U.S. patent application number 10/621382 was filed with the patent office on 2004-01-29 for etching substrate material, etching process and article obtained by etching.
This patent application is currently assigned to DAI NIPPON PRINTING CO., LTD.. Invention is credited to Fujiyama, Koji, Hashimoto, Daisuke, Komatsu, Takayasu, Makita, Akira.
Application Number | 20040018372 10/621382 |
Document ID | / |
Family ID | 18024877 |
Filed Date | 2004-01-29 |
United States Patent
Application |
20040018372 |
Kind Code |
A1 |
Komatsu, Takayasu ; et
al. |
January 29, 2004 |
Etching substrate material, etching process and article obtained by
etching
Abstract
A process of forming a high-definition pattern by etching is
provided. A photosensitive resin layer is formed on a metal
substrate material having a center line-average surface roughness
Ra of up to 0.10 .mu.m and a maximum surface roughness Rmax of up
to 1.0 .mu.m to form a resist pattern. Then, the photosensitive
resin layer provided on the metal substrate material is exposed to
light to form a resist pattern. Finally, etching is carried out to
form a pattern on the metal substrate material.
Inventors: |
Komatsu, Takayasu; (Tokyo,
JP) ; Hashimoto, Daisuke; (Tokyo, JP) ;
Makita, Akira; (Tokyo, JP) ; Fujiyama, Koji;
(Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
DAI NIPPON PRINTING CO.,
LTD.
|
Family ID: |
18024877 |
Appl. No.: |
10/621382 |
Filed: |
July 18, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10621382 |
Jul 18, 2003 |
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09189977 |
Nov 12, 1998 |
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6620554 |
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Current U.S.
Class: |
428/577 ;
428/596; 428/687; 430/318; 430/319; 430/320; 430/323 |
Current CPC
Class: |
Y10T 428/12229 20150115;
Y10T 428/12993 20150115; G03F 7/09 20130101; H01J 9/142 20130101;
C23F 1/28 20130101; C23F 1/02 20130101; G03F 7/115 20130101; Y10T
428/12361 20150115; G03F 7/0007 20130101 |
Class at
Publication: |
428/577 ;
428/596; 428/687; 430/318; 430/319; 430/320; 430/323 |
International
Class: |
B21F 001/00; B21C
001/00; B21H 003/00; B21C 027/00; B21B 001/00; B32B 003/10; B21D
028/00; B23P 009/00; C23F 003/00; G03F 007/20; G03F 007/40 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 1997 |
JP |
9-312070 |
Claims
What we claim is:
1. An etching substrate material comprising a metal substrate
material which is to be provided thereon a pattern by coating a
photosensitive resin layer formed thereon, and exposing the
photosensitive resin layer to light to form a resist pattern,
followed by etching, characterized in that said etching substrate
material has a center line-average surface roughness Ra of up to
0.10 .mu.m and a maximum surface roughness Rmax of up to 1.0
.mu.m.
2. The etching substrate material according to claim 1,
characterized in that a surface roughness of said metal substrate
material has been regulated by at least one process selected from
the group consisting of rolling, chemical polishing, physical
polishing, and electrolytic polishing.
3. The etching substrate material according to claim 1,
characterized in that said metal substrate material is a substrate
material for a shadow mask, an aperture grill or a lead frame.
4. The etching substrate material according to claim 2,
characterized in that said metal substrate material is a substrate
material for a shadow mask, an aperture grill or a lead frame.
5. An etching process of exposing to light a photosensitive resin
layer formed on a metal substrate material to form a resist pattern
thereon, and carrying out etching to form a pattern on said metal
substrate material, characterized in that said photosensitive resin
layer is formed on a metal substrate material having a center
line-average surface roughness Ra of up to 0.10 .mu.m and a maximum
surface roughness Rmax of up to 1.0 .mu.m to form a resist pattern,
followed by etching.
6. An etching process of exposing to light a photosensitive resin
layer formed on a metal substrate material to form a resist pattern
thereon, and carrying out etching to form a pattern on said metal
substrate material, characterized in that after degreasing of said
metal substrate material, said metal substrate material is
surface-treated with a first etchant to regulate a center
line-average surface roughness Ra and a maximum surface roughness
Rmax to up to 0.10 .mu.m and up to 1.0 .mu.m, respectively, and a
photosensitive resin layer is thereafter formed and developed on
said metal substrate material to form a resist pattern thereon,
followed by etching.
