JPS6020333A - Disk for recording and reproducing optical information - Google Patents

Abstract

PURPOSE:To decrease plane runout and warpage owing to a change in temp. and humidity and to obtain recording and reproduction with high quality on both inside and outside circumferences with an optical disk formed by superposing a substrate on which rugged grooves and rugged pits are formed and a protective plate by setting the weight difference between the substrate and the protective plate within apecific %. CONSTITUTION:An optical disk is manufactured by setting the weight difference between substrates 1, 4 consisting of a polymethyl methacrylate (PMMA) having hygroscopicity as a resin within 10%. A layer 2 having rugged grooves and pit signal parts is provided on the surface of the body 1 by using a UV curing resin. A light-absorptive thin film 3 consisting principally of Tex, where 0<x<2.0, is formed on the layer 2. Said substrate 4 is superposed and joined on and to the film 3 of the lower plate 1 by using a UV curing resin 5 to form a protective plate. The warpage and shape change of the disk owing to a temp. and humidity fluctuation are decreased by regulating the weight difference between the plates 1 and 4 and in the above-mentioned way, by which the stability and the quality of the recording and reproducing signal are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an optical information recording device that can be used in the field of office automation and converters, such as recording and reproducing video and audio signals, still images, nine documents, and large-capacity filing of various data. This relates to playback discs.

2. Description of the Related Art Conventional Structure and Its Problems An information reproducing disc having a laminated structure has been known for a long time. This means that even with surface runout of ±1πm, there is little deterioration of the reproduced signal. On the other hand, in the case of a recordable and reproducible disc, focus accuracy during recording has a large effect on signal quality. If the tilt surface runout is large, this focus accuracy will be reduced, and it is an important issue to reduce the surface runout and the inverted shape of the disc for information recording and reproducing disks made of resin substrates.

OBJECTS OF THE INVENTION An object of the present invention is to provide a structure for obtaining high-quality recording and reproducing signals over the inner and outer peripheries of the disc in an optical information recording and reproducing disc having a laminated structure made of resin substrates.

Structure of the Invention The present invention comprises a disk made by overlapping an upper plate and a lower plate,
The disc for optical information recording and reproduction has a weight difference between the upper plate and the lower plate set within 10%.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

As shown in Fig. 1, the optical information recording/reproducing disk II is as follows:
The basic structure is that a reflective layer or a light-absorbing thin film layer 3 is provided on a resin substrate 1 on which uneven grooves and uneven focal points are formed, and a plate having a similar structure or a protective plate 4 is laminated thereon with an adhesive layer 5. composition. 2 is a groove forming layer, and 6 is a center hole.

The resin substrate 1 generally has hygroscopic properties, expands under hygroscopic conditions due to the influence of humidity, and contracts under dry conditions. expansion,
The amount of change in shrinkage is first determined depending on the thickness 9 area of the resin substrate 1.

PMMA is used as the material for the upper plate 4 and the lower plate 1, and the lower plate 1 is preliminarily provided with an uneven groove and a focus signal portion using an ultraviolet curing resin. On top of this, a low oxide film consisting mainly of TeOx 0(x(2,○) is formed. Next, as an adhesive,
The PMMA plate on the upper surface is closely bonded using an ultraviolet curable resin to serve as a protective plate and to form a disc for recording and reproducing optical information. The weights of the upper and lower PMMA plates are measured in advance and divided into predetermined weight ranks.

By combining plates with a weight difference of 10% or less, the amount of warpage change due to moisture absorption can be kept within 300 μm. Preferably, a combination of plates with a weight difference of 4% or less will produce good results including plate thickness accuracy. The grooved layer made of ultraviolet curable resin and the adhesive layer each have a thickness of about 100 μm.

By keeping the areas of the disks the same, this amount of change can be considered to be determined by the weight of the plate.

For a disc with a laminated structure, the difference in the amount of expansion and contraction of the upper and lower plates can be seen as a change in the warpage of the disc.

FIG. 2 is a graph plotting the amount of warpage lΔS1 of a disk having a diameter of 200 mm after lamination against the weight difference % between the upper and lower plates. As the weight difference (%) increases, the amount of warpage change increases to as much as 50 μm.

Changes in the warpage of the disk also occur due to temperature and environmental conditions, and therefore it is desirable to keep the amount of change due to humidity to 300 μm or less. The amount of change due to temperature also depends on the strength and expansion of the upper and lower plates.

It is caused by shrinkage and can be reduced by reducing the weight difference (%) of these plates.

It is also possible to make the upper plate a grooved plate like the lower plate and form a TeOx film. Furthermore, a substrate with a bottom groove,
The same effect can be obtained by using an in-jewel plate as the upper surface protection plate.

Effects of the Invention By setting the weight difference (%) between the upper and lower plates within 10%, changes in the warped shape of the disk are reduced and the stability of the disk is improved. Also, the quality of recording and reproduction signals is improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view of a disc for optical information recording and reproducing according to an embodiment of the present invention, and FIG. 2 shows the weight difference (%) between the lower plate and the upper plate of the same disc and the amount of change in disc warpage 1△81 FIG. 1...Bottom plate, 2...Groove forming layer, 3
...Light-absorbing thin film layer, 4...Top plate, 5...Adhesive layer, 6: Center hole of disk.

Claims (1)

[Scope of Claims] (1) Optical information recording and reproducing in which an upper plate and a lower plate are stacked to form a disk, and the weight difference between the upper plate and the lower plate is set within 1%. Disc for use. (2) A light-absorbing thin film whose state changes thermally when irradiated with light is used in the information recording portion of the disk, and this thin film is formed on the lower plate, and the upper plate is characterized by the following: Optical information recording/reproducing disk according to item 1 (3) The upper plate and the lower plate are made of hygroscopic P.
An optical information recording/reproducing disc according to claim 1, which is an MMA 41 fat plate. (4) Pre-form uneven grooves on the lower plate with an ultraviolet curable resin layer, and form a light-absorbing information recording film on these grooves,
2. The optical information recording/reproducing disk according to claim 1, further comprising an ultraviolet curing resin as an adhesive layer, and the upper plate is bonded to the lower plate. (6) The optical information recording and reproducing disc according to claim 1, wherein both the upper plate and the lower plate are made of PMMA plates, and an adhesive layer is provided between the upper plate and the lower plate.