JPS6254851A - Optical recording card - Google Patents

Abstract

PURPOSE:To obtain film constitution having high utilizing efficiency of energy by providing a recording medium layer, absorption layer and interference layer between transparent substrates and forming the recording medium layer of a metal, alloy or semiconductor forming the crystal structure different from the equil. phase at a room temp. by quick cooling from the solid state of a high temp. CONSTITUTION:Much part of incident energy is absorbed in the absorption layer 5 and is changed to heat energy to quickly elevate the temp. of the absorption layer 5 when the absorption layer 5 consisting of material which absorbs the incident energy is provided on the incident energy side of the recording medium layer 2. As a result, the much heat energy is transferred from the absorption layer 5 to the recording layer 2 by heat transfer and the temp. of the layer 2 rises quickly up to the temp. higher than in the case having no absorption layer 5. The recording medium layer 2 consists of the metal or alloy which has the crystal structure different at the 1st temp. (high temp.) higher than room temp. nd the temp. (low temp.) lower than the 1st temp. in the solid state and has the crystal structure different from the crystal structure having the equil. phase at room temp. by quick cooling from the high temp. Said la perferably generates a volumetric change by a crystal change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention enables high-density recording by using a high-density pulsed laser to reproduce a spot of 1 μm or less in diameter as a recording signal. The present invention relates to applications for bank withdrawal operations and railway ticket gate operations, where magnetic cards have traditionally been used, as well as computer input cards and floppy disk type recording media that utilize rewritability.

[Background of the invention]

In recent years, magnetic recording cards such as bank cards, in which a magnetic layer is formed on a substrate such as paper or a plastic sheet, and information signals are recorded on this magnetic layer, have been used in banks, railways, and various other fields.

Various types are used, such as magnetic commuter passes and magnetic type recording cards. These magnetic cards.

During normal reproduction, the magnetic head comes into strong sliding contact with the magnetic head, and repeated use causes the magnetic layer to wear off or cause scratches on the surface, reducing the reproduction output and causing malfunctions. (Japanese Patent Publication No. 56-50339) Also, as a countermeasure against this problem, a surface protective layer and the like have been considered. However, contact wear between the magnetic card and the head is unavoidable, shortening the life of the magnetic card.

Because magnetic cards use magnetism for recording, they suffer from magnetic contamination due to magnetic fields in the environment, limitations on recording density due to the Ta zonal structure, and stability and reliability as a recording medium due to the low S/N ratio of reproduced signals. Because of its low magnetic properties, conventional magnetic cards were used to simply record small amounts of information.

In recent years, as information recording becomes more dense and digital, various information recording and reproducing methods are being developed. Especially recording information about laser energy.

The optical recording method of optical discs used for erasure and reproduction is industrial rare metal Nα80, 1983 (Optical discs and materials)
As described in , it is possible to achieve higher recording densities than magnetic recording methods, and is a promising method for information recording in the future. Physical changes that occur irreversibly or reversibly in a recording medium due to laser light energy include destroying or shaping the medium in the recording area to create unevenness, and for reproduction, light is generated due to the interference of laser light on these uneven areas. - Utilize changes in the amount of reflection. It is generally known to form irregularities by melting and sublimating Ta or its alloys. This type of vehicle undergoes reversible changes which pose some problems such as toxicity.

Magneto-optical materials are the mainstream for recording media. This method utilizes optical energy to invert and record the local magnetic anisotropy of the medium near the Curie point or compensation point temperature, and the polarization plane of the polarized incident light at that part due to the magnetic Faraday effect and magnetic Kerr effect. Play with the amount of rotation. This method is considered to be the most promising rewritable optical recording method, and active research and development is underway with the aim of putting it into practical use in the next few years. However, there is currently no material with a large amount of rotation of the plane of polarization, and even with various efforts such as multilayer film formation, the S/N and C/
There is a big problem that the output level of N etc. is small.

It also has the disadvantage of being easily contaminated by environmental magnetism. Other methods utilize changes in reflectance due to reversible phase changes between amorphous and crystalline recording media.
onalTechnical Report Von
29 Na 5 ) (1983), there is an alloy in which small amounts of Ge and Sn are added to TeOx.

