JPS5856893A - Light recording material - Google Patents

Abstract

PURPOSE:To obtain the heat mode light recording medium which can be erased and rewritten by including a light absorbing dye or a pigment, and forming a light recording layer. CONSTITUTION:An acrylic resin is a solid which includes atomic group shown by the specified formula (where R1 is a hydrogen atom or an alkyl group and R2 is a substituted or non-substituted alkyl group) and has number averaged molecular weight of about 100,000 or less. The recording layer which includes said acrylic resin and the light absorbing dye or the pigment, is formed on a substrate. The layer, which is generated from a semiconductor such as He and Ne and has the wavelength of about 400-850nm, is converged on said recording layer in order to soften the acrylic resin, and a minute recording bit is formed. In this case, the recording bit does not reach the bottom of the recording layer under the ordinary irradiating conditions, and the acrylic resin and the light absorbing dye or the pigment remain at the botton of the bit. Therefore, sensitivity is excellent and the broadening of recording energy is very small.

Description

DETAILED DESCRIPTION OF THE INVENTION ■ Technical Field The invention of this application relates to an optical recording medium. Furthermore, the present invention relates to a heat mode optical recording medium in which recorded information can be erased and rewritten.

■ Juto technology optical recording media has the feature that the recording medium does not deteriorate due to wear and tear because the medium and the writing/wiring head are not in contact. There is.

Among such optical recording media, heat mode optical recording media are being actively developed because they do not require one-time processing in a dark room.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat, and a part of the medium is melted or removed using a laser beam to form a small hole called a bit. It records information.

However, conventional heat mode optical recording media have the drawback that information recorded as bits cannot be erased, and written information cannot be corrected or rewritten, or it is difficult.

To explain this situation more specifically, one of the conventionally known heat mode optical recording media is:
Some have a recording layer consisting of nitrocellulose and a light absorber. When such a medium is irradiated with a laser beam as recording light in the form of a minute spot of, for example, about 1 #mφ, the irradiated area becomes extremely hot in a short time, and the nitrocellulose ignites and disappears, forming minute holes. l bits of information are recorded. However, recorded information cannot be erased from such media.

On the other hand, heat mode optical recording media having a recording layer made of tellurium or tellurium selenium-arsenic are also known. However, in this case as well, since the bits are formed by melting a metalloid with a high melting point, it is extremely difficult to restore the recorded nine bits.

Further, JP-A-55-161690 describes a heat mode optical recording medium having a recording layer made of a light-absorbing dye and a thermoplastic resin on a reflective substrate. In this medium, the recording layer is thinned to about 6.01 to 0.2 pm, and the resin in the irradiated area is melted and moved by laser light irradiation, or the resin in the irradiated area is made to melt and move. The reflective base is exposed by moving the reflective base in the lateral direction to form a bit. However, in this case as well, it is difficult to return the nine light-absorbing dyes once they have moved, or to once reach the bottom of the layer and backfill the nine holes to make them flat. Therefore, the publication does not disclose or suggest that this medium is capable of erasing and rewriting recorded information.

In contrast, using a medium in which thermoplastic is coated on a conductor, a charge is uniformly applied to the thermoplastic layer, a part of the thermoplastic is melted by laser light irradiation, and the volume change causes electrical attraction. A recording method is known in which a change in force is generated, thereby obtaining bits based on surface irregularities corresponding to laser beam irradiation. In this method, by reheating the medium, the unevenness on the surface can be flattened and the recorded information can be erased, but it requires a corona discharger, etc., and the mechanism of the writing device is complicated. There are disadvantages such as increased power consumption of the device.

■Object of the Invention The invention of this application reflects the above-mentioned actual situation.

The first object of the invention of this application is to provide a heat mode optical recording medium that can be erased and rewritten.

The second purpose is to reduce the optical energy required to form bits in the recording layer in such a front-erasable optical recording medium.
A clear threshold value appears in the temperature, and bits are always formed with good reproducibility when the input energy is above a predetermined value, and when the input energy is below a predetermined value.
Bits are not formed in the lugie, which narrows the range of input light energy or temperature that varies the reproducibility of pit formation, and at the same time, it has high heat resistance and can be written to bits under high temperature storage. There is little deterioration of the 87N ratio of the 9 information signal, and the ti readout light allows bits or
The surface of the peripheral part is not deformed, and the write information signal is 8/N.
The object of the present invention is to provide an optical recording medium that does not deteriorate the ratio, has high writing sensitivity, and has an extremely high reading 8/N ratio.

Other objects of the invention of this application will become clear from the following description.

