JP2002127472A - Printer head for ink jet recording and ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer head for ink jet recording and a recording method in which a good image quality is realized even if an identical control waveform is employed for an ink set containing inks having different values of physical properties or different characteristics. SOLUTION: The printer head for ink jet recording has a plurality of heads which eject ink liquid drops with a different pushing force upon receiving an identical signal for controlling the quantity of ink liquid drop 11 being ejected from the nozzle 5 of respective heads 10. In the recording method, the printer head for ink jet recording having a plurality of heads which eject ink liquid drops with a different pushing force is employed and ink liquid drops are ejected from the heads with a different pushing force upon receiving an identical control signal by delivering an identical signal to these heads.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer head for ink jet recording and an ink jet recording method.

[0002]

2. Description of the Related Art In the case of performing color printing by an ink jet recording method, a three-color ink set of yellow ink, magenta ink and cyan ink is used or black ink is added, as in general color printing. Although color printing is performed using the color ink set, in addition to the above three or four color ink set, light magenta ink and light cyan ink are added in order to further improve the image quality of the highlight portion. Methods using color or six-color ink sets are also widely practiced. When these five-color or six-color ink sets are used, the physical properties (for example, viscosity) and characteristics (for example, on the recording medium after printing) of the ink liquids of all colors are adjusted in order to match the ejection characteristics from the head for each ink. It is preferable that the dot diameters of the dots are uniform.

[0003] For example, when the viscosity of an ink set of six colors is made uniform, the light magenta ink liquid and the light cyan ink liquid generally have a small amount of a coloring material, so that the viscosity becomes low with a composition similar to other color inks. A thickener is added to these light-based ink liquids. However, when ink droplets containing a thickener are ejected onto a recording medium such as printing paper, the ink droplets are often inferior in dryness and / or permeability to ink droplets containing no thickener. In the case where the time remaining on the medium is long and a plurality of colors are printed and mixed colors, it may cause bleeding. In particular, when printing mixed colors under low-temperature and high-humidity conditions, the tendency of bleeding may increase.

[0004] In order to prevent such bleeding of the light-based ink, there has been proposed a technique for reducing the amount of light-based ink to be applied. The first method is to reduce the duty of the light-based ink. In this method, the number of dots is reduced without changing the amount of ink in each dot unit, thereby reducing the amount of the entire light system ink. However, this method has a disadvantage that the image quality is deteriorated because the dots are thinned out.

A second method for reducing the amount of light-based ink ejected is to lower the voltage of a control waveform that controls the amount of light-based ink droplets ejected from the light-based ink head, thereby reducing the amount of light-based ink. This is a method for reducing the amount of droplets. In this method, since the amount of light-based ink applied is reduced by decreasing the amount of light-based ink in each dot unit without changing the total number of dots, the duty is reduced as described above. Although no significant deterioration in image quality occurs, it is necessary to prepare a control waveform for light magenta ink and a control waveform for light cyan ink.

Further, as a third method for reducing the amount of light-based ink ejected, there is known a method in which the viscosity of the light-based ink is further increased to reduce the amount of light-based ink droplets. In this method as well, similarly to the second method, since the amount of light-based ink is reduced by reducing the amount of light-based ink in each dot unit without changing the total number of dots, the amount of light-based ink as a whole is reduced. Although the image quality does not deteriorate as in the method of reducing the duty described above, the ejection amount becomes extremely low because the light type ink liquid becomes more viscous at a low temperature, and the ejection may become impossible. There were drawbacks.

Therefore, five colors or six colors including light inks
It has been desired to develop a technique for solving the above-mentioned problems of the prior art in color printing using a color ink set.

[0008] When color printing is performed by an ink jet recording method, an ink set including an ink that causes a difference in dot diameter even when ejected with the same droplet amount may be used. As described above, if an ink set including inks having different dot diameters depending on the type of color is used,
Even if all the inks are ejected with the same appropriate amount of liquid, the dot diameter differs depending on the color, so that the solid coating may not be sufficiently filled with the color having the minimum dot diameter.

