Fine-pitch electrode, process for producing the same, and fine-pitch electrode unit

A fine pitch electrode is provided in which fine electrode lines are disposed at even intervals and with high precision, and which has improved productivity and quality. The fine-pitch electrode 11 comprises a plurality of fine electrode lines 12, each of which is coated around its periphery with a coating film which is made of an electrical insulator, and a sealing member 19 in which a plurality of the fine electrode lines 12 are disposed on a plane and which is molded so as to incorporate the fine electrode lines 12.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to fine-pitch electrodes and processes for
 producing them, and to fine-pitch electrode units. In particular, the
 present invention relates to fine-pitch electrodes having a structure in
 which fine electrode lines are disposed in a manner that the end surfaces
 thereof are aligned with a fine pitch interval and that the end surfaces
 are disposed on a common plane, and in which electricity can be carried to
 the fine electrode lines individually.
 2. Background Art
 High-speed printing systems have recently been developed in which, under a
 computerized control, an ink film is formed on a rotatable drum, which is
 made of metallic members, using an electrically conductive ink, then a
 pattern of characters or the like is formed by causing electricity to run
 through the ink so as to make the ink coagulate (solidify) to form ink
 dots, and thereafter the pattern of ink dots is transferred onto a
 predetermined sheet of paper. An example of the high-speed printing system
 is shown in FIGS. 15 and 16.
 The high-speed printing system shown in FIGS. 15 and 16 is a direct
 printing system (electronic image formation system), which does not
 require a printing block. This high-speed printing system has the
 advantage that clear and uniform printouts can always be printed
 regardless of the number of printouts.
 According to the printing system of this technique, when the ink is made to
 coagulate (solidify) to form each ink dot d on the rotatable drum 201 by
 causing electricity to run through the ink, the ink is solidified by
 making it coagulate to form each ink dot d by the application of
 instantaneous current between the fine-pitch electrode 101 provided over
 the rotatable drum 201 and the metallic rotatable drum 201, and thereafter
 only the solidified pattern is allowed to remain by scraping off the ink
 portion which has not coagulated since no electricity runs through this
 portion (image revealing), whereby high-speed image transfer to a
 predetermined sheet of paper is possible.
 In this case, adjacent ink dots d overlap or make contact with each other.
 On the other hand, when there are blank spaces between ink dots d, fine
 spaces must be formed between the ink dots d for printing fine characters.
 Accordingly, as the fine-pitch electrode 101 which causes the electric
 coagulation (solidification), one comprising electrode lines 101a having
 diameters and intervals of micrometer levels is often employed.
 FIGS. 14A to 14D show a conventional example of the above-described
 fine-pitch electrode and a process for producing it. In this example, a
 copper wire 103 having a diameter of 20 to 200 .mu.m, for example, is
 wound spirally (at a pitch of 30 to 300 .mu.m) around an acrylic core rod
 104 as shown in FIG. 14A. Then, in a position as shown in FIG. 14B, this
 is immersed in a liquid acrylic resin 105, and the liquid acrylic resin
 105 is cured. Then, this is cut along the central dotted line shown in
 FIG. 14C, and the portion which is shaded in the figure is removed so as
 to obtain a fine-pitch electrode 101 shown in FIG. 14D.
 However, such a fine-pitch electrode 101 is disadvantageous in that when
 the ink used in the above-described printing system is solidified,. the
 solvent of the ink evaporates onto the fine-pitch electrode 101 and
 dissolves the acrylic resin thereof. In addition, since the electrode
 lines 101a protrude to a large extent, the pitch of the electrode lines
 101a is subject to change, which causes displacement of ink dots and
 results in a large degradation of the precision in image formation.
 Moreover, when the fine-pitch electrodes 101 are connected to external
 circuits or the like, each electrode must be properly positioned before
 they are connected.
