Porous structure, ink-jet recording head, methods of their production, and ink jet recorder

TECHNICAL FIELD

The present invention relates to a porous structure superior in water repellency, an ink-jet recording head, a method of manufacturing those, and an ink-jet recording apparatus.

BACKGROUND ART

Water repellency treatment is performed for preventing drop adhesion or for preventing contamination. Various water repellents and water repellency treatments have been developed and used in various products including electronic equipment. Particularly, in an ink-jet recording apparatus, water repellency treatment has been put to practical use as surface treatment of a head which is the heart of the ink-jet recording apparatus. The water repellency treatment is an important treatment influencing printing quality.

Glass, metal, etc. is used as a constituent material component of an ink ejecting surface of an ink-jet recording head. When water-based or oil ink is used in an ink-jet recording head, drops of the ink are apt to adhere to a nozzle surface under the conditions that the water repellency of the nozzle surface is not sufficient. As a result, straight shooting of ejected ink drops is hindered to cause a trouble such as printing turbulence or the like to thereby occasionally affect long-term reliability. In addition, the constituent material of the ink ejecting surface of the ink-jet recording head is characteristically apt to get wet with ink. Therefore, water repellency treatment is given to the ink ejecting surface in order to perfectly prevent water based or oil ink from adhesion.

As for such water repellency treatment, there is a water repellency treatment (super-water-repellency treatment) ideal for an ink-jet recording head, in which the contact angle of water exceeds 120 degrees. As mentioned in “Introduction to Fluorochemistry”, THE NIKKAN KOGYO SHINBUN LTD., published Mar. 1, 1997, from line 10 of p.59 to line 6 of p.63, known is an eutectoid plating method in which polyfluoroethylene particles increased in fluorine atom density are dispersed in nickel film, or a coating method in which such a surface shape as trade name “Kanpenirex” by KANSAI PAINT CO., LTD. is designed to realize super-water-repellency.

However, conventional super-water-repellency treatment methods have problems as follows.

(1) Various surface active agents are added to ink for an ink-jet recording apparatus in order to make pigment disperse stably and permeate paper. In the eutectoid plating method, these surface active agents are absorbed into the nickel surface, so that the quality of the nickel surface may be lowered by ink wetting in long-term printing.

(2) In an ink-jet recording apparatus, a rubbing operation with rubber is required for cleaning paper powder or foreign contamination adhering to the head surface. In the conventional super-water-repellency coating methods, coating may peel off through this operation, so that the quality of the head surface may be lowered.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the foregoing problems. It is an object of the present invention to provide a porous structure in which water repellency is kept for a long term; an ink-jet recording head with a nozzle surface superior in water repellency properties to maintain high printing quality over a long term; a method of manufacturing such a porous structure and such an ink-jet recording head; and an ink-jet recording apparatus equipped with such an ink-jet recording head.

(1) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, heights of the protrusion portions on the surface being made uniform. Incidentally, a height of a protrusion portion formed on a substrate is defined as a level of the top surface of the protrusion portion in the direction of thickness of the substrate, in this invention.

(2) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 250 μm.

(3) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 15 μm.

(4) In the porous structure according to the above paragraph (1), differences in heights of the protrusion portions are within 5 μm.

(5) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, a depth of the recess portions on the surface being not smaller than a predetermined value.

(6) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 1 μm.

(7) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 3 μm.

(8) In the porous structure according to the above paragraph (5), the depth of the recess portions is not smaller than 5 μm.

(9) The porous structure according to the present invention consists of desired protrusion portions and recess portions formed on a surface of a substrate, and has such a size that liquid drops do not fall down into the recess portions, and the liquid drops can surely contact with an air layer in the recess portions.

(10) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 0.2 μm and 500 μm.

(11) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 0.5 μm and 30 μm.

(12) In the porous structure according to the above paragraph (9), widths of the protrusion portions or the recess portions is between 1 μm and 10 μm.

(13) In the porous structure according to the above paragraph (1), (5) or (9), a water repellant film is formed on the substrate having the protrusion portions and recess portions.

