JP3625571B2 - Inkjet printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet printer, and more specifically, 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, thereby making the pixel diameter substantially uniform and high image quality. In addition, the present invention relates to an ink jet printer that quickly dries the ink adhering to the recording paper and prevents the ink on the recording paper from adhering to the other due to undried and preventing the image quality from deteriorating.
[0002]
[Prior art]
As is well known, an ink jet printer is a liquid jet recording apparatus that ejects and records ink droplets on recording paper based on recording information, and an electromechanical conversion means such as a piezoelectric element as pressure generating means for ejecting ink drops, or There is an electrothermal conversion means using a heating resistor.
An ink jet printer using a piezoelectric element as an energy conversion means applies a volume change to an ink liquid chamber due to piezoelectric distortion of a piezoelectric element driven based on recorded information, and drops ink droplets from nozzles provided in a part of the ink liquid chamber. Is based on the principle of spraying and adhering to the recording paper.
In addition, a bubble jet type ink jet printer using a heat generating resistor as an energy conversion means is provided with a heat generating resistor in the vicinity of an opening of a nozzle, and a voltage pulse based on recording information is applied to the heat generating resistor so that ink in the nozzle This is based on the principle of locally heating and evaporating, and ejecting ink in the vicinity of the nozzle opening as ink droplets by the vaporization pressure to adhere to the recording paper.
[0003]
Such an ink jet printer has a recording paper transport unit that can arbitrarily select recording papers of various standard sizes, and information is recorded on the selected recording paper by ink ejected from nozzles. The discharged recording paper is sequentially stacked on a copy receiver. If the environmental temperature, humidity, and drive voltage pulse waveform are constant, the amount of ink droplets ejected from the nozzle is determined by the shape of the nozzle, and a recorded image composed of constant pixels can be obtained.
[0004]
[Problems to be solved by the invention]
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 development is in progress. Furthermore, diversification of recording paper used is also required from an economic viewpoint. However, since recording papers recorded at high speed are stacked on a copy receiver after recording, for example, if the ink on the recording paper is not dry in a high humidity environment, the ink is applied to the back side of the other recording paper on which it is superimposed. Transferred to reduce image quality. This phenomenon occurs frequently when the recording paper itself has a difference in hygroscopicity or when the humidity of the recording paper itself changes, and cannot satisfy the requirement of enabling high-speed recording with high image quality. In addition, when the moisture absorption of the recording paper is different, the pixel diameter varies depending on the moisture absorption even if recording is performed with a constant ink droplet size, and the image quality is lowered.
[0005]
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an inkjet printer capable of high-speed recording while maintaining high image quality even when environmental humidity changes, using recording paper having different hygroscopicity. And
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, an ink jet printer that records an image on recording paper by applying a voltage pulse based on an image signal to the pressure generating means, pressurizing the ink by the pressure generating means and ejecting ink droplets from the nozzles. in the humidity detecting means, and integrated with the inkjet head was placed drop ejecting side of the nozzle of the inkjet head, the amount of ink droplets ejected from the nozzle in response to the humidity signal of said humidity detecting means It is characterized by being variable, so that even when the environmental humidity increases, the drying speed of the recorded ink droplets is kept constant so that a high-quality image can be obtained even at a high speed, and the external shape is almost changed. Thus, a small inkjet printer is provided.
[0008]
In the invention of claim 2, in the ink jet printer according to claim 1, said humidity detecting means is provided a heating element pattern to crosslink the support or cantilevered thin films on an insulating material on a cavity formed in the substrate A humidity sensor utilizing the heat conduction principle of the microbridge structure is used, and the ink jet printer according to claim 1 is a further small and high speed ink jet printer.
[0009]
According to a third aspect of the present invention, in the ink jet printer according to the first or second aspect, the ink jet printer further comprises means for irradiating a portion of the ejected ink droplet on the recording paper or near the adhering portion with heat rays. with, the ink immediately after printing actively drying the, or an ink absorbency of small recording paper, even if the humidity is or changed, is obtained by allowing a high-quality recording at a high speed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, the humidity in the vicinity of the recording paper is detected. When the humidity is high, the particle size of the ink droplet ejected from the nozzle is reduced, and when the humidity is low, the particle size of the ink droplet is reduced. The ink on the recording paper spreads uniformly or is dried in approximately the same time without being affected by humidity. Hereinafter, a piezoelectric element is used as pressure generating means for ejecting ink droplets. An example of the used ink jet printer will be described.
