DE2003816A1 - Process for the refinement of photoelectrophoretic image material particles - Google Patents

Description

Patent attorneys DiPLz-InGvF. Weickmann,

JDiPL, -InG.-HiWEIGEMA-NN, DiPL.-PhYS.DR. K. FlNCKE

. B A-Weickmann, Dipx.-Ghem. B. Huber

8 "MUNICH 86, DEN ■ -...

PO Box 860820

MÖHLSTRASSE 22i CALL NUMBER 48 39 21/22

XEHOX CORPORATION,:.

Roehester, New York 146GJ, V. St. A.

A process for upgrading photo el Ektro phoretiseher Bildstoffteilchen

The main patent V .. (Application P 16 22 376.0-51} relates to a process for the refinement of photoelectrophoretic image material particles, an electrical suffering generated in a suspension of the particles in a non-conductive carrier liquid and exposure to light of limited spectral properties being carried out, see above that there is a migration of particles in the suspension which do not respond to this light, away from the particles which are not or less responsive to this light, and the particles with the desired properties for further use in phdtoeiQktropiiore ^ i ^ ch-en Mapping methods are eliminated. · ■ _.: "" ■ '■ ' ■ '"; ■

Recently, an electrophoretic imaging system has been developed wordeii that color images are able to be produced. at These color images become electrically sensitive particles

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used. The method used is in U.S. Patents 3,383,993, 3,384,565, and 3,384,566 described in more detail. Such imaging systems include Different colored light-absorbing particles in one suspended non-conductive liquid carrier. The suspension is introduced between two electrodes, between where there is a potential difference, and also takes place an image exposure. After these process steps have been carried out, a selective particle migration occurs in an image configuration on. This leaves a visible image on one or both electrodes. Sin x ^ essential component of this system are the suspended particles or particles that have to be electrically light-sensitive and the one Experience change in charge polarity when exposed to activating electromagnetic radiation, by interacting with one of the electrodes. In a monochromatic system, particles become a single one Color used. This creates a monochrome image, which corresponds to a conventional black and white photograph. In a polychromatic system, the images are produced in natural colors as mixtures of particles of two or Several different colors are used, each based on light of a specific wavelength or on light are sensitive to a narrow wavelength range. Particles used in this system must be both highly possess pure colors as well as be highly sensitive to light.

In a subtractive polychromatic system, the particles are selected so that the particles are more different Colors respond to different wavelengths in the visible spectrum according to their absorption bands. It is also important that the particles do not overlap appreciably in their spectral sensitivity curves. In this way there is a color separation and a

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subtractive multicolor imaging possible. In a typical multicolor subtractive system, the particle dispersion should contain cyan particles that are primarily sensitive to red light, magenta particles that are primarily sensitive to green light, and yellow particles that are primarily sensitive to blue light. When these particles are mixed in a carrier liquid, the liquid in question becomes black in appearance. If one or more of the particles is caused to move from one electrode to the other, particles remain which produce a color which corresponds to the color of the light which has hit the dispersion. "For example, a red light exposure causes the cyan particles to migrate. This leaves the magenta particles and the yellow particles that together make up the color red in the final image. In the same way, the colors blue and green are created by adding the yellow and magenta particles. If white light hits the mixture, all particles migrate, and what remains is the color white or a transparent carrier layer. If no exposure occurs, all particles remain. This creates a black image . This is an ideal method of the subtractive color image is in 'the particles fulfill the double function, namely on the one hand, the function as the image dye, and - \ to the other as a photosensitive medium.

