JP2001202828A - Conductive sheet and conductive carrier tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control increase of surface resistance generated when a conductive sheet on which a conductive layer is layered by film-painting and a protective coating layer is installed is molded as a mold for electronic device package. SOLUTION: A carbon black conductive layer having polyvinylpyrrolidone as its binder is layered on a plastic sheet by film-painting, and an urethane resin protective coating layer is layered on the conductive layer by film-painting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article for packaging electronic parts such as a carrier tape, a tray, a lid, and a spacer for a tab (TAB) tape used for conveying, storing and mounting electronic parts such as ICs and transistors. TECHNICAL FIELD The present invention relates to a conductive sheet used for forming a sheet and a conductive carrier tape using the same.

[0002]

2. Description of the Related Art Conventionally, as an electrically conductive sheet for an electrically conductive carrier tape, an electrically conductive sheet made of an ABS resin sheet laminated with an electrically conductive layer of a styrene resin containing carbon black by co-extrusion is known (Japanese Patent Application Laid-Open (JP-A) Sho. 63-299923). In addition, although not particularly intended for molding, a conductive layer is formed on a plastic film as a conductive coating film containing carbon black and polyvinylpyrrolidone, and a thin coating film is formed on the conductive layer. A conductive sheet provided with a protective coat layer of an acrylic resin is known (Japanese Patent Publication No. 3-53726).

[0003]

By the way, in the above-mentioned conventional conductive sheet in which conductive layers are laminated by co-extrusion, the surface resistance is hardly greatly reduced even if the conductive layer is stretched by performing three-dimensional molding. Therefore, there is an advantage that it can be easily used as a raw sheet of a molded article for packaging electronic parts. However, on the other hand, since the conductive layer is exposed on the surface, there is a problem that carbon compounded for imparting conductivity tends to fall off due to friction. In particular, as electronic components have become smaller and densely arranged, the area for obtaining electrical connection (soldered area) has also become smaller. Cause cause. Further, since the conductive layer laminated by co-extrusion is relatively thick, it is difficult to obtain transparency. For this reason, in the case of a molded article for packaging electronic parts, it is difficult to perform a leakage inspection of electronic parts by visual observation from outside or image processing, which is inconvenient in handling.

[0004] The above-mentioned conventional conductive sheet in which a conductive layer is laminated as a coating film and further provided with a protective coating layer of an acrylic resin has the advantage that the protective coating layer can prevent the carbon particles from falling off. Since it can be formed thinner, there is an advantage that transparency can be easily obtained. However, on the other hand, when the conductive layer is stretched by molding, the surface resistance suddenly increases, so it is only used as a packaging material that does not undergo three-dimensional molding, such as a packaging bag. There is a problem that it is difficult to use as a raw sheet.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and a conductive sheet having a conductive layer laminated as a coating film and further provided with a protective coat layer is formed into a molded article for packaging electronic parts. An object of the present invention is to provide a carrier tape having excellent performance using the improved conductive sheet, while effectively suppressing the occasional increase in surface resistance.

[0006]

For this purpose, the present invention provides a plastic sheet in which a conductive layer of carbon black using polyvinylpyrrolidone as a binder is laminated as a coating film on at least one surface of a plastic sheet, and a urethane resin coating is formed on the conductive layer. An object of the present invention is to provide a conductive sheet characterized in that a protective coat layer is laminated as a coating film.

According to the present invention, the protective coat layer is composed of a urethane resin containing polyethylene wax, and the surface resistance of the protective coat layer laminated on the conductive layer is 10 ⁴ to 10 ⁹ Ω. AB plastic sheet
Being an S-based resin sheet, the thickness of the plastic sheet is 0.2 to 1.0 mm, and the thickness of the conductive layer is 0.1 to 1.0
.mu.m and the thickness of the protective coating layer being 0.1 to 3 .mu.m as preferred embodiments thereof.

