JPH0471357B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention generally relates to a method for high resolution electrostatic transfer of high density images to non-porous, non-absorbing, electrically conductive image receiving surfaces. More particularly, the present invention relates to a method for forming and transferring a latent image on an electrostatic imaging surface that can be used repeatedly to form high resolution, high density images on printed circuit boards. . [Technology of the Invention] A five-step process is used to create a printed circuit by forming a conductive wiring diagram on an insulating substrate using a dry film resist using photoimaging technology and other techniques. It's normal. Regardless of the method used for tenting or filling, these five steps include applying or laminating a photosensitive dry film resist onto at least one conductive surface of an insulating substrate to create an artwork. Alternatively, the circuit board is developed by using a phototool to expose the dry film resist to actinic light through the transparent portion of the phototool to form a pattern on the dry film resist, and removing the unexposed portions of the negative dry film resist. etching the conductive substrate from the circuit board in all non-image areas not under the desired conductive circuit pattern that are still covered by the dry film resist, and finally etching the conductive substrate from the unetched portions of the conductive substrate. It involves removing or stripping the dry film resist covering the desired circuit pattern from the section. These five steps must be repeated for each circuit board manufactured. Through the exposure steps of a standard dry film process, sufficient actinic radiation exposure levels and exposure times are required to cause the resist to form straight sidewalls as a result of the pattern of polymer cross-linking in the dry film. It is said that These straight sidewalls should be vertical until they reach the conductive surface. However, in the standard negative dry film photoresist printing and etching process, either underexposure forms sidewall edges that cut into the desired resist pattern, or overexposure forms legs on the bottom conductive surface of the resist. forming sidewall edges that increase the width of the dry film resist. Any of these conditions will cause the width of the final conductive pattern to vary from what is desired, exceeding design and fabrication tolerances for line widths in the conductor plane. The development step in this process ideally involves developing an unexposed negative dry film resist to create an edge in the dry film resist whose line width is ideally equal to the pattern on the phototool and perpendicular to the conductor plane. It must be something that can be removed.
However, in reality, either underdevelopment or overdevelopment of the dry film resist occurs. Underdevelopment can cause resist residue to accumulate in sidewall portions or developed grooves, or to slope toward adjacent sidewalls, resulting in adjacent line spacing being smaller than desired. When overdeveloped, the edges of the unexposed film resist are notched and the spacing between adjacent lines becomes larger than desired. In addition to this, some rounding occurs at the top of the resist surface of the sidewall edge. This shortcoming in accurately reproducing phototools with dry film resist affects the resolution of fine lines and reproduction characteristics when reproducing circuit patterns. The increasing complexity of circuit boards and the widespread use of stacking multiple boards has created a need for denser and finer resolution circuit patterns. Resolution was understood to be the ability to reliably create the thinnest lines and gaps between adjacent lines, and to be achieved reliably through the five steps described above. The thinness or smallness of the lines that can withstand development and the spacing or spacing between adjacent lines in a circuit pattern necessitate fine line resolution. The standard for reproduction in the printed circuit board industry is line width and spacing dimensions of approximately 3.1 mils (0.076 mm) or approximately 6.3 lines/
mm is required to be developed. These standards are used to define the desired density of circuit boards. Attempts to apply the xerographic principle to transfer an image from an electrostatic image on a photoconductor to an image receiving surface with high resolution and high density have been difficult. The primary cause of this difficulty is that circuit boards are made of metals such as copper or non-porous or non-absorbent materials such as plastics such as polyester film sold under the trade name Mylar. It arises from the fact that it consists of things. This non-porous, non-absorbent image receiving surface results in the transferred image being distorted or "squashed", especially when attempted with liquid toner. Xerographic technology solved the problem of image transfer to an absorbent receiving surface, such as paper, by transferring the image formed by toner particles across the gap. The gap is either air or a combination of air and liquid. Attempts to apply this gap transfer technique to non-porous substrates resulted in image "squish" and gap spacing and voltage must be carefully adjusted to create a satisfactory transferred toner image with proper resolution and density. If the voltage and gap spacing, or distance between the photoconductor or electrostatic imaging surface and the conductive image receiving surface, are not carefully adjusted, electrical arcing can occur across the gap. This can permanently damage the electrostatic imaging surface, resulting in pinholes in the transferred toner image. This is particularly important in the printing and etching steps used in the manufacture of printed circuit boards. Furthermore, when using a non-porous image-receiving substrate, in order to obtain a high-resolution transferred image, the photoconductor, that is, the electrostatic image-forming surface and the conductive image-receiving surface must be aligned at the transfer position of the toner image. There is one additional problem in electrically transferring a developed image to a non-absorbing substrate such as copper: forming an electrically conductive image receiving surface. The metal or copper surface is not flat as is the electrostatic imaging surface, so the spacing between the electrostatic imaging and conductive image receiving surface is limited by the contact between the uneven photoconductive surface and the conductive image receiving surface. These problems must be solved by applying a conductive, non-absorbing, non-porous receiving surface to create multiple printed circuits with the desired conductive pattern from a single persistent latent image. liquid-
