JPS62221593A - Method of writing information into optical information recorder - Google Patents

Abstract

PURPOSE:To provide an information writing method enabling high speed recording with high recording sensibility and excellent storing performance of recorded condition by utilizing a charge moving phenomena between donor molecules and acceptor molecules in an organic film for composing an information recording medium. CONSTITUTION:An information recording medium comprises organic thin films 4, 6 respectively containing donor molecules or organic molecules having high ionization potential which provide electrons to other molecules and easily brought into positively ionized condition and acceptor molecules or organic molecules having high electronic affinity which receive electrons from other molecules and easily brought into negatively ionized condition and an electrode 8 for applying voltage onto said films 4, 6. In order to stably maintain the condition where donor molecules and acceptor molecules are ionized through movement of charges, an electronically inert insulative molecule film 7 is preferably placed between the donor molecule film and the acceptor molecule film. When optical excitation is performed selectively with voltage being applied onto said recording medium, writing can be performed efficiently.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an optical information recording device using an organic thin film, and particularly relates to an electron donor (donor-like molecule) and an electron acceptor. The present invention relates to an information writing method for an information recording device that utilizes a charge transfer phenomenon between (acceptor molecules).

(Conventional technology) With the rapid development and spread of computer technology, it has become increasingly important in recent years to store large amounts of information in a high-density and efficient manner and to process it quickly and efficiently. . Under these circumstances, the development of various information recording devices is progressing rapidly.

Among these, information recording devices using optical disks are attracting attention from the viewpoint of performance and cost, and their development is active. For example, research on various optical recording media such as inorganic chalcogenide-based and organic dye-based optical recording media has increased significantly in recent years. On the other hand, in addition to these recording methods, so-called photochemical hole-burning recording, which performs multiple recording using the minute vibrational electronic states of organic molecules, has begun to be actively researched in order to perform even higher-density recording.

However, the conventional optical information recording method has many drawbacks. First, most conventional optical information recording media, whether inorganic or organic, use what is called a heat-thread recording medium. For example, information is recorded by utilizing the melting and evaporation of a recording medium by absorbing light energy such as Rede light. Information is read out by reading the difference in optical reflection or absorption/reflection of the recording site. In such a system, it is necessary to make the optical energy density as high as that of a monk in order to record information. For example, in order to obtain a signal at a predetermined detection level using an inorganic chalcogenide recording medium such as To, the energy density of the recording light source must be at least 3 to 10
Requires 0 mJ/-. For this reason, the recording speed cannot be increased sufficiently. In addition, unlike the heat shade method, optical recording methods using photochromic phenomena that utilize structural changes in organic molecules have the disadvantage that the characteristics of the recording site change over time due to significant deterioration of the molecular structure. be. Furthermore, new recording methods using photochemical hole burning utilize tautomerism due to proton movement in molecules such as porphyrins and phthalocyanines, resulting in low conversion efficiency and speed, and can reduce noise levels only at extremely low temperatures. Contrary to expectations for the potential of ultra-high-density recording, it is difficult to realize it for several reasons.

However, in recent years, advances in material technology using organic molecules have led to expectations for the realization of new functional elements. In particular, advances in oriented layering technology for organic molecules, such as the Langmuir-Project method (LB method), have made it possible to form ultra-thin films of organic molecules, and this has led to the development of new functional devices. The outlook has opened up. In fact, Robert of Durham University, UK
ts) et al. have reported an electronic device called an MIS type light emitting device IS-FET using an organic thin film formed by the LB method as an insulating film. Organic thin films produced by this LB method are considered promising as optical information recording media due to their photoresponsive properties, but they have not yet been put to practical use.

(Problems to be resolved by the invention) As described above, various optical information recording devices or methods that have been proposed in the past have a high density of ultra-high density in terms of writing speed, preservation of recorded state, and other characteristics. The characteristics of optical recording are not fully utilized.

The present invention has been made in view of the above points, and provides an information writing method that uses an organic thin film as an optical information recording medium, enables high-speed recording, has high recording sensitivity, and has excellent recording state preservation characteristics. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) The information recording medium of the present invention consists of a donor molecule, that is, an organic molecule that has a high ionization potential and easily becomes a positive ion state by supplying electrons to other molecules, and an acceptor. In this method, an electrode for applying a voltage is formed using an organic thin film containing organic molecules that have a large electron affinity, accept electrons from others, and easily change into a negative ionic state.

