WO1998007570A1

WO1998007570A1 - Toner supply matrix for a printing apparatus of toner jet type and a method of manufacturing same

Info

Publication number: WO1998007570A1
Application number: PCT/SE1997/001333
Authority: WO
Inventors: Per Sundström
Original assignee: Ito Engineering Ab
Priority date: 1996-08-21
Filing date: 1997-08-08
Publication date: 1998-02-26
Also published as: SE9603032D0; SE9603032L; SE510278C2

Abstract

A toner feeder matrix for a printing apparatus of the type named 'toner jet' printing apparatus, and in which a dry colour powder, generally named 'toner' (2), is transferred, by a direct method, from a rotating toner feeder roll (1), through toner feeder bores (8) of a fixedly mounted toner feeder matrix (3), which is formed with a flexible printing circuit (9), and down onto an object (5) to be printed, for instance a paper, which is conveyed over a support roll (4), whereupon the colour powder which has deposited on the paper (5) is finally fixed to the paper by means of a heating apparatus (12). The toner feeder matrix (3) comprises a base (13) of a thermoplastic material, which, at the upper surface thereof, is laminated with a thin copper foil, which by an etching process has been formed to electrically conducting rings (9) round the toner feeder bores (8), and which, at the lower surface thereof, is laminated with a thin stabilising copper foil (18), and in which the combined matrix (3, 9, 14) is bent to a curved shape adapted to the shape of the toner feeder roll (1) of the actual printing apparatus, and which in the curved shape has been treated by a press and heating process, whereby the thermoplastic base (13) has been solidified in the said curved shape. The invention also relates to a method of manufacturing a toner feeder matrix of the above mentioned type.

Description

TONER SUPPLY MATRIX FOR A PRINTING APPARATUS OF TONER JET TYPE AND A METHOD OF MANUFACTURING SAME

The present invention generally relates to a toner supply matrix for use in a printing apparatus of toner jet type. The invention also relates to an method for manufacturing such a matrix.

Printing apparatus of the toner jet type are used for instance in printers of various types, in copying machines, in telefax machines etc. The printing apparatus operates with a dry colour powder, generally referred to as "toner", which toner is applied, by electric means, to the object to be printed, for instance a paper in that the toner is transferred from a toner feeder roll, through a perforated matrix and down onto a paper which is moved over a support roll, whereupon the toner is fixed to the paper, generally by a heat treatment.

THE TONER JET PRINCIPLE

Printing apparatus of the toner jet type are formed so that a dry colour powder, named "toner", is, by a direct method, transferred from a rotating toner feeder roll which is charged with a predetermined electric voltage, through bores of a fixedly mounted matrix comprising a flexible printing circuit having a large number of through bores, and which can be charged with a variable voltage which is alternatively higher or lower than the voltage of the toner feeder roll, and down onto the object to be printed, for instance the paper, which is conveyed over a support roll which is charged with a voltage which is substantially higher that the voltage of the toner feeder roll and the voltage of the matrix, and whereby the toner powder which has deposited on the paper is finally fixed to the paper by a heat treatment.

The basic idea of the said process is that the toner particles are charged electrically in that the particles rub against each other, whereby said particles get a certain polarity, generally a negative polarity which is opposite to the polarity of the toner feeder roll, and in that the toner is spread and distributed in an even layer by means of a doctor blade, and the toner is sucked to the toner feeder roll by electric and magnetic attraction. For letting the toner particles down onto the paper there is used a matrix comprising a large number of toner feeder bores, and whereby each bore is surrounded by an electrically conducting ring, for instance a ring of copper, which can be charged with a voltage which has the same polarity as the toner feeder roll, but which is higher than said toner feeder voltage, whereby there is provided an electric field from the toner feeder roll to the matrix. The copper rings can alternatively be connected to earth, whereby the field will be the opposite. When the copper ring is charged with a higher voltage than that of the toner feeder roll the matrix bore can be considered "opened", and it is thereby created a first electric field extending from the toner feeder roll to the matrix, and toner particles follow said field to the matrix and are let down through the bores of the matrix. The copper rings which are earthed have a less potential than the potential of the toner feeder roll, and at the bores of said rings there appears an electric field which is directed oppositely to the toner feeder field, and no toner particles are therefore moved towards said bores. The bores of the earthed rings therefore can be considered as "closed" .