Therefore, it has been desired to develop a technique for solving the above-mentioned problems of the prior art in color printing using an ink set having a dot diameter that differs depending on the type of color.

[0010]

SUMMARY OF THE INVENTION The present inventor has proposed means for realizing high image quality when an ink set contains ink liquids having different physical property values and characteristics as described above. We conducted intensive research on.

Specifically, the inventor of the present invention has conducted intensive studies for the purpose of developing a technique for solving the above-mentioned problems of the prior art in color printing using a five-color or six-color ink set including a light-based ink. A technology has been developed that does not cause deterioration in image quality and has no problem in ejection performance at low temperatures. In addition, according to this technique developed by the present inventors, it has been found that the above-mentioned problems of the related art in color printing using an ink set having a difference in dot diameter depending on the color can be solved. That is, this technique developed by the present inventors can be generally applied to the adjustment of the ink droplet ejection amount generated by adjusting the physical properties and characteristics of those ink liquids in an ink jet recording method using a plurality of inks. Was also found.

The present invention is based on such findings.

[0013]

According to the present invention, each head receives the same control signal as a signal for controlling the amount of ink droplet to be ejected from a nozzle of each head included in the printer head for ink jet recording. In this case, the present invention relates to a printer head for ink jet recording, comprising a plurality of heads for ejecting ink droplets from nozzles with different pressing forces.

In a preferred aspect of the apparatus of the present invention, the pushing force of the ink droplets ejecting the ink droplets which are difficult to dry on the recording medium is changed by the ejection force of the ink droplets which easily dry the recording medium on the recording medium. It is weaker than the pushing force of the ink droplet.

In another preferred aspect of the apparatus of the present invention, the pushing force of the ink droplets in the head for ejecting the light-type ink droplets is controlled by the ink droplets in the head for ejecting the ink droplets other than the light-type ink. Weaker than the pushing force of.

In another preferred embodiment of the apparatus of the present invention, a head for discharging ink droplets having a smaller dot diameter is used for an ink set including ink in which a dot diameter differs when discharged with the same droplet amount. Is made stronger than the pushing force of a head that ejects ink droplets having a larger dot diameter.

In still another preferred embodiment of the present invention, a signal for controlling the amount of ink droplets to be ejected from the nozzle of each head controls the amount of displacement of a piezoelectric element provided in each head. Signal.

In the printer head for ink jet recording according to the present invention including the individual heads provided with the horizontal effect type or vertical effect type laminated piezoelectric element, the layer of the piezoelectric thin film constituting the laminated piezoelectric element is provided. By changing the thickness between the individual heads and sending a control signal having the same waveform to each head, the pushing force of the ink droplet can be changed.

In the ink jet recording printer head according to the present invention including the individual heads provided with the lateral effect type laminated piezoelectric element, the displacement direction lengths of the piezoelectric thin films constituting the laminated piezoelectric element are individually set. By sending control signals with the same waveform to each head,
The pushing force of the ink droplet can be changed.

In the printer head for ink jet recording according to the present invention including the individual heads provided with the vertical effect type laminated piezoelectric element, the total layer thickness of the laminated piezoelectric element is changed between the individual heads. By sending a control signal having the same waveform to each head, the pushing force of the ink droplet can be changed.

In an ink jet recording printer head according to the present invention including individual heads provided with a single-layer piezoelectric element, the thickness of the single-layer piezoelectric element is changed between the individual heads. By sending a control signal having the same waveform to the above, the pushing force of the ink droplet can be changed.

In an ink jet recording printer head according to the present invention including individual heads provided with a single-layer piezoelectric element, the length of the pressure generating chamber in the direction perpendicular to the direction of displacement of the single-layer piezoelectric element is determined. By changing between the individual heads and sending a control signal having the same waveform to each head, the pushing force of the ink droplet can be changed.

