Patent Application
20130295500
This invention relates to a method for providing toner images using fluorescing toner particles in which the fluorescing colorant is covalently attached to a polymer within the toner particles.
One common method for printing images on a receiver material is referred to as electrophotography. The production of black-and-white or color images using electrophotography generally includes the producing a latent electrostatic image by uniformly charging a dielectric member such as a photoconductive substance, and then discharging selected areas of the uniform charge to yield an imagewise electrostatic charge pattern. Such discharge is generally accomplished by exposing the uniformly charged dielectric member to actinic radiation provided by selectively activating particular light sources in an LED array or a laser device directed at the dielectric member. After the imagewise charge pattern is formed, it is “developed” into a visible image using pigmented or non-pigmented marking particles (generally referred to as “toner particles”) by either using the charge area development (CAD) or the discharge area development (DAD) method that have an opposite charge to the dielectric member and are brought into the vicinity of the dielectric member so as to be attracted to the imagewise charge pattern.
Thereafter, a suitable receiver material (for example, a cut sheet of plain bond paper) is brought into juxtaposition with the toner image developed with the toner particles in accordance with the imagewise charge pattern on the dielectric member, either directly or using an intermediate transfer member. A suitable electric field is applied to transfer the toner particles to the receiver material in the imagewise pattern to form the desired print image on the receiver material. The receiver material is then removed from its operative association with the dielectric member and subjected to suitable heat or pressure or both heat and pressure to permanently fix (also known as fusing) the toner image (containing toner particles) to form the desired image on the receiver material.
Plural toner particle images of, for example, different color toner particles respectively, can be overlaid with multiple toner transfers to the receiver material, followed by fixing of all toner particles to form a multi-color image in the receiver material. Toners that are used in this fashion to prepare multi-color images are generally Cyan (C), Magenta (M), Yellow (Y), and Black (K) toners containing appropriate dyes or pigments to provide the desired colors or tones.
It is also known to use special spot toners to provide additional colors that cannot be obtained by simply mixing the four “primary” toners. An example is a specially designed toner that provides a color spot or pearlescent effect.
With the improved print image quality that is achieved with the more recent electrophotographic technology, print providers and customers alike have been looking for ways to expand the use of images prepared using electrophotography. Printing processes serve not only to reproduce and transmit objective information but also to convey esthetic impressions, for example, for glossy books or pictorial advertizing.
The desire to provide fluorescing effects has existed for several decades and U.S. Pat. No. 3,713,861 (Sharp et al.) describes coating a fluorescent material over a document image.
Many color images cannot be reproduced using the traditional CYMK color toners. Specifically, fluorescing colors or tones cannot be readily reproduced using the CYMK color toner set. It has been proposed to incorporate fluorescing pigments or dyes into liquid toner particles as described in U.S. Pat. No. 5,105,451 (Lubinsky et al.).
U.S. Patent Application Publication 2010/0164218 (Schulze-Hagenest et al.) describes the use of substantially clear (colorless) fluorescent toner particles in printing methods over color toner images. Such clear fluorescent toner particles can be used for security purposes since they are not colored except when excited with appropriate light. Other invisible fluorescent pigments for toner images are described in U.S. Pat. No. 6,664,017 (Patel et al.).
Printing processes for providing one or more color toner images are known, but it is also desired that fluorescing effects can also be provided for any type of color toner image in order to expand the color gamut while using conventional non-fluorescing color toners. However, it has been difficult to properly design desired fluorescing effects using known fluorescing colorants (dyes and pigments) as many of them are very sensitive to the illuminating radiation.
In addition, some fluorescing colorants are difficult to disperse within various polymeric binders that are used to prepare dry toner particles. The fluorescing colorants could also adversely affect the charging properties of the toner particles. For example, many of the fluorescing colorants are positive-charging and therefore it is very difficult to prepare negative-charging toners using such fluorescing colorants. Furthermore, most of the fluorescing colorants exhibit undesirable solubility in hot silicone fuser oils used during the fixing (fusing) steps of the printing process. This can lead to coloration of the entire image even where no color toner is applied, because the hot fusing oil is absorbed and carried throughout the apparatus by the receiver materials. All of these shortcomings can diminish the effects intended from use of the fluorescing colorants.
There is a need to expand the possible color gamut with fluorescing effects without the noted problems.
This invention provides a fluorescing dry toner particle comprising a polymeric binder phase comprising a non-fluorescing binder polymer, and a polymeric fluorescing colorant dispersed within the non-fluorescing binder polymer, wherein:
(a) the polymeric fluorescing colorant comprises a fluorescing moiety that is covalently attached to a colorant polymer that is the same or different than the non-fluorescing binder polymer, but the polymeric fluorescing colorant is blendable with the non-fluorescing binder polymer to form a homogeneous polymeric binder matrix, and
(b) the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 40 weight %, based on the total fluorescing dry toner particle weight.
A plurality of these fluorescing dry toner particles can be formulated and used a dry mono-component or two-component developers.
This invention also provides a method for providing a toner image, the method comprising:
forming a latent image,
developing the latent image with fluorescing dry toner particles of this invention, to form a developed fluorescing toner image,
transferring the developed fluorescing toner image comprising the fluorescing dry toner particles to a receiver material to form a transferred fluorescing toner image, and
fixing the transferred fluorescing toner image to the receiver material.
In some embodiments, this method comprises:
forming the latent image as an electrostatic latent image on a primary imaging member,
electrostatically transferring the developed fluorescing toner image from the primary imaging member to the receiver material to form the transferred fluorescing toner image, and
fixing the transferred fluorescing toner image to the receiver material at a temperature of at least 135° C.
From this method, the present invention provides an imaged receiver material, comprising a toner image comprising fused fluorescing dry toner particles of this invention.
In addition, this invention provides a method for preparing fluorescing dry toner particles, the method comprising:
dry blending non-fluorescing binder polymer particles with a polymeric fluorescing colorant, and optionally one or more of a charge control agent, wax, lubricant, fuser release aid, or non-fluorescing colorant to form a fluorescing dry blend,
melt extruding the fluorescing dry blend to form an extruded fluorescing composition, and
breaking up the extruded fluorescing composition into fluorescing dry toner particles, each fluorescing dry toner particle comprising a polymeric binder phase comprising a non-fluorescing binder polymer, and a polymeric fluorescing colorant dispersed within the non-fluorescing binder polymer,
wherein:
(a) the polymeric fluorescing colorant comprises a fluorescing moiety that is covalently attached to a colorant polymer that is the same or different than the non-fluorescing binder polymer, but which polymeric fluorescing colorant is blendable with the non-fluorescing binder polymer to form a homogeneous polymeric binder matrix, and
(b) the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 40 weight %, based on the total fluorescing dry toner particle weight.
Such method can further comprise:
providing hydrophobic flow additive particles having an equivalent circular diameter (ECD) of at least 5 nm on the outer surface of the fluorescing dry toner particles, or
mixing the fluorescing dry toner particles with carrier particles to form a two-component dry developer, or both.
Moreover, the present invention provides a unique polymeric fluorescing colorant comprising a fluorescing moiety that is covalently attached to a colorant polymer, wherein the polymeric fluorescing colorant emits at one or more peak wavelengths of at least 420 nm and up to and including 690 nm, and wherein the colorant polymer is derived from a precursor polymer comprising reactive groups selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, which reactive groups are reactive with the fluorescing moiety.
The fluorescing dry toner particles of this invention are useful to provide fluorescing effects when used alone or in combination with color toner images that contain non-fluorescing colorants. This desirable effect can have the appearance of a light magenta shade (or a “pinkish” shade), light yellow, or light cyan shade depending upon the fluorescing moiety used and the density of this effect can be varied by changing the lay down.
It is particularly useful to provide fluorescing magenta and fluorescing yellow effects alone or in combination with composite non-fluorescing color toner images (for example, CYM or CYMK), in any desired sequence of toner image formation. Thus surprisingly new color effects can be obtained, opening a wider gamut of color image options for various purposes. Various amounts of the visible fluorescing dry toner particles providing fluorescing effects, or various amounts of individual or combined non-fluorescing color toner images (various color densities) can further expand the options for various color effects. An infinite number of color toner images with fluorescing effects can be produced.
In the practice of this invention, when the known CYM or CYMK color toner images are used, the addition of the fluorescing dry toner image provides higher chroma images that are reproducible and the effect does not substantially change when different light is used for illumination.
Because the fluorescing moieties used in the dry toner particles of this invention are covalently attached to a polymer in the polymeric binder phase, there are further improvements. For example, there is less dusting and contamination of toner particles inside the imaging apparatus (for example, printer), faster charging rates, good negative charge in the fluorescing dry toner particles, and reduced solubility of the fluorescing moiety in hot silicone fuser oils. It was also surprisingly found that the fluorescing dry toner particles have improved light fastness.
