JP2003165207A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recorder in which the size of dots being printed on a recording medium can be kept constant at the time of printing and a printing with high image quality can be ensured. <P>SOLUTION: Means for selecting a recording medium, a nozzle temperature control means, and a recording medium temperature control means, are provided in an ink jet recording method performing printing by ejecting ink curing upon irradiation with UV-rays or an electron beam from a nozzle and pasting the ink drop to a recording medium. The nozzle comprises a pressure chamber communicating with an ink tank and storing ink, a piezoelectric element generating a pressure variation in the pressure chamber by applying an electric signal, a diaphragm linked with a pressure generating means through a resilient material while forming at least a part of the wall face of the pressure chamber, a restrictor serving as a channel for supplying ink to the pressure chamber, a housing having a common ink passage for supplying ink to the restrictor, and an orifice ejecting an ink drop from the pressure chamber. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus of a printer for forming an ink image on a recording medium by ejecting ink which is cured by ultraviolet rays or electron beams due to pressure generated by a piezoelectric actuator.

[0002]

2. Description of the Related Art As a method of ejecting ink to an inkjet print head, a thermal method of ejecting ink by generating bubbles in the ink by an electric heater,
There is a piezoelectric element method in which a part of the wall surface of the pressurizing chamber is deformed by using a piezoelectric element to eject ink.

Since the piezoelectric element system requires a small amount of displacement of the piezoelectric element, it is necessary to increase the surface area of the vibrating plate of the pressurizing chamber in order to eject the ink. Therefore, it is difficult to reduce the nozzle pitch as compared with the thermal system. Has been done. However, since the piezoelectric element is separated from the ink by using the vibrating plate, there is an advantage that the piezoelectric element is not corroded by the ink and the type of ink is not selected, and it can be said that it is suitable for industrial application.

Conventionally, water-soluble liquid inks have been widely used as ink jet recording inks. Also, by using hot-melt type ink that is made of solid wax at room temperature, it is liquefied by heating, etc., the ink is ejected by using the displacement of the piezoelectric element, and the ink is cooled and solidified while adhering to the recording medium for recording. A hot melt type ink jet recording method for forming dots has been proposed. Since the ink solidifies immediately after adhering to the recording medium, there is no "bleeding", and there are advantages that various recording media such as Japanese paper, drawing paper, and plastic film can be used without pretreatment.

Further, an ultraviolet curable ink has been used for printing on a material which does not absorb ink or has low ink absorbability such as plastic and metal. Nowadays, a method using an ultraviolet curable ink is introduced in almost all printing methods such as offset printing, sticker printing, screen printing, etc., except for gravure printing. However, the above-mentioned printing method requires a large-scale device and is not suitable for in-situ printing. As a method for solving this, an inkjet recording apparatus using an ultraviolet curable ink has been proposed.

Since these inks that can be used in any recording medium have many advantages, additional printing such as variable information printing, indoor / outdoor posters, large signboards, cars, glass, elevators, wall and building decorations, and even cloth, It is expected to be applied to printing on synthetic resins, metals, glass and ceramics.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an ink jet type recording apparatus using a piezoelectric element having a wide range of industrial applications as described above. When the water-based ink is used for printing, it is difficult to print on a recording medium that does not absorb ink, and a large-sized ink drying device is required even when using special paper. Further, due to the problem of bleeding, high-definition printing is difficult and the resolution is limited, so that the application is limited. A solvent ink may be used because of its advantage of quick drying, but it is not desirable in terms of flammability and environmental safety. High-speed printing is possible with the hot-melt ink, but it is difficult to obtain reliability after printing due to its low abrasion resistance.

On the other hand, the method of curing the recording liquid with ultraviolet rays or electron beams enables recording regardless of the recording medium. The recording medium is not limited to paper, and it can be a non-absorbent plastic film or coated cardboard (coated cardboard), and it is an inkjet ink that can be applied to all recording media. It cures the recording liquid with ultraviolet rays or electron beams. Method ink is suitable. However, since these inks are cured almost at the same time as the ink droplets are ejected, the ink droplets are fixed on the recording medium while having a dome-shaped shape in which the ink droplets can be discriminated by touch with a finger. Therefore, depending on the amount of the ink before curing the ink that has adhered permeates the recording medium and the contact angle between the ink and the recording medium, the dot size varies from recording medium to recording medium.
The print quality is degraded.