The problem is solved by the method of the present invention which provides a method for transferring a developed image from an electrostatic imaging surface across a liquid gap. The electrostatic imaging surface can be either a photoconductor or a permanent master. SUMMARY OF THE INVENTION One object of the present invention is to achieve direct, non-contact, high-resolution electrostatic transfer of a developed, high-density image onto a non-porous, non-absorbing substrate. The goal is to provide a method for Another object of the invention is to obtain high density images through the use of dry film resist as a permanent and reusable master. Another object of the invention is an electrostatic transfer process in which a photoconductor or permanent master can be utilized as the electrostatic imaging surface. Another object of the invention is to transfer a developed high density image from an electrostatic imaging surface across a liquid-liquid gap to an electrically conductive image receiving surface, where the liquid acts as the transfer medium. be. Another object of the present invention is that the latent image and the transferred image are approximately 3.1
The object of the present invention is to provide a method that makes it possible to resolve line widths and spacings of mils (0.0759 mm). One feature of the invention is the quality of the image density, the thickness or height of the toner particles forming the image, and the liquid layer that acts as a transfer medium in the gap between the electrostatic imaging surface and the conductive image receiving surface. The thickness of the electrostatic imaging surface and the conductive image receiving surface are adjusted by the voltage applied to create an electric field between the electrostatic imaging surface and the conductive image receiving surface, and by the gap spacing. Another feature of the invention is that the conductive backing material or substrate supporting the electrostatic imaging surface is electrically grounded and the conductive image receiving surface is electrically isolated from ground. A further feature of the present invention is that the individual toner particles making up the colored image move through the liquid to the conductive image receiving surface, so that the developed image is electrostatically transferred through the non-conductive dielectric insulating liquid. Direct transfer from an electrically conductive image forming surface to an electrically conductive image receiving surface. Another feature of the invention is that the gap distance between the electrostatic imaging surface and the conductive image receiving surface is between about 1 mil (0.0245 mm) and about 20 mils (0.49 mm).
and this distance is maintained by using a spacer electrically insulated from ground between the two surfaces. A further feature of the present invention is that a conventional photoconductor or permanent master is used to create large quantities of printed circuit boards without the need for dry film or liquid photoresist for each individual circuit board copy. , it can be used as an electrostatic imaging surface. Additionally, one feature of the present invention is that the transfer of the electrostatic latent image to the conductive image receiving surface is accomplished by applying a DC voltage directly to the conductive image receiving surface, rather than by corona discharge. A further feature of the present invention, which uses a photoconductor as an electrostatic imaging surface, is that additional exposures are required to create each additional latent image. An advantage of the method of the present invention is that high resolution transfer of the toner particles making up the developed image is obtained on the electrically conductive image receiving surface without image distortion. Another advantage of the present invention is that the electrostatic imaging surface is not damaged or worn during processing, so that the surface can be subsequently reused. Yet another advantage of the present invention is that high resolution transfer is achieved because there is no contact between the developed toner particles on the electrostatic imaging surface and the conductive image receiving surface. Yet another advantage of the present invention is that it uses a directly applied voltage rather than a corona discharge to ionize the air, thereby reducing power requirements to accomplish electrostatic transfer. A further advantage of the present invention is that it eliminates the repeated exposure and development steps required with dry film or liquid photoresist for each circuit board, resulting in faster and lower cost printed circuit board manufacturing. It is to be done. To first form an image to be developed on the electrostatic imaging surface, develop the image with charged toner particles, and then create an image portion on the conductive image receiving surface, at least a portion of which is non-conductive. The charged toner particles are transferred across a gap filled with a liquid comprising a polar dielectric solvent, while the gap is at least about 1 mil (0.0245 mm) and about 20 mm thick at the transfer location of the toner particles forming the image. These and other objects, features, and advantages are achieved by using a method of forming a toner pattern on a separate, non-absorbing, conductive surface that is maintained between 0.49 mm and 0.3 mm. DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a standard five-step process conventionally used to make printed circuit boards. For each circuit board produced, applying a dry film using heat and pressure to a conductive substrate, such as copper, that is laminated to a non-conductive substrate, such as glass-filled epoxy. was needed on a daily basis. A mask is then placed over the dry film for selective exposure from a light source or other actinic radiation source to form the desired pattern. Development is carried out to leave only the crosslinked dry film with the desired pattern and remove the uncrosslinked dry film. Etching with an acidic etch removes the conductive copper substrate from the crosslinked portions of the dry film. Finally, the dry film is peeled off from the remaining conductive copper substrate to reveal the desired circuit pattern. This is commonly known as the printing and etching method. However, in the method of the present invention, a permanent master is created by using a coating or photosensitive material, such as a dry film or liquid photoresist on a conductive substrate. After that,