(14) In the porous structure according to the above paragraph (1), (5) or (9), the protrusion and recess portions comprises protrusion portions which are disposed distributively or in the form of stripes or a lattice.

(15) In the porous structure according to the above paragraph (1), (5) or (9), the substrate is of silicon, silicon oxide, or glass.

(16) The ink-jet recording head according to the present invention has water repellency performance given to an ink ejecting surface, wherein the ink ejecting surface except ink ejecting holes is constituted by the porous structure defined in the above paragraphs (1), (5) or (9).

(17) The ink-jet recording head according to the present invention has water repellency performance given to an ink ejecting surface, wherein the ink ejecting surface except ink ejecting holes is constituted by the porous structure defined in the above paragraph (9).

(18) In the method of manufacturing a porous structure according to the present invention, the porous structure defined in the above paragraphs (1), (5) or (9) is manufactured by a photolithography method and an etching method.

(19) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is a trench dry etching.

(20) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an anode electrolysis method.

(21) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an isotropic wet etching method.

(22) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an anisotropic wet etching method.

(23) In the method of manufacturing a porous structure according to the above paragraph (18), the etching method is an isotropic dry etching method.

(24) In the method of manufacturing an ink-jet recording head according to the present invention, the porous structure defined in the above paragraph (16) is manufactured by a photolithography method and an etching method.

(25) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is a trench dry etching method.

(26) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an anode electrosis method.

(27) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an isotropic wet etching method.

(28) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an anisotropic wet etching method.

(29) In the method of manufacturing an ink-jet recording head according to the above paragraph (24), the etching method is an isotropic dry etching method.

(30) The ink-jet recording apparatus according to the present invention has such an ink-jet recording head as defined in the above paragraph (16).

(31) The ink-jet recording apparatus according to the present invention has such an ink-jet recording head as defined in the above paragraph (17).

As described above, according to the present invention, a function of water repellency is obtained by a porous structure having a shape of protrusion-and-recess formed artificially on a surface of a substrate. Accordingly, superior properties of water repellency can be kept for a long term.

In addition, according to the present invention, an ink ejecting surface of an ink-jet recording head expect for ink ejecting holes is made to be such a porous structure. Accordingly, the water repellency performance to ink is improved. As a result, printing quality is superior for a long term.

Incidentally, water repellency performance in the present invention includes oil repellant performance.

Further, according to the present invention, the porous structure is manufactured by a photolithography method and an etching method. Accordingly, it is possible to manufacture a super-water-repellency structure having reproducibility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is an explanatory view of a porous structure according to Embodiment 1 of the present invention.

FIG. 2

is an explanatory view of the contact angle of water when a function of water repellency is exhibited.

FIG. 3

is an explanatory view about the size of recess portions and protrusion portions in FIG.

1

.

FIGS. 4A

,

4

B and

4

C are plan views showing examples of a porous structure

100

in FIG.

1

.

FIG. 5

is an exploded perspective view of an ink-jet recording head according to Embodiment 2 of the present invention.

FIG. 6

is a series of sectional views showing a manufacturing process for forming a porous structure on a surface of a second plate in the Embodiment 2.

FIG. 7

is a top view of the second plate

2

having a porous structure formed on its surface.

FIG. 8

is a series of sectional views showing a manufacturing process for forming a porous structure on a surface of a second plate

2

in Embodiment 3 of the present invention.

FIG. 9

is a series of sectional views showing a manufacturing process for forming a porous structure on a surface of a second plate in Embodiment 4.

FIG. 10

is a series of sectional views showing a manufacturing process for forming a porous structure on a surface of a second plate in Embodiment 5.

FIG. 11

is a series of sectional views showing a manufacturing process for forming a porous structure on a surface of a second plate in Embodiment 6.

FIG. 12

is a series of sectional views showing a manufacturing process of a second plate in Comparative Example 1.

FIG. 13

is a series of sectional views showing a manufacturing process of a second plate in Comparative Example 2.

