JPH05127303A - Optical recording medium and optical recording device using the same - Google Patents

Abstract

PURPOSE:To enable writing and vanishment with light having >=400nm wavelength. CONSTITUTION:A recording layer 2 contg. at least one among a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye and at least one among spiropyran, spiroxazine, spirothiopyran and a 4,5-epoxy-2-cyclopentene deriv. is formed on each substrate 1 of an optical recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for recording information and an optical recording device using the same.

[0002]

2. Description of the Related Art Currently, writing information on an optical recording medium,
A semiconductor laser of 780 nm or 830 nm is used as a light source for erasing, but in order to increase the recording density, the emission wavelength of the semiconductor laser is being shortened, and a semiconductor laser of about 600 nm has already been used. It has appeared as a light source. It is also considered that the advent of an optical recording device using a semiconductor laser that emits light of 390 nm or 415 nm by combining a semiconductor laser of 780 nm or 830 nm with a second-order nonlinear material is not far away.

On the other hand, as an optical recording medium using a photochromic compound such as spiropyran or anthracene, recording or writing is performed by irradiating light having a wavelength corresponding to photoisomerization of each compound. Has been proposed (Japanese Patent Laid-Open No. 62-286036). For example, in the case of a spiropyran derivative, erasing may be performed by irradiating with visible light of 500 to 700 nm, but writing is required to be irradiated with ultraviolet light of around 300 to 370 nm.

In the case of anthracene derivative, 39
It is possible to generate and write a photodimer by irradiating near-ultraviolet light near 0 nm, and to erase by dimerization of the dimer by irradiating near-ultraviolet light near 240 to 280 nm. Therefore, in order to perform writing and erasing only in the photon mode, ultraviolet light of the above wavelength is required.

Although these light sources are still available, they are not practical as a general-purpose optical recording device because of the large size of the device and the high price. In addition, the combination of non-linear elements cannot absorb data because the non-linear elements themselves have absorption in the ultraviolet region and the transmission efficiency is extremely reduced, so that virtually no transmission occurs.

As described above, an optical recording medium using a photochromic compound as a recording material has a problem that ultraviolet light having a wavelength which cannot be obtained by the current semiconductor laser must be used for either writing or erasing. is there.

A recording medium using a photochromic compound capable of recording and erasing without using ultraviolet light as described above has been proposed (JP-A-2-293737). This is called reverse photochromism,
The principle of recording and erasing is to record (write) by irradiating the reverse photochromic material with visible light to change from a colored state to a decolorized state. For erasing, the photochromic material contains an antenna dye as a heat generating source, and the medium is heated by irradiating a laser beam having a wavelength corresponding to the absorption wavelength of the dye to change from a decolored state to a colored state. Is.

[0008]

In the reverse photochromism described above, the writing is performed by irradiating the colored state with visible light to bring it into the decolored state. However, in an ordinary optical disc or the like, tracking and focus settings (d
ect) is required and this is done by injecting light. In the inverse photochromism, since it is initially colored, incident light is absorbed,
There is a problem that it becomes difficult to set tracking and focus. This is a problem regardless of whether the method is a transmissive type or a reflective type, and so-called positive photochromism, which is performed by changing information from a decolored state to a colored state when writing information, is a major factor.

It is an object of the present invention to provide an optical recording medium that does not use ultraviolet light, that is, can be written and erased with light having a wavelength of 400 nm or more.

Another object of the present invention is to use no ultraviolet light,
That is, it is to provide an optical recording medium having a positive photochromism capable of writing and erasing with light having a wavelength of 400 nm or more.

Still another object of the present invention is to provide an optical recording device using the above optical recording medium.

[0012]

Means for Solving the Problems The present inventors have studied the photochromic compound, found that the absorption spectrum changes by irradiation light having a wavelength of 400 nm or more by selecting the compound, and arrived at the present invention.

The gist of the present invention that achieves the above object is as follows.

(1) In an optical recording medium having a recording layer for recording information by light, the recording layer has at least one of (A) a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye. An optical recording medium comprising a seed and (B) at least one of spiropyran, spirooxazine, spirothiopyran and a 4,5-epoxy-2-cyclopentene derivative.

(2) In an optical recording apparatus for converting information into light on an optical recording medium for recording, reading and erasing, the recording layer of the optical recording medium comprises (A) a naphthalocyanine dye, a cyanine dye and a phthalocyanine. An optical recording device comprising at least one kind of a dye based on triphenylmethane and at least one kind of (B) spiropyran, spirooxazine, spirothiopyran and a 4,5-epoxy-2-cyclopentene derivative. ..

FIG. 1 is a schematic sectional view of the optical recording medium of the present invention. In FIG. 1, the recording layer 2 is provided on the substrate 1,
The recording layer may also serve as the substrate.