The principle of information recording utilizes the change in the optical or electrical properties of the film due to the charge transfer phenomenon between donor molecules and acceptor molecules within the organic thin film. When recording information using such an information recording medium, the present invention selectively photoexcites donor molecules while applying a voltage to the organic thin film, and the generated electron-hole pairs are exposed to an external voltage. It is characterized by K so that it can be more effectively separated and transferred to acceptor molecules.

The organic thin film used as the recording medium is preferably formed by the LB method, and in particular, a superlattice structure in which a layered structure of a donor molecular film and an acceptor molecular film is repeatedly laminated is used. is preferred. At this time, each donor molecular film and acceptor molecular film have 5 to 5
ool, preferably controlled within the range of 5 to 100X. In addition, in order to stably maintain the recording state, that is, the state in which donor molecules and acceptor molecules are ionized by charge transfer, an electronically inactive insulating molecular film is placed between the donor and acceptor molecular films. It is preferable to intervene. The inert insulating organic molecular film is, for example, a film of organic molecules in which the density of delocalized π electrons or unpaired n electrons is low.

However, in principle, the recording medium can be configured as a mixed organic thin film containing both donor molecules and acceptor molecules.

(Function) According to the method of the present invention, electronic transition between donor molecules and acceptor molecules in an organic thin film constituting a recording medium is selectively photoexcited while applying a voltage, thereby extremely efficiently and rapidly. It can be carried out. That is, high-speed writing is possible and high recording sensitivity can be obtained. Furthermore, by selecting the material and structure of the organic thin film constituting the recording medium, it is possible to stably maintain the recording state, that is, the state of charge movement. Information is also recorded as changes in the optical or electrical properties of the organic thin film. For example, if changes in absorbance are used as information and read out optically, it is possible to read out information with a high S/N ratio.

The reason why writing is performed efficiently in the present invention by selectively performing optical excitation without applying a voltage to the recording medium will be explained below.

The formation of a charge transfer complex consisting of a donor molecular film and an acceptor molecular film is usually performed at the ionization potential I of each
This occurs when there is an energetic gain that counteracts or exceeds the electron affinity EA. Here, α is M
A constant corresponding to the adslung constant, r is the average distance between both molecules, and <e>2 represents the effective charge possessed by both charged molecules.

Therefore, if no energy is given from outside,
The rate of cargo transfer is almost determined by the distance between both molecules. At this time, the stabilization energy or absorption band (CT band) based on the charge transfer state is expressed by K, where ρ is a constant representing the rate of charge transfer.

On the other hand, when an external voltage is applied to the laminated structure of a donor molecular film and an acceptor molecular film, the energy required for the charge transfer can be reduced by eφ. Furthermore, as in the present invention, donor molecules are selectively excited by light, and a voltage is applied in synchronization with this or with a delay time corresponding to the relaxation time to the lowest excited state, and the energy required for writing information is further reduced. It is possible to reduce the charge transfer state, and to generate a charge transfer state extremely efficiently.

The above will be further explained in detail with reference to the energy model shown in FIG. The donor molecule is in the lowest excited state S1
When selectively excited with a light energy hν that is higher than or equal to the energy of , the excitation relaxation process is
A non-radiative relaxation or emission process to the ground state GD (with a rate constant of
Trace ρ to the rate constant. When an external electric field E is applied during the progress of the relaxation process at t/'1, η(E ) separated state C? A transition to 9 occurs.
, the free both charged species are moved by the electric field, resulting in a state (charge transfer state) in which electrons are transferred to the nearby acceptor molecule A and holes are transferred to the neutral donor molecule.

This kind of charge transfer state can be generated without applying an external electric field.
Although this is possible by photoexcitation alone, in this case, as mentioned above, after electron-hole pair formation in the KEh state, relaxation (quantum yield Φ) to the original ground state (GD and GA) occurs preferentially. As a result, the recorded state disappears instantaneously using the following reaction scheme.

D0+A0-D0+A0-+[D"A"]*-;D0+
A0hν * This quantum yield Φ in the excitation/relaxation process of donor molecules
The values of are shown for the case of zero bias. On the other hand, if a bias is applied as in the present invention, the electron-hole separation occurs at a rate of η(E), so the quantum yield is Φ(E) - CΦ(0) - η( E) )/Φ(0).

