JPS5935014B2 - Electrostatic recording developing material and image forming method using the same - Google Patents

Description

[Detailed description of the invention] The present invention relates to imaging systems.

More particularly, this invention relates to improved compositions useful in electrographic development, their preparation, and their uses. It is well known to electrostatically form and develop images on photoconductive materials.

The basic method is to place a uniform electrostatic charge on a photoconductive insulating layer, expose this layer to a light and shadow image to dissipate the charge in the light-exposed areas of the layer, and then create a static charge. It involves developing an electrolatent image by depositing a fine electroscopic material, referred to in the art as a "toner", onto the image. The toner can be attracted to either the charged areas of this layer or the discharged areas, thereby forming a toner image. This powder image can then be fixed or transferred onto a support surface such as paper. The transferred image is then permanently affixed to the surface of the support by heating or other known techniques. An electrostatic latent image can also be formed by directly discharging a receptive surface in an imagewise manner. This powder image can be fixed onto this surface if it is desired to omit the transfer step. Several methods are known for applying electroscopic particles to an electrostatic latent image to be developed.

One such development method is known as a "cascade" development method. A developer material consisting of relatively coarse carrier particles having fine toner particles electrostatically held thereon is rolled or cascaded over the surface bearing the electrostatic latent image. The composition of the carrier particles is selected so that the toner particles are triboelectrically charged to the desired polarity. As the mixture cascades or rolls over the image-containing surface, toner particles are electrostatically deposited on the charged portions of the latent image;
On the other hand, it does not deposit on uncharged or background portions of the image. Toner particles accidentally deposited in non-image areas are attracted by the rolling carrier because the electrostatic attraction between the toner and the carrier is clearly greater than the electrostatic bow force between the toner and the discharge background. removed. The carrier and excess toner are recycled. Another way to develop electrostatic images
One method is the so-called "magnetic brush" development method.

In this method, a developer material containing toner and magnetic carrier particles is conveyed by a magnet. The magnetic field of this magnet aligns the magnetic carriers into a brush-like arrangement. This "magnetic brush" is brought into contact with the electrostatic image-containing surface, and the toner particles are attracted from the brush to the latent image by the electrostatic attraction of the latent image. Automatic xerography equipment typically charges, exposes, develops,
A xerographic photosensitive plate is used in the form of a cylindrical drum that rotates continuously through transfer and cleaning cycles.

The photosensitive plate is corona charged, usually by means of a corona generator connected to a suitable high power source. After forming a powder image on the electrostatic latent image during the development step, the powder image is electrostatically transferred onto the surface of the support by a corona generating device, such as the corona device described above. In automatic equipment using a rotating drum, the support surface, such as paper, to which the powder image is to be transferred is moved through the equipment at a speed equal to one revolution of the drum, and there is no space between the drum surface and the corona generating device. Contact the drum at the sandwiched transfer site. Transfer is accomplished by a corona generating device that applies an electrostatic charge to attract the powder image from the drum to the support surface. The polarity of the charge required to effect image transfer depends on the visual form of the original copy involved and the electrostatic properties of the developer material used to effect the development.

For example, if a positive copy is to be made from a positive original, a positively polarized corona is typically used to transfer a negatively charged toner image to the surface of the support. When it is desired to make a positive copy from a negative original, a positively charged developer material that is repelled by the charged areas on the photosensitive plate is applied to the discharged areas to form a positive image, and the positive image is can be transferred by a corona of negative polarity. In either case, the residual powder image typically remains on the photosensitive plate after transfer. Therefore, before attempting to reuse the photosensitive plate for the next cycle, remove any residual images and eliminate the "ghost images" that form on subsequent copies.
and a need to prevent the formation of a toner film that forms on the photoreceptor surface. In the aforementioned positive-to-positive copying process, residual developer powder is held tightly onto the photosensitive plate surface by a poorly understood phenomenon that prevents complete transfer of the powder to the support surface, especially its image areas. . Incomplete transfer of toner particles reduces the image density of the final destination copy and requires highly abrasive photoreceptor cleaning techniques to remove residual toner from the photoreceptor surface. Undesirable. This imaging process is normally repeated for each copy produced by the machine many times during the useful life of the developer and drum surface. "Brush"
, "Web" and "Blade"
e) Cleaning techniques Various electrostatic recording photosensitive plate cleaning devices are known.

