Patent Application
20090253064
The present disclosure relates to toners, and, more specifically, to a process and composition for creating customized colors by using a series of neutral gray primaries.
In the process of electro-photographic printing, a photoreceptor containing a photoconductive insulating layer on a conductive layer is imaged by uniformly electrostatically charging the surface. The photoreceptor is then exposed to a pattern of activating electromagnetic radiation, such as light. The radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer, while an electrostatic latent image is formed on the non-illuminated areas. Toner particles are attracted from carrier granules to the latent image to develop the latent image. The toner image is then transferred from the photoconductive surface to a sheet and fused onto the sheet.
Various toner compositions for such a printing system are well known in the art and have been produced having a wide array of additives and constituent materials. Generally, toner particles include a binding material, such as a resin, and any of various additives to provide particular properties to the toner particles. Numerous devices and processes are known for preparing toner particles. Numerous different types of xerographic imaging processes are known wherein, for example, insulative developer particles or conductive developer particles are selected depending on the development systems used. Moreover, of interest with respect to the aforementioned developer compositions is the appropriate triboelectric charging values associated therewith, as it is these values that may enable continued formation of developed images of high quality and excellent resolution.
Triboelectric charging is widely used in the electro-photographic industry to charge toner particles. Triboelectric charging is performed by rubbing two dissimilar materials together, and in the course of such rubbing, a charge is transferred from one body to the other. A disadvantage is that the triboelectric charging phenomenon is very sensitive to surface conditions of the particle as well as temperature and humidity. Charge deposited on particles, particularly irregularly surfaced particles, can easily become non-uniform, resulting in localized areas of higher charge concentration on the particles. This increases the localized adhesion state of such particles to any surface, including the internal structural surfaces of the devices within which the electrostatically charged particles are manipulated.
In two component developer compositions, carrier particles are used in charging the toner particles. Toner particles are mixed with larger, magnetic particles called carrier particles. The toner and carrier particles often contain charge agents that enable the toner particles to become triboelectrically charged by contact with the carrier particles. The developer is contained in a development station that typically includes a roller with a magnetic core, a sump that contains a quantity of developer, a device for determining the concentration of toner in the developer, and a mechanism for replenishing the toner when the toner concentration drops below a certain level. The carrier particles transport the toner into contact with the imaging member bearing the electrostatic latent image. The development station is suitably biased and the toner particles suitably charged so that the proper amount of toner particles is deposited in either the charged or discharged regions of the imaging member.
After the electrostatic latent image on the imaging member has been developed, the toned image is generally transferred to a receiver such as paper or transparency stock. This is generally accomplished by applying an electric field in such a manner to urge the toner from the imaging member to the receiver. In some instances, it is preferable to first transfer the toned image from the imaging member to an intermediate member and then from the intermediate member to the receiver.
Dry blending processes and other mixing to incorporate a carbon black or other conductive material into the polymer coating can be selected, however, to avoid, or minimize transfer of the carbon black from the polymer coating the amount of carbon black that may be blended may be limited, for example, to 20 percent by weight or less, which limits the conductivity achievable by the resultant conductive polymer. In addition, dry blending is the process for powder coatings manufacture where materials are blended in dry form without melting.
A color can be uniquely described by three main perceptual attributes: hue, denoting whether the color appears to have an attribute according to one of the common color names, such as red, orange, yellow, green, blue, or purple (or some point on a continuum); colorfulness, which denotes the extent to which hue is apparent; and brightness, which denotes the extent to which an area appears to exhibit light. Light sources used to illuminate objects for viewing are typically characterized by their emission spectrum and to a reduced degree by their color temperature, which is primarily relevant for characterization of sources with a spectrum similar to a black body radiator. Lightness is the perceptual response to luminance; denoted L* and is defined by the CIE as a modified cube root of luminance. Common notation indicates the lightness or darkness of a color in relation to a neutral grey scale, which extends from absolute black to absolute white.
Gray scale is a strip of standard gray tones, ranging from white to black, placed at the side of original copy during photography to measure tonal range and contrast obtained. A gray scale digital image is an image in which the value of each pixel is a single sample. Displayed images of this sort are typically composed of shades of gray, varying from black at the weakest intensity to white at the strongest, though in principle the samples could be displayed as shades of any color, or even coded with various colors for different intensities. Gray scale images are distinct from black-and-white images, which in the context of computer imaging are images with only two colors, black and white, whereas gray scale images have many shades of gray in between.
