# US 5,707,778 A · Optical recording medium

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- Number: US 5,707,778 A
- Document ID: US5707778A
- Status: Granted
- Kind: A
- Application number: 08/613,720
- Filed: 1996-03-12
- Granted: 1998-01-13
- Earliest claimed: 1993-10-05
- Assignees: Nippon Paper Industries Co., Ltd.
- Inventors: Toshiaki Minami; Tomoaki Nagai; Kaoru Hamada; Akio Sekine; Toshimi Satake; Toshiyuki Takano; Hideki Hayasaka
- Web page: https://patentgrep.com/patent/US5707778A

## CPC

- B41M 5/3333: {Non-macromolecular compounds}
- B41M 5/26: Thermography (B41M5/20, B41M5/24 take precedence); {Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used (B23K takes precedence; thermographic or photothermographic systems using noble metal compounds G03C1/494)}
- B41M 5/46: characterised by the light-to-heat converting means; characterised by the heat or radiation filtering or absorbing means or layers
- B41M 5/465: {Infrared radiation-absorbing materials, e.g. dyes, metals, silicates, C black}
- Y10S 430/145: Infrared
- Y10S 430/146: Laser beam
- Y10S 430/165: Thermal imaging composition
- B41M: PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING, (correction of typographical errors B41J; processes for applying transfer pictures or the like B44C1/16; fluid media for correction of typographical errors by coating C09D10/00; printing textiles D06P)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An optical recording medium including a substrate having thereon a recording layer containing a dye precursor, a color developer reactable with the dye precursor to develop a color, and a light absorbent for converting light to heat, characterized in that the color developer is at least one compound of Formula (1): (R--NH (C.dbd.S) NH)n--Z (1) (wherein R denotes a substituted or unsubstituted alkyl, cycloalkyl, aryl, aralkyl, or alkenyl. n is an integer of 2 or more, and Z denotes a group having a valence of 2 or more.). The optical recording medium is superior in heat resistance and plasticizer resistance of the recorded image, heat resistance of background, water resistance, and moisture resistance.).

## Claims

### Claim 1

A heat resistant optical recording medium comprising a substrate having thereon a recording layer containing a dye precursor, a color developer reactable with said dye precursor to develop a color, and a light absorber for converting light to heat, wherein said color developer is at least one compound of the formula (4): ##STR9## wherein X, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are lower alkyl having 1 to 6 carbon atoms, alkoxy having 1 to 6 carbon atoms, cyclohexyl, nitro, cyano, halogen or hydrogen; and m is an integer from 1 to 3.

### Claim 2 (depends on 1)

The optical recording medium of claim 1, wherein the recording surface of the entire recording medium is laminated with a plastic film by the application of heat.

### Claim 3 (depends on 2)

The optical recording medium of claim 2 wherein the optical recording medium has after lamination been recorded with stroboscopic flash light or laser light.

### Claim 4

An optical recording medium which is heat resistant at temperatures of at least 105.degree. C. comprising a substrate coated with a color developing layer, wherein the color developing layer comprises a dye precursor, a developer which reacts with the dye precursor to cause color development thereof upon heating, and a light absorber for converting light to heat, wherein the developer is at least one bisthiourea compound represented by the formula (4): ##STR10## wherein X, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are lower alkyl having 1 to 6 carbon atoms, alkoxy having 1 to 6 carbon atoms, cyclohexyl, nitro, cyano, halogen or hydrogen; and m is an integer form 1 to 3.

### Claim 5 (depends on 4)

The optical recording medium of claim 4 wherein the Macbeth background value after exposure to heat at a temperature of about 105.degree. C. is 0.20 or less.

### Claim 6 (depends on 4, 5)

The optical recording medium of claim 4 or claim 5, wherein the recording surface of the entire recording medium is laminated with a plastic film by the application of heat.

### Claim 7

A heat resistant optical recording medium comprising a substrate having thereon a recording layer containing a dye precursor, a color developer reactable with said dye precursor to develop a color, and a light absorber for converting light to heat, wherein said color developer is at least one compound of the Formula (4); ##STR11## wherein X, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are lower alkyl having 1 to 6 carbon atoms, alkoxy having 1 to 6 carbon atoms, cyclohexyl, nitro, cyano, halogen or hydrogen; and m is an integer from 1 to 3, and wherein when a laser light is scanned over said optical recording medium, the optical recorded portion has a Macbeth optical density of greater than 0.7, and when said optical recording medium is pressed against a hot plate at 105.degree. C. with a pressure of 8 g/cm.sup.2 for 5 seconds, said optical recording medium other than the recorded portion has a Macbeth optical density of less than 0.2.

### Claim 8 (depends on 7)

The optical recording medium of claim 7 wherein said laser light comprises a 30 mW laser light of 830 nm in oscillation wavelength focused by a lens with a focal length of 4.5 mm and a numerical aperture of 0.45 and is scanned over said optical recording medium at a recording speed of 50 mm/sec and at recording line interval of 50 .mu.m.

### Claim 9 (depends on 4, 7)

The optical recording medium of claim 4 or 7 wherein X and R.sub.1 to R.sub.8 are methyl or chlorine.

### Claim 10 (depends on 4, 7)

The optical recording medium of claim 4 or 7 wherein the formula (4) compound is: ##STR12##

### Claim 11 (depends on 4, 7)

The optical recording medium of claim 4 or 7 wherein the formula (4) compound is ##STR13##

### Claim 12 (depends on 4, 7)

The optical recording medium of claim 4 or 7 wherein the formula (4) compound is ##STR14##

### Claim 13 (depends on 4, 7)

The optical recording medium of claim 4 or 7 wherein the formula (4) compound is ##STR15##