U.S. patent application number 10/570667 was filed with the patent office on 2007-03-15 for process film for use in producing ceramic green sheet and method for production thereof.
This patent application is currently assigned to LINTEC CORPORATION. Invention is credited to Tomomi Fukaya, Toru Nakamura.
Application Number | 20070059536 10/570667 |
Document ID | / |
Family ID | 34386045 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070059536 |
Kind Code |
A1 |
Fukaya; Tomomi ; et
al. |
March 15, 2007 |
Process film for use in producing ceramic green sheet and method
for production thereof
Abstract
There can be provided a casting film for producing a ceramic
green sheet which film comprises a substrarte film, an undercoat
layer and a cured layer, wherein the undercoat layer is composed of
a condensation polymer from a metal alkoxide and/or a partially
hydrolyzed product of a metal alkoxide, and the cured layer is
formed by heat treating at 40 to 120.degree. C., an addition
reaction type silicone resin composition containing a
photosensitizer in a coating amount of 0.01 to 0.3 g/m.sup.2
expressed in terms of solid content, and thereafter ultraviolet
irradiating the composition to cure the same. The casting film,
which is employed for the production of a ceramic green sheet to be
used in a ceramic capacitor, a laminated inductor element and the
like, can easily be produced, has favorable adhesiveness to a
substrate film, is excellent in ceramic slurry coating property and
releasabilty from a ceramic green sheet, and possesses high
flatness that has never been realized by any of the prior arts
together with high antistatic property.
Inventors: |
Fukaya; Tomomi; (Saitama,
JP) ; Nakamura; Toru; (Saitama, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
LINTEC CORPORATION
Tokyo
JP
173-0001
|
Family ID: |
34386045 |
Appl. No.: |
10/570667 |
Filed: |
September 17, 2004 |
PCT Filed: |
September 17, 2004 |
PCT NO: |
PCT/JP04/13645 |
371 Date: |
March 6, 2006 |
Current U.S.
Class: |
428/447 ;
427/372.2; 427/487; 428/448; 428/480 |
Current CPC
Class: |
C04B 35/6264 20130101;
C04B 2235/441 20130101; Y10T 428/31786 20150401; H01G 4/12
20130101; H01G 4/30 20130101; Y10T 428/31663 20150401; C04B
2235/6025 20130101; C04B 35/4682 20130101; C04B 35/62218 20130101;
H01G 4/08 20130101 |
Class at
Publication: |
428/447 ;
427/372.2; 427/487; 428/448; 428/480 |
International
Class: |
B05D 3/02 20060101
B05D003/02; C08F 2/46 20060101 C08F002/46; B32B 27/36 20060101
B32B027/36; B32B 25/20 20060101 B32B025/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2003 |
JP |
2003-334934 |
Claims
1. A casting film, for producing a ceramic green sheet, comprising
a substrate film, an undercoat layer and a cured layer, wherein
said undercoat layer comprises a condensation polymer from a metal
alkoxide, a partially hydrolyzed product of a metal alkoxide, or a
combination thereof, and wherein said cured layer is formed by heat
treating at 40 to 120.degree. C., an addition reaction type
silicone resin composition comprising a photosensitizer in a
coating amount of 0.01 to 0.3 g/m.sup.2 expressed in terms of solid
content, and thereafter ultraviolet irradiating the same to cure
the composition and form the cured layer.
2. The casting film for producing a ceramic green sheet according
to claim 1, wherein said metal alkoxide is tetraalkoxysilane.
3. The casting film of claim 1, wherein the addition reaction type
silicone resin composition comprises polydimethylsiloxane
comprising at least one functional group.
4. The casting film of claim 3, wherein the at least one functional
group is a hexenyl group, a vinyl group, or a combination
thereof.
5. The casting film of claim 1, wherein the substrate film
comprises polyethylene terephthalate.
6. A process for the production of a casting film for producing a
ceramic green sheet, comprising forming, on a substrate film, an
undercoat layer comprising a condensation polymer from a metal
alkoxide, a partially hydrolyzed product of a metal alkoxide, or a
combination thereof, and forming a cured layer on the undercoat
layer to form the casting film, wherein the forming the cured layer
comprises placing an addition reaction type silicone resin
composition comprising a photosensitizer in a coating amount of
0.01 to 0.3 g/m.sup.2 expressed in terms of solid content on the
undercoat layer; heat treating the composition at 40 to 120.degree.
C.; and ultraviolet irradiating the same to cure the composition
and form the cured layer.
7. The casting film of claim 2, wherein the addition reaction type
silicone resin composition comprises polydimethylsiloxane
comprising at least one functional group.
8. The casting film of claim 2, wherein the substrate film
comprises polyethylene terephthalate.
9. The casting film of claim 3, wherein the substrate film
comprises polyethylene terephthalate.
10. The casting film of claim 4, wherein the substrate film
comprises polyethylene terephthalate.
11. The casting film of claim 1, wherein the substrate film
comprises polyethylene naphthalate.
12. The casting film of claim 1, wherein the substrate film
comprises polypropylene.
13. The casting film of claim 1, wherein the substrate film
comprises polymethylpentene.
14. The casting film of claim 1, wherein the substrate film has a
thickness of from 12 .mu.m to 125 .mu.m.
15. The casting film of claim 1, wherein the coating amount is from
0.05 g/m.sup.2 to 0.2 g/m.sup.2.
16. The casting film of claim 1, wherein the heat treating is
performed in the temperature range of from 50.degree. C. to
100.degree. C.
17. The process of claim 6, wherein the coating amount is from 0.05
g/m.sup.2 to 0.2 g/m.sup.2.
18. The process of claim 6, wherein the heat treating is performed
in the temperature range of from 50.degree. C. to 100.degree.
C.
