Abstract:
A cartridge is constituted by a plurality of absorbing materials for retaining liquid, an interface formed by press-contact between opposing surfaces of the absorbing materials, an introducing portion for supplying the liquid out of the absorbing materials, and a filter provided at an end portion of the introducing portion. The absorbing materials press against the filter so that an end portion of the interface reaches the filter.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to an ink jet recording head for ejecting liquid such as ink to a recording medium thereby to effect recording and relates to an ink jet recording cartridge including a liquid reservoir portion for retaining the liquid to be supplied to the ink jet recording head. 
         [0002]    A thermal type ink jet recording cartridge effects recording by causing film boiling of ink through application of driving energy to a heat generating resistor to eject ink droplets from an ink ejection outlet by a pressure generated by the film boiling. 
         [0003]    Generally, the ink jet recording cartridge of this type includes ink ejection outlets for ejecting the ink, ink flow passages communicating with these ink ejection outlets, and heat generating resistors. The heat generating resistors are provided at positions corresponding to the ink ejection outlets in the ink flow passages. 
         [0004]    The ink ejection outlets are arranged in lines to constitute arrays of ink ejection outlets. The respective ink flow passages communicate with associated ones of the ink ejection outlets communicate with a (single) common liquid (ink) chamber at a position opposite from a position at which the ink ejection outlets are formed. The common liquid chamber also communicates with an ink introducing passage provided in a container case including an ink reservoir portion for accommodating the ink. As a result, the ink is supplied from the ink reservoir portion to the ink flow passages through the ink introducing passage and the common liquid chamber. 
         [0005]    At an end of an ink introducing portion forming the ink introducing passage, a filter for preventing supply of impurities to the ink ejection outlets is provided. The filter contacts an ink absorbing material contained in the ink reservoir portion and retains the ink. 
         [0006]    The ink absorbing material is formed of a porous material or a fibrous material and retains the ink by a capillary force of the porous material or the fibrous material. When the ink at the ink ejection outlets is used (consumed) by ejection, the ink is introduced from the ink absorbing material to the ink ejection outlets by the ink flow passages and the ink ejection outlets which are higher in capillary force than the ink absorbing material. As a result, the ink ejection outlets are refilled with the ink. 
         [0007]    In this case, it is ideal that all the ink in the ink absorbing material is used up. However, due to the capillary force of the ink absorbing material, residual interface in the ink absorbing material occurs. For this reason, it is difficult to use up all the ink in the ink absorbing material. Therefore, techniques for reducing the residual ink have been proposed. 
         [0008]    Japanese Laid-Open Patent Application (JP-A) Hei 9-220814 describes an ink container using an ink absorbing material subjected to slit processing. In this ink container, the ink absorbing material is bent in a direction in which a slit portion is opened 180 degrees and accommodated in the ink container. The slit portion is bent to compress the ink absorbing material at an un-processing portion of slit, so that a high density portion is formed. This high density portion is located in the neighborhood of the ink ejection outlets. 
         [0009]    The high density portion is high in capillary force, so that the ink in the ink absorbing material is collected at the high density portion. Therefore, the ink can be efficiently introduced into the ink ejection outlets to reduce the residual ink. 
         [0010]    JP-A Hei 6-15839 describes an ink container using a plurality of ink absorbing materials different in density. In this ink container, the plurality of ink absorbing materials different in density is arranged toward an ink supply port in the order of a lower density ink absorbing material and a higher density ink absorbing material. Further, in order to prevent the ink from being interrupted by inclusion of air in a seam between the ink absorbing materials, the plurality of ink absorbing materials press-contacts each other to eliminate a gap of the seam between the ink absorbing materials. 
         [0011]    In the ink container, the density is increased toward the ink supply port, so that the ink in the ink container is collected at the ink supply port. Therefore, it is possible to reduce residual ink. 
         [0012]    In recent years, the ink jet recording head is improved in performances such as an image quality, a recording speed and the like. In order to improve the image quality, it is necessary to realize variety of species of ink to be supplied, minute ink droplets, and high-density arrangement of ink ejection outlets adapted to eject the minute ink droplets. 
