KR0151079B1 - Manufacturing method of optical recording medium - Google Patents

Abstract

The present invention relates to a method of manufacturing an optical recording medium. Forming a conductive layer on the substrate, forming a recording layer containing a dichroic dye and a side chain type liquid crystal polymer on the conductive layer, forming a reflective layer on the recording layer through sputtering, and then forming a protective layer A method of manufacturing an optical recording medium, comprising: generating a plasma potential in a recording layer during the formation of a reflective layer, whereby an optical recording medium manufactured by using a method of orienting a liquid crystal and a dye in the recording layer is recorded. The degree of orientation of the layer has an effect of going through a separate polling process. Further, according to the present invention, there is an advantage that the manufacturing process of the optical recording medium is simplified.

Description

Method of manufacturing optical recording medium

1 is a cross-sectional view schematically showing one embodiment of an optical recording medium that is generally used.

2 is a cross-sectional view schematically showing the arrangement of the recording layers during the polling process and the recording.

3 schematically illustrates a process for forming a reflective layer in accordance with one embodiment of the present invention.

4 schematically shows a corona polling process according to a conventional method.

* Explanation of symbols for main parts of the drawings

1,21: substrate 2,22: conductive layer

3,23 recording layer 4: reflective layer

5: protective layer 11: liquid crystal

12: pigment 20: chamber

21: power supply 22: target

31: needle 32: power supply

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical recording medium, and more particularly, to provide a method for manufacturing an optical recording medium capable of recording information by orienting a recording layer while eliminating a separate polling step.

Currently, the most widely used recording method is a magnetic recording method, which allows information to be recorded in accordance with the magnetization direction of the magnetic material in the magnetic medium. Examples using this method include various video tapes, audio tapes, floppy disks, and the like.

On the other hand, the explosive increase of various kinds of information due to the high degree of informatization of society in general requires high density, large capacity and high speed of the storage medium. However, in the conventional magnetic recording method, it is difficult to increase the capacity of the recording medium. Therefore, a new recording method, the magneto-optical method, has emerged.

In the magneto-optical system, unlike the magnetic material used for the magnetic recording medium, the magnetization direction is perpendicular to the surface of the recording film, and it is difficult to switch the magnetization direction. The magnetization direction is converted by focusing the laser light to 1 µm or less and changing the magnetic direction to an external magnetic field in a state heated at a curing temperature or more, and information is recorded according to the converted magnetization direction.

In this method, the information recording unit can be made smaller than 1 [mu] m to have a recording density of 10 to 1000 times that of the magnetic memory method, and the non-contact memory reproducing method facilitates recording preservation and long life. However, this method has manufacturing difficulties because it uses a heavy metal-based magnetic material and requires a vacuum thickening or sputtering device in the manufacturing process. In order to solve these drawbacks, attention has been focused on the development of an organic optical recording medium.

The organic optical recording medium is divided into a write once read many (WORM) type that can only be read after writing once and a rewritable (RW) type that can be erased after writing, depending on whether or not it can be erased.

The WORM type is manufactured by coating a pigment composition capable of absorbing a laser on a reflective layer to form a recording layer by coating a mixed composition of a polymer resin, and then forming a protective layer thereon. In addition, in order to record information on the recording medium thus prepared, when the laser is focused on the recording layer within 1 μm, the dye in the recording layer absorbs the laser to generate heat, and the polymer resin is decomposed by the generated heat to pit. The recording is made by forming. In recording and reproducing, the information is read by the difference in reflectance between the portion with and without the pit.

As a manufacturing method of the RW type, the method using the thermoplastic resin and the near-infrared absorbing pigment, and the method using the polymer blend are proposed. However, this method has poor recording sensitivity and record / erase repeatability.

