JPH086045B2 - Novel leuco dye and recording material using the same - Google Patents

Description

The present invention relates to a novel leuco dye that develops color when brought into contact with an electron-accepting substance such as an inorganic acid or an organic acid, a phenolic compound or a derivative thereof, or an oxidizing agent, and an electron-donor thereof. 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 papers, heat-sensitive recording papers, etc., and the usage thereof is increasing year by year. The leuco pressure-sensitive recording material generally utilizes a chemical reaction between a substantially colorless leuco dye and a color developing agent capable of forming a colored image when contacting the leuco dye. Specifically, a coloring agent sheet coated with a microencapsulated solution of a leuco dye in an organic solvent, and a coloring agent sheet coated with a coloring agent together with a binder are laminated on their surfaces, More pressure is applied with a writing pressure to break the capsules and carry out a color reaction.

On the other hand, the leuco thermal recording material is a support in which a leuco dye and a coloring agent are supported on a support, and gives a colored image when an image signal is thermally applied by a minute heat generation low antibody element.

Compared to other recording materials such as electrophotography and electrostatic recording materials, such pressure-sensitive and heat-sensitive recording paper does not require complicated processing such as development and fixing, and can be performed with a relatively simple device for a short time. It is used in various fields because it can obtain records. As a leuco dye of such a recording material, a blue dye typified by crystal violet lactone, leuco crystal violet, a black dye typified by a fluoran compound substituted by 7-anilino, and the like are mainly used. In recent years, optical character readers and label bar code readers have been developed and their usage rate is increasing. In these devices, the light wavelength using a light emitting diode or a semiconductor laser is 700 nm as a light source. The above light sources are generally used. However, the above blue dye and black dye hardly absorb light in the near-infrared region of 700 nm or more, so that the color reading cannot be performed by the reading device. Therefore, under the present circumstances, there is a strong demand for new development of a leuco dye having a light-absorbing wavelength of 700 nm or more in a color former.

Heretofore, some proposals have been made for leuco dyes having long-wavelength absorption, for example, JP-A-51-121035, JP-A-51-121037, JP-A-51-121038, and JP-A-57-1679.
As disclosed in Japanese Patent No. 79, these dyes have the drawbacks that they are difficult to synthesize and the cost is very high.

〔Purpose〕

The present invention provides a novel leuco dye having a strong absorption band in the near infrared region, which has not been found in leuco dyes used in conventional heat-sensitive and pressure-sensitive recording materials, and a recording material using the same. With the goal.

〔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 represent a lower alkyl group), and a leuco dye represented by the above is provided as the second invention. There is provided a recording material comprising a leuco dye represented by the general formula (I) as an electron-donating color former.

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

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

 General formula (II)(Where R₁, R₂, R₃, R_Four, R_Five, R₆, R₇And R₈Is a lower alkyl group
A Represent anions respectively. Anion is inorganic
Derived from acids or organic acids, such as T^-, ClO_Four ^-, Carbo
Examples thereof include acid anions. ) Tetra (dialkylaminophenyl) dia represented by
Boil a nin compound and caustic in an organic solvent for several hours
Crystals precipitate upon reflux. Crystals precipitated after cooling are filtered
The collected crystals were washed with water several times and then
Ton or by cleaning with an organic solvent such as alcohol
The leuco dye represented by the general formula (I) having a higher purity is
can get.

Specific examples of the compound represented by the general formula (I) of the present invention include 1,1,5,5-tetra- (P-dimethylaminophenyl).
-3-Hydroxy-1,4-pentadiene, 1,1,5,5-tetra- (P-diethylaminophenyl)
-3-Hydroxy-1,4-pentadiene, 1,1-di- (P-dimethylaminophenyl) -5,5-di- (P-diethylaminophenyl) -3-hydroxy-
1,4-pentadiene, 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 koiro dye of the present invention, first, microcapsules of a koiro dye-dissolved oil are prepared. In this case, the preparation of microcapsules can be performed, for example, by
In the method as described in U.S. Pat. No. 2,800,457, 1 to 4 are contained in the shell wall in which a resin such as gelatin is hardened.
% Of the leuco dye is dissolved in diisopropylnaphthalene oil or terphenyl oil. The particle size of the microcapsules is usually around 5 μm. The microcapsules are supported on a support such as paper or plastic film using a binder to obtain a color former sheet. By stacking this color developing agent sheet with a color developing agent sheet having an electron-accepting compound layer as a color developing agent, the capsules are broken by applying pressure such as an equal pressure to bring the coil dye and the color developing agent into contact with each other. Then, a colored image can be obtained on the color developing agent sheet.