 SUMMARY OF THE INVENTION
 The present invention was devised in view of the disadvantages of the
 conventional examples. An object of the present invention is to provide:
 fine-pitch electrodes in which fine electrode lines are set at even
 intervals and with high precision, and the productivity and quality of
 which are improved; processes for producing the fine-pitch electrodes; and
 fine-pitch electrode units.
 In order to achieve the above objects, the fine-pitch electrode of the
 present invention comprises:
 a plurality of linear fine electrode lines, each of which is coated around
 its periphery with a coating film, with an approximately uniform
 thickness, which is made of an electrical insulator; and
 a molding member in which a plurality of the fine electrode lines are
 disposed on a plane and which is molded into a plate, for example, so as
 to incorporate the fine electrode lines.
 Here, by setting the diameter of the coating film of each fine electrode
 line to be almost the same as the pitch intervals of the fine electrode
 lines, highly precise and even distances between the fine electrode lines
 can be provided.
 In addition, according to the above-described fine-pitch electrode, by
 simply disposing the fine electrode lines having the coating films with no
 space between them, the fine electrode lines can be set at even intervals
 and with high precision, without necessitating any skill.
 Another fine-pitch electrode of the present invention comprises:
 an electrically insulating substrate such as a glass substrate;
 fine electrode lines each of which comprises a fine electrode film and a
 laminate electrode film, wherein the fine electrode films are strips of
 electrically conductive thin films having a predetermined thickness and
 are disposed on the substrate at predetermined intervals, and the laminate
 electrode films are electrically conductive members with which the fine
 electrode films are laminated;
 an electrical insulator which fills the spaces between the fine electrode
 lines; and
 a sealing member with which the substrate is laminated and the entirety of
 the upper surfaces of both electrical insulators and the fine electrode
 lines is covered.
 Such fine-pitch electrodes make an automated production process therefor
 practicable as will be explained below, and not only uniformity of quality
 and improvement in precision are expected, but fine-pitch electrodes of
 high quality can be produced in large quantities at a low cost.
 A process for producing a fine-pitch electrode according to the present
 invention comprises:
 a thin film formation step in which an electrically conductive thin film
 base is formed on a substrate using a material with good electrical
 conductivity such as copper;
 a step of forming a mask made of a resist film having openings at
 predetermined intervals, whereby a plurality of recesses are formed, each
 of which is defined by the inside surface of the opening and the upper
 surface of the electrically conductive thin film base;
 a plating layer formation step in which a plating layer comprising a
 metallic material is formed by plating on the electrically conductive thin
 film base at the bottom of each recess by filling up the recess;
 a resist film removal step in which the resist film is removed after the
 plating layer formation step;
 a thin film partial removal step, in which after the resist film removal
 step the electrically conductive thin film is removed leaving the
 electrically conductive thin film portions under the plating layers, so as
 to form a plurality of fine electrode lines each of which comprises the
 plating layer and the electrically conductive thin film portion;
 an insulating material application step in which an electrically insulating
 material is applied between a plurality of the fine electrode lines; and
 a fine electrode line sealing-in step in which, after completion of or at
 the same time as the insulating material application step, an electrically
 insulating sealing member is molded to cover the entirety of the fine
 electrode lines except for the surface of one longitudinal end at the tip
 and a part of the other end portion of each fine electrode line, so as to
 seal in the fine electrode lines.
 Such a process for producing a fine-pitch electrode makes it possible to
 automate each production step. In addition, according to this process for
 producing a fine-pitch electrode, uniformity of quality can be maintained,
 and increase in productivity is expected.
 The above-described step of forming a mask may comprise:
 a resist application step in which a resist is applied with a predetermined
 thickness to the electrically conductive thin film base; and
 an exposure-development step in which an image is developed by exposing the
 resist to light through a photomask in the shape of a grating having lines
 which have predetermined widths and which are disposed at predetermined
 intervals, whereby a resist film having a plurality of openings each of
 which has a width corresponding to the width of a fine electrode line is
 formed.