As used herein to define various components of the fluorescing dry toner particles, polymeric binders, fluorescing colorants, non-fluorescing colorants, and other components, unless otherwise indicated, the singular forms “a”, “an”, and “the” are intended to include one or more of the components (that is, including plurality referents).
Each term that is not explicitly defined in the present application is to be understood to have a meaning that is commonly accepted by those skilled in the art. If the construction of a term would render it meaningless or essentially meaningless in its context, the term's definition should be taken from a standard dictionary.
The use of numerical values in the various ranges specified herein, unless otherwise expressly indicated otherwise, are considered to be approximations as though the minimum and maximum values within the stated ranges were both preceded by the word “about”. In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as the values within the ranges. In addition, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.
The terms “particle size”, “size”, and “sized” as used herein in reference to toner particles including the fluorescing dry toner particles used in this invention, are defined in terms of the mean volume weighted diameter (Dvol, in μm) as measured by conventional diameter measuring devices such as a Coulter Multisizer (Coulter, Inc.). The mean volume weighted diameter is the sum of the mass of fluorescing dry toner particle multiplied by the diameter of a spherical particle of equal mass and density, divided by the total fluorescing dry toner particle mass.
“Equivalent circular diameter” (ECD) may be used herein to define the size (for example, in μm) some particles described herein, and it represents the diameter of a circle that has essentially the same area as a particle projected image when the particle is lying flat to the field of view. This allows irregularly shaped particles as well as spherical particles to be measured using the same parameter. Techniques for measuring ECD are known in the art.
The term “electrostatic printing process” as used herein refers to printing methods including but not limited to, electrophotography and direct, solid dry toner printing as described herein. As used in this invention, electrostatic printing means does not include the use of liquid toners to form images on receiver materials.
The term “color” as used herein refers to dry non-fluorescing color toner particles containing one or more non-fluorescing colorants (dyes or pigments) that provide a color or hue having an optical density of at least 0.2 at the maximum exposure so as to distinguish them from “colorless” dry toner particles that have a lower optical density. By non-fluorescing colorants, it is meant that the colorants do not emit light or “fluoresce” upon exposure to light of a different wavelength to a significant degree.
The term “fluorescing” refers to a colorant, moiety, dry toner particle, or toner image that emits at one or more peak wavelengths at least 420 nm and up to and including 690 nm provides a color or hue having an optical density of at least 0.2 when irradiated with appropriate light. The “fluorescing magenta” moieties and polymeric colorants emit at one or more peak wavelengths of at least 510 nm and up to and including 590 nm, and particular at one or more peak wavelengths of at least 520 nm and up to and including 580 nm. The “fluorescing yellow” moieties and polymeric colorants emit at one or more peak wavelengths of at least 510 nm and up to and including 570 nm, and particular at one or more peak wavelength of at least 520 nm and up to and including 560 nm. The “fluorescing cyan” moieties and polymeric colorants emit at one or more peak wavelengths of at least 420 nm and up to and including 480 nm, and particular at one or more peak wavelengths of at least 430 nm and up to and including 470 nm.
The term “peak wavelength” in reference to the visible fluorescing magenta colorants in the visible fluorescing magenta dry toner particles means an emission peak within the noted range of wavelengths that provides the desired fluorescing magenta effect according to this invention. There can be multiple peak wavelengths for a given visible fluorescing colorant. It is not necessary that the λmax be within the noted range of wavelengths or that the peak wavelength of interest be the λmax. However, many useful visible fluorescing colorants will have a λmax within the noted range of wavelengths and this λmax can also be the desired “peak” wavelength.
The term “composite”, when used in reference to developed color toner images or developed and fixed color toner images, refers to the combination of at least 2 (for example, CM) and up to 4 (for example, CYMK), non-fluorescing color toner images in the same multicolor toner image.
The term “covering power” refers to the coloring strength (optical density) value of fixed dry toner particles on a specific receiver material, or the ability of the fixed dry toner particles to “cover” or hide radiation reflected from the receiver material. For example, covering power values can be determined by making patches of varying densities from non-fixed dry toner particles on a receiver material such as a clear film. The weight and area of each of these patches is measured, and the dry toner particles in each patch are fixed for example in an oven with controlled temperature that is hot enough to melt the dry toner particles sufficiently to form a continuous thin film in each patch on the receiver material. The transmission densities of the resulting patches of thin films are measured with a Status A blue filter on an X-rite densitometer (other conventional densitometers can be used). A plot of the patch transmission densities vs. initial patch dry toner weight is prepared, and the weight per unit area of toner thin film is calculated at a transmission density of 1.0. The reciprocal of this value, in units of cm2/g of fixed dry toner particles, is the “covering power”.
Another way of saying this is that the covering power is the area of the receiver material that is covered to a transmission density of 1.0 by 1 gram of dry toner particles. As the covering power increases, the “yield” of the dry toner particles increases, meaning that less mass of dry toner particles is needed to create the same amount of density area coverage in a printed image on the receiver material. Thus, covering power is a measurement that is taken after the dry toner particles are fixed (or fused) to a given receiver material. A skilled worker would be able from this description to measure the covering power of any particular dry toner particle composition (containing polymer binder, colorants, and optional addenda), receiver material, and fixing conditions as used in the practice of this invention.
The present invention comprises fluorescing dry toner particles and compositions of multiple dry toner particles that can be used for reproduction of a fluorescing hue or effect, particularly a fluorescing magenta, fluorescing cyan, or fluorescing yellow hue, by an electrostatic printing process, especially by an electrophotographic imaging process.
These fluorescing dry toner particles can be porous or nonporous. For example, if they are porous particles, up to 60% of the volume can be occupied or unoccupied pores within the polymeric binder phase (matrix). The polymeric fluorescing colorants can be within the pores or within the polymeric binder phase. In many embodiments, the fluorescing dry toner particles are not purposely designed to be porous although pores may be created unintentionally during manufacture. In such “nonporous” embodiments, the porosity of the fluorescing dry toner particles of this invention is less than 10% based on the total particle volume within the external particle surface, and the polymeric fluorescing colorants are predominantly (at least 90 weight %) in the polymeric binder phase.
The fluorescing dry toner particles of this invention are generally non-magnetic in that magnetic materials are not purposely incorporated within the polymeric binder phase.
The fluorescing dry toner particles have an external particle surface and consist essentially of a polymeric binder phase and one or more polymeric fluorescing colorants (described below) that are generally uniformly dispersed within the polymeric binder phase to provide, when fixed (or fused) and excited by appropriate radiation, the fluorescing effects described herein.
As described in more detail below, these fluorescing dry toner particles can be used for imaging in combination with non-fluorescing dry color toner particles as described below that provide one or more non-fluorescing colors in a composite color toner image.
Optional additives (described below) can be incorporated into the fluorescing dry toner particles used in this invention to provide various properties that are useful for electrostatic printing processes. However, only the polymeric binder phase and the polymeric fluorescing colorants described herein are essential for providing the desired fluorescing effects in a fixed composite color toner image and for this purpose, they are the only essential components of the fluorescing dry toner particles.
The polymeric binder phase is generally a continuous polymeric phase comprising one or more non-fluorescing polymeric binders that are suitable for the various imaging methods described herein. Many useful non-fluorescing binder polymers are known in the art as being suitable for forming dry toner particles as they will behave properly (melt and flow) during thermal fixing of the toner particles to a suitable receiver material. Such non-fluorescing polymeric binders generally are amorphous and each has a glass transition temperature (Tg) of at least 50° C. and up to and including 100° C. In addition, the fluorescing dry toner particles prepared from these non-fluorescing polymeric binders have a caking temperature of at least 50° C. so that the fluorescing dry toner particles can be stored for relatively long periods of time at fairly high temperatures without having individual particles agglomerate and clump together.
Useful non-fluorescing polymeric binders for providing the polymeric binder phase include but are not limited to, polycarbonates, resin-modified malic alkyd polymers, polyamides, phenol-formaldehyde polymers and various derivatives thereof, polyester condensates, modified alkyd polymers, aromatic polymers containing alternating methylene and aromatic units, and fusible crosslinked polymers.
Other useful non-fluorescing polymeric binders are vinyl polymers, such as homopolymers and copolymers derived from two or more ethylenically unsaturated polymerizable monomers. For example, useful copolymers can be derived one or more of styrene or a styrene derivative, vinyl naphthalene, p-chlorostyrene, unsaturated mono-olefins such as ethylene, propylene, butylene, and isobutylene, vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, vinyl esters such as esters of mono carboxylic acids including acrylates and methacrylates, acrylonitrile, methacrylonitrile, acrylamides, methacrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether, N-vinyl indole, N-vinyl pyrrolidone, and others that would be readily apparent to one skilled in the electrophotographic polymer art.
