JPH09237420A - Optical recording method, optical recorder and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expose a latent image so as to make the width of the latent image nearly constant regandlessly of the length of the latent image by supplying a driving signal obtained based on a modulated pulse signal converted into a pulse string to a light modulator and driving the light modulator. SOLUTION: This optical recorder 20 includes a pulse string converting circuit 22 provided between an EFM modulation circuit 21 and a driver. During the formation of pit recording, the EFM modulation circuit 21 supplies not only an EFM modulated high frequency recording signal S1 but also a channel clock signal CHCKO to the pulse string converting circuit 22. Thus, a pulse string converting signal S11 outputted from the circuit 22 becomes the signal for which a pit formation pulse based on the signal S1 is converted into a pulse string for each window. Succedingly, a driver 8 supplies a voltage signal S12 based on the signal S11 to a modulation optical unit 3. Thus, a plurality of pits nearly constant in pit width are formed.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order.

TECHNICAL FIELD OF THE INVENTION Conventional Technology (FIGS. 13 and 14) Problems to be Solved by the Invention (FIGS. 15 and 16)
(F)) Means for Solving the Problems Embodiments of the Invention (1) First Example (FIGS. 1 to 7 (F)) (2) Second Example (FIGS. 8 to 11 (F)) (3) Other Examples (FIG. 12) Effects of the Invention

[0003]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording method, an optical recording device and an optical recording medium, for example, a CD (Comp.
It is suitable for application to a laser cutting machine for manufacturing an optical disc such as an act disc).

[0004]

2. Description of the Related Art Conventionally, laser light has been used in the manufacture of a master for an optical recording medium such as an optical disk and a magneto-optical disk, or in the manufacture of a photoresist mask used in the manufacture of a printed wiring board and a semiconductor integrated circuit. An optical recording device is used.

FIG. 13 shows an optical recording apparatus used for producing a master of an optical recording medium such as a CD. In the optical recording device 1, for example, a laser light L1 is emitted from a laser light source 2 having a gas as an amplification medium, such as a helium-cadmium (He-Cd) laser (wavelength 441.6 [nm]), and the laser light L1 is a mirror. The light is reflected by M1 and enters the modulation optical unit 3 as parallel light.

The modulation optical unit 3 is an acousto-optic modulator (AOM: Acousto Op) made of, for example, tellurium oxide (TeO ₂ ).
tic modulator) 4, and a beam reduction lens 5 and a beam expansion lens 6 are provided in front of and behind the optical path of the acousto-optic modulator 4.
(Both have a focal length of 80 mm). The laser beam L1 incident on the modulation optical unit 3 via the mirror M1 is reduced to a predetermined beam diameter by the beam reduction lens 5, and then is incident on the acousto-optic modulator 4.

Here, as shown in FIG. 14, the acousto-optic modulator 4 is an acousto-optic medium (for example, PbMoO ₄ crystal, TeO ₂ crystal, etc.).
Piezoelectric transducer (transducer) on 4A (eg LiNb
A thin film 4B made of O ₃ , ZnO or the like is adhered. In this case, at the time of forming the pit recording, the high frequency recording signal S1 EFM-modulated in the EFM modulation circuit 7 is converted into the voltage signal S2 via the driver 8 and then input to the piezoelectric vibrator 4B of the acousto-optic modulator 4. .

In the acousto-optic modulator 4, the piezoelectric oscillator 4B converts the voltage signal S2 into an ultrasonic signal, and the refractive index of the acousto-optic medium 4A is periodically changed in the acousto-optic medium 4A. , The acousto-optic medium 4A serves as a diffraction grating for light (hereinafter,
This is called an ultrasonic diffraction grating).

In this case, in the Bragg diffraction, the lattice spacing d,
When the laser light wavelength λ and the angle θ between the laser light and the lattice plane are

[0010]

[Equation 1]

The acousto-optic modulator 4 is arranged so that the laser beam L1 can be incident at an angle θ (hereinafter, referred to as a Bragg angle) when satisfying the condition.

In this state, the laser light L1 incident on the ultrasonic wave front at the Bragg angle is diffracted only in the direction forming the same angle as the ultrasonic wave front, and the light intensity of the laser light L1 is changed according to the voltage signal S2. The modulation is intermittently performed depending on the ON state or the OFF state.

As described above, the acousto-optic modulator 4 utilizes the fact that the intensity of the first-order diffracted light in the Bragg diffraction is almost proportional to the ultrasonic power, and the ultrasonic power is transmitted to the driver 8
The optical modulation of the laser beam L1 is performed by performing modulation based on the voltage signal S2 supplied from.

Subsequently, the laser beam L1 whose intensity is modulated by the acousto-optic modulator 4 based on the voltage signal S2 is expanded by the beam expanding lens 6 to its original size, and then the laser beam L1 is expanded. The light is reflected by the mirror M2 and is incident on the lens 10 (having a focal length of 90 mm) on the moving optical table 9. Subsequently, the laser beam L1A is reflected by the mirror M3 through the lens 10 and then condensed through the objective lens 11 (numerical aperture NA = 0.9) to obtain a glass master plate with a photoresist (hereinafter referred to as a glass master plate). The photoresist film 12A coated on the surface 12 is irradiated.

Incidentally, in this case, as the photoresist film 12A applied on the glass master 12, a mercury lamp g line (wavelength: 437) which is generally used for semiconductor manufacturing is usually used.
[Nm]) compatible positive type is used.

Here, the movable optical table 9 is adapted to be movable in the radial direction of the glass master disk 12, and the glass master disk 12 is indicated by an arrow a as the output shaft of a motor (not shown) is rotationally driven. It can rotate at a constant linear velocity (CLV) in the direction shown or in the opposite direction. As a result, the photoresist film 12A of the glass master 12 is spirally irradiated with the laser light L1A, and thus the exposed portion of the laser light L1A of the photoresist film 12A is dissolved by the development process to form a pit.

