GB2374311A

GB2374311A - Method of producing film with through holes

Info

Publication number: GB2374311A
Application number: GB0217501A
Authority: GB
Inventors: Minoru Suzuki
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1997-09-30
Filing date: 1998-09-30
Publication date: 2002-10-16
Anticipated expiration: 2018-09-30
Also published as: GB0217501D0; GB2374311B

Abstract

A method is provided of producing a film (300) made of shape memory resin. Through-holes (305) are punched in the film. Then, the film is heated to a temperature above the shape-providing temperature of the shape memory resin and stretched in at least one direction parallel to a surface of the film, in a state the film is heated to a temperature above the shape-providing temperature of the shape memory resin. The through-holes thus formed are inclined from between a direction of thickness of said film to a direction of stretching. The film may be used in an ink transfer printer.

Description

METHOD OF PRODUCING FILM WITH THROUGH-HOLES This invention relates to a method of producing a film with through-holes.

Generally, such film is made of a plastic film. A punching machine is used to form through-holes in the film.

The punching machine is arranged to pierce the film with needles. In order to improve the accuracy of dimensions (such as diameters and pitches) of the through-holes, it is necessary to improve an operation accuracy of the punching machine. However, such improvement of the punching machine may increase the production cost of the film.

Accordingly, there is a strong demand for a method of producing a film with through-holes which achieves a high accuracy of the dimensions of the through-holes, without increasing the production cost of the film.

Further, it is difficult to produce a film with through-holes whose inclination angles (from a direction of a thickness of the film) are relatively large. This is

because, when the film is pierced with a needle in an inclined direction, the film tends to be bent.

Accordingly, there is a strong demand for a method of producing a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large.

It is therefore an object of the present invention to provide a method of producing a film with through-holes, in which a high accuracy of dimensions of the through-holes is sought without increasing the production cost of the film.

Further, it is another object of the present invention to prvde a method of producing a film with through-holes, in which inclination angles (from a direction of a thickness, of the film) are sought to be relatively large.

According to an aspect of the present invention, there is provided a method including the steps of (1) stretching the film in at least one direction in parallel to a surface of the film, (2) forming through-holes in the film in a state the film is stretched, and (3) terminating the stretching of the film after the through-holes are formed.

After the stretching is terminated, dimensions of the film in the stretching direction decrease. Thus, error of

dimensions (such as diameters and pitches) of the through- holes of the film also decrease. As a result, the accuracy of the dimensions of the through-holes is improved, without improving an operation accuracy (of a punching machine or the like) in the through-hole-forming step. Consequently, it is possible to provide a high accuracy of the dimensions of the through-holes of the film, without increasing the producing cost of the film.

In the through-hole-forming step, it is preferred to form the through-holes by punching. With this, the producing cost is relatively low (compared with a laser machining or the like).

In a particular arrangement, a clamp mechanism is used in the stretching step. The clamp mechanism holds at least two sides of the film to stretch the film. With this, the film can be continuously stretched by means of a simple mechanism. Also, with such a clamp mechanism, biaxial stretching is enabled.

Further, the through-holes are formed on at least one row in the through-hole-forming step. With this, the produced film can be employed in an ink transfer printer described below. In such case, the through-holes are faced with heating elements of a thermal line head.

According to another aspect of the present invention,

there is provided a method of producing a film (made of

I shape memory resin) with through-holes. The producing method includes the steps of (1) heating the film to a temperature above a glass transition temperature of the shape memory resin, (2) stretching the heated film in at least one direction, (3) cooling the stretched film to a temperature below the glass transition temperature, (4) forming throughholes in the film, and (5) heating the film to a temperature above the glass transition temperature.

As the stretched film is cooled before the film recovers its original (non-stretched) shape, the film is solidized in a state the film is stretched. Thus, it is possible to keep the stretched state of the film without continuously applying force to the film.

In a particular arrangement, a pair of heat rollers are used to heat the film and to stretch the film. The film is inserted in a gap between the rollers and pressed therein, so that the film is stretched. Optionally, a fan is used to cool the film in the cooling step. The fan is located in the vicinity of the heat rollers.

