JPH04247334A - Optical memory medium and optical memory device using this medium - Google Patents

Abstract

PURPOSE:To easily record and reproduce information at high density by the characteristics of an org. material relating to the optical recording medium which records and reproduces the information by using the light generated by storage media. CONSTITUTION:Disk-or card-shaped optical memory media 1, 41 are constituted of a photo-thermal conversion part 2, an optical change part 3 mixed with org. material particles 4, and a protective film 7 which allows the transmission of, for example, only the IR rays. Heat is generated in the photo-thermal conversion part 2 by the irradiation of the prescribed intensity from a light source 8 and the optical change part 3 is changed proportionally in optical characteristics from a transparent state to a cloudy state by this heat, by which binary data or analog data are recorded. The data are reproduced by reproducing means 9, 10 which make photodetection.

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 and reproducing information using light from a storage medium.

In recent years, magneto-optical disks and the like have been used as a method of storing information on a storage medium using light. This magneto-optical disk is an optical disk with a large recording capacity that can be erased and rewritten like a magnetic disk. Recording is performed by irradiating light and magnetization, and reproduction is performed by the intensity of reflected light depending on the polarization plane. A simple recording method is desired for such optical storage media. On the other hand, thermoreversible materials whose transparency state reversibly changes in response to thermal changes have been developed, and their uses are attracting attention.

0003

[Prior Art] Conventional magneto-optical disks use polycarbonate resin as a substrate, and a protective film and an amorphous perpendicularly magnetized film such as terevitium iron cobalt (TbFe).
It consists of a Co recording film and a protective film. and,
The track pitch is 1.6 μm, and a guide groove for tracking is formed with a width of about 0.6 μm.

Magneto-optical recording involves raising a magnetic film to the Curie temperature using a laser beam, and reversing the magnetization using a magnetic field in a predetermined direction using a magnetic head. Furthermore, when linearly polarized light is reflected by a magnetized magnetic body, the plane of polarization rotates due to the magnetic Kerr effect depending on the direction and intensity of magnetization on the surface of the magnetic body. In magneto-optical reproduction, the Kerr rotation angle of the plane of polarization is converted into the intensity of light using an analyzer, which is then detected as an electrical signal by a light-receiving element.

[0005] As described above, as a storage medium using light,
The magneto-optical disks mentioned above are the mainstream.

On the other hand, a method of printing by discoloring an organic material by heat is known. Although not shown in the drawings, this includes forming an optically variable layer of an organic substance on a base material such as a resin, and further forming a protective film on the optically variable layer. This optically variable layer can be made transparent or cloudy depending on the processing temperature, so when it is initially transparent, it is heated to a high temperature (e.g. 80°C) using a thermal head, etc., and the areas where the temperature rises become cloudy before printing. Yes, it is used as a printing medium for thermal printers.

[0007]

[Problems to be Solved by the Invention] Incidentally, there is a desire for a storage medium that uses light to be capable of recording and reproducing simple information in addition to the above-mentioned magneto-optical disk. It is desired to expand the applications.

SUMMARY OF THE INVENTION The present invention was made in view of the above problems, and an object of the present invention is to provide an optical storage medium that easily records and reproduces information at high density using the characteristics of organic materials.

[0009]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. 1(A), an optical storage medium 1 is composed of a photothermal conversion section 2 and an optical change section 3. The photothermal conversion section 2 converts the optical energy of light irradiated from the outside into heat, and the optical conversion section 3 has organic material particles 4 mixed therein.
The optical characteristics are reversibly changed by the heat of the photothermal conversion section 2.

Although not shown, a protective film is formed on the optically variable portion 2, and in one embodiment, this protective film is formed of a material that cannot transmit visible light.

[0011] Furthermore, using the optical storage medium 1, an optical storage device is constructed by a light source and a reproducing means. The light source forms data in a predetermined shape by irradiating the optical storage medium with light of a predetermined intensity, or forms and records analog data by changing the irradiation light as appropriate. The reproducing means irradiates the data with weaker light than when forming the data, reproduces the data using the reflected light, and reproduces the analog data based on a change in reflectance.