There is therefore a desire for a method of recovery the pigments ^ from the used image mixture, which is not required for the respective image produced. In the For monochrome imaging, all that is required is to wash off the unused particles from the system or brush off, then add a suitable amount of carrier liquid and transfer the image suspension thus formed again into the

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System to be introduced. However, the problem is more complicated when pigments of more than one color are used. For example, if a red and a yellow pigment were used and the desired image required more yellow pigments as red pigments, the particles so used will lack yellow pigments. Therefore this Pigments cannot be re-incorporated into the pigment mixture without "balancing out"

'"are introduced. The problem becomes even more complicated, when it is desired to produce images in full natural colors, for the particles of three

ψ different colors can be used. The "mixture of three" which is a mixture of cyan particles, magenta particles and yellow particles,

! is commonly used in multi-color subfractive imaging used. This mixture of three enters the "unbalanced" state, i.e. there is a deficiency in one or multiple colors when imaging has been performed. There is therefore a desire to create a system to provide for the recovery of the particles or particles, so that the mixture of three is easily balanced again can be.

From an economic point of view, it is furthermore, it is desirable to recover the image suspension, since the materials used are often expensive treatment steps be exposed to for the photoelectrophoretisehe Illustration to become usable.

The invention is therefore based on the object “a way to show how color particles or particles from a particle suspension which is suitable for use in electrophoretic imaging. further a way is to be shown how Pigmeatteilcheia from a Liquid suspension can be recovered, eo that

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relatively easy one Bildsagpension be reassembled canoe * Furthermore, ^a: economical photoelektrc- phoretic. To create imaging system.

The task outlined above is based on a Process for the refinement of photoelectrophoretic image particles, in which in a suspension of the particles in a non-conductive carrier liquid generates an electrical EeId and exposure to light of limited spectral properties is carried out so that migration of this light-sensitive particles in the suspension away from the no or less light-sensitive particles, and wherein the particles have the desired properties for further use in photoelectrophoretic A "training process can be singled out, according to patent ... (Application 3? 16 22 37 §.O-51)" according to the invention by the execution following procedural steps solved:

a) The dispersed in a non-conductive carrier liquid, electrically photosensitive particles at least two Suspension containing paints is introduced between at least two electrodes,

b) the suspension is electromagnetic radiation a first spectrum exposed in such a way that on this Radiation sensitive particles adhere to an electrode stay and that the unresponsive particles at the left behind on the other electrode, and

c) the electrodes are separated from one another, the Particles from at least one electrode for the other Use in photoelectric imaging processes.

According to one embodiment of the invention, the particle suspension inserted between at least two electrodes, of; one of which is conductive and the other of which is largely

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isolated. One of the two electrodes is at least partially transparent to an activating electromagnetic one Radiation. A radiation of such a wavelength should be directed through the transparent electrode onto the suspension are released through, to which only the desired particles or particles should respond. Across the suspension an electric field is generated. Those particles that respond to the particular wavelength of the radiation used, migrate to the largely insulating electrode. k The other particles or particles remain on the conductive one ■ Electrode back. These undesirable particles are those particles that have low sensitivity for the wavelength used own. After exposure has taken place, the electrodes can be separated and, furthermore, those to the insulating electrode Migrated particles are removed from this electrode for later use in electrophoretic imaging processes will.

In a preferred embodiment of the invention for the recovery of pigments from a used mixture of three becomes the particle suspension containing cyan particles, magenta particles and yellow particles "inserted between two electrodes, one of which is conductive and the other of which is largely insulating Owns surface. One of the two electrodes is at least partially for activating electromagnetic Radiation transparent. After applying an electric field and corresponding irradiation of the suspension, the desired pigments discharged. For example, cyan-colored particles are mainly sensitive to red light; To remove these particles, the suspension is exposed to light, which has a strong red light spectral component and in which the spectral colors green and blue are weakened are. This will make a hike of the mapenta

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Particles and the coloring of the particles are prevented. this can achieve four den by using a light source, which has a strong red light component, or ', " by using a light source emitting white light in conjunction with a filter that eliminates all and green wavelength range and lets the red light through »The cyan-colored partial

· ""'■■' ■■ - '"■'■■" ■■ - """ί chen or ♦ bar particles .then adhere to the surface of the insulating electrode. The. Magenta-colored particles and the yellow-colored particles are in . in successive steps by exposure to green and blue light. In the event that a highly volatile carrier liquid is used up, it may be desirable to add additional carrier liquid to the suspension after the separation step * ^: "-. ": i ^; ·.

