JPS5818222B2 - Polyester film for plate making and drafting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film for plate making and drafting.

Biaxially stretched polyester films, represented by polyethylene terephthalate, have excellent properties such as mechanical properties, electrical properties, chemical resistance, dimensional stability, and transparency, and are widely used in various fields. There is.

In this field, it is required to have high transparency and be able to uniformly process the surface, such as tracing films, trafting films, base films for transparent diazo second original photosensitive paper, and films for overhead glossiers. There are many uses for the film, such as so-called plate making and drafting.

These films have a thickness of 38 to 100μ.
The most commonly used are those of degree.

These films first of all have a high degree of transparency,
Strictly speaking, high light transmittance is required from the ultraviolet region to the visible region.

On the other hand, in the case of this base film and the product film obtained by processing the base film according to the specific use, in order to ensure sufficient handling workability and secondary processability, the film must be (i.e., a low coefficient of dynamic friction).

To achieve this, particles precipitated within the polyethylene terephthalate polymerization system (internal particles) or particles added from the outside (external particles) are dispersed in a polyethylene terephthalate matrix and stretched appropriately.
A method of providing protrusions on the surface of the film is usually used.

However, if chewing particles are mixed in polyethylene terephthalate, there may be a large number of particularly large particles (in which case, when light rays ranging from ultraviolet to visible range are applied, protrusions formed on the film surface or particles themselves inside the film) Due to the voids generated around the particles by stretching, the amount of light scattering becomes relatively large, resulting in a decrease in light transmittance.

It is extremely difficult to maintain such a high degree of transparency and to provide sufficient handling and workability for the base film and the product film obtained from it, and research is still being continued today.

The following methods have been considered so far:

(1) A method of extremely reducing the amount of particles blended. In this case, a high degree of transparency is achieved, but the film surface becomes extremely smooth and the coefficient of friction becomes thick (which results in a thicker base film and product film). Handling workability etc. deteriorates.

(2) A method in which particles with fine particle diameters are mixed as internal particles or external particles. In this case, the transparency of the film is achieved to a certain extent and the friction coefficient is also appropriate to the extent that it is possible, but as will be described later, it is possible to Another problem arises when winding up.

(3) A method in which a large amount of particles with large particle diameters are mixed as external particles or internal particles. In this case, there is no problem in handling the film, but the transparency is significantly deteriorated.

As mentioned above, relatively good results are obtained in case (2), except for case (3) (and polyethylene tele).

After forming a phthalate film, when it is rolled up into a roll, "pimple-like protrusions" occur on the lower part (near the core) of the rolled up roll. Problems such as the coating layer not adhering to the surface of the film occur, and not only does it impair the flatness of the product film, but it also significantly reduces the product value.

Acne-like protrusions are often 2 to 3 mm in height and 2 to 3 U in diameter, but those that can be easily identified with the naked eye (approximately 0.5 mm in height and diameter) have a negative impact on quality. affect

However, in the past, defects caused by the occurrence of "acne-like protuberances" have not been considered (therefore, no suitable preventive measures have been proposed).

In view of this situation, the present inventors have developed
After repeated investigations into the essence of ``acne-like protrusions,'' we found that the occurrence of ``acne-like protrusions'' depends on the distribution of protrusions on the film surface formed by the blended particles, and more specifically, it affects the height, number, and distribution of protrusions on the film surface. By using specific particles and appropriately adjusting the amount of addition and the surface protrusions formed thereby, we aim to suppress "acne-like protrusions" as much as possible or virtually eliminate them. It was also found that a film with good transparency and handling workability could be obtained.

