U.S. patent application number 09/883257 was filed with the patent office on 2002-02-21 for casting film for producing ceramic green sheet.
This patent application is currently assigned to LINTEC Corporation. Invention is credited to Nakamura, Toru, Shibano, Tomishi.
Application Number | 20020022141 09/883257 |
Document ID | / |
Family ID | 18702694 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022141 |
Kind Code |
A1 |
Nakamura, Toru ; et
al. |
February 21, 2002 |
Casting film for producing ceramic green sheet
Abstract
There is disclosed a casting film which is used for producing a
ceramic green sheet and which comprises a substrate film (e.g.
polyethylene terephthalate film) and a releasing layer formed
thereon comprising a cured resin from (A) a stearic acid-modified
alkyd resin and/or a stearic acid-modified acrylic resin and a (B)
amino resin (e.g. melamine resin, urea resin and urea-melamine
resin, each being etherified by a lower alcohol). The above casting
film has excellent wettability of ceramic slurry and moderate
releasability for the ceramic green sheet without the occurrence of
repelling at the time of applying coating, and is well suited for
use in the production of ceramic green sheets that are employed for
ceramic capacitors, laminated inductor elements, etc.
Inventors: |
Nakamura, Toru;
(Saitama-shi, JP) ; Shibano, Tomishi;
(Higashimatsuyama-shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
LINTEC Corporation
Itabashi-ku
JP
|
Family ID: |
18702694 |
Appl. No.: |
09/883257 |
Filed: |
June 19, 2001 |
Current U.S.
Class: |
428/480 ;
428/482; 428/483; 428/522 |
Current CPC
Class: |
Y10T 428/31935 20150401;
Y10T 428/31797 20150401; Y10T 428/31928 20150401; Y10T 428/31786
20150401; Y10T 428/1462 20150115; B32B 27/30 20130101; Y10T
428/1476 20150115; Y10T 428/31794 20150401; C04B 35/62218 20130101;
B32B 27/36 20130101 |
Class at
Publication: |
428/480 ;
428/522; 428/482; 428/483 |
International
Class: |
B32B 027/36; B32B
027/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2000 |
JP |
2000-205642 |
Claims
What is claimed is:
1. A casting film which is used for producing a ceramic green sheet
and which comprises a substrate film and a releasing layer formed
on at least either side thereof, wherein said releasing layer
comprises a cured resin from (A) a stearic acid-modified alkyd
resin and/or a stearic acid-modified acrylic resin and a (B) amino
resin.
2. The casting film for producing a ceramic green sheet according
to claim 1, wherein the stearic acid-modified alkyd resin has a
stearyl group content of 40 to 60% by weight, and/or the stearic
acid-modified acrylic resin has a stearyl group content of 20 to
40% by weight.
3. The casting film for producing a ceramic green sheet according
to claim 1, wherein the (B) amino resin is at least one member
selected from the group consisting of melamine resin, urea resin
and urea-melamine resin each being etherified by a lower
alcohol.
4. The casting film for producing a ceramic green sheet according
to any of claims 1, 2 and 3, wherein the content of the component
(B) is 5 to 40% by weight based on the total sum of the solid
content of the components (A) and (B);
5. The casting film for producing a ceramic green sheet according
to claim 1, wherein the substrate film comprises polyethylene
terephthalate;
6. The casting film for producing a ceramic green sheet according
to claim 1, wherein the component (A) is composed of the mixture of
the stearic acid-modified alkyd resin and the stearic acid-modified
acrylic resin.
7. The casting film for producing a ceramic green sheet according
to claim 1, wherein the cured resin is formed in the presence of an
acid catalyst.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a casting film for
producing a ceramic green sheet. More particularly, it is concerned
with a casting film which is used in the production process of a
ceramic green sheet in producing ceramic electronic part items, and
which has excellent wettability of ceramic slurry and moderate
releasability for the ceramic green sheet.