No dry film or liquid photoresist is used to create the desired conductive circuit pattern on the product circuit board from this permanent master. This permanent master is used as an electrostatic imaging surface as shown in FIG. The conductive backing plate has a photosensitive material, such as a dry film or liquid photoresist, applied to at least one side thereof. This photosensitive material undergoes a change in resistance upon exposure to actinic radiation due to crosslinking of the polymers in the material. A permanent image is created on this photosensitive material by actinic radiation exposure through a mask or by "writing" the desired pattern with a digital laser pen. Both methods create an electrostatic contrast or difference in resistivity between the image and non-image areas on the photosensitive material. This electrostatic imaging surface is insulated from earth and charged with a corona charging device to create a charged latent image. The electrostatic imaging surface is developed by applying, through surface adsorption, a liquid containing at least a portion of a non-polar dielectric solvent that serves as a carrier liquid for toner particles that are charged oppositely to that of the surface. Ru. This can be done by spraying, dipping or pouring onto the electrostatic imaging surface. Charged toner particles are directed toward the latent image portion of the electrostatic imaging surface to develop the image. When developed, an image corresponding to the pattern of the persistent latent image on the permanent master is produced on the electrostatic imaging surface. This developed image is now ready for transfer to an electrically insulated conductive image receiving surface to create a circuit board with the desired conductive wiring pattern. The conductive image receiving surface is first coated with a liquid consisting at least in part of a non-polar dielectric solvent. The solvent is the same or equivalent to that applied to the electrostatic imaging surface and can be applied by sponge, squeegee, rubber roller, or other means capable of providing a thin, uniform film. The solvent should preferably have a high resistance value and a low viscosity so that the charged toner particles migrate or migrate through the solvent from the charged electrostatic latent image portion on the electrostatic imaging surface to the conductive image receiving surface. be. Solvents are generally _C9 to _C11 or _C9
is a mixture of ~ _C12 branched aliphatic hydrocarbons,
manufactured by Exxon Corporation and sold under the trademarks Isopar G and Isopar H, respectively, or equivalents thereof. The electrical resistivity value is preferably on the order of at least 10 ⁹ ohm cm and the dielectric constant is preferably about 3.5 or less. The use of a non-polar dielectric solvent with these properties ensures that the charged toner particle pattern does not dissipate. In order to form an electric field between the electrostatic image forming surface and the conductive image receiving surface, an electric field of about 200 to about 1200 is applied to the conductive image receiving surface.
After applying a DC voltage of volts, the two surfaces are moved sufficiently close to each other to create a complete liquid transfer medium through contact of the two layers of non-polar dielectric solvent. The first surface of the first layer of non-polar dielectric solvent on the electrostatic imaging surface and the second surface of the second layer of non-polar dielectric solvent on the conductive image-receiving surface are bonded to each other. The gap between the two sides of the lever is filled. The voltage required to create an electric field between the electrostatic imaging surface and the conductive image receiving surface can be from about 200 to about 3500 volts, but preferably from about 200 to about 1500 volts, and optimally is as described above. The ability to transfer high resolution images depends on conditions such as toner, carrier liquid, gap spacing and applied voltage. Generally, larger gap spacings require higher voltages for high quality, high resolution image transfer. This uniform spacing between the gap is maintained using a spacer piece or gap spacer, as seen in FIG. 2, which is electrically insulated from ground. The developed image is transferred from the electrostatic imaging surface to
The toner is transferred across the gap through a liquid medium to a conductive image receiving surface, producing image areas with transferred toner particles and non-image areas without particles in a phototool and similar pattern. Transfer of the developed image across the liquid-filled gap causes the first surface to pass through the electrostatic imaging surface.
This occurs at the transfer location by keeping the conductive image receiving surface parallel to the second surface. The transfer position can be a static or rotating transfer position, although there should be no relative movement between the electrostatic imaging surface and the conductive image receiving surface at the transfer position. A drum or web or a fixed flat surface can be used as the electrostatic imaging surface to transfer the developed image to a fixed or moving flat conductive image receiving surface across the gap. The moving electrically conductive image receiving surface may be a stationary drum or web or other suitable means. The electrostatic imaging surface and the conductive image receiving surface must be held in place at the transfer site, for example by vacuum. Alternatively, both sides can be held in place across the gap by magnetism or static electricity. The gap between the electrostatic imaging surface and the conductive image receiving surface is preferably between at least about 3 mils (0.0735 mm) and about 10 mils (0.245 mm) by using spacer strips of desired thickness. maintained, but high quality images were transferred through gaps as large as approximately 20 mils (0.49mm). By maintaining a gap of about 3 mils or more, any incongruities or irregularities between the two surfaces are sufficiently separated;
Contact between the surfaces and scratches or scratches on the master or electrostatic imaging surface are prevented. The spacer strips or gear spacers are selected from either electrically conductive materials, such as metal, or non-conductive materials, such as polyester film, sold under the trade name Mylar, or cellophane. This spacer must be electrically insulated from ground and must have a uniform thickness. The uniform thickness ensures uniform gap spacing between the electrostatic imaging surface and the conductive image receiving surface. The spacer piece should preferably be placed outside the image area. A non-polar insulating solvent is applied to the electrostatic imaging surface and the conductive image-receiving surface by applying first and second layers of non-polar insulating solvent of sufficient thickness to fill the gap between the two. the first of the first and second layers
and a second liquid surface combine with each other to form a continuous liquid transfer medium between the electrostatic imaging surface and the conductive image receiving surface at the transfer location of the charged toner particles. By passing through a continuous liquid transfer medium, there is no surface tension that the charged toner particles must overcome. This force prevents toner particles from migrating from the electrostatic imaging surface to the conductive image receiving surface. Charged toner particles are moved through the liquid transfer medium created by the combination of two layers of non-polar dielectric solvent at the transfer location by an electric field applied at the transfer location. As illustrated in FIG. 2, charged toner particles having a predetermined charge are transferred individually from a cross-linked, oppositely charged image portion of the photosensitive material on the electrostatic imaging surface to the conductive image receiving surface. or migrate as a group. The conductive image receiving surface is laminated onto an insulating dielectric layer such as fiberglass epoxy.