0012

[Operation] As shown in FIG. 1, the optically variable portion 3 is mixed with organic material particles 4 whose optical characteristics change depending on the temperature. That is, as shown in FIG. 1(B), organic material particles 4
At a certain temperature, it is a single crystal, and the number of times that light passes through the crystal interface is small, so it becomes transparent without being scattered. On the other hand, when a predetermined temperature is reached, the organic material particles 4 become polycrystalline, scattering light, and becoming cloudy. That is, data can be recorded on an optical storage medium by distinguishing between a transparent state and a cloudy state.

[0013] In this recording, data is recorded by irradiating light from a light source onto the optical storage medium 1, so that the photothermal converter 2 generates heat, raising the temperature of only the contact area, changing the state from a transparent state to a cloudy state. In this case, by changing the irradiation light from the light source appropriately, the cloudy state changes, and by extracting the change in reflectance by the reproducing means, it becomes possible to record and reproduce analog data.

[0014] In this way, by utilizing the temperature characteristics of organic substances, it is possible to store information in an optical storage medium at high density.

[0015]

Embodiment FIG. 2 shows a configuration diagram of an embodiment of the present invention. FIG. 2(A) shows an optical storage medium 1 formed in a disk shape, and a cross-sectional view thereof is shown in FIG. 2(B). Figure 2 (
In B), the optical storage medium 1 is provided with a light-to-heat converter 2 on a base material 5 with a heat insulating material 6 interposed therebetween. In addition, the photothermal conversion section 2
An optically variable portion 3 is provided thereon, and a protective film 7 is further provided on the optically variable portion 3 .

The base material 5 is made of paper, glass, resin, metal, or the like and has a thickness that is easy to handle (for example, 1 mm) in order to maintain a certain degree of hardness. The heat insulating material 6 is the light heat converter 2
This is for efficiently conducting the heat generated in the optical change section 3, and is made of resin or the like and has a thickness of, for example, 20 μm. The protective film 7 is used to prevent scratches, dust, etc. from adhering to the optical change section 3, and is made of a light-transmitting material and has a thickness of, for example, 1 μm, since it is necessary to transmit light for recording and reproduction. Ru. In this case, since the information recorded in the optical change section 3 can be read out by reflection of light, in order to prevent this, the protective film 7 does not allow visible light to pass through, but only infrared light. It is formed of a material (for example, silicone resin) to prevent the recorded information from being read visually.

The optically variable portion 3 is formed of a thermoreversible material with a thickness of, for example, 5 μm or less, and is made of, for example, resin, low-molecular organic material particles such as behenic acid, Saran resin, vinyl chloride and vinyl acetate copolymer, etc. A mixture of polymeric organic material particles such as coalesced particles is used. For example, low-molecular organic material particles and a resin are dissolved in a solvent, coated on a film, and dried by heating. In addition, when forming the optically variable part 3 with a copolymer of vinyl chloride and vinyl acetate, a tetrahydrofuran solution containing a copolymer of vinylidene chloride and acrylonitrile, docosanoic acid and a leveling agent is placed on a polyester film in a layer of 5 μm or less. It is coated in thickness and dried. Here, the diameter of the organic substance particles is smaller than the thickness of the optically variable portion 3 formed to be 5 μm or less.

This optical change section 3 is shown in FIGS. 1(A) and (B).
), organic particles are precipitated during heat drying,
The organic material particles become dispersed in the resin. The transparent state and the cloudy state reversibly change due to heat, and the two forms are maintained even at room temperature. This is because the sizes of the crystals in the particles of the organic substance in the optically variable part 3 are different. In other words, in the transparent state, the particles of the organic substance are composed of relatively large single crystals, so the light incident on the optically changing part 3 passes through the interface of the crystal less often, and the light passes through the optically changing part without being scattered. 3. This is because the entire structure appears transparent. On the other hand, in a cloudy state, the organic material particles are composed of polycrystals, and the light that enters the optical change section 3 is refracted and scattered many times at the interface of the crystals, resulting in an overall cloudy appearance. be.

