JP3727883B2 - Multilayer film manufacturing method and apparatus - Google Patents

Description

【００３６】
【発明の効果】
以上のように、本発明の多層膜の製造方法によれば、合流部により複数の液を層状に合流させるフィードブロックと、シングルマニホールドを有するダイとの組み合せにより、２層以上の多層膜を製造する方法において、前記合流部から前記シングルマニホールドまでの流路に関し、幅方向寸法をＷｆ、厚さ寸法をＴとしたときに、（Ｗｆ／Ｔ）を２＜（Ｗｆ／Ｔ）＜１０とし、前記ダイの吐出口の幅寸法をＷｄとしたときに、（Ｗｄ／Ｗｆ）を１０≦（Ｗｄ／Ｗｆ）≦２５とするから、多層流延膜の各層の膜厚をより均一にできるから、この多層流延膜から得られるフイルムは、膜厚分布が良好である。
【００３７】
また、本発明の多層膜の製造方法によれば、前記流路の幅寸法Ｗｆが、８０ｍｍ＜Ｗｆ＜２００ｍｍであり、前記厚さ寸法Ｔが、２０ｍｍ＜Ｔ＜５０ｍｍである場合に、前記流路の角部を面取り加工し、その加工寸法が、２ｍｍ＜Ｒ＜１０ｍｍであるから、多層流延膜を構成するためのドープの送液が容易に行なえるため、得られたフイルムの特性が優れている。
【図面の簡単な説明】
【図１】本発明に係る多層膜の製造装置を用いてフイルムを製造する方法を説明するための概略図である。
【図２】図１のII−II線の断面図である。
【図３】図２の III−III 線の断面図である。
【図４】図３のIV−IV線の断面図である。
【符号の説明】
１０ 多層膜製造装置
１１ フィードブロック
１２ 共流延ダイ
１３ 多層流延膜
１４ 流延ベルト
１５ 表面層用ドープ
１６ 中間層用ドープ
１７ 裏面層用ドープ
２０ フイルム
３０，３１，３２，３４，３５ 流路
３３ 合流部
３７ マニホールド
３８ スリット
３９ 吐出口
４０ 合流ドープ
Ｗｆ 流路幅寸法
Ｗｄ 吐出口幅寸法
Ｔ 流路厚さ寸法
Ｒ 流路角部の曲率半径[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing a multilayer film having a feed block, and the film produced using the production method and apparatus is suitable for optical applications.
[0002]
[Prior art]
In recent years, thin transparent plastic films have been used as protective films for polarizing plates in liquid crystal displays, optical compensation films such as retardation plates, plastic substrates, photographic supports, moving picture cells and optical filters, and optical materials such as OHP films. As demand increases.
[0003]
In particular, LCDs have recently been used for personal computers, word processors, portable terminals, televisions, digital still cameras, movie cameras, etc. due to their improved quality and light weight and excellent portability. However, a polarizing plate is essential for this liquid crystal display to display an image. Along with the improvement in the quality of the liquid crystal display, an improvement in the quality of the polarizing plate is required, and at the same time, the transparent plastic film that is a protective film of the polarizing plate is also required to have a higher quality.
[0004]
For optical films such as protective films for polarizing plates, high transparency, low optical anisotropy, flatness, easy surface treatment, high durability (dimensional stability, heat and humidity resistance, Water resistance), no foreign matter in and on the film, no scratches on the surface and scratches are difficult (scratch resistance), moderate film rigidity (handleability), and moderate water permeability It is said that it is necessary to have these characteristics.
[0005]
Examples of the film raw material having these characteristics include cellulose ester, norbornene resin, acrylic resin, polyarylate resin, polycarbonate resin, and the like, but cellulose ester is mainly used from the viewpoint of productivity and material price. In particular, a film of cellulose triacetate is particularly advantageously used for optical applications because it has extremely high transparency, low optical anisotropy, and low retardation.