         [0013]    Further, in order to improve the recording speed of a recording apparatus in which a an ink jet recording cartridge is reciprocated for scanning on a recording medium to effect recording, due to an increase in number of ink ejection outlets adapted to eject ink droplets, it is necessary to increase a recording area during one scanning operation. 
         [0014]    In the case of improving these performances, cost is increased frequently, so that cost reduction is also important factors together with the improvements in performances. 
         [0015]    In the ink container described in JP-A Hei 9-220814, the residual ink can be reduced, so that a volume of the ink retained in the ink absorbing material in advance can be reduced, thus resulting in cost reduction. However, it is necessary to perform such a production step in which the ink absorbing material is subjected to the slit processing and is bent and inserted into the ink container. For this reason, there is a possibility of an increase in cost due to a complicated production process. Further, it is necessary to ensure an un-processing portion of slit with precision, so that the ink absorbing material may be deceased in yield to result in a further increase in cost. 
         [0016]    In the ink container described in JP-A Hei 6-15839, there is no possibility of the increase in cost due to the above-described complicated production process, so that it is possible to decrease the residual ink. However, the ink container is accompanied with the following problem. 
         [0017]    The seam of the ink absorbing materials is press-contacted, so that the neighborhood of the press-contact portion is compressed. As a result, in the neighborhood of the press-contact portion, a density is higher than those at other portions to result in a high capillary force. For this reason, there is a possibility that the ink remains in the neighborhood of the high capillary force portion, i.e., the press-contact portion. 
       SUMMARY OF THE INVENTION 
       [0018]    A principal object of the present invention is, in view of the above-described problem, to provide an ink jet recording cartridge capable of decreasing residual ink. 
         [0019]    According to an aspect of the present invention, there is provided an ink jet recording head comprising: 
         [0020]    an ink jet recording head; 
         [0021]    a plurality of absorbing materials for retaining liquid; 
         [0022]    an interface formed by press-contact between opposing surfaces of the absorbing materials; 
         [0023]    an introducing portion for supplying the liquid from the absorbing materials to the ink jet recording head; and 
         [0024]    a filter provided at an end portion of the introducing portion, 
         [0025]    wherein the absorbing materials press against the filter so that an end portion of the interface contacts the filter. 
         [0026]    According to the present invention, it is possible to decrease the residual ink while suppressing an increase in cost. 
         [0027]    These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a perspective view of an ink jet recording cartridge of First Embodiment of the present invention. 
           [0029]      FIG. 2  is a sectional view of the ink jet recording cartridge of First Embodiment of the present invention. 
           [0030]      FIG. 3  is a perspective view of an ink absorbing material in the First Embodiment of the present invention. 
           [0031]      FIG. 4  is a sectional view showing a state of the ink jet recording cartridge of First Embodiment of the present invention before ink is not used. 
           [0032]      FIGS. 5 and 6  are sectional views each showing a state of partially used ink in the ink jet recording cartridge of First Embodiment of the present invention. 
           [0033]      FIG. 7  is a perspective view of an ink jet recording cartridge of Second Embodiment of the present invention. 
           [0034]      FIG. 8  is a sectional view of the ink jet recording cartridge of Second Embodiment of the present invention. 
           [0035]      FIG. 9  is a perspective view of an ink absorbing material in the Second Embodiment of the present invention. 
           [0036]      FIG. 10  is a sectional view showing a state of the ink jet recording cartridge of Second Embodiment of the present invention before ink is not used. 
           [0037]      FIGS. 11 ,  12  and  13  are sectional views each showing a state of partially used ink in the ink jet recording cartridge of Second Embodiment of the present invention. 
           [0038]      FIG. 14  is a perspective view of an ink jet recording cartridge of Third Embodiment of the present invention. 
           [0039]      FIG. 15  is a sectional view of the ink jet recording cartridge of Third Embodiment of the present invention. 
           [0040]      FIG. 16  is a perspective view of an ink absorbing material in the Third Embodiment of the present invention. 