7. The etching process according to claim 6, characterized in that
said first etchant comprises an aqueous solution of ferric chloride
having at least 50.degree. Bh.
8. The etching process according to claim 5, characterized in that
said metal substrate material is a substrate material for a shadow
mask, an aperture grill or a lead frame.
9. The etching process according to claim 6, characterized in that
said metal substrate material is a substrate material for a shadow
mask, an aperture grill or a lead frame.
10. The etching process according to claim 7, characterized in that
said metal substrate material is a substrate material for a shadow
mask, an aperture grill or a lead frame.
11. An article obtained by exposing to light a photosensitive resin
layer formed on a metal substrate material to form a resist
pattern, followed by etching, characterized in that said metal
substrate material has a center line-average surface roughness Ra
of up to 0.10 .mu.m and a maximum surface roughness Rmax of up to
1.0 .mu.m.
12. The article according to claim 11, characterized in that said
article is a shadow mask or an aperture grill.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to an etching
substrate material and etching process used to form high-definition
patterns by etching metal materials for lead frames, shadow masks,
and so on. More specifically, the invention provides a process of
forming a high-definition metal pattern by surface-treating a metal
substrate material by rolling, chemical polishing, physical
polishing or electrolytic polishing to create a very smooth surface
state, and then carrying out given etching, and a metal article
processed with high definition.
[0002] For a lead frame, shadow mask or aperture grill, a
photosensitive resin is first coated on the surface of a metal
material. Then, the photosensitive resin is exposed to light while
a desired pattern is brought in vacuum close contact therewith,
thereby forming a photoresist pattern. Finally, etching is
performed to form apertures, holes, etc. as desired.
[0003] For metal materials for shadow masks, alloys such as
iron-nickel base alloys, and iron-nickel-cobalt base alloys are
generally used. Thin alloy sheets are produced by preparing an
alloy ingot by a continuous casting process or an ingot-making
process, and then blooming, hot-rolling or cold-rolling the
ingot.
[0004] In a conventional etching process, an exposure pattern
cannot be in vacuum close contact with a substrate material having
too smooth a surface at an exposure step because it is very
difficult to remove gases from a central area thereof by drawing a
vacuum.
[0005] Thus, the surface roughness of the metal sheet used so far
in the art is Ra=ca. 0.20 to 0.70 .mu.m (center line-average
surface roughness) and Rmax=ca. 2.0 to 4.0 .mu.m (maximum surface
roughness).
[0006] For a shadow mask used on a computer display for
high-definition display purposes, on the other hand, it is required
that apertures for transmission of electron beams be located at
narrow intervals and have high precision. With this, a metal should
be micro-etched with an ever higher precision.
[0007] In pattern formation, the larger the amount of etching, the
more slender the influence of asperities formed on the pattern
becomes. However, the smaller the amount of etching the greater the
influence of the deformation of the pattern on etching becomes.
[0008] Thus, a shadow mask used on a display with high definition
is obtained by micro-processing at minute intervals. In this case,
however, the amount of etching is too reduced to prevent a pattern
formed on the substrate from manifesting itself remarkably due to
the deformation of a resist pattern. There is a strong demand for
an etching substrate material and process that enable patterns to
be formed with an ever higher definition.
[0009] One object of the invention is to provide an etching
substrate material which enables a precisely shaped resist pattern
to be formed thereon by etching. Another object of the invention is
to provide a method of processing metals with high definition and
producing a metal article processed with high definition. Yet
another object of the invention is to provide a method of producing
a high-definition processed metal article, e.g., a shadow mask, an
aperture grill, and a lead frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1(A1), 1(A2), 1(B1), 1(B2), 1(C1), and 1(C2)
illustrate a specific relationship between the surface roughness of
a substrate material and the pattern formed on the substrate
material.
[0011] FIGS. 2(A) and 2(B) illustrate a specific relationship
between the accuracy of the pattern and transmittance.
