Patent Application
20090098477
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1. Field of the Invention
The present invention relates generally to combinations of toner colorants that may be used for monitoring toner layer thickness in electrophotographic systems. More specifically, toner may be formulated to include infrared transmissive and/or infrared reflecting colorants that may be utilized to optimize the performance of a toner patch sensor. In particular, the infrared transmissive and/or infrared reflecting colorants may be specifically employed to provide black toners with improved toner patch sensitivity which black toner may optionally incorporate carbon black.
2. Description of the Related Art
Electrostatically printed color images may be produced by depositing toners of various colors onto a recording media, such as a sheet of paper. A wide palette of printed colors may be generated by printing yellow, cyan, magenta and black toners in various proportions and combinations. Each individual color of the producible palette may require a specific proportion and combination of toners. If the particular proportions of toner for a selected color cannot be repeatedly deposited on the printed media then the printed color may not be consistent and vary in hue, chroma, and/or lightness from attempt to attempt of printing. The proportion of each toner color to be deposited is controlled by the thickness of the toner layer of a given color and the halftone area coverage. Therefore, controlling the printed colors, and ensuring reproducibility of the printed colors, may be achieved by controlling the toner layer thickness to ensure consistent color reproduction.
Toner patch sensors have therefore been used in printers and copiers to monitor the toner density of unfused images and provide a method of controlling the print darkness. In color printers and copiers, the toner patch sensors may be used to maintain the color balance and in some cases to modify the gamma correction or halftone linearization as the electrophotographic process changes with the environment and aging effects. However, monitoring the amount of black toner on black intermediate belts or black paper transport belts is problematic due to the low optical contrast between the black toner and the underlying surface.
In a first exemplary embodiment, the present disclosure relates to a toner formulation which may be used in an electrophotgraphic printing device or cartridge. The formulation may contain a binder and an infrared absorbing black pigment such as carbon black at a concentration of 0.25 to 2.0% by weight and one or more infrared transmissive pigments wherein the infrared transmissive pigments are configured to provide a black color.
In a second exemplary embodiment, the present disclosure relates to toner formulation comprising a binder and an IR absorbing black pigment at a concentration of 0.25-2.0% by weight, including one or more infrared transmissive pigments at a level of less than or equal to 15.0% by weight. The infrared transmissive pigments are configured to provide a black color and respond to a toner patch sensor to indicate a mass per unit area of unfused toner of 0.1-1.5 mg/cm2.
In a third exemplary embodiment, the present disclosure relates to a method for calibrating an image forming device using a toner patch sensor and a toner formulation comprising depositing a plurality of toner patches onto a control surface, wherein the toner patches include a first toner patch, including a first toner, a second toner patch including the first toner deposited over a second toner and a third toner patch including the second toner. The first toner may comprise a binder and an IR absorbing black pigment at a concentration of 0.25-2.0% by weight, including one or more infrared transmissive pigments, wherein the infrared transmissive pigments are configured to provide a black color. This may then be followed by measuring signals indicative of reflectivity of the plurality of toner patches and the reflectivity of the control surface by emitting light of a given wavelength in the infrared spectrum and detecting the amount of incident light reflected from the plurality of toner patches and said control surface. The first toner patch may exhibit a first reflectivity RI at the given wavelength, the second toner patch exhibiting a second reflectivity R2 at the given wavelength, the third toner patch exhibiting a third reflectivity R3 at the given wavelength. The control surface exhibits a fourth reflectivity Rcontrol at the given wavelength, wherein Rcontrol≠R3; followed by adjusting a printer operating parameter based upon such measurements.
