U.S. patent application number 13/877742 was filed with the patent office on 2013-08-15 for electronic component packaging sheet, and formed article thereof.
This patent application is currently assigned to DENKI KAGAKU KOGYO KABUSHIKI KAISHA. The applicant listed for this patent is Junpei Fujiwara, Masatoshi Kawata, Tomohiro Osawa. Invention is credited to Junpei Fujiwara, Masatoshi Kawata, Tomohiro Osawa.
Application Number | 20130209748 13/877742 |
Document ID | / |
Family ID | 45927800 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130209748 |
Kind Code |
A1 |
Fujiwara; Junpei ; et
al. |
August 15, 2013 |
ELECTRONIC COMPONENT PACKAGING SHEET, AND FORMED ARTICLE
THEREOF
Abstract
Disclosed is an electronic component packaging sheet including a
surface conductive layer formed on the surface of at least one side
of a substrate sheet. The substrate sheet includes 80,000 to
220,000 Mw of a styrene-conjugated diene block copolymer; 200,000
to 400,000 Mw of a polystyrene resin; and 150,000 to 210,000 Mw of
an impact resistant polystyrene resin. The surface conductive layer
includes an acrylic copolymer resin; and carbon nanotubes. The
electronic component packaging sheet is a transparent conductive
sheet having excellent thermoforming properties, good transparency
after thermoforming, and sufficient electrostatic diffusion
performance to maintain a low surface resistance value. The
electronic component packaging sheet is particularly suited for the
manufacture of embossed carrier tape.
Inventors: |
Fujiwara; Junpei;
(Isesaki-shi, JP) ; Osawa; Tomohiro; (Isesaki-shi,
JP) ; Kawata; Masatoshi; (Isesaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fujiwara; Junpei
Osawa; Tomohiro
Kawata; Masatoshi |
Isesaki-shi
Isesaki-shi
Isesaki-shi |
|
JP
JP
JP |
|
|
Assignee: |
DENKI KAGAKU KOGYO KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
45927800 |
Appl. No.: |
13/877742 |
Filed: |
October 6, 2011 |
PCT Filed: |
October 6, 2011 |
PCT NO: |
PCT/JP2011/073105 |
371 Date: |
April 4, 2013 |
Current U.S.
Class: |
428/172 ;
427/600; 428/323; 428/327; 428/516; 428/517 |
Current CPC
Class: |
C08L 25/06 20130101;
Y10T 428/31913 20150401; B65D 2213/02 20130101; C08L 53/02
20130101; Y10T 428/31917 20150401; H01B 1/20 20130101; C08L 33/04
20130101; C08L 25/06 20130101; C08L 53/02 20130101; C08L 33/04
20130101; C08L 2205/02 20130101; C08L 2203/16 20130101; B65D 73/02
20130101; C08L 2205/16 20130101; Y10T 428/254 20150115; H05K
13/0084 20130101; Y10T 428/31533 20150401; C08L 53/02 20130101;
C08L 25/06 20130101; C08L 81/00 20130101; C08L 25/06 20130101; C08L
2205/02 20130101; Y10T 428/25 20150115; Y10T 428/24612
20150115 |
Class at
Publication: |
428/172 ;
428/516; 428/517; 428/327; 428/323; 427/600 |
International
Class: |
C08L 25/06 20060101
C08L025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 7, 2010 |
JP |
2010-227462 |
Dec 24, 2010 |
JP |
2010-286980 |
Feb 1, 2011 |
JP |
2011-020066 |
Claims
1. An electronic component packaging sheet having a surface
conductive layer formed on a surface on at least one side of a
substrate sheet, wherein the substrate sheet comprises a
styrene-conjugated diene block copolymer (A), a polystyrene resin
(B), and a high impact polystyrene resin (C), the components having
the following weight-average molecular weights (Mw): component (A):
Mw=80,000 to 220,000; component (B): Mw=200,000 to 400,000;
component (C): Mw=150,000 to 210,000; and the surface conductive
layer comprising an acrylic copolymer resin (D) and carbon
nanotubes (E).
2. The electronic component packaging sheet of claim 1, wherein the
peak molecular weight by GPC of polymer blocks of styrenic monomers
in component (A) is in the range of 30,000 to 120,000; and a
half-width of a molecular weight distribution curve of the polymer
blocks of the styrenic monomers is in the range of 0.8 to 1.25.
3. The electronic component packaging sheet of claim 1, wherein the
rubber component in a graft rubber in component (C) is a diene
rubber monomer chosen from the group consisting of 1,3-butadiene
(butadiene), 2-methyl-1,3-butadiene (isoprene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and
2-methylpentadiene, or a thermoplastic elastomer of a
styrene-conjugated diene block copolymer wherein the diene
component is at least 50 mass %.
4. The electronic component packaging sheet of claim 1, wherein the
particle size of the graft rubber in component (C) is .phi. 2.0 to
3.0 .mu.m, and the proportion of rubber in the graft rubber in the
substrate sheet is 0.75 to 1.90 mass %.
5. The electronic component packaging sheet of claim 1, wherein the
substrate sheet is formed of a resin composition comprising 29 to
65 mass % component (A), 51 to 15 mass % component (B) and 20 to 9
mass % component (C).
6. The electronic component packaging sheet of claim 1, wherein the
melt tension of the substrate sheet at 220.degree. C. is 10 to 30
mN.
7. The electronic component packaging sheet of claim 1, wherein the
carbon nanotubes in the surface conductive layer are multiwall
carbon nanotubes of diameter 3 to 15 nm and length 0.5 to 3 .mu.m,
wherein the amount of the multiwall carbon nanotubes contained in
the surface conductive layer is 3 to 10 mass %.
8. The electronic component packaging sheet of claim 1, wherein the
particle size in an aqueous dispersion of the acrylic copolymer
resin (D) in the surface conductive layer is 80 to 350 nm.
9. The electronic component packaging sheet of claim 1, wherein the
glass transition temperature Tg of the acrylic copolymer resin (D)
in the surface conductive layer is 25 to 80.degree. C.
10. The electronic component packaging sheet of claim 1, wherein
the surface resistance of a formed article with a draw ratio for
thermoforming of 1.5 to 3 times is on the order of 10.sup.5.OMEGA.
to 10.sup.7.OMEGA..
11. The electronic component packaging sheet of claim 1, wherein
the coefficient of static friction of the conductive layer formed
on the surface of the substrate sheet is at least 0.85 and at most
2.50, and the coefficient of kinetic friction is at least 0.85 and
at most 2.50.
12. A method for producing the electronic component packaging sheet
of claim 1 comprising steps of: preparing a mixed dispersion by
mixing the aqueous dispersion of an acrylic copolymer with a
dispersion of carbon nanotubes obtained by primary dispersion in a
bead mill of carbon nanotubes in an aqueous solution of a sulfonic
acid type dispersant having aromatics in the molecule, and
secondary dispersion in an ultrasonic dispersion; and applying the
mixed dispersion onto at least one surface of the substrate
sheet.
13. A formed article obtained by thermoforming the electronic
component packaging sheet of claim 1.
