JPH01251445A - Optical card - Google Patents

Abstract

PURPOSE:To obtain a satisfactory reproducing signal by suppressing the generation of a noise by providing a light attraction layer on an optical recording layer at a position opposite to the incident side of recording and reproducing light. CONSTITUTION:A laser beam A is made incident from a transparent substrate 5, and the optical recording layer 4 is irradiated by the beam A, and a pit is formed on the layer 4, then, information is recorded, and also, the information is reproduced by reading the pit formed on the layer 4. At this time, the light attraction layer 3 provided at the side opposite to the incident side of the laser beam of the layer 4 attracts the laser beam transmitting the layer 4. Therefore, it is possible to prevent return light from being made incident on an optical pickup in reproduction, and to obtain the reproducing signal without having the noise accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical cards that are optically writable and readable.

[Prior Art] In recent years, as the magnetic cards widely used in various fields have been required to have higher functionality, optical cards have been proposed as a card medium with a larger storage capacity than magnetic cards. Among them, optical cards that can be used for additional writing are seen as promising because of their wide range of uses.

As a method of optically recording written information, direct
There is a read-after-write (DRAW) format. This type of recording method is heat mode recording, in which recording is performed digitally by irradiating the recording material with synchrotron radiation such as a laser beam as a heat source to cause physical and chemical changes to the recording material. This has the advantage that the recording will not disappear unless the recording material is heated to a temperature that permanently deforms it.

One example of a DRAW format is one that uses a recording medium provided with an optical recording layer made of a metal such as a low-melting point metal or its alloy, and another example is one that uses a recording medium provided with an optical recording layer made of an organic dye. Examples include those using recording media. Recording using an optical recording layer formed of these metals or organic dyes involves irradiating the optical recording layer with recording/reproducing light, such as a laser beam, and elevating the laser beam irradiated portion of the optical recording layer. A method in which the laser beam is heated and melted, and due to the difference in surface tension between the melted laser beam irradiated area and the solidified area around it, the laser beam irradiated area is excluded from the surrounding area to form a hole, that is, a bit. It is carried out by

Conventionally, it has been considered to apply such a RAW format recording medium to produce an optical card capable of additional writing and reading.

[Problems to be Solved by the Invention] However, when manufacturing an optical card by applying the above-mentioned DRAW format, there are the following problems. That is,
In this type of recording medium, recording is performed by forming bits by melting the portion of the optical recording layer that receives the laser beam and expelling it to the surrounding area. For this reason, this type of recording medium generally has a structure in which a space layer is provided between the optical recording layer provided on the transparent substrate and the card substrate, and when forming bits by irradiating the optical recording layer with laser light, The melted portion of the optical recording layer escapes into the space layer and is removed so that bits can be formed. The recording medium is manufactured in the shape of a disk and housed in a strong cartridge to protect it from external forces.

However, cards as recording media are generally used as cash cards or credit cards and are carried around in wallets, etc., and there is a risk of deformation or damage due to the application of various external forces. It needs to have enough strength to withstand, and it needs to be thin for the appearance of the card. For this reason, if a card is manufactured by applying the structure of a conventional DRAW format recording medium in which a space layer (air gap) is provided adjacent to the recording layer,
It is difficult to manufacture an optical card by directly employing the structure of the recording medium described above, since this results in a decrease in the strength of the card and the need for a prototype.

Therefore, in order to apply the DRAW format to produce an optical card that is capable of additional writing and reading, it is necessary to integrate the entire layers of the card substrate, optical recording layer, and transparent substrate without providing a space layer adjacent to the recording layer. Consideration is being given to adopting a structure that allows for close contact to improve mechanical strength and reduce thickness.

However, with a DRAW format optical card that has such a close-contact structure, when reading the bits formed on the optical recording layer by irradiating the optical recording layer with laser light and reproducing the signal, some parts of the reproduced signal are There are problems in that a lot of noise is generated and reliability is poor.

