JPH08323878A - Biaxially oriented film of syndiotactic polystyrene - Google Patents

Abstract

PURPOSE: To improve flatness by a method wherein a biaxially oriented film is constituted of a styrene polymer, having syndiotactic structure satisfying a specified formula and provided with a specified thickness. CONSTITUTION: A biaxially oriented film is constituted of a polystyrene polymer, having syndiotactic structure and satisfying the formula of [Amax/90( deg.)]X[HSmax/R]<=0.01, and is provided with the thickness of 25μm or less. In the case of a sheet type sample, squares, having one side of 100mm long, are cut out of four apexes of a rectangular specimen and the direction of orientation of particles are obtained while the maximum value among the angles of directions of orientations of other three points when the direction of orientation of particles at a measured point at first is specified as 0 deg.. Hsmax is the maximum dimensional changing rate upon the dry heat treatment for 30min at 200 deg.C while contraction is specified so as to be positive. R is equal to Dmm/100mm and the maximum value is 1 (one). D means a distance between a point, whereat the direction of orientation of particles is measured at first, and a point, whereat Amax is shown, and here D is a distance between the intersecting points of diagonals of squares, employed for the measurement.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a syndiotactic polystyrene biaxially stretched film having excellent flatness after metal vapor deposition, more specifically, metal vapor deposition film, when used as a film for capacitors or packaging, metal vapor deposition The present invention relates to a syndiotactic polystyrene-based biaxially stretched film having a thickness of 25 μm or less having good flatness.

[0002]

2. Description of the Related Art Syndiotactic polystyrene biaxially stretched films have been developed that have excellent heat resistance, electrical properties, transparency, etc. (Japanese Patent Laid-Open Nos. 1-110122 and 1-11).
68709, 1-182346, 2-2797.
No. 31, No. 3-74437, No. 3-109453,
3-99828, 3-124427, 3-1
31644), magnetic tapes, capacitors,
It is expected to be applied to various film applications such as packaging. In particular, it is expected to be applied to capacitors that make use of electrical characteristics and packaging that makes use of heat resistance. With the miniaturization and higher capacity of film capacitors, the films used tend to become thinner year by year, especially in metal evaporated film capacitors. Further, since a film is used by being laminated on the capacitor, high accuracy is required for the flatness of the film not only before metal deposition but also after metal deposition. Conventional syndiotactic polystyrene-based biaxially stretched films tend to lose flatness after metal deposition, and especially in a film having a thickness of 25 μm or less, this flatness is significantly disturbed, so that the breakdown voltage is lowered. The important characteristics of the condenser were lost. Further, as a packaging film, an aluminum vapor deposition film is often used for applications that conventionally require gas barrier properties, but if the flatness after aluminum vapor deposition is poor, problems such as distortion during bag making occur. . This tendency was observed in the conventional biaxially stretched syndiotactic polystyrene film. Japanese Unexamined Patent Publication (Kokai) No. 6-91750 discloses a method for improving the flatness of a syndiotactic polystyrene biaxially stretched film. In this method, the flatness before metal deposition is satisfied, but when the metal deposition treatment is performed. The flatness of was not always satisfactory.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a syndiotactic polystyrene biaxially stretched film having a thickness of 25 μm or less, which has improved flatness after metal vapor deposition.

[0004]