14. The formed article of claim 13, which is an embossed carrier
tape.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sheet for packaging
electronic components such as IC's, LED's, connectors and
capacitors, a method for production thereof, and a formed article
formed from said sheet.
BACKGROUND ART
[0002] Generally, carrier tapes are used to store and transport
compact electronic components such as IC's. In particular,
polystyrene (PS) sheets are excellent in transparency and have good
thermoforming properties, so they are widely used for being able to
provide carrier tapes of good pocket shape (see, e.g., Patent
Documents 1 and 2).
[0003] On the other hand, when transporting IC's, the buildup of
static electricity due to friction between the carrier tape and the
content, or generated when peeling cover tape adhered to the top
surface of the carrier tape, can result in destruction of the IC
circuits. Additionally, in the case of very small components, the
components can adhere to the cover tape, causing problems when
mounting them to electronic devices. In order to prevent such
trouble, the surface of the carrier tape is often subjected to an
anti-static treatment (see, e.g., Patent Documents 3 and 4).
However, when treated with a normal anti-static agent, the surface
resistance can become higher, and the anti-static effect can be
insufficient. Therefore, methods of preventing the buildup of
static electricity by providing a conductive layer comprising a
conductive material such as carbon black or a metallic powder are
known (e.g., Patent Document 5), but in that case, it is difficult
to obtain sufficient transparency to read letters inscribed on the
compact electronic components that are contained inside through the
tape or to inspect the products as to whether or not they are
acceptable.
[0004] Additionally, as anti-static treatments for the surface of
films in general, processes of coating the surface of a substrate
film consisting of polycarbonate (PC), polyethylene terephthalate
(PET), polypropylene (PP) or the like and forming a conductive
layer having a certain degree of transparency have been proposed
for various applications (see, e.g., Patent Documents 6 and 7).
[0005] However, sheets and films coated with various types of
conductive agents and conductive compositions on their surfaces as
disclosed in Patent Documents 6 and 7 are such that the materials
of the substrate films are mainly composed of PC, PET and PP
substrates, and no specific examples have been disclosed in the
technical field of the present invention of a favorable arrangement
wherein the surface of a PS sheet is coated. Additionally, when
forming pockets in carrier tape using a sheet having the surface of
the substrate sheet of the material coated with a conductive agent,
the surface resistance of the conductive layer can rise, reducing
the effect of preventing the buildup of electrostatic charge.
Furthermore, when a raw sheet is stored in a wound state,
particularly in a high-temperature high-humidity environment,
blocking and separation of the conductive layer due to blocking may
occur. [0006] Patent Document 1: JP 2003-55526 A [0007] Patent
Document 2: JP 2005-23268 A [0008] Patent Document 3: JP
2003-253069 A [0009] Patent Document 4: JP 2003-320605 A [0010]
Patent Document 5: JP H9-76424 A [0011] Patent Document 6: JP
2003-308733 A [0012] Patent Document 7: JP 2007-157440 A
SUMMARY OF THE INVENTION
[0013] The present invention was achieved in view of the
above-described circumstances, and has the primary purpose of
offering an electronic component packaging sheet capable of
retaining good thermoforming ability due to use of a polystyrene
(PS) type substrate sheet, wherein the transparency does not
deteriorate after forming even when providing a surface conductive
layer, and the surface resistance can be maintained at a
satisfactory level.
[0014] Additionally, the present invention has another purpose of
offering an electronic component packaging sheet with almost no
blocking of sheets and almost no separation of the conductive layer
due to blocking.
[0015] Furthermore, the present invention also has the purpose of
offering a method suitable for producing the aforementioned
electronic component packaging sheet and a formed article produced
using the aforementioned electronic component packaging sheet.
[0016] The antistatic effect is achieved in a carrier tape having a
conductive layer on the surface by dispersing static electricity,
generated by friction with the contents during transport or the
like as described above, through a conductive layer with
sufficiently low surface resistance. Therefore, the present
inventors performed diligent research into compositions wherein the
surface resistance measured at standard intervals is held to a
standard level or less and the transparency is retained even after
pocket formation, whereupon they discovered that an electronic
component packaging sheet capable of solving these problems, and
with almost no blocking of the sheet resulting in separation of the
conductive layer, can be obtained by applying carbon nanotubes to a
substrate sheet using a polystyrene (PS) type resin composition,
wherein each resin has a molecular weight in a specific range.
[0017] In other words, according to a first aspect, the present
invention offers an electronic component packaging sheet having a
surface conductive layer formed on a surface on at least one side
of a substrate sheet, wherein the substrate sheet comprises a
styrene-conjugated diene block copolymer (A), a polystyrene resin
(B), and a high impact polystyrene resin (C), the components having
the following weight-average molecular weights (Mw):
[0018] component (A): Mw=80,000 to 220,000;
[0019] component (8): Mw=200,000 to 400,000;
[0020] component (C): Mw=150,000 to 210,000; and
[0021] the surface conductive layer comprising an acrylic copolymer
resin (D) and carbon nanotubes (E).
[0022] Regarding the above, according to one embodiment, the peak
molecular weight by GPC of polymer blocks of styrenic monomers in
component (A) is in the range of 30,000 to 120,000; and a
half-width of a molecular weight distribution curve of the polymer
blocks of the styrenic monomers is in the range of 0.8 to 1.25. The
rubber component in a graft rubber in component (C) is preferably a
diene rubber monomer chosen from the group consisting of
1,3-butadiene (butadiene), 2-methyl-1,3-butadiene (isoprene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and
2-methylpentadiene, or a thermoplastic elastomer of a
styrene-conjugated diene block copolymer wherein the diene
component is at least 50 mass %. In one example, the particle size
of the graft rubber in component (C) is .phi. 2.0 to 3.0 .mu.m, and
the proportion of rubber in the graft rubber in the substrate sheet
is 0.75 to 1.90 mass %.
[0023] In another embodiment, the substrate sheet is formed of a
resin composition comprising 29 to 65 mass % component (A), 51 to
15 mass % component (B) and 20 to 9 mass % component (C), and the
melt tension of the substrate sheet at 220.degree. C. is 10 to 30
mN.
[0024] In yet another embodiment of the present invention, the
carbon nanotubes in the surface conductive layer are multiwall
carbon nanotubes of diameter 3 to 15 nm and length 0.5 to 3 .mu.m,
and the amount of the multiwall carbon nanotubes contained in the
surface conductive layer is 3 to 10 mass %.
[0025] The particle size in an aqueous dispersion of the acrylic
copolymer resin (D) in the surface conductive layer is 80 to 350 nm
and the glass transition temperature Tg the acrylic copolymer resin
(D) in the surface conductive layer is 25 to 80.degree. C.
Additionally, in a preferred embodiment, the surface resistance of
a formed article with a draw ratio for thermoforming of 1.5 to 3
times is on the order of 10.sup.5.OMEGA. to 10.sup.7.OMEGA..
Additionally, the coefficient of static friction of the conductive
layer formed on the surface of the substrate sheet is preferably at
least 0.85 and at most 2.50, and the coefficient of kinetic
friction is preferably at least 0.85 and at most 2.50.