Brush-type cleaning devices typically have one or more rotating brushes that brush residual powder from the photosensitive plate into an air stream that is discharged through a sifting system. In a typical web cleaning device, residual powder on a photosensitive plate is removed by moving a web of fibrous material over the photosensitive plate. In blade cleaning, a flexible cleaning blade moves the surface of the photoreceptor past the blade to wipe or wipe residual toner from the photoreceptor surface. Unfortunately, each of the cleaning systems described above has the ability to abrade the reusable photoreceptor surface during removal of residual toner particles.

This problem is particularly acute in cleaning systems that use cleaning blades. Because highly abrasive pressure is generally required in conjunction with cleaning metal tools to facilitate removal of residual toner particles, this often results in rapid deterioration of the photoreceptor and/or the formation of an undesirable toner film in its place. encounter. The formation of a toner film on the photoreceptor surface is undesirable because it adversely affects the quality of the deposited image. The toner film problem is particularly acute in high speed copy printing and copying machines where cleaning devices such as cleaning blades contact residual toner particles and the photoreceptor at higher speeds than in conventional electrostatic recording systems. Accordingly, there continues to be a need for better systems for developing electrostatic latent images, transferring the resulting developed image, and then cleaning the image surface. For a detailed discussion of this technique and the special parameters required for its use in electrostatically developed image formation and systems, mention may be made in particular of the following patents, which are hereby incorporated by reference: Incorporate:
U.S. Patent Nos. 2,221,776 and 2,297,691 issued to CarlsOn, U.S. Patent No. 2,618,552 issued to Wise, and U.S. Patent No. 2 issued to Walkup.
No. 638416, No. 2777957 and No. 283
No. 2977, issued to Grieg, No. 2874063, Gundlac.
No. 3166342 issued for k), graph,
Issued to Giunia etc. (Graff, Jr., etal)? No. 3186838, male horn (0sb0
No. 3301126 issued to RN) and No. 3552 issued to ROykaetal.
No. 850.

It is an object of the present invention to provide a development system which overcomes the above-mentioned disadvantages or problems.

Yet another object of the present invention is to provide a development system that more completely transfers the development material. Another object of the present invention is to provide a development system that reduces photoreceptor degradation and wear. Yet another object of the present invention is to provide a development system that reduces toner film formation on the photoreceptor surface. Yet another object of the present invention is to provide a developer material having superior physical, electrical and chemical properties compared to known developer materials. Other objects and advantages will become apparent to those skilled in the art to which the invention pertains upon a thorough reading and understanding of the following description. The above purposes and others generally include the production of stable, strong, non-staining polymeric additives of polystyrene with pigmented or pigmented toner particles and submicron to micron particle sizes. This is achieved by providing a developing material consisting of a small proportion of . This polystyrene additive can be incorporated into the final developer material in any suitable manner,
A physical mix is formed between the additive grains and the developing material grains.

That is, for example, the polystyrene additive grains can be first mixed with carrier grains or toner grains and then introduced into the developer mix. Generally, when the additive is physically mixed with the toner or carrier particles, satisfactory results can be achieved when using from about 0.15% to about 15% of the additive, based on the weight of the toner particles. The additive may be about 0.08% to about 5% based on the weight of toner in the final developer mixture.
%, a greater cleaning effect is achieved with reduced cleaning pressure. Rockwell hardness of at least about R-10 using the dimensions specified for corresponding compositions.
Any suitable polystyrene additive having a polystyrene (ASTM test D/785) can be used in the developer of the present invention. Undesirable toner film formation is inhibited by the use of strong polystyrene doped grains having a Rockwell hardness of about R-10. Optionally, about R-1
Additive materials having Rockwell hardnesses as high as 20 can also be used to form the developers of the present invention. The molecular weight of the polystyrene should be such that the glass transition temperature is at least about 110 below.