FIG. 3 shows a graph of the thermoreversible characteristics of the optically variable portion. In FIG. 3, it is assumed that the optical change section 3 is initially in a cloudy state at room temperature. When this is heated, the transmittance starts to increase from T1 (100°C) and reaches the maximum transmittance (A1) at temperature T2 (120°C). Even if it is cooled to room temperature in this state, the transparent state is maintained (
A2). This is because the organic material particles change from a cloudy polycrystalline state to an anti-molten state during the process of increasing the temperature from T1 to T2, and when cooled to room temperature again, the crystals grow into a transparent single crystal state. . Further, when heated to a temperature of T3 (140° C.) or higher in this transparent state, it returns to a cloudy state (B2). This is because the organic material particles melt at temperatures above T3, and polycrystals are precipitated in the process of cooling to room temperature.

Note that in FIG. 3, the characteristics A1, B1
When the temperature is lowered between C1 and C3, the reflectance of light changes almost linearly (C1 to C3). Therefore, it is possible to record the temperature (light energy to be described later) as analog data by applying it proportionally to the signal to be recorded. In this case, the recorded data is read by irradiating light and
Analog data is reproduced by detecting changes in reflectance of the recorded analog data.

Next, the photothermal conversion section 2 is made of resin, metal, etc. (for example, 10 μm thick) whose surface is coated in black, and when irradiated with light, it absorbs the light and generates heat from the light energy. It is. Therefore, FIG. 4 shows a diagram for explaining the photothermal conversion section. In FIG. 4A, when the photothermal conversion unit 2 is irradiated with a light beam L0 with an area S, there is some repulsion light L1, but the irradiation energy W is
W=h×ν×S (1) It is expressed as follows. Here, h is Planck's constant and ν is the frequency of light. Therefore, the absorbed energy w in the photothermal conversion section 2 is expressed as w=W×η×t (2), where η is the light absorption rate and t is the light irradiation time. That is, heat is generated corresponding to the absorbed energy w. Furthermore, as is clear from equations (1) and (2),
Since the absorbed energy w is proportional to the area S of the light beam L0 and proportional to the irradiation time t, the photothermal conversion unit 2 is
The temperature increases as shown in B). Therefore, by irradiating light onto the photothermal converting section 2 from the outside, the temperature of the irradiated portion can be increased, and the reflectance of the optically changing section 3 changes due to this heat. Note that when recording analog data in the optical change section 3 as described above, this can be done by controlling the temperature rise by appropriately changing the area S and the irradiation time t.

FIG. 5 shows a conceptual diagram of recording and reproducing information on an optical recording medium. In FIG. 5, the optical recording medium 1 is rotated with the protective film (7) on the upper surface, and the reproducing means of a recording light emitting element 8, a reproducing element 9, and a reproducing light receiving element 10 are arranged above. Then, information is recorded concentrically or spirally on the optical storage medium 1 by the recording light emitting element 8. In this case, the diameter of the beam emitted from the recording light emitting element 8 is, for example, 0.5 to 1 μm, and recording is performed at high density.

FIG. 6 shows a diagram for explaining recording and reproduction in FIG. 5. First, if the initial state of the optical change section 3 is a transparent state, when light is irradiated from the recording light emitting element 8, the irradiated light passes through the optical change section 3 and reaches the photothermal conversion section 3, and the light heat conversion section 2 (Figure 6 (A
)). As a result, the photothermal conversion section 2 generates heat, and this heat is conducted to the optical change section 3, and the optical change section 3 becomes cloudy due to this heat (shaded area) and produces an optical change (Fig. 6 (B)
). In addition, although the method described above is based on a method in which the optically variable layer is in a transparent state in the initial state and becomes cloudy when irradiated with light,
The opposite change is also possible depending on how the applied temperature is applied. However, in a cloudy state, the transparency of light is worse than in a transparent state, so it is necessary to consider the intensity of the irradiated light. In this case, the heat generation temperature is controlled by the intensity of the irradiated light and the irradiation time.

Now, with reference to FIG. 6C, a method for writing or erasing information will be described with the initial state of the optically variable portion 3 being cloudy. Figure 6(C) shows the temperature characteristics of the optical change section 3 and the distribution of temperature rise when irradiated with light. Assume that two types of temperatures are given. The optically variable portion 3 changes from a cloudy state to a transparent state when the temperature reaches T1, and becomes completely transparent at a temperature T2. Therefore, the temperature of the writing location for the purpose of irradiation energy is T2
Recording becomes possible by giving the temperature distribution of a. Furthermore, when erasing written information, the temperature of the optical change section 3 may be set to T3 or higher and a temperature distribution of b may be provided. Here, the range in which writing and erasing is performed is determined by the area of the irradiated light, the temperature distribution due to thermal conduction of the optical storage medium 1, and the heat-sensitive characteristics of the optical change section 3, and is determined by controlling these conditions. be able to.

