JP2549282B2 - Static elimination sheet and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a static elimination sheet. This is attached to a tape pad that holds a magnetic tape made of synthetic resin contained in, for example, compact cassettes and video cassettes, and is used to remove static electricity generated when the tape runs. To be done.

(Prior art and its problems) When manufacturing or processing a synthetic resin tape (film), or when using a synthetic resin tape (film) such as a packing tape, an image film, or a magnetic tape. It is well known that static electricity is generated as the tape runs, and dust is attached to the tape or the running guide member, or the tapes are wound around each other.

Conventionally, in order to prevent such damage due to static electricity, a conductive sheet provided with a metal vapor deposition layer on one or both sides of a plastic sheet containing a fluororesin as a main component is cut into strips, and one side thereof is formed into a sawtooth shape. A static eliminator is known in which a cut sheet is fixed to a hard insulating angle, and a hard insulating plate is provided on the other surface of the sheet via a ground conductor layer (Japanese Patent Laid-Open No. 50-74396). However, such a static eliminator has a problem in that when the static eliminator itself is installed in a cassette together with an image film or a magnetic tape, the static eliminator itself occupies a large space, and therefore the entire cassette cannot be downsized.

Further, as the static elimination sheet, the tip of the polyester sheet is formed in order to form a conductive portion and to prevent electricity from flowing from the outside of the magnetic tape cassette to the magnetic tape through the static elimination sheet. It is known that a conductive member is attached to the section so that the end of the section is brought into contact with the magnetic tape in the magnetic tape cassette. However, such a static elimination sheet is contaminated by the adhesive oozing out from the pasted part due to the use at high temperature or for a long time, and due to the vibration caused by the contact with the running magnetic tape. In addition, there is a problem that the bonded portion is peeled off.

(Means for Solving Problems) The present invention solves the above-mentioned problems of the prior art and is a compact one suitable for being incorporated in a magnetic tape cassette or the like, and further causes damage such as peeling during use. It aims to provide a static elimination sheet and its manufacturing method.

 The present invention is the following static elimination sheet.

A sheet for static elimination, which is a sheet made of a thermoplastic synthetic resin containing a conductive material substantially uniformly, wherein the sheet itself has regions showing different electric resistances.

 Further, the present invention is the following method for producing a static elimination sheet.

A thermoplastic synthetic resin containing a conductive material substantially uniformly is melt-extruded into a sheet with a partially different thickness by an extrusion mechanism, and then the molten sheet is processed by a pressure mechanism at a uniform pressure, or Alternatively, the synthetic resin is melt-extruded into a sheet with a uniform thickness by an extruding mechanism, and then the molten sheet is partially processed by a pressure mechanism at different pressures to form a region pressed to the sheet. A process for producing a static elimination sheet having regions where the sheet itself has different electric resistance, which is characterized by producing a region which is not pressurized and solidifying by cooling.

The thermoplastic synthetic resin in the present invention is, for example, polyolefin, polyamide, polyester, ABS resin, vinyl chloride resin, ionomer, acrylic resin, modified acrylic elastomer or the like.

The conductive material in the present invention is acetylene black, thermal black, furnace black, channel black, Ketjen black and the like. The conductive material is mixed to be substantially uniform throughout the sheet.

The static elimination sheet of the present invention has areas having different electric resistances. In the sheet, the electric resistance value in the low electric resistance region is usually less than 10 ⁶ Ωcm, preferably 10 ⁵ Ωcm or less, and the electric resistance value in the high electric resistance region is usually 10 ⁶ Ωcm. cm or more, preferably 10 ⁷ Ω · cm or more. It is preferable that the ratio [B] / [A] of the electric resistance value [B] in the high electric resistance region to the electric resistance value [A] in the low electric resistance region is 10 ³ or more. .

The static elimination sheet of the present invention exhibits different electric resistance values depending on the regions as described above, and has a region having a small electric resistance (also called a conductive part) and a region having a large electric resistance (also called an insulating part). Are close to each other in one sheet, and the electric resistance value is 10 ⁴ Ω
In some cases, it can vary greatly from m to 10 ¹² Ω · cm.