In a fourth exemplary embodiment, the present disclosure relates to a black toner formulation comprising a binder and an IR absorbing pigment and one or more infrared transmissive pigments. The formulation indicates the following spectral characteristics when fused on white paper at a L* value of 9-24:
% R800-1200 nm≧(0.00082×Rvis+0.078) (λ)+1.98 Rvis−9.6
and
% R800-1200 nm≦(0.00082×Rvis+0.078) (λ)+1.98 Rvis+10.0
wherein % R800-1200 nm is the percent reflectance for a given wavelength (λ) in the range 800-1200 nm, Rvis is the average percent reflectance of the fused toner formulation for the 380-730 nm region of the spectrum, and the value of % R800-1200 nm at said given wavelength is less than or equal to 70%.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
The present invention generally relates to image forming media (e.g. toner) containing a binder, which may be understood as a polymeric type resin. Such polymeric resin may therefore include, e.g., those polymers that are typically used in toners to provide appropriate fusing characteristics when used in an electrophotographic type printer. For example, the binder may comprise thermoplastic type polymers such as styrene or styrene-acrylate type polymers, polyester polymers, etc. The image forming media herein may therefore include toner and the image forming apparatus may include an electrophotographic device, copier, fax, all-in-one device or multi-functional device. Toner for electrophotographic (e.g. laser) printing may be prepared according to a number of techniques.
According to a first technique, a so-called “conventional toner” may be prepared from a toner resin that may be melt mixed with pigment and other additives. The melt mixed toner formulation may be crushed, pulverized, milled, and classified to provide fine particles of a desired size. Additives may be incorporated onto the toner particle surfaces as an extra particulate additive. According to another technique, “chemically produced toner” may be prepared in which toner particles may be prepared by chemical processes such as aggregation or polymerization rather than being abraded from much larger size materials by physical processes.
The toner herein may also include an IR absorbing black pigment, such as carbon black, wherein the carbon black is present at a level of about 0.25 to about 2.0 percent by weight, including all values and increments therein. For example, the level of carbon black may be 0.30%, 0.40%, 0.50%, 0.60%, wherein the percent (%) indication is again an indication of a percent by weight with respect to the overall toner composition. As described more fully below, this level of carbon black may be strategically selected to contribute to the development of black pigmentation along with the ability for such toner fonnulation to remain responsive to a toner patch signal (TPS) apparatus. It may therefore be appreciated that in addition to carbon black, IR absorbing black colorants may be provided by materials such as oxidic black pigment, including iron oxide black (Fe3O4) and spinel black (Cu(Cr,Fe)2)O4 IR absorbing black pigmentation may also depend upon the use of what may be understood as organic black colorants (i.e., carbon-based compounds other than simply carbon black).
The toner herein may also include infrared transmissive pigments, wherein such infrared pigments are configured or combined to provide a black color. In the present invention, the black color toner compositions are prepared so that they may have a specific chroma C* value. More specifically, the toner compositions are prepared so that the chroma C* value is less than or equal to about 15.0 for solids and all halftone shade levels, printed on white paper (e.g. Hammermill® Laser Print Paper) including all values and increments between 0-15.0. Lightness index (L*), hue angle (h) and chroma (C*) are based on the L* a* b* calorimetric system standardized by the Commission International de l'Eclairage (CIE) in 1976, which is defined in JIS Z 8729 in the Japanese Industrial Standards (JIS).
The infrared transmissive pigments may also be understood as reference to a pigment that does not compromise the ability of a toner patch sensor, a specific example of which is noted below, to provide information regarding the amount of unfused toner on a given surface. Such transparency may therefore allow the incident IR light to diffuse to underlying toner layers and reflect, thereby increasing the relative amount of reflected light with relatively thicker toner layers. Overall, this may then produce acceptable toner patch sensor sensitivity at selected target mass, which target mass is also described more fully below. Accordingly, the toner formulations herein provide a black toner with better color control and which may still be responsive to a toner patch sensor. Such improved toner layer thickness control may therefore lead to improved ability to accurately and repeatedly produce colors of an image developed on a recording media, e.g. a printed image. Reference to pigment herein is intended to be inclusive of any composition that may independently provide a given color.
