JPS63141065A - Insulation cover for recording element - 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 The present invention relates to a recording element and a coating for a recording element for the electrographic recording of toner images, the coating having electrical, optical and durability properties useful in the recording process. It provides elements with the following.

Kotz rice [Kl special i13,816,840J3 Akim
``b'' discloses an electrographic recording method and apparatus in which an insulating recording element is placed between two electrodes.

An electrically conductive toner powder is used that magnetically adheres to one of the electrodes. This toner powder provides an electrically conductive path between the electrode to which it is constrained and the adjacent surface of the insulating element. A voltage can be applied between the electrodes for a time and magnitude sufficient to generate a force pattern on the toner, causing toner to be deposited on the recording element in response to the force pattern. Since the force pattern is generated directly on the toner rather than on the recording element, the recording element is inactive during operation of the device disclosed in the above-mentioned patent specification.

Mechanical loss-1 resistance to wear and shearing is
This is an important property for the receptor surface of recording elements used in methods where a significant number of images need to be applied and removed. These properties of durability can be determined by repeatedly exposing the receptor surface to this process and observing signs of failure or slow deterioration in the images produced. The number of times completed while retaining the ability to produce images that meet acceptance criteria is a measure of surface wear.

It is often desirable to apply the toner to an insulating recording element that has a background color that provides high contrast to the toner powder. For example, if the contrast between the toner powder and the recording element to which it is applied is high enough, e.g. 0.6 optical density units, the recorded information can be read directly or indirectly;
Or it can even be copied by optical means, all with high fidelity and high resolution. The untransferred, unfused toner powder can then be removed from the recording element and new information can be displayed thereon. In this manner, a system can be established 31 that utilizes recyclable toner powder to optimize the quality of the displayed image regardless of the transfer and fusing characteristics or the cost of depleting the toner powder with each copy. Alternatively, toner powder can be applied to the recording element if desired.

Anodized aluminum has been used as the recording element for the electrographic recording device described therein. An aluminum oxide surface with a suitable electrical response can be formed on the aluminum substrate by anodizing or other conventional means. However, it is well known that such surfaces change over time, particularly when the surfaces are exposed to environments with high relative humidity. This change may not adversely affect the electrical properties of the aluminum oxide surface. Furthermore, in environments of high relative humidity, fused aluminum surfaces tend to collect a film of moisture, which must be removed by special means to preserve a stable electrographic process. Furthermore, anodized aluminum and other such surfaces do not have desirable optical properties for some desirable applications of the methods disclosed in the KOLZ patent.

Materials attached to the receptor surface that have electrical properties suitable for use in rapid cycle electronic recording methods cannot withstand the mechanical abuse that results from bending, cycling, application and removal of toner powder.

A polynisder film with suitable pigments can provide the desired contrast between the recording element and the powder. However, polyester films, or films made from other insulating organic resins, when applied to conductive substrates, generally allow charge build-up resulting in excessive background color formation and ghosting.

Over a period of use, for example during about 100 imaging and removals of images from the recording element, residual charge builds up within the insulative recording element. This accumulation of charge causes excessive background coloring and ghosting, rendering the recording element useless for further imaging.

The selection of a recording element and its insulating coating for use with recirculated imaging powder is based on at least three factors: (1) essentially complete removal of charge from the recording element within one operating cycle of the recording process; (2) The durability of the recording element must be sufficient to make the process economically viable again = (3) The contrast between the toner powder and the recording element must be high 11 e.g. at least 0.6 It can be specified that it is an optical density unit, and it can be seen that it is limited by .

It is relatively difficult to provide a recording element that satisfies any one of the above three constraints. However, it has hitherto been considered extremely difficult to satisfy all three of these requirements at the same time. The problem of charge accumulation has posed great difficulties in finding suitable materials for recording elements. True resistive materials, such as most polymeric materials, have an undesirable tendency to trap charge in their structural matrix. At the voltages and cycle times of the recording method described in Otz, Special Edition J1, accumulation of trapped charge occurs over a period of about 100 nicles. Removal of this trapped charge takes a relatively long time.

The present invention relates to a recording element suitable for use with the electrographic recording method and apparatus described in Otz US Pat. No. 3,816,840.

The recording element consists of a conductive substrate with an insulating coating thereon. The insulating coating is formed from an insulating polymeric material, such as polymethyl methacrylate, having a charge accumulation inhibitor, such as hydrophobic silica, uniformly dispersed within the insulating coating in a sufficiently high concentration.

