JPH02163155A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain an optically homogeneous polyester film, excellent in transparency, smoothness and slipperiness and suitable as optical covering films, etc., by blending 1,4-polycyclohexylenedimethylene terephthalate with one or more of PET, PBT, etc., having specific physical properties. CONSTITUTION:A polyester film, obtained by blending (A) 1,4- polycyclohexylenedimethylene terephthalate with (B) 0.1-20wt.%, preferably 0.5-4wt.% one or more selected from the group consisting of polyethylene terephthalate(PET), polybutylene terephthalate(PBT) and polyethylene-2,6- naphthalate having a higher melt crystallization temperature and lower intrinsic viscosity than those of the component (A) and <5% haze value, forming the resultant blend into a film and having >=90 deg.C glass transition point, >=90% light transmittance, <=10mmu center line average height and <=0.3 sliding friction coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optically homogeneous polyester film having excellent transparency, smoothness, and slipperiness.

[Prior Art] Conventionally, l,4-polycyclohexylene dimethylene terephthalate (hereinafter referred to as PCT)-based polyester films have been produced by adding inorganic or organic additives to PCT, or by adding polyethylene terephthalate (hereinafter referred to as PET) to PCT. Are there any known products obtained by mixing polyesters such as
The properties of the resulting polyester film will vary depending on the additives and other ingredients that are mixed.

As a polyester film made of a mixture of PCT and PET, for example, JP-A No. 6O-2034G discloses a polyester film with low humidity expansion coefficient and high tear strength, and JP-A No. 63-27235 discloses a polyester film with heat sealability and shrinkage. Polyester film with excellent properties, JP-A-62-95:
14! JP-A-58-21430 is a polyester film with excellent printability that has been further corona-treated, and JP-A-57-1059618 is a heat-shrinkable polyester film. A highly shrinkable polyester film with excellent sealing properties is disclosed.

[Disadvantages of the Prior Art] However, these conventional polyester films are not only optically non-uniform, but also do not simultaneously satisfy the three properties of transparency, surface smoothness, and ease of slipping.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to provide an optically homogeneous polyester film that is transparent, has excellent smoothness and easy sliding properties on its surface.

[Means for Solving the Problem] As a result of intensive research, the present inventors found that 1,4-polycyclohexylene dimethylene terephthalate has at least one of polyethylene terephthalate, polyethylene terephthalate, and bocethylene naphthalate, which have specific physical properties. The present inventors discovered that a polyester film with superior transparency, smoothness, and slipperiness compared to conventional ones can be obtained by adding the above-mentioned polyester film.

That is, the present invention provides 1.4-polycyclohexylene dimethylene terephthalate, which has a higher melt crystallization temperature Tsc, a lower intrinsic viscosity IV, and a solution haze value than the 1.4-polycyclohexylene dimethylene terephthalate. less than 5% of at least one selected from the group consisting of polyethylene terephthalate, bobblylene terephthalate and polyethylene-2,5-naphthalate at 0.1
% to 20% by weight.

[Effects of the Invention] According to the present invention, an optically homogeneous polyester film with excellent transparency, smoothness, and ease of slipping is provided, and its characteristics are particularly suitable for optical cover films such as polarizing cover films and optical cards. , cover film for optical tape, and even optical recording perspective! ! It is useful as an electrical insulating material used in panels, capacitors, etc.

[Detailed Description of the Invention] PCT constituting the polyester film of Present No. 9.11 is a polyester mainly containing 1,4-cyclohexydimetatool as a glycol component and mainly terephthalic acid as a dicarboxylic acid component. It is preferable that 90 mol % or more of the glycol component is 1,4-polycyclohexane dimetatool, and it is preferable that 80 mol % or more of the acid component is terephthalic acid. However, if it does not adversely affect the effects of the present invention, a small amount, preferably 10 mol % or less, of other acid components may be included. As an acid component, terephthalic acid/isophthalic acid = 80/20~
A molar ratio of 96/4 can also be preferably used.

