Ink jet recording method

A recording head having a plurality of ink discharge element lines arranged thereon is moved in a direction different from the direction of arrangement of the ink discharge elements to conduct a main scan, and at the end of the main scan, a recording medium is moved by a predetermined width in a direction different from the main scan direction to record an image. A record area of the recording head is divided into a plurality (n) of areas and each unit image area on the recording medium is main scanned n times by using the n divided areas of the recording head and thinned images with a print factor of 1/n are sequentially recorded to complete the record of the unit image area. The print factor for the pixels in the boundary area of adjacent unit image areas is lower than the print factor to the entire unit image area in at least one of the n main scans. Thus, the number of pixels recorded by the same main scan in the boundary area is increased. A high quality image without a joint stripe is attained even for a recording medium having a relatively high ink absorption speed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ink jet recording method. 
2. Related Background Art 
As a copying machine and an information processing equipment such as a word 
processor and a computer as well as a communication apparatus have become 
common, it is rapidly becoming popular to record a digital image by using 
a recording head of an ink jet system as an image forming (recording) 
apparatus therefor. In such a recording apparatus, an integration of a 
plurality of ink discharge ports and ink paths is used as a recording head 
having a plurality of recording elements integrally arranged in order to 
improve a recording speed. Recently, an apparatus having a plurality of 
such recording heads is used to comply with color recording. 
In such an ink jet printer, a recording head having a predetermined 
recording width is moved along a main scan direction, and after the main 
scan, a sheet is fed in a sub-scan direction to record an image. 
In a printer thus constructed, a discharge precision of a nozzle in the 
recording head or a sheet feed precision which is done for each record 
scan is required to some extent. The scatter in the amount of discharge 
and the direction of discharge in the recording head appears as 
irregularity of density in each record area, and the scatter in the amount 
of sheet feed causes a black stripe or a white stripe at a junction of the 
record areas. 
However, as higher and higher quality of image is required for a recent 
recording apparatus, it is difficult to perfectly control those factors 
and a recording method which makes those factors unobstructive without 
completely eliminating those factors has been proposed. Further, it is 
required to comply with recording media of various qualities such as plain 
papers, coated papers and OHP's and recording methods suitable for the 
respective recording media are required. 
In the recording medium such as the coated paper and the plain paper which 
are designed to relatively quickly absorb ink on the surface, the jointing 
stripe which is one of the image troubles frequently appears as a black 
stripe. This is explained below. 
In case of the coated paper, droplets of different colors which are 
simultaneously recorded do not mix with each other and a spread-free high 
resolution image is formed. However, in this type of paper, a density 
easily changes with an ink impact/absorption timing. FIG. 8A shows the 
impact/absorption of a given volume of ink by a paper plane, and FIG. 8B 
shows the impact/absorption of the same volume of ink at two separate 
times. They show that the ink more readily remains on the paper surface 
and the surface density is higher when it is recorded with a smaller 
volume at separate times. The same phenomenon appears at the joint area of 
the record scans. 
FIG. 8C shows a manner in which a record is completed in two image areas in 
two scans. Since the impacted ink dot is always designed to be larger than 
one pixel area, two or more dots overlap at each area. In the joint area 
(or connection section), the swelled-out area is split into two scans and 
recorded at different times so that it forms a darker stripe than other 
area although the volume of ink impacted is same as that of the other 
area. Further, the time interval of the record scans is not always 
constant due to the data transfer time and the recovery time of the 
recording apparatus. If the recording head stands by data at a home 
position after the completion of certain record scans, the density of the 
joint area increases more and more and the image quality is further 
deteriorated. The irregularity of density which appears at the carriage 
rest is called a rest irregularity. 
In the above description, only one head record scan is conducted for each 
print area to complete the image. However, in order to solve all of the 
above problems, the recording in the image area may be divided into a 
plurality of runs, as disclosed in the patent described below. Three 
patents which show background techniques of that patent are first 
explained. 
