JPH11291473A - Ink jet recording device, and drying liquid used for ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the fixing properties of ink while maintaining the reliability in an ink jet recording device. SOLUTION: The ink jet recording device 1 is equipped with ink jet heads 7a-7d for a recording liquid which is filled with the recording liquid and discharges the liquid droplets of the recording liquid to a recording medium 4 and an ink jet head 8 which is filled with a drying liquid for promoting the drying of the recording liquid adhering to the recording medium 4 and discharges the liquid droplets of the drying liquid to the recording medium 4. A heating device 65 for heating the drying liquid is mounted on an ink jet head 8 for the drying liquid.

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 for recording an image by ejecting ink droplets in accordance with an image signal and attaching the ink droplets to a recording medium such as recording paper.

[0002]

2. Description of the Related Art Conventionally, there has been known an ink jet recording apparatus having a piezoelectric member corresponding to a plurality of ink cavities. In this ink jet recording apparatus, at the time of printing, the piezoelectric member is deformed in a thickness direction by a driving voltage applied from a driver, and the ink in the ink cavity pressurized by the deformation is ejected from a nozzle as an ink droplet by a recording paper or the like. Adheres to the recording medium.

Recently, an ink jet recording apparatus of this type has been required to have a higher printing speed especially when used as an OA device. As the speed increases, it is necessary to reliably fix the ink to the recording medium in a short time. In order to improve the fixing property of the ink, it is conceivable to add, to the ink composition, a component that enhances the drying property, such as ethanol. However, ethanol and the like added to the ink evaporate in the vicinity of the nozzle, and a precipitate is formed. This deposit causes nozzle clogging and significantly impairs reliability.

The present invention has been made in view of the problems in the ink jet recording apparatus, and has been made to improve the fixing property of ink while maintaining reliability.

[0005]

According to a first aspect of the present invention, there is provided a recording liquid ink jet head which is filled with a recording liquid and discharges droplets of the recording liquid onto a recording medium. The present invention is to provide an ink jet recording apparatus which is provided with a drying liquid inkjet head which is filled with a drying liquid for accelerating the drying of the recording liquid adhered to the recording medium and discharges droplets of the drying liquid onto a recording medium.

In the ink jet recording apparatus according to the first aspect of the present invention, the evaporation of the drying liquid discharged from the inkjet head for the drying liquid to the recording medium promotes the evaporation of the recording liquid. Be faster. Also, since the drying liquid is not mixed with the recording liquid filled in the recording liquid inkjet head, the drying liquid is filled in a drying liquid inkjet head different from the recording liquid inkjet head, It is possible to prevent a decrease in the reliability of the ink jet head for recording liquid due to a precipitate generated when the drying liquid is evaporated.

It is preferable that the dry liquid contains at least a water-soluble organic solvent and water.

The water-soluble organic solvent contained in the dried liquid has a vapor pressure at −20 ° C. of −15 mmHg or more.
It is preferably at most 00 mmHg.

When the vapor pressure of the water-soluble organic solvent is in this range, the evaporation rate of the drying liquid is a rate that can promote the evaporation of the recording liquid, and also prevents the drying liquid before being discharged from excessively evaporating. be able to.

It is preferable that a heating device for heating the drying liquid filled in the drying liquid inkjet head is provided. When the drying liquid filled in the drying liquid inkjet head is heated by the heating device, the evaporation rate of the drying liquid is further increased, and thus the evaporation of the recording liquid is further promoted.

During printing, it is preferable that the drying liquid is discharged from the drying liquid inkjet head onto the recording medium before the recording liquid discharged from the recording liquid inkjet head.

Specifically, it is preferable that the ink jet head for a drying liquid is disposed downstream of the ink jet head for a recording liquid in the main scanning direction.

According to a second aspect of the present invention, the drying of the recording liquid ejected from a drying liquid inkjet head different from the recording liquid inkjet head for discharging droplets of the recording liquid onto the recording medium and adhering to the recording medium is promoted. Provided is a drying liquid, which contains at least a water-soluble organic solvent and water and is used for an ink jet recording apparatus.