The dye as the component (A) has a wavelength of 400 nm.
It is desirable that the material has an absorption band as described above and is not melted or sublimated by heat generated by the absorbed light. Therefore, a compound having a high melting point is desirable. In particular, examples of compounds that absorb semiconductor laser light of 780 nm or 830 nm include naphthalocyanine dyes and cyanine dyes. Further, it is considered that the phthalocyanine dye and the triphenylmethane dye are effective for the semiconductor laser light of 630 to 680 nm which is expected to become popular in the near future.

An excellent recording layer is formed by blending at least one of spiropyran, spirooxazine, spirothiopyran, and 4,5-epoxy-2-cyclopentene, which are the photochromic compounds as the component (B). You can Among these, spiropyran,
Spirooxazine, spirothiopyran, and 4,5-epoxy-2-cyclopentene derivatives are suitable for high-speed writing / erasing.

The compounding ratio of (A) :( B) is 1: by weight.
1 to 1:10 is desirable. Outside this range, the wavelength of light required for writing or erasing is less than 400 nm,
There is a problem that heat may not be generated even when a laser beam of 400 nm or more is irradiated.

An antioxidant such as phenol or a stabilizer such as amine may be used in combination with the photochromic compound.

The substrate of the recording medium for forming the recording layer is preferably one that does not dissolve in the solvent that dissolves and disperses the photochromic compound. When the substrate also serves as the recording layer, the substrate is molded by dissolving and dispersing the photochromic compound in the solution of the polymer material which is the substrate material. This method is particularly effective when using a photochromic compound that is soluble only in an organic solvent that corrodes the substrate.

On the recording layer, for example, a protective film for preventing physical damage to the recording layer and entry of moisture, a reflective layer 3 for increasing the reflectance of the recording layer at the time of writing / reading / erasing, and the like are provided. Is acceptable as long as it does not adversely affect the recording layer.

[0023]

The principle of writing / erasing of the optical recording medium of the present invention is as follows.

An optical recording medium having a recording layer of a naphthalocyanine dye having an absorption band at a wavelength of 400 nm or more and a spiropyran derivative sensitive to both heat and light will be described as an example.

First, when a recording layer containing a naphthalocyanine dye is irradiated with a semiconductor laser of 830 nm, the naphthalocyanine dye absorbs this light to generate heat, and the heat causes the almost colorless spiropyran derivative to reach its melting point. When heated, it changes to a merocyanine type isomer and is colored. This is writing.

On the other hand, the erasure is changed to the original spiropyran derivative by irradiation with light having a wavelength corresponding to the absorption band generated when the merocyanine type isomer is changed to the colorless state.

The optical recording medium using a photochromic material that can be written and erased by using light having a wavelength of 400 to 1200 nm does not need ultraviolet light.

[0028]

EXAMPLES The present invention will be described based on examples.

Example 1 A naphthalocyanine derivative 1 represented by the formula [1] was formed on a polycarbonate substrate having a diameter of 5 inches.
And 2% by weight of the spiropyran derivative represented by the formula [2]
Was spin-coated (rotation speed: 2000 rpm) with carbon tetrachloride solution in which both were dissolved, and dried at room temperature to obtain the above formula [1].
An optical recording medium having a recording layer of the compound [2] was prepared.

[0030]

[Chemical 1]

The recording layer of the optical recording medium shows a light green color. A semiconductor laser having a wavelength of 830 nm and a power of -3 mW was used to irradiate and write a digital code. When the light irradiation part was observed by a microspectroscope, an absorber having an absorption maximum at 550 nm appeared. Further, it was found that after writing 100 tracks, the written portion turned purple even with the naked eye. 532 nm obtained by combining this medium with a 1064 nm semiconductor laser and a second-order nonlinear material
When the 550 nm absorber disappeared, the purple color disappeared and the original light green color was changed.

From the above, 830 nm near infrared light and 532 n
An optical recording medium capable of writing and erasing with only m visible light was obtained.

[Example 2] Recording of a compound represented by the formula [2] [3] in the same manner as in Example 1 except that the naphthalocyanine derivative represented by the formula [1] was replaced with the cyanine derivative represented by the formula [3]. An optical recording medium having a layer was prepared.

[0034]

[Chemical 2]

The above optical recording medium is also light green. A digital code was written in the same manner as in Example 1. When the written portion was observed with a microspectroscope, an absorber having an absorption maximum at 550 nm appeared. It was also found that after writing 100 tracks, the written portion turned purple even with the naked eye. When this medium is irradiated with visible light in the same manner as in Example 1, it is 5
As the 50 nm absorber disappeared, the purple color disappeared and the original light green color was changed.

[Example 3] A compound represented by the formula [1] or [4] was replaced by the same operation as in Example 1 except that the spiropyran derivative represented by the formula [2] was replaced with the spirooxazine derivative represented by the formula [4]. An optical recording medium having the recording layer of was prepared.

[0037]

[Chemical 3]

The optical recording medium is also light green. This was irradiated with a digital code in the same manner as in Example 1. When the irradiated part was observed with a microspectroscope, an absorber having an absorption maximum at 560 nm appeared. It was also found that after writing 100 tracks, the written portion turned purple even with the naked eye. When this medium was irradiated with visible light in the same manner as in Example 1, it was 560 nm.
As the absorber disappeared, the purple color disappeared and the original light green color was changed.

