冷却部に、ポリエステルフィルムをこの順に搬送して、縦延伸後のポリエステルフィルムを長手方向に直交する幅方向に横延伸する横延伸工程と、を含み
熱固定部および熱緩和部の少なくとも一方において、幅方向のポリエステルフィルムの端部をヒーターにより選択的に輻射加熱し、ヒーターの表面とポリエステルフィルムの表面との最短距離を10mm以上300mm以下とする方法である。
本発明のポリエステルフィルムの製造方法は、さらに他の工程を含んでいてもよい。
横延伸工程は、予熱部と、延伸部と、熱固定部と、熱緩和部と、冷却部とに分かれ、ポリエステルフィルムを各部に搬送する。
さらに、本発明のポリエステルフィルムの製造方法では、横延伸工程における熱固定部もしくは熱緩和部、または熱固定部および熱緩和部の両方において、ポリエステルフィルムのTD方向端部を、フィルム表面から特定の距離だけ離したヒーターにより選択的に輻射加熱する。
例えば、特許文献2として示す特開2001-191406号公報では、次の1)と2)に示す理由から、式(1)~式(4)および式(5)~式(7)を満たすポリエステルフィルムを製造することができないと考えられる。
ポリエステルフィルムのMD熱収縮率は、一般に、フィルムを構成するポリエステルの結晶化度と、MD方向のポリエステル分子の緩和度合いで決まる。ポリエステルの結晶化度およびポリエステル分子の緩和度合いが進んでいるほど、MD熱収縮率は低くなる傾向にある。
通常、二軸延伸装置等の延伸装置で横延伸されるPETの場合、PETの結晶化度およびPET分子の緩和度合いは、延伸装置の熱固定部の温度で決まる。フィルムの熱固定温度が高いほど、ポリエステルの結晶化度は高く、ポリエステルフィルムのMD熱収縮率が低くなる傾向にある。
延伸装置で横延伸および熱固定をする際、フィルムをクリップなどの把持部材で把持するが、この把持部材は、延伸装置の入口(ポリエステルフィルムが予熱部に入ったとき)から出口(ポリエステルフィルムが冷却部から離れたとき)を通じて約100℃~150℃程度の温度になることが多い。フィルムの熱固定温度は、PETの場合、通常、200℃前後になるが、把持部材自体の温度は、熱固定温度に比べて低いため、熱が把持部材側に逃げてしまい、必然的にフィルム端部側の熱固定温度が低くなり易い。そのため、フィルムのMD熱収縮率もフィルム端部が大きくなるような分布が形成され易い。
ポリエステルフィルムのMD方向の長さ分布は、横延伸を行う延伸装置の出口近傍における冷却の態様に依存し易い。一般に、フィルムのMD方向の長さは、急冷された箇所は長くなり、徐冷された箇所は短くなる傾向にある。これは次の理由によるものと考えられる。フィルムは、冷却により収縮するが(熱膨張の反対の現象)、急冷されると収縮する時間が少ないため、フィルムが十分に収縮せず、結果として、MD方向のフィルム長は長くなると考えられる。逆に、フィルムは、徐冷されると、十分に収縮するため、MD方向のフィルム長が短くなると考えられる。
そうなると、フィルム中央部は、未加熱前の元のMD方向のフィルム長が長い上に、加熱搬送時により縮みにくいため、より長くなり、弛みが生じてキズやシワができ易い。
従って、従来のポリエステルフィルムでは、式(1)における「〔(Ss1-Ss2)/CS1/100〕」、及び、式(5)における「〔{SCT-(Ss1+Ss2)/2}/CCT/100〕」が負の値となり、式(1)及び式(5)を満たさない。
本発明のポリエステルフィルムの製造方法は、加熱搬送する前のTD方向のフィルム長が長い箇所(円弧が大きい箇所)のMD熱収縮率を大きくしてやり、逆に短い箇所は熱収縮率を小さくして、元々長い箇所を選択的に縮ませてしまうことで、局所的な長さのムラをなくす手法である。
フィルム成形工程では、ポリエステル原料樹脂をシート状に溶融押出し、キャスティングドラム上で冷却してポリエステルフィルムを成形する。
ポリエステル原料樹脂を溶融押出する方法、及びポリエステル原料樹脂については、特に限定されないが、ポリエステル原料樹脂の合成に用いる触媒や、重合方法等により固有粘度を所望の固有粘度とすることができる。
まず、ポリエステル原料樹脂について説明する。
ポリエステル原料樹脂は、ポリエステルフィルムの原料となり、ポリエステルを含んでいる材料であれば、特に制限されず、ポリエステルのほかに、無機粒子や有機粒子のスラリーを含んでいてもよい。また、ポリエステル原料樹脂は、触媒由来のチタン元素を含んでいてもよい。
ポリエステル原料樹脂に含まれるポリエステルの種類は特に制限されない。
ジカルボン酸成分と、ジオール成分とを用いて合成してもよいし、市販のポリエステルを用いてもよい。
(A)ジカルボン酸成分としては、例えば、マロン酸、コハク酸、グルタル酸、アジピン酸、スベリン酸、セバシン酸、ドデカンジオン酸、ダイマー酸、エイコサンジオン酸、ピメリン酸、アゼライン酸、メチルマロン酸、エチルマロン酸等の脂肪族ジカルボン酸類、アダマンタンジカルボン酸、ノルボルネンジカルボン酸、イソソルビド、シクロヘキサンジカルボン酸、デカリンジカルボン酸、などの脂環族ジカルボン酸、テレフタル酸、イソフタル酸、フタル酸、1,4-ナフタレンジカルボン酸、1,5-ナフタレンジカルボン酸、2,6-ナフタレンジカルボン酸、1,8-ナフタレンジカルボン酸、4,4’-ジフェニルジカルボン酸、4,4’-ジフェニルエーテルジカルボン酸、5-ナトリウムスルホイソフタル酸、フェニルインダンジカルボン酸、アントラセンジカルボン酸、フェナントレンジカルボン酸、9,9’-ビス(4-カルボキシフェニル)フルオレン酸等の芳香族ジカルボン酸などのジカルボン酸もしくはそのエステル誘導体が挙げられる。
なお、「主成分」とは、ジカルボン酸成分に占める芳香族ジカルボン酸の割合が80質量%以上であることをいう。
また、(B)ジオール成分として、脂肪族ジオールの少なくとも1種が用いられる場合が好ましい。脂肪族ジオールとして、エチレングリコールを含むことができ、好ましくはエチレングリコールを主成分として含有する。
なお、主成分とは、ジオール成分に占めるエチレングリコールの割合が80質量%以上であることをいう。
