JPH08142348A - Recording method of ink jet printer - Google Patents

Abstract

PURPOSE: To suppress the thickening of the ink of a nozzle less in an emitting chance and to prevent the clogging of the ink by using black ink as the ink of an ink emitting nozzle row (head nozzle row) applying printing to a recording medium first. CONSTITUTION: A recording medium 8 heated to 100 deg.C or higher to be almost perfectly dried is sucked and fixed on the feed belt of a vacuum suction feeder 2 to be fed to the area just under a full-color line head 1. The full-color line head 1 emits aqueous ink to the recording medium 8 held to a high temp. dry state successively to perform printing but the moisture of the aq. ink containing 90-95% of water is rapidly evaporated and the narrow space between a printing head 1 and the recording medium 8 contains a large amt. of steam. The air of the space containing a large amt. of steam is sucked by a second exhaust slit 7 to be discharged. The second exhaust slit 7 has the length equal to paper width in the same way as first exhaust slits 6, 6'. The clogging of a nozzle can be prevented by covering the vicinity of the emitting orifice of the nozzle with a saturated steam atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus of a type in which ink droplets are ejected toward a recording medium, and is most effectively applied to a color thermal ink jet printer.

[0002]

2. Description of the Related Art An ink jet recording apparatus of a type in which a part of ink is rapidly vaporized by pulse heating and an ink droplet is ejected from an orifice by its expansive force is disclosed in JP-A-48-9622 and JP-A-54-54. No. 51837, for example.

The simplest method of pulse heating is to energize the heating resistor with a pulse, and the specific method is Nikkei Mechanical, December 28, 1992, p. 58,
And Hewlett-Packard-Journal, Aug. 1988. The common basic configuration of these conventional heating resistors is
The thin film resistor and the thin film conductor are coated with an antioxidation layer, and one or two cavitation resistant layers are coated on the antioxidation layer for the purpose of preventing cavitation destruction of the antioxidation layer.

As a radical simplification of this complicated multi-layer structure, the applicant of the present application filed Japanese Patent Application Laid-Open No. 06-71.
As described in Japanese Patent No. 888, there is a method of printing by using a heating resistor that does not require the antioxidant layer and the cavitation resistant layer. In this case, since the thin film resistor is in direct contact with the ink, the rapid vaporization of the ink due to pulse heating and the resulting ink ejection characteristics are greatly improved, and the thermal efficiency and the ejection frequency are significantly improved. I was able to. The biggest reason why we were able to achieve such epoch-making performance is Cr-S, which has excellent pulse resistance, oxidation resistance, and electrolytic corrosion resistance.
This is because the heat generating resistor composed only of the i-SiO alloy thin film resistor and the Ni thin film conductor is used, and no protective layer is required.

As described above, since it is possible to eject ink with much smaller input energy as compared with the prior art,
Even if this heating resistor is formed in the vicinity of the device area on the driving LSI chip, it will no longer heat the LSI device to cause a temperature rise, and realize a monolithic LSI head with a very simple structure. Is now possible. Regarding this, the applicant has previously filed Japanese Patent Application Laid-Open Nos. 06-238901 and 06-297714.
It is as described in the publication. With this new technology,
An on-demand type inkjet print head having many ink jet nozzles can now be manufactured with high density and two-dimensional integration, and a full-color inkjet printer capable of high-speed printing can be realized. .

Further, by utilizing the excellent foam extinguishing property of the thin film heating resistor which does not require a protective layer (Japanese Patent Laid-Open No. 06-297714), an ink droplet is ejected in a direction perpendicular or almost perpendicular to the surface of the heating resistor. In the thermal ink jet print head of No. 6, it was revealed that a new driving method can significantly reduce crosstalk (see Japanese Patent Application No. 06-49202). This indicates that the length of the individual ink passage can be shortened to reduce the flow resistance of the ink, and the replenishment time of the ejected ink can be shortened, that is, the printing speed can be further greatly improved.