Means for Solving the Problems As a result of intensive investigations by the present inventors to improve the flatness after vapor deposition of metal, the molecular orientation direction of the syndiotactic polystyrene-based film in the film width direction determined by microwave Satisfies the flatness after metal deposition by setting the angle (hereinafter referred to as molecular orientation angle) and the dimensional change rate after dry heat treatment at 200 ° C. for 30 minutes (hereinafter referred to as dimensional change rate) to within certain ranges. The inventors have found that it is possible to achieve the present invention and arrived at the present invention.
That is, the present invention relates to a syndiotactic polystyrene film having a thickness of 25 μm or less, characterized in that the value determined by the following formula (1) is 0.01 or less. [Amax / 90 (°)] × [HSmax / R] (1) The syndiotactic polystyrene-based polymer used in the present invention refers to a polystyrene-based polymer having a high syndiotactic structure. The tactic structure has a three-dimensional structure in which phenyl groups or substituted phenyl groups, which are side chains, are alternately located in opposite directions to the plane created when the main chain carbon-carbon bond has a planar zigzag structure. The tacticity thereof is quantified by the 13C nuclear magnetic resonance method, and the syndiotactic polystyrene polymer used in the present invention has a dyad of two consecutive constitutional units of 75% or more, preferably 80% or more. Alternatively, it is desirable that the pentad (5 units) has a syndiotactic structure of 30% or more, preferably 50% or more. . Examples of the polystyrene-based polymer include polystyrene, poly (alkylstyrene) (for example, poly (p-, m- or o-methylstyrene), poly (2,4-, 2,
5-, 3,4- or 3,5-dimethylstyrene), poly (p-tertiarybutylstyrene), etc., poly (halogenated styrene) {eg poly (p-, m- or o-chlorostyrene),
Poly (p-, m- or o-bromostyrene), poly (p-, m- or o-fluorostyrene), poly (o-methyl-p-fluorostyrene), etc.}, poly (halogen-substituted alkylstyrene) { For example, poly (p-, m- or o-chloromethylstyrene), etc., poly (alkoxystyrene) {for example, poly (p-, m- or o-methoxystyrene), poly (p-, m-or
o-ethoxystyrene), etc., poly (carboxyalkylstyrene) {eg poly (p-, m- or o-carboxymethylstyrene) etc., poly (alkyletherstyrene) {eg poly (p-vinylbenzylpropyl) etc. }, Poly (alkylsilylstyrene) {eg, poly (p-trimethylsilylstyrene), etc.}, and further poly (vinylbenzyldimethoxyphosphide) and the like.

In the present invention, polystyrene is particularly preferable among the polystyrene polymers. Also,
The polystyrene polymer having a syndiotactic structure used in the present invention is not necessarily a single compound, and if the syndiotacticity is within the above range, a polystyrene polymer having an atactic structure or an isotactic structure is used. It may be a mixture of, a copolymer and a mixture thereof.

In the biaxially stretched syndiotactic polystyrene film of the present invention, the syndiotactic polystyrene is melt-extruded by a conventional method, and then sequentially or simultaneously biaxially stretched and subjected to tension and / or relaxation heat at a temperature of 150 to 280 ° C. It can be obtained by fixing, or by a film-forming sequence in which stretching and heat-setting are appropriately combined, but preferably transverse stretching is performed in a zone in which the atmosphere temperature at the center of the film is higher than the atmosphere temperature at the film end. Then, the temperature at the center of the film and the temperature at the edges are 10
It is necessary to include the step of performing the second horizontal stretching in a zone (temperature is the central part> the end part) raised by -40 ° C., and more preferably the difference in the atmospheric temperature between the central part and the end part is 20 to 40 ° C. is there.

The molecular orientation determined by microwaves is a parameter that mainly evaluates the degree of alignment of the syndiotactic polystyrene molecular chains in the amorphous portion. The measurement results are obtained in the form of an orientation ellipse, and in the case of syndiotactic polystyrene molecules, the orientation in the direction of weak strength is high. That is, the molecular chains are oriented in the minor axis direction of this ellipse. The angle formed by the minor axis direction and the film width direction is the molecular orientation angle. As this value approaches 0 °, the molecular chains are oriented in the width direction, and as the value approaches 90 °, they are oriented in the longitudinal direction. The inventors have found that when the molecular orientation angle obtained by this microwave has a distribution within the film width plane, the degree of difference between the maximum and the minimum determines the planarity after the metal deposition treatment. . That is, when the difference between the maximum and the minimum of the molecular orientation angle in the film plane is large, the flatness after the metal deposition treatment tends to deteriorate. However, even if the difference between the maximum and the minimum of the molecular orientation angle in the film plane is large, the flatness after post-processing tends to be maintained if the dimensional change rate is small after dry heat treatment at 200 ° C. for 30 minutes. It was also found that when each value satisfies the following formula (1), good flatness after metal deposition can be obtained. [Amax / 90 (°)] × [HSmax / R] ≦ 0.01 (1)

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition,
The evaluation method of the film is shown below. (1) Molecular Orientation Angle A molecular orientation meter (M, manufactured by Kanzaki Paper Mfg. Co., Ltd.)
OA-2001A) is used to cut out a rectangle of 1000 mm in the machine direction in the case of a roll sample and the full width of the sample in the machine orthogonal direction, and in the case of a sheet sample, draw a rectangle with the largest area inscribed in the sample shape. A 100 mm square that shares two sides with the apex of is cut out from the four apexes, the molecular orientation direction is determined by microwaves, and the molecular orientation direction of the first measured point is 0 °, and the other three points are oriented. The maximum value of the angles was calculated as Amax.

