GB1604887A

GB1604887A - Elecrostatic image developers

Info

Publication number: GB1604887A
Application number: GB2054778A
Authority: GB
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1977-05-18
Filing date: 1978-05-18
Publication date: 1981-12-16
Also published as: FR2391496A1; JPS53143326A; DE2821565A1; FR2391496B1; CA1122460A; DE2821565C2

Description

(54) ELECTROSTATIC IMAGE DEVELOPERS (71) We, EASTMAN KODAK COMPANY, a Company organized under the Laws of the State of New Jersey, United States of America of 343 State Street, Rochester, New York 14650, United States of America do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an electrostatic image developer, and a process for using the developer to form visual images, which employs a free-flowing dry-appearing powder containing a large amount of a colorant-containing liquid. The invention is useful for the development of electrostatic images, i.e., electrostatic charge patterns.

In the past, development of electrostatic charge patterns formed by various electrographic techniques has been carried on chiefly y means of dry, electrographic toner powder-containing developers or liquid electrographic developers composed of chargebearing toner particles dispersed in electrically insulating hydrocarbon liquid media. Many modifications and improvements have been made in the formulations of dry tonercontaining developers. One example is the use of two-component dry developers containing a triboelectric mixture of carrier particles and toner powder. Another example is the use of magnetically attractable particulate materials as the carrier particles in vanous "magnetic brush" developers.

Nevertheless, some disadvantages are present in conventional dry and liquid developers and, considerable effort has been expended to provide simpler, less expensive electrographic developers. For example, a well known problem associated with most dry toner powder-containing developers is the considerable amount of heat energy required to fuse and thereby fix the dry toner powder image to a suitable receiver sheet. Although such energy requirements may not be as great a problem with respect to conventional liquid electrographic developers, these developers have generally been avoided for use in conventional high-speed, large-volume electrographic copying devices because of the difficulties associated with disposal of the large amounts of highly volatile hydrocarbon liquids used in such liquid developers.

It would be desirable, if a developer composition could be devised which had the appearance and the characteristics of a free-flowing, dry toner powder and which possessed the ease of handling common to dry free-flowing toner powder-containing developers, while at the same time possessed the ease of fixing exhibited by the various conventional liquid developers. Moreover, if such a developer were developed which contained liquid and colorants therein, one could avoid many of the problems associated with conventional liquid electrographic developers which contain large amounts of organic liquids, e.g., the problem of disposing of hydrocarbon liquids without the objectionable odours and environmental hazards that commonly arise in dealing with organic solvents.

In accordance with the resent invention there is provided an electrostatic image powder developer and a process for producing visual images from electrostatic images or patterns.

The efectrostatic image powder developer comprises an electrostatic image developer comprising from 90 percent to 98 percent by weight of liquid droplets containing a colorant and the remainder dry discrete solid particles surrounding the droplets which solid particles and the remainder dry discrete solid a ides surrounding the droplets which solid particies have a surface energy, as herein described, less than the interfacial tension between the particles and the droplets.

The developer is a dry-appearing, free-flowing, powder-like material that contains at least 90 percent and no more than 98 percent by weight of droplets comprising a colorant-containing liquid. The droplets are completely surrounded by dry, discrete particles that constitute at least 2 percent and no more than 10 percent by weight of the total developer. The surface energy of the dry, discrete particles is less than the interfacial tension between the dry, discrete particles and the droplets they surround, i.e., the droplets do not wet the dry, discrete particles. The developer IS useful in the process of the present invention for forming visual images which comprises forming an electrostatic charge pattern on a surface and contacting that charge pattern with the developer described above.

The developer of the present invention forms a seemingly dry powder which possesses the free-flowing characteristics and ease of handling of a dry electrographic toner powder, but also exhibits the advantages of a liquid electrographic printing ink, namely ease of fixing without the high energy normally required to fuse and fix conventional dry electrographic toner powders.

Although the precise mechanism by which the developers of the present invention provide development of an electrostatic charge pattern is not, at present, fully understood, the following theory is presented by way of partial explanation of the mechanism which is believed to be functioning in the developers of the present invention. Stated briefly, it is believed that the colorant-containing droplets, which are present in the dry-appearing powder tend to acquire an electrostatic charge having either a positive or negative polarity with respect to the dry discrete particles used to surround and prevent coalescence of the droplets.It is believed that by incorporation of appropriate colorant materials, polymeric binders, dispersing aids and other materials in the droplets as described in greater detail hereinafter, it is possible to prepare a dry-appearing liquid-containing developer in accordance with the present invention, wherein the colorant-containing droplets present in the developer tend to exhibit either a positive or negative polarity depending upon the particular composition of the droplets. Similarly, it is believed that the polarity of the droplets contained in the given developer of the invention can be changed by varying the material used to prepare the dry, discrete particles which surround and prevent coalescence of the droplets within the developer.