The applied transfer electric field causes the toner particles to migrate through the non-polar dielectric liquid transfer medium and deposit the toner on the conductive image-receiving surface, revealing image areas with toner particles and non-image areas with no toner. . A photosensitive material, such as dry film or liquid photoresist, on the electrostatic imaging surface acts as a master electrostatic image plate, and the difference in resistance between the image and non-image areas on the electrostatic imaging surface is often relatively constant over a considerable period of time, depending on the photoresist used, allowing large numbers of copies to be made by this electrostatic transfer method. To repeat this procedure, excess non-polar dielectric solvent and excess toner particles on the electrostatic imaging surface should be rinsed off and then removed by physical wiping or squeezing. Any residual charge on the electrostatically imaged area should be removed by charging the photosensitive material surface with an alternating current corona discharge. The desired electrostatic latent image pattern consists of cross-linked image areas of increased resistance for a considerable period of time after the photosensitive material has been exposed to actinic radiation, and areas of the image that are unexposed to actinic radiation and have lower resistance. They are created in photosensitive materials by taking advantage of the material's ability to leave differences in resistance in the form of non-image or background areas that remain intact. Photosensitive materials such as dry film resists are typically composed of polymers that are cross-linked to create image areas that are an order of magnitude more dielectric and electrically resistive than background or unexposed areas. These image areas are the only areas of high resistance that retain a high voltage charge when charged by a DC charging corona, provided the conductive backing is electrically grounded. Non-image or background portions with lower electrical resistance values will very quickly release or leak charge through the grounded backing material. Charged toner particles dispersed in a non-polar dielectric solvent are charged oppositely to these latent image portions, so that the charged toner particles are attracted thereto. This allows the transfer of these charged toner particles across the liquid gap from the electrostatic imaging surface to the conductive image receiving surface as described above. Once a toner image has been formed by the toner particles in the image area on the conductive image receiving surface, the toner particles are fused to the conductive image receiving surface by heating, as shown in FIG. The heat can be applied either by the use of an oven or by application of hot air from an air outlet and is constant enough to reach a temperature at which the binder or polymer that forms the toner particles liquefies and settles in the transferred image. Heat is supplied for a period of time. For example, fusing can be performed at a temperature of about 100° C. to about 180° C. for about 15 to about 20 seconds. The unimaged portions are then etched to create the desired conductive circuit pattern in the form of an unetched conductive image receiving surface covered with toner particles. The etching process uses a solution that does not remove conductive material from the conductive image-receiving surface protected by toner particles, but reacts with and removes conductive material from areas not protected by toner particles. do. The type of etchant used depends somewhat on the conductive material being etched and the type of resist used, so both acidic and fairly alkaline etchants can be used. For example, when the conductive image receiving surface is made of copper, an etchant made of acidic cupric chloride is preferably used. The final step in the electrostatic transfer method for making copies is the stripping step. In this step, the toner particles are rinsed with methylene chloride, acetone, alkaline aqueous solution or a suitable solution.
Appropriately removed or stripped from the image portion. Examples are given below to illustrate the results achieved and without intending to limit the scope of the invention. Examples demonstrate how to obtain a permanent master with a persistent conductive latent image on an electrostatic imaging surface and how gap spacing and voltage levels can be adjusted to achieve good electrostatic image transfer. It will show you if it can be changed. Embodiments also provide that the photoconductor or permanent master is used as an electrostatic imaging surface, in which a dry film or liquid is applied to each conductive image-receiving surface prior to transfer of the developed latent image from the electrostatic imaging surface. It is shown how good electrostatic image transfer can be achieved without the need to apply resist. Example 1 The liquid toner used was made by preparing the following ingredients in the indicated amounts in a high speed disperser:

[Table] -
Each of these components was mixed for 10 minutes at a speed of 8000 rpm, during which time the mixture was maintained at a temperature range of 72° to 109°C. 104.3g lauryl methacrylate and 44.7g
of methyl methacrylate, both available from Rohm and Haas, and 3.0 g of azobisisobutyronitrile, Bazo 64 from Dupont.
606 g of amphipathic graft copolymer system was made by mixing, available as: Next, 108.2 g of Amphipathic copolymer stabilizer was made by the method described below. stirrer,
400g of petroleum ether (bp 90°-120°C) was placed in a reaction flask equipped with a thermometer and a reflux condenser and heated to a gentle reflux under atmospheric pressure. A solution made of 194 g lauryl methacrylate, 6.0 g glycidyl methacrylate, and 3.0 g benzoyl peroxide paste (60% by weight in dioctyl phthalate) was placed in a 250 ml dropping funnel attached to a reflux condenser. This monomer mixture is
It was added dropwise into the refluxing solvent at such a rate that it took 3 hours for the entire volume to be added. Reflux for 40 min at atmospheric pressure after the last monomer is added and 0.5
g of lauryldimethylamine was added and reflux was continued at atmospheric pressure for 1 hour. Then 0.1 g of hydroquinone and 3.0 g of methacrylic acid were added, and reflux was carried out under a nitrogen atmosphere to remove about 52 g of glycidyl groups.
