JPS6320693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an embossed film of polyethylene terephthalate, and more specifically, the present invention relates to a method for producing an embossed film of polyethylene terephthalate, and more specifically, the present invention relates to a method for producing an embossed film of polyethylene terephthalate. The present invention relates to a method for producing a surface covering material which is embossed with a film surface, has a low reflection of light rays on the film surface, and has a stain prevention function. Embossed polyethylene terephthalate films are used in general industrial applications due to their excellent mechanical properties, thermal stability, and chemical resistance. Furthermore, in recent years, with the rapid development of electronic devices such as microcomputers, embossed films are attracting attention as coating materials for keyboards and other applications, as they have low light reflection on the surface and have the effect of preventing surface stains. . Conventional surface covering materials are mostly made of polyvinyl chloride, which satisfies the demand in terms of quantity because it is easy to process during embossing. In addition, unstretched and uniaxially stretched polyethylene terephthalate films are easier to process, so
There were cases where it was used. However, with these conventional surface coating materials,
It is currently not possible to meet the quality design and required characteristics in various application fields. For example, polyvinyl chloride has the disadvantage that it deteriorates upon curing due to its polymer properties, making it particularly unsuitable for external keyboards. Furthermore, polycarbonate films, for example, have problems in chemical resistance, such as being susceptible to stress cracking. In addition, a technique is known in which fine irregularities are formed on the film surface by sandblasting, but this processed film has fine fibrils and crushed pieces generated on the film surface due to the sandblasting process, so it is dust-free.・It has the disadvantage that oil and other substances are easily adsorbed and the surface is easily soiled. In order to solve the above-mentioned problems of the prior art, the present inventor has made a thorough study of the processing conditions for a single-sided embossed polyester film that has mechanical strength, heat-resistant dimensional stability, shape stability, and stain prevention function. , have discovered the manufacturing method of the present invention. That is, the present invention provides a method for producing a surface covering material in which a biaxially oriented polyester film is preheated to a temperature in the range of glass transition point to melting point and then embossed with an embossing roll. heating the roll to a temperature in the range of 150°C to 230°C; the embossing roll has 450 to 10,000 markings per unit area (cm ² ) on its surface; the height of the markings is 5 to 50 microns; and less than half of the film thickness, and 0.1≦D/W between the diameter or diagonal length (D) of the convex part and the length (W) of the concave part in the shape of the concave part and the convex part. This is a method for producing a surface covering material characterized by a relationship of ≦1.5. The present invention will be explained. The polyester used in the present invention is a homopolymer or copolymer containing at least 85 mole % of ethylene terephthalate units. Other examples include polypropylene terephthalate, polybutylene terephthalate, and polybutylene naphthalene dicarboxylate. Polyethylene terephthalate and polyethylene naphthalene dicarboxylate are preferred polymer films from the viewpoint of practicality, crystallinity, and melting point. To emboss polyester film, the film thickness must be 50μ (microns) or more.
A thickness of about 250μ is preferable. Films that are too thin tend to be difficult to emboss with a stable shape, and films that are too thick tend to be difficult to emboss. A biaxially oriented polyester film can be obtained by a known manufacturing method. For example, chips or pellets of polyethylene terephthalate with an intrinsic viscosity of about 0.5 to 0.8 are dried at a temperature of about 170°C for several hours, then melted in a melt extruder and made into a T-die (I-die).
The film is extruded into a thin sheet through a cooling drum, and rapidly cooled and solidified on the surface of a cooling drum to obtain an unstretched cast film. Next, this unstretched film is stretched 2 to 5 times in the machine direction (longitudinal direction) at a temperature of about 80°C to 100°C, and further stretched 2 to 4.5 times in the width direction at a temperature difference of about 90°C to 110°C. If necessary, heat setting is performed at a temperature in the range of 200° C. to 230° C. for about 3 seconds to 5 seconds in order to improve thermal dimensional stability. The polyethylene terephthalate film thus obtained having a density of about 1.385 to 1.40 g/cm ³ is a preferred biaxially oriented polyester film applicable to the present invention. In the above film manufacturing method, biaxial stretching can be carried out simultaneously in the longitudinal direction and the sub-direction, or it is also possible to stretch the film in the width direction first and then stretch it in the longitudinal direction. Of course, it is also possible to apply three or several steps of stretching in the longitudinal direction and the width direction, and this corresponds to a biaxially oriented film that can be applied to the present invention. The embossing process for film is as follows: (a) The film is preheated and shaped using an embossing roll that is not actively heated; (b) The film is not actively heated and only the embossing roll is used to heat the film. A method in which the film is heated to a plasticizing temperature and shaped while being heated and pressed; (c) a method in which both the film and the embossing roll are heated is assumed. In the present invention, the above condition (c) is selected,
There is an advantage that embossed shapes with stable shape can be obtained. In the present invention, the preheating temperature of the film is in the range of glass transition point (Tg) + 30°C to melting point (Tm) -10°C, preferably Tg + 80°C to Tm.
