JPH04110170A - Recorder - Google Patents

Abstract

PURPOSE:To record an image with a constantly stable quality even if the thickness of recording paper in use is changed by a method wherein a voltage or pulse width to be applied to a drive circuit is controlled in accordance with a distance from a control electrode to a tip end of a recording head. CONSTITUTION:To apply a constant electric field to ink, a detection circuit 11 is provided as a detection means for detecting a distance between a control electrode 6 and the ink (a tip end of a head). The detection circuit 11 detects an electrostatic capacity by detecting an impedance between the electrode 6 and an electrode 7 and detects a distance between a tip end of a recording head 1 and the control electrode 6 in accordance with the electrostatic capacity. A control circuit 12 to which the detection signal of the detection circuit 11 is inputted regulates an applied voltage or pulse with by changing a resistance value of a variable resistance of a drive circuit 13 made of an operation amplifier in accordance with the detection signal.

Description

[Detailed Description of the Invention] [Summary Regarding an image recording device applied to a coprinter, facsimile, etc., this recording device can always record images with stable quality even if the thickness of the recording paper used changes. A recording head having a permeable member and a conductive ink in contact with the permeable member or an ink retaining member impregnated with the conductive ink therein, and a recording head provided on the conductive ink side of the recording head. A recording apparatus comprising a drive circuit that applies a voltage between an electrode and a control electrode facing the electrode, and in which the conductive ink passes through the inside of the permeable member and records on the recording paper by driving the drive circuit. It is constituted by a detection means for detecting the distance between the electrode and the tip of the recording head, and a control means for controlling the applied voltage or the applied pulse width of the drive circuit according to the output of the detection means.

[Industrial Application Field] The present invention relates to an image recording device applied to printers, facsimile machines, and the like.

Conventionally, several types of desktop non-impact printers have been put into practical use, including inkjet, thermal transfer, and electrophotography. These methods have many advantages, but they also have advantages and disadvantages in terms of recording speed, reliability, running costs, ease of colorization, etc.

In order to improve the recording speed, it is essential to form the print head into lines, but in principle, in the inkjet method, it is difficult to form the nozzles into lines. For this reason, several improved types have been proposed, but they have not yet been put into practical use. on the other hand,
In the thermal transfer recording method, the ink sheet is a consumable item, so
The problem is that running costs are high.

Therefore, as a new method to improve these problems,
Pressing the mesh sheet and the recording paper with a platen equipped with an ink supply member such as an ink roller and an electrode,
A voltage is applied between the conductive ink and the electrode to generate an electric field. In a steady state, the ink's wettability to the mesh is low, so the ink does not enter the holes in the mesh, or an electrostatic force is applied to the ink. Accordingly, a recording apparatus has been proposed in which ink passes through holes in a mesh and adheres to recording paper.

[Prior Art] Conventional recording devices hold ink inside an independent recording head, or impregnate the inside of an ink holding member with ink, and contact the ink holding member and face recording paper. By adopting a head configuration in which a permeation member made of a mesh or porous film is provided in the part where the
This makes it possible to realize a compact recording device.

In addition, the penetrating member is made of tetrafluoroethylene (hereinafter referred to as Teflon), and the ink holding member has high affinity with ink, so that the meniscus is maintained near the inner end of the penetrating member. . As a result, when no voltage is applied, no ink is transferred even if the recording paper comes into contact with the permeable member.

The voltage is applied between an electrode provided on the ink side and a control electrode facing the electrode, and a drive circuit supplies a constant applied voltage or an applied pulse with a constant pulse width.

[Problem to be solved by the invention] However, in such a conventional recording device,
Even if the thickness of the recording paper used changes, the applied voltage or applied pulse width remains constant, so there is a problem that printing with the same density cannot always be obtained and images of stable quality cannot be recorded. Ta.

The present invention has been made in view of such conventional problems, and provides a recording device that can always record images with stable quality even if the thickness of the recording paper used changes. The purpose is to

Means to solve U issues] FIG. 1 is a diagram explaining the principle of the present invention.

In FIG. 1, reference numeral 1 denotes a recording head that includes a permeation member 3 and a conductive ink in contact with the permeation member 3, or an ink holding member 2 impregnated with conductive ink, and 13 represents the conductive ink side of the recording head 1. An electrode 7 (!: a drive circuit that applies a voltage between the electrode 7 and the control electrode 6 facing the electrode 7,
Reference numeral 5 denotes a recording sheet on which conductive ink passes through the inside of the permeable member 3 and is recorded by driving the drive circuit 13, 11 a detection means for detecting the distance between the control electrode 7 and the tip of the recording head 1, and 12 a detection means. It is a control means that controls the applied voltage or the applied pulse width of the drive circuit 13 according to the output of the detection means 11.