For feeding toner particles onto the paper there is created a second electric field, supplementary to the said first field between the toner feeder roll and the toner matrix, and said second electric field, which is preferably constantly directed downwards, is provided between the matrix and the support roll on top of which the paper is conveyed.

The matrix is formed with a very large number of toner bores, each bore being very little and can have a diameter of for instance 1 00-300 μ . Round each individual such bore there is an electrically conducting ring, for instance of copper, in the following referred to as "copper ring" .

In a practical embodiment of a printing apparatus of the above mentioned type the toner particles were of a type which, when being rubbed against each other, were charged with a negative polarity, and the toner feeder roll had a positive potential of between + 5 V and + 1 00 V, preferably + 50 V. The toner particles thereby are maintained against the toner feeder roll by electric and magnetic attraction. The matrix bore rings which are, for instance, made of copper are arranged for being charged with a positive potential which is higher than the potential of the toner feeder roll, for instance a potential of + 300 V (opened bore) and can be earthed, respectively (closed bore), whereby the electric field between the toner feeder roll and the matrix bore ring, at opened bore, will be + 50 V -=> + 300 V = + 250 V. In the actual case the support roll had a positive voltage of about + 1 500 V, and the electric field between an electrically charged matrix bore ring and the support roll thereby will be + 300 V => + 1 500 V = + 1 200 V. The copper rings of the matrix can be provided on a distance from the toner feeder roll of 0. 1 mm ( = 1 00 μm) and the distance between the matrix and the support roll can be 0.6 mm ( = 600 μm). The field strength between the toner feeder roll and the matrix ring thereby will be 2.5 V/μm, and the field strength between the matrix rings and the support roll will be 2 V/μm. It is said field strength that forces the toner particles, primarily from the toner feeder roll to the matrix, and secondarily from the matrix to the paper conveyed above the support roll.

The function consequently is the following: - the colour powder (toner) gets a negative potential in that the toner particles rub against each other;

- toner is supplied to the toner feeder roll, which is positively charged with a predetermined potential, often a potential which can be controlled between + 5 and + 1 00 V, for instance + 50V, and the colour powder is distributed in an even layer, not too thick, not to thin, on the toner feeder roll using a doctor blade; the toner is kept attracted against the toner feeder roll by electric and magnetic attraction;

- each bore of the matrix, which corresponds to a dot of colour is controlled by a control means, for instance a computer, and is opened in that the matrix bore ring is charged with a positive potential which is higher than the potential of the toner feeder roll, for instance + 300 V; bores corresponding to not colour supporting portions can be earthed, whereby such portions get a less voltage than that of the toner feeder roll, and said bores are considered as "closed" bores; this makes it impossible for toner to be let through; the combination of opened matrix bores create the image to be represented;

- depending on the difference in potential, for instance + 50 V => + 300 V = + 250 V, between the toner feeder roll and the toner matrix negatively charged toner particles are sucked down from the toner feeder roll towards and through the matrix, and depending on the difference in potential between the toner matrix and the support roll mounted underneath the matrix, for instance + 300 V => + 1 500 V = + 1 200 V, toner particles are also sucked from the matrix and deposit on the paper above the support roll;

- the paper with the toner deposited thereon is finally moved through a heater apparatus in which the toner is fixed to the paper. BASIC PROBLEM

A problem in printing apparatus of the toner jet type is to keep the matrix in a correct position over the entire length thereof, which for a normal A-4 printing apparatus can be 21 0 mm. The field strength between the toner feeder roll and the matrix is not allow to vary very much from one matrix bcre to another matrix bore, since, in such case, there is obtained a variation in toner density over the printed page. The little distance, for instance 0.1 mm between the toner feeder roll and the matrix is decisive for the field strength between said parts. With recent technics it does not involve any great problems in maintaining a difference in potential of for instance + 50 V =

