JPH0298423A - Liquid crystal polymer film - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal polymer film superior in shock resistance, by making the title film into a thermotropic liquid crystal polymer having a specific thickness, dapples in thickness and Young's modulus. CONSTITUTION:Since the title film is of that comprised of a composition consisting mainly of a thermotropic liquid crystal polymer, whose difference in Young's modulus between a longitudinal and widthwise directions (longitudinal direction-widthwise direction), thickness and dapples in thickness are respectively 500-600kg/mm<2>, 1-100/mum and within a range of not exceeding 20%, a liquid crystal polymer film whose shock resistance is favorable can be provided as mechanical characteristics possessed by the liquid crystal polymer is maintained. Although the thermotropic liquid crystal polymer is not limited specifically and a matter known to public can be used, in case of thermotropic liquid crystal polyester, it is especially preferable since shock resistance becomes more favorable. In the event that a surface layer part and the central part are oriented respectively in the longitudinal and widthwise directions and in the event that a ratio A/B between a thickness A of, the surface layer part and the while thickness B of the film falls within a range of 0.01-0.7, the shock resistance becomes more favorable. In the event that mean heights of protrusions of the surface of the film is 30-50nm, dapples in thickness becomes more favorable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to liquid crystal polymer films.

[Prior Art] As a liquid crystal polymer film, a film made of a thermotropic liquid crystal polymer is known (for example, Japanese Patent Laid-Open No. 58-53418).

[Problems to be Solved by the Invention] However, the conventional liquid crystal polymer films described above have poor impact resistance because they are biaxially stretched in a molten state or stretched at high temperatures, making it difficult to develop industrial applications. There was a drawback.

An object of the present invention is to improve such problems and provide a liquid crystal polymer film that has good impact resistance while maintaining the mechanical properties of the liquid crystal polymer.

[Means for Solving the Problems] The present invention provides a film made of a composition containing a thermotropic liquid crystal polymer as a main component, wherein the difference in Young's modulus between the longitudinal direction and the width direction (longitudinal direction - width direction) is - 500-600
The present invention relates to a liquid crystal polymer film having a thickness of 1 to 100 μm.

The thermotropic liquid crystal polymer in the present invention is not particularly limited, and examples thereof include ethylene terephthalate/oxybenzoic acid copolymer, 2,6-naph 1 to 1 acid/oxybenzoic acid copolymer, oxybenzoic acid/biphenol/terephthalic acid copolymer, and so on. Although known polymers and the like can be used, thermotropic liquid crystal polyester is particularly preferred because it provides even better impact resistance.

The film of the present invention is a film made of the above-mentioned thermotropic liquid crystal polymer, and the difference in Young's modulus between the longitudinal direction and the width direction (longitudinal direction - width direction) is -500 to 600 kg/m.
m2, preferably -450 to 500 kQ/mm2, more preferably -300 to 300 kg/mm2.

If the difference in Young's modulus is smaller or larger than the above range, the impact resistance will be poor, which is not preferable.

The film of the present invention needs to have a film thickness of 1 to 100 μm, preferably 2 to 75 μm, and more preferably 3 to 40 μm. If the thickness is smaller than the above range, or conversely if it is larger than the above range, the impact resistance will be poor, so it is not preferable.

The thickness unevenness of the film of the present invention is 20% or less, preferably 10% or less.
% or less, more preferably 5% or less. If the thickness unevenness is larger than the above range, the impact resistance will be poor, which is not preferable.

In particular, when the film of the present invention has a surface layer oriented in the longitudinal direction and a central portion oriented in the width direction, the thickness of the surface layer is A
(sum of the thicknesses of both sides) and the total thickness of the film (B), when A/B is in the range of 0.01 to 0.7, especially in the range of 0.1 to 0.5, the impact resistance becomes even better. This is particularly desirable because it provides good results.

The average height of the protrusions on the surface of the film of the present invention is 30 to 5.
In the case of 00 nm, thickness unevenness becomes even better, so it is particularly desirable.

It is particularly preferable that the film of the present invention has a Young's modulus of 500 kg/mm 2 or more in both the longitudinal direction and the width direction, since the impact resistance will be even better.