19. The casting film of claim 1, wherein the photosensitizer is
selected from the group consisting of benzoins, benzophenones,
acetophenones, .alpha.-hydroxy ketones, .alpha.-diketones,
.alpha.-diketone dialkyl acetals, anthraquinones, thioxanthones,
and combinations thereof.
20. The process of claim 6, wherein the photosensitizer is selected
from the group consisting of benzoins, benzophenones,
acetophenones, .alpha.-hydroxy ketones, .alpha.-diketones,
.alpha.-diketone dialkyl acetals, anthraquinones, thioxanthones,
and combinations thereof.
Description
TECHNICAL FIELD
[0001] The present invention relates to a casting film for
producing a ceramic green sheet which film is used in the case of
producing a ceramic green sheet to be used for a ceramic capacitor,
a laminated inductor element and the like and relates to a process
for the production of the casting film. More particularly, the
present invention pertains to a casting film for producing a
ceramic green sheet which film is imparted with favorable
adhesiveness between a silicone resin releasing agent and a
substrate film for a long period of time, is excellent in
antistatic property, ceramic slurry coating property and releasing
property from a ceramic green sheet and at the same time, possesses
high flatness that has never hitherto been realized.
BACKGROUD ART
[0002] In general, accompanying the market demand for
miniaturization and weight-saving for electronic devices in recent
years, the part items which constitute the devices are required to
be thin-walled and lightweight.
[0003] For instance, electronic devices such as a capacitor, a
laminated inductor element and the like that have heretofore been
part items fitted with leads are made possible to be downsized
through the practical application of a technique in which a
monolithic structure equipped with an internal conductor is formed
by simultaneously firing a ceramics layer having a prescribed
pattern along with a laminate composed of an electroconductive
layer. However, further miniaturization thereof is required at the
present time.
[0004] A ceramic capacitor is usually produced by using a process
comprising the steps of firstly preparing slurry by mixing ceramic
powders having a high dielectric constant of a compound having
perovskite-type crystalline structure such as barium titanate, a
binder, an organic solvent and the like; applying coating of the
slurry to a casting film made of polyethylene terephthalate or the
like and drying the same to prepare a ceramic green sheet; then
forming an electrode pattern on the resultant green sheet by means
of screen printing or the like by using a conductive paste; peeling
the ceramic green sheet off the casting film; subsequently
laminating a large number of the printed ceramic green sheets in a
prescribed order; bonding the same under heating and pressurizing;
cutting the same into the form of desirable chips; subjecting the
chips to firing treatment; and sintering the same.
[0005] On the other hand, the laminated inductor element is usually
produced by using a process comprising the steps of firstly
preparing a ceramic green sheet on a casting film by using magnetic
ceramic powders such as ferrite in the same manner as the
foregoing; then forming a coil pattern on the resultant green sheet
by means of screen printing or the like by using a conductive
paste; subsequently peeling the ceramic green sheet off the casting
film; and then following the above-mentioned procedure to prepare
the laminated inductor element in the form of chip.
[0006] The ceramic capacitor and the laminated inductor element
each in the form of chip are required to be more and more miniature
in order to cope with the demand for miniaturization as mentioned
hereinbefore. Accompanying such demand, the ceramic green sheet,
which has a thickness of 5 to 20 .mu.m at the present time, is
required to be thinner.
[0007] Since the previous casting film cannot cope with the green
sheet which is made to have such a small thickness, a film having
further high performances are necessitated, namely a casting film
which is excellent in ceramic coating property and releasability
from a ceramic green sheet and which has an extremely high flatness
free from wrinkles and the like due to thermal shrinkage.
[0008] There has hitherto been generally used as a casting film, a
polyethylene terephthalate film (PET film) which has been subjected
to releasing treatment with a silicone resin based releasing agent
of heat-curable addition reaction type. However, the silicone resin
based releasing agent of heat-curable addition reaction type must
be crosslinked usually at a high temperature of 140.degree. C. or
higher in order to assure a stable cured film. Consequently,
wrinkles due to thermal shrinkage inevitably take place on a PET
film in the releasing treatment step. Wrinkles due to thermal
shrinkage, when being present on a PET film, bring about the
problem in that the ceramic slurry cannot be made into a uniform
thin-film sheet at the time of film forming.
[0009] Under such circumstances, in order to suppress the
occurrence of the wrinkles due to thermal shrinkage to the utmost,
an attempt is made to carry out the processing treatment with the
silicone resin based releasing agent of heat-curable addition
reaction type by lowering the processing rate under a condition of
a lower temperature (110 to 130.degree. C.). Nevertheless, the
above-mentioned attempt gives rise to problems of not only inferior
productivity but also insufficient curing, poor adhesion stability
of the silicone resin for the PET film and poor coating property of
the ceramic slurry.
[0010] In addition, a silicone resin based releasing agent of
ultraviolet-alone-curable type which has a functional group such as
an epoxy group, an acrylate group, a mercapto group or the like is
known as a low temperature-curable silicone resin based releasing
agent. However, the silicone resin based releasing agent just
mentioned is difficult to assure uniform coated surface of the
silicone resin and besides, is unstable and inferior in
releasability of the ceramic green sheet.
[0011] In order to solve the above-mentioned problems, the present
inventors had developed a casting film for producing a ceramic
green sheet which casting film is obtained by applying coating of
an addition reaction type silicone resin composition as a releasing
agent containing a photosensitizer to a substrate film in a
specific thickness, heat treating the coating at a prescribed
temperature, and thereafter irradiating the same with ultraviolet
rays {for instance, refer to Japanese Patent Application Laid-Open
No. 198910/2001}.
[0012] Nevertheless, it has been proved that the film coated with a
silicone resin has a high electrification property, thus causing
various problems. For instance, surface electrification sometimes
allows foreign matters to adhere thereto, thereby bringing about a
defect or fault on the ceramic slurry to be applied onto the film.
