U.S. patent application number 16/463905 was filed with the patent office on 2019-09-26 for adhesive sheet and method for peeling same.
This patent application is currently assigned to MITSUI MINING & SMELTING CO., LTD.. The applicant listed for this patent is MITSUI MINING & SMELTING CO., LTD.. Invention is credited to Toshimi NAKAMURA, Tetsuro SATO.
Application Number | 20190292415 16/463905 |
Document ID | / |
Family ID | 62195894 |
Filed Date | 2019-09-26 |
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United States Patent
Application |
20190292415 |
Kind Code |
A1 |
SATO; Tetsuro ; et
al. |
September 26, 2019 |
ADHESIVE SHEET AND METHOD FOR PEELING SAME
Abstract
Provided is an adhesive sheet including a substrate sheet and a
soluble adhesive layer with an island or stripe pattern disposed on
at least one surface of the substrate sheet, wherein each adhesive
region has a circumscribed circle diameter of 0.1 mm to 10 mm for
the island pattern, or has a stripe width of 0.1 mm to 10 mm for
the stripe pattern. This adhesive sheet can retain an adhesive
force of the adhesive layer until just before releasing and can be
readily released from the adherend at any time without applying of
excessive stress to the adherend.
Inventors: |
SATO; Tetsuro; (Ageo-shi,
JP) ; NAKAMURA; Toshimi; (Ageo-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUI MINING & SMELTING CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUI MINING & SMELTING CO.,
LTD.
Tokyo
JP
|
Family ID: |
62195894 |
Appl. No.: |
16/463905 |
Filed: |
November 24, 2017 |
PCT Filed: |
November 24, 2017 |
PCT NO: |
PCT/JP2017/042290 |
371 Date: |
May 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/12 20130101;
C09J 7/22 20180101; H01L 2221/68381 20130101; H01L 21/4857
20130101; C09J 7/385 20180101; C09J 2467/006 20130101; H01L 23/3121
20130101; C09J 2203/326 20130101; C09J 2433/00 20130101; C09J 7/30
20180101; C09J 7/255 20180101; C09J 2301/18 20200801; H01L
2221/68372 20130101; H01L 2224/18 20130101; H01L 23/49822 20130101;
H01L 21/6835 20130101; H01L 2221/68345 20130101; H05K 3/46
20130101; C09J 2301/204 20200801; H01L 21/6836 20130101; H01L
2221/68359 20130101; H01L 2224/16225 20130101; H01L 2221/68386
20130101; C09J 2301/502 20200801; C09J 2423/046 20130101; C09J 5/00
20130101; H01L 23/49838 20130101 |
International
Class: |
C09J 7/38 20060101
C09J007/38; H01L 21/683 20060101 H01L021/683; C09J 7/25 20060101
C09J007/25; C09J 5/00 20060101 C09J005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2016 |
JP |
2016-230539 |
Feb 2, 2017 |
JP |
2017-017248 |
Claims
1. An adhesive sheet comprising a substrate sheet and a soluble
adhesive layer with an island or stripe pattern disposed on at
least one surface of the substrate sheet, wherein each adhesive
region has a circumscribed circle diameter of 0.1 mm to 10 mm for
the island pattern, or has a stripe width of 0.1 mm to 10 mm for
the stripe pattern.
2. The adhesive sheet according to claim 1, wherein the soluble
adhesive layer contains a solution-soluble resin.
3. The adhesive sheet according to claim 2, wherein the
solution-soluble resin is an alkali-soluble resin.
4. The adhesive sheet according to claim 3, wherein the
alkali-soluble resin includes a polymer containing carboxyl groups
and/or phenolic hydroxyl groups.
5. The adhesive sheet according to claim 1, wherein the soluble
adhesive layer has a thickness of 0.5 .mu.m to 50 .mu.m.
6. The adhesive sheet according to claim 5, wherein the soluble
adhesive layer has a thickness of 3.0 .mu.m to less than 10
.mu.m.
7. The adhesive sheet according to claim 1, wherein the soluble
adhesive layer has the island pattern.
8. The adhesive sheet according to claim 1, wherein the island
pattern is a dotted pattern.
9. The adhesive sheet according to claim 8, wherein the dotted
pattern has a dot diameter of 0.7 mm or less, and the soluble
adhesive layer has a thickness of 1.0 .mu.m to 7.0 .mu.m.
10. The adhesive sheet according to claim 8, wherein the dotted
pattern has a pitch circle diameter (PCD) of 0.45 mm to 3.0 mm.
11. The adhesive sheet according to claim 1, wherein the distance
between the centers of circumscribed circles in the adhesive region
is greater than the mean value of the circumscribed circle
diameters, and is in a range of 0.1 mm to 20 mm.
12. The adhesive sheet according to claim 1, wherein the island
pattern is composed of one or more clusters that form a polygonal,
circular, annular, striped or grid pattern on the whole, and each
of the clusters consists of an aggregate of three or more adhesive
regions.
13. The adhesive sheet according to claim 1, the rate of the
adhesive region to the total surface area provided with the soluble
adhesive layer of the substrate sheet is 3 to 90 area %.
14. The adhesive sheet according to claim 1, wherein the substrate
sheet is composed of at least one resin of poly(ethylene
terephthalate) (PET) and polyethylene (PE).
15. The adhesive sheet according to claim 1, wherein the substrate
sheet is composed of at least one selected from the group
consisting of metal, glass, glass epoxy resin, polyimide resin, and
phenol resin.
16. The adhesive sheet according to claim 15, wherein the substrate
sheet has through-holes in the thickness direction.
17. The adhesive sheet according to claim 1, further comprising a
protective film stacked on the soluble adhesive layer.
18. The adhesive sheet according to claim 17, wherein the
protective film is composed of poly(ethylene terephthalate) (PET)
and/or polyethylene (PE).
19. A method of releasing the adhesive sheet or the substrate sheet
from an adherend to which the adhesive sheet according to claim 1
is bonded, comprising the steps of: impregnating the gaps of the
island or stripe pattern of the soluble adhesive layer with an
alcoholic solution capable of dissolving the soluble adhesive layer
to dissolve or soften the soluble adhesive layer; and releasing the
adhesive sheet or the substrate sheet from the adherend after the
soluble adhesive layer is dissolved or softened.
Description
TECHNICAL FIELD
[0001] The present invention relates to an adhesive sheet and a
method of releasing the same.