 Another process for producing a fine-pitch electrode according to the
 present invention comprises:
 a thin film formation step in which an electrically conductive thin film
 base is formed on a substrate using an electrically conductive material;
 an insulating layer formation step in which an electrically insulating
 layer having a predetermined thickness is formed on the electrically
 conductive thin film base;
 an excision step in which some portions of the electrically insulating
 layer are excised using a cutting means through a mask member in the shape
 of a grating having lines which have predetermined widths and which are
 disposed at predetermined intervals, so as to form a plurality of
 recesses, each of which is defined by the inside surface of each excised
 portion and the upper surface of the electrically conductive thin film
 base;
 a plating layer formation step in which a plating layer comprising a
 metallic material is formed by plating on the electrically conductive thin
 film base at the bottom of each recess by filling up the recess;
 an insulating layer removal step in which the electrically insulating layer
 is removed after the plating layer formation step;
 a thin film partial removal step, in which after the insulating layer
 removal step the electrically conductive thin film is removed leaving the
 electrically conductive thin film portions under the plating layers, so as
 to form a plurality of fine electrode lines each of which comprises the
 plating layer and the electrically conductive thin film portion;
 a second insulating layer formation step in which second electrically
 insulating layers are formed between a plurality of the fine electrode
 lines; and
 a fine electrode line sealing-in step in which, after completion of or at
 the same time as the second insulating layer formation step, an
 electrically insulating sealing member is molded to cover the entirety of
 the fine electrode lines except for the surface of one end at the tip and
 a part of the other end portion of each fine electrode line, so as to seal
 in the fine electrode lines.
 A fine-pitch electrode unit according to the present invention comprises:
 a printed circuit board;
 a fine-pitch electrode which is provided at an end of the printed circuit
 board, and which has a plurality of fine electrode lines, the end surfaces
 of which are uncovered and aligned;
 connectors which are provided on the printed circuit board, and which
 receive external driving currents for the fine electrode lines; and
 printed wiring which electrically connects the fine electrode lines and the
 connectors in an individually operable manner;
 wherein the fine-pitch electrode comprises:
 fine electrode lines each of which comprises a fine electrode film and a
 laminate electrode film, wherein the fine electrode films are strips of
 electrically conductive thin films having a predetermined thickness and
 are disposed on the printed circuit board at predetermined intervals, and
 the laminate electrode films are electrically conductive members with
 which the fine electrode films are laminated; and
 a sealing member with which the printed circuit board is laminated so as to
 fill the spaces between the fine electrode lines and cover the entirety of
 the fine electrode lines.
 In the above fine electrode unit, each fine electrode line may have the
 cross-sectional shape of a rectangle or a polygon.
 Here, the above fine-pitch electrode unit may also comprise:
 an electrode driving circuit, such as an LSI, which is provided on the
 printed circuit board, and which drives the fine electrode lines in
 response to external driving commands; and
 connectors which are provided on the printed circuit board, and which
 receive the external driving commands.
 Accordingly, this fine-pitch electrode unit has the functions and effects
 of the above-described fine-pitch electrode unit. In addition, this
 fine-pitch electrode unit does not require an operation of connecting the
 fine-pitch electrode and the printed circuit board, and thus the
 operability during maintenance or the like of the electrode driving
 circuit (signal processing circuit) or the like such as an LSI can be
 improved.
 With the fine-pitch electrode according to the present invention, since
 each fine electrode line is provided with a coating film, the coating
 films function effectively in that the fine electrode lines can be set at
 even intervals and with high precision by simply disposing the fine
 electrode lines with no space between them, without necessitating any
 skill. Because of this structure, the productivity, the quality, and the
 durability of the fine-pitch electrode can be greatly improved.