+ 300 V = + 250 V between the toner feeder roll and the matrix substantially constant, but on the contrary it may involve great difficulties in maintaining the said distance of only about 0.1 mm constant over the entire length of the paper, for instance 21 0 mm for an A-4 format and 297 mm for an A-3 format. For various reasons the matrix has to be very thin, and the matrix has until now been made of a polyamide material having a maximum thickness of 50 μm (0.05 mm), and to this thickness should be added the thickness of the copper rings and the copper conduits at the upper surface of the matrix, which thickness can be 1 5-20 μm. The distance between the toner feeder roll and the support roll is about

0.7 mm, and within said distance there should be space for conveying a paper having a thickness of 0.1 mm, a distance to the matrix of 0.1 mm and the thickness of the matrix. It is important that toner which has been deposited on the paper is not scraped off against the bottom surface of the matrix - in spite of the very little available distance, that is a distance of maximum about 0.4 mm - since toner at the bottom surface of the matrix can, in turn, smear off against the succeeding paper.

In order to make the matrix be mounted at a fairly stable distance from the toner feeder roll there are to-day two different methods. According to one method the matrix is clamped strongly in an even position between two support bars, so that the matrix is tightened like a "drum head"; according to the second method the matrix is bent in a curvature round the printing zone with a radius which is slightly greater that the radius of the toner feeder roll. By the curvature the matrix gets a natural stiffening. The said last mentioned method is at present the best solution of the problem of providing a stable mounting of the matrix. Still, there are two different problems involved also in this method:

1 . Since the bending strength in the part of the matrix containing the toner feeder bores is different from the bending strength of the parts not having any toner feeder bores it is impossible to provide an even radius without the risk that the matrix gets into contact with toner layer of the toner feeder roll. Therefore it is difficult to provide an even distance between the matrix and the toner feeder roll with a tolerance of ±20 μm, or still narrower tolerance.

2. Another problem which influences the possibility of maintaining the said difference between the toner feeder roll and the matrix constant is that there appears a force between said part each time that a voltage is connected to a copper ring of a matrix bore, and said forces lead to appearance of vibrations of the matrix, whereby the said distance will change following said vibrations. Therefore, there has been a need for a system for providing

- a mechanically optimum stiff and straight toner matrix;

- which can be maintained on a rectilinear tolerance and a parallellity of better than ±20 μm,

- which is less sensitive than previously known matrixes for the vibrations which irrevocably appear during the printing process;

- and which can be manufactured thinner than has so far been possible.

SOLUTION OF THE PROBLEM The said need can be fulfilled by means of a matrix which is first of all composed on a new type of matrix material, which can be shaped to desired appearance by means of tools and with any desired radius using heat and pressure in the shaping tool.

For making it possible to punch out bores in the matrix, to form the copper rings by an etching method, to mount the electric components etc. it is necessary to keep the matrix even using available manufacturing equipment. Matrixes used so far have been built up on a supporting base material of a polyamide, which belongs to the family thermosetting resins which can not be reshaped once it has been shaped. Differing therefrom are "thermoplastic resins" which can be remelted several times and can thereby be reshaped to a new shape. The reshaping of the thermoplastic resin can be made by heating the resin to its so called glass forming (hardening) temperature and by subjecting the resin to a mechanical pressure at said temperature, whereby the resin takes a new, mechanically stable shape, and it forgets is former shape. According to the invention the manufacture starts using a thermoplastic resin as a support for the matrix. A useful material is Staystick® which is manufactured by Alphametals Inc. of New Jersey, USA. For a normal A-4 format it is quite sufficient to use a support material having a thickness of 0.05 mm. On the upper side of said matrix support is a copper foil having a thickness of for instance 0.01 7 mm is laminated, from which is later etched the copper rings with the electric connection, which copper rings are used for "opening" and "closing", respectively, the toner feeder bores; at the bottom surface of the matrix support a copper foil is laminated, which foil is about 0.08 mm thick. In said matrix material a large number of toner feeder bores are drilled, for an A-4 matrix having 8 bores/mm, for instance 1 664 bores; in the upper copper foil copper rings and a conduit pattern is etched out, and in the copper plate corresponding toner feeder bores are etched out. Thereafter all electric circuits are mounted according to known prior technics. All said working is made with the matrix lying in a plane and even condition, and it is thereby possible to perform the working by means of conventional machine tools.