Incidentally, the glass master 1 having the pits formed thereon.
By forming a mold (stamper) by plating a duplicate of No. 2 with Ni and molding transparent resin such as PMMA (polymethylmethacrylate) and PC (polycarbonate) using the mold, minute irregularities are formed. It is possible to form a transparent substrate on which (a pit pattern corresponding to a signal) is transferred. A light-reflecting metal film is provided on the surface of the transparent substrate including these pits, and a protective film is provided to protect the signal pits, whereby an optical disc such as a CD is manufactured.

[0018]

By the way, the conventional CD
In the exposure processing step when manufacturing a stamper of an optical disk such as the above, a plurality of types of pits from the shortest pit length (3T) to the longest pit length (11T) are generated by the exposure pulse corresponding to each pit length. Each is formed on the photoresist film.

In this exposure process, first, when the pits based on the exposure pulse corresponding to each pit length are formed on the g-line positive photoresist film, the pit width (radial direction) is set between the 3T pit and the 11T pit. ) Is almost unchanged.

On the other hand, the γ characteristic value is relatively high (γ
Characteristic value> 4) (that is, a high resolution type) photoresist film (hereinafter, referred to as a high gamma photoresist film). When forming the pits based on the exposure pulse corresponding to each pit length, 3T pits are formed. Even if exposure is performed with a constant amount of light from 3 to 11T pits, there is a tendency that the width of pits becomes wider at 11T pits between 3T pits and 11T pits. In practice, this tendency is due to constant linear velocity (CLV) and constant rotational velocity (CAV).
Appears in both cases of (ular Velocity).

The reason why the longer pit length becomes wider when the high gamma photoresist film is used will be described below. First, in practice, the exposure level rises in accordance with the length of the pit length formed in the photoresist film regardless of the γ characteristic value of the photoresist film. Therefore, the exposure amount is slightly smaller in the 11T pit than in the 3T pit. More. Here, when a normal photoresist film is used, even if the exposure amount slightly differs depending on the length of the pit length, the pit width is hardly affected. On the other hand, when a high gamma photoresist film is used, a slight difference in the exposure amount depending on the length of the pit length is increased with an increase in the γ characteristic value, and as a result, the pit width is affected. Will be extended. Accordingly, when a high gamma photoresist film is used, the longer the pit length, the wider the width.

Incidentally, in FIG. 15, the residual film rate (film thickness after development / coating film thickness) m and the exposure amount per unit area expressed in logarithm when a positive type photoresist film is used.
The characteristic curve K1 showing the relationship with logE is shown.

In this case, the γ characteristic value is represented by the slope of the straight line portion of the characteristic curve K1, that is, the minimum exposure amount required for exposing the photoresist film to light is E _0, and the photoresist film is completely exposed. If the maximum exposure required to expose the film to a non-film state after development is E ₁ ,

[0024]

[Equation 2]

## EQU2 ## When the straight line portion of the characteristic curve K1 is small and it is difficult to estimate the minimum exposure amount E ₀ and the maximum exposure amount E ₁ , the slope of the characteristic curve K1 near the exposure amount E _1/2 when m = _1/2. It may be expressed as.

A concrete mode in which the longer pit length is wider is shown in FIGS. 16 (A) to 16 (F). The 3T pit and the 11T pit correspond to the pit forming pulse (that is, the pulse exposure portion of the high frequency recording signal S1 corresponding to the exposure time) whose pulse widths are P _3T and P _11T based on the EFM-modulated high frequency recording signal S1, respectively. Formed (FIGS. 16A and 16D). At this time, 3T pit and 1
With 1T pits, since a high gamma photoresist film is used, the exposure level E _{11T of} 11 pits is higher than the exposure level E _{3T of} 3T pits (FIGS. 16 (B) and (E)). As a result, the pit width W _11T of the 11T pit becomes wider than the pit width W _{3T of the} 3T pit (FIGS. 16C and 16F).

Therefore, between the 3T pit and the 11T pit, the difference in signal amplitude is further widened due to the difference in the pit widths W _3T and W _11T , so that an optical disk having a stable signal amplitude is produced. There was a problem that made it difficult.

Furthermore, in order to avoid the wide 11T pit,
When the amount of exposure light is reduced as a whole, the 3T pits are not sufficiently formed, and as a result, the modulation factor of the 3T pits may not be sufficiently secured. Actually, according to the experimental results, the exposure process was performed using a high gamma photoresist film with a γ characteristic value of 5, a helium / cadmium laser light source with a wavelength of 441.6 [nm], and an objective lens with a numerical aperture NA = 0.9. In case of doing, the pitch width of 3T pit is 0.27
A value of 0.35 [μm] is obtained for the pitch width of [μm] and 11T pits. This means that there is a difference of about 20% or more between the 3T pit and the 11T pit.

On the other hand, when the exposure process is performed using a normal photoresist film having a γ characteristic value of 2.7, the 3T-pit width is 0.58 [μm] and the 11T-pit width is 0.60 [μm]. .mu.m] is obtained. This means that there is almost no difference in the pit width between the 3T pit and the 11T pit.

As one method for solving such a problem that the difference in the width of the pits occurs, when the pits based on the exposure pulse corresponding to each pit length are formed in the high gamma photo resist film, when the pits are 11T, A method is used in which the exposure light amount is reduced and the exposure is performed by modulating the light amount so that the pitch width becomes the same as the 3T pitch.

However, according to this method, although CLV exposure can be performed, in the case of CAV exposure, since the exposure light amount is modulated by changing the radial position,
It is necessary to further control the modulated signal, and there is a problem that the whole apparatus becomes complicated.

The present invention has been made in consideration of the above points, and an optical recording method, an optical recording apparatus, and an optical recording capable of performing exposure so that the width of the latent image becomes substantially constant regardless of the length of the latent image. It is intended to propose a medium.