 According to the process for producing a fine-pitch electrode, since the
 fine electrode lines are formed step by step and consecutively by such
 techniques as sputtering on the electrical insulator such as a glass
 substrate, exposure-development of resist layer, plating, ion etching, and
 the like, and since the electrically insulating material is applied
 between the fine electrode lines and seals in the entirety of the fine
 electrode lines, the fine-pitch electrodes can be produced automatically
 and continuously. At the same time, the fine electrode lines in the
 fine-pitch electrode can be formed to have arbitrary widths and mutual
 distances. Furthermore, the fine electrode lines can be formed with
 uniformity and improved precision of the widths and mutual distances
 thereof. Accordingly, fine-pitch electrodes of good quality can be
 mass-produced at a low cost.
 Furthermore, the fine pitch electrode unit according to the present
 invention eliminates the necessity of an operation in which electrode
 lines are positioned one by one while connecting the fine-pitch electrode
 and the printed circuit board, or the necessity of the connecting
 operation itself. Accordingly, the fine pitch electrode unit according to
 the present invention provides significant effects which conventional
 units do not provide in that operability during maintenance or the like is
 improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A fine electrode line according to the present invention may have the
 cross-sectional shape of a quadrangle (square, rectangular) or any other
 kind of polygon. A coating film on the fine electrode line may preferably
 be formed from a highly rigid electrical insulator such as glass or
 ceramic.
 Before or after any step in the process for producing a fine-pitch
 electrode, an end surface aligning step may be added in which the end
 surfaces of the above-described fine electrode lines are aligned on a
 common plane.
 The fine electrode film cited above may be formed from a metal with good
 electrical conductivity such as copper. A laminate electrode film may
 comprise an electrically conductive component, such as Ni, Fe--Ni, and
 Fe--Ni--Cr, as a material. Alternatively, a laminate electrode film may
 comprise an electrically conductive component, such as Cu, Ag, Ni, and Au,
 as a material, and at the same time, a rigid film comprising a rigid
 component such as Fe--Ni--Cr may be provided on the surface of the tip of
 the fine electrode line comprising the laminate electrode film and the
 fine electrode film.
 The thin film partial removal step in the process for producing a
 fine-pitch electrode can be implemented by ion etching or acid cleaning. A
 glass member composed of materials which are almost the same as those in
 the substrate may be used for the electrically insulating sealing member
 which is used when sealing in the fine electrode lines. Prior to the
 insulating material application step or the fine electrode line sealing-in
 step, an end surface rigid film formation step may be added in which the
 end surface at the tip of each fine electrode line is provided with a
 rigid film comprising a material which is more rigid than the fine
 electrode lines and which is a good electrical conductor. Alternatively,
 prior to the insulating material application step or the fine electrode
 line sealing-in step, an end surface film formation step may be added in
 which the end surface at the tip of each fine electrode line is provided
 with an end surface film comprising a material which is more thermally
 conductive than the fine electrode lines. Furthermore, alternatively,
 prior to the insulating material application step or the fine electrode
 line sealing-in step, an end surface film formation step may be added in
 which the end surface at the tip of each fine electrode line is provided
 with an end surface film comprising a material which has a melting point
 higher than that of the fine electrode lines.
 Embodiments
 Embodiments of the present invention will be explained below making
 reference to drawings.
 First Embodiment
 According to the first embodiment, a fine-pitch electrode 11 is produced by
 employing a sputtering technique, a plating technique, glass sealing
 technique, and the like. An example of the first embodiment is shown in
 FIG. 1. A procedure for producing the fine-pitch electrode is shown in
 FIGS. 2 to 4, 5A, 5B, 6, 7, 8A, 8B, 9A, and 9B.
