JP2605073B2 - Novel leuco dye and recording material using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel leuco dye which forms a color by contacting it with an electron accepting substance such as an inorganic acid, an organic acid, a phenolic compound or a derivative thereof, or an oxidizing agent, and an electron donating compound. The present invention relates to a recording material used as a color former.

(Prior art)

Recording materials using leuco dyes have been known for a long time, and are used as pressure-sensitive recording paper, heat-sensitive recording paper, and the like, and the amount of use thereof is increasing year by year. A leuco-based pressure-sensitive recording material generally utilizes a chemical reaction between a nearly colorless leuco dye and a color former capable of forming a colored image by contacting the leuco dye upon contact. Specifically, a color former sheet coated with a microencapsulated solution of a leuco dye in an organic solvent and a color former sheet coated with a color former together with an adhesive are superimposed on each other, and from the back. Pressing with pen pressure or the like breaks the capsule to cause a color reaction.

On the other hand, the leuco-based heat-sensitive recording material has a leuco dye and a coloring agent supported on a support, and gives a color-developed image when an image signal is given thermally by a minute heating resistor element.

Such pressure-sensitive and heat-sensitive recording paper can be used in a relatively simple apparatus for a short time without performing complicated processing such as development and fixing compared to other recording materials, for example, electrophotography and electrostatic recording material. It is used in various fields because it is possible to obtain records. The main leuco dyes used for such recording materials are crystal violet lactone, blue dyes represented by leuco crystal violet, and 7
And a black coloring dye represented by an anilino-substituted fluoran compound. In recent years, optical character readers and label barcode readers have been developed, and their use ratio has been increasing.
Light wavelength of 70 using light emitting diode or semiconductor laser
Light sources of 0 nm or more are commonly used. However,
Since the blue coloring dye and the black coloring dye hardly absorb light in the near-infrared region of 700 nm or more, the color reading cannot be performed by the above-described reading apparatus. Therefore, at present, there is a strong demand for new development of leuco dyes in which the light absorption wavelength of the color former is 700 nm or more.

Heretofore, several proposals have been made for long wavelength absorption leuco dyes, for example, JP-A-51-121035, JP-A-51-21037, JP-A-51-121038, JP-A-57-1679.
Although disclosed in Japanese Patent Publication No. 79, these dyes have the drawback that synthesis is difficult and the cost is very high.

〔Purpose〕

The present invention was not found in leuco dyes which have been used in conventional heat and pressure sensitive recording materials. It is an object of the present invention to provide a novel leuco dye having a strong absorption band in the near infrared region and a recording material using the same.

〔Constitution〕

According to the present invention, as a first invention, a compound represented by the general formula (I): (Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are lower alkyl groups, X is an alkyl group, Or And R ₉ represents a hydrogen atom, a lower alkyl group, a halogen atom, a hydroxyl group, a trifluoromethyl group, a nitro group, an amino group, a substituted amino group or an amide group, respectively. The present invention provides, as a second invention, a recording material characterized in that the leuco dye represented by the general formula (I) is used as an electron-donating color former.

The leuco dye represented by the general formula (I) of the present invention is a novel substance, a colorless or slightly colored solid that is stable in the air, and is an inorganic acid such as activated clay and acid clay. Organic acids, phenolic compounds and their derivatives,
When it comes into contact with an electron accepting compound such as an oxidizing agent at the molecular level, a color-forming reaction quickly occurs to form a deep blue dye, and this color-developed dye has excellent preservability, so it is useful as a dye precursor. is there. The λmax of the light absorption spectrum of this dye is about 800 to 820 nm in a solution, and the color-developed part on a recording paper is about 500 to 900 nm.

The leuco dye of the present invention represented by the general formula (I) is produced by the following method.

Method A General formula (II) (Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ represent a lower alkyl group.) Tetra- (p-dialkylaminophenonyl) -3 A hydroxy-1,4-pentadiene compound,
General formula (III) (Wherein X is an alkyl group, Or And R ₉ represents a hydrogen atom, a lower alkyl group, a halogen atom, a hydroxyl group, a trifluoromethyl group, a nitro group, an amino group, a substituted amino group or an amide group, respectively. ) Is reacted for several hours at room temperature to 200 ° C in an organic solvent to which a small amount of a catalyst has been added. After cooling, the solvent is removed, and the reaction product is extracted from the residue with a non-polar solvent such as toluene and benzene. After thoroughly washing with warm water, the solvent is further removed. Then the residue is toluene,
By recrystallizing with a solvent such as ethyl acetate or acetone, a high-purity leuco dye represented by the general formula (I) can be obtained.