% esterification (approximately 16 hours). The resulting product was a slightly viscous, straw-colored liquid. 345.8g Isopar H, Exxon 108.2
g of Amphipateiq copolymer stabilizer and the above amounts of lauryl methacrylate, methyl methacrylate and azobisisobutyronitrile were added to form 606 grams of Amphipateiq graft copolymer system. This solution was heated under nitrogen atmosphere to approx.
Polymerization was carried out by heating at 158° C. (70° C.) for about 4 to about 20 hours. An additional 606 g of Isopar H was added to the above solution and mixing continued at 8000 rpm for 10 minutes while maintaining the temperature between approximately 72° and 82°C. Finally, 3578 g of Isopar H was added and the mixing speed was reduced to 1000-2000 rpm and mixed for an additional 30 minutes. At this last stage, the temperature of the mixture is
The temperature was maintained between 48° and 60°C. A concentrated liquid toner was then made by mixing the following in an attrition mill:

【table】

[Table] Each of these components is heated at 23℃ to make a concentrated toner.
It was milled at 300 rpm for 3 hours at a temperature of . This concentrated toner is further diluted to a solids content of about 1 to about 2% for use in electrostatic imaging. A cadmium sulfide photoconductor (typically of the NP process type) overcoated with a Mylar polyester film layer is corona charged and then subjected to approx.
The circuit pattern was exposed to light at an intensity of 0.75 to about 2.70 microjoules/cm ² . A developed latent image was developed by applying liquid toner to the overcoated cadmium sulfide photoconductor or electrostatic imaging surface. The electrostatic imaging surface of the photoconductor is mounted on an inner aluminum substrate drum. This drum is removed from the copier. The high voltage power supply has its ground conductor connected to the interior of the drum and its positive conductor connected to the copper side of the conductive image receiving surface. Cellophane spacer pieces or gear spacers were used between the drum and the conductive surface. A liquid containing a non-polar insulating solvent is applied to the conductive surface by squeezing it onto the surface. The electrostatic image forming surface of the drum is coated during the development process. A DC current of 1000 volts was applied between the two and the gap was set at 10 mils (0.245 mm). The cadmium sulfide drum was rotated by hand across the spacer piece to form a transfer location of the latent image from the electrostatic imaging surface to the copper of the conductive image receiving surface.
The transferred image was a good result with an image having excellent resolution and good density. Example 2 The cadmium sulfide photoconductor drum of Example 1 was cleaned, dried, and reimaged as in Example 1. A liquid transfer medium was applied to the electrically conductive image receiving surface. A DC voltage of 500 volts was applied with the same gap spacing set in Example 1. Although the image transfer was good, the amount of transferred toner particles forming the transferred image was less than that in Example 1 and was very bright over the entire image area. This indicates that the applied voltage is insufficient to transfer most toner particles through a 10 mil (0.245 mm) gap. Example 3 The same process and liquid transfer medium used in Example 2 was repeated. The conductive image receiving surface was wetted with liquid transfer medium by applying it to the surface with a squeegee. Spacer piece is 3 mil (0.0735mm)
A voltage of 1000 volts was used with a uniform 3 mil spacing between the surfaces. A high resolution with good density was obtained, but some blank areas were visible in the image. The image was uniform and clear. Example 4 The same process and liquid transfer medium as in Example 3 was used, but with three
To set a mil (0.0735 mm) gap, a 3 mil thick gear spacer was used. A 200 volt DC current was applied to create an electric field. A very clear, high resolution image was transferred from the electrostatic imaging surface to the conductive image receiving surface, with good reflective image density. However, the density of the pad areas and line patterns was somewhat less than that achieved in Example 3. This is apparently because not all toner particles were transferred. Example 5 The same process and liquid transfer medium used in Example 2 was used, but the liquid was squeezed. 1 mil (0.0245 mm) between the electrostatic imaging surface and the conductive image receiving surface.