After said manufacturing process the matrix is placed in a press mould in which it is bowed to the desired shape for an actual printing apparatus. The press mould is heated to the glassing (hardening) temperature of the thermoplastic resin, and the thermoplastic support now will take a new, curved shape. The memory of the former even shape of material disappears concurrently therewith. The shaping using heat and pressure only takes a few minutes.

As a last moment of the manufacturing process an electrically insulated layer can be applied over the entire matrix by an evaporation process. Eventually a semi conducting layer can be sprayed onto the matrix for allowing a diverting of not desired static electricity.

The curved matrix, which is now stiff and stable in shape, can, after usual test of the function, be mounted in an actual printing apparatus, whereby said matrix is preferably mounted with the axis of curvature perpendicular to the moving direction of the paper. DESCRIPTION OF A PREFERRED EMBODIMENT

The invention is now to be further described with reference to the accompanying drawings, in which figure 1 diagrammatically and in a perspective view shows the basic principle of a printing apparatus of the toner jet type, and figure 2 diagrammatically shows a cross section view through a printing apparatus of the toner jet type according to the invention. Figure 3 is a diagrammatic cross section view through a printing apparatus, and figure 4 shows, in an enlarged scale, a part of figure 3 which is encircled by phantom lines. In figure 1 there is diagrammatically shown a printing apparatus of toner jet type comprising a toner feeder roll 1 having an outer layer 2 of a toner powder of known type, a toner matrix 3 mounted underneath the toner feeder roll 1 , and a support roll 4 mounted underneath the toner matrix 3 for conveying an object to be printed, normally a paper 5, between the matrix and the support roll. According to the invention the toner matrix is curved and is solidified in its curved shape, and the matrix is clamped with the curvature axis extending transversally to the feeding direction of the paper, for a normal A-4 printer over a width of about 210 mm.

As shown in figure 2 a toner container 6 is mounted on top of the rotatable toner feeder roll 1 , and from said container 6 toner is let down onto the toner feeder roll 1 . A doctor blade 7 spreads and distributes the toner to an even layer of toner 2 on the toner feeder roll 1 . The toner feeder roll is charged with a certain positive voltage of for instance between + 5 and + 100 V, in the apparatus shown in figure 2 a voltage of + 50 V. Since the toner particles rub against each other the particles are charged with a negative polarity, and this makes the toner particles become sucked into contact with the positively charged toner feeder roll 1 by electric and magnetic attraction.

The matrix is formed with a large number of through bores 8, which, in a condition where they are electrically charged with a voltage, are "opened" for letting toner through, and which in absence of voltage charging (earthed condition) are "closed" thereby preventing a transfer of toner therethrough. The bores can have a diameter of 1 00-300 μm. Round each toner bore 8 extends an electrically conducting ring 9, for instance a ring of copper, for controlling the transfer of toner particles. Each copper ring 9, which acts as a control ring, is over a conduit electrically connected to a control means 1 1 ,. which is diagrammatically shown in figure 2, for alternatively, and controlled for instance by a computer, applying a voltage on the copper rings, which voltage is higher than the voltage of the toner feeder roll 1 , for instance a voltage of + 300 V, whereby the matrix bore 8 will be "opened" , or for connecting the copper ring to a voltage which is lower than the voltage of the toner feeder roll 1 , especially a voltage of ±0 V, in that the ring 9 is connected to earth, whereby the matrix bore 8 will be "closed".

Thus, the opening of the toner matrix bore 8 is made in that the copper ring 9 is given a potential of for instance + 300 V, whereby there appears a difference in potential between the toner feeder roll 1 and the matrix 3 of + 300 V to + 50 V = + 250 V. Said difference in potential is so great that the negatively charged toner particles 2 become released from the toner feeder roll 1 and are sucked towards the matrix 3 and through the actually opened matrix bores 8. When the copper ring is earthed the direction of the electric field is reversed and there appears an upwardly directed difference in potential of + 50 V, and toner particles become sucked back towards the toner feeder roll 1 , or are maintained in contact therewith, respectively.

