JP2003266457A - Solution film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the cutting edge of a film from wrinkling in turning-up in a solution film forming method. <P>SOLUTION: A dope prepared by dissolving a polymer such as cellulose acrylate is cast on a casting die and dried into a film 23. In a tenter drying zone, drying air is blasted from above against tenter clips 40, which hold both the side edge parts of the film 23 and convey them under tension. The feeding speed and temperature of the drying air have enough conditions bringing the solvent content of each film edge part 23a bitten in the tenter clips 40 to 17 wt.% or less. No wrinkle in turning-up develops in the cutting edge of the film 23 cut after the release from the tenter drying zone, resulting in realizing the favorable film conveying in the following processes. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution film-forming method, and more particularly to a solution film-forming method for photographic light-sensitive material films such as cellulose triacetate (TAC) and cellulose diacetate (DAC) and optical films.

[0002]

2. Description of the Related Art A solution casting method is a method in which a polymer material is made into a dope by a solvent and then the dope is cast from a die onto a metal support and peeled off at a self-supporting property.
A film is obtained through a drying process. Compared with the melt extrusion method, this method can produce a film with excellent optical isotropy and thickness uniformity, and since it can be filtered accurately, foreign matter is not mixed in. Widely used for optoelectronic applications such as films, retardation films and transparent conductive films.

After casting on a rotating metal support, after passing through a stripping roll and a pass roll from the metal support,
In this method of obtaining a film by introducing the film into a tenter and drying both sides, generally, the film edge deformed by the biting of the tenter clip is trimmed at the exit of the tenter (hereinafter referred to as a slit) and removed.

[0004]

However, the ears after slitting (hereinafter referred to as "ear shavings") will cause creases unless they are conveyed under specific conveyance conditions, and these creases cause the creases. The film may be cut. FIG. 6 is for explaining the occurrence of cracks, and there are bite marks 12 by the tenter clips at both ends of the film 11 at the exit of the seal roll 10. The portion of the bite mark 12 is rapidly dried and contracted by heat conduction by the tenter clip. On the other hand, the product portion 11a on the inner side of the bite mark 12 is left in an excessive state, and the depression 13 is generated. Further, the film ears 11b on the outer side of the bite mark 12 have pits 14 due to the delay in drying, which causes the ears to stretch. For such a film 11,
When the edge cutting line 15 is used to perform edge cutting with a slitter (not shown), a pass roll (not shown) may cause a crease 16 along the bite mark 12, and the crease 16 may cut the film 11.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a solution casting method capable of suppressing the generation of creases in the cutting chips.

[0006]

Means for Solving the Problems As a result of diligent examination of the cause of wrinkles in the ear scraps, the present inventor has found that (1) the solvent content of the film edge portion outside the biting portion of the tenter clip is determined by a tenter drying step. At 17% by weight or less,
(2) When the film after the tenter drying step is conveyed by a pass roll, the coefficient of static friction with respect to the film of the surface portion of the pass roll held by the tenter clip is 0.55 or less. It has been found that the generation of wrinkles of ear cuttings can be suppressed by a method such as blowing air from the film entry side between the film and the film ear. These methods (1) to (3) may be used alone or in combination. The polymer used in the solution film-forming method of the present invention is preferably cellulose acylate, and this cellulose acylate film is used as a polarizing plate or a protective film of a liquid crystal display device.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The starting polymer material in the production method of the present invention is not particularly limited as long as it is various polymer materials which can be formed into a film by the solution film forming method. Particularly preferred is cellulose acylate used for optoelectronic applications such as a polarizing plate protective film.

The film produced by the production method of the present invention can be produced from a dope using various known solvents.
When cellulose acylate is used as the raw material polymer material for the film, halogenated hydrocarbons such as methylene chloride, alcohols such as methanol, esters, ethers, etc. can be used alone or in combination. The present invention also includes the case where a film is formed using these solvents.

The dissolved dope is generally filtered to remove foreign matters and undissolved raw materials. For the filtration, it is possible to use various known filter materials such as filter paper, filter cloth, non-woven fabric, metal mesh, sintered metal filter, and perforated plate. By filtering, foreign substances, undissolved substances, etc. in the dope can be removed, and the deterioration of product performance, damage, and defects due to these can be reduced or removed.

