JPH0513190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel indolenine compound that exhibits strong absorption in the near-infrared region and uses thereof. More specifically, the present invention relates to a novel indolenine compound that is easily soluble in water and methanol and has a robust near-infrared absorption ability, and a recording medium for laser writing and reading containing the same.

BACKGROUND OF THE INVENTION In recent years, dyes that absorb in the near-infrared region have attracted attention. This is because desirable effects can be expected as optical recording materials using laser beams, as well as in printing, photography, and filter materials.
The properties that a material should have will differ depending on the individual application, but if it is given special properties (for example, it easily dissolves in water), its range of applications can be expanded to include the above-mentioned uses. .

US patent as a compound to be compared and contrasted with the present invention
2895955 Although this compound has the advantage of being easily soluble in organic solvents such as water and methanol, it has poor fastness (especially stability against sunlight and heat).
The disadvantage is that it is insufficient.

Problems to be Solved by the Invention The invention is soluble in water and organic solvents (particularly water-miscible organic solvents such as methanol and ethanol) and is stable against sunlight, heat, etc., which is effective in expanding its uses. There is a need for dyes (infrared absorbers) that have the ability to absorb light in the near-infrared region.

Means for Solving the Problems The present inventors have conducted intensive research to find a near-infrared absorber that is easily soluble in water or organic solvents such as methanol and is robust against sunlight and heat, and as a result, the present invention has been developed. This is what led to this. That is, the present invention is based on the formula [In formula (1), Y represents hydrogen or chlorine, M represents hydrogen or an alkali metal, and n represents an integer of 1 to 4, respectively.] An indolenine compound represented by the following and an optical recording characterized by containing the same: Provide the medium.

The indolenine compound represented by formula (1) can be produced by various methods, but it is convenient to produce it by the following method.

That is, equation (2) (In formula (2), Y and n represent the same meanings as above) and 2 moles of the compound represented by formula (3) Under condensation conditions, 1 mole of the compound represented by is treated in the presence of a fatty acid salt catalyst such as potassium acetate in a dehydrating organic acid such as acetic anhydride at 60 to 120°C for 10 to 60 minutes. The compound (free acid) of formula (1) is obtained by condensation. Among the compounds of formula (1), M is an alkali metal, by dissolving a compound of the same formula in which M is a hydrogen atom in a solvent such as methanol, and adding an alkali metal salt such as alkali perchlorate. , obtained by collecting the precipitated crystals.

Since the indolenine compound of the present invention absorbs near-infrared light around 800 nm, it exhibits excellent effects in the field related to semiconductor lasers. When the compound of the present invention is applied to an optical recording medium using a laser beam, a thin film (usually 1 μm or less thick) of the recording medium formed on a support is irradiated with focused laser light to create holes in the thin film. A record is formed by forming the thin film, and the recorded information is reproduced by continuously irradiating laser light and detecting the reflected light from the thin film. In detection using reflected light, the reflectance from the part where the hole is formed (pit) is generally lower than the reflectance from the surrounding part where the hole is not formed, so this change in reflectance can be used to It performs regeneration. The various characteristics required of an optical recording medium based on such basic principles include the following.

The first characteristic is that a thin film must be easily formed on the support (substrate). Methods for forming a thin film on a substrate include a coating method, a sputtering method, and a vacuum deposition method. The vacuum deposition method requires expensive equipment. The coating method involves dissolving the recording medium (infrared absorbing agent) in a solvent and applying it thinly by spin coating or the like. In this case, the solvent for dissolving the recording medium must not have any adverse effect on the substrate. In the above, a glass plate or a transparent plastic plate is generally used as the substrate, but since glass has a higher thermal conductivity than plastic, there are problems when writing. As mentioned above, when plastic is used, a solvent that dissolves the plastic used cannot be used as a solvent for the recording medium. Water or an organic solvent such as methanol or ethanol that dissolves the indolenine compound (recording medium) of the present invention is very advantageous because it does not have any effect on the plastic used as the substrate.

As a second characteristic, the recording medium must have high recording sensitivity. That is, holes (pits) need to be formed efficiently with low laser light sensitivity and with short-time irradiation. Although the mechanism of pore formation has not been fully elucidated theoretically, it is thought to be due to the combined effects of evaporation, decomposition, melting, etc. due to an increase in the temperature of the irradiated area. In order to have high sensitivity, it is first necessary for the recording medium to absorb laser light and cause a strong temperature rise. As the laser light source used, it is convenient to use a semiconductor laser because the device is small and does not require large amounts of power.
Since the oscillation wavelength of a semiconductor laser is usually around 800 nm, the indolenine compound of the present invention, which exhibits strong absorption in this wavelength range and has a large extinction coefficient, is advantageous.

As a third characteristic, stability against light in the non-irradiated area before and after writing is required, and since the indolenine compound of the present invention has excellent light resistance, the indolenine compound of the present invention is also suitable in this respect. It is convenient as a recording medium.

The optical recording medium containing the indolenine compound of the present invention is generally produced as follows.

Dissolving the indolenine compound of formula (1) in a solvent,
Coat on the substrate and dry. If necessary, a resin binder or a singlet oxygen quencher such as acetylacetone can also be added thereto. Examples of the solvent to be used include dichloroethane, methanol, water, etc., but methanol is preferably used in consideration of the solvent's dissolving power, formation of a uniform film, and influence on the substrate.

As for the coating method, the compound of formula (1) is dissolved in a solvent, and if necessary, an appropriate amount of a singlet oxygen quencher and/or binder is mixed and dissolved, and the mixture is coated using a spinner to a thickness of 20 to 100 nm. When using a singlet oxygen quencher, the addition ratio is in the range of 0.05 to 5.0, particularly 0.2 to 1.5, relative to 1 of the compound of formula (1). When using a binder, the addition ratio is as follows:
It is in the range of 0.1 to 3.0 for Compound 1 in (1).