           [0041]      FIG. 17  is a sectional view showing a state of the ink jet recording cartridge of Third Embodiment of the present invention before ink is not used. 
           [0042]      FIGS. 18 ,  19  and  20  are sectional views each showing a state of partially used ink in the ink jet recording cartridge of Third Embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    Hereinbelow, embodiments of the present invention will be described with reference to the drawings. 
         [0044]    In the following description, in the drawings, members or means having the same functions are represented by the same reference numerals or symbols and are omitted from redundant explanation in some cases. 
       Embodiment 1 
       [0045]      FIG. 1  is a perspective view of an ink jet recording cartridge of First Embodiment of the present invention. Referring to  FIG. 1 , an ink jet recording cartridge  100  includes a container case  107  and a container cover  108 . 
         [0046]    To a bottom of the container case  107 , an ink jet recording head  101  for ejecting liquid such as ink (hereinafter referred to as “ink”) to effect recording is attached. Further, to a side surface of the container case  107 , a contact portion  113  as electrical contact for receiving a driving signal or the like from an ink jet recording apparatus (not shown) is provided. The contact portion  113  and the ink jet recording head  101  are electrically connected by an electric wiring tape. 
         [0047]      FIG. 2  is a sectional view of the ink jet recording cartridge  100  taken along a-a line of  FIG. 1 . 
         [0048]    As shown in  FIG. 2 , the ink jet recording cartridge  100  includes an ink reservoir portion  112 , containing an ink absorbing material  102 , formed by the container case  107  and the container cover  108 . 
         [0049]    The ink absorbing material  102  absorbs ink  103 . An interface  104  is formed by press-contact between a plurality of opposing surfaces of the ink absorbing material  102 . The ink absorbing material  102  is a fibrous absorbing material formed of polypropylene fibers. 
         [0050]    At a bottom portion of the container case  107 , an ink introducing portion  105  is provided so that it projects from a portion immediately on the ink jet recording head  101  to the ink reservoir portion  112 . The ink introducing portion  105  is an introducing portion which forms an ink introducing passage  111  for establishing communication between the ink reservoir portion  112  and the ink jet recording head  101  through the ink introducing passage  111 . 
         [0051]    At an end of the ink introducing portion  105  projecting toward the ink reservoir portion  112 , a filter  106  for preventing supply of impurities to the ink jet recording head  101  is provided. In this embodiment, the filter  106  is formed of SUS (stainless steel). 
         [0052]    The container case  107  is openable at an upper portion which is covered with the container cover  108 . The upper surface of the container case  107  is opposite from the bottom of the container case  107  at which the ink introducing portion  105  is formed. 
         [0053]    At a bottom of the container cover  108 , ribs  109  for fixing the ink absorbing material  102  by press-contact are formed so as to project downwardly. The container cover  108  is provided with ambient air communication port  110  for establishing communication between the ink reservoir portion  112  and the ambient air. 
         [0054]    Next, the ink absorbing material  102  will be described more specifically. 
         [0055]      FIG. 3  is a perspective view of the ink absorbing material  102  contained in the ink reservoir portion  112 . In this embodiment, the ink absorbing material  102  is consisting of two ink absorbing materials  102   a  and  102   b.    
         [0056]    The ink absorbing materials  102   a  and  102   b  are contained in the ink reservoir portion  112  in a compressed state in an arrow X direction so that opposing surfaces of the ink absorbing materials  102   a  and  102   b  press-contact each other. Further, the ink absorbing materials  102   a  and  102   b  are contained in the ink reservoir portion  112  also in the compressed state in an arrow Y direction. For this reason, the ink absorbing materials  102   a  and  102   b  are, as shown in  FIG. 2 , contained in such a state that the ink absorbing materials  102   a  and  102   b  hermetically contact an inner wall of the container case  107 . 
         [0057]    In this embodiment, the respective opposing surfaces of the ink absorbing materials  102   a  and  102   b  press-contact each other, so that the interface  104  is formed at a press-contact portion between the ink absorbing materials  102   a  and  102   b.  Accordingly, in the neighborhood of the interface  104 , a compression ratio is higher than those of other portions of the ink absorbing materials  102   a  and  102   b,  so that a capillary force is increased. 
