The present application claims priority to Japanese Patent Application JP2004-014183, filed in the Japanese Patent Office on Jan. 22, 2004; the entire content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to thermal liquid ejection heads for inkjet printers and liquid ejection apparatuses such as inkjet printers including the liquid ejection heads, and more particularly, to a technique for cooling a liquid ejection head, that is, a technique that can reduce thermal variation of the liquid ejection head per unit time.
2. Description of the Related Art
Thermal liquid ejection heads and piezoelectric liquid ejection heads are well known examples of liquid ejection heads used in liquid ejection apparatuses such as inkjet printers. The former utilizes expansion and contraction of bubbles generated by heat, whereas the latter utilizes the variation in shape and volume of piezoelectric elements. The thermal liquid ejection heads include heating elements on semiconductor substrates. When the heating elements heat up, generated heat vaporizes liquid in reservoirs to create bubbles, thereby ejecting liquid drops from nozzles, which are disposed above the heating elements, onto recording media.
Referring to
The nozzle sheet 17 includes nozzles 18 disposed right above the respective heating elements 12. The nozzles 18 have openings from which ink drops are ejected. Since the barrier layer 3 is disposed between the heating elements 12 and the nozzles 18, reservoirs 3a are formed in the spaces enclosed by the barrier layer 3, the heating elements 12, and the nozzles 18.
As shown in
The heating elements 12 are aligned in the vicinity of one side of the semiconductor substrate 11. As shown in
As shown in
Ink supplied from the inlet 22a passes through the supplying flow path 24, the common flow path 23, and the individual flow path 3d to enter the reservoir 3a. When the heating element 12 heats up, a bubble is generated in the reservoir 3a on the heating element 12. The generated bubble ejects a drop of ink in the reservoir 3a through the nozzle 18.
In
In the structure shown in
It is the top surface of the semiconductor substrate 11 that the heat traveling through the semiconductor substrate 11 reaches first. The top surface of the semiconductor substrate 11 is flash with the top surface of the heating elements 12 and is in contact with liquid. Secondly, the heat traveling through the semiconductor substrate 11 reaches the first side surface of the semiconductor substrate 11, that is, the surface forming the common flow path 23 with the dummy chip D.
Now, a mechanism of how a bubble is generated in a thermal liquid ejection head will be described. A heater, e.g., the heating element 12 is in contact with liquid such as ink, and thermal energy from the heater heats up the liquid. When the temperature of the heater exceeds the boiling point of the liquid, the liquid boils. From an academic point of view, “boiling” denotes nucleate boiling. More specifically, the surface of the heater has small scratches or dents in which masses of air, which are called bubble nuclei, exist. Bubbles are generated in these bubble nuclei.
Accordingly, even though the heaters are in contact with liquid, generation of bubbles depends on the condition of the surfaces of the heaters at the same temperature. The number of bubble nuclei determines the number of bubbles generated on the surface of the heater. More bubbles are generated on the surface of the heater with many bubble nuclei than on the surface of the heater with a small number of bubble nuclei. That is, bubbles are readily generated on a rough surface but are hardly any generated on a smooth surface.
The surface of the head chip 1a on which the heating elements 12 are disposed is very precisely finished by a semiconductor process and thus is extremely smooth. By contrast, since the first side surface of the head chip 1a is processed through dicing, that is, cutting using, e.g., a rotary saw, the first side surface of the head chip 1a has irregularities and thus bubble nuclei exist therein.
To prevent bubbles from being generated on the first side surface of the head chip 1a, the following methods are proposed. A first method is that the heating elements 12 are aligned well remote from the first side surface of the head chip 1a such that it is difficult for the heat generated by the heating elements 12 to reach the first side surface. In this way, thermal energy reaching the first side surface of the head chip 1a hardly brings liquid to a boil.
A second method is that the first side surface of the head chip 1a is made smooth such that irregularities in which bubble nuclei exist are eliminated. A third method, which is disclosed in Japanese Unexamined Patent Application Publication No. Hei 9-11479, is that an ink inlet or opening is formed through anisotropic etching in the center area of the head chip 1a and a heating element is disposed in the vicinity of the ink inlet.
With the first method, since a wide gap is disposed between the first side surface of the head chip 1a and the aligned heating elements 12, the gap makes the head 1 large, which contradicts high-density packaging of the head chip 1a. The second method requires an additional step of processing the surface of the head chip 1a after the head chip 1a is cut through dicing, resulting in increased cost.