According to the present invention, there is provided a conductive member comprising any one of the conductive sheets described above, wherein a recess for accommodating an electronic component is formed so that at least an outer surface of the conductive sheet serves as a protective coating layer. It also provides a carrier tape.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A conductive sheet according to the present invention comprises a plastic sheet as a base material, a conductive layer formed on one or both sides of the plastic sheet, and a protective coat layer provided on the conductive layer. It consists of.

The plastic sheet is a sheet of natural resin which does not contain inorganic additives such as a diffusing material, a pigment and a reinforcing material, and can be basically formed three-dimensionally and constitutes a protective coating layer described later. A resin sheet having excellent adhesion to urethane resin is used. Specifically, for example, a thermoplastic resin sheet such as an ABS resin, polyvinyl chloride, polycarbonate, polyester, polymethyl methacrylate, or polyphenyl ether can be used. Among these, excellent moldability, not only easy to obtain the strength required as a molded article for electronic parts packaging, but also does not contain chlorine components, which may have a negative impact on the environment at the time of disposal,
In addition, an ABS resin sheet is particularly preferred because it is difficult to form a curl when wound up in a roll shape.

The above-mentioned ABS resin includes, in addition to an ABS resin composed of an acrylonitrile-styrene copolymer as a resin phase and polybutadiene as a rubber phase, a copolymer of styrene and butadiene, an acrylic rubber, Those containing a copolymer of ethylene and propylene and the like, and those containing, for example, polymethyl methacrylate described later in the resin phase are also included.

As the ABS resin, a rubber phase of polybutadiene is preferable because it has a good balance of physical properties such as hardness and is excellent in moldability, and particularly, a resin having a polybutadiene content of 15 to 25% by weight. Is preferred. For the same reason, the ratio of styrene to acrylonitrile (ST / AN) in the resin phase is 80/20 to 55/45.
It is preferred that Further, when a transparent ABS resin in which the refractive indices of the resin phase (AS resin) and the rubber phase (polybutadiene) are matched by including polymethyl methacrylate in the resin phase is used, the conductive sheet of the present invention and the This is preferable because the transparency of the obtained molded article for electronic parts can be enhanced.

The thickness of the plastic sheet is preferably from 0.2 to 1.0 mm from the viewpoints of moldability into a molded article for packaging electronic parts and maintenance of strength after molding.

The conductive layer provided on at least one side of the plastic sheet is a coating film of carbon black using polyvinylpyrrolidone as a binder. Polyvinylpyrrolidone has a role as a binder that enhances the adhesion of carbon black to form a coating film, and also prevents aggregation, reaggregation and sedimentation due to excessive water absorption of carbon when forming an aqueous paste described below. It also plays the role of. As polyvinylpyrrolidone,
From the viewpoint of easy dispersion of carbon black, those having a molecular weight of about 1,000 to 4,000 are preferable.

The conductive layer can be easily formed by applying and drying a conductive paint obtained by diluting an aqueous paste obtained by mixing carbon black, polyvinylpyrrolidone and water with a lower alcohol (usually methanol is used). .

The conductive layer obtained as a coating film of such a conductive paint is preferably composed of 60 to 70% by weight of carbon black and 40 to 30% by weight of polyvinylpyrrolidone in a dry state. Preferably, carbon black and polyvinylpyrrolidone in the conductive paint are contained in a weight ratio of 6: 4 to 7: 3. In addition, a water-soluble additive may be added in addition to carbon black and polyvinylpyrrolidone in order to improve the paintability of the conductive paint and the performance of the coating film.

The thickness of the conductive layer is 0.1 in a dry state.
It is preferably from 1.0 to 1.0 μm. If the thickness of the conductive layer is too small, the surface resistance increases due to stretching during molding, and it becomes difficult to maintain the required conductivity. If the thickness of the conductive layer is excessively large, not only does the transparency deteriorate, but also the carbon particles easily fall off due to cracking or peeling of the conductive layer during molding.

The protective coating layer provided on the conductive layer is made of a urethane resin or a urethane resin containing polyethylene wax. In particular, when the protective coat layer is formed of a urethane resin to which polyethylene wax is added, for example, when a carrier tape is manufactured using the present conductive sheet, the cover tape (lid material) is easily fused. When a polyethylene wax is added, it is preferably 5 to 20% by weight in the protective coat layer.