         [0058]    Further, as shown in  FIG. 2 , the ink absorbing materials  102   a  and  102   b  are pressed and fixed by the ribs  109  of the container cover  108 . At this time, the ink absorbing materials  102   a  and  102   b  press-contact the filter  106  and fixed so that the interface  104  contacts the filter  106 . Therefore, in the neighborhood of the press-contact portion between the ink absorbing materials  102   a  and  102   b  and the filter  106 , the compression ratio is higher than those of other portions of the ink absorbing materials  102   a  and  102   b,  so that the capillary force is increased. 
         [0059]    Next, a state of the ink used in the ink jet recording cartridge  100  will be described. 
         [0060]      FIGS. 4 to 6  are schematic views for illustrating the state of the ink used in the ink jet recording cartridge  100  of this embodiment. Specifically,  FIG. 4  is a sectional view of the ink jet recording cartridge  100  showing a state before the ink  103  is used (consumed).  FIGS. 5 and 6  are sectional views of the ink jet recording cartridge  100  each showing a state of the partially used ink  103 . 
         [0061]    In the ink jet recording cartridge  100  shown in  FIG. 4 , when the ink  103  is used by ejection thereof by the ink jet recording head  101 , the ink  103  is supplied to the ink jet recording head  101  through the ink introducing passage  111 . During the supply, an inside pressure of the ink reservoir portion  112  is kept at a value equal to that of the ambient pressure by introducing the ambient air into the ink reservoir portion  112  through the ambient air communication port  110 . 
         [0062]    The ink  103  is liable to be retained at a portion, higher in capillary force, of the ink absorbing materials  102   a  and  102   b.  For this reason, as shown in  FIGS. 5 and 6 , the ink  103  is gradually consumed while being attracted to the neighborhood of the interface  104 . This is because as described above, in the neighborhood of the interface  104 , the compression ratio is higher than those of other portions of the ink absorbing materials  102   a  and  102   b,  thus resulting in a higher capillary force. 
         [0063]    As a result, the ink  103  is collected in the neighborhood of the interface  104 , so that the ink  103  remaining at other portions of the ink absorbing materials  102   a  and  102   b  can be reduced. 
         [0064]    Further, the ink absorbing materials  102   a  and  102   b  press-contact the filter  106  as described above, so that the ink  103  retained in the neighborhood of the interface  104  is attracted to the neighborhood of the press-contact portion between the ink absorbing materials  102   a  and  102   b,  thus being supplied to the ink introducing passage  111  formed by the ink introducing portion  105 . 
         [0065]    According to this embodiment, the following effects can be achieved. 
         [0066]    In this embodiment, the filter  106  is provided to the end of the ink introducing portion  105 . The interface  104  is formed by press-contact between the opposing surfaces of the ink absorbing material  102 . The ink absorbing material  102  press-contacts the filter  106  so that the interface  104  contacts the filter  106 . 
         [0067]    The interface  104  is formed by press-contact between the opposing surfaces of the ink absorbing material  102 , so that in the neighborhood of the interface  104 , the compression ratio is higher than those of other portions of the ink absorbing material  102  and the capillary force is increased. Therefore, the ink  103  is collected in the neighborhood of the interface  104 , so that the ink  103  remaining at other portions of the ink absorbing material  102 . 
         [0068]    Further, the ink absorbing materials  102   a  and  102   b  press-contact the filter  106 , so that the ink  103  retained in the neighborhood of the interface  104  is attracted to the neighborhood, of the press-contact portion between the ink absorbing materials  102   a  and the filter  106 , higher in capillary force. As a result, the ink  103  is supplied to the ink introducing passage  111  formed by the ink introducing portion  105  through the filter  106 . 
         [0069]    Therefore, the residual ink can be reduced without using a complicated production process or a constitution, such as a bending step or the like. Thus, it is possible to reduce the residual ink while suppressing an increase in production cost. 