BACKGROUND ART
[0002] Adhesive sheets have been widely used in various
applications, such as adhesion and temporary fixing of articles.
Typical adhesive sheet includes a substrate sheet provided with an
adhesive layer containing an adhesive component thereon. The
adhesive sheets are classified into two types, i.e., "a bondable
adhesive sheet" in which the adhesive layer of the substrate sheet
itself is bonded to an adherend and "a transferable adhesive sheet"
in which the adhesive layer is transferred onto an adherend or
second substrate sheet and then the original substrate is released
to impart adhesiveness to the adherend or second substrate
sheet.
[0003] Adhesive sheets are known that include substrate sheets and
adhesive layers having predetermined printed patterns. For example,
PTL 1 (JP2010-174148A) discloses an adhesive product provided with
an adhesive layer formed by intermittently disposing a dotted
adhesive on a substrate for the purpose of fixing paper articles
such as envelopes. This literature proposes use of an acrylic
adhesive containing an acrylic copolymer to print the pattern of
the adhesive layer precisely and efficiently on the substrate
through, for example, screen printing and gravure printing. PTL 2
(JPH08-333556A) discloses a transferable adhesive sheet having an
adhesive layer consisting of an aggregate pattern of dotted
adhesive, the transferable adhesive sheet being used for bonding by
transfer to, for example, plastic, metal, and ceramic products, and
discloses, for example, acrylic, rubbery, and silicone
adhesives.
[0004] Adhesive sheets have been sometimes used in processes of
manufacturing semiconductor packages to improve the handling
properties of thinned printed wiring boards. For example, PTL 3
(JP2014-7315A) discloses a process of manufacturing a semiconductor
package. The method comprises bonding a heat-resistant film
consisting of a self-adhesive elastomer layer on a heat-resistant
support layer to a printed wiring board; and releasing the
heat-resistant film after mounting of semiconductor chips, reflow
treatment, sealing with resins and curing treatment. This document
also proposes a substantially dotted or striped self-adhesive
elastomer layer.
CITATION LIST
Patent Literatures
[0005] PTL 1: JP2010-174148A
[0006] PTL 2: JPH08-333556A
[0007] PTL 3: JP2014-7315A
SUMMARY OF INVENTION
[0008] As disclosed in PTLs 1 to 3, various adhesive sheets are
known. Since the adhesive layer retains a predetermined adhesive
force, excessive stress may be applied to an adherend to release
the adhesive sheet from the adherend. Although such excessive
stress would not cause a significant problem if the adherend is a
paper product as described in PTL 1 or a plastic product as
described in PTL 2, excessive stress will lead to a critical
problem if the adherend or application are adversely affected by
the excessive stress (for example, precision parts and electronic
parts). In the case that the adhesive sheet is bonded to reinforce
a printed wiring board followed by various processes, such as
mounting of chips, solder reflow and compression molding in the
manufacture of a semiconductor package, the disconnection or
release of the wiring layer occurs by excessive stress applied on
the printed wiring board when the adhesive sheet is released,
resulting in a decrease in yield.
[0009] In this respect, it is conceivable that an adhesive layer is
composed of a material the adhesive force of which decreases by
heat or ultraviolet irradiation and then the adhesive force is lost
through the heat or ultraviolet irradiation during a releasing
operation, to facilitate release of the sheet. In the case of the
ultraviolet irradiation, applicable substrate sheets or adherends
are limited to those capable of transmitting ultraviolet light.
Another problem in this procedure is that the adhesive force of the
adhesive layer is unintentionally reduced by the heat or
ultraviolet irradiation to a level less than a required adhesive
force before the releasing step. For example, if the adhesive layer
contains thermally expandable microcapsules, the thermoplastic
resin constituting the shell of capsules is softened by heat and
the capsules expand and foam into micro-balloons, resulting in a
decrease in the adhesive force of the adhesive layer.
Unfortunately, these thermally expandable microcapsules are not
durable to heating processes such as the solder reflow (for
example, 260.degree. C. or more).
[0010] The present inventors have now found that an adhesive sheet
including a soluble adhesive layer with a predetermined size of
island or stripe pattern can retain the adhesive force of the
adhesive layer until just before releasing and can be readily
released from the adherend at any time without applying of the
excessive stress to the adherend.
[0011] Accordingly, an object of the present invention is to
provide an adhesive sheet that can retain the adhesive force of the
adhesive layer until just before releasing and can be readily
released from the adherend at any time without applying of the
excessive stress to the adherend.
[0012] According to one embodiment of the present invention, an
adhesive sheet is provided, the adhesive sheet comprising a
substrate sheet and a soluble adhesive layer with an island or
stripe pattern disposed on at least one surface of the substrate
sheet, wherein each adhesive region has a circumscribed circle
diameter of 0.1 mm to 10 mm for the island pattern, or has a stripe
width of 0.1 mm to 10 mm for the stripe pattern.
[0013] According to another embodiment of the present invention, a
method of releasing the adhesive sheet or the substrate sheet from
the adherend to which the adhesive sheet is bonded is provided, the
method comprising the steps of: [0014] impregnating the gaps of the
island or stripe pattern of the soluble adhesive layer with an
alcoholic solution capable of dissolving the soluble adhesive layer
to dissolve or soften the soluble adhesive layer; and [0015]
releasing the adhesive sheet or the substrate sheet from the
adherend after the soluble adhesive layer is dissolved or
softened.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a schematic cross-sectional view illustrating one
embodiment of an adhesive sheet of the present invention.
[0017] FIG. 2 is a schematic top view of the adhesive sheet shown
in FIG. 1.
[0018] FIG. 3 is a view for explaining that a releasing liquid
penetrates into gaps in the pattern of the soluble adhesive
layer.
[0019] FIG. 4A is a view illustrating an exemplary shape of an
adhesive region.
[0020] FIG. 4B is a view illustrating another exemplary shape of
the adhesive region.
[0021] FIG. 5 is a view for explaining a pitch circle diameter
(PCD) in a dotted pattern.
[0022] FIG. 6A is a view illustrating an example of an island
pattern.
[0023] FIG. 6B is a view illustrating an example of an island
pattern composed of one or more clusters.
[0024] FIG. 6C is a view illustrating another example of an island
pattern composed of one or more clusters.
[0025] FIG. 6D is a view illustrating another example of an island
pattern composed of one or more clusters.
[0026] FIG. 6E is a view illustrating another example of an island
pattern composed of one or more clusters.
