JP4116653B2 - Feed block type resin solution merging device and feed block type casting die - Google Patents

Description

  The present invention relates to a feed block type resin solution merging apparatus capable of producing a multilayer resin film particularly suitable for optical applications using a multilayer casting method.

  In recent years, thin transparent plastic films (resin 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 cells and optical filters, and OHP films. Demand for optical materials such as these is increasing.

  In particular, LCDs have recently been improved in quality and are lightweight and highly portable, so they are widely used in personal computers, word processors, portable terminals, televisions, digital still cameras, movie cameras, etc. 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 resin film that is a protective film of the polarizing plate is also required to have a higher quality.

  For optical films such as protective films for polarizing plates, high transparency, low optical anisotropy, flatness, easy surface treatment, high durability (dimensional stability, moisture and heat 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.

  As resin films having these characteristics, there are films made of cellulose ester, norbornene resin, acrylic resin, polyarylate resin, polycarbonate resin, etc., but cellulose ester is mainly used from the viewpoint of productivity and material price. Yes. 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.

  As a method for forming these resin films, various film forming techniques such as a solution film forming method, a melt film forming method and a rolling method can be used, but in order to obtain good flatness and low optical anisotropy. For this, the solution casting method is particularly suitable. The solution casting method is a solution in which raw material flakes are dissolved in a solvent, and various additives such as a plasticizer, an ultraviolet absorber, an anti-degradation agent, a slipping agent, and a peeling accelerator are added to the solution as necessary. The dope is cast on a support such as a horizontal endless metal belt or a rotating drum by a dope supply means (referred to as a die), and then dried to some extent on the support. In this method, the self-supporting film provided with rigidity is peeled off from the support, and then the solvent is removed by passing through the drying section by various conveying means.

  When a resin 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.

  Various attempts have been made to find an advantageous method for industrially producing a resin film with high optical uniformity, but it is possible to produce a resin film with high optical uniformity with a single resin film. Because it is not easy, at present, the multilayer resin film produced by using two or more types of dopes with different solution viscosities and forming the multilayer cast resin film using the multilayer casting method and drying it is used for optical applications. Use as a film is the mainstream.

When a multilayer casting resin film or a multilayer resin 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 resin solutions (dope) is joined to the upstream side of the casting die. A typical structure of the feed block type casting die is provided with a flow path for passing a resin solution serving as a core layer in the center, and passing a resin solution serving as a surface layer on the front side and a surface layer on the back side on both sides thereof. And the latter two solution streams are joined to both sides of the former solution stream.
As an example of a method for producing a multilayer resin film using the above feed block type casting die, a resin layer serving as a core layer is made of a relatively high viscosity resin solution, and front and back surface layers are made of a relatively low viscosity resin. There is a method in which a multi-layer cast resin film is formed using a solution and then dried and peeled (for example, described in Patent Document 1). According to the description of this publication, it is said that by using such a manufacturing method, it is possible to manufacture a resin film in which abnormal characteristics such as melt fracture (melt fracture) are unlikely to occur.

Japanese Examined Patent Publication No. 62-43846

  While examining various conditions for producing a multilayer resin film from resin solutions having different viscosities using a feed block type casting die, the present inventor It was noticed that the difference in the residence time affected the thickness unevenness of the produced multilayer resin film.

  Based on the above findings, the present inventors have further studied, and as a result, when the two or more types of resin solutions having greatly different viscosities are formed using a feed block type casting die, the resin solutions have joined together. Thereafter, a multilayer cast resin film with less thickness unevenness can be obtained by limiting the time until ejection from the casting die to a certain range, and from such a multilayer cast resin film with less thickness unevenness, thickness unevenness is obtained. It has been found that a multilayer resin film with less content can be produced.

An object of the present invention is to feed a relatively low viscosity resin solution and a relatively high viscosity resin solution having a viscosity of 2 to 10 times the viscosity of the resin solution through respective flow paths. After the resin solution parallel flow is merged by the block type resin solution merge device to be in contact with each other at the interface, the parallel flow of the resin solution is discharged from the die lip onto the support through the flow path of the casting die, and the multilayer casting is performed. In the method for producing a multilayer resin film comprising forming a resin film and drying the resin film, the discharge from the casting die is performed for 5 to 25 seconds calculated from the time when the resin solution is joined. An object of the present invention is to provide a feed block type resin solution merging device suitable for a method for producing a multilayer resin film.