カルボン酸基の数(a)が3以上のカルボン酸(多官能モノマー)の例として、3官能の芳香族カルボン酸としては、例えば、トリメシン酸、トリメリット酸、ピロメリット酸、ナフタレントリカルボン酸、アントラセントリカルボン酸等が、3官能の脂肪族カルボン酸としては、例えば、メタントリカルボン酸、エタントリカルボン酸、プロパントリカルボン酸、ブタントリカルボン酸等が、4官能の芳香族カルボン酸としては、例えば、ベンゼンテトラカルボン酸、ベンゾフェノンテトラカルボン酸、ナフタレンテトラカルボン酸、アントラセンテトラカルボン酸、ペリレンテトラカルボン酸等が、4官能の脂肪族カルボン酸として、例えば、エタンテトラカルボン酸、エチレンテトラカルボン酸、ブタンテトラカルボン酸、シクロペンタンテトラカルボン酸、シクロヘキサンテトラカルボン酸、アダマンタンテトラカルボン酸等が、5官能以上の芳香族カルボン酸として、例えば、ベンゼンペンタカルボン酸、ベンゼンヘキサカルボン酸、ナフタレンペンタカルボン酸、ナフタレンヘキサカルボン酸、ナフタレンヘプタカルボン酸、ナフタレンオクタカルボン酸、アントラセンペンタカルボン酸、アントラセンヘキサカルボン酸、アントラセンヘプタカルボン酸、アントラセンオクタカルボン酸等が、5官能以上の脂肪族カルボン酸として、例えば、エタンペンタカルボン酸、エタンヘプタカルボン酸、ブタンペンタカルボン酸、ブタンヘプタカルボン酸、シクロペンタンペンタカルボン酸、シクロヘキサンペンタカルボン酸、シクロヘキサンヘキサカルボン酸、アダマンタンペンタカルボン酸、アダマンタンヘキサカルボン酸等が挙げられる。
本発明においては、これらのエステル誘導体や酸無水物等が例として挙げられるが、これらに限定されるものではない。
これらは、1種単独で用いても、必要に応じて、複数種を併用してもよい。
これらは、1種単独で用いても、必要に応じて、複数種を併用してもよい。
また、これらの多官能モノマーのカルボキシ末端に、l-ラクチド、d-ラクチド、ヒドロキシ安息香酸などのオキシ酸類及びその誘導体、そのオキシ酸類が複数個連なったもの等を付加させたものも好適に用いられる。
これらは、1種単独で用いても、必要に応じて、複数種を併用してもよい。
Ti系触媒の例としては、テトラ-n-プロピルチタネート、テトラ-i-プロピルチタネート、テトラ-n-ブチルチタネート、テトラ-n-ブチルチタネートテトラマー、テトラ-t-ブチルチタネート、テトラシクロヘキシルチタネート、テトラフェニルチタネート、テトラベンジルチタネート等のチタンアルコキシド、チタンアルコキシドの加水分解により得られるチタン酸化物、チタンアルコキシドと珪素アルコキシドもしくはジルコニウムアルコキシドとの混合物の加水分解により得られるチタン-珪素もしくはジルコニウム複合酸化物、酢酸チタン、蓚酸チタン、蓚酸チタンカリウム、蓚酸チタンナトリウム、チタン酸カリウム、チタン酸ナトリウム、チタン酸-水酸化アルミニウム混合物、塩化チタン、塩化チタン-塩化アルミニウム混合物、チタンアセチルアセトナート、有機酸を配位子とする有機キレートチタン錯体、等が挙げられる。
ポリエステル原料樹脂に含まれるチタン元素の量が1ppm以上であると、ポリエステルの重量平均分子量(Mw)が上がり、熱分解しにくい。そのため、押出機内で異物が軽減される。ポリエステル原料樹脂に含まれるチタン元素の量が50ppm以下であると、Ti系触媒が異物となり難く、ポリエステルフィルムの延伸の際に延伸ムラが軽減される。
触媒成分であるチタン化合物として、有機酸を配位子とする有機キレートチタン錯体の少なくとも1種が用いられることが好ましい。有機酸としては、例えば、クエン酸、乳酸、トリメリット酸、リンゴ酸等を挙げることができる。中でも、クエン酸又はクエン酸塩を配位子とする有機キレート錯体が好ましい。
また、一般に、末端カルボキシ基量が多いほど耐加水分解性が悪化することが知られており、上記の添加方法によって末端カルボキシ基量が少なくなることで、耐加水分解性の向上が期待される。
このようなチタン化合物の例としては、テトラ-n-プロピルチタネート、テトラ-i-プロピルチタネート、テトラ-n-ブチルチタネート、テトラ-n-ブチルチタネートテトラマー、テトラ-t-ブチルチタネート、テトラシクロヘキシルチタネート、テトラフェニルチタネート、テトラベンジルチタネート等のチタンアルコキシド、チタンアルコキシドの加水分解により得られるチタン酸化物、チタンアルコキシドと珪素アルコキシドもしくはジルコニウムアルコキシドとの混合物の加水分解により得られるチタン-珪素もしくはジルコニウム複合酸化物、酢酸チタン、蓚酸チタン、蓚酸チタンカリウム、蓚酸チタンナトリウム、チタン酸カリウム、チタン酸ナトリウム、チタン酸-水酸化アルミニウム混合物、塩化チタン、塩化チタン-塩化アルミニウム混合物、チタンアセチルアセトナート等が挙げられる。
これにより、重合時の着色及びその後の溶融製膜時における着色が少なくなり、従来のアンチモン(Sb)触媒系のポリエステルに比べて黄色味が軽減され、また、透明性の比較的高いゲルマニウム触媒系のポリエステルに比べて遜色のない色調、透明性を持ち、しかも耐熱性に優れたポリエステルを提供できる。また、コバルト化合物や色素などの色調調整材を用いずに高い透明性を有し、黄色味の少ないポリエステルが得られる。
5価のリン化合物として、置換基として芳香環を有しない5価のリン酸エステルの少なくとも一種が用いられる。例えば、炭素数2以下の低級アルキル基を置換基として有するリン酸エステル〔(OR)3-P=O;R=炭素数1又は2のアルキル基〕が挙げられ、具体的には、リン酸トリメチル、リン酸トリエチルが特に好ましい。
ポリエステルにマグネシウム化合物を含めることにより、ポリエステルの静電印加性が向上する。この場合に着色がおきやすいが、本発明においては、着色を抑え、優れた色調、耐熱性が得られる。
マグネシウム化合物としては、例えば、酸化マグネシウム、水酸化マグネシウム、マグネシウムアルコキシド、酢酸マグネシウム、炭酸マグネシウム等のマグネシウム塩が挙げられる。中でも、エチレングリコールへの溶解性の観点から、酢酸マグネシウムが最も好ましい。
(i)Z=5×(P含有量[ppm]/P原子量)-2×(Mg含有量[ppm]/Mg原子量)-4×(Ti含有量[ppm]/Ti原子量)
(ii)0≦Z≦+5.0
これは、リン化合物はチタンに作用するのみならずマグネシウム化合物とも相互作用することから、3者のバランスを定量的に表現する指標となるものである。
式(i)は、反応可能な全リン量から、マグネシウムに作用するリン分を除き、チタンに作用可能なリンの量を表現したものである。値Zが正の場合は、チタンを阻害するリンが余剰な状況にあり、逆に負の場合はチタンを阻害するために必要なリンが不足する状況にあるといえる。反応においては、Ti、Mg、Pの各原子1個は等価ではないことから、式中の各々のモル数に価数を乗じて重み付けを施してある。
エステル化反応を一段階で行なう場合、エステル化反応温度は230~260℃が好ましく、240~250℃がより好ましい。