THE BEST MODE FOR CARRYING-OUT THE INVENTION

Embodiment 1

FIG. 1

is an explanatory view of a porous structure according to Embodiment 1 of the present invention. In

FIG. 1

, in a porous structure

100

, recess portions

17

and protrusion portions

18

are formed on a surface of a silicon substrate

11

, and a water repellant film

19

is formed on this surface. In addition, an air layer

20

is produced in the recess portions

17

formed on the surface of the silicon substrate

11

.

FIG. 2

is an explanatory view of the contact angle of water when the water repellency function is exhibited. As shown in

FIG. 2

, it is necessary that the contact angle θ of water is not smaller than 120 degrees (in the case of ink drops, not smaller than 90 degrees) in order to exhibit the water repellency function. In the porous structure

100

in

FIG. 1

, in order to exhibit the water repellency function with the contact angle θ of water not smaller than 120 degrees, it is necessary that a recess portion

17

has such a size that a liquid drop

21

can contact with the air layer

20

without falling down into the recess portion

17

.

FIG. 3

is an explanatory view about size of a recess portion

17

and a protrusion portion

18

in FIG.

1

. In

FIG. 3

, A designates protrusion width (based on mask design); B, recess width (based on mask design); C, a working amount (depth based on etching time); and D, a side wall angle (based on etching conditions). When this porous structure is applied to an ink-jet recording head, the above-mentioned values A and B are restricted of themselves based on the relation to the diameter of an ink drop which is about 10 μm. As for the value C, a certain measure of depth is necessary to prevent a phenomenon that an ink drop is enclosed in a state in contact with the bottom surface. Therefore, the values A and B are defined within a range from 0.2 to 500 μm, preferably from 0.5 to 30 μm, more preferably from 1 to 10 m. In addition, the above-mentioned value C is defined to be a depth not smaller than 1 μm, preferably, not smaller than 3 μm, more preferably, not smaller than 5 μm. Further, differences of heights of the protrusion portions defined as levels of the top surfaces of the protrusion portions in the direction of thickness of the substrate are quantatively defined to be not larger than 250 μm or 15 μm for example, preferably not larger than 5 μm in view of scratch-proof

FIGS. 4A

,

4

B and

4

C are plan views showing examples of the porous structure

100

in FIG.

1

.

FIG. 4A

shows an example where the protrusion portions

18

are arranged and distributed regularly;

FIG. 4B

shows an example where the protrusion portions

18

are arranged in lines; and

FIG. 4C

shows an example where the protrusion portions

18

are arranged in a lattice. Although

FIG. 4A

shows an example where the protrusion portions

18

are square poles, they may be other various poles such as triangle ones, pentagonal ones, hexagonal ones, circular ones, etc.

Embodiment 2

FIG. 5

is an exploded perspective view of an ink-jet recording head according to Embodiment 2 of the present invention. This ink-jet recording head has a configuration in which a first plate

1

and a second plate

2

are bonded and stacked on each other so as to form an ink supply portion

3

, a pressure chamber

4

for ejecting ink by vibration of a diaphragm such as an electrostatic diaphragm vibrating electrostatically, a piezoelectric diaphragm of PZT or the like, etc., or by heating of a heating unit, and a flow path

5

passed by the ejected ink. In the second plate

2

, a nozzle hole

6

is formed perpendicularly to the flow path

5

. In addition, the porous structure in

FIG. 1

is formed on a surface of the second plate

2

, and a water repellant film is formed on the surface of the second plate

2

.

FIG. 6

is a series of sectional views showing a manufacturing process for forming the porous structure on the surface of the second plate

2

.

FIG. 7

is a top view of the second plate

2

in which the porous structure is formed on the surface. The manufacturing process of the porous structure will be described with reference to

FIGS. 6 and 7

. Here, description will be made about the case where a porous structure is formed by working a surface of a silicon substrate by a photolithography method and a trench dry etching method.

{circle around (1)} First, a 4-inch single-crystal silicon wafer of crystal orientation (

100

) is prepared as a substrate for manufacturing the second plate

2

. A silicon oxide film

12

having the thickness of about 1,000 Angstroms is formed on at least one surface of the single-crystal silicon substrate

11

by a thermal oxidation method, as shown in FIG.

