Recording head and recording apparatus

A recording head has a channel forming member and an element substrate. A discharge port through which liquid is discharged is formed in the channel forming member. An energy generating element for discharging the liquid is formed in the substrate. A gap forming member is arranged above the channel forming member. A moisture retention liquid retention portion which retains moisture in the vicinity of the discharge port is formed between the gap forming member and the channel forming member so as to be opened toward the discharge port side. Even if the state in which the liquid is not discharged continues, the liquid in the discharge port can be prevented from drying with the recording head having the above configuration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording head and recording apparatus performing recording in a recording medium by discharging liquid, particularly to the recording head and recording apparatus having a structure in which clogging of a discharge port is prevented by keeping a periphery of the discharge port moist.

2. Related Background Art

In a liquid discharge recording head and a liquid discharge recording apparatus on which the liquid discharge recording head is mounted (hereinafter simply referred to as “recording head” and “recording apparatus” respectively), there are various problems caused by ink (liquid) drying.

For example, when a period during which the ink is not discharged becomes longer, moisture in the ink evaporates through the discharge port, which sometimes results in an increase in viscosity of the ink in the discharge port or formation of a solid-state-like film on a surface of a meniscus in the discharge port. Thus, when the increase in viscosity of the ink or the formation of the film occurs, flow resistance of the ink is increased. Therefore, in discharge action, there are problems that discharge speed is decreased and an ink discharge direction is inclined from a predetermined direction by the influence of the solid-state-like film.

Sometimes the problem in the discharge action, which is caused by the ink drying because the ink is not discharged for a long time, is called “first discharge problem.” Particularly the problem becomes easily prominent in the current recording head in which the discharge port and an ink droplet are miniaturized in order to improve image quality.

Conventionally, countermeasures are taken against the problem by forming a configuration shown inFIGS. 5A,5B,6A, and6B.FIG. 5Ais a top view showing the conventional recording head, andFIG. 5Bis a sectional view taken along a line VB ofFIG. 5A.

The recording head, in which a region where a hydrophilic process is performed to a discharge port surface is formed, is disclosed in Japanese Patent Application Laid-Open No. 2002-331678 like a recording head150ofFIG. 5B. In the recording head150ofFIG. 5B, a hydrophilic process portion115in which the hydrophilic process is performed is partially formed in the surface (discharge port surface) of a channel forming member provided as an orifice plate. As shown in the top view ofFIG. 5A, the hydrophilic process portions115are arranged so as to be located on both sides of a discharge port row formed by plural discharge ports107.

When the recording head150having the above configuration is used by mounting the recording head150on the well-known recording apparatus including a suction recovery mechanism of the recording head, in performing suction recovery action, the ink remains while kept in the hydrophilic process portion115. Then, the liquid (ink)114kept in the hydrophilic process portion115gradually evaporates, which allows high humidity to be maintained near the discharge port107. Accordingly, the ink evaporation from the discharge port107is suppressed, and the period can be lengthened until the problem of the discharge action occurs. Namely, the period can be lengthened until the first discharge problem (also referred to as “first discharge time”) occurs.

Then, a recording head250ofFIG. 6Bwill be described.FIG. 6Ais a top view showing the recording head, andFIG. 6Bis a sectional view taken along a line VIB ofFIG. 6A.

In the recording head250, liquid keeping grooves205aare formed near a discharge port207such that a channel forming member205is bored. The liquid keeping groove205ais opened toward the upper surface side. Moisture retention liquid such as the ink is kept in the liquid keeping groove205awhile being in the liquid state. The humidity is kept high near the discharge port207by the evaporation of the moisture retention liquid.

However, in the configuration shown inFIGS. 5A and 5B, the problems are generated as described below.

(1) Because an area of the hydrophilic process portion115is larger when compared with an amount of liquid kept in the hydrophilic process portion115, evaporation speed of the kept liquid is fast. Therefore, it is difficult that the high humidity is kept for a long time in a periphery of the discharge port.

(2) When the surface of the channel forming member105is wiped with a wiping member, the liquid kept in the hydrophilic process portion115is also wiped. Therefore, the effect by the hydrophilic process portion115is not obtained.