That is, the present invention minimizes or substantially eliminates the occurrence of "acne-like protrusions" that occur on the film surface, especially the film surface of the lower part of the roll, when the polyester film is wound into a roll. The purpose of the present invention is to provide a biaxially oriented polyester film that improves handling workability and secondary processability after manufacturing, and also maintains sufficient light transmittance required for plate making and drafting applications. , the gist of which is a biaxially oriented polyethylene terephthalate film with a thickness of 30μ or more and 200μ or less, in which particles of an inert substance are evenly dispersed and mixed, and the film has an internal haze of 25μ. 2% or less in terms of thickness, and the number of protrusions on the film surface measured by multiple interference method at a measurement wavelength of 0.54μ is 25 to 130 protrusions showing secondary interference fringes/-3 The number of protrusions exhibiting the following interference fringes: 5 to 30/- The number of protrusions exhibiting fourth-order interference fringes: 1 to 15/- The polyester film for plate making and drafting has a range of 1 to 15 protrusions/-.

The present invention will be explained in detail below.

In the present invention, polyethylene terephthalate as a film material includes, in addition to polyethylene terephthalate homopolymer, a copolymer containing ethylene terephthalate units as a main component, for example, 70% or more, or a blend product containing these as a main component. It is inclusive.

Particles of an inert substance are then mixed into these polyesters and uniformly dispersed.

These particles have an affinity for polyester, are difficult to form voids during the stretching process, and when made into a stretched film, it is necessary to precisely control the surface protrusions of the film, so particles whose size can be easily controlled are preferred. Preferably, the shape is close to spherical.

Specifically, typical examples include particles of amorphous silica, phosphorus compounds of calcium terephthalate, calcium phosphate, and the like.

A mixture of two or more types may also be used.

Those with flat particles, such as kaolin, are generally not preferred, and those with poor affinity for polyethylene terephthalate, such as calcium terephthalate, are also not preferred.

Conventionally, there are two types of particles used for the purpose of imparting slipperiness to polyethylene terephthalate: precipitated particles, which are precipitated by a reaction within the polymerization system, and additive particles, which are produced outside the polymerization system. The former is not suitable for the film of the present invention because the particle size varies depending on the polymerization conditions, the particles are easily broken, and voids are easily generated. Additive particles must be used.

Based on the above basic concept, the type of additive particles, their particle size, particle size distribution, and amount added are selected so as to meet the film internal haze and film surface protrusion conditions that are the requirements of the present invention.

Commercially available particles may also be used as the additive particles, and pulverization and classification may be combined as appropriate.

The above selection is made so that the film of the present invention has an internal haze of less than 1% when converted to a thickness of 25μ.

If the value exceeds this value, the transparency becomes poor. For this reason, the amount of particles added is generally in the range of 0.01 to 0.10% by weight, preferably 0.03 to 0.06% by weight, based on the polyethylene terephthalate constituting the film.

Generally speaking, if the amount added is less than this range, "acne-like protrusions" will occur, while if it is more than this range, the transparency will deteriorate and the appearance will be poor.

In addition, if the film thickness is 100μ or more, 25μ
It is preferable that the internal haze in terms of thickness is 1.5% or less.

In the film of the present invention, while maintaining the above condition range, the film surface is further measured by multiple interference method, and the type and average particle diameter of the added particles and the amount added are selected so that the number of protrusions falls within the following range.

Number of protrusions with second-order interference fringes: 25 to 130/- Number of protrusions with third-order interference fringes: 5 to 30/- Number of protrusions with fourth-order interference fringes: 1 to 15/- Thus, substantially no protrusions having fifth-order or higher interference fringes are present.

This measured value is a value when the measurement wavelength is 0.54μ.

In addition, this measurement is performed using a finishing microscope, and the measurement wave length is a half wavelength (i.e., λ - 0.27μ) of the measurement wave length λ) (λ = 0.54μ in the above case).
Interference fringes appear every time, and the nth order interference fringes appear at a height of λ/2×n (so, to show this concretely, the second order interference fringes appear at a height of approximately 0.5μ, the third order interference fringes appear at a height of λ/2×n). The interference fringe has a height of approximately 0.8μ, the fourth-order interference fringe has a height of approximately 1.1μ, and the fifth-order interference fringe has a height of approximately 1.4μ.

Therefore, the height of the protrusion having secondary interference fringes is approximately 0.5μ or more, but does not reach approximately 0.8μ.