[0033]

In order to solve the above problems, according to the present invention, the intensity of laser light emitted from a laser light source is modulated by an optical modulator according to a modulation pulse signal based on a predetermined format. After that, by irradiating the exposed surface of the exposed body with the intensity-modulated laser light, an optical recording method for forming an exposure pattern composed of a plurality of latent images of various lengths according to the modulation pulse signal, In an optical recording device and an optical recording medium, each pulse-exposed portion of a modulated pulse signal is converted into a pulse train set to a predetermined pulse width and repeated in the same cycle, and driving based on the modulated pulse signal converted into each pulse train A signal is supplied to the optical modulator to drive and control the optical modulator.

Further, in the present invention, each pulse exposed portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and the signal level of each pulse exposed portion after the conversion is converted. Is adjusted according to the length of each pulse-exposed portion before conversion.

Further, in the present invention, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and is assigned to each pulse exposure portion after the conversion. The sum of each pulse width of the pulse train is adjusted according to the length of each pulse exposed portion before conversion.

Further, in the present invention, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and the pulse divided into windows after the conversion. Each pulse width of the pulse train corresponding to each window in the exposed portion is adjusted according to the length of each pulse exposed portion before conversion.

Further, in the present invention, when converting each pulse exposure portion of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, the pulse train assigned to each pulse exposure portion is converted. The first or last pulse is erased.

Further, in the present invention, the exposed body is made of a photoresist having a γ characteristic value of greater than 4 coated on the master.

Further, in the present invention, the sum of the pulse widths of the pulse trains assigned to the pulse exposed portions of the modulated pulse signal is 10% to 75% with respect to the pulse exposed portions.
It should be included in the ratio of [%].

In this way, when an exposure pattern consisting of a plurality of latent images of various lengths is formed on the exposed surface of the exposed body, all latent images are substantially the same regardless of the length of each latent image. The width of the latent image can be prevented from being wider than that of the latent image having a longer length than that of the latent image having a shorter length.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment In FIG. 1 in which parts corresponding to those in FIG. 9 are assigned the same reference numerals, the optical recording device 20 differs from the optical recording device 1 shown in FIG. 9 in that the EFM modulation circuit 21 and the driver. It has substantially the same configuration except that the pulse train conversion circuit 22 is provided between the eight.

In this case, as shown in FIG. 2 in which parts corresponding to those in FIG.
The modulation circuit 21 uses the EFM-modulated high frequency recording signal S1.
Not only the channel clock signal CHCK0 is also supplied to the pulse train conversion circuit 22.

As shown in FIG. 3, the pulse train conversion circuit 22
In the first delay circuit 30 is the time from the rising time t ₁ of the logic "H" of the channel clock signal CHCK0 t
After delaying to _two , this is delayed by the delayed clock signal CHCK.
1 to the edge extraction and inversion circuit 31 (see FIG. 4).
(A) and (C)).

The edge extracting and inverting circuit 31 extracts a predetermined time from the rising time t2 of the logic "H" of the delayed clock signal CHCK1 and then inverts the inverted clock signal to generate a _second clock signal CHCK2 as the second delay circuit 32 and JK. It is supplied to the set input terminal of the mold flip-flop circuit 33 (FIG. 4D).

[0046] The second delay circuit 32, the time from the rising time t ₂ of the logic "H" of the Kurotsukuetsuji signal CHCK2 t
After delayed until _3, delays this Kurotsukuetsuji signal C
HCK3 is supplied to the reset input terminal of the JK flip-flop circuit 33 (FIG. 4E).

The JK type flip-flop circuit 33 is
Together it rises to a logic "H" at the fall of Kurotsukuetsuji signal CHCK2 (time t _2), clock pulses signal CHCK4 which falls to logic "L" is obtained as Q output at the rise of the delayed Kurotsukuetsuji signal CHCK3 (time t _3), This is given to one input terminal of the AND circuit 34 (FIG. 4 (F)).

On the other hand, in the pulse train conversion circuit 22, D
The type flip-flop circuit 35 receives the channel clock signal CHCK0 from the EFM modulation circuit 21 at its clock input terminal and the high frequency recording signal S1 at its data input terminal (FIGS. 4A and 4B). This D-type flip-flop circuit 35 generates a channel clock signal CHCK0.
It is triggered at the rising time t _1, giving the synchronization frequency recording signal S10 in synchronization with the high-frequency recording signal S1 to the channel clock signal CHCK0 other input terminal of the AND circuit 34 (FIG. 4 (G)).

The AND circuit 34 operates from the time point t ₁ to the time point t ₁ when the synchronized high frequency recording signal S10 rises to the logic "H".
After passing the clock pulse signal CHCK4 up to ₆ , it is used as the pulse train conversion signal S11 by the driver 8
(FIG. 4 (H)).

As described above, the pulse train conversion signal S11 has a window (1T or 3T pits) of a pulse forming pulse based on the high frequency recording signal S1 (that is, a pulse exposure portion of the high frequency recording signal S1 corresponding to the exposure time).
It is converted into a pulse train for every 1 / 1th or 1 / 11T bit, and the waveform is displayed as a pulse train in which the same pulse set to a predetermined pulse width is periodically repeated.

For example, as shown in FIG. 5A, the 3T pit is formed in accordance with the pit forming pulse having a pulse width of P _3T based on the EFM-modulated high frequency recording signal S1.

A pulse width P _{1T obtained} by _{reducing the} pulse width P _3T to 1/3 (hereinafter, referred to as one window width) P _1T is one pulse width by converting the high frequency recording signal S 1 into the pulse train conversion signal S 11. The number of pulses P _1T ′ is converted into a pulse train of 3 (FIG. 5 (B)).