[Function] In the present invention, the distance between the control electrode and the tip of the recording head is detected, and the applied voltage or applied pulse width of the drive circuit is adjusted in accordance with the detection signal.

Therefore, even if the thickness of the recording paper used changes, the applied voltage or the applied pulse width is adjusted according to the thickness, and printing with the same density can always be obtained. That is, as the thickness increases, the voltage or pulse width increases accordingly.

Therefore, it is possible to always record images with stable recording quality.

[Example code] Embodiments of the present invention will be described below based on the drawings.

2 to 4 are diagrams showing one embodiment of the present invention.

First, to explain the structure, in FIG. 2, 1 is a recording head that holds ink, and the recording head 1 includes an ink holding member 2 impregnated with ink, a penetrating member 3 in contact with It consists of 4 outer wall bodies. In principle, the ink only needs to be inside the recording head 1, and the ink retaining member 2 does not need to be provided. However, in order to perform stable recording against vibrations and the like, the ink retaining member 2 is required. A porous member having high affinity with ink is suitable for the ink holding member 2. As a material, polyurethane foam or the like is suitable.

The permeation member 3 is made of Teflon porous film (product name:
Fluorobore (manufactured by Sumida Denko) is a suitable material because it has a high property of repelling ink. In this way, if the ink retaining member 2 has a high affinity for ink and the penetrating member 3 has the property of repelling ink, the position of the ink meniscus will change when no voltage is applied to the electrodes. is located near the boundary between the penetrating member 3 and the ink retaining member 2. Under such conditions, even if the recording paper 5 comes into contact with the outer surface of the permeable member 3, ink will not adhere to it. In addition, the vapor pressure of the ink inside the porous capillary of the permeation member 3 is high, and the ink on the surface of the ink holding member 2 does not dry or solidify.
There is no clogging that occurs with inkjet nozzles.

Although various materials can be used for the permeation member 3, it is also possible to use a material made of an organic film such as polyester, polyamide, polycarbonate, etc., or a metal film with holes made therein and coated with Teflon.

The thickness of the penetrating member 3 can be in the range of 4 to 200 μm. If it is 200 μm or more, the recording voltage will be high, and if it is 4 μm or less, transfer of ink to the recording paper 5 will be observed even without applying a voltage. It was done.

The body 4 of the outer wall of the recording head 1 needs to be made of a material that will not be corroded even when it comes into contact with ink, but plastic that can be processed by molding or the like can be used. In order to apply a voltage between the ink and the control electrode 6, a common electrode 7 is required on the recording head l side, and it is desirable to provide this electrode 7 near the penetrating member 3.

A control electrode 6 is located at a position opposite to an electrode 7 on the ink side via the penetrating member 3 and the recording paper 5, and recording is performed by applying a voltage between the control electrode 6 and the electrode 7 on the ink side. . Recording can be performed by either a method in which the penetrating member 3 at the tip of the recording head 1 is in contact with the recording paper 5, or a method in which recording is performed in a non-contact manner while maintaining a slight gap. The base 8 forming the control electrode 6 is fixed in the vicinity of the platen roller 9 that conveys the recording paper 5, and furthermore, in order to keep the position of the penetrating member 3 at the tip of the recording head 1 and the recording paper 5 constant. A blade guide roller 10 is provided on the recording head 1.

The head guide roller 10 provided on the recording head 1 is
It functions to keep the pressure or gap between the recording paper 5 and the head tip constant. As the head guide roller 10,
Ordinary rubber rollers or metal rollers can be used.

At this time, the recording paper 5 is fixed by the planes of the platen roller 9, the paper guide roller, the head guide roller 10, and the base 8, so high pressure is not applied to the recording head 1 itself, but the recording head 1 and the recording The positional relationship between the paper 5 and the control electrode 6 can be made constant.

The control electrode 6 can be formed on the substrate 8 by a conventional method such as vapor deposition or plate making. Characters and images can be recorded at high speed by line scanning by arranging a plurality of control electrodes 6 at a desired pitch perpendicular to the conveyance direction of the recording paper 5 and selectively applying voltage to the control electrodes 6. I can do it. In order to perform high-resolution recording, it is necessary to arrange a plurality of control electrodes 6 in a staggered manner. The control electrode 6 wears out as the paper is conveyed, so in order to prevent the control electrode 6 from being worn out, the control electrode 6
A wear-resistant organic film is provided on the surface.

As the ink, an aqueous conductive ink can be used.