The static elimination sheet of the present invention can be cut or punched into a predetermined shape as desired, and the static elimination sheet member thus produced has, for example, a strip shape, one end as a conductor and the other end. Acts as an insulator.

The conductive part and the insulating part of the sheet can be distinguished from each other because the former is matte and the latter has gloss, but in order to make the distinction easier, it is possible to distinguish them by color or the conductive part with a symbol such as " Mark a large number of "H" (second
(Fig.)), And it is convenient when attaching the static elimination sheet member to a cassette such as an image film or a magnetic tape.

The manufacturing method of the present invention is to obtain the above-mentioned static elimination sheet,
A thermoplastic synthetic resin containing a conductive material substantially uniformly,
The extruding mechanism partially melts and extrudes the sheet into a sheet having a different thickness, and then the pressurizing mechanism processes the molten sheet at an equal pressure, or the synthetic resin is extruded into a sheet having an even thickness. After melt-extruding into a sheet shape, the molten sheet is partially processed by a pressure mechanism at different pressures to generate an area where pressure is applied to the sheet and an area where pressure is not applied, and the sheet is cooled and solidified.

Here, the pressurizing mechanism is preferably one or two or more of a device composed of a pair of rolls.

In the sheet thus obtained, a non-pressurizing portion and a pressurizing portion are generated, the non-pressurizing portion forms a region (conductive portion) having a small electric resistance, and the pressurizing portion has a region having a large electric resistance. (Insulating part) is formed.

The relationship between the pressurization and the electric resistance described above can be explained as follows. That is, a carbon structure is formed in the molten sheet, but in the non-pressurized portion, it is held as it is and cooled and solidified. A small area (conductive portion) is formed. On the other hand, in the pressure unit,
When pressure is applied, a shearing force partially acts on the molten sheet to destroy the carbon structure, and the carbon structure is cooled and solidified in such a state. (Insulating part) is formed.

In the present invention, the method for producing the pressed region and the unpressurized region on the sheet is one of the following.

(A) A resin is melt-extruded into a sheet with a partially different thickness by an extrusion mechanism, and then the molten sheet is processed by a pressure mechanism at a uniform pressure.

(B) The synthetic resin is melt-extruded into a sheet with a uniform thickness by an extrusion mechanism, and then the molten sheet is partially processed by a pressure mechanism at different pressures.

In the extrusion mechanism used in the method (A), the sheet die for extruding the synthetic resin into a sheet shape is designed, for example, by partially changing the width and thickness of the resin flow path. The molten sheet extruded from such a sheet die has a partial difference in wall thickness. After that, the molten sheet is processed by a pressure mechanism at a uniform pressure. The pressing mechanism used here is preferably one or more of a pair of rolls, which rolls may have a normal flat surface. As described above, the melted sheets are partially different in wall thickness. Therefore, when such a melted sheet is applied to the roll, only the thick portion is pressed by the roll. In this case, the thickness difference between the pressed portion and the non-pressurized portion is preferably 3 μ to 50 μ, and more preferably 5 μ to 20 μ.

The sheet die in the extrusion mechanism used in the method (B) has a normal shape, and the molten sheet extruded from the sheet die has a uniform thickness. Then, the molten sheet is subjected to pressure treatment with, for example, a pair of rolls having a band-shaped groove having a constant width and a constant depth on the peripheral surface of the roll. When the above-mentioned melted sheet is passed through such a roll, only the sheet portion corresponding to the band-shaped groove portion is not pressurized, and the other portions are pressurized.

The extrusion mechanism and the pressurizing mechanism used in the above methods (A) and (B) can be appropriately selected within a range that achieves the object of the present invention, and the processing conditions therefor are, for example, as a thermoplastic synthetic resin. It can be purposefully selected depending on what kind of thing is used.

