JP2006327112A - Production method of stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the in-plane variation of in-plane direction retardation and thickness direction retardation, which is suitable for retardation films used in liquid crystal display devices and the like, particularly optical compensation films used for improving viewing angle and contrast, and widening. A method for producing a simultaneous biaxially stretched film at high speed is provided.
SOLUTION: Holding both sides of a long original film with a plurality of holding means and moving the original film in the longitudinal direction, the holding means interval in the width direction of the original film and the longitudinal direction of the original film By extending the holding means interval in association with the movement in the longitudinal direction of the film, the raw film is stretched, the distribution of the thickness direction retardation of the stretched film is measured, and the measured thickness direction retardation is measured. The stretched film is obtained by comparing the distribution with the distribution of the target thickness direction retardation and adjusting the moving speed in the film longitudinal direction based on the comparison result.
[Selection figure] None

Description

  The present invention relates to a method for producing a stretched film suitable for a retardation film used for a liquid crystal display device, particularly an optical compensation film used for improving viewing angle and contrast, and more specifically, in-plane retardation and thickness direction retardation. The present invention relates to a method for producing a wide simultaneous biaxially stretched film at a high speed.

High contrast liquid crystal display devices using birefringence are used for various screen displays such as personal computers and word processors. In such a liquid crystal display device, the light from the light source becomes linearly polarized light by the polarizing plate, and the incident light becomes elliptically polarized light by birefringence by the liquid crystal cell, but when viewed through the polarizing plate, it is colored yellow or blue Therefore, there is a problem that the visibility of the display is lowered. Therefore, as a means to compensate for the phase difference due to the birefringence of the liquid crystal cell in order to return the elliptically polarized light after passing through the liquid crystal cell to linearly polarized light and prevent coloration, a phase difference plate (optical) made of a stretched film between the liquid crystal cell and the polarizing plate Compensation films) have been proposed.
For example, as a retardation plate for optically compensating the viewing angle characteristics (angle dependence of retardation) of a VA (Vertical Alignment) type liquid crystal, a negative retarder (main refractive index nx, ny in the film plane, film thickness direction) Film having a relationship of nx ≧ ny> nz and Re / Rth <1 when the main refractive index is nz and the film thickness is d; Re = d × (nx−ny), Rth = d × ((nx + ny) / 2 -Nz).) Is known. This negative letterer can be obtained by orienting a resin film having positive intrinsic birefringence in the biaxial direction. A biaxial stretching method is known as a method for orienting a film in a biaxial direction.

  Patent Document 1 discloses a method for producing an optical compensation film in which a thermoplastic resin film is simultaneously biaxially stretched in the longitudinal direction and the transverse direction. According to this method, the in-plane direction retardation value (Re = (nx−ny) × d) is 0 to 500 nm, and the thickness direction retardation value (Rth ′ = (nx−nz) × d) is 0 to 500 nm. It is described that an optical compensation film with Re / Rth ′ <1 can be obtained. Patent Document 2 discloses a method for producing an optical compensation film in which a film having a specific die line made of a norbornene resin is biaxially stretched at a stretch ratio of 1.3 times or more in both the longitudinal direction and the lateral direction. In biaxial stretching, simultaneous biaxial stretching is disclosed using a pantograph type tenter stretching machine (see Patent Document 4 or Patent Document 5), a screw type tenter stretching machine, a linear motor type tenter stretching machine, and the like. However, with only the technique described in Patent Document 1 or Patent Document 2, in-plane variations in in-plane direction retardation and thickness direction retardation are large, and a wide stretched film could not be obtained at high speed.

  Patent Document 3 describes a method for producing a stretched film that maintains the thickness and orientation of the stretched film uniformly at high speed. The manufacturing method of Patent Document 3 includes a step of melting a molding material, an extrusion step having a die for molding the molding material into an unstretched film, and an unstretched film molded by the die is cooled to form an original fabric A raw film forming step, a longitudinal stretching step of stretching the cooled raw fabric in the longitudinal direction with a low-speed roll and a high-speed roll, and a transverse stretching step of gripping both ends of the longitudinally stretched film and stretching in the lateral direction. In a stretched film manufacturing method comprising: a thickness measuring step for measuring the thickness of the film after the longitudinal stretching step or the transverse stretching step in real time; and an orientation degree for measuring the orientation degree of the film after the transverse stretching step in real time A measurement step, and outputs a signal corresponding to the thickness measured in the thickness measurement step to the calculation step, corresponding to the orientation degree measured in the orientation degree measurement step. The calculation step compares and calculates a preset thickness and the measured thickness, and compares and calculates a preset orientation degree and the measured orientation degree. A control signal is output to change the longitudinal stretching ratio when performing longitudinal stretching or the transverse stretching ratio when performing transverse stretching so that it matches the target value set in advance based on the comparison calculation result, and the stretched state is determined by this signal. It is characterized by controlling. However, in the method of Patent Document 3, in the lateral stretching step or the longitudinal stretching step to be performed later, the orientation in the longitudinal stretching step or the lateral stretching step performed earlier is relaxed by heat, and the orientation by the stretching performed later is performed first. Therefore, in order to increase the retardation in the thickness direction so that Re / Rth <1, the film must be stretched at a low temperature. The drawing condition range in which drawing at low temperature can be performed stably and without in-plane variation is very narrow, and it is difficult to control in such a narrow drawing condition range in industrial production.