When high-speed printing becomes possible, it is essential to dry the recording medium after printing at high speed. However, regarding this as well, Japanese Patent Application No.
As described in Japanese Patent Application No. 5-90123 and Japanese Patent Application No. 06-100143, the surface of the recording medium immediately before being printed is pressed and dried by a belt type preheater, and the recording medium which has been heated and dried is adsorbed and conveyed. By printing on the surface, it became possible to effectively dry at high speed. At the same time, high-quality printing is possible without being affected by the type of recording medium or its storage state, and even for inexpensive laser beam printer plain paper and recycled paper without using an expensive recording medium dedicated to inkjet printers. You can now do beautiful full-color printing.

On the other hand, although a large amount of water vapor is generated by performing such high-speed drying, it is possible to clarify the condition that this water vapor is appropriately exhausted and the print quality is not deteriorated by this exhaustion processing. . Regarding this, the applicant previously filed Japanese Patent Application No. 06-13719.
As described in No. 8.

[0009]

Even in the above-described multi-color or full-color ink jet printer containing black ink, the form actually used is overwhelmingly large in character printing including line drawing mainly composed of black ink, and is in a planar state. Full-color printing, which is printing, is 10 to 20% or less. That is, the opportunity of ejecting the yellow, cyan, and magenta inks frequently becomes zero even when printing several pages.
In such a case, the ink of the yellow, cyan, and magenta ink nozzles with the ink drying prevention cap removed is thickened, which is a major cause of nozzle clogging. In particular, in the case of the printer of the present application, which heats the recording medium immediately before printing to a high temperature, the radiant heat to the nozzle that is close to and faces the heated recording medium may accelerate the thickening of the ink in the nozzle. Absent.

It is an object of the present invention to prevent ink clogging of nozzles that are less likely to be ejected, prevent nozzle clogging, and improve printer reliability in an inkjet printer that prints colors on a preheated recording medium. To achieve. At the same time, it is also an object of the present application to realize clear full-color printing.

[0011]

SUMMARY OF THE INVENTION The above-mentioned object is to provide a color ink jet printer which prints on a recording medium by ejecting ink from a plurality of rows of ink ejecting nozzles arranged in parallel to an opposite recording medium. In an ink jet printer having a preheater for press-contact heating the recording medium on the upstream side in the conveying direction of the recording medium and a fixed type or scanning type print head on the downstream side, the ink discharge nozzle array for first printing on the recording medium This is achieved by using black ink for the (first nozzle row).

Further, when the print head is a fixed type line head, fine line-shaped dummy printing is performed by ejecting at least one time from all nozzles in the vicinity of the lowermost stage of the recording medium.

[0013]

In the ink jet printer used in the present invention, the water-based ink printed on the heated recording paper rapidly evaporates the water content, and the ink is sandwiched between the recording paper and the print head surface.
Although it is configured to fill a narrow space of mm with saturated steam, if you use the above printing method, that is, if the first nozzle row of the fixed type print head (line head) is black ink, printing mainly with black ink Even in the case, even the color ink nozzles arranged on the downstream side are surrounded by the saturated vapor atmosphere, and the evaporation of the ink moisture is greatly suppressed.

In addition to the above configuration, dummy ejection is performed at least once from all nozzles of four colors including black ink on the recording paper at the lowermost position where printing of one page is finished, and ink of all nozzles can be refreshed. For example, it is shown in the examples described below that the nozzle is not clogged.

The same applies to the case of the scanning type print head, and when the head nozzle row is black ink, the scanning operation causes the other color ink nozzles to be enclosed in the saturated vapor atmosphere as described above. Particularly, in the case of a printer that performs reciprocal printing by scanning, good results can be obtained by using a head of a nozzle array for five colors and black ink on both sides. Then, after a prescribed number of scans, dummy ejection from all nozzles is performed on the outer side of the recording paper to refresh the ink of all nozzles, so that nozzle clogging does not occur.