Method B General formula (IV)(Where R₁, R_Two, R_Three, R_Four, R_Five, R₆, R₇And R₈Is a lower alkyl group
X represents an alkyl group; Represents an anion, respectively.
The anion is derived from an inorganic acid or an organic acid, for example,
I^-, ClO_Four ^-And carboxylate anions. )
Tetra (dialkylaminophenyl) cia represented by
A nin compound and a compound represented by the general formula (V):(Wherein X is an alkyl group,OrAnd R₉Is a hydrogen atom, lower alkyl group, halogen atom
Child, hydroxyl group, trifluoromethyl group, nitro group, amino
Represents a group, a substituted amino group or an amide group, respectively. ) With the sodium salt of the amide compound
The reaction is performed for several hours in the range of 0 ° C to 150 ° C in a medium. Next
The reaction solution is poured into ice water to precipitate a solid, and the precipitated solid is
After washing well with water, dry. Then the solid is toluene,
Recrystallization with a solvent such as ethyl acetate or acetone
To obtain a highly pure leuco dye represented by the general formula (I).
Can be

Next, specific examples of the compound represented by the above general formula (I) of the present invention are shown below: 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-valeramide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-benzamide, 1,1,5,5-tetra- (p-diethylaminophenyl)
-1,4-pentadiene-3-benzamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-methylbenzamide, 1,1,5,5-tetra- (p-diethylaminophenyl)
-1,4-pentadiene-3-p-methylbenzamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-chlorobenzamide, 1,1,5,5-tetra- (p-diethylaminophenyl)
-1,4-pentadiene-3-p-chlorobenzamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-trifluoromethylbezamide, 1,1,5,5-tetra- (p-diethylaminophenyl)
-1,4-pentadiene-3-p-trifluoromethylbezamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-hydroxybenzamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-aminobenzamide, 1,1,5,5-tetra- (p-dimethylaminophenyl)
-1,4-pentadiene-3-p-nitrobenzamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-p-dimethylaminobenzamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-o-methylbenzamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-o-chlorobenzamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-p-amidobenzamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-α-naphthamide, 1,1,5,5-tetra (p-dimethylaminophenyl)-
1,4-pentadiene-3-β-naphthamide, 1,1,5,5-tetra (p-diethylaminophenyl)-
1,4-pentadiene-3-α-naphthamide, 1,1,5,5-tetra (p-diethylaminophenyl)-
1,4-pentadiene-3-β-naphthamide, and the like.

The leuco dye of the present invention, like the conventional leuco dye,
It can be used as a color former in recording materials such as pressure-sensitive recording materials, heat-sensitive recording materials, and thermal transfer recording materials.

In order to obtain a pressure-sensitive recording material using the leuco dye of the present invention, first, microcapsules of leuco dye-dissolved oil are prepared. In this case, the preparation of the microcapsules is, for example,
In a method such as described in U.S. Pat.
% Leuco dye is dissolved in diisopropylnaphthalene-based or terphenyl-based oil. The particle size of the microcapsules is usually around 5 μm. The color capsule sheet is obtained by supporting the microcapsules on a support such as paper or a plastic film using a binder. By overlaying this color former sheet with a color former sheet having an electron-accepting compound layer as a color former, breaking the capsule by applying pressure with a pen pressure or the like, by contacting the leuco dye with the color former, A color image can be obtained on the colorant sheet.