[0027] FIG. 6F is a view illustrating another example of an island
pattern composed of one or more clusters.
[0028] FIG. 7A is a process flowchart illustrating an exemplary use
of an adhesive sheet in the manufacture of a semiconductor
package.
[0029] FIG. 7B is a process flowchart illustrating an exemplary use
of the adhesive sheet in the manufacture of a semiconductor
package, including steps after the steps shown in FIG. 7A.
[0030] FIG. 7C is a process flowchart illustrating another
exemplary use of the adhesive sheet in the manufacture of a
semiconductor package, including steps after the steps shown in
FIG. 7A.
DESCRIPTION OF EMBODIMENTS
Adhesive Sheet
[0031] The adhesive sheet of the present invention is schematically
illustrated in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the
adhesive sheet 10 of the present invention comprises a substrate
sheet 12 and a soluble adhesive layer 14 provided on at least one
surface of the substrate sheet 12. The soluble adhesive layer 14 is
provided in an island or stripe pattern. Individual adhesive
regions 14a have a circumscribed circle diameter of is 0.1 to 10 mm
in the case of the island pattern, or a stripe width of 0.1 to 10
mm in the case of the stripe pattern. In the present specification,
the numerical range referred to by the expression "A to B"
indicates from A or more to B or less. As described above, the
soluble adhesive layer 14 is provided in the island or stripe
pattern with a predetermined size; hence, the adhesive sheet
retains the adhesive force of the adhesive layer until just before
releasing, and can be readily released from the adherend at any
time without applying of the excessive stress to the adherend. In
other words, the soluble adhesive layer 14, employed in the
adhesive sheet 10 of the present invention, can be dissolved or
softened by immersing the soluble adhesive layer 14 in a soluble
liquid (hereinafter referred to as a releasing liquid).
Furthermore, the soluble adhesive layer 14 is provided in an island
or stripe pattern with a predetermined size; hence, the soluble
adhesive layer 14 can be completely impregnated with the releasing
liquid (for example, an alcoholic solution). As schematically shown
by dotted arrows in FIG. 3, this advantage is probably achieved
based on the effective penetration of the releasing liquid L into
the gaps in the pattern of the soluble adhesive layer 14 and the
promotion of the contact with each adhesive region 14a when the
soluble adhesive layer 14 bonded to the adherend 20 (for example, a
printed wiring board) is immersed in the releasing liquid L. As a
result, the release of the sheet can be facilitated from the
adherend 20. The release of the sheet from the adherend 20 may be
spontaneously achieved by dissolution of the soluble adhesive layer
14, or mechanically achieved after the adhesive force is
significantly reduced by dissolution or softening of the soluble
adhesive layer 14.
[0032] Since the adhesive layer in a general adhesive sheet has a
predetermined adhesive force as described above, excessive stress
may be applied to the adherend to release the adhesive sheet from
the adherend. The excessive stress applied to the adherend may
cause quality matter of the adherend or the application (for
example, precision parts and electronic parts). For example, in
various processes, such as mounting of chips, solder reflow, and
compression molding after bonding the adhesive sheet to reinforce a
printed wiring board in the manufacture of a semiconductor package,
excessive stress applied to the printed wiring board to release the
adhesive sheet causes the disconnection or release of the wiring
layer, resulting in a reduction in yield. In this respect, it is
conceivable that the adhesive layer is composed of a material the
adhesive force of which decreases by heat or ultraviolet
irradiation and then the adhesive force is lost through heat or
ultraviolet irradiation at a releasing operation to facilitate the
release of the sheet. Such a procedure, however, has a problem in
that the heat or ultraviolet irradiation before the release process
unintentionally decreases the adhesive force of the adhesive layer
to a level less than a required adhesive force. In contrast, in the
adhesive sheet 10 of the present invention, the soluble adhesive
layer 14 is completely impregnated with the releasing liquid, and
the sheet can thereby be released without excessive stress to the
adherend. Moreover, the soluble adhesive layer 14 is immersed in
the releasing liquid immediately before the release of the sheet;
hence, the adhesive force of the soluble adhesive layer 14 can be
retained before the release, in other words, the release of the
adhesive layer due to a decrease in adhesive force can be avoided
before the releasing process. Accordingly, the sheet can retain the
adhesive force of the adhesive layer before releasing and can be
released from the adherend at any time.
[0033] In particular, thinning of a laminate is required in view of
recent technical trends that employ fan-out wafer level packaging
(FO-WLP) and panel level packaging (PLP). However, in the case of a
thin laminate, a large local warpage of a build-up layer may occur
when a substrate is removed from the laminate produced by, for
example, a coreless build-up process. Such a large warpage of the
build-up layer may cause the disconnection and separation of the
wiring layer inside the build-up layer, and thereby decrease the
reliability of connection in the wiring layer. In order to address
the disconnection and separation of the wiring layer inside the
build-up layer, a reinforcing sheet may be stacked on a laminate
with an adhesive release layer therebetween. As a result, the
laminate can be reinforced to an extent not causing a large local
warpage, resulting in an improvement in the reliable connection in
the laminate and the flatness (coplanarity) on the surface of the
laminate. The present invention has an advantage in that the
reinforcing sheet tightly adhering to the laminate with the soluble
adhesive layer 14 therebetween can be efficiently released without
applying of excessive stress to the laminate.
[0034] The adhesive sheet 10 may be either a bondable adhesive
sheet or a transferable adhesive sheet. Accordingly, the adhesive
sheet 10 may include a substrate sheet 12 having desired functions
(e.g., a protective function and/or a reinforcing function) after
the adhesive sheet 10 itself is bonded to the adherend, and as
shown in FIGS. 7A (c) and (d), or the adhesive sheet may be used
for transferring the soluble adhesive layer 14 to the second
substrate sheet 12' (e.g., a protective sheet or a reinforcing
sheet) and releasing the initial substrate sheet 12 after
transferring. In the latter case, the laminate having the soluble
adhesive layer 14 transferred to the second substrate sheet 12' is
also included in the scope of the adhesive sheet of the present
invention as a second adhesive sheet 10'.
[0035] The soluble adhesive layer 14 is provided in an island or
stripe pattern on at least one surface of the substrate sheet 12.