The molten sheet treated as described above is cooled and solidified. The cooling may be natural cooling or forced cooling. For example, when nylon 6 is used as the thermoplastic resin,
Chill to 160 ° C and set on a cooling roll to solidify.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view of a magnetic tape cassette incorporating the static elimination sheet of the present invention, and FIG. 2 is a partial plan view of the static elimination sheet of the present invention, which can distinguish between a conductive portion and an insulating portion. As described above, many "H" marks are engraved on the insulating portion. FIG. 3 shows a static elimination sheet member formed by punching so as to be suitable for incorporating the static elimination sheet of FIG. 2 into a magnetic tape cassette. For example, in any of (a), (b) and (c), Good. FIG. 4 is a partially enlarged view of the static elimination sheet members (a), (b), and (c) of FIG. 3 assembled in the magnetic tape cassette of FIG. 1, particularly (b).
In the case of (c), the static elimination effect can be obtained by only lightly contacting the running magnetic tape with the static elimination sheet. In (c), since the static elimination sheet is in contact with the running magnetic tape at the bent portion. It is preferable that the magnetic tape can be smoothly brought into contact with the tape in any of the tape running directions, that is, the feeding and the winding of the magnetic tape, without damaging the magnetic tape.

(Effect of the invention) Since the static elimination sheet of the present invention has the conductive part and the insulating part formed on one sheet itself, unlike the conventional product, there is no pasted part and peeling occurs during use. Absent. Further, the static elimination sheet of the present invention can be easily processed into a static elimination sheet member having a desired shape.
Since it can be manufactured by punching in the process, it has excellent productivity.

Furthermore, when the static elimination sheet of the present invention is incorporated into a device such as a cassette, it occupies a small space, which is useful for downsizing the entire device. other than this,
The static elimination sheet of the present invention is used in a field where static electricity is a problem, such as a manufacturing / processing step of a synthetic resin film (or tape), a coating processing step of a photosensitizer, a coloring agent, an adhesive agent, or a tape packing step. Can be widely used.

Examples and Comparative Examples Example 1 80 parts by weight of nylon 6 (relative viscosity at 25 ° C. of a solution of 1 gram of nylon 6 dissolved in 100 ml of 96% concentrated sulfuric acid 3.6) and 20 parts by weight of acetylene black were mixed in a tumbler. Then, this was put into an extruder to produce pellets. The pellets were dried, re-extruded into an extruder, and a nylon attached to the end of the pellets was used to obtain nylon 6 containing acetylene black uniformly.
Was extruded. The discharge port of the above die has a width of 75 mm
It has a slit-like shape and is provided with a portion with a wide channel at a width of 15 mm at both ends and the central part, so that the melted sheet has thick and thin portions alternating in the width direction. Extruded. A pair of flat rolls that rotate this molten sheet close together (a small "H" on one roll surface
A large number of marks are engraved), and the molten sheet was gradually cooled and solidified, and then taken. This roll treatment was performed by adjusting the roll interval and the take-up speed. By the roll treatment, in response to the difference in the thickness in the lateral direction of the molten sheet of the object to be treated, a region where the partial thickness of the sheet is thinner than the gap of the roll and is not directly passed and pressed, Since it was thicker than the gap, it was sandwiched between the rolls and a region where pressure was applied was generated. Thus, a sheet having a non-pressure application part (conductive part) and a pressure application part (insulating part) was obtained.

In this sheet, the unpressurized area has a thickness of 0.18
7 mm, electric resistance value (measured according to the method of potential drop of BS2044) is 3 × 10 ⁴ Ω · cm, and the pressed area has a thickness of 0.195 mm and electric resistance value of 4 × 10 ¹² Ω · cm. Therefore, the ratio [B] / [A] of the electric resistance value [A] in the region where the electric resistance is small and the electric resistance value [B] in the region where the electric resistance is large.
The value of was about 10 ⁸ .

Next, this sheet is punched out as shown in Fig. 3 (C), and it is installed in a magnetic tape cassette, 20 ° C, relative humidity 60%.
The unwinding and winding test was carried out under. As a result, static electricity damage such as sticking or winding of magnetic tape did not occur, and this static elimination sheet had an excellent static elimination effect.