The image forming device herein may include a closed-loop control system to maintain the proportions of image forming media that may be deposited during the image developing process, i.e., during printing. This may eliminate, or at least reduce, color shifts in printed images. In an exemplary control system the toner layer thickness may be determined based on a light signal reflected by a printed test pattern of unfused toner. For example, a light source may be used to illuminate solid and grayscale printed patterns, or patches, of the four toners, i.e., yellow cyan, magenta, and black printed on a control surface. The reflected light signal may then be used to estimate toner layer density or thickness. One exemplary device herein for monitoring toner density or thickness on an unfused image is the toner patch sensor (TPS) as described in U.S. Pat. No. 6,628,398, whose teachings are incorporated by reference. Accordingly, an infrared light signal reflected by a printed toner layer or test pattern may therefore be generally related to the infrared reflectivity of the toner pigment and to the printed density or toner layer thickness. The TPS may therefore utilize a test patch in combination with a photodiode which may be configured to provide three different scenarios: (1) direct illumination with indirect detection; (2) indirect illumination and detection; and (3) diffuse illumination with direct detection. Relatively accurate density control may therefore be achieved that is substantially independent of a belt surface roughness.
Accordingly, image forming media (e.g., toner) to be measured for density or thickness may be placed on a control surface that may include a transport or transfer belt. The toner patches, i.e., the solid and grayscale toner test patterns, may be printed on the control surface and the control surface may be impinged with light from an infrared light source. At least a portion of the infrared light may be reflected by the toner patches and collected by an infrared detector. The toner layer density and/or thickness may be determined from the reflected signal strength of the toner patches, e.g., by comparison to the reflected signal strength from the test surface itself and/or in comparison to the reflected signal strength of one or more grayscale toner test patterns. Toner layer density as understood herein is reference to a given mass (e.g. grams) of toner per unit area (e.g. cm2). The operating conditions of the printer may then be adjusted according to the detected toner layer density and/or thickness in order to provide the necessary proportions of toner to achieve a desired color.
It may be therefore appreciated that a conventional black IR absorbing colorant, e.g. carbon black, will generally absorb light in the infrared range of the spectrum, which may therefore produce a relatively weak reflected infrared signal for the TPS. The weak reflected infrared signal may then make it relatively difficult to reliably determine a toner layer thickness of a black toner in a system utilizing infrared reflectivity. More specifically, as the toner patch sensors emit and detect light at about 750 nm-1000 nm, and more particularly, 900 nm-1000 nm, the relatively strong absorption of light by the carbon black at such wavelengths can make toner particles containing carbon black relatively opaque and the toner patch sensor reflection signal may therefore indicate a zero slope (no sensitivity) after more than one monolayer of toner is laid down. This may be particularly problematic in those situations where the desired target mass/unit area (M/A) is 1-3 toner monolayers.
The infrared transmissive black colorants herein, that may be used along with the infrared absorbing black pigments (e.g. carbon black) noted above, may therefore first individually include those pigments known as LUMOGEN® Black FK4280 or FK4281 available from BASF, which rely in part upon a perylene type base structure, as illustrated below:
It may therefore be appreciated that the above referenced base perylene structure may be functionalized to include other types of groups, including alkyl groups, carbonyls, imide functionality including imide functionality that contains alkyl and aromatic functionality, etc. The LUMOGEN Black FK4280 is believed to include a perylene isoindolene structure as follows:
As shown in
Another exemplary black infrared transmissive pigment that may be used herein includes BASF PALIOGEN Black S 084, which is a functionalized perylene pigment of the following structure:
wherein the hue of the pigment may be varied by the nature of the subgroup “X” in the above formula. For example, X may be oxygen, an imide or a substituted imide (N—R) where R may be an alkyl group, a hydroxyl-alkyl group, an aromatic group, a substituted aromatic group, such as the following:
wherein Y itself may be a phenyl group, methyl group or hydroxymethyl group. In addition, one form of a black perylene pigment applies in the specific case where X═N—CH2CH2Ph. Such pigment also is known as C.I. Pigment Black 31.