In the present invention, the ratio of PET polybutylene terephthalate and polyethylene-2,6-naphthalate (hereinafter sometimes referred to as "added PET, etc." for simplicity) to be mixed with PCT is 0.1 to the double yang of the entire film. ~20
% by weight, preferably 0.5-4% by weight. If this content exceeds 20%, not only the surface smoothness will be lost but also the transparency will deteriorate.
If the weight is less than 1, it is not only difficult to obtain slipperiness, but also it is difficult to obtain transparency.

Furthermore, additives such as stabilizers, matting agents, lubricants, and antistatic agents T, which are generally added to polyester films, can be added to PCT or added PET, etc., as necessary. However, as the content of the additive added to the added PErl increases, the solution haze increases, so the content of the additive is limited to less than 5% of the solution haze of the added PET, etc.

In the present invention, the melt crystallization temperature of added PET etc. is 1311
: The temperature c is higher than the melt crystallization temperature of PCT, which is the main component of the film. Crystal melting temperature Tmc of added PET, etc.
By using a substance having a crystal melting temperature higher than that of PCT, the added PET or the like acts as a crystal nucleating agent for PCT, thereby improving transparency and, moreover, improving smoothness and slipperiness.

In addition, in the present invention, the intrinsic viscosity of added PET, etc.
It is smaller than the limiting viscosity of CT. By employing added PET or the like having an intrinsic viscosity smaller than that of PCT, it is possible to achieve the effect of improving transparency and smoothness by uniformly and finely dispersing it in PCT.

Furthermore, in order to enhance the transparency of the polyester film of the present invention, the solution haze value of the added PET'$ is less than 5%. When the solution haze value is 5% or more, the transparency and smoothness of the film are impaired.

In order to obtain ease and smoothness of the Bonnisdell film of the present invention, the glass transition point of the film is preferably 90°C or higher, more preferably 95°C or higher.

When the glass transition point is 90'C or higher, the film is less likely to wrinkle and has particularly excellent flatness.

In addition, for the smoothness of the film, the center line average roughness Ra
is preferably 10 times or less, more preferably 8 times or less.

Also, due to the slipperiness of the film, the coefficient of friction is 0.3.
It is preferably less than or equal to 0.25, more preferably 0.25
It is as follows.

Further, from the viewpoint of transparency, it is preferable that the light transmittance is 90% or more, and more preferably 92% or more.

PCT used in the present invention can be manufactured by conventionally known polyester manufacturing methods. For example,
It can be produced by direct esterification of terephthalic acid and 1,4-cyclohexane dimetatool or by transesterification of dimethyl terephthalate and 1,4-cyclohexanedimetatool. The PCT produced in this manner may be copolymerized with a small proportion of the third component as described above.

PET and the like added to PCT in the present invention can also be manufactured by conventionally widely known methods. That is, PET is produced by, for example, i
It can be produced by polymerization or transesterification and polycondensation. Further, polybutylene terephthalate can be produced, for example, by polycondensation of terephthalic acid or its lower alkyl ester and 1,4-butanediol, or by transesterification reaction by heating and polycondensation, according to a well-known method. Further, boethylene 2,6-naphthalate can be produced, for example, by the synthesis or transesterification and polycondensation of 2,6-naphthalene dicarboxylic acid or its lower alkyl ester and ethylene glycol according to well-known methods. The crystal melting temperature Tmc of these added PETs can be adjusted by adjusting the polymer viscosity IV, nucleating agent, molecular structure, etc., and the intrinsic viscosity can be adjusted by changing the polymerization time and additives. Additionally, solution haze can be adjusted by adjusting the amount of additives.

The polyester film of the present invention can be produced by uniformly mixing PCT, added PET, etc., and optionally additives according to a conventional manufacturing method, melt extruding using a melt extruder such as an extruder, cooling, and stretching. It can be made +12 by. A device for uniform mixing is not particularly necessary, but it is preferable to use an extruder that applies high shearing force, or to use a mixer (static/dynamic) attached to the tip of the extruder. The drying conditions for the polymer chips are not particularly limited, and are usually +70° C. for about 3 hours or appropriate. The extrusion temperature is not particularly limited or is usually 28
The temperature is about 0°C to 330°C, preferably about 285°C to 300°C.