[0026] In another embodiment, the present invention offers a method
for producing the aforementioned electronic component packaging
sheet, comprising steps of preparing a mixed dispersion by mixing
the aqueous dispersion of an acrylic copolymer with a dispersion of
carbon nanotubes obtained by primary dispersion in a bead mill of
carbon nanotubes in an aqueous solution of a sulfonic acid
dispersant having aromatics in the molecule, and secondary
dispersion in an ultrasonic dispersion; and applying the mixed
dispersion onto at least one surface of the substrate sheet.
[0027] In yet another embodiment, the present invention offers a
formed article formed by thermoforming the aforementioned
electronic component packaging sheet, and this formed article may,
for example, be an embossed carrier tape.
[0028] According to the present invention, by using a polystyrene
(PS) type substrate sheet, it is possible to obtain an electronic
component packaging sheet that maintains good thermoforming
properties, wherein the transparency after forming does not
deteriorate even when providing a surface conductive layer, and the
surface resistance can be retained at a satisfactory level.
Additionally, the sheet almost never undergoes blocking or
separation of the conductive layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 shows a formed article formed by thermoforming an
electronic component packaging sheet in a pressure-forming machine
according to an example of the present invention.
[0030] FIG. 2 shows standards for evaluation of thermoforming
properties of an electronic component packaging sheet according to
examples of the present invention.
[0031] FIG. 3 shows a method of measurement of surface resistance
of a carrier tape formed article according to an example of the
present invention.
MODES FOR CARRYING OUT THE INVENTION
[0032] Herebelow, modes for carrying out the present invention will
be described in detail.
[0033] The electronic component packaging sheet according to an
embodiment of the present invention has a surface conductive layer
formed on the surface on at least one side of the substrate sheet.
The substrate sheet is formed from a resin composition containing
the respective components, i.e. a styrene-conjugated diene block
copolymer (A), a polystyrene resin (B), and a high impact
polystyrene resin (C), respectively having specific weight-average
molecular weights, and the surface conductive layer comprises an
acrylic copolymer resin (D), and carbon nanotubes (E).
[0034] The styrene-conjugated diene block copolymer (A) is a
polymer including, in its structure, polymer blocks mainly
comprising styrenic monomers and polymer blocks mainly comprising
conjugated diene monomers. Examples of styrenic monomers include
styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene,
1,3-dimethylstyrene, .alpha.-methylstyrene, vinylnapththalene,
vinylanthracene and 1,1-diphenylethylene. In a particularly
preferred embodiment of the invention, the monomers are mainly
styrene, but one or more other components may be included as trace
components.
[0035] Conjugated diene monomers are compounds having conjugated
double bonds in their structure. Examples include 1,3-butadiene
(butadiene), 2-methyl-1,3-butadiene (isoprene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and
2-methylpentadiene, among which butadiene and isoprene are
preferred. One or more types of conjugated diene monomers may be
used. The polymer blocks mainly comprising styrenic monomers refer
to both polymer blocks consisting of only structures derived from
styrenic monomers and polymer blocks comprising structures derived
from styrenic monomers in an amount of at least 50 mass %. The
polymer blocks mainly comprising conjugated diene monomers refer to
both polymer blocks consisting of only structures derived from
conjugated diene monomers and polymer blocks comprising structures
derived from conjugated diene monomers in an amount of at least 50
mass %. The conjugated diene content in the styrene-conjugated
diene block copolymer (A), for every 100 parts by mass of component
(A), should preferably be 10 to 25 mass % in view of the mechanical
properties of the substrate sheet. Here, the conjugated diene
content refers to the proportional mass of structures derived from
conjugated diene monomers in the entire copolymer.
[0036] One or more types of the styrene-conjugated diene block
copolymer (A) may be used. In the present invention, when the
conjugated diene is butadiene, for example, the styrene-conjugated
diene block copolymer may be either a styrene-butadiene (SB)
bipolymer or a styrene-butadiene-styrene (SBS) terpolymer, and may
be a resin composed of a plurality of blocks, with three or more
styrene blocks and two or more butadiene blocks. Furthermore, it
may have a so-called tapered block structure wherein the component
ratio of styrene and butadiene blocks continuously changes between
respective blocks. Additionally, the styrene-conjugated diene block
copolymer may be one that is commercially available used as is.
[0037] In the styrene-conjugated diene block copolymer (A) used in
the present invention, the polymer blocks of styrenic monomers in
the component preferably have a peak molecular weight as measured
by GPC in the range of 30,000 to 120,000, and the molecular weight
distribution curve of the styrenic monomer blocks preferably has a
half-width in the range of 0.8 to 1.25, more preferably 1.05 to
1.25. Use of those in this range enables good formability to be
achieved. The molecular weight distribution curve of the styrene
blocks in component (A) can be determined by the following method.
First, component (A) is subjected to oxidative cleavage by
chloroform using osmium tetroxide as a catalyst, in accordance with
the method described in I. M. Kolthoff, et al., J. Polym. Sci., 1,
429 (1946), then the resulting styrene blocks are dissolved in a
tetrahydrofuran solvent and measured by GPC. The molecular weight
curve can then be used to determine the styrene-converted peak
molecular weight using standard polystyrene (monodisperse). The GPC
measurements may be in accordance with conventional techniques,
with the main measurement conditions being as follows:
[0038] Column temperature: 40.degree. C.
[0039] Detection method: differential refractometry
[0040] Mobile phase: tetrahydrofuran
[0041] Sample concentration: 2 mass %
[0042] Calibration curve: from standard polystyrene
(monodisperse)
[0043] The half-width can be determined using this molecular weight
distribution curve for the styrene blocks. Specifically, when the
molecular weight is placed on the horizontal axis using a
logarithmic scale with the range of 1000 to 1,000,000 being 15 cm,
and the concentration (mass ratio) is placed on the vertical axis
at an arbitrary height, the width of the peak on the horizontal
axis at a height of 50% of the peak top is the half-width. In this
case, the height of the peak top should be that perpendicular to
the horizontal axis, and the width of the peak at 50% of the height
should be parallel to the horizontal axis. The half-width of the
molecular weight distribution curve of the styrene blocks
correlates with the molecular weight distribution of the block
copolymer. While the method of adjusting the molecular weight
distribution is not particularly restricted, block copolymers of
different molecular weights can be obtained by methods such as
adjusting the time of addition of the initiator during the
polymerization of styrene block parts in component (A).
[0044] The polystyrene resin (B) is a resin generally known as a
GPPS, mainly comprising styrenic monomers, but may contain one or
more aromatic vinyl compounds such as o-methylstyrene,
p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene,
.alpha.-methylstyrene, vinylnaphthalene, vinylanthracene and
1,1-diphenylethylene as a trace component, and a commercially
available resin may be used.
[0045] The high impact polystyrene resin (C) is a resin generally
known as a HIPS, and is a polystyrene resin comprising
microparticulate graft rubber to which styrenic monomers have been
grafted. Graft rubber is a type of rubber wherein styrenic monomers
have been graft-copolymerized to a rubber component as described
below to form graft branches. The graft rubber content in component
(C) can be determined by dissolving in a mixed solvent of MEK and
acetone at a mass ratio of 50/50, recovering the undissolved
portion by centrifugation, and calculating from the mass thereof.
