JPH09300619A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high speed recording uniform in pixel diameter and enhanced in image quality even if recording paper different in humidity absorbability is used or environment humidity is changed. SOLUTION: A humidity sensor 10 is arranged between an ink jet head 1 and recording paper 8 to detect the humidity of the recording paper 8. The detected humidity signal is inputted to a printer controller 11 and, when the peripheral humidity or the humidity absorbability of the recording paper is high, a piezoelectric element 6 is driven so that the particle size of ink droplets is reduced to reduce the quantity of bonded ink droplets 9a and the drying speed of ink droplets is increased by setting a pixel diameter to a predetermined size and reducing the area of each of pixels. When the peripheral humidity is low, the piezoelectric element 6 is driven corresponding to humidity by changing poulse width so that the diameter of ink droplets is made large to obtain the same drying state as that at the time of high humidity and, even when high speed recording is executed under a high humidity condition, the drying speed of ink is increased to prevent that ink is bonded to other recording paper to deteriorate image quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly, to a pixel which changes the particle size of ink droplets ejected from the nozzles of the ink jet printer according to the recording paper or the humidity in the vicinity of the recording paper. The present invention relates to an inkjet printer in which the diameters are made substantially uniform and high image quality is maintained, and further, the ink adhered on the recording paper is dried at an early stage, and the ink on the recording paper is prevented from adhering to other parts due to non-drying to deteriorate the image quality.

[0002]

2. Description of the Related Art As is well known, an ink jet printer is a liquid ejecting recording apparatus that ejects and records ink droplets on recording paper based on recording information, and uses an electric device such as a piezoelectric element as pressure generating means for ejecting ink droplets. There is a mechanical conversion means or an electrothermal conversion means using a heating resistor. An ink jet printer using a piezoelectric element as an energy conversion means changes the volume of the ink liquid chamber by the piezoelectric strain of the piezoelectric element driven based on the recording information, and the ink droplets are ejected from a nozzle provided in a part of the ink liquid chamber. It is based on the principle of spraying and adhering on the recording paper. Further, in a bubble jet type ink jet printer using a heating resistor as an energy converting means, a heating resistor is provided in the vicinity of an opening of a nozzle, a voltage pulse based on recording information is applied to the heating resistor, and the ink in the nozzle is ejected. Is locally heated to be vaporized, and the ink in the vicinity of the nozzle opening is ejected as an ink droplet by vaporization pressure to adhere to the recording paper.

Such an ink jet printer has recording sheet conveying means capable of arbitrarily selecting recording sheets of various standard sizes, and information is recorded on the selected recording sheet by ink ejected from nozzles. The recording papers ejected through the conveying means are ejected and sequentially stacked on the copy receiver. The amount of ink droplets ejected from the nozzle is determined by the shape and size of the nozzle if the temperature, humidity and drive voltage pulse waveform of the environment are constant, and a recorded image composed of constant pixels can be obtained.

[0004]

Ink jet printers are required to have high efficiency in recording work and high image quality, and technical development for high-speed recording and high quality image formation is underway. Further, in terms of economy, it is required to diversify the recording paper used. However, since the recording papers recorded at high speed are stacked on the copy receiver after recording, for example, if the inks on the recording papers are not dried in a high humidity environment, the inks will be printed on the back surface of the superposed recording papers. Transferred and deteriorates image quality. This event is
This frequently occurs when the difference in hygroscopicity of the recording paper itself or the humidity of the recording paper itself changes, and it is not possible to satisfy the demand for high-speed recording with high image quality. Further, when the moisture absorption of the recording paper is different, even if the recording is performed with a constant ink droplet diameter, the pixel diameter is changed due to the moisture absorption and the image quality is deteriorated.

The present invention has been made in view of the above-mentioned circumstances, and provides an ink jet printer capable of high-speed recording while maintaining high image quality even when environmental humidity changes, by using recording papers having different hygroscopic properties. The purpose is to

[0006]

According to the invention of claim 1, a voltage pulse based on an image signal is applied to the pressure generating means,
In an ink jet printer that pressurizes ink by the pressure generating means and ejects ink droplets from a nozzle to record an image on a recording paper, having a humidity detecting means for detecting the humidity of the recording paper or the vicinity of the recording paper, It is characterized in that the amount of the ink droplets is made variable according to the humidity signal of the humidity detecting means. Therefore, even if the environmental humidity becomes high, the drying speed of the recorded ink droplets is kept constant, and even at high speeds, It is intended to obtain a quality image.

