JP2612598B2 - Recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to at least one pentadiene compound.
The present invention relates to a recording material characterized by using a seed.

[Problems to be solved by the prior art and the invention]

Conventionally, color formers have been used for various recording materials. The main examples thereof include a pressure-sensitive recording material, a heat-sensitive recording material, an energized heat-sensitive recording material, and a photosensitive recording material. The demand for these recording materials is rapidly increasing with the development of the information industry today, which is called the information age. In recent years, computers have been heavily used for streamlining business processes associated with office automation, or for various rationalizations associated with factory automation, and optical character reading devices for inputting information at that time, Alternatively, optical barcode readers and the like have been developed, and have been remarkably used in recent years.

The present invention relates to a developing material such as an inorganic acid, an organic acid, a phenolic compound, a derivative thereof, a metal salt thereof, or an electron accepting substance such as an oxidizing agent (for example, acid clay, 3,5-diene). -T-butylsalicylic acid, bis (3-
(Chlorophenyl) thiourea, 4,4'-isopropylidenediphenol, zinc 4-nitrobenzoate, benzyl 4-hydroxybenzoate, etc.) and develops a color, and has a strong absorption band in the near infrared region. Another object of the present invention is to provide a recording material characterized by using at least one compound.

At least one of the pentadiene compounds of the present invention
As described above, the recording material using the seed has a characteristic not seen in the color former used for the conventional pressure-sensitive recording material, heat-sensitive recording material, or photosensitive recording material. is there.

Conventionally, typical examples of color formers generally used for recording materials such as pressure-sensitive recording sheets, heat-sensitive recording sheets or photosensitive recording sheets include phthalide-based compounds, fluoran-based compounds, and triphenylmethane-based compounds. Is raised. For example, a typical example of a phthalide compound is crystal violet lactone that develops blue, and a typical example of a fluoran compound is 2- (2-chloroanilino) -6-dibutylaminofluorane that develops black, and triphenylmethane. Representative examples of the compound include leuco crystal violet which emits blue light. However, since these color formers do not absorb light in the near-infrared region around 700-900 nm, the recording images obtained using these color formers have been increasing remarkably in recent years. However, it is not suitable as a recorded image for an optical character reader or an optical barcode reader using light in the near infrared region as a light source.

[Means for solving the problem]

The present invention has the following general formula: (Wherein, R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group, an alkoxyalkyl group, a halogenoalkyl group or a phenyl group or a benzyl group which may be substituted with a halogen atom or a lower alkyl group. And R ¹ , R ²
Can also form a ring together with the bonding nitrogen atom, and R ³ and R ⁴ together with the bonding nitrogen atom, and R ⁵ and R ⁶ can be a hydrogen atom, a halogen atom, R ⁷ represents a lower alkyl group, an alkoxy group, an alkoxyalkyl group or an alkoxycarbonyl group, and R ⁷ represents an alkyl group or a halogen atom, a phenyl group optionally substituted with an alkyl group or an alkoxy group, or a naphthyl group. However, when R ¹ , R ² , R ³ , and R ⁴ are all lower alkyl groups, R ⁵ and R ⁶ are not a hydrogen atom or a lower alkyl group at the 2-position. The pentadiene-based compound represented by the formula (1) is an inorganic acid, an organic acid, a phenolic compound, a derivative thereof, or a metal thereof used in producing a pressure-sensitive recording material, a heat-sensitive recording material, and a photosensitive recording material. A color former that exhibits a green-blue or greenish color tone by contacting with a color-developing material such as an electron accepting substance such as a salt or an oxidizing agent, and that produces a high-density and clear color. For example, a recording image obtained by using a pressure-sensitive recording sheet and a heat-sensitive recording sheet
Since it also has light absorption in the near-infrared region around 0 to 900 nm, an optical character reader or optical device that emits light in the near-infrared region using a semiconductor laser or the like, which has become extremely widely used in recent years. It is suitable as a recording material for a barcode reader.

In the present invention, in producing a pressure-sensitive recording material and a heat-sensitive recording material, one type selected from these color formers may be used alone, or two or more types may be used in combination, or a known color former may be used. Mer, for example, crystal violet lactone, 2- (2-chloroanilino)-
6-dibutylaminofluoran, 2-anilino-3-methyl-6- (N-ethyl-N-tetrahydrofurfurylamino) fluoran, 2-anilino-3-methyl-6
Dibutylaminofluoran, 2-anilino-3-methyl-6-diethylaminofluoran, 2-anilino-3-
Methyl-6- (N-methyl-N-cyclohexylamino) fluoran, 2-anilino-3-methyl-6- (N
-Ethyl-N-isoamylamino) fluoran, 2-N,
It can also be used as a mixture with N-dibenzylamino-6-diethylaminofluoran, benzoylleucomethylene blue, leucocrystal violet and the like. By mixing, the color development and storage stability of the image may be further improved.

