JPS62292440A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To enable reproduction of a recording image of information dot- diameter to keep a recording image quality satisfactory, by a method wherein the heat-drive timings of at least adjacent ink unit areas are shifted to each other when the heated ink unit areas are flows toward a recording sheet. CONSTITUTION:By successive conduction of contacts (c), (d) of a change-over switch 42, drive control signals Mc, Md are respectively inputted to corresponding AND gate groups 23c, 23d, and heating resistor groups 21c, 21d respectively in blocks B3, B4 are heated according to an image information G. On the other hand, ink unit areas Ic, Id corresponding to the heated heating resistors 21c, 21d are heated and flown toward a recording sheet 5 according to a given electrostatic field S as shown by a one-dot chain line or a two-dot chain line. In this manner, the ends of raised ink column 3c, 3d come into contact with the surface of the recording sheet 5 to form respectively ink dots Dc, Dd.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to an inkjet recording method, and particularly relates to improvements in the inkjet recording method necessary to maintain good quality of recorded images. .

[Prior Art] In a conventional inkjet recording method, a large number of ink ejection devices that seal ink are provided with ejection ports (
It is known that the ink ejecting device is provided with a plurality of orifices, respectively, and a pressure pulse is applied to the ink ejecting device to prevent ink from being ejected from the ejecting port.

In this type, the ink ejection rAU from the ejection port
Since it is necessary to maintain a large volume ratio between the ejection ports and the ink ejection device in order to maintain the operation, it is difficult to downsize the ink ejection device. Not only is it impossible to set the image recording density to a high value, but also the ink is ejected by mechanical scanning by applying pressure pulses, which inevitably reduces the recording speed. 11
There is a problem that 1 <.

As a means to solve this problem, magnetic ink is placed near the magnetic electrode array, and the ink bulge caused by the magnetic field is used to form an ink ejection state corresponding to the image density, and the magnetic ink is transferred to the recording sheet using an electrostatic field. The so-called magnetic inkjet recording method in which the inkjet is ejected to the side
Publication No. 69469 ((l: or ' Ink is filled in a slit-shaped ink parallel to the Nh array, and depending on the electric field pattern formed between the electrode and the electrode array facing each other via the recording sheet. The so-called planar inkjet recording method in which ink is ejected toward the recording sheet (Japanese Unexamined Patent Publication No. 1J (56-3)
7163 Publication), or by applying thermal energy to the ink, the ink is rapidly heated to cause film surface boiling, and bubbles are rapidly grown within the ejection port (orifice). A so-called thermal bubble jet recording method (Japanese Unexamined Patent Publication No. 11ij 55-1616 (I4)) has been proposed in which ink is scraped from an ejection port by increasing the pressure caused by the ink.

In each of the conventional inkjet recording methods mentioned above,
In either case, not only can the density of the recorded image be increased, but also high-speed recording can be performed since electronic scanning is possible.

[Problems to be Solved by the Invention] However, in the magnetic inkjet recording method described above, since it is necessary to use an ink mixed with magnetic powder, the ink inevitably becomes black, and the ink becomes black. A problem arises in that it becomes difficult to obtain a color image by overprinting. In addition, in the above planar inkjet recording method, it is possible to improve ink clogging by eliminating the need for a fine orifice, but since a high voltage must be applied to make the ink fly, it is necessary to apply a high voltage to the adjacent, In order to prevent voltage leakage between adjacent electrodes, the arrangement pitch of the electrodes cannot be narrowed more than necessary, which is not a good idea in terms of achieving high density. Furthermore, in the thermal bubble jet recording method described above, it is necessary to rapidly raise the temperature of the heating element in order to cause film surface boiling. There is a problem in that the heat-generating resistor protective layer provided as a means is likely to be thermally degraded.

In order to solve such problems, the inventors of the present invention apply thermal energy to recording ink according to image information consisting of binary signals, and at the same time, heat the ink portion heated based on a predetermined electrostatic field. A so-called thermostatic inkjet recording method has already been proposed in which ink is ejected toward the recording sheet.