JP 2002-196134 A Japanese Patent Laid-Open No. 2005-43740 Japanese Patent Laid-Open No. 11-10728 JP 63-42839 A JP 2004-195712 A

  The object of the present invention is to reduce in-plane variation in in-plane direction retardation and thickness direction retardation, which is suitable for retardation films used in liquid crystal display devices and the like, particularly optical compensation films used for viewing angle improvement and contrast improvement. Another object of the present invention is to provide a method for producing a wide simultaneous biaxially stretched film at high speed.

  As a result of intensive studies to achieve the above object, the present inventors have gripped both ends of a long original film with a plurality of holding means, moved the original film in the longitudinal direction, and By stretching the holding means interval in the width direction of the anti film and the holding means interval in the longitudinal direction of the original film in association with the movement in the longitudinal direction of the film, the original film is stretched to obtain a stretched film. Measure the thickness direction retardation distribution of the stretched film, compare the measured thickness direction retardation distribution with the target thickness direction retardation distribution, and move the film in the longitudinal direction based on the comparison result. By adjusting the speed, the in-plane variation of the in-plane direction retardation and the thickness direction retardation is small, and a wide simultaneous biaxially stretched film can be increased. In found that can be produced. The present inventors have completed the present invention based on this finding. Here, although the thickness direction retardation includes Rth and Rth ′ depending on the calculation method, either of them may be used in the present invention.

Thus, according to the present invention, (1) the both sides of the long original film are held by a plurality of holding means, the original film is moved in the longitudinal direction, and the holding means interval in the width direction of the original film is Stretching the original film by extending the holding means interval in the longitudinal direction of the original film in association with the movement in the longitudinal direction to obtain a stretched film,
Measuring the distribution of the thickness direction retardation of the stretched film,
A step of comparing the distribution of the measured thickness direction retardation and a distribution of the target thickness direction retardation, and a step of adjusting the moving speed in the film longitudinal direction based on the comparison result of the distribution of the thickness direction retardation A process for producing a stretched film is provided.

As a preferred aspect of the present invention, (2) the method further includes the step of adjusting the expansion width of the right and left gripping means when the gripping means interval is widened based on the comparison result of the thickness direction retardation distribution. Of stretched film.
(3) The method for producing the stretched film further comprising a step of adjusting the maximum spreading interval in the width direction or the longitudinal direction of the gripping means based on the comparison result of the thickness direction retardation distribution.
(4) Furthermore, a step of measuring the distribution of in-plane retardation of the stretched film,
The step of comparing the distribution of the measured in-plane direction retardation and the distribution of the target in-plane direction retardation, and the moving speed of the film in the longitudinal direction and the gripping means based on the comparison result of the in-plane direction retardation distribution The method for producing a stretched film, which comprises adjusting a widening width of the right and left gripping means and / or a maximum spreading distance in a width direction or a longitudinal direction of the gripping means when expanding the distance in the width direction.

(5) Furthermore, the process of measuring the thickness distribution of the stretched film,
Based on the step of comparing the measured thickness distribution with the target thickness distribution, and the comparison result of the thickness distribution, the film longitudinal movement speed, the width of the left and right gripping means when the gripping means spacing is widened, and // The manufacturing method of the said stretched film which has the process of adjusting the largest spreading | diffusion space | interval of the width direction or longitudinal direction of a holding means.
(6) The manufacturing method of the said stretched film which has the process of adjusting the temperature distribution at the time of the said extending | stretching to the atmosphere of the range of +/- 0.5 degreeC.
(7) The method for producing the stretched film further includes a step of adjusting the moving speed in the longitudinal direction of the film with a driving device having a rotational accuracy of 1 / 30,000 degree.
(8) The method for producing the stretched film, further comprising a step of warming a gripping means portion for gripping the film.