In the present invention, as a typical example of a solvent for a color former used to obtain a pressure-sensitive recording material, Hisol SAS-296 (a product of Nippon Petrochemical Co., Ltd.) and KMC-113
(Products of Kureha Chemical Industry Co., Ltd.), but various solvents such as monoisopropylbiphenyl, alkylbenzene, alkylbiphenyl, alkylnaphthalene, diarylethane, hydrogenated terphenyl and chlorinated paraffin are used alone. Or mixed.

In the present invention, as an encapsulation method used to obtain a pressure-sensitive recording material, a coacervation method, an interfacial polymerization method, an in-situ method, or the like can be used.

In the present invention, typical examples of the binder used for obtaining the thermosensitive recording material include polyvinyl alcohol, methyl cellulose, methoxy cellulose, ethyl cellulose, hydroxyethyl cellulose, gum arabic, gelatin, casein, starch and derivatives thereof, and polyacetic acid. Examples include vinyl, polyacrylic acid, polyvinylpyrrolidone, polyurethane, polyacrylamide, acrylamide / acrylate copolymer, and styrene-maleic anhydride copolymer.

Further, in order to further improve the light fastness of the recorded image, storage stability, etc., higher fatty acid esters, higher fatty acid amides, phthalic esters, terephthalic esters, benzylbiphenyls, alkylphenols, benzenesulfonamides, Various additives such as antioxidants, deterioration inhibitors, and ultraviolet absorbers such as alkylbenzenesulfonamides and terphenyls can be used in combination.

The pentadiene-based compound represented by the general formula [1] having excellent properties as described above is described in JP-B-53-12802, JP-A-55-45785, JP-A-60-231766, and the like.
It can be synthesized by the following well-known typical method.

However, in the general formulas [2] to [7], R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ ,
R ⁷ is the same as defined in the general formula [1]. That is, the bisstyryl ketone derivative represented by the general formula [4] is obtained by hydroxylating the benzaldehyde derivative represented by the general formula [2] and the benzaldehyde derivative represented by the general formula [3] together with acetone. It can be synthesized by dehydration condensation using an alkali metal salt such as sodium as a catalyst.

Further, the bisstyryl carbinol derivative represented by the general formula [5] can be obtained by catalytically reducing the bisstyryl ketone derivative represented by the general formula [4], and further reducing aluminum lithium hydride or metal powder. And by using sodium borohydride, and more preferably by using sodium borohydride.

Further, the bisstyryl carbenium perchlorate derivative represented by the general formula [6] is obtained by mixing a bisstyryl carbinol derivative represented by the general formula [5] with an alcohol solvent such as methanol at 20 to 100 ° C. It can be synthesized by reacting with perchloric acid.

Further, the pentadiene derivative represented by the general formula [1] is obtained by converting a bisstyrylcarbenium perchlorate derivative represented by the general formula [6] into an alcohol solvent such as methanol at 20 to 100 ° C. It can be synthesized by reacting with an alkali metal salt of a sulfinic acid such as benzenesulfinic acid represented by [7].

The pentadiene compound thus obtained is specifically described as follows.

