JP2002018947A - Biaxially oriented polyester film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film having a low heat shrinkage factor in all directions, satisfying high transparency and take-up or feed workability at the same time and always enabling plate making not generating color shift when used in a photographic photosensitive material using a thermal developing system. SOLUTION: A biaxially oriented film, of which the temperature coefficient of expansion and humidity coefficient of expansion simultaneously satisfy formulae; 1×10-6<=αt<=25×10-6 (1) and 5×10-6<=αh<=25×10-6 (2) [wherein, αt is the temperature coefficient of expansion (cm/cm/ deg.C) of the film before thermal slackening treatment and αh is the humidity coefficient of expansion (cm/cm/% RH) of the film before thermal slackening treatment], is subjected to thermal slackening treatment once or more to manufacture the biaxially oriented polyester film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film having a small heat shrinkage and a method for producing the same. The present invention relates to a biaxially oriented polyester film having high transparency, excellent slipperiness, and excellent rollability, and a method for producing the same.

[0002]

2. Description of the Related Art A polyester film represented by a polyethylene terephthalate film has been widely used as a base film of a photographic photosensitive film.
In recent years, in the development of a photosensitive film, a thermal development method in which the development time is short and the operation is simple has been often used instead of the conventional wet development. In this thermal development method, the photosensitive film is often thermally developed at 80 to 150 ° C., and the photosensitive material receives a higher temperature thermal history than the conventional wet development method.

For this reason, the dimensional change due to heat shrinkage or the like of the photosensitive material is larger than that in conventional wet development, which poses a practical problem. To solve this problem, reduce the thermal contraction rate of the photosensitive material at the thermal development temperature to reduce the deviation of each film when red, green, blue, and black films are overlaid and developed and made. Accordingly, various methods for obtaining an image without color shift have been proposed. For example, JP-A-10-10677
Japanese Patent Application Laid-Open Publication No. HEI 9-264926 proposes a photographic light-sensitive material in which the thermal dimensional change at 120 ° C. for 30 seconds is 0.04% or less in both the longitudinal direction and the width direction. However, even with the use of the low heat shrink film as described above, there is a problem that the overlay accuracy sometimes becomes insufficient, and it is desired to solve the problem.

[0004]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art and provides a biaxially oriented polyester for a photographic light-sensitive material which always has a good overlay accuracy, and is excellent in transparency, slipperiness and winding property. It is an object to provide a film and a method for producing the film.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have conducted a thermal relaxation treatment on a film having a temperature expansion coefficient and a humidity expansion coefficient in a specific range. The biaxially oriented polyester film for photographic light-sensitive materials, which has not only the longitudinal and width directions of the film but also the heat shrinkage in the oblique direction crossing them at 45 ° within a specific range, and always has a good overlay accuracy. Have been found, and the present invention has been completed.

That is, the present invention provides a biaxially oriented polyester film obtained by subjecting a biaxially oriented film having a temperature expansion coefficient and a humidity expansion coefficient that satisfy the following formulas (1) and (2) to at least one heat relaxation treatment. It is a manufacturing method of.

[0007]

1 × 10 ⁻⁶ ≦ αt ≦ 25 × 10 ⁻⁶ (1) 5 × 10 ⁻⁶ ≦ αh ≦ 25 × 10 ⁻⁶ (2) where αt is the film before the heat relaxation treatment. The coefficient of thermal expansion (cm / cm / ° C.) and αh are the coefficients of humidity expansion (cm / cm /% RH) of the film before the thermal relaxation treatment.

Further, the present invention provides a biaxially oriented polyester film obtained by the above method for producing a biaxially oriented polyester film, wherein the heat shrinkage when heat-treated at 120 ° C. for 20 seconds simultaneously satisfies the following formulas (3) to (7). It is an oriented polyester film.

[0009]

(1) 0.001 ≦ S _MD ≦ 0.1 (3) −0.1 ≦ S _TD ≦ 0.1 (4) −0.05 ≦ S ₄₅ ≦ 0.05 (5) −0 .05 ≦ S ₁₃₅ ≦ 0.05 (6) | S ₄₅ −S ₁₃₅ | ≦ 0.05 (7) where S _MD is the heat shrinkage (%) in the film longitudinal direction, and S _TD.
Is the heat shrinkage (%) in the transverse direction of the film, and S ₄₅ and S ₁₃₅ are the heat shrinkage (%) in the 45 ° and 135 ° directions when the film is 0 ° in the transverse direction and 90 ° in the longitudinal direction. is there.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. (Polyester) The polyester constituting the polyester film in the present invention is a thermoplastic polyester containing a dicarboxylic acid component and a glycol component as main components, for example, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, Polyester composed of an aromatic dicarboxylic acid component such as 4'-diphenyldicarboxylic acid and a glycol component such as ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol Are preferable, and especially polyethylene terephthalate and polyethylene-2,6-
Naphthalate is preferred. Further, a copolymerized polyester such as the above components may be used.

When the polyester is polyethylene terephthalate, the lower limit of the intrinsic viscosity thereof (measured at 35 ° C. in an orthochlorophenol solution: unit dl / g) is preferably 0.52, more preferably 0.57. preferable. When the intrinsic viscosity is 0.52 or more, especially 0.57 or more, the tear strength of the polyester film is improved, which is preferable. On the other hand, the upper limit of the intrinsic viscosity is preferably 1.50, particularly preferably 1.00. When the intrinsic viscosity is 1.50 or less, particularly 1.00 or less, the productivity in the raw material production step and the film formation step becomes good. Further, a homopolymer of which repeating structural units are substantially only ethylene terephthalate may be used, and 10% or less, preferably 5% or less of the number of repeating structural units is a polyethylene terephthalate copolymer having another component. There may be. Also, a mixture of polyethylene terephthalate and another polyester may be used.

