TW201331006A - Polyvinyl alcohol type polymer film and cutting method thereof - Google Patents

Abstract

The present invention relates to a polyvinyl alcohol type polymer film having at least one cutting portion along its longitudinal direction. In which, the straightness for each 200 mm of length of the long side for the cross section of the cutting portion is below 0.5 mm. The present invention further provides a cutting method for polyvinyl alcohol type polymer film. The present invention may stabilize the width variation rate of the polyvinyl alcohol type polymer film under the conditions of constant temperature and swelling to reduce the frequency of film breakage during the manufacturing process of polarizer, and to increase the stretching ratio for productivity enhancement.

Description

Polyvinyl alcohol polymer film and cutting method thereof

The present invention relates to a polyvinyl alcohol-based polymer film and a method of cutting the same.

The polarizer converts the natural light that is generally not polarized into a polarized light. LCD liquid crystal displays use this kind of polarized light, coupled with the twisting characteristics of liquid crystal molecules, to control the passage of light. With the wide application of liquid crystal displays, the market demand for polarizers has also risen with the rise of water. The polarizer mainly uses a polyvinyl alcohol (PVA) polymer film as a polarizing substrate. Therefore, the quality of the polyvinyl alcohol polymer film directly affects the use effect of the polarizer.

In the preparation of the polarizer, the polyvinyl alcohol polymer is generally formed into a film, and then the polymer film is stretched, followed by lamination, coating, and the like to complete the production of the polarizer. In order to meet the customer's needs, the film needs to be cut into a specified width to form a polyvinyl alcohol polymer film. However, if the cut surface of the cut film is not flat enough or In the case of a defect, the position of the defect will become a stress concentration point in the subsequent extension process, and film breakage may occur from the defect position during the extension, and a film having a sufficient length cannot be prepared. Therefore, the flattening of the cut surface of the polyvinyl alcohol polymer film is equivalent to that of the subsequent polarizing film. Big relationship.

In the past, various attempts have been made to improve the cutting and cutting surface flatness of the cut film. Some of the reports, such as Japanese Patent No. 4,353,482, Japanese Patent No. 4,570,140, claim to use a circular shape. A method in which a rotatable cutter cuts a direction in which a polyvinyl alcohol-based polymer film is elongated. Because the circular rotatable tool is prone to yaw when rotating, the larger the diameter of the circular rotatable tool, the more obvious the yaw phenomenon, which leads to the snakeing phenomenon of the cutting edge. The knife method is used to improve the yaw phenomenon, but the upper and lower circular rotatable cutters are easy to cause the blade to wear due to mutual shearing, so that the cut surface has shear and tear marks, and the opposite cut end faces are less straightforward; When the cut surface of the film has a high level of flatness, it cannot further reduce the straightness of the film edge.

Therefore, in order to improve the above problems, there is still an improvement in the production method to obtain a polyvinyl alcohol-based polymer film having good straightness, and to increase the elongation and reduce the number of breaks.

The present invention provides a polyvinyl alcohol-based polymer film having at least one cut portion along a longitudinal direction thereof, wherein a long side of a cross section of the cut portion has a true straightness of 0.5 mm or less per 200 mm length.

To this end, the present invention provides a method for cutting a polyvinyl alcohol polymer film, comprising: cutting the polyvinyl alcohol polymer film at least along the longitudinal direction of the polyvinyl alcohol polymer film, A polyvinyl alcohol-based polymer film having at least one cut portion and an ear piece are obtained, wherein the long side of the cross section of the cut portion has a true straightness of 0.5 mm or less per 200 mm length.

According to the invention, the width change rate of the polyvinyl alcohol-based polymer film can be stably exhibited under normal temperature and moistening conditions, the film breaking frequency in the polarizing film process can be reduced, the stretching ratio can be increased, and the yield can be improved.