The present invention has been made based on the above-mentioned circumstances, and provides an optical card that can suppress the generation of noise during reproduction and obtain a good reproduction signal, has excellent reliability, and has sufficient mechanical strength. The purpose is to

[Means and Effects for Solving the Problems] The inventor of the present invention has conducted various studies regarding the fact that a large amount of noise is generated during signal reproduction in a DRAW format optical card with a close-contact structure, and has discovered the following. I found it. In conventional disk-shaped recording media with a spatial layer,
The spatial layer functions to suppress the generation of noise, and for this reason, it was found that a close contact structure without a spatial layer would generate a lot of noise during signal reproduction. That is, in a recording medium, when the optical recording layer is irradiated with laser light, not all of the laser light is absorbed by the optical recording layer, but a portion of the laser light passes through the optical recording layer and exits on the back side thereof. This transmitted light is reflected by some medium, and when the reflected light passes through the optical card again and enters the optical pickup together with normal reflected light, it becomes signal noise. Here, if a spatial layer is provided adjacent to the optical recording layer, the laser beam transmitted through the optical recording layer becomes diffused light (
(light emitted from a point light source with a focus on the optical recording layer), and the light reflected from the back side of the optical recording layer does not become noise during reproduction. On the other hand, in the case of a close-contact structure, there are sufficient interfaces between the materials such that the laser beam transmitted through the optical recording layer is reflected. Therefore, the laser light transmitted through the optical recording layer is sufficiently reflected at the interfaces of the respective materials, and this reflected light enters the optical pickup to generate sufficient signal noise. Therefore, by laminating the optical recording layer with an intermediate layer that suppresses the generation of noise, it becomes possible to construct an optical card with a close-contact structure that can obtain good reproduction signals.

The optical card of the present invention was made based on this knowledge, and includes an optical card in which an optical recording layer is laminated on a card substrate, and the optical card has an optical recording layer on the incident side of the recording/reproducing light with respect to the optical recording layer. It is characterized by providing a light absorption layer on the opposite side.

The structure of the optical card of the present invention will be explained with reference to FIGS. 1 and 2.

In the figure, 1 is a card substrate, 3 is a light absorption layer bonded to the card substrate 1 via an adhesive layer 2, and 4 is an optical recording layer formed on the inner surface of a transparent substrate 5. It is laminated and bonded to the absorbent layer 3. Transparent dyes can be selected from materials that are most suitable for recording and reproducing according to the wavelength of light such as laser light used for recording and reproducing, and have characteristics such as low thermal conductivity and low toxicity. Furthermore, organic dyes have the advantage that an optical recording layer can be easily obtained in large quantities by dissolving them in a solvent and coating them. Examples of organic dyes forming the optical recording layer 4 include anthraquinone, naphthoquinone, triphenylmethane, carbocyanine, merocyanine, xanthine, azo, azine, thiazine, oxazine, phthalocyanine, and squarylium. Examples include azulenium-based and azulenium-based. Furthermore, in order to suppress deterioration due to the use of an optical recording layer made of an organic dye, a singlet oxygen quencher can be mixed with the organic dye or introduced into the optical recording layer as a counter ion of the dye. - As a heavyt oxygen quencher, β-carotene, 1.
4-diazabimicro[2,2゜2]octane, tetramethylethylene, benzoquinone, etc. can be used, but bis(1,2-diaryl-ethylenedithiorad)nickel, bis[4-(dimethylamino)dithiopenzylconickel) Metal rust bodies mainly containing nickel, such as nickel bisbenzenedithiolate, are effective.

When an optical recording layer is created using these organic dyes with a film thickness that is lower than that of metals and has the highest reflectance among them, the laser light that passes through the optical recording layer 4 during recording and reproduction. However, it is effective to provide a light absorption IXt in order to suppress the return light due to reflection from the back side of the optical recording layer.

Furthermore, low melting point metals such as tellurium, bismuth, and aluminum can also be used as the material for forming the optical recording layer 4.

The light absorption layer 3 is provided on the opposite side of the optical recording layer 4 from the incident side of recording/reproducing light, for example, laser light, and absorbs the laser light that has passed through the optical recording layer 4 and regenerates the light. Recording layer 4
It has the function of preventing it from returning to the original state. As the material for forming the light absorption layer 3, the organic dye used in the optical recording layer 4, carbon black, and black pigment can be used alone or mixed in a binder. As a binder, nitrocellulose, cellulose acetate, ethylcellulose, polyvinyl chloride, polyvinylidene chloride,
Polyethylene terephthalate, polystyrene, polymethylmermethacrylate, polybutadiene, polyvinyl acetate, polyvinyl alcohol, polyurethane epoxy resin, etc. are used.

