JPH01131550A - Production of polyester film - Google Patents

Abstract

PURPOSE:To improve handleability of a photographic sensitive material constituted of a base consisting of a polyester film when the photographic sensitive material is used by cutting into sheets by prepg. the polyester film at drawing temps. different for the front side and the rear side of the film. CONSTITUTION:When polyester film is drawn after casting with a specified draw ratio in the longitudinal direction, the curl of the film generated during film-drawing is controlled after straightening habitual curl of the film by changing the drawing temp. of the film for the front side from the drawing temp. for the rear side of the film with an auxiliary heating means 5 such as infrared heater, etc., installed to one or both sides of the film. By this method, the curl of the film generated during drawing of polyester film is controlled simply and effectively, and the handleability of a photosensitive material comprising the film for a base body when it is used by cutting into sheets is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to photographic materials, particularly Rendden photographic films,
The present invention relates to a method for producing a polyester film having curling properties suitable for use in photographic materials used in sheet form, such as microfilm and lithographic film.

(Prior Art) Polyester films are widely used as supports for photographic materials, magnetic recording materials, packaging materials, electrical insulating materials, etc. because of their excellent mechanical, physical, and chemical properties.

Curling of the film is an important quality to consider when using polyester film as a support for photographic materials.6 There are two types of curls that can cause problems: curling curls that occur when the film is wound into a roll; There are two types of film forming curls that are formed in the film forming process.

Among the many plastic films used, polyester film has a rigid molecular chain, and since it is stretched, it is prone to curling, and this kind of curling becomes a problem in applications where it is used exclusively in a roll form. On the other hand, some photographic materials are used in sheet form. Typical examples include Rendden photographic film, microfilm, and lithium film. When a polyester film is used as a support and a photosensitive film is applied thereon, it is usually in a roll state, but is then cut to a required size and stored in a sheet state.

When this is used, film forming curls formed during the film forming process pose a problem in handling such as exposure and development.

In other words, the curl itself gradually eases after it is cut into a sheet from the rolled state, and eventually, although some permanent deformation remains, the film formation originally possessed by polyester film is reduced. Curls become noticeable. Therefore, in the photosensitive materials for the above-mentioned purposes that are used in sheet form, the problematic curls appear after the curls have recovered! ! ! membrane curl,
It has a great impact on the quality of the product, such as its processing properties and stackability.

Conventionally, curling has been mainly investigated, and for example, Japanese Patent Laid-Open No. 54-56817 proposes a method of processing a film by controlling the temperature and humidity within a specific range.

Furthermore, Japanese Patent Publication No. 57-28336 indicates that water permeability can be improved by blending a specific copolymer component into polyester; however, according to the research of the present inventor, such a method can be improved. It is known that modification can also have the effect of alleviating curling during development processing.

However, there are few reported examples of methods for controlling film curl itself;
No. 582 discloses a method of blowing hot air onto the film surface, and JP-A No. 51-131577 discloses a method of manufacturing polyester films of the same type with different intrinsic viscosities and controlling curl by the difference in shrinkage between the front and back sides during heat treatment in a post-process. A method is only proposed.

Although these methods can be expected to have certain effects, they all require large-scale equipment modification, and are insufficient to simply and effectively control curl.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the limitations of the prior art described above.
The purpose is to simply and effectively control the film curl that is formed during the film production of polyester film, and to further improve the handling properties when photosensitive materials using this film as a support are cut into sheets and used. be.

(Another Means to Solve the Problems) This object is achieved by a method for producing a polyester film characterized in that the stretching temperatures on the front and back sides are different.

Specifically, for example, when stretching at a specific magnification in the longitudinal direction after casting, an auxiliary heating means such as an infrared heater is provided on one side or both sides, and the stretching temperature on the front and back sides is changed, so that the curls will appear after recovery. Huntrol the Teguru film curl.

FIG. 1 shows a side view of a longitudinal stretching zone of a polyester film constructed according to the present invention.

After the film 1 after casting is heated by the longitudinal stretching rows 22.3, it passes through cooling rollers 4 and is sent to a transverse stretching zone (not shown). An infrared heater 5 is provided immediately after the stretching roller 3. Moreover, with this configuration, curling can be effectively controlled by keeping the temperature difference between the front and back sides immediately after the infrared heater in the range of 10 to 25°C.

It is believed that the curl control mechanism XA of the third aspect of the present invention is caused by the fact that if the crystallinity and orientation of the front and back sides of the film are different, the volume shrinkage rate during the heat treatment process will be different.

(Function) Although the film forming process is not particularly limited, a case of sequential biaxial stretching in which the film is stretched at a specific magnification in the longitudinal direction after casting and further stretched in the transverse direction using a tenter will be described as a suitable example for the present invention.

In terms of the process, crystallization occurs throughout the entire process from casting to longitudinal and transverse stretching, so the step of imparting a difference in crystallinity between the front and back surfaces is carried out at any time during casting, longitudinal stretching, and transverse stretching. It is conceivable that the settings can be set over multiple steps.

At the time of casting, the film thickness is the thickest, ′&
It has the advantage of making it easy to create a difference in hardness between the front and back sides, but depending on the conditions, it can cause microcrystals to grow, making the film unsuitable as a photographic support due to its optical and mechanical properties, and the resulting difference in crystallinity. Since this appears as a difference in isothermal crystallinity, the crystals are destroyed during the subsequent stretching process, making it impossible to control curling.

