DE2119743A1 - Photoelectrophoretic imaging process - Google Patents

Description

Photoelectrophoretic imaging process

The invention relates to a photoelectrophoretic imaging method, at dew. a suspension of photosensitive particles located between two electrodes is exposed to an electric field and an image-wise distributed activating electromagnetic radiation.

By US patents 3,384,565 and 3,384,566 an electrophoretic Abt-ildungsverfahren is known to be produced by the single color or multicolor images using electrically photosensitive particles Wunen, this case colored, light-absorbing particles are suspended in a non-conductive carrier liquid. The suspension is located between swsi electrodes, to which a voltage is connected, and is irradiated with an image. When these steps are carried out, a selective particle migration takes place in an image-wise distribution, as a result of which a visible image results on one or both electrodes. An essential part of the process are the suspended particles, which must be electrically sensitive to light and evidently experience a change in their self-charge polarity when exposed to activating electromagnetic radiation through interaction with one of the electrodes. A single color process uses particles of a single color corresponding to the

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ühüehen Sohwsrs-WsiB-Fotografie create a monochrome picture. In a multicolored process, the images are created in natural colors, as they are hybrids of particles of two more different colors are used, each only for the light of a certain wavelength or one are sensitive to the narrow wave length band »

For a single-color process, swarm © pigment substances are preferably used, so that a black-and-white BiM results. However, you want to eat many cases also produce different colored images - such as in the production Ύαη posters or Schilderne Several different pigment material _t which .good images can be generated, are beschrieben® in the above-mentioned starting Pateatsohrifteii. Often a pigment material swar favorable Farfe @ igens © fea £ ₉ th has Is not lichtempfissdlieh ausreisend and requires in imaging an excessively long exposure ₀ Icy Pigment substances do not produce images with a predetermined contrast or tint desired density. At the Melsrfsi ^ TbenMldergeugpgs he . der oft cyanf ar Dene _f galbe Oiiel magentafai? ⁷ ö © n © v © r Teilofeea% f © 2idet be, ice pigment material may be less sensitive than the other, wodyrsh © iae na'si-srgetr-aia © FarbreproduktioE substantially laehs ¹ od®F. s © Sim @ rig or also lanmSglieh is there is therefore a need for © in image processing, which allows the image creation of the image production process to be as cheap as possible «

The task dmw Irfiadiaag fa®st, ®t & t, daria, © la tisches AbMlä52agsverfa3a5r © a έμ s @ liaff © a _s that the indicated la © lit © ile ¥ @ s? Aeid @ t tmd © ine change of the li © ate sensitivity © it of the respective ¥ @ ^? © adet @ n PigESütstoffe bsi the single-colored mud d © i »multicolored image generation enabled In particular, the Tömsagsdi ^ M? ® wjioL the contrast releaseSiaften the fotoelectr © p! I © retis © fe © ii Bileld-s ^{51 can be} changed

A procedure de? einasgis naimten kind is to solve this Task according to the invention designed such that one with a photoconductive layer provided, for the radiation at least

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partially permeable electrode is used, iarch the through the radiation exposure takes place.

With the method according to the invention, the density and the The contrast properties of the images produced and the sensitivity of the pigments to light can be changed. Hereinafter will now be an embodiment of the invention with reference to the figures described. Show it:

Fig. 1 shows a simple arrangement for carrying out the invention according to the invention Procedure and

FIG. 2 shows a graphical representation of the image tone density as a function of the irradiation time in the case of the invention Procedure.

In Fig. 1, a transparent electrode 1 is shown, which in the embodiment described here consists of an optical transparent glass plate 2 and a thin, optically transparent layer 3 made of tin oxide applied thereon such material is commercially available under the name NESA glass. This electrode is also referred to below as the "Injecting Electrode". The surface of this Injecting electrode 1 is provided with a photoconductive layer 13. If the layer 13 is very thin, so it can the surface of the injecting electrode 1 can be applied by physical rubbing. Should a thicker layer 13 be used any suitable binder, for example a thermoplastic resin, can be used for bonding to the surface 3 in order to avoid dispersion in the subsequently applied carrier liquid.

