JPH03215B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to biaxially oriented poly 1,4-cyclohexylene dimethylene terephthalate films. More specifically, the film is made of versatile biaxially oriented poly-1,4-cyclohexylene dimethylene terephthalate with a uniform longitudinal and lateral strength ratio, and has a low humidity expansion coefficient and a small in-plane difference in temperature and humidity expansion coefficient. Regarding. Prior Art Conventionally, a biaxially oriented polyethylene terephthalate film is known as a general-purpose biaxially oriented low humidity expansion film. This film has well-balanced properties and is widely used as an excellent industrial material. However, it is still insufficient for applications where dimensional changes due to humidity are particularly important, such as flexible magnetic disks. OBJECTIVES OF THE INVENTION The present invention provides a film that has properties equivalent to the advantages of biaxially oriented polyethylene terephthalate films but has improved long-term thermal deterioration resistance, humidity expansion coefficient, etc. It is an object of the present invention to provide a film suitable as a base for a flexible magnetic disk that has a small difference in direction. Structure of the Invention The present inventor has arrived at the present invention as a result of intensive research into the physical properties of various polymers. That is, in the present invention, the film has an in-plane refractive index of 1.585 to 1.650 including the longitudinal and lateral directions, and a density of 1.220 to 1.650.
1.250, temperature expansion rate 20 to 40 (×10 ^-6 /℃), humidity expansion rate 3 to 8 (×10 ^-6 /%RH), in-plane direction difference in temperature expansion rate within 6×10 ^-6 /℃, 2 so that the in-plane direction difference in humidity expansion rate is within 4 × 10 ^-6 /%RH.
Axially oriented, more than 90 mol% of the glycol component is 1,4-cyclohexanedimethanol, and the acid component is
Poly-1,4 in which 80 mol% or more is terephthalic acid
- cyclohexylene dimethylene terephthalate film. The 1,4-cyclohexanedimethanol in the present invention can be produced, for example, by catalytic reduction of dimethyl terephthalate or terephthalic acid, but it may be produced by any method. Although the ratio of the cis isomer to the trans isomer of 1,4-cyclohexanedimethanol is not particularly limited, it is preferably in the range of cis isomer/trans isomer = 4/6 to 0/10. Poly-1,4-cyclohexylene dimethylene terephthalate in the present invention can be produced by conventional polyester production methods. For example, it can be produced by direct esterification of terephthalic acid and 1,4-cyclohexanedimethanol or by transesterification of dimethyl terephthalate and 1,4-cyclohexanedimethanol. The poly-1,4-cyclohexylene dimethyl terephthalate thus produced may be copolymerized with a third component in a small proportion. In addition, in the poly-1,4-cyclohexylene dimethylene terephthalate, stabilizers such as phosphoric acid, phosphorous acid, and their esters, titanium dioxide, particulate silica, kaolin, calcium carbonate, calcium phosphate, etc. A matting agent, a lubricant, etc. may be included. In the present invention, the poly-1,4-cyclohexylene dimethylene terephthalate biaxially oriented film has a refractive index of 1.585 to 1.650 in each direction of the film surface.
Preferably 1.590-1.630, density 1.220-1.250g/cm
Preferably 1.224~1.240g/cm, temperature expansion rate 20~
40 (×10 ^-6 /℃) preferably 20 to 25 (×10 ^-6 /℃),
Humidity expansion rate 3-8 (×10 ^-6 /%RH) preferably
30 to 7 (×10 ^-6 /%RH), the in-plane difference in temperature expansion coefficient is 6 × 10 ^-6 /℃, preferably within 4 × 10 ^-6 /℃, and the in-plane difference in humidity expansion rate is 4 ×10 ^-6 /%
RH preferably needs to be within 3×10 ⁻⁶ /%RH. If the in-plane refractive index of the film is less than 1.585, the orientation of the molecular chains is insufficient, and the strength of the film, particularly the Young's modulus, is insufficient for engineering purposes. On the other hand, when the in-plane refractive index becomes larger than 1.65,
The refractive index in the 90° direction is less than 1.58, and the orientation of the molecular chains becomes more biased. The purpose of the present invention is to provide a film with good alignment balance that is useful as a film for liquid crystal display panels for flexible disks, and the above-mentioned unbalanced orientation of molecular chains is undesirable. More preferably, it is in the range of 1.590 to 1.630, which further improves the orientation balance. In addition, the density is 1.220-1.250g/cm,
If it is lower than 1.220, crystallization will be insufficient, making it impossible to obtain the desired humidity expansion coefficient. The higher the density, the better, but it is difficult to exceed 1.250. The temperature expansion coefficient is 20 to 40 (x10 ^-6 /°C), more preferably 20 to 25 (x10 ^-6 /°C). The temperature expansion rate is
In general, the smaller the better, but for the base of a flexible magnetic disk, it is preferable that the temperature expansion coefficient be close to that of the disk drive device, as this will reduce the off-track between the magnetic disk and the head. It is easy to set the temperature expansion coefficient of the disk drive device to around 20×10 ^-6 /℃, so it is preferable to choose a value close to 20×10 ^-6 /℃, but it is better to set it to less than 20×10 ^-6 /℃. It is difficult.
