JPH05293977A - Liquid jet recording head and method - Google Patents

Abstract

PURPOSE:To form a document having emphasis of a specific color and to perform halftone recording by applying processing for changing the size of the ink droplet emitted from an orifice corresponding to the color of ink to the orifice and an energy acting part or the vicinities of them. CONSTITUTION:A plurality of passages 8 into which two or more kinds of inks different in color are introduced at every inks are provided. Energy acting parts 6 applying emitting energies to the inks in the passages 8 and the orifices 11 communicating with the passages 8 and emitting a part of the inks to which emitting energies are applied as ink droplets are provided. Altering processing changing the sizes of the ink droplets emitted from the orifices corresponding to the colors of the inks introduced into the passages 8 is applied to the orifices 11 and the energy acting parts 6 or to the vicinities of them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording head and a liquid jet recording method used in a liquid jet recording apparatus for color printing.

[0002]

2. Description of the Related Art The non-impact recording method has been attracting attention for office use and the like because noise generation during recording is so small that it can be ignored. Among them, the liquid jet recording method, which is capable of high-speed recording and can perform recording without requiring a special fixing process on plain paper, is an extremely powerful recording method. Various methods have been proposed, or have already been commercialized and put into practical use.

In such a liquid jet recording method, recording is performed by ejecting a small droplet (ink droplet) of a recording liquid, which is so-called ink, and attaching the ink droplet to a recording medium. The method is roughly divided into several methods according to the method of generating ink drops and the control method for controlling the flight direction of the generated ink drops, but in each method, the advantage that color printing can be easily achieved is utilized. Conventionally, many methods applied to color printing apparatuses have been proposed.

[0004] Among them, there is one disclosed in Japanese Patent Publication No. 1-51346, which is a liquid jet recording apparatus which discharges ink droplets of two or more different colors from a plurality of orifices ( Color inkjet recording device)
In the ink jet recording, at least one color ink is heated or cooled to adjust the liquid viscosity so that the viscous resistances of different inks are aligned and uniform ink droplets are ejected, resulting in high-quality color ink jet recording with little dot shift and color unevenness. The idea is to get an image.

Further, the one disclosed in Japanese Patent Publication No. 1-51347 is a liquid chamber (common ink for storing ink in a color ink jet recording apparatus for ejecting ink droplets of two or more different colors from a plurality of orifices. When the flow path from the chamber to the orifice) has a different liquid chamber length for each ink, a high-quality color inkjet recorded image with little dot shift or color unevenness can be obtained by adjusting the applied energy applied to each ink. Is.

Further, the one disclosed in Japanese Patent Publication No. 63-33459 has a plurality of liquid chambers, and in a color ink jet recording apparatus for ejecting ink droplets of two or more different colors, the liquid chambers are different for each ink. In the case of having a liquid chamber length, by adjusting the liquid viscosity of each ink, dot deviation and color unevenness for each ink are eliminated, and a high quality color inkjet recording image is obtained.

In recent years, it has been desired that office color documents are not simply color documents of a plurality of colors as in conventional business graphics, but rich in gradation and expressed like photographs. For example, it is a color document in which a black and white character portion and a partially inserted color image portion having gradation like a color photograph are mixed.

Here, the concept of changing the size of a pixel formed by ink droplets adhering to a recording medium in order to perform recording with gradation is conventionally known. There is an invention disclosed in Japanese Patent Laid-Open No. 59-207265. In this invention, a group of current pulses is applied to one heater to eject one ink droplet, and the number of ink droplets ejected changes according to the number of applied current pulses. They fly in a state of being coupled to each other and adhere to the same location on the recording medium.

Further, the invention disclosed in Japanese Patent Laid-Open No. 63-53052 is known, and in this invention, a series of ink droplets fused on the recording medium are ejected within the wetting time of the recording medium. This is a method of performing gradation recording. It should be noted that each ink droplet flies at high speed without being combined with each other,
The ink droplets arriving at the recording medium fuse within the wetting time of the recording medium. Then, by increasing the number of ink droplets that coalesce within the wetting time of the recording medium, the diameter of the pixel on the recording medium becomes large.

[0010]

In each of the above-mentioned inventions, which do not take into consideration the gradation recording, the flying characteristics are slightly different for each ink color when performing color printing. It aims to achieve high image quality by compensating for dot deviations on the recording medium so that the dots of each ink are constant, and in that respect, almost the initial purpose has been achieved.

However, with the recent development and popularization of computer graphics, desktop publishing, desktop presentation, etc., color documents,
Or, OHP (overhead projector) or the like is frequently used in general offices, and specific characters, images, or
There are voices wanting to emphasize the color and print it.

Next, in the invention for performing gradation recording disclosed in Japanese Patent Laid-Open No. 207265/1984, the flying speed must be low in order to fly in a state in which a plurality of ink droplets are combined. I won't. Then, the ink droplets flying at a low speed have a bad trajectory, and the reliability of printing is poor. Further, the trajectory of the ink droplets is susceptible to defects of the liquid jet recording head and changes in the moving speed, and if the moving speed of the liquid jet recording head is high, a group of ink droplets flying at low speed adheres to the recording medium. In this case, circular pixels are not formed and the obtained image becomes unclear.

Further, in the invention for performing gradation recording disclosed in Japanese Patent Application Laid-Open No. 63-53052, a bubble is completely collapsed when an ink droplet is ejected and a resistance is required to eject the next ink droplet. The time it takes to heat the element
It is only described that it is within the range of 0.1 μs to 1.0 ms, and specifically, under what conditions should the ink droplets be ejected, or what kind of structure the liquid jet recording head has. It was impossible to realize because there was no description of whether to use.

Therefore, a liquid jet capable of expressing a color image with rich gradation such as a photograph or efficiently producing a document in which such a color image portion and a black and white character portion are mixed can be efficiently produced. There is no recording head or recording method.