[0003] 2. Description of the Related Arts
[0004] A ceramic electronic part item such as a capacitor, a
laminated inductor element, a piezoelectric-part, a thermistor and
a varister is produced by a method comprising the steps of forming
a green sheet by coating a casting film with ceramic slurry which
is well suited to the above-mentioned electronic part items, which
is used in high dielectric-constant, magnetism and the like, and
which is composed of ceramic powders, organic binders,
plasticizers, solvents (an organic solvent or water) and the like
(Step {circle over (1)}); equipping the resultant green sheet with
an electrode made of palladium, silver, nickel or the like by means
of screen printing (Step {circle over (2)}); then peeling off the
green sheet from the casting film and laminating the green sheets
in multi-layer (Step {circle over (3)}); forming ceramic green
chips through steps of pressing and cutting (Step {circle over
(4)}); baking the chips thus obtained (Step {circle over (5)}); and
equipping the baked chips with terminal electrodes made of silver,
silver palladium, nickel, copper or the like (Step {circle over
(6)}). In addition thereto, there has recently been proposed a new
production process in which the above-mentioned Steps {circle over
(1)} and {circle over (2)} are repeated plural times, followed by
the Step {circle over (3)} {refer to Japanese Patent Application
Laid-Open No. 130150/1996 (Heisei-8)}.
[0005] As a casting film used in the production process of ceramic
electronic part items, a polyester film coated with a silicone
based releasing agent has hitherto been frequently employed.
[0006] Further, there is proposed a carrier film which is used for
casting green sheets, and in which a releasing layer is composed of
an alkyd resin, melamine resin and dimethylpolysiloxane {refer to
Japanese Patent Application Laid-Open No. 137218/1995
(Heisei-7)}.
[0007] In addition, there is proposed a releasable base film which
is used for producing ceramic sheets, and in which a releasing
layer is composed of an amino base copolymer resin {refer to
Japanese Utility Model Publication No. 38884/1993 (Heisei-5)}.
[0008] Accompanying miniaturization, weight-saving and improved
performance of ceramic electronic parts in recent years, a
thin-filmed green sheet is in rapid progress, and is required to
have a film thickness of 10 .mu.m or smaller for aqueous ceramic
green sheets and a film thickness of 4 .mu.m or smaller for solvent
base ceramic green sheets. However, it has been difficult for any
of conventional casting films to satisfy at the same time, both the
requirements including wettability such that enables uniform
coating to be formed even for small coating thickness without
causing repelling in the case of applying ceramic slurry, and also
moderate releasability from a green sheet such that, in the case of
a method in which the above-mentioned Steps {circle over (1)} and
{circle over (2)} are repeated plural times so as to constitute a
multi-layer coating, enables favorable multi-layer coating to be
carried out without causing excessive releasability and without
causing relieving and/or peeling off of the firstly formed green
sheet from the casting film when ceramic slurry is repeatedly
applied on and after the second time.
SUMMARY OF THE INVENTION
[0009] In such circumstances, an object of the present invention is
to provide a casting film which is used in the production of a
ceramic green sheet to be employed in a ceramic electronic part
items, and which is imparted with excellent wettability of ceramic
slurry and moderate releasability for the ceramic green sheet,
while occurrence of repelling is suppressed at the time of ceramic
slurry coating.
[0010] Other objects of the present invention will be obvious from
the text of this specification hereinafter disclosed.
[0011] As a result of intensive extensive research and
investigation accumulated by the present inventors in order to
develop a casting film which is used for producing a ceramic green
sheet and which is imparted with the foregoing requisite
performances, it has been found that a casting film which is
adapted to the objects of the invention is obtainable by using, as
a releasing agent which constitutes a releasing layer, a cured
resin from a stearic acid-modified alkyd resin and/or a stearic
acid-modified acrylic resin and an amino resin. The present
invention has been accomplished on the basis of such findings and
information.
[0012] That is to say, the present invention provides:
[0013] (1) a casting film which is used for producing a ceramic
green sheet and which comprises a substrate film and a releasing
layer formed on at least either side thereof, wherein said
releasing layer comprises a cured resin from (A) a stearic
acid-modified alkyd resin and/or a stearic acid-modified acrylic
resin and a (B) amino resin;
[0014] (2) the casting film for producing a ceramic green sheet as
set forth in the preceding item (1), wherein the stearic
acid-modified alkyd resin has a stearyl group content of 40 to 60%
by weight, and/or stearic acid-modified acrylic resin has a stearyl
group content of 20 to 40% by weight;
[0015] (3) the casting film for producing a ceramic green sheet as
set forth in the preceding item (1), wherein the (B) amino resin is
at least one member selected from the group consisting of melamine
resin, urea resin and urea-melamine resin each being etherified by
a lower alcohol;
[0016] (4) the casting film for producing a ceramic green sheet as
set forth in any of the preceding items (1), (2) and (3), wherein
the content of the component (B) is 5 to 40% by weight based on the
total sum of the solid content of the components(A) and (B);
[0017] (5) the casting film for producing a ceramic green sheet as
set forth in the preceding item (1), wherein the substrate film
comprises polyethylene terephthalate;
[0018] (6) the casting film for producing a ceramic green sheet as
set forth in the preceding item (1), wherein the component (A) is
composed of the mixture of the stearic acid-modified alkyd resin
and the stearic acid-modified acrylic resin; and
[0019] (7) the casting film for producing a ceramic green sheet as
set forth in the preceding item (1), wherein the cured resin is
formed in the presence of an acid catalyst.