However, this method has a major problem in that the crystallization temperature of the amorphous phase is low, and the thermal instability of the phase at room temperature affects the reliability of the recorded signal.

On the other hand, as an alloy utilizing one color tone change, JP-A-57-1
Cu-(12-15)wt%AQ-(1
~5) There is wt%Ni. The alloy consisting of (12-15) wt% AQ - (1-5) wt% Ni - residual Cu takes advantage of the fact that it reversibly changes from red to golden yellow at the martensitic transformation temperature. .

Further, the Atg-Zn alloy utilizes the fact that the color changes reversibly from pink to white at the regular-disorder transformation temperature.

[Purpose of the invention]

The present invention achieves high-density recording using an optical recording method, which was not possible with conventional magnetic cards, and is highly functional.

The purpose of the present invention is to provide an optical card with a long service life and multipurpose use value.

[Summary of the invention]

The optical recording card of the present invention has a method of partially erasing a wide area by heating and rapidly cooling.

An example of the recording and reproducing principle of the present invention is as follows. First, the recording medium is locally heated and then rapidly cooled to maintain the crystal structure in the high temperature region in the low temperature region to record predetermined information, or locally heated based on the high temperature phase. Information can be reproduced by recording locally in a low-temperature phase during a high-temperature phase, and by irradiating the recorded portion with light and detecting the difference in optical characteristics between the heated portion and the non-heated portion. Furthermore, the recorded information can be erased by heating the portion recorded as information at a temperature lower or higher than the heating temperature at the time of recording. The light is preferably a laser beam, and a short wavelength laser is particularly preferable.1 Since the reflectance between the heated part and the non-heated part of the present invention is greatest at a wavelength around 500 nm or 800 nm, a laser beam having such a wavelength is used for reproduction. It is preferable to use It is preferable that the same laser source be used for recording and reproducing, and for erasing, a different laser beam having a lower energy density than that for recording is irradiated.

The present invention provides an optical recording card having a recording layer that records information by heating due to the incidence of light energy.
The optical recording card is characterized in that at least one of an interference layer and an absorption layer for the incident light energy is provided on the light energy incident side of the recording layer.

If the reflected energy from the optical recording card can be reduced by some means, the amount of heat input to the recording layer will increase, the temperature of the recording layer will rise rapidly, and high-speed writing will be possible, while also reducing the amount of incident energy. Since writing or erasing can be performed in the same manner, the writing sensitivity or erasing sensitivity is increased and the reliability of recording signal reproduction is increased. The recording layer has at least two types of crystal structures in a solid state, and is a metal or It is characterized by being made of an alloy or a semiconductor. Note that any metal or alloy that causes a change in unevenness can be used even if no crystal change occurs.

(Absorption layer, interference M) As shown in FIG. 1(a), when the absorption layer 5 made of a substance that absorbs incident energy is provided on the incident energy side of the recording layer 2, most of the incident energy is absorbed. It is absorbed in the layer 5 and converted into thermal energy, causing the temperature of the absorption layer 5 to rise rapidly.

As a result, much thermal energy is transferred from the absorption layer 5 to the recording layer 2 by thermal conduction, and the temperature of the recording WI2 also rises rapidly to a higher temperature than in the case without the absorption layer 5. The thickness of the absorption layer 5 is determined by the surface reflectance (ratio of reflected energy/incident energy) of the information recording/reproducing medium.
The thickness is preferably 5% to 80%, and the reflectance is 5.
If it is less than %, the intensity of the reflected light decreases, so the signal-to-noise ratio (S/N ratio) during recorded signal playback, where the recorded signal is read by comparing the reflected light intensity of the recorded part and the unrecorded part, deteriorates. This is a disadvantage. Furthermore, if the reflectance exceeds 80%, most of the incident energy will be reflected at the absorption layer 15 without being converted into thermal energy, so that the temperature of the absorption layer 5 will not rise. As a result, almost no thermal energy is transmitted to the recording layer 2, and no increase in writing sensitivity or erasing sensitivity can be expected.The absorbing layer converts electromagnetic waves (for example, laser beams and light) into thermal energy.

The absorption layer is silicon monoxide and manganese oxide.