In Japanese Laid-Open Patent Application No. 55-113573, only zig-zag 
patterns (or checker/reverse-checker patterns) arranged alternately in 
vertical and horizontal directions are printed in each scan, and an image 
is completed by forward and backward record scans. Adjacent dots are not 
continuously printed to prevent the adjacent dots from being printed 
before the printed dots are dried. In this manner, the dot distortion is 
prevented. In this patent application, the thinning mask is limited to the 
zig-zag pattern. 
In the Japanese Laid-Open Patent Application No. 58-194541 filed by the 
assignee of the present invention, a plurality of recording element lines 
are parallelly arranged and they are reciprocally moved transversely to 
the lines of the recording elements to conduct the main scan of the dot 
matrix recording. In the forward path of the main scan, dots which are 
smaller in number than the total dots to be recorded in at least one of 
each row and each column of the record dot matrix are intermittently 
recorded, and in the backward run of the main scan, the remaining dots in 
at least one of each row and each column are intermittently recorded so 
that the order of overlap of the record in the overlapping dots by the 
record element lines differs between the forward run and the backward run 
of the main scan. Thus, the deterioration of image by the hue distortion 
(color irregularity) due to the overlapped printing of color inks is 
prevented. Since the primary object of this patent application is to avoid 
the hue distortion, there is no specific limitation to the bit positions 
recorded in each scan, and the horizontal thinning in which recording is 
made only vertically and alternately and the vertical thinning in which 
recording is made only horizontally and alternately are shown in addition 
to the zig-zag pattern. 
U.S. Pat. No. 4,748,453 discloses a method which is specifically directed 
to a low ink absorption speed recording medium such as an OHP. 
Interpolating recording is made to pixels located at alternate positions 
in horizontal and vertical directions in one record area by first and 
second (or more) divided record scans to prevent the beading of the ink on 
the recording medium such as OHP. When a color image is to be formed, the 
order of ink impact of the mixed color pixels is reversed between the 
first scan and the second scan (reciprocal recording) so that the color 
banding (color irregularity) is prevented. Since the primary object of 
this patent is to prevent the beading of the pixels, the pixels to be 
recorded in one scan are alternate (non-adjacent) horizontally and 
vertically. 
A common scheme to the above three patents is to complete the recording of 
the pixels of one image area in a plurality of record scans. In this case, 
since the ink of equal volume is dividedly absorbed by one image area, the 
record density of not only the joint area but also the entire image is 
enhanced and the joint area is rendered unobstructive to some extent, as 
shown in FIGS. 8A and 8B. Further, since a large volume of ink does not 
overflow in the record area at one time, the spread at the color boundary 
on the plain paper is prevented. However, for the joint stripe due to the 
paper feed error and the density irregularity due to the scatter of nozzle 
in the recording head, the above patents do not directly effect to solve 
the problem but the problem of image deterioration remain unresolved. 
In the following two patents which disclose a recording method shown in 
FIGS. 9A to 12C and which is an improvement over the above patents, the 
joint stripe is improved to some extent in addition to the effects 
described above. It is an effective method to solve the irregularity of 
image density due to the scatter of nozzles of a multi-nozzle head. 
In FIG. 9A, numeral 91 denotes a multi-nozzle head which is shown as an 
8-nozzle head 92 for simplification purpose. Numeral 93 denotes ink 
droplets discharged from the multi-nozzle head 92. It is desirable that 
the ink droplets are discharged in uniform volume and uniform direction as 
shown in FIG. 9A. If such discharge is attained, the dots of uniform size 
are impacted to the paper plane as shown in FIG. 9B and a uniform image 
without density irregularity is formed (FIG. 9C). In actuality, however, 
each nozzle has a variation as described above, and if the printing is 
done without countermeasure, the sizes and directions of the ink droplets 
discharged from the respective nozzles scatter as shown in FIG. 10A and 
they are impacted to the paper plane as shown in FIG. 10B in which white 
areas which do not meet the area factor of 100% are periodically present, 
or dots overlap unduly, or white stripes may be formed as shown at a 
center of FIG. 10B. The set of dots impacted under this condition has a 
density distribution to the direction of arrangement of nozzles as shown 
in FIG. 10C and it is recognized as the density irregularity by the 
observation of the human eye. In order to solve the problems on the image 
due to the scatter of the volume of discharge and the direction of 
discharge among the nozzles, a print control method called a split 
recording method to be described below has been proposed. 