         [0070]    Further, in this embodiment, the interface  104  is formed by press-contact between the opposing surfaces of the ink absorbing materials  102   a  and  102   b.  For this reason, the interface  104  can be formed easily. 
       Embodiment 2 
       [0071]      FIG. 7  is a perspective view of an ink jet recording cartridge of Second Embodiment of the present invention. Referring to  FIG. 7 , an ink jet recording cartridge  200  includes a container case  207  and a container cover  208 . 
         [0072]    To a bottom of the container case  207 , an ink jet recording head  201  for ejecting ink to effect recording is attached. Further, to a side surface of the container case  207 , a contact portion  213  as electrical contact for receiving a driving signal or the like from an ink jet recording apparatus (not shown) is provided. The contact portion  213  and the ink jet recording head  201  are electrically connected by an electric wiring tape. 
         [0073]      FIG. 8  is a sectional view of the ink jet recording cartridge  200  taken along b-b line of  FIG. 7 . 
         [0074]    As shown in  FIG. 8 , the ink jet recording cartridge  200  includes an ink reservoir portion  212 , containing an ink absorbing material  102 , formed by the container case  207  and the container cover  208 . 
         [0075]    The ink absorbing material  102  absorbs ink  203 . A plurality of inks  204   a  to  204   c  is formed by press-contact between a plurality of opposing surfaces of the ink absorbing material  102 . The ink absorbing material  102  is a fibrous absorbing material formed of polypropylene fibers. 
         [0076]    At a bottom portion of the container case  207 , an ink introducing portion  205  is provided so that it projects from a portion immediately on the ink jet recording head  201  to the ink reservoir portion  212 . The ink introducing portion  205  is an introducing portion which forms an ink introducing passage  211  for establishing communication between the ink reservoir portion  212  and the ink jet recording head  201  through the ink introducing passage  211 . 
         [0077]    At an end of the ink introducing portion  205  projecting toward the ink reservoir portion  212 , a filter  206  for preventing supply of impurities to the ink jet recording head  201  is provided. In this embodiment, the filter  206  is formed of SUS. 
         [0078]    The container case  207  is openable at an upper portion which is covered with the container cover  208 . The upper surface of the container case  207  is opposite from the bottom of the container case  207  at which the ink introducing portion  205  is formed. 
         [0079]    At a bottom of the container cover  208 , ribs  209  for fixing the ink absorbing material  202  by press-contact are formed so as to project downwardly. The container cover  208  is provided with ambient air communication port  210  for establishing communication between the ink reservoir portion  212  and the ambient air. 
         [0080]    Next, the ink absorbing material  202  will be described more specifically. 
         [0081]      FIG. 9  is a perspective view of the ink absorbing material  202  contained in the ink reservoir portion  212 . In this embodiment, the ink absorbing material  202  is provided with slits  215   a  to  215   c.    
         [0082]    The ink absorbing material  202  is contained in the ink reservoir portion  212  in a compressed state in an arrow X direction so that associated opposing surfaces of a plurality of surfaces of the ink absorbing material  102  press-contact each other through each of the slits  215   a  to  215   c.  Further, the ink absorbing material  102  is contained in the ink reservoir portion  212  also in the compressed state in an arrow Y direction. For this reason, the ink absorbing material  102  is, as shown in  FIG. 8 , contained in such a state that the ink absorbing material  102  hermetically contacts an inner wall of the container case  207 . 
         [0083]    In this embodiment, the respective opposing surfaces of the ink absorbing material  102  press-contact each other through each of the slits  215   a  to  215   c,  so that each of the interfaces  204   a  to  204   c  is formed at a press-contact portion of the ink absorbing material  102 . Accordingly, in the neighborhood of each of the interfaces  204   a  to  204   c,  a compression ratio is higher than those of other portions of the ink absorbing material  102 , so that a capillary force is increased. 