In order to obtain a thermosensitive recording material using the leuco dye of the present invention, an auxiliary component such as a leuco dye, a color former (an electron-accepting compound), a filler such as calcium carbonate, and a heat-fusible substance such as stearamide is used. Each of them is dispersed in an aqueous medium, and a mixture thereof is applied on a support together with a binder and dried. In this case, the particle diameter of the leuco dye is preferably about 0.1 to 5 μm in terms of volume average particle diameter. The smaller the particle size, the more contact with the coloring agent improves the sensitivity. However, if the particle size is extremely small, fogging of the background is caused. Therefore, in order to prevent background fog and a decrease in thermal sensitivity, the volume average particle diameter is particularly preferably about 1 to 4 μm.
This thermosensitive recording material is heated by a thermal head or the like, and the leuco dye and the colorant are brought into melting contact with each other,
A color image can be obtained.

To obtain a thermal transfer recording material using the leuco dye of the present invention, a heat-sensitive transfer sheet is prepared by supporting the leuco dye on a support, and a receptor sheet is prepared by supporting a colorant on the support. . When the transfer sheet and the receiving sheet are overlapped and heated from the surface of the transfer sheet, a color image is obtained on the receiving sheet.

The leuco dye of the present invention is used in various fields as well as conventional ones, and in particular, utilizing its excellent near-infrared light absorption properties, for optical character reading devices, label bar coders, It can be used as a color former in a recording material for reading a record by a bar code reader.

When the leuco dye of the present invention is used for a heat-sensitive recording type label sheet, a thermosensitive coloring layer containing the leuco dye of the present invention and a coloring agent is provided on one surface of the support, and is adhered to the other surface of the support. In this case, a protective layer such as a water-soluble resin layer may be provided on the surface of the thermosensitive coloring layer in order to enhance image stability, if necessary. You can also.

〔effect〕

In the recording material using the novel leuco dye represented by the general formula (I) according to the present invention, the coloring portion absorbs light in the near-infrared region, and the coloring material is colored by an image reading device using a general-purpose semiconductor laser. Can be read. Further, the recording material has a high coloring density and the coloring portion is excellent in heat resistance, light resistance and moisture resistance.
Further, the leuco dye of the present invention is applied to various recording fields. In addition, the leuco dye of the present invention can be produced relatively easily at low cost.

〔Example〕

Next, the present invention will be described in more detail with reference to examples. The percentages and parts shown below are based on weight.

REFERENCE EXAMPLE 1 Synthesis of α, α-bis- (p-dimethylaminophenyl) ethylene 4.2 g of magnesium and 50 ml of diethyl ether (anhydrous) were stirred in a four-necked flask in a nitrogen atmosphere. To this, a mixed solution of 25 g of methyl iodide and 50 ml of diethyl ether (anhydrous) was slowly added dropwise at room temperature over 90 minutes. After the dropwise addition, the mixture was boiled under reflux for 1 hour to prepare a Grignard reagent. While maintaining the four-necked flask containing the Grignard reagent in ice water at 15-20 ° C, the Michler's ketone 23.2
500 ml of a benzene solution in which g was dissolved was slowly added over 90 minutes. After the dropwise addition, the mixture was boiled under reflux for 1 hour and left to stand overnight. 40.6 g of glacial acetic acid and 77.3 g of ammonium chloride
Was slowly added to a cold aqueous solution containing and stirred at room temperature for 2 hours. When left for a while, a benzene layer containing the reactant and an aqueous layer were separated. After separating the benzene layer, the reaction product was further extracted from the aqueous layer with benzene and mixed with the benzene layer.
Calcium chloride (CaCl 2) is added to this benzene solution as a dehydrating agent.
₂ ) 30g was added and left overnight to dehydrate. Next, calcium chloride as a dehydrating agent was removed by filtration, and benzene was distilled off using a rotary evaporator. The residue was obtained as a pale yellow-green solid (13.6 g, crude yield 59.0%).
120.2 ° C. The residue was recrystallized from 200 ml of ethyl alcohol to obtain 9.48 g (yield: 41.1%) of a yellow-green powder. The melting point of this compound was 122.5 to 124 ° C.

Reference Example 2 1,1,5,5-tetra- (p-dimethylaminophenyl)-
Synthesis of 2,4-pentadiene-1-ol perchlorate α, α-bis- (p-dimethylaminophenyl) prepared according to the method of Reference Example 1 in a 300 ml Erlenmeyer flask
26.64 g of ethylene, 20 ml of triethyl orthoformate and 200 ml of acetic anhydride were added and mixed and stirred. Next, 7.18 g of 70% perchloric acid
Was slowly added dropwise, and after the addition, the mixture was refluxed for 1 hour and 30 minutes.
Crystals having a metallic luster were precipitated during boiling reflux, and further crystals were precipitated when cooled. The precipitated crystals were collected by filtration and washed several times with water. 29.34 g (91% yield) of crystals were obtained. The melting point of this product was 237.5-238 ° C.