Examples of the rubber components in the graft rubber include, for
example, diene rubbers with 1,3-butadiene (butadiene),
2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene,
1,3-pentadiene, 1,3-hexadiene and 2-methylpentadiene as monomers.
Additionally, a thermoplastic elastomer which is a
styrene-conjugated diene block copolymer wherein the diene
component takes up at least 50 mass % may be used. Among these,
polybutadiene and styrene-butadiene block copolymers are
preferred.
[0046] With the graft rubber in component (C), having a particle
size in the range of at least .phi. 2.0 .mu.m and at most .phi. 3.0
.mu.m, preferably at least .phi. 2.3 .mu.m and at most .phi. 2.7
.mu.m, the substrate sheet excels in transparency and strength
properties. The graft rubber particle size here refers to the
average particle size of the graft rubber component measured by a
laser diffraction type particle analyzer. Additionally, in the
substrate sheet of the present invention, the graft rubber content
derived from component (C) in the substrate sheet when the
substrate sheet is defined as 100 mass % should be 0.75 to 1.90
mass % in order to achieve balance between impact resistance and
transparency of the substrate sheet. The graft rubber content in
component (C) and the proportional content of component (C) in the
substrate sheet should be adjusted to put the graft rubber content
of the substrate sheet in the above-indicated ranges.
[0047] The substrate sheet of the present invention is formed of a
resin composition containing 29 to 65 mass % of component (A), 51
to 15 mass % of component (B), and 20 to 9 mass % of component (C),
with (A) to (C) totaling 100 mass %. By setting the composition in
these ranges, a substrate sheet that is satisfactory in strength
properties, impact resistance and transparency can be obtained.
[0048] The substrate sheet for an electronic component packaging
sheet according to one embodiment of the present invention is
preferably a resin wherein the weight-average molecular weights
(Mw) of the respective components (A) to (C) are in the following
ranges:
[0049] Component (A): Mw=80,000 to 220,000
[0050] Component (B): Mw=200,000 to 400,000
[0051] Component (C): Mw=130,000 to 210,000
[0052] Here, the weight-average molecular weight (Mw) can be
determined from a standard polystyrene-converted molecular weight
distribution curve determined by conventional methods using
GPC.
[0053] By using resins in such ranges of weight-average molecular
weight, not only does it become possible to adjust the appropriate
range of melt tension for this resin composition as described
below, but also a sheet with a good balance of strength properties
and transparency can be obtained, with very good formability when
thermoforming the resulting substrate sheets into carrier tape or
the like, enabling good pocket formation even for deep draw
forming.
[0054] Here, the melt tension is a value (mN) measured using a melt
tension measuring apparatus with an orifice diameter of 1.0 mm
.phi., and orifice length of 10 mm and winding speeds of 10, 30 and
50 m/min. By using components (A) to (C) with weight-average
molecular weights in the above-described ranges, and adjusting the
blending ratio of the components (A) to (C) as needed, the melt
tension at 220.degree. C. of the resulting resin composition can be
adjusted, preferably to the range of 10 to 30 mN. When the melt
tension is in this range, a substrate sheet with particularly good
forming properties can be obtained when thermoforming the substrate
sheet to obtain a container. When the melt tension is less than 10
mN, holes may form when thermoforming the substrate sheet, and when
exceeding 30 mN, the formativeness (sharpness) of the pockets of
the formed articles may be deficient.
[0055] The method of producing the substrate sheet of the present
invention using the resin composition comprising the above
components (A) to (C) is not particularly limited and the sheet may
be produced by a common method. For example, the components (A) to
(C) can be blended in a predetermined ratio and mixed using a
commonly used mixer such as a tumbler, then kneaded in an extruder
to form pellet-shaped compounds. These pellet-shaped compounds can
then be extruded using a .phi. 65 mm extruder with a T-die to
produce substrate sheets. Additionally, so-called "ear" portions
formed during the substrate sheet extrusion process can be
pulverized and returned to the substrate sheet within a range not
greatly affecting the strength of the substrate sheet and the
formed article after forming.
[0056] While the thickness of the substrate sheet is not
particularly limited, when considering the application, it should
be from 50 .mu.m to 3 mm, preferably 100 .mu.m to 1 mm, and more
preferably 150 to 600 .mu.m.
[0057] The surface conductive layer formed on the surface of at
least one side of the substrate sheet comprises carbon nanotubes
and an acrylic copolymer resin. The carbon nanotubes are preferably
multiwall carbon nanotubes (MWCNT). MWCNT is composed of tubes
consisting of a plurality of tubular carbon walls of different
diameter bundled into multiple layers around a central axis, the
carbon walls being formed from a hexagonal mesh structure of
carbon. The MWCNT may be formed with the carbon walls in a
multilayered helical structure. The MWCNT is preferably of a type
wherein the carbon walls are in 2 to 30 layers, more preferably 2
to 15 layers. Use of such a MWCNT greatly improves the transparency
of the resulting conductive transparent film. More specifically, a
MWCNT of diameter .phi. 3 to 15 nm and length 0.5 to 3 .mu.m should
preferably be used. The MWCNT may be dispersed in the aqueous
composition such as to be individually separated, or they may be
dispersed with a plurality being bundled together.
[0058] The acrylic copolymer resin should preferably be used as a
binder in the form of an aqueous dispersion, and should preferably
have a particle size (the average particle size here is the median
diameter value) of 80 to 350 nm, more preferably 100 to 250 nm. By
using those with a particle size in the range of 80 to 350 nm, the
coefficient of static friction and the coefficient of kinetic
friction can be adjusted to at least 0.85 and at most 2.50. While
the transparency after coating could be increased by using an
acrylic copolymer resin with a particle size of less than 80 nm,
there is a risk of the coefficient of static friction and the
coefficient of kinetic friction becoming less than 0.85, resulting
in blocking and separation of the conductive layer due to blocking.
On the other hand, the coefficient of static friction and the
coefficient of kinetic friction could be raised by setting the
particle size of the acrylic copolymer resin to at least 350 nm,
but that may reduce the transparency and make it insufficient.
Additionally, the glass transition temperature Tg of the acrylic
copolymer resin should preferably be 25 to 80.degree. C. in order
to adequately retain the conductivity after thermoforming the sheet
of the present invention.
[0059] The surface conductive layer comprising carbon nanotubes and
an acrylic copolymer resin can be formed on the substrate sheet
surface using a known method such as those described in the
above-mentioned Patent Document 4 and JP 2005-290045 A.
[0060] In a preferred embodiment of the present invention, a mixed
dispersion of carbon nanotubes and acrylic copolymer resin is
obtained by preparing a carbon nanotube dispersion by primary
dispersion in a bead mill of carbon nanotubes in an aqueous
solution of a sulfonic acid type dispersant having aromatics in the
molecule, and secondary dispersion in an ultrasonic dispersion, and
mixing therewith an aqueous dispersion of an acrylic copolymer as a
binder. Next, this mixed dispersion is applied to the surface on at
least one side of the substrate sheet by a gravure coater or the
like, then dried to form a surface conductive layer.