[0011]
FIG. 1 is a diagram for explaining an embodiment of an ink jet printer according to the present invention. FIG. 1 (A) is a block diagram showing the configuration of the ink jet printer, and FIG. 1 (B) is an ink droplet size with respect to humidity. FIG. 1C is a diagram illustrating an example of a pulse waveform of a voltage pulse applied to the piezoelectric element in order to eject ink droplets having a particle diameter having the relationship of FIG. In the figure, 1 is an ink jet 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, 7 is a substrate, 8 is a recording paper, 9 is an ink droplet, 10 Is a humidity sensor, 11 is a printer controller, 12 is a humidity-ink droplet size curve, and 13 is a voltage pulse. In the following drawings from FIG. 1 onwards, the same reference numerals as those in FIG.
[0012]
1 ink jet head 1 shown in (A) is one using a piezoelectric element 6 as pressure generating means, the piezoelectric element 6, for example, a stacked structure that is driven by the d ₃₃ mode, one end of which is fixed to the substrate 7 The other end is joined to a vibration plate 2 a constituting one surface of the ink liquid chamber 2. A nozzle 3 is provided on the surface of the ink liquid chamber 2 facing the vibration plate 2a. The common liquid chamber 4 communicates with the ink liquid chamber 2 via a liquid passage 5, and the ink liquid chamber 2 is always filled with ink. ing. A recording paper 8 is disposed facing the nozzle 3 and is moved in the direction of arrow S by a conveying means (not shown) during recording.
[0013]
Further, a humidity sensor 10 is arranged in the vicinity of the recording paper 8 facing the nozzle 3. The humidity sensor 10 is connected to the printer controller 11 by a conducting wire 11a, and the printer controller 11 and the piezoelectric element 6 are connected by a conducting wire 11b.
[0014]
Next, the operation of the ink jet printer shown in FIG.
The humidity sensor 10 is installed in the vicinity of the recording paper 8 on the nozzle 3 side and measures the humidity (hygroscopicity) 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 a voltage pulse 13 having a constant peak value with a pulse width corresponding to the humidity signal to the piezoelectric element 6. The voltage pulse 13 displaces the piezoelectric element 6 in the arrow + F direction, transmits this to the diaphragm 2a, pressurizes the inside of the ink liquid chamber 2, and ejects and ejects ink droplets 9 from the nozzles 3 on the recording paper 8. Adhering ink droplets 9a to be pixels are formed.
[0015]
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. For example, the humidity-ink droplet size curve shown in FIG. As shown in FIG. 12, when the humidity is low, the ink droplet 9 having a large particle diameter is ejected, and the particle diameter of the ink droplet 9 is reduced as the humidity increases. In order to eject the ink droplet 9 having such a relationship, the voltage pulse 13 applied to the piezoelectric element 6 is used in the case where the ink droplet diameter is reduced in the pulse period τ as shown in FIG. When a voltage pulse 13a having a short pulse width is applied and the particle size is increased, a voltage pulse 13c having a long pulse width is applied. 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.
[0016]
As described above, by setting the humidity-ink droplet diameter curve 12 shown in FIG. 1B in advance, even if the humidity of the recording paper 8 changes, the adhered ink droplet 9a spreads uniformly, or Drying is performed at approximately the same time, and high image quality can be maintained even in high-speed printing. The relationship of the humidity-ink droplet size curve 12 can be similarly applied to a bubble jet type ink jet printer.
[0018]
In the present invention, the humidity sensor 10 is provided integrally with the inkjet head 1 on the opening surface side of the nozzle 3 of the inkjet head 1. Since the interval 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 can be a small inkjet printer. .
[0019]
Invention of claim 2 of the inventions of claims 2, the humidity sensor which was a microbridge structure using heat conduction principles, compact, can measure the humidity with high precision at high response.
[0020]
Figure 2 is a diagram for explaining an example of a humidity sensor according to the invention of claim 2, FIG. 2 (A), a plan view, FIG. 2 (B), the humidity sensor shown in FIG. 2 (A) FIG. 2 is a drive detection circuit diagram, in which 21 is a substrate, 22 is a thin film insulator, 23 is a cavity, 24 is a heating element pattern, 25 is a lead wiring pattern, 26 is a connection portion, 27 is a heater power supply, and 28 is a detection circuit. It is.
[0021]
The humidity sensor 10 shown in FIG. 2 (A) was previously proposed by the present applicant. After the thin film insulator 22 is formed on the upper surface of the square Si (100) substrate 21, the length of the side of platinum or the like is long. After the heating element pattern 24 having a thickness of 100 μm is formed, the heating element pattern 24 has a microbridge structure in which a cavity 23 is formed by anisotropic etching in the lower portion, leaving a bridging portion 22a for forming the heating element pattern 24. In this way, the outermost peripheral edge of the lead wire pattern 25 intersects the lead wiring pattern 25 at a point 26 on the bridging portion 22a to prevent the temperature lowering effect at both ends of the heating element pattern 24.
[0022]
The humidity sensor 10 is connected to the heater power supply 27 and the detection circuit 28 by lead lines A, B, C, and D from the pad portions 25a, 25b, 25c, and 25d. A voltage signal of the heating element pattern 24 is detected.
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. , Subtract the detection voltage when driven with a low voltage pulse from the detection voltage when driven with a high voltage pulse to obtain the absolute humidity at that temperature, from the relationship between the environmental temperature and absolute humidity obtained by applying a low voltage pulse Calculate the humidity.
[0023]
As described above, since the humidity sensor 10 shown in FIG. 2 is used, a humidity that is small and has a high-accuracy response is required, so that the humidity of the recording paper 8 can be accurately detected even in high-speed recording.
[0024]
Invention of Claim 3 According to the invention of claim 3 , when the ink droplets of the recording paper are heated locally and dried quickly in synchronism with ink droplet ejection, the humidity of the recording paper is different. Even when the amount of ink droplets cannot be corrected, the ink is completely dried to maintain high image quality.
[0025]
FIG. 3 is a view 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.
[0026]
In FIG. 3 , the infrared lamp 14 is connected to the printer controller 11 by a conductive wire 11c, and is provided at a position facing the recording paper 8 in the inkjet head 1 or in the vicinity thereof. The infrared lamp 14 is provided with a reflector 15 and a condenser lens 16 as an optical system for focusing the heat rays in the vicinity of the attached ink droplet 9a with respect to the moving direction S of the attached ink droplet 9a or the recording paper 8.
[0027]
The heat rays emitted from the infrared lamp 14 are driven by the printer controller 11 in synchronization with the driving of the piezoelectric element 6 or asynchronously. In other words, it is driven in synchronism with the ejection of the ink droplet 9 and heats the attached 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, it is not always necessary to synchronize with the ink droplet ejection, and the adhered ink droplet 9a may be focused with a constant power.
[0028]
According to the ink jet printer shown in FIG. 3 , even if the paper quality is different and the recording paper has poor ink absorbability, or the ink droplet amount cannot be controlled by humidity detection, the ink can be effectively dried, and high speed printing can be performed. Even in the case of copying, a high-quality image can be formed.
[0029]
【The invention's effect】
An effect corresponding to claim 1: an ink jet that records an image on recording paper by applying a voltage pulse based on an image signal to a pressure generating unit, pressurizing the ink by the pressure generating unit, and ejecting an ink droplet from a nozzle. in the printer, the humidity detecting means, and integrated with the inkjet head was placed drop ejection side of the ink jet head, variably the amount of ink droplets ejected from the nozzle in response to the humidity signal of said humidity detecting means Therefore, even when the humidity of the recording paper or the environmental humidity changes, a high-quality image can be obtained by high-speed printing. Furthermore, since the humidity detecting means is integrated with the ink jet head and disposed on the droplet ejection side of the nozzle of the ink jet head, the ink jet printer can be reduced in size.
[0031]
The effect corresponding to Claim 2 : In the ink jet printer according to Claim 1, the humidity detecting means is provided with a heating element pattern on a thin film insulator supported by bridging or cantilever on a cavity formed on a substrate. In addition, since the humidity sensor uses the heat conduction principle of the microbridge structure, the ink jet printer can be made smaller and faster .
[0032]
The effect corresponding to Claim 3 : In the ink jet printer according to Claim 1 or 2 , since the ink droplets have means for irradiating heat rays to or near the adhering portion of the ejected ink droplets on the recording paper, ink suction High-quality images can be recorded at high speed even when the ambient humidity is low.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of an ink jet printer according to the present invention.
FIG. 2 is a diagram for explaining an example of a humidity sensor according to the present invention.
FIG. 3 is a view for explaining another embodiment of the ink jet printer according to the present invention.
[Explanation of symbols]
DESCRIPTION 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 droplet, 10 ... Humidity sensor 11 ... Printer controller, 12 ... Humidity-ink droplet 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 portion, 27 ... Heater power supply, 28 ... Detection circuit.

Claims (3)

A voltage pulse based on the image signal applied to the pressure generating means, an ink droplet ejected from the nozzle ink by pressure generating means is pressurized, the ink jet printer for recording an image on a recording sheet, a humidity detecting means The ink jet head is arranged integrally with the ink jet head on the droplet ejection side of the nozzle, and the amount of ink droplet ejected from the nozzle is variable in accordance with the humidity signal of the humidity detecting means. Inkjet printer. The humidity detecting means is a humidity sensor using a heat conduction principle of a microbridge structure in which a heating element pattern is provided on a thin-film insulator that is bridged or cantilevered on a cavity formed in a substrate. The inkjet printer according to claim 1 . 3. The ink jet printer according to claim 1, further comprising means for irradiating a portion of the ejected ink droplet attached to the recording paper or near the attached portion with heat rays.

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