         [0084]    Further, as shown in  FIG. 8 , the ink absorbing material  102  is pressed and fixed by the ribs  209  of the container cover  208 . At this time, the ink absorbing material  102  press-contacts the filter  206  and fixed so that each of the interfaces  204   a  to  204   c  contacts the filter  206 . Therefore, in the neighborhood of the press-contact portion between the ink absorbing material  102  and the filter  206 , the compression ratio is higher than those of other portions of the ink absorbing material  102 , so that the capillary force is increased. 
         [0085]    Next, a state of the ink used in the ink jet recording cartridge  200  will be described. 
         [0086]      FIGS. 10 to 13  are schematic views for illustrating the state of the ink used in the ink jet recording cartridge  200  of this embodiment. Specifically,  FIG. 10  is a sectional view of the ink jet recording cartridge  200  showing a state before the ink  203  is used (consumed).  FIGS. 11 to 13  are sectional views of the ink jet recording cartridge  200  each showing a state of the partially used ink  203 . 
         [0087]    In the ink jet recording cartridge  200  shown in  FIG. 10 , when the ink  203  is used by ejection thereof by the ink jet recording head  201 , the ink  203  is supplied to the ink jet recording head  201  through the ink introducing passage  211 . During the supply, an inside pressure of the ink reservoir portion  212  is kept at a value equal to that of the ambient pressure by introducing the ambient air into the ink reservoir portion  212  through the ambient air communication port  210 . 
         [0088]    The ink  203  is liable to be retained at a portion, higher in capillary force, of the ink absorbing material  102 . For this reason, as shown in  FIGS. 11 to 13 , the ink  203  is gradually consumed while being attracted to each of the neighborhood of each of the interfaces  204   a  to  204   c.  This is because as described above, in the neighborhood of each of the interfaces  204   a  to  204   c,  the compression ratio is higher than those of other portions of the ink absorbing material  102 , thus resulting in a higher capillary force. 
         [0089]    As a result, the ink  203  is collected in the neighborhood of each of the interfaces  204   a  to  204   c,  so that the ink  203  remaining at other portions of the ink absorbing material  102  can be reduced. 
         [0090]    Further, each of the interfaces  204   a  to  204   c  contacts the filter  206  as described above, so that the ink  203  retained in the neighborhood of each of the interfaces  204   a  to  204   c  is supplied to the ink introducing passage  211 . 
         [0091]    According to this embodiment, the following effects can be achieved. 
         [0092]    In this embodiment, each of the interfaces  204   a  to  204   c  contacts the filter  206 . For this reason, particularly, when the filter  206  has a large size, it is possible to more efficiently supply the ink  203  retained in the ink absorbing material  202  to the ink jet recording head  201 . Therefore, when the filter  206  has a large size, the residual ink can be decreased. 
         [0093]    Further, in this embodiment, each of the interfaces  204   a  to  204   c  formed by press-contact between the opposing surfaces of the ink absorbing material  102  through each of the slits  215   a  to  215   c.  For this reason, each of the interfaces  204   a  to  204   c  can be formed easily. 
       Embodiment 3 
       [0094]      FIG. 14  is a perspective view of an ink jet recording cartridge of First Embodiment of the present invention. Referring to  FIG. 14 , an ink jet recording cartridge  300  includes a container case  307  and a container cover  308 . 
         [0095]    To a bottom of the container case  307 , an ink jet recording head  301  for ejecting ink to effect recording is attached. Further, to a side surface of the container case  307 , a contact portion  313  as electrical contact for receiving a driving signal or the like from an ink jet recording apparatus (not shown) is provided. The contact portion  313  and the ink jet recording head  301  are electrically connected by an electric wiring tape. 
         [0096]      FIG. 15  is a sectional view of the ink jet recording cartridge  300  taken along c-c line of  FIG. 14 . 
         [0097]    As shown in  FIG. 15 , the ink jet recording cartridge  300  includes an ink reservoir portion  312 , containing an ink absorbing material  302 , formed by the container case  307  and the container cover  308 . 
         [0098]    The ink absorbing material  302  absorbs ink  303 . Each of interfaces  304   a  and  204   b  is formed by press-contact between a plurality of opposing surfaces of the ink absorbing material  302 . The ink absorbing material  302  is a fibrous absorbing material formed of polypropylene fibers. 