It is also possible to induce a charge transfer state simply by applying a KE field without photoexcitation, but in this case, the energy required to generate an electron-hole pair, that is, to form a charge transfer precursor, is expressed in voltage. V = C(I, -E,) - (e
2/F) )/e is required. Therefore, in order to sufficiently increase the charge transfer rate and increase the contrast of the information recording area, the organic thin film must have extremely high breakdown voltage characteristics of about IOV/3, which cannot be used practically.

(Example) The present invention will be explained in detail below.

FIG. 1 shows the configuration of a recording medium in one embodiment. In the figure, 1 is a glass substrate, 2 is a 15 formed on this
0X Nesa film, and 3 is a 500X 8102 film formed thereon. 4. On such a substrate, a donor molecular film (by LB method) is formed. Insulating molecular film5. A stacked structure of acceptor molecular films 6 is repeatedly formed ft8M to form a superlattice structure, and an At electrode 8 is formed thereon.

Specifically, the formation of the LB film is as follows.

As a donor molecule, 2.2′,6.6′-inglobilamine-substituted tetraphenylbipyran-4-ylidene was dissolved in chloroform to prepare an LB membrane developing solution. It was found from the surface pressure-molecule occupied area curve that the film-forming molecules formed a solid condensed film at 15 dyne/F. LB
A commercially available vertical pulling type film forming apparatus was used, and the aqueous phase was kept at a pH of 6.0, a temperature of 23° C., and a cadmium concentration of 0 and 01 rnMKn prior to spreading and accumulation. Then, the substrate on which the Nesa film/5102 film was formed on the glass substrate was placed in the water phase of
8) to accumulate the donor molecular film 4. Next, an insulating molecular film 5 made of arachidic acid is formed at a surface pressure of 25 dyn·/3 in the same manner, and then tetracyanoquinodimethane and stearic acid are mixed in a ratio of 1:1 as an acceptor molecular film 6. A mixed film was also formed using the same method. These operations are sequentially repeated multiple times to form a donor molecular film 4. Insulating molecular film 5゜Acceptor molecular film 6
4 and 7.4 layers were accumulated, respectively. Polyphenylalanine dissolved in chloroform (
After forming an insulating molecular film 7 by accumulating three layers with a molecular weight of 120,000 m at a surface pressure of 23 dyne 7'm, this was placed in a vacuum evaporation apparatus, and an At electrode 8 was formed under a vacuum of 3 x 10 torr. Approximately 5,001 times of this were deposited.

While applying a bias voltage such that the At electrode 8 side is positive at a period of 500 n5ec to the recording medium configured in this way, an Hs+ -N@ laser (λx 633 nm, 1
mW, E) was irradiated in a spot shape while changing the position at a period of 1 On. Absorption at a wavelength of 840 nm was observed at the Rede light irradiation site, that is, at the recording site.

FIG. 2 shows the results of measuring the absorption intensity ΔAcT at 850 nm of the recorded region by varying the applied bias voltage. As is clear from the figure, the absorption intensity significantly increases as the bias voltage increases. Therefore, it can be seen that information can be recorded at high speed and with high efficiency by performing optical excitation while applying a bias voltage.

It was also confirmed that the retention characteristics of information recorded as a difference in light absorption characteristics as in the above are stable and that the optical KS/N can be read out with good accuracy.

Examples of donor molecules used in the donor molecule membrane of the present invention include those shown below.

(1) Fullvalene type donor S with the following structural formula
-8. Here, φ represents a phenyl group.

(3) An amine-type donor (
4) Metal compound type donary 9 with the following structural formula
・1a-・1su (5) Cyanine dye donor R having the following structural formula
R (6) N-heterocyclic donor having the following structural formula (
7) Does it have the following structural formula? Remer-type donor ``\di2ゝ□-1-polyacetylene (1) to (7)
The donor molecule shown in IC can be used as its structural formula or with it as a backbone (n and p+q+4 are 8 or more).
Even derivatives with a hydrophobic group consisting of -〇〇O
H, -OH.

-8o, H, -C0OR', -NH2, -N■(R'
)3Y- (Y is halogen) having a hydrophilic group, or any derivative having both a hydrophobic group and a hydrophilic group.