The dry liquid has a vapor pressure at 20 ° C.
It is preferably from 15 mmHg to 100 mmHg.

[0015]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) FIG. 1 shows an ink jet recording apparatus 1 according to a first embodiment of the present invention. The inkjet recording apparatus 1 includes a moving mechanism 3 for moving the carriage 2 in a main scanning direction indicated by arrows X1 and X2, and a feeding mechanism 5 for moving a recording sheet 4 as a recording medium in a sub-scanning direction indicated by arrow Y. Have. The carriage 2 at the time of printing repeats the operation of moving in the direction of arrow X1 while discharging the ink and the drying liquid onto the recording paper 4, and the operation of moving in the direction of arrow X2 and returning to the position shown in FIG.

As shown in FIG. 2, the carriage 2 is filled with four different colors of ink corresponding to yellow, magenta, cyan, and black, respectively, and has four recording liquids for discharging droplets of these inks. Drying heads 7a, 7b, 7c, 7d, and a drying liquid for facilitating drying of the ink adhered to the recording paper 4, and a drying liquid inkjet head 8 for discharging the drying liquid.
And

In the carriage 2, an ink jet head 8 for drying liquid is arranged on the downstream side in the moving direction of the carriage 2 (downstream in the main scanning direction) at the time of ink ejection indicated by the arrow X1. The recording liquid inkjet heads 7 a to 7 d are arranged on the upstream side in the moving direction of the carriage 2.

Four ink jet heads 7a for recording liquid
7d are arranged close to each other. Between the recording liquid inkjet heads 7a to 7d and the drying liquid inkjet head 8, to prevent heat generated by a heating device 65 described later from affecting the ink in the recording liquid inkjet heads 7a to 7d. Are provided, and a spacer (not shown) is interposed in the gap 9.

The recording liquid ink jet heads 7a to 7a
7d, as shown in FIG. 3 to FIG.
4, the diaphragm 16 and the substrate 18 are integrally combined.

On the back surface of the top plate 12 made of ceramic or the like, a plurality of groove-shaped concave portions are formed by fine processing.
The partition 14 made of an insulating film is adhered to the top plate 12 and covers each of the concave portions. Each of the recesses covered by the partition walls 14 has a cavity 2 for accommodating ink.
0, a supply chamber 22 for accommodating supply ink, and an inlet 24 for communicating each cavity 20 with the supply chamber 22. On the opposite side of the top plate 12 from the inlet 24, a nozzle 26 communicating with the cavity 20 is formed.

The substrate 18 is a flat plate made of a high-rigidity insulating material such as ceramic, and the diaphragm 16 and the spacer member 30 are fixed between the substrate 18 and the partition 14. The vibration plate 16 is made of a well-known piezoelectric material. As shown in FIG. 5, by providing a groove 32, a piezoelectric member 34 facing the cavity 20 via the partition wall 14 and a cavity 20 are formed.
Is separated from the standing wall 36 which faces the side wall 38 via the partition 14. The spacer member 30 has the same thickness as the piezoelectric member 34, and supports one end side of the top plate 12 via the partition wall 14.

An individual electrode 42 made of a metal conductive layer is provided on the surface of the piezoelectric member 34 on the cavity 20 side.
A connection line 52 is connected to each individual electrode 42. The connection line 52 electrically connects the piezoelectric member 34 and an image signal control circuit (voltage applying means) 54 for applying a drive voltage to the piezoelectric member 34. On the other hand, a metal conductive layer that is in common contact with the lower surface of each piezoelectric member 34 and is connected to the ground is formed on the surface of the substrate 18, and functions as a common electrode 44 of the piezoelectric member 34. Further, the piezoelectric member 34 has a region corresponding to the cavity 20 sandwiched between the individual electrode 42 and the common electrode 44 as an active portion 46 by performing a polarization process, and a rear region other than the active portion 46 is a non-polarized inactive state. The section 48 is provided.