Thin films of titanium oxide, chromium oxide, copper oxide, triiron tetroxide, etc. can be used, and semi-permeable films are preferred. In particular, colored ones that have a black body are preferred, and have an energy absorption of 10 to 30% to light, and a 50%
% or less is preferred. Thickness is 50n
As a means of reducing the surface reflectance of 0 nm or less, preferably 30 to 50 nm, there is a method of utilizing the interference effect of incident energy. 6 Use a film with energy transmittance of 50% or more, such as tantalum oxide or alumina. is preferable. Its thickness is 50-500
nm is preferable, and colorless is preferable.

For example, if a colorless and transparent interference layer 1 of an appropriate thickness is provided on the energy incident side of the recording layer 2 as shown in FIG. Ru. The remaining incident energy penetrates into the interference layer 1 and reaches the recording layer 2. Some percentage of the incident energy that has reached the recording layer 2 is reflected by the surface of the recording layer 2, passes through the interference layer 1 in the opposite direction, and reaches the surface of the interference layer 1. At this time,
When the incident energy has a wave nature like an electromagnetic wave, the energy wave reflected on the surface of the interference layer 1 and the energy wave reflected on the surface of the recording layer 2 cause interference. If the phase of the energy wave is shifted by half the wavelength of the energy wave, the peaks and troughs of the energy wave cancel each other out, and the amplitude of the energy wave decreases. About this.

This means that the energy reflected back from the surface of the information recording/reproducing medium is reduced in terms of voice quality.

That is, by setting the thickness of the interference layer 1 to an appropriate value, the energy reflectance can be lowered. In this case, interference layer 1
Since the absorption of light in this area is extremely small, the remaining energy after subtracting the reflected energy from the incident energy is all absorbed by the recording layer 2, and the temperature of the recording layer 2 increases more rapidly than when there is no interference layer 1. temperature rises to high temperature.

The thickness of the interference layer described above can be determined by the following equation derived from the theory of interference.

λ (m=o, 1, 2.3...) where, d: thickness of the interference layer nl: refractive index of the interference layer λ: wavelength of the energy wave or optimal value n of the refractive index of the interference film □′ is similarly derived from the theory of interference and is expressed by the following equation.

n11=5-・1 old...(2) Here, n2=Refractive index of recording layer 2 The layer that reduces the reflectance described above has an independent function as an incident energy absorption layer or an interference layer. However, it is also possible for one layer to have the functions of an interference layer and an absorption layer at the same time.

(Recording layer) As described above, the recording layer of the present invention has a first temperature (high temperature) higher than room temperature and a temperature lower than the first temperature (high temperature) in a solid state.
It is preferable that the metal or alloy is made of a metal or an alloy that has a crystal structure different from that in the equilibrium phase at room temperature upon rapid cooling from the high temperature, and that causes a volume change due to crystal change.

The alloy according to the present invention has at least two types of spectral reflectance at the same temperature by rapid cooling from a high-temperature in-phase state, and can reversibly change the spectral reflection. That is, the alloy according to the present invention has phases with different crystal structures in at least two temperature regions in the same phase state, and among these, the high-temperature phase is quenched and the low-temperature phase state is the standard state without quenching. The reflectance is different, and the spectral reflectance changes reversibly by heating and cooling in the high phase temperature region and heating and cooling in the low temperature phase region.

In addition, when applying to optical recording cards, the recording layer should preferably have a film thickness of 0.01 to 0.2 μm to produce information in a minute area with a recording density of 20 megabits/d or more. It is effective to directly rapidly cool and solidify the material from the gas or liquid phase to form it into a predetermined shape. These methods include PVD (evaporation, sputtering, etc.), CVD
electroplating, a molten metal quenching method in which molten metal is rotated at high speed, made of a member with high thermal conductivity, and is poured onto the circumferential surface of a metal roll and rapidly solidified; and electroplating. There are chemical plating methods, etc. When using a powdered material, it is effective to apply it onto a substrate and adhere it to the substrate. When applying, a binder that does not cause any reaction even when the powder is heated is preferred. Also,
In order to prevent oxidation of the material due to heating, it is also effective to coat the surface of the material, the film formed on the substrate, or the surface of the coating layer.