The method according to the invention can be used to generate any suitable, electrically photosensitive particles: zii. separate. Typical electrically photosensitive particles are listed in the ÜS ^ -Pafeentschrift % _ 384 Λ88.

Any suitable insulating liquid can be used as a carrier liquid for the pigment particles in this system. Typical * Träger.erflus.si.gk ^ iten - contain: MiiieralSl, - '. "'_;". Dean, Dodekan, N-tetradekan ^ paraffin, beeswax: Qder. other thermoplastics, keroseneV long-chain saturated. aliLphat
· it - _'.' ".- - ■ --- ■" - '- ^..: -' .. .- ■ - ",. - ■ "";. . "": "■ _; .-'.-. -;

The electric! Field between the "electrodes" has a strength preferably between 300 and 5OOO volts. The excellence of the field depends on the used particles or particles. It can be expedient be positive with respect to the conductive electrode

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To make insulating electrode for one image suspension and negative for another image suspension.

If a conductive, transparent electrode is used, this electrode can be made of any suitable conductive, transparent material. Typical materials include conductive coated glass, such as tin or indium oxide coated glass, aluminum coated glass, and corresponding coatings on plastic substrates or conductive glass. However, conductive coated mylar, a polyester, ψ is preferred because of its strength and transparency.

The insulating surface of the insulating electrode can comprise any suitable material. Typical materials are: Vinyl polymers; Polyolefins such as polyethylene, polypropylene, polyisobutylene; aromatic substances such as polystyrene, polyalkyds, Polyvinyl toluene, polyphenylene oxides, polysulfone, Polyxylylene; Polyacrylics and their esters; Polyhalocarbons such as vinyl and vinylidene chlorides and fluorides; Polyperfluorinate hydrocarbons such as Polytetrafluoroethylene; Polyvinylether; Polyvinyl acetates; Polyvinyl acetate and ι ketals, such as polyvinyl butyral; Phenolic resins; Polyester.j polyetherj Silicone resins; Polycarbonates; Epoxy resin "; Polyamides; ί polyimides; Urethane resins; Polysulfide and Copolymer © UM Mixtures of these. Polytetrafluoroethylene will be on G; round its excellent insulating properties and ability to be cleaned preferred.

^ ₁ , Although different electrode spacings can be selected, spacings of less than 25 »4 microns and even smaller distances at which the electrodes are pressed together represent a particularly useful finding, since in this way better ones

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can be achieved than with larger distances. As a reason for this improvement will be the high field strength in the suspension viewed during the picture.

With reference to drawings, the invention with its inherent features and advantages is explained in more detail below. Fig. 1 schematically illustrates an electrophoretic system which can be used for separation, of pigments and also for the production of images (in known manner). Figure 2 schematically illustrates a continuously operating electrophoretic system which can be used to separate pigments. , '

In Mg. 1 a transparent electrode i is shown which consists of a layer of optically transparent glass 2 on which a coating 3 of optically transparent tin oxide is provided. Such a plate is commercially available under the designation! ESA glass . This electrode is hereinafter referred to as the "injecting electrode". On the surface of the injecting electrode 1 there is a thin layer M- finely distributed, electrically photosensitive cords which are dispersed in a non-conductive carrier liquid. The term "electrically photosensitive" in the present description refers to the properties of a particle which is initially bound to the injecting electrode and which migrates away from this electrode under the influence of an electric field when exposed to activating electromagnetic radiation. A detailed theoretical explanation of the processes occurring can be found in the above-mentioned US patent documents. If this arrangement is used to separate light-sensitive particles, the suspension consists of a mixture of two or more different colored substances in the carrier liquid.