Further, since the viscosity of the ink is generally larger than that of the water-based ink, the reaction speed at which the displacement of the piezoelectric element reaches the pressure chamber is slow. For example, as disclosed in JP-A No. 11-20165, the piezoelectric element is disclosed. It was difficult to change the amount of ejected ink by controlling the meniscus by the drive waveform that drives the ink.

[0010]

In order to achieve the above object, in the present invention, a pressure chamber that communicates with an ink tank to store ink, and a piezoelectric element that generates a pressure fluctuation in the pressure chamber by applying an electric signal, A diaphragm that forms at least a part of the wall surface of the pressure chamber and is connected to the pressure generating means with an elastic material, a restrictor that is a flow path that supplies ink to the pressure chamber, and a common that supplies ink to the restrictor. From a nozzle having a housing having an ink passage and an orifice for ejecting an ink droplet from a pressure chamber, an ink having a property of being cured by being irradiated with an ultraviolet ray or an electron beam is ejected, and the ink droplet is recorded on a recording medium. An inkjet recording method for printing by adhering the recording medium includes a recording medium selection unit, a nozzle temperature control unit, and a recording medium temperature control unit. To.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. FIG. 1 is a structural explanatory perspective view of a main part of an inkjet print head of the present invention.

In FIG. 1, 2 is an orifice plate having a plurality of orifices 1. The processing accuracy of the opening shape of the orifice 1 has a great influence on the ink ejection characteristics of the inkjet print head. In order to keep these orifice precision variations among a plurality of orifices 1 low, the manufacturing method of the orifice plate 2 requires high processing precision. Therefore, the orifice plate 2 is formed by a precision pressing method of stainless steel, a laser processing method, an electroforming processing of nickel, or the like.

The orifice plate 2 is provided with a chamber plate 4 having a pressure chamber 3 formed therein, and a restrictor 5 for connecting the ink supply passage 10 and the pressure chamber 3 to each other to control the inflow of ink into the pressure chamber 3. Lector plate 6
Are positioned and joined.

Further, a diaphragm having a vibrating plate 7 for efficiently transmitting the pressure of the piezoelectric actuator 13 to the pressure chamber and a filter portion 8 for removing dust and the like in the ink flowing into the restrictor 5 from the common ink passage 10. Housing 1 having a plate 9 and a common ink passage 10 formed therein
1 is similarly positioned and joined.

The chamber plate 4, the restrictor plate 6 and the diaphragm plate 9 are made by a stainless material etching method or a nickel material electroforming method.

The housing 11 is formed by cutting a stainless material or the like, and is joined with an ink introducing pipe 18 for guiding the ink from the ink tank 19 to the common ink passage 10.

Finally, a plurality of laminated piezoelectric elements 14 and a piezoelectric actuator 13 composed of a supporting substrate 16 for fixing them are positioned and joined. Piezoelectric actuator 13
As for the order of manufacturing, first, a plurality of rod-shaped laminated piezoelectric elements are arranged on the support substrate 16 and bonded and fixed. After that, the rod-shaped laminated piezoelectric element is divided by cutting using a dicing saw, a wire saw, or the like. At this time, each of the divided laminated piezoelectric elements 14 corresponds to each pressure chamber.

Further, the support substrate 16 is provided with individual electrodes 17 for transmitting electric signals independent of an external drive circuit to each laminated piezoelectric element 14 and a common electrode (not shown). As a result, a selective electric signal is applied to the piezoelectric element 14 from the external drive circuit, so that the piezoelectric element 14 is distorted. Since the piezoelectric element 14 is bonded onto the highly rigid support substrate 16, the piezoelectric element 14 is preferentially displaced to increase the pressure in the pressure chamber 3. The ink jet print head described in this example is used in an apparatus that forms an ink image on a recording medium by ejecting ink from the orifice 1 based on such a principle.

In this example, the array pitch is set to about 677 μm at 37.5 inch, but the number of nozzles, the number of rows,
The unit configuration is not limited to any combination.

The ink used in the present invention is an ink having the property of being cured by being irradiated with ultraviolet rays or electron beams. The ink can be used to print on various recording media.