Moreover, film surface electrification sometimes causes fluctuation
and repelling of the ceramic slurry to be applied thereto, thus
failing to obtain a uniform thin film sheet. Further, such a
problem is sometimes caused in that the slurry is disintegrated by
defective peeling due to peeling electrification of a casting film
for producing a ceramic green sheet in a step of peeling the
ceramic slurry off the film.
[0013] Accordingly, importance has been attached in recent years to
antistatic property of a casting film for producing a ceramic green
sheet in addition to the above-mentioned adhesiveness to the
substrate film, coating property of the ceramic slurry,
releasability of the ceramic green sheet and a high flatness.
DISCLOSURE OF THE INVENTION
[0014] Under such circumstances, it is an object of the present
invention to provide a casting film for producing a ceramic green
sheet which casting film is employed in the case of producing a
ceramic green sheet to be used for a ceramic capacitor, a laminated
inductor element and the like, is capable of forming a cured
silicone resin composition layer having favorable adhesiveness to a
substrate film, is excellent in coating property of the ceramic
slurry, releasability of ceramic green sheet and at the same time,
has not only a high flatness but also a high antistatic
property.
[0015] In order to achieve the above-mentioned object, various
research and investigation were accumulated by the present
inventors. As a result, it has been found that a casting film for
producing a ceramic green sheet is obtainable which casting film is
capable of solving the aforesaid problems by a method comprising
the steps of forming, on a substrate film, an undercoat layer
composed of a condensation polymer from a metal alkoxide and/or a
partially hydrolyzed product of a metal alkoxide, applying a
coating of addition reaction type silicone resin composition
containing a photosensitizer in a casting film for producing a
ceramic green sheet in a specific quantity to constitute a cured
layer, heat treating the layer, and ultraviolet irradiating the
same. Thus, the present invention has been accomplished based on
the findings. That is to say, the present invention provides the
following: [0016] 1. A casting film for producing a ceramic green
sheet which film comprises a substrate film, an undercoat layer and
a cured layer, wherein said undercoat layer is composed of a
condensation polymer from a metal alkoxide and/or a partially
hydrolyzed product of a metal alkoxide, and said cured layer is
formed by heat treating at 40 to 120.degree. C. an addition
reaction type silicone resin composition containing a
photosensitizer in a coating amount of 0.01 to 0.3 g/m.sup.2
expressed in terms of solid content, and thereafter ultraviolet
irradiating the same to cure the composition. [0017] 2. The casting
film for producing a ceramic green sheet as set forth in the
preceding item 1, wherein said metal alkoxide is tetraalkoxysilane.
[0018] 3. The casting film for producing a ceramic green sheet as
set forth in the preceding item 1 or 2, wherein said addition
reaction type silicone resin composition contains
polydimethylsiloxane having at least one functional group. [0019]
4. The casting film for producing a ceramic green sheet as set
forth in the preceding item 3, wherein said functional group is
hexenyl group and/or vinyl group. [0020] 5. The casting film for
producing a ceramic green sheet as set forth in any of the
preceding items 1 to 4, wherein the substrate film is made of
polyethylene terephthalate. [0021] 6. A process for the production
of a casting film for producing a ceramic green sheet which process
comprises the steps of forming, on a substrate film, an undercoat
layer composed of a condensation polymer from a metal alkoxide
and/or a partially hydrolyzed product of a metal alkoxide by
applying a coating thereof; placing an addition reaction type
silicone resin composition containing a photosensitizer in a
coating amount of 0.01 to 0.3 g/m.sup.2 expressed in terms of solid
content; heat treating the composition at 40 to 120.degree. C.; and
subsequently ultraviolet irradiating the same to cure the
composition.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
[0022] The casting film for producing a ceramic green sheet
according to the present invention (hereinafter sometimes simply
referred to as casting film according to the present invention)
comprises a substrate film, an undercoat layer which is placed
thereon and is composed of a condensation polymer from a metal
alkoxide and/or a partially hydrolyzed product of a metal alkoxide,
and a cured layer wherein an addition reaction type silicone resin
composition containing a photosensitizer has been cured.
[0023] The substrate film, which is not specifically limited, may
be properly selected for use from the publicly known optional
products that have been usable for a casting film for producing a
ceramic green sheet. The substrate film may be exemplified by a
polyester film such as a film made of polyethylene terephthalate or
polyethylene naphthalate; a polyolefin film such as a film made of
polypropylene or polymethylpentene; a polycarbonate film; and
polyvinyl acetate film. Of these, a polyester film is preferable,
and biaxially oriented polyethylene terephthalate film is
particularly preferable. A substrate film having a thickness of 12
to 125 .mu.m is usually used.
[0024] The undercoat layer to be formed on the above-mentioned
substrate film in the casting film according to the present
invention is composed of a condensation polymer from a metal
alkoxide and/or a partially hydrolyzed product of a metal alkoxide.
The undercoat layer, which is formed thereon, imparts antistatic
property to the casting film, and is characterized by its favorable
adhesiveness to both the substrate film and the cured layer. The
metal alkoxide, which is generally represented by the general
formula M(OR)n. The metal M, which is not specifically limited, is
exemplified by an alkali metal such as lithium, sodium and
potassium; an alkaline earth metal such as magnesium, calcium,
strontium and barium; group 3 elements in the Periodic Table such
as scandium and yttrium; group 4 elements in the Periodic Table
such as titanium, zirconium and hafnium; group 5 elements in the
Periodic Table such as vanadium, niobium and tantalum; group 6
elements in the Periodic Table such as molybdenum and tungsten;
group 8 elements in the Periodic Table such as iron; group 12
elements in the Periodic Table such as zinc; group 13 elements in
the Periodic Table such as boron, aluminum, gallium and indium;
group 14 elements in the Periodic Table such as silicon, germanium,
tin and lead; a group 15 elements in the Periodic Table such as
phosphorus, antimony and bismuth; and lanthanoids such as
lanthanum. Of these, silicon is most preferable for its excellent
antistatic property and its high adhesiveness to the cured layer as
described hereinafter. Specifically, tetraalkoxysilane is most
preferable. The above-cited metal alkoxide may be used alone or by
being mixed with a plurality of metal alkoxide species.
