JP2981155B2 - Conductive resin sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive polystyrene resin which is useful for producing a conductive resin sheet, particularly a carrier tape and a tray used for transporting and storing electronic parts such as ICs and transistors. It is about a sheet.

[0002]

2. Description of the Related Art In recent years, the demand for high-performance and small-sized electronic components, particularly chip-type electronic components, has been increasing due to the remarkable progress of surface mounting technology. As this chip type electronic component,
An IC, a transistor, a diode, and the like are exemplified, and these are stored in a carrier tape or a tray, transported, and stored.

[0003] For example, in the case of a carrier tape, it is supplied as a package sealed with a top tape, which is a lid material. To assemble the chip-type electronic components onto an electronic circuit board, the package is sequentially removed. In this method, the top tape is peeled off from the carrier tape while being sent out, and the chip-type electronic component is automatically picked up and automatically mounted on a predetermined portion of the circuit board.

However, in this process, the carrier tape is charged by the static electricity generated by friction or the static electricity generated in the step of peeling off the top tape, so that it is difficult to accurately mount the chip-type electronic component at a predetermined position. In addition, there is a problem that static electricity is destroyed. Therefore, it is necessary to impart conductivity to this package to prevent accumulation of static electricity.

[0005] The carrier tape constituting this package is
Normally, a conductive sheet formed by integrally extruding a conductive polystyrene resin composition obtained by kneading a large amount of a conductive filler such as carbon black into a polystyrene resin on the front and back, using a polystyrene resin as a base layer. Is obtained by sheet secondary processing such as press molding and vacuum molding. The conductive sheet is also used as a tray for electronic components such as ICs, transistors, and diodes, or as a tray for optical components such as lenses that extremely dislike dust and the like.

[0006]

The carrier tape as described above generally causes machine trouble if the feed pitch is shifted during automatic surface mounting, so that dimensional stability of the material and accuracy during processing are important. is there.

However, the above-mentioned conventional carrier tape constituting the package is made of a conductive polystyrene resin in which a polystyrene resin is used as a base material layer and a large amount of a conductive filler such as carbon black is mixed into the polystyrene resin on the front and back sides. A sheet obtained by subjecting a conductive sheet (three-layer conductive sheet of polystyrene resin) formed by integrally laminating the resin composition to co-extrusion by press forming, vacuum forming, or the like, is subjected to secondary processing. Since a large amount of conductive filler such as carbon black is kneaded, when molded as a carrier tape, not only decreases in mechanical strength and workability, or molding accuracy deteriorates, but also costs increase. There was a problem of becoming. In addition, there was a similar problem with the tray.

Also, when the amount of carbon black is increased, there is another problem that the carbon black falls off. Furthermore, the top tape that forms the package by sealing the carrier tape mainly uses a polystyrene-based hot melt for the adhesive layer, and this adhesive force depends on the sealing temperature or easily changes with time. For this reason, there was a defect that good sealing properties could not be obtained with respect to the conventional polystyrene-based three-layer conductive sheet, and the sheet was peeled during storage and transport.

The present invention solves the above-mentioned conventional problems, and improves the formability and dimensional stability of a sheet while maintaining conductivity, and obtains good sealing properties with a top tape or the like. It is an object to provide a conductive resin sheet that can be used.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an acryl-urethane copolymer resin (acryl component: 0.1 ~
50% by weight) 100 parts by weight, particle size 0.05 to 1.
A conductive layer containing 15 to 35 parts by weight of a 0 μm conductive filler is provided.
The gist of the present invention is a conductive resin sheet having a range of 8 Ω.

Hereinafter, the conductive resin sheet of the present invention will be specifically described. In the present invention, a polystyrene-based resin sheet is used as a base material, and an acrylic-urethane-based copolymer resin (hereinafter simply referred to as an acrylic-
Abbreviated as urethane resin. ) And a conductive composition obtained by dissolving a specific amount of a conductive filler in a solvent, followed by drying to provide a conductive layer.