[0012] FIGS. 3(A) and 3(B) illustrate a pattern fabricated by the
process of the invention, and a comparative pattern.
SUMMARY OF THE INVENTION
[0013] The present invention provides an etching substrate material
comprising a metal substrate material which is to be provided
thereon a pattern by coating a photosensitive resin layer formed
thereon, and exposing the photosensitive resin layer to light to
form a resist pattern, followed by etching, characterized in that
said etching substrate material has a center line-average surface
roughness Ra of up to 0.10 .mu.m and a maximum surface roughness
Rmax of up to 1.0 .mu.m.
[0014] Preferably, the surface roughness of the metal substrate
material has been regulated by at least one of rolling, chemical
polishing, physical polishing, and electrolytic polishing.
[0015] Preferably, the metal substrate material is a substrate
material for a shadow mask, an aperture grill or a lead frame.
[0016] The present invention also provides an etching process of
exposing to light a photosensitive resin layer formed on a metal
substrate material to form a resist pattern thereon, and carrying
out etching to form a pattern on said metal substrate material,
characterized in that said photosensitive resin layer is formed on
a metal substrate material having a center line-average surface
roughness Ra of up to 0.10 .mu.m and a maximum surface roughness
Rmax of up to 1.0 .mu.m to form a resist pattern, followed by
etching.
[0017] Further, the present invention provides an etching process
of exposing to light a photosensitive resin layer formed on a metal
substrate material to form a resist pattern thereon, and carrying
out etching to form a pattern on said metal substrate material,
characterized in that after degreasing of said metal substrate
material, said metal substrate material is surface-treated with a
first etchant to regulate a center line-average surface roughness
Ra and a maximum surface roughness Rmax to up to 0.10 .mu.m and up
to 1.0 .mu.m, respectively, and a photosensitive resin layer is
thereafter formed and developed on said metal substrate material to
form a resist pattern thereon, followed by etching.
[0018] Preferably, the first etchant comprises an aqueous solution
of ferric chloride having at least 50.degree. Bh (Baum degree).
[0019] Preferably, the metal substrate material is a substrate
material for a shadow mask, an aperture grill or a lead frame.
[0020] Furthermore, the present invention provides an article
obtained by exposing to light a photosensitive resin layer formed
on a metal substrate material to form a resist pattern, followed by
etching, characterized in that said metal substrate material has a
center line-average surface roughness Ra of up to 0.10 .mu.m and a
maximum surface roughness Rmax of up to 1.0 .mu.m.
[0021] The article obtained by etching is a shadow mask or an
aperture grill.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] The present invention enables a high-definition photoresist
pattern to be formed on the surface of a substrate material by
making the surface roughness of the substrate material used for
etching lower than that of a conventional substrate material.
[0023] For micro-processing, it is required to form a resist
pattern with excellent definition. Never until now, however, is the
surface roughness of a substrate material considered to be a factor
detrimental to the achievement of this. The present invention will
now be explained with reference to the accompanying drawings.
[0024] FIGS. 1(A1), 1(A2), 1(B1), 1(B2), 1(C1), and 1(C2)
illustrate a specific relationship between the surface roughness of
a substrate material and the pattern formed on the substrate
material.
[0025] FIGS. 1(A1), 1(B1), and 1(C1) are views for illustrating a
process of forming a pattern by an etching technique, and FIGS.
1(A2), 1(B2), and 1(C2) are views for illustrating a process of
forming a pattern by an etching technique.
[0026] First consider the case where, as shown in the sectional
view of FIG. 1(A1), a photosensitive resin 2 is coated on a
substrate material 1 having a large surface roughness and the resin
layer is exposed to ultraviolet radiation 4 while an image pattern
3 is in close contact therewith. At an area of the substrate
material having a large surface roughness, the pattern shape is
deformed, shown at 6, by the diffraction effect of local light
caused by asperities 5, resulting in a drop of the resolution of
the pattern. As can be seen from FIG. 1(A2), however, a substrate
material having a small surface roughness enables an undeformed
pattern to be obtained thereon.