Further, the present invention includes a plurality of heads for ejecting ink droplets from the nozzles with different pushing forces when receiving the same control signal as a signal for controlling the amount of ink droplets to be ejected from the nozzles. The present invention also relates to an ink jet recording method using an ink jet recording printer head, sending the same control signal to the plurality of heads, and ejecting ink droplets from nozzles of the individual heads with different pressing forces.

In the present specification, “individual heads”
1 that ejects ink droplets from one nozzle that it has
Means head of unit. In this specification, the term "printer head for inkjet recording" means a device that includes a large number of the "individual heads" on one plate and is installed in the printer for inkjet recording. In the present specification, when "head" means the above-mentioned "ink-jet recording printer head", it is always referred to as "ink-jet recording printer head". Head "or simply" head ".

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an ink jet recording system, a piezo system in which a pressure is applied to an ink pressure chamber using a piezoelectric element, and an ink utilizing a pressure generated by forming and growing bubbles by high heat are mainly used. There is a thermal method for discharging, and the present invention can be applied to any method. Hereinafter, the present invention apparatus and method of the present invention will be described in accordance with an embodiment in which the present invention is applied to an ink jet recording method using a piezoelectric element. Will be described.

FIG. 1 is a sectional view schematically showing a partial structure of each head included in the printer head for ink jet recording. The heads (individual heads) 10 include, for example, a piezoelectric element 1, a lower electrode 2, a vibration plate 3, an ink pressure chamber 4, and a nozzle 5, and an ink liquid is supplied to an ink supply path 6.
From the nozzle 5 provided on the plate substrate 7 as the diaphragm 3 reciprocates in the direction of arrow A due to the displacement of the piezoelectric element 1.
Discharged as 1. The size (droplet amount) of the ink droplet 11 varies depending on the magnitude of displacement of the piezoelectric element 1,
The displacement of the piezoelectric element 1 is controlled by the applied potential.

On the other hand, in a normal printer head for ink jet recording, a signal for controlling the displacement of the piezoelectric element 1 corresponds to each color of the lower electrode 2 and the upper electrode (not shown) as a control waveform of a voltage value. Sent for each ink.
Also, representative control waveform sets include, for example, a signal for discharging a medium-sized droplet (medium droplet discharge signal), a signal for discharging a small droplet (small droplet discharge signal), and a signal for discharging a small droplet. A signal for ejecting a large droplet by combining the droplet ejection signal and the small droplet ejection signal (large droplet ejection signal)
In combination with a control waveform of 0 voltage, that is, a signal (non-ejection signal) for not ejecting liquid droplets, the amount of ink ejected onto the recording medium is controlled for each color (each ink). Therefore, for example, in conventional color printing using a six-color ink set of yellow ink, magenta ink, cyan ink, black ink, light magenta ink, and light cyan ink, if the amount of light magenta ink and light cyan ink applied is set In order to perform the control so as to make the ejection amount smaller than the four-color ink ejection amount, it is necessary to separately prepare a control waveform set to be sent to the light magenta ink head and the light cyan ink head.

On the other hand, in the ink jet recording printer head of the present invention, when the same control waveform (drive waveform) is received by each head, a different pushing force (preferably, increases or decreases at a predetermined rate). A plurality of heads for ejecting ink droplets from nozzles with different pressing forces. For example, when a large droplet ejection signal or a small droplet ejection signal of a certain control waveform set is received, a certain head (or a group of heads) directly outputs a large droplet or a small droplet corresponding to those signals. In contrast, when a certain head (or head group) receives a large droplet ejection signal or a small droplet ejection signal of the same control waveform set, each of the other heads (or head group) contracts at a fixed rate ( Or an increased amount of large droplets or small droplets. Therefore, according to the printer head for ink jet recording of the present invention, a light magenta ink and a light cyan ink are loaded into a head group for discharging droplets reduced at a fixed rate, and the color using the above-described six-color ink set is used. When printing is performed, even if the same set of control signals are transmitted to all the heads, it is possible to control the ejection amounts of the light magenta ink and the light cyan ink to be smaller than the ejection amounts of the other four color inks. Alternatively, when a group of heads that discharge droplets increased at a fixed rate are loaded with yellow ink, magenta ink, cyan ink, and black ink, and color printing using the six-color ink set is performed, Even if the same set of control signals are transmitted, the amount of light magenta ink and light cyan ink applied can be controlled to be smaller than the amount of other four color inks applied.