[0015]

The invention according to claim 1 is
A plurality of flow paths for introducing a plurality of different colors of ink for each ink, an energy acting portion provided in the flow path and for giving ejection energy to the ink in the flow paths, and in the flow path A liquid jet recording head having an orifice for ejecting a part of the ink, which is communicated with the ejection energy, as an ink droplet, and ejects from the orifice according to the color of the ink introduced into the flow path. The ink droplet size changing process for changing the size of the ink droplet is performed on at least one of the orifice, the energy acting portion, the orifice, and the vicinity of the energy acting portion.

According to a second aspect of the present invention, a plurality of flow paths for introducing a plurality of types of ink of different colors into each ink,
An energy acting portion provided in the flow passage and for giving ejection energy to the ink in the passage, and an orifice communicating with the passage are provided, and the ink is ejected by the ejection energy given from the energy acting portion. In a liquid jet recording method in which a part of the ink is ejected from the orifice as an ink droplet, the ejection energy applied to the ink from the energy acting unit is changed according to the color of the ink and the size of the ink droplet ejected. I made it different.

According to a third aspect of the invention, in the first aspect of the invention, the plurality of types of ink are yellow, magenta,
For cyan and black, at least one of the orifice for ejecting black ink and the energy acting portion is larger than the orifice for ejecting ink of another color or the energy acting portion.

According to a fourth aspect of the present invention, in the second aspect of the invention, the plurality of types of ink are yellow, magenta,
It is cyan and black, and the ink droplets of black ink are made larger than the ink droplets of inks of other colors.

According to a fifth aspect of the invention, in the second aspect of the invention, the plurality of types of ink are yellow, magenta,
Cyan and black, the size of ink droplets of yellow, magenta, and cyan inks is made smaller than that of black ink, and the ink droplet formation frequency of yellow, magenta, and cyan inks is changed to that of black ink droplets. It was higher than the formation frequency.

According to a sixth aspect of the present invention, there is provided a liquid jet recording method in which recording is performed using a liquid jet recording head which ejects four color inks of yellow, magenta, cyan and black. In the liquid jet recording method, yellow, magenta and cyan inks are used. The number of drive pulses that are input to the energy application section that gives the ejection energy to the ink is changed according to the image density information, and the number of ink droplets that are ejected is thereby changed and the number of ink droplets that are ejected to approximately the same location on the recording medium And the diameter of the pixel formed on the recording medium is changed.

[0021]

According to the first aspect of the present invention, since the ink droplet size changing process for changing the ink droplet size according to each ink is performed, the size of the ejected ink droplet can be changed depending on the color of the ink. Therefore, it is possible to obtain a sharp color image in which the color of a specific ink having a large ink droplet is emphasized.

According to the second aspect of the present invention, since the ejection energy applied to the ink from the energy acting portion is varied according to the color of the ink, the size of the ejected ink droplet is varied. A sharp color image in which the color of the ink is emphasized can be obtained.

According to the third aspect of the invention, the ink droplets of black ink are larger than the ink droplets of other colors, and in a document in which a color image portion and a black and white character portion are mixed, the sharpness of black characters is emphasized. A document with

According to the fourth aspect of the invention, since the ink droplets of the black ink are made larger than the ink droplets of the inks of other colors, black characters are displayed in the document in which the color image portion and the black and white character portion are mixed. You will get a document with emphasis and clarity.

According to the present invention, the ink droplets of the yellow, magenta, and cyan inks are made smaller than the ink droplets of the black ink, so that the ink droplet formation frequency of the yellow, magenta, and cyan inks is changed to that of the black ink. It is possible to increase the frequency of ink droplet formation.

In the sixth aspect of the present invention, with respect to the yellow, magenta and cyan inks, the number of ink droplets ejected at the same position on the recording medium changes according to the image density information, and at the same time, on the recording medium. The pixel diameter of the formed pixel changes, and gradation recording is performed on the color image portion.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before the description of the embodiments of the present invention, the basic structure of a liquid jet recording head to which the present invention is applied will be described with reference to FIGS. This liquid jet recording head is formed by bonding a heating element substrate 1 and a lid substrate 2, and the heating element substrate 1 is formed on a silicon substrate 3 by a wafer process by an individual electrode 4, a common electrode 5, and a heating element. (Energy acting part) 6 is formed. On the other hand, the lid substrate 2 has a groove 9 for forming a flow path 8 through which the ink 7 is introduced, and a common ink chamber (not shown) that accommodates the ink 7 that is introduced into the flow path 8.
And a recessed area 10 for forming the heat generating element substrate 1 and the lid substrate 2 are joined as shown in FIG. 8 to form the flow path 8 and the common ink chamber. It In the state where the heating element substrate 1 and the lid substrate 2 are bonded, the heating element 6 is disposed on the bottom surface of the flow channel 8 and is introduced into the flow channel 8 at the end of the flow channel 8. An orifice 11 is formed for ejecting part of the ink 7 as an ink droplet. Further, the lid substrate 2 is formed with an ink inlet 12 for supplying the ink 7 into the common ink chamber by a supply means (not shown).

Next, the structure of the heating element 6, the orifice 11 and its peripheral portion will be described with reference to FIGS. 11 and 12. A heat storage layer 13 is formed on the upper surface of the silicon substrate 3.
The heat generating layer 14 is formed on the heat storage layer 13, and the individual electrode 4 and the common electrode 5 are formed on the heat generating layer 14. The portion of the heating element layer 14 sandwiched between the individual electrode 4 and the common electrode 5 is the heating element 6. Furthermore, the individual electrode 4 and the common electrode 5
A protective layer 15 is formed on the heating element 6.

Here, useful materials for the heating element layer 14 include, for example, a mixture of tantalum-SiO ₂ , tantalum nitride, nichrome, silver-palladium alloy, silicon semiconductor, or hafnium, lanthanum,
Examples thereof include borides of metals such as zirconium, titanium, tantalum, tungsten, molybdenum, niobium, chromium and palladium. Among these materials forming the heating element layer 14, metal borides can be particularly mentioned as excellent ones, and among them, hafnium boride has the most excellent characteristics, and then zirconium boride, The order is lanthanum boride, tantalum boride, vanadium boride, and niobium boride.

