JP2006347139A - Manufacturing method of resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a transparent resin sheet with a small residual phase difference and a manufacturing method of a transparent resin sheet having an optical property of a superior visual field angle property and exhibiting a small phase difference even when an incident angle is large. <P>SOLUTION: In the manufacturing method of the resin sheet wherein a sheet is formed by extruding a molten cyclic olefin base resin in a vertical direction from a die 11 mounted onto an extruder 10 and cooling the cyclic olefin resin extruded from the die, a falling down ratio defined by a die outlet opening (mm)/the thickness (mm) of the sheet is 1.05 or more and 1.5 or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a resin sheet having excellent optical characteristics.

  In large televisions and monitors represented by rear pros and liquid crystal projectors, images can be viewed by projecting light emitted from the front or rear of the screen onto the screen using a diffusion plate or the like. In recent years, as the screen becomes larger, a technique for controlling the reflection of external light is required to improve the visibility of the entire screen. In order to prevent reflection of external light, a technique for preventing reflection by external light by using a wave plate called a 1 / 4λ plate is often used. However, when a ¼λ plate is used, the incident light needs to be linearly polarized light when passing through the wave plate. On the other hand, when the light exiting the projection lens passes through an optical member such as a Fresnel lens or a lenticular, and the optical distortion has occurred in the member, after exiting the projection lens, 1 / 4λ Even when linearly polarized light is obtained with a wave plate represented by a plate, since the polarization state is elliptically polarized light, it passes through a 1 / 4λ plate installed in the outermost layer for the purpose of reflecting external light. In this case, there is a possibility that the transmittance is reduced. For this reason, the brightness of the image is lowered, and as a result, there is a problem that the characteristics of the image are not improved even if the reflection of external light can be prevented.

  Furthermore, as an optical substrate used for an optical member such as a touch panel, it is considered to use a plastic plate such as polycarbonate or polyethylene terephthalate as a substrate material with an emphasis on heat resistance. Thinning is aimed at as a technical trend of the touch panel. For this purpose, it is desirable to make the touch panel polarizing plate integrated type in which the touch panel substrate is combined with the polarizing plate. For this purpose, it is essential that there is no optical distortion of the material of the touch panel substrate. However, since the resin sheet made of the above-described material has an aromatic ring in the structure, the photoelastic coefficient is high, and stress is applied to the substrate by touch. If this occurs, there is a concern that optical distortion may occur there. Therefore, development of a transparent resin sheet having a small photoelastic coefficient and no optical distortion has been desired.

  On the other hand, in Patent Document 1, as a method for forming a sheet with less optical distortion, a method in which a resin sheet is sandwiched between a metal roll and a metal belt, and in Patent Document 2, the opening degree of a die lip is defined. Although a method for manufacturing a sheet or film having a small residual retardation is disclosed partially, the phase difference of the sheet is improved when the incident angle is large to improve the viewing angle characteristics. Therefore, even if a sheet having a small residual phase difference is used, there is a problem that the viewing angle characteristics when the sheet is made into an optical member are not improved.

Japanese Patent Laid-Open No. 2000-219752 JP 2000-263628 A

  This invention was made | formed based on the above situations, The 1st objective is to provide the manufacturing method of a transparent resin sheet with a small residual phase difference. The second object of the present invention is to provide a method for producing a transparent resin sheet having excellent viewing angle characteristics and having optical characteristics with a small phase difference even when the incident angle is large.

The method for producing the resin sheet of the present invention comprises:
A method for producing a resin sheet in which a molten cyclic olefin-based resin is extruded in a vertical direction from a die attached to an extruder, and the cyclic olefin-based resin extruded from the die is cooled to form a sheet,
The withdrawal ratio v defined by the following formula is 1.05 or more and 1.5 or less.
v = die outlet opening (mm) / sheet thickness (mm)
In the present invention, “sheet” includes what is generally referred to as “film”.

According to the method for producing a resin sheet of the present invention, a resin sheet having a small residual phase difference and excellent optical characteristics can be produced. For this reason, when the obtained resin sheet is used for a substrate of a display material that uses a wavelength plate of 1 / 2λ or 1 / 4λ, reflection of external light can be prevented. For this reason, the contrast ratio of an image can be increased, and as a result, the visibility of a projector, a television, or the like can be improved. In addition, since the phase difference does not change even at an incident angle other than normal incidence, a sheet with a small viewing angle dependency can be manufactured.
Further, when a sheet having a small residual retardation is used as a substrate in combination with a liquid crystal application and placed in a polarizing plate, it can be suitably used as an optical member having a high light transmittance.