For example, homopolymers and copolymers derived from styrene or styrene derivatives can comprise at least 40 weight % and to and including 100 weight % of recurring units derived from styrene or styrene derivatives (homologs) and from 0 to and including 40 weight % of recurring units derived from one or more lower alkyl acrylates or methacrylates (the term “lower alkyl” means alkyl groups having 1 to 6 carbon atoms). Other useful non-fluorescing polymeric binders include fusible styrene-acrylic copolymers that are partially crosslinked by incorporating recurring units derived from a divinyl ethylenically unsaturated polymerizable monomer such as divinylbenzene or a diacrylate or dimethacrylate. Polymeric binders of this type are described, for example, in U.S. Reissue Pat. No. 31,072 (Jadwin et al.) the disclosure of which is incorporated herein by reference. Mixtures of such non-fluorescing polymeric binders can be used if desired.
Some useful non-fluorescing polymeric binders are derived from styrene or another vinyl aromatic ethylenically unsaturated polymerizable monomer and one or more alkyl acrylates, alkyl methacrylates, or dienes wherein the styrene recurring units comprise at least 60% by weight of the polymer. For example, copolymers that are derived from styrene and either butyl acrylate or butadiene are also useful as non-fluorescing polymeric binders, or these copolymers can be part of blends of non-fluorescing polymeric binders. For example, a blend of poly(styrene-co-butyl acrylate) and poly(styrene-co-butadiene) can be used wherein the weight ratio of the first polymeric binder to the second polymeric binder is from 10:1 to 1:10, or from 5:1 to 1:5.
Styrene-containing polymers are particularly useful and can be derived from one or more of styrene, α-methylstyrene, p-chlorostyrene, and vinyl toluene. Useful alkyl acrylates, alkyl methacrylates, and monocarboxylic acids that can be copolymerized with styrene or styrene derivatives include but are not limited to, acrylic acid, methyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, ethyl methacrylate, butyl methacrylate, and octyl methacrylate.
Condensation polymers are also useful as non-fluorescing polymeric binders in the visible fluorescing magenta dry toner particles. Useful condensation polymers include but are not limited to, polycarbonates, polyamides, polyesters, polywaxes, epoxy resins, polyurethanes, and polymeric esterification products of a polycarboxylic acid and a diol comprising a bisphenol. Particularly useful condensation polymeric binders include polyesters and copolyesters that are derived from one or more aromatic dicarboxylic acids and one or more aliphatic diols, including polyesters derived from isophthalic or terephthalic acid and diols such as ethylene glycol, cyclohexane dimethanol, and bisphenols (such as Bisphenol A). Other useful polyester binders can be obtained by the co-polycondensation polymerization of a carboxylic acid component comprising a carboxylic acid having two or more valencies, an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, or pyromellitic acid), using as a diol component a bisphenol derivative or a substituted compound thereof. Other useful polyesters are copolyesters prepared from terephthalic acid (including substituted terephthalic acid), a bis[(hydroxyalkoxy)phenyl]alkane having 1 to 4 carbon atoms in the alkoxy radical and from 1 to 10 carbon atoms in the alkane moiety (that can also be a halogen-substituted alkane), and an alkylene glycol having from 1 to 4 carbon atoms in the alkylene moiety. Specific examples of such condensation copolyesters and how they are made are provided for example in U.S. Pat. Nos. 5,120,631 (Kanbayashi et al.), 4,430,408 (Sitaramiah), and 5,714,295 (Wilson et al.), the disclosures which are incorporated herein by reference for describing such polymeric binders. A propoxylated bisphenol—A fumarate is a useful polyester.
Useful polycarbonates are described in U.S. Pat. No. 3,694,359 (Merrill et al.) the disclosure of which is incorporated by reference, which polycarbonates can contain alklidene diarylene moieties in recurring units.
Other specific non-fluorescing polymeric binders useful in the fluorescing dry toner particles are described in [0031] of U.S. Patent Application Publication 2011/0262858 (noted above) the disclosure of which is incorporated herein by reference.
In some embodiments, the polymeric binder phase comprises a polyester or a vinyl polymer that is at least partially derived from styrene or a styrene derivative, both of which are described above.
In general, one or more non-fluorescing polymeric binders are present in the fluorescing dry toner particles in an amount of at least 50 weight % and up to and including 80 weight %, or typically at least 60 weight % and up to and including 75 weight %, based on the total fluorescing dry toner particle weight.
The fluorescing dry toner particles used in this invention are not generally perfectly spherical so it is best to define them by the mean volume weighted diameter (Dvol) that can be determined as described above. Before fixing, the Dvol can be at least 4 μm and up to and including 20 μm and typically at least 5 μm and up to and including 12 μm, but larger or smaller particles may be useful in certain embodiments. Some very small particles can be considered as “liquid” toner particles.
The fluorescing polymeric magenta colorants useful in the practice of this invention comprise a fluorescing magenta moiety that can be derived from any pigment or dye that is known in the art for emitting at one or more peak wavelengths of at least 510 nm and up to and including 590 nm or at one or more peak wavelengths of at least 520 nm and up to and including 580 nm. Such compounds can be readily determined from such sources as Honeywell International (New Jersey), Union Pigment (Hongzhau, China), Dayglo Corporation (Ohio), Clariant Corporation (Rhode Island), H.W. Sands (Jupiter Florida), Sun Chemicals (Ohio), and Risk Reactor (California). Mixtures of two or more of the fluorescing moieties can be used if desired.
The fluorescing polymeric yellow colorants useful in the practice of this invention comprise a fluorescing yellow moiety that can be derived from any pigment or dye that is known in the art for emitting at one or more peak wavelengths of at least 510 nm and up to and including 570 nm or typically at one or more peak wavelengths of least 520 nm and up to and including 560 nm. Such compounds can be selected from the color classes group consisting of coumarins, naphthalimides, perylenes, and anthrones. Such compounds can be readily determined from such sources as Honeywell International (New Jersey), Union Pigment (Hongzhau, China), Dayglo Corporation (Ohio), Clariant Corporation (Rhode Island), H.W. Sands (Jupiter Florida), Sun Chemicals (Ohio), and Risk Reactor (California). Mixtures of two or more of the fluorescing yellow moieties can be used if desired.
The fluorescing polymeric cyan colorants useful in the practice of this invention can comprise a fluorescing cyan moiety that can be derived from any pigment or dye that are known in the art for emitting at one or more peak wavelengths of at least 420 nm and up to and including 480 nm. Such compounds can be readily determined from such sources as described above for the fluorescing magenta and fluorescing yellow colorants.
The various fluorescing moieties are provided as groups that are covalently bonded to the backbone of an appropriate colorant polymer that can be the same or different than the non-fluorescing binder polymers used to compose the polymeric binder phase. In many embodiments, the colorant polymer and non-fluorescing binder polymer(s) are of the same class of polymers, for example, both are polyesters or vinyl polymers such as styrene-containing vinyl copolymers.
The fluorescing moieties are chosen to be appropriately reactive with various reactive groups on a precursor polymer, which reactive groups are selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, which reactive groups are reactive with the fluorescing moiety. Upon reaction, the precursor polymer becomes the “colorant polymer” and the reaction product of the colorant polymer and the fluorescing moiety is the polymeric fluorescing colorant.
A skilled working in the art would be able to choose the appropriate precursor polymer and fluorescing moieties to provide a desired polymeric fluorescing colorant. For example, a precursor polymer could have reactive hydroxyl groups and the fluorescing moieties could have carboxylic or amine groups that are reactive with the reactive hydroxyl groups. The conditions for such reactions would be readily apparent to a skilled chemist using routine experimentation.
The one or more polymeric fluorescing colorants are generally present in the fluorescing dry toner particles in an amount of at least 1 weight % and up to and including 40 weight %, or typically at least 5 weight % and up to and including 24 weight %, based on the total fluorescing dry toner particle weight.
The fluorescing moiety that is attached to the polymeric fluorescing colorant is present in the fluorescing dry toner particles in an amount of at least 1 weight % and up to and including 10 weight %, or typically at least 2 weight % and up to and including 5 weight %, based on the total polymeric fluorescing colorant weight.
Some useful polymeric fluorescing colorant are derived from a precursor polymer that is a polyester, polycarbonate, resin-modified malic alkyd polymer, polyamide, phenol-formaldehyde polymer or vinyl polymer,
wherein the precursor polymer comprises one or more reactive groups selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, through which reactive groups the fluorescing moiety is attached to the precursor polymer.
Various optional additives that can be present in the fluorescing dry toner particles can be added in the dry blend of resin particles and polymeric fluorescing colorants described below. Such optional additives include but are not limited to, non-fluorescing colorants (such as dyes and pigments), charge control agents, waxes, fuser release aids, leveling agents, surfactants, stabilizers, or any combinations of these materials. These additives are generally present in amounts that are known to be useful in the electrophotographic art as they are known to be used in other dry toner particles, including dry color toner particles.
