Combination Of Inks Research Articles

The study of light guide plate fabricated by inkjet printing technique

When molding thin light guide plates, high injection speed and high molding pressure are required to fill the mold completely, but it is easy to have parts with defects like high residual stress and high warpage. Inkjet printing is a drop-on-demand (DOD) and direct writing process, there is no need to fabricate stampers for the DOD processes thus it saves lots of time on the development of light guide plates. With those benefits, back light unit suppliers around the world have envisioned the DOD process as a great potential for fabricating thin light guide plates. The aim of this study is to develop a complete light guide plate fabrication process using inkjet printing technology. That includes ink selection, substrate surface treatment, microlens array design, printing process parameters determination, and printing qualities investigation. A Dimatix DMP-2800 inkjet printing machine is used for printing the microlens and a polyacrylamide-based ink is selected. To make the PMMA substrate more hydrophobic, it is coated with a thin Teflon layer before the printing process. For this specific combination of machine, ink and substrate, when the distance between inkjet nozzle and substrate is 0.7mm and the driving voltage is 12V the printed microlens has the best quality. Referring to the microlens size of light guide plates made by industry, the microlens with 38μm in diameter and 26μm in height are selected for this study. A 3″ light guide plate, designed with TracePro software, is successfully fabricated using the proposed ink-jet printing scheme. The optical measurement result indicated that the light guide plate has an averaged luminance of 1012.58 nits and a luminance uniformity of 83.85%. Thus work demonstrates the feasibility and effectiveness of utilizing inkjet printing technique to prepare light guide plates with low cost.

Bi-scale appearance fabrication

Surfaces in the real world exhibit complex appearance due to spatial variations in both their reflectance and local shading frames (i.e. the local coordinate system defined by the normal and tangent direction). For opaque surfaces, existing fabrication solutions can reproduce well only the spatial variations of isotropic reflectance. In this paper, we present a system for fabricating surfaces with desired spatially-varying reflectance, including anisotropic ones, and local shading frames. We approximate each input reflectance, rotated by its local frame, as a small patch of oriented facets coated with isotropic glossy inks. By assigning different ink combinations to facets with different orientations, this bi-scale material can reproduce a wider variety of reflectance than the printer gamut, including anisotropic materials. By orienting the facets appropriately, we control the local shading frame. We propose an algorithm to automatically determine the optimal facets orientations and ink combinations that best approximate a given input appearance, while obeying manufacturing constraints on both geometry and ink gamut. We fabricate the resulting surface with commercially available hardware, a 3D printer to fabricate the facets and a flatbed UV printer to coat them with inks. We validate our method by fabricating a variety of isotropic and anisotropic materials with rich variations in normals and tangents.

The Characterization of Web Offset Equipment Based on the Measurement of Chromaticity

t would be a large effort to use traditional methods of calibration procedures for Web Offset Press equipments. In this paper we proposed a convenient process calibration, which will not only guarantee the product quality meeting the ISO standards, but also save financial and material resources. Firstly, the measurements for determining the best ink thickness in Web Offset Press are discussed. The chromaticity values on solid fields with corresponding combination of paper and ink required by ISO Standards were achieved. Through a optimization process for gray balance, the printed tone values were adjusted to meet the requirements of ISO Standards. Finally several standardized test targets on sampled sheets ware measured, then the ICC profiles were created. This paper proposed an innovative process calibration, therefor using methods of chromaticity measurement, characterization of Web Offset Press can be put to effect to optimize printing processes.

Printing spatially-varying reflectance for reproducing HDR images

We present a solution for viewing high dynamic range (HDR) images with spatially-varying distributions of glossy materials printed on reflective media. Our method exploits appearance variations of the glossy materials in the angular domain to display the input HDR image at different exposures. As viewers change the print orientation or lighting directions, the print gradually varies its appearance to display the image content from the darkest to the brightest levels. Our solution is based on a commercially available printing system and is fully automatic. Given the input HDR image and the BRDFs of a set of available inks, our method computes the optimal exposures of the HDR image for all viewing conditions and the optimal ink combinations for all pixels by minimizing the difference of their appearances under all viewing conditions. We demonstrate the effectiveness of our method with print samples generated from different inputs and visualized under different viewing and lighting conditions.

Printing spatially-varying reflectance for reproducing HDR images

We present a solution for viewing high dynamic range (HDR) images with spatially-varying distributions of glossy materials printed on reflective media. Our method exploits appearance variations of the glossy materials in the angular domain to display the input HDR image at different exposures. As viewers change the print orientation or lighting directions, the print gradually varies its appearance to display the image content from the darkest to the brightest levels. Our solution is based on a commercially available printing system and is fully automatic. Given the input HDR image and the BRDFs of a set of available inks, our method computes the optimal exposures of the HDR image for all viewing conditions and the optimal ink combinations for all pixels by minimizing the difference of their appearances under all viewing conditions. We demonstrate the effectiveness of our method with print samples generated from different inputs and visualized under different viewing and lighting conditions.