The supply chamber 22 is provided with a cartridge type tank 6 which is detachable via a flow path 60 (shown in FIG. 2).
The tank 61 is filled with inks corresponding to the four colors. The ink supplied from the tank 61 to the supply chamber 22 is stored in each cavity 20 via the inlet 24. In this state, when a voltage is applied from the image signal control circuit 54 to the individual electrode 42 via the connection line 52, the active portion 46 of the piezoelectric member 34 is instantaneously deformed in the thickness direction, and the partition 14 is pushed into the cavity 20. . This causes the pressurized ink to be ejected as droplets from the nozzles 26, which adheres to the recording medium to record an image.

As shown in FIG. 2, the drying liquid inkjet head 8 includes a heating device 65 for heating a cartridge type tank 61 filled with the drying liquid and a tank 6.
A temperature sensor 66 for detecting the temperature of the drying liquid in the apparatus 1 is provided.

The heating device 65 is of a known type utilizing the heat generated by the resistance wire, and is provided on the entire outer periphery of the tank 61 and around the flow path 60.
1 and the drying liquid in the flow path 60 can be heated. The temperature detected by the temperature sensor 66 is input to a temperature control circuit 67 schematically shown in FIG. The temperature control circuit 67 controls the heating device 65 based on the temperature signal input from the temperature sensor 66. In the first embodiment, the temperature control circuit 67 controls the heating device 65 so that the temperature of the drying liquid in the tank 61 falls within a range of 45 ° C. ± 2 ° C.

The other structure of the drying liquid inkjet head 8 is the same as the recording liquid inkjet heads 7a to 7d, except that the capacity of the tank 61 is larger than the recording liquid inkjet heads 7a to 7d.

As the drying liquid filled in the tank 61 of the ink jet head 8 for drying liquid, a solution having a drying speed higher than that of the ink is used. Specifically, a solution containing at least a water-soluble organic solvent and water is preferable as the drying liquid. As the water-soluble organic solvent, those shown in Table 1 below can be used.

[0028]

[Table 1]

In Table 1, 1-propanol is the same as propyl alcohol or propanol. Also, 2-propanol is the same as isopropyl alcohol.

The water-soluble organic solvent preferably has a vapor pressure at 20 ° C. of from −15 mmHg to 100 mmHg. This means that if the vapor pressure of the water-soluble organic solvent is within this range, the evaporation rate of the drying liquid will be a rate that can promote the evaporation of the recording liquid, and the drying liquid before ejection will not be excessively evaporated. Because it can be. That is, when the vapor pressure of the water-soluble organic solvent is lower than −15 mmHg,
Even if it is heated by the heating device 65, the evaporation speed of the drying liquid is slow, and the drying of the ink is rather slowed. When the vapor pressure of the water-soluble organic solvent exceeds 100 mmHg,
Even if a head cap (not shown) is attached, the drying liquid filled in the drying liquid inkjet head 8 evaporates significantly into the atmosphere at room temperature, and it is necessary to frequently supply the drying liquid, which poses a practical problem.

More preferably, the water-soluble organic solvent comprises 20
It is desirable that the vapor pressure at ℃ be in the range of 3 mmHg to 30 mmHg. If the vapor pressure of the water-soluble organic solvent is set within this range, the effect of accelerating the evaporation of the recording liquid and the effect of preventing the excessive evaporation of the dry liquid before ejection are further improved.

The content of the water-soluble organic solvent in the dried liquid is 20
wt% or more and 80 wt% or less, more preferably 30 wt%
% Or more and 70 wt% or less. When the content of the water-soluble organic solvent is less than 20% by weight, there is almost no effect of promoting the drying of the ink. When the content of the water-soluble organic solvent exceeds 80% by weight, the drying liquid is heated by the heating device 65, so that the evaporation of the water-soluble organic solvent becomes remarkable. As a result, the composition of the drying liquid changes, and the effect of accelerating the drying of the ink decreases. Further, due to the change in the composition, the droplets do not fly stably from the ink jet head 8 for the drying liquid, and the drying liquid may not be able to adhere to a required position of the recording paper 4.