According to this type, there is no need to use magnetic ink using the so-called magnetic inkjet recording method, and accordingly,
Not only can colorization based on overprinting of ink be easily realized, but it also eliminates the need to fly ink using only an electrostatic field as in the so-called flat inkjet recording method, and the strength of the electrostatic field does not have to be extremely large. This eliminates the need for ink to fly away using only thermal energy, as is the case with the so-called bubble jet recording method, and reduces thermal energy consumption to some extent. , thermal deterioration of ink, etc. can be effectively prevented. Therefore, it is possible to perform high-speed, high-density recording while effectively preventing the drawbacks of conventional methods.

By the way, in order to form ink dots in units of pixel density on a recording sheet in such a thermoelectrostatic inkjet recording method, a means for heating the ink according to the pixel density is installed, and the heated ink portion is placed on the recording sheet i. However, if the image information to be recorded forms a group of adjacent ink dots, the adjacent ink unit areas are heated simultaneously, and both ink unit areas are heated. A situation arises in which it is necessary to simultaneously fly the recording sheets toward the recording sheet side.

Under these circumstances, if you try to set the pixel density to a certain degree higher, the ink unit area corresponding to the pixel density will become narrower, and the ink ridge movement will affect each ink unit area. Not only do the diameters of the ink drums 1 to 1 on the recording sheet side vary, but in extreme cases, the number of ink dots to be recorded is reduced by one, resulting in a problem that the quality of the recorded image is impaired.

[Means for Solving the Problems] In order to solve such problems, the inventors of the present invention have developed a method in which the diameter of an ink dot in an isolated state where there is no ink driver i~ to record in an adjacent area is uniform and stable. In view of this fact, they devised the present invention which reproduces recorded images with uniform dot diameters.

However, this invention is based on a so-called thermoelectrostatic inkjet recording method that enables high-speed, high-density recording, in which each ink unit area according to the pixel density is heated as appropriate in accordance with the image information. , in which heating drive timings of at least adjacent ink unit areas are mismatched when the heated ink unit area is caused to fly toward the recording sheet]- side based on the electrostatic field formed between the ink surface and the recording sheet. It is.

In such technical means, the head body for supplying ink may have a slit-like space in which ink is accommodated, or may have an ink absorbing portion filled with ink, etc. You may change the design as appropriate. Further, as a means for applying thermal energy to the ink, the ink may be heated indirectly using a heating element array made up of a plurality of heating resistors arranged according to the size of the pixel, or the ink may be indirectly heated by radiation. Of course, the ink may be heated for each pixel density using a wire as a heat source, or the ink itself having a predetermined resistivity may be directly energized to cover it with heat, etc., as appropriate. Furthermore, in the type that uses a heating element array, the heating resistor may be placed at an edge portion adjacent to the ink flying surface, or facing the ink flying surface, as long as the position can heat the ink in a predetermined area. It may also be a wall that stretches.

Further, between the ink surface and the recording sheet, it is sufficient to uniformly apply an electrostatic field strong enough to cause the heated ink to fly toward the recording sheet. As a means to do this, the setting S1 may be changed as appropriate.

Further, the ink to be used may be appropriately selected as long as it can be made to fly when a predetermined amount of heat and energy is applied. In this case, the specific ink flying condition is that the ink flies due to the acting electrostatic field and I'? It is essential that the viscosity and surface tension of the ink are reduced to such an extent that the electrical conductivity of the ink is improved.

Furthermore, the number of divisions in the heating drive timing of each heating means according to the pixel density may be selected as appropriate;
If the number of divisions is set too large, the recording speed itself will decrease, so it is necessary to set the number of divisions in consideration of the balance between the variation in ink dot diameter and the recording speed. Regarding specific means for driving each heating means separately, b. The driving timing of each heating means may be appropriately switched by a switching member, or the driving timing of the heating means may be appropriately shifted by a timer means. You may change the design as appropriate, such as by setting the

[Operation] According to the above-mentioned technical means, thermal energy corresponding to image information is not applied to adjacent ink unit areas at the same time, so the ink unit areas to which thermal energy is applied are isolated. In this state, the flying motion is performed toward the recording sheet side (1).Therefore, the rising motion of the ink between adjacent ink unit areas does not affect each other on the phase H.

[Embodiment] Hereinafter, an embodiment of an apparatus for realizing an inkjet recording method according to the present invention will be described in detail based on the accompanying drawings.