As will be appreciated from the foregoing description of the mechanism by which the developers of the present invention are believed to function, the electrical properties of the developer of the present invention are somewhat similar to conventional two-component dry developers composed of a triboelectric mixture of dry toner particles and dry carrier particles. however, this analogy between the developers of the present invention and conventional two-component dry developer mixes is not a perfect one and cannot be carried too far.

For example, as is well known, there is a finite depletion rate associated with conventional two-component dry electrographic developers containing a triboelectric mixture of carrier particles and electrostatically attractable toner particles, which governs the rate at which toner particles are depleted from the developer during the development of electrostatic charge patterns. Accordingly, when such two-component developers are used to develop a series of electrostatic charge patterns, one must provide some means by which to replenish the developer, i.e., to add additional toner particles to the developer to make up for the depletion of toner particles used in the development process.This replenishment process itself its a problem associated with conventional two-component developers, in that it is often quite difficult to add additional toner particles to an existing developer without destroying the stability existing between the carrier particles and toner particles already present in the developer system.

In contrast, although not fully understood, it has been found that with the dry-appearing, liquid-containing developers of the present invention one does not encounter a depletion or replenishment problem of the type associated with conventional two-component dry developer. Rather, it has been found that, although the developers of the present invention appear to act, electrically or triboelectrically, in a manner analogous to known two-component dry developers (as described above), there is no uneven depletion of the colorant-containing droplets and the dry, discrete particles from the developer. In other words, in relation to depletion, the developers of the present invention appear to act like a single-component developer. One is not faced with the problem of attempting to replenish a developer from which the various components are being depleted at different rates.

Accordingly, it is believed that the dry-appearing, liquid-containing developers of the present invention do not require concentration monitoring during usage as is ordinarily the case with conventional two-component dry developers.

When a developer of the present invention is used in a process to develoP electrostatic charge patterns, one can make up for the amount of developer material which is used up in the process simply by adding additional bulk quantities of the developer without having to provide separate mechanisms for monitoring toner particle concentration and for adding toner particles to the developer. In this respect, the developer of the present invention acts much like a conventional liquid ink material which is simply used up in the process of making ink images and can be "replenished" simply by feeding additional liquid ink to the imaging process.

The replenishment problem associated with conventional two-component dry developers as descnbed above is also encountered in many conventional liquid electrographic developers containing electrostatically attractable toner particles. In addition, one also encounters an additional sort of replenishment problem when dealing with such liquid developers. That is, the electrostatic charge images which are developed by such liquid developers tend to draw out a certain amount of this liquid hydrocarbon material (often the amount is quite large). Thus, when the image is dried, one is faced with the problem of venting or removing the liquid hydrocarbon vapour which is formed as a liquid-developed image is dried.In many conventional liquid developer processes, the hydrocarbon vapour is simply vented into the air as the image is dried and fixed and accordingly presents environmental and possibly contamination problems, unless the process is run at a rate slow enough so that the amount of hydrocarbon vapour vented into the air is kept within an acceptable limit. For this reason, many conventional liquid developers are commercially unacceptable in high speed copy systems where one is faced with the problem of venting or removing large amounts of hydrocarbon vapour because of the high rate of image development which would be occurring. In contrast, the developers of the present invention do not contain such carrier-vehicle liquids, and thus avoid the problem of the evaporation of such liquids during the development process.

In order for a developer to function in accordance with the present invention the droplets of liquid and colorant and the dry, discrete particles must have a certain relationship to each other, based on their surface energies. In order for any given combination of droplets and dry, discrete particles to be satisfactory for the practice of the present invention, the surface energy of the dry, discrete particles must be less than the interfacial tension between the dry, discrete particles and the liquid droplets. This is another way of saying that in working combinations of droplets and dry, discrete particles, the droplets do not "wet" the dry, discrete particles.

Those conversant in the field of surface chemistry refer to contact angles when trying to determine if a given liquid will "wet" a given solid. The contact angle is a measurement of the internal angle formed between the surface of a droplet of the hquid in question and a surface of the solid in question at the point where the surface of the liquid first comes into contact with a surface of the solid. The measurement can be made by placing a droplet of the liquid in question on a flat surface consisting of the solid in question and vlsually measuring the angle formed at the point of contact by using a microscope with a protractor superimposed over the eyepiece. The angle measured in this way is sometimes referred to as the "advancing angle", because it is the equilibrium angle formed when liquid is added to the surface of the solid.Similarly, one can measure the "receding angle", the equilibrium angle formed when some of the liquid is removed from the solid, for example, by inclining the flat, solid surface to allow some of the liquid to roll off the solid and then measuring the angle formed between the solid and any liquid still remaining on the surface of that solid.