In general, the lower the humidity expansion coefficient is, the better for any purpose, but the inherent hygroscopic expansion of the material cannot be avoided, and it is difficult to reduce it to 3×10 ^-6 /%RH or less. However, if the RH is set to 8×10 ^-6 /°C RH or less, the effect is clearly improved over the conventionally used polyethylene terephthalate, 11×10 ^-6 /%RH, and it becomes useful. The in-plane direction difference in temperature expansion coefficient is
In order to reduce the off-track, 6×10 ^-6 /℃
Hereinafter, the temperature is preferably 4×10 ⁻⁶ /°C or less. Since the in-plane direction difference in humidity expansion coefficient also reduces off-track, it is preferable to have a smaller value, and is 8×10 ^-6 /%.
RH or less, preferably 7×10 ^-6 /%RH or less. Next, a method for obtaining the numerical values regulated above will be explained. The acid component of poly-1,4-cyclohexylene dimethylene terephthalate used in the present invention has a terephthalic acid content of 80 mol% or more. If the terephthalic acid component is less than this, the crystallinity of the polymer will be insufficient, making it impossible to satisfy the above ranges of refractive index, density, and temperature/humidity. As the third component
Isophthalic acid, oxalic acid, succinic acid, adipic acid, 2,6-naphthalene dicarboxylic acid, etc. can be used within the range of 20 mol% or less. In addition, the glycol component contains 1,4-cyclohexanedimethanol in an amount of 90 mol% or more. If the proportion is too small, the crystallinity of the polymer will decrease, the above-mentioned values, especially the density will fall below the preferred range, and the refractive index will also decrease, making it unsuitable. As the third component, for example, ethylene glycol,
Propylene glycol, 1,4-butanediol, etc. can be used. The above-mentioned 1,4-cyclohexanedimethanol has a cis form and a trans form, and although there are slight changes in physical properties depending on the mixing ratio, there is no major effect, and as mentioned earlier, cis/trans = If it is in the range of 4/6 to 0/10, the preferred range of the above-mentioned physical properties can be obtained. Next, film forming conditions will be explained. It is appropriate to dry polymer chips at 170℃ for around 3 hours.
It is not limited to this. Although an ordinary extruder may be used, it is particularly preferable to use measures to improve the extrusion precision, such as use in combination with a metering pump, pressure control, and the like. Since the temperature of the melt of poly 1,4-cyclohexylene dimethylene terephthalate changes depending on the polymer composition, it is preferable to select the temperature accordingly. For the above polymer compositions, a temperature range of 295-315°C is usually chosen. The appropriate temperature for the casting drum is 10 to 60℃, but poly-1,
It is preferable to rapidly cool the 4-cyclohexylene dimethylene terephthalate homopolymer,
In that case a surface temperature of 20-40°C is suitable. The stretching temperature is usually 80 to 140°C, and this tends to cause stretching unevenness at low temperatures, while the stretching effect tends to decrease at higher temperatures. More preferably, a temperature range of 100 to 120°C is selected, whereby the above-mentioned physical property values can be easily obtained. The stretching ratio is 3.0 to 5.0 times in the longitudinal direction, preferably 3.3 to 4.3
Select 3.0-5.0 times, preferably 3.5-4.5 times in the lateral direction. If the stretching ratio is less than this range, the refractive index will be smaller than the above value, and if the stretching ratio exceeds this range, not only will the film be undesirably cut frequently during production, but even if the film is obtained, it will suffer from humidity expansion. The rate is surprisingly high and good results cannot be obtained. The stretching method may be a known method. For example, longitudinal stretching can be carried out by heating between two rolls with different circumferential speeds, and transverse stretching can be carried out by gripping both ends of the film with clips and heating the film in a row of clips. It is possible to stretch by increasing the row spacing. The obtained biaxially oriented film is heated at 150 to 260°C, preferably 180 to 250°C.