(2) Dimensional change rate A true circle with a diameter of 50 mm is drawn around the intersection of the diagonal lines of the rectangle drawn to determine the molecular orientation angle, and the film is cut slightly larger than this circle. This film piece is hung in a gear oven heated to 200 ° C with no load, left for 30 minutes, taken out, the coordinates after dimension change are read by a digitizer, and the location where the dimension changes most along a straight line passing through the center The length Bmm of the line segment cut by the above-described figure in which the perfect circle is changed was obtained, and the dimensional change rate (HSmax) in the maximum dimensional change direction was obtained by the following equation (1). (HSmax or HS200) = (50−B) / 50 (1)

(3) Flatness after vapor deposition Aluminum was vapor-deposited on one side of the film using a vacuum vapor deposition machine. At this time, an induction heating method is used as a heating means, the degree of vacuum is 4 × 10 −4 torr, and the vapor deposition rate is 3000 Å / s.
After the vapor deposition was carried out under the condition of ec so that the thickness of the vapor deposition film would be 500 Å, the grades 1 to 5 were ranked according to the following criteria. 1st grade; there is a wavy surface even with strong tension 2nd grade; there is some wavy even with strong tension 3rd grade; no waviness when strong tension is applied 4th grade; no waviness when weak tension is applied 5th grade; tension No waviness without applying

Example 1 As a lubricant, the average particle size was 0.5 μm and the degree of dispersion was 20.
%, Silica having an area shape factor of 80% is syndiotactic polystyrene (weight average molecular weight 250,000) 99.
Polymer chips added with 0.5 wt% to 5 wt% and polymer chips without added lubricant were mixed at a weight ratio of 2 to 8, then dried and melted at 290 ° C. It was extruded from a T-die having a lip gap, and was brought into close contact with a cooling roll at 50 ° C. by an electrostatic loading method to be cooled and solidified to obtain an amorphous sheet having a thickness of about 350 μm. The amorphous sheet is first preheated with an infrared heater heated to a surface temperature of 350 ° C. at a distance of 20 mm from the film,
After continuously stretching 1.8 times in the machine direction using a rubber roll heated to a surface temperature of 130 ° C., it was stretched 2.20 times in the machine direction using a ceramic roll heated to a surface temperature of 110 ° C. Next, preheat at 110 ° C with a tenter, the atmosphere at the center of the film is 150 ° C, and the atmosphere at the edges of the film is 1
1.8 in the lateral direction in the zone where the temperature was set to 20 ° C.
The film was stretched twice and further cooled without cooling the film. In the zone where the atmosphere at the center of the film was 170 ° C. and the atmosphere at the film edge was 140 ° C., 1.
It was stretched 8 times. Then, heat fixing with tension at 260 ° C, 230
3% relaxation treatment continuously in the width direction at ℃, thickness 23μm
Was obtained. This film has Amax = 18.
5 °, HSmax = 0.042, D = 1300 mm. Therefore, [Amax / 90 (°)] × [HSmax
/ R] was 0.0086. The flatness of this film after vapor deposition was grade 5.

Example 2 Melt extrusion was performed under the same conditions as in Example 1 to obtain a thickness of 140 μm.
A m-shaped amorphous sheet was obtained, and longitudinal stretching was performed under the same conditions as in Example 1. Then, by preheating with a tenter at 110 ° C., the atmosphere at the center of the film was 140 ° C. and the atmosphere at the edge of the film was 120 ° C.
The film was stretched 5 times, and further, without cooling the film, it was stretched 2.13 times in the transverse direction in a zone in which the atmosphere at the center of the film was 170 ° C. and the atmosphere at the edge of the film was 140 ° C. Then, heat fixing with tension at 260 ° C,
A relaxation treatment of 3% was continuously performed in the width direction at 230 ° C. to obtain a film having a thickness of 8.5 μm. This film is Ama
x = 13.0 °, HSmax = 0.034, D = 116
It was 0 mm. Therefore, [Amax / 90 (°)] ×
[HSmax / R] was 0.0049. The flatness of this film after vapor deposition was grade 5.