In this way, measurements are taken using a microscope, and the number of second-order objects, as well as the number of third-order and fourth-order objects, is counted.

If the number of protrusions of the order of magnitude on the film surface measured in this manner is less than the lower limit of the range characterized by the present invention specified above, the workability is poor, and when the film is wound into a roll, "pimple-like protrusions" are formed. ” occurs.

On the other hand, when the number of protrusions exceeds the upper limit of each of the above ranges in each order, the transparency becomes poor.

Thus, the light transmittance of the film of the present invention is within the following range for a film having a thickness of 75 μm.

Light wavelength transmittance 400 mμ to 600 mμ 75% or more 700 mμ 85% or more Next, methods for measuring and evaluating the physical properties of the film of the present invention will be explained.

(1) Internal haze (Ho): Apply liquid paraffin to both surfaces of the film to be measured,
The value is measured using a commercially available haze meter (according to JISK-6714), and the thickness is 25 μm in proportion.

(2) Number of protrusions on the film surface by multiple interference method: Aluminum is deposited on the film surface, interference fringes are produced at the measurement wavelength (0.54μ) using multiple interference method, and the interference fringes are photographed.
For an imaging area of 2.34-, the interference fringes of orders higher than 2 are counted and converted into units of -.

Measuring instrument: Made by Nippon Kogaku ■, Surfice Finish Microscope mirror reflectance: 65% Microscope magnification: 200x (3) Light transmittance measurement method: Continuously measure light transmittance from 400 mμ to 800 mμ by changing the spectroscopic needle was measured.

Measuring instrument; manufactured by Shimadzu Corporation, spectrally variable needle Double beam type UV-200 Light source: tungsten lamp Note that the wavelength calibration was based on ASTM E-308.

(4) Determining the frequency of occurrence of "acne-like protrusions": presence or absence and frequency of occurrence of "acne-like protrusions" when rolling up several types of target films into a roll with a hardness that does not cause misalignment. Observe.

After winding, the roll is cut open and the presence or absence and frequency of acne-like protrusions are observed.

(Those that can be easily identified with the naked eye are called "acne-like protrusions."

) (5) Coefficient of Dynamic Friction: One film placed on a flat surface was wrapped around a core with a radius of 4 mytt and the other film was pressed against it, the pressure contact width (contact width) of both films was 12 mvt, the pressure contact load was 301, and the relative movement was The dynamic friction force F(y) was measured at a speed of 40 mm/min, and F
/30 was taken as the coefficient of dynamic friction.

This measured value represents the slipperiness and is practically 0.5
If it is below, I can be satisfied.

Next, Examples and Comparative Examples will be explained. The inert material particles used in these examples are commercially available and in-house produced particles, and large particles were crushed using a crusher (Aeroplex 200AS). However, small particles were classified as they were (using a Microplex classifier) and adjusted to the desired particle size.

A Coulter Counter (manufactured by Nihon Kagaku Kikai Co., Ltd.) was used to measure the particle size distribution.

The average particle diameter of the particles used was equivalent to a cumulative weight fraction of 5 when converted to an isostatic sphere.
It is represented by the particle size (d50) when it becomes 0%, and the respective particle size distributions are as follows.

d25 and d75 each have a cumulative quantity ratio of 25%,
This is the particle size when it becomes 75%.

Example l 300 ppm of calcium oxide was added as a catalyst to a mixture of ethylene glycol and dimethyl terephthalate,
Particles with an average particle size of 1.26μ obtained by heating to perform a transesterification reaction and then classifying commercially available amorphous silica [amorphous silica (B) listed in Table 1] 0.05% by weight was added, and further 300 ppm of antimony trioxide and 370 ppm of phosphorous acid were added to conduct a polycondensation reaction, [η)=
0.66 polyethylene terephthalate was obtained.

Dry this polyethylene terephthalate at 180°C,
The mixture was melt-extruded at 290°C and rapidly solidified on a Kixteig drum maintained at 70°C to obtain a quenched sheet with a thickness of 870μ.