1‧‧‧Polyvinyl alcohol polymer film

11‧‧‧Polyvinyl alcohol polymer film

11a‧‧‧cutting department

12‧‧‧ ear

21‧‧‧First conveyor roller

22‧‧‧Second transfer roller

23‧‧‧Upper pressure roller

24‧‧‧Winding roller

3‧‧‧ straight knife

4‧‧‧Transmission/collection device

V1‧‧‧ first transmission speed

V2‧‧‧second transmission speed

V3‧‧‧3rd transmission speed

θ‧‧‧Cutter angle

1 is a schematic view showing a cutting method of the present invention; FIG. 2 is a schematic view showing a polyvinyl alcohol-based polymer film of the present invention; and FIG. 3 is a schematic view showing a preferred cutting method of the present invention.

The technical contents and embodiments of the present invention are described in detail below by way of specific embodiments, and those skilled in the art can readily understand the advantages and functions of the present invention from the disclosure of the present disclosure. The present invention may be embodied or applied in various other specific embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

It is to be understood that the structure, the proportions, the size, and the like of the present invention are intended to be used in conjunction with the disclosure of the specification, and are not intended to limit the invention. The conditions are limited, so it is not technically meaningful. Any modification of the structure, change of the proportional relationship or adjustment of the size should remain in this book without affecting the effects and the objectives that can be achieved by the present invention. The technical content disclosed in the invention can be covered. In the meantime, the terms "upper", "lower", "previous", "post" and "one" are used in this specification for convenience of description and are not intended to limit the invention. Fan Changes or adjustments in the relative relationship are considered to be within the scope of the invention.

The uncut polyvinyl alcohol-based polymer film used in the present invention can be prepared in any manner. For example, a polyvinyl alcohol casting solution may be prepared, and then the polyvinyl alcohol casting solution is cast to a casting drum, and dried to form a polyvinyl alcohol-based polymer film.

Specifically, in the above method for producing a polyvinyl alcohol polymer film, the polyvinyl alcohol casting solution mainly comprises polyvinyl alcohol, a plasticizer and water, and the polyvinyl alcohol is polymerized by a vinyl ester resin monomer to obtain a poly The vinyl ester resin is further subjected to a saponification reaction. Examples of such polyvinyl ester monomers include, but are not limited to, vinyl ester polymers such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl octanoate, and the like. It is vinyl acetate. Further, an olefin compound such as ethylene, propylene, butylene or the like, or an acrylate derivative such as acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate or the like and the above ethylene A copolymer formed by copolymerizing an ester monomer may also be used. Usually, the polyvinyl alcohol-based resin has a degree of saponification of 90% or more, preferably 99% or more, to obtain preferable optical characteristics. The polyvinyl alcohol-based resin used in the method of the present invention has a polymerization degree of from 800 to 10,000, a polymerization degree of more than 2,200, and a preferable processing property. If it is more than 10,000, it is disadvantageous for dissolution.

In general, in the polyvinyl alcohol casting solution used, if the content of the polyvinyl alcohol-based resin is insufficient, the viscosity of the casting solution is too low, and the drying load is too large, which may cause deterioration of the film forming efficiency. On the other hand, if the polyvinyl alcohol resin is contained When the amount is too high, the polyvinyl alcohol-based resin is not easily dissolved, and the viscosity of the casting solution is too high, and the insoluble matter generated gels to affect the uniformity of film formation. Therefore, in the polyvinyl alcohol casting solution used in the method of the present invention, the content of the polyvinyl alcohol-based resin is usually from 10 to 60% by weight, preferably from 15 to 40% by weight, and more preferably between 20 to 30% by weight.

In addition to the polyvinyl alcohol-based resin, the polyvinyl alcohol-based casting solution may further contain a plasticizer to improve the processability of film formation. Examples of commonly used plasticizers include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, glycerin, etc., preferably ethylene glycol and glycerol. The plasticizer content is insufficient, and the formed polyvinyl alcohol-based polymer film is liable to cause crystallization and affect the dyeing efficiency of subsequent processing. On the other hand, if the content of the plasticizer is too high, the mechanical properties of the polyvinyl alcohol-based polymer film are destroyed. Therefore, the amount of the polyol plasticizer added is usually from 3 to 30 parts by weight, preferably from 7 to 20 parts by weight, based on the polyvinyl alcohol resin.