It is also possible to further improve the solubility by heating the dope once dissolved. For heating, there are a method of heating while stirring in a stationary tank, and a method of heating while transferring the dope by using various heat exchangers such as a multitubular type and a jacket pipe with a static mixer. Also,
It is also possible to provide a cooling step after the heating step and pressurize the inside of the apparatus to heat it to a temperature above the boiling point of the dope. By performing these heat treatments, minute undissolved substances that could not be completely dissolved can be dissolved completely or to the extent that it can be practically ignored, reducing foreign matter in the product film and filtering. The load of can be reduced.

Known additives can be added to the dope of the present invention. Examples of the additive include, but are not limited to, an ultraviolet absorber, a dispersant, and a plasticizer. It is also possible to add silica, kaolin, talc, etc. as other additives in the dope. These additives can be mixed at the same time when preparing the dope, or can be mixed in-line by using a static mixer or the like when transferring after preparing the dope.

FIG. 1 shows a solution film-forming line for carrying out the solution film-forming method of the present invention. After the stationary defoaming, the dope 20 passed through the filter by the liquid feeding pump was
No. 1 is cast on a band 22 as a metal support, and the solvent is gradually volatilized by drying with hot air, so that it has a self-supporting property. Here, the film 23 is peeled off from the band 22 by the peeling roll 24, conveyed while being in contact with a plurality of pass rolls 25, and introduced into the tenter drying zone 26. The film 23 exiting the roll 27 of the tenter drying zone 26 is sent to the slitter 29 via the pass roll 28 different from the above, and the ears 23a are cut. The film 23b from which the ears are cut and removed is further separated into a plurality of pass rolls 3
It is introduced into the roll drying zone 31 through 0, is dried with hot air while being conveyed by the roll 32 in the roll drying zone 31, and is then wound around the winding core 33.

In the tenter drying zone 26, as shown in FIG. 2, the film 23 is bitten into a tenter clip 40, and tension is applied by a pulling device 41 to dry the film while it is being conveyed. The tenter clip 40 is composed of a clip body 40a having a U-shaped cross section and a sandwiching piece 40b, and sandwiches the film both ears 23a. An air supply duct 42 is arranged above the tenter clip 40.

The air supply duct 42 has an air supply nozzle 42a, from which the dry air is sent toward the tenter clip 40. An opening 40c is formed on the upper surface of the clip body 40a, and the dry air hits the film ear 23a located outside the bite mark 12 (see FIG. 5) by the tenter clip 40 through the opening 40c. The drying of the part is promoted. The temperature and flow rate of the dry air are such that the solvent content rate of the film ears 23a covered with the tenter clip 40 is 1
It is set to be 7% by weight or less. The solvent content is preferably 15% by weight or less, more preferably 13% by weight or less.

By promoting the drying in this way,
It is possible to suppress the occurrence of a stretched edge in the film edge portion 23a, and to obtain an effect of suppressing wrinkles. If the air supply duct 42 here is one that can locally blow dry air to the portion bitten by the tenter clip 40,
It is not limited to what is shown. The solvent content rate (unit:% by weight) of the film is calculated by the formula (X−Y) / Y × 100, where X gram is the sample weight immediately before the tenter drying and Y gram is the sample weight after the tenter drying. .

FIG. 3 shows the steps from the tenter drying zone 26 to the pass roll 30 after trimming. The film 23 exiting the roll 27 of the tenter drying zone 26,
It is sent to the slitter 29 through the pass roll 28, and the film edge portion 23a is slit here. The slit film edge portion 23a is transported by the cutting edge pull-out roll 50 and the transport roll 51, and then reused as a raw material. The film product portion 23b is transported to the roll drying zone by the transport roll 30 separately from the ears 23a.