 In FIG. 1, the fine-pitch electrode 11 comprises: a glass substrate 13;
 fine electrode lines 12 each of which comprises a fine electrode film 15
 and a laminate electrode film 17, wherein the fine electrode films 15 are
 strips of electrically conductive thin films having a predetermined
 thickness and are disposed on the glass substrate 13 at predetermined
 intervals (for example, 30 to 300 .mu.m), and the laminate electrode films
 17 are electrically conductive members with which the fine electrode films
 15 are laminated; and a sealing member 19 with which the glass substrate
 13 is laminated and the entirety of the fine electrode lines 12 is covered
 and the spaces between the fine electrode lines 12 are filled. This
 fine-pitch electrode 11 is for use with the above-explained direct
 printing system (electronic image formation system) as a conventional
 example as shown in FIG. 16, and comprises a predetermined (plural) number
 of poles. Here, the glass substrate 13 may be replaced by a substrate made
 of another type of electrically insulating material such as a ceramic.
 These materials do not dissolve in a solvent contained in the ink, and
 thus the pitch of the fine electrode films 15 is not subject to change.
 The above-described fine electrode films 15 can be formed of a metal with
 good electrical conductivity such as copper. In this embodiment, the fine
 electrode films 15 are formed to have a thickness of 2000 angstroms (0.2
 .mu.m) by a sputtering technique as explained below. Accordingly,
 lamination with the electrode films 17 and adhesion of the same become
 possible by a plating method, and an excellent laminate electrode films 17
 can be obtained.
 The laminate electrode films 17 may comprise an electrically conductive
 component, such as Ni, Fe--Ni, and Fe--Ni--Cr, as a material.
 Next, a process for producing the fine-pitch electrode 11 of the first
 embodiment will be explained, making reference to FIGS. 2 to 4, 5A, SB, 6,
 7, 8A, 8B, 9A, and 9B. FIGS. 2 to 4, 5A, 6, 7, 8A, and 9A are views from
 the side of the surface to face a rotatable drum used in a direct printing
 system (end surface). FIGS. 5B, 8B, and 9B are diagonal views
 corresponding to FIGS. 5A, 8A, and 9A, respectively.
 As shown in FIGS. 2 to 4, 5A, 5B, 6, 7, 8A, 8B, 9A, and 9B, the fine-pitch
 electrode 11 is formed via a thin film formation step (FIG. 2), a resist
 application step (FIG. 3), an exposure-development step (FIG. 4), a
 plating layer formation step (FIGS. 5A, 5B), a resist film removal step
 (FIG. 6), an electrode film base removal step (thin film partial removal
 step) (FIG. 7), an insulating material application step (FIGS. 8A and 8B),
 and s fine electrode line sealing-in step (FIGS. 9A and 9B).
 The thin film formation step (cf. FIG. 2) is a step in which an
 electrically conductive thin film is formed from a material with good
 electrical conductivity such as copper (Cu) on the glass substrate 13 so
 as to serve as the fine electrode film base 15. The resist application
 step (cf. FIG. 3) is a step in which a resist is applied to the fine
 electrode film base 15 to form a resist layer 16 having a predetermined
 thickness.
 In the thin film formation step, as shown in FIG. 2, the fine electrode
 film base (underlayer) 15 having a predetermined thickness (for example,
 2000 angstroms (0.2 .mu.m)) as described above is formed on the glass
 substrate 13 according to a sputtering technique using copper as a
 material. The thickness of the resist layer 16 according to the resist
 application step (cf. FIG. 3) is adjusted to 20 to 100 .mu.m. Instead of
 copper, Fe--Ni--Cr, Au, Ag, or the like may also be used.
 The thickness of the resist layer 16 is adjusted in advance to be the same
 as the desired thickness of the laminate electrode film 17 to be formed
 by, for example, Fe--Ni plating. That is to say, the height of the fine
 electrode lines 12 are determined by the thickness of this resist layer
 16.