The present inventors conducted various studies for this purpose and found that a recording layer is formed by incorporating a light-absorbing dye or pigment into a predetermined acrylic resin, and an erasable/rewritable medium is created. The inventors have found that the above-mentioned objects can be achieved, and have come up with the invention of this application.

That is, the invention of this application forms a recording layer containing a thermoplastic resin and a light-absorbing dye or pigment on a substrate, and when irradiated with recording light, the recording layer melts and softens to form recording pits. A layer containing both a thermoplastic resin and a light-absorbing dye or pigment remains at the bottom of the good recording bit formed in the recording layer, and the recording bit is formed and the recording layer is heated. An optical recording medium configured such that the surface of the recording layer is flat, wherein the thermoplastic resin is an acrylic resin containing an atomic group represented by the following formula. be.

2 R.

CH-C- C-OR.

1 (In the above formula, R and r represent a hydrogen atom or an alkyl group, and R2 represents a substituted or unsubstituted alkyl group.) ■ Specific structure of the invention Below, the specific structure of the invention of this application is explained. Explain in detail.

The optical recording medium in this application has a recording layer provided on the base.

The recording layer contains a predetermined acrylic resin. This acrylic resin is a thermoplastic resin that softens or melts and deforms as the temperature rises in the area irradiated with the recording light, forming recording bits on the surface.

The acrylic resin used contains an atomic group represented by the above formula. In this case, in the above formula, R1 is a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, 41
The hydrogen atom is preferably a methyl group. 9, RI may be a substituted or unsubstituted alkyl group, but the alkyl group preferably has 1 to 4 carbon atoms, and when R1 is a substituted alkyl group, the alkyl group The substituent for substituting is preferably a hydroxyl group, a halogen atom, or an amino group (particularly a dialkylamino group).

The atomic group represented by the above formula may form a copolymer with other repeating atomic groups to constitute various acrylic resins, but usually one type of atomic group represented by the above formula is used. Alternatively, a single metal body containing two or more types as a backing unit forms a copolymer to constitute an acrylic resin.

The number average molecular weight of such acrylic resin is preferably 100.000 or less as long as it can be obtained as a solid.

This is because if the number average molecular weight is 10 (1,000 or less), the writing sensitivity and readout N ratio of 87 will become much higher.

Such an acrylic resin is produced by a conventionally known method, and is used after molecular weight fractionation or purification, if necessary.

Alternatively, commercially available products may be used as they are, or after fractionation, purification, etc.

On the other hand, in the recording layer, along with such acrylic resin,
Contains light-absorbing dyes or pigments.

This light-absorbing dye or pigment exhibits a large light absorption rate with respect to the recording light, and is used to enable a temperature rise in the irradiated area. Therefore, depending on the wavelength of the recording light, 4
Various known dyes, carbon black, ultrafine metal powder, and various known inorganic or organic pigments such as lake pigments that absorb wavelength light of 0.00 to 8005 m can be used.

On the other hand, the content ratio of the acrylic resin and the light-absorbing dye or pigment contained in the recording layer is generally selected within a wide range of about 0.002 to 10 parts by weight per 1 part by weight of the acrylic resin. can do.

The silver layer described above is coated on the substrate by various known methods such as a spinner coater.

The thickness is generally 0.05 μm to 1 μm.

Note that such a recording layer may contain other additives in addition to the above-mentioned acrylic resin and light-absorbing dye or pigment.

An example of such an additive is an oligomer or polymer. In this case, the polymer or oligomer is contained in an amount of approximately 30% by weight or less based on the acrylic resin to improve adhesion to the support, improve coatability, and change the softening temperature. be able to.

In addition, various plasticizers, surfactants, antistatic agents, lubricants,
Flame retardants, ultraviolet ls absorbers, antioxidants, stabilizers, dispersants, etc. can be included.

On the other hand, the substrate on which such a recording layer is provided and supported is not particularly limited, and various materials can be used for the substrate.

Nine, in terms of thermal conductivity, various types of glass, various ceramics, or various types of polymethacrylic resin, polyacrylic resin, polycarbonate resin, phenol resin, epoxy resin, diallyl phthalate resin, unsaturated polyester resin, polyimide resin, etc. It is preferable to use a resin layer. Furthermore, the shape and dimensions can be varied depending on the intended use, such as a disk, tape, belt, or drum.

In this case, the medium of this application may have the above-mentioned recording layer on one surface of such a substrate, or may have recording layers on both surfaces thereof. Also, two substrates with recording layers coated on one side are used, and the recording layers are placed facing each other with a predetermined gap between them, and they are sealed to prevent dust and scratches. You can also choose not to have one.

Note that the above-mentioned nine media may be provided with a subbing layer such as a metal reflective layer or various resin layers, if necessary, and a recording layer may be provided on the subbing layer.