When the polyester is polyethylene-2,6-naphthalate, the lower limit of the intrinsic viscosity is preferably 0.40, particularly preferably 0.50.
It is preferable that the intrinsic viscosity is 0.40 or more, particularly 0.50 or more, since the film cutting or the like is reduced in the step of forming the polyester film. On the other hand, the upper limit of the intrinsic viscosity is preferably 0.90, and particularly preferably 0.80. When the intrinsic viscosity is 0.90 or less, particularly 0.80 or less, the productivity in the raw material production step and the film formation step becomes good. Further, the homopolymer of which repeating structural unit is substantially only ethylene-2,6-naphthalate may be used, and 10% or less, preferably 5% or less of the number of repeating structural units is polyethylene, which is another component. It may be a -2,6-naphthalate copolymer. Also, a mixture of polyethylene-2,6-naphthalate and another polyester may be used.

The above-mentioned polyethylene terephthalate or polyethylene-2,6-naphthalate is not limited by its production method. For example, in the case of polyethylene terephthalate, terephthalic acid and ethylene glycol are subjected to an esterification reaction and then obtained. A method of subjecting the reaction product to a polycondensation reaction to a desired degree of polymerization to obtain polyethylene terephthalate, or a transesterification reaction between dimethyl terephthalate and ethylene glycol, and then subjecting the resulting reaction product to the desired polymerization. (Hereinafter sometimes abbreviated as "melt polymerization") can be used. The polyethylene terephthalate or copolymerized polyethylene terephthalate obtained by the above method (melt polymerization) may be polymerized in a solid state as needed (hereinafter, may be abbreviated as “solid state polymerization”). Further, a polymer having a high degree of polymerization can be obtained.

Polyethylene-2,6-naphthalate can also be obtained by the above-mentioned melt polymerization. Among them, ester-forming derivatives of the above-mentioned acid components, for example, 2,6-naphthalate
Those produced by subjecting a lower alkyl ester of naphthalenedicarboxylic acid to a transesterification reaction with ethylene glycol by a known method and then performing polycondensation can be preferably used.

In the above transesterification reaction, 2,6
Reacting a lower alkyl ester of naphthalenedicarboxylic acid or a lower alkyl ester of terephthalic acid with ethylene glycol in the presence of a transesterification catalyst.
As the transesterification catalyst, a manganese compound can be preferably used. Examples of the manganese compound include oxides, chlorides, carbonates, and carboxylate salts. Of these, acetate is preferably used.

The catalyst used in the polycondensation reaction includes:
Antimony compounds (Sb compounds), titanium compounds (Ti
Compounds) and germanium compounds (Ge compounds). Antimony trioxide is particularly preferred as the antimony compound. Further, as the germanium compound, it is preferable to use germanium dioxide, and among them, it is preferable to use a so-called amorphous germanium having no crystalline form because particles precipitated in the polymer can be reduced.

In the above transesterification reaction, it is preferable to add a phosphorus compound when the reaction is substantially completed to deactivate the transesterification catalyst. As the phosphorus compound, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and orthophosphoric acid can be used. Of these, trimethyl phosphate is preferred.

If necessary, additives such as antioxidants, heat stabilizers, viscosity modifiers, plasticizers, hue improvers, lubricants and nucleating agents can be added to the polyester.

(Additional Fine Particles) It is preferable to add lubricant fine particles to the polyester of the present invention to improve the workability (slidability) of the polyester film. As the lubricant fine particles, any one can be selected. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, barium sulfate and the like. Also,
Examples of the organic lubricant include silicone resin particles and crosslinked polystyrene particles. Among these, porous silica particles, which are aggregated particles of primary particles, are particularly preferable because voids are hardly generated around the particles when the film is stretched, and the transparency of the film can be improved.

The average particle size of the primary particles constituting the porous silica particles is preferably in the range of 0.001 to 0.1 μm. If the average particle size of the primary particles is less than 0.001 μm, ultrafine particles are generated by crushing in the slurry stage, and these may form aggregates, which may be a cause of deterioration in transparency. On the other hand, when the average particle size of the primary particles exceeds 0.1 μm, the porosity of the particles is lost, and as a result, the feature of less generation of voids may be lost.

[0021] The porous silica particles or other lubricant particles are usually used at any time during the reaction for producing the polyester, for example, during the transesterification reaction or polycondensation reaction in the case of transesterification, or by the direct polymerization method. Can be added to the reaction system at any time (preferably as a slurry in glycol). In particular,
It is preferable to add porous silica particles to the reaction system at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

(Polyester Film) The polyester film of the present invention is obtained by preparing a biaxially oriented film having a coefficient of temperature expansion and a coefficient of humidity expansion satisfying the above expressions (1) and (2) simultaneously before the thermal relaxation treatment. The film obtained by the above-described heat relaxation treatment can be obtained. The obtained heat-relaxed film is biaxial so that the heat shrinkage at the time of treatment at 120 ° C. for 20 seconds simultaneously satisfies the above formulas (3) to (7). It is an oriented polyester film. When a polyester film is used as a base film of a photographic photosensitive film and development is performed by a heat development method, the development temperature is generally around 120 ° C., and the dimensions of the film are stable at this temperature. It is important.