According to still another aspect of the present invention, there is provided a method of producing a film with through-holes. The film is made of shape memory resin.

The method includes the steps of (1) forming

through-holes in the film, (2) heating the film to a temperature above a shape-providing temperature of the shape memory resin, and (3) stretching the film in at least one direction in parallel to a surface of the film, in a state the film is heated to a temperature above the shape- providing temperature.

The produced film is thinner than the film in the -t-hrough-hole-forming step. Further, dimensions of the 'produced'film in the stretching direction are larger than those of the film in the through-hole-forming step. Thus, the inclination angles of the through-holes (from a direction of a thickness of the film) of the produced film are larger than those of the through-holes formed in the through-hole-forming step. Accordingly, it is possible to produce a film with through-holes which inclination angles (from a direction of a thickness of the film) are relatively large.

In a particular arrangement, a pair of rollers are used in the stretching step. The film is inserted in a gap between the rollers and pressed therein. The rollers are heated to a temperature above the shape-providing temperature.

The film produced by the above-described producing method can be used in an ink transfer printer. The ink

transfer printer includes (1) a thermal head comprising a plurality of heating elements, the thermal head being faced with the film so that the heating elements are faced with the through-holes of the film, (2) a space formed between the thermal head and the film, which holds ink therein, (3) a platen member which urges a recording media to a surface of the film. When the heating elements selectively heat the ink in the space and the film, ink permeates the throughholes of the film and transferred to the recording media.

Examples of the present invention will now be described with reference to the accompanying drawings, in which :- Figs. 1A, IB, 1C and 1D are schematic views showing a method of producing a film with through-holes of a. first embodiment ; Fig. 2 is a perspective view of the film of Fig. 1; Fig. 3 is a sectional view of an ink transfer printer using the film of Fig. 2; Fig. 4 is an exploded perspective view showing a main part of the ink transfer printer of Fig. 3; Figs. SA and 5B are schematic views illustrating an ink transferring process; Fig. 6 is an enlarged view of the film nipped by a thermal head and a platen roller of the ink transfer printer of Fig. 3;

Fig. 7 is a diagram showing an example of a characteristic of a shape memory resin of a second embodiment ; Figs. SA, 8B, 8C and 8D. are schematic views showing a method of producing a film with through-holes of the second embodiment; and Figs. 9A, 9B, 9C and 9D are schematic views showing a method of producing a film with through-holes of a third embodiment.

The embodiments of a method of producing a film with through-holes of the present invention are described below.

Figs. 1A, IB, 1C and ID are schematic views showing a method of producing a film with through-holes of a first embodiment. A film 2 shown in Fig. 1A is made of polytetrafluoroethylene (Teflon (trademark) ). The film 2 has a square shape, each side thereof having the length L. The thickness t of the film 2 is from 0.03 to 0.08 mm. In Fig.

1A, an X-direction and a Y-direction are defined along two adjacent sides of the film 2.

As shown in Fig. IB, the film 2 is stretched in two directions. A clamp mechanism is used to stretch the film 2.

The clamp mechanism has four clamps 110 which respectively hold four sides of the film 2 (one of clamps 110 is not shown in Fig. 1B) and stretches the film 2 in the X- direction and the Y-direction. The film 2 is stretched so that the length of each side becomes 2L, and so that the. thickness of the film 2 becomes t/4.

As shown in Fig. 1C, through-holes 25 are punched in the film 2 by means of needles 115 of a punching machine- The through-holes 25 have a certain diameter D, and are arranged on two rows with a certain pitch P. The film 2 is pierced with the needle 115 in a direction that is inclined from between a direction of a thickness of film 2 to the Y- direction. That is, the through-holes 25 are inclined to the Y-direction. Due to the operation accuracy of the punching machine, error in dimensions (such as diameters and pitches) of the through-holes 25 is approximately 0.02 mm. After the through-holes 25 are formed, the stretching of the film 2 is terminated, so that the film 2 recovers its original (non- stretched) thickness as shown in Fig. 1D. With this, the film 2 with through-holes 25 is produced. The'produced' film 2 is shown in Fig. 2.