According to a second aspect of the present invention, in the ink jet printer according to the first aspect, the humidity detecting means includes:
It is characterized in that it is configured integrally with the inkjet printer, and the humidity detecting means is arranged on the surface of the nozzle of the inkjet printer on the droplet ejection side, and thus a small inkjet printer with almost no change in external shape. It was done.

According to a third aspect of the invention, in the ink jet printer according to the first or second aspect, the humidity detecting means generates heat on a thin film insulator which is bridge-supported or cantilever-supported on a cavity formed in a substrate. A humidity sensor utilizing the principle of heat conduction of a microbridge structure provided with a body pattern is used, and the inkjet printer according to claim 2 is further miniaturized.

According to a fourth aspect of the present invention, in the ink jet printer according to the first, second or third aspect, there is provided means for irradiating a portion of the ejected ink droplet on the recording paper or a vicinity thereof with a heat ray. Characterized by
Therefore, even if the ink immediately after recording is actively dried and it is a recording paper with low ink absorption or the environmental humidity changes,
It enables high-speed, high-quality recording.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

According to the invention of claim 1, the humidity in the vicinity of the recording paper is detected, and when the humidity is high, the particle diameter of the ink droplet ejected from the nozzle is reduced, and when the humidity is low, the particle diameter of the ink droplet. Is set so that the ink on the recording paper spreads uniformly or dries at substantially the same time without being affected by humidity. Hereinafter, a piezoelectric element is used as a pressure generating means for ejecting ink droplets. An example of the used inkjet printer will be described.

FIG. 1 is a diagram for explaining an embodiment of an ink jet printer according to the present invention, and FIG.
Is a block diagram showing the configuration of an inkjet printer,
FIG. 1 (B) is a diagram showing the relationship between ink droplet diameter and humidity, and FIG. 1 (C) is applied to a piezoelectric element to eject ink droplets having a particle diameter having the relationship shown in FIG. 1 (B). 2 is a diagram showing a pulse waveform example of a voltage pulse to be generated, in which 1 is an inkjet head, 2 is an ink liquid chamber, 3 is a nozzle, 4 is a common liquid chamber, 5 is a liquid passage, 6 is a piezoelectric element, and 7 is Substrate, 8 recording paper, 9 ink drops, 10 humidity sensor, 11 printer controller, 12 humidity-ink drop particle size curve, 13
Is a voltage pulse. In the drawings shown in FIG. 1 and subsequent figures, the same reference numerals as those in FIG. 1 are attached to the portions having the same operations as those in FIG.

The ink jet head 1 shown in FIG. 1A uses a piezoelectric element 6 as a pressure generating means.
The piezoelectric element 6 has a laminated structure driven in, for example, the d ₃₃ mode, and has one end fixed to the substrate 7 and the other end joined to the vibration plate 2 a forming one surface of the ink liquid chamber 2. A nozzle 3 is provided on the surface of the ink liquid chamber 2 facing the vibrating plate 2a, and a common liquid chamber 4 communicates with the ink liquid chamber 2 through a liquid passage 5.
The ink liquid chamber 2 is always filled with ink. Nozzle 3
The recording paper 8 is arranged so as to face with, and during recording, it is moved in the direction of arrow S by a conveying means (not shown).

Further, a humidity sensor 10 is arranged near the recording paper 8 facing the nozzle 3. Humidity sensor 10
Is connected to the printer controller 11 by a conductive wire 11a, and between the printer controller 11 and the piezoelectric element 6,
They are connected by a conductor 11b.

Next, the operation of the ink jet printer shown in FIG. 1 (A) will be described. The humidity sensor 10 is installed near the recording paper 8 on the nozzle 3 side and measures the humidity (moisture absorption) of the recording paper 8. The humidity signal from the humidity sensor 10 is input to the printer controller 11, and the printer controller 11 applies to the piezoelectric element 6 a voltage pulse 13 having a constant peak value having a pulse width corresponding to the humidity signal. The voltage pulse 13 displaces the piezoelectric element 6 in the direction of the arrow + F, transmits this to the diaphragm 2a, pressurizes the inside of the ink liquid chamber 2, ejects the ink droplet 9 from the nozzle 3, and jets it onto the recording paper 8. An attached ink droplet 9a that becomes a pixel is formed.