The polyester film of the present invention has a coefficient of thermal expansion of 1 × 10 ⁻⁶ cm / cm / ° C. or more and 25 × 10 ⁻⁶ c.
A biaxially oriented film of m / cm / ° C or less can be obtained by one or more thermal relaxation treatments. When the thermal expansion coefficient exceeds 25 × 10 ^-6 cm / cm / ° C, the thermal relaxation treatment is performed. The flatness of the film sometimes deteriorates, and the heat shrinkage at 120 ° C. for 20 seconds after the heat relaxation treatment exceeds a desired range, which is not preferable. In addition, 1 × 10 ⁻⁶ cm / cm /
It is difficult to realize the temperature lower than 0 ° C., and if it is forcibly realized, the flatness becomes poor such as wrinkles.

Further, the biaxially oriented polyester film of the present invention has a coefficient of humidity expansion before heat relaxation treatment of 5 × 10 ⁻⁶ cm.
Can be obtained by subjecting a biaxially oriented film of not less than / cm /% RH to 25 × 10 ⁻⁶ cm / cm /% RH to thermal relaxation treatment at least once, but the coefficient of humidity expansion is out of the above range. Then, the flatness of the film is deteriorated during the heat relaxation treatment, and the heat shrinkage at 120 ° C. for 20 seconds after the heat relaxation treatment exceeds a desired range. The biaxially oriented polyester film of the present invention has a longitudinal heat shrinkage of not less than 0.001% and not more than 0.1% when heat-treated at 120 ° C. for 20 seconds.
These are: If the heat shrinkage in the vertical direction exceeds 0.1%, color misregistration and image distortion may occur during plate making. Further, it is difficult to achieve a thermal shrinkage ratio of less than 0.001% in the vertical direction, and if it is forcibly implemented, the flatness will deteriorate such as wrinkles.

The biaxially oriented polyester film of the present invention has a heat shrinkage in the horizontal direction of -0.1% or more and 0.1% or less when heat-treated at 120 ° C. for 20 seconds. If the heat shrinkage in the horizontal (width) direction is out of this range, problems such as color misregistration and image distortion occur during plate making.

The biaxially oriented polyester film of the present invention has a heat shrinkage of -0.05 when subjected to heat treatment at 120 ° C. for 20 seconds in 45 ° and 135 ° perpendicular to it when the transverse direction is 0 °. % Or more and 0.05% or less. Negative means growth. If the heat shrinkage in the 45 ° direction and in the 135 ° direction perpendicular thereto (hereinafter sometimes referred to as the “oblique direction”) is out of this range, color misregistration and image distortion occur during plate making, which is a problem.

In the biaxially oriented polyester film of the present invention, the absolute value of the difference in heat shrinkage in the 45 ° direction and in the 135 ° direction perpendicular thereto is 0.05% or less. If this value exceeds 0.05%, color misregistration and image distortion occur during plate making.

The biaxially oriented polyester film of the present invention must satisfy these requirements at the same time, and must not be unsatisfactory even for one.

The heat shrinkage in the diagonal direction seems to fall within the control range naturally if the heat shrinkage in the vertical direction and the horizontal direction is controlled, but there are cases where this is not the case. The portion where the heat shrinkage in the oblique direction is larger than the heat shrinkage in the vertical and horizontal directions is a portion near both ends in the width direction when the biaxially oriented polyester film is manufactured. In this part, the orientation axis is 4
The direction is around 5 ° (the opposite end is around 135 °), and the degree of molecular orientation is remarkably deviated in the orientation axis direction. Therefore, the heat shrinkage in the direction of the orientation axis is large, and the heat shrinkage in the direction orthogonal to the direction is small, but rather, it is often elongated. Therefore, there are cases where the heat shrinkage in the oblique direction is large even if the heat shrinkage in the vertical and horizontal directions is small. When such a film having a large heat shrinkage in the oblique direction is used as a support for a photographic light-sensitive material, there arises a problem that the overlay accuracy is reduced when the film is developed by a heat development method.

The orientation anisotropy of the portion near both ends in the width direction is a phenomenon peculiar to the method of successive stretching in the longitudinal and transverse directions and the tension heat setting employed in producing most biaxially oriented polyester films. However, even if the conditions can be alleviated only by setting the conditions, it cannot be avoided. Also, a low heat shrinkage within the scope of the present invention is difficult to obtain without any post-treatment.

(Film Forming Method) In the present invention, the biaxially oriented polyester film used for the heat relaxation treatment can be produced by a conventionally known method. For example, it can be manufactured by a method in which polyester containing lubricant fine particles is dried, melt-extruded, biaxially stretched, and heat-fixed. In this method, for example, a molten polyester extruded from a T-die is quenched and solidified on a cooling drum to form an unstretched film, and the unstretched film is longitudinally stretched 2.5 to 4 times at 70 ° C. to 130 ° C. Laterally stretched 3 to 6 times at 80 to 130 ° C,
The polyester film can be obtained by heat setting at 40 ° C. In addition, if necessary, for example, a water-dispersible coating is applied to one or both surfaces of the film after longitudinal stretching, for example, after longitudinal stretching, so that the film has an adhesive property or lubricity of 0.0%.
A film having a thickness of 1 to 0.1 μm can also be formed.