Hereinafter, the present invention will be described in detail.
<Cyclic olefin resin>
The resin sheet obtained by this invention consists of cyclic olefin resin. This cyclic olefin-based resin has thermoplasticity, and birefringence due to molecular orientation is less likely to occur when the molecules are oriented compared to other thermoplastic transparent resins such as polycarbonate and polystyrene. It is useful for various uses in
Such a cyclic olefin-based resin includes a polymer or copolymer (hereinafter referred to as “(co)” obtained from a monomer represented by the following general formula (1) (hereinafter also referred to as “specific monomer”). It is preferable to use a (co) polymer having a structural unit represented by the above general formula (1), particularly preferably the above general formula (2). (Co) polymer having a structural unit.

(In the formula, R ^{1 to} R ⁴ are a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or other monovalent organic group, and may be the same or different from each other. Any two of ^{1 to} R ⁴ may be bonded to each other to form a monocyclic or polycyclic structure, m is 0 or a positive integer, and p is 0 or a positive integer.)

(In the formula, the definitions of R ^{1 to} R ⁴ are the same as those in the above formula (1).)

Specifically, the polymers or copolymers shown in the following (a) to (e) can be preferably used.
(A) Ring-opening polymer of specific monomer (hereinafter also referred to as “specific ring-opening polymer”)
(B) a ring-opening copolymer (hereinafter referred to as “specific ring-opening copolymer”) of a specific monomer and a cyclic monomer copolymerizable therewith (hereinafter also referred to as “copolymerizable cyclic monomer”). Also referred to as “polymer”.)
(C) Saturated copolymer of specific monomer and unsaturated double bond-containing compound (hereinafter also referred to as “specific saturated copolymer”)
(D) Hydrogenated (co) polymer (e) specific ring-opening polymer or specific ring-opening copolymer (hereinafter also referred to as “specific ring-opening (co) polymer”) Hydrogenated (co) polymer obtained by cyclization of ring-opened (co) polymer by Friedel-Craft reaction and hydrogenation

[Specific monomer]
As a preferable specific monomer, in the above formula (1), R ¹ and R ³ are a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and R ² and R ⁴ are a hydrogen atom or a monovalent organic group. And at least one of R ² and R ⁴ represents a polar group other than a hydrogen atom and a hydrocarbon group, m is an integer of 0 to 3, p is an integer of 0 to 3, and the value of m + p is 0. -4, more preferably 0-2, particularly preferably 1.
Among the specific monomers, the specific monomer in which R ² and R ⁴ have a polar group represented by the following formula (3) has a high glass transition temperature (hereinafter also referred to as “Tg”), and moisture absorption. It is preferable at the point from which a cyclic olefin type thermoplastic resin with low property is obtained.

^{_{- (CH 2) n COOR 5}} (3)
(Wherein, R ⁵ represents a hydrocarbon group having 1 to 12 carbon atoms, n is an integer from 0 to 5.)

In the above formula (3), R ⁵ is preferably an alkyl group.
Moreover, the smaller the value of n, the higher the Tg of the resulting cyclic olefin-based thermoplastic resin, which is preferable. In particular, the specific monomer having n of 0 is preferable because it can be easily synthesized.

In the above formula (1), R ¹ or R ³ is preferably an alkyl group, more preferably an alkyl group having 1 to 4 carbon atoms, still more preferably an alkyl group having 1 to 2 carbon atoms, particularly A methyl group is preferred. Furthermore, it is preferable that this alkyl group is bonded to the same carbon atom as the carbon atom to which the polar group represented by the above formula (3) is bonded.
Moreover, the specific monomer whose m is 1 in the said Formula (1) is preferable at the point from which the thermoplastic resin composition with higher Tg is obtained.

As specific examples of the specific monomer represented by the above formula (1),
Bicyclo [2.2.1] hept-2-ene,
Tricyclo [5.2.1.0 ^2,6 ] -8-decene,
Tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
Pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] -4-pen Tadesen,
Pentacyclo [7.4.0.1 ^2,5 . 19 ^9,12 . 0 ^8,13 ] -3-pentadecene,
Tricyclo [4.4.0.1 ^2,5 ] -3-undecene,
5-methylbicyclo [2.2.1] hept-2-ene,
5-ethylbicyclo [2.2.1] hept-2-ene,
5-methoxycarbonylbicyclo [2.2.1] hept-2-ene,
5-methyl-5-methoxycarbonylbicyclo [2.2.1] hept-2-ene,
5-cyanobicyclo [2.2.1] hept-2-ene,
8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-ethoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-n-propoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-isopropoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-n-butoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-ethoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-n-propoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-isopropoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-n-butoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,