(9) Gripping both ends of the long original film with a plurality of holding means, moving the original film in the longitudinal direction, and the holding means interval in the width direction of the original film and the longitudinal direction of the original film Stretching the raw film by expanding the gripping means interval in association with the movement in the film longitudinal direction to form a stretched film,
Measuring the distribution of the thickness direction retardation of the stretched film, the thickness distribution and / or the in-plane direction retardation distribution,
Time-series data of the moving speed in the longitudinal direction of the film, time-series data of the spreading width of the right and left gripping means when the spacing of the gripping means is expanded in the width direction, and / or time-series data of the maximum spreading interval in the width direction or longitudinal direction of the gripping means ,
Time series data of distribution of measured thickness direction retardation, time series data of measured thickness distribution and / or time series data of distribution of measured in-plane direction retardation,
A process for building a transfer function model for producing stretched film from
Future thickness direction retardation caused by adjusting the moving speed of the film in the longitudinal direction, the expansion width of the right and left gripping means when the gripping means interval is widened in the width direction, and / or the maximum spreading distance in the width direction or longitudinal direction of the gripping means. Predicting the distribution, thickness distribution and / or in-plane retardation distribution by the transfer function model, and the prediction results and the desired thickness-direction retardation distribution, thickness distribution and / or in-plane direction letter The distribution of the foundation is compared, and based on the comparison result, the moving speed in the film longitudinal direction, the spread width of the right and left gripping means when the gripping means interval is widened in the width direction, and / or the maximum in the width direction or longitudinal direction of the gripping means A method for producing a stretched film having a step of adjusting a spread interval is provided.

  According to the production method of the present invention, it is possible to easily obtain a film in which the decrease in birefringence due to thermal relaxation of orientation is small and the absolute value of thickness direction retardation is large. In addition, since the in-plane variation of the in-plane direction retardation and the thickness direction retardation is small, the thickness unevenness is small, and a wide simultaneous biaxially stretched film can be obtained, the trimming width on both side portions is small, which is wasteful. Can be reduced. Furthermore, in-plane direction retardation, in-plane variation of thickness direction retardation, and thickness unevenness can be reduced in a short time from the start of production, and the amount of raw film that is wasted while finding the optimum value of the stretching conditions is small. Therefore, it is suitable for industrial production of retardation films used for liquid crystal display devices and the like, especially optical compensation films used for improving viewing angle and contrast.

  The method for producing a stretched film of the present invention includes gripping both side ends of a long original film with a plurality of holding means, moving the original film in a longitudinal direction, and holding means intervals in the width direction of the original film. The step of stretching the original film to form a stretched film by extending the holding means interval in the longitudinal direction of the original film in association with the movement in the longitudinal direction of the film, the thickness direction retardation of the stretched film The step of measuring the distribution, the step of comparing the distribution of the measured thickness direction retardation and the distribution of the target thickness direction retardation, and the film longitudinal direction moving speed based on the comparison result of the distribution of the thickness direction retardation It has the process to adjust.

  The long original film used in the present invention is a film made of a transparent resin. A transparent resin is a resin that is transparent to a desired wavelength. Examples of the transparent resin include acrylic resin, polycarbonate resin, polyester resin, and polyolefin resin. In the present invention, an alicyclic structure-containing polymer resin is preferable. The alicyclic structure-containing polymer resin used in the present invention is a polymer having an alicyclic structure in the main chain and / or side chain. From the viewpoint of mechanical strength and heat resistance, a resin containing an alicyclic structure in the main chain is preferable. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, but a cycloalkane structure is preferable from the viewpoint of mechanical strength, heat resistance, and the like. In addition, examples of the alicyclic structure include monocyclic, polycyclic, condensed polycyclic, and bridged rings. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 in the range of mechanical strength and heat resistance. And various properties of formability and moldability are highly balanced. Further, the alicyclic structure-containing polymer resin used in the present invention is usually thermoplastic.

  The alicyclic structure-containing polymer resin usually contains a repeating unit derived from an olefin having an alicyclic structure (hereinafter sometimes referred to as an alicyclic olefin). The proportion of the repeating unit derived from the alicyclic olefin in the alicyclic structure-containing polymer resin is appropriately selected according to the purpose of use, but is usually 30 to 100% by weight, preferably 50 to 100% by weight, more preferably. 70 to 100% by weight. When the ratio of the repeating unit derived from the alicyclic olefin is excessively small, the heat resistance is inferior, which is not preferable. The repeating unit other than the repeating unit derived from the alicyclic olefin is not particularly limited and is appropriately selected depending on the purpose of use.

  The alicyclic structure-containing polymer resin may have a polar group. Examples of the polar group include hydroxyl group, carboxyl group, alkoxyl group, epoxy group, glycidyl group, oxycarbonyl group, carbonyl group, amino group, ester group, carboxylic anhydride residue, amide group, imide group, etc. In particular, an ester group, a carboxyl group or a carboxylic anhydride residue is preferred.

  The alicyclic structure-containing polymer resin is usually subjected to addition polymerization or ring-opening polymerization of an alicyclic olefin, and optionally hydrogenating an unsaturated bond portion, or addition polymerization of an aromatic olefin, and It can be obtained by hydrogenating the aromatic ring portion of the polymer. In addition, the alicyclic structure-containing polymer resin having a polar group is obtained by, for example, introducing a compound having a polar group into the alicyclic structure-containing polymer resin by a modification reaction, or a monomer having a polar group. It is obtained by copolymerizing as a copolymerization component.

