JPS6181449A - Base film for optical recording medium - Google Patents

Abstract

PURPOSE:To produce the titled film having excellent reproducibility of record and resistant to the deterioration of the recording layer with time, by adding a specific amount of a specific methacryl resin to a polyvinylidene fluoride resin, and biaxially drawing the obtained composition. CONSTITUTION:(A) A polyvinylidene fluoride resin preferably having a number- average molecular weight of 5X10<4>-10<6> and a molecular weight distribution of 2-40 is mixed with (B) a polymethacryl resin preferably having a number- average molecular weight of 1X10<4>-20X10<4> and a glass transition temperature of >=50 deg.C, preferably a terpolymer of methyl methacrylate, (meth)acrylic acid and ethyl methacrylate, at a weight ratio (A/B) of (19-3)/1, preferably (9-3.3)/1, and a film made of said composition is drawn biaxially to obtain a base film for optical recording, having a longitudinal tensile strength of >=20kg/mm<2>, a Young's modulus of >=200kg/mm<2>, thermal shrinkage of <=5% at 120 deg.C, trans mittance of >=85% at 260-1,000nm, wavelength, and planar refractive index fluctuation of <=8X10<-3>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a base film for optical recording media.

[Prior art]

Traditionally, acrylic resins such as polymethyl methacrylate have been used as base materials for plastic optical recording media.

Alternatively, polycarbonate resins were widely used.

[Disadvantages of conventional technology]

However, if such a conventional plastic base material is made into a thin film and an attempt is made to use it as a base film for an optical recording medium, there are the following drawbacks. That is, since both acrylic resins and polycarbonate resins have poor quality, no improvement can be expected at all due to deterioration of physical properties due to stretching (mainly heat shrinkage). On the other hand, when an unstretched film is used, the surface roughness is large, so when an optical recording layer is placed on the film, the reproducibility of recording is greatly deteriorated.

Furthermore, the inherent properties of the resin include low elongation and low strength, making it virtually impossible to use it in unstretched films. For these reasons, conventional resins have a drawback that they cannot be used as base films for optical recording media.

[Object of the present invention]

The object of the present invention is to create a product which does not have the above-mentioned disadvantages, that is, it can be used as a thin film-like product in itself, and at the same time.

It is an object of the present invention to provide a substantially biaxially stretched film that can provide a recording medium with a very good S/H when a recording layer is mounted and optical recording or magneto-optical recording is performed. be.

[11.b of the invention] The present invention provides polyvinylidene heptadide resin (A) and polymethacrylic resin (B) at a mixing ratio (A/!3) of 19/1 to
A film whose main body is a 3/1 mixed group 1 material, and the tensile strength in the longitudinal direction of the film is 1 or more in 20 bags/20 bags, and the Young's modulus is 200'q/mm' or more,
Fighting shrinkage rate at 120℃ is 50% or less, 260-11
The present invention is characterized by a biaxially stretched optical recording base film having a light transmittance of 85% or more at 000 nm and a variation in refractive index in one in-plane direction of 8×10 2 or less.

The polyvinylidene fluoride resin (A) in the present invention is
It is a well-known polyvinylidene fluoride resin.

Among them, the melting peak temperature is 155-180°0°, preferably 165-175°C, and the H
A polyvinylidene fluoride resin having an ead to head bond of 20% or less, preferably 15% or less, more preferably 10% or less is suitable, and the number average molecular weight of the resin (
Mn) is preferably selected from 5x10 to 10. If the molecular weight is too low, the impact strength tends to be low, while if the molecular weight is too large, melt extrusion becomes difficult or heat shrinkage increases, which is not preferable.

In addition, the molecular weight distribution (weight average molecular weight/number average molecular weight) is
2-40, preferably 5-8 is suitable.

If the molecular weight distribution is too narrow, the stretchability will decrease, and if the molecular weight distribution is too wide, the heat shrinkage rate will tend to increase, which is not preferred. Other fluorine-based polymers or monomers other than vinylidene fluoride may be added or copolymerized to the polyvinylidene fluoride resin within a range that does not impair its properties, specifically in an amount of 5 weight or less.