The protective coating layer is formed by applying and curing a mixture of isocyanate and polyol or a mixture of polyethylene polyol and polyethylene isocyanate, and serves to firmly adhere the conductive layer to the plastic sheet. In addition, when the present conductive sheet is subjected to molding, the state of adhesion of the conductive layer to the plastic sheet is maintained while following the expansion of the plastic sheet, so that a rapid increase in surface resistance due to the expansion of the plastic sheet is suppressed. Is what you can do.

The thickness of the protective coating layer is preferably from 0.1 to 3 μm. If the thickness is too large, the surface resistance of the protective coating layer laminated on the conductive layer becomes large, making it difficult to obtain the required conductivity. Conversely, if it is too thin, it becomes difficult to maintain the adhesion of the conductive layer. The protective coat layer is preferably provided such that the surface resistance of the protective coat layer laminated on the conductive layer is 10 ⁴ to 10 ⁹ Ω from the viewpoint of maintaining necessary conductivity and maintaining adhesion of the conductive layer. .

In particular, the protective coating layer of the present invention not only suppresses a rapid increase in surface resistance following the elongation during molding as described above, but also has the advantage that blocking is unlikely to occur. Each of the conductive sheet of the present invention and a carrier tape obtained from the conductive sheet is wound into a roll, stored, and provided for transportation. The protective coat layer in the present invention is less likely to cause blocking during storage and transport, and thus can prevent quality deterioration due to blocking.

The conductive carrier tape according to the present invention is obtained by slitting the conductive sheet of the present invention into a tape, and forming a concave portion for accommodating an electronic component in the tape and a sprocket hole meshing with a transport sprocket. Can be easily obtained. Usually, the conductive sheet used for the conductive carrier tape has a conductive layer and a protective coating layer provided on one side of a plastic sheet, and the concave portion is formed such that the protective coating layer side is the outer surface.

The formation of the concave portion can be performed by embossing as in the prior art. The sprocket holes can be formed by punching. The shape and size of the recess are
What is necessary is just to select according to the electronic component to be accommodated, and the position and pitch of a sprocket hole should just match the conveyance sprocket of the automatic mounting machine to be used.

[0024]

EXAMPLES Example 1 ABS resin (Styrac IM2 manufactured by Asahi Kasei Corporation)
0 ") was extruded with a T-die at a reference film thickness of 300 µm on one side of an ABS resin sheet, a conductive paint was applied by a bar coater and dried. Carbon black (CB) was 67% by weight, polyvinylpyrrolidone (PVP). ) Was formed as a coating film of 33% by weight. As the conductive paint, an aqueous paste obtained by kneading CB, PVP and water was diluted with methanol.

Next, a polyester-based polyol (“AD-76H” manufactured by Toyo Morton Co., Ltd.) is provided on the conductive layer.
Isocyanate (TOYO MORTON “CAT-10”)
And polyethylene wax ("MAT-2" manufactured by Huaken Gosei Co., Ltd.)
5T ") was applied with a bar coater and cured with a bar coater to form a protective coating layer of a polyethylene wax-containing urethane resin to prepare a conductive sheet.

The thickness of the conductive layer in the conductive sheet is 0.5.
The thickness of the protective coat layer was 0.7 μm.

In order to check how much the surface resistance increases when each of the conductive sheets is stretched by molding, a test piece cut to a width of 24 mm and a length of 95 mm was pulled with a thermostatic case. The elongation is 20 with the testing machine
The protective coat layer was stretched so as to have three types of 0%, 250% and 300%, and the surface resistance value of the surface of the protective coat layer before and after stretching was measured. Table 1 shows the results.