The addition of a charge accumulation inhibitor in an insulating polymeric material can provide a
The insulating coating can be used for imaging and image removal processes that exceed 0.000 cycles. The conductive substrate can be formed from a conductive material, such as a base, a photoconductive material.

The surface of the insulating coating is sufficiently durable that the recording element can be used repeatedly before requiring replacement, e.g., the coating can withstand at least ioo, ooo cycles of imaging with toner powder and its removal. can. The insulating coating preferably provides a high contrast between the toner powder and the recording element, for example at least 0.6 optical density units, so that the image formed by said toner powder particles can be transmitted by optical means, for example a camera, Photocells can be read and/or copied by projection onto a recording surface, while at the same time retaining high fidelity and high resolution on the reading surface and/or on copies made therefrom.

FIG. 1 is a schematic diagram of one embodiment of the recording element of the present invention.

FIG. 2 is a schematic diagram of another embodiment of the recording element of the present invention.

FIG. 3 is a partial diagram of an electrographic recording system incorporating the recording element of the present invention.

No. 4Fj4 is a schematic diagram of an apparatus that can be used to test insulating materials to determine compliance with the present invention.

1 and 2 show another embodiment of the recording element of the invention.

Referring now to the drawings (with particular reference first to FIG. 3), there is shown a recording system 1 using the recording element of the invention. This recording system 1 includes a circular n-shaped developer roll 3 and a rotatable recording element 2o.

Current @[1-3 is, for example, US Pat. No. 3.455°27
A device of the type disclosed in No. 6 Akira 4 (Andcrson) has an internal magnet assembly 5 and an electrically non-conductive, non-magnetic external cylindrical shell 6. The magnet assembly 5 includes a cylindrical magnet-retaining core 7 and several permanent magnet sectors 8 arranged in a cylindrical peripheral layer of the core 7, the latter defining a surface with alternating north and heavy poles. . The developer roll 3 is mounted on a mandrel 9 and the magnet assembly 5 is configured to rotate clockwise, whereas the outer shell 6
is preferably spaced apart from the magnet assembly 5 and fixed in place. A large number of individually spaced apart recording electrodes 10 (
(only one of which is shown) are arranged on a line extending parallel to the holding center 7, and these protrude from the periphery of the shell 6, but the outer end of the electrode 1o is flush with the outer surface of the shell 6. It is sometimes arranged in the shell 6 so that it looks like this.

Since the ViA 10 is magnetically permeable and passes a large amount of the magnetic flux emanating from the magnet sector 8 of the developer roll 3, the developer roll 3 thus serves as a means of force imparting a relatively high magnetic flux density to the outer end of the electrode 10. It becomes like this. Each electrode 10
is used to print a dot with a definition determined by its shape, density and density distribution, and the electrode 10 is threaded through to serve as a printing matrix. The number of electrodes 10 used depends on the printing application for which the matrix is to be used. 136 5x
For a standard computer output linewidth of 7 dot matrix characters, approximately 10 dots spaced at 70 dots per inch.
00 electrodes are used.

For more complex character fonts and simple graphical applications, electrode vA spacing of 100/inch to 400/inch or more is required. A power supply 11 supplies recording potential difference pulses to the electrodes 10 in a manner and for purposes described below.

The recording element 20 is attached to the mandrel 12, the latter being parallel to the developer roll 3 and the developer roll magnet assembly 5
It is rotated clockwise so that it rotates in the same direction. Element 20 is spaced apart from electrode 10 to define a narrow recording area 13 therebetween. Element 2o is formed from an electrically conductive cylindrical electrode 21 and a seamless insulating coating 22 placed over the cylindrical surface of electrode 21. The electrode 21 is preferably electrically grounded.

A power supply 11 supplies voltage recording pulses to the electrode 10 to
0 and the grounded electrode 13. This potential difference causes the deposition of toner on the insulating coating 22. The electrode 10 is selectively pulsed by the power source 11 and the coating A toner image is formed on the surface of the object 22. The portion of the toner 14 that is deposited on the coating 22 in the form of a toner image initially has a relatively high charge and is electrically charged. It is held on top of the coating 22 by the dark potential difference with the voltage 1421.

Preferably, the toner is electrically conductive so that it can be magnetically attracted. Toners suitable for the described apparatus are disclosed in US Pat. No. 3,639,245 (NOISOn).

A layer of electrically conductive toner 14 that is magnetically attracted to an electrically conductive toner 14 is
A doctor blade 23 extending at a fixed axial distance from 410 is metered onto the surface of the electrode 14i10.