The drying liquid may contain only one kind of the water-soluble organic solvent, or may contain two or more kinds. In the case of containing two types of water-soluble organic solvents having different vapor pressures, the distribution of the evaporation rate with respect to the temperature expands,
The sensitivity of the evaporation of the drying liquid to ambient temperature is reduced. Therefore, in this case, evaporation of the drying liquid from the drying liquid inkjet head 8 can be suppressed, and the replacement cycle of the tank 61 is extended.

Further, the drying liquid may contain a water-soluble resin such as a water-soluble urethane resin. In this case, by covering the ink on the recording paper 4 with the resin, the fixability and the storage stability can be improved. However, the content of the water-soluble resin and the like must be set so as not to cause clogging of the nozzle 26.

Further, the drying liquid may contain other components such as a fungicide as long as it does not cause clogging of the nozzle 26.

Next, the operation of the ink jet recording apparatus according to the first embodiment will be described. When the main power supply of the ink jet recording apparatus is turned on in step S1 of FIG. 6, the power supply for the heating device (not shown) is turned on and the temperature sensor 66 is turned on in step S2. In step S3, if the temperature control circuit 67 detects that the temperature of the drying liquid in the tank 61 is out of the set temperature range (45 ° C. ± 2 ° C.), the heating device 65 operates, and printing during this period is stopped. You. On the other hand, in step S3, when the temperature control circuit 67 detects that the temperature of the drying liquid is within the set temperature range, the printing operation is started.

At the time of printing, as described above, the carriage 2
Is moved in the direction of arrow X1, ink is ejected. First, droplets of the drying liquid heated to a temperature within the set temperature range by the heating device 65 are discharged from the nozzle 26 of the drying liquid inkjet head 8 to a required position of the recording paper 4. The drying liquid adhering to the required position on the recording paper 4 starts drying. Immediately thereafter, the ink jet heads 7a to 7d for recording liquid moved to the position opposite to the position where the drying liquid is attached by the movement of the carriage 2 in the direction of arrow X1.
A droplet of ink is ejected from the nozzle 26 of.

The ejected ink droplets adhere to the recording paper 4 from above the drying liquid. However, since the drying liquid has already started to evaporate as described above, it evaporates together with the drying liquid. Ink evaporation is promoted. In particular, in the first embodiment, since the drying liquid is heated to the set temperature range, the evaporation rate of the drying liquid is faster than in the normal temperature state, and the evaporation of the ink is effectively promoted. Further, since the drying liquid is heated to the set temperature range by the heating device 65 as described above, the temperature of the ink also increases, and this temperature increase also promotes the evaporation of the ink.

As described above, in the ink jet recording apparatus 1 of the first embodiment, since the evaporation of the ink is promoted by the heated drying liquid, the drying speed of the ink is high, and the fixing property of the ink on the recording paper 4 is improved. Is good. Therefore, even when recording paper on which images are printed is laminated at short time intervals, a so-called offset phenomenon occurs in which the ink of the recording paper one layer below the recording paper is retransferred to the back surface of each recording paper. Is prevented. Therefore, high-speed printing is possible with the inkjet recording apparatus of the first embodiment. Specifically, when A4 paper is fed vertically (the longitudinal direction is indicated by an arrow y
(In the case where printing is performed while feeding the paper so as to coincide with the sub-scanning direction indicated by (3)), high-speed printing of about 3 sheets / minute or more is possible.

In the first embodiment, in particular, since the drying liquid adheres before the ink adheres to a required position on the recording paper 4, the ink adhering to the recording paper 4 is immediately evaporated by the drying liquid, and It has a high effect of promoting drying.

(Second Embodiment) A second embodiment of the present invention shown in FIG.
In the embodiment, the heating device 65 of the drying liquid inkjet head 8 is provided only around the flow channel 60, and is not provided on the outer periphery of the tank 61. When the heating device 65 has such a configuration, the drying liquid is not heated in the tank 61, and the flow path 6 immediately before being supplied to the supply chamber 22 is not heated.
Since the heating is performed at 0, the evaporation of the dry liquid before the discharge can be reduced. In this case, the size of the heating device 65 can be reduced, and the cost can be reduced. Other configurations and effects of the second embodiment are the same as those of the first embodiment.