[0025] In the general formula, R represents an alkyl group, which
has preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon
atoms in the present invention. A plurality of alkyl groups, when
being present in one kind of metal alkoxide, may be the same as or
different from one another. The symbol n is an integer to be
determined by the valency of the metal M and is usually in the
range of 1 to 5.
[0026] The metal alkoxide may be partially hydrolyzed in advance.
Likewise a mixture of a metal alkoxide and a partially hydrolyzed
metal alkoxide may be used.
[0027] Usable method for forming the undercoat layer is not
specifically limited, but may be any of various methods, and the
layer is preferably formed by applying a coating of liquid
containing a metal alkoxide and/or a partially hydrolyzed product
of a metal alkoxide to the substrate film.
[0028] The coating amount of the undercoat layer expressed in terms
of solid content is not specifically limited, but is in the range
of preferably 0.01 to 0.3 g/m.sup.2. The coating amount, when being
0.01 g/m.sup.2 or more, brings about such advantages as assuring
uniform coated film, assuring favorable adhesiveness between the
substrate film and the undercoat layer and between the undercoat
layer and the cured layer and at the same time, assuring sufficient
antistatic property. On the other hand, the coating amount, when
being 0.3 g/m.sup.2 or less, brings about such advantage as
assuring coated surface in a uniform state. From the
above-mentioned point of view, the coating amount of the undercoat
layer expressed in terms of solid content is in the range of more
preferably 0.05 to 0.2 g/m.sup.2.
[0029] As a method for applying the coating solution, usually
customarily used methods may be properly optionally usable, and are
exemplified by gravure coating method, bar coating method, spray
coating method and spin coating method. It is possible at the time
of coating to dissolve the metal alkoxide and/or a partially
hydrolyzed product of a metal alkoxide in a solvent and to
preferably use an organic solvent. Usable organic solvents are not
specifically limited, but are exemplified by alcohol based solvents
such as ethanol and isopropanol; and ketone based solvents such as
methyl ethyl ketone.
[0030] The aforesaid metal alkoxide and/or a partially hydrolyzed
product of a metal alkoxide form a condensation polymer by
hydrolytic reaction and polycondensation reaction, thereby
constituting the undercoat layer. In order to promote the
hydrolytic reaction, an acid catalyst such as hydrochloric acid and
nitric acid may be added thereto.
[0031] For the purpose of accelerating the polycondensation
reaction of the metal alkoxide and/or a partially hydrolyzed
product of a metal alkoxide and drying the same after they have
been applied in the aforesaid method, it is preferable to heat
treat the same. The heating conditions are not specifically limited
within the extent that the object as mentioned above is achievable,
but are preferably in the range of usually 40 to 120.degree. C. as
heating temperature and 20 seconds to 2 minutes as heating time.
With a view to enhance the productivity and prevent wrinkle due to
thermal shrinkage, it is further preferable that the heating
temperature be in the range of 80 to 110.degree. C., and the
heating time be in the range of 30 seconds to 1 minute. Taking into
consideration the strength of the under coat layer, the degree of
polymerization of the condensation polymer is in the range of
preferably 5 to 7000, approximately.
[0032] The cured layer of the silicone resin composition formed on
the undercoat layer that is placed on the above-mentioned substrate
film in the casting film according to the present invention is
formed by subjecting the addition reaction type silicone resin
composition containing a photosensitizer to both heating treatment
and ultraviolet irradiation to cure the composition.
[0033] The previous silicone resin based releasing agent of heat
curable addition reaction type, which needs a high temperature
treatment in order to obtain a stable cured film, cannot afford
satisfactory performances when treated at a low temperature owing
to insufficient curing. As a countermeasure thereagainst, mention
may be made of increasing the amount of a catalyst to be added and
lowering the processing rate. However, increasing the amount of a
catalyst affects the pot life, and lowering the processing rate
leads to decrease in the productivity.
[0034] As opposed to the foregoing, the present invention enables,
by adding a photosensitizer and curing by heating and ultraviolet
ray irradiation together, to obtain a casting film which forms
cured silicone resin composition layer having favorable
adhesiveness to both the substrate film and the undercoat layer,
which has an extremely high flatness free from wrinkle due to
thermal shrinkage and at the same time, which is imparted with
excellent ceramic slurry coating property, favorable releasability
for ceramic green sheet and further antistatic property.
[0035] The addition reaction type silicone resin composition
containing a photosensitizer to be used in the present invention
comprises principal ingredients which are composed of a addition
reaction type silicone resin (for instance, polydimethylsiloxane
having a functional group) and a cross-linking agent (for instance,
a cross-linking agent composed of silicone resin and the like such
as polymethylhydrogensiloxane), and which are incorporated with a
catalyst (for instance, platinum based catalyst) and a
photosensitizer, and as desired, an addition reaction inhibitor, a
release modifier such as silicone gum and silicone varnish, an
adhesion improver and the like.
[0036] The addition reaction type silicone resin is not
specifically limited, but may be selected for use from a variety
thereof, for instance, from those that have been customarily used
as conventional heat curable addition reaction type silicone resin
based releasing agents. Such silicone resin may be exemplified by
at least one species selected from polyorganosiloxane bearing an
alkenyl group as a functional group in a molecule. Preferable
examples of the above-exemplified polyorganosiloxane bearing an
alkenyl group as a functional group in a molecule include
polydimethylsiloxane bearing a vinyl group as a functional group,
polydimethylsiloxane bearing a hexenyl group as a functional group
and mixtures thereof. Of these, is particularly preferable the
polydimethylsiloxane bearing a hexenyl group as a functional group
in view of its excellent curability and stable favorable
releasability being assured for a green sheet.