Surface chemists express the relationship between the contact angle and the surface energetics of the system in question as follows: I Cos A = Es - Ts@ EL in which A is the contact angle, Es is the surface energy of the solid, EL is the surface energy of the liquid, and TSL is the interfacial tension between the solid and the liquid when m contact with each other. A liquid is said not to "wet" a solid, and thus provide a liquid-solid combination useful in the present invention, whenever the advancing contact angle is greater than 90 degrees or the receding contact angle is greater than 0 degrees.By substituting these values into equation I, above, one obtains the following descriptions of solid-liquid combinations useful in the present invention: when the receding angle is measured, II ES - TSL < 1.0 EL or III EL > Es - TSL and when the advancing angle is measured, IV ES - TSL < 0 EL or V Es < TSL Because Es, EL, and TSL are always positive numbers, both equations III and V, which respectively describe the relationships that hold when receding angles and advancing angles are measured for solid-liquid combinations useful in the present invention, are satisfied whenever the surface energy of the dry, discrete particles (E5) is less than the interfacial tension between the dry, discrete particles and the droplets (TsL). It is recognized that at the present time these surface energy relationships are not directly measurable by any readily convenient means; however these relationships can be determined indirectly by simple procedures such as the two methods described below.

In one method that will suffice for choosing combinations of droplets and dry, discrete particles having surface-energy relationships useful in the present invention, one need only measure either the receding or the advancing contact angle of the system as described previously. The dry, discrete particles can be formed into a solid surface for this measurement by depositing the particles on a glass slide that has just been coated with a layer of acrylic adhesive that has not yet dried. Care must be taken to cover the adhesive layer with sufficient quantities of dry, discrete particles so that the resulting surface of the slide will consist totally of the particles themselves; otherwise the adhesive will interfere with the liquid-solid surface energetics and result in incorrect angle measurements.If the measured advancing angle is greater than 90 degrees, or if the measured receding angle is greater than 0 degrees, the dry, discrete particles can be used to surround the droplets of colorant-containing liquid without being wet by the droplets and thus form a developer in accordance with the present invention. Further information about contact angles and their measurement can be found in, Adamson, A. W., Physical Chemistry of Surfaces, 2d ed., N.Y.., Wiley & Sons, 1967.

An alternative and perhaps simpler method of deciding whether a liquid-solid combination has surface-energy relationships enabling them to be used in a developer in accordance with the present invention, i.e., the droplets do not wet the dry, discrete particles, is first to form a surface of the dry, discrete particles on the glass slide as described above. The slide is then dipped into a solution or dispersion of the liquid and colorant in question. When the slide is withdrawn from the solution or dispersion, it is visually observed to determine if a continuous film of the solution or dispersion still remains on the solid surface. If it does not, then the liquid does not wet the solid and the combination has surface-energy relationships sufficient for the practice of the present invention. Further description of this method is provided in the Examples.

Although any of the combinations of droplets and dry, discrete particles chosen according to the criteria described above can be useful in developers for forming visual images, certain components will be more useful for particular applications. The liquid component of the droplets comprises a liquid such as water, vanous polyols or certain amides.

Typical of useful polyols are the lower alkyl polyols containing two or more hydroxy groups and from one to seven carbon atoms in the alkyl group. A partial listing representative of such polyols includes glycerol (sometimes referred to as glycerin), ethylene glycerol, propylene glycol, mixtures of the foregoing materials and other similar highly polar glycols, i.e., viols, triols and mixtures thereof.

An especially preferred class of liquids which have been found useful in the present invention, because of the extremely high surface energy exhibited by the liquids, are such liquids as water, glycerol, ethylene glycol, formamide, mixtures of the foregoing materials with each other and mixtures of the foregoing materials with other liquids, for example various other lower alkyl polyols such as those listed above.

As noted above, the amount of colorant-containing droplets employed in the developer of the present invention is less than 98 percent and greater than 90 percent by weight, based on the total weight of the developer. The amount of liquid component present in the droplet phase of the developers of the invention often represents more than 40 weight percent of the total weight of the developer (which is equivalent to more than 67 weight percent of the total weight of the droplet phase of the developers).However, it has been found that useful results can be attained wherein the liquid component of the droplet phase represents no more than 5 percent by weight of the total weight of the developer which is equivalent to 8 percent by weight of the droplet phase), the remaining portion of the droplet phase containing other necessary or desirable addenda as set out hereinafter such as colorants, dispersing aids, binders and magnetic materials.

