3823022

Information

• Patent Grant
• 3823022

• References
• Source

• Patent Number

  3,823,022

• Date Filed

  Not available

• Date Issued

  Tuesday, July 9, 1974
  50 years ago

• CPC

  • G09B3/085 - with invisibly printed correct answer; the answer being rendered visible by special optical means
  • B41M3/001 - using chemical colour-formers or chemical reactions
  • Y10S101/29 - Printing involving a color-forming phenomenon

• US Classifications

  • 503 - Record receiver having plural interactive leaves or a colorless color former, method of use, or developer therefor
  • 101 - Printing
  • 434 - Education and demonstration