[0037] The cross-linking agent is exemplified by polyorganosiloxane
bearing in its one molecule, at least two hydrogen atoms each
bonded to a silicon atom, specifically by
dimethylsiloxane/methylhydrogen-siloxane copolymer the end of which
is hindered with dimethylhydrogensiloxy group,
dimethylsiloxane/methylhydrogen-siloxane copolymer the end of which
is hindered with trimethylsiloxy group,
poly(methylhydrogen-siloxane) the end of which is hindered with
trimethylsiloxy group and poly(hydrogen-silsesquioxane). The amount
of the exemplified cross-linking agent to be used is selected in
the range of 0.1 to 100 parts by weight, preferably 0.3 to 50 parts
by weight based on 100 parts by weight of the addition reaction
type silicone resin.
[0038] Examples of the silicone resin having the function of
modifying the release characteristics of the cured film include for
instance, polyorganosiloxane not bearing in its one molecule, an
alkenyl group or a hydrogen atom each bonded to a silicon atom,
specifically by poly(dimethylsiloxane) the end of which is hindered
with trimethylsiloxy group and poly(dimethlysiloxane) the end of
which is hindered with dimethylphenylsiloxy group.
[0039] There is usually used as a catalyst, a platinum based
compound, which is exemplified by particulate platinum, particulate
platinum adsorbed on a carbon powder carrier, chloroplatinic acid,
alcohol-modified chloroplatinic acid, an olefin complex of
chloroplatinic acid, a palladium based catalyst and a rhodium based
catalyst. The amount of the catalyst to be used is in the range of
1 to 1000 ppm by mass approximately expressed in terms of a
platinum based metal on the basis of the total amount of the
addition reaction type silicone resin and the cross-linking
agent.
[0040] The photosensitizer to be used in the addition reaction type
silicone resin composition is not specifically limited, but may be
properly optionally selected for use from those that have
heretofore been customarily used in ultraviolet curable resin.
Examples thereof include benzoins, benzophenones, acetophenones,
.alpha.-hydroxy ketones, .alpha.-amino ketones, .alpha.-diketons,
.alpha.-diketone dialkyl acetals, anthraquinones, thioxanthones and
the other compounds.
[0041] Examples of benzoins include benzoin, benzoin methyl ether,
benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl
ether, benzoin isobutyl ether and a compound in which benzoin is
ether linked to both the ends of polydimethylsiloxane. Examples of
benzophenones include benzophenone, p-phenylbenzophenone,
4,4'-diethylaminobenzophenone, dichlorobenzophenone,
trimethyl-silanized benzophenones and 4-methoxybenzophenone.
Examples of acetophenones include acetophenone,
dimethylaminoacetophenone, 3-methylacetophenone,
4-methylacetophenone, 4-allylacetophenone, 3-pentylacetophenone and
propiophenone. Examples of .alpha.-hydroxy ketones include
2-hydroxy-1-(4-isopropyl)phenyl-2-methylpropane-1-one,
2-hydroxy-2-methyl-1-phenylpropane-1-one,
1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methlypropane-1-one and
1-hydroxycyclohexylphenyl ketone. Examples of .alpha.-amino ketones
include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one
and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butane-1-one.
Examples of .alpha.-diketons include benzyl diketone and diacetyl
diketone. Examples of .alpha.-diketone dialkyl acetals include
benzyldimethyl acetal and benzyldiethyl acetal. Examples of
anthraquinones include 2-methyl anthraquinone, 2-ethyl
anthraquinone, 2-tert-butyl anthraquinone and 2-amino
anthraquinone. Examples of thioxanthones include
2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone,
2,4-dimethylthioxanthone and 2,4-diethylthioxanthone. Examples of
other compounds include tertiary amines such as triphenylamine and
p-dimethylaminobenzoic acid ester and azo compounds such as
azobisisobutyronitrile.
[0042] The above-exemplified photosensitizer may be used alone or
in combination with at least one other species. The amount thereof
to be used is selected in the range of usually 0.01 to 30 parts by
weight, preferably 0.05 to 20 parts by weight on the basis of 100
parts by weight of the total sum amount of the above-mentioned
addition reaction type silicone resin and the cross-linking
agent.
[0043] The addition reaction inhibitor is the component which is
used for the purpose of imparting shelf life stability at room
temperature to the composition and is specifically exemplified by
3,5-dimethyl-1-hexyne-3-ol, 3-methyl-1-pentene-3-ol,
3-methyl-3-pentene-1-in, 3,5-dimethyl-3-hexene-1-in, cyclic
tetravinylsiloxane and benzotriazole.
[0044] According to the present invention, a coating solution
having viscosity enabling coating is prepared by adding in an
organic solvent, the above-mentioned addition reaction type
silicone resin composition containing a photosensitizer and a
variety of components to be used as desired each at a prescribed
ratio. In this case, any of various organic solvents may be used
without specific limitation. Examples thereof include hydrocarbon
compounds such as toluene, hexane and heptane in the beginning,
ethyl acetate, methyl ethyl ketone and mixtures thereof.
[0045] According to the present invention, 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, spray coat method, spin coat method, so that there is
formed a layer of the addition reaction type silicone resin
composition containing a photosensitizer in a coating amount within
the range of 0.01 to 0.3 g/m.sup.2 expressed in terms of solid
content. The coating amount, when being 0.01 g/m.sup.2 or more,
brings about favorable releasability of the ceramic green sheet,
whereas the coating amount, when being 0.3 g/m.sup.2 or less, gives
rise to favorable coating property of ceramic slurry such as
capability of suppressing the repelling at the time of applying the
slurry. Taking into consideration the releasability of the ceramic
green sheet and the coating property of the ceramic slurry, the
coating amount is in the range of preferably 0.05 to 0.2 g/m.sup.2,
particularly preferably 0.07 to 0.15 g/m.sup.2.