An essential feature of the droplets contamed in the developers of the invention is the colorant component. A wide variety of suitable materials useful as colorants may be used in the droplets of the present invention. The colorant may be dissolved in the liquid (for example, a water soluble dye in the case where the droplet contains an aqueous liquid base), or it may be dispersed in the liquid in the form of a pigment material. or example, finely-divided carbon black has been found to provide especially useful colorants for the developers of the present invention.Of course, as will be appreciated, a large number of suitable dyes and pigments have been effectively employed in various printing ink and electrographic liquid developers and therefore would be available for use in the present invention depending upon the particular colour which is desired, and the particular physical, chemical and electrical properties which one may wish to impart to the liquid droplets. It may be noted, as suggested hereinabove and demonstrated in the examples below, that the choice of a particular colorant can have an effect on the electrical properties of the droplets contained in the developer of the present invention.That is, it has been found that by varying the particular colorant used in a given developer, one can apparently modify the electrical properties associated with the developer such that the developer preferentially tends to develop either negative charge patterns or positive charge patterns.

TyPically, the amount of colorant present represents an amount within the range of from 0.to 50 weight percent based on the total weight of the developer.

In addition to a colorant, the liquid droplets used in the present invention may also contain, if desired, various dispersing agents of the type used in the printing ink and electrographic liquid developer industry to facilitate the incorporation of various colorant into the liquid droplets and to prevent settling out of the colorant from the liquid droplets.

Various such agents are known in the art for this purpose and are commercially available as common surfactants or as dispersing aids for ink compositions.

In addition to a dispersing ald, the liquid droplets used in the developers of the present invention may also contain any of vanous polymeric binders dispersed, suspended, or dissolved in the liquid media to serve as useful fixing agent to adhere the resultant colorant image to a desired receiving sheet.A variety of such polymeric binders, are available and well known in the printing ink and electrographic liquid developer industry including such materials as: gums such as gum arabic and xanthan gum, waxes, starch, cellulose derivatives such as methyl cellulose; carboxy methyl cellulose; ethyl hydroxyethyl cellulose; poly(vinyl acetate); poly(vinyl alcohol); poly(vinyl butyral); poly(vinyl formal); poly(vinyl chloride); polyolefins; acrylic resins; polyialkyl vinyl ethers); poly(methyl vinyl ether-co-maleic anhydride); she lac; rosin and rosin derivatives; asphalts; phenolic resins; alkyd resins; coumarone/indene resins; urea-formaldehyde resins; polyamide resins; rubbers; and epoxy.

resins.

When dispersing aids and polymeric binder materials such as those noted hereinabove are used in the colorant-containing droplets employed in the developers of this invention, it is generally desirable to use such aids and binders in amounts ranging from 0.5 to 50 weight percent based on the total weight of the developer, including both the droplets of the developer and the dry, discrete particles.

In addition, if it is desired to apply the developer of the present invention to a surface bearing an electrostatic latent image by use of a magnetic applicator system, the liquid-containing droplets may also contain an amount of magnetically attractable particles, such as iron, nickel, cobalt and ferrites, effective to render the resultant developer magnetically attractable to known magentic applicators, such as magnetic brush applicators used in conventional electrographic magnetic brush development systems.

A further essential component of the dry-appearing, liquid-containing developer of the present invention is the finely-divided particuLate material that forms a network of dry, discrete particles surrounding and preventing coalescence of the colorant-containing droplets contained in the developer of the invention.Modified silicon dioxide powders which have been found useful are finely-divided silicon dioxide powders having a surface area in excess of 50 m2/g of powder, typically in excess of 150 m2/g, and which have been treated such that the exposed surface of an individual silicon dioxide particle, rather than being comprised of hydroxy groups which normally populate the surface of silicon dioxide powders, is modified at least in part, by organo-silicon groups such as trimethylsiloxyl groups, by chemically bonding the desired organo-silicon groups to oxygen atoms at the surface of the typical silicon dioxide particle. By replacing a number of the hydroxyl groups which normally populate the surfaces of a typical silicon dioxide powder, with the above-described organo-silicon groups, one creates surfaces on the resultant powder that have a low surface energy relative to certain liquids.Such surface-modified silicon dioxide powders can be obtained by contacting an ordinary pyrogenic silicon dioxide powder with a compound containing hydrocarbon groups, for example, alkyl, aryl, alkaryl or aralkyl groups under conditions which cause a chemical reaction to occur with a substantial portion of the hydroxyl groups typically present on a surface of pyrogenic silicon dioxide particles, whereby new surface structures largely composed of such hydrocarbon groupings are created on the outer exposed portions of the silicon dioxide particles. The preparation of such low-surface-energy silicon dioxide powders is described, for example, in U.S. Patent 3,393,155, as is the use of these powders to surround large amounts of aqueous liquids.

Such modified silicon dioxide powders are available commercially from Degussa, Inc.

under the trademark 'Aerosil' R 972 and also from the Tulco Corporation under the trademark 'Tullanox' 500. Technical literature concerning 'Aerosil' R 972 and 'Tullanox' 500 can be obtained from both Degussa, Inc. and the Tulco Corporation describing further properties of such modified silicon dioxide powders.