Further, in the conventional color printing using an ink set containing an ink liquid in which the dot diameter is different even when the same droplet amount is ejected, there is a disadvantage that the color in which the dot diameter becomes small causes insufficient solid coating. For the purpose of eliminating, temporarily
In order to control the ejection amount of the ink liquid with a smaller dot diameter to be greater than the ejection amount of other ink liquids with a larger dot diameter, prepare by changing the control waveform set sent to the head for each color. There is a need to.

On the other hand, as described above, when the same control waveform (drive waveform) is received by the individual heads, the ink jet recording printer head of the present invention uses different pressing forces (preferably at a predetermined ratio). A plurality of heads for ejecting ink droplets from nozzles at different increased or decreased pushing forces. Therefore, according to the printer head for ink jet recording of the present invention, color printing using a color ink set is performed by loading the ink that reduces the dot diameter into the head group that discharges the droplets increased at a fixed rate. Then, even if the same set of control signals are transmitted to all the heads, it is possible to control so that the amount of ink to be ejected with a smaller dot diameter is greater than the amount of other ink to be ejected.

In the present invention, the amount of displacement of the piezoelectric element provided in each head can be changed by various methods.

Examples of the piezoelectric element provided in each head include a single-layer piezoelectric element and a laminated piezoelectric element. As the laminated piezoelectric element, for example, a lateral effect type laminated element is used. Type piezoelectric element or a vertical effect type laminated piezoelectric element.

The amount of displacement of the single-layer piezoelectric element changes the thickness of the single-layer piezoelectric element or changes the length of the pressure generating chamber in the direction perpendicular to the direction of displacement of the single-layer piezoelectric element. Can be changed. When the thickness of the single-layer piezoelectric element is increased, the amount of displacement decreases, and when the thickness is reduced, the amount of displacement increases. In addition, when the length of the pressure generating chamber (the length of the pressure generating chamber in the direction perpendicular to the displacement direction of the piezoelectric element) is increased, the displacement increases, and when the length is shortened, the displacement decreases. For example, the single-layer piezoelectric element 1 shown in FIG.
When the thickness T of the single-layer piezoelectric element 1 sandwiched between the upper electrode 2a and the lower electrode 2 is increased, the amount of displacement transmitted to the diaphragm 3 is reduced, and when the thickness T is reduced, , The displacement increases. The length L of the pressure generating chamber 4
When the length (the length of the pressure generating chamber in the direction perpendicular to the direction of displacement of the piezoelectric element) is increased, the displacement increases, and when the length is shortened, the displacement decreases. In the head shown in FIG. 2, nozzles and ink supply paths are omitted.

In the case of a laminated piezoelectric element, the amount of displacement can be changed by changing the layer thickness or the length in the direction of displacement. FIG. 3 schematically shows a lateral effect type laminated piezoelectric element in which eight piezoelectric element units fixed to a fixed substrate 33 and sandwiched between a plurality of electrodes 31 are laminated. Arrow F is the direction of the electric field, and arrow D is the direction of displacement. L ₁ is the initial length of the movable portion, La is the length of the movable portion when _a voltage is applied, _Lo is the length of the active portion, and t is the layer thickness of the piezoelectric element unit. It is. Displacement of the lateral effect type laminated piezoelectric element shown in FIG. 3 (△ L) is the difference between L ₁ and L _a (L ₁ -L _a), the following equation (1):

[Equation 1] Wherein, △ L is displacement, d31 is the d constant of the lateral effect type laminated piezoelectric element (m / V), L _o is the length of the active part, V is the applied voltage (v ), And t is the layer thickness (m)]. Therefore, in the lateral effect type laminated piezoelectric element, the displacement (△ L) decreases as the layer thickness (t) increases, and the displacement (△ L) increases as the layer thickness (t) decreases. Also, when the length (L _o ) in the displacement direction is increased, the displacement amount (△ L) increases, and when the length (L _o ) in the displacement direction is shortened, the displacement amount (△ L) decreases.

