JPS61144735A - Optical recording device - Google Patents

Abstract

PURPOSE:To equalize the pitch of a disk between the inner peripheral part and inner peripheral part by making a successively laminated recording layer constant in thickness and decreasing the thickness of a highly heat-conductive layer from the inner periphery to the outer periphery. CONSTITUTION:Rectangular recording laser light 5a or step-shaped recording laser light 5b is projected on the optical disk which rotates at a constant rotating speed through a lens 4. The optical disk consists of a transparent substrate 1, the recording layer 2, and the highly heat-conductive layer 3. When information is recorded with the recording laser light 5, the linear speed is low at the inner peripheral part, so its temperature rises as compared with the outer peripheral part. For the purpose, the highly heat-conductive layer 3 having high heat conductivity like metal is made thick at the inner peripheral part and then heat conducted from the recording layer 2 to the highly heat-conductive layer 3 is large in value at the inner peripheral part, so the inner peripheral part and outer peripheral part become equal in temperature. The temperature when the step-shaped laser light 5b is used is a little bit lower than that when the rectangular laser light 5a is used, so the precision of pit size is improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical recording device.

[Conventional technology]

2. Description of the Related Art In recent years, commercialization and development of optical recording devices, especially optical disk devices, as a type of large-capacity memory have been active. Currently, the following optical recording media are being commercialized or under development: (1) perforation recording, (2) pulp forming recording, (2) phase transformation recording, and (2) magneto-optical recording. In commercialized optical disk devices, these recording materials are formed on a substrate so that there is no unevenness in thickness or unevenness in physical properties, and recording is performed by irradiating this optical recording medium with rectangular laser pulses. However, when recording with rectangular pulses, the heat is biased in the direction of laser beam movement, so the actual recorded bits and ideal bits deviate in the length direction.Also, in the case of 0AV (constant angular velocity) Because the relative speed between the laser beam and the disk is greater at the outer periphery and smaller at the inner periphery, the temperature of one irradiated area is higher at the inner periphery.Therefore, the bits on the inner periphery are higher than the bits on the outer periphery. As the width increases, the deviation in the length direction also increases.As the bit width increases, crosstalk occurs between adjacent tracks and the S/N deteriorates.S/N deterioration causes read errors.On the other hand, Bit misalignment also causes read errors, which are a big problem when using optical discs as data memory for combinators.

A patent to solve this problem has been filed by Philips Corporation (Japanese Patent Laid-Open No. 116946/1983). The gist of this patent is that as shown in FIG. 2(α)I(j5), when a bit is formed, the intensity of the reflected light 100 from the optical disk decreases, so this reflected light 100 is detected during recording,
This value is compared with a predetermined value using a comparator, and when the value falls below this value, the intensity of the recording laser beam 101 is automatically reduced. That is, this is a method in which the time Y of the recording laser beam is adjusted over the entire surface of the disk.

[Problem that the invention seeks to solve]

However, in the above-mentioned Philips patent, since the powers P and P' of the recording laser beam are constant over the entire surface of the disk, nonuniform bit width and bit shift tend to occur when the irradiation time 'rp is long.

The reason for this will be explained with reference to FIGS. 3(W), (A)I(C). Reference numeral 102 indicates a recording laser beam at the outer circumference, and reference numeral 103 indicates a recording laser beam at one local area. The second half of the recording laser beam is 1
This is equivalent to the rectangular wave shown in 04. This is because there is almost no influence of heat due to the power P at the tip in the latter half of 'rp. When recording with a rectangular wave, the temperature is higher in the inner circumference because the speed is slower. As a result, nonuniform pitch F width and bit deviation occur in the latter half of the bit. In the method of reducing the recording laser light intensity in response to the reflected light intensity, unless p/ is also changed according to the radius of the recording position,
Inaccuracies in bit dimensions inevitably remain.

However, even if reflected light is detected, it is difficult to determine the radius of the recording position. Therefore, another method will be required.

In addition, in order to adjust the recording laser beam over the entire surface of the disk, a comparator and a laser drive circuit that reduces the intensity of the laser beam according to the output of the comparator are required, making the circuit complex and increasing costs. I have no choice but to.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide an inexpensive optical recording device in which the bit width is equal between the outer circumference and the inner circumference of an optical disc, there is no bit shift, and there is no bit shift. It is to be.

[Means for solving problems]

In the original disc, in which a recording layer whose optical properties or myelinological shape change upon irradiation with light and a high heat transfer layer are sequentially laminated on a transparent substrate, the thickness of the recording layer is constant, and the thickness of the recording layer is The thickness of the heat transfer layer decreases from the inner circumference to the outer circumference, and furthermore, recording is performed using the recording laser beam in which the power at the beginning of the irradiation time is greater than the power at the end. Characteristic optical recording device.