To obtain a heat-sensitive recording material using the leuco dye of the present invention, a leuco dye, a colorant (electron-accepting compound), a filler such as calcium carbonate, and an auxiliary component such as a heat-fusible substance such as stearic acid amide are used. Each is dispersed in an aqueous medium, and a mixed solution thereof is coated 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. A smaller particle size brings more contact with the coloring agent, which leads to an improvement in sensitivity, but extremely fine particles cause fog on the background. Therefore, in order to prevent the background fog and the decrease in heat sensitivity, it is particularly preferable that the volume average particle diameter is about 2 to 4 μm.
This heat-sensitive recording material is heated by a thermal head or the like to melt-contact the leuco dye and the coloring agent,
A colored 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 superposed 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 like the conventional ones, but particularly, by utilizing its excellent near-infrared light absorption property, for a device for reading an optical character, a label bar coder, It can be used as a color-developing agent in a recording material for reading a record by a barcode reader.

When the leuco dye of the present invention is used in a thermosensitive recording label sheet, a thermosensitive coloring layer containing the leuco dye of the present invention and a coloring agent is provided on one side of the support, and the other side of the support is contacted. It may have a structure in which a release mount is provided via an agent layer, and in this case, a protective layer such as a water-soluble resin layer is provided on the surface of the thermosensitive coloring layer in order to enhance image stability, if necessary. You can also

〔effect〕

The recording material using the novel leuco dye represented by the general formula (I) according to the present invention has a coloring portion that absorbs light in the near-infrared region and is colored by an image reading device using a general-purpose semiconductor laser. Has the advantage that it can be read. Further, the recording material has a low color development start temperature and a high color density, and the color development portion thereof is excellent in 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. All% and parts shown below are based on weight.

Reference Example 1 Synthesis of α, α-bis- (P-dimethylaminophenyl) ethylene In a four-necked flask having a nitrogen atmosphere, 4.2 g of magnesium and 50 ml of diethyl ether (anhydrous) were added and stirred. 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. 23.2 g of Michler's ketone while keeping a four-necked flask containing Grignard reagent at 15 to 20 ° C with ice water.
500 ml of a benzene solution in which was dissolved was slowly added over 90 minutes. After dropping, the mixture was boiled under reflux for 1 hour and left to stand overnight. This reaction mixture was mixed with glacial acetic acid 40.6 g and ammonium chloride 77.3 g.
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 ) 30 g was added and left overnight for dehydration. 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%) with a melting point of 118.3.
It was ~ 120.2 ° C. 200 ml of this residue is ethyl alcohol
Recrystallization was performed to obtain 9.48 g (yield 41.1%) of yellowish green powder.
The melting point of this compound was 122.5-124 ° C.

Reference Example 2 1,1,5,5-Tetra- (P-dimethylaminophenyl)
Synthesis of -2,4-pentadiene-1-ol perchlorate α, α-bis- (4-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 with a metallic luster were deposited during boiling and reflux, and further crystals were deposited upon cooling. The precipitated crystals were collected by filtration and washed with water several times. 29.34 g (91% yield) of crystals were obtained.
The melting point of this product was 237.5-238 ° C.

Example 1 1,1,5,5-Tetra- (P-dimethylaminophenyl)
Synthesis of 3-hydroxy-1,4-pentadiene 1,1,5,5-tetra- (P-dimethylaminophenyl) -2,4-pentadiene-1-ol prepared according to the method of Reference Example 2 Perchlorate 7.7 g methanol 100 ml
And then add 1.52 g of sodium hydroxide and boil under reflux for 2 hours. Crystals precipitated by cooling after boiling under reflux were collected by filtration, washed with water several times and then washed with acetone to give almost white crystals 6.3 g (melting point 147.5-148.5).
° C).