The refractive index, density, and temperature/humidity expansion coefficient of the present invention can be obtained by heat fixing at ℃ for 1 to 100 seconds. When a film is formed by a normal longitudinal and lateral stretching method, the in-plane difference in temperature/humidity expansion coefficient is included in the scope of the present invention near the center in the width direction of the film. However, the quantitative percentage included varies depending on film forming conditions and polymer composition. Typically, 10 to 70% of the total width is within the scope of the present invention. On the other hand, in the portions near both ends of the film in the width direction, there is a large in-plane difference in temperature/humidity expansion coefficient, and this generally falls outside the scope of the present invention. The reason for this is the bowing phenomenon that occurs during heat-setting in a tenter. In order to reduce the in-plane difference in temperature/humidity expansion coefficient in any part of the film width, heat setting should be carried out at a temperature of 120 to 180°C, and after it has been wound, it should be heat set again while unwinding. 150
It is preferable to carry out the process at a temperature of ~250°C while holding both ends of the film with clips, but the present invention is not limited thereto. By performing heat treatment two or more times in different heat treatment directions in this way, the effect of bowing can be removed by selecting the temperature conditions, and the in-plane refractive index difference,
The temperature/humidity expansion rate difference can be reduced, and the proportion of products compatible with the present invention can be increased. Since the optimum range changes depending on the polymer composition, it is necessary to select conditions appropriately. For example, the acid component is 87 mol% of terephthalic acid and 13 mol% of isophthalic acid, and the glycol component is 100% 1,4
- In the case of a polymer having the composition of cyclohexanedimethanol, the heat setting conditions are preferably 230 to 240°C and 20 to 40 seconds. The biaxially oriented film of the present invention can have an appropriate thickness depending on its use, but a thickness of 2 to 500 μm, usually 12 to 125 μm, and 50 to 100 μm for use as a flexible disk base is selected. The method for measuring characteristic values in the present invention is as follows. (1) Refractive index: Based on Atsube's refractometer. (2) Density: by normal heptane-tetrachlorine carbon density gradient tube. (3) Temperature expansion rate: Measure by placing a constant load elongation tester (TTL2 type) manufactured by Japan Automatic Control Co., Ltd. in a constant temperature and humidity chamber. The measurement sample is heat-treated in advance under predetermined conditions (for example, 70℃, 30 minutes), and this sample is attached to the test machine at a temperature of 20℃ and a relative humidity of 60%.
The temperature expansion coefficient is measured by reading the dimensional change between The original sample length at this time was 505 mm, and the sample width was 1/4 inch. The weight applied during measurement is
It was fixed at 5g/1/4 inch width. If a long sample cannot be obtained, measurement can be performed using a thermomechanical analyzer TM-3000 manufactured by Shinku Riko Co., Ltd. When determining the difference between the maximum and minimum temperature expansion coefficients, use TM-3000. The dimensions of the sample are 15 mm in length and 5 mm in width, with a temperature of 10°C and humidity of 0%RH and a temperature of 40°C and humidity of 0%.
Determine by reading the dimensional change at RH. (4) Humidity expansion rate: As in the case of determining the temperature expansion rate, use a constant load elongation tester manufactured by Japan Automatic Control Co., Ltd., and attach a sample that has been pretreated at a temperature of 40°C and humidity of 90% RH. Temperature 20℃, humidity
Determine the humidity expansion rate by reading the dimensional changes between 30%RH, 20℃, and 70%RH.