Example 4 The spiropyran derivative represented by the formula [2] was replaced with a spirothiopyran derivative represented by the formula [5], and the compound represented by the formula [1] [5] was prepared in the same manner as in Example 1 below. An optical recording medium having a recording layer was produced.

[0040]

[Chemical 4]

The above optical recording medium is also light green. This was irradiated with a digital code in the same manner as in Example 1. When the irradiated part was observed with a microspectroscope, an absorber having an absorption maximum at 580 nm appeared. It was also found that after writing 100 tracks, the written portion turned purple even with the naked eye. When this medium is irradiated with visible light in the same manner as in Example 1, it is 580 nm.
As the absorber disappeared, the purple color disappeared and the original light green color was changed.

[Example 5] The spiropyran derivative represented by the formula [2] was replaced with the 4,5-epoxy-2-cyclopentene derivative represented by the formula [6], and the same procedure as in Example 1 was followed. An optical recording medium having a recording layer composed of two compounds represented by [6] was prepared.

[0043]

[Chemical 5]

The above optical recording medium is also light green. This was irradiated with a digital code in the same manner as in Example 1. When the irradiated part was observed with a microspectroscope, an absorber having an absorption maximum at 530 nm appeared. It was also found that after writing 100 tracks, the written portion turned red even with the naked eye. Next, when the visible light was irradiated in the same manner as in Example 1, the absorber at 530 nm disappeared, and the red color disappeared to the original light green color.

Example 6 5 mg of the naphthalocyanine derivative represented by the formula [1], 50 mg of the spiropyran derivative represented by the formula [2], and 10 g of the polycarbonate pellets were dissolved in 50 ml of tetrahydrofuran and poured into a flat-bottomed Petri dish having a diameter of 12 cm. After leaving it in a room with low humidity to disperse most of the tetrahydrofuran and then drying under reduced pressure to completely disperse the tetrahydrofuran, a recording compound was dispersed in the substrate, that is, an optical recording medium in which the substrate also functions as a recording layer was prepared. did.

The optical recording medium is light green. This medium was irradiated with a semiconductor laser emitting at 830 nm.
When the irradiated part was observed with a microspectroscope, an absorber having an absorption maximum at 550 nm appeared. Next, when visible light was irradiated in the same manner as in Example 1, the absorber at 550 nm disappeared.

An optical head having a laser oscillator, a rotating means for rotating an optical recording medium for recording information by a laser from the optical head, and a drive circuit for controlling the operation of the optical head and the rotating means. An optical recording device equipped with a processor for giving a command to the drive circuit and an information input / output unit for inputting / outputting information to / from the processor, records and reproduces information using the optical recording medium obtained in each of the embodiments After erasing, the specified characteristics could be obtained.

[0048]

The optical recording medium according to the present invention can be written and erased only by the current general-purpose semiconductor laser light. The recording layer can be easily manufactured as an optical recording medium by a simple coating method or dispersion method.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of an optical recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Substrate, 2 ... Recording layer, 3 ... Reflective layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Ohara 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hiritsu Manufacturing Co., Ltd.

Claims (6)

[Claims] 1. An optical recording medium having a recording layer for recording information by light, wherein the recording layer comprises at least one of (A) a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye. And (B) at least one of spiropyran, spirooxazine, spirothiopyran, and a 4,5-epoxy-2-cyclopentene derivative, and an optical recording medium. 2. An optical recording medium having a recording layer for recording information by light, wherein the recording layer comprises at least one of (A) a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye. And (B) at least one of spiropyran, spirooxazine, spirothiopyran, and 4,5-epoxy-2-cyclopentene derivative, and being capable of writing and erasing by a change in absorption spectrum due to irradiation light having a wavelength of 400 nm or more. Optical recording medium. 3. The optical recording medium according to claim 1, wherein the compounding ratio of (A) :( B) is 1: 1 to 1:10 by weight. 4. An optical recording medium for converting information into light and recording the information.
In an optical recording device for reading and erasing, the recording layer of the optical recording medium comprises (A) at least one of a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye, and (B) spiropyran, An optical recording device comprising at least one of spirooxazine, spirothiopyran, and a 4,5-epoxy-2-cyclopentene derivative. 5. An optical recording medium, which converts information into light and records the information,
In an optical recording device for reading and erasing, the recording layer of the optical recording medium comprises (A) at least one of a naphthalocyanine dye, a cyanine dye, a phthalocyanine dye and a triphenylmethane dye, and (B) spiropyran, An optical recording device comprising at least one of spirooxazine, spirothiopyran, and a 4,5-epoxy-2-cyclopentene derivative. 6. The optical recording apparatus according to claim 4, wherein the compounding ratio of (A) :( B) is 1: 1 to 1:10 by weight.