A thin layer 4 of finely divided photosensitive particles, which are dispersed in a non-conductive carrier liquid, is applied to the layer 13. The term "photosensitive ^11" is intended to refer in the following to the properties of a particle which, after initially binding to

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the photoconductive and injecting electrode migrates therefrom under the influence of an applied electric field upon exposure to electromagnetic radiation to which it is sensitive. A detailed theoretical explanation of the functions on which this process is based can be found in US Patents 3,384,565 and 3,384,566 is connected via a switch 7. The other pole of the voltage source 6 is connected to the injecting electrode * 1, so that when the switch 7 is closed, an electric field is generated on the suspension 4 and the layer 13 between the electrodes 1 and 5. A Image projector with a light source 8, a transparent image 9 and an optical system 10 is used to irradiate the dispersion 4 with a light image of the original image 9, which is to be reproduced is connected to the voltage source 6. The core is coated with a layer of a barrier electrode material 12, for this purpose b For example, Tedlar or another dielectric material can be used. The pigment suspension is irradiated with the image to be reproduced, while a voltage is connected to the blocking electrode and the injecting electrode by closing the switch 7. The roller 5 is moved over the surface of the injecting electrode 1 with the switch 7 closed and exposed to radiation. This irradiation causes the irradiated pigment particles, which were initially bound to the electrode 1, to migrate through the carrier liquid and then adhere to the surface of the barrier electrode, so that a pigment image remains on the surface of the layer 13, which is a duplicate of the original image 9 is. The particles adhering to the surface of the barrier electrode 5 can be removed, and the image forming steps are repeated if necessary. By cleaning the barrier electrode and repeating the irradiation, the color purity and color balance can be improved. After the image generation, the relatively evaporates

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volatile carrier liquid, so that a pigment image remains remain. The image can be transferred to a receiving sheet, for example a sheet of paper, for which purpose one of the known methods can be used",

Layer 13 can contain any photoconductive material which the properties of the pigment suspension and the can change images created with it «

The imaging properties of an by using a photoconductive composition on the injecting electrode influenceable pigment suspension are shown in Fig. 2 * The curve shown shows the dependence of the image tone density on the exposure time. The maximum and the minimum Tint densities are denoted by Dmax and Dmin. The slope of the curve shows the image contrast or the gamma value. The photographic sensitivity is in the direction of the exposure axis measured to any point on the lower curve of the curve indicated by the dashed line. at With the right choice, the photoconductor on the injecting electrode can have the values Dmax and Dmin, gamma, sensitivity and that Change the sensitivity spectrum. A photoconductor that has a higher resistance than the pigment in the image suspension, causes a substantial increase in the Dmax value and also affects the Dmin value to some extent. A more conductive composition reduces the values Dmax and Dmin. A more sensitive composition increases photosensitivity, while a relatively insensitive composition which reduces photosensitivity. The photoconductor generally increases the sensitivity of the pigment of the image suspension in the spectral range in which it absorbs. A magenta photoconductor absorbs for example mainly in the green area of the spectrum, so it increases the green sensitivity of the image substance suspension.

For a naturally colored image, cyan, magenta and yellow pigment particles are used, each of which is sensitive to light of a certain wavelength band. For multicolor subtractive imaging, cyan

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Particles are used which mainly absorb red light and are sensitive to it, furthermore yellow particles which mainly absorb and are sensitive to blue light, as well as rodent-colored particles that mainly absorb green light and are sensitive to it.

The use of a photoconductive layer on the injecting Electrode allows a change in color sensitivity by increasing or decreasing the sensitivity of a particular one Pigment substance. For example, if the images on the injector have too little magenta remaining Creates a pigment that gives the picture a reddish tone j a photoconductor is used that absorbs green light, so that the sensitivity of the magenta pigment increases will,

The injecting electrode can be coated with any suitable photoconductor. The choice of composition for a specific use depends on the desired effect and the spectral as well as electrical properties of the Pigment. For monochrome imaging, photoconductive ones are used Layers with a more panchromatic behavior are preferred. For multi-colored imaging, photoconductive ones are used Layers with a limited range of sensitivity are used. Any suitable photoconductor can be used. Typical Photoconductors are: Inorganic substances such as selenium, zinc oxide? Zinc sulfide, Cadmium sulfide, cadmium sulfoselenide and mixtures thereof Fabrics.