The powder is preferably formed by a Gaia atomization method in which molten metal is ejected together with a gaseous or liquid refrigerant and then poured into water to be rapidly cooled.The particle size is preferably 0.1 m or less, particularly 1 μm or less. Ultrafine powder is preferred.

The film was deposited by vapor deposition, sputtering, or CVD as described above.

It can be formed by electroplating, chemical plating, etc.

In particular, sputtering is preferable to form a film with a thickness of 0.1 μm or less. Sputtering allows easy control of the target alloy composition.

The optical recording card of the present invention allows double-sided recording. 1st
As shown in Figures (b) and (d), by using two recording layers, independent signals can be recorded and reproduced on both sides.

Can be erased. This is a feature not found in magnetic cards and magneto-optical cards, and is a great advantage of the optical recording card of the present invention. In (b) and (d) above, it is effective to provide an absorption layer and an interference layer on both sides, respectively. 1st
Figure (C) shows a structure in which a recording layer is sandwiched between two transparent acrylic resin plates, and the acrylic resin plates have a heat retaining effect and durability.

FIG. 2(a) shows a structure in which the recording layer is made of metal or an alloy to prevent energy dissipation due to thermal conduction in the surface direction. FIG. 5B shows a structure for double-sided recording.

(Substrate) For the substrate of the guard, it is preferable to use plastics such as polyvinyl chloride, transparent acrylic resin, and polycarbonate, which are lightweight, have sufficient support, and have good processing precision.In particular, materials with good adhesion to metals or alloys are preferred. Preferably, if the difference in thermal expansion between the substrate and the recording layer causes high temperature deformation, AQ
It is preferable to use a plate or the like as the substrate.゛[Embodiments of the invention] (Example 1) FIG. 3(b) is the interference layer ICTaxO of FIG. 1(a).
This is the spectral reflection characteristic of the film configuration with the addition of s* (thickness: 500 nm), and it can be seen that significant interference occurs. FIG. 4(a) shows Ag-
The 40 wt % Zn alloy film 2 alone was sputter-deposited, and the reflectance was high in both the recorded and unrecorded areas.
) figure uses the valley of interference, but Ar laser (λhr
= 488 nm) and semiconductor laser (λb = 8
It can be seen that the reflectance decreases significantly at each wavelength (30 nm). That is, compared to the case without an interference layer as shown in FIG. 3(a), the energy of the laser beam is absorbed into the recording medium more efficiently, and recording and erasing can be achieved with less power. In addition, here, the interference [1 is Ta, O, which has a high refractive index, and is 500 nm. Similarly, in other examples using such light interference, it is desirable that the interference layer 1 has a high refractive index and is transparent;
This is the case where ○ is used as an interference layer, and if the film thickness is adjusted to the interference conditions, the reflectance will similarly decrease.0 Figure 4 (a) and (b)
The recording film was made of Cu-14% by weight Al-4% by weight Ni12
(a) without the interference film 1, and (b) with the interference film (Ta*o*e 500 nm
This shows the spectral reflection characteristics of a film configuration with added thickness.
In this case as well, similarly to the A g -'40 wt % Zn alloy film 2 in FIG. 3, it can be seen that the reflectance is significantly reduced at each wavelength of the Ar laser and the semiconductor laser. It was confirmed that digital and analog recording and playback can be performed with a width of 1 μm or less using a semiconductor laser. It was also confirmed that concave or convex portions were recorded on the base surface at the same time as these color changes, and that the original flat surface was restored by erasing.

Therefore, according to the present invention, low energy recording, reproducing and erasing is possible, and a device dedicated to optical recording cards can be made compact.

(Example 2) As in Example 1, (a) of FIG. 5 shows the vinyl chloride substrate 3.
An Ag-40 wt % Zn alloy film 2 (thickness 10100 nm) was formed on the film by sputter deposition, and a Cr-ox
(Chromium oxide) 5 was provided to a thickness of 5 to 10 nm by vacuum evaporation. As described above, this Cr.Ox is added as a heat absorption layer on the metal information recording layer having high reflectance. The above-mentioned crystal-crystal phase change alloy film itself has a high reflectance, so the heat input efficiency of the laser beam is poor.
13 are provided. Figure 5 is.