FIG. 6(D) shows the case of reproducing the written information, and the light from the reproducing light emitting element 9 has a small irradiation energy, and if the temperature rise due to the irradiation energy is below T1, the light emitted from the reproduction light emitting element 9 is , the written information does not constitute interference. Therefore, by irradiating such a small light energy,
Information can be read by looking at the reflected light. That is, when light is irradiated onto a cloudy part of the optically changing part 3, the irradiated light is reflected by the cloudy part and detected by the reproduction light receiving element 10. Further, when the transparent portion is irradiated with light, the irradiated light transmits through the optical change portion 3 and is irradiated onto the photothermal conversion portion 2 and absorbed in that portion, so that no reflection occurs. Therefore, it is possible to irradiate the rotating optical storage medium 1 with light and read out and reproduce written information based on the magnitude of the reflected light.

For example, FIG. 7 shows a diagram for explaining information recording and reproduction of binary logic. FIG. 7(A) shows the time of recording, and FIG. 7(B) shows the time of reproduction. In FIG. 7(A), while moving (rotating) the optical storage medium 1, the recording light emitting element (light source) 8 is blinked by the drive circuit 11 according to the write information of "1" and "0", and the optical storage medium 1 is moved (rotated). 1, the information is recorded. On the other hand, in FIG. 7B, the optical storage medium 1 is moved (rotated), the light emitting element for reproduction (light emitting section) 9 emits light, and the light receiving element for reproduction (light receiving section) 10 is used to optically change the optical change section 3. The information recorded by receiving the reflected light from the cloudy part of the
, "0" is reproduced as read information. Note that during recording and reproduction, the optical storage medium 1 is moved (rotated).
Instead, a recording light emitting element (light source) 8 and a light emitting unit 9,
The light receiving section 10 may be moved. Further, recording and reproduction of analog information are as shown in FIG.

Next, FIG. 8 shows a configuration diagram of an embodiment of the optical storage device of the present invention. FIG. 8(A) is a conceptual diagram of an optical storage device, and FIG. 8(B) is a configuration diagram of an optical head. Figure 8
In (A), in an optical storage device 20, a disk-shaped optical storage medium 1 is rotated by a spindle motor 21, and an optical head section 22 is disposed above. The optical head section 22 is slid in the radial direction of the optical storage medium 1 by a slide motor 23, and a light emitting element (laser diode) for recording and reproduction is laser driven by a control section 24, and a light receiving element for reproduction is driven by a light receiving element for reproduction. detect the signal.

As shown in FIG. 8(B), this optical head section 22 is configured such that a laser beam from a laser diode 30 whose irradiation intensity is changed during recording and reproduction is transmitted through a collimator lens 31,
The beam is focused on a predetermined portion of the optical storage medium 1 via the beam splitter 32 and the objective lens 33 (e.g., 0.5 to 1 μm in diameter).
) to be done. In this case, the objective lens 33 tracks left and right and moves up and down to focus. Further, during reproduction, the reflected light from the optical storage medium 1 is direction-changed by the beam splitter 32 via the objective lens 33 and converged onto the light receiving element 35 via the converging lens 34. The light is then electrically converted by the light receiving element 35 and reproduced as an electrical signal.

Next, FIG. 9 shows a configuration diagram of another embodiment of the present invention. In the optical storage device 40 of FIG. 9, an optical storage medium 41 formed in a card shape is held between a roller 43a rotated by a motor 42 and a freely rotating roller 43b and moved in the horizontal direction. Here, the structure of the card-shaped optical storage medium 41 is such that the base material is made of resin, paper, synthetic paper, etc., and the rest is the disk-shaped optical storage medium 1 in FIG.
It is similar to An optical head section 44 is positioned above this card-shaped storage medium 41 and is slid by a slide motor 45 in a direction perpendicular to the direction in which the card-shaped optical storage medium 41 travels. Further, the optical head section 44 is shown in FIG.
), the control unit 46 drives the light emitting element for storage and reproduction with a laser and detects the signal from the light receiving element for reproduction.