Further, the ratio of the thickness A (sum of both surfaces, unit: nm) of the surface layer of the thermotropic liquid crystal polymer film of the film of the present invention to the average surface roughness Ra (nm) in the width direction of at least one side, Ra/A, is 00OO1 to A value in the range of 10 is particularly desirable because the impact resistance becomes even better.

Although the film of the present invention is the above-mentioned thermotropic liquid crystal polymer film, the impact resistance of the film can be greatly improved by laminating it with a thermoplastic resin film.

Next, a method for producing the film of the present invention will be explained.

A thermotropic liquid crystal polymer is extruded into a sheet through a slit in a die using a known melt extruder, and is cooled with a casting roll to form an unstretched film. In this case, the method of casting while setting the draft ratio (ratio of die slit gap/unstretched film thickness) to ]0 to 100 and applying an alternating current electric field can reduce the thickness unevenness within the range of the present invention to a predetermined film thickness. It is extremely effective for producing a Young's modulus within the range of the present invention. Next, this unstretched film is stretched in the width direction, at a stretching speed of 200.0 to 2.
000'O%/min and 3.0% while microwave heating.
Stretching at a stretching ratio of ~20.0 times is extremely effective in obtaining Young's modulus and thickness unevenness within the range of the present invention. Although the stretching temperature is not necessarily constant depending on the type of polymer, it is effective to conduct the stretching at a temperature above the glass transition point and below the melting point of the polymer in order to obtain the Young's modulus and thickness unevenness within the range of the present invention. This film may then be heat treated if desired. In this case, the temperature is suitably above the glass transition point of the polymer and below the melting point, and the time is suitably within the range of 0.1 to 120 seconds.

[Function] In the present invention, the thickness unevenness and Young's modulus of the thermotropic liquid crystal polymer film can be made within a specific range by a special film forming method that uses electrical energy, and the synergistic effect of these has increased the excellent effect by 1q. Presumed.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Glass transition point Tg, cold crystallization temperature Tcc, and melting point Measured using a DSC (differential scanning calorimeter) type II manufactured by Perkinelfle. The DSC measurement conditions are as follows. That is, a 10 m sample (] was set in the DSG device,
Incubate the melt for 5 minutes at a temperature above the isotropic transition temperature and quench in liquid nitrogen. This rapidly cooled sample was heated at a rate of 10°C/min,
Detect the glass transition point Tg. The temperature was continued to rise gradually, and the melting point and isotropic transition temperature were measured.

(2) Surface average roughness Ra Measured using a high-precision thin film step measuring device ET-10 manufactured by Koita Research Institute. The conditions were as follows, and the average value of 20 measurements was taken as the value.

・Stylus tip radius: 0.5 μ'n ・Stylus load: 5 mQ ・Measurement length: 1 mm ・Cutoff 1st shift: o, oamm The definition of Ra and average spacing of protrusions sm is, for example,
This is shown in "Measurement and Evaluation Method of Surface Roughness" by J. Nara (Sogo Technological Center, 1983).

(3) Average protrusion height h Two-detector scanning electron microscope [ESM-3200,
■Lionix Co., Ltd. wA] and cross-sectional measuring device [PMS-1]
, ■ manufactured by Lionix Co., Ltd.] with the height of the flat surface of the film set as O. The measured value of the height of the protrusion is sent to an image processing device [I BAS2000, manufactured by Carl Zeiss Co., Ltd. 1, and image processing is performed. Reconstruct the film surface projection image on the device. Next, with this surface protrusion image, the protrusion part is binarized and the area of each protrusion is calculated by 1q, which is equivalent to a circle (￥
Find this and use it as the average diameter of the protrusion. Furthermore, the highest value among the binarized individual protrusions is defined as the height h of the protrusion, and this is determined for each protrusion. This measurement is repeated 500 times at different locations, and the heights of the measured protrusions are determined.

(4) Film thickness unevenness The width direction of the film (length 1.5 m>) was continuously measured using an electronic thickness meter.The difference between the thickness of the thickest part and the thickness of the thinnest part was calculated as the average thickness. This was divided by 100 and multiplied by 100 to obtain the thickness unevenness (%).