Casting is preferably carried out by electrostatic application, and the temperature of the casting ink drum is not particularly limited, but is usually 5°C to 60°C, preferably 15°C to 30°C. Further, stretching after cooling may or may not be performed, and from the viewpoint of improving mechanical properties, it is preferable to perform stretching in one direction or in two directions. When stretching is carried out, the temperature is usually 70°C to 150°C, preferably 80°C.
Under a temperature of 110℃ to 110℃, usually 2.5 to 6.0 times
The stretching ratio is 2 times. After stretching, it is preferable to heat set the film, which is usually between 150°C and 28°C.
The reaction is carried out at a temperature of 0°C, preferably 170°C to 240°C, for usually 1 to 20 seconds, preferably 5 seconds to 15 seconds. Note that the glass transition point of the film can be adjusted by changing the structure of the polymer and the degree of molecular orientation.

In addition, the center line average roughness Ra of the film depends on the type of additive,
The sliding friction coefficient can be adjusted by the type and amount of the additive, and the stretching conditions, and the light transmittance can be adjusted by the type and amount of the additive, as well as the stretching and cooling conditions.

The transparent, smooth, and smooth polyester film of the present invention can be used for optical applications such as polarizing films and optical recording cover films, electrical insulation materials for capacitors, other metal vapor deposition applications, and graphic applications. .

Next, the film characteristics specified in the present invention and the method for evaluating the effects of the present invention adopted in the following examples will be explained.

(1) Melt crystallization temperature T■C Sample 51Ig was set in a scanning calorimeter (DSC), and N
Tac is the crystallization exothermic peak temperature that occurs when the sample is heated at a rate of 20° C./min under two air currents, kept at a temperature 40° C. higher than the crystal melting temperature of the sample for 5 minutes, and then cooled at a rate of 10° C./min.

(2) Intrinsic viscosity 1v Measured according to ASTM DI601.

(3) Add 13 grams of solution haze to puree (phenol/tetrachloroethane = 3
/2) Add to 20 cc and dissolve at Ion℃ for 160 minutes, then cool in tap water for 15 minutes and in a constant temperature bath at 25℃ for 20 minutes.Next, the sample was placed in a cell with a light transmission thickness of 20 ITS and exposed to light for 30 seconds. The total scattered light intensity at JIS-5
Measured using 714.

(4) Glass transition point Tg Set sample 5B in a scanning calorimeter (DSC) and use the endothermic peak that appears when the temperature is raised at 20°C/min under a N2 stream or the point at which it deviates from the baseline. .

(5) Light transmittance according to JIS-6714, Hitachi spectrophotometer 3
Measured values at a wavelength of 550 nm using a Model 23 are used.

(6) Center line average roughness Ra JIS B12O3-1976 (cutoff 0.25
llu ).

(7) Sliding friction coefficient body.

ASTM D 1894-6].

(8) Optical homogeneity A film with a thickness of 25 μl is observed with the naked eye using transmitted light.

r4Constant NoﾾPem○゛Things without any optical fluctuations Detect the film using RJA and M detect whether there is any white flickering.

Judgment, (semi- I can't see the O4 white flickering thing at all.

×: I can see something flickering.

[Example] Hereinafter, the present invention will be explained in more detail based on Examples.

However, the present invention is not limited to the following examples.

Example 1 90 mol% of terephthalic acid and 10 mol% of isophthalic acid were used as acid components, 100 mol% of 1,4-cyclohexane dimetatool was used as a glycol component, and titanium oxide was used as a catalyst at a ratio of 0.05 mol% to the acid component. Add mole%, put in an autoclave, heat under stirring to transesterify,
Subsequently, polycondensation was performed to obtain PCT. The melt crystallization temperature and intrinsic viscosity of the obtained PCT are shown in the table below.

PET was produced by transesterification and polycondensation of dimethyl terephthalate and ethylene glycol according to a conventional method. The melt crystallization temperature TlIC1 intrinsic viscosity and solution haze value of the obtained PET are shown in the table below.

797 parts by weight of the obtained PC and 73 parts by weight of PE were uniformly mixed and dried. This polyester was melt-extruded at 290°C and cooled on a quenching drum kept at 40°C.
An unstretched film of 0#L* was obtained.