DESCRIPTION OF PREFERRED EMBODIMENT
[0020] The casting film for producing a ceramic green sheet
(hereinafter referred simply to as "casting film") according to the
present invention comprises a substrate film and a releasing layer
formed on at least either side thereof. The releasing agent
constituting the releasing layer comprises a cured resin from (A) a
stearic acid-modified alkyd resin and/or a stearic acid-modified
acrylic resin and a (B) amino resin, and may further be
incorporated as desired, with a release modifier, an adhesion
improver and the like.
[0021] The alkyd resin and acrylic resin as the component (A) are
each modified with stearic acid, whereas any of alkyd resin and
acrylic resin that are not modified therewith fails to assure
favorable releasing performance for the green sheet and attain the
objects of the present invention.
[0022] The degree of modification in the above-mentioned resins is
not specifically limited, but it is suitable to select said degree
so that the stearic acid-modified alkyd resin has a stearyl group
content of about 40 to 60% by weight, and the stearic acid-modified
acrylic resin has a stearyl group content of about 20 to 40% by
weight from the viewpoint of the balance between favorable
wettability of ceramic slurry and the releasability of green
sheets.
[0023] As the above-mentioned alkyd resin and acrylic resin, there
are usable the alkyd resin and acrylic resin that have hitherto
been customarily used as a resin component of alkyd resin paint and
heat curable acrylic resin paint, respectively.
[0024] The alkyd resin is produced by well known esterification
reaction of combinational components of a polyol, a polybasic acid
or an anhydride thereof, and any of a variety of modifying agents
that are used at need.
[0025] Examples of the above-mentioned polyol include ethylene
glycol; propylene glycol; diethylene glycol; butylene glycol;
neopentyl glycol; hexanediol; 2,2-dimethylpentanediol-1,3;
hydrogenated bisphenol A; hexylene glycol; glycerol;
trimethylolethane; trimethylolpropane; 1,2,6-hexnaetriol;
trimethycyclohaxane; pentaerythritol; sorbitol; diglycerol; and
dipenta-erythritol. There are also usable in addition to the
foregoing, tris(2-hydroxyethyl)isocyanurate;
2,2-dimethyl-3-hydroxypr- opanol; and the like. Any of the
above-exemplified polyol components may be used alone or in
combination with at least one other.
[0026] The above-mentioned polybasic acid and an anhydride thereof
are exemplified by phthalic anhydride, isophthalic acid,
terephthalic acid, tetrahydrophthalic anhydride, maleic anhydride,
fumaric acid, succinic acid, glutaric acid, adipic acid,
trimethyladipic acid, sebacic acid, trimellitic anhydride and
butanetetracarboxylic acid and the like. Any of the aforesaid
polybasic acid and anhydride thereof may be used alone or in
combination with at least one other.
[0027] The modifying agents are exemplified by fatty acids, phenol,
rosin, styrene and acrylic compounds, of which is used in the
present invention, stearic acid which is one of the fatty
acids.
[0028] On the other hand, the heat curable acrylic resin is the
acrylic resin which has reactive groups in the molecules and which
is heat-cured by the use of a crosslinking agent such as an amino
resin, an epoxy resin, a phenolic resin or the like. For instance,
there is known the heat curable acrylic resin which is produced by
a process wherein a starting material such as an acrylic ester,
styrene and acrylamide is reacted, and then further reacted with
formalin so that an aldehyde is bonded to the amide in the polymer.
During the process, the acrylic resin can be modified by the use of
various modifying agents. In the present invention, the modifying
agent is stearic acid.