エステル化反応を多段階に分けて行なう場合、第一反応槽のエステル化反応の温度は230~260℃が好ましく、より好ましくは240~250℃であり、圧力は1.0~5.0kg/cm2が好ましく、より好ましくは2.0~3.0kg/cm2である。第二反応槽のエステル化反応の温度は230~260℃が好ましく、より好ましくは245~255℃であり、圧力は0.5~5.0kg/cm2、より好ましくは1.0~3.0kg/cm2である。さらに3段階以上に分けて実施する場合は、中間段階のエステル化反応の条件は、第一反応槽と最終反応槽の間の条件に設定するのが好ましい。
重縮合は、エステル化反応で生成されたエステル化反応生成物を重縮合反応させて重縮合物を生成する。重縮合反応は、1段階で行なってもよいし、多段階に分けて行なうようにしてもよい。
本発明におけるフィルム成形工程では、上記のようにして得られるポリエステル原料樹脂を溶融押出し、さらに冷却してポリエステルフィルムを成形する。
ポリエステル原料樹脂の溶融押出は、例えば、1本又は2本以上のスクリュを備えた押出機を用い、ポリエステル原料樹脂の融点以上の温度に加熱し、スクリュを回転させて溶融混練しながら行なわれる。ポリエステル原料樹脂は、加熱及びスクリュによる混練により、押出機内で溶融してメルトとなる。また、押出機内での熱分解(ポリエステルの加水分解)を抑制する観点から、押出機内を窒素置換して、ポリエステル原料樹脂の溶融押出しを行なうことが好ましい。押出機は、混練温度が低く抑えられる点で二軸押出機が好ましい。
溶融されたポリエステル原料樹脂(メルト)は、ギアポンプ、濾過器等を通して、押出ダイから押出す。押出ダイは、単に「ダイ」とも称する〔JIS B8650:2006、a)押出成形機、番号134参照〕。
このとき、メルトは、単層で押出してもよいし、多層で押出してもよい。
ポリエステル原料樹脂に末端封止剤を含める工程を設けることで、耐候性が向上する上、熱収縮を低く抑えることができる。また、ポリエステルフィルムを成形した場合において、ポリエステル末端に結合して分子鎖の末端部分が嵩高くなり、フィルム表面の微細凹凸量が増えるため、アンカー効果が発現しやすくなり、ポリエステルフィルムと該フィルム上に塗布形成される塗布層との密着が向上する。
末端封止剤の含有比率が0.1質量%以上であることで、AV低下効果による耐候性向上を達成できる上、低熱収縮性及び密着性を付与することができる。また、末端封止剤の含有比率が5質量%以下であると、密着性が向上するほか、末端封止剤の添加によるポリエステルのガラス転移温度(Tg)の低下が抑制され、これによる耐候性の低下や熱収縮の増加を抑制することができる。これは、Tgが低下した分、相対的にポリエステルの反応性が増加することで生じる加水分解性の増加を抑制したり、Tg低下で増加するポリエステル分子の運動性が増加し易くなることで生じる熱収縮が抑制されるためである。
カルボジイミド化合物、エポキシ化合物、及びオキサゾリン系化合物の例示及び好ましい態様等の詳細は、「ポリエステルフィルム」の項において既述した通りである。
キャスト処理により得られるフィルム状のポリエステル成形体の厚みは、0.1mm~5mmであることが好ましく、0.2mm~4.7mmであることがより好ましく、0.3mm~4.6mmであることがさらに好ましい。
フィルム状のポリエステル成形体の厚みを5mm以下とすることで、メルトの蓄熱による冷却遅延を回避し、また、0.1mm以上とすることで、押出しから冷却までの間に、ポリエステル中のOH基やCOOH基がポリエステル内部に拡散され、加水分解発生の要因となるOH基及びCOOH基がポリエステル表面に露出することを抑制する。
冷却手段は、上記の中でも、連続運転時のフィルム表面へのオリゴマー付着防止の観点から、冷風による冷却及びキャストドラムを用いた冷却の少なくとも一方が好ましい。さらには、押出機から押出されたメルトを冷風で冷却すると共に、メルトをキャストドラムに接触させて冷却することが特に好ましい。
本発明の縦延伸工程では、フィルム成形工程で成形されたポリエステルフィルムを長手方向に縦延伸する。
また、縦横の延伸倍率の積で表される面積延伸倍率は、延伸前のポリエステルフィルムの面積の6倍~18倍が好ましく、8倍~17.5倍であることがより好ましく、10倍~17倍であることがさらに好ましい。
ポリエステルフィルムの縦延伸時の温度(以下、「縦延伸温度」とも称する)は、ポリエステルフィルムのガラス転移温度をTgとするとき、Tg-20℃以上Tg+50℃以下であることが好ましく、より好ましくはTg-10℃以上Tg+40℃以下、さらに好ましくはTg℃以上Tg+30℃以下である。
なお、「ポリエステルフィルムの長手方向(搬送方向、MD)と直交する方向(TD)」とは、ポリエステルフィルムの長手方向(搬送方向、MD)と垂直(90°)をなす方向を意図するものであるが、機械的な誤差などから実質的に長手方向(すなわち搬送方向)に対する角度が90°とみなせる方向(例えば、MD方向に対し90°±5°の方向)が含まれる。
次に、本発明における横延伸工程について詳細に説明する。
本発明における横延伸工程は、縦延伸後のポリエステルフィルムを長手方向に直交する幅方向に横延伸する工程であるが、この横延伸を、
(a)縦延伸後のポリエステルフィルムを延伸可能な温度に予熱する予熱部、
(b)予熱されたポリエステルフィルムを長手方向と直交する幅方向に緊張を与えて横延伸する延伸部、
(c)縦延伸及び横延伸を行なった後のポリエステルフィルムを加熱し結晶化させて熱固定する熱固定部、
(d)熱固定されたポリエステルフィルムを加熱し、ポリエステルフィルムの緊張を緩和してフィルムの残留歪みを除去する熱緩和部、並びに、
(e)熱緩和後のポリエステルフィルムを冷却する冷却部
に、ポリエステルフィルムをこの順に搬送し、
(c)熱固定部および(d)熱緩和部の少なくとも一方において、ポリエステルフィルムのTD方向端部をヒーターにより選択的に輻射加熱し、ヒーターの表面とポリエステルフィルムの表面との最短距離を10mm以上300mm以下とすることにより行う。
本発明における横延伸工程では、上記構成でポリエステルフィルムが横延伸される態様であればその具体的な手段は制限されないが、上記構成をなす各工程の処理が可能な横延伸装置又は2軸延伸機を用いて行なうことが好ましい。