This unstretched film was preheated by contacting it with a metal roll adjusted to 90'C, and then heated using an infrared heater (surface temperature 1000C).
) was stretched in the longitudinal direction by 3.6 times between rolls with a difference in circumferential speed. Next, the longitudinally stretched film was stretched 11 times using a tenter.
It was laterally stretched 3.7 times at 5°C. The obtained biaxially stretched film was held at both ends with clips, heat-set at 200° C., and then wound up to obtain a film having a thickness of 75 mm.

For comparison, PET/
A film was produced in the same manner as in the case of "I only".

Melt crystallization temperature Tsc ('C), intrinsic viscosity Iv (dt/g), sliding friction coefficient PL, center line roughness Ra (kLm), optical homogeneity and optically heterogeneous particles of the obtained film The presence or absence of was measured or evaluated using the method described above. The results are shown in the table below.

As is clear from the table below, the obtained film has a small sliding friction coefficient and a small center line average roughness, and is excellent in slipperiness and smoothness. Furthermore, it had excellent optical homogeneity and no optically foreign particles were present.

几] Rainbow Example 2 A film was produced in the same manner as in Example 1, except that 0.21% of silica (SiO2) with an average particle size of 300-μ was added to the film as an additive instead of PET. . The physical properties, optical homogeneity, and absence of optically foreign particles of the obtained film are shown in the table below.

As is clear from the table below, the film obtained in Comparative Example 1 has a large center line roughness value and is poor in smoothness. Furthermore, optical homogeneity is poor, and optically heterogeneous particles are present.

Comparative Example 2 Polyethylene terephthalate/isophthalate was produced according to a conventional method using 85 mol% of terephthalic acid and 15 mol% of isophthalic acid as the acid component and 100 mol% of ethylene glycol as the glycol component. The physical properties of this polyester are shown in the table below.

3 parts by weight of this polyester and PCT97 obtained in Example 1
The heavy canning section was melted and extruded in the same manner as in Example 1, cooled,
I stretched it and got a film.

The physical properties and optical homogeneity of the obtained film are shown in the table below.

As is clear from Table 11, the isophthalic acid-containing PET obtained in Comparative Example 2 has a lower crystal melting temperature than that of PCT (smooth film has a large centerline average roughness value and is smooth There are also optically foreign particles.

Comparative Example 3 A film was produced in the same manner as in Example 1 except that the amount of PET added was 25% by weight based on the film. The physical properties and optical homogeneity of the obtained film are shown in the table below.

As is clear from the table below, the amount of PET added in the film obtained in Comparative Example 3 was larger than the range of the present invention, and the obtained film had a large centerline average roughness value and was inferior in smoothness. . There are also optically foreign particles.

Comparative Example 4 PET was produced by transesterification and polycondensation of dimethyl terephthalate and ethylene glycol according to a conventional method. That is, after completing polymerization in a molten state, the polymer was subjected to solid state polymerization to have a high intrinsic viscosity. The melt crystallization temperature, intrinsic viscosity, and solution haze value of the obtained PET are shown in the table below.

PC797 obtained using 1 part of this PET triple jJi and Example 1
Melt extrusion, cooling, and cooling in the same manner as in Example 1 using the bulk part
A film was obtained by stretching. The physical properties and optical homogeneity of the obtained film are shown in the table below.

As is clear from the table below, the intrinsic viscosity of PET obtained in Comparative Example 4 is greater than that of PCT, and the resulting film has a large centerline average roughness value and is poor in smoothness. There are also optically foreign particles.

Claims (2)

[Claims] (1) 1,4-polycyclohexylene dimethylene terephthalate and a melt crystallization temperature Tmc higher than that of the 1,4-polycyclohexylene dimethylene terephthalate;
A polyester film containing 0.1 to 20% by weight of at least one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, which has a small intrinsic viscosity IV and a solution haze value of less than 5%. (2) Glass transition point is 90℃ or higher, light transmittance is 90%
The polyester film according to claim 1, wherein the centerline average roughness R_a is 10 mμ or less and the sliding friction coefficient μ_s is 0.3 or less.