Dimethanooctahydronaphthalene,
Ethyltetracyclododecene,
6-ethylidene-2-tetracyclododecene,
Trimethanooctahydronaphthalene,
Pentacyclo [8.4.0.1 ^2,5 . 1 ^9,12 . 0 ^8,13] -3-hexadecene, heptacyclo [8.7.0.1 ^3,6. 1 ^10,17 . 1 ^12,15 . 0 ^2,7 . 0 ^11,16 ] -4-Eicosen,
Heptacyclo [8.8.0.1 ^4,7 . 1 ^11,18 . 1 ^13,16 . 0 ^3,8 . 0 ^12,17 ] -5- ^Haneikosen ,
5-ethylidenebicyclo [2.2.1] hept-2-ene,
8-ethylidenetetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
5-phenylbicyclo [2.2.1] hept-2-ene,
8-phenyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,

5-fluorobicyclo [2.2.1] hept-2-ene,
5-fluoromethylbicyclo [2.2.1] hept-2-ene,
5-trifluoromethylbicyclo [2.2.1] hept-2-ene,
5-pentafluoroethylbicyclo [2.2.1] hept-2-ene,
5,5-difluorobicyclo [2.2.1] hept-2-ene,
5,6-difluorobicyclo [2.2.1] hept-2-ene,
5,5-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,6-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5-methyl-5-trifluoromethylbicyclo [2.2.1] hept-2-ene,
5,5,6-trifluorobicyclo [2.2.1] hept-2-ene,
5,5,6-tris (fluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,5,6,6-tetrafluorobicyclo [2.2.1] hept-2-ene, 5,5,6,6-tetrakis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene En,
5,5-difluoro-6,6-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,6-difluoro-5,6-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,5,6-trifluoro-5-trifluoromethylbicyclo [2.2.1] hept-2-ene,
5-fluoro-5-pentafluoroethyl-6,6-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,6-difluoro-5-heptafluoro-iso-propyl-6-trifluoromethylbicyclo [2.2.1] hept-2-ene,
5-chloro-5,6,6-trifluorobicyclo [2.2.1] hept-2-ene,
5,6-dichloro-5,6-bis (trifluoromethyl) bicyclo [2.2.1] hept-2-ene,
5,5,6-trifluoro-6-trifluoromethoxybicyclo [2.2.1] hept-2-ene,
5,5,6-trifluoro-6-heptafluoropropoxybicyclo [2.2.1] hept-2-ene,

8-fluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene, 8-fluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-difluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-trifluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-pentafluoroethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8-difluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,9-difluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,9-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8-trifluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9-trifluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9-tris (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9,9-tetrafluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9,9-tetrakis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8-difluoro-9,9-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,9-difluoro-8,9-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9-trifluoro-9-trifluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9-trifluoro-9-trifluoromethoxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,8,9-trifluoro-9-pentafluoropropoxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-fluoro-8-pentafluoroethyl-9,9-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,9-difluoro-8-heptafluoroiso-propyl-9-trifluoromethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-chloro-8,9,9-trifluorotetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8,9-dichloro-8,9-bis (trifluoromethyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8- (2,2,2-trifluoroethoxycarbonyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene,
8-methyl-8- (2,2,2-trifluoroethoxycarbonyl) tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene.

Of these specific monomers, 8-methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene, 8-ethylidenetetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene, 8-ethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene, pentacyclo [7.4.0.1 ^2,5 . 1 ^9,12 . 0 ^8,13 ] -3-pentadecene is preferable in that a cyclic olefin-based thermoplastic resin having excellent heat resistance can be obtained.

[Copolymerizable cyclic monomer]
As the copolymerizable cyclic monomer for obtaining a specific ring-opening copolymer, it is preferable to use a cycloolefin having 4 to 20 carbon atoms, particularly 5 to 12 carbon atoms. Specific examples thereof include cyclobutene and cyclopentene. , Cycloheptene, cyclooctene, tricyclo [5.2.1.0 ^2,6 ] -3-decene, 5-ethylidene-2-norbornene, dicyclopentadiene, and the like.