[Visible absorption spectrum]

λmax (acetic acid) 809 nm: ε1.4 × 10 ⁵ 640 nm: ε4.6 × 10 ⁴ [infrared absorption spectrum] (KBr tablet method) 3450 cm ^-1 νO-H, 2890 cm ^-1 νsCH ₃ , 1610 cm ^-1 νC = C, 1
520 cm ^-1 benzene nucleus, 1065cm ^-1 νC-0 Example 2 1,1,5,5-tetra - (P- diethylaminophenyl)
Synthesis of 3-hydroxy-1,4-pentadiene 1,1,5,5-tetra- (P-diethylaminophenyl)
-2,4-Pentadiene-1-all perchlorate 7.6g
Is dissolved in 100 ml of methanol and then sodium hydroxide
Add 2.1 g and boil to reflux for 2 hours. After boiling and refluxing, cooling and precipitating crystals were collected by filtration, washed several times with water and then with acetone to obtain 5.9 g of pale yellow-green crystals (melting point).
139.5-141.5 ° C).

[Visible absorption spectrum]

.lambda.max (acetic ^{acid) 814nm: ε1.4 × 10 5 662nm} : ε5.8 × 10 4 [Infrared absorption spectrum] (KBr tablet ^{method) 3450cm -1 νO-H, 3040cm} -1 νCH, 2960cm -1 νasCH 3, 292
5cm ^-1 νasCH ₂ , 2890cm ^-1 νsCH ₃ , 2850cm ^-1 νsCH ₂ , 1610cm
^-1 νC = C, 1520 cm ^-1 Benzene Nucleus, 1070 cm ^-1 νC-0 Example 3 Production of Thermal Recording Paper Each mixture having the following composition was dispersed in a hole mill to prepare liquids [A] to [D]. .

[Liquid A]

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 size of 2.86.
μm.

[Liquid B]

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] at a ratio of 1: 1: 13 to prepare a coating liquid, and this coating liquid has a dry adhesion amount of 0.45 g / dye only on a fine paper of 50 g / m ² basis weight. A thermal recording paper was obtained by applying the coating solution to m ² and drying.

The thermal recording paper thus obtained was subjected to color development at 130 ° C. for 1 second (applied pressure 2.0 sg / cm ² ) using a thermal tilt tester.
The color density at this time was 1.42 as measured by a Macbeth densitometer black filter (Filter No: Kodak Ratten No25), and the background density was 0.13. The color tone is deep blue, and the color region has an absorption region of about 500 to 900 nm, and has a very strong absorption. 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 after storage than before storage, and has excellent heat resistance, moisture resistance and light resistance in the color-developed portion.

Comparative Example A thermosensitive recording paper was obtained in the same manner as in Example 3 except that PSD-150 (trade name, manufactured by Shinjuku Soka Kogyo Co., Ltd.) was used as the leuco dye, and the color was developed. The reflection spectrum of the colored 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.
Almost no light absorption is shown above m.

Example 4 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 2% of the leuco dye of Example 2 was further added. 40 parts of dissolved diisopropyl naphthalene oil is emulsified and dispersed. The emulsification is stopped when the average size of the oil droplets reaches 5 μm, and water is added at 40 ° C. to make the whole 900 parts, and stirring is continued. At this time, keep the liquid temperature 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. Further, the stirring is continued, and after 20 minutes, cooling is performed to gelate the coacervate film deposited around the oil droplets. The liquid temperature is adjusted to 20 ° C., 7 parts of 37% formaldehyde is added, and after reaching 10 ° C., a 15% aqueous sodium hydroxide solution is added to adjust the pH to 9. At this time, caustic soda is added slowly and carefully. Then, stir for 20 minutes and heat to 50 ℃
When set to, microcapsules of a leuco dye-dissolved oil are prepared. The obtained microcapsules were coated with 6 g / m ² on the lower surface of the support using water-soluble starch as a binder and dried to obtain an 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 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): color image reflection spectrum of the thermosensitive recording paper obtained in Example 3 Curve 2 (dotted line): color image reflection spectrum of the thermosensitive recording paper obtained in Comparative Example

Claims (2)

[Claims] 1. A general formula (Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ represent a lower alkyl group). 2. General formula (Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ represent a lower alkyl group), and a leuco dye represented by the formula was used as an electron-donating color former. Recording material characterized by.