JPS60129294A - Base for optical recording medium and optical recording medium - Google Patents

Abstract

PURPOSE:To prevent a recording layer from being deteriorated, burst errors from occurring and the surface of a glass base from being discolored, by a method wherein a soda-lime glass or the like is subjected to a low temperature type ion exchange treatment to replace Na<+> on the surface of the glass by K<+>, and a thin strain layer is provided at a surface layer part. CONSTITUTION:In a disk form transparent base for constituting an optical recording medium such as an optical-type information recording medium and an opto-magnetic recording medium, a disk form glass base having a ratio Na2O/ K2O (wt%) of larger than 1 is subjected to a low temperature type ion exchange treatment to set the ratio Na2O/K2O (wt%) in proximity to the surface of the base to 4X10<-2>-1. Further, the strain layer having a thickness of 5-100mum is provided at the surface layer part of the base.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a writable/readable optical information recording medium provided with a recording layer such as Te, and a writeable/readable/erasable optical information recording medium provided with a magneto-optical recording layer such as GdFe. The present invention relates to a novel disc-shaped glass substrate for optical recording media (hereinafter referred to as "glass substrate") constituting an optical recording medium such as a magneto-optical recording medium, and an optical recording medium constructed from this glass substrate. be.

Generally, an example of this type of optical recording medium has a basic configuration as shown in FIG. That is, the recording layers 3 and 4 are placed on the disc-shaped transparent substrate 1.2 so as to face each other, and the recording layers 3.4e placed on the disc-shaped transparent substrate 1.2 are placed facing each other. 5. The inner spacer 6 is the recording layer 3
．． It is inserted so as not to cover 4. The material of the disk-shaped transparent substrate 1.2 is PMMA resin, polycarbonate resin, glass, etc., but glass has the light transmittance, hardness, water absorption rate, etc. required for the disk-shaped transparent substrate.
Glass has been widely used in recent years because it has excellent properties such as coefficient of linear expansion, surface precision, flatness, surface defect density, and thermal deformation temperature.

However, the materials of conventional glass substrates are usually expensive quartz glass and non-alkali glass, and are easily available and inexpensive glasses with a ratio of (Na2O weight %)/(K20 weight %) exceeding 1, such as soda lime glass. However, with the glass substrate of this scale, the deterioration of the recording layer tends to be significantly accelerated due to the influence of Na ions near the glass surface, and furthermore, errors occur in a concentrated manner during playback.
That is, there is a drawback that burst errors occur and the reproduction function of the optical recording medium is inhibited. In addition, in conventional glass substrates, the surface opposite to the glass surface on which the recording layer is provided becomes cloudy over time due to the influence of Na ions near the surface.
Hereinafter, it will be referred to as [Yata].

) occurs, which has the disadvantage that the light transmittance of the glass substrate is significantly reduced. As a result, conventional glass substrate optical recording media have a recording sensitivity of (<.-R)/(R+R).
There was a drawback that the signal contrast, expressed as (Ro: reflectance of the recording layer before recording, R: reflectance of the recording layer after recording), was extremely deteriorated.

The present invention is intended to eliminate the above-mentioned drawbacks, and is made of soda lime glass (Na20% by weight)/(K20
By using a low-temperature ion exchange method, the Na ions near the surface of the glass are replaced with ions, and the ratio of (N2 aO weight %)/(K20 weight fA%) near the surface is 4 x 10. ~1 and further provide a strained layer of 100 μm or less on the surface layer of the glass surface to prevent deterioration of the recording layer, prevent burst errors, and prevent discoloration of the glass substrate surface. It is to provide.

Hereinafter, the present invention will be explained in detail based on one embodiment. First, the composition ratio of the main components is as shown in Table 1, and the outer diameter is 305+u.
+φ, a center hole diameter of 35+++a+φ, and a thickness of 1.2ms+ disk-shaped soda lime glass is prepared.

Table 1 Next, by low-temperature ion exchange method, a temperature range that does not exceed the transition temperature of the soda lime glass, for example 40
The soda lime glass was immersed in a molten salt containing ions at 0°C for 8 hours, Na ions near the surface of the soda lime glass were replaced with Na ions, and Na ions were added to the surface of the soda lime glass to a depth of 1 μm. The average content of Na2O is 3.2%, and (NaO weight%) / (K20
ffiffi%) is 0.3, and roughly 1% from the above surface.
A strained layer up to 4 μm is provided to produce a glass substrate for an optical recording medium.