Typical organic photoconductors are substances such as polyvinyl carbazole, alone or sensitized with trinitrofluorenone. Preferred fabrics for multicolor imaging are highly pigmented fabrics with a relatively narrow range of photosensitivity. Typical such substances are: Algol Yellow GC, 1,2,5,6-di (C ₁ C ¹ -diphenyl-thiazolanthraquinone, CINo. 67300, available from General Dye Stuffs; N-2 "-pyridyl-8,13-dioxodinaphtho - (i, 2-2 ^l, 3 ^I) furan-6-carboxamide; calcium Litho Red, the

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Calcium dye of i - ^ - azo-naphthalene-i'-sulfonic acid) -2-naphthol, CI No. 15630 available from Collway Coilers; Cyan Blue GTNF, the beta form of copper phthalocyanine, CIIJo. 74160 available from Collway Colors; Diane Blue, 3, 3 ^1- methoxy-4,4 ^I -diphenyl-bis- (1 "-azo-2 ⁿ -hydroxy-3" -naphthalenide), CINo. 21180 available from Harmon Colors; 2,4-Di- (1 »-Anthraquinonyl-amino) -6- (1 ⁿ -pyrenyl) -triazine Duol Carmine, the calcium dye of 1- (4 ^I -methylazobenzene-2 ^I -sulfonic-acid) -2-hydroxy -3-naphthenic _{acid, CI 0} No.15850, available from EI duPont de Nemours, Inc .; Indanthrene Brilliant Orange RK, 4,10-dibromo-6,12-anthanthrone, CINo. 59300, available from General Dye Stuffs; Indofast Brilliant Scarlet toner 3,4,9,10-bis / "ΐϊ, ϊί ¹ - (p-methoxy-phenyl) -imido_7-perylene, CINo 71140, available from Harmon Colors; N-3". (1 ^{H, 2! L} »^ ⁿ -triazole) -8,13-dioxodinaphtho- (2,1-b; 2 * _f 3 ^I -d) -furan-6-carboxamidj Indofast Violet Lake, Dichlor-gjie-isoviolanthron, CI No.6001O available from Harmon Colors; Indofast Yellow Toner, Flavanthron, CI. No ₀ 70600 available from Harmon Colors; 2- (4 ¹ -carboxyphenylazo) -4-isop ^I o po-xy-1- naphthol; 1-cyano-2,3- (3'-nitro) -phthaloyl-7,8-benzopyrrocoline; Locarno Red X-1686, 1- (4 ^l -methyl-5 ^t -chlorobenzene-2 ^l -sulfonic acid) -2-hydroxy-3-naphthenic acid, CI. IJo. 15865 available from American Cyanamide; Methyl Violet, a phosphorus tungsten molybdenum ^{dye of 4- (N, N I} > N ^I -trimethylanilino) -methylene-N ¹ , l! I ^I -dimethylaniline chloride, CINo. 42535 available from Collway Collors; Naphthol Red B, 1 - ^ «- Ilethoxy-S ¹ -nitrophenylazo) -2-hydroxy-3" -nitro-3-naphthaiilide, CINo.12355, available from Collway Colors; Monolite Fast Blue GS, a mixture of the alpha- and beta-form metal-free phthalocyanine, available from Arnold Hoffman Co .; Permagen Red L Toner 51-500, 1- (4 ¹ Me-OIyI-S ¹ -chlorazobenzene-2 * -sulfonic acid) -2-hydroxy-3-naphthenic acid, C ₀ I. No.15865, available from Collway Colors; Vulcan Fast Red BBE Toner 35-2201, 3,3 * -dimethoxy-4,4'-biphenyl-bis {1 ° -phenyl-3 "-methy1-4 ⁿ -azo-2 "-pyrazolin-5 ^ll -one), CI. No.21200, available from Collway Colors; Quindo Magenta RV-6803, a substituted quinocridone available from Harmon Colors; Watehung Red B, 1- (4'- Methyl-5'-chlorazobenzene ~ 2 ^f -sulfonic acid) -2-hydroxy-3-naphthenic acid, CI. No. 15865, available from EI duPont de Nemours; and 8,13-dioxodinaphtho- (1,2-b; 2 * , 3 ^I -d) -furan-6-carbox-4 ^ll -methoxyanilide,

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The layer of photosensitive material on top of the injecting Electrode can be up to 1 micron thick. The thicker layers can contain a binder, for example Polyvinyl, polystyrene, epoxy resins, phenolic resins, silicone resins, urethanes and mixtures and copolymers of these Fabrics. However, the best results are achieved with very thin layers ,, layers with an optical density of about 0.05 have excellent properties and are therefore preferably used. Layers of this thickness do not require any Binder. They are simply rubbed off by rubbing their composition onto the surface of the injecting electrode applied and create a layer that is created by the suspension of the light-sensitive pigment substances and their carrier liquid is not disturbed.