[0061] By forming the substrate sheet from a resin composition
comprising resin components (A) to (C) of specific weight-average
molecular weights and forming a surface conductive layer comprising
carbon nanotubes (E) and an acrylic copolymer resin (D) on the
surface thereof, it is possible to obtain a sheet for packaging
electronic components such as an embossed carrier tape, with
excellent thermoforming properties, wherein the transparency will
not be reduced after forming, and the surface resistance is
maintained at a satisfactory level. In particular, when a carrier
tape or the like is thermoformed from a substrate sheet having
formed thereon a surface conductive layer comprising preferably 3
to 10 mass % of carbon nanotubes, particularly MWCNT, preferably of
diameter .phi. 3 to 15 nm and length 0.5 to 3 .mu.m, in the surface
conductive layer, the formability of the surface conductive layer
is very good and the surface conductive layer will exhibit good
transparency even after forming.
EXAMPLES
[0062] Herebelow, Examples 1 to 18 and Comparative Examples 1 to 7
of the sheet for packaging electronic components of the present
invention shall be explained with reference to Tables 1 to 6 and
FIGS. 1 to 3.
[0063] Table 1-1 to Table 1-3 show the specifications for each
component (A), (B) and (C) in the resin composition of the
substrate sheet used in the examples and comparative examples.
[0064] Table 1-1 shows the weight-average molecular weight (Mw) and
butadiene/styrene mass % ratio of the compositions of the
styrene-conjugated diene block copolymer (A), and the peak
molecular weight of the styrene blocks and peak half-width of the
styrene blocks in component (A). Table 1-2 shows the weight-average
molecular weight (Mw) of the compositions of the polystyrene resin
(B). Table 1-3 shows the weight-average molecular weight (Mw),
graft rubber part (mass %) and graft rubber average particle size
(.mu.m) of the compositions of the high impact polystyrene resin
(C).
TABLE-US-00001 TABLE 1-1 Styrene Styrene Weight Block Block Average
Butadiene/ Peak Peak Molecular Styrene Molecular Half-width Weight
(Mw) (Mass %) Weight (cm) Styrene- A-1 150,000 20/80 40,000 1.11
Conjugated A-2 140,000 24/76 109,000 0.94 Diene A-3 80,000 16/84
34,000 0.98 Copolymer A-4 220,000 17/83 77,000 1.09 (A) A-5 280,000
18/82 140,000 0.70 A-6 70,000 40/60 15,000 1.30
TABLE-US-00002 TABLE 1-2 Weight Average Molecular Weight (Mw)
Polystyrene (B) B-1 330,000 B-2 290,000 B-3 210,000 B-4 370,000 B-5
470,000 B-6 120,000
TABLE-US-00003 TABLE 1-3 Weight Graft Rubber Average Average
Molecular Graft Rubber Particle Size Weight (Mw) Part (mass %)
(.mu.m) High-Impact C-1 180,000 8.6 2.5 Polystyrene (C) C-2 190,000
7.9 2.0 C-3 150,000 8.8 2.3 C-4 200,000 7.4 2.3 C-5 100,000 6.1 1.8
C-6 250,000 7.3 2.8
[0065] Table 24 and Table 2-2 show the specs for components (D) and
(E) in the surface conductive layer used for the examples and the
comparative examples.
[0066] Table 2-1 shows the compositions (mass %) of the acrylic
copolymer resin (D) as well as the glass transition point (.degree.
C.) and average particle size (nm) of the resins, and Table 2-2
shows the shapes of the carbon nanotubes (CNT) (E), among which NC
7000 in E-1 is an MWCNT produced by Nanocyl, and Graphistrength
C100 in E-2 is an MWCNT produced by Arkema.
TABLE-US-00004 TABLE 2-1 Composition in Resin (mass %) Glass
Average Methyl Butyl Butyl Cyclohexyl Transition Particle No
Methacrylate Acrylate Methacrylate Methacrylate Point (.degree. C.)
Size (nm) Acrylic D-1 40 41 8 11 40 130 Copolymer D-2 73 8 8 11 75
210 Resin (D) D-3 75 7 7 11 85 870 D-4 81 4 4 11 90 230 D-5 40 35
14 11 70 70
TABLE-US-00005 TABLE 2-2 Shape diameter (nm) length (.mu.m) Note
CNT (E) E-1 9.5 1.5 NC-7000 (Nanocyl) E-2 12.0 5.0 Graphistrength
C100 (Arkema)
[0067] Table 3 shows the component ratios by mass % of the
components (A), (13) and (C) used in Examples 1 to 18 and
Comparative Example 1 to 7, and the graft rubber content in the
substrate sheet, and Table 4 shows the melt tension measured at
winding speeds of 10, 30 and 50 mm/min for the resin composition of
the substrate sheet. The method of measuring melt tension will be
discussed below.
TABLE-US-00006 TABLE 3 Styrene-Conjugated Diene Block Polystyrene
Copolymer (A) (mass %) (B) (mass %) A-1 A-2 A-3 A-4 A-5 A-6 B-1 B-2
B-3 B-4 B-5 B-6 Example 1 58 33 Example 2 55 25 Example 3 58 33
Example 4 58 33 Example 5 58 33 Example 6 58 33 Example 7 58 33
Example 8 40 51 Example 9 35 45 Example 10 58 33 Example 11 58 33
Example 12 58 33 Example 13 58 33 Example 14 58 33 Example 15 58 33
Example 16 58 33 Example 17 58 33 Example 18 58 33 Comp. Example 1
58 33 Comp. Example 2 58 33 Comp. Example 3 58 33 Comp. Example 4
58 33 Comp. Example 5 100 Comp. Example 6 58 Comp. Example 7 58 33
High Impact GraftRubber Polystyrene (C) (mass %) Content C-1 C-2
C-3 C-4 C-5 C-6 (mass %) Example 1 9 0.77 Example 2 20 1.58 Example
3 9 0.77 Example 4 9 0.77 Example 5 9 0.77 Example 6 9 0.66 Example
7 9 0.79 Example 8 9 0.77 Example 9 20 1.72 Example 10 9 0.77
Example 11 9 0.77 Example 12 9 0.77 Example 13 9 0.77 Example 14 9
0.77 Example 15 9 0.77 Example 16 9 0.77 Example 17 9 0.77 Example
18 9 0.77 Comp. Example 1 9 0.77 Comp. Example 2 9 0.77 Comp.
Example 3 9 0.65 Comp. Example 4 9 0.54 Comp. Example 5 0.00 Comp.
Example 6 42 3.61 Comp. Example 7 9 0.77
TABLE-US-00007 TABLE 4 Melt Tension Melt Tension Melt Tension (10
m/ (30 m/min) (50 m/min) min) mN mN mN Example 1 18 20 21 Example 2
15 17 18 Example 3 14 15 16 Example 4 19 21 22 Example 5 19 20 22
Example 6 20 21 22 Example 7 17 18 19 Example 8 26 30 31 Example 9
22 26 27 Example 10 18 20 21 Example 11 18 20 21 Example 12 18 20
21 Example 13 18 20 21 Example 14 18 20 21 Example 15 18 20 21
Example 16 18 20 21 Example 17 18 20 21 Example 18 18 20 21 Comp.