Although the conditions for forming the film are not specified, it is desirable to select conditions that reduce the anisotropy at both ends of the film, minimize the heat shrinkage as much as possible, and have good flatness. It is difficult to satisfy all of them, but relatively desirable conditions are as follows.

The longitudinal stretching ratio is preferably 2.5 to 4.0 times. The lower limit of the longitudinal stretching ratio is more preferably 3.0 times, and the upper limit is more preferably 3.6 times. When the longitudinal stretching ratio is less than 2.5 times, unevenness in thickness may be deteriorated. Further, when the ratio exceeds 4.0 times, the orientation in the longitudinal direction becomes strong, the residual stress in the longitudinal direction becomes strong, and when the film is softened by heating in the heat treatment step, both ends are grasped by the grasping tool. Therefore, the films do not move with each other,
The central part moves to the upstream side, and the anisotropy of both ends becomes strong.
Although this phenomenon cannot be prevented by longitudinal and horizontal sequential biaxial stretching, it can be somewhat reduced by making the film relatively horizontal.

The transverse stretching ratio is preferably 3 to 6 times. The lower limit of the transverse stretching ratio is more preferably 3.6, and the upper limit is more preferably 5.0 times. If the transverse stretching ratio is less than 3.0 times, thickness unevenness is poor. If it is 6.0 times or more, frequent cutting occurs during stretching.

The heat treatment temperature is Tg + 100 ° C. or higher and Tg + 1
40 ° C. or lower is preferred. If the heat treatment temperature is lower than Tg + 100 ° C., the dimensional change rate is large, exceeding the range of the above formulas (1) and (2), and at the same time, the oligomer is easily precipitated and whitened, and wrinkles are generated during the heat relaxation treatment. As a result, the flatness deteriorates. When the heat treatment temperature exceeds Tg + 140 ° C,
The anisotropy at both ends increases, the film tends to be opaque, and thickness unevenness increases.

It is effective to reduce the heat shrinkage (particularly in the horizontal direction) by narrowing the guide rail of the gripper in the heat treatment step and performing the relaxation treatment. The width relaxation rate is preferably 0.5 to 5%. If it is less than 0.5%, the effect is small, and if it is 5% or more, the flatness deteriorates. Usually, the gripper has a film temperature of 10
The film is released when the temperature becomes 0 ° C. or less,
Releasing at 120 ° C. and lowering the pulling tension is effective in lowering the heat shrinkage in the longitudinal direction. If this temperature exceeds 150 ° C., the flatness deteriorates, and if it is lower than 120 ° C., the effect is small. Release from the gripper is performed, for example, by using a knife near the gripper.
A blade such as a razor may be inserted and separated.

(Heat Relaxation Treatment) The biaxially oriented film of the present invention is formed with care as described above, and is further added once to a film having a heat shrinkage in the range of the above formulas (1) and (2). The above can be obtained by performing the thermal relaxation treatment. Although the method of the thermal relaxation treatment is not specified, a suspension relaxation heat treatment method is particularly preferable. In the suspension-type relaxation heat treatment method, after the tension on the sending side of the film to be processed is cut off by a nip roller, the film is dripped downward by its own weight via a roller installed above while preheating to ensure flatness, and on the way. Then, the film is turned in a substantially horizontal direction with a lower roller, and the film is cooled and the winding tension is cut off with a nip roller while maintaining the flatness. The tension between the upper and lower rollers can be achieved by installing a tension pickup in the processing section, adjusting the motor of each nip roller on the feeding side and the winding side.

The tension during the relaxation heat treatment is preferably from 1 kPa to 500 kPa. The lower limit of the tension during the relaxation heat treatment is more preferably 10 kPa,
Particularly preferably, it is 0 kPa. Further, the upper limit of the tension during the relaxation heat treatment is more preferably 450 kPa, and particularly preferably 400 kPa. If the tension at the time of the relaxation heat treatment is less than the above lower limit, the flatness is deteriorated, and the film tends to meander during the film conveyance, which is not preferable because the productivity is deteriorated. If the tension during the relaxation heat treatment exceeds the above upper limit, the dimensional change is likely to increase, which is not preferable.

The hanging distance during the heat relaxation treatment is 1 m or more and 10
m or less is preferable. If the hanging distance is less than 1 m, the heating range is short, so that the processing speed is slow and the productivity is poor, which is not preferable. On the other hand, if it exceeds 10 m, the film tends to meander during transportation, and the flatness is also poor, which is not preferable.

The number of times of the thermal relaxation treatment is required at least once in order to obtain a desired dimensional stability, and it is more preferable to carry out the heat relaxation at least twice. This number of times can be performed any number of times until the desired dimensional stability is ensured. As a method for performing the heat relaxation treatment two or more times, during the heat relaxation treatment step, two or more zones for performing the heat relaxation treatment in a suspended state are continuously provided, or the film that has been subjected to the heat relaxation treatment once is again used. In the same step, the heat treatment is performed by heat-relaxing the film so that the film is turned upside down. The reason why the film is turned upside down at this time is to prevent unevenness in dimensional stability in the width direction during the heat relaxation treatment process.

In the heat relaxation treatment, there is no particular limitation as long as there are measures to overcome these. Although there is no restriction on the heating method, infrared heating is preferable because it can be heated immediately.