[Effect]

According to the above-described configuration of the present invention, the bit width can be made equal between the outer circumferential portion and the inner circumferential portion, thereby eliminating bit misalignment. The principle is shown in Figure 1 (α), (A), (C), (d), (gi
This will be explained using (f).

FIG. 1 (α-1) is a sectional view of an optical disc according to the present invention. Further, FIG. 1 (α-2) (a) and (b) show the relationship with the irradiation intensity of the laser beam. 1 is a transparent substrate, 2 is a recording layer, 3 is a high heat transfer layer, 4 is an objective lens, 5 is a laser beam, 5α
is a rectangular recording laser beam and a 5b step type recording laser beam. It is assumed that this optical disk is rotating at a constant rotation speed. First, consider the case of recording with a rectangular recording laser beam 5α. Since the speed is slow in the inner circumference, the temperature is higher than that in the outer circumference. Therefore, if the thickness of the high heat transfer layer 3, which has high thermal conductivity such as metal, is made thicker at the inner circumference, the amount of heat flowing from the recording layer 2 to the high heat transfer layer 5 at the inner circumference will be smaller than that at the outer circumference. also becomes larger. In other words, the temperature at the outer circumferential portion and the inner circumferential portion are the same. FIG. 1(b) shows the positional relationship between ideal bit 6 and actually recorded bit 7. 8 is the laser beam moving direction. ΔX is the displacement of the tip, and Δy is the displacement of the end. FIG. 1(C) shows the bit width (A), the deviation angle ΔX (B), and the irradiation time Tp of the rectangular recording laser beam.
It depicts Δy()・).

The signs of ΔX and Δy are positive when they shift to the right in FIG. 1Cb). 9 and 9' are the bit widths at the outer and inner circumferences, respectively, and 10.10' are the Δ! at the outer and inner circumferences, respectively.
, 11.11' indicate Δy at the outer circumference and the inner circumference, respectively. For the same irradiation time, the bit width is
It can be seen that the values are the same at the inner circumference, and that the bit width becomes constant when the irradiation time exceeds a certain value. Although bit deviations ΔX and Δy occur, they are smaller than when zero is written on a conventional optical disc. Furthermore, for the same irradiation time, the amount of deviation is the same at the outer and inner circumferences. The fact that the bit width is constant over the entire surface of the disk and the amount of deviation is also constant for the same irradiation time indicates that the thermal characteristics of the disk are uniform over the entire surface. That is, when recording, it is not necessary to know the radius of the recording position. Therefore, when recording with the step-type recording laser beam 5h, the first
The characteristics are as shown in figure (d). 12.12' indicates ΔX(b) at the outer circumference and inner circumference, respectively, and 1'#14' indicates Δy()·) at the outer and inner circumference, respectively. It can be seen that the bit width is constant over the entire disk surface for the same irradiation time, and that ΔX and Δy are small over the entire disk surface at any irradiation time.

The reason why ΔX becomes smaller is that the laser light intensity at the part where irradiation starts is greater than the rectangular laser light intensity and the temperature becomes higher. The reason why Δy is small is that the laser light intensity from the middle to the latter half of the irradiation time is less than the rectangular laser light intensity by degrees, and the temperature t is somewhat lower. This improves the precision of the bit dimensions. Figure 1 (i
indicates a step-shaped recording laser beam. Since the optical disc according to the present invention has uniform thermal characteristics over the entire surface, PI*'! is independent of the size of Tp and the radius of the recording position. ,
To takes a constant value. Therefore, there is no need to detect the intensity of the reflected light and reduce the intensity of the recording laser beam in response to this intensity, which simplifies the circuit configuration. This leads to cost reduction. FIG. 1 (1) shows another example of the recording laser beam, with Fl
*'t is a constant value.

[Embodiment 1] FIG. 4 shows an embodiment of the present invention. This is a phase change optical disc. 15 is a PMMA substrate, 16 is a thickness of 10Q
sm TeOx, 17 is AA, inner circumference thickness 200am
, the thickness of the outer peripheral portion is 100% m.

[Embodiment 2] FIG. 5 shows another embodiment of the present invention. This is a magneto-optical disk. 18 is a PC board, 19 is AtN with a groove of 80% thickness, and 2G is GdTb with a groove of 100% thickness? e and 21 are At grooves with a thickness of 20011 on the four circumferences and a thickness of 100% on the outer circumference. Due to the enhancement effect of the htM layer,
Magneto-optical rotation angle (L7@, reflectance 21%. Furthermore,
()+ITI) Since the thickness of 1e is thick, 7 Alade rotation is not added to the enhancement. The layer between the substrate and the recording layer is a dielectric material such as atN, Bias, SiO, or Sin, a semiconductor such as ZnS, α-81, or an organic material such as crystal violet chikton, PMMA, or Teflon. It can be used to adjust reflectance for media other than recording.