A 1 mil thick gap spacer was used to set the gap (mm). A DC of 1000 volts was applied to generate an electric field. The transferred image had good image density, but had many hollow spots due to arc discharge. There is also some image distortion, apparently due to the two surfaces being too close together, and also as a result of "squashing" of the toner particles. The use of something like a vacuum holding system that holds the receiving substrate firmly and flat will reduce image distortion. Most of the transferred images were undistorted. Example 6 A 4×5 inch (10×
A 12.5 cm) electrically conductive substrate was chosen as the conductive substrate to create the electrostatic imaging surface of the permanent master. The copper substrate was checked to see if it needed degreasing. If this is necessary, the substrate can be cleaned, such as with methyl chloride, methylene chloride, or trichloroethylene, to ensure good adhesion of the photoresist to the clean surface in the subsequent lamination step. No cleaning was necessary in this example. DuPont Liston as a photosensitive material
215 dry film photoresist was laminated to the substrate. This lamination was performed using a Western Magnum XRL-360 laminator manufactured by Dynachem. Lamination is approximately 220〓(105
Approximately 6 feet (183 cm) per minute at a roll temperature of
was carried out at a speed of Polyethylene terephthalate (hereinafter referred to as PET) approximately 1 mil (0.0245 mm) thick
A top protective layer of film was held over the dry film photoresist of the copper/Liston 215 laminate. The laminate was exposed to actinic radiation through a negative phototool using an Optic Beam 5050 exposure system manufactured by Optical Radiation. This exposure was carried out following the lamination step and after the laminate had cooled to room temperature. Exposure level is about 250
It takes about 60 seconds in millijoules. The phototool used was a 1.0 cycle/mm or 1.0 tool/piece sold by Photographic Sciences.
The microcopy test target was a T-10 resolution test chart with line groups varying from mm to 18 cycles/mm or 18 lines/mm. The exposed electrostatic imaging surface is then cooled at room temperature for about 30 minutes, thereby completing crosslinking in the dry film. The protective layer of PET film is removed. The copper substrate is grounded, the electrostatic imaging surface is corona charged, and the image area receives a positive charge. After a period of about 1 second or more to allow discharge of the background areas, the charged persistent image is then electrostatically developed using the liquid toner of Example 1. Excess toner particles were rinsed from the permanent master developed with Isopar H solvent without drying the toner. The developed permanent image on the electrostatic master is now ready for transfer to a conductive image receiving surface. The electrostatic master thus made is typically placed flat on a flat work surface. Mylar polyester spacer strips are placed along a pair of parallel opposing edges of the master outside the developed image area.
It was placed approximately 10 mils (0.245mm) thick. The flexible, conductive image surface, made of a 1 mil (0.0245 mm) thick Kapton polyimide insulation layer laminated with 0.5 oz (14.18 g) copper foil, is wrapped around a 1.5 in. (3.68 cm) diameter drum, with both ends was fixed with tape. The receiving surface was moistened with a layer of Isopar H solvent by dipping the cylinder. The receiving surface can also be painted by pouring a liquid onto it. A voltage of approximately 1000 volts is set to create an electric field across a 10 mil (0.245 mm) gap.
The conductive image receiving surface of the copper foil is positively charged in relation to the master conductive copper substrate for use with negatively charged toner particles. This 1.5 inch (3.68 cm) diameter drum, with a fixed conductive image receiving surface, is rolled over spacer pieces at each end of the master. As the roller passes over the master, toner particles are transferred from the master to the conductive image receiving surface at individual transfer locations.
The transferred image showed excellent resolution up to approximately 3.6 lines/mm. This is considered to be as if 100% of the toner particles were transferred to the conductive image receiving surface. The conductive image receiving surface is then exposed to the air for approximately 30 seconds until the non-image area, which constitutes the background area, dries. The non-image areas should be dry, but the image areas are kept moist so that the polymers in the toner particles can be solvated in the solvent and do not come out of the image areas. An air knife can also be used to dry the non-image areas. The transferred image on the conductive image receiving surface is then fused by placing it in an oven for about 30 seconds. The temperature of the furnace was approximately 180°C before the door was opened. This fusing is accomplished through a temperature gradient that is effectively created because the temperature within the furnace decreases when the furnace door is opened to place the conductive image receiving surface therein. The temperature of the furnace gradually increases again after the door is closed to a temperature level of 180℃. Example 7 The permanent master of Example 6 was wiped and dried. The same liquid toner and charging method as in Example 6 was used to electrostatographically develop the charged permanent image. The developed electrostatic master was placed on a common flat work surface and Mylar polyester spacer strips were used as in Example 6 to create a thickness of approximately 15 mils (0.368 mm). A flexible copper foil conductive image surface is attached to an approximately 1.5 inch (3.68 cm) drum;
It was moistened as described in Example 6. A potential of approximately 1000 volts was set as in Example 6 to generate an electric field. The 1.5 inch diameter drum was rolled over spacer strips at each end of the master to transfer the toner particles to the conductive image receiving surface. The transferred image showed excellent resolution of approximately 5.0 lines/mm with very little distortion. This is considered to be as if 70 to 80% of the toner particles were transferred to the conductive image receiving surface. The transferred image was then dried and fused as in Example 6. Example 8 The permanent master of Example 6 was wiped and dried. The same liquid toner and charging method as in Example 6 was used to electrostatographically develop the charged permanent image. The developed electrostatic master was placed on a common flat work surface and Mylar polyester spacer strips were used as in Example 6 to create a thickness of approximately 20 mils (0.49 mm). A flexible copper foil conductive image surface is attached to an approximately 1.5 inch (3.68 cm) drum;
It was moistened as described in Example 6. To generate an electric field, about 1000
Volt potential was set. The 1.5 inch diameter drum was rolled over spacer pieces at each end of the mask to transfer the toner particles to the conductive image receiving surface. The transferred image showed excellent resolution up to 4.0 lines/mm with slight distortion. This is considered to be as if 50 to 60% of the toner particles were transferred to the conductive image receiving surface. The transferred image was then dried and fused as in Example 6. Example 9 The permanent master of Example 6 was wiped and dried. The same liquid toner and charging method as in Example 6 was used to develop the charged permanent image electrostatographically. The developed electrostatic master was placed on a common flat work surface and Mylar polyester spacer strips were used as in Example 6 to create a thickness of approximately 25 mils (0.61 mm). A flexible copper foil conductive image surface is attached to an approximately 1.5 inch (3.68 cm) drum;
It was moistened as described in Example 6. To generate an electric field, about 1500
Volt potential was set. This 1.5 inch (3.68 cm) diameter drum was rolled over spacer strips at each end of the master to transfer the toner particles to the conductive image receiving surface. The transferred images were distorted and inconsistent.