On the other hand, as shown in FIG.
A vertical effect type laminated piezoelectric element in which eight piezoelectric element units sandwiched between a plurality of electrodes 32 are laminated is schematically shown. Arrow C
Is the direction of the electric field and the direction of the displacement. Further, T _a is the length of the movable part when a voltage is applied, T _o is the length of the initial movable portion, t is the layer thickness of the piezoelectric element units. Displacement of the longitudinal effect-type laminated piezoelectric element shown in FIG. 4 (△ T) is, T _a and T _o
(T _a −T _o ), and the following equation (2):

[Equation 2] Wherein, △ T is the amount of displacement, d33 is the d constant of the longitudinal effect-type laminated piezoelectric element (m / V), T _o is the length of the initial of the movable part, V is the applied voltage (V), and t is the layer thickness (m)]. Accordingly, in the longitudinal effect type piezoelectric element, the displacement (ΔT) decreases as the layer thickness (t) increases, and the displacement (ΔT) increases as the layer thickness (t) decreases. In addition, the length in the displacement direction (T
_{When the} length _o ) is increased, the displacement (ΔT) increases, and when the length (T _o ) in the displacement direction is shortened, the displacement (ΔT) decreases.

When the present invention is applied to a thermal ink jet recording system, the amount of ink droplets should be adjusted by adjusting the capacity of the heater, the place where the heater is installed, or the volume of the ink chamber. Can be.

According to the present invention, an ink jet recording printer head including a plurality of heads for ejecting ink droplets from nozzles with different pushing forces when receiving the same control signal set as a control signal for the ink droplet amount is provided. Since it is used, it can be applied to various usage forms.

For example, the pushing force of ink droplets in a head that ejects ink droplets that are difficult to dry on a recording medium is as follows.
It can be made weaker than the pushing force of the ink droplets in the head that ejects the ink droplets that easily dry on the recording medium. As a result, it is possible to effectively prevent bleeding due to the ink that is difficult to dry on the recording medium.

Alternatively, the pushing force of the ink droplets in the head that ejects the ink droplets that are hardly permeated on the recording medium is determined by the pushing force of the ink droplets in the head that ejects the ink droplets that easily permeate the recording medium. Can also be weakened. As a result, it is possible to effectively prevent bleeding due to the ink that does not easily penetrate the recording medium.

Further, as described above, in color printing using a five-color or six-color ink set, in ink-jet recording using yellow ink, magenta ink, cyan ink, light magenta ink, light cyan ink, and optionally black ink, The pushing force of the ink droplets in the head that ejects the magenta ink and / or light cyan ink droplets is changed to the pushing force of the ink droplets in the head that ejects the yellow ink, magenta ink, cyan ink, and possibly black ink droplets. By making the output weaker, it is possible to effectively prevent bleeding due to the light-based ink.

Further, as described above, in color printing using an ink set including an ink in which the dot diameter varies when the same droplet amount is discharged, the ink in the head that discharges the ink droplets having the smaller dot diameter is used. The push-out force of the droplets is made stronger than the push-out force of the ink droplets in the head that discharges the other ink droplets, so that it is possible to provide a good image quality in which sufficient solid filling can be obtained for all colors.

As described above, the above-described head can provide exactly the same effect as adjusting the physical properties based on the difference in various properties such as the drying properties, permeability, and viscosity of the ink liquid.

[0045]

According to the present invention, in an ink set using inks having different physical property values and characteristics in combination,
Even if the same control waveform (drive waveform) is used, a print head in which the pressing force is changed for each individual head is used. Therefore, good printing can be performed without limiting the duty for each color or changing the drive voltage. Image quality can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating the structure of each head included in a printer head for inkjet recording.

FIG. 2 is a cross-sectional view schematically showing a structure of a head including a single-layer piezoelectric element.