(1) 1,5-bis [4- (N, N-diethoxyethylamino) phenyl] -5-phenylsulfonylpenta-1,
3-diene (2) 1,5-bis [4- (N, N-di (2-chloroethyl)
(Amino) phenyl] -5-phenylsulfonylpenta-1,3-diene (3) 1,5-bis [4- (N-ethoxyethyl-N-ethylamino) phenyl] -5-phenylsulfonylpenta-1,3 -Diene (4) 1,5-bis [4- (N- (2-chloroethyl)-
N-ethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene (5) 1,5-bis [2-ethoxy-4- (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta- 1,3-diene (6) 1,5-bis [4- (N, N-diethoxyelamino)
Phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene (7) 1,5-bis [4- (N, N-di (2-chloroethyl)
Amino) phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene (8) 1,5-bis [4- (N-ethoxyethyl-N-ethylamino) phenyl] -5- ( 4'-methylphenylsulfonyl) penta-1,3-diene (9) 1,5-bis [4- (NN-chloroethyl) -N
-Ethylamino) phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene (10) 1,5-bis [2-ethoxy-4- (N, N-diethylamino) phenyl] -5 -(4'-methylphenylsulfonyl) penta-1,3-diene (11) 1,5-bis [4- (N, N-diethoxyethylamino) phenyl] -5- (β-naphthylsulfonyl) penta- 1,3-diene (12) 1,5-bis [4- (N, N-di (2-chloroethyl)
(Amino) phenyl] -5- (β-naphthylsulfonyl) penta-1,3-diene (13) 1,5-bis [4- (N-ethoxyethyl-N-ethylamino) phenyl] -5- (β- Naphthylsulfonyl) penta-1,3-diene (14) 1,5-bis [4- (N- (2-chloroethyl)-
N-ethylamino) phenyl] -5- (β-naphthylsulfonyl) penta-1,3-diene (15) 1,5-bis [2-ethoxy-4- (N, N-diethylamino) phenyl] -5 (Β-naphthylsulfonyl) penta-1,3-diene (16) 1,5-bis [4- (N, N-diethoxyethylamino) phenyl] -5- (α-naphthylsulfonyl) penta-1,3 -Diene (17) 1,5-bis [4- (N, N-di (2-chloroethyl)
(Amino) phenyl] -5- (α-naphthylsulfonyl) penta-1,3-diene (18) 1,5-bis [4- (N-ethoxyethyl-N-ethylamino) phenyl] -5- (α- Naphthylsulfonyl) penta-1,3-diene (19) 1,5-bis [4- (N- (2-chloroethyl)-
N-ethylamino) phenyl] -5- (α-naphthylsulfonyl) penta-1,3-diene (20) 1,5-bis [2-ethoxy-4- (N, N-diethylamino) phenyl] -5 (Α-naphthylsulfonyl) penta-1,3-diene (21) 1,5-bis (4-pyrrolidinophenyl) -5
(4'-methylphenylsulfonyl) penta-1,3-
Diene (22) 1,5-bis (4-piperidinophenyl) -5-phenylsulfonylpenta-1,3-diene (23) 1,5-bis [4- (4-diphenylamino) phenyl] -5 -(Β-naphthylsulfonyl) penta-1,
3-diene (24) 1,5-bis [4- (N, N-dibenzylamino) phenyl] -5- (α-naphthylsulfonyl) penta-1,
3-diene (25) 1,5-bis [2-ethoxy-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene (26) 1,5-bis [2 -Methoxycarbonyl-4- (N, N
-Dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene (27) 1,5-bis [2-ethoxyethyl-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpentane -1,3-diene (28) 1,5-bis [2-methyl-4- (N, N-diethoxyethylamino) phenyl] -5- (4'-methoxyphenylsulfonyl) penta-1,3- Diene (29) 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-
1,3-diene (30) 1,5-bis [2-bromo-4- (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta-
1,3-diene (31) 1,5-bis [2-methyl-4-pyrrolidinophenyl] -5-phenylsulfonylpenta-1,3-diene (32) 1,5-bis [2-methyl-4 -Piperidinophenyl] -5-phenylsulfonylpenta-1,3-diene (33) 1- [2-ethoxy-4- (N, N-diethylamino) phenyl] -5- [2-methyl-4- ( N, N-diethylamino) phenyl] -5- (4'-methoxyphenylsulfonyl) penta-1,3-diene (34) 1,5-bis [4- (N, N-diphenylamino) phenyl] -5 (Phenylsulfonyl) penta-1,3-
Diene (35) 1,5-bis [4- (N, N-dibenzylamino) phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene (36) 1,5-bis [ 4- (N, N-di (4-chlorophenyl) amino) phenyl] -5-phenylsulfonylpenta-1,3-diene (37) 1,5-bis (4-piperidinophenyl) -5-phenylsulfonyl Penta-1,3-diene (38) 1,5-bis (4-pyrrolidinophenyl) -5
(4'-methylphenylsulfonyl) penta-1,3-
Diene (39) 1,5-bis (4-morpholinophenyl) -5
(4'-methylphenylsulfonyl) penta-1,3-
Diene (40) 1,5-bis [4- (N, N-di (4-methylphenyl) amino) phenyl] -5- (4'-chlorophenylsulfonyl) penta-1,3-diene (41) 1, 5-bis [4- (N, N-di (4-chlorophenyl) amino) phenyl] -5- (4'-chlorophenylsulfonyl) penta-1,3-diene (42) 1,5-bis [3-methyl -4- [N, N-dimethylamino) phenyl] -5-octylsulfonylpenta-
1,3-diene (43) 1,5-bis (4-pyrrolidinophenyl) -5-ethylsulfonylpenta-1,3-diene and the like.