Higher numbers are normally preferred. Generally, the polystyrene additive particles have an average particle size that is smaller than the approximate particle size of the toner particles. Average particle sizes of about 0.05 to about 10 microns can be used. 1 or less, preferably 0.2
Particularly good results are obtained when using average particle sizes of from about 0.4 microns to about 0.4 microns.

This is because effective cleaning is achieved without adversely affecting image density as a result of the presence of additive particles in the transferred toner image. The additives of the invention may be in any suitable form. Typical shapes include flakes, cylinders, spheres, granules, and irregularly shaped particles. However, optimal results are obtained when using additive grains with a spherical shape. This is because residual toner particles can be more effectively removed with a lower cleaning force. Any suitable pigmented or dye-colored electroscopic toner can be treated with the polystyrene additives of this invention.

Typical toner materials include polystyrene resin, acrylic resin, polyethylene resin, polyvinyl chloride resin,
Polyacrylamide resin, ethacrylate resin, polyethylene terephthalate resin, polyamide resin, 2,2-bis-(4-hydroxyisopropoxyphenyl)-
Includes resinous condensation products of propane and fumaric acid, and copolymers, polyblends and mixtures thereof. Vinyl resins having melting points or melting ranges beginning at least about 110 degrees Fahrenheit are particularly suitable for use in the toners of the present invention. These vinyl resins can be homopolymers or copolymers of two or more vinyl monomers. Typical monomer units that can be used to form vinyl polymers include:
Styrene; vinylnaphthalene; ethylene, propylene,
Monoolefins such as butylene, isobutylene, etc.;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc.; methyl acrylate,
Alpha-amethylene aliphatic monomers such as ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. Esters of carboxylic acids include vinyl ethers such as vinyl methyl ether, pinyl isobutyl ether, vinyl ethyl ether, etc.; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, etc., and mixtures thereof. Generally, suitable vinyl resins for use in toners have an average molecular weight of about 3,000 to about 500,000. Magnetic toner materials can also be used. Toner resins containing a relatively high proportion of styrene resin are preferred because a higher degree of image ring can be achieved with a certain amount of additive material.

Additionally, denser images are obtained when the styrene resin is present in the toner at least about 25% by weight based on the total weight of resin in the toner. Styrenic resins can be homopolymers of styrene or styrene homologs, or copolymers of styrene with another group of monomers containing one methylene group attached to a carbon atom by a double bond. That is, typical monomer substances that can be copolymerized with styrene through addition polymerization include: vinylnaphthalene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. Vinyl esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, methacrylate esters of alpha-amethylene aliphatic monocarboxylic acids such as butyl acid; vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; and It includes mixtures thereof. Styrenic resins can also be formed by polymerization of mixtures of two or more such unsaturated monomeric materials and styrene monomer. Vinyl resins, including styrenic resins, can also be blended with one or more other resins, if desired.

When blending vinyl resin with another resin,
Preferably, the added resin is another vinyl resin. This is because the resulting formulations may have particularly good tribostatic stability and uniform resistance to physical degradation characteristics. The vinyl resin used in blending the styrene compound with other vinyl resins may be prepared by addition polymerization of any suitable vinyl monomer, such as those mentioned above. Other thermoplastic resins may also be blended with the vinyl resins of this invention. Other resins that may be used include non-vinyl thermoplastic resins such as: rosin-modified phenol formaldehyde resins, oil-modified epoxy resins, polyurethane resins, cellulose resins, polyether resins, polycarbonate resins, polyester resins. , polyamide resins and mixtures thereof. The specific compositions for the units contained in the additives and resins of this invention represent the wide variety of units present, but exclude the presence of other monomeric units or reactants other than those shown. It should be understood that it is not a thing.