As the acceptor molecule, the following molecules can be used.

(8) Quano compound type acceptor having the following structural formula (9) Quinone type acceptor C having the following structural formula
N CN α1 From the nitro compound type acceptor (8) with the following structural formula, the acceptor molecules shown in the graph can be used as they are, or with this as a backbone, CH, (CH2
+n, CH,4CH2-)+CH2=CH2+-+c
H2), (n and q and P+q+t are 8 or more), or -COOH, -OH, -8o3H.

-COOR', -NH2, -N■(R'), Y-(
Y may be a derivative having a hydrophilic group consisting of halogen) or a derivative having both a hydrophobic group and a hydrophilic group.

In the donor molecule film and acceptor molecule film in the present invention, the insulating molecules used in combination with the donor molecule and acceptor molecule, or the insulating molecules used in the insulating molecule film, are as follows. molecules are used.

0]) Substitutable saturated and unsaturated hydrocarbon derivatives -X represented by the following general formula, where R is substitutable CH, (CH2) n- or CH, +OH2++CH2-CH2÷+CH2+L(
However, n and pp q + q + t are 8 or more hydrophobic groups. Moreover, X represents a hydrophilic group, -COOH, -OH, -8o, H.

-COOR', -Nf(2, -N■(R'), Y-
(Y is halodan), etc.

(6) Various polymerizable molecules, such as vinyl polymers such as substitutable acrylates, methacrylates, vinyl ethers, styrene, vinyl alcohols, acrylamides, and acrylics. Alternatively, α-amino acids such as alanine, glutamate, aspartate, etc., and amino acids other than α-amino acids such as ε-aminocaproic acid. A polyamide polymer consisting of a 1:1 mixture of a diamine such as hexamethylene diamine and a dicarboxylic acid such as hexamethylene dicarboxylic acid.

These molecules are used in combination with unilinear molecules if they can be accumulated by themselves.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to construct an information recording frame that utilizes the charge transfer phenomenon between donor molecules and acceptor molecules in an organic thin film, and to perform efficient information writing. Therefore, according to the present invention, it is possible to realize an optical information recording device with unprecedented ultra-high density and excellent characteristics.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an information recording medium according to an embodiment of the present invention, Fig. 2 is a diagram showing its information writing characteristics, and Fig. 3 is a diagram for explaining the principle of the information writing method in the present invention. . 1... Glass substrate, 2... Nesa film, 3... S10
□Membrane, 4... Donor molecular film, 5, 7... Insulating molecular film, 6... Acceptor molecular film, 8... AL electrode. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (8)

[Claims] (1) Electrodes are provided on both sides of an organic thin film containing an electron donor and an electron acceptor to form an information recording medium, and the optical or electrical properties of the organic thin film are controlled by charge transfer between the electron donor and electron acceptor. An optical device for recording changes as information, characterized in that the electron donor is selectively excited by light irradiation while a voltage is applied between electrodes on both sides of the organic thin film to cause electron transition. A method for writing information into an information recording device. (2) Information of the optical information recording device according to claim 1, wherein the organic thin film has a laminated structure of a first organic thin film containing an electron donor and a second organic thin film containing an electron acceptor. How to write. (3) The organic thin film is constructed by repeatedly laminating a structure in which a first organic thin film containing an electron donor and a second organic thin film containing an electron acceptor are laminated via an insulating molecular film. An information writing method for an optical information recording device according to scope 1. (4) The information writing method for an optical information recording device according to claim 1, wherein the organic thin film is a mixed thin film containing both an electron donor and an electron acceptor. (5) The information writing method for an optical information recording device according to claim 1, wherein the organic thin film is formed by a Langmuir-Prodgett method. (6) Information writing in the optical information recording device according to claim 1, wherein the wavelength of the light source used for optical excitation is shorter than the wavelength corresponding to the lowest excited singlet energy of donor molecules contained in the organic thin film. Method. (7) The information writing method for an optical information recording device according to claim 1, wherein the organic thin film is formed on a light-transmitting substrate on which a transparent electrode is formed. (8) Information writing in the optical information recording device according to claim 1, characterized in that an insulating organic molecular layer or silicon oxide layer is interposed between the organic thin film and the upper and lower electrodes. Method.