Example 3 An amorphous sheet having a thickness of 300 μm was obtained in the same manner as in Example 1, longitudinal stretching was carried out under the same conditions as in Example 1, and then preheated at 110 ° C. in a tenter, and the atmosphere in the center of the film was changed. Is 1
The film was stretched 1.8 times in the transverse direction in a zone where the atmosphere at the film edge was 120 ° C. at 50 ° C., the atmosphere at the center of the film was 180 ° C., and the atmosphere at the film edge was 1.
1.8 in the lateral direction in the zone where the temperature was set to 40 ° C.
It was stretched twice. Then, heat fixing at 260 ℃, 230 ℃
Then, 3% relaxation treatment was continuously performed in the width direction to obtain a film having a thickness of 20 μm. This film has Amax = 19.6.
°, HSmax = 0.040, D = 890 mm.
Therefore, [Amax / 90 (°)] × [HSmax /
R] was 0.0098. The flatness of this film after vapor deposition was grade 4.

Example 4 Melt extrusion, longitudinal stretching and transverse stretching were carried out under the same conditions as in Example 1, followed by tension heat fixing at 240 ° C. and continuous 3% relaxation treatment at 220 ° C. in the width direction to give a thickness of 22 μm. I got a film of. This film has Amax = 17.3 °,
HSmax = 0.051 and D = 1005 mm. Therefore, [Amax / 90 (°)] × [HSmax / R]
= 0.0098. The flatness of this film after vapor deposition was grade 3.

Example 5 A film was formed in the same manner as in Example 2 and cut into arbitrary shapes with scissors to obtain a sample. This film has Amax =
It was 6.0 °, HSmax = 0.034, and D = 450 mm. Therefore, [Amax / 90 (°)] × [HSma
x / R] = 0.0050. The flatness of this film after vapor deposition was grade 5.

Comparative Example 1 Melt extrusion was carried out in the same manner as in Example 1 to obtain a thickness of 250 μm.
The amorphous sheet is obtained, preheated with an infrared heater heated to a surface temperature of 260 ° C. at a distance of 20 mm from the film, and continuously stretched 3.2 times in the machine direction using a rubber roll heated to 130 ° C. Next, using a tenter, 110
Preheat at ℃, and then draw 3.2 times transversely at 120 ℃, 26
After fixing by tension heat at 0 ° C., relaxation treatment was performed at 230 ° C. in the width direction by 3% to obtain a film having a thickness of 22 μm. This film has Amax = 23.0 °, HSmax = 0.037,
It was D = 835 mm. Therefore, [Amax / 90
(°)] × [HSmax / R] = 0.113. The flatness of this film after vapor deposition was grade 2.

Comparative Example 2 The same steps as in Example 1 up to the longitudinal stretching step were carried out, the transverse stretching was preheated at 110 ° C. using a tenter, and 120 ° in the transverse direction.
Stretched 3.5 times and heat set at 220 ℃, then 200 ℃
Was subjected to 2% relaxation treatment in the width direction to obtain a film having a thickness of 24 μm. This film has Amax = 19.7 °, HSm
It was ax = 0.065 and D = 1260 mm. Therefore,
[Amax / 90 (°)] × [HSmax / R] = 0.
It was 0142. The flatness of this film after vapor deposition is 1
It was class.

Comparative Example 3 Melt extrusion, longitudinal stretching, and transverse stretching were performed under the same conditions as in Comparative Example 1, and tension and relaxation heat fixation conditions were the same as in Comparative Example 2 to obtain a film having a thickness of 23 μm. This film is
Amax = 26.2 °, HSmax = 0.067, D =
It was 1100 mm. Therefore, [Amax / 90
(°)] × [HSmax / R] = 0.195. The flatness of this film after vapor deposition was first grade. Table 1 shows the physical properties and evaluation results of Examples 1, 2, 3, 4, 5, and Comparative Examples 1, 2, and 3.