With the third method, anisotropic etching is performed on the head chip 1a and thus the surface on which the ink inlet is formed is extremely smooth. Therefore, bubbles do not develop on this smooth surface of the head chip 1a. Unfortunately, since the ink inlet is provided in the center area of the head chip 1a, the head chip 1a has a complex structure. Thus, provision of the ink inlet is not suitable for the structure of the head chip 1a including the heating elements 12 aligned close to the first side surface of the semiconductor substrate 11.
The influences of development of bubbles on the first side surface of the head chip 1a will now be described.
Theoretically, bubbles generated in ink move upward by its buoyancy. In actual use, however, ejection of ink drops reduces the amount of ink in the reservoir 3a. Accordingly, ink in the bubbling region is drawn towards the nozzle 18, that is, towards the reservoir 3a, and the bubbles are also drawn towards the common flow path 23 and the individual flow path 3d.
Even when the number of bubbles generated in the individual flow paths 3d and the common flow path 23 close to the individual flow paths 3d is very small, ejection of ink may be influenced by these bubbles to some extent. When the number of generated bubbles is large, small bubbles may be united into larger bubbles. In this case, the surface tension of the bubbles decreases the amount of ink supplied to narrow flow paths, that is, the individual flow paths 3d. Moreover, ink cannot flow into the individual flow paths 3d at all in some cases.
Due to a decrease in the amount of ink supplied to the individual flow path 3d, a sufficient amount of ink cannot be ejected as ink drops. Moreover, sometimes no ink is ejected from a nozzle at all. A serial head for a serial printer prints an image or character by multiple ink ejection by being slightly moved while printing and thus the amount of ejected ink can be evened out over the print sheet. Thus, failure in ink ejection is not noticeable. On the other hand, a line head for a line printer prints an image or character by a single ink ejection. Therefore, when the line head encounters failure in ink ejection, the resulting printing has a line (white line) at a position corresponding to the part of the head suffering from the failure.
It is an object of the present invention to minimize the distance Yn in
According to a liquid ejection head of the present invention includes: a substrate; at least one head chip including a plurality of heating elements on a surface of the substrate; a nozzle layer having nozzles disposed above the respective heating elements; a barrier layer disposed between the head chip and the nozzle layer; reservoirs disposed between the heating elements and the nozzles, the reservoirs being defined by part of the barrier layer; a common flow path communicating with the reservoirs, the common flow path supplying liquid to the reservoirs; and a liquid storage chamber disposed on at least one region of the surface of the substrate excluding a region on which the reservoirs are disposed, the liquid storage chamber being defined by part of the barrier layer, the liquid storage chamber communicating with the common flow path and the reservoirs, the liquid storage chamber storing liquid such that part of the nozzle layer is in contact with the liquid. In the liquid ejection head, heating energy is applied to the heating elements to generate bubbles on the heating elements, and the generated bubbles expel liquid in the reservoirs to be ejected through the nozzles.
According to the liquid ejection head and the liquid ejection apparatus of the invention, when liquid is supplied to the liquid ejection head, not only reservoirs but also the liquid storage chamber is filled with liquid. Liquid in the liquid storage chamber is in contact with the nozzle layer. Thus, heat generated by the heating elements in the head chip is transmitted to the nozzle layer by way of the liquid in the liquid storage chamber.
In the liquid ejection head and the liquid ejection apparatus of the present invention, the operational temperature of the head chip is lower than that of the known head. Accordingly, nucleate boiling hardly occurs, that is, bubbles are hardly any generated, thereby suppressing temperature increase. Furthermore, the frequency for ink ejection is increased and thus the ejection/refill cycle is accelerated, thereby realizing high-speed printing.
When the liquid ejection head constitutes the line head, the temperatures of all head chips in the line head are approximately the same. Accordingly, variation in amount of ejected liquid due to temperature change is reduced, thereby suppressing unevenness of ink density in printing.
Embodiments according to the present invention will now be described by referring to the accompanying drawings.
Referring to
According to the head chip 1a of a known type, the barrier layer 3 accounts for most of the top surface of the semiconductor substrate 11 except the regions where the reservoirs 3a, the individual flow paths 3d, and a connecting electrode region (not shown) are disposed. That is, the reservoirs 3a and the individual flow paths 3d account for only about less than 10% of the top surface of the semiconductor substrate 11 in the head chip 1a of a known type.