At this time, a duty (duty) ratio is defined as a value obtained by standardizing one pulse width P _1T ′ with one window width P _1T , and the duty ratio is one window width P _1T.
And the ratio (P _1T '/ P _1T ) of the pulse width P _1T ' after being converted into a pulse train. According to the experiment, by setting the duty ratio between 10% and 75%, it is possible to obtain a result that the uniformity of the pit width can be maintained between the 3T bit and the 11T bit.

Subsequently, in the driver 8, the voltage signal S12 based on the pulse train conversion signal S11 is supplied to the acousto-optic modulation deflector 4.
To supply.

In the acousto-optic modulation deflector 4, the piezoelectric vibrator 4B converts the voltage signal S12 into an ultrasonic wave signal, and the acousto-optic medium 4A in the acousto-optic medium 4A.
The acousto-optic medium 4A plays a role of an ultrasonic diffraction grating for light by periodically changing the refractive index of. In the Bragg diffraction, the acousto-optic modulator / deflector 4 is arranged so that the laser beam L1 can enter at the Bragg angle (equation (1)).
To place.

In this state, the laser light L1 incident on the ultrasonic wave front at the Bragg angle is diffracted only in the direction forming the same angle as the ultrasonic wave front, and the light intensity of the laser light L1 is changed according to the voltage signal S12. The modulation is intermittently performed depending on the ON state or the OFF state. Further, by changing the frequency of the ultrasonic waves, the grating interval d of the ultrasonic diffraction grating is changed, that is, the Bragg angle is changed, and as a result, the angle of light deflection of the laser light L1X can be changed.

Subsequently, the laser light L1X, whose intensity is modulated by the acousto-optic modulation deflector 4 on the basis of the voltage signal S12 and whose light deflection angle is changed, keeps the beam horizontal height of the laser light L1 and keeps the lens horizontal. It is reflected by the mirror M3 via 11. The laser light L1X reflected by the mirror M3 is condensed via the objective lens 12 and is applied to the photoresist film 14 applied on the glass master disk 13.

Here, in FIG. 6, the table shows each of the 3T and 11T pit widths corresponding to the change of the duty ratio. According to this table, the duty ratio is 12.5 [%]
In this case, the widths of the 3T and 11T pits are 0.36 [μm] and 0.37 [μm], respectively. When the duty ratio is 30%, the widths of the 3T pit and the 11T pit are 0.40 [μm] and 0.41 [μm], respectively.
Furthermore, when the duty ratio is 50%, 3T pitch and 1
The 1T pit width is 0.38 [μm] and 0.40, respectively.
[Μm] In this way, the duty ratio is 12.5 [%]
From 50 to 50%, the difference between the width of the 3T pit and the width of the 11T pit is 5% or less, and the 3T pit and the 11T pit can sufficiently maintain the uniformity of the pit width.

However, when the duty ratio is 80%, the pitch widths of the 3T and 11T pits are respectively.
It becomes 0.36 [μm] and 0.40 [μm], and the difference between the width of the 3T pit and the width of the 11T pit is 10 [%], which means that there is some difference. Therefore, according to the experimental results,
By setting the duty ratio between 10% and 75%, it is possible to maintain the uniformity of the pit width between the 3T pit and the 11T pit.

In the above configuration, by converting the EFM-modulated high frequency recording signal S1 into the pulse train conversion signal S11, as shown in FIGS. 7A to 7F, the 3T and 11T bits are respectively pulsed. The pit forming pulse having a width of P _3T and P _11T is converted into 3 and 11 pulse trains having a pulse width of P _1T ′ for each window, respectively (FIGS. 7A and 7D). In this case, the duty ratio is preset between 10 [%] and 75 [%].

At this time, regardless of the pit length, by repeatedly exposing each window (1T pit) with one pulse width P _1T ′, the exposure corresponding to the length of the pit length when a high gamma photoresist film is used. It is possible to avoid increasing the difference in quantity. As a result, 3T
The exposure level E _3T ′ of the pit and the exposure level E _11T ′ of the 11T pit show almost the same numerical value (FIG. 7).
(B) and (E)). Therefore, even when the high gamma photoresist film is used, the pitch width W _3T ′ of the 3T pit is 1 Wt.
The 1T pit width W _11T ′ can be made almost the same pit width (W _3T ′ = W _11T ′) (FIG. 7C).
And (F)).

In this way, when a plurality of types of pits from 3T pits to 11T pits are formed on the high gamma photo resist film, all pit widths can be made almost the same regardless of each pit length. Thus, it is possible to prevent the pit width from becoming wider with a longer pit length than with a shorter pit length.

Thus, after making a die (stamper) from the glass master 12 on which a plurality of types of pits having a substantially constant pit width regardless of such pit length are formed,
By manufacturing an optical disk such as a CD based on the mold, the signal characteristics of the reproduction signal obtained from the optical disk can be significantly improved.

Further, in the optical recording device 20, a high gamma photoresist film having a γ characteristic value = 6 is used, and the recording density (track pitch 0.8
[Μm], the length of the 3T pit is 0.41 [μm]) and the exposure ratio is 50%, the pit width of the 3T pit is 0.29 [μm] and 11T.
The pit width of the pit is 0.31 [μm].
This means that there is almost no difference in the pit width between the 3T pit and the 11T pit, so that the present invention is applied to a pit with a small pit width such as a recording density of 4 times. be able to.

According to the above construction, 11 from 3T pits
When a plurality of types of pits up to T pits are formed on the high gamma photo resist film, the pulse width of the pit forming pulse corresponding to each pit is set to a predetermined number with a short pulse width for each window (1T pit). By converting to a pulse train, it is possible to realize an optical recording apparatus capable of performing exposure so that the pit width becomes substantially constant regardless of the pit length.