Another exemplary black IR transmissive pigment may include azomethine black. An exemplary azomethine black may have the following structure:
wherein R represents a group selected from the group consisting of alkyl groups having 1 to 3 carbon atoms and alkoxy groups having 1 to 3 carbon atoms, n may be an integer from 1-5, and when n is at least 2, Rs may be the same or different.
Yet another IR transmissive pigment may include aniline black, which may be understood as a black dye based upon aniline (C6H5NH2). A commercial form of aniline black is available as BS-890 from Degussa Corporation. Aniline black may have the formula (CH3)2NC6H4N═NC6H4NH2 which may then indicate the following structure:
The IR transmissive black pigments herein that may be formulated in the toner, along with the IR absorbing black pigment (e.g. carbon black), may also include combinations of IR transmissive colored pigments that when combined provide a black color (as noted above, a Chroma of less than 15.0). For example, the infrared transmissive pigments may include two or more of the following: blue pigment, cyan pigment, green pigment, yellow pigment, orange pigment, brown pigment, red pigment, magenta pigment, violet pigment. Accordingly, when such pigments are combined they may provide such black color. For example, the IR transmissive pigments may therefore specifically include phthalocyanine or carmine, such as carmine HF4C, and may be, for example, pigment blue 15:3 and pigment red 185 at approximately 1:2 proportions respectively. The IR transmissive pigments that may also be combined to provide a black color may include cyan and orange, cyan and red, cyan and brown, blue and yellow, blue and orange, blue and red, blue and brown, green and violet, and cyan, magenta and yellow. It should be noted that the inclusion of black pigments like carbon black in multi-pigment black mixtures may help to minimize any potential hue issues. These hue issues may arise because of scattering of light by the pigments and imperfect spectral balance of the color pigment combinations. In such regard it may be appreciated that the aforementioned pigments that may be utilized to combine and provide such black color may have the following spectral characteristics as noted in Table 1:
A series of toners were therefore prepared utilizing the above described IR transmissive colorants (LUMOGEN Black 4280) with carbon black loadings at 0%, 1.0%, 2.0%, 3.0% and 4.0% by weight in a sample toner. These toners were then evaluated for toner patch sensor response utilizing direct illumination with indirect detection, as referenced above. At a carbon black loading of about 2.0% by weight or less, it was observed that an acceptable black toner was produced with acceptable toner patch sensitivity. Reference to the “about” herein may therefore be understood to include ±0.10% by weight of the total toner composition. In particular, it was observed that toner patch sensitivity was acceptable in detecting toner at a target mass per unit area (M/A) of about 0.4-0.5 mg/cm2 with 6 micron toner. Accordingly, it is contemplated herein that the target toner mass range that may be detected utilizing the above referenced black IR transmissive pigment(s), alone or in combination with an IR absorbing black pigment, may have a M/A value of about 0.1 to 1.5 mg/cm2, including all values and increments therein.
In a broad aspect it may now be appreciated that a toner formulation capable of optimally responding to a toner patch sensor (TPS) may include at least one infrared transmissive pigment alone or in combination with an IR absorbing black pigment such as carbon black. The IR transmissive pigment itself may also: (1) itself be sourced from one or more IR transmissive black pigments (e.g. a perylene base structure, a functionalized perylene structure, and/or an azomethine compound) and/or (2) itself be obtained from a combination of color pigments which when combined provide a black color (Chroma less than or equal to 15.0); and/or (3) include a combination of IR transmissive black pigments and color pigments. The IR transmissive pigments may be present in a given toner formulation at levels of about 1-1.5% by weight, including all values and increments therein. Such compositions therefore may provide an acceptable black color as well as allowing for performance of a toner patch sensor for identifying a given unfused toner at a target M/A range of about 0.1 to 1.5 mg/cm2.