[0029] The component (A) to be used for constituting the releasing
layer in the casting film according to the present invention may be
any of stearic acid-modified alkyd resin, stearic acid
modified-acrylic resin and a mixture thereof. Of these a mixture
thereof is preferable to assure favorable wettability of ceramic
slurry and releasability for green sheet.
[0030] On the other hand, there are usable as the amino resin of
the component (B), conventional amino resins that are well known as
a curing agent for alkyd resin paint, heat curable acrylic resin
paint and the like. Specific examples of the foregoing amino resins
include melamine resin, urea resin, urea-melamine resin, guanamine
resin, glycoluryl-formaldehyde resin, succinylamide-formaldehyde
resin, ethyleneurea-formaldehyde resin, each of which having
hydroxy groups or alkoxy groups. Any of the above exemplified resin
can readily be obtained by a process wherein melamine, urea,
guanamine, glycoluryl, succinylamide, ethyleneurea or the like is
reacted for methylolation with formalin in boiling water, and as
the case may be the reaction product is further reacted for
etherification with methanol, ethanol, propanol, butanol or the
like.
[0031] It is preferable in the present invention from the aspect of
accelerating the curing of the resin to use at least one member
selected from the group consisting of melamine resin, urea resin
and urea-melamine resin each being etherified, methyl etherified,
ethyl etherified or butyl etherified with a lower alcohol.
[0032] It is preferable in the present invention to use the amino
resin of the component(B) in an amount in the range of 5 to 40% by
weight based on the total sum of the solid content of resin
components (A) and (B). The amount thereof, when being less than 5%
by weight based thereon, brings about insufficient curing, making
it difficult to form a releasing layer having desirable physical
properties, whereas the amount thereof, when being more than 40% by
weight based thereon, causes lowered releasability for ceramic
green sheet. In consideration of the curability of the resin,
releasability for ceramic green sheet and the like factors, the use
amount of the amino resin as the component (B) is particularly
preferably in the range of 10 to 30% by weight based thereon.
[0033] In order to accelerate the curing reaction in curing with
the amino resin, there may be used as desired, an acid catalyst,
for instance, para-toluenesulfonic acid in an amount of at most 20
parts by weight based on 100 parts by weight of the total sum of
the solid content of the resin components (A) and (B).
[0034] The substrate film to be used in the present invention is
not specifically limited, but it may be properly optionally
selected for use from the well known films which have heretofore
been usable as a substrate film for a casting film for producing a
ceramic green sheet. Examples of such films include a polyester
film made of polyethylene terephthalate(PET), polyethylene
naphthalate or the like, a polyolefin film made of polypropylene,
polymethylpentene or the like, a polycarbonate film and polyvinyl
acetate film. Of these, a polyester film is preferable and a
biaxially oriented polyethylene terephthalate film is preferable in
particular from the aspects of smoothness, heat resistance and
cost. There is usually used a substrate film having a thickness in
the range of 12 to 125 .mu.m.
[0035] In order to obtain the casting film in accordance with the
present invention, a coating solution for forming the releasing
layer is prepared at first. The aforesaid coating solution is
prepared by adding the above-mentioned stearic acid-modified alkyd
resin and/or stearic acid-modified acrylic resin as the component
(A) and the amino resin as the component (B) and as desired, the
acid catalyst and the like in a proper organic solvent such as
toluene, ethyl acetate, methyl ethyl ketone, a denatured alcohol
and hexane, and forming a coating solution having a viscosity which
enables coating work.
[0036] The coating solution may be incorporated at need, with an
alkyd resin and/or an acrylic resin each being modified with a
fatty acid other than stearic acid; a filler; an antistatic agent;
a dye; a pigment; an other additive; and the like.
[0037] The coating solution thus prepared is applied to either or
both sides of the aforesaid substrate film by means of, for
instance, gravure coat method, bar coat method, multi-roll coat
method, spray coat method, spin coat method or the like.
[0038] The coating amount expressed in terms of solid content is in
the range of suitably 0.04 to 2.00 g/m.sup.2, preferably 0.07 to
1.00 g/m.sup.2 in particular. The coating amount, when being less
than 0.04 g/m.sup.2, brings about poor releasability of the ceramic
green sheet, whereas the coating amount, when being more than 2.00
g/m.sup.2, gives rise to possibility of causing repelling at the
time of ceramic slurry coating.