Reference Example 3 Synthesis of α, α-bis- (p-diethylaminophenyl) ethylene 4.2 g of magnesium and 50 ml of diethyl ether (anhydrous) were stirred in a four-necked flask in a nitrogen atmosphere. To this, a mixed solution of 25 g of methyl iodide and 50 ml of diethyl ether (anhydrous) was slowly added dropwise at room temperature over 90 minutes. After the dropwise addition, the mixture was boiled under reflux for 1 hour to prepare a Grignard reagent. While keeping the four-necked flask containing the Grignard reagent at 15 to 20 ° C. using ice water, 500 ml of a benzene solution in which 28.0 g of 4,4′-bis- (diethylamino) benzophenone was dissolved was slowly added over 90 minutes. After the dropwise addition, the mixture was boiled under reflux for 1 hour and left to stand overnight. The reaction mixture was slowly added to an aqueous ice solution containing 40.6 g of glacial acetic acid and 77.3 g of ammonium chloride, and stirred at room temperature for 2 hours. When left for a while, a benzene layer containing the reactant and an aqueous layer were separated. After separating the benzene layer, the reaction product was further extracted from the aqueous layer with benzene and mixed with the benzene layer. To this benzene solution was added 30 g of anhydrous sodium sulfate (Na ₂ SO ₄ ) as a dehydrating agent, and the mixture was left overnight to perform dehydration. Next, sodium sulfate as a dehydrating agent was removed by filtration, and benzene was further distilled off by a rotary evaporator. The residue is a pale green liquid, 2
5.8 g (crude yield 91.3%) was obtained and crystallized on standing for a while. The residue was recrystallized from 400 ml of ethyl alcohol to obtain 22.1 g (yield: 79.4%) of pale yellow-green plate-like crystals. The melting point of this compound was 103-104 ° C.

Reference Example 4 1,1,5,5-tetra- (p-diethylaminophenyl)-
Synthesis of 2,4-pentadiene-1-ol perchlorate α, α-bis- (p-diethylaminophenyl) prepared according to the method of Reference Example 3 in a 300 ml Erlenmeyer flask
32.25 g of ethylene, 20 ml of triethyl orthoformate and 200 ml of acetic anhydride were added and mixed and stirred. Next, 7.18 g of 70% perchloric acid
Was slowly added dropwise, and after the addition, the mixture was refluxed for 1 hour and 30 minutes.
Next, the reaction solution was poured into 400 ml of ice water and stirred for a while.
Crystals with metallic luster precipitated. The precipitated crystals were collected by filtration and washed several times with water. 26.2 g of crystals (69.4% yield)
Obtained. The product decomposed at 190 ° C.

Example 1 1,1,5,5-Tetra- (p-dimethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-benzamide 3 g of 60% sodium hydride was dispersed in 400 ml of sufficiently dried N, N-dimethylformamide (DMF), and 9.09 g of benzamide was added little by little at room temperature. Then, the mixture was heated to 40 ° C., stirred for 1 hour, cooled to room temperature, and then 32.16 g of 1,1,5,5-tetra- (p-dimethylaminophenyl) -2,4-pentadiene-1-ol perchlorate was added. Add little by little,
The reaction was performed at room temperature for 1 hour. Next, the reaction solution was poured into ice water 1 to precipitate a solid, and the precipitated solid was thoroughly washed with water.
It was dried under reduced pressure. By recrystallizing with acetone after drying, 24.8 g of pale yellow-green crystals were obtained. The melting point of this compound was 190-190.5 ° C.