Example 1 18 20 21 Comp. Example 2 18 20 21 Comp. Example 3 31 33
34 Comp. Example 4 8 10 11 Comp. Example 5 10 11 13 Comp. Example 6
14 15 15 Comp. Example 7 18 20 21
[0068] Table 5 shows the component ratios by mass % of the acrylic
copolymer resin (D) and the carbon nanotubes (E) in the surface
conductive layer formed on the substrate sheets of Examples 1 to 18
and Comparative Examples 1 to 7. In Comparative Example 2, tin
oxide with a particle size of .phi. 10 nm was used instead of the
carbon nanotubes. Additionally, in Comparative Example 7, an
aqueous dispersion of a water-soluble epoxy resin (bisphenol A) was
used as a binder instead of an aqueous dispersion of an acrylic
copolymer resin.
TABLE-US-00008 TABLE 5 Acrylic Copolymer CNT (E) Resin (D) mass %
mass % D-1 D-2 D-3 D-4 D-5 E-1 E-2 Example 1 95 5 Example 2 95 5
Example 3 95 5 Example 4 95 5 Example 5 95 5 Example 6 95 5 Example
7 95 5 Example 8 95 5 Example 9 95 5 Example 10 95 5 Example 11 97
3 Example 12 90 10 Example 13 95 5 Example 14 95 5 Example 15 95 5
Example 16 95 5 Example 17 95 5 Example 18 95 5 Comp. Example 1 100
Comp. Example 2 85 15 (*.sup.1) Comp. Example 3 95 5 Comp. Example
4 95 5 Comp. Example 5 95 5 Comp. Example 6 95 5 Comp. Example 7 95
(*.sup.2) 5 Note: (*.sup.1) Tin oxide, particle size 10 nm
(*.sup.2) Epoxy binder
Example 1
[0069] As shown in Table 3, 58 mass % of the styrene-butadiene
block copolymer (A) of A-1 in Table 1-1 (Mw: 150,000; butadiene
content 20 mass %), 33 mass % of the polystyrene resin (B) of B-1
in Table 1-2 (Mw: 330,000) and 9 mass % of the high impact
polystyrene resin (C) of C-1 in Table 1-3 (Mw: 180,000; rubber
particle size 25 .mu.m) were dry-blended and formed into a film by
a .phi. 40 mm extruder (L/D=26) and 600 mm wide T-dice, resulting
in a substrate sheet of thickness 250 .mu.m. Additionally, 5 parts
by mass of an aqueous dispersion of the multiwall carbon nanotubes
(MWCNT) (E) of E-1 shown in Table 2-2 (fiber diameter 95 nm, fiber
length 1.5 .mu.m) and 95 parts by mass of an aqueous dispersion of
the acrylic copolymer (D) of D-1 shown in Table 2-1 (glass
transition point: 40.degree. C.) were mixed together to obtain a
mixed dispersion wherein the component ratios in a conductive layer
formed on the surface of a substrate sheet is 5 mass %195 mass % as
shown in Table 5. Next, this mixed dispersion was coated onto the
surface of a corona-treated substrate sheet in a gravure coater
using a gravure roll, then dried at 90.degree. C. to form a surface
conductive layer of average thickness 3 .mu.m after drying. The
results of evaluation tests of a substrate sheet on which this
surface conductive layer was formed are shown in Table 6.
Examples 2 to 18 and Comparative Examples 1 to 7
[0070] Substrate sheets having surface conductive layers formed
thereon were obtained in the same manner as Example 1, aside from
the fact that as the resin components (A) to (C), resins chosen
from A-1 to A-6 in Table 1-1, B-1 to B-6 in Table 1-2 and C-1 to
C-6 in Table 1-3 were used and blended at the mass ratios shown in
Table 3 to prepare the substrate sheet, and a mixed aqueous
dispersion of components (D) and (E) chosen from D-1 to D-5 shown
in Table 2-1 and E-1 and E-2 shown in Table 2-2 as shown in Table
5.
[0071] Of Examples 1 to 18, only Example 10 used E-2 shown in Table
2-2 as the MWCNT. Example 15 used D-4 as the acrylic copolymer and
Example 16 used D-5 as the acrylic copolymer.
[0072] Of Comparative Examples 1 to 7, Comparative Example 1 does
not contain a MWCNT. In Comparative Example 2, tin oxide of
particle size .phi. 10 nm was used instead of a MWCNT. In
Comparative Example 3, the polystyrene of B-5 shown in Table 1-2
(weight-average molecular weight Mw: 470,000) was used as component
(B), and in Comparative Example 4, B-6 (Mw: 120,000) shown in Table
1-2 was used as component (B) and the high impact polystyrene of
C-5 shown in Table 1-3 (weight-average molecular weight Mw:
100,000) was used as component (C). Comparative Example 5 contained
neither component (B) nor component (C), and Comparative Example 6
did not contain component (B). In Comparative Example 7, an aqueous
dispersion of a water-soluble epoxy resin (bisphenol A) was used as
a binder instead of the aqueous dispersion of an acrylic copolymer
resin.
[0073] The evaluation results for the examples and comparative
examples are shown together in Table 6.
TABLE-US-00009 TABLE 6 Surface Cond Buckle Coefficient Surf Res
Formability Resistance (.OMEGA.) Draw Crack Haze (%) Str (N)
Friction Blk after Blk Ftiv Hol Sheet Article Ratio Y/N Sheet Bottm
Article Stat Kin Y/N Eval. (.OMEGA.) Example 1 5 N 5.0 .times.
10.sup.4 7.8 .times. 10.sup.6 2.8 N 24 8 20 1.51 1.50 N 5.1 .times.
10.sup.4 Example 2 5 N 4.3 .times. 10.sup.4 7.1 .times. 10.sup.6
2.8 N 29 13 18 1.51 1.50 N 4.3 .times. 10.sup.4 Example 3 5 N 7.0
.times. 10.sup.4 4.5 .times. 10.sup.5 1.8 N 23 7 27 1.52 1.51 N 7.5
.times. 10.sup.4 Example 4 5 N 6.2 .times. 10.sup.4 5.4 .times.
10.sup.5 1.8 N 23 8 31 1.51 1.50 N 6.3 .times. 10.sup.4 Example 5 5
N 7.9 .times. 10.sup.4 5.3 .times. 10.sup.5 1.8 N 24 8 31 1.52 1.50
N 8.1 .times. 10.sup.4 Example 6 5 N 8.7 .times. 10.sup.4 6.8
.times. 10.sup.6 2.8 N 23 8 21 1.52 1.50 N 8.9 .times. 10.sup.4
Example 7 5 N 6.6 .times. 10.sup.4 7.1 .times. 10.sup.6 2.8 N 23 7
19 1.52 1.51 N 6.9 .times. 10.sup.4 Example 8 5 N 8.8 .times.