6

(

a

).

{circle around (2)} Next, as shown in FIG.

6

(

b

), about 2 ml of photosensitive resin OFPR-800 (viscosity 30 cps) made by Tokyo Ohka Kogyo Co., Ltd. is dropped onto the silicon oxide film

12

of the single-crystal silicon substrate

11

, and spin-coated thereon for

30

seconds at speed of 5,000 revolutions per minute so as to form a photosensitive resin film

13

. Under this spin-coating conditions, it is possible to coat the photosensitive resin with the average film thickness of about 1 μm with dispersion of 10% within the surface of the wafer. The film thickness is changed suitably in accordance with the size of grooves to be worked. The maximum value of the photosensitive resin film thickness is 2 μm when the width of the grooves is 2 μm.

{circle around (3)} Next, being dried for 30 minutes in an oven at about 90 Celsius degrees, the substrate

11

is cooled down to the room temperature. As shown in FIG.

6

(

c

), the photosensitive resin film

13

is photolithographically patterned to form arranged areas for square protrusion portions each of which has sides each having a length in the range from 0.2 μm to 200 μm. Then, the photosensitive resin is cured in an oven at about 120 Celsius degrees so as to improve the resistance to etching.

{circle around (4)} As shown in FIG.

6

(

d

), the silicon oxide film in arranged areas for recess portions is etched with fluoric acid, and the photosensitive resin is removed with release agent.

{circle around (5)} Next, a plasma synthetic film

14

is formed by a trench dry etching apparatus using gas with C and F, as shown in FIG.

6

(

e

). Successively, after the dry etching apparatus is evacuated, silicon in the arranged areas

15

for recess portion is etched into grooves with plasma of gas the formula of which is SF

6

or CF

4

, as shown in FIG.

6

(

f

).

At this time, etching is not performed on the arranged areas for the protrusion portions because the silicon oxide film

12

exists in the areas, as shown in FIG.

6

(

f

). On the other hand, anisotropic etching is effectively performed on the arranged areas for the recess portions by the effect of the plasma synthetic film formed on the portions corresponding to the side walls of the grooves. Such a plasma synthesizing step and a plasma etching step are repeated, so that the surface of the single-crystal silicon substrate

11

is etched into grooves having the depth of about 5 μm to form the recess portions

17

and the protrusion portions

18

, as shown in FIG.

6

(

g

). These protrusion portions

18

are laid out regularly on the surface of the single-crystal silicon substrate

11

, as shown in FIG.

3

.

{circle around (6)} Next, nozzle holes

6

(see

FIG. 5

) are worked, and fluoroalkylsilane or polyfluoroethylene water-repellant material is deposited on the single-crystal silicon substrate

11

by a vacuum deposition method so as to form a water repellant film

19

(see FIG.

1

).

{circle around (7)} Finally, the first plate

1

is bonded with the thus formed second plate

2

, so as to complete the ink-jet recording head.

Embodiment 3

FIG. 8

is a series of sectional views showing a process showing another examples of a manufacturing process for forming a porous structure on a surface of a second plate

2

. Here, description will be made about the case where a porous structure is formed by working a surface of a silicon substrate by a photolithography method and an anode electrolysis method.

{circle around (1)} First, an n-type single-crystal silicon substrate

11

of crystal orientation (

100

) having the thickness of, for example, about 200 μm is prepared as a substrate for manufacturing the second plate.

{circle around (2)} Silicon nitride films

23

and

24

having the thickness of about 0.3 μm are formed as etching resistance film on this silicon substrate

11

by a CVD apparatus, as shown in FIG.

8

(

a

).

{circle around (3)} Next, after the silicon nitride film

24

is removed by a dry etching method, photo-etching is given to the silicon nitride film

23

, so that portions

22

of the silicon nitride film

23

, corresponding to the recess portions

17

of the porous structure, is etched as shown in FIG.

8

(

b

).

{circle around (4)} Next, using the silicon nitride film

23

as mask, V-groove-shaped etching pyramids

25

are formed in the silicon substrate

11

by an anisotropic etching method with potassium hydrate water-solution. Then as shown in FIG.