Gamut Mapping Spatially Varying Reflectance with an Improved BRDF Similarity Metric

AbstractRecent spatially varying reflectance (svBRDF) printing systems can reproduce an input document as a combination of matte, glossy and metallic inks. Due to the limited number of inks, this reproduction process incurs some distortion. In this work, we present an svBRDF gamut mapping algorithm that minimizes distortions in the angular and spatial domains. To preserve a material's perceived variation with lighting and view, we introduce an improved BRDF similarity metric that builds on both experimental results on reflectance perception and on the statistics of natural lighting environments. Our experiments show better preservation of object color and highlights, as validated quantitatively as well as through a perceptual study. As for the spatial domain, we show how to adapt traditional color gamut mapping methods to svBRDFs. Our solution takes into account the contrast between regions, achieving better preservation of textures and edges.

The effect of different standard illumination conditions on color balance failure in offset printed images on glossy coated paper expressed by color difference

One of the biggest problems in color reproduction processes is color shifts occurring when images are viewed under different illuminants. Process ink colors and their combinations that match under one light source will often appear different under another light source. This problem is referred to as color balance failure or color inconstancy. The main goals of the present study are to investigate and determine the color balance failure (color inconstancy) of offset printed images expressed by color difference and color gamut changes depending on three of the most commonly used in practice illuminants, CIE D50, CIE F2 and CIE A. The results obtained are important from a scientific and a practical point of view. For the first time, a methodology is suggested and implemented for the examination and estimation of color shifts by studying a large number of color and gamut changes in various ink combinations for different illuminants.

Simple Color Prediction Model Based on CIEXYZ Using an Effective Coverage Map

Most of the color prediction models use a single dot gain curve for each primary ink. In the proposed model, the behaviour of the dot gain of each primary ink is characterized by three curves based on CIEXYZ tri-stimulus values. In our previous works, it was shown that the usage of three characterization curves for each primary ink reduced the color difference between the predicted and measured data compared with the simple Yule-Nielsen model. In the present paper, an effective coverage map based on CIEXYZ is created. This map presents the effective coverage values of the primary inks corresponding to different ink combinations. Given any reference ink combination, the effective coverage values of the involved primary inks are estimated by cubic interpolation. Compared to our previous models, the proposed model gives significant reduction in the color difference between the predicted and the measured data.

A predictive thermal dynamic model for parameter generation in the laser assisted direct write process

The laser assisted direct write (LADW) method can be used to generate electrical circuitry on a substrate by depositing metallic ink and curing the ink thermally by a laser. Laser curing has emerged over recent years as a novel yet efficient alternative to oven curing. This method can be used in situ, over complicated 3D contours of large parts (e.g. aircraft wings) and selectively cure over heat sensitive substrates, with little or no thermal damage.In previous studies, empirical methods have been used to generate processing windows for this technique, relating to the several interdependent processing parameters on which the curing quality and efficiency strongly depend. Incorrect parameters can result in a track that is cured in some areas and uncured in others, or in damaged substrates. This paper addresses the strong need for a quantitative model which can systematically output the processing conditions for a given combination of ink, substrate and laser source; transforming the LADW technique from a purely empirical approach, to a simple, repeatable, mathematically sound, efficient and predictable process.The method comprises a novel and generic finite element model (FEM) that for the first time predicts the evolution of the thermal profile of the ink track during laser curing and thus generates a parametric map which indicates the most suitable combination of parameters for process optimization. Experimental data are compared with simulation results to verify the accuracy of the model.

HANS – Unlocking New Print Control Alternatives By Bringing Color Separation And Halftoning Closer Together

Color separation is currently used to decide how much of each available colorant to use for each printable color and halftoning then builds patterns that meet those choices. Print color, however, depends not only on how much of each colorant is used, but also on how those colorants are superimposed. Furthermore, there are many halftone patterns that correspond to a given combination of ink amounts. HANS (Halftone Area Neugebauer Separation), which we introduced at last year's IS&T's CIC conference, is a move towards specifying halftone pattern statistics and enables control over print properties beyond their current limits. While the benefits of HANS for color gamut and ink use efficiency have been shown, at this year's NIP, we would like to look more closely at how to determine the set of all possible halftone patterns that match a given color and demonstrate how access to such sets – metamer sets – benefits print control. We will also illustrate how even for a simple CMY ink set, which using current approaches leads to exactly one ink combination per printable color, there are sets of alternative halftone patterns that match a given color. Such sets in turn allow for tradeoffs to be made, e.g., between grain and ink use, even in this simple case.