図3に示すように、2軸延伸機100は、1対の環状レール60a及び60bと、各環状レールに取り付けられ、レールに沿って移動可能な把持部材2a~2lとを備えている。環状レール60a及び60bは、ポリエステルフィルム200を挟んで互いに対称配置されており、把持部材2a~2lでポリエステルフィルム200を握持し、レールに沿って移動させることによりフィルム幅方向に延伸可能なようになっている。
図3は、2軸延伸機の一例を上面から示す上面図である。
把持部材2a、2b、2e、2f、2i、及び2jは、環状レール60aに沿って反時計回りに移動し、把持部材2c、2d、2g、2h、2k、及び2lは、環状レール60bに沿って時計回りに移動する。
2軸延伸機100は、延伸部20において、ポリエステルフィルム200をTD方向に延伸する横延伸を可能とするものであるが、把持部材2a~2lの移動速度を変化させることにより、ポリエステルフィルム200をMD方向にも延伸することができる。すなわち、2軸延伸機100を用いて同時2軸延伸を行なうことも可能である。
予熱部では、縦延伸工程で縦延伸した後のポリエステルフィルムを延伸可能な温度に予熱する。
図3に示すように、予熱部10においてポリエステルフィルム200を予熱する。予熱部10では、ポリエステルフィルム200を延伸する前に予め加熱し、ポリエステルフィルム200の横延伸を容易に行なえるようにする。
なお、予熱部終了点は、ポリエステルフィルム200の予熱を終了する時点、すなわち予熱部10の領域からポリエステルフィルム200が離れる位置をいう。
延伸部では、予熱部で予熱されたポリエステルフィルムを長手方向(MD方向)と直交する幅方向(TD方向)に緊張を与えて横延伸する。
図3に示すように、延伸部20では、予熱されたポリエステルフィルム200を、少なくともポリエステルフィルム200の長手方向と直交するTD方向に横延伸してポリエステルフィルム200に緊張を与える。
ポリエステルフィルム200の長手方向(搬送方向、MD)と直交する方向(TD)への延伸(横延伸)は、ポリエステルフィルム200の長手方向(搬送方向、MD)と垂直(90°)の角度の方向に延伸することを意図するものであるが、機械誤差の範囲の方向であってもよい。機械誤差の範囲とは、ポリエステルの長手方向(搬送方向、MD)と垂直とみなせる角度(90°±5°)の方向である。
また、ポリエステルフィルム200の横延伸時の膜面温度(以下、「横延伸温度」ともいう。)は、ポリエステルフィルム200のガラス転移温度をTgとするとき、Tg-10℃以上Tg+100℃以下であることが好ましく、より好ましくはTg℃以上Tg+90℃以下、さらに好ましくはTg+10℃以上Tg+80℃以下である。
横延伸工程でのポリエステルフィルム200の縦延伸は、延伸部20のみで行なってもよいし、後述する熱固定部30、熱緩和部40、又は冷却部50で行なってもよい。複数の箇所で縦延伸を行なってもよい。
熱固定部では、既に縦延伸及び横延伸が施された後のポリエステルフィルムを加熱し結晶化させて熱固定する。
熱固定とは、延伸部20においてポリエステルフィルム200に緊張を与えたまま加熱し、ポリエステルを結晶化させることをいう。
熱固定温度が160℃以上であると、ポリエステルが結晶化し易く、ポリエステル分子を伸びた状態で固定化することができ、ポリエステルフィルムの耐加水分解性を高めることができる。また、熱固定温度が240℃以下であると、ポリエステル分子同士が絡み合った部分で滑りが生じにくく、ポリエステル分子が縮みにくいため、ポリエステルフィルムの耐加水分解性の低下を抑制することができる。換言すれば、熱固定温度が160℃~240℃となるように加熱することで、ポリエステル分子の結晶を配向させて、ポリエステルフィルムの耐加水分解性を高めることができる。
熱固定温度は、上記同様の理由から、170℃~230℃の範囲が好ましく、175℃~225℃の範囲がより好ましい。
なお、最高到達膜面温度(熱固定温度)は、ポリエステルフィルム200の表面に熱電対を接触させて測定される値である。
上記の中では、最高到達膜面温度のバラツキは、上記と同様の理由から、0.5℃以上7.0℃以下がより好ましく、0.5℃以上5.0℃以下が更に好ましく、0.5℃以上4.0℃以下が特に好ましい。
このとき、加熱は、熱固定工程での加熱面における加熱直後の表面温度が、加熱面と反対側の非加熱面の表面温度に比べて0.5℃以上5.0℃以下の範囲で高くなるように行なわれることが好ましい。熱固定時の加熱面の温度がその反対側の面より高く、その表裏間の温度差が0.5~5.0℃であることで、フィルムのカールがより効果的に解消される。カールの解消効果の観点からは、加熱面とその反対側の非加熱面との間の温度差は、0.7~3.0℃の範囲がより好ましく、0.8℃以上2.0℃以下が更に好ましい。
熱緩和部40においてフィルムのTD方向端部を輻射加熱するときは、熱固定部30での輻射加熱を省略してもよいし、熱固定部30および熱緩和部40の両方において行ってもよい。
輻射加熱可能なヒーターとしては、例えば、赤外線ヒーターが挙げられ、特にセラミック製のヒーター(セラミックスヒーター)を用いることが好ましい。
輻射加熱可能なヒーターは1つのみ使用してもよいし、2つ以上を用いてもよい。
ポリエステルフィルム表面とヒーターとの最短距離が10mm未満であると、ヒーターピッチで温度ムラが生じ易く、300mmを超えるとフィルムに輻射熱が十分伝わりにくい。
ヒーター表面とフィルム表面の最短距離は、50mm以上250mm以下であることが好ましく、80mm以上200mm以下であることがより好ましい。
セラミック製ヒーターの少なくとも1つの表面温度は、300℃以上700℃以下であることが好ましい。表面温度が300℃以上であることで、フィルムに輻射熱が十分に伝わり易く、700℃以下であることで、フィルムの過加熱を抑制することができる。
セラミック製ヒーターの表面温度は、400℃以上650℃以下であることがより好ましく、450℃以上650℃以下であることが更に好ましい。
中でも、滞留時間は、上記同様の理由から、8秒以上40秒以下が好ましく、10秒以上30秒以下がより好ましい。
熱緩和部では、熱固定されたポリエステルフィルムを加熱し、ポリエステルフィルムの緊張を緩和してフィルムの残留歪みを除去する。
既述のように、本発明のポリエステルフィルムの製造方法では、熱固定部および熱緩和部の少なくとも一方において、ポリエステルフィルムのTD方向端部をヒーターにより選択的に輻射加熱する。熱緩和部でのポリエステルフィルムのTD方向端部の選択的輻射加熱は、熱固定部でのポリエステルフィルムのTD方向端部の選択的輻射加熱と同様の方法で行えばよく、加熱温度の数値範囲および好ましい態様も同様である。
