DE2852353A1 - ELECTROSTATIC PRINT HEAD - Google Patents

Description

PHQ.77-006

DEEN / AVDV

8.6.78

"Electrostatic Print Head"

The invention relates to an electrostatic print head with a number of at least a row of writing electrodes arranged in groups, with corresponding writing electrodes different groups are electrically connected to each other.

Such a printhead can be used in electrostatic printers of the type disclosed in US Pat DE-PS 1 946 815 is described.

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-jC- ? HQ. 77-006

μ 8.6.78

One with most electrostatic

The problem that occurs with printheads is that, on the one hand, the writing electrodes are placed very close to one another ■ Must be a legible font or a tj to get high resolving power, while on the other hand at the point where connections are made between the electrodes and a control circuit, the distance between the connection points large enough must be to avoid short circuits.

US-PS 3,618,118 describes a structure in which this problem has been solved in such a way that the printhead is composed of a number of plates, on which the electrodes with connecting conductors as pressure wiring are appropriate. At the location of the electrodes, the circuit boards are narrow, making the electrodes very small standing close to each other and at the point of the connections they are wide, so that the distance between the connections is quite big. A disadvantage of this solution is that a number of Boards must be put together, the narrow parts must be placed exactly next to each other, and the wide parts lie on top of each other like roof tiles. The exact positioning of the narrow parts is difficult and time consuming and therefore expensive. Also is 'It is necessary for a print head of the type mentioned at the beginning

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that each electrode is connected to a number of other electrodes. This must be the case with the known printhead take place outside the circuit boards, which makes complicated wiring necessary, The invention is based on the object

to create a printhead which has the disadvantages mentioned avoids. The print head according to the invention is for this purpose characterized in that the print head after the Technique of multilayer printed wiring is constructed and consists of a first insulation plate, which is attached to is provided on both sides with conductor tracks each having a first end at one edge of the plate, the one Forms the writing electrode, while the other end has a metallized hole in a second, to the first 'Plate running parallel and thus mechanical

connected insulation plate electrically with an atxf the second plate attached connecting track is connected, which connects a number of electrodes together. With this structure, only a small number of them are required in the manufacture of the multilayer circuit board of masks in a corresponding manner with respect to one another positioned to get all of the electrodes in place. This mask positioning is a tried and tested technique that does not pose any problems

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brings. Because the necessary connections between the electrodes are on the multilayer board itself only needs a relatively small number of conductors via a plug to be connected to the further control circuit.

If necessary, this control circuit can be complete 'or partially on the circuit board.

A preferred embodiment of the invention The printhead, in which the electrode distance is extremely small, is characterized in that the electrodes form two rows, one on each side of the first plate, each electrode of the one Row except the last opposite the middle of the space between two electrodes of the other ■ row lies.

Embodiments according to the invention

are explained in more detail below with reference to the drawing. Show it:

Fig. 1 is a schematic representation of the

p _{O most} essential part of an electrostatic printer for understanding the invention,

2 shows a cross-section through part of a first exemplary embodiment of one according to the invention Printhead,

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Fig. 3 is a schematic representation of the structure of the print head shown in Fig. 2;

FIG. K shows a cross section through part of a second exemplary embodiment of a print head according to the invention, and FIG

Fig. 5 is a schematic representation of the construction of the write head shown in Fig k.,

Fig. 1 shows schematically the printing part

an electrostatic printer in which a print head according to the invention can be used to advantage. The printer 'contains a printhead 1 with writing— electrodes 3 »which work together with counter electrodes 5 to apply punctiform electrostatic charges to a recording medium, which consists of a dielectric layer 7 ″ and a substrate 9, which is a relatively good conductor.

The writing electrodes 3 are distributed in η groups which are each distributed in two subgroups. The subgroups are designated in Fig. 1 with Gr ₁ to Gr ". Each group contains m writing electrodes 3> whose numbers 1 to -gm are accommodated in the first subgroup and whose numbers - ^ - m + 1 to m are accommodated in the second subgroup. The corresponding numbered electrodes of all groups are connected to one another and

PHQ. 77-006 η 8.6.78

can therefore by closing one of the switches

Z. to Z via a selector switch S with a potential of 1 m

-Ud connected ". The position of the selector switch S determines. whether the writing electrodes of the first or those of the second subgroup can be switched on.

There are 2n + 1 counter-electrodes 5j which are each connected to a potential 0 or to a potential + U _{D via one of the switches G to G_}

xs

can be. According to the detailed description in the DE-PS 1 9Λ6 815 are by closing a the switch Z with the appropriate position of the selector switch S the identically numbered writing electrodes 3 all group prepared, after which by flipping two consecutively numbered switches G one of these writing electrodes is selected and a point-like charge image on 'dom recording medium attaches.