FIG. 2 shows an example of the ink jet recording apparatus of the present invention using the print head and the ink having the property of being cured by being irradiated with ultraviolet rays. The figure shows an example of continuous paper as a recording medium, and does not limit the type of recording medium. The recording medium 23 supplied from the paper supply unit 25 is transferred to the paper stacker 27 by the paper transport belt 26.
Sent to. In the process, the recording medium 23 is sent to the inkjet print head 28, ink is ejected from the nozzles, and the ink adheres to the recording paper to form an image. Next, it is sent to the ultraviolet irradiation device 29, where ultraviolet rays are irradiated and the ink is fixed on the recording paper. Recording is performed on the recording medium in this process.

As described above, the ink ejected from the nozzle forms an ink image on the recording medium and then irradiates ultraviolet rays or an electron beam to fix the ink on the recording medium for printing. However, since it takes time for the ink to adhere to and be fixed on the recording medium, the amount of ink bleeding into the recording medium varies depending on the recording medium, and the dot size varies depending on the contact angle with the recording medium. The print quality is different. For example, when the recording medium is plain paper, the ink permeates the surface of the recording medium and the recording medium to some extent as shown in FIG. It was However, when the recording medium is cardboard, the ink becomes large dots bleeding into the recording medium as shown in FIG. 3- (b), and the print quality is degraded in a blurred image. On the other hand, when the recording medium is a synthetic resin such as an acrylic plate, the ink forms a dome shape due to the contact angle with the recording medium without bleeding into the recording medium as shown in FIG. Therefore, the print quality was deteriorated in the image with white streaks.

On the other hand, there is the following relationship between the ink viscosity and the dot size. The dots to which the highly viscous ink adheres on the recording medium are small dots that do not spread on or in the recording medium. On the contrary, the dots to which the low-viscosity ink adheres on the recording medium spread on or in the recording medium, and large dots can be obtained.

By utilizing the above properties, the ink viscosity is changed according to the recording medium and printing is performed. For example, when the recording medium is cardboard, the ink viscosity on the recording medium is made lower than usual to reduce ink bleeding on the recording medium, and the target dot size is obtained. Further, when printing on a recording medium such as an acrylic plate, the ink viscosity was made higher than usual to spread the ink on the recording medium and obtain the target dot size. That is, high-quality printing can be performed by controlling the ink viscosity according to the recording medium.

The method of changing the ink viscosity is as follows. FIG. 4 shows the temperature dependence of the ink viscosity. The ink has a high viscosity when the temperature is low, and a low viscosity when the temperature is high.

FIG. 5 shows a configuration in which a heater plate 22 provided with a heater 20 and a temperature sensor 21 is added to an ink jet print head for ejecting ink by utilizing this property. The ink jet print head is heated by the heater 20 so that the ink temperature can be set according to the recording medium. The temperature is constantly detected by the temperature sensor 21 so that the temperature of the inkjet print head can be controlled to a target temperature. This makes it possible to easily change the ink viscosity and obtain a desired dot size for each recording medium.

The ink temperature can also be controlled by transferring heat from the recording medium. By setting the surface temperature of the recording medium according to the recording medium, heat is transferred from the recording medium to the ink adhering to the recording medium, the temperature of the ink is changed, and the ink viscosity can be changed. Now you can get the size of the dot.

The method for controlling the ink temperature may be a combination of temperature control of the ink jet print head and control of the surface temperature of the recording medium. For example, in the case of a recording medium having a high heat transfer coefficient such as a metal plate, it is more effective to control the ink viscosity by combining both of them than controlling the temperature of only one of the ink jet print head or the recording medium surface. is there.

FIG. 6 shows an example of the ink jet recording apparatus according to the present invention. The figure shows an example of continuous paper as a recording medium, and does not limit the type of recording medium. First, by selecting the type of recording medium by the operator, the print head controller 30 is controlled so that the temperature becomes appropriate.
Controls the temperature of the print head 28. Here, the printer has a panel, a switch, and the like (not shown) as a storage medium selection unit, and an operator operates it to select the type of medium. Although the storage medium selection unit is usually provided in the printer, the data selected by the user on an external device, for example, a personal computer,
It is also possible to transmit directly to the controller of the printer.