[Unsaturated double bond-containing compound]
Examples of the unsaturated double bond-containing compound for obtaining a specific saturated copolymer include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-nonconjugated diene copolymer, and carbon- An unsaturated hydrocarbon polymer containing a carbon-carbon double bond can be used.
The ratio of the specific monomer and the copolymerizable cyclic monomer or unsaturated double bond-containing compound used is the weight ratio of the specific monomer: copolymerizable cyclic monomer or unsaturated double bond-containing compound. It is preferably 100: 0 to 50:50, and more preferably 100: 0 to 60:40.
When the proportion of the copolymerizable cyclic monomer or unsaturated double bond-containing compound is excessive, the Tg of the resulting copolymer is lowered, and as a result, the heat resistance of the resin is lowered. It becomes difficult to obtain a sheet having high heat resistance.

(Ring-opening polymerization catalyst)
The ring-opening polymerization reaction of the specific monomer is performed in the presence of a metathesis catalyst. The metathesis catalyst includes at least one metal compound selected from a tungsten compound, a molybdenum compound, and a rhenium compound (hereinafter referred to as “component (a)”) and a Deaming periodic table group IA element (for example, Li, Na). , K etc.), Group IIA elements (eg Mg, Ca etc.), Group IIB elements (eg Zn, Cd, Hg etc.), Group III B elements (eg B, Al etc.), Group IVA elements (eg Ti, Zr etc.) ) Or a group IVB element (e.g., Si, Sn, Pb, etc.) compound having at least one element-carbon bond or element-hydrogen bond (hereinafter referred to as " (B) “component”), and contains an additive (hereinafter referred to as “component (c)”) to enhance the catalytic activity. It may be.

Specific examples of suitable metal compounds constituting the component (a) include metal compounds described in JP-A-1-240517 such as WCl ₆ , MoCl ₅ , and ReOCl ₃ .
Specific examples of the compound constituting the component (b) include n-C ₄ H ₉ Li, (C ₂ H ₅ ) ₃ Al, (C ₂ H ₅ ) ₂ AlCl, (C ₂ H ₅ ) _1.5 AlCl _1.5 , (C ₂ H ₅ ) AlCl ₂ , methylalumoxane, LiH and the like, compounds described in JP-A-1-240517 can be mentioned.
As the component (c), alcohols, aldehydes, ketones, amines and the like can be preferably used, but other compounds shown in JP-A-1-240517 can be used.

[Hydrogenation]
The cyclic olefin resin used in the present invention is obtained by hydrogenating a specific (co) ring-opening polymer in addition to the specific (co) ring-opening polymer and the specific saturated copolymer. A hydrogenated (co) polymer obtained by cyclizing a hydrogenated (co) polymer and a specific (co) ring-opened polymer by Friedel-Craft reaction and then hydrogenating it can be used.
Since such a hydrogenated (co) polymer has excellent thermal stability, it can prevent its properties from being deteriorated by heating when it is molded or used as a product. it can.
Here, the hydrogenation rate in the hydrogenated (co) polymer is usually 50% or more, preferably 70% or more, more preferably 90% or more, still more preferably 95% or more, and particularly preferably 97% or more.

The cyclic olefin resin used in the present invention preferably has an intrinsic viscosity (ηinh) measured in chloroform at 30 ° C. of 0.2 to 5.0 dl / g.
The average molecular weight of the cyclic olefin-based resin is 8,000 to 100,000 in terms of polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC), and 20,200 in weight average molecular weight (Mw). The thing of the range of 000-300,000 is suitable.
Furthermore, it is preferable that the Vicat softening point of cyclic olefin resin is 160 degreeC or more.

At least one surface of the resin sheet obtained by the production method of the present invention is a smooth surface, and the surface roughness Ra is 0.01 μm or less, preferably 0.008 μm or less. When the surface roughness exceeds 0.01 μm, the smoothness of the surface is low. Therefore, when the surface roughness is incorporated into a liquid crystal display, unevenness of the display screen tends to occur.
The resin sheet has a thickness of 0.3 to 1.5 mm, preferably 0.3 to 1.2 mm, more preferably 0.3 to 1.0 mm, and particularly preferably 0.5 to 1.mm. 0 mm.
The thickness distribution of the resin sheet is usually within ± 5%, preferably within ± 4%, more preferably within ± 3%, and particularly preferably within ± 2% of the average value. When the thickness distribution exceeds ± 5%, the dependency of the phase difference on the incident angle becomes large, which is not preferable.

Further, the resin sheet obtained by the present invention has a residual phase difference of 10 nm or less, preferably 8 nm or less, particularly preferably 5 nm or less, measured with an incident angle of 0 degree. The residual phase difference measured at an incident angle of 40 degrees is 30 nm or less, preferably 20 nm or less, particularly preferably 18 nm or less. The low residual phase difference is preferable because high contrast can be obtained when the liquid crystal display element is incorporated, and contrast unevenness is less likely to occur.
Furthermore, the resin sheet obtained in the present invention is preferably a transparent resin sheet having a total light transmittance of 85% or more, particularly 90% or more.
The resin sheet obtained in the present invention has excellent optical properties because its thickness and residual retardation are in a specific range, and is suitable for polarizing plates, retardation plates, diffusion plates, lenticulars, Fresnel lenses, etc. Can be used.