Examples of the alicyclic olefin used for obtaining the alicyclic structure-containing polymer resin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, and tetracyclo [7.4. 0.1 ^{10, 13} . 0 ^2,7] trideca -2,4,6,11- tetraene unsaturated hydrocarbons and their derivatives polycyclic structure such as, cyclobutene, cyclopentene, cyclohexene, 3,4-dimethyl cyclopentene, 3-methyl cyclohexene, 2- Unsaturated hydrocarbons having a monocyclic structure such as (2-methylbutyl) -1-cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4, 7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene And derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the aromatic olefin include styrene, α-methylstyrene, divinylbenzene and the like. The alicyclic olefin and / or aromatic olefin can be used alone or in combination of two or more.

  A monomer copolymerizable with an alicyclic olefin or an aromatic olefin can be subjected to addition copolymerization as necessary. Specific examples thereof include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1 -Pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, etc., ethylene or α-olefin having 2 to 20 carbon atoms; 1,4-hexadiene, 4-methyl-1, Non-conjugated dienes such as 4-hexadiene, 5-methyl-1,4-hexadiene and 1,7-octadiene; conjugated dienes such as 1,3-butadiene and isoprene It is. These monomers can be used alone or in combination of two or more.

Polymerization of the alicyclic olefin and / or aromatic olefin can be performed according to a known method.
The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of -50 ° C to 100 ° C and a polymerization pressure of 0 to 50 kgf / cm ² . The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst.

Specific examples of the alicyclic structure-containing polymer resin include a ring-opening polymer of a norbornene monomer and a hydride thereof, an addition polymer of a norbornene monomer, a norbornene monomer and a vinyl compound (ethylene, addition polymers with α-olefins, etc., polymers of monocyclic cycloalkenes, polymers of alicyclic conjugated diene monomers and their hydrides, polymers of vinyl alicyclic hydrocarbon monomers and Examples thereof include hydrides thereof and aromatic ring hydrides of aromatic olefin polymers. Among these, ring-opening polymers of norbornene monomers and their hydrides, addition polymers of norbornene monomers, addition weights of norbornene monomers and vinyl compounds (= ethylene, α-olefins, etc.) Preferred are aromatic ring hydrides of polymers and aromatic olefin polymers, and particularly preferred are hydrides of ring-opening polymers of norbornene monomers. Note that the norbornene monomer refers to a compound having a norbornene ring.
The above alicyclic structure-containing polymer resins can be used alone or in combination of two or more.

  The transparent resin used in the present invention is not particularly limited by the molecular weight. The molecular weight of the transparent resin is a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using cyclohexane or toluene as a solvent, and is usually 1,000 to 1,000,000, preferably 5 The range is from 10,000 to 500,000, more preferably from 10,000 to 250,000. When the weight average molecular weight (Mw) of the transparent resin is within this range, heat resistance, adhesiveness, surface smoothness and the like are balanced, which is preferable.

  The molecular weight distribution of the transparent resin is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by GPC using cyclohexane or toluene as a solvent, and is usually 5 or less, preferably 4 or less. More preferably, it is 3 or less. The glass transition temperature (Tg) of the transparent resin may be appropriately selected according to the purpose of use, but is preferably 70 ° C. or higher, more preferably 120 ° C. or higher, and most preferably 140 ° C. or higher. The transparent resin used in the present invention appropriately contains colorants such as pigments and dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, antioxidants, lubricants, solvents, etc. You may mix | blend.

The raw film used in the present invention may be a single layer film or a multilayer film formed by laminating two or more kinds of resins. Specific examples of the multilayer film include a multilayer film comprising a transparent resin layer having negative intrinsic birefringence and a transparent resin layer having positive intrinsic birefringence. The raw film may be already stretched.
The raw film is not particularly limited by its production method, and a film obtained by a known film molding method such as a cast molding method or an extrusion molding method can be used.

Next, how to stretch the original film in the production method of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an embodiment of a simultaneous biaxial stretching machine that can be used in the production method of the present invention.
The simultaneous biaxial stretching machine of FIG. 1 is called a pantograph type tenter stretching machine. Other simultaneous biaxial stretching machines include a screw type tenter stretching machine, a linear motor type tenter stretching machine, etc., but only the driving system for widening the holding means interval is different. Therefore, any type of simultaneous biaxial stretching machine can be applied to the production method of the present invention.

  For example, in the simultaneous biaxial stretching machine of FIG. 1, a plurality of gripping means 2 for gripping the end of the original film 1 are provided on both side ends of the original film 1, and a plurality of isometric lengths formed in a fold shape are provided. An endless link device (a part of the link and one endless link in the figure is omitted) 3 constituted by a link device is provided, and the endless link device 3 is driven by an inlet-side sprocket 4 of the original film 1 to travel in the traveling direction. The raw material in which the end portion is gripped by gradually increasing the distance between the gripping means 2 guided by guide rails 5, 6, 7 and 8 arranged in a divergent shape (from left to right in FIG. 1). The film 1 is stretched simultaneously in two longitudinal and transverse directions to obtain a stretched film 10, and after stretching, the end of the stretched film 10 is removed from the gripping means 2, and the endless link device 3 is driven by an outlet-side sprocket 9. Side sprawl And it is configured so as to return to Tsu door 4.