.den suspension 4- there is a second electrode 5j which is referred to below as the "blocking electrode" and which is connected to one pole of a voltage source 6 via a switch 7. The other pole of the voltage source is connected to / indicating electrode 1, so that when the switch 7 is closed in the liquid suspension M- between the electrodes 1 and 5 si ⁿ electrical PeId is generated. A projector consisting of a light source 8 and an element in the form of a see-through image or filter and an objective 10 is provided for exposing the dispersion 4- with light of a desired color or with a light image of an image to be reproduced. If the arrangement is used to separate desired and undesired particles, the element 9 consists of a filter which transmits light of the desired color to expose the suspension 4. If the arrangement is used to produce a multicolor image, the element 9 consists of a naturally colored slide image, for example a Kodachrome slide. In this case, the electrode 5 is in the form of a roller with a conductive core 11 which is connected to the voltage source 6. The core is covered with a layer of barrier electrode material 12, for which baryta paper can be used. The particle suspension is exposed to an image to be reproduced while a voltage is applied to the electrodes by closing the switch 7. The roller 5 is passed over the surface of the injecting roller 1 with the switch 7 closed during exposure. The exposure causes the particles initially bound to the electrode 1 to migrate through the liquid and to adhere to the surface of the barrier electrode, with the particles not responding to the incident light remaining on the injecting electrode. If the arrangement is used to separate differently colored particles, the particles can be one

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specific color either on the injecting electrode 1 or deposited on the barrier electrode 5, whatever of the depends on the light used, as already described became. If the arrangement is used to produce images (in a known manner); so stays on the injecting Electrode 1 is a multicolored one corresponding to the original image Image back while the particles not required for image formation have migrated to the barrier electrode5.

If the arrangement is used to separate different colored particles and has that which impinges on the suspension Light is a color that is absorbed by the desired particles is, the ones on the blocking electrode 5 will be Particles removed and for further use. the multicolored electrophoretic imaging determined. Has the light incident on the suspension. Color by the Particles that are not absorbed; that is how the desired ones remain Particles back on the injecting electrode 1. you will be removed from this and for further use in electrophoresis Image generation determined. In this way the parts can be consecutively other colors than of the color in question are absorbed by the suspension.

The arrangement shown in Fig. 1 enables a good Separation of the particles and thus a production of excellent Pictures. Since this is, however, a sentence procedure and only small amounts of the separated particles can be produced; Be aware of the process of separation on an ongoing basis to execute *

In Fig *. 2 is a continuously operating arrangement for Separation of electrically photosensitive particles shown. The injecting electrode 20 is in the form of a transparent one Cylinder, which may consist of (Jl as and with a thin ^

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transparent tin oxide coating on its outer surface is provided. The barrier electrode rollers 21 and 22 are arranged so that they are on the injecting Unroll electrode 20. They each consist of a conductive core 23 or 24 and a layer 25 or 26 of a barrier electrode material, for example made of baryta paper. For synchronous movement of the injecting Any suitable means may be used for electrode 20 and barrier electrodes 21 and 22. For example, can Synchronous motors or gears may be provided which drive the cylinder 20 and the rollers 25 and 26 at such speeds rotate so that there are no differences in their peripheral speeds. There are also projection devices 27 and 28 provided the light with a desired spectral property to those Project points onto the suspension, at which the blocking electrode 21 and the blocking elecetore 22 are the injecting Touch electrode 20. The projection devices 27 and contain filters with which the spectral properties of the emitted light can be changed. There are also adjustable slit diaphragms 29 and 30 provided »with those the amount of light incident on the suspension can be limited, for which purpose its width is changed. To the blocking electrode rollers 21 and 22 as well as the cylinder 20 of the injecting electrode is the voltage of the voltage source 31 turned on. This is with the conductive cores of the barrier electrode rollers 21 and 22 and with the conductive Surface of the injecting electrode cylinder. O 30 across the wiper 32 and the switch 33 connected, in operation The device creates a uniform layer of separated particles in a non-conductive carrier liquid are dispersed, applied to the surface of the injecting electrode 20 from the reservoir 34 ·. To illustrate