In the method disclosed above, after the polyvinyl alcohol-based resin and the plasticizer are dissolved in the solution to form a polyvinyl alcohol casting solution, the filter is used for filtration, and finally the gear pump and the T-die are used. The head coater casts the polyvinyl alcohol casting solution onto a casting drum, which is dried at a high temperature to form a polyvinyl alcohol polymer film, and the polyvinyl alcohol polymer film is peeled off from the casting drum. Typically, the film has a thickness of from 10 to 100 um, preferably from 30 to 80 um.

In order to meet the customer's needs, the process is to cut the film edge to the appropriate width for the customer to use.

The cutting tool used in the present invention is a straight knife, that is, the blade is linear By. The material used for the straight knife can be metal or ceramic, and the metal material is preferred. The thickness of the straight knife is 0.1 to 1 mm, and preferably 0.1 to 0.4 mm. If the blade is too thick, it is easy to produce dust.

As shown in Fig. 1, the polyvinyl alcohol-based polymer film 1 obtained by the above method is conveyed on a conveying line in which the first conveying roller 21, the straight knife 3, and the second conveying roller 22 are sequentially disposed. The first conveying roller 21 and the second conveying roller 22 have a wheel diameter of 5 to 30 cm, preferably 8 to 15 cm. Further, the wheel diameters of the first conveying roller 21 and the second conveying roller 22 may be the same or different, but are generally the same.

The first conveying roller 21 is spaced apart from the second conveying roller 22 by 10 cm to 150 cm, and the optimum distance is 15 cm to 60 cm, and the straight knife 3 is at any position between the first conveying roller and the second conveying roller, and the holder is designed as It can be swung up and down slowly, so that the contact between the film and the tool does not always be at the same point, causing the blade to wear quickly. The swing speed can be 1 to 10 mm/min, and the best is 2 to 6 mm/min. The swing distance can be 1 to 20 mm, preferably 2 to 6 mm. Further, in the present specification, the distance between the straight knives or the rolls is calculated by the straight knives or the cut points at which the rolls are in contact with the film.

On the conveying line, from the first conveying roller 21 to the second conveying roller 22, 1 to 20 m/min, preferably 1 to 8 m/min, more preferably 3 to 8 m/min, the first conveying speed V1. The polyvinyl alcohol-based polymer film 1 is conveyed, and the polyvinyl alcohol-based polymer film 1 is cut along the longitudinal direction of the polyvinyl alcohol-based polymer film 1 by the straight blade 3 to form at least one cut portion 11a. A polyvinyl alcohol-based polymer film 11 (see Fig. 2) and an ear piece 12. And the polyvinyl alcohol-based polymer film 11 having at least one cut portion 11a The ear piece 12 is conveyed in parallel to the second conveying roller 22.

If necessary, a plurality of straight knives (for example, two) may be used to simultaneously cut (not shown) the two opposite longitudinal directions of the polyvinyl alcohol-based polymer film 1, and a plurality of cut portions are produced, and the straight portions are formed. After the blade 3 is cut, the polyvinyl alcohol-based polymer film 11 and the ear piece 12 having at least one cut portion 11a are conveyed in parallel to the second transfer roller 22, that is, both when passing through the second transfer roller 22 The parties are allowed to separate.

The cutter angle θ of the surface of the straight knife 3 and the polyvinyl alcohol polymer film 1 of the present invention is preferably from 5 to 170 degrees, and preferably from 100 to 160 degrees. The angle of the cutter refers to the angle from the cutting edge of the cutting tool to the side of the plane above the polyvinyl alcohol film. When the angle is too close to 0 or 180 degrees, the blade face cannot perform a good cutting effect.