Example 2 A static elimination sheet was produced in the same manner as in Example 1 except that polyacetal (homopolymer, MI = 3.2) was used in place of nylon 6.

In this product, the unpressurized area has a thickness of 0.20 mm, the electric resistance is 1 × 10 ³ Ω · cm, and the pressed area has a thickness of 0.22 mm.
The electric resistance value was 1 × 10 ⁷ Ω · cm.

Example 3 In Example 1, an extruder provided with a die having slit-shaped discharge ports having a uniform flow passage in the width direction, and a band-shaped groove having a width of 15 mm and a depth of 0.1 mm on the circumferential surface of the roll was formed in the circumferential direction of the roll. A sheet was manufactured in the same manner as in Example 1 except that rolls provided at equal intervals were used.

In this product, the unpressurized area has a thickness of 0.14 mm, the electric resistance value is 2 × 10 ⁴ Ω · cm, and the pressed area has a thickness of 0.1
The electrical resistance value at 5 mm was 5.6 × 10 ¹¹ Ω · cm.

Comparative Example 1 In Example 3, a sheet was produced without removing one of the pair of rolls and pressing with the rolls.

The obtained sheet had a thickness of 0.14 mm and an electric resistance value of 2 × 10 ⁴ Ω · cm over the entire sheet. When attempting to use this as a static elimination sheet, it was not possible to prevent the inflow of electricity from the outside of the magnetic tape cassette to the magnetic tape through the static elimination sheet, and the desired static elimination effect was not obtained.

Example 4 In Example 3, 15 mm wide and 0.1 m deep on the peripheral surface of the roll.
A sheet was manufactured in the same manner as in Example 3 except that a large number of m band-shaped grooves were provided at 15 mm intervals in the axial direction of the roll. The obtained sheet was a good sheet for static elimination, as in Example 3.

[Brief description of drawings]

FIG. 1 is a plan view of a magnetic tape cassette incorporating the static elimination sheet of the present invention, FIG. 2 is a partial plan view of the static elimination sheet of the present invention, and FIG. 3 is a punching process of the static elimination sheet of the present invention. The sheet member for static elimination is shown in three different shapes. FIG. 4 shows a partially enlarged view of the static elimination sheet of the present invention when the magnetic tape cassette shown in FIG. 1 is incorporated. [Explanation of Reference Numbers in the Drawings] 1 is a magnetic tape cassette, 2 is a static elimination sheet member, 3 is a magnetic tape, 4 is a static elimination sheet, 5 is a conductive part, 6 is an insulating part, and 7 is stamped on the insulating part. The mark "H", 8 is a guide rod, and 9 is a static elimination sheet support member.

Claims (4)

(57) [Claims] 1. A sheet for static elimination, which is a sheet made of a thermoplastic synthetic resin containing a conductive material substantially uniformly, wherein the sheet itself has regions showing different electric resistances. 2. The sheet itself has an electric resistance value [A] of 10 ⁵ Ω · cm or less in a low electric resistance region and an electric resistance value [B] of 10 ⁷ Ω · cm or more in a high electric resistance region. And the ratio [B] / [A] value is 10 ³ or more, the static elimination sheet according to claim (1). 3. A thermoplastic resin containing a conductive material substantially uniformly is melt-extruded into a sheet with a partially different thickness by an extruding mechanism, and then the molten sheet is uniformly extruded by a pressing mechanism. The synthetic resin is processed or melt-extruded into a sheet with a uniform thickness by an extrusion mechanism, and then the melted sheet is partially pressurized by a pressure mechanism to apply pressure to the sheet. A method for producing a static elimination sheet having a region where the sheet itself exhibits different electric resistance, which is characterized in that a region which is subjected to pressure and a region which is not pressurized are generated and solidified by cooling. 4. The manufacturing method according to claim 3, wherein the pressing mechanism is a pair of rolls.