(Visible absorption spectrum)

λmax (acetic acid) 806 nm, ε: 1.6 × 10 ⁴ 613 nm, ε: 5.0 × 10 ⁴ 501 nm, ε: 3.8 × 10 ⁴ [Infrared absorption spectrum] (KBr tablet method) 3440 cm ⁻¹ ν NH, 2800 cm ⁻¹ ν CH, 1665 cm ^-1 ν C = O, 1605 cm ^-1 ν C = C, 1520 cm ^-1 benzene nucleus, Example 2 1,1,5,5-tetra- (p-dimethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-p-methylbenzamide 3 g of 60% sodium hydride in 400 ml of sufficiently dried DMF
Then, at room temperature, 10.13 g of p-methylbenzamide was added little by little, and the mixture was heated to 40 ° C and stirred for 1 hour. Next, after cooling to room temperature, 32,16 g of 1,1,5,5-tetra- (p-dimethylaminophenyl) -2,4-pentadiene-1-ol perchlorate was added little by little, and the mixture was reacted at room temperature for 1 hour. . Next, post-treatment and purification were performed in the same manner as in Example 1, to obtain 21.4 g of almost white crystals. The melting point of this compound is 139.5-14
0.5 ° C.

(Visible absorption spectrum)

λmax (acetic acid) 806 nm, ε: 2.0 × 10 ⁴ 612 nm, ε: 5.1 × 10 ⁴ 504 nm, ε: 4.2 × 10 ⁴ [Infrared absorption spectrum] (KBr tablet method) 3440 cm ⁻¹ ν NH, 2880 cm ⁻¹ ν CH, 1660 cm ^-1 ν C = O, 1605 cm ^-1 ν C = C, 1520 cm ^-1 benzene nucleus, Example 3 1,1,5,5-tetra- (p-diethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-p-methylbenzamide 3 g of 60% sodium hydride in 400 ml of sufficiently dried DMF
Then, at room temperature, 10.13 g of p-methylbenzamide was added little by little, and the mixture was heated to 40 ° C and stirred for 1 hour. Next, after cooling to room temperature, 37.77 g of 1,1,5,5-tetra- (p-diethylaminophenyl) -2,4-pentadiene-1-ol perchlorate was added little by little, and the mixture was reacted at room temperature for 1 hour. Subsequently, post-treatment and purification were carried out in the same manner as in Example 1 to obtain 19.0 g of a pale yellow green crystal.

(Infrared absorption spectrum)

(KBr tablet ^{method) 3360cm -1 ν NH, 2980cm -1} ν CH, 2890cm -1 ν sCH, 1660cm -1 ν C = O, 1610cm -1 ν C = C, 1520cm -1 benzene nucleus, Example 4 1, 1,5,5-tetra- (p-dimethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-p-nitrobenzamide 3 g of 60% sodium hydride in 400 ml of sufficiently dried DMF
Then, 12.46 g of p-nitrobenzamide was added little by little at room temperature, and the mixture was heated to 40 ° C and stirred for 1 hour. Next, after cooling to room temperature, 32,16 g of 1,1,5,5-tetra- (p-dimethylaminophenyl) -2,4-pentadiene-ol perchlorate was added little by little, and the mixture was reacted at room temperature for 1 hour. Subsequently, post-treatment and purification were carried out in the same manner as in Example 1 to obtain 20.2 g of pale orange crystals. The melting point of this compound is 151.5-156 ° C
Met.

(Visible absorption spectrum)

λmax (acetic acid) 807 nm, ε: 2.3 × 10 ⁴ 618 nm, ε: 4.4 × 10 ⁴ 501 nm, ε: 2.8 × 10 ⁴ [Infrared absorption spectrum] (KBr tablet method) 3420 cm ⁻¹ ν NH, 2800 cm ⁻¹ ν CH, ^{1670cm -1 ν C = O, 1605cm} -1 ν C = C, 1520cm -1 benzene _{^{nucleus, 1345cm -1 ν s NO 2 870cm}} -1 ν CN, example 5 1,1,5,5-tetra - (p -Dimethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-β-naphthamide 3 g of 60% sodium hydride was thoroughly dried in 400 ml of DMF.
Then, at room temperature, 12.84 g of β-naphthamide was added little by little, and the mixture was heated to 40 ° C and stirred for 1 hour. Then, after cooling to room temperature, 1,1,5,5-tetra- (p-dimethylaminophenyl) -2,4-pentadiene-1-ol perchlorate 3
2.16 g was added little by little and reacted at room temperature for 1 hour. Subsequently, post-treatment and purification were carried out in the same manner as in Example 1 to obtain 25.5 g of a pale yellow green crystal. The melting point of this compound is 124-12
6 ° C.