-20℃ range, more preferably Tg+110℃~Tm
-30℃ range can be selected. Also, the temperature of the embossing roll is in the range of 150℃ to 230℃, preferably
Keep the temperature between 180℃ and 220℃. In actual embossing, the biaxially oriented film is preheated to a temperature in the range of Tg+30°C to Tm-30°C (100°C to 230°C in the case of polyethylene terephthalate). In this preheated state, the biaxially oriented polyethylene terephthalate film is plasticized and has the property of being easily shaped, and is engraved according to the embossed uneven pattern on the surface of the embossing roll. The embossing roll used in the present invention has a specific uneven pattern on the roll surface.
Since this embossing roll imparts minute unevenness changes in the thickness direction of the film, the depth of the unevenness and the distribution density (frequency) of the unevenness are important. If the depth (height) due to the unevenness of the film surface is too large, the diffused reflection of light rays will be significant and the film will become unsuitable as a surface coating material. Of course, if the surface unevenness is shallow and has almost no depth, it will not be satisfactory as a coating material because the surface will not have the effect of preventing light reflection. The depth of the unevenness of the single-sided embossed metal roll for thick film used here is about 5 to 50 microns, and preferably the embossing depth is about 10 to 30 microns is more effective. Generally, when the film is thin, the embossing depth needs to be reduced in accordance with the thickness of the film. For films less than 100μ,
The embossing depth needs to be 1/2 or less of the film thickness. When extremely deep embossing is applied to a thin film, there is a risk that the film will be locally excessively deformed, resulting in a loss of mechanical strength and the formation of local damage or holes. Therefore, the embossing depth is 5 to 50μ within 1/2 of the film thickness.
It is best to choose one. Next, if the distribution density of the unevenness on the surface of the embossing roll is not appropriate, it will reflect light or become opaque, making it unsuitable for use as a surface covering material for keyboards, etc. As a result of various studies to eliminate these drawbacks, it has been found that the appropriate density range for the unevenness is 450 pieces/cm ² to 10,000 pieces/cm ² . Preferably 2000 pieces/ ^cm2
~6000 pieces/ ^cm2 . The embossed pattern may be shaped like crushed ice cubes or may be a regular grain pattern. Since a large number of fine patterns are engraved on the embossing roll, it is easier to roll the roll if it is regular. Examples of regular patterns include circles (dots), hexagons, and squares. If the length of the diagonal line (longest side/diameter) of the embossed part is D, and the interval between the boundaries is W, then if the stamp is engraved to satisfy the condition of 0.1≦D/W≦1.5,
The embossed film has good light reflectivity when used as a keyboard. As an embossing roll, it has the ability to heat up to 150°C to 230°C, and when marking the surface, it has the following characteristics: emboss depth (h), unevenness frequency (N), diameter of embossed part or diagonal length (D), emboss The distance between the boundary (W) and the adjacent embossing and the film thickness t is 450 pieces/cm ² ≦N≦10,000 pieces/cm ² 2h≦t (unit: μ) 5≦h≦50 0.1 It can be said that those satisfying the relationship ≦D/W≦1.5 can be used in the present invention. As explained above, a significant improvement in the present invention is that by using a biaxially stretched heat-set film, both thermal stability and mechanical properties are sufficiently maintained. Another important improvement for surface coatings is planarity. By using a biaxially stretched heat-setting film as in the present invention, it is possible to minimize the deterioration in flatness that occurs during embossing. Note that dirt is a problem with surface covering materials such as keyboards, so an antistatic agent is applied to the surface of the biaxially stretched film, and then embossed to give the surface material an antistatic effect and stain resistance. It can also have an effect on sex. According to the present invention, a surface covering material having a delicate ability to prevent reflection of light rays such as a keyboard can be obtained. According to the present invention, even biaxially oriented and heat-set polyester films can be easily embossed. Further, the present invention is also applicable to cases where the film forming, stretching and embossing steps are carried out in an integrated manner. This will be further explained below with reference to Examples. Example 1 It is more effective to perform embossing at a high temperature, but on the other hand, the higher the temperature, the greater the risk of deteriorating the flatness. Also, the depth of the unevenness,
The flatness is also affected by the distribution density, etc., and mutually optimal regions are determined. The embossing machine used had a roll for the embossing section with a diameter of 100 mm and a width of 300 mm, and a back-up roll (paper roll) with a diameter of 200 mm.
