JPH0485044A - Ink jet recorder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an inkjet recording apparatus using an inkjet recording head that ejects droplets using energy from an ejection energy generating means.

[Conventional technology]

Conventionally, this type of inkjet recording apparatus has an inkjet recording head that ejects droplets using energy from an ejection energy generating means, and a relative movement means that relatively moves a recording medium and the inkjet recording head,
Image formation is performed by arranging the inkjet recording head and a recording medium to face each other.

FIG. 9 is a configuration diagram showing a conventional example of an inkjet recording apparatus, in which 1'' is an inkjet recording head (hereinafter referred to as a ``recording head''), 42° is a pressure generating means, and 7' is a recording medium, which is a recording head. The ink 43' in 1 is pushed out by the pressure generated by the pressure generating means 42', and ink droplets are deposited on the recording medium 7° and conveyed in the direction of arrow A by a recording medium conveying means (not shown) to form an image.

[Problems to be Solved by the Invention] In the conventional inkjet recording device described above, there is an electric field between the recording medium and the recording head, and when the droplets are charged, their movement is caused by the electric force. As a result, droplets may not land on the intended location on the recording medium, causing image disturbances. Especially when the humidity of the recording medium changes, the electric field between the recording medium and the recording head changes.
Since the electrical force with respect to the movement of the droplet changes, there is a problem that the landing position changes and image disturbance is amplified.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an inkjet recording apparatus that does not adversely affect the movement of droplets.

[Means to solve the problem]

The inkjet recording apparatus of the present invention includes: an inkjet recording head that discharges droplets; a relative movement means that relatively moves a recording medium and the inkjet recording head; a humidity detection means that detects the humidity of the recording medium; and the recording medium. A potential difference adjustment means for adjusting a potential difference between a medium and the inkjet recording head, and a value of the potential difference by the potential difference adjustment means is changed according to a humidity value of the recording medium detected by the humidity detection means. let

Preferably, the relative movement means is an electrostatic adsorption conveyance means, and more preferably, the inkjet recording head is a full-line type having a plurality of ejection ports over the entire width of the recording area of the recording medium, or an inkjet The recording head uses thermal energy to eject ink from ejection ports, and has an electrothermal converter as a means for generating thermal energy.

(Function) When the relative movement means relatively moves the recording medium and the inkjet recording head, the humidity detection means detects the humidity of the recording medium, and based on the detection result, the potential difference adjustment means adjusts the humidity between the recording medium and the inkjet recording head. By adjusting the potential difference between the inkjet recording head and the recording medium, ink droplets are accurately ejected from the inkjet recording head to the recording medium.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram schematically showing a first embodiment of an inkjet recording apparatus of the present invention.

IBk, ly, 1m, and lc each have a bubble jet type inkjet recording head (hereinafter referred to as "recording head J") that corresponds to black, yellow, magenta, and cyan ink colors, and the built-in ejection energy key generator generates heat. Using a resistor, the ink droplets are ejected from the ejection port by bubbles generated in the ink using thermal energy generated when the heating resistor is energized, and each recording head is fixed to the block 2. is 40
4736 ejection ports are arranged at a density of 0 dpi (dot bar inch).

Reference numeral 3 designates a capping unit, which pulls up the block 2 to the NA indicated by the dotted chain line in the figure during recording, such as during standby, and caps the block 2 by placing the unit 3 facing the pulled-up block 2. Further, the capping unit 3 also serves as a receiver I for waste ink sent from a recovery pump (not shown) and an ink supply system and pushed out from the ejection port during circulation recovery. The waste ink is led to a waste ink tank (not shown).

4 is a charging adsorption belt for supporting and conveying the recording sheet 7, and includes recording heads Bk, ty.

They are arranged facing each other at a predetermined distance from each other at a distance of 1 m and lc, and are charged by a charging roller 31, which will be described later, and are driven by a drive source (not shown).

Reference numeral 5 denotes a back platen which is disposed opposite to each recording head with a charging adsorption belt 4 interposed therebetween.

6 is a paper feed cassette that stores recording sheets 7 such as plain paper and is removably attached to the main body of the apparatus; 8 is a pickup roller that feeds and feeds only one recording sheet 7 on the uppermost surface; The recording sheet 7 sent out from the pickup roller 8 is conveyed to a conveyance path 10 by a pair of conveyance rollers 9, and then conveyed onto the charged adsorption belt 4 by a pair of conveyance rollers 11 arranged on the exit side of the conveyance path 10. .

13 and 14 are heaters and fans that use hot air to dry and fix ink droplets that have adhered to the recording sheet 7 during recording; 15 is a discharge roller that discharges the recording sheet 7 that has been fixed to the outside of the apparatus; and 16 is a discharged record. This is a tray for sequentially stocking sheets 7. Reference numeral 32 denotes a brush-like electrode for injecting charge from a power source 35 onto the recording sheet 7, and a humidity measuring means 33 is disposed near the brush-like electrode.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, the recording operation will be explained. When an operation to start recording is performed, a recording sheet 7 of a specified size is sent out from the paper feed cassette 6 by a pickup roller 8. The fed-out recording sheet 7 is transferred to the conveyor roller 9.11.
The charging roller 31 charges +2k in advance.
It rotates while being charged so as to have a surface potential of approximately V, and is placed on the charged adsorption belt 4 which is made into a planar shape by the back platen 5. At this time, the humidity of the recording sheet 7 is measured by the humidity measuring means 33, and the voltage applied to the brush-like electrode 32 is controlled according to the measured value (described in detail later). As the leading edge of the recording sheet 7 reaches the lower part of each of the recording heads lc, 1m, ly, and IBk, the energy generator of each recording head is activated according to the image data via a drive circuit (not shown). drive. By this driving, ink droplets corresponding to image information are ejected from the ejection ports onto the surface of the recording sheet 7, thereby performing recording.

If the recording sheet 7 has poor hygroscopicity, the droplets adhering to the surface will not dry and will be rubbed, causing print stains, and the heater 1
3 and fan 14 to perform forced drying and fixation. The recording sheet 7 that has been fixed is transferred to the ejection roller 15.
The paper is discharged onto the tray 16 by the following steps.

As mentioned above, cyan, magenta, yellow,
Recording head IBk, ly, compatible with black ink
1m, lc with respective recording heads IBk, ly, 1m
, lc is applied to form a color image.

Next, the ejection principle of the inkjet recording head used in the apparatus of this embodiment will be explained.

Inkjet recording heads applied to inkjet recording devices generally have fine liquid ejection ports (orifices),
The apparatus includes a liquid flow path, an energy acting part provided in a part of the liquid flow path, and an energy generating means for generating droplet forming energy to act on the liquid in the acting part.

Energy generating means for generating such energy include a recording method using an electromechanical transducer such as a piezo element, irradiating a laser or electromagnetic wave, etc., and causing the liquid there to absorb energy and generate heat. There are recording methods using energy generating means that ejects and flies droplets due to the effect of this heat generation, and recording methods that use energy generating means that heats the liquid with an electrothermal converter and ejects the liquid.

Among these, the recording head used in the inkjet recording method that discharges liquid using thermal energy has a high density array of liquid discharge ports (orifices) for discharging recording droplets to form flying droplets. This makes it possible to record with high resolution. Further, a recording head using an electrothermal converter as an energy generating means can easily be made more compact as a whole.

Furthermore, it is possible to fully utilize the advantages of IC technology and micro-processing technology, which have seen remarkable technological advances and improved reliability in the semiconductor field in recent years, and can easily be made into long and planar shapes (two-dimensional). For these reasons, it is possible to provide an inkjet recording head that is easy to implement with multiple ejection ports/high-density packaging, has good productivity in mass production, and is inexpensive to manufacture.

In this way, using an electrothermal converter as an energy generation means,
Inkjet recording heads manufactured through a semiconductor manufacturing process generally have a liquid flow path corresponding to each ejection port, and apply thermal energy to the liquid that fills each liquid flow path. An electrothermal converter is provided as a means for ejecting liquid from an orifice to form flying droplets, and each liquid flow path is supplied with liquid from a common liquid chamber communicating with each liquid flow path. The structure is such that

FIG. 2 shows a schematic configuration of the above-mentioned inkjet recording head. This recording head undergoes semiconductor manufacturing process steps such as etching, vapor deposition, and sputtering.
The electrothermal converter I03.2 formed on the electrothermal converter I03. Electrode I04. Liquid channel wall 105. It is composed of a top plate 106.

The recording liquid 112 is supplied from a liquid storage chamber (not shown) to the common liquid chamber 10 of the recording head 101 through a liquid supply pipe +07.
8. In the figure, 109 is a liquid supply pipe connector. The liquid 112 supplied into the common liquid chamber +08 is supplied into the liquid flow path (liquid path) +10 by capillary action, and is stably held by forming a meniscus at the discharge port surface 111 at the tip of the liquid path. By energizing the electrothermal converter +03, the liquid on the surface of the electrothermal converter is heated, a bubbling phenomenon occurs, and the energy of the bubbling causes droplets to be ejected from the ejection port surface I11.

With the above-described configuration, a multi-ejection orifice inkjet recording head is formed with a high-density ejection orifice arrangement such as an ejection orifice density of 400 dpi.

The application of voltage to the brush-shaped electrode according to the measured value by the measuring means will be explained with reference to FIG.

The ink 43 in the recording heads IBk, ly, 1m, lc is ejected by the pressure generated by the pressure generating means 42, and droplets are ejected and attached onto the recording sheet 7.

The area around the core of the charged adsorption belt 4 is conductive rubber, and a voltage of approximately +2 kV is applied to the core (applied by the power source 34).
The charging roller 31 to which the voltage is being applied is brought into contact with the charging roller 31, and a positive charge is placed on the charging adsorption belt 4. By bringing the recording sheet 7 into close contact with the charging attraction belt 4, negative charges are induced on the charging attraction belt side of the recording sheet 7, and an attraction force between the recording sheet 7 and the charging attraction belt is generated. The side of the recording sheet 7 that is not on the charged adsorption belt side (recording heads IBk, l
A positive charge is induced on the side opposite to y, im, lc), and the recording spatula)"IBk.

A potential difference occurs between ly, 1m, lc and the recording sheet 7, and an electric field is formed.

The strength of this potential difference, that is, the strength of the electric field, depends on the dielectric constant of the recording sheet 7 and the attenuation rate of the surface potential of the charged adsorption belt 4, but these change depending on the surrounding environment, and in the conventional configuration, the strength of the electric field In the past, it was not possible to control the shift in the droplet landing position, which changes depending on the strength of the electric field, causing unintended image holes.

In the present invention, the humidity measuring means 33 and the brush-like electrode 3
2 and a variable power source 35 that changes according to the measured value by the humidity measuring means 33, and the recording sheet 7 and the recording head IBk.
, ly, 1m, the strength of the electric field between Ic is approximately zero regardless of humidity (-100v/ll1ff1~+100■/ll
11).

The relationship between the measured humidity and the dielectric constant of the recording sheet 7 is measured in advance and tabulated as shown in FIG. 4, and the dielectric constant of the recording sheet 7 can be estimated from the measured humidity. Furthermore, the relationship between the dielectric constant and the magnitude of the potential induced on the recording sheet 7 is also known in advance. By utilizing these previously known relationships and changing the voltage applied by the variable power supply 35 according to the humidity as shown in FIG. 5, the electric field between the recording sheet 7 and the recording head can be adjusted as shown in FIG. 6. Keep the strength constant regardless of humidity.

The humidity measuring means 33 is placed at a recording head IBk, ly, 1 m as shown in FIG.

The arrangement is not limited to the vicinity of the IC, but may be arranged near the recording sheet 7 in the paper feed cassette 6, as shown by B in FIG.

Although the relationship between humidity and the voltage applied to the variable power source 35 is derived from the relationship between humidity and dielectric constant, the present invention is not limited to this, but also takes into account the relationship between humidity and the surface potential attenuation rate on the recording medium. Good too.

5 Self-recording sheet 7 and recording head tBk, ty.

Although the electric field strength between 1 m and lc is controlled to be about zero, the present invention is not limited to this.

The ink droplet may be controlled to a range of plus 100 V/mm to plus 300 V/mm and have a means for negatively charging the ink droplet, so that the droplet is drawn toward the recording sheet side by electric force. Since the strength of the electric field can be controlled by the configuration of this embodiment, it is possible to control the electric force acting on the droplet, and it is possible to prevent unintended image disturbances due to fluctuations in the electric force.

Although the case of positive charging is shown, the present invention is not limited to this. The same applies to the case of negative charge.

Although the object to be measured is humidity, the present invention is not limited to this, but has means for measuring things related to the dielectric constant of the recording sheet and the strength of the electric field between the recording head and the recording sheet. Alternatively, the relationship between the measured value and the applied voltage may be made into a table and the optimum applied voltage may be determined. The measurement target is, for example, temperature.

In the configuration of the first embodiment, the power source to be controlled is described as a constant voltage power source, but it is not limited to this, and may be a constant current power source.

FIG. 7 is a block diagram showing a second embodiment of the present invention.

In the first embodiment, the voltage applied to the brush-like electrode 32 was set to the variable power supply 35, but in this embodiment, a power supply 37 is connected to the brush-like electrode 32, and the voltage applied to the core of the charging roller 31 is made variable. The variable power source 36 is controlled according to the value of the humidity measuring means 33. In addition, a brush-like electrode 32 and a charging roller 31
It is clear that both power sources may be controlled.

FIG. 8 is a block diagram showing a third embodiment of the present invention.

In this embodiment, the voltage of the variable power supply 38 applied to the ink 43 is controlled by the value of the humidity measuring means 33. In this case, since there is no feedback sequence, there is an advantage that the time required for control is shorter than in the first and second embodiments.

The present invention brings about excellent effects particularly in recording heads and recording apparatuses of the bubble jet recording method proposed by Canon Co., Ltd. among inkjet recording methods.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type, but especially in the case of the on-demand type, it corresponds to the sheet or liquid path where the liquid (ink) is held, and By applying at least one drive signal that provides a rapid temperature rise above boiling. This is effective because it causes the electrothermal transducer to generate thermal energy, and as a result, bubbles in the liquid (ink) can be formed in one-to-one correspondence with this drive signal. The growth of this bubble,
The contraction causes liquid (ink) to be ejected through the ejection opening to form at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, so that ejection of liquid (ink) with particularly excellent responsiveness can be achieved. This pulse-shaped drive signal is described in US Pat. No. 4,463,359 and US Pat.
345262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 concerning the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be achieved.

The configuration of the recording head includes, in addition to the combination configuration of an ejection port, a liquid path, and an electric heat exchanger (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting part. U.S. Pat. No. 4 discloses an arrangement in which the
558333 and US Pat. No. 4,459,600, respectively. In addition, JP-A-59-12367 discloses a configuration in which a common slit is used as a discharge part for a plurality of electrothermal converters.
No. 0 and JP-A-59-138461 which discloses a configuration in which a discharge portion has an opening that absorbs pressure waves of thermal energy.
The present invention is also effective with a configuration based on the publication.

Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can record the recording layer value, the length can be increased by combining multiple recording heads as disclosed in the above-mentioned specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head formed integrally may be used, but the present invention can more effectively exhibit the above-mentioned effects.

In addition, a replaceable chip-type recording head that is attached to the device body enables electrical connection to the device body and ink supply from the device body, or a chip-type recording head that is installed integrally with the recording head itself. The present invention is also effective when a cartridge type recording head is used.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. for the recording head, which are provided as a configuration of the recording apparatus of the present invention, because the effects of the present invention can be further stabilized. Specifically, these include: a caving means, a cleaning means, a pressurizing or suction means for the recording head, a heating element separate from the electrothermal converter, or a preheating means using a combination of these; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from printing in order to perform stable printing.

Furthermore, the recording mode of the recording device is not limited to a recording mode in which only the mainstream color such as black is used; the recording head may be configured integrally or in combination with a plurality of recording heads; The present invention is also extremely effective for devices equipped with at least one full color image.

In the embodiments of the present invention described above, the ink is explained as a liquid, but the ink solidifies at room temperature or lower, and becomes soft or liquid at room temperature, or
The ink may be one that softens or becomes liquid in the temperature range of 30°C or more and 71°C or less, which is the temperature range generally used for temperature adjustment in inkjet printers. In addition, the temperature rise caused by thermal energy can be actively prevented by using it as energy to change the state of the ink from a solid state to a liquid state, or the ink can be left to solidify for the purpose of preventing evaporation. In any case, the ink may be liquefied by applying thermal energy in accordance with the recording signal and ejected as liquid ink, or the ink may already begin to solidify by the time it reaches the recording medium. It is also applicable to the present invention to use ink that is liquefied only by thermal energy. In such a case, the ink may be ink as described in JP-A-54-56847 or JP-A-60-71260.
The porous sheet may be held in a liquid or solid state in the recesses or through-holes of the porous sheet, facing the electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

〔Effect of the invention〕

As explained above, the present invention controls the electric potential difference between the recording medium and the inkjet recording head based on the detection result of the humidity detection means to reduce the fluctuation of the electric field between the two. This has the effect of making it possible to keep the mechanical force constant regardless of the humidity of the recording medium, thereby eliminating disturbances in image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing a first embodiment of an inkjet recording apparatus of the present invention, FIG. 2 is a diagram showing the structure of an inkjet recording head, and FIG. 3 is a control section of the embodiment of FIG. 1. FIG. 4 is a graph showing the change in dielectric constant of the recording sheet with respect to humidity, and FIG.
6 is a graph showing the strength of the electric field between the recording sheet and the inkjet recording head in the embodiment of FIG. 1, and FIGS. 7 and 8 are graphs showing the applied voltage according to the embodiment of the present invention. 2. A configuration diagram showing the third embodiment, and FIG. 9 is a configuration diagram showing a conventional example. 2... Block, 3... Capping unit, 4... Charge adsorption belt, 5... Back platen,
6... Paper cassette, 7... Recording sheet, 8...
... Pickup roller, 9.11 ... Conveyance roller, 31 ... Charging roller, 3
2... Brush-shaped electrode, 33... Humidity measuring means,
34.37...Power supply, 35.36.38...Variable power supply. Figure 5 of 109 tags Figure 5

Claims (1)

[Scope of Claims] 1. An inkjet recording head that discharges droplets, a relative movement means that relatively moves a recording medium and the inkjet recording head, a humidity detection means that detects the humidity of the recording medium, and the recording medium. A potential difference adjustment means for adjusting a potential difference between a medium and the inkjet recording head, and a value of the potential difference by the potential difference adjustment means is changed according to a humidity value of the recording medium detected by the humidity detection means. An inkjet recording device characterized by: 2. The inkjet recording apparatus according to claim 1, wherein the relative movement means is an electrostatic adsorption conveyance means. 3. Claim 1, wherein the inkjet recording head is a full-line type having a plurality of ejection ports over the entire width of the recording area of the recording medium.
Or the inkjet recording device according to claim 2. 4. Any one of claims 1 to 3, wherein the inkjet recording head uses thermal energy to eject ink from an ejection port, and has an electrothermal converter as a means for generating thermal energy. The inkjet recording device described in 2.