On the other hand, Fig. 1 shows one type of optical recording medium which is generally used, in which the substrate 1, the conductive layer 2, the recording layer 3, the reflective layer 4, and the protective layer 5 are formed in this order. It is. The dual recording layer 3 mainly consists of a liquid crystal polymer and a dichroic dye, and the mesogen 11 and the dichroic dye 12 of the side chain type liquid crystal polymer are formed by corona polling. Orientation, and then information recording is possible. In other words, when the recording layer is initially formed, both mesogin and dichroic dye exist in a disordered state, and mesogin and dichroic dye are homeotropically arranged so that light can be easily transmitted through the polling process. do. Therefore, when light is transmitted through the recording layers arranged in this manner, the mesogin group and the dichroic dye in the transmitted portion are disturbed, isotropic, and the reflectance is changed so that information is recorded (see FIG. 2).

Looking at the polling process in more detail, the polling process forms an electric field through a corona discharge while the polymer in the formed recording layer is heated to near the glass transition temperature, thereby arranging liquid crystals and pigments, and then lowering the temperature to adjust the arrangement. As a process to hold | maintain, there exists a problem that it is very complicated.

Accordingly, an object of the present invention is to provide a method of manufacturing an optical recording medium capable of solving the above problems and eliminating a separate polling step to shorten the manufacturing process and to record information by orientation of the recording layer.

In the present invention to achieve the above object,

Forming a conductive layer on the substrate;

Forming a recording layer containing a dichroic dye and a side chain type liquid crystal polymer on the conductive layer;

A method of manufacturing an optical recording medium, comprising: forming a reflective layer on the recording layer through sputtering, and then forming a protective layer;

The present invention provides a method for manufacturing an optical recording medium characterized by orienting a liquid crystal and a pigment in a recording layer by generating a plasma potential in the recording layer during the formation of the reflective layer.

That is, the present invention is characterized in that it is not necessary to go through a separate polling process by orienting the recording layer homeotropically in the process of forming the reflective layer using the plasma potential.

In the present invention, the substrate is not particularly limited as long as it is conventionally used as a material having excellent thermal and mechanical properties and excellent light transmissive properties. And the like, and more preferably, polycarbonate, aromatic polyolefin, and the like.

The material of the conductive layer or the reflective layer used in the present invention is also not limited thereto, but gold, aluminum, silver, palladium, copper, silver, chromium or an alloy thereof may be used.

The recording layer contains a side chain type liquid crystal polymer and a dichroic dye. Here, specific examples of the side chain type liquid crystal polymer include liquid crystal polyester, liquid crystal polycarbonate, liquid crystal polymethacrylate, liquid crystal polyimide, liquid crystal polyamide, and the like.

Moreover, as a specific example of a dichroic dye, there exists a pigment | dye represented by following formula (I), (II), (III).

Hereinafter, the present invention will be described in detail through the manufacturing process of the optical recording medium.

In the present invention, it is manufactured by a general method except for orienting the recording layer at the same time in the process of forming the reflective layer without going through a separate polling step for orienting the recording layer. That is, as shown in FIG. 1, the substrate 1 can be formed, and then the conductive layer 2, the recording layer 3, the reflective layer 4, and the protective layer 5 can be formed in this order.

3 schematically illustrates a process of forming a reflective layer according to an embodiment of the present invention. As can be seen in FIG. 3, a sputter (not shown) placed on a substrate 1 having a recording layer 3 formed therein in the sputtering chamber 20 and operated by a separate external power supply 21. A metal, such as gold or aluminum, is deposited from the target onto the recording layer. In this process, when the RF (Radio Frequency) bias voltage is applied to the substrate, the plasma potential E is generated on the substrate to align the liquid crystal homeotropically. Particularly, if the diol component compatible with the mesogin group of the liquid crystal is contained in the recording layer, the alignment is more easily performed. Preferred diol components include cyanobiphenyl diol and tolan diol.

The optical recording medium is manufactured by orienting the recording layer in this manner, forming a reflective layer and then forming a protective layer in a conventional manner.

