JPH0443572B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to optical recording media.

(Prior Art) Optical recording systems are a field of active development because they allow inexpensive, large-capacity recording media to be obtained. Conventionally, in this field, an inorganic metal thin film is used as a recording film, and the near-infrared output of a semiconductor laser is converted into heat, and the heat is used to make a hole in the recording film or to cause a phase change to change the surface. A so-called heat mode optical recording method that reads changes in reflectance has been put into practical use. Furthermore, in recent years, a new heat mode optical recording method using an organic dye as a recording film has been proposed. However, optical recording methods using heat mode have a limit in sensitivity because heat is dissipated through the substrate etc. when converting the output of a semiconductor laser into heat, and methods based on drilling holes have limitations on the sensitivity. Difficult to erase. From these points of view, as a method to prevent the absorbed light from dissipating as heat and preventing deformation of the recording film, it is possible to use the absorbed light as it is as photon energy and use the subsequent photoreactions to record and reproduce information. A photon mode optical recording method has been proposed and is being actively researched as a means to obtain reversible optical recording materials that can erase information. For these purposes, proposals have been made to use photochromic materials as recording film materials; for example, spiropyran derivatives having a linear alkyl group are disclosed in JP-A-57-59956, and JP-A-60-123,838 discloses spiropyran derivatives having a linear alkyl group. A proposal has been made to use a chemical vapor deposited film of a similar spiropyran compound as the recording layer. For the same purpose, Heller (A.
Heller et al., Journal of Chemical Society Perkin I, p. 202 (1981), describe the properties of a photochromic compound called fulgide and its application to optical recording materials. Various methods for optical recording of these compounds have been proposed, but in general, photochromic compounds such as spiropyrans and fulgide compounds are initialized by irradiating the entire surface with ultraviolet light to strongly color the photochromic compounds, and then photochromic recording is performed. Information is recorded and read out by irradiating visible light that matches the color change area of the compound. These are generally carried out in the ultraviolet to visible light range, but recently there have been publications on spiropyrans that match the oscillation wavelength range of semiconductor lasers (for example, in Proceedings of the 50th Spring Annual Meeting of the Chemical Society of Japan, I, p. 259 (1985)). ing.

(Problems to be Solved by the Invention) However, one of the problems when using conventional photochromic compounds as optical recording materials is that these photochromic compounds destroy information when read. The initial state and colored state of a photochromic compound have a common or crossed excited state with a high probability, and information can be recorded by irradiating the absorption of the colored species with light, and information can later be read out using light. This is due to the fact that the excitation state is the same as that of the readout, and readout destruction is unavoidable. A method to avoid this problem is usually to weaken the light intensity of the readout light, but since optical excitation itself is the only reaction process, it is impossible to differentiate based on the threshold value, and there is always a certain probability that Read corruption can occur, creating problems when repeatedly reading information.

(Means for solving the problems) The present invention was made in view of the above problems, and unlike conventional photochromic materials,
An object of the present invention is to provide an optical recording medium on which information can be recorded and reproduced without causing reading damage.

The present invention provides an optical recording medium containing a photosensitizer, an electron-donating substance, and an electron-accepting substance, and at least one of the electron-donating substance and the electron-accepting substance is a substance capable of taking a mixed valence state. Regarding the medium.

In the optical recording medium of the present invention, a photosensitizer is used as a molecule that performs recording by writing light, an electron-donating substance and/or an electron-accepting substance that is used as a reading molecule, and the photo-excitation of the photosensitizer by these substances. This is a different molecule from the reaction product in which electrons are transferred from an electron-donating substance to an electron-accepting substance through interaction with the state, and the excited states of the two can be distinguished, and the read light can be completely distinguished from the write light. Therefore, read corruption can be avoided in principle. This is illustrated in FIG. 1. In Figure 1, the photosensitizer S is an excited type photosensitizer S ^* by the writing light.
becomes.

S ^* is active and transfers electrons to electron-accepting substance A to form oxidized S ⁺

Claims (1)

[Scope of Claims] 1. Contains a photosensitizer, an electron-donating substance, and an electron-accepting substance, and at least one of the electron-donating substance and the electron-accepting substance is represented by the following general formula (), A transition metal complex selected from the compounds represented by () or (), and the first
has a redox potential of −0.5 V to +0.8 V (vs. saturated calomel electrode), and the redox potential of the photosensitizer at its base energy level is lower than the redox potential of the electron donating substance. , an optical recording medium whose redox potential at its excitation energy level is higher than the redox potential of the electron-accepting substance. In formulas () and (), Z is an atom or atomic group selected from O, S and NR (R is hydrogen or an alkyl group), and may be different at each position, and X and X' are hydrogen, alkyl group, substituted alkyl group, halogen, alkoxy group, alkylamino group, nitro group or cyano group,
and X′ may be the same, n is an integer from 1 to 4, m
is an integer from +2 to -2, A is an anion, cation, or a group thereof having the number of charges required to neutralize the charge specified by m, and M is a transition metal ion (provided that when m is 0, A does not exist in that case). In formula (), Z' is selected from S and NR (R is hydrogen or an alkyl group) and may be different at each position, and Y is hydrogen, an alkyl group, a substituted alkyl group, a phenyl group, a substituted phenyl group, and selected from cyano groups, which may be different at each position, where m is an integer from +2 to -2, and A is an anion, cation, or The group and M represent transition metal ions (provided that when m is 0, A
does not exist). 2. The optical recording medium according to claim 1, wherein the electron-donating substance and the electron-accepting substance are substantially separated. 3. Claims No. 3 in which the optical recording medium has an electron-donating substance or a layer containing the same, a photosensitizer or a layer containing the same, and an electron-accepting substance or a layer containing the same, laminated in this order. The optical recording medium according to item 1 or 2. 4. The optical recording medium according to claim 1, 2 or 3, wherein the optical recording medium has a reflective layer.