8

(

c

), an indium-tin oxide film (ITO film)

6

is formed on the surface opposite to the surface with the silicon nitride film

23

.

{circle around (5)} Successively, an electrolytic cell is composed in a manner that the surface with the silicon nitride film

23

contacts with electrolytic solution, and light is radiated from the opposite surface, so that grooves 27 having the depth of about 5 μm are formed by etching as shown in FIG.

8

(

d

). Then, the silicon nitride film and the indium-tin oxide film are removed so as to produce the recess portions

17

and the protrusion portions

18

(FIG.

8

(

e

)).

{circle around (6)} Nozzle holes

6

(see

FIG. 5

) are worked, and fluoroalkylsilane or polyfluoroethylene water repellant material is deposited on the second plate by a vacuum deposition method, so as to form a water repellant film

19

(see FIG.

8

(

f

)).

{circle around (7)} Finally, the first plate

1

is bonded with the thus formed second plate

2

, so as to complete the ink-jet recording head.

Embodiment 4

FIG. 9

is a series of sectional views showing another example of a manufacturing process for forming a porous structure on a surface of a second plate. Here, description will be made about the case where a porous structure is formed by working a surface of a silicon substrate by a photolithograph method and an anisotropic wet etching method.

{circle around (1)} First, a 4-inch single-crystal silicon wafer of crystal orientation (

100

) is prepared as a substrate for a plate

2

. A silicon oxide film

112

having the thickness of about 1,000 Angstrom is formed on at least one surface of the single-crystal silicon substrate

111

by a thermal oxidation method, as shown in FIG.

9

(

a

).

{circle around (2)} Next, as shown in FIG.

9

(

b

), about 2 ml of photosensitive resin OFPR-800 (viscosity 30 cps) made by Tokyo Okka Kogyo Co., Ltd. is dropped onto the silicon oxide film

112

of the single-crystal silicon substrate 111, and spin-coated thereon for 30 seconds at speed of 5,000 revocations per minute so as to form a photosensitive resin film

113

. Under this spin-coating condition, it is possible to coat the photosensitive resin with the average film thickness of about 1 m with dispersion of 10% within the surface of the wafer. The film thickness is changed suitably in accordance with the size of grooves to be worked. The maximum value of the photosensitive resin coating film thickness is 2 μm when the width of the grooves is 2 μm.

{circle around (3)} Next, being dried for 30 minutes in a oven at about 90 Celsius degrees, the substrate

111

is cooled down to the room temperature. As shown in FIG.

9

(

c

), the photosensitive resin film is photolithographically patterned to form arranged areas for square protrusion portions each of which has sides each having a length from 0.2 μm to 200 μm. Then, the photosensitive resin is cured in an oven at about 120 Celsius degrees so as to improve the resistance to etching.

{circle around (4)} As shown in FIG.

9

(

d

), the silicon oxide film in arranged areas for recess portions is etched with fluoric acid, and the photosensitive resin is removed with release agent.

{circle around (5)} Next, using the silicon oxide film

112

as mask, etching pyramids

114

each having a V-shaped cross section are formed on the silicon substrate

111

as shown in FIG.

9

(

e

), by an anisotropic etching method with potassium hydrate water-solution. Then, the silicon oxide film

112

is removed (FIG.

9

(

f

)). The etching pyramids

114

thus formed correspond to recess portions

17

in FIG.

1

. Protrusion portions

18

are naturally formed in accordance with forming of the recess portions

17

so that they are laid out regularly on the surface of the single-crystal silicon substrate

111

.

{circle around (6)} Next, fluoroalkylsilane or polyfluoroethylene water-repellant material is deposited on the substrate by a vacuum deposition method so as to form a water-repellant film

19

(FIG.

9

(

g

)).

Embodiment 5

FIG. 10

is a series of sectional views showing another example of a manufacturing process for forming a porous structure on a surface of a second plate

2

. Here, description will be made about the case where a porous structure is formed by working a surface of a glass substrate by a photolithography method and an isotropic wet etching method.