The support roll 4 is constantly charged with a voltage which is higher than the highest voltage of the matrix 3, that is a voltage which is higher than + 300 V, in the illustrated case a voltage of between + 1 000 and + 1 500 V. When the matrix bores 8 are "opened" there will consequently be a downwards directed difference in potential of between + 700 V and + 1 200 V, and said difference in potential makes toner particles become sucked down from the matrix towards the support roll 4. The toner particles thereby deposit as dots of toner on the paper 5 which is conveyed over the support roll 4. A series of such toner dots successively form the image or images to be represented on the paper.

The paper 5 with the toner particles which have deposited thereon is thereafter passed through a heat treatment apparatus, for instance between two heater rolls 1 2, in which the toner powder becomes fixed to the paper 5. The distances between the various parts of the apparatus shown in figure 2, like also the very parts of the apparatus, are strongly exaggerated for the sake of clearness. The distance between the toner feeder roll 1 and the copper rings 9 of the matrix 3 can for instance be 0.1 mm, and the distance between the bottom surface of the matrix 3 and the support can for instance be 0.3-0.5 mm. According to the invention the matrix is formed by a matrix base 1 3 of a thermoplastic material, for instance a material of the type which is marketed under the trade name Staystik® by Alphametals Inc., New Jersey, USA. For a normal A-4 format the matrix base can have a thickness of 50 μm. The thermoplastic base 1 3 is, at the upper surface thereof, laminated with a copper foil having a thickness of for instance 1 7 μm, which during the manufacture of matrix, is etched to form the electrically conducting copper rings 9 and the belonging connection conduits 10. At the bottom surface the thermoplastic layer 1 3 a thin metallic support layer 1 4 is laminated, for instance a copper foil having a thickness of for instance 80 μm. The copper layer is etched so as to form through bores 1 5 corresponding to each toner feeder bore 8 of the matrix 3. The bores 1 5 of the support layer 14 can be slightly greater than the toner feeder bores 8, and the edges of the bores 1 5 can be slightly bevelled. The manufacture of the matrix is accomplished in two basic stages, in the first stage with all parts of the matrix smooth and plane, in the second stage by bending the matrix to a curvature and solidifying same in said curved shape.

STAGE 1

- the method is commenced using a smooth and plane thermoplastic material as a carrier 1 3 of the matrix; a useful material is Staystick® which is supplied by Alphametals Inc., New Jersey, USA. For a normal A-4 format it is quite sufficient to use a carrier material having a thickness of 0.05 mm; - on the upper surface of the matrix carrier 1 3 is laminated a copper foil having a thickness of for instance 0.017 mm, from which is intended to etch out the copper rings with the electric connections which are to be used for "opening" and "closing" the toner feeder bores;

- at the bottom surface the matrix carrier is laminated with a copper foil 1 4 having a thickness of about 0.08 mm;

- in said matrix material 9 + 1 3 + 1 4 a large number of toner feeder bores 8 are drilled, for instance for an A-4 matrix having 8 bores/mm a number of 1 664 bores;

- in the upper copper foil copper rings 9 and a conduit pattern 1 0 is etched out; - in the bottom support-copper-foil 14 bores corresponding to the toner feeder bores 8 are etched out;

- thereafter all electric circuits are mounted as known in the art.

STAGE 2

- after the above manufacturing steps, which are performed while the matrix is in a plane condition, and it is thereby possible to perform the working using conventional manufacturing machines, the matrix 3 is placed in a press mould, in which the matrix is bent in a curvature corresponding to the desired shape of the printer; the press mould is heated to the glassing (hardening) temperature of the thermoplastic material; the thermoplastic carrier thereby will take a new, curved shape; the memory of the former plane shape disappears concurrently therewith; the shaping including heating and pressing takes only some few minutes; - as a successive step of the manufacturing process an electrically insulating layer can be applied by an evaporattion method over the entire matrix; eventually also a semi conducting layer can be sprayed over the matrix for diverting not desired static electricity.

The matrix is thereby ready to be mounted, in its solidified, curved condition, in the printer as diagrammatically shown in the drawings.