Two soluble adhesive layers 14 may be provided on the two surfaces
of the substrate sheet 12. Individual adhesive regions 14a have a
circumscribed circle diameter in the range of 0.1 to 10 mm,
preferably 0.1 to 5.0 mm, more preferably 0.1 to 2.0 mm in the
island pattern, and a stripe width in the range of 0.1 to 10 mm,
preferably 0.1 to 5.0 mm, more preferably 0.1 to 2.0 mm in the
stripe pattern. Such a range can sufficiently maintain the adhesive
force of the soluble adhesive layer 14 before immersion in the
releasing liquid and promote the impregnation of the releasing
liquid into the gaps in the pattern of the soluble adhesive layer
14, and thereby facilitate the release of the sheet from the
adherend through, for example, a dissolution release.
[0036] The soluble adhesive layer 14 is preferably provided in an
island pattern. The island pattern indicates that each adhesive
region 14a is surrounded by a non-adhesive region 14b not having
the soluble adhesive layer 14. Examples of the specific shape of
each adhesive region 14a constituting the island pattern include
polygons and circles; in specific, polygons consisting of an
intricate straight contour such as a star shape shown in FIG. 4A;
and consisting of an intricate curved line contour such as an ameba
shape shown in FIG. 4B. The island pattern is preferably a dotted
pattern, and the shape of each dot may be typically a circle, or a
shape close to a circle. The dot diameter defined as the
circumscribed circle diameter of each dot constituting the dotted
pattern is preferably 10 mm or less, more preferably 0.1 to 5.0 mm,
further more preferably 0.1 to 2.0 mm. Such a configuration causes
an increase in surface area of the soluble adhesive layer 14 and an
enhancement of solubility, resulting in an improvement in
releasability. In addition, the dotted pattern has a pitch circle
diameter (PCD) of preferably 0.45 to 3.0 mm, more preferably 0.6 to
2.4 mm, further more preferably 0.8 to 2.0 mm. In the present
specification, "a pitch circle diameter (PCD) of a dotted pattern"
is defined to indicate a diameter (pitch circle diameter) of an
imaginary circle (pitch circle (PC)) which can be formed by
connecting the centers of three closest dots in the dotted pattern
as shown in FIG. 5. The above range of the PCD can sufficiently
maintain the adhesive force of the soluble adhesive layer 14 before
immersion in the releasing liquid and promote the penetration of
the releasing liquid into the gaps in the pattern of the soluble
adhesive layer 14, thereby further facilitating the release of the
sheet from the adherend.
[0037] The soluble adhesive layer 14 has a thickness of preferably
0.5 to 50 .mu.m, more preferably 1.0 to less than 30 .mu.m, further
more preferably 1.0 to 20 .mu.m, particularly more preferably 2.0
to 15 .mu.m, most preferably 3.0 to 10 .mu.m. The above range of
the thickness allows the releasing liquid to rapidly penetrate into
the gaps in the pattern of the soluble adhesive layer 14, resulting
in an improvement in releasability of the adhesive sheet 10, as
well as a decrease in indentation corresponding to the island or
stripe pattern on the adherend. In particular, when mounting of
chips, solder reflow and compression molding are performed after
bonding an adhesive sheet to reinforce a printed wiring board in
the manufacture semiconductor package, the indentation derived from
the adhesive region 14a may remain on the printed wiring board.
However, the soluble adhesive layer 14 with a thickness of 7.0
.mu.m or less has an advantage in that the indentation barely
remains on the printed wiring board after the compression molding.
In this respect, in the soluble adhesive layer 14 having a dotted
pattern, a dot diameter of 0.7 mm or less and a thickness of the
soluble adhesive layer 14 of 1.0 to 7.0 .mu.m are particularly
preferred from the viewpoint of more effective realization of both
the reduction in indentation and the improvement in
releasability.
[0038] The distance between the centers of the circumscribed
circles in the adhesive regions 14a is preferably larger than the
mean diameter of the circumscribed circles, because a sufficient
gap can be secured among the individual adhesive regions 14a. From
this point of view, the distance between the centers of the
circumscribed circles in the adhesive region is preferably 0.1 to
20 mm, more preferably 0.2 to 10 mm, further more preferably 0.3 to
5.0 mm, particularly more preferably 0.4 to 2.0 mm. Such a range
allows the releasing liquid to rapidly penetrate into the gaps in
the pattern of the soluble adhesive layer 14, resulting in an
improvement in releasability.
[0039] The island pattern may be composed of one or more clusters
that form a polygonal, circular, annular, striped or grid pattern
on the whole, and each of the clusters may consist of an aggregate
of three or more adhesive regions. In other words, the island
pattern (for example, a dotted pattern) has not only an embodiment
where the adhesive regions are uniformly provided over the entire
surface of the substrate sheet 12 as shown in FIG. 6A, but also an
embodiment that wholly illustrates the polygonal pattern (e.g., a
square as shown in FIG. 6B), the circular pattern as shown in FIG.
6C, the annular pattern as shown in FIG. 6D, the striped pattern
shown in FIG. 6E, or the grid pattern as shown in FIG. 6F, where
all these patterns are formed by clusters 18 each composed of an
aggregate of three or more adhesive regions 14a. In this manner,
the island pattern has some advantages other than an improvement in
appearance: For example, the adhesive region 14a can be formed so
as to avoid the areas that do not require higher adhesion strength
and the areas where the indentation of the adhesive region 14a
tends to remain; the quantity of the soluble adhesive can be
reduced per one adhesive sheet; and the soluble adhesive layer 14
can be efficiently dissolved because the releasing liquid rapidly
penetrates into the region where the adhesive region 14a is not
formed.
[0040] The rate of the adhesive region 14a to the total surface
area provided with the soluble adhesive layer 14 of the substrate
sheet 12 is preferably 3 to 90 area %, more preferably 3 to 75 area
%, further more preferably 5 to 60 area %, particularly more
preferably 5 to 40 area %. In the present specification, "the total
surface area provided with the soluble adhesive layer 14 of the
substrate sheet 12" indicates the total area of the surface
adjacent to the soluble adhesive layer 14 of the substrate sheet 12
if the soluble adhesive layer 14 is provided on one side of the
substrate sheet 12, or the total area of two sides of the substrate
sheet 12 if the soluble adhesive layer 14 is provided on two sides
of the substrate sheet 12. The above range of the rate of the
adhesive region 14a can sufficiently educe the adhesive force of
the soluble adhesive layer 14 before immersion in the releasing
liquid, and promote the penetration of the releasing liquid into
the gaps in the pattern of the soluble adhesive layer 14 and
thereby further facilitate the release of the sheet from the
adherend. However, any range may be employed in applications that
require only a minimum adhesive force in the process for the
purpose of simple fixation.