The pulse width of the voltage pulse 13 output from the printer controller 11 is output in accordance with a predetermined relationship based on the humidity signal.
As shown by the humidity-ink drop particle size curve 12 shown in FIG. 1B, when the humidity is low, the ink drop 9 having a large particle size is ejected, and the particle size of the ink drop 9 is increased as the humidity increases. I'm making it small. The voltage pulse 13 applied to the piezoelectric element 6 in order to eject the ink droplets 9 having such a relationship, as shown in FIG. When the voltage pulse 13a having a short pulse width is applied and the particle size is increased, the voltage pulse 13c having a long pulse width is added. Since the displacement amount of the piezoelectric element 6 is proportional to the voltage, the peak value of the voltage pulse 13 may be related to the target ink droplet diameter.

As described above, the humidity shown in FIG.
By setting the ink droplet diameter curve 12 in advance, even if the humidity of the recording paper 8 changes, the adhered ink droplets 9a spread evenly or dry at substantially the same time. However, high image quality can be maintained. Further, the relationship between the humidity and the ink droplet diameter curve 12 can be similarly applied to a bubble jet type inkjet printer.

According to a second aspect of the invention, the humidity sensor 10 is installed integrally with the ink jet head 1 on the surface 1a side of the ink jet head 1 on the nozzle 3 side, and a small ink jet printer. It becomes possible to

FIG. 2 is a configuration block diagram for explaining another embodiment of the ink jet printer according to the invention of claim 2, wherein the humidity sensor 10 is provided on the opening side of the nozzle 3 of the ink jet head 1. It is provided integrally with the head 1. Since the distance between the inkjet head 1 and the recording paper 8 is actually very small, the humidity sensor 10 substantially measures the humidity of the recording paper 8 and is small in size, and the same effect as that of claim 1 is obtained. To be

Invention of Claim 3 In the invention of claim 3, the humidity sensor has a micro-bridge structure utilizing the principle of heat conduction, and can measure humidity with high accuracy and with a small size.

FIG. 3 is a view for explaining an example of the humidity sensor according to the invention of claim 3, FIG. 3 (A) is a plan view,
FIG. 3B is a drive detection circuit diagram of the humidity sensor shown in FIG. 3A, in which 21 is a substrate, 22 is a thin film insulator,
Reference numeral 23 is a cavity, 24 is a heating element pattern, 25 is a lead wiring pattern, 26 is a connecting portion, 27 is a heater power supply, and 28 is a detection circuit.

The humidity sensor 10 shown in FIG. 3 (A) was previously proposed by the present applicant, and has a rectangular shape Si (10).
0) After forming the thin film insulator 22 on the upper surface of the substrate 21, after forming the heating element pattern 24 of which the side length is on the order of 100 μm, such as platinum, the bridge portion 22a that forms the heating element pattern 24 is left underneath. The heating element pattern 24 has a microbridge structure in which the cavity 23 is formed by anisotropic etching, and the outermost side of the heating element pattern 24 and the lead wiring pattern 25 intersect at a point 26 on the bridge portion 22a. The effect of lowering the temperature at both ends is prevented.

The humidity sensor 10 includes pad portions 25a and 25a.
Voltages of the heating element pattern 24 between the heater power source 27 and the detection circuit 28 connected to the heater power source 27 and the detection circuit 28 by the leads A, B, C, D from b, 25c, 25d, and between the heating element pattern 24, which is the soaking temperature portion of the wiring pattern 25 Detect the signal. The heater power supply 27 and the detection circuit 28 are built in the printer controller 11, and the printer controller 11 is driven by a low voltage pulse that detects an environmental temperature that is not affected by absolute humidity and a high voltage pulse that is affected by absolute humidity. The absolute humidity at that temperature is calculated by subtracting the detection voltage when driving with a low-voltage pulse from the detection voltage when driving with a high-voltage pulse. Calculate the humidity to obtain it.

As described above, the humidity sensor 1 shown in FIG.
By using 0, the humidity of the recording paper 8 can be detected even in the case of high-speed recording, because a small size and a highly accurate humidity with excellent response are required.

According to a fourth aspect of the present invention, in synchronization with the ejection of ink droplets, the ink droplets on the recording paper locally heat the portion where the ink droplets adhere to dry quickly, and the paper quality of the recording paper differs. Even if the ink drop amount cannot be corrected by calculating the humidity, the ink is completely dried and high image quality is maintained.

FIG. 4 is a diagram for explaining another embodiment of the ink jet printer according to the present invention, in which 14 is an infrared lamp, 15 is a reflector, and 16 is a lens.

In FIG. 4, an infrared lamp 14 is connected to the printer controller 11 by a conducting wire 11c, and is provided at a position facing the recording paper 8 at or near the ink jet head 1. The infrared lamp 14 is provided with a reflector 15 and a condenser lens 16 as an optical system for focusing a heat ray in the vicinity of the attached ink droplet 9a or the moving direction S of the recording paper 8 in the vicinity of the attached ink droplet 9a.