As the base material of the conductive resin sheet of the present invention, a polystyrene resin sheet is used. The polystyrene resin used for the polystyrene resin sheet is a resin composition composed of a styrene polymer and a block copolymer. Here, the styrene copolymer is
Polymers obtained by polymerizing styrene monomers such as styrene, α-methylstyrene, pt-butylstyrene, p-methylstyrene, alone or in mixtures, and monomers copolymerizable with styrene monomers For example, styrene copolymers with acrylonitrile butadiene, butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, acrylic acid, maleic anhydride, and the like. Particularly preferred are polystyrene and acrylonitrile-butadiene-styrene copolymer. In particular, when the acrylic component, particularly methyl methacrylate (MMA), is contained in the range of 0.1 to 50% by weight in the resin components, the adhesion to the conductive layer is improved, and the moldability as a substrate is improved. It is more preferable in this respect.

On one or both surfaces of the polystyrene resin sheet, a conductive layer mainly composed of an acrylic-urethane resin as a binder and a conductive filler is provided.

The conductive layer has a particle size of 0.0 with respect to 100 parts by weight of an acryl-urethane resin as a binder.
It is important to contain 15 to 35 parts by weight of a conductive filler of 5 to 1.0 μm. When the particle size of the conductive filler is less than 0.05 μm, the dispersibility in the coating agent for forming the conductive layer is poor, and when the particle size exceeds 1.0 μm, the smoothness of the formed conductive layer is reduced. Is not obtained, which adversely affects the sealing property with the top tape when used as a carrier tape, which is not preferable. In addition, when the content of the conductive filler is less than 15 parts by weight, required conductivity cannot be obtained, and when the content exceeds 35 parts by weight, the conductive filler drops off from the conductive layer. Undesirably appears.

The binder used in the present invention includes:
An acryl-urethane resin is used in consideration of perfect adhesion to the base material and stable sealing with the top tape. The acrylic-urethane resin includes acrylic methyl (meth) acrylate and ethyl (meth) acrylate.
Acrylate, isobutyl (meth) acrylate, n-
Examples include hexyl (meth) acrylate, acrylamide, and the like, and urethane-based copolymers such as polyether-based, polyester-based, polycarbonate-based, and epoxy-modified types.

Here, in general, as a bonding mechanism of the binder to the plastic, a chemical reaction with a surface functional group of the plastic, an intermolecular force with a surface polar group, or mutual dissolution of a surface polymer and a binder molecule can be considered. However, since a polystyrene resin as a base material conventionally used has a small number of functional groups and polar groups on the surface, a method of mechanically adhering the surface polymer and the binder molecule by mutual dissolution is adopted.

However, if a coating agent containing a large amount of a highly polar solvent such as toluene or ethyl acetate is used as a coating agent for forming a conductive layer in order to improve adhesion to a substrate, the polystyrene resin itself may be used. Is not only easily degraded,
Fine cracks (stress cracking) are also formed in the conductive layer formed on the surface of the resin, and a continuous and uniform coating film is lost, so that it is difficult to obtain a stable surface resistance.

[0018] In most cases, even if it appears to be in close contact due to mutual dissolution, the contact is incomplete in most cases. The cause of the incomplete adhesion is that a solvent having a strong polarity cannot be used, and the solubility coefficient (SP
(Value).

[0019]

[Table 1]

In other words, those having similar SP values shown in Table 1 have mutual solubility and acrylic is also an amorphous plastic and is mechanically adhered by mutual dissolution of surface polymer and binder molecule. In view of the fact that the method is adopted, the polystyrene-based resin as the base material used in the present invention is also used as a component system, in particular, methyl methacrylate (MM
It is desirable to select a type of resin containing A). However, the binder of acrylic alone has problems in the sealing property of the top tape, the moldability (elongation of the conductive layer) in the secondary processing of the sheet, and the damage resistance, and therefore, an acrylic-urethane-based binder is used as the binder.