Toner 14 is held by the magnetic field exerted by magnet sector 8 and attracted to electrode 10 .

The electronic properties of the recording element affect the performance of the electrographic recording system described in Otz patent No. 11m, and the limitations placed on these properties depend on the particular implementation. However, this υ1 limit often arises from the following considerations.

The resistivity of the recording element must be high enough to prevent large charges from draining from the toner to the recording element at a rate that reduces the electrical forces to a level that is not strong enough to overcome the magnetic forces in the image area. . Preferably, the resistivity of the iJ3 Ir U.S. Pat.
．． It should be at least 10 times the resistivity of the toner in an electric field comparable to that experienced by the material of 840M Akim JJ (incorporated by reference in Motokawa's book). Resistivity values can be measured using an electrical resistance meter connected to two copper rods with both rods placed in contact with the insulating surface of the recording element.

For low voltage operation, which is desirable from an economical and reliability point of view, a high electronic capacity ii! for the recording element! ! It is desirable to have . It is more advantageous to achieve this with a thin insulation coating than with a high dielectric constant in combination with a thin insulation coating.

The insulation should be thick enough to withstand the voltages applied during this process. Suitable thickness is at least 5X1
0' centimeters (500 angstroms). The thicker the insulation coating is than the minimum thickness, the greater the voltage required to create a given force for the same dielectric constant.

Generally, for practical reasons, the thickness of the insulation coating is kept to a minimum above the thickness at which electrical breakdown occurs, since thick insulation coatings reduce the resolution of the developed pattern.

Sufficient charge accumulation inhibitors must be added to the insulating coating to suppress charge accumulation in the filtration layer in the insulating coating. This charge accumulation inhibitor prevents charge accumulation through the triboelectric effect. It has been found that hydrophobic silica acts as an excellent charge accumulation inhibitor. It is preferred to use a high concentration of hydrophobic silica in the insulation coating. for example,
From about 30 to about 95]R% of the total solids material of the insulation coating can be hydrophobic silica. Preferably, the concentration of hydrophobic silica is from about 50 to about 75% of the total solids material of the insulation coating. The remainder of the solid material of the insulation coating generally consists of a polymeric material.

From the 12 description of the constraints on electronic properties, it is clear that the thickness of the insulating coating has a significant effect on the electrographic recording process. The thickness of the coating is from about 0.05 mm to about 5 mm.
0 micrometers, preferably about 0.3 to about 2.0
It is better to cover micrometers. Coatings with thicknesses much greater than 2.0 microD meters compromise image resolution, degrade toner powder background, or require undesirably high voltages. coatings with thicknesses well below 0.3 micrometers tend to They tend to lack sufficient durability and also tend to produce poor images.

Typical ranges of parameters for insulating coatings suitable for the present invention are as follows: Recorder voltage 5 to 40 volts Imaging voltage minimum Several milliseconds to several seconds Cycle time Less than ohm-alpha Recording element electronic Other features that may affect properties are described in detail in US Pat. No. 3,816,840.

While many materials are known that exhibit electronic properties suitable for use in the method described in the KotZ patent, there are some materials that exhibit durability and optical properties that make them useful for some commercial applications, viz. Relatively few are visible optically on the receptor.

The insulative coating should last for more than 20,000 cycles of imaging and removal, preferably 10,000 cycles of imaging and removal, before the coating becomes worn to the point that it adversely affects the performance of the recording element. It has been determined that the required level of durability was achieved even when the test was carried out. However, some users of the recording elements of the present invention require only a low level of durability of the insulating coating.

Preferably, the insulating coating has a sufficiently low reflective optical density to ensure sufficient contrast between the recording element and the toner powder. For example, a suitable contrast level is at least +0.6 optical contrast level. If the coating is transparent, the contrast level between the ]-ner powder and the material consisting of the conductive substrate is, for example, at least l-0,6
Medium optical density.

The insulating coating according to the present invention! The selection of suitable polymeric materials for A construction is based on the requirements of the particular application in which the recording element is to be used. In general, the main requirement is that if a solvent is used to apply the polymer to the conductive layer,
Electric storage? 11!7+ The inhibitor must be easily dispersed within the polymer/solvent system or, if no solvent is used, within the polymer itself. Other considerations include adhesion to the C conductive layer, color or clarity, durability, tolerance to extreme IA conditions, and ease of handling. Representative examples of useful aggregate types include acrylic, polyester, polycarbonate, polyvinyl acetate, polyvinyl chloride, polyvinyl butyral, cellulose acetate, polyvinyl alcohol, polyacrylonitrile,
Epoxy resin, polyamide °, polyvinylpyrrolidone,
These include polyvinyl acetal, cellulose acetate butyrate, polystyrene/butadiene, polyimide and ethylcellulose.