[0006]
Various film forming techniques such as solution film forming method, melt film forming method and rolling method can be used as a method for forming these films, but in order to obtain good flatness and low optical anisotropy. The solution casting method is particularly suitable. The solution casting method is a polymer solution in which raw material flakes are dissolved in a solvent, and various additives such as a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a slipping agent, and a peeling accelerator are added thereto as necessary ( Hereinafter, the dope is cast on a support such as a horizontal endless metal belt or a rotating drum by a dope supply means (hereinafter referred to as a casting die), and then the support. This is a method comprising drying to a certain extent above, peeling the self-supporting film to which rigidity has been imparted from the support, and then passing the drying section through various transport means to remove the solvent.
[0007]
When a film is used for optical applications, it is naturally necessary that the above-mentioned properties are excellent, but it is also necessary that the thickness of the entire film is highly uniform. That is, when there is “unevenness” in the thickness of the entire film, “unevenness” occurs in the optical characteristics at the unevenness portion, and this often causes a problem as an optical film.
[0008]
Various attempts have been made to find an advantageous method for industrially producing a film with high optical uniformity, but it is not easy to produce a film with high optical uniformity with a single resin film. . Therefore, at present, two or more types of dopes having different solution viscosities are used, a multilayer casting film is formed using a multilayer casting method, and this is dried to produce a high-quality optical film. It has become.
[0009]
When a multilayer casting film or a multilayer film is produced using a solution casting method, a feed block type casting die is often used. This feed block type casting die is a casting apparatus in which joining means for joining two or more kinds of dopes is joined to the upstream side of the casting die. A typical structure of the feed block type casting die is provided with a channel for passing a dope serving as a core layer in the center, and a dope forming a front surface layer and a back surface layer on both sides thereof, and the latter The two solution streams are joined to both sides of the former solution stream.
[0010]
As an example of a method for producing a multilayer film using the above feed block type casting die, a relatively high viscosity dope is used for the resin layer as the core layer, and a relatively low viscosity dope is used for the front and back surface layers. Japanese Patent Publication No. 62-43846 discloses a method of performing dry peeling after forming a multilayer cast film. According to the description of this publication, it is said that by using such a manufacturing method, it is possible to manufacture a film in which abnormal characteristics such as melt fracture (melt fracture) are unlikely to occur.
[0011]
[Problems to be solved by the invention]
However, even with the above-described method, there has been a problem that a distribution difference occurs in the thickness of each layer when multi-layer casting is performed using a feed block type casting die. Japanese Patent Application Laid-Open No. 2000-317960 describes a method for improving the distribution difference by setting the residence time from dope joining to die discharge to 5 to 25 seconds. However, even with this method, the channel volume of the dope is limited, and it is difficult to maintain the adjustment range as productivity increases.
[0012]
An object of the present invention is to provide a method and apparatus for producing a multilayer film that uses a feed block type casting die to make the thickness distribution of each layer of the multilayer cast film more uniform.
[0013]
[Means for Solving the Problems]
The method for producing a multilayer film of the present invention is a method for producing a multilayer film having two or more layers by combining a feed block that joins a plurality of liquids in a layer form at a joining part and a die having a single manifold. With respect to the flow path from to the single manifold, when the width dimension is Wf and the thickness dimension is T, (Wf / T) is 2 <(Wf / T) <10, and the width of the discharge port of the die When the dimension is Wd, (Wd / Wf) is 10 ≦ (Wd / Wf) ≦ 25. The width dimension Wf of the flow path is preferably 80 mm <Wf <200 mm, and the thickness dimension T is preferably 20 mm ≦ T <50 mm. Furthermore, it is more preferable that the corner portion of the flow path is chamfered and the processing dimension is 2 mm <R <10 mm. Furthermore, it is preferable that the average residence time from the junction of the liquid to the discharge port of the die is 1.5 to 10 seconds.
[0014]
The multilayer film manufacturing method of the present invention includes a multilayer film that is a polarizing plate protective film having a film thickness of 30 to 200 μm or an optical compensation film.