(2) Second Embodiment In FIG. 8 in which parts corresponding to those in FIG. 1 are designated by the same reference numerals, the optical recording device 40 differs from the optical recording device 20 in the first embodiment in a pulse train conversion circuit 41. It has almost the same configuration except that the configuration is different. That is, as shown in FIG. 9 in which parts corresponding to those in FIG. 2 are assigned the same reference numerals, the pulse train conversion circuit 41 includes a high frequency recording signal S1 and a channel clock signal CHCK supplied from the EFM modulation circuit 21.
Based on 0, the pulse train conversion signal S21 whose signal level is changed according to the length of the pit is supplied to the driver 8.

This driver 8 has a pulse train conversion signal S2.
The voltage signal S22 based on 1 is supplied to the acousto-optic modulator 4.

In this case, the pulse train conversion signal S21 is the same pulse as the pulse train conversion signal S11 (FIGS. 1 and 2) in which the high frequency recording signal S1 is periodically repeated with the same pulse set to a predetermined pulse width. It is converted into a pulse train. As a result, the exposure light amount of the laser light L1 that is intensity-modulated in the acousto-optic modulator 4 based on the voltage signal S22 changes according to the duty ratio.

Therefore, the pulse train conversion circuit 41 adjusts the signal level of the pulse train conversion signal S21,
The exposure light amount of the laser light L1 is adjusted.

Here, as an experimental result, in FIG.
The duty ratio is set to 50% and the pulse widths of the respective pulse lengths when the signal level of the pulse train conversion signal S21 is changed corresponding to the respective pulse lengths are shown in the table. FIG.
According to the table shown in 0, the pit width of each pit length is 0.30 [μ
m], the signal level of the pulse train conversion signal S21 is 1.0 [V] at 3T pits, 0.8 [V] at 5T pits, 7T pits, 9T pits and 1
At 1T pit, it may be adjusted to 0.75 [V]. Thus, according to the experimental results, in order to always keep the pit width of each pit constant, it is sufficient to lower the signal level of the pulse train modulation signal S21 as the pit length becomes longer.

In the above structure, by converting the EFM-modulated high frequency recording signal S1 into the pulse train conversion signal S21, as shown in FIGS.
In the pits and 11T pits, the pit forming pulses having pulse widths P _3T and P _11T , respectively, are converted into 3 and 11 pulse trains each having a pulse width P _1T ′ for each window (FIG. 11 (A ) And (D)). In this case, the duty ratio is preset to 50 [%].

At this time, each pit is repeatedly exposed with one pulse width P _1T ′ for each window (1T pit), and at the same time, the signal level of the pulse train conversion signal S21 (that is, pulse train conversion) corresponding to the pit length of each pit. By adjusting the signal level of the generated pit forming pulse), it is possible to prevent the difference in the exposure amount depending on the length of the pit length from increasing when a high gamma photoresist film is used, and to increase the pit length. Nevertheless, the pit width can always be kept constant.

That is, in the pulse train conversion signal S21, the signal level V _{3T at 3T} pits and the signal level V _11T at 11T pits are lower than the signal level V _11T at 11T pits (V _3T > V _11T ) (FIGS. 11A and _11D ), and as a result,
3T pits 'exposure levels E _11T and 11T pits' exposure levels E _3T of, and thus showing the same number (11
(B) and (E)).

Therefore, even when the high gamma photoresist film is used, the pit width W _3T ′ of _3T pit and the pit width W _11T ′ of 11T pit are almost the same (W _3T ′).
= W _11T ′) (FIGS. 11C and 11F).

In this way, when a plurality of types of pits from 3T pits to 11T pits are formed on the high gamma photo resist film, the same pit width can be set regardless of each pit length. Thus, it is possible to prevent the pit width from becoming wider with a longer pit length than with a shorter pit length.

According to the above construction, 11 from 3T
When a plurality of types of pits up to T pits are formed on the high gamma photo resist film, the pulse width of the pit forming pulse corresponding to each pit is set to a predetermined number with a short pulse width for each window (1T pit). By converting to a pulse train and adjusting the signal level of the pit forming pulse converted to a pulse train corresponding to the pit length of each pit, exposure is performed so that the pit width is always constant regardless of each pit length. The obtained optical recording device can be realized.

(3) Other Embodiments In the above-mentioned embodiments, the case where the helium / cadmium (He-Cd) laser is used as the laser light source 2 has been described, but the present invention is not limited to this, and argon ( Ar ⁺ )
A gas laser such as a laser and a krypton (Kr ⁺ ) laser may be used. Further, in the above-described embodiments, the case where the present invention is applied to a CD as an optical recording medium for forming a pit has been described, but the present invention is not limited to this, and for example, a high density optical disc (DVD: Digital Versatile Disc) or the like. May be applied to.

In this case, the signal input to the acousto-optic modulator 4 via the driver 8 is EFM-modulated (8 → 14 modulation: Eigh).
t to Fourteen Modulation) High-frequency recording signal S1
Rather than EFM plus modulation (8 → 16 modulation: Eight to S
It is necessary to set the high-frequency recording signal (not shown) subjected to ixteen modulation.

Further, the present invention is not limited to the optical disc, but may be applied to other optical elements such as an optical card.

Further, in the above-mentioned embodiment, the case of manufacturing the stamper of the optical disc such as the CD is described, but the present invention is not limited to this, and may be applied to the case of manufacturing the photomask, for example. By using the present invention, it is possible to form a high-performance photomask pattern whose width is almost constant regardless of the length of the pit.

Further, in the above-described embodiment, the pulse train conversion signal S obtained from the pulse train conversion circuits 22 and 41 is used.
11 and S21 are respectively stored in a memory (not shown), and when a plurality of types of 3T to 11T pits are formed on the high gamma photoresist film, pulse train conversion signals S11 and S2 from each memory are formed.
1 may be read. In this case, by temporarily storing the pulse train conversion signals S11 and S21 in the memory, mechanical control during exposure recording can be omitted and the transfer rate for the driver 8 can be adjusted.