Although the above-described modified silicon dioxide powder has been found to provide an especially preferred embodiment of the present invention, other finely-divided particles have been found to be useful in the practice of the invention. Any of such dry, discrete particles that have a surface energy less than the interfacial tension between these particles and the liquid-containing droplets of choice, as determined by the contact-angle measurements or wettability dip test described above will be useful in the practice of this invention.For example, finely-divided, particles such as polyolefin wax particles and polytetrafluoroethylene articles, also provide useful powders for the developers of the present invention providing that the surface energy of these articles has the appropriate relationship to the liquid droplets as described above, so that the particles can surround and prevent coalescence of the colorant-containing droplets without absorbing them.

Other useful dry, discrete particles may be those formed as part of an autophobic system.

Autophobic systems are those in which adsorption of a layer of molecules from the liquid of choice on the dry, discrete particles results in a new "solid" surface on these particles having an energy so low that the liquid no longer wets the surface. Fatty acids, for example, can be deposited on a solid surface by a retraction method from a solution or melt of the fatty acids to give a new surface which comes out "dry" as the solid is removed from the liquid solution or melt. Such systems are described in Adamson, A.W., Physical Chemistry of Surfaces, 2d ed., N.Y., Wiley & Sons, 1967, p. 197.

The amount of dry, discrete particles which is present in the dry-appearing, liquidcontaining developers of the invention is typically relatively small in comparison to the rather large amount of colorant-containing droplets contained in the resultant developer.

The developers contain no more than 20 percent by weight of the dry, discrete particles to provide satisfactory results in accord with the invention. Generally, it is found that at least 2 percent and preferably from 5 to 10 percent by weight based on the total weight of the resultant developer is composed of the above-noted dry, discrete particles.

The dry, free-flowing, liquid-containing developers othe present invention may be prepared by several of various techniques. For example, useful developer of the invention have been prepared simply by mixing small amounts of approximately 10 percent by weight of the above-described surface-modified silicon dioxide particles into a blender containing approximately 90 percent by weight of the above-described colorant- and liquid-containing composition. The blender is turned on for less than a minute. As a consequence, one obtains the desired dry-appearing, finely-divided, liquid-containing powder developer of the invention.Such a developer has the appearance of a powder and when the developer is contacted with a charge pattern produced by any of the well known electrophotographic or electrographic techniques on a suitable support, one finds that the charge pattern is developed into a visible image corresponding to the original charge pattern. Such relatively simple blending and milling techniques as described above, are especially effective with low viscosity liquid media, such as water, glycerol, ethylene glycerol, formamide and mixtures thereof, and low-surface energy particles such as the above-described modified silicon dioxide particles. In other cases wherein the liquid medium of the composition has a surface energy not quite as high as water, glycerol, ethylene glycol, or formamide or in situations where the dry, discrete particles do not possess a surface energy quite so low as the above-described modified silicon dioxide particles, it has been found useful to prepare first the colorant-and liquid-containing composition into finely-divided droplets such as by atomizeing the liquid to form a fine mist of colorant-containing droplets and then propelling such a mist into a second mist composed solely of the dry, discrete particles. Alternatively, one can co-atomize the colorant- and liquid-containing composition together with a suitable amount of appropriate dry, discrete particles to form the developer of the present invention.Further details concerning such mixing techniques are presented hereinafter in the Examples (Note: in some of the Examples 'Silanox' 101, formerly available from Cabot Corporation, is used. This material is no longer available, but 'Tullanox' 500 from Tulco Corporation is identical to 'Silanox' 101.) Example I Table I below lists contact angle measurements of various liquids in combination with 'Silanox' 101 (a modified silicon dioxide powder from the Cabot Corporation). The results indicate that contact angle measurements are predictive of utility in the practice of the present invention. Useful developers exhibited advancing angles greater than 90 degrees and receding angles greater than 0 degrees.