It should be noted that the above-mentioned refresh by dummy ejection should be executed for all print modes.
As a result, high reliability of the head can be achieved.

[0017]

FIG. 1 shows an embodiment of the present invention.

The recording medium 8 is first heated by the belt type preheater 3 to 100 ° C. or higher, and then sent to the vacuum suction transfer means 2. At this time, in the case where the recording medium 8 is a hygroscopic recording paper, the moisture absorbed immediately after being separated from the preheater 3 by being heated to 100 ° C. or higher is rapidly released. From the back side, the first exhaust slit 6,
Suction and exhaust by 6 '. The first exhaust slit has a length equal to the paper width. Of course, a guide is provided in this portion so that the recording paper 8 can be smoothly fed to the vacuum suction conveyance means 2, but this is omitted in FIG. The belt type preheater is described in detail in Japanese Patent Application No. 06-100143 filed previously by the applicant of the present invention, and therefore the description thereof will be omitted.

The recording medium (including the OHP sheet) 8 which is heated to a temperature of 100 ° C. or more and is almost completely dried is adsorbed and fixed on the conveyor belt of the vacuum adsorption conveyor 2 to be a full color line head. It is transported to the position just below 1. The full-color line head 1 sequentially ejects and prints the aqueous ink on the recording medium 8 in the high-temperature dry state. However, the aqueous ink 90 to 95% of which is water rapidly evaporates the water, and the print head 1 and A narrow space (height of about 1 mm) sandwiched by the recording medium 8 contains a large amount of water vapor. The air in the space containing a large amount of water vapor is sucked and exhausted by the second exhaust slit 7. Like the first exhaust slit, the second exhaust slit 7 has a length equivalent to the paper width. Since the vapor temperature after printing is slightly higher than the ambient temperature, it is exhausted by the second exhaust means so that dew condensation does not occur on the print head surface or the like.

Regarding the full-color line head 1, Japanese Patent Application Laid-Open No. 06-297714 filed earlier by the present applicant,
Japanese Patent Application No. 05-318272, Japanese Patent Application No. 06-49202
In addition, the details of the vacuum suction transfer means 2 are also described in Japanese Patent Application No. 06-100143, and the details of the head cleaner 4 and the head cap 5 are described in Japanese Patent Application No. 06-65005. Since it is described, its structure and detailed contents are omitted.

FIG. 2 is an enlarged sectional view of the full color line head 1 used in this embodiment. Head 1 is 210mm A
There are 3360 ink ejection nozzles of 400 dpi in the width of 4 sheets, and linearly in the direction perpendicular to the plane of FIG.
Four rows are arranged at 6 mm intervals, the head nozzle row 11 (on the side of the first exhaust slit 6) is black ink, and the remaining nozzle rows 12 and 1
3 and 14 are configured to be color inks. Since the ink ejection frequency is variable from 0 to 15 KHZ, if the drying speed after printing is ignored, the printing speed of this head 1 is such that full-color printing can be performed on A4 paper at a speed of 100 ppm or more. ing.

In this embodiment, the head 1 is 20 ppm.
It was printed on and evaluated. Among the ink discharge nozzles arranged in four rows of the print head 1, the evaluated method was a case where the first nozzle row 11 (on the side of the first exhaust slit 6) was black ink, and a comparative example was the last nozzle row (second exhaust nozzle). Slit 7
The printing quality and the frequency of occurrence of nozzle clogging when the side) was black ink were investigated. Table 1 shows the results.

[0023]

[Table 1]

The recording medium used is plain paper for a laser beam printer. The frequency of occurrence of clogging is an approximate relative value.

When full-color printing was performed on the recording paper preheated to 120 ° C., there was no difference in the occurrence frequency of clogging, but when the last nozzle row was black ink, black ink bleeding was relative. It was found that the print quality was slightly large and the print quality was slightly inferior. It has been found that the reason is that the bleeding of the first dot printed on the heated dry paper is small and the bleeding of the next dot printed on it is large.