This is considered to be as if 30 to 40% of the toner particles were transferred to the conductive image receiving surface. The transferred image was then dried and fused as in Example 6. Example 10 The permanent master of Example 6 was wiped and dried. The same liquid toner and charging method as in Example 6 was used to develop the charged permanent image electrostatographically. The developed electrostatic master was placed on a common flat work surface and Mylar polyester spacer strips were used as in Example 6 to create a thickness of about 5 mils (0.123 mm). A flexible copper foil conductive image surface is attached to an approximately 1.5 inch (3.68 cm) drum;
It was moistened as described in Example 6. To generate an electric field, about 800
Volt potential was set. The 1.5 inch diameter drum was rolled over spacer strips at each end of the master to transfer the toner particles to the conductive image receiving surface. The transferred image has a matching image pattern and approximately 5.6 lines/mm
It showed excellent resolution up to. This is as if
It is believed that about 50% of the toner particles were transferred to the conductive image receiving surface. The transferred image was then dried and fused as in Example 6. While preferred methods incorporating the principles of the invention have been shown and described, it is to be understood that the invention is not limited to the methods or specific details so shown, and in fact may vary widely. These means and methods may be used in carrying out the invention in its broader aspects. For example, the electric field established between an electrostatic imaging surface and a conductive image receiving surface for transfer may be positive or It can be charged to either negative polarity. Charged toner particles of negative polarity will be attracted to the positively charged conductive image receiving surface or will be repelled by the negative back charge of the electrostatic imaging surface. If positively charged toners are used, they will be attracted to the negatively charged conductive image receiving surface and repelled by the positive back charge of the electrostatic imaging surface. Non-polar dielectric solvents can be equally used, as long as mineral spirits have high resistance and low viscosity. A web-to-web arrangement may also be used to maintain gap spacing, which would also maintain the electrostatic imaging surface and the conductive image receiving surface at a predetermined distance. The electric field can be set up in a variety of ways. For example, in a conductive receiving surface such as a copper laminate, or where a dielectric material such as Mylar polyester film is backed by a conductive surface, the electric field is generated by direct charging. In the case of a dielectric receiving surface such as Mylar polyester film, conventional corona charging or roller charging methods can be used from either the front or the back. The electrostatic imaging surface can be a photoconductor such as a cadmium sulfide mylar polyester film or a polystyrene or polyethylene overcoat, a selenium photoconductor surface, or a suitable organic photoconductor such as carbazole and carbazole derivatives, polyvinyl carbazole and anthracene. You can use your body etc. When the electrostatic imaging surface uses a persistent latent image as a permanent master, the electrostatic imaging surface may be a zinc oxide or organic photoconductor, dry powder, etc., which is developed by a toner fused onto the master. It may be a film or liquid photoresist. The type of photosensitive material applied to the conductive backing to form the permanent master can vary as long as it is permanently imageable and provides suitable electrical resistance. For example, when a dry film resist is used, the film is water-based,
It can be semi-aqueous or solvent-based. A photoconductive insulating film of zinc oxide dispersed in a resin binder can also be used. The methods disclosed herein are described in the context of fabricating printed circuit boards. However, the method of transferring an electrostatic image from a permanent master is
It can equally be used for applications such as label creation, high-speed document reproduction and photochemical manipulation or shredding. The claims are intended to cover all obvious changes in details, materials, and formulation figures that would occur to one skilled in the art upon reading this disclosure.

[Brief explanation of the drawing]

FIG. 1 illustrates a conventional printing and etching process for making printed circuit boards. FIG. 2 shows that charged toner particles migrate across a liquid-filled gap from a master to a conductive image receiving surface to create multiple copies of a desired conductive circuit pattern on an insulating dielectric layer.
1 illustrates the process of the present invention using a reusable permanent master.