[0041] The soluble adhesive layer 14 has, needless to say,
adhesiveness at room temperature, and can be dissolved or softened
in the releasing liquid. Accordingly, the soluble adhesive layer 14
preferably contains a solution-soluble resin, for example, an
acid-soluble resin or an alkali-soluble resin. The solution-soluble
resin can be efficiently dissolved or softened through the contact
with the releasing liquid, resulting in more effective release of
the sheet from the adherend.
[0042] The solution-soluble resin is preferably an alkali-soluble
resin for the following reason: It is preferred that the soluble
adhesive layer 14 be not substantially dissolved in a neutral or
acidic solution in the application to articles that may come in
contact with the neutral or acidic solution in the manufacturing
process, such as a printed wiring board. For example, in the case
that the soluble adhesive layer 14 is applied to a printed wiring
board, the use of resins (for example, water-soluble resins) that
dissolve in a neutral solution may cause the dissolution of resins
in a water washing process in the manufacturing process of the
printed wiring board, or the degradation of resins due to
adsorption of moisture in the air. The selection of resins that
dissolve only in an acidic solution (that is, resins that does not
dissolve in a neutral or alkaline solution) may cause a decrease in
adhesive force of the soluble adhesive layer 14, because the acidic
solution is used in many micro-etching and etching steps for
formation of circuit, which are cleaning steps of the surface in
the manufacturing process of a printed wiring board. However, it is
understood that the resins that dissolve in the neutral or acidic
solution can be used in the applications where the article or
adherend does not come in contact with the neutral or acidic
solution in the manufacturing process.
[0043] In particular, the alkali-soluble resin preferably includes
a polymer containing carboxyl groups and/or phenolic hydroxyl
groups. Such a polymer can particularly readily dissolve in an
alkaline solution, and thereby can promote the dissolution of the
soluble adhesive layer 14 and cause the release of sheet from the
adherend in a shorter time. Examples of the polymer containing
carboxyl groups and/or phenolic hydroxyl groups include acrylic
resins containing carboxyl groups and phenol novolac resins
containing phenolic hydroxyl groups. The acrylic resin adhesive can
be synthesized through copolymerization of an acrylic monomer (for
example, acrylic acid or methacrylic acid) having a carboxyl group
and an unsaturated double bond in the molecule with ethyl acrylate
or butyl acrylate. In the synthesis, the type and ratio of the
acrylic monomer is adjusted to control the adhesive force of the
soluble adhesive layer 14 and the solubility of the soluble
adhesive layer 14 in the alkaline solution. The adhesive force of
the soluble adhesive layer 14 and the solubility of the soluble
adhesive layer 14 in the alkaline solution can also be controlled
through addition of a resin which triggers a crosslinking reaction
of the carboxyl groups (for example, an epoxy resin) to the acrylic
resin containing the carboxyl groups. Since crosslinking of some of
the carboxyl groups in the acrylic resin with a resin such as an
epoxy resin causes an increase in the molecular weight, the
adhesive force and the solubility in the alkaline solution are
reduced although the heat resistance is improved. In contrast, use
of the phenol novolac resin containing the phenolic hydroxyl groups
as the alkali-soluble resin decreases the adhesive force of the
soluble adhesive layer 14; hence, a tackifier, such as rosin, is
preferably mixed to yield appropriate adhesiveness.
[0044] For a soluble adhesive layer 14 containing an alkali-soluble
resin, the alkaline solution used as the releasing liquid is
preferably a sodium hydroxide solution and/or a potassium hydroxide
solution. These solutions have preferably a concentration of 0.5 to
50 wt %. Within such a range, the solution has high alkalinity and
high solubility, and sodium hydroxide and/or potassium hydroxide is
less likely to precipitate even in lower room temperature when the
releasing liquid is used. Moreover, an organic material (e.g.,
ethanolamine) an aqueous solution of which exhibits alkalinity may
be used alone or in combination with the above solution.
[0045] In order to shorten a dissolution time of the soluble
adhesive layer 14, an organic solvent capable of dissolving the
acrylic resin and/or the novolac resin (e.g., 2-propanol) may be
added to the alkaline solution. The preferred concentration of this
organic solvent is 5 to 50 wt % for 100 wt % of the alkaline
solution. Such a range can desirably shorten the dissolution time
and reduce the volatilization of the solvent during the process,
resulting in facilitating the control of the concentration of
alkaline material and an improvement in safety. The organic solvent
is preferably alcohol, and preferred examples of the alcohol
include 2-propanol, methanol, ethanol, and 2-butanol.
[0046] An appropriate amount of surfactant may be added to the
alkaline solution. The addition of the surfactant can improve the
impregnation and wettability of the solution to the resin, and thus
further shortens the dissolution time in the soluble adhesive layer
14. Any type of surfactant may be added. For example, the
water-soluble surfactant may be any of anionic, cationic and
nonionic surfactants.
[0047] The substrate sheet 12 may be in any form, such as a sheet
generally referred to, a film, a plate, and a foil. The substrate
sheet 12 may be also a laminate of these sheets, films, plates, and
foils. Moreover, for adjusting the adhesive force between the
substrate sheet 12 and the soluble adhesive layer 14, the surface,
to which the soluble adhesive layer 14 is applied, of the substrate
sheet 12 may be preliminarily subjected to known surface treatment,
such as polishing, application of a releasing agent, and/or plasma
treatment.
[0048] According to a preferred embodiment of the present
invention, the substrate sheet 12 is composed of preferably at
least one resin of poly(ethylene terephthalate) (PET) and
polyethylene (PE), and more preferably poly(ethylene terephthalate)
(PET). In particular, when the adhesive sheet 10 is used as a
transferable adhesive sheet, it is preferred that the substrate
sheet 12 support the soluble adhesive layer 14 and transfer the
soluble adhesive layer 14 to the adherend or the second substrate
sheet separately provided. The substrate sheet 12 of the present
embodiment is suitable for such use. The substrate sheet 12 as the
transferrable adhesive sheet has a thickness of preferably 10 to
200 .mu.m, more preferably 20 to 150 .mu.m, further more preferably
25 to 75 .mu.m.