In FIG. 1, an ink cartridge recording head applies thermal energy in units of pixel density to a head body 1 having a slit space 2 and ink 3 accommodated in a slit space 2. It includes a plurality of lower heating stages 4, an electrostatic field forming means 6 for forming a predetermined electrostatic field between the ink 3 surface and the recording sheet 5, and a drive control means 7 for driving each heating means 4 in a time division manner. There is.

In this embodiment, the head main body 1 has insulating substrates 11 and 12 made of alumina lamic, etc., spaced apart by a spacer member (not shown), as shown in FIG. However, a slit-like space 2 of about 100μ7n is secured between the two insulating substrates 11 and 12. The ink 3 accommodated in the slit-like space 2 is made by dispersing a pigment or dissolving a dye in an oily solvent such as paraffin or olefin, and its physical properties are as follows: The viscosity is 20-30
0 CDS, the viscosity decreases by more than one digit when heated (for example, 200° C.), and the volume resistivity is approximately 1070 α.

Further, the heating means 4 is constituted by a heating element array formed by arranging heating resistors 21 according to the pixel density, and each heating resistor 21 is made of Ta2N, for example. A pair of current-carrying electrodes 22 is connected to each heating resistor 21, which is disposed facing the edge of the side opening. An AND gate 23 as a switching element that opens and closes in response to an image control signal from the first drive control stage 7 is connected to each current-carrying electrode 22 . Reference numeral 24 denotes an insulating layer made of 8102 or the like, which insulates the heating resistor 21 and each current-carrying electrode 22 to a thickness of about 2 μm, and 25 represents a power supply for energizing each heating resistor 21.

Furthermore, the electrostatic field forming means 6 includes a Cr (chromium)/
A conductive layer 31 made of a C11 (copper)/Cr metal layer, and a roll-shaped electrostatic induction electrode 32 that is spaced a predetermined distance from the three ink surfaces and also functions as a support surface for the recording sheets 5. , for conductive layer 31 and electrostatic induction? 1IJU32
4N of static induction electricity is inserted between the 3 ink sides! 32
The electrostatic induction power source 33 forms an electrostatic field directed toward the side.

Furthermore, in this embodiment, the heating resistor 21
The group consists of four blocks B1 (21a-1
, 21a-2, 21a-i), B2 (21b-
1,21b-2...21b-i) B3(21C-
1,21C-2...21cm1) and 84(21
d-1, 216-2...21d-i). Therefore, the drive control means 7 temporarily stores one line of image information G, and outputs the group of image information G in parallel in synchronization with a predetermined clock timing C to act as a switching element. A shift register 41 having an input of 1 at one input end of each AND gate 23, and a changeover switch 42 which operates four normally open contacts a to d in sequence at a predetermined timing. The other input terminal of each group of AND gates 23 is connected to each contact point a to d of a changeover switch 42 corresponding to each block B1 to B4 of the heating resistor 21.

Next, the construction of the inkjet recording apparatus according to this embodiment will be explained.

At B3 in FIG. 3, when a group of image information G consisting of one line of binary signals is transferred to the shift register 41, each image information G is shifted in synchronization with a predetermined number [) ts (,3qct). l-Regisf 41 and each AND gate 2
It is connected to one input end of 3. At this point,
By sequentially switching the contacts a to d of the changeover switch 42, a drive control signal M (specifically, M
a to Md), and in synchronization with the switching timing of the changeover switch 42, apply a pulse signal N to the static induction lightning K132 from the electrostatic induction power supply 33 at the J timing shown in FIG. Then, the recording operation of image information G is performed in each block B.