Further, in the above-mentioned embodiments, the case where the high γ photoresist film 12A is applied as the organic material having the γ characteristic value of greater than 4 applied on the glass master 12 has been described. Not limited to, for example, γ
It is also possible to use an organic dye system having a characteristic value of more than 4 and subject the organic dye system to pulse exposure according to the present invention to form a desired uneven pattern.

Further, in the above-mentioned embodiment, the case where the acousto-optic modulator (AOM) 4 is used as the optical modulator has been described, but the present invention is not limited to this, and for example, an electro-optic modulator (EOM: Electro Optic). Other optical modulators such as a modulator) may be used.

Furthermore, in the above-mentioned embodiment, the case where the glass master disk 12 is rotated by the CLV along with the rotational driving of the output shaft of the motor (not shown) has been described, but the present invention is not limited to this, and the glass master disk is not limited thereto. The present invention can be applied even if 12 is rotated by CAV.

Further, in the second embodiment, the case where the duty ratio is set to 50 [%] has been described, but the present invention is not limited to this, and the duty ratio is set to a desired value such as 33.3 [%]. It may be done. In short, regardless of the value of the duty ratio, the signal level of the pulse train conversion signal S21 may be adjusted according to the pit length of each pit.

Furthermore, in the second embodiment, the EFM-modulated high-frequency recording signal S1 is converted into the pulse train conversion signal S21, and the signal level of the pulse train conversion signal S21 is adjusted according to the pitch length of each pit. However, the present invention is not limited to this, and the first or last pulse of the pulse train conversion signal S21 (that is, the first or last pulse of the pulse train converted pit forming pulse) may be erased.

That is, by eliminating the first or last pulse of the pulse forming pulse-converted pit forming pulse, when multiple exposure is repeatedly performed with a predetermined pulse width for each window, a multiple component of the exposure amount generated between adjacent pulses is removed. You can As a result, it is possible to avoid increasing the difference in exposure amount depending on the length of the pit length when a high gamma photoresist film is used, and it is possible to always keep the pit width constant regardless of the pit length. .

Specifically, in the optical recording device 40, γ
Using a high gamma photoresist film with a characteristic value of 6,
4 times the recording density (track pitch
0.74 [μm], 3T pit length 0.40 [μm])
Then, the high frequency recording signal S1 stored in the hard disk memory is converted into the pulse train conversion signal S21 and exposure processing is performed so that the duty ratio becomes 50%. In this case, the table of FIG. 12 shows the width of each pulse length when the signal level of the pulse train conversion signal S21 is changed corresponding to each length as in the second embodiment.

Thus, according to the table shown in FIG. 12, the signal level of the pulse train conversion signal S21 is 1.0 [V] at 3T pits, 0.7 [V] at 5T pits, and 0.67 at 7T pits. [V], 9T and 11T pits are adjusted to 0.65 [V], that is, as the pit length becomes longer, the pit width is adjusted to 0.28 [μm]. Can be set. As a result, the present invention can be applied to a pit having a minute pit width such as a recording density of 4 times.

Further, in the second embodiment, the EFM-modulated high frequency recording signal S1 is converted into the pulse train conversion signal S21, and the signal level of the pulse train conversion signal S21 is adjusted according to the pitch length of each pit. Although the present invention is not limited to this, the present invention is not limited to this, and the high frequency recording signal S1 is converted into the pulse train conversion signal S21, and the duty ratio is adjusted according to the pitch length of each pit. The same effect can be obtained.

That is, the duty ratio can be adjusted by adjusting the pulse width of the pulse train conversion signal S21 corresponding to the pit length of each pit, and as a result, the case where the signal level of the pulse train conversion signal S21 is adjusted. Similarly, the exposure light amount of the laser light L1 can be adjusted.
Thus, also in this case, the exposure can be performed so that the pit width is always constant regardless of the pit length.

[0092]

As described above, according to the present invention, the laser light emitted from the laser light source is intensity-modulated in accordance with a modulation pulse signal based on a predetermined format using an optical modulator, and then the intensity modulation is performed. Recording method, optical recording device and optical recording method for forming an exposure pattern composed of a plurality of latent images of various lengths according to a modulated pulse signal by irradiating the exposed surface of an exposed object with the generated laser light In the recording medium, each pulse-exposed portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and a drive signal based on the modulated pulse signal converted into each pulse train is used as an optical modulator. And an optical recording method capable of performing exposure control so that the width of the latent image becomes substantially constant regardless of the length of the latent image by controlling the drive of the optical modulator. It is possible to realize a recording apparatus and optical recording medium.

Further, according to the present invention, each pulse exposure portion of the modulated pulse signal is converted into a pulse train which has a predetermined pulse width and is repeated in the same cycle.
By adjusting the signal level of each pulse-exposed portion after the conversion according to the length of each pulse-exposed portion before conversion, the width of the latent image is always constant regardless of the length of the latent image. It is possible to realize an optical recording method, an optical recording device, and an optical recording medium that can be exposed to light.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an optical recording device in a first embodiment.

FIG. 2 is a schematic diagram showing a configuration of an acousto-optic modulator in the first example.

FIG. 3 is a block diagram showing the configuration of a pulse train conversion circuit in the first embodiment.

FIG. 4 is a signal waveform diagram for explaining the operation of the pulse train conversion circuit shown in FIG.

FIG. 5 is a signal waveform diagram for explaining a duty ratio.

FIG. 6 is a chart showing the relationship between changes in duty ratio and pit width.

FIG. 7 is a schematic diagram showing an exposure state of a 3T pit and an 11T pit according to the first embodiment.

FIG. 8 is a block diagram showing a configuration of an optical recording device in a second embodiment.

FIG. 9 is a schematic diagram showing a configuration of an acousto-optic modulator in a second example.