[0049] According to another preferred embodiment of the present
invention, the substrate sheet 12 is preferably composed of at
least one selected from the group consisting of metal (preferably a
metal plate or a metal foil), glass, glass epoxy resin, polyimide
resin, and phenol resin (Bakelite). The substrate sheet 12 for
disposable use is preferably composed of phenol resin (Bakelite)
from the viewpoint of material cost, whereas the substrate sheet 12
for repeated use is preferably composed of metal from the viewpoint
of material strength. Since all of these materials are
heat-resistant, deterioration can be prevented in the heat
treatment process. In the case that the adhesive sheet 10 is used
as a bondable adhesive sheet, it is preferred that the substrate
sheet 12 have a function of supporting the soluble adhesive layer
14, as well as a function as a reinforcing sheet for improving
handling properties and preventing or restraining the warpage of
the printed wiring board in the process of manufacturing the
semiconductor package. The substrate sheet 12 of the present
embodiment is suitable for such use. The substrate sheet 12 as a
bondable adhesive sheet has a thickness of preferably 10 .mu.m to 1
mm, more preferably 50 to 800 .mu.m, further more preferably 100 to
600 .mu.m from the viewpoint of strength retention of the substrate
sheet 12 and ready handling for the substrate sheet 12.
[0050] In the case that the adhesive sheet 10 is used as a bondable
adhesive sheet, the substrate sheet 12 preferably has a lower
Vickers hardness than the adherend (e.g., the printed wiring
board). This lower hardness causes the stress that may be generated
during stacking and releasing to be appropriately relieved by warp
of the substrate sheet 12 itself when the adhesive sheet 10 is
stacked on or released from the adherend (e.g., a printed wiring
board), resulting in effective prevention or restraint of the
warpage on the adherend (e.g., a printed wiring board). The Vickers
hardness of the substrate sheet 12 is preferably 2 to 99%, more
preferably 6 to 90%, and further more preferably 10 to 85% of that
of the adherend (e.g., a printed wiring board). The substrate sheet
12 has a Vickers hardness of preferably 50 to 700 HV, more
preferably 150 to 550 HV, further more preferably 170 to 500 HV. In
the present specification, the Vickers hardness is measured in
accordance with the "Vickers hardness test" described in JIS Z
2244-2009.
[0051] For reference, the Vickers hardness HV of various candidate
materials is exemplified as follows: sapphire glass (2300 HV), hard
metal alloy (1700 HV), cermet (1650 HV), quartz (rock crystal)
(1103 HV), SKH 56 (high speed tool steel, HSS) (722 HV), tempered
glass (640 HV), SUS 440 C (stainless steel) (615 HV), SUS 630
(stainless steel) (375 HV), titanium alloy 60-types (64 titanium
alloy) (about 280 HV), Inconel (heat resistant nickel alloy) (150
to 280 HV), S 45 C (carbon steel for machine structural use) (201
to 269 HV), Hastelloy alloy (corrosion resistant nickel alloy) (100
to 230 HV), SUS 304 (stainless steel) (187 HV), SUS 430 (stainless
steel) (183 HV), cast iron (160 to 180 HV), titanium alloy (110 to
150 HV), brass (80 to 150 HV), and bronze (50 to 100 HV).
[0052] When the adhesive sheet 10 is used as a bondable adhesive
sheet, the substrate sheet 12 has a spring limit value Kb.sub.0.1
in the range of preferably 100 to 1500 N/mm.sup.2, more preferably
150 to 1200 N/mm.sup.2, further more preferably 200 to 1000
N/mm.sup.2 as measured in accordance with the repeated deflection
test of JIS H 3130-2012. Such a range causes the stress that may be
generated during stacking and releasing to be appropriately
relieved by warping of the substrate sheet itself when the adhesive
sheet 10 is stacked on or released from the adherend (e.g., a
printed wiring board), resulting in effective prevention or
restraint of the warpage on the adherend (e.g., a printed wiring
board). Since the substrate sheet 12 warped when stacked or
released can instantaneously return back to the original flat shape
due to its resiliency, the flatness (coplanarity) of the adherend
(e.g., a printed wiring board) can be more effectively maintained.
In addition, the use of the tenacity and resiliency of the
substrate sheet 12 can urge the substrate sheet 12 to which the
releasing force is applied in the direction of the release (that
is, in the direction away from the adherend (e.g., a printed wiring
board)), resulting in further smooth release.
[0053] For reference, spring limit values Kb.sub.0.1 for various
candidate materials are illustrated in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Material (JIS Number) Tempering Kb.sub.0.1
SUS301CSP 1/2H 315 (stainless steel) 3/4H 390 H 490 EH 590 SHE(1)
650 SUS304CSP 1/2H 275 (stainless steel) 3/4H 335 H 390 SUS631CSP O
635 (stainless steel) 1/2H 635 3/4H 835 H 980 SUS632J1CSP 1/2H 1200
(stainless steel) 3/4H 1400 C1700 O 685 (beryllium-copper alloy)
1/4H 785 1/2H 835 H 855 C1720 O 735 (beryllium-copper alloy) 1/4H
835 1/2H 885 H 930 C1720M OM 390 (beryllium-copper alloy) 1/4HM 440
*mill-hardened material 1/2HM 540 HM 635
TABLE-US-00002 TABLE 2 Material (JIS Number) Tempering Kb.sub.0.1
C5210 1/2H 245 (phosphor bronze) H 390 EH 460 SH 510 ESH 560 C5240
H 430 (phosphor bronze) EH 510 SH 570 ESH 630 XSH 700 C7270 O 490
(nickel-tin-copper alloy) 1/4H 590 1/2H 635 H 685 EH 735 SH 785
C7270M OM 440 (nickel-tin-copper alloy) 1/4HM 490 *mill-hardened
material 1/2HM 540 HM 590 EHM 685 XHM 785 C7701 1/2H 390
(nickel-zinc-copper alloy) H 480 EH 560 SH 620 C1990M 1/4HM 440
(titanium-copper alloy) EHM 590 *mill-hardened material
[0054] In the case that the adhesive sheet 10 is used as a bondable
adhesive sheet, the substrate sheet 12 preferably has through-holes
in the thickness direction. Before the adhesive sheet 10 is
released from the adherend (e.g., a printed wiring board), the
releasing liquid can penetrate into the gaps in the pattern of the
soluble adhesive layer 14 though these through-holes provided in
the substrate sheet 12, and the soluble adhesive layer 14 is more
efficiently dissolved, resulting in a further improvement in
releasability.
[0055] As shown in FIG. 7A (a) described later, the adhesive sheet
10 further preferably includes a protective film 16 stacked on the
soluble adhesive layer 14, resulting in ready handling. The
protective film 16 is composed of any material, preferably a resin.