The temperature of the thermal relaxation treatment is Tg or more and Tg + 14.
0 ° C. or lower is preferred. The lower limit of the temperature of the thermal relaxation treatment is Tg
The temperature is more preferably + 10 ° C, and particularly preferably Tg + 20 ° C. Further, the upper limit of the temperature of the thermal relaxation treatment is more preferably Tg + 120 ° C., and Tg + 1
Particularly preferred is 10 ° C. If the temperature of the thermal relaxation treatment is lower than Tg, it is difficult to reduce the dimensional change at 120 ° C. On the other hand, when the temperature exceeds Tg + 140 ° C., the flatness tends to be deteriorated, and the oligomer may precipitate and the film may become white. This whitening depends on the pressure history. For example, if the hanging belt is transported over the film portion of the film roll, the portion in contact with the belt is likely to whiten even at Tg + 140 ° C. or lower, so care must be taken. The film temperature is desirably measured using a non-contact infrared thermometer (for example, a Burns radiation thermometer). According to this suspension-type relaxation heat treatment method, the dimensional change rate can be kept within the range of the present invention even for films near both ends during film formation.

There are other methods for preparing the biaxially oriented polyester film of the present invention, but the method can be adopted if the method has more defects and can avoid the defects. The following is an example.

(1) When the Obliquely Oriented Portion can be Diverted to Other Uses Only the central portion of the film forming width is treated by an arbitrary heat relaxation treatment method. Although it depends on the characteristics of the material to be processed, 50 to 80% can be used.

(2) In the case of using a horizontal stretching machine having a gripper and having a device capable of making the width at the entrance almost equal to the width at the exit, the treatment temperature is lowered in the heat treatment step described in the film forming method. The film is formed with the movement amount of the central part being about half of the usual amount. The amount of movement is determined by drawing a straight line in the horizontal (width) direction with ink rope or the like on the film before entering the horizontal stretching machine, and calculating the amount by which the straight line after exiting the horizontal stretching machine is bent in an arc shape. This film is heat-treated at 200 to 245 ° C. by a transverse stretching machine having a gripper and passed through a device capable of making an entrance width and an exit width almost equal. At this time,
It is important to perform processing so that the running direction is reversed during the film formation and during the heat treatment, and conditions are set so that the arc-shaped line returns to a substantially straight line. By this treatment, the anisotropy at both ends is corrected, and the heat shrinkage in the oblique direction can be prevented from increasing.

The biaxially oriented polyester film of the present invention can be produced by subjecting this film to a thermal relaxation treatment by any method. However, a reduction in productivity and a decrease in yield due to disposal of the gripper are inevitable, and there are disadvantages. This is a method that can be adopted only when equipment can be handled.

(3) A floating traveling thermal relaxation air stream is alternately blown from below and above onto the film.
The film is moved in the horizontal direction while floating in a sinusoidal shape, and is heated and thermally relaxed during this time. The coating and drying of the coating has the advantage that the roller does not contact the film, but it is unexpectedly difficult to maintain a low tension for thermal relaxation, and the low thermal shrinkage of the present invention may not be realized.

(4) Thermal relaxation between rollers This is a method in which the film is reduced in tension between two rollers having a nip roller, and heated at that portion to perform thermal relaxation. The film is easy to meander, and stable running is difficult. Also,
Pressing with a nip roller prior to heating is not preferred because it tends to cause whitening as described above. It can be used after solving these.

(Film Thickness) The thickness of the polyester film of the present invention is preferably 50 μm or more and 200 μm or less. If the thickness exceeds 200 μm, the transparency is lowered and it is uneconomical. Thickness 50
If it is less than μm, the strength, particularly the stiffness, is insufficient, and the plate making workability is reduced. In addition, during suspension-type relaxation heat treatment, running tends to be unstable due to the influence of airflow.

(Haze Value) The haze value of the biaxially oriented polyester film of the present invention is preferably 4% or less, and
0.3% is more preferred. If the haze value exceeds 4%, the sharpness of the image is poor, which is not preferable. Further, it is difficult to make the content less than 0.3%.

(Surface Roughness Ra) The biaxially oriented polyester film of the present invention preferably has a surface roughness Ra of 3 to 15 nm. If it is less than 3 nm, the coefficient of friction becomes excessive, workability is poor, and scratches are likely to occur. 1
If it exceeds 5 nm, the haze value increases and the sharpness of the image decreases.

(Coefficient of friction) The coefficient of friction of the biaxially oriented polyester film of the present invention is preferably 0.5 or less.
The following are more preferred. The lower limit of the coefficient of friction is preferably closer to 0, but is particularly preferably 0.2. If the coefficient of friction exceeds 0.5, there is a problem in transportability, workability and winding property, which is not preferable. Although it is preferable that the coefficient of friction is small, the surface roughness must be increased in order to make the coefficient of friction smaller than 0.2, and as a result, the haze value increases.

(Curved amount) When the film is slit into small widths and left standing without applying tension so that there is no wrinkle on the plane, the film taken from near the center in the width direction at the time of film formation is almost straight. And the film nearer to both ends is more curved.
When the deviation from a straight line per 1 m of length is the amount of curvature,
The amount of curvature of the film is 10 mm or less per m, especially 5 m
m or less. The amount of bending is 5 mm, especially 1
If it exceeds 0 mm, the film may meander when a photosensitive agent for a photographic film is applied, resulting in a defective product.

[0054]

EXAMPLES The present invention will be further described below with reference to examples. Incidentally, various physical properties and properties in the present invention,
It is measured and defined as follows.