{circle around (1)} First, a glass substrate

211

having thickness of 200 μm, for example, is prepared as a substrate for a second plate

2

.

{circle around (2)} A silicon nitride film

212

having thickness of about 0.03 μm is formed as etching resistance film on the glass substrate

211

as shown in FIG.

10

(

a

), by a spattering apparatus.

{circle around (3)} Next, the silicon nitride film

212

is subjected to photolithoetching to etch film portions corresponding to recess portions of the porous structure, as shown in FIG.

10

(

b

).

{circle around (4)} Next, using the silicon nitride film

212

as mask, etched recess portions

215

are formed on the glass substrate

211

by an isotropic etching method with hydrofluoric acid water-solution, as shown in FIG.

10

(

c

).

{circle around (5)} Next, the silicon nitride film is removed with heated phosphonic acid to complete the recess and protrusion portions as shown in FIG.

10

(

d

).

{circle around (6)} Finally, a fluoroalkylsilane film is deposited on the glass substrate

211

by a vacuum deposition method so as to form a water-repellant film

19

(FIG.

10

(

e

)).

Embodiment 6

FIG. 11

is a series of sectional view showing another example of a manufacturing process for forming a porous structure on a surface of a second plate

2

. Here, description will be made about the case where a porous structure is formed by working a surface of a glass substrate by a photolithography method and an isotropic dry etching method.

{circle around (1)} First, a glass substrate

311

having thickness of 200 μm, for example, is prepared as a substrate for a second plate

2

.

{circle around (2)} A photosensitive resin film

312

having thickness of about 5 μm is formed as etching resistance film on the glass substrate

311

as shown in FIG.

11

(

a

), by a spin coating apparatus.

{circle around (3)} Next, the photosensitive resin film

312

is subjected to photolithoetching to etch film portions corresponding to recess portions of the porous structure, as shown in FIG.

11

(

b

).

{circle around (4)} Next, using the photosensitive resin film

312

as mask, etched recess portions are formed on the glass substrate

11

by an isotropic plasma etching method with CF

4

gas, as shown in FIG.

11

(

c

).

{circle around (5)} Next, the photosensitive resin film is removed with heated phosphonic acid to complete the recess and protrusion portions as shown in

FIG. 11

(

d

).

{circle around (6)} Finally, a fluoroalkylsilane film is deposited on the glass substrate

311

by a vacuum deposition method so as to form a water-repellant film

19

(FIG.

11

(

e

)).

It was confirmed that the porous structures (water repellant structures) formed in the above Embodiment 3 to 6 had uniform heights (less dispersion in heights) of the protrusion portions, and as a result, provided the same water repellency function, durability and scratch proof function as the porous structure in Embodiment 2.

Incidentally, as any porous structure (water repellant structures) in the above Embodiments 2 to 6 is formed by using photolithography method and an etching method, uniform depths of the recess portions, that is uniform heights of protrusion portions, can be obtained. Further, a surface of a substrate is shifted to top surfaces of protrusion portions so that the top surfaces can naturally be placed on an even surface with accuracy.

Embodiment 7

Although the above-mentioned embodiments have been described about the case where a silicon substrate or a glass substrate is used as material of the second plate

2

, the material of the second plate

2

is not limited to those materials, but metal material such as stainless steel or organic polymer material may be used in the present invention, presenting the same function.

Embodiment 8

It was confirmed that high-quality printing could be obtained when printing was performed by an ink-jet recording apparatus mounted with an ink-jet recording head according to either of the above-mentioned Embodiments 2 and 3. Particularly, it was confirmed that the ink-jet recording apparatus had wear resistance against rubbing in cleaning because the water repellant function was produced by a recess/protrusion mechanism so that the apparatus could endure long-term use.

Embodiment 9

In addition, a porous structure according to the present invention is superior in water repellency, and therefore effective also as, for example, a waterproof/anti-contamination structure in electronic equipments.

