JPH04353444A - Non-crystalline polyolefin film - Google Patents

Abstract

PURPOSE:To provide a non-crystalline polyolefin film excellent in surface smoothness and mechanical characteristics without deteriorating optical characteristics such as double refraction by laminating a layer of non-crystalline polyolefin with a low MW to at least the single surface of a layer of a non-crystalline polyolefin polymet with a high MW in thickness of 0.1mum or more. CONSTITUTION:A non-crystalline polyolefin film is constituted by laminating a layer composed of a non-crystalline polyolefin polymer B with a low MW to at least the single surface of a layer composed of a non-crystralline polymer A with a high MW in thickness of 0.1mum or more. The non-crystalline polyolefin polymer B is laminated to the single surface or both surfaces of the layer of the polymer A but pref. laminated to both surfaces thereof because the curl of the film after molding is prevented and effect for reducing double refraction is shown. The thickness of one layer of the polymer B is 0.1mum or more and 20% or less of the whole thickness of the film from an aspect keeping the mechanical strength of the film as a whole and making the surface of the film sufficiently smooth.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to amorphous polyolefin films and sheets, in particular mechanical properties,
This invention relates to amorphous polyolefin films and sheets with excellent optical properties.

0002

[Prior Art] Conventionally, amorphous polyolefins such as norbornene-based polymers and dicyclopentadiene ring-opening polymers have excellent transparency and low water absorption. 218721,
It has been proposed to use it for optical purposes in Japanese Patent Laid-Open No. 63-234201 and the like.

0003

[Problems to be Solved by the Invention] However, in order to use the amorphous polyolefin as a film for optical purposes,
It is necessary to form a film with a very smooth surface and no defects. In order to obtain a film with a smooth surface, it is customary to use a nip roll method, a calender method, etc. during extrusion molding. In the nip roll method, calender method, etc., a molten or softened polymer is pressed between rolls or a casting drum to reduce irregularities on the polymer surface.

However, since the above-mentioned amorphous polyolefin generally has a high melt viscosity, a sufficient smoothing effect cannot be obtained by the nip roll method, calender method, etc., and it is difficult to sufficiently reduce the surface roughness of the film. moreover,
The circumferential speeds of opposing castings or rolls cannot be made completely constant, and therefore some shear stress is applied to the polymer between the rolls, which gives the film birefringence and optical Reduce properties. Further, if the polymer is drafted after extrusion, this will also increase the birefringence of the film. In contrast to such factors that deteriorate the optical properties of a film, polymers with high melt viscosity or high viscosity when softened have disadvantageous conditions for optical properties, such as increased shear stress. Further, when smoothing the surface by applying pressure, increasing the pressure has a greater smoothing effect, but this is not preferable because it increases birefringence for the reasons mentioned above.

The purpose of the present invention is to overcome the difficulty of molding, which is a drawback of amorphous polyolefins, and to produce an amorphous polyolefin with a smooth surface and excellent mechanical properties without deteriorating optical properties such as birefringence. It's about getting the film.

[0006]

[Means for Solving the Problems] The present invention provides a layer consisting of a high molecular weight amorphous polyolefin polymer (A) and at least one side of which a low molecular weight amorphous polyolefin polymer (B) is laminated to a thickness of 0.1 μm or more. The present invention relates to an amorphous polyolefin film characterized by:

[0007] Amorphous polyolefin polymers generally have a crystalline melting point that is difficult to observe in thermal measurements, and a typical example of the amorphous polyolefin polymer (A) referred to in the present invention is dicyclopentadiene dicyclopentadiene. One or more selected from a hydride of a ring polymer, a hydride of a copolymer of dicyclopentadiene and ethylene, and a norbornene polymer, and has a glass transition point of 100°C or higher, preferably 130°C
In the above, those having a water absorption rate of less than 0.1% are preferable.

[0008] Hydrogenated ring-opening polymers of dicyclopentadiene are conventionally known substances, such as those disclosed in Japanese Patent Publication No. 58-43
No. 412, JP-A No. 63-218727, etc., are well known. Copolymers of dicyclopentadiene and ethylene are known from JP-A No. 63-314220, and norbornene polymers are known from US Pat. No. 2,883,372,
As shown in Japanese Patent Publication No. 46-14910, Japanese Patent Application Publication No. 1-149738, etc., a polycyclic norbornene compound having 4 or more rings is obtained from a mixture of dicyclopentadiene and genophile and then made into a polymer. etc. are known. Of course, dicyclopentadienes also include alkyl substituents such as methyl and ethyl substituents, endo isomers, xo isomers, and mixtures thereof.

The glass transition point of these amorphous polyolefin polymers is preferably as high as 100° C., preferably 130° C. or higher, so that the physical properties of the film do not change over time.

The amorphous polyolefin polymer (A) constituting the base layer of the present invention and the amorphous polyolefin polymer (B) laminated on at least one side of the base layer are selected from the above-mentioned amorphous polyolefins. However, it is preferable that the polymer (A) and the polymer (B) have substantially the same structure, and in the case of different types of polymers, the adhesive force at the laminated interface may be reduced,
Optical properties are likely to deteriorate due to differences in refractive index.

The molecular weight of the polymer (A) of the present invention is 30,000 or more and less than 70,000 in terms of number average molecular weight, preferably 35
000 or more and less than 60,000. If the molecular weight is too low, it will be difficult to maintain the mechanical strength of the entire film, especially the impact strength. If the molecular weight is too high, the melt viscosity will become extremely high, making molding difficult, and the surface smoothing effect of calendering will be reduced. This is not preferable because it lowers the temperature. On the other hand, the molecular weight of the polymer (B) is 10,000 or more in number average molecular weight.
It is less than 0,000, preferably 15,000 or more and less than 25,000. If the molecular weight is less than 10,000, the mechanical strength after molding will be too low, resulting in brittleness and cracking of the surface layer.
If it is larger, the melt viscosity will increase and the smoothing effect will not be obtained, which is not preferable.

Amorphous polyolefin polymer (B) of the present invention
is laminated on one or both sides of the polymer (A) layer,
Laminating on both sides is preferable in order to prevent the film from curling after molding, and is also preferable in terms of the effect of reducing birefringence. The lamination thickness of each layer of polymer (B) is 0.1μ
m or more, preferably 1.0 μm or more, and 20% or less of the total thickness of the amorphous polyolefin film, in order to maintain the mechanical strength of the entire film, and to smooth the film surface. is sufficient.

The birefringence of the amorphous polyolefin film of the present invention is preferably 0.005 or less, more preferably 0.001 or less. If the birefringence is large, it may cause color spots when the film of the present invention is used, for example, as a protective film for a liquid crystal display panel.

The average surface roughness (Ra) of the amorphous polyolefin film of the present invention is preferably 0.1 μm or less, more preferably 0.05 μm or less, in view of the needs of the optical applications in which the film is used.

Any known additives may be added to the polyolefin film of the present invention, such as color inhibitors, antioxidants, heat stabilizers, crystal nucleating agents, antistatic agents, adhesion improvers, slip agents,
It is clear that antiblocking agents, weatherproofing agents, antifoaming agents, clarifying agents, viscosity modifiers, and the like may be included.

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

[0017] The amorphous polyolefin polymer (A) and the polymer (B) each preferably have a content of ultra-low molecular volatiles with a molecular weight of less than 100, such as moisture, gas, melt, volatile matter, decomposition products, etc., of 0. After reducing the amount to 0.5% by weight or less, the molten sheet is melted and laminated by a well-known method such as using a composite tube, and then the molten sheet is discharged from a die and solidified in close contact with a cooling drum to obtain a cast sheet. Casting methods include nip roll method, calendar method, electrostatic application contact method, air knife method,
An air camber method can be used, and in the case of the present invention, a nip roll method and a calendar method are preferred. Further, it is preferable to use a surface drum made of chrome plating or stainless steel and having a surface roughness Rmax of 0.2 μm or less. Although the drum surface temperature depends on the type of amorphous polyolefin polymer, it is preferably near the glass transition temperature of the polymer, and a temperature of 105 to 165°C is often used. Further, it is preferable that the draft ratio is as small as 20 or less, since this results in an optically isotropic film.

[0018] If necessary, heat treatment or stretching may be added, coextrusion with other polymers, lamination, coating, etc. may be added.

[0019]

[Evaluation method of physical properties]

(1) Number average molecular weight Measured by gel permeation chromatography using toluene as a solvent.

(2) Birefringence The in-plane birefringence of the film is measured using the sodium D line (589
The sample film surface is placed perpendicular to the optical axis on a polarizing microscope equipped with crossed nicols as a light source, and the optical path difference Γ caused by the birefringence of the sample is determined from the compensation value of the compensator, and Γ/d is It was assumed to be birefringence. Here d is the thickness of the sample film.

(3) Average surface roughness (Ra) DIN47
Stylus type surface roughness meter HOMMEL T specified by 68
Cutoff 0.25m measured with ESTERT10 model
It is expressed as center line average roughness in m.

(4) Charpy impact strength JIS B
Based on the method of No. 7722.

[0023]

EXAMPLES The present invention will be explained below by way of examples.

Examples 1-2, Comparative Examples 1-2 Ethylene 71
．． 1 mol%, DMOB (4,9,5,8-dimethano-3
a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene: I) 22.8 mol%, DMO
F (1,4,5,8-dimethano-1,4,4a,4b,
A copolymer containing 6.1 mol% of 5,8,8a,9a-octahydro-9H-fluorene) was hydrogenated to obtain an amorphous polyolefin polymer (A) having a number average molecular weight of 53,000.

Polymer (B) was obtained with the same composition as Polymer (A) and a number average molecular weight of 21,000.

These polymers were heated in a hot air oven for 10
After drying at 0°C for 12 hours, the mixture was melted in an extruder, combined and extruded through a T-type nozzle, adhered onto a drum at 100°C with nip rolls, and cooled to obtain an amorphous polyolefin film with a thickness of approximately 400 μm. . At this time, the pressing force of the nip roll was 10 kg/cm in linear pressure.

In Examples 1 and 2, films with good mechanical strength, surface roughness, and optical properties were obtained, but Comparative Example 1 was inferior in birefringence and surface roughness, and Comparative Example 2 was inferior in birefringence and surface roughness. Although the surface roughness was small, it was not possible to obtain a film with sufficient impact strength for practical use.

Examples 1 and 2 and Comparative Examples 1 and 2 are shown in the table.

[0029]

[Table 1]

[0030]

[Effects of the present invention] By laminating a low molecular weight amorphous polyolefin polymer layer on at least one side of a high molecular weight amorphous polyolefin polymer layer, the surface can be smoothed without deteriorating optical properties such as birefringence. An amorphous polyolefin film with excellent mechanical properties is obtained.

Therefore, the amorphous polyolefin film of the present invention is suitably used as a protective film for compact discs, video discs, optical cards, polarizing films, and the like.

Claims (5)

[Claims] Claim 1: A layer made of a low molecular weight amorphous polyolefin polymer (B) with a thickness of 0.1 μm on at least one side of the layer made of a high molecular weight amorphous polyolefin polymer (A).
An amorphous polyolefin film characterized by being formed by laminating the above. 2. The amorphous polyolefin film according to claim 1, wherein the polymer (A) and the polymer (B) have substantially the same structure. [Claim 3] The number average molecular weight of the polymer (A) is 300.
00 or more and less than 70,000, and the number average molecular weight of the polymer (B) is 10,000 or more and less than 30,000. [Claim 4] The amorphous polyolefin polymer (A) is
Selected from hydrides of ring-opening polymers of dicyclopentadiene, hydrides of copolymers of dicyclopentadiene and ethylene, hydrides of copolymers of dicyclopentadiene reaction products and ethylene, and norbornene polymers. Claim 1 characterized in that it consists of one or more types of
The amorphous polyolefin film according to any one of Items 1 to 3. 5. The surface of the layer made of the amorphous polyolefin polymer (B) has an average surface roughness (Ra) of 0.1 μm or less,
The amorphous polyolefin film according to any one of claims 1 to 4, which has a birefringence of 0.005 or less.