         [0099]    At a bottom portion of the container case  307 , an ink introducing portion  305  is provided so that it projects from a portion immediately on the ink jet recording head  301  to the ink reservoir portion  312 . The ink introducing portion  305  forms an ink introducing passage  311  for establishing communication between the ink reservoir portion  312  and the ink jet recording head  301  through the ink introducing passage  311 . 
         [0100]    At an end of the ink introducing portion  305  projecting toward the ink reservoir portion  312 , a filter  306  for preventing supply of impurities to the ink jet recording head  301  is provided. In this embodiment, the filter  306  is formed of SUS. 
         [0101]    The container case  307  is openable at an upper portion which is covered with the container cover  308 . The upper surface of the container case  307  is opposite from the bottom of the container case  307  at which the ink introducing portion  305  is formed. 
         [0102]    At a bottom of the container cover  308 , ribs  309  for fixing the ink absorbing material  302  by press-contact are formed so as to project downwardly. The container cover  308  is provided with ambient air communication port  310  for establishing communication between the ink reservoir portion  312  and the ambient air. 
         [0103]    Next, the ink absorbing material  302  will be described more specifically. 
         [0104]      FIG. 16  is a perspective view of the ink absorbing material  302  contained in the ink reservoir portion  312 . In this embodiment, the ink absorbing material  302  is provided with slits  315   a  and  315   b  extending perpendicular to each other. 
         [0105]    The ink absorbing material  302  is contained in the ink reservoir portion  312  in a compressed state in an arrow X direction so that associated opposing surfaces of the ink absorbing material  302  press-contact each other through each of the slits  315   a  and  315   b.  Further, the ink absorbing material  302  is contained in the ink reservoir portion  312  also in the compressed state in an arrow Y direction. For this reason, the ink absorbing material  302  is, as shown in  FIG. 16 , contained in such a state that the ink absorbing material  302  hermetically contacts an inner wall of the container case  307 . 
         [0106]    In this embodiment, the opposing surfaces of the ink absorbing material  302  through the slit  315   b  press-contact each other, so that the interface  304   b  is formed at a press-contact portion of the ink absorbing material  302 . 
         [0107]    Further, as shown in  FIG. 15 , the ink absorbing material  302  is pressed and fixed by the ribs  309  of the container cover  308 . At this time, the ink absorbing material  302  press-contact the filter  306  and fixed so that the interface  304   b  contacts the filter  306 . Therefore, in the neighborhood of the press-contact portion between the ink absorbing material  302  and the filter  306 , the compression ratio is higher than those of other portions of the ink absorbing material  302 , so that the capillary force is increased. 
         [0108]    Further, the opposing surfaces of the ink absorbing material  302  through the slit  315   a  press-contact each other, so that the interface  304   a  is formed at a press-contact portion of the ink absorbing material  304 . As described above, the interface  304   b  is also formed at another press-contact portion of the ink absorbing material  304 , so that in the neighborhood of each of the interfaces  304   a  and  204   b,  the compression ratio is higher than those of the other portions of the ink absorbing material  302 , thus resulting in a higher capillary force. 
         [0109]    Next, a state of the ink used in the ink jet recording cartridge  300  will be described. 
         [0110]      FIGS. 17 to 20  are schematic views for illustrating the state of the ink used in the ink jet recording cartridge  300  of this embodiment. Specifically,  FIG. 17  is a sectional view of the ink jet recording cartridge  300  showing a state before the ink  303  is used (consumed).  FIGS. 18 to 20  are sectional views of the ink jet recording cartridge  300  each showing a state of the partially used ink  303 . 
         [0111]    In the ink jet recording cartridge  300  shown in  FIG. 17 , when the ink  303  is used by ejection thereof by the ink jet recording head  301 , the ink  303  is supplied to the ink jet recording head  301  through the ink introducing passage  311 . During the supply, an inside pressure of the ink reservoir portion  312  is kept at a value equal to that of the ambient pressure by introducing the ambient air into the ink reservoir portion  312  through the ambient air communication port  310 . 