 After completion of the resist application step (cf. FIG. 3), the
 exposure-development step (cf. FIG. 4) follows. In this
 exposure-development step, an image is developed by exposing the resist
 layer 16 to light through a photomask (not shown in the drawings) in the
 shape of a grating having lines which have widths predetermined in advance
 and which are disposed at intervals predetermined in advance, whereby a
 resist film having a plurality of openings each of which has a width
 corresponding to the width of a fine electrode line 12 is formed. The
 inside surfaces (which are almost perpendicular to the upper surface of
 the substrate) of the openings and the upper surface of the fine electrode
 film base 15 define a plurality of recesses 15b. The exposure-development
 step may also be implemented by excising the opening portions with a
 cutter from an electrically insulating layer which is formed in place of
 the above resist layer. For example, a plurality of the recesses are
 formed by irradiating the electrically insulating layer with a laser to
 burn through it. Alternatively, the recesses 15b may be formed by an
 etching technique.
 For the openings, an example is shown in which the inside surfaces are
 perpendicular to the upper surface of the substrate and in which the
 cross-section of each opening is in the shape of a square or a rectangle.
 However, by properly selecting the type of resist, inside surfaces forming
 slopes are obtainable. In this case, the cross-section will be
 trapezoidal.
 After completion of this exposure-development step (cf. FIG. 4), the
 plating layer formation step follows (FIG. 5). In this plating layer
 formation step, a plating layer comprising a metallic material (for
 example, an electrically conductive material such as Ni, Fe--Ni, and
 Fe--Ni--Cr) is formed, so as to serve as the laminate electrode film 17,
 on the fine electrode film base 15 at the bottom of each recess 15b, which
 is uncovered by the exposure-development step, by filling up each recess
 15b with the metallic material. The plating layers extend from the end
 surfaces facing the drum in a direction perpendicular to the surface of
 the drum. The pitch of the plating layers may be arbitrarily selected.
 Accordingly, the pitch may be easily adjusted for connectors to connect
 with an external circuit.
 After completion of this plating layer formation step (cf. FIGS. 5A and
 5B), the resist film removal step (cf. FIG. 6) follows.
 The electrode film base removal step (thin film partial removal step) (cf.
 FIG. 7) follows, in which a portion of the fine electrode film base 15,
 which was on the bottom of the resist film, is removed.
 Accordingly, a plurality of fine electrode lines 12, corresponding to a
 desired number of poles, are exposed. Here, the electrode film base
 removal step (thin film partial removal step) (cf. FIG. 7) may be
 implemented by an ion etching technique or, alternatively, silicic acid
 cleaning. According to this step, the fine electrode lines 12 are
 electrically separated from each other.
 Subsequently, the insulating material application step (cf. FIGS. 8A and
 8B) and fine electrode line sealing-in step (cf. FIGS. 9A and 9B) are
 carried out step by step.
 The insulating material application step is a step in which a predetermined
 electrically insulating material 21 (for example, a glass material which
 is of the same type as the sealing member) is applied in the spaces
 between the fine electrode lines 12 while the plating layers (laminate
 electrodes films 17) are masked, whereby the above-described recesses 15b
 are filled. Instead of the masking, a liquid or powder may be applied to
 the front surfaces of the plating layers.
 The fine electrode line sealing-in step (cf. FIGS. 9A and 9B) is a step in
 which, after completion of the insulating material application step, an
 electrically insulating sealing member (for example, a glass material or
 the like) is molded to cover the entirety of the fine electrode lines 12
 except for the surface of one end at the tip and a part of the other end
 portion of each fine electrode line 12, so as to seal in the fine
 electrode lines 12. The surface of one end and the other end portion are
 uncovered (exposed) even after the sealing-in step. Namely, the one end is
 exposed to face the electrically conductive drum 22, whereby electricity
 can be carried to the electrically conductive drum 22 through the exposed
 surface. Reference numeral 19 indicates a sealing member formed from a
 material which is the same as the material of the above-described
 substrate 13.