The method is explained with reference to FIGS. 11A to 12C. The 
multi-nozzle head 91 is scanned three times to complete the print area 
shown in FIGS. 9A to 10C, but the half thereof, that is, the 4-pixel area 
is completed in two passes. The eight nozzles of the multi-nozzle head are 
divided into an upper 4-nozzle group and a lower 4-nozzle group, and the 
number of dots printed by one nozzle in one scan is approximately one half 
of a regular image data, thinned in accordance with a predetermined image 
data array. In a second scan, dots are filled to the remaining half of the 
image data to complete the printing of 4-pixel areas. This recording 
method is called the split recording method. 
By using the split record method, the printed image appears as shown in 
FIG. 11B because the affect to the print image inherent to the nozzle is 
halved even if the same recording head as that shown in FIGS. 10A to 10C 
is used, and the black stripe and the white stripe shown in FIG. 10B are 
rendered unobstructive. Accordingly, the density irregularity is also 
significantly reduced compared with FIGS. 10A to 10C, as shown in FIG. 
11C. 
In such recording, the image data for the first scan and the second scan 
are divided in accordance with the predetermined array so that they 
interpolate each other, and the image data array (thinning pattern) is 
usually a horizontally and vertically zig-zag pattern as shown in FIGS. 
12A to 12C. Accordingly, in the unit print area (4-pixel unit area in the 
present example), the print is completed by the first scan to print the 
zig-zag pattern (or checked pattern) and the second scan to print the 
complementary zig-zag pattern (or reverse-checker pattern). FIGS. 12A, 12B 
and 12C show how the recording of a given area is completed by the 
8-nozzle head as it is in FIGS. 9A to 11C by using the zig-zag pattern and 
the complementary zig-zag pattern. 
In the first scan, the zig-zag pattern .largecircle. is recorded by using 
the lower four nozzles (FIG. 12A). In the second scan, the paper is fed by 
four pixel length (1/2 of the head length) and the complementary zig-zag 
pattern .largecircle. is recorded (FIG. 12B). In the third scan, the paper 
is again fed by four pixel length (1/2 of the head length) and the zig-zag 
pattern is recorded (FIG. 12C). In this manner, the paper feed of four 
pixel length and the recording of the zig-zag pattern and the 
complementary zig-zag pattern are alternately conducted to complete the 
4-pixel record area for each scan. 
FIGS. 13A to 13C show the effect of the split recording method to the joint 
stripe. FIG. 13A shows the recording at the first, second and third record 
areas. In FIGS. 8A to 8C, the image is completed in one record scan except 
the boundary area. In the boundary area, since the dots of the respective 
areas are overlapped in the printing of the opposite edges which occur at 
different times, the density increases at those areas. In FIGS. 13A to 
13C, since the entire image area is recorded by overlapping the dots in 
two consecutive record scans, the same condition as that of the joint area 
of FIGS. 8A to 8C appears throughout the image. Accordingly, the joint 
area is less obstructive than FIGS. 8A to 8C. Further, since half of the 
pixels of the pixel trains following to the joint area are recorded by the 
nozzles at the center of the head, the scatter of the paper feed is also 
halved and the joint stripe is rendered unobstructive. 
The above recording method is disclosed in Japanese Laid-Open Patent 
Application No. 60-107975 and U.S. Pat. No. 4,967,203 and the effect to 
the density irregularity and the joint stripe are described therein. In 
the former, it is described that "it is characterized by the provision of 
means for forming an overlapped portion by setting the paper feed in each 
main scan smaller than the width of the main scan so that two adjacent 
main scans overlap, and means for arranging the print dots of the 
overlapped portion such that they do not overlap in the two main scans." 
In this patent, the thinning mask is printed such that "the odd-numbered 
stage and the even-numbered stage of alternate columns are printed in a 
zig-zag pattern" in one instance, but it is printed such that the 
odd-numbered stage is printed in the first main scan and the even-numbered 
stage is printed in the second scan in other instance, and they are 
randomly printed in still another instance. Thus, the thinning mask and 
the paper feed width are not completely defined. 