[0015]
The apparatus for producing a multilayer film of the present invention is an apparatus for producing a multilayer film having two or more layers by combining a feed block that joins a plurality of liquids in layers by a joining part and a die having a single manifold. With respect to the flow path from to the single manifold, when the width dimension is Wf and the thickness dimension is T, (Wf / T) is 2 <(Wf / T) <10, and the width of the discharge port of the die When the dimension is Wd, (Wd / Wf) is 10 ≦ (Wd / Wf) ≦ 25. The width dimension Wf of the flow path is preferably 80 mm <Wf <200 mm, and the thickness dimension T is preferably 20 mm ≦ T <50 mm. Furthermore, it is more preferable that the corner portion of the flow path is chamfered and the processing dimension is 2 mm <R <10 mm.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
[Polymer compound]
Examples of the polymer compound used as a raw material for the film used in the present invention include lower fatty acid esters of cellulose (for example, cellulose triacetate), polyolefins (for example, norbornene-based polymer), polyamides (for example, aromatic polyamide). Etc.), polysulfones, polyethers (for example, including polyether sulfones and polyether ketones), polystyrenes, polycarbonates, polyacrylic acids, polyacrylamides, polymethacrylic acids (for example, polymethyl methacrylate, etc.) , Polymethacrylamides, polyvinyl alcohols, polyureas, polyesters, polyurethanes, polyimides, polyvinyl acetates, polyvinyl acetals (eg, polyvinyl formal, polyvinyl Lahr, etc.), and proteins (e.g., there may be mentioned gelatin, etc.), it is not limited thereto. Of these, a lower fatty acid ester of cellulose is preferable as a raw material for an optical use film, and cellulose triacetate is particularly preferable.
[0017]
[solvent]
The dope for producing the film can be prepared by dissolving the above-described polymer compound in a suitable solvent. As the solvent, any of inorganic and organic solvents can be used, but an organic solvent is preferably used. Examples of organic solvents include halogenated hydrocarbons (eg, dichloromethane), alcohols (eg, methanol, ethanol, butanol, etc.), esters (eg, methyl formate, methyl acetate, etc.), ethers (eg, Dioxane, dioxolane, diethyl ether, etc.) and ketones (for example, acetone, methyl ethyl ketone, cyclohexanone, etc.), but are not limited thereto.
[0018]
[Preparation of dope]
Any known method can be used to prepare the dope. For example, a method of mixing and dissolving the polymer compound in a solvent may be used, or the polymer compound is swollen with a solvent using a cooling dissolution method, and then the swollen mixture is cooled to −10 ° C. or lower. Then, a method of dissolving by heating to 0 ° C. or higher may be used. The viscosity of the solution is usually in the range of 3 to 300 Pa · s (measured value at 35 ° C.). At this time, it is preferable that the dope viscosity of the intermediate layer is higher than the dope viscosity of the front and back layers. In addition, the dope includes various known plasticizers such as triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, and polyester polyurethane elastomer, or, if necessary, an ultraviolet absorber, an anti-degradation agent, a slip agent, and a release accelerator. Various known additives such as may be added at any stage in the dope preparation.
[0019]
[Method for producing multilayer film]
FIG. 1 is a schematic perspective view for producing a film using a multilayer film production apparatus according to the present invention. A multilayer film manufacturing apparatus 10 shown in FIG. 1 includes a co-casting die 12 having a feed block type resin solution merging device (hereinafter referred to as a feed block) 11 and a lower side of the die lip of the co-casting die 12. It comprises a casting belt 14 that supports a multilayer casting film 13 discharged from the die lip at the tip of the co-casting die 12 while continuously moving. As the casting belt, any rotating drum such as a cooling drum or any other known one can be used as long as it functions as a support for the multilayer casting film in the production process of the multilayer film.
[0020]
The dopes 15, 16, and 17 for forming the surface layer, intermediate layer, and back layer described above are charged into each mixing tank and stirred with a stirring blade to prepare a uniform dope. In that case, it is also possible to mix an additive with each dope. Each dope is sent to each filter at a constant flow rate by each pump to remove impurities, and then sent to the feed block 11. The surface layer dope 15, the intermediate layer dope 16, and the back layer dope 17 fed to the feed block 11 are merged in the feed block 11 to be a parallel flow merged dope and introduced into the co-casting die 12. The combined dope is spread in the width direction of the casting belt 14 and then discharged from the die lip to the surface of the casting belt 14 to form the multilayer casting film 13. The casting belt 14 is stretched around rollers 18 and 19 and rotated by a driving device (not shown). On the casting belt 14, the solvent of the multilayer casting film 13 is gradually volatilized to form a self-supporting film 20. The film 20 is peeled off from the casting belt 14 by a peeling roller 21, sent to a drying device, dried, and then wound up by a winder. Any known means can be used as means for drying the multilayer cast film 13.
[0021]
FIG. 2 shows a cross-sectional view taken along line II-II in FIG. The feed block 11 is fed with the surface layer dope 15, the intermediate layer dope 16, and the back surface layer dope 17, and passes through the respective flow paths 30, 31, 32, and merges at the merge portion 33. After that, it is sent to the co-casting die 12 through the flow path 34. The merged dope passes through the flow channel 35 by the co-casting die 12, is widened by the manifold 37 attached to the flow channel 35, and passes from the discharge port 39 to the casting belt 14 (see FIG. 1) via the slit 38. Be cast. The amount of the dope 15, 16, and 17 and the form of the feed block 11 and the co-casting die 12 are set so that the residence time from the joining portion 33 of the joining dope to the discharge port 39 is 1.5 to 10 seconds. Is preferable in order to make the thickness distribution of each layer of the multilayer cast film 13 more uniform.
[0022]
FIG. 3 shows a cross-sectional view taken along line III-III in FIG. The merged dope 40 that has passed through the flow path 34 of the feed block 11 is sent to the co-casting die 12, is widened by the manifold 37 through the flow path 35, and passes through the slit 38 from the discharge port 39 to form the multilayer cast film 13. Be cast. Manifold plugs (not shown) are attached to both sides of the manifold 37 to prevent the merging dope 40 from flowing out from the side surface of the co-casting die 12. Further, the width dimension of the flow channel 35 of the co-casting die 12 is Wf, and the width dimension of the merged dope 40 discharged from the discharge port 39 is Wd. In addition, the flow path 35 and the manifold 37 may be provided as a single unit, or may be formed by connecting separate components.
[0023]
Further, when the length L0 of the co-casting die 12 shown in FIG. 3 in the direction in which the combined dope flows is 50 to 200 mm and the length L1 is 200 to 400 mm, the length L2 of the flow path 35 is 20 to 80 mm, The length L3 of the manifold area is preferably 30 to 120 mm, and the length L4 of the slit area is preferably 60 to 200 mm. The slit area preferably has 2 to 4 slits with different clearances. The clearance may be a combination that narrows in the discharge direction or a combination that becomes narrower after becoming wider. The slit length preferably includes slits having a gentle distribution in the width direction and slits constant in the width direction. The slit on the die discharge port 39 side is preferably constant in the width direction. The clearance of the slit area is preferably 0.5 to 8 mm.
[0024]
4A shows a cross section of the cross section (IV-IV line in FIG. 3) of the flow path 35, and FIG. 4B shows an enlarged view of the corner. As shown in FIG. 4A, the width dimension Wf and the thickness dimension of the flow path 35 are T. In the present invention, the relationship between Wf, T, and Wd described above is 2 <(Wf / T) <10 and 10 ≦ (Wd / Wf) ≦ 25.
By doing so, the thickness distribution of each layer of the multilayer cast film 13 can be made uniform. More preferably,
3 <(Wf / T) <7 and 14 ≦ (Wd / Wf) ≦ 21
Thus, the thickness distribution of each layer of the multilayer cast film can be made more uniform.
[0025]
Further, in the present invention, the flow path 35 shown in FIG. 4 is configured in the ranges of 80 mm <Wf <200 mm and 20 mm <T <50 mm to make the distribution of the thickness of each layer of the multilayer cast film uniform. Therefore, it is preferable. Moreover, although the flow path 35 is formed in a substantially rectangular shape as shown in the figure, it is preferable that the corners are chamfered and formed in a substantially arc shape in order to uniformly feed the merged dope. The corner of the channel 35 preferably has a radius of curvature R in the range of 2 mm <R <10 mm. If it is 2 mm or less, the substantially arc formed at the corner of the flow path 35 is too small, and the function of uniformly feeding the end portion of the merged dope is hardly exhibited. Moreover, when it is 10 mm or more, the shape of the flow path 35 is not substantially rectangular, and liquid feeding of each layer in the multilayer to the manifold 37 is difficult to be performed uniformly in the width direction.
[0026]
The dope merging means used for continuously merging the dopes in the present invention is not limited as long as it is of a feed block type. The internal shape of the co-casting die may be any shape such as a coat hanger die or a T die. Further, although omitted in FIG. 2, vanes and distribution pins may be provided in the flow paths 30 and 32. By rotating this vane, the thickness pattern of each layer at the time of merging of the dopes 15, 16 and 17 can be changed by changing the opening degree of the vane and the distribution focus.
[0027]
The thickness of the film 20 produced by the multilayer film production method of the present invention is preferably 30 to 200 μm, although it varies depending on the raw material and use of the film. The obtained film can be used as a polarizing plate protective film which is a polarizing plate protective film. A polarizing plate can be formed by sticking this polarizing plate protective film on both surfaces of a polarizing film made of polyvinyl alcohol or the like. Furthermore, it can also be used as an optical functional film such as an optical compensation film in which an optical compensation sheet is pasted on this film, or an antireflection film in which an antiglare layer is laminated on the film. From these products, a part of the liquid crystal display device can be constituted.
[0028]
【Example】
Examples 1 to 6 and Comparative Examples 1 to 5 are listed below, but the present invention is not limited thereto.
[0029]
A film was manufactured using the multilayer film manufacturing apparatus according to the present invention described above, and the film thickness distribution was measured. The film thickness distribution is determined by measuring the film after drying with an infrared film thickness meter to obtain a distribution width in the 100 mm range of the thickness. If the distribution width is less than 0.5 μm, it is very good (（), 0.5-1 If it is less than 0.0 μm, it is good (◯), and if it is 1.0 to 2.0 μm, the film thickness distribution is slightly wide, but it can be used depending on the product (Δ). The thickness distribution width was too large, and a three-step evaluation was made that the product could not be used (x). The results are summarized in Table 1 later.
[0030]
[Preparation of dope for intermediate layer]
100 parts by weight of cellulose triacetate (acetylation degree 60.9%) is used as a raw material, charged into a mixed solvent (300 parts by weight of methylene chloride and 65 parts by weight of methanol), and further, triphenyl phosphate 7 which is a plasticizer is used as an additive. .8 parts by weight, 3.9 parts by weight of biphenyl diphenyl phosphate and 1.0 part by weight of an ultraviolet absorber were added and dissolved to prepare a dope for the intermediate layer. As for the physical properties of this dope, the viscosity at 34 ° C. was 50 Pa · s, and the solid content weight was 23.6%.
[0031]
[Preparation of dope for front surface layer and back surface layer]
As a raw material, 87 parts by weight of cellulose triacetate (wood pulp, acetylation degree 60.9%) is charged into a mixed solvent (300 parts by weight of methylene chloride and 65 parts by weight of methanol), and further, a plasticizer is added as a tri- valent plasticizer. An intermediate layer dope was prepared by adding and dissolving 6.8 parts by weight of phenyl phosphate, 3.4 parts by weight of biphenyl diphenyl phosphate and 0.9 part by weight of an ultraviolet absorber. As for the physical properties of this dope, the viscosity at 34 ° C. was 36 Pa · s, and the solid content weight was 21.1%.
[0032]
[Example 1]
Using the above-described dope for intermediate layer, dope for surface layer, and dope for back layer, a film comprising the multilayer film shown in FIG. 1 was produced. As the co-casting die 12, Wf, T, Wd, and R shown in FIGS. 3 and 4 were 200 mm, 34 mm, 2000 mm, and 4 mm, respectively. The dope 15 for the front layer, the dope 16 for the intermediate layer, and the dope 17 for the back layer are fed so that the film thickness after drying is 3 μm for the front layer and the back layer, and 54 μm for the intermediate layer. Manufactured. When the respective dopes 15, 16, and 17 were fed, the residence time from the merging portion 33 to the discharge port 39 shown in FIG. 2 was 3 seconds. Further, when the film thickness distribution of the obtained film was measured, the width of the distribution was 0.4, and a good film (◯) was obtained.
[0033]
Table 1 summarizes the experimental conditions of Examples 2 to 6 and the evaluation results of residence time and film thickness distribution. The same conditions as in Example 1 are omitted.
[0034]
Table 1 also shows the experimental conditions of Comparative Examples 1 to 5 and the evaluation results of the residence time and the film thickness distribution. The same conditions as in Example 1 are omitted.
[0035]
[Table 1]

[0036]
【The invention's effect】
As described above, according to the method for producing a multilayer film of the present invention, a multilayer film having two or more layers is produced by combining a feed block that joins a plurality of liquids in layers at a junction and a die having a single manifold. In this method, regarding the flow path from the merging portion to the single manifold, when the width direction dimension is Wf and the thickness dimension is T, (Wf / T) is 2 <(Wf / T) <10, When the width dimension of the discharge port of the die is Wd, since (Wd / Wf) is 10 ≦ (Wd / Wf) ≦ 25, the thickness of each layer of the multilayer cast film can be made more uniform. The film obtained from this multilayer cast film has a good film thickness distribution.
[0037]
Further, according to the multilayer film manufacturing method of the present invention, when the width dimension Wf of the flow path is 80 mm <Wf <200 mm and the thickness dimension T is 20 mm <T <50 mm, Since the corners of the road are chamfered and the processing dimensions are 2 mm <R <10 mm, the dope liquid for constructing the multilayer cast film can be easily fed, so the characteristics of the obtained film are Are better.
[Brief description of the drawings]
FIG. 1 is a schematic view for explaining a film manufacturing method using a multilayer film manufacturing apparatus according to the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along line IV-IV in FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Multilayer film production apparatus 11 Feed block 12 Co-casting die 13 Multilayer film 14 Cast belt 15 Surface layer dope 16 Middle layer dope 17 Back layer dope 20 Film 30, 31, 32, 34, 35 33 Merge section 37 Manifold 38 Slit 39 Discharge port 40 Merge dope Wf Channel width dimension Wd Discharge port width dimension T Channel thickness dimension R Radius of curvature at channel corner

Claims (8)

In a method for producing a multilayer film of two or more layers by combining a feed block that joins a plurality of liquids in layers by a joining portion and a die having a single manifold,
Regarding the flow path from the junction to the single manifold,
When the width direction dimension is Wf and the thickness dimension is T,
(Wf / T) is 2 <(Wf / T) <10,
When the width of the discharge port of the die is Wd,
(Wd / Wf) is defined as 10 ≦ (Wd / Wf) ≦ 25. The width dimension Wf of the flow path is 80 mm <Wf <200 mm,
2. The method for manufacturing a multilayer film according to claim 1, wherein the thickness dimension T is 20 mm ≦ T <50 mm. Chamfering the corner of the channel,
3. The method for producing a multilayer film according to claim 2, wherein the processing dimension is 2 mm <R <10 mm. The method for producing a multilayer film according to any one of claims 1 to 3, wherein an average residence time from the confluence portion of the liquid to the discharge port of the die is 1.5 to 10 seconds. 5. The method for producing a multilayer film according to claim 1, wherein the multilayer film is a polarizing plate protective film having a film thickness of 30 to 200 μm or an optical compensation film. In an apparatus for producing a multilayer film of two or more layers by a combination of a feed block that joins a plurality of liquids in layers by a joining part and a die having a single manifold,
Regarding the flow path from the junction to the single manifold,
When the width direction dimension is Wf and the thickness dimension is T,
(Wf / T) is 2 <(Wf / T) <10,
When the width of the discharge port of the die is Wd,
(Wd / Wf) is defined as 10 ≦ (Wd / Wf) ≦ 25. The width dimension Wf of the flow path is 80 mm <Wf <200 mm,
7. The multilayer film manufacturing apparatus according to claim 6, wherein the thickness dimension T is 20 mm ≦ T <50 mm. Chamfering the corner of the channel,
8. The apparatus for producing a multilayer film according to claim 7, wherein the processing dimension is 2 mm <R <10 mm.

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