[0046] According to the present invention, the substrate film
equipped thereon with the above-mentioned undercoat layer and the
layer of the addition reaction type silicone resin composition is
firstly heat treated at a temperature in the range of 40 to
120.degree. C. so as to preliminarily cure the layer of the
addition reaction type silicone resin. The heat treatment
temperature, when being higher than 40.degree. C., enables
sufficient drying and preliminarily curing, whereas the
temperature, when being lower than 120.degree. C., results in
suitable state without causing any wrinkle due to thermal
shrinkage. In view of more sufficient drying and preliminarily
curing and also the suppression of wrinkle due to thermal
shrinkage, the heat treatment temperature is in the range of more
preferably 50 to 100.degree. C.
[0047] In the present invention, the preliminarily cured layer of
the silicone resin composition is subjected to inline ultraviolet
ray irradiation to completely cure the composition. In this case
usable ultraviolet lamps are available from previously well known
lamps such as high pressure mercury vapor lamp, metal halide lamp,
high power metal halide lamp and non-electrode ultraviolet lamp. Of
these, non-electrode ultraviolet lamp is preferable from the
viewpoints of less thermal damage to the substrate film and
favorable curability of the silicone resin due to suitable
ultraviolet emission efficiency, an amount of infrared ray
irradiation and the like. The foregoing lamp is available from D
bulb, H bulb, H+bulb, V bulb and the like manufactured by Fusion
Corporation, of which H bulb and H+bulb are particularly
preferable. The ultraviolet irradiation output, which may be
properly optionally selected, is in the range of usually 30 W/cm to
600 W/cm, preferably 50 W/cm to 360 W/cm.
[0048] The temperature at the time of ultraviolet irradiation
treatment is not specifically limited, but may be any of a heated
state immediately after the heat treatment and a state of room
temperature, provided that inline irradiation treatment is carried
out.
[0049] In the foregoing manner, there is formed the cured layer in
which the addition reaction type silicone resin composition is
cured on either or both sides of the substrate film equipped with
the undercoat layer, while assuring satisfactory adhesion to both
the substrate film and the undercoat layer, whereby the casting
film according to the present invention is obtainable which is free
from wrinkle or the like due to thermal shrinkage, is imparted with
an extremely high flatness, is excellent in the coating property of
the ceramic slurry and also releasability of the ceramic green
sheet and at the same time, has high antistatic property.
[0050] The casting film according to the present invention is used
for producing ceramic green sheets, and is well suited for
producing ceramic green sheets having a thickness of preferably 20
.mu.m or less, more preferably 10 .mu.m or less, particularly
preferably 6 .mu.m or less.
[0051] Examples of the ceramic green sheet to which the casting
film according to the present invention is applied include a
ceramic green sheet having a high dielectric constant which is used
for a ceramic capacitor in the form of a chip and a magnetic
ceramic green sheet which is used for a laminated inductor element
in the form of a chip. In particular, it is desirable to apply the
casting film according to the present invention to the production
of a green sheet used for a ceramic microcapacitor which has a chip
size of 1005 type and is intended to miniature portable
devices.
[0052] Examples of the ceramics having a high dielectric constant
in a ceramic green sheet to be used for a ceramic capacitor include
a compound having a perovskite type crystalline structure, for
instance, barium titanate (BaTiO.sub.3) in the beginning,
PbTiO.sub.3, KNbO.sub.3, Pb(Ni.sub.1/3Nb.sub.2/3)O.sub.3),
Cd.sub.2Nb.sub.2O.sub.7, PbNb.sub.2O.sub.6 and
PbTa.sub.2O.sub.6.
[0053] On the other hand, examples of the magnetic ceramics in the
ceramic green sheet which is used for a laminated inductor element
include spinel type ferrite or hexagonal crystal type ferrite such
as Zn base ferrite, Ni base ferrite, Mn base ferrite, Mg base
ferrite, Ni--Zn base ferrite, Mn--Zn base ferrite, Mg--Zn base
ferrite, Ni--Cu--Zn base ferrite, Mn--Mg--Zn base ferrite.
[0054] In the case of producing a ceramic green sheet, slurry is
prepared for instance, by mixing ceramic powders, a proper solvent
and a binder such as polyvinyl alcohol, carboxymethyl cellulose, a
butyral base binder and an acrylate base binder, the resultant
slurry is applied as a coating by the use of a doctor blade or the
like onto the casting film according to the present invention, and
the coating is treated for drying to form a ceramic green sheet
having a thickness of preferably 20 .mu.m or less, more preferably
10 .mu.m or less, particularly preferably 6 .mu.m or less.
[0055] In the case of a green sheet to be used for a ceramic
capacitor, a desirable electrode pattern (internal electrode
pattern) is formed on the green sheet thus formed through screen
printing or the like by the use of ceramic powders having the
above-mentioned high dielectric constant as the ceramic powders and
conductive paste for printing containing a metal conductor. The
resultant ceramic green sheets thus formed are released from the
casting film, and usually at least 100 sheets are laminated, bonded
under heating and pressure, thereafter cut into the form of
desirable chip, then fired and sintered, whereby a ceramic
capacitor is obtained which has monolithic constitution with a form
of a chip and is equipped with the internal electrode.
[0056] In the case of a laminated inductor element, a desirable
coil pattern (internal conductor pattern) is formed on the ceramic
green sheet by the use of the above-mentioned magnetic ceramic
powders as the ceramic powders and in the same manner as in the
case of the ceramic capacitor and subsequently, the procedures same
as the foregoing are carried out, whereby a laminated inductor
element is obtained which has monolithic constitution with a form
of a chip and is equipped with the internal electrode
conductor.
EXAMPLE
[0057] In the following, the present invention will be described in
more detail with reference to working examples, which however shall
never limit the present invention thereto.
(1) Curability
[0058] The surfaces of the cured coat of the casting film were
strongly rubbed ten times with fingers, whereupon smear and rubbing
off were observed. Thus, the curability of the film was evaluated
on the basis of the under-mentioned criterion.