FIG. 4 is an enlarged view of one end of the pass roll 28. Film ears 23a of the pass roll 28
The portion that comes into contact with is coated with a fluororesin coating 28a. The fluororesin coating portion 28a and the central portion 28b are flush with each other. The surface of the central portion 28b is plated with hard chrome. As a result, the static friction coefficient of the coating portion 28a with respect to the film 23 becomes lower than that of the central portion 28b of the pass roll 28, and is set to less than 0.55.
As a result, the holding force of the film ears 23a is reduced by the amount by which the static friction coefficient is reduced, and the effect of suppressing wrinkles is obtained. As the fluororesin to be coated, in addition to polytetrafluoroethylene, a known fluororesin-based coating agent can be used, but the fluororesin is limited as long as it is a coating agent capable of making the coefficient of static friction of the film less than 0.55. Not done. Regarding the setting of the static friction coefficient, less than 0.50 is more preferable, and less than 0.45 is particularly preferable.

In the above embodiment, the air supply duct 42 for sending the dry air to the film ears 23a held by the tenter clip 40 and the pass roll 28 coated with fluororesin at both ends are provided. Even if used selectively, the effect of suppressing creases can be obtained.

Further, it is preferable to take various measures shown in FIG. 3 in order to enhance the effect of suppressing cracking. For example, the air supply duct 60 is provided on the film exit side of the roll 27. In this case, the film wind portion 23a is floated by the dry air blown from the air supply duct 60, and the film holding force at this portion is lowered, so that the same effect of suppressing the creases is obtained.

Further, the contact area and contact surface pressure between the roll 27 and the film 23 are reduced by reducing the wrap angle of the roll 27 and the plurality of pass rolls 28 connected to the roll 27 thereafter. Further, the diameter of the pass roll 28 may be reduced by about 2 mm only at the side end portion to reduce the contact surface pressure of the film 23 on the pass roll 28. Also in this case, the film holding power is lowered, and the same effect is obtained. Further, as shown in FIG. 5, an air supply duct 61 for supplying air from the film entrance side may be provided at a portion of the pass roll 28 which is in contact with the film edge portion 23a to reduce the holding force of the film edge portion 23a. The air supply duct 61 has an air supply nozzle 61a and sends dry air from here, but any air supply duct can be used as long as it can supply air sufficiently and sufficiently to reduce the holding force of the pass roll 28. Not limited to.

Further, the cutting edge 23a of the film cut and removed by the slitter 29 is supplied to the cutting edge drawing roll 50 by an air supply duct 62 different from the two air supply ducts 60 and 61.
By blowing more dry air, it conveys while floating.
The creases of the ear scrap 23a may be suppressed. Further, although not shown, even if the film thickness of the film ears 23a is increased by selecting the casting diffusion plate, the occurrence of creases in the ears may be suppressed. Good.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples, but the contents of the present invention are not limited thereto. The preparation of the raw material dope is the same as in the examples and comparative examples, so this will be described first, and the film production and the results will be described later. Regarding the inspection of the film for wrinkles, the portion where the film edge portion 23a after drying the tenter and the pass roll 28 are inspected is visually inspected. (Preparation of dope) Cellulose triacetate 100 parts by weight Triphenyl phosphate 7 parts by weight Biphenyldiphenyl phosphate 5 parts by weight A solid content of 5 parts by weight is appropriately added to a mixed solvent of methylene chloride 92 parts by weight and methanol 8 parts by weight, and the mixture is stirred. Solid content concentration 1
A 7.5 wt% dope was prepared. After the stationary dope was defoamed, it was sent to the die through a filter by a liquid sending pump.

Example 1 The above dope was formed into a film by a solution film forming process as shown in FIG. The dope 20 was cast from a die 21 onto a band 22 as a metal support, which was set at a rotational movement speed of 35 m / min, and dried with hot air until it had self-supporting property, and a film 23 was peeled off. The film 23 was introduced into the tenter drying zone 26, and both ends of the film 23 were held by tenter clips 40 to dry while applying tension. At this time, a drying air of 120 ° C. was blown from above the tenter clip 40 to set the solvent content of the tenter clip holding portion to 13.0 wt%. When the film 23 exits the tenter drying zone 26, the deformed film both ears 2 are held by the tenter clip 40.
3a was cut and removed, further heated and dried in the roll drying zone 31, and then wound on the winding core 33. When visually inspected, no creasing occurred on the film edge portion 23a that was in contact with the pass roll 28 after the tenter drying, and the conveyance was extremely stable.