Preferred examples of the resin constituting the protective film
include poly(ethylene terephthalate) (PET), polyethylene (PE), or a
combination thereof, and more preferably poly(ethylene
terephthalate) (PET). The protective film 16 has a thickness of
preferably 10 to 40 .mu.m, more preferably 15 to 30 .mu.m. Since
the protective film 16 protects the soluble adhesive layer 14
before the adhesive sheet 10 is used, the protective film is
released from the adhesive sheet 10 in use of the adhesive sheet
10. Accordingly, the adhesive force (e.g., release strength)
between the soluble adhesive layer 14 and the protective film 16 is
preferably lower than the adhesive force (e.g., release strength)
between the soluble adhesive layer 14 and the substrate sheet 12.
This difference in the adhesive force allows the protective film 16
to be preferentially released to the substrate sheet 12, thereby
the protective film 16 can be released readily and smoothly while
stably maintaining the adhesion between the substrate sheet 12 and
the soluble adhesive layer 14. In order to adjust the adhesive
force between the protective film 16 and the soluble adhesive layer
14, the surface, on which the soluble adhesive layer 14 is applied,
of the protective film 16, may be preliminarily subjected to
surface treatment by a known procedure, such as polishing
treatment, application of release agent, and plasma treatment.
Use of Adhesive Sheet in Manufacture of Semiconductor Package
[0056] The adhesive sheet 10 of the present invention can be
applied to various adherends that require a desired adhesiveness,
and used in any field, most preferably for reinforcing of printed
wiring boards. FIGS. 7A to 7C illustrate steps for manufacturing a
semiconductor package using the adhesive sheet 10 of the present
invention. The steps shown in FIG. 7B may be carried out after the
steps shown in FIG. 7A, or the steps shown in FIG. 7C may be
carried out after the steps shown in FIG. 7A. In any case, the
process shown in FIG. 7A includes the following steps: The adhesive
sheet 10 provided with the substrate sheet 12, the soluble adhesive
layer 14, and the protective film 16, in sequence, is prepared to
be a transferable adhesive sheet (step (a)); The protective film 16
is released (step (b)); The soluble adhesive layer 14 is
transferred by a roll lamination process to the second substrate
sheet 12' functioning as a reinforcing sheet (step (c)); and The
substrate sheet 12 is released (step (d)). In these steps, the
second adhesive sheet 10' comprising the second substrate sheet 12'
to which the soluble adhesive layer 14 is transferred as described
above is also categorized within the scope of the adhesive sheet,
as a bondable adhesive sheet, of the present invention. The second
adhesive sheet 10' is bonded to the printed wiring board 20p by a
vacuum lamination process (step(e)). As shown in FIG. 7B, the
resulting laminate may be immersed in an alkaline solution after
the printed wiring board 20p is subjected to solder paste printing
(step (i)), and the second substrate sheet 12' (reinforcing sheet)
may be released (step (j)). In contrast, as shown in FIG. 7C, the
resulting laminate may be immersed in an alkaline solution (step
(i)), and the second substrate sheet 12' (reinforcing sheet) may be
released (step (j)) after being subjected to mounting of the
semiconductor chip 22 (chip mounting) (step (f)), solder reflow
(step (g)), and compression molding (step (h)). As shown in FIG.
7C, the semiconductor chip 22 may be sealed with the insulating
resin 24 in the step (h). Since the second substrate sheet 12'
serves as the reinforcing sheet in any case, the reliability of
connection and the surface flatness (coplanarity) on the printed
wiring board 20p can be enhanced, resulting in simplification in
processes and an improvement in yield. Since the adhesive force of
the soluble adhesive layer 14 can be maintained until the releasing
step, an unintended release does not occur to cause no trouble in
handling. In the final step, immersing in the alkaline solution
allows the second substrate sheet 12' to be readily released from
the printed wiring board 20p without applying of the excessive
stress to the printed wiring board 20p.
Release of Adhesive Sheet
[0057] The adhesive sheet 10 of the present invention is used to be
bonded to any adherend 20. The following procedures are preferably
performed for the release of the adhesive sheet 10 or the substrate
sheet 12 from the adhered 20 to which the adhesive sheet 10 is
bonded.
[0058] An alcoholic solution capable of dissolving the soluble
adhesive layer 14 is penetrated into gaps in the island or stripe
pattern of the soluble adhesive layer 14 to dissolve or soften the
soluble adhesive layer 14. The penetration of the alcoholic
solution into the gaps may be performed by bringing the whole or
part of the adherend 20 to which the adhesive sheet 10 is bonded
into contact with an alcoholic releasing solution through, for
example, immersion. Examples of the alcohol contained in the
alcoholic solution capable of dissolving the soluble adhesive layer
14 include preferably 2-propanol, methanol, ethanol, and 2-butanol,
and most preferably 2-propanol from the viewpoint of high
miscibility with water and superior releasability. The alcohol in
the alcoholic solution has a concentration in the range of
preferably 5 to 90 wt %, more preferably 10 to 70 wt %, further
more preferably 20 to 50 wt %. Such a range allows the soluble
adhesion layer 14 to be more effectively dissolved or softened, and
causes the alcoholic solution to be hard to ignite due to the
reduced alcoholic concentration and thereby improve the safety. The
alcoholic solution preferably contains a basic substance, such as
KOH, NaHCO.sub.3, Na.sub.2CO.sub.3, NaOH, to control and stabilize
the releasability, and the basic substance has a concentration of
preferably 0.1 to 30 wt %, more preferably 0.5 to 20 wt %, further
more preferably 1.0 to 15 wt % in the alcoholic solution.
Accordingly, the alcoholic solution may contain the alkaline
solution as described above.
[0059] After the soluble adhesive layer 14 is dissolved or
softened, the adhesive sheet 10 or the substrate sheet 12 is
released from the adherend 20. The release of the sheet from the
adherend 20 may be spontaneously achieved by dissolution of the
soluble adhesive layer 14, or mechanically achieved after the
adhesive force is significantly reduced by dissolution or softening
of the soluble adhesive layer 14.