With reference to the problem (1), the improvement can be achieved somewhat by increasing the area of the hydrophilic process portion115. However, the recording head is enlarged, and a degree of improvement effect is not so large.

Further, in the configuration shown inFIGS. 6A and 6B, the problem is generated as described below.

(3) The liquid keeping grooves205aare formed such that the channel forming member205is bored. Accordingly, a depth of the liquid keeping groove205ais limited to a thickness of the channel forming member205. As a result, the amount of liquid kept in the liquid keeping groove205acannot be increased to a sufficient extent. This means that the period is short until the liquid in the liquid keeping groove205aevaporates completely. Consequently, it is difficult that the high humidity is kept for a long time in the periphery of the discharge port.

On the other hand, the number of liquid keeping grooves205ais increased and the opening of one liquid keeping groove205ais widened, which results in the sight improvement of the problem. However, there is a possibility that the improvement leads to the problem of the enlargement of the recording head. Further, even if the number of grooves is increased or the opening is widened, because the opening is separated away from the periphery of the discharge port, it is not expected that the improvement effect is sufficient.

SUMMARY OF THE INVENTION

An object of the invention is to provide a recording head and a recording apparatus which can prevent the drying of the liquid in the discharge port for a long time even if the liquid discharge continues.

In order to achieve the object, a recording head according to the invention includes an energy generating element which generates energy utilized in order to discharge liquid; a flow path (channel) forming member which has a discharge port surface, a discharge port which discharges the liquid is provided in the discharge port surface, the channel forming member being communicated with the discharge port; and a gap forming member which faces the discharge port surface, the gap forming member being arranged such that a gap is provided between the discharge port surface and the gap forming member except for a position corresponding to the discharge port, wherein the gap is communicated with an opening portion which is opened toward a direction of the discharge port, and moisture retention liquid is supplied to the gap.

According to the recording head of the invention, the moisture retention liquid is kept near the discharge port by the capillary attraction, and the moisture retention liquid becomes an evaporation source near the discharge port. Namely, the humidity near the discharge port can preferably be kept with a very simple configuration without providing the particular apparatus such as an evaporation apparatus. The drying of the liquid in the discharge port can be prevented for a long time by keeping the humidity near the discharge port in the preferable state. Further, according to the recording apparatus of the invention in which the recording head of the invention is used, the generation of the problem can be suppressed at the minimum in the discharge action, when the liquid discharge resumes after the state in which the liquid is not discharged continues.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the invention will be described below with reference to the accompanying drawings.

In the specification, “recording” should widely be interpreted rather than the formation of significant information such as characters and graphics. Particularly, there is no need for either significance or insignificance, or there is no need for whether visualization is performed such that a human can visually recognize or not, “recording” should widely mean the formation of an image, a design, a pattern, and the like on the recording medium or processing of the medium.

“Recording medium” should mean not only paper used in the general recording apparatus, but also materials, such as cloth, a plastic film, a metal plate, glass, ceramics, wood, and leather, which can receive the ink.

“Ink” or “liquid” should widely be interpreted as with the definition of the above “recording.” Particularly, “ink” or “liquid” are used for the formation of the image, the design, the pattern, and the like or the processing of the recording medium by giving “ink” or “liquid” on the recording medium. Specifically, “ink” or “liquid” should mean the printing ink of the characters and the image, a material used for the formation of a wiring pattern, and the liquid which can be provided for the ink process (for example, solidification or insolubilization of a colorant in the ink given to the recording medium).

First Embodiment

FIG. 8is a perspective view showing a schematic configuration of a liquid discharge recording apparatus to which a recording head according to the invention is applicable. Referring toFIG. 8, a recording head38which discharges the liquid such as the ink is mounted on a main scanning carriage36while positioned. The main scanning carriage36is guided and supported while being reciprocally movable along a main scanning rail37. The main scanning carriage36is reciprocally driven in a main scanning direction (direction of the main scanning rail37) by a drive source (not shown).