As shown in Fig. 2, the polyvinyl alcohol-based polymer film 11 obtained by the above method has a long side on the cut portion 11a (i.e., corresponding to the plane above the plane and the cross section of the polyvinyl alcohol film) at every 200 mm. The true straightness of the length is 0.5 mm or less. Here, the true straightness means that under the specified length, when the cutting edge is measured by the reference line set by the instrument, the trimming edge will fluctuate up and down on the reference straight line to form a cross-sectional area, and the area above the reference straight line is a positive value, the reference straight line The area below is a negative value, and the average of the sum of the positive and negative areas of the test length is the true straightness. When this value is closer to 0, it means that the line to be measured is closer to the true "straight line", that is, the cutting is smooth. Since the polyvinyl alcohol-based polymer film obtained by the present invention has a good film edge straightness, the elongation can be 4 to 8 times, and the polyvinyl alcohol-based polymer film can be cut to a stretch length of 1000 m. The number of times dropped to 0.

Further, a preferred method for producing the polyvinyl alcohol-based polymer film of the present invention is as shown in Fig. 3. Here, the upper transfer roller 22 may be repeatedly disposed on the second transfer roller 22 to form a nip roll to sandwich the cut polyvinyl alcohol polymer film 11 and the ear piece 12. The upper roller 23 has a wheel diameter of 5 to 30 cm, preferably 8 to 15 cm, and provides 0.5 to 15 kg/cm 2 for the polyvinyl alcohol polymer film 11 and the ear 12 (kg _f / The pressure under cm ² ) is preferably 2 to 5 kg _f /cm ² .

Further, after the formed polyvinyl alcohol-based polymer film 11 and the ear piece 12 are passed through the lower pressing wheel, the polyvinyl alcohol-based polymer film 11 can be subsequently conveyed/collected by the conveying/collecting device 4, usually using a collecting roller (not The illustrations are collected and may be transferred to subsequent processes for subsequent processing. The conveying/collecting device 4 is placed at the other side of the second conveying roller 22 with respect to the straight knife 3, and supplies the polyvinyl alcohol-based polymer film 11 with a second conveying speed V2. Among them, the conveying/collecting device 4 can supply the polyvinyl alcohol-based polymer film 11 with the second conveying speed V2. The second transfer speed V2 and the first transfer speed V1 may be the same or different. In one embodiment, the second transfer speed V2 is from 90% to 105% of the first transfer speed V1, with 95% to 100% being optimal.

The ear material 12 can be naturally dropped with gravity or taken up by the take-up roll 24 (as shown in Fig. 3). Preferably, the take-up roll 24 is taken up while the take-up roll 24 provides the third transfer speed V3 to the ear piece 12. The third transfer speed V3 may also be the same as or different from the first transfer speed V1 or the second transfer speed V2 described above. In an embodiment, the third transmission speed V3 is preferably 90% to 105% of the first transmission speed V1, wherein 95% to 100% is good.

According to the present invention, the width change rate of the polyvinyl alcohol-based polymer film can be stably exhibited under normal temperature and moistening conditions, the film breaking frequency in the polarizing plate process can be reduced, the stretching ratio can be increased, and the yield can be improved.

Example

The embodiments of the present invention are exemplified by the following examples, which are intended to illustrate the principles of the present invention and its effects, and are not intended to limit the invention.

In this embodiment, a polyvinyl alcohol-based polymer film is used. After cutting the respective examples described later, the following characteristics of the cut film obtained in each example were tested and evaluated:

a) stretching ratio

The polyvinyl alcohol-based polymer film sample was placed at 20 ° C, 65% humidity under constant temperature and humidity for one day, and the film side sample was taken for 10 mm × 150 mm for testing, and the tensile tester was tested by a tensile tester, model: HT-9102.

b) Polarization

Spectrophotometer, model: PE Lambda 750S 60mm Sphere test.

c) Number of broken films

The test was carried out by a conventional polarizing plate process, and a 1000 m long polyvinyl alcohol polymer film was prepared to produce a polarizer. First, the polyvinyl alcohol-based polymer film is swelled in a swelling tank; after swelling, it is directly dyed with an iodine compound or a dye to dye a polyvinyl alcohol-based polymer film, and the polyvinyl alcohol is uniaxially stretched. The polymer film is unidirectionally extended to have a bias The polyvinyl alcohol-based polymer film having optical characteristics was fixed at a total stretching ratio of 6 times, and the number of film breaks was counted in the dyeing extension process of the cumulative 1000-meter stretched polyvinyl alcohol-based polymer film.

d) True measurement

Measured by CNC Video Measuring System, model: Nikon INEXIV VMA-2520.