For example, some commercially available materials, such as polystyrene, contain trace amounts of congeners or unreacted monomers or even partially reacted monomers. Small amounts of such substitutes may be present in the materials of the invention. Any suitable pigment or dye can be used as a colorant for the toner particles.

Toner colorants are well known, such as carbon black, nigrosine dye, nigrosine salt dye, aniline blue calco oil blue.
), Chrome Yellow, Ultramarine Blue, DupOntOilRed, QuinollneYellOw, Methylene Blue Chloride, Phthalocyanine Blue Malachite Green Oxalate
Oxalate), Lampblack, Rose Bengal (
ROseBengal) and mixtures thereof.

The pigment or dye should be present in the toner in an amount sufficient to highly pigment the toner so as to form a clearly visible image on the recording element. Thus, for example, if a conventional xerographic copy of a typed document is desired, the toner may be a black pigment such as carbon black or an Amaplast Black dye.
ckDye) [National Aniline Products Co., Ltd. (Na
tiOnalAnilineProducte, Inc.
．． may contain black dyes such as those available from ).

Preferably, the amount of pigment is from about 1 to about 20% by weight based on the total weight of the pigmented toner. Use in the amount of If the toner colorant used is a dye, substantially less colorant can be used. Whether the resin component is a homopolymer or copolymer or blend, the combination of resin component, colorant, and additive should have a locking temperature of at least about 110'F. .

When the toner is characterized by a blocking temperature of less than about 110'F, the toner particles tend to agglomerate during storage and mechanical handling, and the quality of the image on the surface of a reusable photoreceptor decreases. tend to form undesirable films that have a negative impact on The toner compositions of the present invention may be made by any well known toner mixing and grinding techniques. For example, the components can be blended, mixed, and then pulverized to thoroughly mix each component, and then the resulting mixture can be made into a fine powder. Another known technique for forming toner particles is to spray dry a ball-milled toner composition consisting of colorant, resin, and solvent. The toner should have an average particle size of less than about 30 microns, preferably from about 4 to about 20 microns, for optimal results. Suitable coated and uncoated carrier materials for developers are well known in the art.

The carrier grains are capable of acquiring a charge having a polarity opposite to that of the toner grains, such that when in close contact with the toner grains, the toner grains adhere to and surround the carrier grains. It may consist of any suitable solid material, so long as it is present. If a positive reproduction of the electrostatic image is desired, the carrier particles are selected such that the toner particles acquire a charge having a polarity opposite to that of the electrostatic image. Instead of this,
If it is desired to reproduce the inverse of the electrostatic image, the carrier is selected so that the toner particles acquire a charge having the same polarity as that of the electrostatic image. That is, when the materials for the carrier particles are mixed or brought into contact with each other, one component of the developer becomes positively charged if the other component is less than or equal to the first component in a triboelectric charging system; The other component is selected according to its triboelectrification properties with respect to the electrodetectable toner, such that if the other component is greater than or equal to the first component in the triboelectrification system, it will be negatively charged.
By appropriately selecting the carrier material according to its triboelectric charging action, the polarity of its charge when mixed will cause the electroscopic toner particles to adhere to and coat the surface of the carrier particles. , and to the portion of the electrostatic image-containing surface that has a greater attraction to the toner than the carrier grains. Typical carriers include steel, frit shot, aluminum potassium chloride, Rothsiel salt,
Includes nickel, aluminum nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, vitreous silicon dioxide, etc. The carrier can be used coated or uncoated. Preferably, the diameter of the final coated carrier particles is about the same as the toner size to about 2000 microns, so that the carrier particles have sufficient density and inertia to avoid sticking to the electrostatic image during processing. It is from. The adhesion of carrier beads to the xerographic drum creates deep scratches on its surface during the imaging transfer and drum cleaning process, especially when cleaning is performed with a web cleaner or flexible cleaning blade. Therefore, it is undesirable. Print obliteration also occurs when carrier beads adhere to the xerographic imaging surface. Generally speaking, satisfactory results are obtained when about 1 part toner is used with about 10 to about 1000 parts by weight carrier.
The polystyrene grains of the present invention are characterized by a high degree of dimensional uniformity, size uniformity and smooth surface. Polystyrenes generally useful in the present invention have high molecular weights and critical surface energies of about 33 to about 35 dynes/centimeter.
gy).