In the present invention, it is preferable that an acrylic component is contained in the binder from the viewpoint of adhesion to the substrate, and the ratio of the acrylic component is 0.1 to 50% by weight.

In the conductive resin sheet of the present invention, the use of a type containing both acrylic resin and polystyrene resin as the base material enhances the synergistic effect of the SP value and mutual dissolution, thereby obtaining better adhesion. Can be.

Examples of the solvent used for the coating agent for forming the conductive layer according to the present invention include aromatic compounds such as toluene and xylene, ketone compounds such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and ethyl acetate and butyl acetate. And alcohol-based solvents such as methanol, ethanol, isopropyl alcohol and secondary butanol, and the above-mentioned alcohol-based solvents are preferred from the viewpoint of the solvent resistance of the polystyrene-based resin. Specifically, it is more preferable that the ratio of the alcohol to the entire solvent is 40% or more.

As the conductive filler used in the present invention, carbon black, tin oxide, indium oxide, antimony oxide and the like can be mentioned, but carbon black is desirable in view of the adhesion to the substrate. Examples of the carbon black include Ketjen black, furnace black, channel black, and acetylene black. In particular, Ketjen black is preferred because high conductivity can be obtained with a small amount.

The conductive resin sheet of the present invention has a surface specific resistance in the range of 10 ⁴ to 10 ⁸ Ω, and this range is 10 ⁴ Ω.
If it is lower than Ω, the terminals of the electronic components are conductive and short-circuited. If it is higher than 10 ⁸ Ω, static electricity is charged due to friction such as vibration accompanying movement of the container or the like, and the circuit of the electronic components is destroyed. The surface specific resistance value here is a value measured on the surface on which the conductive layer is provided.

In order to obtain conductivity, a coating agent containing a conductive filler such as carbon black is coated on one or both surfaces of the substrate. At this time,
Since the amount of carbon black used in the coating agent to be coated is large in order to obtain good conductivity, the problem of falling off of carbon black is likely to occur. It is desirable to use One reason is that the carbon black particles are preferably fine particles in order to obtain a stable sealing property with the top tape. Further, in order to prevent the conductive layer from being elongated by the secondary processing of the conductive resin sheet and to reduce the surface resistivity, the coating amount is preferably dry and the thickness is at least 0.1 mm or more. From the viewpoint of workability, the thickness is preferably 0.1 to 30 μm, more preferably 0.5 to 2.0 μm.

As a coating method for obtaining the conductive layer constituting the conductive resin sheet of the present invention, direct gravure, gravure offset, and wire bar are generally used, but in order to obtain better conductivity, coating is performed. A reverse coating method such as three-reverse or gravure reverse is required because the film must be uniform and the coating amount must be small so as not to adversely affect the moldability of the conductive resin sheet. It is desirable to use

As described above, the conductive resin sheet of the present invention uses a polystyrene resin as a base material and coats an acryl-urethane resin of a specific component as a binder, so that the sealing property with a top tape or the like is obtained. Also, the moldability (elongation of the conductive layer) in the secondary processing is good.

Further, the conductive resin sheet of the present invention is obtained by adding a specific amount of a conductive filler as a conductive layer and controlling the surface specific resistance to a specific range, thereby forming the sheet into an electronic component. When molded as a package such as a storage tray or a carrier tape, the terminals of the electronic components to be stored are not short-circuited or static electricity is charged and the circuit of the electronic components is not broken.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

(Examples) Next, the embodiments of the present invention will be described with reference to examples and comparative examples. The molding accuracy and sealing property with the top tape in the examples show the following measurement results. .

(Molding accuracy) The thickness of the formed bottom surface and the feed pitch of the carrier tape were visually judged. Molding accuracy:…: good, ×: poor,

(Sealability with Top Tape) Sealing was performed using a top tape (SP-82: trade name, manufactured by Shin-Etsu Polymer Co., Ltd.) under the following conditions. An evaluation was performed.