図3に示す熱緩和部40において、ポリエステルフィルム200の表面の最高到達膜面温度が、熱固定部30におけるポリエステルフィルム200の最高到達膜面温度(T熱固定)よりも5℃以上低い温度となるように、ポリエステルフィルム200を加熱する態様が好ましい。
以下、熱緩和時におけるポリエステルフィルム200の表面の最高到達膜面温度を「熱緩和温度(T熱緩和)」ともいう。
T熱緩和が「T熱固定-5℃」以下であると、ポリエステルフィルムの耐加水分解性により優れる。また、T熱緩和は、寸法安定性が良好になる点で、100℃以上であることが好ましい。
更には、T熱緩和は、100℃以上で、かつT熱固定よりも15℃以上低い温度領域(100℃≦T熱緩和≦T熱固定-15℃)であることが好ましく、110℃以上で、かつT熱固定よりも25℃以上低い温度領域(110℃≦T熱緩和≦T熱固定-25℃)であることがより好ましく、120℃以上で、かつT熱固定よりも30℃以上低い温度領域(120℃≦T熱緩和≦T熱固定-30℃)であることが特に好ましい。
なお、T熱緩和は、ポリエステルフィルム200の表面に熱電対を接触させることで測定される値である。
冷却部では、熱緩和部で熱緩和した後のポリエステルフィルムを冷却する。
図3に示すように、冷却部50では、熱緩和部40を経たポリエステルフィルム200が冷却される。熱固定部30や熱緩和部40で加熱されたポリエステルフィルム200を冷却することにより、ポリエステルフィルム200の形状が固定化される。
ここで、冷却部出口とは、ポリエステル200が冷却部50から離れるときの、冷却部50の端部をいい、ポリエステルフィルム200を把持する把持部材2(図3では、把持部材2j及び2l)が、ポリエステルフィルム200を離すときの位置をいう。
これはすなわち、図3において、ポリエステル200が冷却部50から離れるときの、冷却部50の端部に位置するポリエステル200の表面(膜面)の温度を40℃~140℃とすることを意味する。
そのために、ポリエステルフィルムが把持部材から離脱するときのフィルムのTD方向端部の温度を、TD方向の中央部に比べて1℃~20℃低くすることが好ましい。
ポリエステルフィルムは、延伸装置で把持部材に把持されている状態でも、MD方向に縮み易いが、把持部材から離脱させた状態の方が、張力の緊張から解放された状態になるため、より縮む傾向にある。そのため、ポリエステルフィルムが把持部材から離脱するときのフィルム温度を、TD方向の端部よりTD方向の中央部が高くなるようにすることで、TD方向のフィルム中央部を選択的に縮ませ、TD方向のフィルム長さを、TD方向の中央部がTD方向の端部より小さくなるようにすることが好ましい。
かかる観点から、ポリエステルフィルムが把持部材から離脱するときのポリエステルフィルムの表面の温度を40~140℃の範囲で制御することが好ましい。
ポリエステルフィルムが把持部材から離脱するときのポリエステルフィルムの表面の温度は、50℃以上120℃以下であることがより好ましく、60℃以上100℃以下であることが更に好ましい。
冷却工程で冷却されたポリエステルフィルム200は、TD方向両端のクリップで握持された把持部分をカットし、ロール状に巻き取られる。
予熱部10においてポリエステルフィルム200の幅方向(TD)の両端部を、片端部につき、少なくとも2つの把持部材を用いて把持する。例えば、ポリエステルフィルム200の幅方向(TD)の片端部の一方を把持部材2a及び2bで把持し、他方を把持部材2c及び2dで把持する。次いで、把持部材2a~2dを移動させることにより、予熱部10から冷却部50までポリエステルフィルム200を搬送する。
上記のように、把持部材2a-2b間の間隔、及び把持部材2c-2d間の間隔を、MD方向上流側よりも下流側で狭めることで、ポリエステルフィルム200のMD方向の緩和を行なうことができる。したがって、MD方向の緩和を熱固定部30又は熱緩和部40で行なう場合は、把持部材2a~2dが熱固定部30又は熱緩和部40に到達したときに、把持部材2a~2dの移動速度を遅くして、ポリエステルフィルム200の搬送速度を小さくし、把持部材2a-2b間の間隔、及び把持部材2c-2d間の間隔を、予熱部における間隔よりも狭めればよい。
すなわち、横延伸工程におけるポリエステルフィルムの幅が最大になるときのポリエステルフィルムの幅W1と、冷却部からポリエステルフィルムが離れる冷却部の端部におけるポリエステルフィルムの幅W2とが、下記式(I)を満たし、かつ、予熱部におけるポリエステルフィルムの搬送速度Sp1と、冷却部の端部におけるポリエステルフィルムの搬送速度Sp2とが、下記式(II)を満たすことが好ましい。
図3においては、予熱部10における延伸前のポリエステルフィルム200の幅W0が、延伸部20によりポリエステルフィルム200がTD方向に拡幅されて幅W1となり、熱緩和部40で緊張が解かれて、ポリエステルフィルム200が冷却部50から離れるときに幅W2となっていることが示されている。図3においては、W0<W2<W1の順に幅が大きい。すなわち、W1は、予熱部10~冷却部50に至る横延伸工程におけるポリエステルフィルム200の最大の幅である。
図3に示すように、延伸部20を過ぎたポリエステルフィルム200は、その後、熱固定部30にて、緊張が与えられたまま加熱されるため、通常、幅W1は、熱固定部30におけるポリエステルフィルム200の幅(TD方向の長さ)ともいえる。
ポリエステルフィルムを把持する把持部材が、ポリエステルフィルムを離すことで、ポリエステルフィルムは、冷却部の領域から離れる。例えば、図3に示す把持部材2jがP点において、また、把持部材2lがQ点において、それぞれ、ポリエステルフィルム200を離すとき、冷却部50の端部(MD方向の端部)は、P点とQ点とを結んだ直線で表される。
また、「冷却部の前記端部におけるポリエステルフィルムの搬送速度Sp2」は、冷却部に位置し、ポリエステルフィルムを把持する把持部材(図3では、把持部材2jおよび2l)が、ポリエステルフィルムを離すときにおけるポリエステルフィルムの搬送速度である。図3を用いて換言すると、例えば、把持部材2jがP点において、また、把持部材2lがQ点において、それぞれ、ポリエステルフィルム200を離すとき、「冷却部50の前記端部におけるポリエステルフィルム200の搬送速度Sp2」は、ポリエステルフィルム200がP点とQ点とを結んだ直線を超えるときの搬送速度に相当する。さらに換言すると、「冷却部50の前記端部におけるポリエステルフィルム200の搬送速度Sp2」は、把持部材2jおよび2lが、ポリエステルフィルム200を離す直前の把持部材2jおよび2lの移動速度に相当する。