The simultaneous biaxial stretching machine preferably used in the manufacturing method of the present invention is such that a member that supports each node of the pantograph between the left and right (upper and lower in FIG. 1) guide rails 5 and 6 and between 7 and 8 is the length of the guide rail. It is held so as to be movable in the direction. One set of guide rails 5 and 6 and one set of guide rails 8 and 7 can be slid independently, and by the rail layout that can be made by this slide, how to spread the holding means interval in the MD direction (film longitudinal direction), It is possible to adjust how the gap between the gripping means in the TD direction (film width direction) is expanded.
That is, when the distance between the guide rail 6 and the guide rail 8 changes, the opening width of the pantograph changes, and the interval in the MD direction of the gripping means attached to the tip of the pantograph can be adjusted. When the distance between the guide rail 6 and the guide rail 8 becomes long, the pantograph of the link device 3 is closed and the MD direction gripping means interval is narrowed. Conversely, when the distance between the guide rail 6 and the guide rail 8 is shortened, the pantograph of the link device 3 is opened, and the MD direction gripping means interval is increased. Since each guide rail can slide independently, the distance between the upper guide rail 6 and the guide rail 8 in the figure and the distance between the lower guide rail 6 and the guide rail 8 in the figure are independent. By adjusting, the way of spreading the upper MD direction gripping means interval and the way of spreading the lower MD direction gripping means in FIG. 1 can be made the same or different.

On the other hand, the distance in the TD direction of the gripping means can be adjusted by the distance between the TD directions of the left and right guide rails 5. Since each guide rail can be slid independently, the spread width of the upper guide rail 5 in the TD direction on the upper side (t1 in FIG. 1) and the spread width of the lower guide rail 5 on the lower side in the TD direction. (T2 in FIG. 1) can be made the same or different.
The place where the change between the distance between the guide rail 6 and the guide rail 8 and the distance between the upper and lower guide rails 5 in the TD direction and the place where the change ends may be the same place or different places. If the change start place or the change end place is the same, stretching in the MD direction and the TD direction starts at the same time and ends at the same time. When the change start location or the change end location is different, the stretching start and stretching end times in the MD direction and the TD direction can be shifted.

  Since the distance between the gripping means 2 is substantially determined by the arrangement of the guide rails, the speed at which the distance between the gripping means is spread and how to spread by changing the speed at which the link device 3 moves on the guide rail, that is, the moving speed in the film longitudinal direction. Etc. change in association with movement in the longitudinal direction of the film.

  The raw film 1 is stretched by the above method to obtain a stretched film 10, and then the distribution of the thickness direction retardation of the stretched film 10, and the in-plane direction retardation distribution and the thickness distribution as required are measured. The measurement may be performed before the end of the stretched film 10 is removed from the gripping means 2, but it is preferably performed after the end of the stretched film 10 is removed from the gripping means in order to obtain a more accurate value.

  Since the thickness direction retardation, in-plane direction retardation and thickness often have distributions in the MD direction of the film, the distribution in the MD direction is measured. Then, these measured values are compared with the target thickness direction retardation distribution, if necessary, the in-plane direction retardation distribution and the thickness distribution, and the film longitudinal movement speed is adjusted based on the comparison result. . In the production method of the present invention, the moving speed in the film longitudinal direction on the inlet side is different from the moving speed in the film longitudinal direction on the outlet side. Although the longitudinal movement speed of the exit side, that is, the stretched film may be adjusted, the longitudinal movement speed of the exit side is likely to change depending on the stretching ratio in the MD direction. It is preferable to adjust with.

  In the present invention, the moving speed in the longitudinal direction of the film is usually 5 to 50 m / min, preferably 10 to 30 m / min. Since the film longitudinal direction moving speed is an important factor for adjusting the thickness direction retardation distribution, and in-plane direction retardation distribution and thickness distribution as required, it is preferably 30,000 minutes as an apparatus for adjusting the moving speed. It is preferable to use a drive device having a rotational accuracy of 1 degree.