In some embodiments, a spacing agent, fuser release aid, flow additive particles, or combinations of these materials can be provided on the outer surface of the fluorescing dry toner particles, and such materials are provided in amounts that are known in the electrophotographic art. Generally, such materials are added to the fluorescing dry toner particles after they have been prepared using the dry blending, melt extrusion, and breaking process (described below).
Inorganic or organic non-fluorescing colorants (pigments or dyes) can be present in the fluorescing dry toner particles to provide any suitable color, tone, or hue other than fluorescing effect that is achieved with the described fluorescing colorants.
Such colorants can be incorporated into the polymeric binders in known ways, for example by incorporating them in the dry blends described below. Useful colorants or pigments include but are not limited to the following compounds unless they are fluorescing colorants: titanium dioxide, carbon black, Aniline Blue, Calcoil Blue, Chrome Yellow, Ultramarine Blue, DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Malachite Green Oxalate, Lamp Black, Rose Bengal, Colour Index Pigment Red 48:1, Colour Index Pigment Red 57:1, Colour Index Pigment Yellow 97, Colour Index Pigment Yellow 17, Colour Index Pigment Blue 15:1, Colour Index Pigment Blue 15:3, phthalocyanines such as copper phthalocyanine, mono-chlor copper phthalocyanine, hexadecachlor copper phthalocyanine, Phthalocyanine Blue or Colour Index Pigment Green 7, and quinacridones such as Colour Index Pigment Violet 19 or Colour Index Pigment Red 122, and pigments such as HELIOGEN Blue™, HOSTAPERM Pink™, NOVAPERM Yellow™, LITHOL Scarlet™, MICROLITH Brown™, SUDAN Blue™, FANAL Pink™, and PV FAST Blue™. Mixtures of colorants can be used. Other suitable colorants or pigments are described in U.S. Reissue Pat. 31,072 (noted above) and U.S. Pat. No. 4,160,644 (Ryan), 4,416,965 (Sandhu et al.), and 4,414,152 (Santilli et al.), the disclosures of which are incorporated herein by reference.
One or more of such non-fluorescing colorants can be present in the fluorescing dry toner particles in an amount of at least 1 weight % and up to and including 20 weight %, or typically at least 2 and up to and including 15 weight %, based on total fluorescing dry toner particle weight, but a skilled worker in the art would know how to adjust the amount of colorant so that the desired fluorescing effect can be obtained when the fluorescing colorants are mixed with the non-fluorescing colorants.
The non-fluorescing colorants can also be encapsulated using elastomeric resins that are included within the fluorescing dry toner particles. Such a process is described in U.S. Pat. No. 5,298,356 (Tyagi et al.) the disclosure of which is incorporated herein by reference.
Suitable charge control agents and their use in toner particles are well known in the art as described for example in the Handbook of Imaging Materials, 2nd Edition, Marcel Dekker, Inc., New York, ISBN: 0-8247-8903-2, pp. 180ff and references noted therein. The term “charge control” refers to a propensity of the material to modify the triboelectric charging properties of the fluorescing dry toner particles. A wide variety of charge control agents can be used as described in U.S. Pat. Nos. 3,893,935 (Jadwin et al.), 4,079,014 (Burness et al.), 4,323,634 (Jadwin et al.), 4,394,430 (Jadwin et al.), 4,624,907 (Motohashi et al.), 4,814,250 (Kwarta et al.), 4,840,864 (Bugner et al.), 4,834,920 (Bugner et al.), and 4,780,553 (Suzuka et al.), the disclosures of which are incorporated herein by reference. The charge control agents can be transparent or translucent and free of pigments and dyes. Generally, these compounds are colorless or nearly colorless. Mixtures of charge control agents can be used. A desired charge control agent can be chosen depending upon whether a positive or negative charging fluorescing dry toner particle is needed.
Examples of useful charge control agents include but are not limited to, triphenylmethane compounds, ammonium salts, aluminum-azo complexes, chromium-azo complexes, chromium salicylate organo-complex salts, azo-iron complex salts, an azo-iron complex salt such as ferrate (1-), bis[4-[5-chloro-2-hydroxyphenyl)azo]-3-hydroxy-N-phenyl-2-naphthalene-carboxamidato(2-)], ammonium, sodium, or hydrogen (Organoiron available from Hodogaya Chemical Company Ltd.). Other useful charge control agents include but are not limited to, acidic organic charge control agents such as 2,4-dihydro-5-methyl-2-phenyl-31-1-pyrazol-3-one (MPP) and derivatives of MPP such as 2,4-dihydro-5-methyl-2-(2,4,6-trichlorophenyl)-3H-pyrazol-3-one, 2,4-dihydro-5-methyl-2-(2,3,4,5,6-pentafluorophenyl)-3H-pyrazol-3-one, 2,4-dihydro-5-methyl-2-(2-trifluoroethylphenyl)-3H-pyrazol-3-one and the corresponding zinc salts derived therefrom. Other examples include charge control agents with one or more acidic functional groups, such as fumaric acid, malic acid, adipic acid, terephthalic acid, salicylic acid, fumaric acid monoethyl ester, copolymers derived from styrene and methacrylic acid, copolymers of styrene and lithium salt of methacrylic acid, 5,5′-methylenedisalicylic acid, 3,5-di-t-butylbenzoic acid, 3,5-di-t-butyl-4-hydroxybenzoic acid, 5-t-octylsalicylic acid, 7-t-butyl-3-hydroxy-2-napthoic acid, and combinations thereof. Still other acidic charge control agents which are considered to fall within the scope of the invention include N-acylsulfonamides, such as, N-(3,5-di-t-butyl-4-hydroxybenzoyl)-4-chlorobenzenesulfonamide and 1,2-benzisothiazol-3(2H)-one 1,1-dioxide. Another class of charge control agents include, but are not limited to, iron organo metal complexes such as organo iron complexes, for example T77 from Hodogaya. Still another useful charge control agent is a quaternary ammonium functional acrylic polymer.
Other useful charge control agents include alkyl pyridinium halides such as cetyl pyridinium halide, cetyl pyridinium tetrafluoroborates, quaternary ammonium sulfate, and sulfonate charge control agents as described in U.S. Pat. No. 4,338,390 (Lu Chin) the disclosure of which is incorporated herein by reference, stearyl phenethyl dimethyl ammonium tosylates, distearyl dimethyl ammonium methyl sulfate, and stearyl dimethyl hydrogen ammonium tosylate.
One or more charge control agents can be present in the fluorescing dry toner particles in an amount to provide a consistent level of charge of at least −40 μCoulomb/g and to and including −65 μCoulomb/g for a toner particle having a Dvol of 8 μm, when charged. Examples of suitable amounts include at least 0.1 weight % to and including 10 weight %, based on the total fluorescing dry toner particle weight.
Useful waxes (can also be known as lubricants) that can be present in the fluorescing dry toner particles include low molecular weight polyolefins (polyalkylenes) such as polyethylene, polypropylene, and polybutene, such as Polywax 500 and Polywax 1000 waxes from Peterolite, Clariant PE130 and Licowax PE190 waxes from Clariant Chemicals, and Viscol 550 and Viscol 660 waxes from Sanyo. Also useful are ester waxed that are available from Nippon Oil and Fat under the WE-series. Other useful waxes include silicone resins that can be softened by heating, fatty acid amides such as oleamide, erucamide, ricinoleamide, and stearamide, vegetable waxes such as carnauba wax, rice wax, candelilla wax, Japan wax, and jojoba wax, animal waxes such as bees wax, mineral and petroleum waxes such as montan wax, ozocerite, ceresine, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax, and modified products thereof. Irrespective to the origin, waxes having a melting point in the range of at least 30° C. and up to and including 150° C. are useful. One or more waxes can be present in an amount of at least 0.1 weight % and up to and including 20 weight %, or at least 1 weight % and up to and including 10 weight %, based on the total fluorescing dry toner particle weight. These waxes, especially the polyolefins, can be used also as fuser release aids. In some embodiments, the fuser release aids are waxes having 70% crystallinity as measured by differential scanning calorimetry (DSC).
In general, a useful wax has a number average molecular weight (Mn) of at least 500 and up to and including 7,000. Polyalkylene waxes that are useful as fuser release aids can have a polydispersity of at least 2 and up to and including 10 or typically of at least 3 and up to and including 5. Polydispersity is a number representing the weight average molecular weight (Mw) of the polyalkylene wax divided by its number average molecular weight (Mn).
Useful flow additive particles that can be present inside or on the outer surface of the fluorescing dry toner particles include but are not limited to, a metal oxide such as hydrophobic fumed silica particles. As noted above, the flow additive particles can be incorporated into the fluorescing dry toner particles, or they can be disposed on the outer surface of the fluorescing dry toner particles. Alternatively, the flow additive particles can be both incorporated into the fluorescing dry toner particles and on their outer surface. In general, such flow additive particles have an average equivalent spherical diameter (ESD) of at least 5 nm and are present in an amount of at least 0.01 weight % and up to and including 10 weight %, based on the total fluorescing dry toner particle weight.