[Effects of the Invention] As described above, according to the present invention, in an optical disc whose rotational speed is constant, the high heat conductive layer is brought into close contact with the recording layer, and the thickness of the high heat conductive layer is decreased toward the outer periphery. We were able to make the thermal characteristics uniform over the entire surface.

The first effect of the present invention is that when recording with a rectangular laser beam,
This means that the bit width can be made equal at the outer and inner peripheries.

This eliminates crosstalk from adjacent tracks and improves S/N. This alone will reduce reading errors. This effect is also significant in applications such as document 9 image files, memory, etc., where reading errors do not have to be much of a problem.

The second effect of the present invention is that when recording with a step laser beam or a laser beam that decreases over time, bit deviation is extremely small and the bit width is uniform over the entire disk surface regardless of the irradiation time. . This effect could not be sufficiently achieved in the conventional example. Bit misalignment is eliminated, the bit width becomes uniform, and the accuracy of bit dimensions is improved. This results in no read errors, improved bit error rate, and
Third aspect of the present invention that enables application of optical disks to memory
The advantage of this method is that since the thermal characteristics of the disk are uniform, the recording laser power can be changed in a constant manner over the entire surface of the disk. That is, there is no need to reduce the intensity of the recording laser beam in response to the intensity of the reflected light. This simplifies the circuit configuration and enables inexpensive optical recording devices.

[Brief explanation of drawings]

Figure 1 (α-1) t (8-2) - (a) (α-2)
-(B) is a diagram for explaining the present invention in detail.
> is a diagram showing the positional relationship between ideal bits and actually recorded bits. FIGS. 1(c), -(a), (b), and (c) are diagrams showing the bit width and deviation amounts ΔX and Δy with respect to the irradiation time of a rectangular laser beam. Figure 1(d)-(a), (b), and (c) show the bit width, deviation amount ΔX, and Δy with respect to the irradiation time of the step laser beam.
Diagram showing. [1(a) is a diagram showing a step type laser beam. FIG. 1 (1) is a diagram showing a laser beam whose power decreases over time. FIG. 2 (α) is a diagram showing reflected light detected during recording in a conventional example. FIG. 2(J) is a diagram showing a conventional recording laser beam whose power is reduced in response to the intensity of reflected light. FIGS. 3(α), (A), and (c) are diagrams for explaining the problems of the conventional example. FIG. 4 is a diagram showing an embodiment of the present invention. FIG. 5 is a diagram showing another embodiment of the present invention. 1...Transparent substrate 2...Recording layer 3...High heat transfer layer 4...Objective lens 5... Laser beam 5α... Rectangular recording laser beam 5b... Step-shaped recording laser beam 6...
...Ideal bit 7...Actually recorded bit 8...
・・・・・・Laser beam movement direction 9・・・・・・Bit width at outer periphery 9′・・・・・・Pips at inner periphery）I
llilo・・・Bit deviation ΔX10 at the outer periphery
'...Bit deviation ΔX11 at the inner circumference...
Bit deviation at the outer circumference Δy11'... Bit deviation at the inner circumference Δy12... Pit at the outer circumference) Illi
11'...Pick at inner circumference) 11%11S...
...Bit deviation at the outer circumference ΔX15/...Bit deviation at the inner circumference ΔX14...Bit deviation at the outer circumference Δy14'...Bit deviation at the inner circumference Δy15・
...PMMA substrate 16 ... Te0X recording layer 17 ... -hl high heat transfer layer 1B ... PC board 19 ... AtM layer 20 ... ...GdTbFe recording layer 21...At high heat transfer layer 100...Reflected light 101...Recording laser beam 102...Recording laser beam 105...at outer circumference part Recording laser beam 104...Equivalent rectangular wave in the latter half of the irradiation time
Up

Claims (6)

[Claims] (1) In an optical disc in which a recording layer whose optical properties or geometrical shape changes upon irradiation with light and a high heat transfer layer are sequentially laminated on a transparent substrate, the thickness of the recording layer is constant, and the thickness of the recording layer is constant. An optical recording device characterized in that the thickness of the heat transfer layer decreases from the inner circumference to the outer circumference. (2) The optical recording apparatus according to claim 1, wherein recording is performed using a recording laser beam whose power at the beginning of the irradiation time is greater than the power at the end. (3) The optical recording device according to claim 1, wherein the high heat transfer layer is made of metal. (4) A layer with a constant thickness formed of one of dielectric, semiconductor, or organic material on a transparent substrate, a recording layer whose optical properties or geometric shape change when irradiated with light, and a high heat transfer layer. What is claimed is: 1. An optical recording device in which the thickness of the recording layer is constant, and the thickness of the high heat transfer layer decreases from the inner circumference to the outer circumference in an optical disk in which the recording layers are sequentially stacked. (5) The optical recording apparatus according to claim 4, characterized in that recording is performed using a recording laser beam in which the power at the beginning of the irradiation time is greater than the power at the end. (6) The optical recording device according to claim 4, wherein the high heat transfer layer is made of metal.