What is the polymethacrylic resin CB) in the present invention?

A resin mainly composed of polymethyl methacrylate (1) polymethyl methacrylate homopolymer, or (2) methacrylic acid/acid or an ester of methacrylic acid and an aliphatic alcohol having 2 to 8 carbon atoms, or acrylic acid or A copolymer of methyl methacrylate and one or more monomers selected from esters of acrylic acid and aliphatic alcohols having 1 to 8 carbon atoms, containing 60 or more moles of methyl methacrylate, preferably 85 or more moles, or,
(3) The copolymer of (2) is blended with (1) in an amount of 5Qwt%, preferably 25wt% or less.

It is preferable to select a number average molecular weight of 1x10 to 20x10 as the polymethacrylic tetrafunctional resin used in the present invention. This is because if the number average molecular weight is too small, stress cranking resistance deteriorates, while if it is too large, compatibility becomes poor. In addition, in order to improve the heat resistance of the obtained film, the glass transition temperature of the polymethacrylic resin is 50°C or higher.

Preferably, one with a temperature of 75°C is selected.

Examples of polymethacrylic resins include homopolymers of methyl methacrylate or acrylic acid, methacrylic acid, or acrylic acid.

Ethyl ester and butyl ester of methacrylic acid.

Examples include copolymers with inpropylene, small esters, and the like. Among them, methacrylic acid, acrylic acid, or acrylic acid methyl ester is added to methyl methacrylate.
15 mol% (preferably 5-12 mol%) and methacrylic acid ethyl ester 2-15 mol% (preferably 4-12 mol%).
It is particularly preferable to use a copolymerized terpolymer (8 moles) because it provides excellent optical recording reproducibility.

The polymethacrylic acid resin used in the present invention is.

Regardless of whether it is a homopolymer or a copolymer, those exhibiting a syndiotactic structure are preferred. In particular, it is particularly preferable that the men's type probability Pm of H)l is 0iO-0.38.

It is preferable that 50% or more of the hydrogen contained in the resin CB) is deuterated because the light transmittance at a wavelength of 500 to 11,000 nm is improved.

The present invention mainly consists of a composition of resin (A) and resin (B), specifically, polystyrene, fluorine-containing methacrylate resin, poly(4-methylpentene). Additives such as polyvinyl chloride, other fluororesins, or other additives such as stabilizers may be added to 25 parts per 100 parts of the composition of satiety (A) and resin (B) within a range that does not impair the characteristics of the present invention. It may be added in less than 2 hours.

In the present invention, the mixing ratio of resin (A) and resin CB) (weight of resin (A)/weight of resin (B)) is 19/1 to 6/1.
Is it necessary to do so? When the mixing ratio exceeds 19/1 (when resin B is small), the tensile strength, Young's modulus, and light transmittance are insufficient, and when used as a base film for optical recording, the recording reproducibility is insufficient. Undesirable. On the other hand, when the mixing ratio is less than 3/1 (when there is too much resin (B)), it is #f thermal.

The tensile strength becomes insufficient, and in this case too, the reproducibility of recording becomes insufficient, which is not suitable. Especially (when the ratio of red fat (A) and resin (B) is in the range of 9/1 to 3.371,
It is preferable because it is easy to obtain the highest strength, highest Young's modulus, and lowest heat loss coefficient, and the recording reproducibility is remarkable as a base film for optical recording.

The present invention; Part 1: The film has a tensile strength of 20 kg.
/mm' or more (the upper limit is not particularly limited or is substantially 4
0 Heron/appropriate), Young 5200 z/=m”
or more (the upper limit is not particularly limited or is practically 400)
q/'Jul'), the heat shrinkage rate at 120°C is 50 cm or less, and the light transmittance at 260 to 11,000 nm is 85% or more (the upper limit is not particularly limited or is practically about the same ) The variation in refractive index in one in-plane direction must be 8×10 2 or less. Although not particularly limited, those in which the difference between N, rlax and the refractive index (Nz) in the thickness direction exceeds 10 are more preferable as they have high strength.