As shown in Fig. ID, since the film 2 recovers its original (non-stretched) thickness, the thickness of the film 2 changes from t/4 to t. Also, the length of each side of the film 2 changes from 2L to L. Accordingly, the

diameter of the through-holes 25 changes from D to D/2. Also, the pitch of the through-holes 2 changes from P to P/2.

As a result, even if the error of the dimensions of the through-holes 25 is 0.02 mm in the punching step (Fig. 1C), the error of the dimensions of the through-holes 25 of the 'produced'film 2 (Fig. ID) is 0.01 mm. That is, the -'accuracy of the dimensions of the through-holes 25 is doubled.

As described above, by punching the through-holes 25 in the film 2 in a state where the film 2 is stretched, the accuracy of dimensions of through-holes 25 can be consequently improved, without improving the operation accuracy of the punching machine.

In the above-described first embodiment, it is possible to form through-holes 25 throughout the surface of the film 2. Further, it is possible to stretch the film 2 in only one direction (instead of two directions). In case the film 2 is stretched in the Y direction, the shape of the through-holes 25 of the produced film 2 is ellipse that is elongated in the X direction.

An ink transfer printer using the film 2 will now be described. Fig. 3 is a sectional view of the ink transfer printer. The ink transfer printer includes a thermal line head 3 having

multiple heating elements 35 arranged in a row. The above-described film 2 with through-holes (not shown in Fig. 3) is supported by a board 3a of the thermal line head 3 via a spacer 8 provided. therebetween, so that the film 2 and the thermal line head 3 face each other.

. The spacer 8 and the board 3a of the thermal line head 3 are made of materials which do not allow the permeation of -ink. Thus, ink is stored in a space surrounded by the spacer 8, the board 3a of the thermal line head 3 and the film 2. A platen roller 4 is provided at the opposing side of the film 2 with respect to the thermal line head 3, so that a recording media R is sandwiched by the platen roller 4 and the film 2. The circumferential surface of the platen roller 4 is made of rubber. A rotation shaft 4a of the platen roller 4 is orientated in a direction in which the heating elements 35 of the thermal line head 3 are arranged. When the platen roller 4 is rotated, the recording media R is fed in the direction shown by an arrow in Fig. 3, due to a traction between the recording media R and platen roller 4.

Fig. 4 is an exploded perspective view of the ink transfer printer except the platen roller 4. The spacer 8 is a thin plate member which surrounds the heating elements 35 of the thermal line head 3. That is, the spacer 8 defines four side borders of the ink space 1 in which the heating elements 35 are located. In order to supply ink to the ink

space 1, an ink tank 6 is provided on the board 3a of the thermal line head 3 so that the ink tank 6 is adjacent to the spacer 8. The ink tank 6 has a cavity (not-shown) in which ink can be stored. Ink stored in the ink tank 6 is introduced into the ink space 1 through a slit-shaped outlet opening 62 formed on the ink tank 6 and a slit-shaped connecting opening 85 formed on the spacer 8, due to - capillary action. The film 2 is attached to the upper surface of the spacer 8 so that the through-holes 25 are faced with the heating elements 35 of the thermal line head 3.

Figs. SA and 5B are schematic views showing an ink transferring process. As shown in Fig. SA, the diameter of the through-holes 25 is small so that ink does not permeate the through-holes 25. The film 2 is almost in contact with the heating element 35 of the thermal line head 3. When the heating element 35 is heated, ink located in the vicinity of the heating element 35 is heated. As shown in Fig. SB, the heated ink is vaporized and expanded, causing an increase in the local pressure of ink. Also, a portion of the film 2 located in the vicinity of the heating element 35 is heated.

The elastic coefficient of the heated portion of the film 2 decreases, so that the heated portion of the film 2 is easily deformed. Due to the increase in the local pressure in ink, ink is pushed into the through-hole 25 of the film

2. Further, the through-hole 25 is widened so as to allow the permeation of ink. With this, ink permeates the through-hole 25 and is transferred onto the recording media R (Fig. 3) which is in contact with the upper surface of the film 2. After the heating of the heating elements 35 is stopped, the heated, ink is cooled by the surrounding ink, so that the increase in the local pressure in ink disappears. Further, - the heated portion of the film is also cooled by ink. With this, the widened through-holes 25 recover their original diameters so that the. through-holes 25 do not allow the permeation of ink.