FIG. 10 is a chart showing a relationship between a pit length and a corresponding signal level.

FIG. 11 is a schematic diagram showing an exposure state of a 3T pit and an 11T pit according to the second embodiment.

FIG. 12 is a chart showing a relationship between a pit length and a corresponding signal level.

FIG. 13 is a block diagram showing the configuration of a conventional optical recording device.

FIG. 14 is a schematic diagram showing a configuration of a conventional acousto-optic modulator.

FIG. 15 is a characteristic curve diagram showing a γ characteristic value.

FIG. 16 is a schematic diagram showing an exposure state of a conventional 3T pit and 11T pit.

[Explanation of symbols]

1, 20, 40 ... Optical recording device, 2 ... Laser light source,
3 ... Modulation optical unit, 4 ... Acousto-optic modulator, 5 ...
… Beam reduction lens, 6… Beam expansion lens, 7, 2
1 ... EFM modulation circuit, 8 ... Driver, 9 ... Moving optical table, 10 ... Lens, 11 ... Objective lens, 1
2 ... Glass master, 12A ... Photoresist film, 2
1, 41 ... Pulse train conversion circuit, M1, M2, M3 ...
mirror.

Claims (39)

[Claims] 1. A laser beam emitted from a laser light source is intensity-modulated using an optical modulator in accordance with a modulation pulse signal based on a predetermined format, and the intensity-modulated laser beam is exposed on an object to be exposed. In an optical recording method for forming an exposure pattern consisting of a plurality of latent images of various lengths according to the modulated pulse signal by irradiating the exposed surface, each pulse exposed portion of the modulated pulse signal is given a predetermined value. The first step of converting each pulse train into a pulse train having a pulse width and repeating in the same cycle, and a drive signal based on the modulated pulse signal converted into each pulse train are supplied to the optical modulator, and the optical modulator. And a second step for controlling the drive of the optical recording method. 2. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. 2. The optical recording method according to claim 1, wherein the signal level of the portion is adjusted according to the length of each pulse-exposed portion before the conversion. 3. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. 2. The optical recording method according to claim 1, wherein the sum of the pulse widths of the pulse trains assigned to the portions is adjusted according to the length of each pulse exposed portion before the conversion. 4. In the first step, each pulse-exposed portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same period, and each converted window is converted. 2. The optical recording according to claim 1, wherein each pulse width of the pulse train corresponding to each window in the divided pulse exposed portion is adjusted according to the length of each pulse exposed portion before the conversion. Method. 5. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. The sum of the signal levels of the portions and the pulse widths of the pulse trains assigned to the pulse-exposed portions after the conversion is adjusted according to the length of the pulse-exposed portions before the conversion. Item 2. The optical recording method according to Item 1. 6. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. The signal level of the portion and each pulse width of the pulse train corresponding to each window in the pulse exposure portion divided for each window after the conversion are adjusted according to the length of each pulse exposure portion before the conversion. The optical recording method according to claim 1, wherein: 7. In the first step, when each pulse-exposed portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, each pulse-exposed portion is converted into a pulse train. The optical recording method according to claim 1, wherein the first or last pulse of the assigned pulse train is erased. 8. The modulated pulse signal is EFM modulated or E
The optical recording method according to claim 1, wherein the recording signal is FM plus modulated. 9. The optical recording method according to claim 1, wherein the object to be exposed is made of an organic material having a γ characteristic value of greater than 4 applied on a master. 10. The sum of the pulse widths of the pulse trains assigned to the pulse exposure portions of the modulated pulse signal is included in the pulse exposure portion at a rate of 10 [%] to 75 [%]. The optical recording method according to claim 1, wherein 11. The object to be exposed is γ coated on a master.
The sum of pulse widths of the pulse trains assigned to the pulse-exposed portions of the modulated pulse signal is 10% to 75 [%] with respect to the pulse-exposed portions. ] The optical recording method according to claim 1, wherein the optical recording method is included. 12. The pulse width of the pulse train corresponding to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10% to 75% with respect to the window. ] The optical recording method according to claim 1, wherein the optical recording method is included. 13. The object to be exposed is γ coated on a master.
Each pulse width of the pulse train, which is made of an organic material having a characteristic value larger than 4, and which corresponds to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10 with respect to the window. [%] ~
The optical recording method according to claim 1, wherein the optical recording method is contained in a ratio of 75 [%]. 14. A laser light emitted from a laser light source is intensity-modulated by an optical modulator according to a modulation pulse signal based on a predetermined format, and the intensity-modulated laser light is applied to an object to be exposed. In an optical recording device that forms an exposure pattern consisting of a plurality of latent images of various lengths according to the modulated pulse signal by irradiating the exposed surface, each pulse exposed portion of the modulated pulse signal is The pulse train is set to a pulse width and is converted into a pulse train that is repeated in the same cycle, and a drive signal based on the modulated pulse signal that is converted into each pulse train by the pulse train converter is supplied to the optical modulator. And a drive control means for controlling the drive of the optical modulator. 15. The pulse train converting means converts each pulse-exposed portion of the modulated pulse signal into a pulse train which has a predetermined pulse width and is repeated in the same cycle, and each pulse-exposed portion after the conversion. 15. The optical recording apparatus according to claim 14, wherein the signal level of is adjusted according to the length of each pulse exposed portion before the conversion. 16. The pulse train converting means converts each pulse-exposed portion of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse-exposed portion after the conversion. 15. The optical recording apparatus according to claim 14, wherein the sum of the pulse widths of the pulse trains assigned to the pulse train is adjusted according to the length of each pulse exposed portion before the conversion. 17. The pulse train converting means converts each pulse-exposed portion of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, and divides each converted window. 15. The optical recording apparatus according to claim 14, wherein each pulse width of the pulse train corresponding to each window in the pulse exposed portion is adjusted according to the length of each pulse exposed portion before the conversion. . 