REFERENCE NUMERALS

1 toner feeder roll 1 0 conduit

2 layer of toner 1 1 control means

3 toner matrix 1 2 heater rolls

4 support roll 1 3 matrix base

5 paper 14 laminated plate

6 toner container 1 5 bore

7 doctor blade

8 toner feeder bore

9 copper ring

Claims

C L A I S

1 . A toner feeder matrix for a printing apparatus of the type named "toner jet" printing apparatus, and in which a dry colour powder, generally named "toner" (2) is transferred, by a direct method, from a rotating toner feeder roll ( 1 ) which is charged with a certain predetermined, relatively low positive potential (e.g. + 50 V), through toner feeder bores (8) of a fixedly mounted toner feeder matrix (3) which bores can be opened and closed by electrical means, and which matrix is in the form of a printing circuit (9), whereupon the colour powder is transferred to an object (5) to be printed, for instance a paper, which is conveyed over a support roll (4) having a certain predetermined, relatively high potential (e.g. + 1000 to 1 500 V), and in which the colour powder which has deposited on the paper (5) is finally fixed to the paper by means of a heating apparatus (1 2), characterized in that the toner feeder matrix (3) comprises a carrier (1 3) of a thermoplastic material, which, at the upper surface thereof, is laminated with a thin copper foil, which by an etching step has been formed to electrically conducting rings (9) round the toner feeder bores (8), and which, at the lower surface thereof, is laminated with a thin stabilising copper foil ( 1 8), and in that the combined matrix (3) is bent to a curved shape adapted to the shape of the toner feeder roll ( 1 ) of the actual printing apparatus, and which in the curved shape is treated by a press and heating process, whereby the thermoplastic support ( 1 3) has been solidified in the said curved shape.

2. A toner feeder matrix according to claim 1 , characterized in that the thermoplastic material ( 1 3) of the matrix, for a matrix having a length of about

21 0 mm, has a thickness of about 50 μm, and in that the copper foil (14) applied to the bottom surface of the thermoplastic material has a thickness of about 80 μm.

3. A toner feeder matrix according to claim 1 or 2, characterized in that the matrix is composed of a thermoplastic base ( 1 4) and, at the upper surface thereof, current conducting rings (9) including electrical conduits ( 1 0) and, at the bottom surface thereof, a laminated copper foil ( 1 4) and having over the matrix an electrically insulating layer which has been applied over the entire matrix by an evaporation process.

4. A toner feeder matrix according to claim 3, characterized in that the entire matrix is formed with a surface layer which is sprayed over the matrix for making it possible to divert not desired static electricity.

5. A method for manufacture of a toner feeder matrix according to any of the preceding claims, characterized in that the matrix is manufactured in two stages, namely a first stage performed in a plane condition, whereby the matrix is laminated with a base layer (1 3) of a thermoplastic material, at the upper surface thereof, a layer (9) of another material and, at the bottom surface thereof a layer (1 4) of another material, and a second stage, in which the combined matrix (3) is bent to a curvature, is pressed and heated, whereby the thermoplastic layer is solidified in its curved shape.

6. A method according to claim 5, characterized in that the thermoplastic layer (1 3), for a matrix having a length of about 210 mm, has a thickness of about 50 μm, and in that said thermoplastic layer ( 1 3), in the said first stage, is laminated with a metallic layer, especially a copper layer, on the upper surface of thereof, and in that said copper layer is etched to provide copper rings (9) extending round the toner feeder bores (8) of the matrix, and having current connections, and in which the copper layer has a thickness of about 1 7 μm.

7. A method according to claim 6, characterized in that the thermoplastic layer, at the bottom surface thereof, is laminated with a stabilising copper layer ( 1 4) having a thickness of about 80 μm, in which bores (1 5) are etched, which bores are matching the bores of the upper copper rings (9).

8. A method according to claim 5, characterized in that a large number of through bores (8) for feeding of toner are drilled through the matrix comprising the base (1 3) of the thermoplastic material, the upper foil (9) and the bottom foil ( 1 4).

9. A method according to any of claims 5-8, characterized in that the matrix comprising the base ( 1 3) and the laminated layer(s) (9, 1 ) are covered, by an evaporation method, with a thin insulating layer.

10. A method according to claim 9, characterized in that the matrix, as a complete, is spray covered with a semi conducting layer for diverting not desired static electricity.