TABLE 1 CONTACT ANGLES OF COMBINATIONS OF VARIOUS LIQUIDS AND SILANOX' 101 POWDER Developer EL Aadv.* ARec. Useful In The Liquid Dynes/cm2 Degrees CosAAdv. Degrees CosARec. Present Invention? 40% Ethanol 31.7 53 Av. 0.601 0 1.000 No (50-56) 35% Ethanol 33.5 70 Av. 0.342 0 1.000 No (67-73) 30% Ethanol 35.0 152 Av. -0.882 36 Av. 0.809 Yes (146-158) (19-49) Water 72.6 137 Av. -0.743 32 Av. 0.848 Yes (120-158) (17-45) Ethylene Glycol 48.3 103 Av. -0.225 25 Av. 0.906 Yes (93-108) (15-31) Glycerol 63.4 159 Av. -0.934 159 Av. -0.934 Yes Formamide 58.2 180 Av. -1.000 180 Av. -1.000 Yes Glycerol: Ethylene 58.5 122 Av. -0.530 39 Av. 0.777 Yes Glycol, 2::1 (118-125) (32-40) *Av. = average value of the contact angle, A (Numbers in parenthesis indicate the range of values measured.) AAdv. = advancing angle ARec. = receding angle Example 2 - Wettability Test A glass microscope slide was sprayed with a clear acrylic lacquer ('Krylon' No. 1301 from Borden, Inc.). Before the lacquer dried, the slide was repeatedly pressed into the powder to be tested. The object was to obtain a continuous coating of embedded partides. The lacquer was then allowed to dry. The slide was then dipped into the liquid in question for five seconds. If, upon removal of the slide, a continuous film of liquid coated the embedded articles, the liquid was said to wet the particles. If a continuous film was not formed, the liquid was said not to wet the particles.Useful liquids for the present invention are those which do not wet the particles.

Several liquids were subjected to the wettability test to determine whether they would wet 'Silanox' 101 (Cabot Corp.) particles. The liquids were then tested for usefulness in the present invention by placing in a Micro-Mill 10 grams liquid and 4.3 grams 'Silanox' 101.

The Micro-Mill was turned on for 5 seconds and the result examined. The liquid was deemed useful with 'Silanox' 101 if the product was a dry-appearing powder. The liquid was not useful if the product was a paste or liquid.

The wettability test was a good predictor in determining whether a combination of liquid and particle was useful in the present invention (Table II).

TABLE II Wettability Tests Of Various Liquids In Combination with 'Silanox' 101 Liquid - 'Silanox' 101 Does Liquid Wet Combination Useful in Liquid 'Silanox' 101? Present Invention? water no yes ethanol/water (20/80) no yes ethanol/water P0/70) no yes ethanol/water (35/65) yes no ethanol/water (40/60) yes no ethanol yes no glycerol no yes ormamide no yes ethylene glycol no yes methanol yes no acetone yes no triethylene glycol no yes butyl lactate yes no ethyl lactate yes no diethylene glycol no yes Example 3 The following were added to a Micro-Mill (Chemical Rubber Company): 10 grams -- Carter's Black Stamp Pad Ink 0.5 gram -- 'CMR' Cellulose Gum, Type 7-MP (Hercules Powder Company) The mill was operated for 20 seconds resulting in a black paste.To the mill was then added 1.0 gram of 'Silanox' 101 (Cabot Corp.), coated fumed silica, and the mill operated for another 20 seconds. The result was a black fluffy powder.

A photoconductor element was charged to -1000 volts, negative, exposed 4.5 seconds to an image comprising both line copy and solid areas. Weyerhauser E28AK dielectric coated paper was placed on the photoconductor, hand rubbed on the photoconductor, and then removed from the photoconductor. The transferred charge pattern on the paper was then developed by cascade methods using the above-described powder. Fringe development resulted and image quality was good with low background.

The experiment was repeated except that the photo-conductor layer was charged to 1000 volts positive. Image quality was poor with little development in the image areas indicating that the developer is attracted to negatively charged electrostatic image patterns.

Example 4 A photoconductor element was charged to 100 volts negative exposed and developed as described in Example 3. The developed image was then transferred and fixed by placing a sheet of International Paper Company 'Xerographic' white paper (substance 2 on the photoconductor layer, passing a rubber roll over the sandwich, and removing the paper.

The image quality was good and the toner image was well-fixed to the paper.

Example 5 An ink was prepared by dissolving 3 grams of Methylene Blue in 100 grams of distilled water. To a Micro-mill was added 20 grams of this ink and 2 grams of 'Silanox' 101. The mill was operated for 20 seconds and the result was a blue powder.

The photoconductor element was charged to 1000 volts positive and exposed to an image for 4.5 seconds. The latent electrostatic image was charge transferred to Weyerhauser E28AK paper and developed by the technique described in Example 2. Fringe development resulted and. image quality was good with low background.

The experiment was repeated except the photoconductor was charged to 1000 volts negative. Image quality was poor with little development in the image areas indicating that this developer is attracted to positively charged electrostatic image patterns.

Example 6 An ink was prepared by dissolving 2 grams of Methylene Blue in 100 grams of distilled water. Ten grams of this ink was frozen and placed in a cooled Micro-Mill (Chemical Rubber Co.). Three grams of 'Nopcowax' 22-DS powder (the trade mark of a synthetic, low-molecular-weight polyolefin wax from Nopco Chemical Division of Diamond Shamrock Chemical.) was cooled and also placed in the Micro-Mill.

The Micro-Mill was turned on in short bursts of 5 seconds followed by longer cooling periods in dry ice. The resulting blue developer was then allowed to warm to room temperature.