A recording sheet30such as recording paper is delivered into an apparatus main body by a sheet-feed roller31, and the recording sheet30is sandwiched between a pinch roller (not shown) and a sheet pressing plate33on a sheet-conveying roller (conveying roller)32. The recording sheet is conveyed through a position (recording position) which is separated from a front surface (in this case, a head surface provided in the bottom surface of the recording means) of recording means (recording head) constituted by a head38at a predetermined interval by controlling rotation of the sheet-conveying roller32. The image including the characters is recorded (printed) by driving a recording head1based on recording information. A home position HP of the main scanning carriage36is set at a position (right end portion ofFIG. 8) which is located outside a recording area. The position is also located within the moving range of the main scanning carriage36.

Capping means provided with a cap made of an elastic rubber material is arranged near the home position HP. The capping means can seal the discharge port while abutting on (coming into close contact with) the head surface (surface in which the discharge port is formed) of the recording head38. Suction means including a suction pump is also arranged. In the capping condition, the suction pump can generate negative pressure suction force in the discharge port through the cap. Further, a recording head recovery device35including cleaning means is arranged. The cleaning means includes a cleaning member which slides closely on the head surface of the recording head38to wipe deposits such as the ink and dust. The recording head recovery device35generates negative pressure in the cap with the suction pump while the discharge port portion of the recording head38is capped. The negative pressure sucks foreign matters such as viscosity-increased ink, bubble, sticking ink, and the dust along with the ink by the negative pressure to evacuate and remove the foreign matters from the discharge port. Therefore, recovery action which recovers ink discharge performance of the recording head38can be achieved.

FIGS. 1A and 1Bshow a configuration of a recording head according to a first embodiment of the invention,FIG. 1Ais a top view showing the recording head, andFIG. 1Bis a sectional view taken along a line IB ofFIG. 1A. The line IB is one which perpendicularly intersects both the discharge port surface and an opening portion while passing through the center of the discharge port.

A recording head50shown inFIG. 1Bhas the generally known configuration of such a kind of the recording head, except that a gap forming member12is arranged above channel forming member5(liquid discharge direction). In the recording head50, the channel forming member5is arranged as an orifice plate on an element substrate1in which a heater2is formed, and a flow path (ink channel)6is formed between the element substrate1and the channel forming member5. A heater2is formed in the ink channel6. The heater2generates the bubble by giving the thermal energy to the liquid such as the ink, which discharges the ink. A part of the ink channel6, where the heater2is formed, functions as a pressure chamber. In the surface (discharge port surface) of the channel forming member5, a discharge port7is formed at a position corresponding to the heater2. As shown inFIG. 1A, the plural discharge ports7are formed in line at predetermined intervals. Namely, one discharge port row is formed by the plural discharge ports7. Although the one discharge port row is formed in the first embodiment, the invention can also be applied to the recording head in which at least two discharge port rows are formed.

Then, the gap forming member12and its peripheral structure will be described.

One gap forming member12is formed by a flat plate member, and the gap forming member12is arranged on each of the both sides of the discharge port row. As shown inFIG. 1A, a discharge port side-end portion12aof the gap forming member12is parallel to the discharge port row while separated from the discharge port row by a predetermined distance. In the first embodiment, the peripheral structure of the gap forming member12has a symmetrical shape with respect to the discharge port row. As shown inFIG. 1B, the gap forming member12is arranged while separated from the discharge port surface (upper surface) by a constant interval (gap).

Thus, the arrangement of the gap forming member12makes a moisture retention liquid retention portion8between the gap forming member12and the channel forming member5. The moisture retention liquid keeping portion8, which is formed as a flattened gap portion, keeps moisture retention liquid. The moisture retention liquid keeping portion8has an opening portion8awhich is opened toward the discharge port7side, and the opening portion8ais formed in parallel with the discharge port row. More specifically, however only a part of the opening portion8ais shown inFIG. 1A, the opening portion8ais formed in the long shape in the range in which the opening portion8ais opened for all the discharge ports7formed. Therefore, the moisture retention can substantially evenly be performed for the periphery of the discharge port7.