ICC Profile Extension for Device MTF Characterization

We propose a method to maintain image sharpness consistency across different devices, analogous to the way ICC profiles are used to maintain color consistency. The method is based on creating a profile of the perceived blur caused by the printing and viewing process. We show how to measure and analyze the sharpness profile of a printer, and demonstrate that the profile consists of multiple 2D modulation transfer functions (MTF's), varying over different ink combinations and colors. We propose storing the sharpness profile within an ICC profile. The profile can then be used to adaptively pre-compensate for the induced blur, and maintain sharpness consistency.

Spectral-based color separation method for a multi-ink printer

A spectral-based 8-ink characterization model is developed to accurately predict the recipe for a multi-ink printer. The 8-ink color separation method is a union of five 3-ink and six 4-ink combinations based on the cellular Yule-Nielsen spectral Neugebauer model with a recipe selection strategy. The performance levels of the forward and backward models are evaluated for individual ink combinations using printed testing samples. Furthermore, the spectral-based method performs better compared with the XYZ-based approach. On the basis of the backward model performance, a novel fast recipe selection strategy is proposed and estimated.

A Novel Sensor to Visually Track Fading of Printed Material

As printed papers, banners, packages are pervasive, so is the recognition that they will fade over time due to exposure to light, pollutants and handling. However, few people can easily quantify the degree of fading that has already occurred until it is well-advanced and often irreversible. An assurance of the accuracy / validity of color samples is especially important in the commercial realm. For example, a user of a Pantone book or an alternative set of printed reference color samples needs to know that the sample colors are still accurate and valid. The only currently used marker is a printed date. We propose the use of a simple visual reference marker that is based on a side-by-side color comparison. We used our understanding of the fading process of printed material to create a novel type of fade sensors. These sensors are based on the concept that inks fade non-linearly and at different rates. Selecting the right combination of inks enables us to display visual cues or messages at various stages of the fading process. In our first experiment, we accumulated empirical fade data for several combinations of HP original ink and media and 3rd party company refill ink and media. We developed algorithms and visualization programs to analyze a dataset of 536 colors per ink and media sets through 80 years of fading and reduced the pool of marker color candidates to 20-40. In this initial phase, the final selection was done manually to account for the directionality of the color difference (luminance, chrominance, or hue) and to incorporate previous research on text readability. In the future we are planning to automate the final selection process. Adding our sensor to a set of reference color samples would visually communicate that the colors samples are not valid anymore and that the set needs to be replaced.

Pearl and Wagner: One Funny Day (review)

Reviewed by: Pearl and Wagner: One Funny Day Hope Morrison McMullan, Kate. Pearl and Wagner: One Funny Day; illus. by R. W. Alley. Dial, 2009 40p. ISBN 978-0-8037-3085-4 $14.99 R Gr. 1–2 Wagner the mouse is actually having not a funny day but a terrible day. After oversleeping and arriving late to school, he finds himself the butt of a slew of April Fool’s pranks, and he just doesn’t see the humor. In the second chapter, he gets fooled in the other direction when his good friend Pearl the rabbit chooses Bud as her dance-contest partner over Wagner (“‘April fools, right?’ said Wagner. ‘No,’ said Pearl. ‘For real’”). Finally, though, Wagner gets into the swing of things, faking a highly contagious illness that is spread by sneezing and ending the story with a loud, “Ah . . . ah . . . ah . . . April fools!” This latest in the Pearl and Wagner series (see Pearl and Wagner: Three Secrets, BCCB 9/04) focuses less on the duo’s friendship than on Wagner’s personal predicament. McMullen is successful at presenting the seriousness of that situation to the readers, who will definitely empathize with the frustration, hurt, and, ultimately, satisfaction that Wagner feels throughout the short chapters. Alley uses a combination of pen, ink, and watercolor to illustrate an expressive and carefully characterized animal cast. There is lots of contrast among the characters and abundant emotion detailed in their facial expressions, and the compositions are imbued with energy and movement. The short sentences and easygoing dialogue in combination with the detailed illustrations make this an excellent choice for early readers, and many among this group are likely to relate to Wagner’s not-so-funny feelings about his not-so-funny day. [End Page 412] Copyright © 2009 The Board of Trustees of the University of Illinois

Multi Color Pigmented Inks for Large Format Ink-Jet Printing

The benefits of new pigment inks and an new ink set for large format printers (LFPs) were validated. The ink hues were optimized to provide efficient coverage of special colors used primarily in the printing industry. Targets for effective hues were set, and a combination of inks with well-balanced hues were verified for the best ink set. An ink set with orange and green, along with optimized CMY process colors, was found to be effective.