<Method for producing resin sheet>
The method for producing a resin sheet in the present invention includes an extrusion molding method in which a molten cyclic olefin resin is extruded in a vertical direction from a die attached to an extruder, and the cyclic olefin resin extruded from the die is cooled to form a sheet. It is. As the extrusion molding method, the resin is melted by an extruder, the molten resin is quantitatively supplied by a gear pump, impurities are removed by filtration with a metal filter, the film is shaped by a die, and the take-out machine A method is generally used in which the film is cooled using a winder and wound using a winder.
Examples of the method for cooling the film extruded from the die to form a sheet include a nip roll method, an electrostatic application method, an air knife method, a calendar method, a single-sided belt method, a double-sided belt method, and a three-roll method. In order to manufacture a sheet with less distortion, a sheet manufacturing apparatus called a single-side belt type, particularly a sleeve type as shown in FIG. 1, is preferably used.

In the method for producing a resin sheet of the present invention, the draw ratio v determined from the lip gap at the die exit and the desired sheet thickness is:
v = die outlet opening (mm) / sheet thickness (mm)
It is an essential requirement that the deduction ratio v is 1.05 or more and 1.5 or less. This value is preferably 1.08 to 1.45, particularly preferably 1.1 to 1.4. A resin sheet with less optical distortion can be obtained by producing under such conditions that the reduction ratio is obtained.

If the value of v is less than 1.05, the resulting resin sheet has uneven thickness, which is not preferable. On the other hand, when the value of v exceeds 1.5, the influence on the thickness unevenness of the resin sheet is not great, but molecular orientation occurs when the sheet is stretched in the flow (x) direction, and the refractive index in the x direction. Becomes larger. For this reason, the residual phase difference (or residual birefringence), which is an index representing the refractive index anisotropy, is increased. In particular, when both sides of a sheet are pressure-bonded using a metal belt as in the above method, the z-direction refractive index Nz is reduced because the z-direction orientation of the sheet is completely relaxed. For this reason,
Rth = ((Nx + Ny) / 2−Nz) × d
(Where d is the thickness of the sheet)
Rth expressed by When Rth becomes large, the phase difference from the oblique direction becomes large when the sheet is bonded to the optical member, so that the viewing angle characteristics from the oblique direction are deteriorated. For this reason, it is not preferable to increase the withdrawal ratio because the viewing angle characteristics from an oblique direction are deteriorated.

  The die exit opening degree for deriving the draw ratio v can be adjusted by adjusting the lip interval of the discharge port. If it is much larger than the thickness of the resin sheet that can obtain the lip interval, a resin pool called a bank will be generated before transfer of the roll, and if this is involved, the residual phase difference of the sheet will increase, or the bank will increase in the thickness direction. This causes a problem such as narrowing of the viewing angle due to crushing, which is not preferable.

Drawing 1 is an explanatory view showing the outline in an example of the manufacture device used for the manufacturing method of the resin sheet of the present invention. In this figure, 10 is an extruder, 11 is a die attached to the tip of the extruder 10, and this die 11 is arranged so that its discharge port 12 faces downward. Below the die 11, a cooling belt 30 made of a metal cooling roll 20 and a metal endless belt is in pressure contact with each other, and the contact end E of both is the discharge port 12 of the die 11. It is arranged in a state of being directly below.
The cooling belt 30 is in a state of being pressed against the cooling roll 20 by a first holding roll 31 and a second holding roll 32 provided so as to be in contact with the inner surface thereof, and in a state where tension is applied. Is retained. Further, a peeling roll 40 for peeling the cyclic olefin-based thermoplastic resin pressure-bonded to the cooling roll 20 from the cooling roll 20 is arranged in parallel with the cooling roll 20.

As the extruder 10, any of a single screw, a twin screw, a planetary type, a kneader and the like may be used, but a single screw extruder is preferably used. Further, examples of the screw shape of the extruder include a vent type, a tip dull mage type, a full flight type, and the like, and a full flight type is preferable. The gear pump used for measuring the resin may be either an internal lubrication type or an external lubrication type, but the external lubrication type is preferred.
Examples of the filter used for filtering foreign substances include a leaf disc type, a candle filter type, a leaf type, and a screen mesh.