In the latter U.S. Pat. No. 4,967,203, it is disclosed that 
"(a) alternate pixel positions which are not adjacent vertically and 
horizontally and which are in only upper half of a first band are printed 
in a first pass, 
(b) pixels in the first band which were not printed in the first pass are 
printed in a second pass, 
(c) pixels in the first band which were not printed in the first and second 
passes are printed in a third pass, and the first pass is conducted for 
the immediately following band". In this patent, the thinning mask for the 
split recording is limited to the alternate pixel array which are not 
adjacent horizontally and vertically. 
In this patent, a pseudo pixel (super pixel) is formed by combining several 
pixels for tone expression or color expression and alternate thinning 
printing for horizontally and vertically non-adjacent pixels is conducted 
in the pseudo pixels (super pixel) block. In this method, it is described 
that "Once a system to implement the above method is built in a program 
software or a printer firmware, the program may be called by a color 
number of a combination designated for the super pixel, and the quality of 
print is improved without making a work to generate a computer program for 
generating a number of colors unduly complex". Thus, the simplification of 
the programming for the multi-color expression is recited as one of the 
effects. Since it is intended that each super pixel is sensed as one 
uniform color, it is stated that the spread of colors in the super pixel 
is harmless. 
As described above, as the print is completed in one area by two different 
nozzles, the density irregularity and the joint stripe in the image area 
are avoided. 
However, the above methods do not fully solve the problems. 
In the split recording method shown in FIGS. 13A to 13C, the full image 
area is recorded in two scans and the same conditions as that of the joint 
area appear throughout the image and the joint area is not obstructive. In 
actuality, however, the printing is made in two continuous record scans, 
for example, the first image area is printed in the first record scan and 
the second record scan and the second image area is printed in the second 
record scan and the third record scan, but in the boundary area, the 
record is completed in the three continuous record scans, the first to 
third record scans. Accordingly, the boundary area has the joint 
overlapped in the two continuous scans, the second record scan and the 
third record scan, and the joint which is recorded in the first record 
scan and the third record scan which are spaced by one scan period and 
which is created by the fact that the bits recorded in the first record 
scan and the bits recorded in the third record scan are arranged 
obliquely. In the record by the two dots shown in FIG. 8B, it is known 
that the larger the difference of times of impact is, the higher is the 
density. Accordingly, in the joint area of FIGS. 13A to 13C, the joint 
area of the records of the first scan and the third scan shown by dark 
black has a higher density than other area. 
Whenever the number of split records is increased, the relation of the time 
difference in the joint area is not corrected. So long as the record areas 
are recorded with the equal distribution in each record scan, for example, 
the zig-zag pattern and the complementary zig-zag pattern, the number of 
times of record scan in the joint area is necessarily one larger than that 
of other record area. This gap appears more or less and it is a cause of 
the degradation of the image. This phenomenon frequently appears in the 
high ink absorption speed coated paper. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved ink jet 
recording method. 
It is another object of the present invention to provide an ink jet 
recording method which prevents a joint stripe and permits the recording 
of a high quality and smooth image. 
It is another object of the present invention to provide an ink jet 
recording method which prints pixels located in a boundary area of each 
image area by as many simultaneous record scans as possible to prevent a 
paper feed joint stripe in the image area boundary due to a time 
difference of ink impact for even a recording medium having a relatively 
high ink absorption speed so that a high quality image is formed. 
The above and other objects of the present invention will be apparent from 
the drawings and the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 5 shows a perspective view of an ink jet recording apparatus to which 
the present invention is applied. In FIG. 5, numeral 701 denotes an ink 
cartridge which comprises ink tanks filled with inks of four colors, black 
(Bk), cyan (C) magenta (M) and yellow (Y) and a multi-nozzle head 702 for 
the respective colors. FIG. 6 shows multiple nozzles of the multi-nozzle 
head as viewed in the direction of z axis. Numeral 801 shows multiple 
nozzles arranged on the multi-nozzle head 702. 