Image suspensions that are suitable for the method according to the invention are described, for example, in US Pat. No. 3,384,488.

The following examples serve for further specific explanation of the method of the invention in terms of modifying the photoelectrophoretic imaging properties by using a photoconductive layer on the injecting electrode, proportions and percentages based on weight, unless otherwise stated »The following examples represent some preferred embodiments of the method according to the invention.

All of the following examples are carried out with an apparatus of the type shown in FIG. The HESAJ glass plate is with a switch, a voltage source and the conductive one The core of a roll connected in series, the surface of which is coated with baryta paper. The roller has a diameter of approx. 6.5 cm and is moved over the plate surface at a speed of approx. 1.5 cm / sec. The used plate

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has a size of 7.5 x 7.5 cm and is irradiated with an intensity of approx. 86 100 lux, measured on the uncoated glass plate surface. Unless otherwise specified, in each example 7 percent by weight of the specified pigment is suspended in Sohio Odorless Solvent 3440, a kerosene fraction available from Standard Oil of Ohio. The level of the applied voltage is 2500 Voit ₀ The irradiation is carried out with a lamp of 3200 ⁰ K. The pigment substances are leached out in solvents and milled to reduce their particle size to preferably 1 micron or less _o

Example I «known technique

A suspension of a yellow pigment, 8,13-dioxodinaphtho- (1,2-b; 2 ', 3 ^l -d) -furan-6-carbox-4 "-methoxyanilide in Sohio Odorless Solvent 3440 is prepared and applied to the surface of the A negative voltage of about 2500 volts is applied to the roller electrode. The image is projected onto the suspension while the roller electrode is passed over the injecting electrode The value Dmax is quite small and is about 0.05.

Example II

A pigment suspension is prepared according to Example I. Watchung Red B, 1-4 "-Methyl-5" -chlorazobenzene 2'-sulfonic acid-2-hydroxy-3-naphthenic acid, C.I. No.15865 available from EoI. duPont de Nemours and Co., is on the NESA electrode surface rubbed on until the layer has an optical density of approx. 0.05 o The Watchung Red B is more resistant than the yellow pigment used in the image suspension. The suspension is then applied to the injecting electrode, and a negative voltage is switched on to the roller electrode The suspension is irradiated in the manner described, resulting in an image on the surface of the injecting electrode that corresponds to the original image. The image quality is noticeably improved »The value Dmax is increased to approx. 0.5 approx. 11 levels of a neutral gray wedge filter are reproduced.

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Example III

A yellow pigment suspension is prepared as in Example I. The surface of the NESA electrode is rubbed with wonolite Fast Blue GS _t, a mixture of the alpha and beta form metal-free phthalocyanine, available from Arnold Hoffmann Co., until an optical density of approx. 0.05 is reached. The yellow pigment suspension is applied as a layer to the indicating electrode and a negative voltage is switched on to the roller electrode. The plate electrode is irradiated with a black and white slide, which has a standard neutral gray wedge filter. While the density of the image produced is still very low, the sensitivity to white light is greater because the sensitivity of the suspension to red light has increased.

Example IV. Known Technique

A suspension with approx. 7 parts Watchung Red B and approx. 100 parts Sohio Odorless Solvent 3440 is manufactured. The suspension is applied as a layer on the injecting electrode, and a negative voltage is applied to the blocking electrode. The suspension appears through a transparency exposed, which contains colored spots and a neutral gray wedge filter. An image is created on the NESA disk that corresponds to the Corresponds to the original image. The image has a value Dmax of approx. 1.5. The suspension is primarily sensitive to green light and has a certain sensitivity to blue. The suspension is relatively insensitive to red light.

Example V

The coating and imaging according to Example IV are repeated with the difference that the NESA plate with Monolite Fast Blue GS is rubbed in to an optical density of approx. 0.05 before the pigment suspension is applied will. Monolite Fast Blue GS is more sensitive to red light than the magenta pigment in the suspension. That resulting image has a low Dmax value of approx. 0.5 »There is no effect on the Dmin value with green or blue

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Determine exposure. The red sensitivity of the suspension is increased.

Example VI

The coating and imaging according to Example IV are repeated with the difference that the NESA glass plate with the yellow pigment from Example I is rubbed in to an optical density of about 0.03 before the pigment suspension is applied to them. The yellow pigment has a lower resistance than the magenta pigment of Image suspension. The Dmax value has been reduced from approx. 1.5 on the clean NESA plate to approx. 0.5. It is a at the same time slight increase in blue sensitivity to be observed.