式(II)は、ポリエステルフィルム200をMD方向に緩和するときは、ポリエステルフィルム200の予熱部10における搬送速度Sp1が、冷却部50において2%~15%減速するように緩和することが好ましいことを意味する。
ΔWおよびΔSpが共に2%以上であることで、ポリエステルフィルムが式(1)~(7)を満たしやすくなり、加熱搬送時のシワおよび傷を抑制し易くなる。ΔWおよびΔSpが共に15%以下であることで、ポリエステルフィルムが延伸装置で縮みきり易く、弛みを抑制し得る。
本発明のポリエステルフィルムは、加熱搬送されてもシワ及び傷が生じにくく、フィルム上に塗布液や機能性部材シート等を貼りつけても、塗布ムラ、シート貼り合わせ時の気泡混入等の故障を生じにくい。従って、加熱搬送して加工または成形される種々の用途に用いることができる。
例えば、光学用フィルム、電気絶縁用フィルムに好適に用いることができる。
太陽電池モジュールは、一般に、太陽光の光エネルギーを電気エネルギーに変換する太陽電池素子を、太陽光が入射する透明性の基板と既述の本発明のポリエステルフィルム(太陽電池用バックシート)との間に配置して構成されている。具体的な実施態様として、電気を取り出すリード配線(不図示)で接続された発電素子(太陽電池素子)をエチレン・酢酸ビニル共重合体系(EVA系)樹脂等の封止剤で封止し、これを、ガラス等の透明基板と、本発明のポリエステルフィルム(バックシート)との間に挟んで互いに張り合わせることによって構成される態様に構成されてもよい。
(ポリエステル原料樹脂1)
以下に示すように、テレフタル酸及びエチレングリコールを直接反応させて水を留去し、エステル化した後、減圧下で重縮合を行なう直接エステル化法を用いて、連続重合装置によりポリエステル(Ti触媒系PET)を得た。
第一エステル化反応槽に、高純度テレフタル酸4.7トンとエチレングリコール1.8トンを90分かけて混合してスラリー形成させ、3800kg/hの流量で連続的に第一エステル化反応槽に供給した。更にクエン酸がTi金属に配位したクエン酸キレートチタン錯体(VERTEC AC-420、ジョンソン・マッセイ社製)のエチレングリコール溶液を連続的に供給し、反応槽内温度250℃、攪拌下、平均滞留時間約4.3時間で反応を行なった。このとき、クエン酸キレートチタン錯体は、Ti添加量が元素換算値で9ppmとなるように連続的に添加した。このとき、得られたオリゴマーの酸価は600当量/トンであった。なお、本明細書中において、「当量/t」は1トンあたりのモル当量を表す。
上記で得られたエステル化反応生成物を連続的に第一重縮合反応槽に供給し、攪拌下、反応温度270℃、反応槽内圧力20torr(2.67×10-3MPa)で、平均滞留時間約1.8時間で重縮合させた。
得られたポリマーは、IV=0.67、末端カルボキシ基の量(AV)=23当量/トン、融点=257℃、溶液ヘイズ=0.3%であった。IV及びAVの測定は、以下に示す方法により行なった。
ポリエステル原料樹脂の固有粘度(IV)は、ポリエステル原料樹脂を、1,1,2,2-テトラクロルエタン/フェノール(=2/3[質量比])混合溶媒に溶解し、該混合溶媒中の25℃での溶液粘度から求めた。
ポリエステル原料樹脂の末端COOH量(AV)は、未延伸ポリエステルフィルム1をベンジルアルコール/クロロホルム(=2/3;体積比)の混合溶液に完全溶解させ、指示薬としてフェノールレッドを用い、基準液(0.025N KOH-メタノール混合溶液)で滴定し、その適定量から算出した。
以上のようにして、ポリエステル原料樹脂1を合成した。
ポリエステル原料樹脂1をバッチ法で固相重合を実施した。すなわち、ポリエステルのペレットを容器に投入した後、真空にして撹拌しながら、150℃で予備結晶化処理し、その後190℃で30時間の固相重合反応を行なった。
以上のようにして、ポリエステル原料樹脂2を合成した。
二塩基酸として、2,6-ナフタレンジカルボン酸ジメチルエステル97.6部(100モル%)及び二価アルコールとしてエチレングリコール49.6部(100モル%)を、エステル交換槽に投入し、メタノールを留去さてエステル交換反応を進行させながら昇温させ、メタノールが理論量まで留出した時点で、反応物を重縮合槽に移して、重縮合触媒として酸化ゲルマニウム0.016部を添加した後、高真空に減圧しながら290℃まで加熱してエチレングリコールを留去した。攪拌トルクが目標値に達したところで反応を終了させ、得られたポリマーを水中に直径2.5mmのストランド状にして取り出した。得られたストランド状のポリマーをチップカッターでチップ状に切断した。得られたポリマーの固有粘度(IV)は、0.60であった。
以上のようにして、ポリエチレン-2,6-ナフタレート(PEN)のポリエステル原料樹脂3を得た。
特開2001-191406号公報の段落番号[0072](実施例1)を参考に、固有粘度(オルソクロロフェノール、35℃)0.65のPETのポリエステル原料樹脂4を用意した。
<未延伸ポリエステルフィルムの作製>
-フィルム成形工程-
ポリエステル原料樹脂1を、含水率20ppm以下に乾燥させた後、直径50mmの1軸混練押出機のホッパーに投入した。ポリエステル原料樹脂1は、300℃に溶融し、下記押出条件により、ギアポンプ、濾過器(孔径20μm)を介し、ダイから押出した。なお、ポリエステルシートの厚さが3mmとなるように、ダイのスリットの寸法を調整した。ポリエステルシートの厚さは、キャストドラムの出口に設置した自動厚み計により測定した。
未延伸ポリエステルフィルムの固有粘度(IV)は、未延伸ポリエステルフィルムを、1,1,2,2-テトラクロルエタン/フェノール(=2/3[質量比])混合溶媒に溶解し、該混合溶媒中の25℃での溶液粘度から求めた。
未延伸ポリエステルフィルムの末端COOH量(AV)は、未延伸ポリエステルフィルムをベンジルアルコール/クロロホルム(=2/3;体積比)の混合溶液に完全溶解させ、指示薬としてフェノールレッドを用い、基準液(0.025N KOH-メタノール混合溶液)で滴定し、その適定量から算出した。
得られた未延伸ポリエステルフィルム1について、以下の方法で逐次2軸延伸することによって延伸し、厚み250μm、フィルム幅(TD方向の全長)2.5mの2軸延伸ポリエステルフィルム1を作製した。
未延伸ポリエステルフィルム1を周速の異なる2対のニップロールの間に通し、下記条件で縦方向(搬送方向)に延伸した。