Surface treatment agents can also be on the outer surface of the fluorescing dry toner particles in an amount sufficient to permit the fluorescing dry toner particles to be stripped from carrier particles in a dry two-component developer by electrostatic forces associated with the charged image or by mechanical forces. Surface fuser release aids can be present on the outer surface of the fluorescing dry toner particles in an amount of at least 0.05 weight % and up to and including 1 weight %, based on the total dry weight of fluorescing dry toner particles. These materials can be applied to the outer surfaces of the fluorescing dry toner particles using known methods for example by powder mixing techniques.
Spacing treatment agent particles (“spacer particles”) can be attached to the outer surface by electrostatic forces or physical means, or both. Useful surface treatment agents include but are not limited to, silica such as those commercially available from Degussa as R972 and RY200 or from Wasker as H2000. Other suitable surface treatment agents include but are not limited to, titania, aluminum, zirconia, or other metal oxide particles, and polymeric beads all generally having an ECD of less than 1 μm. Mixture of these materials can be used if desired, for example a mixture of hydrophobic silica and hydrophobic titania particles.
The fluorescing dry toner particles of this invention can be prepared using any suitable manufacturing procedure wherein colorants are incorporated within the particles and polymeric colorants can also be incorporated into such particles. Such manufacturing methods include but are not limited to, melt extrusion methods, coalescence, spray drying, and other chemical techniques. The fluorescing dry toners can be prepared as “chemically prepared toners”, “polymerized toners”, or “in-situ toners”. They can be prepared using controlled growing instead of grinding. Various chemical processes include suspension polymers, emulsion aggregation, micro-encapsulation, dispersion, and chemical milling. Details of such processes are described for example in the literature cited in [0010] of U.S. Patent Application Publication 2010/0164218 (Schulze-Hagenest et al.) the disclosure of which is incorporated herein by reference. Such dry toner particles can also be prepared using limited coalescence process as described in U.S. Pat. No. 5,298,356 (Tyagi et al.) that is incorporated herein by reference, or a water-in-oil-in-water double emulsion process as described in U.S. Patent Application Publication 2011/0262858 (Nair et al.) the disclosure of which is incorporated herein by reference, especially if porosity is desired in the fluorescing dry toner particles. Another method for preparing fluorescing dry toner particles is by a spray/freeze drying technique as described in U.S. Patent Application Publication 2011/0262654 (Yates et al.) the disclosure of which is incorporated herein by reference.
In a particularly useful manufacturing method, a desired non-fluorescing polymer binder (or mixture of non-fluorescing polymeric binders) for use in the visible fluorescing magenta dry toner particles is produced independently a suitable polymerization processes known in the art. The one or more non-fluorescing polymeric binders are dry blended or mixed as non-fluorescing polymeric resin particles with the desired polymeric fluorescing colorants described above to form a dry blend. The optional additives, such as charge control agents, waxes, fuser release aids, and colorants are also incorporated into the dry blend with the two essential components. The amounts of the essential and optional components can be adjusted in the dry blend in a suitable manner that a skilled worker would readily understand to provide the desired amounts in the resulting fluorescing dry toner particles. The conditions for mechanical dry blending are known in the art.
For example, the method can comprise dry blending the non-fluorescing polymeric resin particles with the polymeric fluorescing colorant(s), and a charge control agent, and optionally with a wax or colorant, or any combination of these optional components, to form a dry blend. The dry blend can be prepared by mechanically blending the components for a suitable time to obtain a uniform dry mix.
The dry blend is then melt processed in a suitable apparatus such as a two-roll mill or hot-melt extruder. In some embodiments, the dry melt is extruded under low shear conditions in an extrusion device to form an extruded composition. However, these low shear conditions are not always required in the practice of this invention. The melt processing time can be from 1 minute to and including 60 minutes, and the time can be adjusted by a skilled worker to provide the desired melt processing temperature and uniformity in the resulting extruded composition.
For example, it is useful to melt extrude a dry blend of the noted components that has a viscosity of at least 90 pascals sec to and including 2300 pascals sec, or typically of at least 150 pascals sec and up to and including 1200 pascals sec.
Generally, the dry blend is melt extruded in the extrusion device at a temperature higher than the glass transition temperature of the one or more non-fluorescing polymeric binders used to form the polymeric binder phase and the one or more polymeric fluorescing colorants, and generally at a temperature of at least 90° C. and up to and including 240° C. or typically of at least 120° C. and up to and including 160° C. The temperature results, in part, from the frictional forces of the melt extrusion process.
The resulting extruded composition (sometimes known as a “melt product” or a “melt slab”) is generally cooled, for example, to room temperature, and then broken up (for example pulverized) into fluorescing dry toner particles having the desired Dvol as described above. It is generally best to first grind the extruded composition prior to a specific pulverizing operation. Grinding can be carried out using any suitable procedure. For example, the extruded composition can be crushed and then ground using for example a fluid energy or jet mill as described for example in U.S. Pat. No. 4,089,472 (Seigel et al.). The particles are then further reduced in size by using high shear pulverizing devices such as a fluid energy mill, and then classified as desired.
The resulting fluorescing dry toner particles can then be surface treated with suitable hydrophobic flow additive particles having an equivalent circular diameter (ECD) of at least 5 nm to affix such hydrophobic flow additive particles on the outer surface of the particles. These hydrophobic flow additive particles can be composed of metal oxide particles such as hydrophobic fumed oxides such as silica, alumina, or titania in an amount of at least 0.01 weight % and up to and including 10 weight % or typically at least 0.1 weight % and up to and including 5 weight %, based on the total fluorescing dry toner particle weight.
In particular, a hydrophobic fumed silica such as R972 or RY200 (from Nippon Aerosil) can be used for this purpose, and the amount of the fumed silica particles can be as noted above, or more typically at least 0.1 weight % and up to and including 3 weight %, based on the total fluorescing dry toner particle weight.
The hydrophobic flow additive particles can be added to the outer surface of the fluorescing dry toner particles by mixing both types of particles in an appropriate mixer.
The resulting treated fluorescing dry toner particles can be classified (sieved) through a 230 mesh vibratory sieve to remove non-attached silica particles, silica agglomerates, and any other components that may not have been incorporated into the fluorescing dry toner particles. The temperature during the surface treatment can be controlled to provide the desired attachment and blending.
Non-fluorescing dry color toner particles useful in the practice of this invention can be prepared in various ways as described above, including the melt extrusion processes described above for the fluorescing dry toner particles of this invention.
The various non-fluorescing dry color toner particles can be prepared using a suitable polymeric binder phase comprising one or more polymeric binders (as described above) and one or more of non-fluorescing cyan, yellow, magenta, or black colorants. For example, such colorants can be in principle any of the colorants described in the Colour Index, Vols. I and II, 2nd Edition (1987) or in the Pantone® Color Formula Guide, 1st Edition, 2000-2001. The choice of particular colorants for the cyan, yellow, magenta, and black (CYMK) color toners is well described in the art, for example in the proceedings of IS&T NIP 20: International Conference on Digital Printing Technologies, IS&T: The Society for Imaging Science and Technology, 7003 Kilworth Lane, Springfield, Va. 22151 USA ISBM: 0-89208-253-4, p. 135. Carbon black is generally useful as the black toner colorant while other colorants for the CYM color toners include but are not limited to, red, blue, and green pigments, respectively. Specific colorants can include copper phthalocyanine and Pigment Blue that can be obtained as Lupreton Blue™ SE 1163. Other colorants useful in non-fluorescing dry color toners are also described above as non-fluorescing colorants for the fluorescing dry toner particles of this invention.
The amount of one or more non-fluorescing colorants in the non-fluorescing dry color toners can vary over a wide range and a skilled worker in the art would know how to pick the appropriate amount for a given non-fluorescing colorant or mixture of colorants. In general, the total non-fluorescing colorants in each non-fluorescing dry color toner can be at least 1 weight % and up to and including 40 weight %, or typically at least 3 weight % and up to and including 25 weight %, based on the total dry color toner weight. The non-fluorescing colorant in each non-fluorescing dry color toner can also have the function of providing charge control, and a charge control agent (as described above) can also provide coloration. All of the optional additives described above for the fluorescing dry toner particles of this invention can likewise be used in the non-fluorescing dry color toners.
The fluorescing dry toner particles of this invention can be used as a dry mono-component developer, or combined with carrier particles to form dry two-component developers. In all of these embodiments, a plurality (usually thousands or millions) of such individual fluorescing dry toner particles are used together.
Such dry mono-component or dry two-component developers generally comprise a charge control agent, wax, lubricant, fuser release aid, or any combination of these materials within the fluorescing dry toner particles, or they can also include flow additive particles on the outer surface of the particles. Such components are described above.