 In the first embodiment, since the fine electrode lines 12 are formed step
 by step and consecutively by such techniques as sputtering on an
 electrical insulator such as a glass substrate, exposure-development of a
 resist layer, plating, ion etching, and the like, the fine-pitch
 electrodes can be produced automatically and continuously. At the same
 time, the fine electrode lines 12 in the fine-pitch electrode 11 can be
 formed to have arbitrary widths and mutual distances. Furthermore, the
 fine electrode lines 12 can be formed with uniformity and improved
 precision of the widths and pitch thereof. Accordingly, fine-pitch
 electrodes 11 of good quality can be mass-produced at a low cost.
 Second Embodiment
 Next, a second embodiment will be explained making reference to FIGS. 10
 and 11.
 The second embodiment is characterized in that a part of each fine
 electrode line 12 is formed of a metal with good electrical conductivity
 such as copper (Cu), silver (Ag), gold (Au), nickel (Ni), or an alloy of
 some of these metals, and in that a rigid film 12B comprising, as a
 material, a rigid component with good electrical conductivity may be
 provided on the surface of an end at the tip of each fine electrode line
 12 (the surface facing the surface of the metallic drum 22 in the vicinity
 thereof).
 Here, a material such as Fe--Ni--Cr, Fe--Ni, and the like is used in the
 rigid film 12B in this embodiment. However, any other material may also be
 used, as long as it functions in a manner similar to the above materials.
 Alternatively, any other film which functions as the rigid film in a
 manner similar to the rigid film may also be formed. In order to have a
 film function in a manner similar to the rigid film, the characteristics
 of 1) a high thermal conductivity, 2) a high melting point, or 3) a low
 electrical resistance may be imparted to the electrode lines, so as to
 inhibit deterioration of the electrode lines due to the heat generated by
 the electrical resistance when electricity is running.
 The end surface rigid film formation step for forming this rigid film 12B
 is incorporated into the process for forming a fine-pitch electrode
 according to the first embodiment prior to the insulating material
 application step (cf. FIGS. 8A and 8B) or the fine electrode line
 sealing-in step (cf. 9A and 9B). The end surfaces of the fine electrode
 lines may be immersed into a bath of Fe--Ni--Cr or Fe--Ni plating solution
 so as to plate only the end surfaces. Furthermore, subsequently, the
 plated end surfaces may be ground for smoothness.
 The other part of the structure is the same as the above-described first
 embodiment.
 The above structure also results in the same functions and effects as those
 according to the first embodiment. In addition, since the fine electrode
 lines 12 portion is formed of a metal with good electrical conductivity,
 such as copper (Cu), silver (Ag), gold (Au), nickel (Ni), and the like,
 the fine electrode lines 12 have low electrical resistance, and thus
 generation of heat can be effectively avoided. Because of this, as well as
 the enhanced abrasion resistance imparted by the rigid film 12B which is
 provided on the surface of the end at the tip of each fine electrode line
 12, the second embodiment is advantageous in that durability can be
 enhanced.
 Third Embodiment
 Next, a third embodiment will be explained making reference to FIGS. 12A,
 12B, and 12C.
 The third embodiment is characterized in that a fine-pitch electrode 30A,
 which is equivalent to the fine-pitch electrode 11 in the first or second
 embodiment, is integrated with a printed circuit board 31 by directly
 forming the fine-pitch electrode 30A at an end of the printed circuit
 board 31.
 In FIGS. 12A, 12B, and 12C, reference numeral 30 indicates a fine-pitch
 electrode unit. Reference numeral 35 indicates a driver provided outside
 the fine-pitch electrode unit 30. The fine-pitch electrode unit 30
 comprises: a printed circuit board 31; a fine-pitch electrode 30A which is
 provided at an end of the printed circuit board 31, and which has a
 plurality of fine electrode lines 12, the end surfaces of which are
 uncovered and aligned on a common plane; connecting terminals 33 which
 serve as connectors which are provided on the printed circuit board 31,
 and which receive external driving currents for the fine electrode lines
 12 from the external driver 35; and printed wiring 33 which electrically
 connects the fine electrode lines 12 and the connecting terminals 33 in an
 individually operable manner.