(Visible absorption spectrum)

λmax (acetic acid) 805 nm, ε: 2.9 × 10 ⁴ 612 nm, ε: 5.2 × 10 ⁴ 504 nm, ε: 4.3 × 10 ⁴ [Infrared absorption spectrum] (KBr tablet method) 3410 cm ⁻¹ ν NH, 2790 cm ⁻¹ ν CH, ^{1655cm -1 ν C = O, 1600cm} -1 ν C = C, 1520cm -1 benzene nucleus, 1295cm ^-1 ν CN example 6 1,1,5,5-tetra - (p-dimethylaminophenyl) -
Synthesis of 1,4-pentadiene-3-valeramide 3 g of 60% sodium hydride in 400 ml of sufficiently dried DMF
7.6 g of valeramide is added little by little at room temperature,
The mixture was heated to 40 ° C and stirred for 1 hour. Next, after cooling to room temperature,
1,1,5,5-tetra- (p-dimethylaminophenyl)-
32.16 g of 2,4-pentadiene-1-all perchlorate
Was added little by little, and reacted at room temperature for 1 hour. Then, post-treatment and purification were performed in the same manner as in Example 1 to obtain pale yellow-green crystals 2
6.6 g were obtained. The melting point of this compound was 110.5-115 ° C.

(Visible absorption spectrum)

.lambda.max (acetic) 804nm, ε: 1.4 × 10 4 609nm, ε: 3.0 × 10 4 492nm, ε: 1.9 × 10 4 [Infrared absorption spectrum] ^{3410cm -1 ν NH, 2800cm -1 ν} CH, 1655cm -1 ν C = O, 1610 cm ^-1 ν C = C, 1520 cm ^-1 benzene nucleus, Example 7 1,1,5,5-tetra- (p-dimethylaminophenyl)-
Synthesis of 1,4-pentadiene-3-p-trifluoromethylbenzamide 3 g of 60% sodium hydride was thoroughly dried in 400 ml of DMF.
In p-trifluoromethylbenzamide at room temperature
13.0 g was added little by little, heated to 40 ° C., and stirred for 1 hour. Next, after cooling to room temperature, 32,16 g of 1,1,5,5-tetra- (p-dimethylaminophenyl) -2,4-pentadiene-1-ol perchlorate was added little by little, and the mixture was reacted at room temperature for 1 hour. . Next, post-treatment and purification were carried out in the same manner as in Example 1 to obtain 27.8 g of pale yellow-green crystals. The melting point of this compound was 125.5-131.5 ° C.

(Visible absorption spectrum)

λmax (acetic acid) 804 nm, ε: 7.1 × 10 ⁴ 614 nm, ε: 4.3 × 10 ⁴ 496 nm, ε: 3.1 × 10 ⁴ [Infrared absorption spectrum] (KBr tablet method) 3470 cm ⁻¹ ν NH, 2810 cm ⁻¹ ν CH, ^{1680cm -1 ν C = O, 1610cm} -1 ν C = C, 1520cm -1 benzene ^{nucleus, 1325cm -1 ν sC-F,} 1170cm -1, 1130 -1 ν asC-F, prepared in example 8 heat-sensitive recording paper Each mixture having the following composition was dispersed in a ball mill to prepare solutions [A] to [D].

[A liquid]

Leuco dye of Example 1 10 parts Hydroxyethyl cellulose 10% aqueous solution 10 parts Water 55 parts The dispersed particles of the leuco dye have a volume average particle diameter of 2.18.
μm.

[B liquid]

Stearamide 20 parts 5% aqueous solution of methylcellulose 20 parts Dispersant 2 parts Water 60 parts [liquid C] 30 parts Calcium carbonate 30 parts 5% aqueous solution of methylcellulose 30 parts Dispersant 2 parts water 60 parts [liquid D] Bisphenol A 40 parts polyvinyl alcohol 20% 10% aqueous solution 140 parts water [Solution A], [Solution B], [C
Liquid) and (D liquid) were mixed at a ratio of 1: 1: 1: 3 to prepare a coating liquid, and the coating liquid was dried on a high-quality paper having a basis weight of 50 g / m ^{2 with} a dry adhesion of only 0.45 g / m ² was applied and dried to obtain a thermosensitive recording paper.