Materials useful in the present invention are particularly those manufactured by Tau Chemical Company (DOwC).
commercially available from Chemical Company) and Polyscience Company (POlyscience2lnc.). Submicron to micron sized polystyrene particles useful in the present invention can be obtained by emulsion polymerization using standard techniques.

Radiation without electrodes
plasma-initiated polymerization (P) that often induces adiO)
lasma-InitiatedpOlymeriza
tiOn) is useful for producing submicron-sized polystyrene particles. This polymerization process is carried out by varying the degree of cross-linking, which advantageously improves the mechanical properties of polystyrene and its durability. The developer compositions of the present invention can be used to develop latent electrostatic images on any suitable latent electrostatic image-containing surface, including conventional photoconductive surfaces.

Well-known photoconductive materials include vitreous selenium, organic or inorganic photoconductors embedded in non-uniformly photoconductive matrices, and the like. Representative patents describing photoconductive materials include Ullrich, U.S. Pat. No. 2,803,542;
No. 2970906 against Middleton (
No. 3121006 for MiddletOn);
and No. 3151 to COrrsin.
No. 092, the disclosures of which are incorporated herein by reference. Cleaning systems for abrasively removing residual toner particles from the surface of reusable photoreceptors are well known, as noted above.

Blade cleaning systems include doctor blades made from a wide variety of moderately filled or unfilled natural and synthetic materials.
Use a DOctOrblade or a Wipingblade. Generally, flexible blades made of elastomeric materials such as polyurethane are preferred as they are more effective in removing residual toner particles from the reusable photoreceptor surface. Other elastomeric materials include natural rubber, synthetic rubbers such as BunaS and neoprene, and plasticized polyvinyl chloride. The following examples define, describe, and compare exemplary methods of making and using the development system components of the present invention in development processing. Parts and percentages are by weight unless otherwise specified. The non-control examples are also illustrative of various preferred embodiments of the invention and are not to be considered as limitations on the invention, which is contemplated by the claims.

Reference Example A vitreous selenium drum of an automatic copying machine is corona charged to a positive potential of about 800 volts and exposed to a light and shadow image to form an electrostatic latent image.

This selenium drum is then rotated through a cascade development station. Made by the method described in Example 1 of U.S. Pat. No. 3,079,342 having a critical surface tension value of about 30 dynes/cm and containing styrene-butyl methacrylate copolymer and about 10% by weight carbon black. A control developer consisting of 1 part toner and about 100 parts steel core carrier beads made by the method described in U.S. Pat. No. 2,618,551 is used at this development station.

The toner particles have an average particle size of about 10 microns and the carrier beads have an average particle size of about 450 microns. After developing the electrostatic latent image at this development site, the resulting toner image is transferred to a paper sheet at a transfer site. The remaining toner particles remaining on the selenium drum after passing through the transfer site are removed using a blade having a blade extending obliquely to the photoconductor surface.
Cleaning blade consisting of a 32 inch thick rectangular strip of polyurethane elastomer.