In the production method of the present invention, when the gap between the gripping means is expanded in the width direction based on the comparison result of the thickness direction retardation distribution, if necessary, the comparison result of the in-plane direction retardation distribution and the comparison result of the thickness distribution. It is preferable to adjust the expansion width (t1 and t2 in FIG. 1) of the left and right gripping means. That is, the spread angle of the upper guide rails 5 and 6 in FIG. 1 to the upper side in the TD direction can be made larger than the spread angle of the lower guide rails 5 and 6 to the lower side in the TD direction. The spread angle of the upper guide rails 5 and 6 to the upper side in the TD direction can be made smaller than the spread angle of the lower guide rails 5 and 6 to the lower side in the TD direction. The in-plane orientation direction is preferably a desired angle (for example, parallel) with respect to the TD direction. However, the in-plane orientation direction becomes bowed or slanted due to a so-called bowing phenomenon. The distribution in the in-plane orientation direction can be corrected by adjusting the expansion width (t1 and t2 in FIG. 1) of the left and right gripping means when the gripping means interval is widened in the width direction.
Further, the widthwise or longitudinal maximum spread interval of the gripping means is adjusted based on the comparison result of the thickness direction retardation distribution, if necessary, based on the comparison result of the in-plane direction retardation distribution and the comparison result of the thickness distribution. It is preferable. The distance between the gripping means used for stretching is usually 1.1 to 3.0 times in the TD direction (width direction), preferably 1.2 to 2.0 times, and usually 1 in the MD direction (longitudinal direction). .1 to 3.0 times, preferably 1.2 to 2.0 times.

  The adjustment of the moving speed in the film longitudinal direction, the spreading width of the right and left gripping means, and / or the maximum spreading interval in the width direction or longitudinal direction of the gripping means may be automatically performed using a computer or the like. You may go on.

  For example, the thickness direction retardation distribution x1, the in-plane direction retardation distribution x2 and the thickness distribution x3, which are state quantities, and the operation amount, the film longitudinal direction moving speed u1, the expansion width u2 of the left and right gripping means, and the gripping Since the maximum spread interval u3 in the width direction or the longitudinal direction of the means is related to each other, in order to control a plurality of state quantities of any of x1, x2 and x3, u1, u2 and u3 It is preferable to linearize the relationship with one of the manipulated variables by a determinant such as Equation 1, and to construct a transfer function that does not cause interference.

  Equation 2 is a determinant showing an example of PID control. According to Equation 1, the gains D, E, and D for the proportional component (P), the integral component (I), and the differential component (D), respectively, with respect to the difference between the target values h1, h2, and h3 and the state quantities x1, x2, and x3. The operation amounts u1, u2 and u3 can be adjusted by multiplying F and summing them.

  I and j in Equations 1 and 2 are arguments of digital time series data. FIG. 2 is a block diagram showing an example of a general feedback control system. It shows that the state quantity x is observed and compared with the target value h, and the manipulated variable u is input to the system.

In the stretching machine through which the film passes, a preheating section (A section in FIG. 1) for heating to a temperature suitable for stretching the raw film 2 and a stretching section (FIG. 1) in which the holding means interval is widened (FIG. 1). (B section in the middle) and a fixed section (C section in FIG. 1) for stabilizing the stretched state of the stretched film 10. The temperature in each section is not particularly limited, but is usually Tg-5 ° C to Tg + 20 ° C in section A, preferably Tg-3 ° C to Tg + 15 ° C, and usually Tg-5 ° C to Tg + 20 ° C in section B, preferably Tg. -3 ° C to Tg + 15 ° C. In the C section, it is usually adjusted to Tg-5 ° C to Tg + 20 ° C, preferably Tg-3 ° C to Tg + 15 ° C. Each section is preferably maintained at a constant temperature, and specifically, it is preferably in an atmosphere having a temperature distribution in a range of ± 0.5 ° C.
In section C, the distance between the gripping means is not normally changed, but the distance between the gripping means can be slightly changed as necessary. By this minute change, the in-plane direction retardation and the thickness direction retardation can be finely adjusted. For example, the distribution in the in-plane orientation direction can be adjusted by making the gripping unit interval in the TD direction slightly steep in the C section.

  In the manufacturing method of the present invention, when the film is gripped by the gripping means and the gripping means interval is widened, a phenomenon occurs where a portion of the film not gripped by the gripping means is bowed. If this constriction becomes extremely large, it becomes impossible to adjust the thickness direction retardation distribution, the in-plane direction retardation distribution and the thickness distribution at both ends of the film, and the portions must be cut off. Therefore, in the present invention, it is preferable to further warm the grip means for gripping the film. Since the grip means has a different heat capacity compared to other parts, even if the inside of the stretching machine is in a constant temperature state, the temperature of only the grip means may not be easily increased. By warming the gripping means, this constriction phenomenon can be suppressed and the number of parts that must be cut off can be reduced.

  When feedback control is performed based on the measured value after removal from the gripping means, the control delay becomes large, and it may take time to stabilize the film characteristics at the target value. On the other hand, if the measurement is made before removing from the gripping means, the tension by the gripping means 2 still remains, so the measured value needs to be evaluated in consideration of the tension. Therefore, the characteristic transfer function of the stretched film is obtained, and based on this, the value after removal from the gripping means is estimated, the operation amount is provisionally determined based on the estimated value, and the feedback control is provisionally performed based on the operation amount. Then, after a measurement value (a value that seems to be accurate) after being removed from the gripping means is obtained, a deterministic operation amount is determined and the provisional operation amount is corrected.