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Establishing the working method of the Einrichtuiig is considered the case, that the container 34 suspends cyan particles " contained in a non-conductive carrier liquid. Reach the cyan-colored parts stand the gap between the roller 21 and cylinder 20, they are exposed to light of a color to which they should not respond. Are the Particles cyan; so this light must be blue and green. Particles with a spectral sensitivity in the blue and green range of light migrate to the surface of the barrier electrode roller 21. Particles that do not have such a sensitivity own, remain on the surface of the injecting Electuode cylinder 20 back. Is the non-conductive one If the carrier liquid evaporates too much, the surface of the injecting electrode 20 can be removed by means of a spray device 35 aries are moistened, creating additional non-conductive Carrier liquid is applied. Reaches the particle suspension the gap between the barrier electrode roller 22 and the injecting electrode cylinder 20, the Suspension exposed to light to which the particles should respond. In the case of cyan-colored particles, * has the light a red color. The particles with the correct sensitivity to light migrate onto the surface of the barrier electrode roll 22. Particles that are either not sensitive or the have insufficient sensitivity, remain on the surface of the injecting electrode cylinder 20. at further rotation of the barrier electrode roller. 22 reach the desired particles the scraper 36., which scrapes them from the surface of the hule 22 so that they get into the container 37. These particles have a total of a © strong light sensitivity and the © rv / desired properties of the sensitivity spectrum. The particles that meanwhile toward the surface of the barrier electrode roller 21 have migrated from this surface with the aid of the 38 discharged and introduced the container 39 in general.

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In a corresponding way, those particles that are relatively insensitive and those on the injecting reach reach Electrode 20 remains, the scraper 40, from which they enter the container 4-1. The ones in containers 39 and 4-1 contained particles can again be added to the device or removed. By using this Systems can produce any desired amount of a mix of different colored Particles are separated.

Of course, if desired, rollers 21 and 22 and cylinder 20 could each one around the rollers Wrapped strap included.

For the purpose of using the system to recover the pigment particles from a used image mixture, the used suspension is introduced into the container 34. If the suspension is introduced into the gap between the roller 21 and the cylinder 20 in which the field is present, the suspension is exposed to radiation specific to the pigment to be removed. In this example, red light is used, which causes the cyan-colored particles to adhere to the roller 21. The cyan particles are then removed by the scraper 38 and introduced into the container 39. The suspension is then exposed to an electric field and exposure to green light, causing the magenta particles to migrate and adhere to the roller 22. Magenta particles are collected in the container 37. The remaining yellow-colored particles are, as shown, removed or electric sorry, and an exposure at a third (not shown) liolle exposed.

An embodiment of the invention will be further explained using the following example. The proportions and percentages given in each case relate to weights _}

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unless otherwise stated. .

The following example is carried out with an arrangement of the general type shown in FIG. 1, in which the particle mixture is applied to the HESA glass plate as a coating, through which the exposure takes place> The NESA glass plate is "- !. with" ■ ". a switch, a voltage source and a conductive core of a roll with a ■" baryta paper cover connected in heat. The ball has a diameter of approx. 6.5 cm. and is at a speed of 4 cm / sec over -the ;: plate surface; emotional. The ν er * _; turned plate has a size ¹ of 7 »5 ^x / N 5 cm; it is measured at approx. 387 lux (corresponding to 3 & ftcd) - on d: he uncoated Η! Ε3Α ^ Ο-ϊ & ^ ρΐΕΪΐ ^ ..- ^ -. ^ · Θ "1;1οΗΐ""β' ¹ ΐ; . All particles mit.einer ^relative: handeis- large particle size, conventional or made type are for hours in a ball mill, to reduce their size and thus the manufacturing ■ provision of a more stable dispersion milled, whereby the Auflösungderendgültigen images is improved in any case. . the Suspensionmifc light of the desired color exposed wozu.das Mcht by appropriate color filter is projected in the, case that © is added in ijösungsmittel is sufficient ^{lJÖsungsmittel;} added, 8 to an approximately 50 * to ■ - thick 76.2 microns. ; Train to form ^{... - .- ■;:} , "-; ■■ '""

■ -. · " ^: - ^; - ^; ..."Example; 1st ^: ; ■ "■ -.