The object of the present invention is also a resin solution A having a relatively low viscosity, a resin solution B having a relatively high viscosity having a viscosity 2 to 10 times that of the resin solution, and 1 of the viscosity of the resin solution B. Resin solution C having a viscosity of / 2 to 1/10 and having a relatively low viscosity is fed from each flow path and merged by a feed block type resin solution merging device, and resin solution A / resin solution B / resin After making the resin solution parallel flow in contact with each other in the order of solution C, the resin solution parallel flow is discharged from the die lip onto the support through the flow path of the casting die to form a multilayer cast resin film. In a method for producing a multilayer resin film comprising: drying a resin film, wherein the discharge from the casting die is performed for 5 to 25 seconds calculated from the time of joining the resin solution. Suitable feed bro Also to provide a click-type resin solution merging device.

The present invention provides an intermediate layer flow path for circulating a dope forming a central resin layer of a multilayer cast resin film, and two dopes for circulating dope forming an outer resin layer formed on both sides of the central resin layer. The notch groove pin for adjusting the flow rate of the dope that merges from the outer layer flow path is provided at the junction, and the depth of the notch groove of the notch groove pin Is in the range of 0.1 to 5 mm, a feed block type resin solution merging device is provided.
The resin used for the production of the multilayer resin film of the present invention is preferably a cellulose ester, and particularly preferably cellulose triacetate. The viscosity of the relatively low viscosity resin solution used in the production of the multilayer resin film of the present invention is preferably in the range of 50 to 700 poise, and the viscosity of the relatively high viscosity resin solution is 500 to 2500. It is desirable to be within the poise range.

  When manufacturing a multilayer resin film using a solution casting method, a multilayer resin film with high thickness accuracy can be obtained by using the manufacturing conditions of the present invention. Therefore, the multilayer resin film obtained by the production method of the present invention can be suitably used particularly for optical applications.

  First, the manufacturing method of the multilayer resin film of this invention is demonstrated, referring drawings.

  FIG. 1 shows the configuration and operation of an apparatus including a casting die equipped with a feed block type resin solution merging apparatus that can be used for forming a multilayer casting resin film for the production of the multilayer resin film of the present invention. FIG. In FIG. 1, a multilayer casting resin film manufacturing apparatus continuously moves on a co-casting die 2 provided with a feed block type resin solution (dope) merging device 1 and the lower side of the die lip of the co-casting die 2. While supporting the multilayer cast resin film discharged from the die lip at the tip of the co-casting die 2 (meaning a metal belt or rotating drum that functions as a support in the multilayer resin film manufacturing process) 3 and It is composed of The dope merged in the feed block type resin solution (dope) merging apparatus 1 to become a parallel flow is introduced into the co-casting die 2, and the parallel dope flow is expanded in the width direction and supported from the die lip. The multilayer cast resin film 4 is formed by being discharged onto the surface of the body 3. The multilayer cast resin film 4 is partially dried while moving continuously with the support 3, and then peeled off from the support 3 by a peeling roll 5. The multilayer cast resin film manufacturing apparatus itself shown in FIG. 1 is already known.

  FIG. 2 is a cross-sectional view showing the configuration of the co-casting die 2 provided with the feed block type resin solution merging device 1 in more detail. In the feed block type resin solution merging apparatus 1, the resin solution is fed along the arrow.

  FIG. 3 shows a state of a resin solution flow discharged from the co-casting die 2 onto the surface of the support 3 in a multilayer state, and a multilayer cast resin film 3 generated on the surface of the support 4 from the resin solution flow. It is a perspective view which shows a state.

  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. The support for the multilayer cast resin film may be a continuous metal band (see FIG. 1) having a mirror-finished surface, or a rotating drum such as a cooling drum.

  The multilayer cast resin film that has been dried to some extent on the support and becomes self-supporting is peeled off from the support by a known means, and further passed through a drying section using a known appropriate transporting means, and further solvent is removed. Can be removed to obtain a multilayer resin film which is an object of the present invention. Any known various means can be used as means for drying the cast film.

  Examples of raw material resins used in the production of multilayer cast resin films and multilayer resin films that are the production targets of the present invention include lower fatty acid esters of cellulose (eg, cellulose triacetate), polyolefins (eg, norbornene-based polymers), polyamides (Eg, aromatic polyamide), polysulfones, polyethers (including polyether sulfones and polyether ketones), polystyrenes, polycarbonates, polyacrylic acids, polyacrylamides, polymethacrylic acids (eg, poly Methyl methacrylate), polymethacrylamides, polyvinyl alcohols, polyureas, polyesters, polyurethanes, polyimides, polyvinyl acetates, polyvinyl acetals (eg, polyvinyl formal, polyvinyl butyral), and Protein (e.g., gelatin) may be mentioned. Among 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.