Production of Adhesive Sheet
[0060] A soluble adhesive is provided, and an island or stripe
pattern of the soluble adhesive can be printed on the substrate
sheet 12 to form a soluble adhesive layer 14. The adhesive sheet 10
can thereby be produced. Since the pattern of the soluble adhesive
layer 14 and the size and shape of the individual adhesive regions
14a are substantially equivalent to a block design in printing, the
desired soluble adhesive layer 14 is formed by appropriately
modifying the block design. The printing may be performed using any
known process, for example, dot pattern printing, screen printing,
or gravure printing (intaglio printing). The gravure printing that
can employ a roll to roll process is preferably used from the
viewpoint of stable continuous printing and high mass
productivity.
EXAMPLES
[0061] The invention will be described in more detail by the
following examples.
Examples 1 to 3
(1) Production of Adhesive Sheet
[0062] A curing agent (1 wt %, TETRAD-C, available from Mitsubishi
Gas Chemical Co., Ltd.) was added to a carboxyl group-containing
acrylic resin (COPONYL.TM. N-2584, available from Nippon Synthetic
Chemical Industry Co., Ltd.) to prepare a soluble adhesive
containing a polymer having carboxyl groups. A predetermined dotted
pattern shown in Table 3 of this soluble adhesive was
gravure-printed on a poly(ethylene terephthalate) (PET) sheet to
give an adhesive sheet. The gravure printing was carried out with
an engraved printing block (a cylinder having a print width of
about 700 mm and a diameter of 200 mm) in which a printed image of
the dotted pattern satisfied the specifications: a dot diameter
(i.e., a circumscribed circle diameter of individual dots), a pitch
circle diameter (PCD), and the rate of adhesive region shown in
Table 3 such that the total thickness of the substrate sheet and
the soluble adhesion layer was 100 .mu.m.
(2) Evaluation of Adhesive Sheet
[0063] The resultant adhesive sheet was subjected to evaluation of
the following properties.
<Evaluation 1-1: Releasability (in Alkaline Solution)>
[0064] The releasability in an alkaline solution was evaluated
according to a process flowchart shown in FIGS. 7A and 7B. In this
process flow, a stainless-steel plate was stacked as a second
substrate sheet 12' on the surface provided with the soluble
adhesive layer 14 of the adhesive sheet 10 (step (c)), and then the
substrate sheet 12 was released from the laminate (Step (d)). The
soluble adhesive layer 14 of the adhesive sheet 10 was transferred
to the stainless-steel plate that is the second substrate sheet
12'. The second substrate sheet 12' (the stainless-steel plate) is
bonded to the printed wiring board 20p with the soluble adhesive
layer 14 therebetween to produce a laminate 26 for evaluation (step
(e)). The laminate 26 was stationarily immersed in a releasing
liquid (10 wt % sodium hydroxide solution) (step (i)). The time
(maximum 18 hours) is measured that is required from the start of
immersion to the release of the second substrate sheet 12' (the
stainless-steel plate) from the printed wiring board 20p (step
(j)), and classified into the following grades. The results are as
shown in Table 3.
[0065] Grade AA: The soluble adhesive layer was dissolved and the
stainless-steel plate was released within 30 minutes, resulting in
a significant improvement in productivity due to a significantly
high dissolution rate of the soluble adhesive layer.
[0066] Grade A: The soluble adhesive layer was dissolved and the
stainless-steel plate was released within more than 30 minutes to
one hour, resulting in an improvement in productivity due to a high
dissolution rate of the soluble adhesive layer.
[0067] Grade B: The soluble adhesive layer was dissolved and the
stainless-steel plate was released within more than one hour to
three hours, resulting in a releasing rate sufficient in the case
of no particular requirement for acceleration of processing.
[0068] Grade C: The stainless-steel plate was not released even
after immersion for 18 hours.
<Evaluation 1-2: Releasability (in Alcoholic Solution)>
[0069] Example 2 was subjected to evaluation of the releasability
as in Evaluation 1-1 except that the releasing liquid was a mixed
alcoholic solution of 1.5 wt % potassium hydroxide and 25 wt %
2-propanol, instead of the alkaline solution. The results are shown
in Table 3.
<Evaluation 2: Indentation Marks (after Compression
Molding)>
[0070] The indentations marks after compression molding were
evaluated according to the process flowchart shown in FIGS. 7A and
7C. In detail, the laminate for evaluation 26 was produced as in
Evaluation 1 (steps (c) to (e)); the semiconductor chip 22 was
mounted on the printed wiring board 20p of the laminate 26 (step
(f)); solder reflow is performed (step (g)); and compression
molding was then performed at 175.degree. C. under 8 MPa to give a
laminate 28 for evaluation of the indentation marks (step (h)).
This laminate 28 for evaluation of the indentation marks was
stationarily immersed in a releasing solution (10 wt % sodium
hydroxide solution) (step (i)); and the second substrate sheet 12'
(the stainless-steel plate) was released from the printed wiring
board 20p (step (j)). The indentation marks remaining on the
printed wiring board 20p were then observed with a microscope, and
classified into the following grades. The results are shown in
Table 3.
[0071] Grade A: The depth of indentation was less than 5 .mu.m.
[0072] Grade B: The depth of indentation was 5 .mu.m to 10 .mu.m.
This depth of indentation did not adversely affect the subsequent
steps, but caused inferior appearance.
[0073] Unevaluated: Since the stainless-steel plate was not
released even after immersion for 18 hours, the indentation marks
was not evaluated.
Example 4 (Comparative)
[0074] An adhesive sheet was produced, and Evaluations 1-1 and 2
were performed as in Example 1, except that a printing cylindrical
block which a printing image was not engraved was used to form a
soluble adhesive layer through solid coating. The results are shown
in Table 3.
TABLE-US-00003 TABLE 3 Example Example 1 Example 2 Example 3 4*
Printed image Dot diameter (mm) 1.0 0.7 1.0 -- engraved on Pitch
circle diameter 1.80 1.26 1.80 -- printing block (PCD) (mm)
(cylinder) Rate of adhesive region 38 38 38 -- (area %) (Calculated
value based on printing block design) Soluble Pattern Dotted Dotted
Dotted Solid adhesive layer printed Dot diameter (mm) 0.98 0.70
0.97 -- Thickness (.mu.m) 7 7 15 7 Evaluation Evaluation 1-1: B A A
C Releasability (alkaline solution) (releasing liquid: 10 wt % NaOH
solution) Evaluation 1-2: -- AA -- -- Releasability (alcoholic
solution) (releasing liquid: 1.5 wt % KOH + 25 wt % 2-propanol)
Evaluation 2: A A B Unable Indentation marks to (after compression
evaluate molding) *Comparative example
* * * * *