In addition, the compositions herein may, in bulk powder, exhibit a reflectivity of greater than or equal to about 7.5% and less than or equal to 60% at a wavelength of about 940 nanometers, for toner particles having a diameter of about 5.5-10.0 microns. Bulk powder reflectivity may be understood herein as reflectivity at saturation (i.e. sufficient toner mass is present such that the effects of any underlying layer become irrelevant with respect to reflectivity at 900-1900 nm).
In a further exemplary embodiment, the toner compositions may include, in addition to the infrared transmissive colorants described above, one or more infrared reflective colorants. In that context, reference is made herein to U.S. application Ser. No. 11/362,383 entitled “Image Forming Media Containing Reflective Pigments” whose teachings are incorporated herein in their entirety by reference. Infrared reflective colorants may therefore be understood as colorants which are capable of reflecting at least about 5% or more and up to 99%, including all values and increments therein, of the incident light in the infrared spectrum including wavelengths in the range of about 700 to 3,000 nm. Such colorants may also substantially absorb all light in the visible spectrum of about 400-700 nm (i.e. 90% or more of all light over the wavelengths of about 400-700 nm).
Such IR reflecting colorants may therefore include oxide complexes such as chromium (III) oxide, titanium oxide, titanium oxide including coatings of iron titanium oxide and other oxides. Such exemplary colorants may also be available from Shepherd Color, Cincinnati, Ohio under the trade name SHEPHERD BLACK 411, from Titan Kogyo, KK, Japan under the product number ETB-100 and from Ferro Corp., Cleveland, Ohio, under the product designation ECLIPSE 10201. The infrared reflective colorants may be present in the range of about 1 to 15% by weight of the toner composition, including all values and increments therein. Accordingly, the IR reflective colorants may include those pigments that provide different colors, as well as those that are effectively black.
By way of further example, a given toner composition herein may therefore include about 1-15% by weight of IR transmissive colorant and 1-15% of IR reflective colorant. For example, BASF LUMOGEN BLACK FK4280 which may be combined with a chromium III oxide pigment such as SHEPHERD BLACK 411 (C.I. Pigment brown 29) to provide a black toner with acceptable TPS sensitivity. Another contemplated combination includes BASF LUMOGEN BLACK FK4280 blended with ETB-100 which is commercially available from Titan Kogyo, K.K., Japan. ETB-100 is IR absorptive at 940 nm, so it could be used in place of carbon black to make a semi-absorptive black toner.
It may now be noted that toner patch sensor measurements of unfused toner may be correlated with the print density (L*) of fused toner test patches, wherein an L* value of 0 represents an ideal black patch with no first surface reflection and an L* of 100 represents an ideal white surface. Such a correlation is illustrated in
More specifically, referring back to
Accordingly, it should be appreciated that various toner compositions and intermediate transfer belts may provide different reflective ratio plots having different slopes. Furthermore, the data may be otherwise interpolated and/or extrapolated using predictive formulas derived from measured data points. In addition, it may be appreciated that tolerances may be set for the values such that the process may be adjusted depending on whether the reflective ratio is within a given tolerance.
In addition, toner patch sensor measurements of the toner compositions described herein may be used in combination with an improved toner patch sensor algorithm. Such algorithm is described in U.S. patent application Ser. No. 11/771,121, filed on Jun. 29, 2007, the subject matter of which is incorporated by reference herein. In general terms, the toner patch algorithm may be utilized to nominalize the toner patch sensor measurements, wherein toner patch measurements may include toner patches of the toner compositions described herein, toner patches of the toner compositions described herein on a control surface, such as an intermediate transfer belt, toner patches of the toner compositions described herein disposed over toner patches of either magenta, cyan or yellow toner and measurements of the magenta, cyan or yellow toner, and the bare control surface. Utilizing the TPS signals one may determine a reflective ratio (RR) being the reflectivity of a given toner as compared to the reflectivity of the belt.