Figs. 2 and 3 show the structure of a first

Exemplary embodiment of a print head according to the invention which is suitable for the printer shown in FIG. This printhead contains a first insulation plate 11, those on one side with conductor tracks I3 and on the the other side is provided with conductor tracks I5. With adhesive layers 17 and 19 on each side of the

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First plate 11 a second plate 21 or 23 is attached, which two plates carry connecting tracks 25 and 27 on their side facing away from the first plate. Each of the conductor tracks 13 and 15.besitzt a first end on _a R walls of the plate 11, which forms a writing electrode. 3

This writing electrodes form two rows, in which, as in Fig. 2 can be clearly seen, the writing electrodes _s ιό by the ends of the conductor tracks I3 on one side of the plate 11 formed from the center of the spaces between the Schreibelekt to lie formed by the ends of the conductors I5 on the other side (one of the writing electrodes of each row (the last one) is of course not opposite a gap in the other row).

As a result, the smallest distance between two writing electrodes is greater than it would be if all the writing electrodes were to be used would lie in the same plane, so that a large number of pixels are printed per millimeter 'can without the risk of a short circuit between neighboring electrodes or their conductor tracks. This can be ensured by the later excitation of the writing electrodes in one row than those in the other row that the pixels printed by both rows lie on one line (see US Pat. No. 2,997,361). .

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The distance between the two rows of writing electrodes must be a whole number of times the distance between two rows of dots to be written.

The conductor tracks 15 are connected in a manner customary in the art of multilayer printed wiring via metalized holes · 2 ° - in the second plate 21 to the connecting tracks 27 on this plate (shown in FIG. 3 with dashed lines). In the same way, the conductor tracks 13 are connected to the connecting tracks 25 (indicated by dashed lines) via metallized holes 31 i * ^{1 of} the other second plate 23. The connecting tracks 25 and 27 end on the side of the print head 1 in connections 33 'which can be connected to a control circuit via a plug. This control circuit contains, inter alia, the 'shown in Fig. 1 switches Z to Z and S, which -preferably designed as semiconductor switching elements. The control circuit can also be built up entirely or partially on the plates 21 and 23 as required. · The number of writing electrodes 3 per group

and the number of groups can be very large. Of the. For the sake of clarity, eight writing electrodes per group are indicated in FIG. 1 and only four in FIG. 3. For a real printhead, this number was 6k.

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/ ff

There were 27 groups, making a total of I728 electrodes each with a cross-section of 70 x 70 / do available was. The space between two electrodes on a row was 180 / um, so the distance between two ί pixels was 55 / do and eight pixels per mm were printed. The thickness of the first plate 11 was 60 / µm, so that the smallest distance between two electrodes was 82 / µm.

FIGS. H and 5 show a second exemplary embodiment with a first insulation plate 35 with conductor tracks 37 & h on both sides. A second insulation plate 39 is attached to one side of the first plate 35 with the aid of an adhesive layer 41. On the side facing the first plate 35, this second plate carries connecting tracks 43 (indicated in FIG. 5 with dashed lines). The conductor tracks 37 have first ends located at the edge of the first plate 35, which form writing electrodes 3, while their second ends are connected to the connecting tracks 43 via metallized holes 45. Each conductor track 37 on one side of the plate 35 is opposite a corresponding conductor track on the other side and the metallized holes k-5 go through both the first and the second plate, so that they each have two corresponding conductor tracks with one another

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associate. The lying on the edge of the first plate 35 corresponding ends of two conductive tracks, the writing electrodes 3 form, have according to FIG. H each have a rectangular cross section. Its thickness is, for example, 50 μm and its width 150 μm. Because the thickness of the first plate 35 is also approximately 50 μm, it can be achieved that the charge images applied simultaneously to a recording medium by these two writing electrodes are received after development Form a square pixel of well 150 χ 150 / µm. Since the charge image is always slightly larger than the electrodes, the two charge images flow together to form a whole.

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L e r s e i t e

Claims (2)

PHQ.77-006 B. 6.78 PATENT CLAIMS ; (1,. Electrostatic print head with a number of writing electrodes arranged in at least one row and distributed in groups, with corresponding writing electrodes of different groups being electrically connected to one another, characterized in that the printing head (i) is constructed according to the technique of multilayer printing wiring and consists of a first insulating plate (11, 35), which is provided on both sides with ladder bars (i3 »15j 37), each having a first end at the edge of the plate, which forms a writing electrode (3), while the other end has a metalized one Hole (29, 31j ^ 5) in a second insulation plate (21, 23, 39), which runs parallel to the first plate and is mechanically connected to it, is electrically connected to a connecting track (25, 27jk3 ) attached to the second plate, which is a number of ■ connects electrodes to one another. 2. Print head according to claim 1, characterized in that the electrodes (3) have two rows, one each on each side dex- first plate (11) form, each electrode of one row except the last opposite the center of the space between two electrodes of the other row. 9S23 / 0821 VHQ .. 77-006 9 8.6.78 3 · Print head according to claim 1, characterized in that each of the conductor tracks (37) on one side of the first plate {35) lies opposite a corresponding conductor track (37) ^on the other side of this plate, which two conductor tracks via a metallized hole ( 4fj) are connected to one another in the first plate. 909523/05 ^ 2 1