This sheet was stretched 3.3 times in the longitudinal direction at a temperature of 95°C.
The film was then sequentially stretched 3.3 times in the transverse direction at a temperature of 110°C and heat-set at 230°C for 2 seconds to obtain a biaxially stretched film with a thickness of 75μ suitable for plate making and drafting.

The properties of this film are shown in Table 2.

Example 2 Instead of adding a classified amorphous silica product with an average particle size of 1.26 μm in Example 1, a classified amorphous silica product with an average particle size of 1.50 μm [amorphous silica powder listed in Table 1] was added to 0.00 μm. A biaxially stretched film with a thickness of 75 μm was obtained in the same manner as in Example 1, except that 0.4% by weight was added.

The properties of this film are shown in Table 2.

Comparative Example 1 Instead of adding classified amorphous silica with an average particle size of 1.26μ in Example 1, 0.023% by weight of a classified kaolin product with an average particle size of 1.1μ [listed in Table 1] was added. Except for this, a biaxially stretched film having a thickness of 75 μm was obtained in the same manner as in Example 1.

The properties of this film are shown in Table 2.

Comparative Example 2 Instead of adding a classified amorphous silica with an average particle size of 1.26 μ in Example 1, a classified amorphous silica with an average particle size of 1.8 μ [amorphous silica (C) listed in Table 1] was added. The thickness was 75 μm in the same manner as in Example 1 except that 0.06% by weight was added.
A biaxially stretched film was obtained.

The properties of this film are shown in Table 2.

Example 3 Instead of adding the amorphous silica classified product with an average particle size of 1.26μ in Example 1, 0.06 weight of a crushed and classified calcium terephthalate product (listed in Table 1) with an average particle size of 1.8μ was added. % and reacted with a phosphorus compound in the polymerization tank (it is thought that the particle size etc. will not change substantially), and the rest is as in Example 1.
A film with a thickness of 75 μm was obtained in the same manner as above.

The properties of this film are shown in Table 2.

Comparative Example 3 Instead of adding the amorphous silica classified product with an average particle size of 1.26μ in Example 1, 0.06% by weight of a crushed and classified calcium terephthalate product (listed in Table 1) with an average particle size of 1.8μ was added. A film with a thickness of 75 μm was obtained in the same manner as in Example 1.

The properties of this film are shown in Table 2.

In addition, in the above table, handling workability is evaluated by winding workability.
Comprehensive judgment was made by observing winding misalignment, wrinkles, tension hunting, etc. when winding into a roll.

As is clear from the above table, in Comparative Example 1, the number of protrusions on the film surface was small in all of the second to fourth orders (the physical properties of the film were that "acne-like protrusions" were significantly generated, and the coefficient of dynamic friction and handling workability were poor.

The film of Comparative Example 2 had too many surface protrusions in both 2nd and 4th order, had a large internal haze, and had poor light transmittance, ie, transparency, as physical properties.

In addition, compared to Example 3, the film of Comparative Example 3 has a high affinity with polyethylene terephthalate, although the average particle size and particle size distribution are the same, with the only difference being that the additive particles are not reacted with the phosphorus compound. is low, the internal haze value is high and the light transmittance is poor.

The explanations and examples given above are for the purpose of helping the understanding of the present invention, and the present invention is not limited by these examples (other changes and modifications may be made within the spirit of the invention). It is something that can be done.

Claims (1)

[Scope of Claims] 1. A biaxially oriented polyethylene terephthalate film having a thickness of 30μ or more and 200μ or less, in which particles of an inert substance are uniformly dispersed and mixed, and the film has an internal haze of 25μ. 2% or less in terms of thickness, and the number of protrusions on the film surface measured by multiple interference method at a measurement wavelength of 0.54μ is 25 to 130 protrusions showing secondary interference fringes/Va 3 The number of protrusions exhibiting the following interference fringes: 5 to 30 pieces/m4 The polyester film for plate making and drafting has a number of protrusions exhibiting the 4th order interference fringes: 1 to 15 pieces/-.