By contrast, according to the head chip 10a of the first embodiment, the barrier layer 13 has a portion having a comb-shape (comb-shaped portion). The reservoirs 13a and the individual flow paths 3d are disposed in the spaces defined by the comb-shaped portion. An area connected to the comb-shaped portion is a liquid storage chamber 13b including a great number of columns 13c. These columns 13c connect the barrier layer 13 to the nozzle sheet 17 when the barrier layer 13 is bonded to the nozzle sheet 17. Since all the columns 13c have the same height, the heights of all the reservoirs 13a are identical.
The heights of the columns 13c are the same as the height of the comb-shaped portion defining the reservoirs 13a and the individual flow paths 13d. Each column 13c is substantially rectangular in plan view, for example, measuring 20 μm×30 μm. The columns 13c can be disposed in any arrangement at any pitch.
The barrier layer 13 has three walls on the semiconductor substrate 11. These walls are disposed in the three sides of the semiconductor substrate 11 except the side where the comb-shaped portion is disposed. A connecting-electrode region 19 is disposed on one of the walls. The liquid storage chamber 13b is enclosed by the walls and the comb-shaped portion of the barrier layer 13.
The liquid storage chamber 13b has openings on the side close to a common flow path so as to communicate with the common flow path. The common flow path of the first embodiment is identical to the common flow path 23 of the head chip 1a of a known type and supplies liquid to the reservoirs 13a. The openings in the liquid storage chamber 13b are disposed in the right front side in
Referring to
As described above, the comb-shaped portion of the barrier layer 13 defines the reservoirs 13a and the individual flow paths 13d. The reservoirs 13a are disposed between the heating elements 12 and the respective nozzles 18. The individual flow paths 13d communicate with the reservoirs 13a and supply liquid to the reservoirs 13a. The liquid storage chamber 13b for storing liquid is disposed on the area of the surface of the semiconductor substrate 11 except the regions including the reservoirs 13a and the individual flow paths 13d. The liquid storage chamber 13b is defined by part of the barrier layer 13. The liquid storage chamber 13b communicates with the reservoirs 13a.
Ink supplied from, e.g., an ink tank first flows into the common flow path and then passes through the individual flow paths 13d to fill the reservoirs 13a. Concurrently, ink from the common flow path enters the liquid storage chamber 13b communicating with the common flow path to fill the liquid storage chamber 13b.
Prior to the entrance of ink, the liquid storage chamber 13b is filled with air. Therefore, when ink enters the liquid storage chamber 13b, air in the liquid storage chamber 13b is discharged outside through the exhaust holes 17a. Accordingly, the liquid storage chamber 13b is filled with ink, containing no air.
When the liquid storage chamber 13b is filled with ink, ink comes in contact with the exits of the exhaust holes 17a, that is, the surface of the nozzle sheet 17. If the exhaust holes 17a have the same areas as those of the nozzles 18, surface tension on the orifice planes in the exhaust holes 17a and the nozzles 18 is identical. Thus, the nozzles 18 and the exhaust holes 17a, which are only exits for ink, are influenced by the pressure applied to ink. However, according to the first embodiment, since the areas of the exhaust holes 17a are smaller than those of the nozzles 18, ink does not leak through the exhaust holes 17a when pressure is applied to ink.
Therefore, even though environments of the head chip 10a change such as during transport, the exhaust holes 17a do not require special care but can be treated as part of the nozzles 18.
When the head 10 is operated, that is, ink supplied to the reservoirs 13a is ejected as droplets, ink from the common flow path passes through the individual flow paths 13d to fill the reservoirs 13a. At this time, hardly any ink moves in the liquid storage chamber 13b.
The bottom surface of the nozzle sheet 17 is bonded to the top surfaces of the columns 13c. Ink in the liquid storage chamber 13b is in contact with the bottom surface of the nozzle sheet 17 except the portions bonded to the top surfaces of the columns 13c.
According to the head chip 1a of a known type, most of heat generated by the heating elements 12 is transmitted to the nozzle sheet 17 through the barrier layer 3. Since the barrier layer 3 is composed of a photosensitive resist rubber or a dry film resist to be hardened by exposure and thus has low thermal conductivity, the barrier layer 3 does not well transmit the heat generated by the heating elements 12. Accordingly, heat generated by the heating elements 12 is not sufficiently dissipated from the nozzle sheet 17.