In the present invention, true straightness means

Where f(x) is the function of the trimming line that fluctuates up and down on the reference line, and the L system measures the fixed length. In various embodiments of the invention, L is 200 mm.

e) roughness measurement

The surface roughness was measured by an optical 3D surface profile scanning instrument using a non-contact conjugate focal length and interference technique, and the measured value was defined in accordance with JIS B 0601-2001 standard model: SENSOFAR PLu.

Example 1

A plasticizer and a polyvinyl alcohol-based resin having a saponification degree of 99.9% are dissolved in a solution to form a 30% by weight polyvinyl alcohol casting solution, which is filtered using a filter, and finally a gear pump and a T are used. a die coater for casting the polyvinyl alcohol casting solution to a casting drum, drying at a high temperature to form a polyvinyl alcohol polymer film, and then peeling the polyvinyl alcohol polymer film from the casting drum, and heat-treating through the oven After the coiling, a polyvinyl alcohol-based polymer film having a film thickness of 60 μm was obtained.

The polyvinyl alcohol-based polymer film is conveyed at a speed of 5 m/min in the direction of the first conveying roller, the straight knife, and the second conveying roller on a conveying line provided with the first conveying roller, the straight knife, and the second conveying roller. . Wherein, the film surface of the cutting section is at an angle of 140 with the straight knife, and after cutting, the upper pressing roller (uppressing pressure is 3Kg _f /cm ² ), so that the finished polyvinyl alcohol polymer film product continues along the mechanical direction. The transfer (transfer speed was 5 m/min), and the ear part was taken up by a separate take-up roll (winding speed of 5 m/min); the finished product was subjected to elongation test, and the results are shown in Table 1.

Example 2

In the same polyvinyl alcohol-based polymer film prepared in the manner as in Example 1 but after the cutting through the film press roll (press-on pressure of 0.5Kg _f / cm ^2). The finished product was tested by extension and the results are shown in Table 1.

Example 3

A polyvinyl alcohol-based polymer film was prepared in the same manner as in Example 1, but was not subjected to an upper press roll after the film was cut. The finished product was tested by extension and the results are shown in Table 1.

Example 4

A polyvinyl alcohol-based polymer film was prepared in the same manner as in Example 1, but after the film was cut, the ear portion was allowed to fall naturally without being taken up by a reel. The finished product was tested by extension and the results are shown in Table 1.

Example 5

A polyvinyl alcohol-based polymer film was prepared in the same manner as in Example 1 except that the film was not subjected to the upper pressing roller after cutting, and the ear portion was allowed to fall naturally without being taken up by a reel. The finished product was tested by extension and the results are shown in Table 1.

Comparative Example 1

A polyvinyl alcohol-based polymer film was prepared in the same manner as in Example 1, except that a cutting blade was used. The finished product was tested by extension and the results are shown in Table 1.

Comparative Example 2

A polyvinyl alcohol-based polymer film was prepared in the same manner as in Comparative Example 1, but after the film was cut, the ear portion was allowed to fall naturally without being taken up by a reel. The finished product was tested by extension and the results are shown in Table 1.

As shown in Table 1, in Examples 1 to 5 of the present invention using a straight knife, no film breakage occurred when the film was stretched. Comparing Example 3 with Comparative Example 1, it can be seen that in the same ear picking mode, a straight edge straightness, a better stretching ratio, and a smaller number of broken films can be obtained by using a straight knife. In addition, when When the proper pressure roller condition and the ear material collection method are selected, the values of the straightness and the stretching ratio of the trimming edge can be further improved.