On the other hand, the difference in crystallinity that occurs during the stretching process appears as a difference in the orientation crystallinity, so it is difficult to destroy, and the stretching section is usually equipped with means for heating and cooling, so auxiliary heating means are not required. Since it is easy to add, it is suitable to apply the method of the present invention in the stretching process.

Furthermore, when comparing the longitudinal stretching process and the m-stretching process, the area of the film is several times larger in the latter, and the necessary equipment modification is inevitably larger.

Therefore, in the step of sequential biaxial stretching as described above,
It is optimal to impart a difference in crystallinity between the front and back sides of the longitudinally stretched Li.

(Example) After melt-extruding a polyester chip with an intrinsic viscosity of 0.65, it was stretched 3.4 times in the longitudinal direction and 4 times in the transverse direction,
9 biaxially stretched polyester films with a thickness of 175μ
When producing one film, an infrared heater was installed as an auxiliary heating source on one side of the #1 drawing zone (in this example, the side in contact with the casting drum during casting: hereinafter referred to as the CD side) as shown in FIG.

The temperature of the film 1 on the stretching roller 3 is, for example, about 77°C.
When the infrared heater voltage was 190 V, the surface temperature on the CD side was about 96°C. At the exit of the longitudinal stretching zone, the temperature difference between the front and back sides was approximately 2°C. Figure 612 shows the relationship between the infrared heater voltage and the curl value after film formation, and Figure 3 shows the relationship between the infrared heater voltage and the curl value after film formation. The relationship with the curl value after applying the gelatin film is shown. Curl measurement is
The samples were left at 23° C. and 81160% for at least 3 hours, cut into sheets of a certain size, half of the area was fixed on a flat surface, and the bending of the remaining free end was measured. 1
3 and 4 show that by changing the infrared heater voltage, curling of the film after film formation and after application of gelatin film can be controlled.

The tjS4 diagram shows the measurement results of the density on the front and back sides of the film after R stretching for infrared heater voltages of 170 V and 190 V, respectively. N, C, and S on the horizontal axis in the figure are film 1
indicates the position in the width direction, N is one end, C is the center,
S indicates the other end. The density of the surface opposite to the CD surface heated by the infrared heater 5 (hereinafter referred to as the "anti-CD surface") is increased, and this is noticeable when the infrared heater voltage is high.

Figure 5 also shows the infrared heater voltage of 170V and 190V.
The X#X diffraction patterns of the front and back surfaces of the film after longitudinal stretching are shown in FIG. The horizontal axis of the figure shows the diffraction angle, and the vertical axis shows the diffraction intensity. The steeper the peak of the diffraction intensity, the higher the degree of orientation. From the results in Figure 5, the degree of orientation is high on the anti-CD surface opposite to the surface heated by the infrared heater 5, and when the infrared heater voltage is high, it is g-type, and the density results in Figure 4 corresponds well with

As mentioned above, the degree of crystallinity and orientation on the anti-CO side differs depending on the degree of temperature rise on the CD surface, which is reflected in the difference in density and vxea diffraction pattern. It can be seen that this controls the curling of the film after gelatin film application.

(Effects) As described above, according to the present invention, with a slight equipment modification,
The curl of the polyester film can be effectively controlled, and the handling properties are further improved when the photographic material made using the polyester film obtained according to the present invention is cut into sheets. is obtained.

In the above example, in the step of in-shell sequential biaxial stretching [
Although it has been shown that it is preferable to provide a temperature difference between the front and back sides during stretching, in the case of other configurations such as -axial stretching or simultaneous biaxial stretching, it is preferable to provide a temperature difference between the front and back bases during the stretching process. A similar effect can be obtained.

The polyester in the present invention is preferably a thermoplastic polyalkylene terephthalate, which is called an aromatic polyester in the shell, and polyethylene terephthalate is a typical example.

Of course, it is also possible to mix in other polyesters or copolymer components such as 7-talate, 1,4-cyclohexanomethanol, etc., and there is no particular limitation.

Furthermore, as a means for imparting slipperiness, it is possible to contain a non-filler or to apply a white film suitable for use as high-grade photographic paper.

Further, there are no particular limitations on the application, and the present invention is effective for products used in sheet form, for example, for 70-tube discs that require flatness. Furthermore, the curl can be controlled to some extent by emphasizing the curl at the time of 91 film on the opposite side to the winding direction.

[Brief explanation of the drawing]

FIG. 1 shows a side view of a longitudinal stretching zone according to the invention. Figure 2 shows the relationship between the infrared heater voltage and the curl after ui, and Figure F53 shows the relationship between the infrared heater voltage and the curl after gelatin film coating. Figure 14 shows the density difference between the front and back sides of the film, and Figure 5 shows the same <xi
Each shows the difference in diffraction patterns. 1...Film 2.3...Longitudinal stretching roller 4...Cooling roller 5...Infrared heater patent jaw person '''Screaming floor'C filter l,・'p Co., Ltd.
＋toten・)饗←gae1guθ−→l

Claims (1)

[Claims] A method for producing a polyester film characterized by having a difference in stretching temperature between the front and back sides.