JPS6264555A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To stabilize an ink meniscus by setting the tip of an upper recording head backward by a prearranged length from the tip of a lower recording head, coating the upper surface of the tip of the upper recording head with a lyophilic substance and the upper surface of the tip of the lower recording head with a lyophobic substance. CONSTITUTION:The upper surface of the tip of a lower recording head 1 on a recording head H is coated with an oleophilic substance 21, whilst the upper surface of the tip of an upper recording head 2 is covered with an oleophobic substance 22. A fluororesin fluoro coating material is used as an oleophilic substance 21, and is applied as a coat having a thickness of 1-2mum. In addition, polyvinyl alcohol is used as an olephobic substance 22 and is applied evenly as a coat about 5-10mum thick. Thus it is possible to maintain an ink meniscus in the tip of a recording head always in stable condition and subsequently assure satisfactory printing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an inkjet type recording device that is installed in, for example, a printer or a facsimile machine.

[Technical background of the invention and its problems]

Inkjet recording devices have traditionally been applied to printers and facsimiles as plain paper recording devices that do not require developing or fixing operations, but electronic plane scanning is desired to improve high-speed recording performance and simplicity. This electronic planar scanning has been studied mainly by using multiple nozzles, but at present it has not been put into practical use due to the problem of reduced reliability due to ink clogging in each recording nozzle.

Therefore, the following slit-jet method has been proposed as a plane scanning ink-jet method that does not have the disadvantages of the nozzle method.

That is, FIGS. 2 and 3 show diagrams of the principle of the slit jet recording method that the present inventors have already proposed.

1 in the figure is the lower recording head section, and this lower recording head section 1
has an insulating substrate 1a, and on this substrate 1a there are a plurality of individual electrodes 3a, 3b patterned, for example, at 8 pieces per square or 16 pieces per lXS, and individual electrodes ja.

3b are separated from each other by a predetermined gap d and are opposed to each other on a one-to-one basis. Between the gap ds, for example, amorphous selenium (hereinafter referred to as a-8e) or amorphous silicon<mv
It is written as ta-st. ) photoconductive film 18 is deposited. Further, the individual electrodes 3b are electrically connected to the first common electrode 14.

Further, an upper recording head section 2 having a second common electrode 4 is provided apart from the lower recording head section 1 by a minute gap dt. These lower and upper recording head sections 1
, 2 constitute a recording head section H. The tip of the recording head H has a slit-like opening with a small slit gap. In addition, the recording head section H and the minute gap d
Roller-shaped opposing electric fences 8 facing each other with a distance of 1 are provided,
A recording medium 11 such as plain paper is provided between the recording head section H and the opposing pole 8.

Ink 5 is supplied from the ink storage container 13 to the tip of the recording head H. Further, above the photoconductive film 18, there are a lens array 17, a light source 15, and a document table 16.
As the document moves in the direction of the arrow, the optical image of the document passes through the lens array 17 and is irradiated onto the photoconductor 118.

Next, the recording principle of the slit jet recording method will be explained. The document table 16 and the recording medium 11 operate in synchronization with the switch ON, the light source 15 turns on, and the optical image of the document is irradiated onto the photoconductor film 18 through the fiber lens array 17.

For example, a DC power source 6 of O is connected to the I-th common electrode I4, and a DC power source 7 of ■ is connected to the second common electrode 4. The potential of the tip jCK□ of the recording head H is outputted, and the potential of e is outputted for the dark area.

The principle of the above signal output will be explained using the equivalent circuit shown in FIG. That is, the photoconductor g! The resistance during light irradiation of 18 is ρp
h, resistance in the dark is ρDark.

If the resistance 5' of the ink 5 between the second common electrode 4 and the recording electrode 3a = ρINK, then ρph<ρINK ρpar
Since the ink resistance ρINK is adjusted so that the relationship k holds, ρ! during light irradiation. A potential e is output to the recording electrode tip 3C by the stain source 6 in which NK is dominant, and a potential ii is output in the dark time to the stain source 7 in which ρDark is dominant.

Next, a pulsed voltage is applied to the roller-shaped counter electrode 8 on the e side with respect to Ov, and the above-mentioned recording electrode tip jcK
When the potential of $ is output, the ink meniscus 12 becomes ■
The electric charge is injected, and the ink 5 flies to the counter electrode 8 side, so that selective recording corresponding to the original image can be performed on the recording medium 11.