This is a comparison of the spectral reflection characteristics with and without a heat absorption layer. As you can see from this figure, about 300-
It can be seen that in the wavelength range of 1000 nm, the reflectance of the film structure with a heat absorption layer decreases. Furthermore, the first
The recording layer in figure (a) is made of Cu-14% by weight and N-4% by weight.
i, with Cr.Ox added in the same way. It was found that this case also had the effect of lowering the reflectance. In addition, in addition to heat absorbing M5, Cu, 014, Fa, 0415
Even when replaced with , the same effect of lowering the reflectance can be seen. The volume change of the recording layer occurred in the same manner as described above.

(Example 3) Similarly to Example 1, A g -40% by weight Z was deposited between the transparent acrylic substrates 4 by sputter deposition as shown in FIG. 1(c).
Approximately 1100 nm of n alloy film 2 is provided, and Cr.
Ox was provided by air evaporation to a thickness of 10-20 nm. This C
In addition to having the property of a heat absorption layer, r-0x is made to have an increased thickness, and at the same time aims to reduce the reflectance due to interference.

Since this Cr-ox has transparency and a large refractive index, a large interference effect was obtained with a small film thickness. FIG. 5 shows the spectral reflection characteristics in the case of the above film structure aiming at both heat absorption and interference effects and in the case of only the recording layer 8.
As can be seen from this figure, in the wavelength region of 500 to 11,000 nm, the reflectance decreases significantly due to interference effects, and at the same time absorption effects are also observed, resulting in a decrease in the overall reflectance. Similarly, C
r.Ox is also suitable for lowering the reflectance and increasing the heat input efficiency of laser light, and it can be said that the film structure as shown in FIG. 1(c) is very practical. The volume change of the recording layer occurred in the same manner as described above.

(Example 4) Vinyl chloride, acrylic resin or aluminum plate was used as a card-shaped substrate of 5.4 x 8.5 x O, 75t, and Ag-40wt% was used as a recording layer on the substrate.
Zn alloy sputtered or vacuum deposited film (thick film 200n
m) *A sputtered or vacuum-deposited film (thick film of 500 nm) of Ta and O was provided as an interference layer. As shown in Figure 2 (C), a recording spot of 1 μmφ or less can be created using a 20 mW focused semiconductor laser (830 m + wavelength).
Similarly, we were able to stably reproduce digital signals using a semiconductor laser.

Thereafter, when the recording spot was synchronously irradiated with a 20 mW defocused semiconductor laser, the recording spot was erased. From the above, it has been found that erasable optical recording cards are effective.

(Example 5) A recording material made of an AgZn alloy having a film thickness of 20 to 50 nm was prepared by a sputtering method, a vacuum evaporation method, etc. on a polyimide resin sheet having particularly excellent plasticity and strength as a support. As shown in FIG. 6, this can be deformed from a planar shape into a roll shape, and as shown in FIG. 7, it can be wound around a feed roller to form a shape suitable for high-speed recording and reproduction.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a film structure with high energy utilization efficiency, especially when applied to optical recording cards that utilize spectral reflectance differences due to phase changes between crystals or reflectance differences due to volume changes. .

[Brief explanation of the drawing]

Figures 1 to 2 are layer structure diagrams of an optical recording card according to an embodiment of the present invention, Figures 3 to 5 are diagrams showing spectral reflection characteristics, and Figure 6 is a diagram showing spectral reflection characteristics.
．． FIG. 7 is a detailed explanatory diagram of the present invention. DESCRIPTION OF SYMBOLS 1... Interference layer, 2... Recording layer, 3... Vinyl chloride substrate, 4... Transparent acrylic resin plate, 5... Absorption layer, 6... Metal plate. Agent: Patent attorney Ogawa 9/2 Lee, Maro' 飄, ■ 8. ' 1st port (α) 2nd port (a,) (C) 3rd port;

Claims (1)

[Claims] 1. At least both sides of a metal or resin substrate with high mechanical support, or between at least two optically transparent resin substrates with high mechanical support, a recording layer and the light of the recording layer Optical recording, characterized in that an absorption layer and an interference layer are provided on the incident side, and the recording layer is made of a metal, alloy, or semiconductor that forms a crystal structure different from an equilibrium phase at room temperature by rapid cooling from a high-temperature solid state. card.