One convenient test method has been developed to determine whether a given material is suitable as a charge accumulation inhibitor. The apparatus for carrying out this test is shown in FIG.

A sample of insulation coating 30 material is movably mounted in close proximity to an electrically grounded toner station 32. When the toner 34 rubs against the insulating material 1'130, an electric charge is generated on the material due to frictional electricity. The magnitude and polarity of this charge is monitored and recorded. The sample is preferably prepared as a layer of insulating material in the form of a belt. Typically, the belt is placed over a pair of rollers 36 and 38, with one of the rollers being placed close to toner station 32. Electrical contact 40 must be made to the conductive layer below the layer of insulating material, and the conductive layer must be held at ground potential.

The magnitude and polarity of the charge on the layer of insulating material 30 is measured using an electrostatic voltmeter 41, such as a Honroe Electron.
ics Co., Ltd. can be used for detection. Rotate the toner station 32 several times, for example about 10 times.
The electrical potential is recorded through the insulating material by moving the probe approximately 100 revolutions from the center.

The toner station 32 consists of a magnetic roller 42,
It is fixed against rotation, and the electrically conductive shell 44 is allowed to rotate. Ideally, one of the poles 46 should face the nip area 48 created between the two rollers 38 and 42. Electrical connections 50 to shell 44 must be provided so that the shell is held at ground potential. Typical values for toner stations are:
Number of Poles: 4 to 8 Typically, the potential of the insulating material initially rises from its initial ground potential (either positive or negative) and then stabilizes. Toner adhesion is due to image forces on the toner caused by the accumulation of charge on the insulating material. The value of the charge on the insulating material alone can be measured by blowing the toner away from the insulating layer using compressed air or rreonR gas. The magnitude of charge rr1 accumulation depends on the relative humidity and should therefore be adjusted.

If the charge magnitude, as measured by the method described above, is from about 1 volt to about 10 pol i, the material will be successful as a directed anti-accumulation agent. It is important to note that if the printing polarity of the autolog h1 is opposite to that measured in the above test, then the material under investigation is only successful as a charge accumulation inhibitor. If the polarity of the recorder's printing voltage were the same as that measured in this test, excessive background color formation and/or ghosting would occur.

Hydrophobic silica is a typical example of a charge accumulation inhibitor suitable for the recording element according to the present invention. Hydrophilic silicas are not useful for this invention.

The conductive substrate is formed from a self-supporting conductive material, or
or may be formed from a layer of conductive material applied to a non-conductive support substrate, e.g. a flexible belt made from a composite material, and in the latter case the element B itself becomes a flexible bamboo. Will. In one example of a self-supporting conductive material, as shown in FIG. A manufactured metal drum will do. The conductive substrate is in contact with the ground to create a potential difference between its surface and the ground plane. Alternatively, a layer of conductive material can be applied to the surface of a non-conductive support substrate, such as a polymeric film, and in this case the conductive layer is a combination of the polymeric film and the insulating coating. It occupies the middle gate position in between. A concrete example of this is shown in FIG.

Suitable materials for the conductive layer include metal foils or sheets, such as aluminum or copper, metal coatings, such as gold, or metals deposited by one of several means, such as vapor, vapor deposition, or plasma deposition; metal oxide films, such as indium tin oxide, which can be deposited by several means.

The conductive layer is required to exhibit sufficient conductivity to transport charge at a rate consistent with the desired application.

It has been found that conductive layers exhibiting a resistivity of less than 5000'A-m/sq are generally useful for most applications.

Preferably, the conductivity of the conductive layer does not decrease below a desired level over time or when the recording element is exposed to changing environmental conditions, such as by exposure to high or low relative humidity.

In situations where a visual display or optical projection of a toner image is intended, and where the insulating layer is transparent, its conductive layer may also be modified to suit the transparency, reflectance, or opacity of the desired effect. You have to show that.

If visual display or optical projection of the reflected toner image is intended, it is preferred that the recording element produces non-specular rather than specular reflection. When considering optical projection, the use of a non-reflective background for the image simplifies the alignment of optical elements.

It is often preferred that the non-conductive supporting substrate of the recording element is a flexible composite film. This film is relatively inexpensive, easy to coat, and the resulting product can be converted into seamless belts for use in a variety of shapes and processes, such as electrographic recording systems.