As constructed above, by controlling the thermal line head 3 to selectively heat the heating elements 35 and by rotating the platen roller 4 to feed the recording media R, a desired image is formed on the recording media R.

In the above-described ink transfer printer, it is possible to arrange that the film 2 is sandwiched by the heating elements 35 and the platen roller 4 as shown in Fig.

6. Since the through-holes 25 of the film 2 are inclined from a direction of the thickness of the film 2, the throughholes 25 are almost closed. With such an arrangement, even if an unintentional pressure is applied to ink (or to the film 2), an unintentional permeation of ink is prevented.

Thus, the ink leakage is prevented. Further, it is possible to constitute the spacer 8 of an adhesive agent instead of

the thin plate member.

A second embodiment of the present invention will now be described. In the second embodiment, a film 200 is made of. shape memory resin which exhibits different characteristics

above/below a glass transition temperature T.. Fig. 7 is a .... diagram showing an example of the characteristics of the shape memory resin. When the shape memory resin is heated to a temperature above a glass transition temperature T (and below a shape-providing temperature To described below) as shown by"b"in Fig. 7, the shape memory resin exhibits a rubber state, in which Brownian motion of molecules is activated. When the shape memory resin is cooled to a temperature below the glass transition temperature T- as shown by"a"in Fig. 7, the shape memory resin exhibits a solid state in which Brownian motion of molecules is frozen.

Further, if the shape memory resin is heated to a temperature above a shape-providing-temperature To as shown by"c"in Fig. 7, the shape memory resin exhibits a fluidized state in which molecules are fluidized. In this fluidized state, the shape memory resin is given an original shape. Examples of the shape memory resin are as follows: (1) polynorbornene, (2) trans-l, 4-polyisoprene, and (3) polyurethane. In this embodiment, polyurethane resin (which is low cost and has excellent moldability) is used. In this

embodiment, the glass transition temperature Tg of the shape memory resin is from 60'C to 80*C. The shape memory resin is disclosed in Japanese Laid-Open Patent Application Nos. HEI 5-305666 and HEI 8-49960.

Figs. 8A, 8B, 8C and 8D are schematic views showing a method according to a second embodiment. As shown in Fig. 8A, the film 200 made of the shape memory resin has a thickness t of 2 mm. This film 200 is inserted in a gap between two heat rollers 210. The heat rollers 210 are heated at 70'C, which is higher than the glass transition temperature Tg of the shape memory resin. The film 200 is heated so that the film 200 exhibits a rubber state and is pressed by the heat rollers 210, so that the film 200 is stretched in one direction (referred to as the Y- direction). The film 200 is stretched so that the thickness of the film 200 is 0.05 mm (t/40). A pair of fans 220 are located at downstream side of the heat rollers 210. The film 200 which moves out of the gap between the heat rollers 210 is rapidly cooled by the fans 220 to a temperature below the glass transition temperature Tg. That is, the film 200 is cooled just after the film 200 is stretched and before the film 200 becomes thicker. With this, the film 200 exhibits ! the solid state in a state where the film 200 is stretched.

Further, as shown in Fig. 8C, through-holes 205 are punched in the film 200 by means of needles 215. The

diameters of the through-holes 205 are denoted by D in Fig. 8C. After punching of the through-holes 205, the film 200 is heated to a temperature above a glass transition temperature Tg by means of a heater (denoted by H'. in Fig. 8D). As a result, the film 200 recovers its original thickness as shown, in Fig. 8D. That is, the thickness of the film 200 is changed from 0.05 mm (t/40) to 2 mm (t). The diameter of the through-holes 205 in the stretching direction (Y-direction) becomes D/40. With this, the film 200 with through-holes 205 is produced. The film 200 produced by the process shown in Figs. 8A through 8D can be used as the film 2 in the ink transfer printer shown in Fig. 3.