(2) Specific Effects of the Invention Using the optical recording medium of this application constructed as described above, information can be loaded and erased in the following manner.

First, recording light is irradiated. The recording light can be various lasers,
For example, various lasers such as He-No, He-Cd, XAr1 semiconductors, etc. having a wavelength of 400 to 850 nm and a wavelength of 9 degrees can be condensed, and various outputs can be used. Furthermore, the scanning conditions of the laser beam, the pulse width, the focusing conditions, etc. can be changed over a wide range of four ways.

Then, by irradiating the distribution light with such a laser, 1
The acrylic resin in the recording layer melts and softens, and minute recording bits corresponding to the irradiated light are formed on the surface of the recording layer in the irradiated portions. In this case, under normal recording light irradiation conditions, the recording bit does not reach the bottom of the recording layer, and a layer containing the acrylic resin and the light-absorbing dye or pigment remains at the bottom of the bit.

As a result of forming bits in this manner, erasing, which will be described later, becomes possible. With the medium of this application, a bit with extremely high sensitivity and a good shape can be obtained. The threshold broadening of the recording light energy required to form nine pits is also extremely small. Furthermore, even when stored at high temperatures, the 8/N ratio of the read light from the bits deteriorates very little.

On the other hand, in order to read the information written on the medium from the bits formed in this way, a reading laser beam with a lower power than the recording beam is used, which is focused and scanned to transmit transmitted light or Detect any output of reflected light.

At this time, as described above, the nine pits formed in the medium of this application have a good shape and are well rounded, so that a high 8/N ratio can be obtained during reading. Further, the reading light does not deteriorate the 8/N ratio of nine pieces of information recorded on the medium, and there is no possibility that unnecessary information is recorded in areas other than the bit portion.

On the other hand, to delete information distributed in this way,
All you have to do is reheat the medium. At this time, the surface that has been recorded and has become an uneven bit is remelted and returns to a flat surface. As heating for erasing, any of laser light irradiation, heating with various heaters, infrared lamp irradiation, etc. may be used.

When such erasing and writing are repeated, the writing sensitivity is always good, the bit always shows a good shape, and reading is performed with a high S/N ratio, and with further reading, the 8/N ratio deteriorates. Since the surface always returns to a flat surface after erasing, even if the erase is repeated many times,
Erasing and writing can always be performed reliably and satisfactorily.

■Specific Effects of the Invention According to the optical recording medium of this application, once written information can be easily and reliably erased.

Further, the broadening of the threshold value of optical energy or temperature required for forming bits in the recording layer is extremely small, and the range of input optical energy or temperature that balances the reproducibility of pit formation is extremely narrow.

Furthermore, it has high heat resistance, and even if it is stored at a high temperature of about 50 to 60° C. or higher, there is very little deterioration in the 8/N ratio of the K-recorded information signal.

In addition, there is very little change in the shape of the bit or the shape around the bit due to the readout light.
/N ratio deterioration is extremely small.

In addition, the writing sensitivity is good, and a high 8/N ratio can be obtained whether using transmitted light or reflected light for reading.

Furthermore, since erasing is always performed stably, information can be written in a sufficiently stable manner even if erasing and rewriting are repeated many times.

In this case, the number average molecular weight of the acrylic resin is i o o,
These effects become even more excellent when using a material of less than o o o.

The present inventors conducted various experiments to confirm the effects of the present invention. One example is shown below.

Experimental Example 1 Methyl methacrylate was polymerized using benzoyl peroxide as an acrylic resin, and the molecular weight was fractionated to obtain polymethyl methacrylate having a number average molecular weight of 20.000.

This polymethyl methacrylate and lake pigments (C, I
, P1gm@nt B1t+*l, color index number 42595-Lake, BAST's Fanal BlusB 5upra) at a weight ratio of 3:1, dispersed with a sand grind mill, and then filtered to a fineness of 0.5 pm or more. removes particles of
The bar code was coated on a 150 mm diameter, 1.2 inch thick Viletta glass plate at a thickness of 30 am and 100 m thick to obtain the medium of the invention of this application.

Separately, for comparison, polymethyl methacrylate was
Three types of media for comparison were obtained by replacing the media with polystyrene, polyethylene, and polypropylene each having a number average molecular weight of 10,000,000.

Among these four types of media, the relationship between deformation of the recording layer surface and temperature was measured for one having a recording layer with a thickness of 30 μm. That is, the medium is placed in a constant temperature bath, and the recording layer surface K O,
64-1. Place a 50f enclosure, raise the temperature at 5℃/min, and measure the relationship between the degree of penetration of the enclosure into the layer. The temperature is measured from the time the pit begins to penetrate until it reaches a constant penetration depth Kf, and the broadening of the pit formation threshold is evaluated. The results are shown in Table 1 below.