[Embodiment 2] Drying air is not blown from above the tenter clip 40, and the tenter drying zone 2 is used.
After leaving 6, the pass roll 2 in contact with the film edge portion 23a
The same procedure as in Example 1 was carried out except that coating treatment 28a with polytetrafluoroethylene was applied to both side end portions of No. 8 to set the static friction coefficient to the film 23 to 0.43. Film ears 23a in contact with the pass roll 28
No creases were found on the surface and the transportation was extremely stable.

[Third Embodiment] Drying air is not blown from above the tenter clip 40, and the tenter drying zone 2 is used.
After leaving 6, the pass roll 2 in contact with the film edge portion 23a
The same operation as in Example 1 was carried out except that a dry air at room temperature was blown to both end portions of No. 8 at a wind speed of 40 m / sec. Pass roll 28
No wrinkles are generated in the film ears 23a that come into contact with
The transport was extremely stable.

[Comparative Example 1] The same operation as in Example 1 was carried out except that dry air was not blown from above the tenter clip 40. That is, the static friction coefficient reduction treatment for the film 23 of the pass roll 28 by the fluororesin coating, the both end portions of the pass roll 28 and the film edge portion 23.
It was carried out without spraying a dry air between a and a.
The solvent content of the tenter clip holder is 17.5% by weight.
And the static friction coefficient with respect to the film 23 at both end portions of the pass roll 28 in contact with the film edge portion 23a is 0.
It was 60. When visually inspected, pass roll 2
8 has a wrinkle on the film edge 23a that comes into contact with
After cutting, the ear scrap 23a was cut. The film portion 23b to be the product was also cut from the slit portion.

[0027]

INDUSTRIAL APPLICABILITY As described above, the solution film-forming method of the present invention suppresses the generation of film wrinkles, and exhibits excellent film transportability and film production process stability.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a solution film-forming line for carrying out the solution film-forming method of the present invention.

FIG. 2 is a schematic view showing a tenter clip portion.

FIG. 3 is a schematic diagram showing a line from a tenter drying process to a pass roll after edge cutting.

FIG. 4 is a plan view showing a pass roll whose both ends are coated.

FIG. 5 is a plan view showing another embodiment in which air is supplied to both ends of the pass roll.

FIG. 6 is a plan view showing a state of a film immediately after drying by a tenter in a conventional solution casting method.

[Explanation of symbols]

23 films 23a film ear 23b Film Products Department 26 tenter drying zone 28 pass rolls 28a coating part 29 slitters 40 tenter clip 42 Air supply duct 61 Air supply duct

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F205 AA01 AG01 AK02 AM32 AR20                       GA07 GB02 GC06 GE11 GE22                       GF24 GN21 GN24 GN30 GW15                       GW23                 4F210 AA01 AG01 AH73 AH79 AJ14                       AM32 AR20 QA02 QD01 QD19                       QD25 QG01 QG18

Claims (6)

[Claims] 1. A solution casting method comprising a tenter drying step of drying a film while stretching the film using a clip, wherein the solvent content of the film ear portion outside the biting portion by the clip is 17 in the tenter drying step.
A manufacturing method characterized in that the content is less than or equal to% by weight. 2. The coefficient of static friction of the surface portion of the pass roll, which is in contact with the edge portion of the film held by the clip, with respect to the film when the film after the tenter drying step is conveyed by the pass roll is less than 0.55. The solution film forming method according to claim 1. 3. The solution casting method according to claim 1, wherein air is blown between the pass roll and the film edge portion from the film entrance side. 4. A solution casting method having a tenter drying step of drying a film while stretching the film using a clip, which has a pass roll for conveying the film after the tenter drying to the next step, and the pass roll has a surface. A solution casting method, wherein the static friction coefficient of the portion of the film held by the clip in contact with the film is less than 0.55. 5. A solution casting method having a tenter drying step of drying a film while stretching it using a clip, comprising a pass roll for transporting the film after the tenter drying step to the next step, and the pass roll and the A solution casting method, characterized in that air is blown from the film entry side between the film and the ear. 6. The solution film-forming method according to claim 1, wherein the polymer is cellulose acylate.