Useful dry one-component developers generally include the fluorescing dry toner particles as the essential component. Dry two-component developers generally comprise carrier particles (also known as carrier vehicles) that are known in the electrophotographic art and can be selected from a variety of materials. Carrier particles can be uncoated carrier core particles (such as magnetic particles) and core magnetic particles that are overcoated with a thin layer of a film-forming polymer such as a silicone resin type polymer, poly(vinylidene fluoride), poly(methyl methacrylate), or mixtures of poly(vinylidene fluoride) and poly(methyl methacrylate).
The amount of fluorescing dry toner particles in a two-component developer can be at least 4 weight % and up to and including 20 weight %.
The fluorescing dry toner particles of this invention can be applied to a suitable receiver material (or substrate) of any type using various methods such as a digital printing process such as an electrostatic printing process, or electrophotographic printing process as described in L. B. Schein, Electrophotography and Development Physics, 2nd Edition, Laplacian Press, Morgan Hill, Calif., 1996 (ISBN 1-885540-02-7), or by an electrostatic coating process as described for example in U.S. Pat. No. 6,342,273 (Handels et al.) the disclosure of which is incorporated herein by reference.
Such receiver materials include, but are not limited to, coated or uncoated papers (cellulosic or polymeric papers), transparent polymeric films, ceramics, paperboard, cardboard, metals, fibrous webs or ribbons, and other substrate materials that would be readily apparent to one skilled in the art. In particular, the receiver materials (also known as the final receiver material or final receiver material) can be sheets of paper or polymeric films that are fed from a supply of receiver materials.
For example, the fluorescing dry toner particles can be applied to a receiver material by a digital printing process such as an electrostatic printing process that includes but is not limited to, an electrophotographic printing process, or by a coating process such as an electrostatic coating process including an electrostatic brush coating as described in U.S. Pat. No. 6,342,273 (noted above).
In one electrophotographic method, a latent image (that is an electrostatic latent image) can be formed on a primary imaging member such as a charged photoconductor belt or roller using a suitable light source such as a laser or light emitting diode. This latent image is then developed on the primary imaging member by bringing the latent image into close proximity with a dry one-component or dry two-component developer comprising the fluorescing dry toner particles described herein to form a developed fluorescing dry toner image on the primary imaging member. Thus, this developed fluorescing dry toner image can be a developed fluorescing magenta toner image, fluorescing yellow toner image, or fluorescing cyan toner image, or combinations of two or more of such toner images. These fluorescing toner images can be provided on the receiver material as the sole toner images, or they can be provided under or over non-fluorescing color toner images, or both.
In the embodiments of multi-color printing, multiple photoconductors can be used, each developing a separate non-fluorescing color dry toner image and one or more other photoconductors for developing one or more fluorescing dry toner images. Alternatively, a single photoconductor can be used with multiple developing stations where after each latent non-fluorescing image and each fluorescing toner image is developed, it is transferred directly to the “final” receiver material, or it is transferred to an intermediate transfer member (belt or rubber) and then to the “final” receiver material after all of the toner images have been accumulated on the intermediate transfer member.
In some embodiments, it is desirable to develop and fix the latent image with sufficient dry toner particles to form an enhanced composite non-fluorescing developed color toner image wherein the covering power of the fluorescing dry toner particles (fluorescing magenta, fluorescing yellow, or fluorescing cyan) in the enhanced composite non-fluorescing developed color toner image is at least 350 cm2/g and up to and including 1100 cm2/g, and the covering power of each of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles in the enhanced composite non-fluorescing developed color toner image is at least 1500 cm2/g and up to and including 2300 cm2/g.
In more particular embodiments, the covering power of the fluorescing dry toner particles (fluorescing magenta, fluorescing yellow, or fluorescing cyan) in the enhanced composite non-fluorescing developed color toner image is at least 400 cm2/g and up to and including 600 cm2/g, and the covering power of each of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles in the enhanced composite non-fluorescing developed color toner image is at least 1700 cm2/g and up to and including 2100 cm2/g.
While a developed dry toner image can be transferred to a final receiver (receiver material) using a thermal or thermal assist process as is known in the art, it is generally transferred using an electrostatic process including an electrophotographic process such as that described in L. B. Schein, Electrophotography and Development Physics, 2nd Edition, Laplacian Press, Morgan Hill, Calif., 1996. The electrostatic transfer can be accomplished using a corona charger or an electrically biased transfer roller to press the receiver material into contact with the primary imaging member while applying an electrostatic field. In an alternative embodiment, a developed toner image can be first transferred from the primary imaging member to an intermediate transfer member (belt or roller) that serves as a receiver material, but not as the final receiver material, and then transferred from the intermediate transfer member to the final receiver material.
Electrophotographic color printing generally includes subtractive color mixing wherein different printing stations in a given apparatus are equipped with non-fluorescing cyan, yellow, magenta, and black toner particles, to be used in any desired sequence. Thus, a plurality of toner images of different non-fluorescing colors can be applied to the same primary imaging member (such as dielectric member), intermediate transfer member, and final receiver material, including one or more non-fluorescing color toner images in combination with the toner image comprising the fluorescing dry toner particles described herein. Such different toner images are generally applied or transferred to the final receiver material in a desired sequence or succession using successive toner application or printing stations as described below.
The various transferred toner images are then fixed (thermally fused) on the receiver material in order to permanently affix them to the receiver material. This fixing can be done using various means such as heating alone (non-contact fixing) using an oven, hot air, radiant, or microwave fusing, or by passing the toner image(s) through a pair of heated rollers (contact fixing) to thereby apply both heat and pressure to the toner image(s) containing toner particles. Generally, one of the rollers is heated to a higher temperature and can have an optional release fluid to its surface. This roller can be referred to as the fuser roller, and the other roller is generally heated to a lower temperature and usually serves the function of applying pressure to the nip formed between the rollers as the toner image(s) is passed through. This second roller can be referred to as a pressure roller. Whatever fixing means is used, the fixing temperature is generally higher than the glass transition temperature of the various toner particles, which Tg can be at least 45° C. and up to and including 90° C. or at least 50° C. and up to and including 70° C. Thus, fixing is generally at a temperature of at least 95° C. and up to and including 220° C. or more generally at a temperature of at least 135° C. and up to and including 210° C.
As the developed toner image(s) on the receiver material is passed through the nip formed between the two rollers, the various fluorescing and non-fluorescing dry toner particles in the developed toner image(s) are softened as their temperature is increased upon contact with the fuser roller. The melted toner particles generally remain affixed on the surface of the receiver material.
For example, the method of this invention can comprise:
forming a non-fluorescing black, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing cyan dry toner images, in sequence, in a composite non-fluorescing developed color image on a receiver material,
then forming the fluorescing dry toner image, over the composite non-fluorescing developed color toner image, and
fixing both the composite non-fluorescing developed color toner image and the fluorescing dry toner image to the receiver material.
It is advantageous that the present invention can be used in a printing apparatus with multiple printing stations, for example where the fluorescing dry toner particles can be applied to a receiver material at the last or first printing station, over, under, or around the composite non-fluorescing developed color toner image.
Certain embodiments of the invention where multiple color toner images are printed along with the fluorescing dry toner image can be achieved using a printing machine that incorporates at least five printing stations or printing units. For example, the printing method can comprise forming composite non-fluorescing cyan (K), non-fluorescing yellow (Y), and non-fluorescing magenta (M) toner images, or composite non-fluorescing black (C), non-fluorescing yellow (Y), non-fluorescing magenta (M), and non-fluorescing cyan (C) toner images, and the fluorescing toner image using the fluorescing dry toner particles of this invention is formed last, on the receiver material using at least five sequential toner stations in a color electrophotographic printing machine. The fluorescing toner image using the fluorescing dry toner particles can be formed over the composite non-fluorescing CYM or non-fluorescing KYMC toner images, or the fluorescing toner image can be formed in different regions of the receiver material so that it is not directly on the non-fluorescing color toner images. Alternatively, some of the fluorescing dry toner particles can be applied to some or to all of the non-fluorescing color toner image and additionally applied to areas of the receiver material that do not have any non-fluorescing color toner image.
A useful printing machine is illustrated in
Receiver materials 5 as shown in
Each of the printing modules M1-M5 includes a photoconductive imaging roller 111, an intermediate transfer roller 112, and a transfer backup roller 113, as is known in the art. For example, at printing module M1, a particular toner separation image can be created on the photoconductive imaging roller 111, transferred to intermediate transfer roller 112, and transferred again to a receiver member 5 moving through a transfer station, which transfer station includes intermediate transfer roller 112 forming a pressure nip with a corresponding transfer backup roller 113.
A receiver material can sequentially pass through the printing modules M1 through M5. In each of the printing modules a toner separation image can be formed on the receiver material 5 to provide the desired color toner image described herein.