A triple mix is made as follows; About four parts Mönölite Fast Blue; Gß, about _; ; four: file untreated Watchung Hed, E and about four parts N-S'-8 ^ i ^ -dioxodinaphthol-CSji-bjS ^, J; ¹ -d) -furan-6-earboxamid v / earth dispersed in about 100 parts of Sohio Odorless Solvent J4-4O. '".:

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This three-part mix is applied to a NESA backing layer a device of the type shown in Fig. 1 applied. Each suspension comes with a natural color image exposed using a Kodachrome slide placed between the light source and the NESA electrode. After exposure of the suspension, a complete color image was found on the NESA electrode is formed that corresponds to the original image.

^ This creates a series of images. To * the formation of each image will be the ah of the barrier electrode Adhering unused particles are removed and put back into suspension in Sohio Odorless Solvent-Solution 3440. The pigments are then separated and prepared as follows.

. The suspension is applied to the NESA carrier layer as well as being exposed to a field and red light. The cyan pigments adhere to the roller electrode. From this roller electrode these oyan particles are then removed. In addition, Sohio-Odorless solution is applied to the indexing Sprayed an electrode on which two or more pigments are still present. The cleaned roll is then over the image suspension led, which is exposed to the field and green light. The magenta particles adhering to the roller electrode are discharged. Additional Sohio-Odorless solution is sprayed onto the injecting electrode. The cleaned role is then passed over the image suspension again, which is exposed to the field and blue light. That leaves them yellowish particles on the roller electrode which they will then be led away. About four doors of the so Recovered pigments are then added to 100 parts of Sohio-Odorless solution suspended. The image suspension thus formed again is then given in accordance with that given in Example I.

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exposed lieise with a full-color Kodachrome slide. The picture obtained in this way shows one excellent color balance and low deposits unwanted pigments in the background areas.

Although in the "above example" special components and proportions have been given, other suitable substances than those listed above can also be obtained corresponding results .be used. Furthermore other materials can be used in the particles or the particle suspensions be added in order to have a synergistic, improving or otherwise modifying effect on the properties to achieve. Typically, the particles or suspensions can be colored or electrical, if desired be made sensitive.

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Claims (1)

Patent claims ί £ Γ) Process for the refinement of photoelectrophoretic image material particles, where in a suspension of the particles in a non-conductive carrier liquid an electrical Field, generated and. an exposure to light more limited "Spectral properties are made so that a Y / change of particles responding to this light in the suspension of the particles not responding or less responsive to this light, and wherein the Particles with the desired properties for further use in photoelectrophoretic imaging processes be separated out, according to patent ... (application P 16 22 376.0-51) * characterized by the following Procedural steps, a) dispersed in a non-conductive carrier liquid, suspension (4) containing electrically photosensitive particles of at least two colors inserted between at least two electrodes (1,5), b) the suspension (4) is exposed to electromagnetic radiation of a first spectrum in such a way that that particles which are responsive to this radiation stick to an electrode and that those which do not respond Particles remain on the other electrode, and c) the electrodes (1,5) are separated from one another and the particles are carried away by at least one electrode. 2. The method according to claim 1, characterized in that the process steps p), b), c) using a electromagnetic radiation of a second spectrum can be repeated. 009838/1908 5. The method according to claim 2, .. characterized in that the .Verfahren steps a), b) and ή are repeated using electromagnetic radiation of a third spectrum. - '· ■ " 4. The method according to claim 2, characterized in that cyan-colored particles ^ magentaf-arbene -leilchan and yellow color ^ ne {Deilehen are used as pigment particles, that the electromagnetic; e radiation, of the first .. spectrum so. is selected ^: that pigment particles of a first color adhere to an electrode and that the electromagnetic radiation of the second spectrum is selected so that particles of a second color adhere to an electrode. 009838/1908