A visible image was produced by cascading the powdered developer over a dielectric surface containing a negative electrostatic image. This image was pressure transferred to paper at room temperature with two steel rolls.

Example 7 Example 6 was repeated except that Whitcon 5 TFE powder (a polytetrafluoroethylene powder from Whitford Chemical Corp.) was used in place of 'Nopcowax' 22-DS.

A visible image was produced by cascading the powdered developer over a dielectric surface containing a positive latent electrostatic image. This image was pressure transferred to paper at room temperature with two steel rolls.

Example 8 An ink was prepared by blending together on a ball mill for 6.5 days: 83.9 grams glycerine 1.1 grams 'Tamol' SN (Rohm and Haas - the trademark of a sodium salt of a condensed aryl sulphonic acid) 15 grams 'Regal' 300R carbon black (Cabot Corp.) Fifteen grams of this ink was placed in a Micro-Mill with 1.5 grams of 'Silanox' 101 (Cabot Corp.) The mill was run for 15 seconds resulting in a black powdered developer which was then passed through a 325 mesh screen to remove any large droplets.

A visible image was produced by cascading the powdered developer over a dielectric surface containing a negative latent electrostatic image. This image was pressure transferred to paper at room temperature with two steel rolls.

Example 9 An ink was prepared by blending together in a 'Waring' Blender the following: 100 grams ethylene glycol 2 grams 'Tamol' SN 10 grams 'Regal' 300R Carbon Black Final dispersion was achieved ultrasonically.

Two grams of 'Silanox' 101 was placed in a polyethylene beaker and fluidized using a magnetic stirrer. Twenty grams of the ink was sprayed into the fluidized 'Silanox' 101 thereby producing a black powdered developer. The developer was sieved through a 325 mesh screen to remove any large droplets.

Example 10 An ink was prepared by blending together in a Waring Blender the following: 200 grams formamide 1 gram 'Tamol' SN 20 grams 'Regal' 300R Carbon Black Final dispersion was achieved ultrasonically.

Ten grams of this ink was frozen and placed in a cooled Micro-Mill. One gram of cooled 'Silanox' 101 was also placed in the Micro-Mill. The Micro-Mill was turned on in short bursts of 5 seconds followed by longer cooling periods in dry ice. The resulting powdered developer was then allowed to warm to room temperature.

Example 11 -- Polymer Binder Dissolved in Liquid An ink was prepared by blending together: 10.00 grams -- 'Gantrez' AN-139 [the trade mark of a poly(methyl vinyl ether-co-maleic anhydride) from GAFF.

0.6 grams -- CMC Cellulose Gum (Hercules Powder Co.).

0.5 grams -- 'Tamol' SN (a sodium salt of a condensed aryl sulphonic acid from Rohm and Haas).

8.5 grams -- 'Regal' 300R carbon black (Cabot Corp.).

47.1 grams -- water 33.3 grams -- glycerol Twenty grams of this ink was placed in a Micro-Mill with 2 rams of 'Silanox' 101. The mill was run for 5 seconds resulting in a black powdered developer.

The developer was cascaded over a latent electrostatic image on a dielectric surface. The resulting image was pressure transferred to paper at room temperature with two steel rolls.

Example 12 -- Polymer Binder Dispersed in Liquid An ink was prepared by dispersing together: 25 grams -- J-Pryl P-200 (carboxylated styrene latex from Ionac Corp.).

39.4 grams -- glycerol 0.8 grams -- water 9.5 grams -- 'Regal' 300R carbon black (Cabot Corp.).

0.3 grams -- 'Tamol' SN (Rohm and Haas).

Fifteen grams of this ink was placed in a Micro-Mill with 1.5 grams of 'Silanox' 101 (Cabot Corp.). The mill was run for 5 seconds resulting in a black powdered developer.

The developer was cascaded over an electrostatic image on a dielectric surface. The resulting image was pressure transferred to paper at room temperature with two steel rolls.

Example 13 -- Magnetic Component in Developer An ink was prepared by blending together: 53.5 grams -- glycerol 26.7 grams -- ethylene glycol 16.0 grams -- 'Mapico' Black (the trade mark of an iron oxide from Columbian Carbon Cho.) 2.7 grams -- 'Regal' 300R carbon black (Cabot Corp.).

1.1 grams -- 'Tamol' SN (Rohm and Haas).

Fifteen grams of this ink were placed in a Micro-Mill with 1.5 grams of 'Silanox' 101. The mill was run for 7 seconds resulting in a black powdered developer.

A latent electrostatic image on a dielectric surface was developed using magnets to transport the black powder. The resulting image was pressure transferred to paper at room temperature with two steel rolls.