The film was 300 mm wide and processed at a film running speed of 5 m/min. Roll pressure is 70Kg/cm ² G~90Kg/
cm ² G treatment. Film for embossing
The film is a 194μ biaxially stretched heat-set polyethylene terephthalate film, and the temperature of the film immediately before embossing treatment was examined from room temperature to 220°C, but was preferably about 150°C to 200°C. The temperature of the embossing roll was also examined from 10°C to 210°C, but the optimum temperature range for the embossing roll was 150°C to 200°C. As a result of testing under these various conditions, deeper embossing was possible when both the film temperature and the embossing roll temperature were higher;
It was found that flatness deteriorates when the temperature exceeds 200°C. In addition, as the processing temperature increases, the tension during processing also becomes a problem; if the tension is too low, wrinkles are likely to appear and the flatness is impaired, but even when the film temperature is high, the tension of the film is relatively low. The higher the thickness, the better the flatness. Example 2 A stretched film of 194 μm of polyethylene terephthalate was prepared by a conventional sequential biaxial stretching method, and then heat-set at 220° C. for 5 seconds. The above sequentially biaxially stretched heat-set film was used and further heated with an infrared heater to bring the film surface temperature to 200°C. The surface of the embossing roll was also measured at 200°C using a contact type surface thermometer. The film was fed between an embossing roll and a back-up roll at a speed of 5 m/min and subjected to embossing heat treatment. The pressure between the rolls at this time is 80Kg/cm ² G
It was hot. The test results are shown in Table 1. Comparative Example 1 Embossing was carried out on a biaxially stretched heat-set film at an embossing roll temperature of 60°C. At this time, the pressure between the rolls was examined up to a maximum of 90 kg/cm ² G.
The temperature of the treated film immediately before embossing was 200°C. The results are shown in Table 1. Comparative Example 2 The biaxially stretched heat-set film was not heated with an infrared heater, but the temperature of the embossing roll was
The temperature was raised to 200℃. Roll pressure during embossing process
It was set to 90Kg/cm ² G. The results are shown in Table 1. Comparative Example 3 A biaxially stretched heat-set film was heated with an infrared heater, and the embossing roll was cooled, so that the surface temperature of the roll was 10°C. At this time as well, the pressure between the rolls was applied at the maximum of 90 kg/cm ² G. Results first
Shown in the table. 【table】

Claims (1)

[Claims] 1. In a method for producing a surface covering material in which a biaxially oriented polyester film is preheated to a temperature in the range of glass transition point or melting point and embossed with an embossing roll, The embossing roll is heated to a temperature in the range of 150°C to 230°C, the embossing roll has 450 to 10,000 markings per unit area (cm ² ) on its surface, and the height of the uneven markings is 5 to 50°. micron and less than half the film thickness, and the difference between the diameter or diagonal length (D) of the convex part and the length (W) of the concave part in the shape of the concave part and the convex part is 0.1
A method for producing a surface covering material, characterized in that there is a relationship of ≦D/W≦1.5. 2. The method for producing a surface covering material according to claim 1, wherein the polyester is polyethylene terephthalate. 3 The number of protrusions on the surface of the embossing roll is 2000 or more.
2. The method for producing a surface covering material according to claim 1, which uses an embossing roll with an embossing roll of 6000 embossing rolls/cm ² .