Primary Colors are usually three colors, which are combinable to produce a range of other colors within a color mixing model. All non-primary colors are mixtures of two or more primary colors. Red, green, and blue (R, G, B) are the standard additive primary colors. Cyan, magenta, and yellow (C, M, Y) are the standard subtractive primary colors. Black (K) colorant absorbs light energy substantially uniformly over the full extent of the visible spectrum and may be added to enhance color and contrast and to improve certain printing characteristics. Cyan, magenta, and yellow (CMY) are the subtractive complements of red, green, and blue, (RGB) respectively, and they absorb the light energy in the long, middle, and short wavelength regions, respectively, of the visible spectrum, leaving other regions of the visible spectrum unchanged. Ideally, the absorption bands of individual CMY colorants are non-overlapping and completely cover the visible region of the spectrum.
Two predominant modes for producing color are: additive color, whereby color is produced by the addition of spectrally selective lights to a dark background that is otherwise substantially devoid of light; and subtractive color, whereby color is produced by spectrally selective subtraction of light energy from the light emitted by a source. Red, green and blue lights are typically used as the primaries that are mixed together in an additive system. In a subtractive system, colorants are typically used as the subtractive primaries. These colorants selectively absorb, or subtract, a portion of the visible spectrum of incident light while transmitting the remainder. Cyan, Magenta, and Yellow colorants are typically used.
Color in printed images results from the combination of a limited set of colorants deposited on a substrate over a small area in densities selected to integrate the desired color response. This is accomplished in many printing devices by reproducing so called “separations” of the image, where each separation provides varying gray values of a single primary color. When the separations are combined together, the result is a full color image.
Colorants that are deposited on a reflective substrate, such as a paper sheet, selectively transmit incident light in a first pass to the surface of the substrate whereupon the transmitted light is then reflected by the substrate and is again filtered by the colorants in a second pass, thus encountering additional selective absorption before being perceptible as a particular color by an observer. It is also common for colorants to possess a degree of scattering, and the color appearance of a colorant on a printed substrate is determined by the amount and types of the colorants present, and the combination of their absorption and scattering properties.
Thus, cyan, magenta, and yellow colorants absorb red, green and blue light, respectively. The idealized absorption bands for the cyan, magenta, and yellow colorants are referred to as the block-dye assumption. In reality, colorants exhibit significant deviations from this idealized behavior, including scattering in the colorants. Thus, dry blended custom colors that lie in the neutral region have the potential for greater visual color variation due to their proximity to the neutral axis. In other words, small variations in dE caused by errors in primary constituents and/or instabilities caused by the printing process, i.e., xerography can lead to large shifts in the hue angle. These hue angle shifts often are very perceptible to the eye because they can be very different shades of colors, i.e., brown or green vs. gray. Without a neutral gray primary, these colors can currently be made using black and white to tune to a gray color, which leads to higher graininess appearance in the blend due to the combination of particles which have a large contrast, i.e., black compared to white.
None of these methods has presented a desirable solution for minimizing the graininess appearance in the blend to acceptable levels. Therefore, it would be highly desirable to provide a process and composition that provides for and enables an efficient and reliable method of customizing colors by successfully shifting the hue of a desired target primary color in order to minimize the graininess appearance of color primaries.
A process for creating custom colors, the process comprising: creating a plurality of neutral gray scale primary components of varying darkness levels; selecting one or more non-gray scale primary components; and combining one or more of the plurality of neutral gray scale primary components with the one or more non-gray scale primary components; the plurality of neutral gray scale primary components are compatible with dry blending techniques of the one or more non-gray scale primary components in order to shift a hue of a designated target primary.
A composition for creating custom colors, the composition comprising: a first toner device for creating a plurality of neutral gray scale primary components of varying darkness levels; and a second toner device for creating one or more non-gray scale primary components; wherein the one or more of the plurality of neutral gray scale primary components are combined with the one or more non-gray scale primary components; and the plurality of neutral gray scale primary components are compatible with dry blending techniques of the one or more non-gray scale primary components in order to shift a hue of a designated target primary.
A computer program product for creating custom colors, the computer program product comprising: a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for facilitating a method comprising: creating a plurality of neutral gray scale primary components of varying darkness levels; selecting one or more non-gray scale primary components; and combining one or more of the plurality of neutral gray scale primary components with the one or more non-gray scale primary components; the plurality of neutral gray scale primary components are compatible with dry blending techniques of the one or more non-gray scale primary components in order to shift a hue of a designated target primary.