The heating element layer 14 can be formed by using a method such as electron beam evaporation or sputtering using the above materials. The thickness of the heating element 6, which is the portion sandwiched between the individual electrode 4 and the common electrode 5 in the heating element layer 14, is such that the amount of heat generated per unit time is as desired. , Material and shape, and further, it is determined according to the actual power consumption and the like, but in the usual case, 0.001 to 5 μm, preferably 0.01 to 1 μm
m.

As the material forming the individual electrodes 4 and the common electrode 5, many of the commonly used electrode materials are effectively used. Specifically, for example, Al and A are used.
Examples thereof include g, Au, Pt, and Cu. These are used and provided at a predetermined position by a technique such as vapor deposition, and have a predetermined size, shape, and thickness.

The characteristics required of the protective layer 15 do not prevent the heat generated by the heat generating element 6 from being effectively transferred to the ink 7, and the ink 7 can generate heat and the heat generating element 6 and the electrodes 4, 5.
Is chemically and physically protected, and at the same time, a short circuit between the electrodes 4 and 5 and an electrical leak between the adjacent electrodes 4 and 5 are prevented through the ink 7.
Examples of useful materials for forming the protective layer 15 include silicon oxide, silicon nitride, magnesium oxide,
Examples thereof include aluminum oxide, tantalum oxide, zirconium oxide and the like, and these can be formed by using a technique such as electron beam evaporation or sputtering. The thickness of the protective layer 15 is usually 0.01 to 10 μm, preferably 0.1 to 5 μm, and most preferably 0.1 to 3 μm.

Next, the principle of ejection of the ink droplets 16 in the above-mentioned liquid jet recording head will be described with reference to FIG. The figure (a) is a steady state, and the surface tension of the ink 7 and the external pressure are kept in equilibrium on the orifice surface. FIG. 2B shows a state in which the heating element 6 is heated and the surface temperature of the heating element 6 rapidly rises, a boiling phenomenon occurs in the adjacent ink layer, and minute bubbles 17 are scattered on the surface of the heating element 6. is there. FIG. 6C shows a state in which the adjacent ink layer that has been rapidly heated on the entire surface of the heating element 6 is instantly vaporized to form a boiling film, and the bubble 17 has grown. At this time, the pressure in the channel 8 is equal to that of the bubbles 1
7 rises by the amount of growth, the balance with the external pressure on the orifice surface is lost, and the ink column begins to grow from the orifice 11. In the same figure (d), the bubble 17 has grown to the maximum, and the ink 7 corresponding to the volume of the bubble 17 is pushed out from the orifice surface. At this time, the heating element 6 is already in a state in which no current flows, and the surface temperature of the heating element 6 is decreasing. The timing at which the volume of the bubble 17 reaches the maximum value is slightly behind the timing at which the drive pulse is applied to the electrodes 4 and 5. FIG. 7E shows a state in which the bubble 17 is cooled by the ink 7 or the like and starts contracting. It should be noted that the tip of the ink column moves forward while maintaining the pushing speed, and the bubbles 17 are generated at the rear end of the ink column.
The ink in the flow path 8 flows backward due to the pressure decrease in the flow path 8 due to the contraction of the ink, and the ink column is constricted. The same figure (f)
The air bubbles 17 further contract, and the ink 7
Is in a state in which the upper surface of the heat generating element 6 is further rapidly cooled by contacting with each other. On the orifice surface, the external pressure is higher than the pressure inside the flow path 8, so that the meniscus is large and the flow path 8 is large.
It is inside. On the other hand, the tip of the ink column becomes an ink droplet 16, which is 5 to 10 m toward the recording paper (not shown).
Discharge at a speed of / s. In the same figure (g), the ink 7 is supplied to the inside of the flow path 8 again by the capillary phenomenon after the ejection of the ink droplet 16 is completed, and the state returns to the same state as in the figure (a), and the bubble 17 is completely removed. Has disappeared.

Next, the basic structure of another type of liquid jet recording head to which the present invention is applied and the principle of ejection of ink droplets 16 will be described with reference to FIGS. 14 and 15. This liquid jet recording head has a flow path 8 through which the ink 7 is introduced.
A piezo element 18 is provided inside as an energy acting portion. When a pulsed signal voltage is applied to the piezo element 18 to distort the piezo element 18 as shown in FIG. 7A, the volume of the flow path 8 is reduced and a pressure wave is generated, and the pressure wave causes an orifice. Ink droplets 16 are ejected from 11. FIG. 6B shows a state in which the strain of the piezo element 18 has disappeared and the volume of the flow path 8 has increased.

Further, as another type of liquid jet recording head to which the present invention is applied, there is a system (Tele type system) disclosed in US Pat. No. 30,60429. In this method, ink droplets are generated by electrostatic attraction, and the generated ink droplets are controlled by an electric field according to a recording signal.
The recording is performed by selectively adhering ink droplets on the recording paper.

As another type of liquid jet recording head to which the present invention is applied, there is also a system (Sweet system) disclosed in US Pat. No. 3,596,275 and US Pat. No. 3,298,030. is there. In this method, ink droplets whose charge amount is controlled by a continuous vibration generation method are generated, and the ink droplets whose charge amount is controlled are made to fly between the deflection electrodes to which a uniform electric field is applied, and onto the recording paper. The recording is performed by attaching them.

Here, in FIG. 16, four liquid jet recording heads described in FIGS. 8 to 12 are arranged and unitized, and inks of different colors (yellow “Y”, magenta “) are formed for each liquid jet recording head. M ", cyan" C ",
1 shows a conventional liquid jet recording head (color head unit) in which color printing is performed by ejecting black “B”) 7. In addition, FIG.
Is a color head unit of another conventional example in which four similar liquid jet recording heads are stacked to form a unit.

Next, a first embodiment of the present invention will be described with reference to FIG. The same parts as those described in FIGS. 8 to 17 are designated by the same reference numerals, and the description thereof will be omitted (the same applies hereinafter). In this embodiment, a liquid jet recording head (color head unit) for color printing is formed by arranging four liquid jet recording heads described in FIGS. 8 to 12 into a unit, and FIG. The structure is substantially the same as that of the color head unit shown. However, as an ink droplet size changing process for changing the size of the ink droplet 16 ejected from the orifice 11 in each liquid jet recording head, heat generation which is an energy acting portion provided in the flow path 8 in each liquid jet recording head is performed. The size of the body 6 is changed, and the heating element 6 of the liquid ejecting recording head that ejects the black ink 7 is larger than the heating element 6 of the liquid ejecting recording head that ejects the yellow, magenta, and cyan inks 7. Largely formed.

In such a configuration, the ink droplet 16 of the black ink in which the size of the heating element 6 is increased becomes larger than the ink droplet 16 of the ink 7 of other colors (yellow, magenta, cyan). When a document in which a color image part and a black and white character part are mixed is printed,
A crisp text with black letters highlighted is obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, a liquid jet recording head (color head unit) for color printing is formed by stacking four liquid jet recording heads described in FIGS. 8 to 12, and is shown in FIG. The structure is substantially the same as that of the color head unit. However, the size of the orifice 11 in each liquid jet recording head is changed as the ink droplet size changing process for changing the size of the ink droplet 16 ejected from the orifice 11 in each liquid jet recording head. The opening area of the orifice 11 of the liquid jet recording head for ejecting the ink 7 is set larger than the opening area of the orifice 11 of the liquid jet recording head for ejecting the ink 7 of another color.

In such a configuration, the ink droplet 16 of the black ink 7 ejected from the orifice 11 having the larger opening area is larger than the ink droplet 16 of the ink 7 of another color. Then, when a document in which a color image part and a black and white character part are mixed is printed, a sharp document in which black characters are emphasized can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a color head unit is formed by arranging four liquid jet recording heads described in FIGS. 8 to 12 into a unit, and has a structure substantially the same as that of the color head unit shown in FIG. is there. However, as the ink droplet size changing process for changing the size of the ink droplet 16 ejected from the orifice 11 in each liquid jet recording head, the size of the flow path 8 in each liquid jet recording head is changed, and black Flow path 8 in a liquid jet recording head for ejecting ink 7
Is set to be larger than the size of the flow path 8 in the liquid jet recording head that ejects the ink 7 of another color.

In such a structure, the ink droplet 16 of the black ink 7 discharged from the large-sized flow path 8
Is larger than the ink droplets 16 of other colors ejected from the flow path 8 having a small size. Then, when a document in which a color image part and a black and white character part are mixed is printed, a sharp document in which black characters are emphasized can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, a color head unit is formed by arranging four liquid jet recording heads described in FIGS. 8 to 12 into a unit, and has a structure substantially the same as that of the color head unit shown in FIG. is there. However, as the ink droplet size changing process for changing the size of the ink droplet 16 ejected from the orifice 11 in each liquid jet recording head, the size of the heating element 6 provided in the flow path 8 in each liquid jet recording head and The position, the size of the flow path 8 and the opening area of the orifice 11 are changed, and the liquid jet recording head that ejects the black ink 7 is different from the liquid jet recording head that ejects the ink 7 of another color. The heating element 6 is large, the distance from the orifice 11 to the heating element 6 is long, and the size of the flow path 8 and the opening area of the orifice 11 are set large.

In such a structure, the ink droplet 16 of the black ink 7 becomes larger than the ink droplets 16 of other colors. Then, when a document in which a color image part and a black and white character part are mixed is printed, a sharp document in which black characters are emphasized can be obtained.

Here, in each of the embodiments shown in FIGS. 1 to 4, the liquid jet recording apparatus in which the color head unit is formed by using the liquid jet recording head described in FIGS. 8 to 12 has been described. The present invention is not applied only to a liquid jet recording apparatus using such a bubble jet type liquid jet recording head, and as described with reference to FIGS. 14 and 15, the piezo element 18 is used as a drive source for ink ejection. The present invention can also be applied to a drop-on-demand type liquid jet recording head and a liquid jet recording apparatus using the above-described Tele type type or Sweet type liquid jet recording head.

In the embodiment shown in FIG. 2, the ink droplet size changing process has been described by exemplifying a case in which the opening area of the orifice 11 is changed according to the color of each ink 7. As the ink droplet size changing process, it is conceivable to change the thickness of the orifice 11 (length in the direction perpendicular to the opening surface), or change the material or surface roughness of the orifice portion.

Next, the experimental results in the case where a color head unit is specifically configured and color printing is performed will be described below. The first specific example has a configuration of a color head unit as shown in FIG. 1, and the size of the heating element 6 in the liquid jet recording head for ejecting the black ink 7 is 130 × 28 μm (resistance value 108Ω. ) And inks 7 of other colors (yellow, magenta, cyan)
The size of the heating element 6 in the liquid jet recording head for ejecting is 110 × 26 μm (resistance value 118Ω). Then, under other conditions, the liquid jet recording head that ejects the black ink 7 and the liquid jet recording head that ejects the ink 7 of another color are all the same as described below. Distance from heating element 6 to orifice 11 120 μm Orifice 11 size 25 × 25 μ
m Orifice 11 array density 400 dpi Heater 6 drive voltage 26V Heater 6 drive pulse width 6 μs Heater 6 drive pulse frequency 6.2 kHz Color image unit and black and white using a color head unit under conditions above When a document with a mixture of character parts of is printed, the characters printed with black ink 7 are
A black, thick, clear, and very legible document was obtained.
On the other hand, as shown in FIG. 16, a sensitivity test in which a similar document is printed by a color head unit in which all of the heating elements 6 have the same size and is compared with the document obtained by the printing according to the first specific example. As a result, all 10 subjects answered that the document obtained by the printing according to the first specific example was easier to see.

As a second specific example, a color head unit as shown in FIG. 2 is used, and the size of the orifice 11 in the liquid jet recording head for ejecting the black ink 7 is 27 × 27 μm. The size of the orifice 11 in the liquid jet recording head for ejecting the ink 7 of another color is 25 × 25 μm. The other conditions in each liquid jet recording head were all the same as shown below. Distance from heating element 6 to orifice 11 120 μm Size of heating element 6 110 × 26
μm Resistance value of heating element 6 118Ω Orifice 11 array density 400 dpi Driving voltage of heating element 6 26V Driving pulse width of heating element 6 μs Driving pulse frequency of heating element 6 Color head unit used under 6.2 kHz or more When a document in which a color image part and a black and white character part are mixed is printed, the character printed by the black ink 7 is
A black, thick, clear, and very legible document was obtained.
On the other hand, as shown in FIG. 17, a sensitivity test is performed in which a similar document is printed by a color head unit in which all the dimensions of the orifices 11 are the same, and is compared with the document obtained by the printing according to the second specific example. As a result, all 10 examinees answered that the document obtained by printing the second specific example was easier to see.

As a third concrete example, FIG. 14 and FIG.
As shown in FIG. 17, a color head unit was formed by stacking the liquid jet recording head having the piezo element 18 as an energy acting portion as shown in FIG. The various structural conditions of each liquid jet recording head were the same as follows. Dimensions of the orifice 11 50 × 50 μm Arrangement density of the orifice 11 50 dpi Size of the piezo element 18 2.5 × 12 mm As described above, the piezo element in the liquid jet recording head for ejecting the black ink 7 using the color head unit as described above. The drive voltage of 18 was set to 65V, and the drive voltage of the piezo element 18 in the liquid jet recording head for ejecting the ink 7 of another color was set to 50V. By increasing the drive voltage, the amount of deformation of the piezo element 18 increases and the ink droplet 1 ejected from the orifice 11
The size of 6 also becomes large.

Under the above conditions, when a document in which a color image part and a black and white character part are mixed is printed, the character printed by the black ink 7 is thick, easy to see, and a powerful document is obtained. .. On the other hand, the drive voltage of the piezo element 18 in the liquid jet recording head that ejects the black ink 7 is set to 5 as in the drive voltage of the piezo element 18 in the liquid jet recording head that ejects the ink 7 of another color.
When a sensitivity test was conducted by printing the document at 0V and comparing it with the document obtained by the imprinting according to the third example, all 10 test subjects were imprinted with the imprinting according to the third example. I answered that the document obtained by copying was more powerful and persuasive.

As a fourth specific example, the same color head unit as in the first specific example described above is used, and the heating element 6 is used.
Drive voltage is increased to 28 V in the liquid jet recording head that ejects the black ink 7,
In the liquid jet recording head for ejecting, the voltage was kept at 26V.

Then, a sensitivity test was conducted to compare the document obtained by the printing according to the fourth specific example with the document obtained by the printing according to the first specific example. As a result, 10 subjects were examined. Nine of the respondents answered that the document obtained by the printing according to the fourth specific example had black letters, thick letters, clear letters, and was easy to see.

As a fifth specific example, in the color head unit using the piezo element 18 as described in the third specific example, the piezo element 18 (of the liquid jet recording head for ejecting the black ink 7) 2.5 x 2
5 mm) is made larger than the piezo element 18 (2.5 × 12 mm) of the liquid jet recording head for ejecting another color, and the driving voltage is also high (70 V and 50 V).
V).

Then, a sensitivity test was conducted to compare the document obtained by the printing according to the fifth specific example with the document obtained by the printing according to the third specific example. As a result, 10 subjects were examined. All of them answered that the document obtained by the printing according to the fifth specific example is a document in which characters are black, thick, and powerful.

As the sixth specific example, the same color head unit as in the second specific example described above is used, and the heating element 6 is used.
Drive voltage is increased to 28.5V in a liquid jet recording head that ejects black ink 7, and 26V in a liquid jet recording head that ejects ink 7 of another color.
I left it as it was.

Then, a sensitivity test was conducted to compare the document obtained by the printing according to the sixth specific example with the document obtained by the printing according to the second specific example. Nine of the respondents answered that the document obtained by the printing according to the sixth specific example had the characters in black, thick, clear and easy to see.

As a seventh specific example, in the liquid jet recording head in which the same color head unit as in the first specific example described above is used and the black ink 7 is ejected, the size of the heating element 6 is set to 130. × 28 μm (resistance value 10
8Ω), the distance from the heating element 6 to the orifice 11 is 14
0 μm, the width of the flow path 8 reaching the orifice 11 is 35 μm,
In a liquid jet recording head in which the size of the orifice 11 is 26 × 26 μm and the ink 7 of another color is ejected,
The size of the heating element 6 is 110 × 26 μm (resistance value 118
Ω), the distance from the heating element 6 to the orifice 11 is 120
μm, the width of the flow path 8 reaching the orifice 11 was 30 μm, and the size of the orifice 11 was 25 × 25 μm. On the other hand, the driving conditions and the like of the heating element 8 are the same as those in the first specific example in all the liquid jet recording heads.

Under the above conditions, when a document in which a color image part and a black and white character part are mixed is printed, the characters printed by the black ink 7 are black, thick, clear, and very easy to see. The document obtained was easier to read than the document obtained in the one specific example.

As an eighth specific example, a color head unit for stacking three liquid jet recording heads as shown in FIGS. 8 to 12 to eject ink 7 of three colors of yellow, magenta and cyan is constructed. did. At that time, the orifice 1 of the liquid jet recording head for ejecting the magenta ink 7
1 has a size of 26 × 26 μm, and the orifice 1 of the liquid jet recording head that ejects the yellow and cyan inks 7
The size of 1 was 25 × 25 μm. On the other hand, the size of the heating element 6 (110 × 26 μm), the resistance value (118 Ω), the distance from the heating element 6 to the orifices 11 (120 μm), the array density of the orifices 11 (400 dpi), the driving conditions of the heating elements 6, etc. Is the same for all liquid jet recording heads.