(Third Embodiment) In the third embodiment shown in FIG. 8, contrary to the first embodiment and the second embodiment, the carriage 2 at the time of ink discharge is indicated by an arrow X1 in the carriage 2. The inkjet heads 7a to 7d for recording liquid are arranged on the downstream side in the moving direction (downstream in the main scanning direction), and the inkjet head for drying liquid is located on the upstream side in the moving direction of the carriage 2 at the time of discharging the ink (upstream in the main scanning direction). A head 8 is provided.

As in the first embodiment, a heating device 65 is provided on the entire outer periphery of the tank 61 and around the flow path 60 in the ink jet head 8 for the drying liquid. The drying liquid inside can be heated.

During printing, ink is ejected when the carriage 2 moves in the direction of arrow X1. Recording paper 4
First, ink droplets ejected from the nozzles 26 of the recording liquid inkjet heads 7a to 7d adhere to the required positions. Immediately thereafter, the carriage 2 moves in the direction of the arrow X1 to move the drying liquid heated to a temperature within the set temperature range from the nozzle 26 of the drying liquid inkjet head 8 moved to a position facing the ink adhering position. Droplets are ejected. The drying liquid adhering to the required position of the recording paper 4 from above the ink starts to evaporate, and evaporates together with the drying liquid to promote the evaporation of the ink. Since the ink is heated to the set temperature range, the evaporation speed of the drying liquid is higher than that at normal temperature, and the temperature of the ink is also increased, so that the evaporation of the ink is further promoted.

In the third embodiment, evaporation of the four colors of ink adhered to the recording paper 4 can be uniformly promoted. That is, since the ink jet heads 7a to 7d for recording liquid and the ink jet head 8 for dry liquid were arranged in the above-described manner, all of the ink adhered to the required positions of the recording paper 4 in the order of yellow, magenta, cyan, and black. Later, since the drying liquid adheres to a required position of the recording paper 4,
The evaporation promotion effect of the dry liquid acts on the four color inks all at once. Therefore, in the third embodiment, the drying speed and the degree of drying of the four color inks are made uniform, and good image quality is obtained.
Other configurations and effects of the third embodiment are the same as those of the first embodiment.

(Fourth Embodiment) A fourth embodiment of the present invention shown in FIG.
The ink jet recording apparatus of the embodiment has the same structure as that of the third embodiment except that the heating device 65 is provided only in the flow channel 60 of the ink jet head 8 for a drying liquid. In the ink jet recording apparatus according to the fourth embodiment, since the heating device 65 is provided around the flow path 60, it is possible to reduce evaporation of the dry liquid into the atmosphere before discharging, as in the second embodiment. Can be. Further, from the downstream side in the main scanning direction, the recording liquid inkjet heads 7 a to 7
d, since the ink jet heads 8 for drying liquid are arranged in this order, the evaporation promoting action works uniformly for the four color inks. Other configurations and effects of the fourth embodiment are the same as those of the first embodiment.

(Fifth Embodiment) In a fifth embodiment shown in FIG. 10, a fixing liquid inkjet head 10 is provided in a carriage 2 in addition to the recording liquid inkjet heads 7a to 7d and the drying liquid inkjet head 8. Have been.

This fixing ink jet head 10
Has the same structure as the recording liquid inkjet heads 7a to 7d and the drying liquid inkjet head 8, and a tank 61 is filled with a fixing liquid. This fixer
This is for improving the fixability and preservability of the ink on the recording paper 4, and contains water and a water-soluble resin such as a water-soluble urethane resin.

The arrangement of the heads in the carriage 2 is, in order from the upstream side in the main scanning direction, the drying liquid inkjet head 8, the recording liquid inkjet heads 7a to 7d, and the fixing liquid inkjet head 10.

The heating device 65 of the recording liquid inkjet head 8 heats the drying liquid on the outer periphery of the tank 61 and the flow channel 60 as in the first embodiment. However, the heating device 65 may heat only the drying liquid in the flow channel 60 as in the second embodiment.