(Example of the present invention)

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 14 parts of gelatin having an isoelectric point of 8.5 and 12 parts of gum arabic were heated to 50 ° C.
Was dissolved in 150 parts of deionized water, and 3.5 parts of 10% funnel oil was added as an emulsifier, and 1,5-bis [2-chloro-4- (N, N-
[Dimethylamino] phenyl] -5-phenylsulfonylpenta-1, 3-diene
296 (diarylethane oil, Nippon Petrochemical Co., Ltd.
(Product) 70 parts were added and emulsified with a homomixer at 7000 rpm to obtain an O / W emulsion. 40 ℃ in this emulsion
Was added and diluted with 100 parts of deionized water, and a 10% aqueous acetic acid solution was added dropwise while stirring with a propeller-type stirrer at 350 rpm to adjust the pH to 4.3.

Then, 13 parts of an aqueous solution of 20% Melment F10 (product of Showa Denko KK) and 40% Newcol 271A (Nippon Emulsifier Co., Ltd.)
3.5 parts of an aqueous solution of (product) was added, and the mixture was cooled from the outside of the vessel while continuing to stir.
Five parts were added and a 10% aqueous sodium hydroxide solution was added dropwise over 15 minutes to adjust the pH to 9.5, and while continuing to stir, the liquid temperature was raised to 50 ° C. for 30 minutes to give 1,5-bis [2 -Chloro-4
A microcapsule slurry of-(N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene dissolved oil was prepared.

This microcapsule slurry was applied on paper and dried, and then closely adhered to a commercially available pressure-sensitive color developing sheet. When a pen pressure or a typewriter impact was applied, a green-blue color recording image was obtained in each case. Further, when the reflection and absorption characteristics of the recorded image were measured, it was found to have a maximum at 811 nm and strong electromagnetic wave absorption in the near infrared region.

Example 2 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
Instead of 3-diene, 1,5-bis [2-chloro-4- (N,
N-Diethylamino) phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene was treated in the same manner as in Example 1 to give 1,5-bis [2-chloro-4 -(N, N-diethylamino) phenyl] -5-
(4'-methylphenylsulfonyl) penta-1,3-
A microcapsule slurry of diene dissolved oil was prepared.

This microcapsule slurry was applied on paper and dried, and then closely adhered to a commercially available pressure-sensitive color developing sheet. When a pen pressure or a typewriter impact was applied, a green-blue color recording image was obtained in each case. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 3 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
1,5-bis [2-ethoxy-4-
Except for using (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene, the same treatment as in Example 1 was carried out to give 1,5-bis [2-ethoxy-4-
A (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene dissolved oil microcapsule slurry was prepared.

This microcapsule slurry was applied on paper and dried, and then closely adhered to a commercially available pressure-sensitive color developing sheet. When a pen pressure or a typewriter impact was applied, a green-blue color recording image was obtained in each case. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 4 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
Example 1 was repeated except that 1,5-bis [2-methoxycarbonyl-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene was used instead of 3-diene. In the same manner, a microcapsule slurry of 1,5-bis [2-methoxycarbonyl-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene dissolved oil was prepared. .

This microcapsule slurry was applied on paper and dried, and then closely adhered to a commercially available pressure-sensitive color developing sheet. When a pen pressure or a typewriter impact was applied, a green-blue color recording image was obtained in each case. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 5 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
2.0 parts of 3-diene and 20 parts of a 10% aqueous polyvinyl alcohol solution were dispersed and mixed at room temperature for 24 hours using a ball mill to obtain a colorless slurry as "liquid A". The particle size of the solid material in this slurry was about 3 microns.

On the other hand, 7.5 parts of bisphenol A was dispersed and mixed with 40 parts of a 10% aqueous polyvinyl alcohol solution and 10 parts of deionized water at room temperature for 24 hours using a ball mill.
A slurry was prepared as a “liquid”. The particle size of the solid material in this slurry was about 5 microns.

The above "Solution A" and "Solution B" were mixed, stirred at room temperature for 1 hour, uniformly dispersed and mixed to prepare a mixed slurry. This mixed slurry is applied to one side of plain paper of 50 g / m ² using a wire bar coder so as to have a uniform film thickness, and is air-dried at room temperature to obtain a heat-sensitive recording sheet having an almost colorless heat-sensitive layer. It was created.