FIG. 3 is a cross-sectional view schematically illustrating a structure of a lateral effect type laminated piezoelectric element.

FIG. 4 is a cross-sectional view schematically showing a structure of a vertical effect type laminated piezoelectric element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element 2 ... Lower electrode 3 ... Vibration plate 4 ... Ink pressure chamber 5 ... Nozzle 6 ... Ink supply path 7 ... Plate substrate 11 ... Ink liquid drop 31 32 ... electrodes 33 ... fixed substrate a ... displacement direction L _o ... active length of the portion L _1, T _o ... initial movable portion length L _a, T _a · · · voltage length of the movable portion of the time of application

Claims (11)

[Claims] When different heads receive the same control signal as a signal for controlling the amount of ink droplets to be ejected from a nozzle of each head included in a printer head for ink jet recording, the ink has a different pressing force. Having a plurality of heads for discharging droplets from nozzles,
Printer head for inkjet recording. 2. The method according to claim 1, wherein the ejection force of the ink droplets ejected from the recording medium on the recording medium is determined by the ejection force of the ink droplets ejected on the recording medium. 2. The ink jet recording printer head according to claim 1, wherein said ink jet recording head is also weakened. 3. The method according to claim 1, wherein the pressing force of the ink droplets in the head that discharges the light-based ink droplets is weaker than the pressing force of the ink droplets in the head that discharges the ink droplets other than the light-based ink. Item 2. An ink jet recording printer head according to item 1. 4. An ink set including an ink having a difference in dot diameter when ejected with the same amount of droplets, the pushing force of a head that ejects ink droplets having smaller dot diameters is set to a larger value. 2. The printer head for ink jet recording according to claim 1, wherein the pushing force is higher than the pushing force of a head that discharges the ink droplets. 5. A signal for controlling an amount of ink droplet to be ejected from a nozzle of each head is a signal for controlling a displacement of a piezoelectric element provided in each head. The printer head for inkjet recording according to any one of claims 1 to 4. 6. An ink jet recording printer head including individual heads provided with a horizontal effect type or a vertical effect type laminated piezoelectric element, wherein a layer of the piezoelectric thin film constituting the laminated piezoelectric element is provided. 6. The ink jet recording printer head according to claim 5, wherein the thickness is changed between the individual heads, and a control signal having the same waveform is sent to each head to change the pushing force of the ink droplet. 7. A printer head for ink jet recording including individual heads provided with a lateral effect type laminated piezoelectric element, wherein the length of the piezoelectric thin film constituting the laminated piezoelectric element in the displacement direction is individually set. 6. The ink jet recording printer head according to claim 5, wherein the print power of the ink droplet is changed by changing between the heads and sending a control signal having the same waveform to each head. 8. An ink jet recording printer head including individual heads provided with a longitudinal effect type laminated piezoelectric element, wherein the total layer thickness of the laminated piezoelectric element is changed between individual heads. 6. The ink jet recording printer head according to claim 5, wherein a control signal of the same waveform is sent to each head to change the pushing force of the ink droplet. 9. An ink jet recording printer head including individual heads provided with a single-layer type piezoelectric element,
6. The ink jet recording according to claim 5, wherein the thickness of the single-layer type piezoelectric element is changed between the individual heads, and a control signal having the same waveform is sent to each head, thereby changing the pushing force of the ink droplet. For printer head. 10. An ink jet recording printer head including individual heads provided with a single-layer piezoelectric element, wherein a length of the pressure generating chamber in a direction perpendicular to a displacement direction of the single-layer piezoelectric element is set. 6. The ink jet recording printer head according to claim 5, wherein the printing power of the ink droplet is changed by changing between the individual heads and sending a control signal having the same waveform to each head. 11. An ink jet recording printer including a plurality of heads for ejecting ink droplets from nozzles with different pressing forces when receiving the same control signal as a signal for controlling the amount of ink droplets to be ejected from nozzles. An ink jet recording method, comprising using a head, sending the same control signal to the plurality of heads, and ejecting ink droplets from nozzles of the individual heads with different pressing forces.