The passing surface of the cleaning blade is arranged to form an acute angle of about 22 planes with the contact line extending through the blade contact line. Sufficient pressure is applied to this blade to achieve maximum removal of toner particles from the drum surface. After the drum surface passes the cleaning blade, it is rotated at a surface speed of about 10 inches/second to make 500 copies.
After only a few copies have been made, the copies and the drum surface are each inspected for quality and condition. The copies made at the beginning and the copies made near the end of the test are characterized by high background, stripes, and irregular image density. Most of the drum is covered with a continuous toner film and has induced streaks and scratches. Measuring the electrical properties of this drum reveals irregularities across the surface due to toner deposits and bow scratches. Example 1 The development process of the reference example is repeated under substantially the same conditions except that about 1 part of polystyrene particles is added to about 100 parts of toner particles.

The polystyrene particles are spherical, with a particle size range of about 0.2 microns to about 1 micron, and a shore D of about 70-80.
Hardness (ASTM test D676) (Rockwell hardness 80
~95) and a glass transition temperature of 125'F. Also, a new vitreous selenium drum is used in place of the drum used in Example 1. After approximately 500 copies have been made, the copies and the xerographic drum surface are each inspected for quality and condition. Copies produced throughout this test were characterized by high density print quality and virtually no background toner deposits. Measurements of the electrical properties of this drum show that it exhibits substantially the same response before and after the test. The surface of this drum shows no signs of toner film formation, streaking or scratches. Example 2 The development process of Example 1 is repeated under substantially the same conditions except that instead of 1 part, about 0.25 part of polystyrene granules is added to about 100 parts of toner particles.

The quality of the copies obtained near the end of this test and the degree of drum damage observed are substantially the same as described in Example 2. As used herein, the expression "developer material" includes electroscopic toner materials or combinations of toner materials and carrier materials.

Although the above example described specific materials and conditions,
These are merely examples of the invention.

Various other suitable toner components, additives, colorants and development techniques, such as those described above, can be used in place of each of this example with similar results. Other materials may also be added to the toner or carrier to improve sensitivity, synergy, or other imaging properties or other desired system properties. Other modifications of the invention will occur to those skilled in the art from reading this description.

Claims (1)

Claims: 1. A stable, strong, substantially non-staining polystyrene particle additive having fine toner particles and an average particle size of about 0.05 to about 10 microns less than the average particle size of the toner particles. wherein the polystyrene particles have a Rockwell hardness of at least about R-10, a glass transition temperature of at least about 110°F, and a critical surface energy of about 33 to about 35 dynes/cm, and the toner particle weight An electrographic developing material characterized in that it is present in an amount of about 0.05 to about 15% by weight. 2. The electrographic developer material of claim 1, wherein the additive has an average particle size of less than about 1 micron. 3. The electrographic developer material of claim 1, wherein the additive has a Rockwell hardness of about R-10 to about R-120. 4. The electrostatic recording developing material according to claim 1, wherein the additive consists of spherical particles. 5 Forming an electrostatic latent image on an imageable surface, which imageable surface is divided into a fine mark-forming material and a small percentage based on the weight of the mark-forming material, the average particle size of a fine toner material. A stable, strong, and substantially non-contaminating material having a smaller average particle size, thereby allowing at least a portion of the fine mark-forming material to be deposited and retained on the imaging surface in conformity with the electrostatic latent image. 1. A method of forming an image comprising forming a toner image on an imageable surface by contacting the toner image with an electrographic developing material comprising particles containing a polystyrene additive. 6 to form an electrostatic latent image on an imageable surface and to form the imageable surface with a fine toner material having an average particle size of less than about 30 microns, based on the weight of the toner material from about 0.05 to about in an amount of 15% by weight having an average particle size of less than about 1 micron, thereby stably and strongly depositing and retaining at least a portion of the fine toner material on the imaging surface in conformity with the electrostatic latent image. forming a toner image on the imageable surface by contacting it with an electrographic developer material comprising particles containing a substantially clean polystyrene additive, and transferring the toner image to a receptive surface; cleaning the imageable surface of any residual toner material and then repeating the steps of forming an electrostatic latent image, forming a toner image, transferring the toner image, and cleaning the residual toner material at least one more time. An image forming method.