Separately, the following experiment was conducted on four types of media each having a recording layer with a thickness of IJvn.

First, a 10mW H@-No laser was focused to 1 μm using an objective lens with an AN (numerical aperture) of 0.55.40 times, and pulse irradiation was performed. The pulse width was changed and the pulse width at which bits were formed on the surface of the recording layer was measured, and the reciprocal of the writing sensitivity (μ-eel) was determined. The results are shown in Table 1.
An experiment was conducted with the ambient temperature lowered by 20°C and the broadening of the input energy threshold was evaluated. At the above threshold energy, bits were formed in all of the comparative media, whereas No pit formation occurred in the media of the invention of the application.

Next, the pulse width of the laser was fixed at 0.5 #mse and writing was performed, followed by 1 mW of H.-N.

The laser is focused to 1 μmφ using the same optical system as above,
1 μl@e, (fi) was irradiated at a return frequency of 10 Hz, the reflected light was detected by a photodiode, and the S/N ratio was calculated. In this case, the amplifier system was one with a 10 MHz band, and the noise was The RMS value (effective value) was used.

The results are shown in Table 1.

In addition, each medium was stored at 70° C. for 100 hours, and the deterioration of the S/N ratio (h) thereafter was measured to evaluate heat resistance.
The results are shown in Table 1.

Furthermore, the pulse repetition frequency of the readout laser was changed, irradiation was performed for 10 seconds, and the readout light frequency at which bits were formed on the surface of the recording layer was measured. The results are shown in Table IK.

The results shown in Table IK show that methyl methacrylate has extremely superior properties compared to other resins.

Experimental Example 2 In the medium of this application in Experimental Example 1, the number average molecular weight of the polyester was 5.000.20.00.
0.80.000 and 300.000, and the organic pigments (referred to as OP) were replaced with copper-phthalocyanine dye oleosol fast blue EL (manufactured by Sumitomo Chemical Co., Ltd., referred to as D) and 13 mμ carbon, respectively. Instead of black (referred to as CB) and ultrafine nickel powder with an average diameter of 10 nm (manufactured by Shinku Yakini Co., Ltd., referred to as Nl),
Various media were prepared and an experiment similar to Experimental Example 1 was conducted.

The results are shown in Table 2.

In addition, regarding heat resistance, all media showed only -6- or less deterioration.

(9) Regarding the generation of noise due to readout light, no pit formation was observed in all media at a readout light frequency of 300 Is.

From the results in Table 2, it can be seen that when the number average molecular weight of polymethyl methacrylate is 100.000 or less, favorable results can be obtained.

Experimental Example 3 Various media as shown in Tables 3 to 5 below were prepared,
We regret to obtain the results shown in the table.

In this case, Copolymer 1 in Table 3 is composed of methyl methacrylate (h1=CHs, R,=CH,), ethyl methacrylate (R,=CH,, 8-fold "Cm Ha), and cyclohexyl methacrylate (R+ =CHI N Rt
= CI HlI).

First, copolymer 2 in Table 4 is composed of methyl methacrylate and butyl methacrylate (Rt=CHsn, ""C
4H, ) and dimethylamineethyl methacrylate [R,
=CH,,R* =(CH*)*NC(Hj)*'
It is an i:1:i copolymer with 1.

Furthermore, Copolymer 3 in Table 5 is a 1:1:1 copolymer of methyl methacrylate, ethyl methacrylate, and hydroxyethyl methacrylate (R,=CH,,R,=CH,CM鵞01()). Covered with polymer.

From the results shown in Table 3, it can be seen that all the media of this application exhibit excellent properties.

It has been confirmed that such effects can be similarly achieved even when dyes or pigments used for semiconductor lasers are used.

Agent Patent Attorney Yo Ishii -

Claims (1)

[Claims] A recording layer containing a thermoplastic resin and a light-absorbing dye or pigment is formed on one substrate, and when irradiated with recording light, the recording layer melts and softens to record. A pit is formed and the above 1
At the bottom of the recording bit formed in the recording layer, a layer containing both a thermoplastic resin and a light-absorbing dye or pigment remains, and the above-mentioned recording bit is formed and the above-mentioned layer is heated. . An optical recording medium configured such that the surface of the recording layer is flat, wherein the thermoplastic resin is an acrylic resin containing an atomic group represented by the following formula. Formula R. 1 CH-C- C-0R. 1! (In the above, RI represents a hydrogen atom or an alkyl group, and RI represents a substituted or unsubstituted alkyl group.) 2. Claim 1 in which the number average molecular weight of the acrylic resin is 10@,000 or less. The optical recording medium described.