Although a structure which supports the gap forming member12is not shown inFIG. 1A and 1B, for example, it is possible that an end portion of the gap forming member12, which is located on the side opposite from the discharge port7, is supported by a support member (not shown). Alternatively, it is possible that the gap forming member12is supported by providing a rib or a boss between the gap forming member12and the channel forming member5. Therefore, the gap forming member12is supported more stably, and mechanical strength is also improved. When the structural stability of the gap forming member12is improved by providing the rib or the boss, it is desirable that the provision of the rib or the boss decreases a volume of the moisture retention liquid keeping portion8too much.

As shown inFIG. 1B, during the use of the recording head50, the moisture retention liquid is kept in the moisture retention liquid keeping portion8. Any kind of the liquid can be used as the moisture retention liquid as long as the liquid can moisturize the periphery of the discharge port7by evaporation. For example, the same liquid as the discharged liquid can be used as the moisture retention liquid, and the ink, water, or the ink in which dye is removed can also be used.

Then, the dimension of each portion in the recording head which is applicable to the invention will be described.

As shown inFIG. 9, it is assumed that a height (distance between the discharge port surface and the gap forming member) of the moisture retention liquid keeping portion is set at h, a diameter of the discharge port is set at φ, and an interval between the moisture retention liquid keeping portions which are provided on both sides across the discharge port is set at W.

Because an amount of evaporation depends on an area of a liquid surface, it is required that an opening area of the discharge port is not more than an opening area of the opening portion8aof the moisture retention liquid keeping portion. In order to further enhance the moisture retention effect, it is preferable that “the diameter φ of the discharge port is not more than the height h of the moisture retention liquid keeping portion”. The diameter φ of the discharge port is set by a size of the liquid to be discharged. When a discharged droplet is about 0.5 pl, the diameter φ becomes about 6 μm. When the discharged droplet is about 2 pl, the diameter φ is in the range from about 10.5 μm to about 12 μm. When the discharged droplet is about 5 pl, the diameter φ becomes about 16 μm.

It is also possible that a production process is simplified by causing the height h of the moisture retention liquid keeping portion to coincide with a height H of the ink channel6. Generally the height H of the ink channel ranges from about 10 μm to about 20 μm.

Then, the interval W between the moisture retention liquid keeping portions arranged on the both sides across the discharge port will be described.

When the interval W becomes larger, the opening portion8ahaving the moisture retention liquid is separated away from the discharge port, which decreases the moisture retention effect. When the ratio of moisture in atmosphere in proximity of discharge port which moisture is derived from that the moisture retention liquid evaporates and diffuses is substantially equal to the ratio of moisture in atmosphere in proximity of the discharge port which moisture is evaporated from the discharge port in case where the moisture retention liquid is not present. For example, assuming that the diameter φ of the discharge port is 6 μm and the height h of the moisture retention liquid keeping portion is 1000 μm, the moisture retention effect with a degree to which the discharge failure is improved can be obtained when the interval W is not more than 300 μm. When the interval W is not more than 100 μm, the evaporation can ideally be suppressed. Because generally the discharge failure caused by the drying becomes prominent as the diameter of the discharge port is decreased, it is preferable that the moisture retention liquid keeping portion corresponding to the small discharge port is located near the discharge port.

When the interval W is too narrowed, as shown inFIG. 10A, there is a possibility that the moisture retention liquid and the discharge liquid are coupled to each other. It is also related with tank pressure (the negative pressure) under which the discharge liquid is kept. Therefore, as shown inFIG. 10B, the configuration of the recording head in which the moisture retention liquid and the discharge liquid are not coupled to each other will be described.

FIG. 11is an enlarged view showing the moisture retention liquid keeping portion and the periphery of the discharge port.

It is assumed that an end portion of the surface (surface facing the recording medium) of the gap forming member12is E and an end portion of the discharge port formed in a discharge port surface D of the channel forming member5is F. Due to the sectional view, the end portions E and F are shown as a point respectively. It is assumed that a circle having a radius R0 which passes through the points E and F is C and a distance between the discharge port surface D and the surface of the gap forming member12is L. The distance L is one in which a thickness of the gap forming member is added to the height h of the moisture retention liquid keeping portion.