  As the die 11, it is essential to make the resin flow inside the die uniform, and in order to maintain the uniformity of the film thickness, the pressure distribution inside the die near the die outlet should be constant in the width direction. It is essential. Manifold dies, fishtail dies, coat hanger dies, and the like can be used to satisfy such conditions, and among these, coat hanger dies are preferable. A bending lip type is preferable for adjusting the flow rate of the die. A die having a function of adjusting thickness by automatic control by a heat bolt method is particularly preferable. Attaching a choke bar to adjust the flow rate or attaching a lip block to adjust the thickness creates a step in the attachment part, or traps air etc. in the gap of the attachment part. This is not preferable because it may cause generation or die line. The exit of the die 11 is preferably coated with a carbide coating such as tungsten carbide.

Examples of the material of the die 11 include SCM steel and stainless steel such as SUS, but are not limited thereto.
The die 11 is made of TiN, TiAlN, TiC, CrN, DLC (diamond-like carbon), etc., whose surface is plated with chromium, nickel, titanium or the like, or PVD (Physical Vapor Deposition). Those having a coating film, those having other ceramics sprayed thereon, those having the surface nitrided, and the like can be used. Such a die has a high surface hardness and a small friction with the resin, so that it is possible to prevent burnt dust and the like from being mixed into the transparent resin sheet to be obtained and to prevent the occurrence of a die line. It is preferable in that it can be performed.

  The cooling belt 30 preferably has a thickness of 0.5 mm or less, and particularly preferably has a thickness of 0.35 mm or less. If the thickness of the cooling belt 30 exceeds 0.5 mm, it is necessary to increase the outer shape of the roll that supports the belt, which is not preferable. The outer diameter of the cooling roll 20 is preferably 400 mmΦ or less at the outer periphery. More preferably, it is 350 mmΦ, and more preferably 300 mmΦ or less. When the outer periphery of the cooling roll 20 is larger than 400 mmΦ, it takes a long time until the molten resin is pushed out of the die and comes into contact with the cooling roll. There is a possibility of causing deterioration of the surface appearance of the obtained resin sheet and occurrence of residual retardation.

The cooling roll 20 has a heating means and a cooling means inside, and its surface roughness is preferably 0.5 μm or less, particularly preferably 0.3 μm or less.
As the cooling roll 20, a metal roll plated is preferably used, and a chrome plated or electroless nickel plated is particularly preferable.
As the cooling belt 30, a seamless belt is preferably used. When a cooling belt having a seam is used, a seam mark is formed on the obtained transparent resin sheet, which is not preferable.
Further, it is preferable to use a cooling belt 30 having a mirror finish with a surface roughness of 0.3 μm or less.
The thickness of the cooling belt 30 is preferably 0.6 to 1.2 mm. When the thickness is less than 0.6 mm, the belt is easily deformed, which is not preferable. On the other hand, when the thickness exceeds 1.2 mm, the belt is not preferable because the flexibility becomes small.
As a material constituting the cooling belt 30, stainless steel or the like can be used.

The first holding rolls 31 are arranged at a height level substantially the same as that of the cooling roll 20 so as to be spaced apart from the cooling roll 20 in parallel. The surface of the first holding roll 31 is preferably coated with silicone rubber or other heat-resistant elastomer, and the thickness of the coating layer is more preferably 5 to 15 mm. By providing such a coating layer, when the cyclic olefin-based thermoplastic resin is sandwiched between the cooling roll 20 and the cooling belt 30, the compressive stress acting on the resin is relieved, so that the obtained transparent An increase in phase difference due to residual strain in the resin sheet can be prevented.
Moreover, it is preferable that a 1st holding roll has a heating means and a cooling means inside.

  The second holding roll 32 is arranged below the cooling roll 20 in parallel with the cooling roll 20. This second holding roll is a contact distance adjusting roll for adjusting the contact distance between the cooling roll 20 and the cooling belt 30 and can be moved in an arc shape with the central axis of the cooling roll 20 as a reference, for example. Is provided.

  In the above, the cooling roll 20 and the cooling belt 30 are preferably arranged as close to the die 11 as possible. For example, the cooling roll 20 and the cooling belt 30 are arranged from the discharge port 12 of the die 11. It is preferable that the perpendicular distance D connecting to the contact end E is 300 mm or less, particularly 250 mm or less. When the distance D exceeds 300 mm, the molten cyclic olefin-based thermoplastic resin discharged from the discharge port 12 of the die 11 is remarkably cooled before being sandwiched between the cooling roll 20 and the cooling belt 30. Therefore, a phase difference due to residual distortion is likely to occur.