As described above, even if the error in the dimensions (in Y-direction) of the through-holes 205 is 0.02 mm in the punching step (Fig. 8C), the error in the dimensions (in Y- direction) of the through-holes of the produced film 200 is 0. 0005 mm. That is, the accuracy of the through-holes of the produced film 200 in Y direction is improved. Further, since the film is solidized in a state the film is stretched, it is possible to keep the stretched state of the film without continuously applying force to the film.

A third embodiment of the present invention will now be described. In the third embodiment, a film 300 is made of a shape memory resin similar to that of the second embodiment.

Figs. 9A, 9B, 9C and 9D are schematic views showing the producing process of the third embodiment. As shown in Fig. 9A, a film 300 made of the shape memory resin has a thickness t of 2 mm. First, as shown in Fig. 9B, through-holes 305 are punched in the film 300 by means of needle. 315. The piercing direction of the needle 315 is

inclined to one direction (referred to as the Y-direction).

-'I11e inclination angle of the piercing direction of the needle 315 from a direction of the thickness of the film 300 is denoted by a. The diameter of the through-holes 30 is denoted by D in Fig. 8C.

After the through-holes 305 are formed, the film 300 is inserted in a gap between two heat rollers 310 in the Ydirection. The heat rollers 310 are heated at 150'C, which is higher than the shape-providing temperature To of the shape memory resin of the film 300. The film 300 is heated so that the film 300 exhibits a rubber state and is pressed by the heat rollers 310, so that the film 300 is stretched in the Y-direction. The film 300 is stretched so that the thickness of the film 300 is 0. 05 mm (t/40). Since the film 300 is heated to a temperature above the shape-providing temperature To'this shape of the film 300 (having the thickness of 0. 05 mm) becomes an original shape of the film 300. With this, the film 300 with through-holes 305 is produced. The film 300 produced by the process shown in

Figs. 9A through 9D can be used as the film 2 in the ink transfer printer shown in Fig. 3.

As shown in Fig. 9D, the inclination angle of the through-holes 305 of'the'produced'film 300 from a direction of the thickness of the film 300 is larger than inclination angle a the piercing direction (Fig. 9B) of the needle 315. Accordingly, it is possible to form the film 300 with through-hole 305 whose inclination angle from a direction of the thickness of the film 300 is relatively large.

Although the methods of producing a film with through- holes are described herein with respect to the preferred embodiments, many modifications and changes can be made without departing from the scope of the invention.

Claims

CLAIMS:

1. A method of producing a film with through-holes, said film being made of shape memory resin, said method comprising 5 the steps of :- forming through-holes in said film; heating said film to a temperature above a shape- providing temperature of said shape memory resin; and stretching said film in at least one direction parallel 10 to a surface of said film, in a state said film is heated to a temperature above said shape-providing temperature; wherein said through-holes are inclined from between a direction of thickness of said film to a direction of stretching.

15

2. A method according to claim 1, wherein a pair of rollers are used in said stretching step, wherein said film is inserted in a gap between said rollers and pressed therein.

20

3. A method according to claim 1 or 2, wherein said rollers are heated to a temperature above said shape-providing temperature.

4. A method according to any one of claims 1 to 3, wherein 25 said through-holes are formed in a row in said through-hole- forming step.

5. A method according to any one of claims 1 to 4, wherein said through-holes are formed by punching in said through- 30 hole-forming step.

6. A film produced by the method of any one of claims 1 to 5.

7. An ink transfer printer using said film with through- holes according to claim 6, said ink transfer printer comprising: a thermal head comprising a plurality of heating 5 elements, said thermal head being positioned in use, such that said heating elements are faced with said through-holes of said film; . a space formed between said thermal head and said film, in which ink can be stored; 10.. a platen member which urges a recording media to a surface of said film; wherein said heating elements selectively heat said ink in said space and said film so that ink permeates said through-holes of said film and is transferred to said 15 recording media.

8. A method of producing a film substantially as hereinbefore described with reference to Figures 8A to 8D or 9A to 9D of the drawings.

20

9. A film substantially as hereinbefore described with reference to Figures 8A to 8D or 9A to 9D of the drawings.