It is assumed that a circle which passes through the point E and indicates the liquid level is M and a radius of the circle M is Rm. In case where the negative pressure in the tank is low, when ink in the nozzle is suctioned, the liquid level is separated from the point F, which allows the moisture retention liquid and the ink to be coupled to each other. At this point, the radius Rm of the circle M is larger than the radius of the circle C. On the other hand, when a negative pressure in the tank is high, the radius Rm of the circle M becomes small to be close to the radius of circle C. Further, when the negative pressure in the tank becomes higher, the radius Rm of circle M becomes smaller than the radius of circle C. At this time, the shape shown inFIG. 10Bcan be held while the moisture retention liquid surface and the ink liquid level are not coupled to each other.

Thus, the following expression (1) can be obtained:
Rm<R0  (1)

Pressure P which is of the pressure (a force exerted from ink), derived from the negative pressure in the tank, applied to the meniscus shown by the above-mentioned circle M is obtained by the following expression (2):
P=(γ/Rm)  (2)
where γ is surface tension of the liquid such as the discharged ink.

The following expression (3) is obtained from the expressions (1) and (2):
(γ/P)<R0  (3)
where R0 is determined by the diameter φ of the discharge port, the interval W of the moisture retention liquid keeping portions arranged on the both sides across the discharge port, and the distance L in which the thickness of the gap forming member is added to the height h of the moisture retention liquid keeping portion as shown inFIG. 11. Accordingly, as shown inFIG. 10B, the moisture retention liquid and the liquid such as the discharged ink can be held while being not coupled to each other by using the recording head, the ink, and the tank having the configurations of the diameter φ, the interval W, and the distance L which satisfy the expression (3).

According to the recording head having the above configuration, the moisture retention liquid keeping portion which keeps the moisture retention liquid for moisturizing the periphery of the discharge port is formed as the gap portion between the gap forming member arranged above the discharge port surface and the discharge port surface. The appropriate change in dimension of the gap forming member can form the moisture retention liquid keeping portion which can keep a large amount of moisture retention liquid. Accordingly, the advantage that the large amount of moisture retention liquid can be kept in the moisture retention liquid keeping portion enables the moisture retention in the periphery of the discharge port for a long time.

Methods of supplying the moisture retention liquid to the moisture retention liquid keeping portion8will be described below.

(1) Method with Suction Recovery Mechanism of Recording Apparatus

When the recording apparatus includes a suction recovery mechanism11as shown inFIG. 4A, the ink can be kept as the moisture retention liquid in the moisture retention liquid keeping portion8of the recording head50by utilizing the suction recovery mechanism11. With reference to the action of the suction recovery mechanism11, a cap11aof the suction recovery mechanism11is caused to abut on the surface side of the recording head50. Particularly, the cap11aabuts on the surface (surface facing the recording medium) of the gap forming member12in the recording head50, and the cap11ais formed such that at least a region where the discharge port7is formed and the opening portion8aof the moisture retention liquid keeping portion8are covered therewith in the recording head50. The ink is forcedly sucked from the discharge port7by driving the pump of the suction recovery mechanism11. The pump is connected to the cap11a. In the recovery action, the ink overflowing from the discharge port7is kept within a space formed between the gap forming member12and the cap11a. Therefore, the overflowing ink is drawn into the moisture retention liquid keeping portion8by capillary attraction, which allows the ink to be kept as the moisture retention liquid in the moisture retention liquid keeping portion8.

(2) Method with Moisture Retention Liquid Supplying Mechanism Provided in Recording Apparatus

As shown inFIG. 4B, a moisture retention liquid supply mechanism10is newly provided in the recording apparatus, and the moisture retention liquid is supplied into the moisture retention liquid keeping portion8by the moisture retention liquid supply mechanism10.