[0039] In order to cure the coating solution thus applied thereto,
it is subjected to heating treatment with an oven of a coating
machine. In the case of heating treatment, the condition thereof is
not specifically limited provided that a period of time for
sufficient curing is assured at a temperature in the range of 100
to 160.degree. C. , and it is usually suitable to carry out the
heating treatment for 5 to 120 seconds thereat.
[0040] In order to further enhance the adhesiveness between the
substrate film and the releasing layer, the substrate film may in
advance, be subjected to adhesiveness enhancing treatment such as
corona discharge treatment, ozone treatment, flame treatment,
anchor coat agent coating and the like. Moreover for the purpose of
antistaticity, an antistatic agent may be kneaded in advance into
the coating solution. Alternatively, a substrate film coated with
an antistatic agent may be used.
[0041] Moreover, the releasing agent may be applied to the entire
surface of the substrate film or to part of the surface thereof,
for instance, pattern coating in which a non-coating portion is
placed at both the ends so as to regulate the releasability and
adhesiveness.
[0042] The casting film thus obtainable according to the present
invention is used for producing a ceramic green sheet. It is
preferable that the ceramic green sheet has a thickness of 20 .mu.m
or smaller, and is more preferable that the ceramic green sheet has
a thickness of 10 .mu.m or smaller for an aqueous system, and 4
.mu.m or smaller for a solvent system.
[0043] In summarizing the working effect of the casting film
according to the present invention, the casting film which is
imparted with excellent wettability of ceramic slurry and moderate
releasability for ceramic green sheets can readily be obtained by
forming on a substrate film, a releasing agent layer composed of a
cured resin from a stearic acid-modified alkyd resin and/or a
stearic acid-modified acrylic resin and an amino resin.
[0044] The casting film according to the present invention is well
suited for use in the production of ceramic green sheets that are
employed for ceramic capacitors, laminated inductor elements and
the like.
[0045] In the following, the present invention will be described in
more detail with reference to comparative examples and working
examples, which however shall never limit the present invention
thereto.
[0046] Evaluations were made of the various characteristics of each
of the casting films that were obtained through the working
examples and comparative examples according to the evaluation
procedures as described hereunder.
[0047] (1) Wettability of Ceramic Slurry
[0048] A blend of 100 parts by weight of barium titanate powder, 10
parts by weight of a water-soluble acrylic resin and 10 parts by
weight of polyethylene glycol was prepared, and mixed for 24 hours
with a pot stand by the use of zirconia beads having a diameter of
10 mm to produce aqueous ceramic slurry. The resultant ceramic
slurry was applied to releasing surfaces of a casting film so that
the thickness of the coating after dryness was made to be 6 .mu.m ,
followed by drying treatment to prepare a green sheet. During the
procedure, the wettability (repelling, unevenness of coating being
present or not) of the ceramic slurry was visually observed, and
the result was evaluated in accordance with the following
criterion.
[0049] .circleincircle.: no repelling nor unevenness of coating
observed showing excellent coating surface (not causing practical
problem)
[0050] .smallcircle.: no repelling observed (not causing practical
problem)
[0051] X: repelling observed (causing practical problem)
[0052] X X: film being non formable
[0053] (2) Releasability of Green Sheet
[0054] <Evaluation by Hand Peeling>
[0055] Evaluations were made of the releasability of the green
sheets that were prepared in the foregoing procedure (1) by means
of hand peeling test.
[0056] .circleincircle.: releasability being moderate (not causing
practical problem)
[0057] .smallcircle.: releasability being somewhat interior thereto
(not causing practical problem)
[0058] X: difficult to release (causing practical problem)
[0059] X X: impossible to release (causing practical problem)
[0060] <Peeling Force of Green Sheet>
[0061] The green sheet which had been prepared in the aforesaid
procedure (1) was laminated with a pressure sensitive adhesive tape
(manufactured by Nitto Denko Corporation under the trade name "31B
Tape") to prepare samples. The resultant samples were allowed to
stand under the conditions of 23.degree. C. and 65% R.H. for 24
hours and thereafter were cut into pieces each having a width of 20
mm to prepare test pieces. Subsequently, the casting film was
peeled off at angles of 180 degrees at a velocity of 100 m/minute
by the use of a tensile testing machine to determine the force
required for peeling (peeling force).