Example VII. Known Technique

A suspension is made with approx. 5 parts of Calcoloid Gray 2, a pigment available from American Cyanamid, made according to US Pat. No. 2,456,589, and about 55 parts Sohio Odorless Solvent 3440. The roller electrode has a positive voltage of approx. 2500 volts. The suspension comes with a picture exposed through a black and white slide containing a neutral gray wedge filter. After the imaging steps there is an image on the NESA glass plate that corresponds to the original image. The picture is of good quality, and there are 5 filter levels recognizable.

Example VIII

A suspension is prepared and imaged as in Example VII, with the difference that the injecting NESA electrode with Monolite Fast Blue GS on an optical Density of about 0.16 is coated before the suspension is applied. The image obtained is of higher quality, and there are about 7 filter levels recognizable.

Example IX

An image suspension is prepared and used for image generation used as in Example VII with the difference that

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the injecting electrode with Monolite Fast Blue GS on a optical density of about 0.2 is coated before the pigment suspension is applied. The image obtained has a excellent quality, and approx. 11 filter levels can be recognized. A decrease in the Dmin value and an increase in the spectral range and sensitivity result in use this layer on the injecting electrode. The sensitivity of the suspension is approx. 64 times greater than in the example VII using an uncoated injecting electrode.

t Example X. known technique

™ An image suspension is prepared with approx. 3 parts by weight of the cyan pigment Monolite Fast Blue GS, the alpha-form metal-free phthalocyanines, approx. 3 parts by weight of the yellow pigment N-2 "-pyridyl-8,13-dioxodinaphtho- (2.1 -b; 2 ^!, 3'-d) -furan-6-carboxamide and about 5 parts of the magenta pigment Bonadur Red B, an insoluble azo dye, C, I.No. 15865, in which sodium is substituted by hydrogen. 90 parts of Sohio Odorless Solvent 3440 are used as the carrier liquid This suspension is applied to the NESA-i glass plate and irradiated with a fully colored "Kodachrome" slide »The light intensity is approx. 6450 Lux, measured on the non-coated NESA glass plate Two role transitions

} are performed with the roller electrode having a negative voltage of approx. 3000 volts compared to the IIESA glass plate. the Colored positive images produced on the NESA glass plate are transferred to paper. Every picture has a good quality with one corresponding fourth Dmin for magenta, furthermore poor rendering of green and yellow due to the presence of undesired liagentatelichen.

Example XI

The process according to Example X is repeated with the difference that the NESA electrode is first coated as in Example II. An examination of the generated image shows that the Dmin value for magenta is reduced and that the reproduction of green and yellow is improved, _etc.

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Example XIi. known technique

The procedure from Example X is repeated with the difference that Watchung Red B is used as the dye in the suspension will. Examination of the generated image shows that the drain value for magenta is a poor reproduction of green and yellow Consequence has ο

Although specific components and quantities preferably wise in the above explanation embodiments of the invention having been stated, other suitable materials, such as those listed above, may be used with similar results "Furthermore, additional materials can be provided _9, the image pulp suspension and of the pigment material layer impart other properties or influence their properties in a favorable manner. For example, photoconductive layers coated with a transparent synthetic resin can be provided in order to improve their durability.

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Claims (5)

- 14 claims Photoelectrophoretic imaging process in which a Image suspension between two electrodes is more sensitive to light Particles an electric field and an image-wise distributed activating electromagnetic radiation is exposed, characterized in that one provided with an xotoconductive layer (13) for the radiation at least partially permeable electrode (1) is used through which the radiation exposure occurs « 2. The method according to claim 1, characterized in that the photoconductive layer (13) by rubbing on a photoconductive one Material composition applied to the electrode (1) will. 3ο method according to claim 1 or 2, characterized in that the photoconductive layer (13) is used in a thickness of up to 1 micron. 4. The method according to any one of claims 1 to 3 _f, characterized in that the photoconductive layer (13) is applied to the electrode (1) up to an optical density of approximately 0.05. 5. The method according to any one of claims 1 to 4, characterized in that that an image suspension (4) is used which contains particles of at least two colors, each particle has photosensitive properties that fall substantially within its range of primary spectral absorption. Method according to claim 5, characterized in that in the image substance suspension (4) cyan-colored particles mainly Red light sensitivity, magenta colored particles mainly sensitive to green light and yellow particles mainly used with blue light sensitivity. 109845/1719