Hereinafter, the features of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

Example 1

First, aluminum was deposited on a 1.2 mm thick polycarbonate substrate to form a 5 nm thick conductive layer. In a separate container, 1.0 g of AVC71 (side chain type liquid crystal polymer, Akzo Nobel Co., Ltd.), 0.02 g of a dichroic dye represented by the following formula, and 0.05 g of cyanobiphenyl diol as an additive were dissolved in 10 ml of diacetone alcohol. Spin coating was carried out at 2000 rpm on the layer to form a recording layer having a thickness of 0.21 mu m. Using a sputter, a 100 nm thick reflective layer was formed on the recording layer. At this time, the sputtering target was 6 aluminum, a movable chamber pressure of 15 mtorr, a DC power supply of 500 W, a deposition time of 5 minutes, and a plasma potential of -200 V. Subsequently, a protective layer having a thickness of 10 μm was formed of an ultraviolet curable resin to prepare an optical recording medium.

Using a laser wavelength of 780 nm, the recording medium was recorded with a 3T pattern of EFM and reproduced with a power of 0.7 mW, and the CNR (carrier-to-noise ratio) was 49 dB and the reflectance was 67%.

Example 2

An optical recording medium was produced in the same manner as in Example 1 except for using a dichroic dye represented by the following formula and setting the plasma potential to -150V. The characteristics of the recording medium thus produced were evaluated in the same manner as in Example 1, with a CNR of 46 dB and a reflectance of 59%.

Comparative Example 1

First, aluminum was deposited on a 1.2 mm thick polycarbonate substrate to form a 5 nm thick conductive layer. In a separate container, 1.0 g of AVC71 (side chain type liquid crystal polymer, Akzo Nobel Co., Ltd.), 0.02 g of a dichroic dye represented by the following formula was dissolved in 10 ml of diacetone alcohol, followed by spin coating at 2000 rpm on the conductive layer to 0.23 μm. A recording layer of thickness was formed. Then, the recording layer was oriented in the polling apparatus as shown in FIG. At this time, the corona discharge condition was set to an applied voltage of 8 kV, and the polling process was performed by maintaining the substrate at a maximum temperature of 110 ° C for 5 minutes. Finally, a 100 nm thick reflective layer was formed using the sputtering apparatus used in Example 1, and then a 10 μm thick protective layer was formed of an ultraviolet curable resin to prepare an optical recording medium.

Using a laser wavelength of 780 nm, the recording medium was recorded with a 3T pattern of EFM and reproduced with a power of 0.7 mW. The CNR (carrier-to-noise ratio) was 46 dB and the reflectance was 61%.

Comparative Example 2

After the recording layer was formed, an optical recording medium was produced in the same manner as in Example 1, except that heat treatment was performed at 110 ° C. for 15 minutes, and plasma potential was not applied in the process of forming the reflective layer. The characteristics of the recording medium thus produced were evaluated in the same manner as in Example 1, with a CNR of 35 dB and a reflectance of 55%.

Comparative Example 3

An optical recording medium was produced in the same manner as in Example 1 except that no diol component was added to the recording layer. The characteristics of the recording medium thus produced were evaluated in the same manner as in Example 1, with a CNR of 38 dB and a reflectance of 50%.

As can be seen from the comparison between Example 1 and Comparative Example 1, the CNR and reflectance values of the optical recording medium produced according to the present invention are similar to the optical recording medium produced according to the conventional method. In other words, according to the present invention, the alignment effect of the recording layer can be obtained without a separate polling process.

As can be seen from the above, according to the present invention, since the optical recording medium in which the recording layer is oriented can be manufactured without a separate polling process, the production efficiency is greatly improved.

Claims (4)

Forming a conductive layer on the substrate; Forming a recording layer containing a dichroic dye and a side chain type liquid crystal polymer on the conductive layer; A method of manufacturing an optical recording medium, comprising: forming a reflective layer on the recording layer through sputtering, and then forming a protective layer, wherein the plasma layer is generated on the recording layer in the reflective layer formation process, thereby recording. The liquid crystal and a pigment | dye in a layer are orientated, The manufacturing method of the optical recording medium characterized by the above-mentioned. The method of manufacturing an optical recording medium according to claim 1, wherein a diol component is contained in said recording layer. The method of manufacturing an optical recording medium according to claim 2, wherein the diol component is at least one selected from the group consisting of cyanobiphenol diol and tolan diol. The method of manufacturing an optical recording medium according to claim 1, wherein said dye is one dichroic dye selected from the group represented by the following formulas (I), (II) and (III).