An example of the moisture retention liquid supply mechanism can be cited as follows. Namely, the moisture retention liquid supply mechanism includes a reserve vessel in which the moisture retention liquid containing the ink in which the water and the dye are removed is stored, a passage member (for example, a pipe member10asuch as a tube) which transports the moisture retention liquid in the reserve vessel to the moisture retention liquid keeping portion8, and a pump provided in the midstream of the passage member. In this case, in the configuration shown inFIGS. 1A and 1B, it is possible that a connection portion is formed in the end portion on the side opposite from the discharge port7of the moisture retention liquid keeping portion8and the passage member is connected to the connection portion. It is also possible that a sensor which detects the amount of moisture retention liquid remaining in the moisture retention liquid keeping portion8is provided and utilized.

The moisture retention liquid supply mechanism having the above configuration is driven at predetermined timing in which the amount of moisture retention liquid remaining is low in the moisture retention liquid keeping portion8. Namely, the moisture retention liquid in the reserve vessel is supplied into the moisture retention liquid keeping portion8through the passage member by driving the pump of the moisture retention liquid supply mechanism10.

Since the suction recovery mechanism incorporated in the recording apparatus is used in the method (1), the method (1) has the advantage in that the particular supply mechanism is not required unlike the method (2). Since the moisture retention liquid in the reserve vessel is supplied in the method (2), the method (2) has the advantage in that various kinds of the moisture retention liquid suitable for the moisture retention can be used in addition to the ink.

As described above, according to the recording head50of the fist embodiment, the moisture retention liquid keeping portion8is formed between the gap forming member12and the surface (discharge port surface) of the channel forming member5. Since the volume of the moisture retention liquid keeping portion8becomes larger for example when compared with the conventional configuration shown inFIGS. 6A and 6B, the larger amount of moisture retention liquid can be kept in the moisture retention liquid keeping portion8, which allows the moisture retention to be performed in the periphery of the discharge port7for longer time. The moisture retention liquid keeping portion8is formed in the flat shape, and the moisture retention liquid is stably kept by the capillary attraction between the gap forming member12and the channel forming member5. The opening portion8aof the moisture retention liquid keeping portion8is opened in the horizontal direction (direction parallel to the discharge port surface) while faced toward the discharge port7side. As a result, when compared with the conventional configuration in which the liquid keeping groove is opened toward the direction (upward direction) perpendicular to the discharge port surface as shown inFIGS. 6A and 6B, the periphery of the discharge port7can be moisturized more effectively. The opening portion8ais formed in long so as to be opened for all the discharge ports7, and the distance between each discharge port7and the opening portion8ais kept constant.

Therefore, all the discharge ports7can substantially evenly be moisturized.

The various modifications can be made in the configuration of the recording head50. For example, in order to supply the ink into the moisture retention liquid keeping portion8, it is possible that the moisture retention liquid keeping portion8and a common liquid chamber (not shown) of the recording head50are communicated with each other. Further, in order to supply the ink into the moisture retention liquid keeping portion8, it is possible that the moisture retention liquid keeping portion8and the ink tank of the recording apparatus are communicated with each other. At this point, the common liquid chamber means a structure, which is formed in the element substrate1and stores the ink supplied to the ink channels6.

Second Embodiment

The descriptions on the structure of the apparatus and the like, which are similar to the first embodiment, will be omitted.

FIGS. 2A and 2Bshow configurations of a recording head according to a second embodiment of the invention.FIG. 2Ais a top view of the recording head, andFIG. 2Bis a sectional view taken along a line IIB ofFIG. 2A.

A recording head51shown inFIG. 2Bfurther has a communication port12bformed in the gap forming member12in addition to the configuration of the recording head50shown inFIG. 1B. In other structures, the recording head51is similar to the recording head50. Therefore, in the recording head51, the same structure as for the recording head50is indicated by the same reference numeral, and the description will be omitted.

The communication port12bis formed while piecing through the gap forming member12. As shown in the top view ofFIG. 2A, the communication port12bis formed so as to become one long hole. Since the communication port12bis formed in the above manner, while a moisture retention liquid keeping portion8bis not only partially opened toward the discharge port7side, but also partially opened toward the surface of the gap forming member12.FIG. 2Bshows the state in which the moisture retention liquid is kept in the moisture retention liquid keeping portion8b.