When a color image for a poster of a dusk landscape is printed with such a color head unit, it is possible to obtain an image with a reddish tinge and a good dusk atmosphere, and to enhance the dusk image. Was confirmed.

The above example is an example in which gradation printing is not performed and a specific color is simply emphasized and printed. Therefore, the size of the ink droplet 16 or various means for changing it (the heating element 6 and the orifice 1)
Changes such as dimensions (1 etc.) take relatively small values.

Next, the features of the present invention in consideration of gradation recording will be described. Basically, as in the case where the above gradation recording is not performed, the ink droplet 1 of the ink 7 of a specific color is
The size of 6 is changed to the size of the ink droplet 16 of the ink 7 of another color, or the dimension of the means is changed, but the point that the dimension is changed is different from the above example. There is. In particular,
For example, the ink droplet 16 of each of the yellow, magenta, and cyan inks 7 is sized so as to print 800 dpi, and the ink droplet 16 of the black ink 7 is 400.
The size is set so as to perform printing equivalent to dpi. In order to eject the ink droplet 16 having such a size, the heating element 6 and the orifice 11 of each liquid jet recording head are used.
The dimensions such as are also set to correspond to them.

By doing this, yellow, magenta,
Since the mass of the ink droplet 16 of each cyan ink 7 is small, the ejection frequency can be increased. In FIG. 5, the yellow, magenta, and cyan inks 7 are continuously ejected at a high ejection frequency, and the ink droplets 16 are ejected from the recording medium 19.
It shows a state in which one pixel 20 is formed by implanting in the same place above. The important point here is
That is, each ink droplet 16 is separated, ejected and ejected independently, and adheres to the recording medium 19 (Japanese Patent Laid-Open No. 59-20726).
In the invention disclosed in Japanese Patent Publication No. 5, the ink droplets are ejected and fly while being connected to each other). In addition, each ink droplet 16 flies in the form of an elongated column (Japanese Patent Laid-Open No. 63-53).
In the invention disclosed in Japanese Patent No. 052, each ink droplet flies in a spherical shape). The size of the ink droplet 16 flying in the form of an elongated column is 3 to 10 times as long as its diameter.

Here, the conditions for the ink droplets 16 to fly in the form of elongated columns are that the flying speed is high and they are not easily affected by disturbance (for example, the flow of surrounding air). Therefore, the relationship between the shape of the ink droplet 16 and the flying speed, and the relationship between the shape of the ink droplet 16 and the deviation amount (pixel position accuracy) from the target position on the recording medium 19 were investigated and shown in Table 1. ..

[0066]

[Table 1]

In the liquid jet recording head used here, the size of the orifice 11 is 17 × 17 μm, the size of the heating element 6 is 14 × 84 μm, and the resistance value of the heating element 6 is 75Ω. Further, when measuring the shape and flight speed of the ink droplet 16, a vehicle of the following components (a transparent liquid obtained by removing a dye component from the ink) was used instead of the ink.

Glycerin 18.0% Ethyl alcohol 4.8% Water 77.2% On the other hand, the ink of the following components was used for the measurement of pixel position accuracy.

Glycerin 18.0% Ethyl alcohol 4.8% Water 75.0% C.I. I. Acid Blue 29 2.2% As the recording medium 19 to which the ink droplets 16 are attached, PPC paper 6200 manufactured by Ricoh Co., Ltd. was used, and the frequency of the drive pulse input to the heating element 6 was 20 kHz.

From Table 1, I _L / I _D , that is, the ratio of the length dimension “I _L ” of the ink droplet 16 to the diameter dimension “I _D ” of the ink droplet 16 is 2.8 or less. Since the flight speed of 16 is slow (does not reach 5.0 m / s), the ink droplet 16 cannot be ejected to a target position on the recording medium 19, and the image quality is deteriorated when the ink droplet 16 is displaced by at least one dot. It turns out to be impractical. That is, it can be seen that the flying ink droplets 16 must be ejected under the condition that they are columnar (I _L / I _D is 3 or more).

Next, FIG. 6 shows the shape of the ink droplet 16 in more detail. The ink droplet 16 shown in FIG. 9A has the most ideal shape, but as shown in FIG. 9B, it flies with a mist-like very small ink droplet called a satellite 16a. Two ink droplets 16 (three in some cases) as shown in FIGS.
In some cases, it may fly separately. These differences are due to the size of the orifice 11, the physical properties of the ink (viscosity, surface tension),
Depending on the shape of the driving pulse, etc.
The number of drive pulses input to is one. Therefore, here, even when what should originally be one ink drop 16 separates and flies as shown in FIGS. 7C and 7D, one ink drop 16 is applied to one drive pulse. Are treated as formed. Even if the satellites 16a are separated in this way or fly with the satellites 16a, if the flying speed is 5 to 10 m / s or more as described above, the satellites 16a and the separated ink droplets 16 are not covered. Since the pixels 20 are attached to substantially the same position on the recording medium 19, the formed pixels 20 are close to a perfect circle, and the problem of deterioration in image quality does not occur.

Next, in FIG. 7, the number of ink droplets 16 forming one pixel 20 is changed by changing the number of drive pulses continuously input to the heating element 6, and the size of the pixel 20 formed thereby is changed. This is a view showing how the angle changes. In FIG. 1A, one driving pulse is input to the heating element 6 and one ink droplet 1 is discharged from the orifice 11.
6 is ejected, and one ink droplet 16 adheres on the recording medium 19 to form one pixel 20. The same figure (b)
Then, three drive pulses are input, three ink droplets 16 are ejected, and the three ink droplets 16 are recorded.
One pixel 20 is formed by being driven into the same place on 9. In FIG. 7C, five driving pulses are input, five ink droplets 16 are ejected, and the five ink droplets 16 are ejected to the same position on the recording medium 19 to form one ink droplet 16. Pixels 20 are formed. In FIG. 7D, eight driving pulses are input, eight ink droplets 16 are ejected, and the eight ink droplets 16 are ejected to the same location on the recording medium 19 to form one ink droplet. Pixels 20 are formed. Note that the pixels 20 formed become larger as the number of ink droplets 16 ejected to the same location increases.