(5) V-leg ratio Using an Instron type tensile tester, AST
25° according to the method specified in M-D-882
Measurement was carried out at C165% RH at a tensile speed of 30 o mm for 7 minutes (trial run: 5 Q mm).

(6) Measure the thickness profile of molecular orientation in the longitudinal direction and width direction of the film using the oriented film cross-section Raman method or thin film section method (refractive index, infrared spectroscopy). The case is defined as a longitudinal direction, and the case where the direction is in the longitudinal direction and the width direction is defined as a width direction. For example, in the case of refractive index, the larger the index, the higher the orientation.

(7) Impact resistance (a>according to the method specified in ASTM-D-256,
The Charpy impact strength of the film (unit: KCJ) was measured using a Toyo Seiki Seisakusho Charpy impact tester.
-cm/mm2) measured L/ta. In ASTM, strength is expressed in Kg·cm, but here it is expressed by dividing by the cross-sectional area of the film. This measurement was carried out when the film was set horizontally with the longitudinal direction as the fulcrum and when it was let horizontally with the width direction as the fulcrum, and the arithmetic average value was taken as the impact strength value.

(b) The tear propagation resistance in the longitudinal and width directions of the film was measured using the Elmendorf tear test manufactured by Toyo Seiki Seisakusho at 25°C and 65% RH according to the method specified in Jl5-P-8116. (Unit: C1/mm) was measured, and the arithmetic average value in both directions was taken as the tear propagation resistance.

The above impact strength is 20 or more, and the tear propagation resistance is 10
85 impact resistance when 0 or more: Good, above (a), (b)
If either of these was unsatisfactory, the impact resistance was determined to be poor.

[Effects of the Invention] The present invention uses a special film-forming method to produce a thermotropic liquid crystal polymer film with a specific thickness, uneven thickness, and Young's modulus, so a liquid crystal polymer film with excellent impact resistance can be obtained. be. In general, due to the improved manufacturing method, the thickness of the film is less uneven compared to films made by simultaneous biaxial stretching of molten thermotropic liquid crystal polymer in the molten state, or films made by two-wheel stretching at extremely high temperatures exceeding 200°C. It can be made small and also has advantageous industrial productivity (cost), so it is preferably used for various purposes.

Although the use of the film of the present invention is not particularly limited, it can be used as a base material for magnetic recording media by taking advantage of the characteristics of liquid crystal polymer and its impact resistance. It is particularly useful for thermal transfer ribbons, flexible circuit boards, and packaging.

[Example] The present invention will be explained based on examples.

Examples 1 to 7, Comparative Examples 1 to 5 Several thermotropic liquid crystal polymers were supplied to a melt extruder and melted at 290°C, and these polymers were extruded into a sheet form from a die with varying draft ratios, and
While applying an alternating current electric field of W (frequency 13°56 MH2), the film was wound around a casting drum with a surface temperature of ao'c and cooled and solidified to obtain an unstretched film (Comparative Examples 1 to 5).
produced an unstretched film without applying an electric field). These unstretched films were stretched in the transverse direction using a stenter at a temperature of 120°C. At this time, products using microwave heating (Examples 1 to 7) and comparative examples 1 to 5 without microwave heating were prepared.

The stretching speed was 3000%/min. Furthermore, by changing the discharge rate of the extruder, final films with different thicknesses were produced. The thickness, thickness unevenness, and Young's modulus in the longitudinal direction and width direction of these films are as shown in Table 1. The impact resistance was good, but otherwise a film with good impact resistance could not be obtained. −

Claims (3)

[Claims] (1) A film made of a composition containing a thermotropic liquid crystal polymer as a main component, and the difference in Young's modulus between the longitudinal direction and the width direction (longitudinal direction - width direction) is -500 to 600 kg.
/mm^2, a thickness of 1 to 100 μm, and a thickness unevenness of 20% or less. (2) The liquid crystal polymer film according to claim 1, wherein the surface layer portion of the film is oriented in the longitudinal direction, and the central portion is oriented in the width direction. (3) The liquid crystal polymer film according to claim 1, wherein the thickness ratio of the surface layer portion oriented in the longitudinal direction (surface layer portion thickness/total film thickness) is in the range of 0.01 to 0.7.