Thus, according to the recording head51of the second embodiment, the moisture retention liquid in the moisture retention liquid keeping portion8bcan be evacuated through the communication port12bby the suction of the moisture retention liquid. Therefore, the recording head51has the advantage that exchange of the moisture retention liquid is facilitated in the moisture retention liquid keeping portion8b.

For example, it is possible that the exchange action is performed with the suction recovery mechanism as follows. In this case, the moisture retention liquid is the ink. First the cap of the suction recovery mechanism is caused to abut on the surface side of the recording head51. When the pump is driven, the ink is forcedly sucked from the discharge port7, and the ink in the moisture retention liquid keeping portion8bis also sucked through the communication port12b. Accordingly, while the old ink kept in the moisture retention liquid keeping portion8bis evacuated, the ink overflowing from the discharge port7is drawn into the moisture retention liquid keeping portion8bby the suction action. Thus, the moisture retention liquid (ink) is exchanged in the moisture retention liquid keeping portion8b.

In the case where the ink is used as the moisture retention liquid, since the moisture in the ink kept in the moisture retention liquid keeping portion8bevaporates with the passage of time, the performance of the ink is gradually decreased as the moisture retention liquid in the moisture retention liquid keeping portion8b. In order to take the countermeasure against the above problem, the second embodiment is configured to easily exchange the ink in the moisture retention liquid keeping portion8b. Therefore, the second embodiment has the advantage in that the ink having the high moisture content can be kept in the moisture retention liquid keeping portion8b.

The various modifications can be made in the shape of the communication port12bprovided in the gap forming member12. For example, it is possible that the shape of the communication port12bis formed as shown inFIGS. 3A and 3B.FIG. 3Ais a top view of the recording head, andFIG. 3Bis a sectional view taken along a line111B ofFIG. 3A.

In a recording head52shown inFIG. 3B, communication ports12care independently provided while formed in a through-hole. The total opening area of the communication ports12cis smaller than the opening area of communication port12bofFIGS. 2A and 2B. According to the recording head52having the above configuration, in addition to the advantage of the recording head51, there is also obtained the advantage that the amount of evaporation of the ink from the communication ports12ccan be suppressed by decreasing the total opening area of the communication ports12c. This means that the useless evaporation of the ink can be suppressed at the minimum to moisturize the periphery of the discharge port7for a long time.

Third Embodiment

The descriptions on the structure of the apparatus and the like, which are similar to the first embodiment, will be omitted.

In the recording head50of the first embodiment, the two moisture retention liquid keeping portions8are formed on the both sides across the discharge port7. However, the invention is not limited to the first embodiment. For example, it is possible that the moisture retention liquid keeping portion8is formed on one side.FIG. 7shows an example of the moisture retention liquid keeping portion8which is formed on one side. In this case, the advantage is obtained when the surface side of the recording head50is wiped with the wiping member formed by the elastic rubber member66.

Namely, the case in which the wiping member wipes the surface of the recording head50by the horizontal movement inFIGS. 1A and 1Bwill be described.

The wiping member is moved from one side where the moisture retention liquid keeping portion8is formed to the other side (arrow direction ofFIG. 7) where the moisture retention liquid keeping portion8is not formed. The wiping member wipes the surface of the gap forming member12, and then the wipes the surface (discharge port surface) of the channel forming member5after the wiping member goes beyond the opening portion8aof the gap forming member12.

Therefore, the discharge port7and its periphery are kept in the clean state. Thus, when the moisture retention liquid keeping portion8is formed only on one side, even if the recording head has the moisture retention liquid keeping portion8, the good wiping can be performed to the discharge port surface of the recording head.

In the conventional configuration shown inFIGS. 5A,5B,6A and6B, even the moisture retention liquid is collected by the wiping. Further, there is the possibility that the upper-end opening portion of the liquid keeping groove205ais clogged with the dust by the wiping (SeeFIGS. 6A and 6B). However, the moisture retention liquid keeping portion8has the configuration which is hardly affected by the wiping.

This application claims priority from Japanese Patent Application No. 2004-245370 filed Aug. 25, 2004, which is hereby incorporated by reference herein.