予熱温度 :80℃
縦延伸温度:90℃
縦延伸倍率:3.1倍
縦延伸応力:12MPa
縦延伸したポリエステルフィルム1(縦延伸ポリエステルフィルム1)に対し、図3に示す構造を有するテンター(2軸延伸機)を用いて、下記の方法、条件にて延伸した。
予熱温度を110℃とし、延伸可能なように加熱した。
予熱された縦延伸ポリエステルフィルム1を、縦延伸した方向(長手方向)と直交するフィルム幅方向(TD方向)に下記の条件にて緊張を与え、横延伸した。
<条件>
・延伸温度(横延伸温度) :125℃
・延伸倍率(横延伸倍率) :4.0倍
・延伸応力(横延伸応力):18MPa
次いで、ポリエステルフィルムの最高到達膜面温度(熱固定温度)を下記範囲に制御して加熱し、結晶化させた。
・最高到達膜面温度(熱固定温度T熱固定):225〔℃〕
ここでの熱固定温度T熱固定が、DSCのプレピーク温度〔℃〕である。
熱固定後のポリエステルフィルムを下記の温度に加熱し、フィルムの緊張を緩和した。このとき、フィルム幅方向の両端部を、熱固定と同様にキャスト面側から赤外線ヒータ(ヒータ表面温度:350℃)で輻射加熱した。
・熱緩和温度(T熱緩和):150℃
・熱緩和率:TD方向(TD熱緩和率;ΔW)=5%
MD方向(MD熱緩和率;ΔSp)=0%
次に、熱緩和後のポリエステルフィルムを、フィルムのTD方向中央部の温度が88℃、フィルムのTD方向端部の温度が80℃となる冷却温度にて冷却した。
冷却終了後、ポリエステルフィルムの両端を20cmずつトリミングした。その後、両端に幅10mmで押出し加工(ナーリング)を行なった後、張力25kg/mで巻き取った。
上記で作製した2軸延伸ポリエステルフィルムに対し、下記の測定、評価を行なった。測定と評価の結果は下記表2に示す。
2軸延伸ポリエステルフィルムのMD方向端部のうち、一端を地面から26mよりも高い所に固定し、2軸延伸ポリエステルフィルムを、無張力下で吊るした。高所に固定したMD方向の端部から他端までの距離が26m(図1におけるL=26m)となるように、フィルムを裁断し、フィルム幅(W)が表1に示される大きさ(実施例1においてはW=2.5m)で、MD方向のフィルム長(L)が26mとなるフィルムFを用意した。
上記のようにして得たフィルムFを裁断し、フィルムFの、MD方向のフィルム長(L=26m)の半分となる位置(図1の直線CL上)におけるTD方向の両端部と、TD方向中央部の試料片Mを作製した。なお、試料片Mは、TD方向30mm、MD方向120mmの大きさにした。
試料片Mに対し、MD方向で100mmの間隔となるように、2本の基準線を入れ、無張力下で150℃の加熱オーブン中に30分間放置した。この放置の後、試料片Mを室温まで冷却して、2本の基準線の間隔を測定し、この値をA(単位;mm)とした。測定されたAおよび「100×(100-A)/100」の式から算出された数値をMD熱収縮率とした。
測定されたMD熱収縮率SS1およびSS2からフィルムFのS1側およびS2側を特定し、フィルムFの全幅円弧CS1を測定した。また、フィルムFのMD方向端部の辺における中心CwuおよびCwdを結ぶ直線(図1における直線Y1)に沿って、フィルムFを裁断し、半裁フィルムを得た。
得られた半裁フィルムの湾曲の大きさであるCC1およびCC2を測定した上、半裁フィルムのCCTを算出した。
結果を表2に示す。
また、得られたSS1、SS2、SCT、CS1、CCT及びWに基づき、式(1)~(7)を構成する要素「ΔS(=SS1-SS2)」、「SAV〔=(Ss1+Ss2+SCT)/3〕」、「{SCT-(Ss1+Ss2)/2}」、「{SCT-(Ss1+Ss2)/2}/CCT/100」、「W/2000」、「W/1000」、及び「2W」を表2に示した。
得られた2軸延伸ポリエステルフィルムの厚みは、以下のようにして求めた。
2軸延伸ポリエステルフィルムに対して、接触式膜厚測定計(アンリツ社製)を用い、縦延伸した方向(長手方向)に0.5mにわたり等間隔に50点をサンプリングし、さらにフィルム幅方向(長手方向に直交する方向)にフィルム全幅にわたり等間隔(幅方向に50等分)に50点をサンプリングした後、これらの100点の厚みを測定した。これら100点の平均の厚みを求め、ポリエステルフィルムの厚みとした。
フィルムFの、図1の直線CL上となる位置において、TD方向の一方の端部から他方の端部の全幅に対して、等間隔で11点をサンプリングし、試料片M2を得た。各位置の試料片M2について、DSCプレピーク温度(Tpp)を測定した。測定された複数のTpp値の最大値と最小値の差(ΔTpp)を、DSCプレピーク温度のムラとした。
なお、DSCプレピーク温度は、株式会社島津製作所製のDSC-60に、サンプリングした試料片M2のフィルムを所定量(2~10mg)セットし、10℃/minの昇温速度で、300℃まで昇温して測定した。ポリエステル(PET)の融解ピーク手前に現れる吸熱ピークのピーク温度をDSCプレピーク温度(Tpp)として読み取った。
得られた2軸延伸ポリエステルフィルムについて、温度170℃、MD方向の搬送速度1.0m/sで40秒加熱搬送したときのフィルム表面上のシワの有無および傷の有無を、目視により観察し、下記の評価基準に従って評価した。
AA:シワの発生はほとんどみられなかった。
A:シワの発生が僅かにみられたが、フィルム面は良好であった。
B:シワの発生がみられたが、実用上は支障のない程度であった。
C:シワの発生が顕著にみられた。
AA:傷の発生はほとんどみられなかった。
A:傷の発生が僅かにみられたが、フィルム面は良好であった。
B:傷の発生がみられたが、実用上は支障のない程度であった。
C:傷の発生が顕著にみられた。
実施例1において、表1に示す条件を変更したほかは、いずれも同様にして、実施例2~実施例15、及び、比較例1~比較例5の2軸延伸ポリエステルフィルムを得た。
また、得られた2軸延伸ポリエステルフィルムについて、実施例1の2軸延伸ポリエステルフィルムと同様の方法で、2軸延伸ポリエステルフィルムの物性評価、並びに、シワ及び傷の有無についての評価を行った。結果を表2に示す。
特開2001-191406号公報の段落番号[0072]~[0073]を参照して、特開2001-191406号公報の実施例1に準拠した2軸延伸ポリエステルフィルムを得た。
得られた2軸延伸ポリエステルフィルムについて、実施例1の2軸延伸ポリエステルフィルムと同様の方法で、2軸延伸ポリエステルフィルムの物性評価、並びに、シワ及び傷の有無についての評価を行った。結果を表2に示す。