[0027] FIGS. 1(B1) and 1(B2) are plan views of linear patterns
formed on substrate materials. On one substrate material having a
large surface roughness, a resist pattern 7 is deformed or is not
in an accurate linear form, as can be seen from FIG. 1(B1). On
another substrate material having a small surface roughness,
however, a linear pattern is obtainable as can be seen from FIG.
1(B2).
[0028] FIGS. 1(C1) and 1(C2) show the shapes of such patterns upon
etching. An aperture pattern 8 obtained by etching has asperities
as can be seen from FIG. 1(C1). This aperture pattern has
difficulty in application to a shadow mask, because it is difficult
to provide accurate electron beam irradiation due to the presence
of the asperities. When an accurate resist pattern is obtained,
however, it is possible to form an accurate aperture pattern as can
be seen from FIG. 1(C2).
[0029] FIGS. 2(A) and 2(B) show specific relationships between the
accuracy of patterns and transmittance.
[0030] Here consider an aperture grill with a pitch of 150 .mu.m
and an aperture of 30 .mu.m. This aperture grill has a
transmittance of 20%. When 3-.mu.m deformations are found on both
ends of a tape portion as shown in FIG. 2(A), a local transmittance
drop of as large as 20% occurs. Consequently, when this aperture
grill is used on a cathode-ray tube, some considerable image
quality degradation is found. When the amount of deformation is
about 1.0 .mu.m as shown in FIG. 2(B), on the other hand, the local
transmittance drop is limited to about 10%, resulting in
substantial prevention of such image quality degradation.
[0031] This is also true of a linearity difference. When an
aperture grill has a pitch of 300 .mu.m and an aperture of 60
.mu.m, the local transmittance difference is 10%, and 5%,
respectively, between which any noticeable image quality difference
is not found.
[0032] When an aperture grill or shadow mask is fabricated with
higher definition, the edge linearity of an aperture pattern upon
etching is a very important factor for CRT image quality. The finer
the pitch and the smaller the aperture size, the higher the degree
of definition becomes. In this case, however, a minute size
difference between asperities on the edge area is largely reflected
on image quality.
[0033] The substrate material of the invention may be produced by a
process wherein the surface of a steel sheet obtained by the
rolling of a steel ingot is regulated to a given surface roughness
by means of rolls each having a regulated surface roughness, and a
process wherein the surface of a steel sheet upon rolling is
polished by physical polishing using abrasives, chemical polishing,
electrolytic polishing or the like. In the physical polishing
process, use may be made of buffing, a roll polishing material, and
a film polishing material, among which preference is given to the
roll or film polishing material because powders and particles are
unlikely to pass into the next step.
[0034] When the surface roughness is regulated by use of an
etchant, the concentration of the etchant used can be higher than
that of an etchant used for the formation of a pattern by etching.
For instance, a ferric chloride solution having a high
concentration of at least 50.degree. Bh may be used.
[0035] For the substrate material of the invention, for instance,
iron-nickel base alloys, iron-nickel-cobalt base alloys, low-carbon
steel may be used.
[0036] The surface roughness of the substrate material according to
the present invention has preferably a center line-average
roughness Ra of up to 0.10 .mu.m and a maximum roughness Rmax of up
to 1.0 .mu.m as measured by a probe type shape measuring device
(e.g., Tarysurf 6 made by Rank Taylor Hobson Co., Ltd.). For
pattern formation, it is preferred that both Ra and Rmax be small.
When the center line-average roughness Ra is greater than 0.10
.mu.m or the maximum roughness Rmax is greater than 1.0 .mu.m, any
satisfactory pattern linearity is not obtainable. A drop of pattern
linearity may often cause a quality drop of a shadow mask or
aperture grill, and so may make it impossible to obtain any
high-definition shadow mask or aperture grill.
[0037] In a conventional etching process, an exposure pattern
cannot be in vacuum close contact with a substrate material having
too smooth a surface at an exposure step because it is very
difficult to remove gases from a central area thereof by drawing a
vacuum. Thus, the surface roughness of the metal sheet used is
Ra=ca. 0.20 to 0.70 .mu.m and Rmax=ca. 2.0 to 4.0 .mu.m. A poor
contact problem with the vacuum close contact may be solved by use
of a device disclosed by the inventors in JP-A's 3-265835,
3-265836, and 3-265837. That is, pressures on both sides of an
exposure pattern are reduced by means of two independently located
vacuum chambers whose pressures are controllable, so that the
exposure pattern can be brought in close contact with the substrate
material from its center due to a difference in the pressures on
both sides thereof, thereby preventing gases from remaining in the
central area of the exposure pattern, and forming a space.