When the heat-sensitive recording sheet thus prepared was colored using a thermal gradient tester, a blue-green color recording image was obtained. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 6 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
Instead of 3-diene, 1,5-bis [2-chloro-4- (N,
N-Diethylamino) phenyl] -5- (4'-methylphenylsulfonyl) penta-1,3-diene was used and treated in the same manner as in Example 5, to give 1,5-bis [2-chloro-4 -(N, N-diethylamino) phenyl] -5-
(4'-methylphenylsulfonyl) penta-1,3-
A colorless slurry of diene was obtained as "liquid C". The particle size of the solid material in this slurry was about 3 microns.

The above-mentioned “Solution C” and the “Solution B” prepared in Example 5 were mixed, stirred at room temperature for 1 hour, and uniformly dispersed and mixed to prepare a mixed slurry. 50 g /
using a wire bar coater on one surface of the plain paper m ^2, it was coated so as to have a uniform thickness, and air dried at room temperature to a heat-sensitive recording sheet which hardly with colorless heat-sensitive layer.

When the heat-sensitive recording sheet thus prepared was colored using a thermal gradient tester, a blue-green color recording image was obtained. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 7 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
1,5-bis [2-ethoxy-4-
Except for using (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene, the same procedure as in Example 5 was repeated to give 1,5-bis [2-ethoxy-4-
A colorless slurry of (N, N-diethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene was obtained as "D solution". The particle size of the solid material in this slurry was about 3 microns.

The above-mentioned "Solution D" and the "Solution B" prepared in Example 5 were mixed, stirred at room temperature for 1 hour, and uniformly dispersed and mixed to prepare a mixed slurry. 50 g /
using a wire bar coater on one surface of the plain paper m ^2, it was coated so as to have a uniform thickness, and air dried at room temperature to a heat-sensitive recording sheet which hardly with colorless heat-sensitive layer.

When the heat-sensitive recording sheet thus prepared was colored using a thermal gradient tester, a blue-green color recording image was obtained. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

Example 8 1,5-bis [2-chloro-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,
Example 5 was repeated except that 1,5-bis [2-methoxycarbonyl-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene was used instead of 3-diene. The same treatment was carried out to give a colorless slurry of 1,5-bis [2-methoxycarbonyl-4- (N, N-dimethylamino) phenyl] -5-phenylsulfonylpenta-1,3-diene as "solution E" As obtained. The particle size of the solid material in this slurry was about 3 microns.

The above “Solution E” and the “Solution B” prepared in Example 5 were mixed, stirred at room temperature for 1 hour, and uniformly dispersed and mixed to prepare a mixed slurry. 50 g /
using a wire bar coater to one side of the m ² of plain paper,
Apply so that it has a uniform film thickness, air-dry at room temperature,
A heat-sensitive recording sheet having an almost colorless heat-sensitive layer was prepared.

When the heat-sensitive recording sheet thus prepared was colored using a thermal gradient tester, a blue-green color recording image was obtained. When the reflection and absorption characteristics of this recorded image were measured, it was found that the recorded image had strong electromagnetic wave absorption in the near infrared region.

〔The invention's effect〕

As described above, the present invention has strong absorption in the near-infrared region in a colored state, and has excellent storage stability when used for a pressure-sensitive recording sheet, and extremely excellent when used for a heat-sensitive recording sheet. A recording material characterized by using at least one of pentadiene-based compounds having excellent sensitivity characteristics. Further, the present invention has the effect of expanding the range of use of the recording material.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-45785 (JP, A) Patent 2520701 (JP, B2) Patent 2520704 (JP, B2)

Claims (1)

(57) [Claims] 1. The following general formula [1] (Wherein, R ¹ , R ² , R ³ and R ⁴ each independently represent an alkyl group, an alkoxyalkyl group, a halogenoalkyl group or a phenyl group or a benzyl group which may be substituted with a halogen atom or a lower alkyl group. And R ¹ , R ²
Can also form a ring together with the bonding nitrogen atom, and R ³ and R ⁴ together with the bonding nitrogen atom, and R ⁵ and R ⁶ can be a hydrogen atom, a halogen atom, R ⁷ represents a lower alkyl group, an alkoxy group, an alkoxyalkyl group or an alkoxycarbonyl group, and R ⁷ represents an alkyl group or a halogen atom, a phenyl group optionally substituted with an alkyl group or an alkoxy group, or a naphthyl group. However, when R ¹ , R ² , R ³ , and R ⁴ are all lower alkyl groups, R ⁵ and R ⁶ are not a hydrogen atom or a lower alkyl group at the 2-position. A recording material characterized by using at least one of the novel pentadiene compounds represented by the formula: