JPS61102248A - Film for optical record medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a film for optical recording media.

[Prior art]

Conventionally, acrylic resins such as polymethyl methacrylate, polycarbonate resins, and the like have been widely used as base materials for plastic optical recording media.

[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 film for an optical recording medium, there are the following drawbacks.

That is, both acrylic resins and polycarbonate resins have low elongation and low strength, so it is virtually impossible to use them in the form of thin films, and they cannot be used as films for optical recording media.

[Object of the present invention]

The object of the present invention is to provide a recording medium that does not have the above-mentioned drawbacks, that is, it can withstand use as a thin film-like material in itself, and at the same time has a recording layer mounted thereon and has very good recording reproducibility when optical recording or magneto-optical recording is performed. It is an object of the present invention to provide a fluororesin-based laminate that can be obtained.

[Structure of the invention]

In the present invention, the polyvinylidene fluoride resin (a) and the polymethacrylic resin (b) have a mixing ratio (a/b) of 19/1 to 11.
A biaxially oriented layer mainly composed of the composition mixed in step 15 (
A), polyvinylidene fluoride resin (c') and polymethacrylic resin (d") at a mixing ratio (c/d) of 65/35~
A laminate consisting of a substantially non-oriented layer (B) mainly composed of a composition mixed at a ratio of 2/8, and the thickness of the layer (B) is 5 times or more the thickness of the layer (Δ). The film for optical recording media is characterized by:

Polyvinylidene fluoride resin (a), (c) in the present invention
) has a melting peak temperature of 155 to 180°C (particularly preferred when used for resin (a)).

The temperature is 160-180℃), and the Heac+to-1ad binding measured by 4F-NM,R is 30% or less (
In particular, when used in resin (a), the content is preferably 20% or less, more preferably 10% or less.

The number average molecular weight (Mn) of the resin is 5×103
It is preferable to select one having a diameter of ˜5×10 6 . This is not preferable if the molecular weight is too small because it will become brittle.
On the other hand, if the molecular weight is too large, the heat resistance (heat shrinkage rate) will deteriorate, the melt extrusion characteristics, and crosstalk with the resins (b) and (d) will deteriorate, which is not preferable. In particular, the resin (c) is preferably one having a molecular grade of 5 x 103 to 5 x 10S.

Further, it is preferable to select a polyvinylidene fluoride resin having a molecular weight distribution (weight average molecular weight/number average molecular weight) of 2 to 40, preferably 3 to 8. If the molecular weight distribution is too narrow, crosstalk with resins (b) and (d), transparency,
This is not preferred because properties such as stretchability deteriorate. On the other hand, if it is too wide, the heat resistance (thermal shrinkage rate) will deteriorate, which is not preferable.

Do not damage the properties of the vinylidene fluoride resin.

Other fluorine-based monomers or other fluorine-containing monomers such as chlorine may be copolymerized within a certain range, specifically up to 5 mol%.

The polymethacrylic resins (b) and (d) in the present invention are resins mainly composed of polymethyl methacrylate (1
) polymethyl methacrylate homopolymer, or (2)
Ester of methacrylic acid and aliphatic alcohol having 2 to 8 carbon atoms, or acrylic acid having 1 to 8 carbon atoms
A copolymer of methyl methacrylate and one or more esters selected from esters with aliphatic alcohols, containing 60 mol% or more of methyl methacrylate, preferably 85 mol%
or (3) the copolymer of item (2) is blended with item (1) above in an amount of 50 wt%, preferably 25 wt% or less. The polymethacrylic resin used in the present invention has a number average molecular weight of 1X104 to 20X
It is better to choose 104. This is because if the number average molecular weight is too small, stress cracking resistance will deteriorate. On the other hand, if it is too large, the compatibility will be poor. Further, in order to improve the heat resistance of the obtained film, it is preferable to select a polymethacrylic resin having a glass transition temperature of 50°C or higher, more preferably 75°C. Examples of polymethacrylic resins include homopolymers of methacrylic acid methyl ester, and copolymers of the same with acrylic acid, methacrylic acid, or ethyl ester, butyl ester, isopropyl ester, etc. of acrylic acid or methacrylic acid. Among them, methacrylic acid, acrylic acid, or acrylic acid methyl ester is added to methyl methacrylate in an amount of 1 to 15 mol %, more preferably 5 to 12 mol %, and methacrylic acid ethyl ester is added in an amount of 2 to 15 mol %, more preferably 4 to 1 mol %. It is particularly preferable to use a terpolymer copolymer copolymerized with an amount of 8 mol %, since the reproducibility of optical recording is excellent. The polymethacrylic resin used in the present invention, regardless of whether it is a homopolymer or a copolymer, preferably exhibits a syndiotactic structure and has a pm of 0.30 to 0.38.

When 50% or more of the hydrogen contained in the resins (b) and (d) is deuterated, the wavelength is 500 nm to 1100 nm.
This is preferable because the light transmittance at 0n is improved.

Layers (A) and (B) of the present invention are mainly composed of a mixture of resins (a) and (b) and resins (c) and (d), but do not impair the characteristics of the present invention. Additives such as resins such as polystyrene, fluorine-containing methacrylate resin, poly(4-methylpentene), polycarbonate, polyvinyl chloride, and other fluorine-based resins, stabilizers, or ultraviolet absorbers to 100 parts of the mixture. In contrast, adding less than 25 parts,
May be mixed.

In the layer (A>) of the present invention, resin (a> and resin (b)
It is necessary to mix them at a mixing ratio (a/b) of 19/1 to 1115. If the amount of resin (b) is less than the above range, the stretchability during biaxial stretching will deteriorate significantly, and the light transmittance will also deteriorate, resulting in poor recording reproducibility when used as a film for optical recording media. This is not desirable as it will make things worse. On the other hand, if the amount of resin (b) is too large, the heat resistance and mechanical properties will deteriorate rapidly, which is not preferable.

In addition, in the layer (B) of the present invention, the resin (c)''
and resin (d) at a mixing ratio (c/d) of 65/35 to 2
It is necessary to mix at /8. Especially 65/35~4515
A range of 5 is preferable because mechanical properties and recording reproducibility are improved.

The layer (A) in the present invention must be biaxially stretched. In the case of an unstretched or uniaxially stretched film, the strength, Young's modulus, and surface roughness are insufficient, resulting in poor recording reproducibility, which is not preferable. Also, the layer (
A) may be stretched in biaxial directions regardless of the method, but simultaneous biaxial stretching is more preferable because the variation in the refractive index in the in-plane direction is reduced. Further, the area stretching ratio is preferably 6 times or more and 15 times or less. This is not preferable because if the areal stretching ratio becomes too large, the refractive index in the thickness direction will drop significantly and the recording reproducibility will deteriorate. That is, the layer (△) used in the present invention includes the length of the film,
Strength in each width direction is 15 kg/mm2 or more, elongation is 5
A biaxially stretched film having a Young's modulus of 0% or more, a Young's modulus of 200 average/ff1m2 or more, a surface roughness of 0.03 μm or less, and a refractive index in the in-plane direction and a refractive index in the thickness direction of 20×1Q-3 or less is suitable. It is.

Layer (B) in the present invention must be substantially non-oriented. This is because when reading records using linearly polarized light, reproducibility is greatly reduced.

Furthermore, "substantially non-oriented" refers to a state in which the difference in refractive index between the in-plane direction and the thickness direction is 8X10-3 or less, preferably 5X10-3 or less, and more preferably 1.5X10-3 or less. .

The film of the present invention is a laminate of layer (A) and layer (B), and the thickness of layer (B) needs to be at least 5 times, preferably at least 8 times the thickness of layer (A). It is. The upper limit of layer (B) is not particularly determined, but is usually 50 times or less, preferably 25 times or less.

This is because if the layer (B) is thin, the recording reproducibility will be poor.

The laminate in the present invention is a laminate in which one or more layers (A> and (B)) are alternately laminated, but it is essential that at least one surface layer is layer (A). In addition, in the case of multi-layer lamination (the upper limit is not limited, but practically 100 layers or less), the total thickness of the laminated layers (A) is the thickness of the layer (A), and the total thickness of the laminated layers (A) is the thickness of the layer (B). The total thickness shall be read as the thickness of layer (B).

Further, the thickness of the laminate film in the present invention is not particularly limited, but is usually 8 to 1,500 μm, preferably 50 to 1,500 μm.
The range is 600 μm.

When the composite of the present invention is viewed as a whole, the in-plane refraction (the product of the difference in refractive index in the width direction and the longitudinal direction and the film thickness) is 30 nm or less, preferably 20 nm or less.
nm or less, more preferably 10 nl or less, and the product of the maximum difference between the refractive index in the thickness direction and the in-plane direction and the film is 400 parts m or less, preferably 300 parts m or less, optical recording is possible. This is particularly preferred because the reproducibility is stable.

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

The polymethacrylic resins (b) and (d) are dried in vacuum at a predetermined temperature (for example, 80° C. in the case of ordinary polymethyl methacrylate). Resin (b) thus obtained, (
d) and resins (a) and (c) are mixed in a predetermined ratio by a tri-blend method to prepare raw materials for layers (A) and II (B). At this time, various additives may be added as necessary. Raw materials (A) and (B) are each compressed at a compression ratio of 1.8 to 5.5.
The mixture is melt-kneaded using a screw at 180 to 280°C and then extruded to form pellets. After drying the pellets (A) and (B) thus obtained under predetermined conditions,
Using an extruder (A) for the pellet (Δ) and an extruder (B) for the pellet (B), each equipped with a screw with a compression ratio of 1.8 to 5.5, the surface temperature is 10 to 95 °C. The composite is extruded onto a casting drum to obtain an unstretched composite film. The sheet thus obtained was stretched at a temperature of 12
Sequential biaxial or simultaneous biaxial stretching is performed at 0 to 170°C. Alternatively, the biaxially stretched film may be stretched again in the longitudinal direction, if necessary. In short, it is sufficient that the layer (A) is finally biaxially stretched. When stretched at the above temperature, layer (B) is
The film is drawn by drawing and is mostly unoriented, but if some orientation remains, the film may be heat-treated at 14.0 to 170° C. under tension or while being relaxed.

The temperature of the casting drum is preferably a low temperature unless the adhesion between the drum and the film is impaired.
It is best to keep it below ℃. As mentioned above, the composite film may be biaxially stretched, but if it is a film with about two to five layers, for example, it is biaxially stretched in the same manner as shown above. It can also be obtained by extrusion laminating a resin corresponding to layer (B) to a predetermined thickness on or between single films.

The pelletizing step may be omitted if necessary.

On the composite film thus obtained, a single layer of polymer in which silver was dispersed, an amorphous thin film of AsTe, etc.
A known optical recording thin film such as a thin film of bFe or a thin film of Te0X is mounted and used.

〔Effect of the invention〕

The present invention is a laminated film made of a composition in which polyvinylidene fluoride resin and polymethacrylic resin are mixed, and is composed of a biaxially oriented layer and a substantially non-oriented layer, so that the following effects can be obtained. .

(1) When used as a film for optical recording media□
Excellent recording reproducibility.

(2) A film with excellent flexibility, strength, and Young's modulus was obtained.

(3) It is relatively inexpensive.

[Measurement method and evaluation criteria for physical properties]

In addition, the measurement method and evaluation criteria of the characteristics in the present invention are as follows:
It is as follows.

(1) Breaking strength: JTS C2318-1972
According to the test method for polyester film, tensile speed 3
It was pulled at 00 mm/min using an Instron type tensile tester and its breaking strength was determined.

(2) Impact resistance: A sheet with a thickness of 1.0 mm was made and cut with scissors with a blade width of 13 cm. Those with cracks were marked as "x", and those with no cracks were marked as "○". .

(3) Birefringence: Using sodium D line (589 nm) as a light source, place the sample film surface perpendicular to the optical axis on a polarizing microscope equipped with crossed Nicols, and use the compensator to compensate for a caused by the optical path difference of the sample. Find it from the value, α/d
is birefringence. Here d is the thickness of the sample film. Note that the measurement was performed at 25° C. and 65% RH.

(4) Centerline average roughness The average roughness at a cutoff of 25 μm was measured using a universal surface profile measuring instrument 5F-3E manufactured by Koita Research Institute.

(5) Refractive index: Measured using an Atsube refractometer using methylene iodide as a mounting liquid and a sodium lamp as a light source. The maximum refractive index is Nma when measured in the longitudinal direction, width direction, and direction inclined at 45 degrees from the longitudinal direction to the width direction.
x, the refractive index in the thickness direction is shown as Nd. However, measurement
Measure the biaxially stretched film side.

(6) Recording reproducibility: Amorphous Te low oxide (Te
02 and Te) are evaporated to a thickness of about 120 nm on the substrate in a vacuum of about 1×10 −5 mmHg as an evaporation source. The film of the present invention was passed through this recording layer at a wavelength of 830 nm.
The recording layer is irradiated with a 25 mw laser to blacken the recording layer. The fouling rate of linearly polarized waves emitted from a semiconductor laser having a wavelength of 830 nm and a wavelength of 5 mW is evaluated for the thus obtained blackened layer and the untreated layer. If the reflectance changes by 10% or more and the return light when the recording layer is irradiated with the laser through the beam splitter and 1/4 wavelength plate is 0.05% or less, it is marked as "○", otherwise it is marked as "○". It was judged as "x".

〔Example〕

Embodiments of the present invention will be described below based on Examples.

Examples 1 to 7 As polyvinylidene fluoride resins (a) and (c), "Kynar" 74.0 manufactured by Henwald Co., Ltd. (melting temperature 169°C, JIS K676
The melt flow rate measured at 230°C is 0.
3C]/10 minutes, "HeadtoH measured by FNMR
"Acrypet" VHOOI manufactured by Mitsubishi Rayon Co., Ltd. (glass transition temperature 101°C, ASTM-D
-1 Prepare a melt flow rate of 1.9c+/10 minutes measured at 230°C according to 238-65. After drying the polymethacrylic resin in an 80'C vacuum dryer for 12 hours, the polyvinylidene fluoride resin and the layer (A) and layer (A) of Table 1 were added.
Mix in the proportions shown in B). The resin composition is L/D=
28, 40 mm with a screw with a compression ratio of 3.8
The mixture is melt-kneaded at 230°C using a φ extruder to form pellets. After drying the pellets in a vacuum dryer at 80° C. for 12 hours, the composition of layer ('A) is melt-kneaded at 230° C. using the same screw and extruder used for pelletizing.

On the other hand, the composition of layer (B) was prepared using a 30 mmφ extruder equipped with a screw with L/D=22 and a compression ratio of 3.6.
Melt and knead at 0°C. Layer in molten state (A
), the composition of layer (B) is laminated in a predetermined lamination state and thickness ratio in the short tube portion, and then extruded from a die onto a casting drum whose surface temperature is 35° C. to form a composite sheet with a thickness of 3.5 mm. The sheet was T. M. Stretching speed: 1,000%/min, temperature: 1 using a Lona film stretcher
After simultaneous biaxial stretching was carried out at 60° C. three times in the longitudinal and transverse directions, tension fixing heat treatment was carried out at the same temperature, and the physical properties were evaluated. Within the scope of the present invention, all exhibit good impact resistance and recording reproducibility regardless of the lamination state or lamination thickness ratio. In particular, Example 6 in which the ratio of layer A was small showed particularly excellent recording reproducibility.

Comparative Examples 1 to 6 Using the same polyvinylidene fluoride resin and polymethacrylic resin as in the example, the mixing ratio and thickness ratio were set outside the range of the present invention as shown in Table 2, and sheeting and biaxial production were performed in the same manner as in the example. Stretching was performed and physical properties were evaluated. However, in Comparative Example 6,
The physical properties of the cast unstretched composite film having a thickness of 380 μm were investigated.

In Comparative Example 1, in which the ratio of (c) in layer (B) was too high, the birefringence was large and the amount of returning light was large, making it unsuitable for use as a film for optical recording media.

Comparative Example 2, in which the ratio of (c) was too low, could not be used due to insufficient impact resistance. In layer (A) (b
) in Comparative Example 3, the stretching was not done uniformly and the physical properties varied widely, making it unusable. Also(
Comparative Example 4, which had a high ratio of b), had poor recording reproducibility and could not be used due to poor heat resistance (heat shrinkability). layer(
In Comparative Example 5, which had a large thickness ratio in A), there was a lot of reflected light and it was unsuitable. Comparative Example 6, which was not biaxially stretched and remained an unstretched composite film, had a low breaking strength and a large surface roughness, resulting in poor recording and recirculating properties.

Comparative Example 7.8 Using the same polyvinylidene fluoride resin and polymethacrylic resin as in the example, a single-layer film with a thickness of 380 μm and only the layer (A) or only the layer (B) was prepared in the same manner as in the example. The film was formed and evaluated.

Comparative Example 7, which included only layer (A), had a large Nmax-Nd, increased return light, and poor recording reproducibility. Comparative Example 8, which included only layer (B), had insufficient impact resistance and recording reproducibility.

Patent applicant Higashi Shishikikai Co., Ltd. = 19-

Claims (1)

[Claims] (1) Mixing ratio (a/b) of polyvinylidene fluoride resin (a) and polymethacrylic resin (b) 19/1 to 11/5
Biaxially oriented layer (A) mainly composed of a composition mixed with
and a substantially non-oriented layer mainly composed of a composition in which polyvinylidene fluoride resin (c) and polymethacrylic resin (d) are mixed at a mixing ratio (c/d) of 65/35 to 2/8. (B), the thickness of layer (B) is that of layer (A)
A film for optical recording media that is five times or more thicker than .