[0059] A: no smear nor rubbing off observed at all.
[0060] B: slight smear observed (practically no problem)
[0061] C: smear and rubbing off observed to some extent (sometimes
causing a practical problem)
[0062] D: much smear observed with frequent rubbing off (usually
causing practical problem)
[0063] E: much rubbing off observed with insufficient curing.
(2) Flatness (Wrinkle Due to Thermal Shrinkage)
[0064] Visual observation was made of wrinkle if any on the casting
film, and ceramic slurry was applied onto the cured coating so as
to become 3 .mu.m in thickness to examine whether or not uniform
coating was possible. Thus, the flatness of the film was evaluated
on the basis of the under-mentioned criterion.
[0065] A: no wrinkle on the surface at all enabling slurry coating
in a uniform thickness
[0066] B: surface wrinkle confirmed, but enabling slurry coating in
a uniform thickness
[0067] C: surface wrinkle confirmed, but enabling slurry coating,
causing slightly non-uniform slurry thickness (sometimes causing a
practical problem)
[0068] D: much surface wrinkle confirmed, but enabling slurry
coating, causing markedly non-uniform slurry thickness (usually
causing a practical problem)
[0069] E: film formation impossible due to surface wrinkle
(3) Adhesiveness of Cured Layer
[0070] The surfaces of the cured coat of the casting film after the
lapse of 30 days from the treatment with silicone were strongly
rubbed ten times with fingers, whereupon smear and rubbing off were
observed. Thus, the adhesiveness of the film was evaluated on the
basis of the criterion same as the above.
(4) Releasability of the Green Sheet
(a) Peeling Force
[0071] BaTiO.sub.3 slurry was prepared by adding 80 parts by mass
of mixed liquid of toluene and ethanol (ratio by mass being 1:1) to
100 parts by mass of barium titanate (BaTiO.sub.3) powder, 7 parts
by mass of polyvinyl butyral and 3 parts by mass of dioctyl
phthalate, and mixing and dispersing the mixture with a ball mill
to prepare BaTiO.sub.3 slurry. The resultant slurry was uniformly
applied onto a casting film by means of doctor blade method so as
to become 3 .mu.m in thickness after drying, and was treated for
drying to prepare a green sheet. A tacky adhesive tape
(manufactured by Nitto Denko Corporation under the trade name 31B
Tape) was stuck onto the green sheet, which was allowed to stand
for 24 hours under the conditions of 23.degree. C. and 50% RH, cut
into a width of 20 mm. The tape was peeled off on the side of the
casting film at an angle of 180.degree. and a velocity of 100
m/minute by the use of a tensile tester to measure the power
required for peeling (releasing power).
(b) Releasability of Green Sheet
[0072] A green sheet was prepared in the same manner as in the
preceding item (a), and evaluations were made of the releasability
of the green sheet from the releasing film in accordance with the
under-mentioned criterion.
[0073] A: excellent
[0074] B: good (practically no problem)
[0075] C: somewhat inferior (sometimes causing a practical
problem)
[0076] D: inferior (causing a practical problem)
[0077] E: markedly inferior
(5) Releasability of Cured Layer
[0078] The casting films in Example 1 and Comparative Example 4
were allowed to stand for 24 hours under the conditions of
23.degree. C. and 50% RH to carry out moisture conditioning,
thereafter a tacky adhesive tape (manufactured by Nitto Denko
Corporation under the trade name 31B Tape) was stuck onto the
surfaces of the cured layer. The films were further allowed to
stand for 24 hours under the conditions of 23.degree. C. and 50%
RH, cut into a width of 50 mm, peeled off on the side of the tape
at an angle of 180.degree. and a velocity of 0.3 m/minute by the
use of a tensile tester to measure the force required for peeling
(peeling force) (prior to polishing).
[0079] Subsequently the surfaces of the cured layer for the casting
film were polished by the use of a Gakushin testing machine, and
the peeling force was measured in the same manner as prior to
polishing (after polishing), wherein the measurement was made under
the conditions including a load of 1 kg and polishing times of
reciprocal 50 by the use of, as the Gakushin testing machine, a
durable friction testing machine (manufactured by Daiei Kagaku
Seiki Seisakusho under the trade name RT-200) and using a polishing
piece made of non-oriented polypropylene with 80 .mu.m
thickness.
(6) Antistatic Property
[0080] A charged film was allowed to stand for 24 hours under the
conditions of 23.degree. C. and 50% RH, and thereafter surface
electric resistance thereof was measured by the use of a measuring
apparatus (manufactured by Advantest Corporation under the trade
name R12704 Resistivity Chamber and by Takeda Riken Kogyo Co., Ltd.
under the trade name Digital Electrometer TR 8652). The antistatic
property increases with a decrease in the measured value.
Example 1
[0081] A coating solution A with a solid concentration of 1.5% by
mass was prepared by diluting, with isopropyl alcohol, a partially
hydrolyzed product of tetraalkoxysilane (trade name of Colcoat
N-103X) as a partially hydrolyzed product of an metal alkoxide. The
coating solution A intended for forming an undercoat layer was
uniformly applied onto a 38 .mu.m thick biaxially oriented
polyethylene terephthalate (hereinafter abbreviated to PET) film by
the use of a meyer bar so that the solid coating amount is made to
be 0.1 g/m.sup.2. The resultant coating was heated and dried at
100.degree. C. for 1 minute to prepare an undercoat layer with a
thickness of 0.1 .mu.m after drying.