At the time of printing, first, droplets of the drying liquid heated to the set temperature range from the nozzle 26 of the drying liquid inkjet head 8 are discharged to a required position on the recording paper 4, and the attached drying liquid immediately starts drying. I do. Immediately thereafter, ink droplets are ejected from the nozzles 26 of the recording liquid inkjet heads 7a to 7d, and evaporation of the ink is promoted by the drying liquid. Immediately thereafter, droplets of the fixing liquid from the fixing liquid inkjet head 1 adhere to required positions of the recording paper 4 to which the drying liquid and the ink have adhered.

When the fixing liquid ejected from the fixing liquid ink jet head 10 is adhered as in the fifth embodiment, the fixing strength of the ink adhering to the recording paper 4 is further improved. Further, since the ink on the recording paper 4 is covered with the fixing liquid, the storability of the ink on the recording paper 4 is improved. In the fifth embodiment, since the fixing liquid is not contained in the drying liquid, the fixing liquid is ejected by a dedicated fixing liquid inkjet head 10 provided separately from the drying liquid inkjet head 8. In addition, clogging of the nozzle 26 of the inkjet head 8 for drying liquid can be prevented. Other configurations and effects of the fifth embodiment are the same as those of the first embodiment.

(Sixth Embodiment) A sixth embodiment shown in FIG. 11 includes a fixing liquid inkjet head 10 similarly to the fifth embodiment, and the carriage 2 has a downstream side in the main scanning direction. To inkjet head 7a for recording liquid
7d, a drying liquid inkjet head 8 and a fixing liquid inkjet head 10 are sequentially arranged.

At the time of printing, droplets of ink, a drying liquid, and a fixing liquid are ejected to required positions of the recording paper 4 in this order. Therefore,
The drying liquid promotes the drying of the ink, and the fixing liquid improves the fixing property and the storability of the ink on the recording paper 4. Further, since the fixing liquid is discharged by the dedicated fixing liquid inkjet head 10, clogging of the nozzles 26 of the drying liquid inkjet head 8 can be prevented. Other configurations and effects of the sixth embodiment are the same as those of the second embodiment.

An experiment was conducted to confirm the effects of the present invention. In this experiment, four items of drying speed, show-through, offset property and fixing / isolating strength were tested for Experimental Examples 1 to 5 and Comparative Example.

The compositions of the dried liquids in Experimental Examples 1 to 5 are as follows:
It is as shown in Table 2. In addition, the comparative example is a case where a dry liquid is not used.

[0057]

[Table 2]

The dried liquids of Experimental Examples 1 to 5 were prepared by the following manufacturing steps. First, an equivalent amount of the composition shown in Table 2 was placed in a flask, and about 10 wt.
For a minute. However, in Experimental Examples 3 and 4, the water-soluble organic solvent was added while the additives were dissolved and stirred in water first. Thereafter, dust was removed by filtration through a filter having a pore size of 0.5 μm.

As for the inks, Experimental Examples 1 to 5 were used.
For all of the comparative examples, those having the compositions shown in Table 3 were used.

[0060]

[Table 3]

Printing was performed using the ink jet recording apparatus of the first embodiment (see FIGS. 1 to 5) except for the drying speed test.

The experimental results of the drying speed, show-through, offset property and fixing / isolating strength of the experimental examples and comparative examples are as shown in Table 4 below.

[0063]

[Table 4]

(Drying speed) The drying speed was tested in Experimental Example 1.
From Experimental Example 5, the dried liquid heated to 45 ° C.
About 1 ml was dropped on a recording paper (EP paper made by Minolta) using a commercially available dispenser (liquid metering device), and about 1 m of black ink shown in Table 3 was further dropped thereon.
Then, the drying time was measured. In Comparative Example 1, about 1 ml of the black ink shown in Table 3 was dropped on the recording paper using the dispenser, and the drying time was measured. The drying time is a time required for a blade of urethane rubber having a thickness of 1 mm to slidably contact the ink surface with a load of 50 g until bleeding (spreading of the ink) does not occur. Therefore, the shorter the drying time, the faster the ink drying speed.