By contrast, according to the head 10 of the first embodiment, heat generated by the heating elements 12 is transmitted to ink in the liquid storage chamber 13b. Since ink in the liquid storage chamber 13b is in contact with the bottom surface of the nozzle sheet 17, heat generated by the heating elements 12 is readily transmitted to the nozzle sheet 17 through the ink in the liquid storage chamber 13b. Accordingly, the heat can be dissipated from the top surface of the nozzle sheet 17, whereby heat is well dissipated in the head chip 10a.
In this context, the liquid storage chamber 13b can also be referred to as a heat-storage liquid layer/chamber or thermal condenser layer/chamber. The heat capacity in the head chip 10a of the first embodiment is constant. Accordingly, as the amount of heat dissipation is increased in the head chip 10a, the temperature of the head chip 10a is decreased.
According to the head 1 of a known type, heat generated by the heating element 12 is transmitted through a region including an area above the reservoir 3a and an area disposed on the left side of the area above the reservoir 3a. This region is designated by XX in
More specifically, according to the first embodiment, ink having a large specific heat capacity is disposed between the head chip 10a including the heating elements 12 and the nozzle sheet 17. The temperature of the head chip 10a does not increase sharply. Moreover, ink having higher thermal conductivity than the barrier layer 13 can transmit heat to the nozzle sheet 17. Therefore, heat is immediately transmitted to the nozzle sheet 17, and the heat radiates from the nozzle sheet 17 to cool down the head 10.
The nozzle sheet 17 can be composed of various kinds of materials. When the nozzle sheet 17 is composed of metal or a material chiefly made of metal, heat is effectively dissipated. Furthermore, the head 10 may include a plurality of the head chips 10a. For example, the head 10 is used as a color printer head including the head chips 10a for respective colors, or as a line head for a line printer including a plurality of the head chips 10a disposed along the common flow path. In this structure also, the head 10 is preferably provided with a single nozzle sheet 17 including the nozzles 18 for all the head chips 10a. In this way, the temperature of the head 10 is maintained constant at all times.
When the head chips 10a are used in the line head, an amount of ejected ink-drops, namely, the amount how much the head chip 10a is operated differs depending on the head chips 10a. Therefore, some head chips 10a radiate a lot of heat, while some radiate hardly any heat. Since the semiconductor substrate 11 in the head chips 10a composed of, e.g., silicon has excellent thermal conductivity, all the head chips 10a have substantially the same temperature. If the semiconductor substrate 11 cannot effectively radiate heat, it readily heats up.
However, by sharing a single nozzle sheet 17 among all the head chips 10a, the head chips 10a can have substantially the same temperature. Since ink contained in the liquid storage chambers 13b for all the head chips 10a provides large thermal capacity and a large area for dissipating heat, the temperatures of the head chips 10a increase gradually, thereby suppressing increase in the temperatures of the head chips 10a. Hence, this suppresses bubbling of ink in the head chips 10a, particularly, between the individual flow paths 13d and the reservoirs 13a.
The nozzle sheet 17 in
The head 10 and the liquid ejection apparatus including the head 10 such as an inkjet printer according to the first embodiment have the following advantages.
(1) When a distance Yn from the center of the heating element 12 to the left side surface of the head chip 10a in contact with the common flow path is large, nucleate boiling utilizing bubble nuclei in irregularities on the left side surface of the head chip 10a is prevented, that is, bubbles are not generated. Furthermore, with the aforementioned structure of the first embodiment, the operational temperature of the head chips 10a can be lower than that of the head chips 1a of a known type under the same conditions. Therefore, in order to maintain the same temperature as that of the head chips 1a of a known type, the distance Yn of the head chip 10a can be made smaller than the distance Yn of the head chip 1a of a known type.
(2) Even when the distance Yn is not made small in the head chip 10a, the operational temperature of the head chip 10a having the aforementioned structure can be reduced and thus nucleate boiling hardly ever occurs. That is, the head chip 10a of the first embodiment has a tolerance to a temperature increase.
(3) According to the first embodiment of the present invention, since a chance for nucleate boiling to occur on the left side surface of the head chip 10a is decreased, frequency for ink ejection can be increased. Therefore, the cycle of ejection and refill can be shortened and thus the head chip 10a can realize high-speed printing.