10.sup.4 7.6 .times. 10.sup.6 2.8 N 24 8 24 1.51 1.50 N 9.1 .times.
10.sup.4 Example 9 5 N 8.9 .times. 10.sup.4 7.7 .times. 10.sup.6
2.8 N 29 13 22 1.51 1.50 N 9.1 .times. 10.sup.4 Example 10 5 N 9.4
.times. 10.sup.4 1.8 .times. 10.sup.8 2.8 N 24 8 20 1.52 1.51 N 9.5
.times. 10.sup.4 Example 11 5 N 8.9 .times. 10.sup.4 3.1 .times.
10.sup.7 1.8 N 23 7 30 1.50 1.49 N 8.7 .times. 10.sup.5 Example 12
5 N <1.0 .times. 10.sup.4 2.3 .times. 10.sup.5 1.8 N 24 8 30
1.54 1.52 N <1.0 .times. 10.sup.4 Example 13 5 N 5.4 .times.
10.sup.4 3.6 .times. 10.sup.6 2.8 N 24 8 20 1.55 1.53 N 5.3 .times.
10.sup.4 Example 14 5 N 5.7 .times. 10.sup.5 2.1 .times. 10.sup.6
2.8 N 45 25 20 1.64 1.62 N 5.9 .times. 10.sup.5 Example 15 5 N 7.6
.times. 10.sup.4 .sup. 5.2 .times. 10.sup.10 2.8 Y (*.sup.2) 26 10
20 1.51 1.50 N 7.9 .times. 10.sup.4 Example 16 5 N 5.2 .times.
10.sup.4 6.8 .times. 10.sup.6 2.8 N 24 8 20 0.75 0.73 Y >1.0
.times. 10.sup.14 Example 17 5 N 6.1 .times. 10.sup.4 5.6 .times.
10.sup.7 3.2 N 24 8 17 1.52 1.51 N 6.3 .times. 10.sup.4 Example 18
5 N 5.9 .times. 10.sup.4 .sup. 5.1 .times. 10.sup.11 4.0 Y
(*.sup.2) 26 11 16 1.51 1.50 N 5.7 .times. 10.sup.4 Comp. 5 N
>1.0 .times. 10.sup.14 >1.0 .times. 10.sup.14 2.8 N 24 7 20
1.40 1.38 N >1.0 .times. 10.sup.14 Example 1 Comp. 5 N 8.5
.times. 10.sup.7 >1.0 .times. 10.sup.14 2.8 Y (*.sup.2) 23 8 20
1.55 1.54 N 8.8 .times. 10.sup.7 Example 2 Comp. 2 (*.sup.1) N 7.8
.times. 10.sup.4 5.2 .times. 10.sup.6 2.8 N 24 9 35 1.52 1.51 N 7.5
.times. 10.sup.4 Example 3 Comp. 5 N 7.5 .times. 10.sup.4 6.5
.times. 10.sup.6 2.8 N 23 8 10 1.51 1.50 N 7.8 .times. 10.sup.4
Example 4 Comp. 5 N 8.5 .times. 10.sup.4 5.4 .times. 10.sup.6 2.8 N
7 6 8 1.52 1.50 N 8.7 .times. 10.sup.4 Example 5 Comp. 5 N 8.0
.times. 10.sup.4 5.8 .times. 10.sup.6 2.8 N 40 19 10 1.52 1.50 N
8.1 .times. 10.sup.4 Example 6 Comp. 5 N 4.8 .times. 10.sup.5
>1.0 .times. 10.sup.14 2.8 Y (*.sup.2) 24 8 20 1.91 1.89 N 4.8
.times. 10.sup.5 Example 7 Note (*.sup.1) The shape of the corner
portions was poor. (*.sup.2) Cracks occurred in the conductive
layer during formation.
<Measurement and Evaluation>
[0074] The raw material resins used in Examples 1 to 18 and
Comparative Examples 1 to 7, and formed articles obtained by
forming a surface conductive film on the surfaces of substrate
sheets prepared from these raw material resins, then embossing,
were evaluated by the below-described measurement methods.
(Molecular Weight of Raw Material Resin)
[0075] The molecular weights of the resin raw materials of (A) to
(C) were determined as a standard polystyrene-converted
weight-average molecular weight (Mw) using GPC (gel permeation
chromatography). Tetrahydrofuran was used as the measuring
solvent.
(Melt Tension of Raw Material Resin)
[0076] The melt tension (mN) was measured using a melt tension
measuring apparatus (Toyo Seiki) with an orifice diameter of .phi.
1.0 mm, an orifice length of 10 mm, windup speeds of 10, 30 and 50
m/min and a cylinder temperature of 220.degree. C.
(Glass Transition Temperature of Raw Material Resin)
[0077] A dispersion comprising an aqueous dispersion of an acrylic
copolymer resin was dried at 90.degree. C..times.1 min and formed
into a thin film to create samples for use as measuring samples,
which were measured using a DSC (differential scanning calorimeter
manufactured by SII).
(Particle Size of Acrylic Copolymer Resin)
[0078] A Horiba laser diffraction/scattering type particle size
distribution measurer LA-920 (the average particle size here was
the median diameter) was used to take measurements.
(Coefficient of Friction Measurement)
[0079] The coefficient of static friction and the coefficient of
kinetic friction were measured in accordance with JIS-7125 using a
friction measurer (Toyo Seiki). The measurements were made with a
sample size of 63 mm.times.63 mm, a load of 200 g and a speed of
500 mm/min. Additionally, the coefficient of static friction and
the coefficient of kinetic friction were the coefficients of
friction between conductive layers.
(Blocking)
[0080] Substrate sheets coated on both sides were slit into sheet
samples 44 mm wide to produce 200 m wound slit raw sheets (winding
tension 1.0 kgf). The slit raw sheets were stored for one week at
52.degree. C..times.95% RH. After one week, the slit raw sheets
were extracted and the sheets were wound out. After unwinding, they
were inspected for the presence or absence of blocking between the
conductive layers on the surfaces of overlapping substrate sheets,
and separation of the conductive layer due to blocking was
evaluated by measuring the surface resistance between overlapping
conductive layers at 23.degree. C..times.50% RH in accordance with
JIS K6911, and observing whether the surface resistance
increased.
(Formability of Sheets)
[0081] Using a pressure-forming machine on substrate sheets having
a surface conductive layer formed on each example and comparative
example, pockets were formed of draw ratio 1.8 (pocket depth 3.0
mm), draw ratio 2.8 (pocket depth 6.0 mm), draw ratio 3.2 (pocket
depth 9.0 mm) and draw ratio 4.0 (pocket depth 12.0 mm) and their
formativeness was evaluated by evaluating the "sharpness" of the
formed articles into five grades. Additionally, the pockets were
visually inspected for the presence or absence of holes due to
formation. The surface conductive layers were visually inspected
for the presence or absence of cracks in the bottom surfaces of the
pockets. FIG. 1 shows a formed article obtained by molding with a
pressure-forming machine.