  In addition, for example, the distribution of thickness direction retardation, thickness distribution and / or in-plane direction retardation distribution of the stretched film is measured, the time-series data of the moving speed in the longitudinal direction of the film, the expansion width of the right and left gripping means Time-series data and / or time-series data of the maximum spreading interval in the width direction or longitudinal direction of the gripping means, time-series data of the distribution of the measured thickness direction retardation, time-series data of the measured thickness distribution and / or A transfer function model at the time of producing a stretched film is constructed from the time series data of the distribution of the measured in-plane direction retardation. Examples of the transfer function model include a moving average model and a least square model. Using this transfer function model, the operation amount at the present time i (the film longitudinal movement speed, the spread angle of the gripping means and / or the maximum spread interval in the width direction or the longitudinal direction of the gripping means) u0, A state quantity x1 ′ (thickness direction retardation distribution, thickness distribution and / or in-plane direction retardation distribution) is predicted, and the prediction result and the target thickness direction retardation distribution, thickness distribution and / or surface are predicted. Contrast with the distribution of the inward retardation, and based on the comparison result, the operation amount u1 (the moving speed in the film longitudinal direction, the spread angle of the gripping means and / or the maximum spread interval in the width direction or the longitudinal direction of the gripping means) adjust. When the true state quantity at the next time point i + 1 (measured value of the thickness direction retardation distribution, thickness distribution and / or in-plane direction retardation distribution) x1 is obtained, u1 and x1 are determined. Based on the added new time series data, a new transfer function model is reconstructed, and the above operation is repeated using this model. FIG. 3 is a block diagram showing an example of a control system constructed by an observer using a transfer function model. The operation quantity u is input to a transfer function that models the relationship between the operation quantity u and the state quantity x to estimate the next state quantity x ′, and the estimated value is compared with the target value h to obtain a new operation quantity. u is input to the system. It shows that the true state quantity x is reflected in the transfer function. By adopting such a method, it is possible to minimize the control delay of the time required for measurement. Further, if the learning level of the transfer function model increases, it becomes possible to control without measuring the true state quantity.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not restrict | limited to the following Example. Parts and% are based on weight unless otherwise specified.
Example Using a simultaneous biaxial stretching machine as shown in FIG. 1, an original film having a thickness of 200 μm, a width of 440 mm, and an in-plane direction retardation of less than 40 nm was formed into a thickness direction retardation (Rth) of 130 nm and an in-plane direction retardation. (Re) Simultaneous biaxial stretching with 50 nm, Re distribution ± 5 nm, Rth distribution ± 5 nm, and thickness distribution ± 1 nm as target values.
The set values (initial values) at the start of simultaneous biaxial stretching are the same as the left and right spread widths t1 and t2, and the MD direction maximum spread interval (FDR) 1.5 times and the TD direction maximum spread interval (SDR) 1.5 times. A section temperature was 148 ° C., B section temperature was 148 ° C., C section temperature was 148 ° C., and the line speed was 18 m / min.
Simultaneous stretching was started at the initial value, and the thickness direction retardation of the film that came out of the stretching machine was measured with an online measuring device “KOBRA-WIS / RT (manufactured by Oji Scientific)”, and the in-plane direction retardation was measured with an online measuring device “ With KOBRA-WI (manufactured by Oji Scientific), the thickness was measured with an on-line measuring device “KURABO RX-100 (manufactured by Kurashiki Spinning Co., Ltd., infrared film thickness meter)”. The difference between the measured value and the target value is obtained, and the MD direction maximum spread interval, TD direction maximum spread interval, A section temperature, B section temperature, C section temperature, and line speed are adjusted by PID control based on the difference. did.
A film having a target thickness direction retardation of 130 nm and an in-plane retardation of 50 nm can be stably obtained after 35 steps from the start of simultaneous biaxial stretching control. In this PID control, the maximum spread distance in the MD direction remains unchanged at 1.5 times, the maximum spread distance in the TD direction is adjusted between 1.5 and 1.7 times, and the in-plane retardation increases as the magnification increases. As the magnification increased, the in-plane retardation tended to decrease as the magnification decreased, and it was around 1.6 when stabilized. The A section temperature, the B section temperature, and the C section temperature were slightly adjusted, and all were 149 ° C. when stabilized. The line speed is adjusted between 12 and 26 m / min. When the line speed increases, the thickness direction retardation increases, and when the line speed decreases, the thickness direction retardation tends to decrease. It was close. In this example, t1 and t2 were hardly adjusted.
Table 1 shows a part of the change over time of the manipulated variable u and the state quantity x. It can be seen that the manipulated variable u is changed so that the state quantity x matches the target value, and gradually approaches the target value. In Table 1, only the data up to 14 steps are shown, but after that, the manipulated variable u is finely adjusted, and the state quantity is set to the target value even if disturbances due to environmental fluctuations around the simultaneous biaxial stretching machine occur. It was possible to adjust immediately.