Thereafter, the recording medium 23 conveyed by the sheet conveying belt 26 is controlled by the recording medium temperature control device 31 using the recording medium heating heater 32 to a surface temperature of an appropriate temperature according to the recording medium. In this state, ink is ejected from the print head 28 and adheres to the recording paper to form an image. After that, the ultraviolet ray is irradiated by the ultraviolet ray irradiating device 29, and the ink is fixed on the recording sheet, so that it is possible to perform high-quality printing in which the dot size is uniform regardless of the recording medium.

Paying attention to the fact that the dot size changes depending on the ink temperature, printing was performed using two or more print heads as shown in FIG. 5, for example. By setting the temperatures of the print heads to different temperatures, different dots could be printed on the same recording medium. This is an effective method in the printing method using gradation expression. In other words, by ejecting ink from a nozzle controlled to a temperature of two or more values, dots of different sizes are printed,
It is possible to obtain a high quality image by performing gradation expression.

[0032]

According to the present invention, when printing with an ink jet print head using an ink having the property of being cured by irradiation with ultraviolet rays or electron beams,
It is possible to always print with high image quality without the dot size changing depending on the recording medium. Even if the same inkjet print head is used, different dot sizes can be printed simply by controlling the nozzle temperature, gradation can be expressed, and high quality printing can be performed.

[Brief description of drawings]

FIG. 1 is a structural explanatory perspective view of a main part of an inkjet print head according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an inkjet printhead recording apparatus according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram showing a recording medium and dot sizes.

FIG. 4 is a diagram showing temperature dependence of ink viscosity.

FIG. 5 is a structural explanatory perspective view of a main part of the inkjet print head according to the embodiment of the present invention.

FIG. 6 is a diagram showing an example of an inkjet printhead recording apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 is an orifice, 2 is an orifice plate, 3 is a pressure chamber, 4 is a chamber plate, 5 is a restrictor, 6 is a restrictor plate, 7 is a vibrating plate, 8 is a filter part, 9
Is a diaphragm plate, 10 is a common ink passage, 11
Is a housing, 12 is an adhesive, 13 is a piezoelectric actuator, 14 is a laminated piezoelectric element, 15 is a conductive joining member, 1
6 is a support substrate, 17 is an individual electrode, 18 is an ink introduction pipe, 19 is an ink tank, 20 is a heater 21, a temperature sensor, 22 is a heater plate, 23 is a recording medium, 2
4 is ink, 25 is a paper feed section, 26 is a paper transport belt, 2
7 is a paper stacker, 28 is an inkjet print head, 29 is an ultraviolet irradiation device, 30 is a print head temperature control device, 31 is a recording medium temperature control device, and 32 is a recording medium heating heater.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoru Tobita             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. (72) Inventor Akemi Ouchi             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. (72) Inventor Tsutomu Maekawa             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd. F term (reference) 2C056 EA09 EB07 EB13 EB30 EB45                       EC07 EC13 EC29 ED01 FA04                 2C057 AF26 AF39 AG16 AG48 AL21                       AL25 AM15 AM40 AP02 AP22                       AP23 AP38 AQ06 CA01

Claims (4)

[Claims] 1. A pressure generating means for forming a pressure chamber communicating with an ink tank for storing ink, a piezoelectric element for generating a pressure fluctuation in the pressure chamber by applying an electric signal, and forming at least a part of a wall surface of the pressure chamber. And a diaphragm connected by an elastic material, a restrictor which is a flow path for supplying ink to the pressure chamber, a housing having a common ink passage for supplying ink to the restrictor, and ink droplets ejected from the pressure chamber. In the inkjet recording method, an ink having a characteristic of being cured by being irradiated with an ultraviolet ray or an electron beam is discharged from a nozzle having an orifice, and the ink droplet is adhered to the recording medium to perform printing, and a recording medium selecting unit is provided. An inkjet recording apparatus comprising: a nozzle temperature control unit and a recording medium temperature control unit. 2. The ink jet recording apparatus according to claim 1, wherein the temperature of the nozzle is controlled according to a recording medium. 3. The ink jet recording apparatus according to claim 1, wherein the surface temperature of the recording medium is controlled according to the recording medium. 4. The ink jet recording apparatus according to claim 1, wherein the ink is ejected from a nozzle whose temperature is controlled to have a binary value or more even if the same ink is used.