         [0112]    The ink  303  is liable to be retained at a portion, higher in capillary force, of the ink absorbing material  302 . For this reason, as shown in  FIGS. 11 to 13 , the ink  303  is gradually consumed while being attracted to the neighborhood of the interface  304 . This is because as described above, in the neighborhood of each of the interfaces  304   a  and  204   b,  the compression ratio is higher than those of other portions of the ink absorbing material  302 , thus resulting in a higher capillary force. 
         [0113]    As a result, the ink  303  is collected in the neighborhood of each of the interfaces  304   a  and  304   b,  so that the ink  303  remaining at other portions of the ink absorbing material  302  can be reduced. 
         [0114]    The interface  304   a  is perpendicular to the interface  304   b  as described above and the interface  304   b  contacts the filter  306 . For this reason, the ink  303  retained in the neighborhood of the interface  304   a  is attracted to the neighborhood of the interface  304   b  and is retained in the neighborhood of the interface  304   b.  Further, supplied to the ink introducing passage  311 . 
         [0115]    According to this embodiment, the following effects can be achieved. 
         [0116]    In this embodiment, the interfaces  304   a  and  304   b  are perpendicular to each other. Further, the interface  304   b  contacts the filter  306 . For this reason, particularly, when the ink reservoir portion  312  has a large size, i.e., when the ink absorbing material  302  is large, the ink  303  retained in the ink absorbing material  302  can be further efficiently supplied to the ink jet recording head  301 . Therefore, particularly, when the ink absorbing material  302  is large in size, the residual ink can be decreased. 
         [0117]    In the above-described embodiments, the illustrated constitutions are merely examples and the present invention is not limited to the constitutions. 
         [0118]    For example, in First Embodiment, the number of the ink absorbing materials is two but may appropriately be changed to three or more. In the case where the number of the ink absorbing materials is more than two, the number of the interfaces  104  is two or more. In this case, each of the interfaces  104  may contact the filter  106  or each of the interfaces  104  is connected to another interface and at least one of the interfaces  104  may contact the filter  106 . 
         [0119]    In Second Embodiment, the number of the slits is three but can be appropriately changed. For example, in the case of a single slit, an interface formed by press-contact between both wall surfaces of the slit is only required to contact the filter  206 . In the case where the number of slits is two or more, each of a plurality of interfaces formed by press-contact between associated both wall surfaces of the plurality of slits is only required to contact the filter  206 . 
         [0120]    In Third Embodiment, the number of the slits is two but can also be appropriately changed to three or more. In the case where the number of the slits is three or more, the number of interfaces is three or more. In this case, each of the interfaces is connected to another interface and at least one of the interfaces is only required to contact the filter  306 . 
         [0121]    The ink jet recording cartridge may also employ a plurality of ink absorbing materials at least one of which includes a slit. In this case, interfaces in the ink jet recording head include an interface formed by press-contact between opposing surfaces of the plurality of ink absorbing materials and an interface formed by press-contact between opposing surfaces through the slit in combination. Further, in the ink jet recording cartridge, the interface may also be formed by press-contact between opposing surfaces formed by bending a single ink absorbing material. 
         [0122]    In First, Second and Third Embodiments, the ink absorbing materials  102 ,  202  and  302  are the fibrous absorbing material formed of the polypropylene fibers but can be appropriately changed. For example, the ink absorbing materials  102 ,  202  and  302  may also be a fibrous absorbing material formed of other fibers or an absorbing material formed of a porous member such as urethane form. 
         [0123]    The filters  106 ,  206  and  306  in First, Second and Third Embodiments are formed of SUS but can also be changed appropriately. The filters  106 ,  206  and  306  may also be formed of, e.g., fibers or the like so long as they can prevent supply of impurities to the ink jet recording heads  101 ,  102  and  301 . 
         [0124]    While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims. 
         [0125]    This application claims priority from Japanese Patent Application No. 263171/2007 filed Oct. 9, 2007, which is hereby incorporated by reference.