The polymeric film can be any material that is sufficiently stable to undergo the processing steps necessary to fabricate the recording element and to operate with acceptable durability and stability in electrographic recording systems. good. Polymeric materials suitable for forming polymeric films include polyesters, polyolefins, polyamides, polyimides, and vinyls.

Polyester films are particularly suitable because they can be produced with a smooth surface, resistant to solvent attack,
This is because it can withstand thermal distortion and has good physical properties such as good tensile strength. A typical example of a commercially available polyester film is 5cotcbparR (Hin
ncsota Mining and)4anufac
turing Company), various equal amounts of Hy
larR(E, T, Dupont da Neff
1 ours Corporation vJ), and various equivalent amounts of HclinexR (ICI vJ).

The following examples are intended to illustrate the invention and are not intended to limit it. Parts and percentages are by weight unless otherwise specified.

Example 1 The following ingredients were used to produce a composition for the insulating coating of a recording element: Ingredients
(g) ROhlll a
nd 1Iaas, Inc.) 2 Methyl Ethyl Ketone 47.5 Toluene
47.5 Hydrophobic silica (“8e
rosil R972J, Dcgussa, Inc.
(obtained from ) 3 resins in a solvent mixture;
The mixture was stirred until the resin was dissolved. The silica is then added to the mixture, and the silica
A separation device was installed using a paxJ separation device. The resulting dispersion was then coated to a wet thickness of 2 mils and dried under 200°C for 4 minutes.

A2 Repeat Example 1, except that (a) 1 gram of 8-cryloid A-21J tree is used instead of 2 grams, and (b) ﾾerosil R
14 ackcr instead of 3 grams of 972J hydrophobic silica
Only 4 grams of RHD K 2000 J hydrophobic silica, available from Co., Ltd., was used. The composition of Example 2 is particularly suitable because it allows for higher loadings of silica and allows for more stable dispersions. Both compositions range from 50.000 to 100.000. OOO”l-Iku/L,
The above-mentioned device gave excellent imaging performance over m problems consisting of .

Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention.

It is to be understood that the invention is not to be unduly limited to the alternative embodiments set forth in Book II.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an integral example of the recording element of the present invention, FIG. 2 is a schematic diagram of another specific example of the recording element of the present invention, and FIG. 3 is an electrograph incorporating the recording element of the present invention. FIG. 4 is a partial view of the recording device, and FIG. 4 is a schematic diagram of the insulating material testing device. 3... Developing roll, 1o... Electrode, 2o... Recording element, 22... Insulating coating, 21... Cylindrical electrode, 3
0...Insulating material, 42...Magnetic roller.

Claims (13)

[Claims] (1) In a recording element suitable for use in an electrographic recording device for recording toner images on the recording element, said device comprises first and second electrodes spaced apart to define a recording area. two opposed electrodes, means for driving a recording element into said recording area, electrically conductive toner powder from a toner reservoir into said recording area, selectively driving a voltage pulse across said electrodes onto said recording element; Depending on the application, said recording element comprises means for selectively depositing and conveying, said recording element comprising a conductive substrate having an insulating coating of a polymeric material containing an anti-charge accumulation agent. . (2) The recording element according to claim 1, wherein the charge accumulation inhibitor comprises hydrophobic silica. 3. The recording element of claim 1, wherein the charge accumulation inhibitor is present in the insulating coating in an amount sufficient to generate a triboelectric charge that prevents charge accumulation in the insulating coating. (4) The charge accumulation inhibitor is about 30% to about 95% of the insulation coating.
Recording element according to claim 1, comprising up to % by weight. (5) The charge accumulation inhibitor is about 50% to about 75% of the insulation coating.
Recording element according to claim 1, which accounts for % by weight. 6. The recording element of claim 1, wherein the element has a sufficiently low optical density such that the contrast between the recording element and the toner is at least 0.6 optical density units. (7) A recording element according to claim 1, wherein the conductive substrate is made of a conductive metal. (8) The recording element according to claim 1, wherein the conductive substrate comprises a conductive layer supported by a non-conductive insulating substrate. (9) the electrically conductive substrate is transparent to visible light;
A recording element according to claim 1. (10) The recording element according to claim 1, wherein the insulating coating is transparent to visible light. (11) The recording element according to claim 1, wherein the thickness of the insulating coating is about 0.05 micrometer to about 5.0 micrometer. (12) The recording element according to claim 1, wherein the thickness of the insulating coating is about 0.3 micrometers to about 2.0 micrometers. (13) A recording element according to claim 1, wherein the element is flexible.