EXAMPLE 1
[0062] A resin mixture was prepared by mixing a stearic
acid-modified alkyd resin (stearyl group content of 50% by weight)
a stearic acid-modified acrylic resin (stearyl group content of 33%
by weight) and melamine resin which had been subjected to methyl
etherification in amounts expressed in terms of solid content of
40%, 40% and 20% each by weight, respectively. The resultant resin
mixture was diluted with an organic solvent composed principally of
toluene and then, was incorporated with para-toluenesulfonic acid
in an amount of 5 parts by weight based on 100 parts by weight of
the solid content of the resin mixture to prepare a coating
solution having a solid content of 3% by weight.
[0063] The coating solution was uniformly applied through gravure
coat method, to a biaxially oriented polyethylene terephthalate
(PET) film having a thickness of 38 .mu.m so as to form a coating
amount expressed in terms of solid content being 0.2 g/m.sup.2.
Subsequently the coated PET film was heat-treated for 30 seconds in
a hot air circulation type dryer at 130.degree. C. to cure the
coating solution and prepare a casting film. Various
characteristics of the casting film thus obtained are given in
Table 1.
EXAMPLE 2
[0064] The procedure in Example 1 was repeated to prepare a casting
film except that stearic acid-modified alkyd resin, stearic
acid-modified acrylic resin and melamine resin which had been
subjected to methyl etherification in amounts expressed in terms of
solid content of 20%, 60% and 20% each by weight, respectively
instead of 40%, 40% and 20%. Various characteristics of the casting
film thus obtained are given in Table 1.
EXAMPLE 3
[0065] The procedure in Example 2 was repeated to prepare a casting
film except that stearic acid-modified alkyd resin (stearyl group
content of 50% by weight) and melamine resin which had been
subjected to methyl etherification in amounts expressed in terms of
solid content of 70% and 30% each by weight, respectively instead
of 40% and 20%. Various characteristics of the casting film thus
obtained are given in Table 1.
COMPARATIVE EXAMPLE 1
[0066] An organic solvent composed principally of toluene was used
to dilute a solvent type addition reaction type silicone based
releasing agent (solid content of 30% by weight, manufactured by
Toray Dow corning Silicone Corporation under the trade name
"SRX-211") comprising as a principal ingredient,
polydimethyl-siloxane having vinyl group as a functional group and
a cross linking agent (polymethylhydrogen siloxane). To the diluted
releasing agent were added a platinum base catalyst (solid content
of 100% by weight, manufactured by Toray Dow corning Silicone
Corporation under the trade name "SRX-212") in an amount of one
part by weight based on 100 parts by weight of the silicone based
releasing agent to prepare a coating solution having a solid
content of 2% by weight.
[0067] The coating solution thus prepared was uniformly applied
through gravure coat method, to a biaxially oriented PET film
having a thickness of 38 .mu.m so as to form a coating amount
expressed in terms of solid content being 0.1 g/m.sup.2.
Subsequently the coated PET film was heat-treated for 30 seconds in
a hot air circulation type dryer at 130.degree. C. to cure the
coating solution and prepare a casting film. Various
characteristics of the casting film thus obtained are given in
Table 1.
COMPARATIVE EXAMPLE 2
[0068] The procedure in Example 1 was repeated to prepare a casting
film except that a resin mixture composed of hydroxymethacrylic
resin in an amount in terms of solid content of 11% by weight and
melamine resin which had been subjected to butyl etherification in
an amount in terms of solid content of 89% by weight was diluted
with an organic solvent composed principally of toluene, was
incorporated with one part by weight of para-toluenesulfonic acid
based on 100 parts by weight in terms of solid content of the resin
mixture, and heat-treated under the conditions of 170.degree. C.
and 30 seconds. Various characteristics of the casting film thus
obtained are given in Table 1.
1 TABLE 1 Releasability of green sheet Coatability of Evaluation by
Peeling force ceramic slurry hand peeling ( mN / 25 mm ) Example 1
.largecircle. .circleincircle. 5.98 Example 2 .circleincircle.
.circleincircle. 4.12 Example 3 .largecircle. .largecircle. 7.50
Comparative X X -- -- Example 1 Comparative .circleincircle. X X --
Example 2
* * * * *