Here, in the present invention, obtaining a large pixel 20 can be realized by increasing the number of drive pulses and increasing the number of ink droplets 16 continuously ejected.
Increasing the number of drive pulses inevitably increases the time required to form one pixel 20. Therefore, if the ejected ink droplets 16 are connected to each other as disclosed in Japanese Patent Laid-Open No. 207265/1984, as described above, the flight trajectory of the ink droplets 16 is deteriorated and the reliability of printing is deteriorated. Therefore, it is an important point to increase the recording speed to generate the ink droplets 16 as frequently as possible in a range where the ink droplets 16 are not connected to each other.

Next, as a ninth specific example, a color head unit as shown in FIG. 4 was formed. This color head unit is a liquid jet recording head for ejecting black ink 7 from the size from the heating element 6 to the orifice 11, the size of the orifice 11, the size of the heating element 6 and the resistance value of the heating element 6. And the liquid jet recording head for ejecting the ink 7 of another color as described below, and the arrangement density of the orifices 11 is common in that 128 orifices 11 are arranged at 400 dpi. ..

[0075]

[Table 2]

The used ink 7 has the following composition.

[0077]

[Table 3]

When the conditions for forming the ink droplets 16 were examined using such a color head unit, a liquid jet recording head for ejecting the yellow, magenta, and cyan inks 7 responded to a drive pulse frequency of 51 kHz at maximum. Ink droplet 16 can be ejected and ink droplet 1
The flight speed (Vi) of No. 6 was 11.3 m / s. The driving conditions at this time are a driving voltage of 5.9 V and a driving pulse width (Pw) of 4 μs. On the other hand, a liquid jet recording head that ejects black ink 7 has a maximum of 9 kH.
The ink droplet 16 could be ejected in response to the drive pulse frequency of z, and the flight speed (Vi) of the ink droplet 16 was 10.1 m / s. The driving condition is that the driving voltage is 27V and the driving pulse width (Pw) is 7 μs.

Next, using a liquid jet recording head for ejecting magenta ink 7, one to a plurality of ink droplets 1 are ejected to the same position on the paper surface (Mitsubishi Co., Ltd. McCourt paper NM).
When 6 is set and one pixel is measured, the pixel diameter of the pixel 20 formed by one ink droplet 16 is φ31.3 μm, and the pixel diameter of the pixel 20 formed by two ink droplets 16 is The pixel diameter is φ64.6 μm, and the pixel diameter of the pixel 20 formed by the four ink droplets 16 is φ8.
A round pixel having a pixel diameter of 3.5 μm and a pixel diameter of φ97.8 μm formed by six ink droplets 16 was obtained. The drive pulse frequency at this time is 48 kHz.
The pixel formation frequency was set to 8 kHz.

On the other hand, the pixel diameter of the pixel 20 formed by one ink droplet 16 of the black ink 7 is φ95.6.
was μm.

From the above basic data, the liquid jet recording head for ejecting each of the yellow, magenta, and cyan inks 7 can change the number of ink droplets 16 ejected by changing the number of drive pulses input to the heating element 6. Can
Since it was found that the size of one pixel could be changed by this, when a mixed document of photographs and characters was printed using this color head unit, the image part of the photograph was comparable to the color photograph of the original manuscript. It was possible to obtain an image with high image quality and high gradation, and to obtain the same beautiful print quality as the character part typed with a typewriter. At this time, in each liquid jet recording head that ejects the yellow, magenta, and cyan inks 7, the frequency of generation of the ink droplets 16 (driving pulse frequency) is set to 48 kHz, and the ink droplets that are ejected to the same location in order to change the pixel diameter. The number of 16 was changed from 1 to 6 according to the image density information. Therefore, the pixel formation frequency is set to 8 kHz. On the other hand, the drive pulse frequency of the liquid jet recording head for ejecting the black ink 7 was 6 kHz.

[0082]

As described above, the invention according to claim 1 is provided with a plurality of flow paths for introducing a plurality of types of inks of different colors for each ink, and inside the flow paths. A liquid ejecting recording head having an energy acting portion for applying ejection energy to the ink, and an orifice that is connected to the flow path and ejects a part of the ink to which the ejection energy is applied as an ink droplet, Ink droplet size changing processing for changing the size of an ink droplet ejected from the orifice according to the color of the ink introduced into the flow path is performed in the orifice, the energy acting portion, the orifice, or the vicinity of the energy acting portion. Since it was applied to at least one of the above, it is possible to change the size of the ink droplets ejected from the orifice according to the color of the ink, What has the effect of such a color image can be obtained with a sharp emphasizing the color of a particular ink to increase the ink droplet.

According to the second aspect of the invention, as described above, a plurality of flow paths for introducing a plurality of types of inks of different colors for each ink, and a plurality of flow paths provided in the flow path and in the flow path are provided. An energy acting portion for giving ejection energy to the ink and an orifice connected to the flow passage are provided, and a part of the ink is ejected from the orifice as an ink droplet by the ejection energy given from the energy acting portion. In the liquid jet recording method described above, since the ejection energy given to the ink from the energy acting portion is made different according to the color of the ink and the size of the ejected ink droplet is made different, the energy acting portion changes to the ink. If the size of the ejected ink droplet is different by changing the applied ejection energy according to the color of the ink Rukoto can, therefore, have an effect such as only electrical control it is possible to obtain a color image with emphasis on sharp color of a particular ink.

As described above, the invention of claim 3 is the invention of claim 1, wherein the plurality of types of ink are yellow, magenta, cyan, and black, and an orifice for ejecting black ink and energy action. Since at least one of the parts is made larger than the orifice or the energy application part for ejecting ink of another color,
The ink droplet of black ink ejected from a large orifice or given the ejection energy from a large energy acting portion can be made larger than the ink droplets of inks of other colors, and a color image portion and a black and white character portion are mixed. When the document is printed, it is possible to obtain a sharp document with emphasized black characters.