(4) When the head 10 is used as a line head including lines of the head chips 10a, the operational temperatures of all the head chips 10a are maintained substantially the same in the head 10. Accordingly, variations in the amount of ejected ink due to a temperature change become small and thus unevenness of ink density in printing is suppressed.
Accordingly, the distance between the centers of the adjacent nozzles 18 is greater than the pitch at which the heating elements 12 (nozzles 18) are arranged. Ink in the nozzles 18 and in the vicinity of the nozzles 18 is hardly influenced by the pressure change due to ejection of ink drops and thus an amount of ejected ink-drops and a direction of ejection can be stabilized. This technique has already been proposed by this assignee in Japanese Unexamined Patent Application Publication No. 2003-383232.
Barrier layers 13 having substantially rectangular shapes in plan view are disposed on both sides of the heating elements 12 in the direction along which the heating elements 12 are disposed. Individual flow paths 13d are disposed between the barrier layers 13 on both sides of the heating elements 12 in the direction orthogonal to the direction along which the heating elements 12 are disposed, namely, on the common flow path side and the side opposite from the common flow path side. The individual flow paths 13d disposed close to the liquid storage chamber 13b communicate with the liquid storage chamber 13b.
According to the second embodiment, although the individual flow paths 13d directly connect the reservoirs 13a to the liquid storage chamber 13b, ink does substantially not flow in the liquid storage chamber 13b except in the vicinity of the reservoirs 13a.
Examples of the present invention will now be described. A head 1 of a known type including the head chip 1a and heads 10 according to Examples 1 and 2 including the head chips 10b of the second embodiment, shown in
The length of the region filled with ink in the head chip 10b according to the example was approximately three times that of the head chip 1a. In the head chip 1a and the head chip 10b, the barrier layer 3 and the barrier layer 13 were bonded to the nozzle sheets 17 over a large contact area in the vicinity of the nozzles 18 such that the barrier layer 3 and the barrier layer 13 were not separated from the nozzle sheets 17 by pressure applied for ink ejection. Thus, the areas of the nozzle sheets 17 in contact with ink in the vicinity of the nozzles 18 were relatively small in both the head chip 1a and the head chip 10b. Consequently, the area in the nozzle sheet 17 in contact with ink in the head chip 10b was substantially four or five times that of the head chip 1a.
To compare temperature increase in the head 1 and the head 10, the following method can be employed. The head chip 1a and the head chip 10b are operated for the same period of time (the same number of print sheet), i.e., 20 sheets of A4 size paper to print the same material, i.e., a monochrome dot pattern with a printing rate of 20%, and temperature increase in both heads is measured. However, the heads are provided with no means for measuring the temperatures of the interiors thereof. Therefore, first of all, bubbling was compared in the head 1 and the head 10.
To observe the interiors of the heads, transparent nozzle sheets 17 composed of a polymeric material (polyimide) having a thickness of 25 μm were used in experiments, instead of nozzle sheets formed with nickel by electroforming.
Normally, these bubbles are relatively stabilized and thus will disappear when temperatures around the bubbles decrease. However, with the head 1 of a known type, some of the bubbles were united with other bubbles generated at a later time, and it took several hours for all the bubbles to disappear.
By contrast, referring to
When a lot of bubbles are generated, the exhaust holes 17a can effectively reduce bubbles. As can be understood from
As described above, it is difficult to accurately measure the temperatures of the interiors of the head chips 1a and 10b. The head chips 1a and 10b were, however, provided with the connecting-electrode regions 19 (e.g., 14 electrodes). The electrodes were connected to outside components through metal bonding wires. That is, bonding terminals were directly connected to the head chips 1a and 10a. The temperatures of the vicinities of the bonding terminals were proximate to those of the interiors of the head chips 1a and 10a. Therefore, the temperatures of the surfaces of the bonding terminals were measured.