[0082] The draw ratio was calculated using the below-given formula
based on the dimensions of the formed article. Additionally, in
these formed articles, the area of the bottom surface of the
pockets was roughly equal to the area of the mouth portions of the
pockets (areas enclosed by the solid lines).
Method of Calculating Draw Ratio:
[0083] Draw Ratio = pocket area ( bottom area + four side areas ) /
pocket mouth area = ( X .times. Y ) + 2 .times. ( X .times. Z ) + 2
.times. ( X .times. Y ) / ( X .times. Y ) ##EQU00001##
[0084] (where X is the formed article advancement direction, Y is
the direction perpendicular to the formed article advancement
direction and Z is the pocket depth).
<Forming Conditions>
[0085] Pressure forming: heater temperature 220.degree. C.
<Evaluation Standards of Formativeness>
[0086] As shown in FIG. 2, the pocket corners 11 of the formed
articles 10 having pockets 20 formed therein were inspected, and
their "sharpness" was visually evaluated into five grades in
accordance with the samples 1 to 5 shown in FIG. 2.
(Transparency of Formed Articles)
[0087] The pocket side surfaces of the formed articles obtained by
forming in a pressure-forming machine were cut out, clamped between
black plates with holes of .phi. 6 mm (2826 mm.sup.2), and the
bottom surfaces of the formed articles were measured for their haze
and total light transmittance in accordance with the ASTM D1044
standard using a Haze-gard plus from BYK Gardner of Germany. The
standard haze value was such that the haze was 15% or less at the
bottom surface of the formed article in order to provide
transparency enabling components placed in the formed articles to
be visually confirmed.
(Surface Resistance of Formed Article)
[0088] Measurements were made at 23.degree. C..times.50% RH. The
surface resistance was measured using a Mitsubishi Chemical Hiresta
with a two-terminal probe (UA) as the probe. Additionally, the
surface resistance of the entire pocket of the formed article was
measured by a method as shown in FIG. 3. Additionally, the
conductive layers on the pocket bottom surfaces and side surfaces
were inspected by eye for the presence or absence of cracks during
formation. Measurements were made by bringing a two-terminal probe
into contact with the probe terminal contact positions 50a and 50b
on the flanges 12a and 12b on both ends of the pocket. At this
time, if the seal portions 13a and 13b of the carrier tape formed
article 10 remain, then the conductive circuit 40 is formed on the
seal portions 13a, 13b, so the entire pocket 20 cannot be measured.
Therefore, as shown in FIG. 3, the seal portions 13a, 13b were cut
along the dashed lines at cut positions 30a, 30b, the pocket side
surfaces 60a, 60b were further cut away, and measurements were made
while clamped in a jig of insulating material. The standard surface
resistance value was on the order of 10.sup.5 or less in a formed
body with a draw ratio of 1.5 to 3 when thermoforming, and on the
order of 10.sup.7 or less for the formed article.
(Buckle Strength of Formed Article)
[0089] A Strograph (Toyo Seiki) was used to measure the strength of
the pocket bottom surface portion of a formed article obtained by
molding in a pressure-forming machine with the pocket mouth portion
facing down, when compressed by 1.5 mm in the depth direction for a
formed article of draw ratio 1.8 (pocket depth 3.0 mm), 3.0 mm for
a formed article of draw ratio 2.8 (pocket depth 6.0 mm), 4.5 mm
for a formed article of draw ratio 3.2 (pocket depth 9.0 mm) and
6.0 mm for a formed article of draw ratio 4.0 (pocket depth 12.0
mm), and this was recorded as the buckle strength. In the event of
a buckle strength of 15 N or more, the formed article is viable for
use as a container.
[0090] The results shown in Table 6 revealed the following.
(i) Examples 1 to 18 using polystyrene type resin compositions of
weight-average molecular weights in the predetermined ranges for
the substrate sheet exhibited excellent formability, formativeness
and sufficient buckle strength. In contrast, Comparative Example 3
using B-5 having a weight-average molecular weight of 470,000 Mw
for the polystyrene resin (B) of the substrate sheet and C-6 having
a weight-average molecular weight of 250,000 Mw as the high impact
polystyrene resin (C) had problems in the formativeness.
Additionally, Comparative Example 4 using A-6 having a
weight-average molecular weight of 70,000 Mw as the
styrene-conjugated diene copolymer (A) in the substrate sheet and
C-5 having a weight-average molecular weight of 100,000 Mw as the
high impact polystyrene (C), Comparative Example 5 having a
substrate sheet consisting only of the styrene-conjugated diene
copolymer (A), and Comparative Example 6 not containing the
polystyrene resin (B) all exhibited low buckle strength. (ii)
Examples 1 to 18 using polystyrene type resin compositions of
weight-average molecular weights in the predetermined ranges for
the substrate sheet and an acrylic copolymer resin (D) together
with the carbon nanotubes (E) for the surface conductive layer
exhibited relatively low surface resistances as both sheets and
formed articles. In contrast, the surface resistance of Comparative
Example 1 not containing a MWCNT in the surface conductive layer
was high, on the order of 10.sup.14.OMEGA. for both sheet and
formed article, and Comparative Example 2 using tin oxide instead
of a MWCNT in the surface conductive layer and Comparative Example
7 using an epoxy as the binder in the surface conductive layer both
had high surface resistances on the order of 10.sup.14.OMEGA. for
the formed article, and resulted in cracking of the conductive
layer in the formed article.
[0091] While the present invention has been explained by referring
to embodiments above, the technical scope of the present invention
is naturally not limited to the scope described by the above
embodiments. Those skilled in the art will recognize that various
modifications and improvements could be made to the above-described
embodiments. Additionally, the fact that embodiments including such
modifications or improvements can still be contained within the
technical scope of the present invention will be readily apparent
from the recitations of the claims.
INDUSTRIAL APPLICABILITY
[0092] By making use of known methods for forming (thermoforming)
sheets such as vacuum forming, pressure forming and press forming
on the sheets for packaging electronic components of the present
invention, it is possible to obtain electronic component packaging
containers of any shape such as carrier tapes (embossed carrier
tapes) and trays. Using the sheets for packaging electronic
components of the present invention, it is possible to form
packaging containers of large container depth, and packaging
containers of excellent strength can be obtained. In particular,
they are very useful for embossment of carrier tape. After placing
electronic components in the receptacle portions, the embossed
carrier tape is covered by cover tape and wound into reels to form
carrier tape bodies, which can then be used to store and transport
electronic components. Carrier tape bodies contain electronic
components inside a carrier tape. There are no particular
limitations on the electronic components to be packaged, and
examples include IC's, LED's (light emitting diodes), resistors and
capacitors. Additionally, they can be used for packaging
intermediary products or final products using such electronic
components.
DESCRIPTION OF REFERENCE NUMBERS
[0093] 10 formed article [0094] 11 pocket corner [0095] 12a, 12b
flange [0096] 13a, 13b seal portion [0097] 20 pocket [0098] 30a,
30b cut position [0099] 40 conductive circuit [0100] 50a, 50b probe
terminal contact position [0101] 60a, 60b pocket side surface
* * * * *