An exemplary illustration of such measurements is illustrated in
Multiple test patches of the black and black over magenta (or yellow or cyan) toner may be printed and at least one or more test patches of the magenta toner may be printed. The patches may then be measured using a toner patch sensor, wherein, as described above, incident light is measured by an optical element, providing a voltage. The measurements or signals indicative of the reflectivity may then be correlated utilizing the following formula to return a calculated Ratio (A:B) to compare to a predetermined Ratio (A:B), wherein
and RK/M may be a signal indicative of the reflectivity of the black over magenta toner patch, RK may be a signal indicative of the reflectivity of the black toner patch, RM may be a signal indicative of the reflectivity of the magenta toner patch, Rb,It may be a signal indicative of the reflectivity of the belt and RM≠Rbelt. Ratio (A:B) (calculated or predetermined) may range from 0 to 1, wherein 1 may indicate that little to no absorptive or black toner has been deposited. A value approaching zero may indicate that the absorptive toner may be nearly saturated. The predetermined Ratio (A:B) may be a given number provided based on the desired L* value, the bulk reflectivity of the toner, or combinations thereof. The bulk reflectivity of the toner may be understood as a saturated reflectivity, such that the effects of an underlying surface are not detected or negated by the toner.
In utilizing a toner formulation that may not include pigments with low infrared absorption at the TPS wavelength, as illustrated in
To correctly render images, the printer may need to lay down the proper amount of toner not just for regions with 100% coverage, but for all halftone shade levels. To enable the TPS to properly monitor the printing of black halftone TPS test patterns, the black toner may need to exhibit adequate reflective contrast relative to the intermediate belt.
Exemplary black toner formulations which employ mixtures of absorptive and transmissive pigments exhibit markedly higher reflectivities above 800 nm compared to the visible range, 400-700 nm. This characteristic has been found to be true not only for unfused toner powder, but also for fused toner layers on paper.
Analysis of the spectral data for the 2% carbon black loaded toner's print spectra has shown that the infrared reflectance of printed (fused) solid area patches of this toner may be correlated to the average reflectance for wavelengths between 380-730 nm. Attention is directed to
It may therefore be appreciated that in the context of the present disclosure, one may formulate a black toner composition herein that indicates a percent reflectance for a given wavelength (λ) in the 800-1200 nm region of the spectrum (% R800-1200 nm) that falls within the following range on white paper at L* values of 9-24:
% R800-1200 nm≧(0.00082×Rvis+0.078) (λ)+1.98 Rvis−9.6 (I)
and
% R800-1200 nm≦(0.00082×Rvis+0.078) (λ)+(1.98 Rvis+10.0 (II)
wherein Rvis is again the average % reflectance of the printed solid area patch for the 380-730 nm region of the spectrum with the additional feature that the percent reflectance at a given wavelength in the 800-1200 nm region is less than or equal to 70%. In such regard, attention is directed back to
In an exemplary embodiment, the algorithm analysis performed herein may be 5 accomplished by, as illustrated in
It should now also be clear that embodiments of the methods described above may be implemented in a computer program that may be stored on a storage medium having instructions to program a system to perform the methods. The storage medium may include, but is not limited to, any type of disk including floppy disks, optical disks, compact disk read-only memories (CD-ROMs), compact disk rewritables (CD-RWs), and magneto-optical disks, semiconductor devices such as read-only memories (ROMs), random access memories (RAMs) such as dynamic and static RAMs, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), flash memories, magnetic or optical cards, or any type of media suitable for storing electronic instructions. Other embodiments may be implemented as software modules executed by a programmable control device.
Thus, as may be understood from the above, an aspect of the present disclosure relates to the use of the toner formulations described herein in image forming devices that may include toner patch sensors. In addition, a method is provided for adjusting printing parameters based upon the use of a toner patch sensor in combination with the toner formulations above. Furthermore, a method is provided for determining a correlation between reflectance ratios between printed toner and a control (such as an intermediate belt), which may be utilized in process adjustment in an image forming device.
The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.