The top view which shows one Embodiment of the simultaneous biaxial stretching machine which can be used for this invention manufacturing method. The block diagram which shows an example of the control system used for this invention manufacturing method. The block diagram which shows another example of the control system used for this invention manufacturing method.

Explanation of symbols

1: Raw film 2: Gripping means 3: Endless link device 4: Entrance side sprocket 5, 6, 7, 8: Guide rail 9: Outlet side sprocket 10: Stretched film A: Preheating section B: Stretching section C: Fixed section h: target value u: manipulated variable x: state quantity x ′: transfer function model estimated state quantity

Claims (9)

The both ends of the long original film in the width direction are held by a plurality of holding means, the original film is moved in the longitudinal direction, and the holding means interval in the width direction of the original film and the original film Stretching the original film by extending the holding means interval in the longitudinal direction in association with the movement in the longitudinal direction of the film to form a stretched film,
Measuring the distribution of the thickness direction retardation of the stretched film,
A step of comparing the distribution of the measured thickness direction retardation with the distribution of the target thickness direction retardation; and
Having a step of adjusting the moving speed in the film longitudinal direction based on the comparison result of the distribution of the thickness direction retardation,
Production method of stretched film. Furthermore, the manufacturing method of the stretched film of Claim 1 which has the process of adjusting the expansion width of a right-and-left holding means, when expanding the holding means space | interval to the width direction based on the contrast result of the distribution of the said thickness direction retardation. Furthermore, the manufacturing method of the stretched film of Claim 1 or 2 which has the process of adjusting the largest spreading | diffusion space | interval of the width direction or longitudinal direction of a holding means based on the comparison result of the distribution of the said thickness direction retardation. Furthermore, a step of measuring the distribution of in-plane retardation of the stretched film,
The step of comparing the distribution of the measured in-plane direction retardation and the distribution of the target in-plane direction retardation, and based on the comparison result of the distribution of the in-plane direction retardation, the longitudinal movement speed of the film, The stretched film according to any one of claims 1 to 3, further comprising a step of adjusting an expansion width of the right and left gripping means and / or a maximum spreading interval in a width direction or a longitudinal direction of the gripping means when the spacing of the gripping means is expanded in the width direction. The manufacturing method. Furthermore, a step of measuring the thickness distribution of the stretched film,
Based on the step of comparing the measured thickness distribution with the target thickness distribution, and the comparison result of the thickness distribution, the film longitudinal movement speed, the width of the left and right gripping means when the gripping means spacing is widened, and The method for producing a stretched film according to any one of claims 1 to 4, further comprising a step of adjusting the maximum spreading interval in the width direction or the longitudinal direction of the gripping means. Furthermore, the manufacturing method of the stretched film in any one of Claims 1-5 which has the process of adjusting the temperature distribution at the time of the said extending | stretching to the atmosphere of the range of +/- 0.5 degreeC. Furthermore, the manufacturing method of the stretched film in any one of Claims 1-6 which has the process of adjusting the adjustment of the said film longitudinal direction moving speed with the drive device which has a rotational accuracy of 1 / 30,000 degree. Furthermore, the manufacturing method of the stretched film in any one of Claims 1-7 which has the process of warming the holding means holding the film. The both sides of the long original film are held by a plurality of holding means, the original film is moved in the longitudinal direction, the holding means interval in the width direction of the original film and the holding means interval in the longitudinal direction of the original film And extending the raw film in association with the movement in the longitudinal direction of the film to make a stretched film,
Measuring the distribution of the thickness direction retardation of the stretched film, the thickness distribution and / or the in-plane direction retardation distribution,
Time-series data of the moving speed in the longitudinal direction of the film, time-series data of the spreading width of the right and left gripping means when the spacing of the gripping means is expanded in the width direction, and / or time-series data of the maximum spreading interval in the width direction or longitudinal direction of the gripping means ,
Time series data of distribution of measured thickness direction retardation, time series data of measured thickness distribution and / or time series data of distribution of measured in-plane direction retardation,
A process for building a transfer function model for producing stretched film from
Future thickness direction retardation caused by adjusting the moving speed of the film in the longitudinal direction, the expansion width of the right and left gripping means when the gripping means interval is widened in the width direction, and / or the maximum spreading distance in the width direction or longitudinal direction of the gripping means. Predicting the distribution, thickness distribution and / or in-plane retardation distribution by the transfer function model, and the prediction results and the desired thickness-direction retardation distribution, thickness distribution and / or in-plane direction letter The distribution of the foundation is compared, and based on the comparison result, the moving speed in the film longitudinal direction, the spread width of the right and left gripping means when the gripping means interval is widened in the width direction, and / or the maximum in the width direction or longitudinal direction of the gripping means The manufacturing method of a stretched film which has the process of adjusting a spreading | diffusion space | interval.

Images