10・・・・・・予熱部
20・・・・・・延伸部
30・・・・・・熱固定部
40・・・・・・熱緩和部
50・・・・・・冷却部
60・・・・・・環状レール
100・・・・・2軸延伸機
200・・・・・ポリエステルフィルム
Claims (13)
- 下記式(1)~(4)を満たすポリエステルフィルム。
W/1000<〔(Ss1-Ss2)/CS1/100〕<2W ・・・(1)
0<(Ss1-Ss2)<0.5 ・・・(2)
-1<(Ss1+Ss2+SCT)/3<3 ・・・(3)
0<Cs1<0.2 ・・・(4)
〔式(1)~(4)中、
Ss1は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表し、
Ss2は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が小さい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表す。
SCTは、ポリエステルフィルム幅方向の中央部における、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率 [%]を表す。
CS1は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、湾曲の大きさの最大値[m]を表す。
Wは、ポリエステルフィルム幅[m]を表す。〕 - さらに下記式(5)~(7)を満たす請求項1に記載のポリエステルフィルム。
W/2000<〔{SCT-(Ss1+Ss2)/2}/CCT/100〕<W ・・・(5)
-0.5<{SCT-(Ss1+Ss2)/2}<0.5 ・・・(6)
-0.2<CCT<0.2 ・・・(7)
〔式(5)~(7)中、
Ss1は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が大きい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表し、
Ss2は、ポリエステルフィルム幅方向の端部のうち、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率が小さい側の端部における、前記ポリエステルフィルム幅方向と直交する方向の熱収縮率[%]を表す。
SCTは、ポリエステルフィルム幅方向の中央部における、前記ポリエステルフィルム幅方向と直交する方向の150℃、30分での熱収縮率[%]を表す。
CCTは、ポリエステルフィルム長手方向の両端部におけるポリエステルフィルム幅方向の中央を結んだ直線に沿ってポリエステルフィルムを裁断して得られる2つの半裁ポリエステルフィルムの幅方向の端部における湾曲の大きさの最大値を足して2で割った値[m]を表す。
Wは、フィルム幅[m]を表す。〕 - 前記フィルム幅Wが、0.3m以上8m以下である請求項1または請求項2に記載のポリエステルフィルム。
- 前記フィルム幅方向における、示差走査熱量測定(DSC)で測定されるプレピーク温度のムラが0.5℃以上10℃以下である請求項1~請求項3のいずれか1項に記載のポリエステルフィルム。
- ポリエステルフィルムの固有粘度が、0.55dL/g以上0.90dL/g以下である請求項1~請求項4のいずれか1項に記載のポリエステルフィルム。
- ポリエステルフィルムの末端カルボキシ基の量が、5eq/トン以上35eq/トン以下である請求項1~請求項5のいずれか1項に記載のポリエステルフィルム。
- 3官能以上の多官能モノマーに由来の構成単位の含有比率が、ポリエステルフィルム中のポリエステルの全構成単位に対して、0.005モル%以上2.5モル%以下である請求項1~請求項6のいずれか1項に記載のポリエステルフィルム。
- ポリエステル原料樹脂をシート状に溶融押出し、キャスティングドラム上で冷却してポリエステルフィルムを成形するフィルム成形工程と、
成形された前記ポリエステルフィルムを長手方向に縦延伸する縦延伸工程と、
前記縦延伸後のポリエステルフィルムを延伸可能な温度に予熱する予熱部、予熱された前記ポリエステルフィルムを前記長手方向と直交する幅方向に緊張を与えて横延伸する延伸部、前記縦延伸及び前記横延伸を行なった後の前記ポリエステルフィルムを加熱し結晶化させて熱固定する熱固定部、前記熱固定されたポリエステルフィルムを加熱し、ポリエステルフィルムの緊張を緩和してフィルムの残留歪みを除去する熱緩和部、並びに、熱緩和後のポリエステルフィルムを冷却する冷却部に、前記ポリエステルフィルムをこの順に搬送して、前記縦延伸後のポリエステルフィルムを前記長手方向に直交する幅方向に横延伸する横延伸工程と、を含み
前記熱固定部および前記熱緩和部の少なくとも一方において、前記幅方向のポリエステルフィルムの端部を、ヒーターにより選択的に輻射加熱し、前記ヒーターの表面と前記ポリエステルフィルムの表面との最短距離を10mm以上300mm以下とするポリエステルフィルムの製造方法。 - 前記輻射加熱は、少なくとも1つのセラミック製ヒーターで行う請求項8に記載のポリエステルフィルムの製造方法。
- 前記セラミック製ヒーターの少なくとも1つの表面温度は、300℃以上700℃以下である請求項9に記載のポリエステル樹脂フィルムの製造方法。
- 前記セラミック製ヒーターの少なくとも1つは、格子状の金属カバーで覆われている請求項9または請求項10に記載のポリエステルフィルムの製造方法。
- 前記横延伸工程は、前記予熱部、前記延伸部、前記熱固定部、前記熱緩和部、及び前記冷却部を備え、前記予熱部において前記ポリエステルフィルムの幅方向の両端部を、片端部につき、少なくとも2つの把持部材を用いて把持して、前記予熱部から前記冷却部まで前記ポリエステルフィルムを搬送する2軸延伸装置を用い、
前記ポリエステルフィルムが前記把持部材から離脱するときの前記ポリエステルフィルムの表面の温度を、40℃~140℃とする請求項8~請求項11のいずれか1項に記載のポリエステルフィルムの製造方法。 - 前記ポリエステルフィルムが前記把持部材から離脱するときの前記ポリエステルフィルムの表面の温度は、前記ポリエステルフィルムの幅方向の中央部における表面温度に対して、前記把持部材から前記幅方向に200mm離れた位置における前記ポリエステルフィルムの表面温度を1℃~20℃低くする請求項12に記載のポリエステルフィルムの製造方法。
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