The exemplary embodiments of the present disclosure pertain to creating a series of neutral gray primaries of varying darkness (L*) in combination with the other primary colors to create dry blended custom colors. This new series of neutral gray primaries falls along the neutral axis, thus splitting up the color space stretching from white to black. The series can consist of one or more neutral gray primaries. The creation of the additional neutral gray primaries along the L* axis can be used to formulate the desired neutral colors mentioned above which can be difficult. The neutral gray primaries may also be used in blend formulations instead of white and black to modify the L* of a color which can in many cases lead to lower color graininess. These features and aspects will become better understood with regard to the following description of the exemplary embodiments. However, before describing
CIE L*a*b* (CIELAB) is a color model used conventionally to describe all the colors visible to the human eye. It was developed for this specific purpose by the International Commission on Illumination. The asterisk (*) after L, a, and b is part of the full name, since they represent L*, a* and b*, to distinguish them from L, a, and b.
The three basic coordinates represent the lightness of the color (L*, L*=0 yields black and L*=100 indicates white), its position between red/magenta and green (a*, negative values indicate green while positive values indicate magenta) and its position between yellow and blue (b*, negative values indicate blue and positive values indicate yellow).
The L*a*b* color model has been created to serve as a device independent model to be used as a reference. Therefore, the visual representations of the full gamut of colors in this model are not always accurate. They are there just to help in understanding the concept, but they are inherently inaccurate. Since the L*a*b* model is a three-dimensional model, it can only be represented properly in a three-dimensional space. However, in some of the exemplary embodiments of the present disclosure the L*a*b* model is presented as a two-dimensional model for convenience.
The series of neutral gray primaries 18 can be produced by using conventional toner manufacturing, as well as chemical toner manufacturing. The pigment levels (e.g., carbon black and/or pigments) are selected to produce varying levels of gray along the neutral axis, L* axis 12 of the L*, a*, b* plot 10. The series of neutral gray primaries 18 can be produced in a manner that is compatible with dry blending with toners of a same product line.
By using the series of neutral gray primaries 18 shown in
In addition, within the color space of the plot 10, any hue angle can be achieved by combining two of the 3 primaries (e.g., blue primaries 20, red primaries 22 and/or yellow primary 24). The intention of combining these colors is to move the target primary hue towards grey (decrease saturation), which is known as the graying agent. However, as that graying agent has an inherent hue of its own, it also shifts its hue as it changes the saturation of the resulting color. The most efficient way to change the saturation of a given color while maintaining the same hue angle is to combine one or more color primaries (e.g., blue primaries 20, red primaries 22 or yellow primary 24) with one or more of the series of gray neutral primaries 18.
Before describing
The PMS expands upon existing color reproduction systems such as the CMYK process. The CMYK process is a standardized method of printing color by using four inks, which is, cyan, magenta, yellow, and black. The majority of the world's printed material is produced using the CMYK process. The Pantone system is based on a specific mix of pigments to create new colors also referred to as spot colors. The Pantone system also allows for many “special” colors to be produced such as metallics and fluorescents. While most of the Pantone system colors are beyond the printed CMYK gamut, those that it is possible to simulate through the CMYK process are labeled as such within the company's guides.
In a similar fashion, dry toners that work in a Docutech 180 HLC print engine can also be formulated into 14 base toners that can be dry blended using Pantone's formulas and some minor fine tuning to provided Xerox Docutech 180 HLC customers with identical custom colors.
To create arbitrary highlight colors within a three-dimensional color gamut, blends of 4 components are needed. In addition to blending red, yellow, and green to get a particular shade of orange, both black and white or black and clear toners are needed to fine tune the darkness of the mixture. In
When the desired color is relatively close to a parent toner (e.g., yellow primary 86), as shown in
The increased number of base toners needed can be determined experimentally based on acceptable limits of image graininess. While fixed color toners (e.g., blended pigments) may always be less grainy than dry blended toners, adding additional base toners to the set of available components for dry blending extends the use of dry blended toners by creating more acceptable custom colors. As a result, combining one or more primary colors with a series of neutral gray primaries can result in less hue shift of the target primary and thus create less grainy images.
It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. The claims can encompass embodiments in hardware, software, or combinations thereof.