  Further, the contact distance between the cooling roll 20 and the cooling belt 30 is preferably 20 cm or more, and particularly preferably 25 cm or more. When the contact distance is less than 20 cm, the resin may not be sufficiently cooled by the cooling roll 20 and the cooling belt 30.

A resin sheet is manufactured by the above apparatus, for example, as follows.
Usually, before introducing the cyclic olefin-based resin into the extruder, water, gas (oxygen, etc.), residual solvent, etc. contained in the resin are removed in advance so as to have an appropriate Tg or less of the resin. Dry the resin at temperature.
As the dryer used for drying, an inert gas circulation dryer or a vacuum dryer is preferably used. It is also preferable to use a vacuum hopper that can absorb moisture in the hopper or seal the hopper with an inert gas such as nitrogen or argon, or can be kept in a reduced pressure state in order to suppress oxygen absorption.
The extruder cylinder is preferably sealed with an inert gas such as nitrogen or argon in order to prevent the resin from being oxidized during the melt extrusion and generating a gel or the like.

  The cyclic olefin-based resin melted by the extruder 10 is extruded into a sheet shape from the discharge port 12 of the die 11 downward in the vertical direction. The temperature distribution at the outlet of the die 11 is preferably ± 1 ° C. or less, and if it exceeds ± 2 ° C., a difference in the melt viscosity of the resin is likely to occur, and thickness unevenness, stress distribution unevenness, etc. are likely to occur.

  Thereafter, the extruded cyclic olefin resin is pinched by the cooling roll 20 and the cooling belt 30, thereby cooling the cyclic olefin resin. Then, the cyclic olefin-based resin pressure-bonded to the surface of the cooling roll 20 is peeled off from the surface of the cooling roll 20 by the peeling roll 40, whereby a resin sheet is manufactured. A release sheet 40 is disposed so as to be in contact with the cooling belt 30, and the extruded cyclic olefin-based resin is pressure-bonded to the surface of the cooling belt 30 and peeled off from the surface of the cooling belt 30. You may get

  In the present invention, the cyclic olefin-based resin pressure-bonded to the surface of the cooling roll 20 is preferably cooled to a temperature equal to or lower than the Tg, and then peeled off from the cooling roll 20. When the cyclic olefin-based resin is peeled at a temperature exceeding its Tg, a phase difference due to residual strain may occur when peeling or after peeling.

  From the viewpoint that the processing temperature of the cyclic olefin-based resin, that is, the set temperature of the extruder 10 and the die 11 can discharge the resin in a molten state with uniform fluidity from the die 11 and can suppress deterioration of the resin. It is preferable that it is Tg + 100 degreeC or more and Tg + 200 degreeC or less of the said cyclic olefin resin. When the processing temperature is less than Tg + 100 ° C., the fluidity of the resin is non-uniform, and therefore, it is not preferable because the resin sheet is not stably discharged and thickness unevenness easily occurs in the resulting resin sheet. On the other hand, when the processing temperature exceeds Tg + 200 ° C., the resin molecular chain is broken or oxidized when discharged from the die 11, so that the resin is easily deteriorated.

The surface temperature of the cooling roll 20 is preferably Tg-30 ° C. or higher of the cyclic olefin resin used. When the surface temperature of the cooling roll 20 is less than Tg−30 ° C., the resin is rapidly cooled by the cooling roll 20, so that a phase difference due to residual strain is likely to occur.
For the same reason, the surface temperature of the first holding roll 31 is preferably Tg-30 ° C. or higher of the resin.

  The take-up speed of the resin sheet is preferably lower than the rotational peripheral speed of the cooling roll 20, and specifically, when the rotational peripheral speed of the cooling roll 20 is V1 and the take-up speed of the resin sheet S is V2, the ratio V2 / V1 is preferably 0.7 to 0.99, more preferably 0.75 to 0.9, and particularly preferably 0.8 to 0.85. If this ratio V2 / V1 is less than 0.7, the sheet is likely to sag. On the other hand, if this ratio V2 / V1 exceeds 0.99, excessive tension acts on the sheet, The sheet may break.

The following examples illustrate the invention, but the invention is not limited to these examples.
[Example 1]
Under the following conditions, the resin is melted with an extruder, the molten cyclic olefin resin is extruded vertically from a die attached to the extruder, and the resin is sandwiched between a cooling roll and a cooling belt. The obtained sheet was peeled off to obtain a resin sheet having a thickness of 0.68 mm. About the obtained resin sheet, the residual phase difference is measured by “KOBRA-21ADH” manufactured by Oji Scientific Co., Ltd., and the surface roughness of the release surface of the resin sheet from the cooling belt is measured by Kosaka Laboratory. The total was measured with “Surf Coder CT-30K”. Further, the phase difference at a viewing angle of 40 degrees was measured using the above-mentioned “KOBRA-21ADH”.