In addition, the present invention also compares the straightness and roughness of the trimming. It can be found that the roughness value of the film is not absolutely positively correlated with the straightness. As shown in Example 3 and Comparative Example 1, the two have similar roughness, but the true straightness of Comparative Example 1 is as high as three times that of the third embodiment. the above. In addition, it can be found that the high roughness does not necessarily increase the number of broken films, but the high straightness value of the trimming edge obviously has more number of broken films. Furthermore, in Comparative Example 5 and Comparative Example 1, Comparative Example 1 having a lower roughness had more number of broken films.

The above embodiments are intended to illustrate the principles of the invention and its effects, and are not intended to limit the invention. Any of the above-described embodiments may be modified by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the appended claims.

1‧‧‧Polyvinyl alcohol polymer film

11‧‧‧Polyvinyl alcohol polymer film

12‧‧‧ ear

21‧‧‧First conveyor roller

22‧‧‧Second transfer roller

3‧‧‧ straight knife

V1‧‧‧ first transmission speed

θ‧‧‧Cutter angle

Claims (13)

A polyvinyl alcohol-based polymer film having at least one cut portion along a longitudinal direction thereof, wherein a long side of a cross section of the cut portion has a true straightness of 0.5 mm or less per 200 mm length. The polyvinyl alcohol-based polymer film according to claim 1, wherein the polyvinyl alcohol-based polymer film has a stretching ratio of 4 to 8 times. The polyvinyl alcohol-based polymer film according to claim 1, wherein the polyvinyl alcohol-based polymer film has a length of 1,000 m or more. The polyvinyl alcohol-based polymer film according to claim 1, which is used as a polarizing film. A method for cutting a polyvinyl alcohol polymer film, comprising: cutting the polyvinyl alcohol polymer film at least along a longitudinal direction of the polyvinyl alcohol polymer film to obtain at least one cut portion The polyvinyl alcohol-based polymer film and the ear material, wherein the long side of the cross section of the cut portion has a true straightness of 0.5 mm or less per 200 mm length. The method for cutting a polyvinyl alcohol-based polymer film according to claim 5, wherein the straight knife is disposed between the first conveying roller and the second conveying roller, and is oriented from the first conveying roller The second conveying roller conveys the polyvinyl alcohol-based polymer film at a first conveying speed of 1 to 20 m/min, and is cut by the straight knife, and the polyvinyl alcohol-based polymer film and the ear having at least one cutting portion The feed system is conveyed in parallel to the second transfer roller. The method for cutting a polyvinyl alcohol-based polymer film according to claim 5, wherein the angle between the straight knife and the surface of the polyvinyl alcohol-based polymer film is between 5 and 170 degrees. . The method for cutting a polyvinyl alcohol-based polymer film according to claim 6, wherein the first conveying roller is spaced from the second conveying roller by from 10 cm to 150 cm. The method for cutting a polyvinyl alcohol-based polymer film according to claim 6, further comprising using an upper pressing roller to sandwich the polyvinyl alcohol-based polymerization having at least one cut portion with the second conveying roller Film and the ear. The scope of the patent cutting method of item 9 of the polyvinyl alcohol-based polymer films 28, wherein between the platen roller ² under the pressure of the pressure line between 0.5 and 15 kg _f / cm. The method for cutting a polyvinyl alcohol-based polymer film according to claim 6, further comprising a conveying/collecting device disposed at the other side of the second conveying roller with respect to the straight knife The polyvinyl alcohol based polymer film provides a second transfer speed, wherein the second transfer speed is from 90% to 105% of the first transfer speed. The method for cutting a polyvinyl alcohol-based polymer film according to claim 11, further comprising winding the ear material using a take-up roll and providing a third transfer speed to the ear material. The method for cutting a polyvinyl alcohol-based polymer film according to claim 12, wherein the third conveying speed is 90% to 105% of the first conveying speed.