18. The pulse train converting means converts each pulse exposure part of the modulated pulse signal into a pulse train which has a predetermined pulse width and is repeated in the same cycle, and each pulse exposure part after the conversion. And the sum of the pulse widths of the pulse trains assigned to the converted pulse-exposed portions is adjusted according to the length of the pulse-exposed portions before the conversion. 14. The optical recording device according to 14. 19. The pulse train converting means converts each pulse-exposed portion of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse-exposed portion after the conversion. Signal level and each pulse width of the pulse train corresponding to each window in the pulse exposure portion divided for each window after the conversion according to the length of each pulse exposure portion before the conversion. The optical recording device according to claim 14, wherein: 20. The pulse train converting means, when converting each pulse exposure part of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, is assigned to each pulse exposure part. The optical recording apparatus according to claim 14, wherein the first or last pulse of the pulse train to be erased is erased. 21. The optical recording apparatus according to claim 14, wherein the modulated pulse signal is a recording signal that is EFM-modulated or EFM-plus-modulated. 22. The object to be exposed is γ coated on a master.
The optical recording device according to claim 14, wherein the optical recording device is made of an organic material having a characteristic value greater than 4. 23. The sum of the pulse widths of the pulse trains assigned to the pulse exposure portions of the modulated pulse signal is included in the pulse exposure portion at a rate of 10 [%] to 75 [%]. The optical recording device according to claim 14, wherein: 24. The object to be exposed is γ coated on a master.
The sum of pulse widths of the pulse trains assigned to the pulse-exposed portions of the modulated pulse signal is 10% to 75 [%] with respect to the pulse-exposed portions. ] The optical recording device according to claim 14, wherein the optical recording device is included. 25. Each pulse width of the pulse train corresponding to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10% to 75% with respect to the window. ] The optical recording device according to claim 14, wherein the optical recording device is included. 26. The object to be exposed is γ coated on a master.
Each pulse width of the pulse train, which is made of an organic material having a characteristic value larger than 4, and which corresponds to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10 with respect to the window. [%] ~
15. It is contained in a ratio of 75 [%].
The optical recording device according to. 27. A laser beam emitted from a laser light source is intensity-modulated in accordance with a modulation pulse signal based on a predetermined format using an optical modulator, and then the intensity-modulated laser beam is applied to an object to be exposed. By irradiating the exposed surface, an optical recording medium produced based on a mold obtained by forming an exposure pattern composed of a plurality of latent images having various lengths according to the modulated pulse signal, A first step for converting each pulse-exposed portion of the pulse signal into a pulse train having a predetermined pulse width and being repeated in the same cycle, and a drive signal based on the modulated pulse signal converted into each pulse train are used as the optical signals. An optical recording medium produced by being supplied to a modulator and undergoing a second step for controlling the drive of the optical modulator. 28. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. 28. The optical recording medium according to claim 27, wherein the signal level of the portion is adjusted according to the length of each pulse-exposed portion before the conversion. 29. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. 28. The optical recording medium according to claim 27, wherein the sum of the pulse widths of the pulse trains assigned to the portions is adjusted according to the length of each pulse exposed portion before the conversion. 30. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each converted window is converted. 28. The optical recording according to claim 27, wherein each pulse width of the pulse train corresponding to each window in the divided pulse exposure portion is adjusted according to the length of each pulse exposure portion before the conversion. Medium. 31. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train which has a predetermined pulse width and is repeated in the same cycle, and each pulse exposure after the conversion. The sum of the signal levels of the portions and the pulse widths of the pulse trains assigned to the pulse-exposed portions after the conversion is adjusted according to the length of the pulse-exposed portions before the conversion. Item 28. The optical recording medium according to item 27. 32. In the first step, each pulse exposure portion of the modulated pulse signal is converted into a pulse train having a predetermined pulse width and repeated in the same cycle, and each pulse exposure after the conversion is performed. The signal level of the portion and each pulse width of the pulse train corresponding to each window in the pulse exposure portion divided for each window after the conversion are adjusted according to the length of each pulse exposure portion before the conversion. The optical recording medium according to claim 27, wherein: 33. In the first step, when converting each pulse-exposed portion of the modulated pulse signal into a pulse train having a predetermined pulse width and repeated in the same cycle, each pulse-exposed portion is converted into a pulse train. 28. The optical recording method according to claim 27, wherein the first or last pulse of the assigned pulse train is erased. 34. The optical recording medium according to claim 27, wherein the modulated pulse signal is a recording signal that is EFM-modulated or EFM-plus-modulated. 35. The object to be exposed is γ coated on a master.
The optical recording medium according to claim 27, wherein the optical recording medium is made of an organic material having a characteristic value greater than 4. 36. The sum of the pulse widths of the pulse trains assigned to the pulse exposure portions of the modulated pulse signal is contained in a ratio of 10 [%] to 75 [%] with respect to the pulse exposure portions. The optical recording medium according to claim 27, wherein: 37. The object to be exposed is γ coated on a master.
The sum of pulse widths of the pulse trains assigned to the pulse-exposed portions of the modulated pulse signal is 10% to 75 [%] with respect to the pulse-exposed portions. ] The optical recording medium according to claim 27, wherein the optical recording medium is contained in the following ratio. 38. Each pulse width of the pulse train corresponding to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10% to 75% with respect to the window. ] The optical recording medium according to claim 27, wherein the optical recording medium is contained in the following ratio. 39. The object to be exposed is γ coated on a master.
Each pulse width of the pulse train, which is made of an organic material having a characteristic value larger than 4, and which corresponds to each window obtained by dividing each pulse exposure portion of the modulated pulse signal for each window is 10 with respect to the window. [%] ~
28. It is contained in a ratio of 75%.
4. The optical recording medium according to claim 1.