The effects on the 17 states of the glass substrates manufactured as described above are not shown in FIG. 2 and will be described in terms of transmittance. first,
The glass substrate according to the above embodiment was heated at a temperature of 60°C and a humidity of 90°C.
% environment, the transmittance does not decrease even after 40 days (a in the same figure).On the other hand, when the soda lime glass shown in Table 1 as a comparative example is left in the above environment for 40 days, the transmittance does not decrease (see figure a). As shown in the figure, the transmittance decreases from 90% to 45%. Next, the relationship between (Na20% by weight)/(K20% by weight) and transmittance was determined for the glass substrate subjected to low-temperature ion exchange and the soda lime glass not subjected to ion exchange, as in the above example. Shown in Figure 3. The figure shows the state after 10 days at a temperature of 60° C. and a humidity of 90%. As is clear from C1 and C2 in the same figure (C1 is the initial value, C2 is after 10 days), the glass substrate subjected to low-temperature ion exchange is (Na20 weight% 1%) / (K20 weight%) ≦
If it is 1, it has the effect of preventing a decrease in transmittance.On the other hand, for example, soda lime glass that has been subjected to low-temperature ion exchange and has a ratio of 6N (Na20% by weight)/(K20ffim%) exceeding 1, As shown in Figures dl and d2 (dl is the initial value, d2 is after 10 days), the transmittance decreases.

As described above, glass substrates for optical recording media are subjected to low-temperature ion exchange treatment to remove (Na) near the surface of the glass substrate.
By setting 0 weight%)/(K2O weight%)≦1,
Prevents 7 things and improves recording sensitivity, signal control, and last one.
1 (can be prevented from decreasing.

Next, an example of an optical recording medium using the glass substrate of the above example will be described in detail below.

First, the two glass substrates (outer diameter 3
A recording layer of Te with a thickness of 300 mm was deposited on each glass substrate with a diameter of 0.5 mmφ, a center hole diameter of 35 mmφ, and a thickness of 1.2 mm, and the glass substrates were placed so that these recording layers faced each other. Further, a member such as a spacer for sealing the recording layer and maintaining the gap between the glass substrates, such as a spacer, is inserted between the two glass substrates to produce an optical recording medium.

Next, the deterioration of the recording layer of the optical recording medium of the above example will be explained in detail with reference to FIG. In order to clarify this explanation, one glass substrate coated with the recording layer used in the optical recording medium of the above example was left in an environment with a temperature of 60°C and a humidity of 90%. A laser beam of 830 nm is irradiated from the side to measure the reflectance of the recording layer. As a comparative example, a recording layer forming the optical recording medium of the above example was deposited on a glass substrate of soda lime glass having a composition shown in Table 1. Calculate the rate.

According to FIG. 4e, the reflectance of the recording layer of the optical recording medium of the above example is 0 even after 30 days when the initial value is 1.
．． On the other hand, the reflectance of the soda lime glass recording layer shown in FIG. Therefore, it does not function as a recording layer. In addition, the recording layer was left to deteriorate in the same manner as above at a temperature of 60°C and a humidity of 90%, and (Na2O
Figure 5 shows the relationship between the ratio of % by weight)/(% by weight of K2O) and the time required for the reflectance to decrease by, for example, 10% from the initial value. According to the fifth diagram, if low-temperature ion exchange is performed to reduce the ratio of (N820wt%)/(K, 20wtM%) to 1 or less, the time for the reflectance to decrease by 10% will be longer (K2Owt%). As shown in the figure, the time for the reflectance to decrease by 10% is shorter than when the temperature is 1.
/(K2O weight %)> The same tendency of the reflectance of the recording layer as in 1) is shown. In other words, if only to prevent the glass substrate from burning, low-humidity ion exchange should be performed so that (Na20wM%)/(K2Owt%) near the surface of the glass substrate is 1 or less. In order to prevent deterioration of the recording layer, (Na20@rEp%)/(K2O wt%) should be at least as long as the reflectance reduction time of 1 (Na20@rEp%)/(K2O (% by weight) is required. Therefore, in the above, even if the reflectance of the recording layer is reduced by 10% from the initial value, 0 and h in FIG. 5 are 11! Since it moves in parallel in the i-direction, the above 4×
The range is from 162 to 1. Furthermore, a strained layer of 5 to 100 μm is provided that can maintain the time for the reflectance of the glass (Na 0 wt%)/(K2O wt%) recording layer to decrease through low-temperature ion exchange. It is possible to prevent deterioration of the recording layer. Further, in the optical recording medium formed as described above, when the number of recording layers is 150, for example, the recording sensitivity and signal contrast remain at the initial level of 100 μs even after 40 days have elapsed.