In Table 4, “○” indicates that the drying time was within 1 second, “△” indicates that the drying time exceeded 1 second and was within 5 seconds, and “×” indicates that the drying time was within 1 second.
Has a drying time of 5 seconds or more. “○” indicates that the drying speed is good, and “△” indicates that the drying speed depends on the printing speed.
If the printing speed is up to sheets / minute, there is no practical problem.

As shown in Table 4, in the comparative example, the evaluation of the drying speed was “×”, whereas the experimental examples 1 to 5
In each case, the evaluation of the drying rate is “○”. From this experimental result, it can be confirmed that the drying speed of the ink is increased according to the present invention.

(Show-through) Show-through is a phenomenon in which an image printed on the surface (rear surface) opposite to the printing surface of the recording paper is shown. In the show-through test, first, 100 μm dot diameter printing was performed at 85 μm pitch on recording paper (EP paper manufactured by Minolta) using the inkjet recording apparatus of the first embodiment. Next, the reflection optical density of the printed image was measured from the back surface of the recording paper using a commercially available reflection optical densitometer (PDA manufactured by Konica Corporation). The lower the reflection optical density, the better the printing with less show-through.

In Table 4, “○” indicates that the reflection optical density is 0.2 or less, “△” indicates that the reflection optical density is more than 0.2 and less than 0.3, and “×” indicates that the reflection optical density is 0.3. That is all. As shown in Table 4, the evaluation of show-through was “△” in the comparative example, whereas the evaluation of show-through was “○” in all of Experimental Examples 1 to 5. From these experimental results, it can be confirmed that the inkjet recording apparatus of the present invention can perform good printing even with regard to show-through.

(Offset property) The offset means that when recording paper on which an image is printed as described above is stacked, the ink of the recording paper one layer below the recording paper is retransferred to the back of the recording paper. A phenomenon. In the offset test, similarly to the test for show-through, first, printing was performed with a dot diameter of 100 μm on recording paper (EP paper manufactured by Minolta) at a pitch of 85 μm using the inkjet recording head of the first embodiment. Next, a piece of 10 cm square recording paper (EP paper made by Minolta) is placed on the printing surface and
A load of 0 g was applied. Thereafter, the reflection optical density of the ink transferred to the paper piece was measured using the reflection optical densitometer.

In Table 4, “○” indicates that the reflection optical density is 0.2 or less, “△” indicates that the reflection optical density is more than 0.2 and less than 0.3, and “×” indicates that the reflection optical density is 0.3. That is all. As shown in Table 4, the evaluation of the offset property is “×” in the comparative example, whereas the evaluation of the offset property is “○” in all of Experimental Examples 1 to 5. From the experimental results, it can be confirmed that in the ink jet recording apparatus of the present invention, the occurrence of the offset phenomenon is effectively suppressed due to the increased drying speed of the ink as described above.

(Fixing Isolation Strength) In the fixing isolation strength test, first, 100 μm was applied to recording paper (EP paper manufactured by Minolta) using the ink jet recording head of the first embodiment.
Printing with an m dot diameter was performed at a pitch of 85 μm, and the reflection optical density was measured using the reflection optical densitometer. Next, as shown in FIG. 12, a commercially available eraser 68 (drawing eraser No. 502 manufactured by Lion Corporation) 68 having a corner portion of 90 ° and cut so as to have the dimensions shown in FIG.
The eraser 68 is attached to the paper piece at a contact angle of 4
Contact was made at 5 ° with a pressure load of 1 kg, and reciprocated three times in a one-way stroke of 10 cm. It took about 20 seconds for one round trip. Thereafter, the reflection optical density was measured again using the commercially available reflection optical densitometer, and the rate of decrease in the reflection optical density was calculated.

In Table 4, “○” indicates that the reduction rate of the reflection optical density was 5% or less and the fixing / isolating strength was good. Further, “△” indicates that the rate of decrease of the reflection optical density is more than 5% and less than 10%, and “×” indicates that the rate of decrease of the reflection optical density is 10% or more. From the experimental results, it can be confirmed that, in the ink jet recording apparatus of the present invention, the fixing speed of the ink is improved by increasing the drying speed of the ink as described above.