[0019]

[Table 1] [Amax / 90 (°)] × [HSmax / R] (1) From Table 1, it can be seen that Examples 1, 2, 3, 4, and 5 are excellent in flatness after metal deposition.

[0020]

EFFECTS OF THE INVENTION In the present invention, the molecular orientation angle and the dimensional change rate are set as described in the above-mentioned claims, so that the syndiotactic polystyrene system having a thickness of 25 μm or less, which is extremely excellent in flatness after metal deposition. It is possible to provide a biaxially stretched film.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Example 1 As a lubricant, the average particle size was 0.5 μm and the degree of dispersion was 20.
%, Silica having an area shape factor of 80% is syndiotactic polystyrene (weight average molecular weight 250,000) 99.
Polymer chips added with 0.5 wt% to 5 wt% and polymer chips without added lubricant were mixed at a weight ratio of 2 to 8, then dried and melted at 290 ° C. It was extruded from a T-die having a lip gap, and was brought into close contact with a cooling roll at 50 ° C. by an electrostatic loading method to be cooled and solidified to obtain an amorphous sheet having a thickness of about 350 μm. First, the amorphous sheet was heated to a surface temperature of 350 ° C. to obtain a diameter of 10
3 mm rod-shaped silicon nitride infrared heaters (reflected red
Made of stainless steel so that the outside wire hits the film
(With an umbrella) , preheated at a distance of 20 mm from the film, and continuously stretched 1.8 times in the machine direction using a rubber roll heated to a surface temperature of 130 ° C., and then heated to a surface temperature of 110 ° C. Using the above-mentioned ceramic roll, it was drawn 2.20 times in the machine direction. Next, the film was preheated with a tenter at 110 ° C. and stretched 1.8 times in the transverse direction in a zone in which the atmosphere at the center of the film was 150 ° C. and the atmosphere at the edges of the film was 120 ° C., and the film was further stretched. Without cooling, the film was stretched laterally 1.8 times in a zone in which the atmosphere at the center of the film was 170 ° C. and the atmosphere at the edge of the film was 140 ° C. Next, tension heat fixing is performed at 260 ° C., and 3% relaxation treatment is continuously performed at 230 ° C. in the width direction,
A film having a thickness of 23 μm was obtained. This film is Am
ax = 18.5 °, HSmax = 0.042, D = 13
It was 00 mm. Therefore, [Amax / 90 (°)] ×
[HSmax / R] was 0.0086. The flatness of this film after vapor deposition was grade 5.

Claims (3)

[Claims] 1. A biaxially stretched syndiotactic polystyrene film having a thickness of 25 μm or less, which is substantially made of a styrene polymer having a syndiotactic structure and satisfies the following formula (1). [Amax / 90 (°)] × [HSmax / R] ≦ 0.01 (1) Amax: 1000 in the machine direction in the case of a roll sample
mm, a rectangle with the full width of the sample is cut out in the machine orthogonal direction, and in the case of a sheet-like sample, draw a rectangle with the largest area inscribed in the sample shape, and 100 mm that shares two sides with the vertex of the rectangle.
A square is cut out from four vertices, the molecular orientation direction is determined by microwaves, and the maximum value of the angles of the other three points when the molecular orientation direction of the first measured point is 0 ° (Unit: °) HSmax: Dimensional change rate in the direction of maximum dimensional change during dry heat treatment at 200 ° C for 30 minutes (shrinkage is expressed as positive) R = Dmm / 1000mm: However, R exceeds 1 In this case, set to 1. D: Distance between the first measured point and the point indicating Amax when the molecular orientation direction was determined. However, it refers to the distance between the intersections of the square diagonals used for measuring the molecular orientation direction. 2. The Amax of the film according to claim 1 is 2
A biaxially stretched syndiotactic polystyrene film, which is 0 ° or less. 3. The film according to claim 1 at 3 ° C. at 3 ° C.
The dimensional change rate (contraction is expressed as positive) in the direction in which the maximum dimensional change occurs during 0 minute dry heat treatment is -0.05 to 0.0
5. A syndiotactic polystyrene-based biaxially stretched film which is No. 5.