<Types of cyclic olefin thermoplastic resins>
Manufactured by JSR Corporation; ARTON D4532. Tg 147 ° C., polystyrene-reduced weight average molecular weight measured by gel permeation chromatography (GPC) is 60,000, intrinsic viscosity ηinh measured in chlorobenzene is 0.47, and melt flow rate (10 kg load) at 260 ° C. is 29g / 10min.
<Resin molding conditions>
Extruder: Cylinder inner diameter 65mm, screw L / D32, cylinder set temperature 270 ° C, extrusion rate 64kg / hr
・ Die: Coat hanger Manny hold type with chrome plating on the surface ・ Discharge port width: 600mm
・ Lip gap of discharge port 0.8mm
・ Set temperature of discharge port: 270 ℃
・ Distance between the discharge port and the contact line between the cooling roll and the cooling belt: 80 mm
・ Cooling roll ・ Cooling belt: Sleeve type film take-up device manufactured by Chiba Machine Industry.
-Cooling roll: surface roughness 0.1 μm, surface temperature 120 ° C., peripheral speed 3 m / min
・ Cooling belt: thickness 0.3mm, surface roughness 0.1μm
First holding roll: 10 mm thick silicone rubber coated roll, surface temperature 120 ° C.

Next, the obtained resin sheet was sandwiched between two polarizing plates (manufactured by Polaroid, TECH SPEC: average transmittance 38%) and placed in a crossed Nicol state. This was measured for spectral transmittance at 550 nm using “Spectrophotometer U-3310 type spectrophotometer” manufactured by Hitachi, Ltd. When the transmittance of 550 nm crossed Nicol of only two polarizing plates was measured, the transmittance was 2%.
The results are shown in Table 1.

[Example 2]
A resin sheet having a film thickness of 0.83 mm was obtained in the same manner as in Example 1 except that the lip gap at the discharge port was 1.0 mm and the peripheral speed of the cooling roll was changed to 2.5 m / min. Evaluation similar to Example 1 was performed and the results are shown in Table 1.
[Example 3]
A resin having a film thickness of 0.68 mm was used in the same manner as in Example 1 except that a cyclic olefin-based resin (manufactured by JSR Corporation; D4531) having a Tg of 130 ° C. was used as the resin and the surface temperature of the cooling roll was set to 105 ° C. A resin sheet was obtained. Evaluation similar to Example 1 was performed and the results are shown in Table 1.

[Comparative Example 1]
The film thickness is the same as in Example 1 except that polycarbonate (made by Teijin Chemicals, Panlite AD5503) is used as the resin, the surface temperature of the cooling roll is 130 ° C., and the peripheral speed of the cooling roll is 3 m / min. A 0.65 mm resin sheet was obtained. Evaluation similar to Example 1 was performed and the results are shown in Table 1.
[Comparative Example 2]
A resin sheet having a thickness of 0.68 mm was obtained in the same manner as in Example 3 except that the lip gap at the discharge port was 1.5 mm. Evaluation similar to Example 1 was performed and the results are shown in Table 1.

It is a schematic diagram showing the apparatus used for the manufacturing method of the resin sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Extruder 11 Die 12 Discharge port 20 Cooling roll 30 Cooling belt 31 First holding roll 32 Second holding roll 40 Peeling roll E Contact end of cooling roll and cooling belt

Claims (2)

A method for producing a resin sheet in which a molten cyclic olefin-based resin is extruded in a vertical direction from a die attached to an extruder, and the cyclic olefin-based resin extruded from the die is cooled to form a sheet,
A method for producing a resin sheet, wherein a withdrawal ratio v defined by the following formula is 1.05 or more and 1.5 or less.
v = die outlet opening (mm) / sheet thickness (mm) The cyclic olefin resin is a polymer obtained from a monomer represented by the following general formula (1), or a monomer represented by the following general formula (1) and a monomer copolymerizable therewith. The manufacturing method of the resin sheet of Claim 1 which is a copolymer obtained.

(In the formula, R ^{1 to} R ⁴ are a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or other monovalent organic group, and may be the same or different from each other. Any two of ^{1 to} R ⁴ may be bonded to each other to form a monocyclic or polycyclic structure, m is 0 or a positive integer, and p is 0 or a positive integer.)

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