As a result of studies by the present inventors, it has been found that recording by ink flying can be performed satisfactorily under the process setting conditions shown below. That is, the applied voltage of the first common electrode 4: 6 C) 50 to 1 KV The applied voltage of the second common electrode 14 is 720 to ■IKV The applied voltage of the roller-shaped counter electrode 8: 0-02. OKV frequency: 10 to 10 KHz Gap d110 μm to 500 μm Give dl 10 μm to 300 μm The value of the gap d3 varies depending on the specific resistance of the photoconductor film 18, but for example, if the photoconductor film 18 is an a-8i film, 2 if there is
In the case of 0 μm to 80 μm-8e, and a-8eTe, it is 5 μm to 50 μm.

When the photoconductor film 18 is, for example, an a-3i film, ρna
rk is 10”~10”Ωtan, ρpha t is 105~1
01Ω, so ink resistance 5' = ρINK is 10
6~10! I have to choose OΩ wound.

Of the light image irradiated onto the photoconductor film 18, there are 50 bright areas.
Lux ~500 Lux.

However, the above-described recording method has the following drawbacks.

That is, as shown in FIG. 5, when a large amount of ink 5 is stored in the ink storage container 13, the static pressure of the ink 5 is high, and the ink menicus 12 at the tip of the recording head H is pressed against the recording electrodes 3a... The tip 3C also protrudes toward the back electrode 8 side.

For this reason, the back electrode 8 has 01. When a bypass of about OK V is applied, no concentration of electric field occurs between the tips 3C of the recording electrodes 3a and the back electrode 8, but a strong electric field concentrates between the ink menicus 12 and the back electrode 8.

Therefore, as shown in FIG. 6, in an experiment in which the photoconductive film 18 is turned on and off only in part B by an optical signal and an electric signal is output to its tip, it is necessary to When the ink 5 flies from the ink meniscus 12, the electric field concentrates on all the ink meniscus 12 in the vicinity, resulting in the state shown by the dotted line and the ink recording becomes a solid black recording.

Therefore, in order to eliminate the above-mentioned disadvantages, a device as shown in FIG. 7 has been considered. That is, by reversing the tip of the upper recording head section 2 of the recording head H by 0.5 to 1.5 degrees from the tip of the lower head section 1, the ink menicus 12 is placed behind the tip of the recording electrode 3a... Since it bulges upward without bulging toward the electrode 8, the above-mentioned disadvantage can be solved.

However, it has been found that in this case, the following new drawback arises.

That is, as shown in FIG. 8, as the ink 5 in the ink storage container 13 decreases, the static pressure of the ink 5 decreases, and as a result, the ink menicus 12 reaches the tips of the recording electrodes 3a... The ink cartridge 12 is no longer supplied to the tips of the recording electrodes 3a, and the ink 5 no longer flies.

[Purpose of the invention]

The present invention has been made in view of the above circumstances.

The purpose is to provide an inkjet recording device that stabilizes the ink menicus at the tip of the recording head and allows ink to be selectively ejected in a good manner regardless of the amount of ink in the ink storage container. .

[Summary of the invention]

In order to achieve the above object, the present invention retracts the tip of the upper recording head by a predetermined distance from the tip of the lower recording head,
By coating the upper surface of the tip of the upper recording head section with a lyophilic substance and coating the upper surface of the tip of the lower recording head section with a lyophobic substance, an ink meniscus is formed in the area where there is a large amount of ink. This prevents the ink from bulging toward the back electrode side, and prevents ink from flowing into the upper surface of the upper recording head when the amount of ink is small.

[Embodiments of the invention]

The present invention will be explained below with reference to an embodiment shown in FIG. Note that the same parts as those shown in FIGS. 7 and 8 are given the same reference numerals, and the explanation thereof will be omitted. The upper surface of the tip of the lower recording head section 1 of the recording head H is coated with an oleophilic substance 21, and the upper surface of the tip of the upper recording head section 2 is coated with an oleophobic substance 22. As the lipophilic substance 21, a fluororesin-based fluorocoating material is used, for example, and is coated with a thickness of 1 to 2 μm.

Further, as the oleophobic substance 22, for example, polyvinyl alcohol is used and is uniformly coated with a thickness of about 5 to 10 μm.

(Experimental Example) Therefore, the tip of the upper recording head 2 is the tip of the lower head 1.#)d,=1. A flying experiment of ink 5 was conducted under the following conditions with the Qiij retracted.