If the tensile strength, Young's modulus, and thermal shrinkage rate are outside the range of the present invention, recording reproducibility deteriorates with repeated use, which is not preferable. Furthermore, if the terminal birefringence in light transmission is outside the range of the present invention, it is not preferable because good recording reproducibility cannot be obtained from the beginning.

The film in the present invention needs to be biaxially stretched. For unstretched or single-motion stretched films,
Dispersion in bonding, tensile strength, Young's modulus, and in-plane refractive index are all inappropriate because they do not fall within the scope of the present invention. The film of the present invention may be biaxially stretched regardless of the crushing method, but simultaneous biaxial stretching reduces the variation in refractive index in one in-plane direction. Particularly preferred. The thickness of the film used in the present invention is not particularly limited, but is 8μ to 5001Lm,
tt m is preferable.

The base of the base film refers to the tensile strength of the layers provided on one side of the optical recording layer and the other side (
The measurement method is the same as the method for measuring tensile strength of the present invention), and when compared, it refers to the layer with the higher tensile strength.

Next, a method for manufacturing the film of the present invention will be described, but the method is not limited thereto.

After drying the polymethacrylic resin (B) under vacuum at a constant temperature (80°0 in the case of Kamejo's polymethyl methacrylate), it is mixed with the resin (A) at a predetermined ratio. The resin composition thus obtained was processed using an extruder equipped with a screw having a compression ratio of 18 to 5.5.

Melt extrusion is performed at 180 to 280°C to form pellets.

After drying this pellet under specified conditions, the compression ratio was 1.8.
180 using an extrusion with a screw of ~5.5
Melt 1 eclipse extrusion 9 surface temperature 1 at ~280'C (〕~95
Cast a sheet of 7 layers and a thickness of 30 #I to 3 strokes on a casting drum of ゛c.

The sheet obtained in this way was heated to a temperature of 120 to 16 g.
Sequential biaxial stretching or simultaneous biaxial stretching is performed at 5°C. Alternatively, the biaxially stretched film may be stretched again in the longitudinal direction, if necessary. In short, it is acceptable as long as the film is finally stretched in two directions. The beletizing step may be omitted as appropriate. Also. The temperature of the casting drum should be as low as possible, as long as the adhesion between the drum and the film is not impaired, and the surface temperature is usually 40'C or higher. Stretching of the sheet is preferably from 145 to 165'c
, W is preferably carried out at 150 to 165°C.

It is preferable to stretch the film at a stretching ratio of 2.5 times or more in the width direction and in the longitudinal direction. In particular, if the film is stretched at a stretching ratio of 3.5 times or more in the longitudinal direction and at an area magnification of 10 times or more, a film with preferable physical properties can be obtained. . It is also preferable to subject the obtained film to heat treatment, since it is possible to reduce the heat shrinkage rate. Especially in the width direction or longitudinal direction, 0
．． 115-165℃ without relaxing 5-8%
Preferably by performing heat treatment at 150 to 160°C.

This is preferable because it can minimize the decrease in mechanical properties and maximize the decrease in heat yield rate.

5bOx on the film thus combined.

GeOx, TeOx, Marx, InO
When the difference in transmittance before and after irradiation with light pulses and its change over time were investigated by placing a known optical recording thin film such as By biaxially stretching a composition containing a specific amount of polymethacrylic resin, a base film for a former recording medium with excellent recording reproducibility and little deterioration of the recording layer was obtained.

[Method of measuring characteristics. Evaluation criteria〕

The characteristics measurement method and evaluation criteria in the present invention are as follows.

(1) Tensile strength: JIS C2518-1972
According to the polyester film test method of
Measure the tensile strength at break of 00an/min.

(2) Young's modulus: JIS-Z-, 1702
Measurements are made using an Instron type tensile tester at a tensile speed of 20 mm/min.