The test piece was stretched by a tensile tester with a constant temperature case, the temperature in the constant temperature case was set to 130 ° C., the test piece was set at a chuck interval of 50 mm of the tensile tester, and left until the equilibrium temperature was reached (about 20 minutes). Later, 30
The stretching was performed at a speed of 0 mm / min until a predetermined length was reached. In addition, the measurement of the surface resistance before stretching is performed on the test piece before setting in a tensile tester, and the measurement of the surface resistance after stretching is performed after stretching.
The test piece was taken out by opening the door of the constant temperature case and cooling. The measurement of the surface resistance was performed using a tester manufactured by Mitsubishi Chemical Corporation. The lower limit of measurement of this tester was 1. E + 04Ω, upper limit of measurement is 1. E + 13Ω.

Further, after the test pieces were separately stacked and placed in a thermostat at 60 ° C. for 1 hour with a 1 kg weight placed thereon, the stacked test pieces were peeled off to examine the blocking resistance. Table 1 shows the results.場合 indicates that no blocking occurred, and X indicates that blocking occurred.

Further, the test piece was lightly rubbed on a white paper, and the CB falling resistance was examined based on the state of CB adhered to the paper.
Table 1 shows the results. A sample with little black mark on the paper was marked as ○, indicating that the CB was hard to fall off, and a mark with a clear black mark on the paper was marked as x, indicating that the CB was easily dropped.

Example 2 The same test as in Example 1 was performed except that the thickness of the conductive layer was changed to 0.2 μm.

The results are shown in Table 1.

Example 3 The same test as in Example 1 was conducted except that the conductive layer was changed to 60% by weight of CB and 40% by weight of PVP.

Table 1 shows the results.

Example 4 The same test as in Example 1 was performed except that a 235 μm thick polyvinyl chloride sheet (PVC: manufactured by Sumitomo Bakelite Co., Ltd.) was used as the plastic sheet.

The results are shown in Table 1.

Comparative Example 1 The same experiment as in Example 1 was carried out except that the protective coat layer was formed by applying and drying an acrylic resin paint (“Brannet SV” manufactured by Origin Electric Co.).

The results are shown in Table 1.

Comparative Example 2 The same experiment as in Example 1 was performed except that the protective coat layer was formed by applying and curing a vinyl acrylic resin paint (“CAV” manufactured by Seiko Advance Co., Ltd.).

The results are shown in Table 1.

Comparative Example 3 A similar experiment was conducted in the same manner as in Example 1 for a three-layer conductive sheet ("Thermosheet EC" manufactured by Denki Kagaku Kogyo KK) having a thickness of 400 μm of ABS resin sheet / CB + polystyrene (PS). went.

The results are shown in Table 1.

[0043]

[Table 1]

[0044]

The present invention is as described above, and is a conductive sheet that not only easily removes carbon particles, easily obtains transparency, but also has a small increase in surface resistance even when formed by deep drawing. Can be obtained. Further, by using this conductive sheet, a conductive carrier tape having excellent performance can be obtained.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4F100 AA37B AD11B AJ11C AK01A AK02B AK04C AK51C AK74A BA03 BA07 BA10A BA10C CC00B CC00C DD05 GB15 GB41 JG01B JG04 JG04C YY00C 5G307 GA02 GB01 GC02

Claims (6)

[Claims] 1. A conductive layer of carbon black using polyvinylpyrrolidone as a binder is laminated as a coating film on at least one side of a plastic sheet, and a protective coating layer of urethane resin is further laminated as a coating film on this conductive layer. A conductive sheet characterized by the above-mentioned. 2. The conductive sheet according to claim 1, wherein the protective coat layer is made of a urethane resin containing polyethylene wax. 3. The conductive sheet according to claim 1, wherein the surface resistance of the protective coating layer laminated on the conductive layer is 10 ⁴ to 10 ⁹ Ω. 4. The conductive sheet according to claim 1, wherein the plastic sheet is an ABS resin sheet. 5. The plastic sheet has a thickness of 0.2 to 0.2.
The conductive sheet according to claim 1, wherein the thickness of the conductive layer is 1.0 to 1.0 μm, and the thickness of the protective coating layer is 0.1 to 3 μm. 6. A conductive sheet according to claim 1, wherein a concave portion for accommodating an electronic component is formed so that at least an outer surface thereof becomes a protective coat layer. Conductive carrier tape.