EXAMPLE 1

As Example 1 of the present invention, samples of second plates (as seen in

FIG. 5

) manufactured in the above Embodiments were prepared as shown in Table 1. First, substrate materials for samples 1 to 7 of second plates shown in Table 1 were prepared. Square protrusion portions having a size from 0.2 μm to 1,000 μm were formed on a surface of each substrate material (see FIG.

4

). In addition, a water repellant film was formed on the surface by deposition of fluoroalkylsilane or polyfluoroethylene water-repellant material. This water repellency treatment was not performed on the samples 2, 4 and 6.

TABLE 1

Substrate

Protrusion size

Water repellency

Material

(micron square)

treatment

Sample 1

Silicon

0.2

given

Sample 2

Silicon

0.2

not-given

Sample 3

Glass

5

given

Sample 4

Quartz Glass

5

not-given

Sample 5

Quartz Glass

10

given

Sample 6

Silicon

10

not-given

Sample 7

Glass

500

given

(COMPARATIVE EXAMPLE 1)

FIG. 12

is a series of sectional views showing a manufacturing process of a second plate as shown in

FIG. 5

, in this Comparative Example 1 where water repellent material is applied onto a second plate of stainless steel.

{circle around (1)} First, as shown in FIG.

12

(

a

), a substrate

31

for the second plate is worked to form nozzle holes

32

, and then ultrasonically cleaned with alkaline solvent.

{circle around (2)} The substrate

31

is immersed in nickel plating electrolytic solution including polyfluoroethylene particles increased in fluorine atom density. An eutectoid plated film

33

in which polyfluoroethylene particles

34

increased in fluorine atom density are dispersed is produced on a surface of the substrate

31

by electro-plating, as shown in FIG.

12

(

b

). This plated film

33

contains the polyfluoroethylene particles

34

increased in fluorine atom density.

(COMPARATIVE EXAMPLE 2)

FIG. 13

is a series of sectional views showing a manufacturing process of a second plate as shown in

FIG. 5

, in this Comparative Example 2 where water repellent material is applied onto a second plate of polysulfonate.

{circle around (1)} First, as shown in FIG.

13

(

a

), a substrate

41

for the second plate is worked to form nozzle holes

42

, and then ultrasonically cleaned with alkaline solvent.

{circle around (2)} Successively, tradename “Kanpenirex” made by KANSAI PAINT CO., LTD. is coated on a surface of the substrate

41

so as to produce a coating film

43

, as shown in FIG.

13

(

b

).

Table 2 shows the results of measuring the contact angle of the surfaces of the second plates prepared in the above-mentioned Example 1, and Comparative Examples 1 and 2, to water and ink respectively.

TABLE 2

Water contact

Ink contact

angle (degree)

Angle (degree)

Example 1

sample 1

160

130

sample 2

150

110

sample 3

160

125

sample 4

140

115

sample 5

150

120

sample 6

145

90

sample 7

140

110

Comparative Example 1

130

60

Comparative Example 2

160

120

As shown in the above Table 2, the contact angle of the second plate in each sample of this Example 1 was larger than 120 degrees in the case to water and larger than 90 degrees in the case to ink. Each sample in the Example 1 takes higher values of the contact angle than those in Comparative Example 1.

Each of the second plates according to samples

1

to

7

in Example 1 and Comparative Examples 1 and 2 was bonded a first plate as shown in

FIG. 5

to form an ink-jet recording head and it was mounted on a recording apparatus. Printing text was given on the apparatus including respective second plate, under initial condition and accelerating conditions corresponding to two years. Then, the results shown in Table 3 were obtained. Table 3 shows the results of judgement of printing quality, where the mark ⊚ designates a superior result in which printing quality is good and no ink mist adheres to the surface of the second plate, the mark ∘ designates a good result in which printing quantity is good but ink mist adheres to the surface of the second plate, and the mark × designates a inferior result with defective printing quantity caused by bending of ink flight.

