Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2001-02-27
2002-08-27
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S480000, C428S690000, C428S690000, C428S910000, C528S308000, C528S308100, C264S288400, C264S289600, C264S290200, C430S523000, C430S531000, C430S533000
Reexamination Certificate
active
06440532
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a biaxially oriented polyester film having small thermal shrinkage, production method thereof and use thereof as a base film for photosensitive materials. More specifically, it relates to a biaxially oriented polyester film which has high superposition accuracy and excellent transparency, slipperiness and winding properties when it is used as a base film for a photosensitive material of a thermal development system, production method thereof and use thereof as the above base film.
DESCRIPTION OF THE PRIOR ART
Polyester films typified by a polyethylene terephthalate film have been widely used as a base film for photosensitive films. In recent years, a thermal development system characterized by a short development time and easy operation has been frequently used to develop photosensitive films in place of the conventional wet development system. In this thermal development system in which a photosensitive film is developed at a temperature of 80 to 150° C. in most cases, a photosensitive material receives higher heat history than the conventional wet development system. Therefore, a dimensional change caused by thermal shrinkage and the like of the photosensitive material is larger than in the conventional wet development system, causing a problem to be solved for practical application.
To cope with this problem, there is proposed a method for obtaining an image free from a color drift by reducing the dislocation of each film when red, green, blue and black films are placed one upon another to be developed so as to make a plate by reducing the thermal shrinkage factor of a photosensitive material at a thermal development temperature. JP-A 10-10677 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes a photosensitive material which has a thermal dimensional change in longitudinal and transverse directions of 0.04% or less when it is heated at 120° C. for 30 seconds. However, even when the above low thermal shrink film is used, sometimes there arises such a problem as insufficient superposition accuracy. A solution to this problem is awaited.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a biaxially oriented polyester film which has solved the above problem of the prior art and always has high superposition accuracy and excellent transparency, slipperiness and winding properties.
It is another object of the present invention to provide a method of producing the biaxially oriented polyester film of the present invention.
It is still another object of the present invention to provide use of the biaxially oriented polyester film as a base film for photosensitive materials.
Other objects and advantages of the present invention will become apparent from the following description.
Firstly, according to the present invention, the above objects and advantages of the present invention are attained by a biaxially oriented polyester film whose thermal shrinkage factors satisfy relationships represented by the following expressions (1) to (5) at the same time when it is heated at 120° C. for 20 seconds:
0.001
≦S
MD
≦0.1 (1)
−0.1
≦S
TD
≦0.1 (2)
−0.05
≦S
45
≦0.05 (3)
−0.05
≦S
135
0.05 (4)
|S
45
−S
135
|≦0.05 (5)
wherein S
MD
is a thermal shrinkage factor (%) in machine direction of the film under the above conditions, S
TD
is a thermal shrinkage factor (%) in a direction perpendicular to that direction under the above conditions, and S
45
and S
135
are thermal shrinkage factors (%) in a 45° direction and a direction perpendicular to the 45° direction under the above conditions when the mechanical axial direction of the film is 0° and a direction perpendicular to that direction is 90°, respectively.
Secondly, according to the present invention, the above objects and advantages of the present invention are attained by a method of producing a biaxially oriented polyester film which satisfies all the above expressions (1) to (5) by thermally relaxing at least once a biaxially oriented polyester film whose thermal shrinkage factors do not satisfy at least one of the above expressions when the film is heated at 120° C. for 20 seconds while it is suspended.
Thirdly, according to the present invention, the above objects and advantages of the present invention are attained by a base film for photosensitive materials which comprises the biaxially oriented polyester film of the present invention.
The present invention will be described in detail hereinafter.
Polyester
The polyester forming the polyester film of the present invention is a thermoplastic polyester which comprises a dicarboxylic acid component and a glycol component as the main ingredients. For example, the polyester is preferably a homopolyester or copolyester which comprises an aromatic dicarboxylic acid component such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid or 4,4′-diphenyldicarboxylic acid and a glycol component such as ethylene glycol, 1,4-butanediol, 1,4-cyclohexane dimethanol or 1,6-hexanediol. Out of these, polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferred.
When the polyester is polyethylene terephthalate, the lower limit of intrinsic viscosity (measured at 35° C. in an orthochlorophenol solution, unit: dl/g) is preferably 0.52, particularly preferably 0.57. When the intrinsic viscosity is 0.52 or more, particularly 0.57 or more, the tear strength of the polyester film becomes high. The upper limit of intrinsic viscosity is preferably 1.50, particularly preferably 1.00. When the intrinsic viscosity is 1.50 or less, particularly 1.00 or less, productivity in the raw material production step and productivity in the film formation step become high. The polyester may be a homopolymer which substantially consists of ethylene terephthalate as the only recurring structural unit or a polyethylene terephthalate copolymer which comprises other components in a total amount of 10% or less, preferably 5% or less based on the total number of all the recurring structural units. Further, the polyester may be a mixture of polyethylene terephthalate and another polyester.
When the polyester is polyethylene-2,6-naphthalene dicarboxylate, the lower limit of intrinsic viscosity is preferably 0.40, particularly preferably 0.50. When the intrinsic viscosity is 0.40 or more, particularly 0.50 or more, the breakage of the film rarely occurs in the step of forming a polyester film. The upper limit of intrinsic viscosity is preferably 0.90, particularly preferably 0.80. When the intrinsic viscosity is 0.90 or less, particularly 0.80 or less, productivity in the raw material production step and productivity in the film formation step become high. The polyester may be a homopolymer which substantially consists of ethylene-2,6-naphthalene dicarboxylate as the only recurring structural unit or a polyethylene-2,6-naphthalene dicarboxylate copolymer which comprises other components in a total amount of 10% or less, preferably 5% or less based on the total number of all the recurring structural units. Further, the polyester may be a mixture of polyethylene-2,6-naphthalene dicarboxylate and another polyester.
The polyester used in the present invention is not limited by its production method. Preferred examples of the production method are one in which an esterification reaction is carried out between terephthalic acid or 2,6-naphthalenedicarboxylic acid and ethylene glycol and then the polycondensation reaction of the obtained reaction product is carried out until the targeted degree of polymerization is achieved to obtain a polyester such as polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate (direct polymerization method) and one in which an ester exchange reaction is carried out between an ester forming derivative of terephthalic acid or 2,6-naphthalenedicarboxylic acid (for example, a lower alky
Fukuda Masayuki
Ishikawa Toshifumi
Ogawa Tatsuya
Taguchi Susumu
Chen Vivian
Teijin Limited
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