In FIG. 5, the multi-nozzles 801 are arranged in parallel to the Y axis 
although they may be sightly inclined on the XY plane. In this case, the 
head travels in the X direction while the nozzles print with offset 
timing. 
Turning back to FIG. 5, numeral 703 denotes a paper transport roller which 
is rotated in a direction of arrow while it presses a print paper P with 
an auxiliary roller to transport the print paper P in the Y direction. 
Numeral 705 denotes a paper feed roller which feeds the print paper and 
also functions to press the print paper P as the paper transport roller 
703 and the auxiliary roller 704 do. Numeral 706 denotes a carriage which 
carries four ink cartridges and moves them as the print proceeds. The 
carriage 706 stays at a home position h shown by a broken line when the 
printing is not performed or during a recovery operation of the 
multi-head. 
In the present embodiment, the recording head of each ink jet cartridge 
discharges an ink droplet by causing a change in the state of ink by using 
thermal energy. 
The four ink jet cartridges mounted on the carriage 706 are arranged to 
superimpose inks of black, cyan, magenta and yellow, in this sequence, 
when the carriage is reciprocally moved. Accordingly, in the return 
movement of the carriage, the inks are superimposed in the reverse 
sequence to that in the forward movement. Half-tone colors may be attained 
by appropriately superimposing the ink dots of the respective colors C, M 
and Y. Namely, red is attained by superimposing M and Y, blue by C and M, 
and green by C and Y. 
Usually, black is attained by superimposing three colors C, M and Y but the 
black is separately printed because the color of black created by the 
three colors is poor, edging of a color appears because of the difficulty 
in precisely superimposing the three colors and the ink impact density per 
unit time is too high. 
FIG. 7 shows a block diagram of a control unit of the ink jet recording 
apparatus shown in FIG. 5. In FIG. 7, numeral 1201 denotes a control unit 
which comprises a CPU, a ROM and a RAM and it controls the respective 
units in accordance with a program stored in the ROM. Numeral 1202 denotes 
a driver for driving a carriage motor 1205 which drives the carriage 706 
in the x direction (main scan) in accordance with a signal from the 
control unit 1201, numeral 1203 denotes a driver for driving a paper feed 
roller 705 and a paper transport roller 703 and driving a transport motor 
1206 which transports a recording medium in the y direction (sub-scan) in 
accordance with a signal from the control unit 1201, numeral 1204 denotes 
a driver for driving multi-heads 1207-1210 for the respective colors 
(corresponding to 702 in FIG. 5) in accordance with print data from the 
control unit 1201, numeral 1211 denotes a console display unit for key 
entering various data and displaying various data, and numeral 1212 
denotes a host unit for supplying the print data to the control unit 1201. 
The carriage 706 is at the position h (home position) shown in FIG. 5. When 
a print command is issued, it is forwardly moved in the x direction so 
that the printing is made on the paper by the n multi-nozzles 801 on the 
multi-head 702. When the printing of the data up to the end of paper is 
completed, and the multi-head reaches the reversal point, the carriage 
starts the return movement toward the home position and the data is 
printed again. After the end of the first printing in the forward movement 
of the carriage and before the return movement of the carriage, the paper 
transport roller 703 is rotated in the direction of arrow to transport the 
paper in the y direction in accordance with the width of the record area. 
In the split recording to be described later, the paper feed length is 1/m 
of the width which is recorded by n multi-nozzles, where m (m.gtoreq.2) is 
the number of splits. By repeating the print by the multi-head and the 
paper feed (sub-scan) in accordance with the scan (main scan) of the 
carriage, the printing of data on one sheet is completed. 
A specific embodiment of the recording method by the ink jet recording 
apparatus thus constructed is explained below. 