WHAT WE CLAIM IS: 1. An electrostatic image powder developer comprising from 90 percent to 98 percent by weight of liquid droplets containing a colorant and the remainder dry discrete solid particles surrounding the droplets which solid particles have a surface energy, as herein described, less than the interfacial tension between the particles and the droplets.

2. The developer as claimed in Claim 1 in which the liquid droplets include a polymeric binder dispersed or dissolved in the liquid.

3. The developer as claimed in Claims 1 or 2 in which the droplets include a dispersing aid to facilitate the incorporation of the colorant.

4. The developer as claimed in any of the preceding Claims in which the liquid droplets

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 10 An ink was prepared by blending together in a Waring Blender the following: 200 grams formamide 1 gram 'Tamol' SN 20 grams 'Regal' 300R Carbon Black Final dispersion was achieved ultrasonically. Ten grams of this ink was frozen and placed in a cooled Micro-Mill. One gram of cooled 'Silanox' 101 was also placed in the Micro-Mill. The Micro-Mill was turned on in short bursts of 5 seconds followed by longer cooling periods in dry ice. The resulting powdered developer was then allowed to warm to room temperature. A visible image was produced by cascading the powdered developer over a dielectric surface containing a negative latent electrostatic image. This image was pressure transferred to paper at room temperature with two steel rolls. Example 11 -- Polymer Binder Dissolved in Liquid An ink was prepared by blending together: 10.00 grams -- 'Gantrez' AN-139 [the trade mark of a poly(methyl vinyl ether-co-maleic anhydride) from GAFF. 0.6 grams -- CMC Cellulose Gum (Hercules Powder Co.). 0.5 grams -- 'Tamol' SN (a sodium salt of a condensed aryl sulphonic acid from Rohm and Haas). 8.5 grams -- 'Regal' 300R carbon black (Cabot Corp.). 47.1 grams -- water 33.3 grams -- glycerol Twenty grams of this ink was placed in a Micro-Mill with 2 rams of 'Silanox' 101. The mill was run for 5 seconds resulting in a black powdered developer. The developer was cascaded over a latent electrostatic image on a dielectric surface. The resulting image was pressure transferred to paper at room temperature with two steel rolls. Example 12 -- Polymer Binder Dispersed in Liquid An ink was prepared by dispersing together: 25 grams -- J-Pryl P-200 (carboxylated styrene latex from Ionac Corp.). 39.4 grams -- glycerol 0.8 grams -- water 9.5 grams -- 'Regal' 300R carbon black (Cabot Corp.). 0.3 grams -- 'Tamol' SN (Rohm and Haas). Fifteen grams of this ink was placed in a Micro-Mill with 1.5 grams of 'Silanox' 101 (Cabot Corp.). The mill was run for 5 seconds resulting in a black powdered developer. The developer was cascaded over an electrostatic image on a dielectric surface. The resulting image was pressure transferred to paper at room temperature with two steel rolls. Example 13 -- Magnetic Component in Developer An ink was prepared by blending together: 53.5 grams -- glycerol 26.7 grams -- ethylene glycol 16.0 grams -- 'Mapico' Black (the trade mark of an iron oxide from Columbian Carbon Cho.) 2.7 grams -- 'Regal' 300R carbon black (Cabot Corp.).

1.1 grams -- 'Tamol' SN (Rohm and Haas).

comprise water, glycerol, formamide, ethylene glycol or a mixture thereof.

5. The developer as claimed in any of the preceding Claims in which the dry discrete solid particles are composed of polyolefin wax, polytetrafluoroethylene, or pyrogenic silcon dioxide particles chemically modified by having hydrophobic hydrocarbon groups distributed over the surface thereof.

6. The developer as claimed in any of the preceding Claims in which the liquid droplets include magnetically attractable particles

7. The developer as claimed in any of the preceding Claims in which the liquid droplets contain less than 8 per cent by weight liquid.

8. The developer as claimed in any of the preceding Claims which comprises more than 90 percent by weight of liquid droplets containing a colorant.

9. The developer as claimed in any of the preceding Claims in which the colorant comprises from 0.5 to 50 percent by weight based on the total weight of the developer.

10. The developer as claimed in Claim 9 in which the colorant is carbon black.

11. Electrostatic image developers as claimed in Claim 1 and as herein described.

12. A method of forming a visual image from an electrostatic charge pattern comprising contacting the pattern with an electrostatic image developer as claimed in any of the Claims 1 to 11.

13. The method as claimed in Claim 11 wherein the surface carrying the electrostatic charge pattern is first contacted with the electrostatic image developer and thereafter the deposited droplet pattern is transferred to a receiving sheet.

4. The method as claimed in Claim 12 wherein the surface carrying the electrostatic charge pattern is first contacted with the electrostatic image developer and thereafter the deposited droplet pattern is dried or otherwise treated to fix the visual image.

15. Surfaces carrying visual images whenever made by the method of either of the Claims 13 or 14.