To be more specific, first, when the contact a of the changeover switch 42 becomes conductive, the AND gate 23a corresponding to this becomes conductive.
A drive control signal M is input to the group, and the image information G passes only within the range of the AND gate 23a group, and the heating resistor 21a group in the block B1 generates heat appropriately according to the image information G. do. On the other hand, electrostatic Li I electrode 3
When a predetermined applied pulse signal N is applied to the ink 3
Face and record sea!・A predetermined electrostatic field S is formed between the heating resistor 21 and the heating resistor 21, which generates heat, as shown by the solid line in FIG.
The ink unit area 141a corresponding to a is heated, the viscosity and surface tension of this ink unit area Ia are reduced, and its electrical conductivity is improved, and this ink unit area Ia becomes F2.
Electrostatic field S1. : Based on this, the ink column 3a flies toward the recording sheet 1-5 side, and the raised end of the ink column 3a comes into contact with the surface of the recording sheet 5, forming an ink dot Oa. Next, when the contact point of the changeover switch 42 becomes conductive, one stage of drive control M is input to the corresponding AND gate 23bRT, and image information G passes only within the range of this AND gate 23a group. Then, the group of heating resistors 21b in the block B2 generates heat as appropriate in accordance with the image information G. When a predetermined electrostatic field S is formed by a predetermined applied pulse signal j3N, the ink unit area I corresponding to the heating resistor 21b that generates heat is heated, as shown by the dotted line in FIG. Based on the electrostatic field S, the recording sheet 5
The end portion of the ink column 3b that flies to the side and rises comes into contact with the surface of the recording sheet 5, thereby forming an ink dot D. Thereafter, when the contacts c and d of the changeover switch 42 are sequentially turned on, the drive control signals M0 and M are input to the corresponding Antoge 1-23C and 23d groups, respectively, and the respective blocks B
, B4 generate heat appropriately according to the image information G, while the heating resistors 21c, 21 generate heat as shown by the dashed line and the dashed double dotted line in FIG.
The ink unit areas I and T corresponding to d are heated and fly toward the recording sheet 5 based on a predetermined electrostatic field S,
The ends of the raised ink columns 3C13d come into contact with the surface of the recording sheet 5, forming ink dots D and Dd.

In such a recording process, each unit ink area ■ or! As shown in FIG. The uplift speed, etc. no longer differ between adjacent unit ink areas, and the diameter of each ink dot D formed on the recording sheet 5 is assumed to be approximately equal.

When the series of recording operations for the middle of each block B is completed, the recording process of image information for one line is completed, and at this stage, the image information G in the shift register 41 is completed.
is updated, the recording sheet 5 is advanced by one step, and the next line of image information is recorded in the recording cycle.

Furthermore, in order to demonstrate the above-mentioned recording binding, the inventors of the present application set the heating time of each heating resistor 21 to 05+es, the applied power to O, SW, and the applied pulse for forming the electrostatic field S to 1000. (V) / 300μ7A, 0.
When we conducted a recording experiment at 5ms, each ink drive)-D
The average diameter was 150 μm, with a standard deviation of 13 μm. At this time, when each heating resistor 21 is heated and driven at the same time, the diameter of each ink dot D is 170 μm, with a standard deviation of 30 μm, and considering that there was a recording failure of about 10%, conventional It can be confirmed that the recording operation is stable and the diameter of the ink dots D is uniform compared to the above.

When a similar experiment was carried out using two blocks of the heat generating unit 21 in the example, it was confirmed that the diameter of each ink dot D was 150 μm on average, with a standard deviation of 15 μm.

[Effects of the Invention] As described above, the inkjet recording method according to the present invention is based on a thermoelectrostatic inkjet recording method, and is capable of ejecting ink according to image information regardless of adjacent unit ink areas. Since the operation can be performed stably, even if the pixel density is increased to a certain extent, the recording operation can be performed reliably.Moreover, the diameter cutting method for the ink drive to be recorded can be uniformly used for recording. Good image quality can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an embodiment of an apparatus for realizing the inkjet recording method according to the present invention, FIG. 2 is a perspective explanatory diagram showing the structure around the head body used in the embodiment, and FIG. A specific example of the drive control means used in the example is shown in Fig. 1. Fig. 4 is a timing chart of the operation timing of a series of recording 01 production processes in this invention, and Fig. 5 is a timing chart of the operation timing of a series of recording steps in this invention. FIG. 3 is a TFA diagram showing the recording operation process. [Explanation of symbols] (1, I , I , I, )...Ink medium area b
c (1)...Head body (2)...Slit-shaped space (3)...Ink (4)...Heating means (5)...
...Recording sheet (6)...Electrostatic field forming means (7)...
・Drive control means patent applicant Fuji Xerox Co., Ltd. Agent
Patent attorney Tomohiro Nakamura (2 others) Is3 diagram ↓ Figure 4 Figure 5

Claims (1)

[Claims] Each ink unit area corresponding to the pixel density is heated appropriately in accordance with the image information, and the heated ink unit area is caused to fly toward the recording sheet based on the electrostatic field formed between the ink surface and the recording sheet. An inkjet recording method characterized in that the heating drive timings of at least adjacent ink unit areas are made inconsistent.