As described above, the invention according to claim 4 is the invention according to claim 2, wherein the plurality of types of ink are yellow, magenta, cyan, and black, and the ink droplets of the black ink are changed to the inks of other colors. Since the ink droplets are larger than the ink droplets, it is possible to obtain a sharp document in which black characters are emphasized when a document in which a color image portion and a black and white character portion are mixed is printed.

As described above, the invention according to claim 5 is the invention according to claim 2, wherein the plurality of types of ink are yellow, magenta, cyan, and black, and the size of the ink droplets of the yellow, magenta, and cyan inks is large. Since the ink droplet size of the yellow, magenta, and cyan inks is made higher than that of the black ink, the ink droplet formation frequency is made higher than that of the black ink droplets, resulting in minute ink droplets and a small mass. It is easy to increase the frequency of ink droplet formation of the yellow, magenta, and cyan ink droplets, and the ink droplets can be printed at the same position on the recording medium.
Gradation recording can be performed on the color image portion by ejecting a plurality of ink droplets from one piece and adjusting the number of ejected ink droplets, and since the frequency of ink droplets for gradation recording is high, it is possible to print on the recording medium. Even if printing is performed such that a plurality of ink droplets are ejected to the same place, it is possible to prevent the printing speed from decreasing.

According to the sixth aspect of the invention, as described above, in the liquid jet recording method for performing recording by using the liquid jet recording head for ejecting ink of four colors of yellow, magenta, cyan and black, yellow and magenta are used. And the number of drive pulses input to the energy application section that gives ejection energy to cyan ink are changed according to the image density information, and the number of ejected ink droplets is thereby changed and the ink is ejected to approximately the same location on the recording medium. Since the number of ink droplets is changed and the pixel diameter of the pixel formed on this recording medium is also changed, for yellow, magenta, and cyan ink, the ink droplets that are ejected to the same position on the recording medium are The number can be changed according to the image density information, and the pixel diameter of the pixels formed on the recording medium can be changed. , Therefore, it has an effect such as can be performed gradation recording the color image portion.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a second embodiment of the present invention.

FIG. 3 is a plan view showing a third embodiment of the present invention.

FIG. 4 is a plan view showing a fourth embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a flying state of ink droplets.

FIG. 6 is an explanatory diagram showing in detail the shape of a flying ink droplet.

FIG. 7 is an explanatory diagram showing the relationship between the number of drive pulses, the number of ejected ink droplets, and the size of a pixel formed.

FIG. 8 is a perspective view showing a liquid jet recording head for ejecting a single color ink in a conventional example.

FIG. 9 is a perspective view showing a state in which a liquid jet recording head of a conventional example is separated into a heating element substrate and a lid substrate.

FIG. 10 is a perspective view showing a state where the lid substrate is viewed from the back surface side.

FIG. 11 is an enlarged front view showing an orifice and its peripheral portion.

FIG. 12 is a vertical sectional side view showing a heating element and its peripheral portion in an enlarged manner.

FIG. 13 is an explanatory diagram showing the principle of ink droplet ejection in the liquid jet recording head.

FIG. 14 is a vertical sectional side view showing a part of a conventional liquid jet recording head using a piezo element.

FIG. 15 is a plan view showing the whole of a conventional liquid jet recording head using a piezo element.

FIG. 16 is a plan view showing a conventional color head unit.

FIG. 17 is a perspective view showing another conventional color head unit.

[Explanation of symbols]

 6 Energy Action Section 7 Ink 8 Flow Path 11 Orifice 16 Ink Drop

Claims (6)

[Claims] 1. A plurality of flow paths for introducing a plurality of types of inks of different colors for each ink, and an energy acting portion provided in the flow paths and for applying ejection energy to the ink in the flow paths. A liquid jet recording head having an orifice that discharges a part of the ink, which is connected to the flow path and is supplied with the discharge energy, as an ink droplet, in accordance with the color of the ink introduced into the flow path. The ink droplet size changing process for changing the size of the ink droplet ejected from the orifice is performed on at least one of the orifice, the energy acting portion and the orifice or the vicinity of the energy acting portion. Liquid jet recording head. 2. A plurality of flow paths for introducing a plurality of types of inks of different colors for each ink, and an energy acting portion provided in the flow paths and for giving ejection energy to the ink in the flow paths. A liquid jet recording method, wherein an orifice connected to the flow path is provided, and a part of the ink is ejected as an ink droplet from the orifice by the ejection energy given from the energy acting part. A liquid jet recording method, characterized in that the ejection energy applied to the ink from a portion is made different according to the color of the ink and the size of the ejected ink droplet is made different. 3. A plurality of types of ink are yellow, magenta, cyan, and black, and at least one of an orifice for ejecting black ink and an energy acting portion is an orifice for ejecting ink of another color or The liquid jet recording head according to claim 1, wherein the liquid jet recording head is larger than the energy acting portion. 4. The liquid according to claim 2, wherein the plurality of types of ink are yellow, magenta, cyan, and black, and the ink droplets of black ink are larger than the ink droplets of inks of other colors. Jet recording method. 5. The plurality of types of inks are yellow, magenta, cyan, and black, and the size of ink droplets of yellow, magenta, and cyan inks is made smaller than that of black inks, and yellow, magenta, and cyan are also included. 3. The liquid jet recording method according to claim 2, wherein the ink droplet formation frequency of the above ink is set higher than the ink droplet formation frequency of the black ink. 6. A liquid ejecting recording method for performing recording using a liquid ejecting recording head for ejecting inks of four colors of yellow, magenta, cyan and black, the energy for giving ejection energy to the inks of yellow, magenta and cyan. The number of drive pulses input to the action portion is changed according to the image density information, thereby changing the number of ink droplets to be ejected and changing the number of ink droplets to be ejected at substantially the same position on the recording medium. A liquid jet recording method, wherein a pixel diameter of a pixel formed on the body is changed.