The material of the substrate forming the recording layer is not particularly limited, and may be any of various resins, glass, ceramics, metals, etc., but there are certain considerations such as molding of the substrate, difficulty in handling, storage stability, and prevention of dye migration to the substrate. For these reasons, acrylic resin plates or polycarbonate resin plates are preferable.

Further, as a light source for writing and reading records using the indolenine compound of the present invention, it is convenient to use a near-infrared laser, for example, a semiconductor laser beam of 830 nm.

In addition to optical recording media, the following applications utilize the characteristics of the indolenine compound of the present invention: good solubility in water and methanol, large extinction coefficient, and high light resistance.

The indolenine compound of the present invention can be added to a water-soluble ink for an inkjet printer to improve the reading efficiency of near-infrared light when printed on a bar coder. In addition, by selectively absorbing specific near-infrared rays, it can be used to verify and prevent tampering with banknotes, securities, bankbooks, certificate cards, and the like. Furthermore, when used in optical filters, water-soluble polymers (casein, gelatin, polyvinyl alcohol, etc.) coated on a glass substrate can be uniformly dyed using water or methanol, making it possible to create uniform near-infrared absorbing filters. There are advantages. In recent years, many silver halide photosensitive materials that are sensitive to near-infrared light with a wavelength of 700 nm or more have been developed. This is a silver halide photosensitive material that has infrared sensitivity so that it can be exposed using a diode or semiconductor laser that emits light in the infrared region, but the indolenine compound of the present invention
When added to the above-mentioned silver halide photosensitive materials, it has excellent sensitizing effects and antihalation effects. in this case,
Gelatin, casein, etc. are used as supports for silver halide photosensitizers, and since the indolenine compound of the present invention is water-soluble, it has good compatibility with gelatin and casein, and can be used at the stage of aqueous development. It has the advantage that it easily falls off and does not adversely affect the finished developed product.

In addition, studies are underway on polyvinyl alcohol-based polarizing films that absorb in the near-infrared region by utilizing the molecular structure with good linearity, but this indolenine-based compound has a high affinity for polyvinyl alcohol and has high fastness. Therefore, it is effective in this field as well.

Example The present invention will be explained in more detail with reference to Examples.

Example 1 Add 5.9 g of CH ₃ COOK to 120 ml of acetic anhydride at 90°C.
After heating for 15 minutes, the mixture was cooled to room temperature, and the precipitated crystals were collected, washed with acetic anhydride, then acetone, and dried to obtain 16.8 g of the following compound.

Example 2 Indolenine compound obtained in Example 1 7.0
Dissolve g in 70 ml of methanol and add to this solution.
After adding 10.5 g of NaCl0 ₄ and refluxing for about 10 minutes, the mixture was stirred at room temperature overnight, and the resulting precipitate was taken out and dried.
Suspend the dry powder in 180ml of acetone and add 20~
After refluxing for 30 minutes, it was heated. By repeating this operation three times, 6.7 g of the following highly pure compound containing no NaClO ₄ was obtained.

Methanol Water λmax (nm) 782 774 ε 230000 170000 Example 3 In Example 1 of Other than that, the process was almost the same as in Example 1.
19.1 g of the following compound was obtained.

Example 4 Indolenine compound obtained in Example 3 7.0
Example 2
6.7g of the following compound was obtained by treating in substantially the same manner as above.

Methanol Water λmax 792 783 ε 233000 172000 Example 5 Indolenine compound obtained in Example 2 1.5
g, polyamide 1.0 g, and nickel acetylacetonate 0.3 g dissolved in 100 ml of methanol, applied to an acrylic substrate with a spinner and dried to a thickness of 60 nm.
An optical recording medium having an optical recording layer was obtained. This recording medium uses a semiconductor laser with a wavelength of 830 nm, a beam diameter of 1 μm, a linear velocity of 1.2 m/sec, and a writing power of 5 m.
Signals were recorded at W, 0.7MHz.

When the surface of the recorded optical recording medium was observed using a scanning electron microscope, clear pits were observed. In addition, this optical recording medium has a low output of 830nm.
When a semiconductor laser was applied to the sample and the reflected light was detected, a waveform with a high S/N ratio was obtained.

Examples 6 to 12 Indolenine compounds shown in the following table were obtained according to Examples 1 to 4. λmax is the value in methanol. An optical recording medium was prepared according to Example 5 using the obtained indolenine compound. Signals were easily recorded on the optical recording medium using a semiconductor laser, and the signals could also be easily read using the semiconductor laser.

Example Y n M λmax (nm) 6 H 2 Na 780 7 H 4 Na 784 8 Cl 2 Na 789 9 Cl 4 Na 794 10 H 3 Li 782 11 Cl 3 K 792 12 H 1 K 776 In the above table, Y, n and M are based on the following formula (1).

Effects of the Invention An indolenine compound which is soluble in water and organic solvents such as methanol and ethanol and is robust against sunlight and heat was obtained. Since this material exhibits absorption close to the near-infrared region, it is effective as an infrared absorbing agent, and has particularly shown excellent effects as a recording medium for optical recording media that use laser light for writing and reading.

Claims (1)

[Claims] 1 formula (In the formula, Y represents hydrogen or a chlorine atom, M represents hydrogen or an alkali metal, and n represents an integer of 1 to 4). 2 formulas (In the formula, Y represents hydrogen or a chlorine atom, M represents hydrogen or an alkali metal, and n represents an integer of 1 to 4.) An optical recording medium characterized by containing an indolenine compound represented by the following formula.