Referring to
Next, cooling effects of the head 1 and the head 10 were compared using equivalent circuits. The states of the heads can be represented by simple electric circuits by replacing the heating element 12 with a power supply, the thermal resistance (thermal conductivity) with electrical resistance, thermal capacitance for each component with a capacitor, and the temperature of a point of interest with a voltage. In an equivalent circuit in
Considering a transient state where the overall temperature of the head is not stabilized, thermal capacity needs to be taken into consideration and thus the equivalent circuit becomes complex, as shown in
Using the observed temperatures shown in
R1/(R2+R3)=(350−62.5)/(62.5−25)=287.5/37.5. Equation 1
The only difference in the head 1 and the head 10 was the structure of the barrier layers 3 and 13, and the rest of the structures including the head chip 1a and the head chip 10b were the same. Therefore, in the head 10, R1 was the same as that of the known head. The temperature change at the point P2 was caused by the change in R2 and R3. Therefore, as described above, R2 and R3 in Equation 1 were replaced with R2′ and R3′ in Equation 2 for the head 10. The ratio R1/(R2′+R3′) was calculated from Equation 2:
R1/(R2′+R3′)=(350−57.7)/(57.7−25)=292.3/32.7. Equation 2
From Equations 1 and 2, the ratio (R2′+R3′)/(R2+R3) was calculated by the following Equation 3:
(R2′+R3′)/(R2+R3)≈0.86 Equation 3
The temperature on the surface of the nozzle sheet 17 of the head 1 was the same as that of the head 10. The ratios R2/R3 and R2′/R3′ were calculated by the following Equation 4 and Equation 5:
R2/R3=(62.5−32.4)/(32.4−25)=4.07 Equation 4
R2′/R3′=(57.7−32.4)/(32.4−25)=3.42 Equation 5
Substitution of R2=4.07×R3 from Equation 4 and R2′=3.42×R3′ from Equation 5 into Equation 3 yielded (1+3.42)R3′/(1+4.07)R3=0.86. From this, the ratio R3′/R3 was calculated by the following Equation 6:
R3′/R3=0.99 Equation 6
Similarly, by substituting R3=R2/4.07 from Equation 4 and R3′=R2′/3.42 from Equation 5 into Equation 3, the ratio R2′/R2 was calculated by the following Equation 7:
R2′/R2=0.83. Equation 7
The results of Equations 6 and 7 confirmed that the head 1 and the head 10 equally dissipated heat from the nozzle sheet 17, but the efficiency to transmit heat to the nozzle sheet 17 in the head 10 was improved by about 17% as compared to the head 1.
Even though the region filled with ink in the head 10 had an area several times larger than that of the head 1, the efficiency to transmit heat to the nozzle sheet 17 was improved only by about 17%. This may be caused by the fact that when ink was supplied, hardly any ink moved in the liquid storage chamber 13b, whereas a fairly large amount of ink moved in the heating elements 12 in the heads 1 and 10.
Number | Date | Country | Kind |
---|---|---|---|
2004-014183 | Jan 2004 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
4835553 | Torpey et al. | May 1989 | A |
5847737 | Kaufman et al. | Dec 1998 | A |
6045214 | Murthy et al. | Apr 2000 | A |
6053599 | Maeda | Apr 2000 | A |
6074050 | Perez et al. | Jun 2000 | A |
6139761 | Ohkuma | Oct 2000 | A |
6283584 | Powers et al. | Sep 2001 | B1 |
6312112 | Pietrzyk | Nov 2001 | B1 |
6409318 | Clark | Jun 2002 | B1 |
6450625 | Fujii et al. | Sep 2002 | B1 |
6485128 | Elshaik et al. | Nov 2002 | B1 |
6540337 | Pollard | Apr 2003 | B1 |
6561632 | Feinn et al. | May 2003 | B2 |
6834944 | Wang et al. | Dec 2004 | B2 |
6922203 | Giere et al. | Jul 2005 | B2 |
20020101479 | Giere et al. | Aug 2002 | A1 |
20020163563 | Blair | Nov 2002 | A1 |
20030048333 | Rapp et al. | Mar 2003 | A1 |
20030058307 | Eguchi et al. | Mar 2003 | A1 |
20030137561 | Conta et al. | Jul 2003 | A1 |
20030156162 | Hirota et al. | Aug 2003 | A1 |
20040109044 | Conta et al. | Jun 2004 | A1 |
20050200662 | Eguchi et al. | Sep 2005 | A1 |
Number | Date | Country |
---|---|---|
0627318 | Dec 1994 | EP |
59-138461 | Aug 1984 | JP |
63-183855 | Jul 1988 | JP |
09-011479 | Jan 1997 | JP |
2003-080711 | Mar 2003 | JP |
2003-136737 | May 2003 | JP |
Number | Date | Country | |
---|---|---|---|
20050179734 A1 | Aug 2005 | US |