Printing apparatus 100 has a fuser of any well known construction, such as the shown fuser assembly 60 using fuser rollers 62 and 64. Even though a fuser 60 using fuser rollers 62 and 64 is shown, it is noted that different non-contact fusers using primarily heat for the fusing step can be beneficial as they can reduce compaction of toner layers formed on the receiver material 5, thereby enhancing tactile feel.
A logic and control unit (LCU) 230 can include one or more processors and in response to signals from various sensors (CONT) associated with the electrophotographic printer apparatus 100 provides timing and control signals to the respective components to provide control of the various components and process control parameters of the apparatus as known in the art.
Although not shown, the printer apparatus 100 can have a duplex path to allow feeding a receiver material having a fused toner image thereon back to printing modules M1 through M5. When such a duplex path is provided, two sided printing on the receiver material or multiple printing on the same side is possible.
Operation of the printing apparatus 100 will be described. Image data for writing by the printer apparatus 100 are received and can be processed by a raster image processor (RIP), which can include a color separation screen generator or generators. The image data include information to be formed on a receiver material, which information is also processed by the raster image processor. The output of the RIP can be stored in frame or line buffers for transmission of the color separation print data to each of the respective printing modules M1 through M5 for printing color separations in the desired order. The RIP or color separation screen generator can be a part of the printer apparatus or remote therefrom. Image data processed by the RIP can at least partially include data from a color document scanner, a digital camera, a computer, a memory or network. The image data typically include image data representing a continuous image that needs to be reprocessed into halftone image data in order to be adequately represented by the printer.
While these embodiments refer to a printing machine comprising five sets of single toner image producing or printing stations or modules arranged in tandem (sequence), a printing machine can be used that includes more or less than five printing stations to provide a color toner image on the receiver material with two or more different toner images including at least one fluorescing toner image. Useful printing machines also include other electrophotographic writers or printer apparatus.
The present invention provides at least the following embodiments and combinations thereof, but other combinations of features are considered to be within the present invention as a skilled artisan would appreciate from the teaching of this disclosure:
1. A fluorescing dry toner particle comprising a polymeric binder phase comprising a non-fluorescing binder polymer, and a polymeric fluorescing colorant dispersed within the non-fluorescing binder polymer,
wherein:
(a) the polymeric fluorescing colorant comprises a fluorescing moiety that is covalently attached to a colorant polymer that is the same or different than the non-fluorescing binder polymer, but the polymeric fluorescing colorant is blendable with the non-fluorescing binder polymer to form a homogeneous polymeric binder matrix, and
(b) the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 40 weight %, based on the total fluorescing dry toner particle weight.
2. The fluorescing dry toner particle of embodiment 1 that has a mean volume weighted diameter (Dvol) before fixing of at least 4 μm and up to and including 20 μm,
3. The fluorescing dry toner particle of embodiment 1 or 2, wherein the polymeric fluorescing colorant is present in an amount of at least 5 weight % and up to and including 24 weight %, based on the total fluorescing dry toner particle weight.
4. The fluorescing dry toner particle of any of embodiments 1 to 3, wherein the fluorescing moiety emits at one or more one peak wavelengths of at least 420 nm and up to and including 690 nm.
5. The fluorescing dry toner particle of any of embodiments 1 to 4, wherein the fluorescing moiety of the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 10 weight %, based on the total polymeric fluorescing colorant weight.
6. The fluorescing dry toner particle of any of embodiments 1 to 5, wherein the colorant polymer is derived from a precursor polymer comprising reactive groups selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, which reactive groups are reactive with the fluorescing moiety.
7. The fluorescing dry toner particle of any of embodiments 1 to 6, wherein the fluorescing moiety is a magenta fluorescing moiety that emits at one or more peak wavelengths of at least 510 nm and up to and including 590 nm.
8. The fluorescing dry toner particle of any of embodiments 1 to 6, wherein the fluorescing moiety is a yellow fluorescing moiety that emits at one or more peak wavelengths of at least 510 nm and up to and including 570 nm.
9. The fluorescing dry toner particle of any of embodiments 1 to 6, wherein the fluorescing moiety is a cyan fluorescing moiety that emits at one or more peak wavelengths of at least 420 nm and up to and including 480 nm.
10. The fluorescing dry toner particle of any of embodiments 1 to 9, further comprising a non-fluorescing colorant, a charge control agent, wax, lubricant, fuser release aid, or any combination of these materials, and optionally further comprising, on the dry toner particle outer surface, a fuser release aid, flow additive particles, or both of these materials.
11. The fluorescing dry toner particle of any of embodiments 1 to 10, wherein the polymeric binder phase comprises a polyester or a vinyl polymer derived at least in part from styrene or a styrene derivative as the non-fluorescing binder polymer, and the polymeric colorant is the same or different polyester.
12. A dry mono-component or two-component developer comprising a plurality of the fluorescing dry toner particles of any of embodiments 1 to 11.
13. A method for providing a toner image, the method comprising:
forming a latent image,
developing the latent image with fluorescing dry toner particles of any of embodiments 1 to 11 to form a developed fluorescing toner image, transferring the developed fluorescing toner image comprising the fluorescing dry toner particles to a receiver material to form a transferred fluorescing toner image, and
fixing the transferred fluorescing toner image to the receiver material.
14. The method of embodiment 13, comprising:
forming the latent image as an electrostatic latent image on a primary imaging member,
electrostatically transferring the developed fluorescing toner image from the primary imaging member to the receiver material to form the transferred fluorescing toner image, and
fixing the transferred fluorescing toner image to the receiver material at a temperature of at least 135° C.
15. The method of embodiment 13 or 14, further comprising developing the latent image using one or more of non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black dry toner particles to provide one or more of developed non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner images.
16. The method of embodiment 13 or 14, further comprising developing the latent image using non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black dry toner particles, in any sequence, to provide developed non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner images.
17. The method of embodiment 16, wherein the fluorescing toner image is applied over or under one or more of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner images.
18. The method of any of embodiments 13 to 17, wherein the fluorescing toner image provides a fluorescing magenta, fluorescing yellow, or fluorescing cyan toner image that is the only color image in the fixed color toner image.
19. An imaged receiver material provided by the method of any of embodiments 13 to 18, comprising a toner image comprising fused fluorescing dry toner particles,
wherein each fused fluorescing dry toner particle comprises a polymeric binder phase comprising a non-fluorescing binder polymer, and a polymeric fluorescing colorant dispersed within the non-fluorescing binder polymer,
wherein:
(a) the polymeric fluorescing colorant comprises a fluorescing moiety that is covalently attached to a colorant polymer that is the same or different than the non-fluorescing binder polymer, but which polymeric fluorescing colorant is blendable with the non-fluorescing binder polymer to form a homogeneous polymeric binder matrix, and
(b) the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 40 weight %, based on the total fluorescing dry toner particle weight.
20. A method for preparing fluorescing dry toner particles of any of embodiments 1 to 11, the method comprising:
dry blending non-fluorescing polymer resin particles with a polymeric fluorescing colorant, and optionally one or more of a charge control agent, wax, lubricant, fuser release aid, or non-fluorescing colorant to form a fluorescing dry blend,
melt extruding the fluorescing dry blend to form an extruded fluorescing composition, and
breaking up the extruded fluorescing composition into fluorescing dry toner particles, each fluorescing dry toner particle comprising a polymeric binder phase comprising a non-fluorescing binder polymer, and a polymeric fluorescing colorant dispersed within the non-fluorescing binder polymer,
wherein:
(a) the polymeric fluorescing colorant comprises a fluorescing moiety that is covalently attached to a colorant polymer that is the same or different than the non-fluorescing binder polymer, but which polymeric fluorescing colorant is blendable with the non-fluorescing binder polymer to form a homogeneous polymeric binder matrix, and
(b) the polymeric fluorescing colorant is present in an amount of at least 1 weight % and up to and including 40 weight %, based on the total fluorescing dry toner particle weight.
21. The method of embodiment 20 further comprising:
providing hydrophobic flow additive particles having an equivalent circular diameter (ECD) of at least 5 nm on the outer surface of the fluorescing dry toner particles.
22. The method of embodiment 20 or 21 further comprising:
mixing the fluorescing dry toner particles with carrier particles to form a two-component dry developer.
23. A polymeric fluorescing colorant comprising a fluorescing moiety that is covalently attached to a colorant polymer, wherein the polymeric fluorescing colorant emits at one or more peak wavelengths of at least 420 nm and up to and including 690 nm, and wherein the colorant polymer is derived from a precursor polymer comprising reactive groups selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, which reactive groups are reactive with the fluorescing moiety.
24. The polymeric fluorescing colorant of embodiment 23, wherein the fluorescing moiety is a magenta fluorescing moiety that emits at one or more peak wavelengths of at least 510 nm and up to and including 590 nm.
25. The polymeric fluorescing colorant of embodiment 23, wherein the fluorescing moiety is a yellow fluorescing moiety that emits at one or more peak wavelengths of at least 510 nm and up to and including 570 nm.