EXAMPLE
[0038] The present invention will now be explained with reference
to the following examples.
Example 1
[0039] 0.10 mm thick substrate samples 1 and 2 varying in surface
roughness were obtained by cold-rolling. After degreasing and water
washing of the surface of each sample, casein photoresist
containing 1% by weight of ammonium bichromate was coated and dried
thereon at a post-drying thickness of 5 .mu.m.
[0040] Then, a linear pattern having an array of 15 .mu.m apertures
was exposed to light while it was in close contact with the
photoresist using a photomask, and developed. Following this, the
sample was dipped in a 1% by weight bichromic acid solution, washed
with water, and heated at 200.degree. C. for 1 minute.
[0041] Then, a 5 .mu.m deep etching was carried out by spraying of
a ferric chloride solution.
[0042] The surface roughness of sample 1 was found to be Ra=0.20
.mu.m and maximum roughness Rmax=2.0 .mu.m as measured by a probe
type shape measuring device (Tarysurf 6 made by Rank Taylor Hobson
Co., Ltd.). Likewise, the surface roughness of sample 2 was found
to be Ra=0.06 .mu.m and maximum roughness Rmax=0.8 .mu.m.
[0043] The surface shape of each pattern obtained by etching was
observed under an electron microscope. The results are shown in
FIG. 1 that are plan views of the asperities of the patterns.
Sample 1 has an asperity of a=3.0 .mu.m as shown in FIG. 3(A), and
sample 2 has an asperity of b=1.1 .mu.m as shown in FIG. 3(B).
Example 2
[0044] Substrate samples 3 and 4, having a thickness of 0.030 mm
and varying in surface roughness, were obtained from an iron-nickel
base alloy (Invar alloy) by cold-rolling. As in Example 1, etching
was carried out by spraying a ferric chloride solution onto both
sides of each sample, thereby forming an array of apertures of 20
.mu.m in width.
[0045] The surface roughness of sample 3 was found to be Ra=0.50
.mu.m and maximum roughness Rmax=3.2 .mu.m as measured as in
Example 1. Likewise, the surface roughness of sample 4 was found to
be Ra=0.09 .mu.m and maximum roughness Rmax=0.9 .mu.m. The surface
shape of each pattern was observed under an electron microscope.
The results are shown in FIG. 1 that are plan view of the
asperities of the patterns. Sample 3 has an asperity of a=3.4 .mu.m
as in FIG. 3(A), and sample 4 has an asperity of b=1.3 .mu.m as in
FIG. 3(B).
Example 3
[0046] Sample 1 in Example 1 was degreased, and then
surface-treated at 40.degree. C. for 2 minutes, using a ferric
chloride solution of 51.degree. Bh. Following this, etching was
carried out under such conditions as in Example 1 to form a
pattern. The surface shape of the pattern was measured as in
Example 1. A linear shape of an area opened by etching has an
asperity of b=1.4 .mu.m as in FIG. 3(B).
Example 4
[0047] Sample 1 in Example 1 was degreased, and then
surface-treated by buffing with alumina powders of 1 .mu.m in
particle size, thereby obtaining a surface roughness as represented
by Ra=0.06 .mu.m. Following this, etching was carried out under
such conditions as in Example 1 to form a pattern. The surface
shape of the pattern was measured as in Example 1. A linear shape
of an area opened by etching has an asperity of b=1.2 .mu.m as in
FIG. 3(B).
[0048] As explained in the foregoing, the surface roughness of the
etching substrate material is regulated to a given range of
roughness by the process of the invention, whereby a photosensitive
resin pattern formed on the etching substrate material can be
accurately shaped. It is thus possible to obtain a high-quality
shadow mask for high-definition displaying purposes, etc.
* * * * *