&lt;First Embodiment&gt; 
A first embodiment is explained. FIG. 1 shows a print status when the 
printing is made by a head having 16 nozzles. In the present embodiment, 
the nozzles arranged in the head are equally divided into two record 
sections or areas and each area always uses the same thinning mask. FIG. 1 
shows a record status of the present embodiment. The head having 16 
nozzles on the left side of FIG. 1 is divided into two sections or areas 
as shown. A mask shown on the right corresponds to each nozzle which is 
recorded in accordance with this mask in all scans. In each record scan, 
the thinned printing is made for the unit image area at a predetermined 
print factor of 50%. The image record status is shown on the right. The 
dark solid pixel shows that it is recorded in each record scan, and the 
gray pixel shows that it has been recorded in the previous scan. 
In the second record area in which the first recording is made for each 
image area, the print factor at the leading edge of the paper feed is high 
(75%) and low (25%) at the trailing edge. In the first record area which 
is complementary to the second record area, the print factor at the 
leading edge is low (25%) and high (75%) at the trailing edge. In the 
printing done for each image area in accordance with such record mask, the 
area of higher record factor is first printed in the first record scan and 
the area having the lower record factor is later recorded in the second 
scan. In this record status, since 75% of the pixels in the boundary of 
the first image area and the second image area are simultaneously 
recorded, the joint stripe due to the time difference of the record scan 
do not substantially appear in this area. 
FIG. 2 shows the joint area which appears by the time difference of the 
record scan, of the image recorded by the present embodiment. The 
overlapped area of the dots recorded in the different scans is emphasized 
by black. A broken line shows a paper feed joint area. In the prior art 
shown in FIG. 8C, the high density areas which appear due to the time 
difference of the record scan are concentrated in the paper feed joint 
area. In the present embodiment, they are uniformly distributed to each 
image area. 
In accordance with the present embodiment, the division factor of the pixel 
lines is not uniform in the nozzle main scan direction. Accordingly, the 
scatter of a nozzle may be harder to be resolved compared to the 
conventional split recording method. However, since they are recorded by 
other nozzle at a rate of 1/4, the effect of the split recording method is 
not totally lost. 
In accordance with the present embodiment, the recording head is split into 
two record areas and each image area is recorded in two record scans. In 
the first record scan of each image area, the upper (the forward paper 
feed direction) print factor is high and the lower (the backward paper 
feed direction) print factor is low. In the second record scan, the upper 
print factor is low and the lower print factor is high. In this manner, 
the pixels arranged in the boundary area are recorded by as many 
simultaneous recording scans as possible to render the joint stripe caused 
by the time difference of the print to be less obstructive so that a 
uniform and high quality image is formed. 
&lt;Second Embodiment&gt; 
A second embodiment is now explained. The present embodiment relates to a 
3-pass split recording method, and unlike the first embodiment, it is an 
improved recording method of the first embodiment. FIG. 3 shows an image 
formation status of the present embodiment. In the present embodiment, the 
head record scan is done three times for the unit image area. The nozzles 
of the head are divided into three for the record areas. Like the first 
embodiment, each record area uses the fixed thinning mask, and the paper 
is fed by 1/3 head width for each record scan. The print status of the 
paper feed joint area of the present embodiment is shown in FIG. 4, like 
the first embodiment. In the present embodiment, since one image area is 
completed in three record scans, there are three types of dot overlap 
timings of the image area. The overlap area resulting from two consecutive 
scans such as the first and second scans or the second and third scans is 
shown by grey, and the overlap area resulting from the alternate record 
scans such as the first and third scans is shown by dark black. As seen 
from FIG. 4, the overlap areas are uniformly distributed throughout the 
image area, as they are in the first embodiment. In the present 
embodiment, the uniform image with unobstructive joint area is formed, as 
it is in the first embodiment. 
In the present embodiment, since the period is 3-pixel length in the main 
scan direction, it is hard to be tuned with the input binarized image data 
having a period which is normally a multiple of 2, and the image data of 
any duty can be split-recorded by two types of nozzles. Since the entire 
unit image area is completed in three record scans at the print factor of 
1/3 to that of the first embodiment and the opposite end areas are 
completed in two record scans with the print factors of 1/3 and 2/3, 
respectively, the color boundary spread on the paper surface such as the 
plain paper is further improved and the density is further enhanced as a 
whole. 