Regarding the physical properties of ink, optimization of surface tension is particularly important. Suitable physical properties of the ink depend on the material and pore size of the permeation member 3, and when Teflon is used, its critical surface tension is 28.5 dyne/cm, so the surface tension of the ink is 30. ~70 d7ne/cm can be used. The pore diameter of the permeable member 3 is as follows:
It can be selected within the range of 0.1 to 10 μm.

The recording paper 5 is Xerox paper, which is commonly used.
Various types of recording paper can be used, including printing paper, bond paper, and films used for OHP.

Here, the distance between the ink and the control electrode 6 changes depending on the thickness of the recording paper 5 used, so if the applied voltage is constant, the electric field applied to the ink surface changes and printing with a constant density cannot be obtained. , as shown in FIG. 3, in this example,
In order to keep the electric field applied to the ink constant, a detection circuit 11 is provided as a detection means for detecting the distance between the control electrode 6 and the ink (the tip of the head). The detection circuit 11 detects the distance between the ink and the control electrode 6 by detecting the capacitance between the ink side electrode 7 and the control electrode 6 in the recording head 1 . That is, the detection circuit 11 detects the picture electrodes 6,
By detecting the impedance between the recording head 1 and the control electrode 6, the capacitance is detected, and the distance between the tip of the recording head 1 and the control electrode 6 is detected from the capacitance.

Reference numeral 12 denotes a control circuit (control means) to which the detection signal of the detection circuit 11 is input, and the control circuit 12 controls the applied voltage by changing the resistance value of the variable resistor of the drive circuit 13 consisting of an operational amplifier according to the detection signal. Or adjust the applied pulse width.

FIG. 4 shows the relationship between the distance between the ink tip and the control electrode and the driving voltage at which the ink is transferred, and the driving voltage is adjusted according to the distance.

As shown in FIG. 3, the drive circuit 13 is supplied with pulses from a pulse generator 14, and the pulse generator 14 is supplied with an image signal from an image memory 15.

Further, when a detection signal exceeding a reference value is input to the comparator 16 from the detection circuit 11, an alarm display (lamp display) is performed. This prevents recording from being performed when the thickness of the recording paper 5 is equal to or greater than the allowable thickness.

Next, the effect will be explained.

As an ink, the surface tension is 61. 7d7ne/cm
.

Using a water-based ink with a viscosity of 3 cp, the penetrating member 3 is as follows:
Using Teflon (fluorobore film) with a pore diameter of 5 μm and a thickness of 60 μm, recording was carried out with a recording energy of 600 V and a pulse width of 1 ms, resulting in dots with a diameter of 70 μm on a 125 μm thick recording paper. The driving voltage at this time was 600V. In addition, as a result of a recording experiment using a recording paper 5 with a thickness of 60 μm as the recording paper 5,
Similar dots could be formed. The adjusted driving voltage at this time was 350 Ω.

It goes without saying that the same results can be obtained when an OHP film is used instead of the recording paper 5.

In this way, even if the thickness of the recording paper 5 used changes, images with stable recording quality can always be recorded at high speed.

Further, the recording apparatus according to this embodiment has the advantage that the structure is simple, the apparatus is small, the running cost is low, and the reliability is high.

[Effects of the Invention] As described above, according to the present invention, the distance between the control electrode and the head tip is detected, and the applied voltage or applied pulse width of the drive circuit is adjusted according to the detection signal. Even if the thickness of the recording paper used changes, images with stable quality can always be recorded.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention; Figure 3 is a circuit configuration diagram, FIG. 4 is a graph showing the relationship between distance and drive voltage. In the figure, 1...recording head, 2... ink holding member, 3... Penetration member, 4...Body, 5...recording paper, 6... control electrode, 7... Ink side electrode, 8...Foundation, 9...Platen roller, 10...head guide roller, 11...detection circuit (detection means), 12... control circuit (control means), 13... drive circuit, 14...pulse oscillator, 15... image memory, 16... Comparator.

Claims (1)

[Claims] A permeable member (3) and a conductive ink in contact with the permeable member (3) or an ink retaining member (2) impregnated with conductive ink.
a recording head (1) having a recording head (1) inside;
) provided on the conductive ink side of the electrode (7) and the electrode (7)
A drive circuit (13) is provided which applies a voltage between the control electrode (6) facing the recording paper (
5) in a recording device for recording, the detection means (11) detecting the distance between the control electrode (6) and the tip of the recording head (1);
) A recording apparatus comprising a control means (12) for controlling an applied voltage or an applied pulse width of the drive circuit (13) according to the output of the drive circuit (13).