Furthermore, this light absorption layer 3 can be formed by printing black ink on the surface of the optical recording layer 4 on the card substrate 1. The light absorption layer 3 is preferably arranged adjacent to the optical recording layer 4 as shown in FIG. However, if it is highly transparent, it will not pose a problem.

Therefore, the optical card configured in this way is capable of receiving laser light A.
enters from the transparent substrate 5 and irradiates the optical recording layer 4 to form pits in the optical recording layer 4 to record information.
The information is reproduced by reading the pits formed. Most of the laser light irradiated onto the optical recording layer 4 is reflected, but the remaining part is transmitted through the optical recording layer 4. However, the light absorption layer 3 provided on the opposite side of the optical recording layer 4 to the laser light incident side absorbs the laser light transmitted through the optical recording layer 4, and this transmitted light returns to the optical recording layer 4 and enters as light. I have nothing to do. That is, this returned light does not mix with the reflected light reflected by the optical recording layer 4 and exit the optical card again. Therefore, during reproduction, no returning light enters the optical pickup, and only the reflected light from the optical recording layer 4 enters, so that noise-free and accurate signal reproduction can be performed.

In addition, this optical card has a structure in which the card substrate 1, light absorption layer 3, optical recording layer 4, and transparent substrate 3 are all laminated and closely spaced together, so it has high mechanical strength and can be made thinner. can be achieved.

Furthermore, the optical card of the present invention can also be configured as shown in FIG. 2 in addition to the structure shown in FIG.

In this structure, a light absorption layer 3 is printed on a card substrate 1, and an optical recording layer 4 is adhered via an adhesive 2 and an intermediate layer 7 for protecting the optical recording layer 4 from the adhesive 2. .

``Example: A cyanine dye (CY-9 manufactured by Nippon Kayaku Co., Ltd.) was applied to a film thickness of 6 mm on a transparent substrate made of acrylic resin on which predetermined tracking grooves were formed.
It was applied so that the temperature was 0r+m.

Next, this optical recording layer was coated with styrene oligomer (ST-95 Sanyo Kasei'!A) using carbon black as a binder.
) was applied to a film thickness of 2p to form an optical recording layer. Furthermore, after bonding the card substrate and epoxy resin adhesive (Araldite), the entire structure was punched out to produce an optical card. This optical card is connected to a semiconductor laser (830 nm, 10 kHz).
After the signal was recorded using z), it was reproduced with a power of 0.6 mw, and a good reproduced signal with little noise was obtained.

Furthermore, instead of applying styrene oligomer to the transparent substrate as in the above embodiment, the light absorption layer was formed by applying black ink to the card substrate. Then, as a result of recording and reproducing signals in the same manner as in the above embodiment, a good reproduced signal with little noise was obtained.

[Effects of the Invention] As explained above, according to the present invention, among the recording and reproducing light irradiated to the optical recording layer, the light that has passed through the optical recording layer is absorbed by the light absorption layer, so noise generation during reproduction is prevented. You can obtain a good playback signal by holding down. Therefore, it is possible to obtain a card with improved mechanical strength and reduced thickness by closely adhering each layer.

Particularly, the present invention is effective when applied to an optical card whose optical recording layer is formed of an organic dye.

[Brief explanation of the drawing]

1 and 2 show an example of the structure of the optical card of the present invention, FIG. 1 is a sectional view, FIG. 2 is a plan view, and FIG. 3 is another example of the structure of the optical card. FIG. DESCRIPTION OF SYMBOLS 1... Card substrate, 3... Light absorption layer, 4... Optical recording layer, 5... Transparent substrate. Applicant's representative Patent attorney Takehiko Suzue] Figures 1 and 10, Figure 2

Claims (2)

[Claims] (1) An optical card in which an optical recording layer is laminated on a card substrate, characterized in that a light absorption layer is provided at a position on the opposite side of the optical recording layer from the incident side of recording and reproducing light. A light card. (2) Claim 1, wherein the optical recording layer is made of an organic dye.
Optical card as described.