In the optical storage device 40, since the optical storage medium is in the form of a card, off-track is likely to occur due to variations in the dimensional deviation of the card, the deviation in the card conveyance guide, and the accuracy of the mounting position of the light source (light emitting element). Therefore, the information to be stored in the card-shaped optical storage medium 41 is formed into a bar shape or an ellipse shape.

FIG. 10 shows a diagram for explaining information recording on a card-shaped optical storage medium. FIG. 10 shows the optical head 4
4 shows a case where information is recorded by irradiating a card-shaped optical storage medium 41 with rod-shaped light. Figure 10(A)
By enlarging the writing irradiation light from the light source 50 through the collimator lens 51 and the cylindrical lens 52a in a direction perpendicular to the moving direction of the card-shaped optical storage medium 41, as shown in FIG. 10(C), This is an expanded writing width of writing information. Also, Figure 10
(B) is a case in which rod-shaped information is written on the card-shaped optical storage medium 41 using a cylindrical lens 52b that does not enlarge one side and converges the other.

Therefore, as shown in the conceptual diagram of reproduction in FIG. 10 of FIG. 11, the bar-shaped information 60 is written on the card-shaped optical storage medium 41 with a vertical deviation (generally ±0.5 mm). Also, since it is long in the horizontal direction, it can be easily positioned on the line of irradiation light 61 for reproduction. This makes it possible to prevent off-tracking due to variations in card dimension deviations, card transport guide deviations, and variations in light source (light emitting element) attachment position accuracy.

[0033]

As described above, according to the present invention, predetermined data can be recorded and reproduced by changing the optical characteristics of the optical change section in which organic material particles are mixed by the heat of the photothermal conversion section. The characteristics of organic materials allow for easy high-density recording and reproduction of data.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a graph of thermoreversible characteristics of an optically variable part.

FIG. 4 is a diagram for explaining a photothermal conversion section.

FIG. 5 is a conceptual diagram of recording and reproducing information on an optical storage medium.

FIG. 6 is a diagram for explaining recording and reproduction in FIG. 5;

FIG. 7 is a diagram for explaining information recording and reproducing of binary logic.

FIG. 8 is a configuration diagram of an embodiment of the optical storage device of the present invention.

FIG. 9 is a configuration diagram of another embodiment of the present invention.

FIG. 10 is a diagram for explaining information recording on a card-shaped optical storage medium.

FIG. 11 is a conceptual diagram of reproduction in FIG. 10;

[Explanation of symbols]

1 Optical storage medium 2 Photothermal conversion section 3 Optical change part 4. Organic material particles 5 Base material 6 Insulation material 7 Protective film 20, 40 Optical storage device 21 Spindle motor 22, 44 Optical head section 23,45 Slide motor 24, 26 Control section 41 Card-shaped optical storage medium

Claims (5)

[Claims] 1. A photothermal conversion unit (2) that converts the optical energy of light irradiated from the outside into heat; and the photothermal conversion unit (2).
1. An optical storage medium comprising: an optically variable portion (3) in which organic material particles whose optical properties change reversibly due to heat are mixed therein; 2. A light transmitting protective film (7) is formed on the optically changing portion (3).
Optical storage medium as described. 3. The optical storage medium according to claim 2, wherein the protective film (7) is formed of a material through which visible light cannot pass. 4. A photothermal conversion section (2) that converts the optical energy of light irradiated from the outside into heat, and the photothermal conversion section (2).
Organic material particles whose optical properties change reversibly due to the heat of
4), and an optical storage medium (1) having an optically variable portion (3) in which a mixture of It is characterized by comprising a light source (8) for recording, and reproducing means (9, 10) for irradiating the optical storage medium (1) with light that is weaker than when the data was formed and reproducing the data using the reflected light. optical storage device. 5. The light source (8) records the analog data on the optical storage medium (1) by changing the irradiation light as appropriate, and the reproducing means (9, 10) records the analog data on the optical storage medium (1) by changing the reflectance. 5. The optical storage device according to claim 4, wherein the optical storage device reproduces analog data.