When characters were printed using only black ink, a difference of 3 to 4 times was found in the frequency of clogging of the color nozzles. However, in this evaluation experiment, the value of the clogging occurrence frequency of 1 is a rough value that the clogging nozzle starts to occur after continuous printing of about 10 sheets. Therefore, the occurrence frequency of 6 indicates the printing of 1 to 2 sheets. Indicates that the clogging nozzle starts to occur. This tendency is noticeable in the pigment type ink, but this is related to the difficulty of redissolving (redispersing) the pigment of the ink once thickened, and it is more difficult to prevent clogging than the dye type ink. This is a point that requires attention.

As described above, the excellent effect obtained when the head nozzle row is made of black ink has been observed. However, in normal printing, a waiting time occurs even when printing is continuously performed, and most of the paper sheets are blank sheets. Mixed. Therefore, it is a reality that the frequency of occurrence of clogging nozzles increases, and in order to improve the reliability of a large-scale highly integrated head, the final stage portion of one recording paper (from 0.5 to 1 mm from the bottom). However, it is necessary to perform dummy ejection from all nozzles at least once. The width of the print line by this dummy ejection is at most about 0.2 mm, which is a practically allowable range. As a result, there is no clogging due to thickening of the ink.

[0028]

Example 2 A scanning full color head (128 nozzles × 4 rows or 5 rows) was placed at the same position in place of the line head 1 shown in FIG. However, the printing speed is 4 ppm. It should be noted that in the case of one-way printing, the head nozzle row has four heads with black ink, and in the case of a printer for reciprocal printing, the head has five nozzle rows with one nozzle row increased and the nozzle rows at both ends with black ink. Becomes

With the above structure, if the dummy discharge is performed from all the nozzles outside the recording paper once every two to three scans, the nozzle clogging of the color inks is clogged even when only the black ink is printed. I have confirmed that there will be nothing. In addition,
It goes without saying that in the case of the scanning type head, the saturated water vapor of the black ink moves so as to cover the nozzle surface of the other ink by the scanning of the head itself, and the same effect as that of the first embodiment is obtained.

Further, in the case of such a scanning type full color printer, the amount of water vaporized per unit time decreases as the printing speed becomes slower, and the running head cartridge diffuses the air in the vicinity thereof. In this case, the first exhaust means and the second exhaust means, which are required in the above case, become unnecessary. This contributes to downsizing and cost reduction of the printer.

[0031]

According to the present invention, since the vicinity of the discharge ports of all nozzles can be covered with a saturated steam atmosphere, the drying of the ink is delayed and the nozzles can be prevented from clogging. Further, even in the case of the line head, dummy ejection for periodically ejecting the thickened ink is executed in the lowermost portion of the recording paper, so that a highly reliable printer can be realized without lowering the printing speed. .

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an inkjet printer according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the head portion of FIG.

[Explanation of Codes] Print head 2. Vacuum suction transfer means 3. Preheater 4. Head cleaner 5. Head cap 6, 6 '. First exhaust slit 7. Second exhaust slit 8. Recording medium 11. Black nozzle row 12-14. Color nozzle row

Claims (2)

[Claims] 1. A color ink jet printer for ejecting ink from a plurality of rows of ink ejection nozzles arranged in parallel to an opposite recording medium to print on the recording medium, the upstream side in the conveying direction of the recording medium. In a pre-heater for press-heating the recording medium, an ink jet printer having a print head disposed on the downstream side uses black ink as the ink of the ink ejection nozzle row (first nozzle row) that is first printed on the recording medium. And a recording method for an inkjet printer. 2. The printing head is a fixed type line head, and fine line-shaped dummy printing is performed in the vicinity of the lowermost stage of the recording medium by discharging at least once from all nozzles. The recording method of the described inkjet printer.