(1) Average particle size of particles CP-50 type centrifuge particle size analyzer (Centrifug, manufactured by Shimadzu Corporation)
al Particle Analyzer). The particle size corresponding to 50 mass% was read from the integrated curve of the particles of each particle size and the remaining amount calculated based on the obtained Liaoshin sedimentation curve, and this value was defined as the above average particle size (“particle size”). Measuring Technology ”Published by Nikkan Kogyo Shimbun, 197
5 years, see pages 242-247).

(2) Average particle size when the inert particles are agglomerated particles When the inert fine particles as the added lubricant are secondary particles resulting from the aggregation of the primary particles, the average particle size is determined by the method described in (1). Since the particle size obtained by diameter measurement may be smaller than the actual average particle size, the following method was employed.

The film containing the particles was cut into ultrathin sections having a thickness of 100 nm in the cross-sectional direction, and the particles were observed at a magnification of about 10,000 times using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL Ltd.). Particles (secondary particles) were observed. Using this photograph, the diameter equivalent to the circular area of each particle was measured for 1000 particles using an image analyzer or the like, and the number averaged particle diameter was defined as the average secondary particle diameter. The identification of the particle type can be performed using SEM-XMA, quantitative analysis of a metal element by ICP, or the like. The average primary particle size was measured in accordance with the average secondary particle size measurement method, except that the transmission electron microscope was used at a magnification of 100,000 to 1,000,000 times.

(3) Thermal expansion coefficient before thermal relaxation treatment A film sample was cut into a length of 15 mm, set on TM-3000 manufactured by Vacuum Riko Co., Ltd., and pretreated at 60 ° C. for 30 minutes in a nitrogen atmosphere. Thereafter, the temperature was lowered to room temperature, and then the temperature was raised from 25 ° C. to 70 ° C. at a rate of 2 ° C./min. The sample length at each temperature was measured, and the thermal expansion coefficient (αt) was calculated from the following equation.

[0059]

Αt = {[(L ₂ −L ₁ ) × 10 ⁶ ] / (L ₁ × {T)} where L ₁ ; sample length (mm) at 45 ° C. L ₂ ; Sample length (mm) ΔT; 10 (= 55-45 ° C.).

(4) Humidity expansion coefficient before thermal relaxation treatment A sample of the film was cut into a length of 15 mm and a width of 5 mm, set on TM-3000, manufactured by Vacuum Riko Co., Ltd., and placed in a nitrogen atmosphere at a humidity of 20% RH. , And humidity 80% R
H was kept constant, the length of the sample at that time was measured, and the humidity expansion coefficient (αh) was calculated from the following equation.

[0061]

Αh = {[(L ₄ −L ₃ ) × 10 ⁶ ] / (L ₃ × {H)} where L ₃ ; sample length at 20% RH (mm) L ₄ ; humidity 80 Sample length at% RH (mm) ΔH; 60 (= 80-20% RH).

(5) Heat-relaxation treatment Heat-shrinkage rate A film whose exact length has been measured beforehand is placed in a thermostatic chamber set at 120 ° C. in a non-tension state, held for 20 seconds, taken out, and taken out at room temperature. After returning, read the dimensional change. From the length R ₀ before the heat treatment and the length R after the heat treatment, the heat shrinkage is determined by the following equation.

[0063]

The heat shrinkage ratio = (R ₀ −R) × 100 / R ₀ (%) The sample was defined as 0 °, 45 °, 90 °, 1
Collect from each direction at 35 °. In addition, it was sampled from a portion near the end in the width direction during film formation.

(6) Film Thickness The thickness of the film was determined by measuring 100 points with an external micrometer and calculating the average value.

(7) Haze value According to the method of JIS K-6714, the total haze value per film is measured with a commercially available haze meter. Assuming that the number of measurements is n = 5, the average value is used as the measurement value.

(8) Surface Roughness (Center Line Surface Roughness Ra) Both the front and back sides of the film were measured with a surface roughness meter (Surfcom 111A, Tokyo Seimitsu Co., Ltd.), and the average value was calculated to obtain the surface roughness.

(9) Coefficient of friction According to ASTM D 1894-63, a dynamic friction coefficient (μd) was measured with a glass plate as a thread plate and a load of 1 kg using a slippery measuring device (manufactured by Toyo Tester).

(10) Amount of Curve A film having a length of 20 m is sampled from a film roll and adhered to a flat floor without distortion. Next, the starting point and the end point of one end in the film width direction are connected by a straight line, and the amount of deviation in the film width direction at the longitudinal middle point (10 m point) with respect to this straight line is determined. I do. This value is converted into a value per 1 m of the film length, and is defined as a bending amount.

(11) Dimensional deviation after thermal development A simulation test using a biaxially oriented polyester film was performed without actually processing the photosensitive material. If the properties of the biaxially oriented polyester film of the present invention are maintained without applying excessive tension during processing of the photosensitive material, good results similar to those in this test can be expected in actual thermal development.

A sample of 60 (length) × 55 cm is taken from the center and both ends in the width direction during film formation. This was conditioned at 25 ° C. and 60% RH for 24 hrs, and the four corners were marked with substitutes for register marks (register marks) at intervals of 50 cm in the upper, lower, left and right directions. % Humidified for 24 hours under 3% RH
The film pairs were overlaid, and the maximum deviation of the register mark was measured with a magnifying glass. If this shift exceeds 60 μm, the color shift is perceived by the naked eye during plate-making, so it was made unacceptable. ：: The maximum deviation of the register mark is 60 μm or less at both the center and both ends. Δ: The maximum deviation of the register mark is 60 μm or less at either the center or both ends. X: The maximum deviation of the register mark exceeds 60 μm at both the center and both ends.