TABLE 3

After accelerating printing test

Initial

Corresponding to two years

Example 1

sample 1

⊚

⊚

sample 2

⊚

∘

sample 3

⊚

⊚

sample 4

⊚

∘

sample 5

⊚

⊚

sample 6

⊚

∘

sample 7

⊚

⊚

Comparative Example 1

∘

x

Comparative Example 2

⊚

x

As described above, the ink-jet recording heads using the second plate in this Example 1 were superior in printing quality under the initial conditions and the accelerating conditions corresponding to two years. The reproducibility of the superior printing quality was also confirmed. Among the second plates in Example 1 having square protrusion portions of a size within a range from 0.2 μm to 500 μm, the plates having a water repellant film formed by coating water repellant agent exhibited the best printing quality. However, in the ink-jet recording heads using the second plates according to Comparative Examples 1 and 2, the water repellency and printing quantity deteriorated under the accelerating conditions corresponding to two years because ink adhered to the surface of the second plates.

EXAMPLE 2

In Example 2 of the present invention, contact angles of surfaces having porous structures with the respective shapes of protrusion portions formed into square poles, in lines and in a lattice (see

FIGS. 4A

,

4

B and

4

C) were examined to water and ink. Table 4 shows data of the examination. In each sample according to the present invention (No. 1 to No. 10), the contact angle was not smaller than 120 degrees in the case of water, and not smaller than 90 degrees in the case of ink. It was understood that the water repellency function was obtained. In Comparative Example in Table 4, a water repellant film was formed on a mirror-polished surface (corresponding to the prior art). This example did not satisfy necessary conditions for obtaining the water repellency function.

TABLE 4

Water Repellency

Initial

Structural size (actual survey)

Performance

protrusion

Recess

Working

side wall

Purified

HQ284C

width

width

quantity

angle

water

ink

No.

Structure

A(μm)

B(μm)

C(μm)

D(°)

(°)

(°)

1

Square

0.2

24

3.2

14

140

98

pole

2

square

1.0

6.0

6.8

1

158

102

pole

3

in lines

1.2

2.0

7.8

1

138

122

4

square

1.5

2.5

3.6

3

140

113

pole

5

square

3.4

3.8

5.0

12

140

128

pole

6

square

4.0

6.0

8.6

0

150

106

pole

7

in lines

4.0

6.0

8.0

4

131

107

8

square

5.2

4.8

2.8

4

149

105

pole

9

square

6.0

4.0

3.2

18

158

107

pole

10

lat-tice

4.3

6.0

10.0

2

123

92

Comparative Example; water repellency treatment on mirror surface

115

70

EXAMPLE 3

Molding was performed by using, for example, resin as a raw material and using a porous struture of Example 1 or 2 (water repellency treatment is not necessarily required) as a mold. Molded products thus obtained had an rugged pattern on the surface which had been transferred from the rugged pattern of the mold. It was confirmed that the porous structures of the molded product with or without water repellency treatment had superior characteristics similar to Examples 1 and 2.

Number	Date	Country	Kind
9-245121	Sep 1997	JP
10-170952	Jun 1998	JP

Number	Name	Date	Kind
5674625	Takahashi et al.	Oct 1997	A
5693236	Okumura et al.	Dec 1997	A
5759421	Takemoto et al.	Jun 1998	A
5790151	Mills	Aug 1998	A
6210750	Cho et al.	Apr 2001	B1

Number	Date	Country
06093121	Apr 1994	JP
10130844	May 1998	JP
10156282	Jun 1998	JP
410203819	Aug 1998	JP

	Number	Date	Country
Parent	PCT/JP98/04034	Sep 1998	US
Child	09/307992		US

Porous structure, ink-jet recording head, methods of their production, and ink jet recorder

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (2)

Parent Case Info

US Referenced Citations (5)

Foreign Referenced Citations (4)

Non-Patent Literature Citations (4)

Continuation in Parts (1)

Entry
Introduction to Fluorochemistry The Nikkan Kogyo Shinbun Ltd., publsihed Mar. 1, 1997, From line 10 of p. 59 to line 6 of p. 63 and English translation thereof.
Patent Abstracts of Japan of JP 10-130,844 of May 1998.
Patent Abstracts of Japan of JP 06093121 of Apr. 1994.
Patent Abstracts of Japan of JP 10156282 of Jun. 1998.