0.75 Te, conventional (Na20wt%)/(K2O
Recording sensitivity of an optical recording medium using a glass substrate with a glass substrate with a weight % of more than 1 (after 15 days, the initial 98 μs to 320 μs
s), signal contrast l” (after 15 days, initial 0,
75 to 0.25) is also excellent. Also, burst errors are much lower than in conventional optical recording media.

As described above, according to the present invention, the ratio (N820% by weight M)/(K2O% by weight) of the glass to be subjected to low-temperature ion exchange should be more than 1, but more preferably 50 or less. That is, (Na2O weight%)/(K20'Am%) is 5
When the value exceeds 0, Na2O near the surface of the glass substrate decreases due to low-temperature ion exchange, but Na2O inside the glass substrate decreases.
11 degrees of 2o does not change and light absorption occurs, so (Na2
It is desirable that the ratio (O weight percent)/(K2O weight percent) exceeds 1 and is 50 or less. Further, the recording layer used in the optical recording medium of the present invention does not need to be on both glass substrates, and may be on only one glass substrate, and the vJ quality of the recording layer is not limited to TO.
Se, GeTe, InTe, TeC.

It may be a chalcogen element, a chalcogen compound, or a chalcogenide such as Te-〇, Te-(3e-0, Te-As-0, etc.), or it may be a magneto-optical recording material such as GdFe, TeFe, -GeTeFe, etc.

2. According to the present invention, by providing a strained layer near the surface of the glass substrate, 17 cracks on the surface of the glass substrate can be prevented.
It is effective in preventing deterioration of the recording layer of an optical recording medium and burst errors, and is also effective in increasing the hardness of the glass substrate surface and the bending strength of the glass substrate.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the structure of a general optical recording medium, Figure 2 is a characteristic diagram showing the transmittance of the glass substrate over time in this example and a comparative example, and Figure 3 is a diagram showing the transmittance of a glass substrate over time in this example and a comparative example. of(
A characteristic diagram showing the transmittance of the glass substrate for Na (0 wt%)/(K2O2 wt%), and Figure 4 shows the reflectance of the recording layer over time in the present example and comparative example (when the initial value is 1). Characteristic diagram showing 5th
The figure shows (Na 0 wt%)/(K2
01H1n%) of the recording layer is 1 from the initial value.
It is a characteristic diagram that does not show the time for a decrease of 0%. Figure 2 Time (B) Figure 3

Claims (2)

[Claims] (1) In a disc-shaped transparent substrate forming an optical recording medium such as an optical information recording medium or a magneto-optical recording medium, (Na
A disk-shaped glass substrate in which the value of 2 (NaO7mf!i%)/(K20 weight%) exceeds 1 is subjected to low-temperature ion exchange treatment, and 2 (NaO7mf!i%)/(K20 weight%) near the surface of the disk-shaped glass substrate is weight%) 4×1
0 to 1, and further 5 on the surface layer of the disk-shaped glass substrate.
A substrate for an optical recording medium, characterized in that it is a disc-shaped transparent substrate provided with a strained layer of ~100 μm. (2) A disk-shaped glass substrate with a ratio of (Na20% by weight)/(K20% by weight) exceeding 1 is subjected to low-temperature ion exchange treatment, and a 5 to 100μ
m of two optical recording medium substrates provided with a strained layer, a recording layer is provided on the surface of at least one of the optical recording medium substrates,
The recording layer and the other optical recording medium substrate are installed to face each other, and a gap is provided between the two optical recording medium substrates to seal the recording layer and between the two optical recording medium substrates. An optical recording medium comprising at least the two optical recording medium substrates, a recording layer, and the member, into which a member for holding is inserted.