(12) Sharpness of Image An image forming layer was provided on the film, an image was formed by thermal development, and the number of n was set to 10. The sharpness and contrast of the image were visually judged. ◎: very good (within the object of the present invention and particularly preferable) ：: good (within the object of the present invention and preferable) Δ: slightly poor (not reaching the object of the present invention) ×: bad (the present invention) Does not reach the purpose of

(13) Secondary transition point (Tg) The sample (10 mg) was heated at a heating rate of 20 ° C./min using a DSC (V4.OB2000 model manufactured by DuPont) to reduce the glass transition temperature. Measure.

(14) Comprehensive Evaluation The results were comprehensively evaluated for the amount of curvature of the film, the dimensional deviation after thermal development, the sharpness of the image, and the coefficient of friction. ：: good (all of the above results are good) △: slightly poor (some of the above results have some unsatisfactory parts) ×: bad (one of the above results has a fatal defect)

[Examples 1 to 4] An average of dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and aggregated particles as a lubricant. Porous silica particles having a particle size of 1.7 μm are added so as to be 0.007% by weight with respect to the polymer and polymerized by a conventional method, and intrinsic viscosity (orthochlorophenol, 35 ° C.)
0.65 polyethylene terephthalate (Tg: 78)
° C). Polyethylene terephthalate has a melting temperature of 2
Melted at 95 ° C., and filtered through a nonwoven fabric filter having an average opening of 24 μm consisting of a stainless fine wire having a wire diameter of 13 μm,
It was extruded from a T-die and extruded on a rotary cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain an unstretched film. The unstretched film thus obtained is heated at 75 ° C.
Preheat to 15mm between low speed roller and high speed roller
The film was heated by one infrared heater having a surface temperature of 800 ° C. from above and stretched 3.1 times, quenched and then supplied to a stenter, and stretched 3.9 times horizontally at 120 ° C.
The obtained biaxially oriented film was heat-set at a temperature of 235 ° C. for 5 seconds, during which the width was relaxed by 1.5%. I got Table 1 shows the thermal expansion coefficient and humidity expansion coefficient of this film before thermal relaxation treatment.
Shown in Also, the film is suspended using a thermal relaxation device,
Relaxation heat treatment was performed under the conditions shown in Table 1 to obtain a final product. Table 1 shows the results of evaluating the properties of this film.

Example 5 Manganese acetate tetrahydrate was added to a mixture of dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol, and a transesterification reaction was carried out while gradually raising the temperature from 150 ° C. to 240 ° C. During the reaction, when the reaction temperature reached 170 ° C., antimony trioxide was added,
Further, the porous silica particles having an average particle size of 1.7 μm 0.0
7 parts by weight were added, followed by transesterification, and after the transesterification was completed, trimethyl phosphate was added. Thereafter, the reaction product was transferred to a polymerization reactor,
To a polyethylene-2,6-naphthalate (PEN, Tg) having an intrinsic viscosity of 0.62 measured in o-chlorophenol at 25 ° C. under a high vacuum of 0.2 mmHg or less. : 121 ° C) to obtain a polymer.

The PEN polymer was mixed with an extruder for 300
℃, melt extruded from T-die into sheet, 30 ℃
Cooling and solidifying by adhering to the water-cooled casting drum of
An unstretched sheet was obtained. This unstretched film is 3.0 mm in the longitudinal direction (machine axis direction) by roll stretching combined with infrared heating.
It was stretched twice. Thereafter, the film is successively biaxially stretched 4.0 times at 140 ° C. in the transverse direction (width direction) and subjected to a 1.2% relaxation treatment in the width direction while being heat-treated at 240 ° C. for 5 seconds, until the film temperature reaches about 130 ° C. When lowered, it was separated from the gripping tool to obtain a biaxially oriented polyester film. The temperature expansion coefficient and humidity expansion coefficient of this film before thermal relaxation treatment are shown.
Shown in 1. Further, the film was subjected to a relaxation heat treatment under the conditions shown in Table 1 using a suspension type thermal relaxation device to obtain a final product.
Table 1 shows the results of evaluating the properties of this film.

Example 6 A biaxially oriented polyester film was prepared in the same manner as in Example 1 except that the floating thermal relaxation was carried out under the conditions shown in Table 1 in place of the suspension thermal relaxation. I got Table 1 shows the results of evaluating the properties of this film.

Example 7 In Example 1, kaolin clay having an average particle size of 0.9 μm was added in place of the porous silica so as to be 0.25% by weight with respect to the polymer.
Except for this point, a biaxially oriented polyester film was obtained in the same manner as in Example 1. Table 1 shows the results of evaluating the properties of this film.