If the sample cannot be taken for a long time, a thermomechanical analyzer manufactured by Shinku Riko Co., Ltd. was placed in a constant temperature and humidity environment, and the measurement was performed under the above conditions, as in the case of measuring the coefficient of thermal expansion. (5) In-plane directional difference in temperature/humidity expansion coefficient: Measure the value in each direction every 15° or 30° using the method explained in (3) and (4) above, and calculate <maximum value - minimum value>. demand. EXAMPLES Next, the present invention will be specifically explained using examples. Example 1 85 mol% of terephthalic acid as dibasic acid component,
15 mol% of isophthalic acid, 100% of 1,4-cyclohexanedimethanol as the glycol component, 0.05 mol% of titanium oxide (based on the acid component) as a catalyst, and 0.5% by weight of kaolin clay with an average particle size of 0.6 microns as a lubricant. In addition, the mixture was placed in an autoclave and heated under stirring for transesterification, followed by polycondensation to obtain poly-1,4-cyclohexylene dimethylene terephthalate. This polyester was melt-extruded at 300℃, then 40℃
The film was cooled on a quenching drum held at 1000 mL to obtain an unstretched film of 1000 microns. This unstretched film
After being brought into contact with a metal roll adjusted to 90°C and preheated, it was stretched 3.6 times in the longitudinal direction between rolls with a difference in circumferential speed while being irradiated with an infrared heater (surface temperature 1000°C).
Next, the longitudinally stretched film was stretched at 115 kg using a tenter at 3.7 kg.
It was horizontally stretched twice. While holding both ends of the obtained biaxially stretched film with clips, it was heat-set at 140°C and wound up. Next, while unwinding this film, both ends of the film were gripped and heat set again at 235°C, resulting in a product with a thickness of 75 microns. The physical property values are shown in Table 1. Example 2 In Example 1, the dibasic acid component was terephthalic acid.
100mol%, melting temperature 310℃, quenching drum temperature
20℃, preheating temperature 80℃, first heat fixing temperature 180℃,
Furthermore, a 75 micron biaxially oriented film was obtained in the same manner as in Example 1 except that the reheat setting temperature was 250°C. The physical property values are shown in Table 1. Example 3 In Example 1, the first heat setting was carried out at 235°C, and a 75 micron biaxially oriented film was obtained without further heat setting. Other conditions are the same as in Example 1. Table 1 shows the physical properties of this film. Comparative Example 1 Polyethylene terephthalate was polymerized by a conventional method. Under the film forming conditions of Example 1, the melting temperature was 290°C,
A biaxially oriented film of 75 microns was obtained in the same manner as in Example 1, except that the quenching drum temperature was 20°C, the longitudinal stretching preheating temperature was 80°C, the transverse stretching temperature was 105°C, and the reheat setting temperature was 225°C. Table 1 shows the physical properties of this film. Comparative Example 2 A biaxially oriented film of 75 microns was obtained in the same manner as in Example 2 except that the stretching ratio was 4.3 times in the vertical direction and 3.5 times in the horizontal direction. Table 1 shows the physical properties of this film. The center portions of the films of Examples 1, 2, and 3 satisfied the target values of the present invention.

[Table] Effects of the Invention The biaxially oriented film of the present invention is suitable as a base for a flexible magnetic disk. The reason for this is that the humidity expansion rate is lower than that of polyethylene terephthalate film, and as a result, the off-track between the magnetic track and the head is small, and high recording density can be obtained. Although the temperature expansion rate is relatively large,
This is not a major drawback since the temperature expansion rate of the drive unit can be matched with that of the disk. Furthermore, since the in-plane difference in temperature and humidity expansion coefficients is small, it is advantageous because it can easily be used to reduce off-track by a tracking servo mechanism. On the other hand, it has a small in-plane direction difference in refractive index, and is used for transparent conductive films for liquid crystal display devices.
Also suitable for protective covers.

Claims (1)

[Claims] 1 In-plane refractive index including vertical and horizontal directions 1.585 ~
1.650, density 1.220~1.250, temperature expansion coefficient 20~40 (×
10 ^-6 /℃), humidity expansion rate 3 to 8 (×10 ^-6 /%RH)
The in-plane direction difference in temperature expansion coefficient is within 6×10 ^-6 /℃,
The glycol component is biaxially oriented so that the in-plane difference in humidity expansion rate is within 4×10 ^-6 /%RH.
A poly-1,4-cyclohexylene dimethylene terephthalate film containing 90 mol% or more of 1,4-cyclohexanedimethanol and 80 mol% or more of the acid component being terephthalic acid.