Absorption Mechanism of Aqueous and Solvent Inks into Synthetic Nonwoven Fabrics

In order to obtain high quality printing results, it is important to understand the mechanisms of ink absorption and setting on various substrates. The final position of ink pigments determines the ink density and the resolution of the printed product. Absorption rates of aqueous and solvent inks into nonwoven fabrics were characterized with a Bristow absorption wheel. A model based on Darcy's Law was applied to predict the ink absorption rate into the nonwoven fabrics. The model links the void fraction, pore size, contact angle, and the Darcy permeability coefficients to the absorption rate. The results showed a good correlation between the experimental data and the predicted results for many combinations of substrates and inks, but in a few cases, the absorption rates were different than expected. A clear difference of microscale distributions between aqueous and solvent inks on the nonwoven fabrics could be obtained by confocal laser scanning microscopy.

Spectral Gamut Characteristics based on Number of Primaries and their Characteristics

In applications that require spectral color information, such as fine art printing field, industry has been able to improve reproduction quality substantially in the past decade by increasing the printer gamut space and improving other print quality attributes such as metamerism. As the number of inks used in the printer is increasing and researchers are able to understand the ink and media interaction more in detail, attempting to match a color in spectral space has been possible. Similar trend is happening for electronic displays such that now there are cameras and displays with 4 or 6 color channels or filters available.This paper focuses on the following two fundamental question in spectral color reproduction:1. What is the optimal number of inks, and which types of inks to use?2. How to create the ink combination that replicates a given spectral reflectance as closely as possible?

Multi-Ink Color-Separation Algorithm Improving Image Quality

Current color-printing technologies often use more than the minimum three or four inks: cyan, magenta, yellow, and black (CMYK). When the number of inks exceeds three, there is the usual color-management one-to-many mapping problem. Additional constraints have to be applied to achieve greater determinacy. For CMYK ink sets, the black ink is constrained. When additional chromatic inks are added, traditional methods subdivide either colorimetric or colorant space to achieve a one-to-one mapping. However, these traditional methods cannot take advantage of all the ink combinations available for improving image quality. Alternatively, additional constraints can be defined as perceptual metrics such as color constancy, graininess, color gamut, and color look-up table smoothness. A novel color separation algorithm was developed in order to optimize color look-up tables for improved image quality. This algorithm was tested with a six-pigmented ink (CMYKGO), ink jet proofing printer. Various four and a six-ink look-up tables were created based on different metrics. The perceptual performances of these look-up tables in color reproduction accuracy, color inconstancy, graininess and gamut volume were evaluated. The results show that the additional inks not only extend color gamut but also provided the potential to improve print quality.

The absorption mechanism of aqueous and solvent inks into synthetic nonwoven fabrics

To obtain high quality printing result with aqueous inks, it is important to understand the mechanisms of ink absorption and setting on various substrates. The final position of ink pigments determines the ink density and the resolution of the printed product. Recently, it has become desirable to develop higher quality printing results on nonwoven fabrics and synthetic fiber sheets.Absorption rates of aqueous and solvent inks into nonwoven fabrics were characterized with a Bristow absorption wheel. Several nonwoven fabrics, made with polyvinyl alcohol fibers or polypropylene fibers, were tested with aqueous and solvent inks. A model based on Darcy's law was applied to predict the ink absorption rate into the nonwoven fabrics. The model links the void fraction, pore size, contact angle and the Darcy permeability coefficients to the absorption rate. The results showed a high correlation between the experimental data and the predicted results for most combinations of substrates and inks, but in a few cases, the absorption rates were different than expected.The micro-scale distribution of aqueous and solvent inks on the nonwoven fabrics was evaluated with a confocal laser scanning microscope (CLSM) in order to characterize the deposition uniformity of the nonwoven fabrics. A clear difference of micro-scale distributions between aqueous and solvent inks could be obtained by CLSM.

Laser Direct-Write of Metallic Nanoparticle Inks

The combination of nanoparticle inks with laser direct-write allows the laser printing of fine electrically-conductive patterns on substrates requiring extremely low processing temperatures (< 250 oC). Silver lines with widths under 20 microns and thicknesses under one micron have been laser printed (using a 355 nm laser direct-write system) on polyimide substrates. These features are equivalent to those seen in typical vapor deposited and lithographically patterned thin films. Electrical resistivities of these lines in the range of 5-10 times bulk silver have been demonstrated. The low processing temperature of the nanoparticle inks also allows the laser-curing of printed silver lines without damage to the sensitive substrate. A cw 532 nm laser was used to cure asdeposited silver lines with a resistivity similar to that achieved in oven-curing. This approach is ideally suited for the prototyping and short production runs of interconnects for flexible electronics, RFID antennas and OLED displays. This work will show how these nanoparticle inks are processed using laser direct-write, and will discuss the structure and electrical properties of these printed lines on polyimide substrates.