COMPARATIVE EXAMPLES 1-2 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterified catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and aggregated particles as a lubricant were used. Porous silica particles having a particle size of 1.7 μm are added so as to be 0.007% by weight with respect to the polymer and polymerized by a conventional method, and intrinsic viscosity (orthochlorophenol, 35 ° C.)
0.65 polyethylene terephthalate (Tg: 78)
° C). Polyethylene terephthalate has a melting temperature of 2
Melted at 95 ° C., and filtered through a nonwoven fabric filter having an average opening of 24 μm consisting of a stainless fine wire having a wire diameter of 13 μm,
It was extruded from a T-die and extruded on a rotary cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain an unstretched film. The unstretched film thus obtained is heated at 75 ° C.
Preheat to 15mm between low speed roller and high speed roller
It was heated by one infrared heater having a surface temperature of 800 ° C. from above and stretched 3.6 times, quenched, and subsequently supplied to a stenter, and stretched 3.7 times transversely at 120 ° C.
The obtained biaxially oriented film was heat-set at 235 ° C. for 5 seconds to obtain a biaxially oriented polyester film. Table 1 shows the thermal expansion coefficient and the humidity expansion coefficient of the film before the thermal relaxation treatment. Further, the film was subjected to a relaxation heat treatment under the conditions shown in Table 1 using a suspension type thermal relaxation device to obtain a final product.
Table 1 shows the results of evaluating the properties of this film.

[0080]

[Table 1]

As is clear from the results shown in Table 1, the biaxially oriented polyester film of the present invention has transparency, slipperiness,
It has excellent winding properties and is excellent as a support for photographic light-sensitive materials.

[0082]

According to the present invention, low heat shrinkage in all directions, high transparency and workability of winding and transporting are simultaneously satisfied. The present invention provides a biaxially oriented polyester film capable of performing plate-free printing. Further, it can be widely used for applications requiring high dimensional stability, such as tracing films, microfilms, and OHP sheets, and has a high industrial value.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08L 67:00 C08L 67:00 F term (Reference) 2H023 AA00 FA01 FA12 FA13 4F071 AA45 AF27 AF27Y AF28Y AF30 AF32Y AF53 AF54Y AH12 AH19 BA01 BB06 BB08 BC01 BC10 BC12 BC16 4F210 AA24 AA26 AH73 AM32 AP11 AR12 QA02 QC06 QD36 QD44 QG18 QL02 QL17 QM03 QM11 QM13 QW07 QW11 QW15

Claims (14)

[Claims] 1. A method for producing a biaxially oriented polyester film, comprising subjecting a biaxially oriented film having a coefficient of thermal expansion and a coefficient of humidity expansion satisfying the following formulas (1) and (2) to one or more thermal relaxation treatments. . 1 × 10 ⁻⁶ ≦ αt ≦ 25 × 10 ⁻⁶ (1) 5 × 10 ⁻⁶ ≦ αh ≦ 25 × 10 ⁻⁶ (2) (where αt is a film before thermal relaxation treatment) Is the coefficient of thermal expansion (cm / cm / ° C.), and αh is the coefficient of humidity expansion (cm / cm /% RH) of the film before the thermal relaxation treatment. 2. The method for producing a biaxially oriented polyester film according to claim 1, wherein the film is subjected to a thermal relaxation treatment in a suspended state. 3. The heat shrinkage obtained by the heat treatment at 120 ° C. for 20 seconds obtained by the method for producing a biaxially oriented polyester film according to claim 1 simultaneously satisfies the following expressions (3) to (7). Biaxially oriented polyester film. (2) 0.001 ≦ S _MD ≦ 0.1 (3) −0.1 ≦ S _TD ≦ 0.1 (4) −0.05 ≦ S ₄₅ ≦ 0.05 (5) −0 .05 ≦ S ₁₃₅ ≦ 0.05 (6) | S ₄₅ −S ₁₃₅ | ≦ 0.05 (7) (where S _MD is the heat shrinkage (%) in the film longitudinal direction, S
_TD is the thermal shrinkage (%) in the horizontal direction of the film, and S ₄₅ and S ₁₃₅ are the thermal shrinkage (%) in the 45 ° and 135 ° directions when the horizontal and vertical directions are 0 ° and 90 °, respectively. It is. ) 4. The method for producing a biaxially oriented polyester film according to claim 2, wherein the transport tension during the thermal relaxation treatment in the suspended state is in the range of 1 kPa to 500 kPa. 5. The method for producing a biaxially oriented polyester film according to claim 2, wherein the temperature during the heat relaxation treatment in the suspended state is not lower than Tg of the polyester and not higher than Tg + 140 ° C. 6. The biaxially oriented polyester film according to claim 3, wherein the polyester constituting the film is polyethylene terephthalate. 7. The biaxially oriented polyester film according to claim 3, wherein the polyester constituting the film is polyethylene-2,6-naphthalate. 8. A film having a thickness of 50 μm or more and 200 μm or more.
m. The biaxially oriented polyester film according to claim 3, wherein m is equal to or less than m. 9. The biaxially oriented polyester film according to claim 3, wherein the haze value of the film is 4.0% or less. 10. The biaxially oriented polyester film according to claim 3, wherein at least one surface of the film has a surface roughness Ra of 3 μm or more and 15 nm or less. 11. The biaxially oriented polyester film according to claim 3, wherein the coefficient of friction of at least one surface of the film is 0.5 or less. 12. A film having a curve length of 1 m.
The biaxially oriented polyester film according to claim 3, which has a thickness of 0 mm or more and 5 mm or less. 13. The biaxially oriented polyester film according to claim 3, which is used as a support for a photographic light-sensitive material. 14. The biaxially oriented polyester film according to claim 13, wherein the developing system of the photographic light-sensitive material is a thermal developing system.