JPS63214936A - Optical recording member - Google Patents

Abstract

PURPOSE:To obtain a member which quadruples the density of a recording surface and contributes to the reduction in the cost of an optical pickup and the enhancement of the performance thereof by using a nonlinear optical material for an intermediate layer between a recording layer and substrate of an optical recording member and converting the wavelength of a light source for optical recording to a half wavelength. CONSTITUTION:The nonlinear optical material 11 and the recording layer 2 are successively laminated on the substrate 1 and are covered by a protective cover 5. Light of a wavelength past the substrate 1 is made into the light of lambda/2 wavelength by the effect of the material 11 and arrives at the recording layer 2. In general, the efficiency of a nonlinear effect is small but the just before arriving at the recording layer 2 past an objective lens has sufficient photon density. The nonlinear effect, therefore, increases sufficiently and second order higher harmonics can be generated. Since the recording layer 2 is subjected to the recording by the light of lambda/2 the wavelength in such a manner, the spot size is made into 0.5mum and the density of the recording surface is quadrupled. Reduction of NA of the objective lens to a half is also possible. The high-performance optical pickup is obtd. at a lower cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording member that records information by irradiating light.

[Summary of the invention]

The present invention provides a layer between a recording layer and a substrate of an optical recording member;
Alternatively, by using a nonlinear optical material in the substrate itself, the wavelength of the optical recording light source is converted to half the wavelength and irradiated onto the recording layer, thereby halving the spot diameter and quadrupling the conventional optical storage density. It is something.

[Conventional technology]

Conventionally, the structure of an optical recording member used for optical recording is as shown in FIG.
．． Adhesive 4. It is known that protective covers 5 are stacked one after another. The light enters from the substrate 1 side and records 11W2.
The light is reflected by the substrate 1 and then exits through the substrate 1. The cover 211!3 functions to shield the recording M2 from moisture, etc., and the protective cover 5 functions to protect the recording H2.

Furthermore, as shown in FIG. 3, at least a semiconductor laser 6, a collimator lens 7, a beam splitter 8, an objective lens 9, etc. are required as the structure of the optical pickup for making light incident on the optical recording member.

(Problems to be Solved by the Invention) In the optical pickup configured as described above, the light of the wavelength λ from the semiconductor laser 6 is directly irradiated onto the disk 10. Therefore, on the disk 10, for example, λ-78
When a 0n- semiconductor laser and an objective lens of NA-0.5 are used and the disk has the above structure, the spot size will be about 1 point. However, since the objective lens with NA-0.5 is a lens with a high angle of view and good aberration correction, it is expensive and heavy. Furthermore, since the spot size recorded on the disk is about 1 spider, it was not possible to record bits smaller than this. Therefore, in order to sufficiently increase the recording surface density, it was necessary to shorten the wavelength of the light source used, and it was necessary to use a gas laser such as a 1le-He laser (λ = 632.8n■). However, gas lasers are difficult to handle and are also difficult to use, so they have not been used in practice.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention uses a nonlinear optical material in the intermediate layer between the recording layer and the substrate of the optical recording member, or in the substrate itself, and converts the wavelength of the optical recording light source to half the wavelength. I decided to do it.

[Effect]

As mentioned above, by generating second harmonics using a nonlinear optical material, the wavelength of the optical recording light source can be halved, so if a lens with the same NA is used, the spot size can be halved. Therefore, the recording surface density is quadrupled, making it possible to achieve higher recording density. Or, if you want to get the same spot diameter,
Since the NA of the objective lens used can be halved, a lens with a low angle of view can be used, making it extremely inexpensive and at the same time allowing for transvaginal administration. This reduces the burden on the actuator that drives the objective lens, making it possible to provide an inexpensive and high-performance optical pickup.

In addition, the occurrence of coma aberration due to disk inclination is suppressed to a low level, resulting in high stability and reliability.

(Example) Hereinafter, the present invention will be explained in detail based on examples thereof.

As shown in FIG. 1, a nonlinear optical object vJ11 is placed on the substrate 1.
．． Recording layers 2 are laminated one after another and covered with a protective cover 5. The light of wavelength λ that has passed through the substrate 1 becomes light of wavelength λ/2 due to the action of the nonlinear optical material 11 and is recorded! Reach 2. Generally, the efficiency of the nonlinear effect is small, but the objective lens 9
The light just before it reaches the recording layer 2 is narrowed down to almost one line, so is there enough light? -It has become dense.

Therefore, the nonlinear effect becomes sufficiently large and it is possible to generate second harmonics. In this way, since recording is performed on the first layer 2 with light having a wavelength of λ/2, the spot size increases to 0.5, and the recording surface density quadruples. Or
The NA of the objective lens 9 shown in FIG. 3 can be halved. At this time, high density recording cannot be achieved, but since the objective lens has a low angle of view, it is lighter and the load on the actuator and drive circuit is reduced, making it possible to achieve an inexpensive, high-performance optical pickup. I can do that. Another embodiment uses a nonlinear optical material in the substrate itself, as shown in FIG. In this case, nonlinear optics! ! Recorded on f (substrate) 11 112. The protective covers 5 are stacked one after another. At this time, the spot size of the light focused by the objective lens 9 is still about 1 m on the substrate, but it becomes about 1 meter just before it reaches the recording layer 2, so the photon gradually increases in the substrate. The density increases, the nonlinear effect can be made sufficiently large, and the second harmonic can be generated. below,
Increased recording surface density, lower cost of optical pickup,
The same factors as in the previous embodiment contribute to the improvement in performance.

Note that the nonlinear optical material 11 shown in the above embodiments may be any material as long as it generates second harmonics.

Example Eva, LiNbQsJc! Organic nonlinear optical materials such as JL B II nonlinear materials and MNA crystals may be used.

Further, although not shown in the above embodiments, it goes without saying that even if a protective film or the like is laminated, it does not impede the present invention.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an optical recording member that has a recording surface density of 4 and contributes to lower cost and higher performance of optical pickup.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an optical recording member according to the present invention, FIG. 2 is a configuration diagram of a conventional optical recording member, FIG. 3 is a configuration diagram of a conventional optical pickup, and FIG. 4 is a configuration diagram of a conventional optical recording member. FIG. 3 is another configuration diagram of the optical recording member according to the invention. 1... Substrate 2... Recording layer 3... Dielectric protective film 4... Adhesive 5... Protective cover 6... Semiconductor laser 7... Collimator lens 8... Beam splitter 9 ...Objective lens 10...Disk 11...Nonlinear optical material Applicant Seiko Electronics Co., Ltd. Agent Patent attorney Tsutomu Mogami (and 1 other person) Figure 1 tC side of the can 7? .../7's Jicheng Figure 3 Figure 4

Claims (2)

[Claims] (1) In an optical recording member that records or reads information by light irradiation, a nonlinear optical material that converts the wavelength of the emitted light from the optical recording light source to half the wavelength is used between the recording layer and the substrate of the optical recording member. An optical recording member characterized by having an intervening layer or substrate. (2) The optical recording member according to claim (1), characterized in that a semiconductor laser is used as a light source for optical recording.