Claims (1)

[Scope of Claims] 1 (a) A charged electrostatic latent image portion is formed on the electrostatic image forming surface; (b) At least a portion of the latent image portion of the electrostatic image forming surface is non-polar. (c) applying charged toner particles suspended in a liquid comprising an insulating solvent to develop the electrostatic latent image portion to form a first liquid layer having a first liquid surface; (d) forming an electric field between the conductive image-receiving surface and the electrostatic imaging surface; (e) a gap is maintained between the conductive image receiving surface and the electrostatic imaging surface and the first liquid surface is in contact with the second liquid surface to form a liquid transfer medium in the gap; (f) transferring a developed image from the electrostatic imaging surface through a liquid to the conductive image receiving surface at a transfer location so that the toner particles are transferred; (g) During transfer of the developed image, the gap between the electrostatic imaging surface and the conductive image receiving surface at the transfer location is at least about 1 mil ( 0.0245 mm) and approximately 20 mils (0.49 mm); and (h) fusing the transferred toner particle image to the conductive image receiving surface. How to form a toner pattern on top. 2. Maintaining a gap between the electrostatic image receiving surface and the conductive image receiving surface at the transfer location between at least about 3 mils (0.0735 mm) and about 10 mils (0.245 mm). the method of. 3. The method of claim 1, wherein the electrostatic imaging surface is maintained parallel to the conductive image receiving surface at the transfer position. 4. The method according to claim 3, wherein the conductive image receiving surface is held fixed at the transfer position. 5. The method of claim 4, wherein the conductive image receiving surface is held flat at the transfer location. 6. The method of claim 3, wherein the conductive image receiving surface is held stationary at the transfer position. 7. The method of claim 6, wherein the electrostatic imaging surface is fixed at the transfer position. 8. The method according to claim 6, wherein the electrostatic image forming surface is held at the transfer position so that the electrostatic image forming surface and the conductive image receiving surface do not move relative to each other at the transfer position. 9. The method according to claim 3, wherein the conductive image receiving surface is moved. 10. The method of claim 9, wherein the electrostatic imaging surface is fixed at the transfer location. 11. The method of claim 4, wherein a vacuum is used to hold the conductive image receiving surface in place. 12. The method of claim 3, wherein a vacuum is used to hold the electrostatic imaging surface in place. 13. The method of claim 4, wherein the conductive image receiving surface is held in place magnetically. 14. The method of claim 3, wherein the electrostatic imaging surface is held in place magnetically. 15. The method of claim 4, wherein the conductive image receiving surface is held in place electrostatically. 16. The method of claim 3, wherein the electrostatic imaging surface is held in place electrostatically. 17. The method according to claim 1, wherein the transferred toner particle image is fused by heat. 18. The method of claim 1, wherein the transferred toner particle image is fused in an oven. 19 Claim 1, in which the transferred toner particle image is fused by exposing it to air from an air outlet.
The method described in section. 20 A charge opposite the polarity of the charged toner particles is imparted to the conductive image receiving surface to direct the charged toner particles passing through the liquid and across the gap from the electrostatic imaging surface to the conductive image receiving surface. The method described in section. 21. A method of applying a backside charge to the electrostatic imaging surface of the same polarity as the polarity of the charged toner particles to direct charged toner particles passing through the liquid and across the gap from the electrostatic imaging surface to the conductive image receiving surface. The method described in Scope 1. 22 The electrostatic image forming surface is made of selenium, cadmium sulfide,
The method of claim 1, wherein the photoconductor is formed in a photoconductor selected from the group consisting of cadmium sulfide coated on mylar and an organic photoconductor. 23 forming a persistent latent image on the electrostatic imaging surface;
A method according to claim 1. 24. The method of claim 23, wherein a persistent latent image is formed in an electrostatic imaging surface selected from the group consisting of dry film photoresists, liquid photoresists, zinc oxide, and organic photoconductors. 25. The method of claim 1, wherein a voltage of about 200 to about 3500 volts is applied to the conductive image receiving surface to create an electric field. 26. The method of claim 1, wherein a voltage of about 200 to about 1500 volts is applied to the conductive image receiving surface to create an electric field. 27. The method of claim 1, wherein a voltage of about 200 to about 1200 volts is applied to the conductive image receiving surface to create an electric field. 28 (a) forming a charged electrostatic latent image portion on the electrostatic imaging surface; (b) dispersing the latent image portion of the electrostatic imaging surface in a liquid consisting at least in part of a non-polar insulating solvent; developing the electrostatic latent image portion to form a first liquid layer having a first liquid surface; (c) at least a portion of the non-polar insulating surface on the conductive image receiving surface; applying a liquid comprising a solvent to form a second liquid layer having a second liquid surface; (d) forming an electric field between the electrically conductive image receiving surface and the electrostatic imaging surface; to the electrostatic imaging surface such that a gap is maintained between the image receiving surface and the electrostatic imaging surface and the first liquid surface contacts the second liquid surface to form a liquid transfer medium in the gap. (f) transferring the developed image from the electrostatic imaging surface through a liquid to the conductive image receiving surface at a transfer location so that the toner particles are separated from the transferred image portion and the toner particles; (g) during transfer of the developed image, maintain a gap between the electrostatic imaging surface and the conductive image receiving surface at the transfer location of at least about 1 mil (0.0245 mm) and about 20 mm; (h) fusing the transferred toner particle image to the conductive image-receiving surface; (i) etching the non-image portions of the conductive image-receiving surface onto the conductive laminate; forming a pattern on the non-absorbent conductive image receiving surface, comprising the steps of: removing the conductive image receiving surface from the non-image portion of the image receiving surface; and (j) removing toner particles from the image portion of the conductive image receiving surface; Method.