High-Technology Applications of Organic Colorants Peter Gregory Specialties Research Centre ICI Specialties Imperial Chemical Industries PLC Blackley, Manchester, England Plenum Press New York and London
Contents PART I. Historical Perspectives PART II. Colorants for Electronics 1. Liquid Crystal Dyes 1.1. Introduction 7 1.2. Dye Types 9 1.3. Future Trends 11 1.4. Summary 13 References 13 2. Micro Color Filters 2.1. Introduction 15 2.2. Fiat Screen Televisions 16 2.3. Color Filter Preparation 17 2.3.1. Dyeing Method 17 2.3.2. Pigment Method 19 2.4. Spectral Characteristics 22 2.5. Summary 24 References 25 3. Laser Dyes 3.1. Introduction 27 3.2. Basic Theory 28 3.3. Dye Types 29 3.4. Summary 31 References 32 ix
X Contents 4. Colorants for Nonlinear Optics 4.1. Introduction 33 4.2. Nonlinear Optical Effects and Applications 33 4.3. Molecular Polarizability 35 4.4. Nonlinear Optical Molecules 36 4.5. Molecular Alignment 40 4.6. Summary 43 References 43 5. Solar Cells 5.1. Introduction 45 5.2. Photosynthesis Mimics 45 5.3. Miscellaneous Colorants 47 5.4. Luminescent Solar Cells 47 5.5. Applications 51 5.6. Summary 51 References 52 6. Electrochromic Dyes 6.1. Introduction 53 6.2. Electrochromic Displays 53 6.3. Electrochromic Printing 54 6.4. Summary 55 References 56 PART III. Colorants for Reprographics 7. Electrophotography 7.1. Introduction 59 7.2. Photocopying and Laser/Light Emitting Diode Printing Processes 59 7.2.1. Photocopying Process 60 7.2.2. Laser/Light Emitting Diode Printing Process.... 63 7.2.3. Color Copying Process 65 7.3. Key Chemical Components 67 7.4. Photoconductors 68 7.4.1. General Features 68 7.4.2. Inorganic Photoconductors 75 7.4.3. Organic Photoconductors 75 7.4.4. Photoconductive Mechanism 86
Contents XI 7.5. Toners 87 7.5.1. General Features 88 7.5.2. Charge Control Agents 90 7.5.2.1. Negative Charge Control Agents 91 7.5.2.2. Positive Charge Control Agents 94 7.5.2.3. Noncolored Charge Control Agents 95 7.5.2.4. Polymerie Charge Control Agents 97 7.5.2.5. Mode of Action 97 7.5.3. Colored Toners 99 7.6. Photoactive Pigment Electrophoresis 103 7.6.1. Basic Process 103 7.6.2. Füll Color Process 104 7.6.3. Problems of Photoactive Pigment Electrophoresis... 107 7.6.4. Correlation with Organic Photoconductors 109 7.7. Special Effects 110 7.7.1. Nonphotocopiable Documents 110 7.7.2. Photomicrolithography 113 7.7.3. Prepress Proofing 114 7.7.4. Transfer Printing Toners 116 7.8. Summary 118 References 119 8. Thermography 8.1. Introduction 123 8.2. Direct Thermal Printing 124 8.3. Pressure-Sensitive Printing 129 8.4. Mead Photocapsule (CYCOLOR) Process 134 8.5. Thermal Wax Transfer 143 8.5.1. Color Sheet 144 8.5.2. Receiver Sheet 147 8.5.3. Patent Activity 147 8.5.4. Electrothermal Printing 147 8.5.5. Laser Transfer 148 8.6. Dye Diffusion Thermal Transfer 148 8.6.1. Electronic Photography 149 8.6.2. History and Development 151 8.6.3. Dye Diffusion Thermal Transfer Process 152 8.6.4. Dyesheet 153 8.6.5. Dye Diffusion Thermal Transfer Dyes 154 8.6.5.1. YellowDyes 157 8.6.5.2. Magenta Dyes 159 8.6.5.3. CyanDyes 163 8.6.6. Receiver Sheet 168