O Applied voltage of lower common electrode 14 0300 VO Pressure applied to upper common electric fence 4 ■ 300 VO Applied pulsed voltage of roller-shaped back electrode 8 C) 700 V, number of circumferences 1.0 K H
z, fx-T0 Distance d between the tip of the lower recording head 1 and the back electrode 8 = 150 μm As the photoconductive layer 18, an a-8i:H film is used as shown in FIG. 6 (a-8i :Only at a predetermined location B on the H film 18, approximately 150 JuX was turned on and off using an LED, and the other location A was exposed to tungsten light over the entire surface.

As the O ink 5, an oil-based ink having a resistance of 10 Ω was used.

Under the above conditions, an ink 5 flight experiment was first conducted with the ink storage container 13 sufficiently filled with ink 5.
The ink meniscus 12 had an appropriate shape as shown in FIG. 1, and the ink 5 was selectively ejected only onto the recording electrodes 3a corresponding to the on/off portions of the LEDs.

In addition, under the same conditions, an experiment was conducted in which the ink 5 flew until almost all the ink 5 in the ink storage container 13 was used up.
There was no change in the ink meniscus 12 at the tip of the lower recording head 2, and therefore good selective ink flight recording could be maintained.

In addition, in the structure shown in FIG. 2, in which a focusing optical fiber lens 17 (commercial SELFOC lens), a halogen lamp 15, and a moving original 16 are provided on the photoconductive layer][a-8i:H photoconductive layer] However, even if the amount of ink in the ink storage container 13 decreased, a copy image with excellent resolution was obtained.

In the above example, an oil-based ink was used due to the limitation of ink resistance. However, when a water-based ink is used in the slit jet method, the lipophilic substance described above can be changed to a hydrophilic substance, and the lipophobic substance can be changed to a hydrophobic substance. It goes without saying that you can expect exactly the same effect if you change the substances.

In addition, it goes without saying that the present invention can be modified in various ways within the scope of its gist.

〔Effect of the invention〕

As explained above, the present invention retracts the tip of the upper recording head by a predetermined distance from the tip of the lower recording head, coats the upper surface of the tip of the upper recording head with a lyophilic substance, and coats the upper surface of the tip of the upper recording head with a lyophilic substance. Since the upper surface of the tip of the recording head is coated with a lyophobic material, the ink menicus at the tip of the recording head is always kept in a stable state regardless of the amount of ink in the ink container (size of static ink pressure). , it is possible to maintain stable and good recording by selectively flying ink.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an inkjet recording apparatus which is an embodiment of the present invention, FIGS. 2 to 6 are diagrams showing a first conventional example, and FIG. 2 is a schematic configuration diagram showing an inkjet recording apparatus. 3 is a plan view showing the electrode section, FIG. 4 is an equivalent circuit diagram showing signal output to the electrode section, FIG. 5 is an explanatory diagram showing the ink meniscus, and FIG. 6 is an explanatory diagram showing the recording state. , FIG. 7 and FIG. 8 show the second conventional example. FIG. 7 is an explanatory diagram showing the ink meniscus when the amount of ink is large, and FIG. 8 is an explanatory diagram showing the ink meniscus when the amount of ink is small. This is an explanatory diagram. H... Recording head section, 1... Lower recording head section, 2
...Upper recording head section, 3a...Recording electrode, 13.
... Ink storage section, 5 ... Liquid ink, 8 ... Back electrode, 11 ... Recording object, 2 No. ... Lyophilic substance, 2
2...Liquiophobic substance.

Claims (3)

[Claims] (1) Consisting of a lower recording head section and an upper recording head spaced apart from and facing the lower recording head section, the recording head section has a recording electrode at its tip opening, and liquid is supplied from an ink storage section to the recording electrode. In the apparatus for recording information by supplying ink and causing this liquid ink to fly from the recording electrode to a recording medium supported by a back electrode, the tip of the upper recording head section is connected to the tip of the lower recording head section. An inkjet recording apparatus characterized in that the upper recording head is moved back by a predetermined distance, and the upper surface of the tip of the upper recording head is coated with a lyophilic substance, and the upper surface of the tip of the lower recording head is coated with a lyophobic substance. (2) The ink jet recording apparatus according to claim 1, wherein the leading end of the upper recording head section is set back from the leading end of the lower recording head section by 0.1 to 1.5 mm. (3) The inkjet recording apparatus according to claim 1 or 2, wherein the lyophilic substance is a fluororesin-based fluorocoating material, and the lyophobic substance is polyvinyl alcohol.