(3) Heat shrinkage rate: Five strip samples each having a width of 1 am and a length of 20 cm are cut out in the longitudinal direction and the width direction of the film. A mark with a gauge distance of 15 ca+ is placed on the sample, one end of the sample is fixed with a chuck, and a 2 g load is applied to the other end, and heat treatment is performed in a hot air open at 120° C. for 15 minutes. The distance between gauges after heat treatment is measured in both the longitudinal direction and the width direction, and the average thereof is defined as L.

Thermal shrinkage rate = ((15-L)/15]xl[lo) Calculate.

(4) Refractive index: Using an Asope refractometer, methylene iodide is used as the mounting liquid and a sodium lamp is used as the light source. One width direction in the longitudinal direction of the film.

The refractive index in a direction inclined at 45° from the longitudinal direction to the width direction (hereinafter referred to as the bias direction) is measured, and the maximum refractive index c Nma) < ) and the minimum refractive index (Nmi
n) was selected and +Nmax'min was taken as the variation in the refractive index in the in-plane direction. In addition, the refractive index in the thickness direction was measured and defined as N2.

(5) Light transmittance: Hitachi ■Using a self-recording spectrophotometer, the wavelength was varied from 400 nm to 10 DOnm.

The parallel light transmittance was determined as σilj, which was defined as the light transmittance.

((31 Recording reproducibility: amorphous Te low oxide (T
ea, ) and Te as an evaporator, approximately 1 x 10
The base film is deposited to a thickness of about 120 nm in a vacuum of mn+Hg. If this recording layer has a base film, IJI
A 25 mW laser with a wavelength of 830 nm is irradiated from the 1 river to blacken the recording layer. Evaluate the reflectance of the thus obtained blackened layer and the untreated layer using a 5 mW laser at a wavelength of 830 nm. 9 If the reflectance changes by 12% or more, record reproducibility "◎" 1 reflectance Recording reproducibility is rated "○" if there are 10 or more changes in 12 or more.

When the reflectance is less than 10%, the recording reproducibility is evaluated as "x".

In addition, the tensile strength of the sample with a blackened recording layer was 1 kg/mm.
After repeating the expansion and contraction at '' 50 times, 9 reflectances were measured, and the results determined using the same criteria were shown as recording reproducibility over time.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on Examples.

Examples 1-5. Comparative Examples 1 to 2 As polyvinylidene fluoride resin (PVDF) (A), “Kynar” 740 manufactured by Pennwald [melting peak temperature 169°C, melt flow rate (JIS K676
0.3g710min.

Measured by FNMR, Head is also o Head bond 8 bond 8
Head measured by FNMR at 0.5 g/10 min of polyfluorinated vinyliso-7II resin (melting peak temperature 158°C, Nordflowre) obtained by suspension polymerization method.
to Head connection 82%]. In addition, as the resin (B), syndiotactic polymethyl methacrylate (hereinafter abbreviated as PMMA) [manufactured by Mitsubishi Rayon Co., Ltd. 1
Acrypet #vHOO1 (glass transition temperature 101℃,
Melt flow rate (all acrylic resins are AST)
(measured at 230'c according to MD-1238-65) 1.9 l/10 min) and isotactic PM
Prepare MA (glass transition temperature 58'c, melt flow rate 1.2 g/10 minutes).

Resin (A) and resin (B) dried for 12 hours in a vacuum dryer at (transition temperature of glass 1 - 10)'c were mixed in a predetermined ratio (
(shown in Table 1) in a triblend. The resin composition thus obtained is bath-melted and kneaded into pellets using a 40 mmφ extruder equipped with a screw having L/D=28° and a compression ratio of 3.8. The obtained pellets were dried under the same conditions as those used for pelletizing, and then bath-melted using the same screw and extruder used for pelletizing and a 250-width die, followed by casting at a surface temperature of 65°C. It is rapidly cooled on a drum to form an unstretched film with a thickness of 200 μm. The film obtained in this way is T, M
.