Xll Contents 8.7. Summary 169 References 171 9. Ink-Jet Printing 9.1. Introduction 175 9.2. History and Development 176 9.3. Technology 176 9.3.1. Continuous Ink-Jet 177 9.3.2. Drop-on-Demand Ink-Jet 179 9.4. Ink-Jet Inks 180 9.4.1. General Features 180 9.4.2. Aqueouslnks 181 9.4.3. Solvent Inks 182 9.4.4. Hot-Melt Inks 182 9.4.5. Ink-Paper Interactions 182 9.5. Ink-Jet Colorants 184 9.5.1. Properties Required 184 9.5.1.1. Color 184 9.5.1.2. Color Strength 185 9.5.1.3. Solubility 186 9.5.1.4. Insolubles 187 9.5.1.5. Electrolytes/Metals 187 9.5.1.6. Fastness Properties 188 a. Light Fastness 188 b. Water Fastness 188 c. Smear Fastness 189 9.5.1.7. Shade 189 9.5.1.8. Toxicology 190 9.5.1.9. Thermal Stability 190 9.5.2. DyeTypes 192 9.5.3. Black Dyes 192 9.5.3.1. Water Soluble 192 9.5.3.2. Solvent/Resin Soluble 196 9.5.4. Yellow Dyes 197 9.5.4.1. Water Soluble 197 9.5.4.2. Solvent/Resin Soluble 197 9.5.5. Magenta Dyes 197 9.5.5.1. Water Soluble 197 9.5.5.2. Solvent/Resin Soluble 201 9.5.6. CyanDyes 201 9.5.6.1. Water Soluble 201 9.5.6.2. Solvent/Resin Soluble 201
Contents XÜi 9.6. Applications of Ink-Jet Printing 202 9.7. Summary 203 References 204 10. Electrography, lonography, and Magnetography 10.1. Introduction 207 10.2. Electrography 207 10.3. lonography 209 10.4. Magnetography 211 10.5. Summary 212 References 212 PART IV. Future Perspectives 11. Infrared Absorbers 11.1. Introduction 215 11.2. Effects of Infrared Absorbers 218 11.3. Classification of Infrared Absorbers 218 11.3.1. Nitroso 219 11.3.2. Cyanines 219 11.3.3. Nigrosines 225 11.3.4. Triphenylmethanes 225 11.3.5. Imminium and Diimminium 227 11.3.6. Squariliums and Croconiums 229 11.3.7. Nickel Dithiolenes and Related Compounds.... 230 11.3.8. Quinones 232 11.3.8.1. Simple Naphthoquinones 235 11.3.8.2. Extended Quinones 235 11.3.8.3. CI Disperse Blue 60 Analogues 236 11.3.8.4. Benzoquinones 236 11.3.9. Phthalocyanines 236 11.3.9.1. Polymorphie Pigments 236 11.3.9.2. Metallation 237 11.3.9.3. Donor Substitutents 239 11.3.9.4. Extended Conjugation 239 11.3.10. Azo 240 11.3.11. Indoanilines 242 11.3.12. Donor-Acceptor Molecules '.... 243 11.3.13. OtherClasses 243
XIV Contents 11.4. Applications of Infrared Absorbers 243 11.4.1. Heat-Ray Blocking 243 11.4.2. Energy Conversion 244 11.4.2.1. Thermal Imaging 244 11.4.2.2. Flash Fusion of Toners 245 11.4.2.3. Solar Heating 245 11.4.3. Optical Effects (Utilizing Laser Radiation) 246 11.4.3.1. Organic Photoconductors 246 11.4.3.2. Optical Data Storage 246 11.4.3.3. Automatic Identification 248 11.4.4. Optical Effects (Utilizing Electromagnetic Radiation). 250 11.5. Colorless Infrared Absorbers 251 11.6. Summary 251 References 253 12. Toxicology 12.1. Introduction 255 12.2. Hazards of Colorants 255 12.3. Regulations and Registration 256 12.4. Structure-Carcinogenicity Guidelines for Organic Colorants and Related Intermediates 258 12.4.1. Effect of Physical Properties on Carcinogenicity... 258 12.4.2. Classes of Carcinogens by Chemical Structure.... 259 12.4.2.1. Carcinogens from Nitrogen Electrophiles.. 259 a. Aromatic Nitro and Amino Compounds 259 b. Nitrosamines 260 c. Hydrazines and Hydroxylamines.... 262 d. Azo Dyes 264 e. Anthraquinone Dyes 266 f. Cationic Dyes 266 12.4.2.2. Carcinogens from Carbon Electrophiles... 267 a. Direct Acting Alkylating Agents.... 267 b. Polycyclic Aromatic Hydrocarbons... 268 c. Michael Acceptors 269 12.4.3. Metals. 270 12.4.4. Carcinogenic Impurities 270 12.5. Risk Assessment 271 12.6. Summary 272 References 272 13. Future Trends 13.1. Introduction 273 13.2. Colorants for Electronics 273
Contents XV 13.3. Colorants for Reprographics 274 13.3.1. The Paperless Office 274 13.3.2. Competing Technologies 275 13.3.3. General Predictions 276 13.3.4. Specific Predictions 278 13.3.4.1. Electrophotography 278 13.3.4.2. Thermal 279 13.3.4.3. Ink-Jet 281 13.3.4.4. Other Technologies 282 13.4. Toxicology 282 13.5. Summary 283 Reference 283 Index 285