Sealing machine: Vanguard VN3200 (trade name, manufactured by Vanguard Systems Co., Ltd.) Sealing condition: 140 ° C. × 2 seconds, peeling tester: Vanguard VG-10 (trade name, manufactured by Vanguard Systems Co., Ltd.) Peeling condition: 300 mm / min . 180 degree peeling

(Evaluation) Adhesion of coating film (according to JIS K 5400) ○ (8 to 10) × (0 to 7) ・ Sealability with top tape ○ ... Good × ... Poor ・ Drop off carbon black ○ ... No ×… Yes

(Examples 1 and 2) Sheets (A to F) shown in Table 2 were selected as polystyrene-based resin sheets containing an acrylic component, and the conductive compositions shown in Table 3 (Examples 1 and 2) were used. 2) wet-coated about 10 g / m ² on both sides by direct gravure method;
After drying at 0 ° C. for 30 seconds, a conductive layer having a thickness of 0.8 μm was formed. Next, the obtained conductive polystyrene resin sheet was formed into a carrier tape having a storage portion with a depth of 5 mm by press molding, and the physical properties thereof were examined. The results shown in Table 4 were obtained. Was done.

Example 3 Sheet H shown in Table 2 was selected as an acrylonitrile-butadiene-styrene (hereinafter abbreviated as ABS) resin sheet, and a conductive composition (Example 3) shown in Table 3 was wetted. About 10 g / m ² on both sides by direct gravure coating.
After drying at 30 ° C. for 30 seconds, a conductive layer having a thickness of 0.8 μm was formed. Next, the obtained conductive ABS-based resin sheet was formed into a carrier tape having a storage portion with a depth of 5 mm by press molding, and the physical properties thereof were examined. The results shown in Table 4 were obtained. Was done.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

(Comparative Examples 1 to 6) Sheet A shown in Table 2 was selected as a type containing an acrylic component in a polystyrene resin sheet, and a conductive composition shown in Table 3 (Comparative Example 1)
To 6) were wet-coated at about 10 g / m ² on both surfaces by a direct gravure method and dried at 80 ° C. for 30 seconds to form a conductive layer having a thickness of 0.8 μm. Next, the obtained conductive polystyrene-based resin sheet was formed into a carrier tape having a storage portion having a depth of 5 mm by press molding, and the physical properties thereof were examined. The results shown in Table 5 were obtained. .

(Comparative Example 7) A thermosheet EC which is a sheet G shown in Table 2 as a kneaded type polystyrene resin sheet was formed into a carrier tape having a storage portion with a depth of 5 mm by press molding. As a result, the results shown in Table 5 were obtained.

[0042]

[Table 5]

[0043]

As is clear from the above examples, the conductive resin sheet of the present invention is formed of an acrylic-urethane resin (acryl component: 0.1 to 50% by weight) as a binder on one or both surfaces of a polystyrene resin sheet. A) a conductive layer comprising 15 to 35 parts by weight of a conductive filler having a particle size of 0.05 to 1.0 μm is applied to 100 parts by weight to form a conductive layer. Not only is it possible for the layers to adhere perfectly, but unlike the conventional conductive three-layer type polystyrene resin sheet,
The conductive layer provided on the surface of the sheet can be set thin, and an excellent conductive resin sheet having improved mechanical properties and molding accuracy can be provided. Further, since the conductive resin sheet of the present invention is useful for applications such as carrier tape,
Its industrial utility value is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B65D 73/00 B32B 27/18 H01B 1/24 C08J 7/04

Claims (1)

(57) [Claims] 1. An acrylic-urethane copolymer as a binder on one or both surfaces of a polystyrene resin sheet.
Coalescent resin (acrylic component: 0.1 to 50% by weight) 100
A conductive layer containing 15 to 35 parts by weight of a conductive filler having a particle size of 0.05 to 1.0 μm with respect to parts by weight is provided, and its surface specific resistance is in a range of 104 to 108 Ω. Conductive resin sheet.