The heat ray emitted from the infrared lamp 14 is driven by the printer controller 11 in synchronism with or asynchronously with the driving of the piezoelectric element 6. That is, the ink droplet 9
Is driven in synchronism with the ejection of the ink, and heats the adhered ink droplet 9a or its vicinity. As a result, the ink on the recording paper 8 is rapidly dried. Although the infrared lamp 14 is used as a means for emitting heat rays, a laser or other heating means may be used. Further, the attached ink droplet 9a may be focused with a constant power without necessarily synchronizing with the ink droplet ejection.

According to the ink jet printer shown in FIG. 4, even if the recording paper has different paper quality and poor ink adsorption,
Alternatively, even if the ink drop amount cannot be controlled by humidity detection, the ink can be effectively dried, and a high-quality image can be formed even in high-speed printing.

[0029]

According to the first aspect of the present invention, the voltage pulse based on the image signal is applied to the pressure generating means, the pressure generating means pressurizes the ink to eject the ink droplets from the nozzle, and the recording paper is ejected. An inkjet printer for recording an image has a humidity detecting means for detecting the humidity of the recording paper or the vicinity of the recording paper, and the amount of the ink droplet is made variable according to a humidity signal of the humidity detecting means. High-quality images can be obtained by high-speed printing even when the humidity of the paper or environmental humidity changes.

Effect corresponding to claim 2: In the ink jet printer according to claim 1, the humidity detecting means is integrally formed with the ink jet printer, and the humidity detecting means is ejected from the nozzle of the ink jet printer. Since it is arranged on the side surface, it is possible to reduce the size of the ink jet printer having the same effect as the first aspect.

Effect corresponding to claim 3: Claim 1 or 2
In the inkjet printer described in the paragraph 1, the humidity detecting means uses a heat conduction principle of a microbridge structure in which a heating element pattern is provided on a thin film insulator that is bridge-supported or cantilevered on a cavity formed in a substrate. Since the humidity sensor is used, a smaller inkjet printer can be obtained.

Effect corresponding to claim 4: Claim 1 or 2
Or the inkjet printer according to the third aspect, which has means for irradiating a heat ray to a portion where the ejected ink droplets adhere to the recording paper or the vicinity of the adhered portion, so that high speed is achieved even when the ink suction property is low and the environmental humidity is high. Enables high quality recording.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of an embodiment of an inkjet printer according to the present invention.

FIG. 2 is a configuration block diagram for explaining another embodiment of the inkjet printer according to the present invention.

FIG. 3 is a diagram for explaining an example of a humidity sensor according to the present invention.

FIG. 4 is a diagram for explaining another embodiment of the inkjet printer according to the present invention.

[Explanation of symbols]

1 ... Inkjet head, 2 ... Ink liquid chamber, 3 ... Nozzle, 4 ... Common liquid chamber, 5 ... Liquid passage, 6 ... Piezoelectric element, 7 ...
Substrate, 8 ... Recording paper, 9 ... Flying ink drop, 10 ... Humidity sensor, 11 ... Printer controller, 12 ... Humidity-ink drop particle size curve, 13 ... Voltage pulse, 14 ... Infrared lamp,
15 ... Reflector, 16 ... Lens, 21 ... Substrate, 22 ...
Thin film insulator, 23 ... Cavity, 24 ... Heating element pattern, 25
... Lead-out wiring pattern, 26 ... Connection part, 27 ... Heater power supply, 28 ... Detection circuit.

Claims (4)

[Claims] 1. An ink jet printer for recording an image on a recording paper by applying a voltage pulse based on an image signal to a pressure generating means, pressurizing the ink by the pressure generating means to eject ink droplets from a nozzle, A humidity detecting means for detecting the humidity of the recording paper or the vicinity of the recording paper,
An ink jet printer characterized in that the amount of the ink droplets is made variable according to a humidity signal of the humidity detecting means. 2. The humidity detecting means is integrally formed with the ink jet printer, and the humidity detecting means is arranged on a surface of the ink jet printer on the droplet ejection side of the nozzle. Inkjet printer. 3. The humidity sensor utilizing the heat conduction principle of a microbridge structure, wherein the humidity detecting means has a heating element pattern provided on a thin film insulator which is bridge-supported or cantilevered on a cavity formed in a substrate. The inkjet printer according to claim 1 or 2, wherein 4. The inkjet printer according to claim 1, further comprising means for irradiating a portion of the ejected ink droplets on the recording paper or a portion near the adhered portion with a heat ray.