[0082] Subsequently, to 100 parts by mass of an addition reaction
type silicone resin based releasing agent (manufactured by Dow
Corning Toray Silicone Co., Ltd. under the trade name LTC-760A)
consisting essentially of principal ingredients composed of
polydimethylsiloxane having hexenyl groups as a functional group
and a cross-linking agent (polymethylhydrogen siloxane) were added
2 parts by mass of a platinum based catalyst (manufactured by Dow
Corning Toray Silicone Co., Ltd. under the trade name SRX-212)
based on 100 parts by mass of the aforesaid principal ingredients
and 1 part by mass of acetophenone as a photosensitizer based on
the same. The resultant mixture was diluted with an organic solvent
composed principally of toluene to prepare a coating solution B
intended for forming a cured layer having a solid concentration of
1%.
[0083] The resultant coating solution B was uniformly applied onto
the above-mentioned undercoat layer by the use of a meyer bar so
that the thickness of the coating after drying was made to be 0.1
.mu.m (solid coating amount of 0. 1 g/m.sup.2). Subsequently, the
coated undercoat layer was heat treated for 20 seconds with a hot
air circulation type dryer at 50.degree. C. and immediately
thereafter was irradiated with ultraviolet ray by the use of a
conveyer type ultraviolet irradiating machine fitted with one 240
W/cm Fusion H bulb under the condition of conveyer speed being 40
m/minute to cure the silicone resin composition, thereby preparing
a casting film. The various properties of the casting film are
given in Table 1.
Example 2
[0084] The procedure in Example 1 was repeated to prepare a casting
film except that the temperature of the hot air circulation type
dryer was altered to 90.degree. C. in the heat treatment of the
coating solution B. The various properties of the casting film are
given in Table 1.
Example 3
[0085] To 100 parts by mass of an addition reaction type silicone
resin based releasing agent (manufactured by Dow Corning Toray
Silicone Co., Ltd. under the trade name SRX-211) consisting
essentially of principal ingredients composed of
polydimethylsiloxane having vinyl groups as a functional group and
a cross-linking agent (polymethylhydrogen siloxane) were added 2
parts by mass of a platinum based catalyst (manufactured by Dow
Corning Toray Silicone Co., Ltd. under the trade name SRX-212)
based on 100 parts by mass of the aforesaid principal ingredients
and 1 part by mass of acetophenone as a photosensitizer based on
the same. The resultant mixture was diluted with an organic solvent
composed principally of toluene to prepare a coating solution C
intended for forming a cured layer having a solid concentration of
1% by mass. In the same manner as in Example 1, a casting film was
prepared. The various properties of the casting film are given in
Table 1.
Comparative Example 1
[0086] A coating solution D having a solid concentration of 1% by
mass was prepared by adding 1 part by mass of a curing agent
(manufactured by Shin-Etsu Chemical Co., Ltd. under the trade name
CAT-PL-50T) to 100 parts by mass of a heat curable silicone
(manufactured by Shin-Etsu Chemical Co., Ltd. under the trade name
KS-847 H) and diluting the mixture with toluene. The resultant
coating solution D was uniformly applied onto a PET film by the use
of a meyer bar so that the thickness of the coating after drying
was made to be 0.1 .mu.m (solid coating amount of 0. 1 g/m.sup.2).
Subsequently, the coated film was dried with a hot air circulation
type dryer for 1 minute at a drying temperature of 140.degree. C.
to prepare a casting film. The various properties of the casting
film are given in Table 1.
Comparative Example 2
[0087] The procedure in Comparative Example 1 was repeated to
prepare a casting film except that the temperature of the hot air
circulation type dryer was altered to 90.degree. C. in the heat
treatment of the coating solution D. The various properties of the
casting film are given in Table 1.
Comparative Example 3
[0088] In the same manner as in Example 1, the coating solution A
was uniformly applied onto a 38 .mu.m thick PET film by the use of
a meyer bar so that the thickness of the coating after drying was
made to be 0.1 .mu.m. Subsequently the resultant coating was dried
at 100.degree. C. for 1 minute to form an undercoat layer. The
coating solution D which had been prepared in Comparative Example 1
was applied onto the above-prepared undercoat layer by the method
as described in Comparative Example 1, and was dried to prepare a
casting film. The various properties of the casting film are given
in Table 1.
Comparative Example 4
[0089] In the same manner as in Example 1, the coating solution A
was uniformly applied onto a 38 .mu.m thick PET film by the use of
a meyer bar so that the thickness of the coating after drying was
made to be 0.1 .mu.m. Subsequently the resultant coating was dried
at 100.degree. C. for 1 minute to form an undercoat layer. Then,
the procedure in Comparative Example 1 was repeated to prepare a
casting film by applying the coating solution D which had been
prepared in Comparative Example 1 onto the resultant undercoat
layer and drying the coating except that the drying temperature was
made to be 90.degree. C. The various properties of the casting film
are given in Table 1. TABLE-US-00001 TABLE 1 Example Comparative
Example 1 2 3 1 2 3 4 Curability A A A A C A B Flatness (Wrinkle
due to thermal A A A E A D A shrinkage) Adhesiveness A A A B D A B
Releasability Peeling force 5.39 5.39 9.41 --** 16.66 --** 13.02 of
(mN/20 mm) green sheet Releasability A A B --** E --** D
Releasability Peeling Before 56 -- -- -- -- -- 58 of force
polishing cured layer (mN/50 After 62 -- -- -- -- -- 420 mm)
polishing Antistatic surface resistance 10.sup.9 10.sup.9 10.sup.9
10.sup.15 10.sup.15 10.sup.9 10.sup.9 property
('.OMEGA./.quadrature.) **Owing to the occurrence of wrinkle due to
thermal shrinkage it was impossible to uniformly apply the ceramic
slurry and to form the film.
INDUSTRIAL APPLICABILITY
[0090] The casting film according to the present invention, which
is employed for the production of a ceramic green sheet to be used
in a ceramic capacitor, a laminated inductor element and the like,
can easily be produced, has favorable adhesiveness to a substrate
film, is excellent in ceramic slurry coating property and
releasabilty from a ceramic green sheet, and possesses high
flatness that has never been realized by any of the prior arts.
* * * * *