 Here, as the fine-pitch electrode 30A, one constructed in a manner
 equivalent to the construction of the fine-pitch electrode 11 in FIG. 1
 can be used as described above. Specifically, the fine-pitch electrode 30A
 can be constructed by, for example, laying fine electrode lines 12 between
 a glass layer which is a constituent of the printed circuit board 31 and
 another glass layer 36, applying the above-described production process of
 the first embodiment.
 Accordingly, the third embodiment exhibits the same functions and effects
 as those of the first embodiment. In addition, the necessity of an
 operation for connecting the fine-pitch electrode 30A and the printed
 circuit board 31 is eliminated, and thus the third embodiment is
 advantageous in that the operability during maintenance or the like is
 improved.
 In addition, the trouble of connecting the fine electrode lines 12 and the
 printed wiring 33 one by one can be saved by preparing the mask in such a
 manner that the widths and the pitch of the fine electrode lines 12
 correspond to those of the printed wiring 33 in the vicinity of the
 connections between the fine electrode lines 12 and the printed wiring 33
 which electrically connects the fine electrode lines 12 and the connecting
 terminals 32 as connectors which receive driving currents from the
 external driver 35.
 Fourth Embodiment
 Next, a fourth embodiment will be explained making reference to FIGS. 13A
 and 13B. The fourth embodiment shown in FIGS. 13A and 13B is characterized
 in that a fine-pitch electrode 11 as in the first embodiment is integrated
 by directly forming it at an end of a printed circuit board 41, which is
 equipped with a signal processing circuit (electrode driving circuit) or
 the like.
 In FIGS. 13A and 13B, reference numeral 40 indicates a fine-pitch electrode
 unit. Reference numeral 45 indicates a driver provided outside the
 fine-pitch electrode unit 40. The fine-pitch electrode unit 40 comprises:
 a printed circuit board 41; a fine-pitch electrode 40A which is provided
 at an end of the printed circuit board 41, and which has a plurality of
 fine electrode lines 12, the end surfaces of which are uncovered and
 aligned on a common plane; an electrode driving circuit 42, such as an
 LSI, which is provided on the printed circuit board 41, and which drives
 the fine electrode lines 12 in response to external driving commands from
 an external driver 45; connectors 43 which are provided on the printed
 circuit board 41, and which receive the external driving commands for the
 electrode driving circuit 42 from the external driver 45; and printed
 wiring 44 which electrically connects the fine electrode lines 12, the
 electrode driving circuit 42, and the connectors 43 in an individually
 operable manner.
 Here, as the fine-pitch electrode 40A, one constructed in a manner
 equivalent to the construction of the fine-pitch electrode 11 in FIG. 1
 can be used.
 Accordingly, the fourth embodiment exhibits the same functions and effects
 as those of the first and third embodiments. In addition, the necessity
 for an operation of connecting the fine-pitch electrode 40A and the
 printed circuit board 41 is eliminated, and thus the fourth embodiment is
 advantageous in that the operability during maintenance or the like of
 electrode driving circuit 42, in particular, or the like is improved.
 It is noted that although each embodiment is explained with regard to a
 fine-pitch electrode which is used to equip a direct printing system
 (electronic image formation system), the present invention, as it is, is
 applicable to a fine-pitch electrode, having the same functions, which is
 used to equip an electronic apparatus other than the direct printing
 system.
 Although the invention has been described in detail herein with reference
 to its preferred embodiments and certain described alternatives, it is to
 be understood that this description is by way of example only, and it is
 not to be construed in a limiting sense. It is further understood that
 numerous changes in the details of the embodiments of the invention, and
 additional embodiments of the invention, will be apparent to, and may be
 made by, persons of ordinary skill in the art with reference to this
 description. It is contemplated that all such changes and additional
 embodiments are within the spirit and true scope of the invention as
 claimed.