In the present embodiment, the ink jet recording apparatus which forms the 
flying droplet by using the thermal energy is used for the ink jet 
recording system. Typical construction and principle thereof are 
preferably those disclosed in U.S. Pat. No. 4,723,129 and U.S. Pat. No. 
4,740,796. It is applicable to either an on-demand type or a continuous 
type. In case of the on-demand type, at least one drive signal for causing 
rapid temperature rise beyond nucleate boiling in accordance with the 
record information is applied to an electro-thermal transducer arranged 
for a sheet which holds liquid (ink) or a liquid path so that a thermal 
energy is generated in the electro-thermal transducer and bubbles are 
formed in the liquid (ink) which corresponds to the drive signal. The 
liquid (ink) is discharged through a discharge port by the growth and 
contraction of the bubble to form at least one droplet. When the drive 
signal is pulsive, the growth and constraction of the bubble are instantly 
and properly effected and the highly responsive discharge of the liquid 
(ink) is attained. 
The pulsive drive signal is preferably one disclosed in U.S. Pat. No. 
4,463,359 and U.S. Pat. 4,345,262. When the condition described in U.S. 
Pat. No. 4,313,124 relating to the temperature rise on the thermal action 
plane is adopted, improved recording is attained. 
The recording head may be a combination (linear liquid path or transverse 
liquid path) of the discharge port, the liquid path and the 
electro-thermal transducer, as disclosed in the above-mentioned patents, 
or those disclosed in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600. 
In addition, a construction disclosed in Japanese Laid-Open Patent 
Application No. 59-123670 in which a slit common to a plurality of 
electro-thermal transducers is used as a discharge port of the 
electro-thermal transducers, or Japanese Laid-Open Patent Application No. 
59-138461 in which an opening for absorbing a pressure wave of thermal 
energy is provided for the discharge port may be used. 
Further, in a full line type recording head having a length corresponding 
to a maximum recording medium width which the recording apparatus can 
record, the length may be met by a combination of a plurality of recording 
heads as disclosed in the above-mentioned patents or by an integrally 
constructed recording head. 
In addition, the present invention is also effective to a replaceable chip 
type recording head which permits electrical connection with the main unit 
of the apparatus and the supply of ink from the main unit of the 
apparatus, and a cartridge type recording head having an ink tank 
integrally mounted on the recording head. 
The addition of the recovery means and auxiliary means to the recording 
head is preferable as they further stabilize the effect of the present 
invention. Specifically, they are capping means for the recording head, 
cleaning means, pressure or suction means, pre-heating means including an 
electro-thermal transducer, a separate heating element or a combination 
thereof. A preliminary discharge mode for discharging separately from the 
recording is effective for stable recording. 
In the present embodiment, the ink is used as the liquid. The ink may 
solidify at or below a room temperature or it may be softened at a room 
temperature or may be liquid. In the ink jet system, the ink which is of 
liquid phase when the record signal is applied may be used because it is 
common to control the ink within a range of 30.degree. C. to 70.degree. C. 
to keep the viscosity of the ink within a stable discharge range. 
In addition, the temperature rise by the thermal energy may be used as the 
energy of the status change from the solid state to the liquid state of 
the ink, or the ink which is solidified when it is left to prevent the 
evaporation of the ink may be used. The ink may be liquidified by the 
application of the thermal energy in accordance with the recording signal 
and may be discharged as liquid ink, or it may start to be solidified when 
it arrives at the recording medium and solidified by the thermal energy. 
In this case, the ink may be held in porous sheet recesses or 
through-holes in liquid or solid state and arranged to face the 
electro-thermal transducer, as disclosed in Japanese Laid-Open Patent 
Application No. 54-56847 or Japanese Laid-Open Patent Application No. 
60-71260. In the present invention, the execution of the film boiling 
system is most effective to the inks described above. 
In addition, the recording apparatus of the present invention may be an 
image output terminal of an information processing apparatus such as a 
word processor and a computer, whether it is integral or separate, or a 
copying machine combined with a reader, or a facsimile machine having a 
transmission and reception function. 
The present invention is applicable not only to the ink jet system which 
utilizes the thermal energy but also the ink jet system which utilize a 
piezoelectric element.