It was stretched at a stretching speed of 1000%/min using a Long film stretcher (stretching temperature is shown in the table).
. After the film thus obtained was subjected to tension heat treatment (relaxation rate 0%) at 150'c x 1 minute (comparative example 1 was 120'0), the physical properties were measured and shown in the table. Requirements of the present invention, namely:

Since the tensile strength, Young's modulus, and thermal shrinkage ratio have predetermined values, stable recording reproducibility is exhibited regardless of aging. Among them, the use of polyvinylidene fluoride with a high head-to-head ratio results in PMM having a syndiotactic structure rather than isotactic.
In the case of A, the recording nose is excellent. On the other hand, resin (B
) in Comparative Example 1, the tensile strength and Young's modulus are low, and the heat shrinkage rate is very thick (and the recording reproducibility over time deteriorates. Also, if the resin CB) is too small, it is uniform. Since the film cannot be stretched, the physical properties vary and the transparency becomes insufficient, resulting in a significant deterioration in recording reproducibility.

Examples 6 to 8 Kynar' 740, which is the same as in Example 1, is prepared as polyvinylidene fluoride m1lW (A).Resin (B)
Polymethyl methacrylate (polymethyl methacrylate) copolymerized with 10% by weight of butyl methacrylate (HMA) as '4t4
[Glass transition temperature 96℃, melt flow rate 1.4
g710 minutes], 1 ethyl methacrylate (EMA)
0-fold ta Z copolymerized polymethyl methacrylate position (1 effect [glass + 1 transition temperature 99°C, melt flow rate 1.2 g/10 min]) and methacrylic [(MA) 10
Polymethyl methacrylate resin copolymerized with 5% ethyl methacrylate (EMA) [glass transition temperature 98°C, melt flow rate 1.3 g/10 min]
to use, to use. Resin (A) and resin (B) were produced using the same horn method as in Example 1 and stretched, and the physical properties are shown in Table 1.

As shown in the table, when butyl methacrylate was copolymerized (Example 6), recording reproducibility comparable to that of ordinary PMMA was obtained. It can be seen that when ethyl methacrylate was copolymerized (Examples 7 and 8), the recording reproducibility immediately and over time was significantly improved. Such an improvement effect was not completely observed in the unstretched film, and became apparent only after biaxial stretching.

Examples 9 to 12 The same “Kynar” 740 as in Example 1 was prepared as polyvinylidene fluoride sanitary resin (A). The same syndiotactic PMMA as in Example 3 was prepared as resin CB).

Resin (A) and resin CB) are mixed and formed into a film in the same manner as in Example 1. The unstretched film thus obtained was stretched using a ToM film stretcher manufactured by Long Co., Ltd. at a stretching speed of 1000%/min, in the longitudinal direction in Example 9.
Biaxial stretching was carried out 5 and 6 times each in the width direction, and Example 10
Then, the samples were sequentially biaxially stretched 6 times in the longitudinal direction and 6 times in the width direction, and then each sample was heat treated in the same manner. In addition, the film stretched under the same conditions as in Example was subjected to relaxation heat treatment for 1 minute at 150'C with the relaxation rate changed to 2% in Example 11 and 6% in Example 12 in the longitudinal and width directions, respectively. was evaluated.

As shown in the table, in Example 10, which was sequentially stretched by 2+111, the variation in the refractive index in one in-plane direction increases, although slightly. On the other hand, Example 9 has a thick area magnification of 11 times.
It has high permanence strength and Young's modulus, and has excellent recording reproducibility over time. Example 11 in which relaxation was applied during heat treatment
1 to 12 are preferable from the viewpoint of recording reproducibility because the thermal shrinkage rate can be reduced without changing the mechanical properties much.

Claims (1)

[Claims] (1) A film having a composition in which polyvinylidene fluoride resin (A) and polymethacrylic resin (B) are mixed at a mixing ratio (A/B) of 19/1 to 3/1, and The tensile strength of the film in the longitudinal direction is 20 kg/mm^2
Above, Young's modulus is 200kg/mm^2 or above, 120℃
Thermal shrinkage rate is 50% or less, 260 to 1000 nm
A biaxially stretched optical recording base film having a light transmittance of 85% or more and a variation in refractive index in the in-plane direction of 8×10 or less.