26. The polymeric fluorescing colorant of any of embodiments 23 to 25, wherein the colorant polymer is derived from a precursor polymer that is a polyester, polycarbonate, resin-modified malic alkyd polymer, polyamide, phenol-formaldehyde polymer or vinyl polymer,
wherein the precursor polymer comprises one or more reactive groups selected from the group consisting of carboxyl groups, hydroxyl groups, amine groups, ester groups, aldehyde groups, urethane groups, isocyanate groups, and halides, through which reactive groups the fluorescing moiety is attached to the precursor polymer.
The following Examples are provided to illustrate the practice of this invention and are not meant to be limiting in any manner.
Dry toner particles were prepared using a polymeric binder resins particles that were melt processed in a two roll mill or extruder with appropriate colorants and addenda. A preformed mechanical blend of particulate polymer resin particles, colorants, and toner additives can also be prepared and then roll milled or extruded. Roll milling, extrusion, or other melt processing was performed at a temperature sufficient to achieve a uniform melt processed composition. This composition, referred to as a “melt product” or “melt slab” was then cooled to room temperature. For a polymeric binder having a Tg of at least 50° C. to and including 120° C., or a Tm of at least 65° C. to and including 200° C., a melt blending temperature of at least 90° C. to and including 240° C. was suitable using a roll mill or extruder. The melt blending times (that is, the exposure period for melt blending at elevated temperature) was in the range of from 1 minute to 60 minutes.
The components were dry powder blended in a 40 liter Henschel mixer for 60 seconds at 1000 RPM to produce a homogeneous dry blend that was then melt compounded in a twin screw co-rotating extruder to melt the polymer binder and disperse the pigments, charge agents, and waxes uniformly within the resulting polymeric binder phase. Melt compounding was done at a temperature of 110° C. at the extruder inlet, increasing to 196° C. in the extruder compounding zones, and 196° C. at the extruder die outlet. The melt extrusion conditions were a powder blend feed rate of 10 kg/hr and an extruder screw speed of 490 RPM. The extruded composition (extrudate) was cooled to room temperature and then broken into about 0.32 cm size granules.
These granules were then finely ground in an air jet mill to a Dvol of 8 μm as determined using a Coulter Counter Multisizer. The finely ground toner particles were then classified in a centrifugal air classifier to remove very small particles and fines that were not desired in the finished dry toner composition. After classification, the toner particles had a particle size distribution with a width, expressed as the diameter at the 50% percentile/diameter at the 16% percentile of the cumulative particle number versus particle diameter, of 1.30 to 1.35.
The classified toner particles were then surface treated with fumed hydrophobic silica (Aerosil® R972 from Nippon Aerosil) wherein 2000 grams of toner particles were mixed with 20 grams of the fumed hydrophobic silica so that 1 weight % silica was attached to the toner particles, based on total toner particle weight using a 10 liter Henschel mixer with a 3-element impeller for 2 minutes at 2000 RPM.
The silica surface-treated toner particles were sieved using a 300 mesh vibratory sieve to remove non-dispersed silica agglomerates and any toner particle flakes that may have formed during the surface treatment process.
The melt extrusion composition was cooled and then pulverized to a Dvol of from about 5 μm to about 20 μm. It is generally preferred to first grind the melt extrusion composition prior to a specific pulverizing operation using any convenient grinding procedure. For example, the solid melt extrusion composition can be crushed and then ground using, for example, a fluid energy or jet mill, such as described in U.S. Pat. No. 4,089,472 (noted above) and the ground particles can then be classified in one or more steps. If necessary, the size of the particles can be further reduced by use of a high shear pulverizing device such as a fluid energy mill and classified again.
Two-component electrographic developers were prepared by mixing toner particles prepared as described above with hard magnetic ferrite carrier particles coated with silicone resin as a concentration of 8 weight % toner particles and 92 weight % carrier particles.
A 4 gram two-component dry developer sample comprising 8 weight % toner particles was prepared by mixing 3.2 g of carrier particles and 0.8 g of toner particles on a device that simulates the mixing that occurs in a printer developer station to charge toner particles. The triboelectric charge of the toner particles was then measured after 2, 10, and 60 minutes of mixing using a MECCA device that comprises a set of parallel plate electrodes, spaced 1 cm apart by insulative plastic spacers. A weighed two-component dry developer sample (typically 0.1 g) was placed on the lower electrode, which is connected to a power supply typically set to 2000V, with the same polarity as that of the toner particles to be measured. The upper electrode is connected to a coulomb-meter. The two-component dry developer sample is magnetically agitated by means of a 60 Hz AC coil positioned under the lower electrode. Two-component dry developer was agitated in the presence of the electric field, resulting in the toner particles transferring to the upper plate, where the amount of transferred charge was measured using a coulombmeter. The collected toner particles were weighed, the measured charge is divided by the measured weight to calculate charge per mass in units of μcoulombs/g, and the measured weight of toner particles was divided by the starting weight of two-component dry developer to calculate the toner particle concentration.
The amount of dust was measured at the 10-minute level as milligram of toner particles that dust off per gram of admixed fresh toner particles. The two-component dry developer was subsequently stripped of all toner and rebuilt with fresh toner particles. The triboelectric charge of the toner particles is then measured after 2 and 10 minutes of mixing. The amount of dust was again measured at the 10-minute level as mg of toner particles that dust off per gram of admixed fresh toner.
In an electrographic printer, replenishment toner can be added to each developer station to replace toner particles that are removed during the process of printing copies of images. The replacement toner particles are uncharged and gain a triboelectric charge by mixing with the two-component dry developer. During this mixing process, uncharged or low charged toner particles can become airborne and result in background on prints or dust contamination within the printer.
A “dusting test” was performed during experimentation to evaluate the potential for replenishment toner particles to form background or dust. A 4 g two-component dry developer sample (8 weight % toner) was exercised on a rotating shell and magnetic core developer station. After 10 minutes of exercising, 0.4 g of fresh uncharged replenishment toner particles were added to the two-component dry developer. A fine filter over the developer station then captured airborne dust that was generated when the replenishment toner particles were added, and the dust collected was weighed as milligrams of dust per 0.4 grams of added replenishment toner particles. The lower values for this “dust” measurement correspond to better performance of the toner particles. Typically, low values of dust (less than 10 milligrams per gram of fresh added toner particles) in addition to low levels of toner charge (from −25 to −70 μCoulomb/g) are desirable.
Samples of dry toner particles were prepared with the visible fluorescing pigments described below in TABLE I. Each sample of dry toner particles were formulated by compounding 100 parts of a branched Bisphenol A polyester as polymeric binder and two parts of visible fluorescing pigment. Each formulation was melt-blended on a two roll mill at 150° C. and a 10.24 cm roll mill, allowed to cool to room temperature, and ground down to form dry toner particles having a Dvol of about 8 μm.
Two-component dry developers were prepared by combining 10 grams of the toner particles with 90 grams of carrier particles comprising strontium ferrite cores that had been coated at 230° C. with 0.75 parts of poly(vinylidene fluoride) (Kynar™ 3011′ from Pennwalt Corporation) and 0.50 parts of poly(methyl methacrylate) (Soken 1101 from Esprix Chemicals).
TABLE I below shows the various toner particles that were prepared using the various fluorescing colorants, and the results observed for each sample of toner particles. The fluorescing colorants were obtained from the following commercial sources:
The two-component dry developers were used to determine charging behavior of the toner particles as a function of the visible fluorescing colorant concentration. The charging rate was measured by the “dust” measurement. Some toner particles were capable of charging well at low fluorescing colorant concentration but absolute charge was lowered as fluorescing colorant concentration was increased, indicating the negative effect of fluorescing colorant on toner particle charging. TABLE I summarizes the overall charging performance of the toner particles prepared with the visible fluorescing colorants.
To determine the solubility of the fluorescing colorants in fusing oil, 2% of each fluorescing colorant was placed in NexPress™ fuser oil at 200° C. and kept at that temperature for 30 minutes. The color of the oil was observed to determine fluorescing colorant solubility in the oil. The fluorescing dyes that were covalently attached to the polymeric backbone (reactive hydroxyl groups) did not exhibit any staining of the fuser oil. The fuser oil solubility results for the fluorescing colorants are also reported in TABLE I.
As reported in TABLE I, Comparative Examples C-1 and C-2 show that when the fluorescing colorant molecules are not covalently attached to the polymer backbone, the hot fuser oil solubility can be a concern and the fluorescing colorant appears to affect the charge of toner particles. By covalently attaching the fluorescing colorant to the polymer, fuser oil solubility is reduced. The results also show that the color strength was different for the same fluorescing magenta and yellow colorants as the backbone polymer was varied.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
This is a Continuation-in-part of copending and commonly assigned U.S. Ser. No. 13/462,133, filed on May 2, 2012 by Tyagi and Granica.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13462133 | May 2012 | US |
| Child | 13837546 | US |