The thus obtained heat-sensitive recording paper was colored at 130 ° C. for 1 second (applied pressure: 2.0 kg / cm ² ) using a thermal gradient tester. The color density at this time was 1.01 as measured with a black filter (filter No .: Kodak Ratten No. 25) of a Macbeth densitometer, and the background density was 0.10. The color tone is deep blue, and the absorption area of the colored part is about 500 to 9
It has a very strong absorption up to 00 nm. The reflection spectrum is shown in the drawing (curve 1).

The storage stability test results of the obtained heat-sensitive recording paper are as shown in the following table.

From the table, it can be seen that the recording paper of the present invention has a smaller decrease in color density even after storage than storage rain, and has excellent heat resistance, moisture resistance and light resistance in the color-developed part.

Comparative Example A heat-sensitive recording paper was obtained in the same manner as in Example 7, except that PSD-150 (trade name, manufactured by Shin Nisso Chemical Co., Ltd.) was used as the leuco dye, and was colored. The reflection spectrum of the coloring portion is shown in the drawing (curve 2).

As is clear from the drawing, this color forming part has a light wavelength of about 700n.
Above m, there is almost no light absorption.

Example 9 Production of pressure-sensitive copying paper 10 parts of gelatin and 10 parts of gum arabic were dissolved in 400 parts of water at 40 ° C., 0.2 parts of funnel oil was added as an emulsifier, and the leuco dye of Example 2 was added in 2%. 40 parts of the dissolved diisopropyl naphthalene oil are emulsified and dispersed. The emulsification is stopped when the size of the oil droplets reaches an average of 5 μm, and water is added at 40 ° C. to make the whole 900 parts, and stirring is continued. At this time, make sure that the liquid temperature does not fall below 40 ° C. Next, 10% acetic acid is added to adjust the pH of the solution to 4.0 to 4.2 to cause coacervation. Stirring is further continued and cooled after 20 minutes to gel the coacervate film deposited around the oil droplets. The liquid temperature was adjusted to 20 ° C, 7 parts of 37% formaldehyde was added, and after the temperature reached 10 ° C, a 15% aqueous solution of caustic soda was added.
Adjust the pH to 9. At this time, caustic soda is added slowly and carefully. Subsequently, the mixture is heated to 50 ° C. with stirring for 20 minutes to produce microcapsules of leuco dye-dissolved oil. The obtained microcapsules were coated on the lower surface of the support at 6 g / m ² using water-soluble starch as a binder, and dried to obtain upper paper.

When the upper sheet and a commercially available pressure-sensitive coloring sheet were overlapped and pressed with pen pressure or the like, a clear copy image of deep blue was obtained on the coloring sheet.

[Brief description of the drawings]

The drawing shows the reflectance for each light wavelength of the color image of the thermosensitive recording paper obtained by using the electron donating color former of the present invention and the thermosensitive recording paper obtained by using the commercially available electron donating color former. Curve 1 (solid line): Reflected color image spectrum of thermosensitive recording paper obtained in Example 8 Curve 2 (dotted line): Reflected color image reflectance spectrum of thermosensitive recording paper obtained in Comparative Example

Claims (2)

(57) [Claims] (1) General formula (Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are lower alkyl groups, X is an alkyl group, And R ₉ represents a hydrogen atom, a lower alkyl group, a halogen atom, a hydroxyl group, a trifluoromethyl group, a nitro group, an amino group, a substituted amino group or an amide group, respectively. A novel leuco dye represented by: 2. The general formula (Wherein, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are lower alkyl groups, X is an alkyl group, And R ₉ represents a hydrogen atom, a lower alkyl group, a halogen atom, a hydroxyl group, a trifluoromethyl group, a nitro group, an amino group, a substituted amino group or an amide group, respectively. A recording material comprising a leuco dye represented by the formula (1) as an electron-donating color former.