[0073]

As is apparent from the above description, the ink jet recording apparatus of the present invention is provided with a drying liquid ink jet head for discharging droplets of a drying liquid onto a recording medium, separately from the recording liquid ink jet head. As the drying liquid evaporates, the evaporation of the recording liquid is accelerated, and the drying speed of the recording liquid is increased. Therefore, occurrence of offset or the like can be prevented, and high-speed printing can be performed.
Also, since the drying liquid is not mixed with the recording liquid filled in the recording liquid inkjet head, but is charged in the drying liquid inkjet head, the recording liquid caused by the precipitate generated when the drying liquid evaporates. The reliability of the inkjet head for printing can be prevented. Furthermore, in the case where a heating device for heating the drying liquid filled in the drying liquid inkjet head is provided, the evaporation rate of the drying liquid is increased by heating, so that the evaporation of the recording liquid is further promoted. As a result, the drying speed of the recording liquid is further increased.

[Brief description of the drawings]

FIG. 1 is a partial perspective view illustrating an inkjet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a carriage according to the first embodiment.

FIG. 3 is a bottom view of the recording liquid inkjet head.

FIG. 4 is a longitudinal sectional view of a recording liquid inkjet head.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a flowchart illustrating an operation of the inkjet recording apparatus according to the first embodiment.

FIG. 7 is a schematic diagram illustrating a carriage of an ink jet recording apparatus according to a second embodiment.

FIG. 8 is a schematic diagram illustrating a carriage of an inkjet recording apparatus according to a third embodiment.

FIG. 9 is a schematic diagram illustrating a carriage of an inkjet recording apparatus according to a fourth embodiment.

FIG. 10 is a schematic diagram illustrating a carriage of an inkjet recording apparatus according to a fifth embodiment.

FIG. 11 is a schematic diagram illustrating a carriage of an ink jet recording apparatus according to a sixth embodiment.

FIG. 12 is a schematic perspective view for explaining a test method of fixing isolation strength.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inkjet recording device 4 recording paper (recording medium) 7 a to 7 d inkjet recording head for recording liquid 8 inkjet recording head for drying liquid 10 inkjet recording head for fixing liquid 20 cavity 24 inlet 22 supply chamber 26 nozzle 60 flow path 61 tank 65 heating Device 66 Temperature sensor 67 Temperature control circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kenichi Tabata 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Noboru Ueda Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd.

Claims (8)

[Claims] An ink jet head for recording liquid, which is filled with a recording liquid, discharges droplets of the recording liquid onto a recording medium, and is filled with a drying liquid for promoting drying of the recording liquid attached to the recording medium. And an ink jet recording head for discharging a droplet of the drying liquid onto a recording medium. 2. The ink jet recording apparatus according to claim 1, wherein the drying liquid contains at least a water-soluble organic solvent and water. 3. The water-soluble organic solvent contained in the dry liquid has a vapor pressure at −20 ° C. of −15 mmHg to 100 mm.
The inkjet recording apparatus according to claim 2, wherein the pressure is equal to or less than mmHg. 4. The ink jet recording apparatus according to claim 1, further comprising a heating device for heating the drying liquid filled in the drying liquid ink jet head. 5. The printing method according to claim 1, wherein during printing, the drying liquid is discharged from the drying liquid inkjet head onto the recording medium before the recording liquid discharged from the recording liquid inkjet head. The inkjet recording apparatus according to claim 4. 6. The ink jet head for a drying liquid,
The ink jet recording apparatus according to claim 5, wherein the ink jet recording apparatus is disposed downstream of the recording liquid ink jet head in the main scanning direction. 7. A drying liquid which is discharged from a drying liquid inkjet head which is different from a recording liquid inkjet head which discharges a recording liquid droplet onto a recording medium, and which promotes drying of the recording liquid adhered to the recording medium. A dry liquid used in an ink jet recording apparatus containing at least a water-soluble organic solvent and water. 8. A vapor pressure at 20 ° C. of -15 mmHg
The drying liquid according to claim 7, wherein the drying liquid is at least 100 mmHg or less.