  A resin solution (dope) for producing a multilayer resin film can be prepared by dissolving a raw material resin in a suitable organic solvent. Examples of organic solvents include halogenated hydrocarbons (dichloromethane, etc.), alcohols (methanol, ethanol, butanol, etc.), esters (methyl formate, methyl acetate, etc.), ethers (dioxane, dioxolane, diethyl ether, etc.) Can be mentioned. When cellulose ester is used as the raw material resin, various known plasticizers such as triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, and polyester polyurethane elastomer are used in the solution, or further, an ultraviolet absorber, a deterioration, if necessary. Various known additives such as an inhibitor, a slipping agent, and a peeling accelerator may be added.

  For the preparation of the solution (dope), a method of mixing and dissolving a raw material resin or the like in a solvent by a known method may be used, or a raw material resin or the like is swollen with a solvent by using a cooling dissolution method. Thereafter, the swelling mixture may be cooled to −10 ° C. or lower and then heated to 0 ° C. or higher and dissolved. The viscosity of the solution is usually in the range of 30 to 3000 P (measured at Poise, 35 ° C.).

  FIG. 4 is a diagram showing an internal structure of a device corresponding to the feed block type resin solution (dope) merging device 1 of FIGS. 1 and 2.

  The feed block type resin solution (dope) merging apparatus shown in FIG. 4 includes an intermediate layer flow path through which the dope forming the central resin layer of the multilayer cast resin film is circulated, and outer resin layers formed on both sides of the central resin layer. It consists of two outer layer channels for circulating the dope to be formed, and a notch groove pin for adjusting the flow rate of the dope that merges from the outer layer channel is provided at the junction. FIG. 5 shows the structure of the notched groove pin. The depth of the groove of the notch pin is appropriately adjusted according to the thickness of the target outer resin layer, but is usually selected from a range of about 0.1 to 5 mm.

  The thickness of the multilayer resin film produced by the production method of the present invention varies depending on the film raw material and application, but is generally in the range of 20 to 500 μm, preferably in the range of 40 to 200 μm.

[Examples 1-2]
(1) The following high viscosity dope for forming the center layer and low viscosity dope for forming the outer layer were prepared.
1) High viscosity dope for central layer formation Resin: Cellulose triacetate Solvent: Mixed solvent of methylene chloride, methanol and butanol Plasticizer: Triphenyl phosphate and biphenyl diphenyl phosphate Additive: UV absorber Viscosity: 700 poise
2) Low-viscosity dope for outer layer formation Resin: Cellulose triacetate Solvent: Mixed solvent of methylene chloride, methanol and butanol Plasticizer: Triphenyl phosphate and biphenyl diphenyl phosphate Additives: Colloidal silica, degradation inhibitor, UV absorber Viscosity: 200 Poise

(2) Dope retention from the above high viscosity dope and low viscosity dope using the feed block type resin solution merging device having notched pins shown in FIGS. By changing the time, a three-layer resin film having a total thickness of 60 μm was produced. And the thickness precision (ratio) of the obtained three-layer resin film was measured using the continuous thickness meter. The results are shown in Table 1.

[Comparative Examples 1-2]
A three-layer resin film having a total thickness of 60 μm was produced using the same high-viscosity dope and low-viscosity dope as in Example 1 and Example 2 and the same feed block type resin solution merging apparatus except that the dope residence time was changed. . And the thickness precision (ratio) of the obtained three-layer resin film was measured using the continuous thickness meter. The results are shown in Table 1.

Table 1 ─────────────────────────────────────────
Pin groove depth Residence time Thickness accuracy (judgment)
────────────────────────────────────────
Example 1 0.2 mm 9 seconds 0.99 (pass)
Example 2 3.5 mm 23 seconds 1.01 (pass)
────────────────────────────────────────
Comparative Example 1 0.2 mm 3 seconds 0.86 (failed)
Comparative Example 2 3.5 mm 30 seconds 1.16 (failed)
────────────────────────────────────────

[Examples 3 to 4]
(1) The following high viscosity dope for forming the center layer and low viscosity dope for forming the outer layer were prepared.
1) High viscosity dope for central layer formation Resin: Cellulose triacetate Solvent: Mixed solvent of methyl acetate, ethanol, cyclohexanol Plasticizer: Triacetin Additive: UV absorber Viscosity: 1500 poise
2) Low viscosity dope for outer layer formation Resin: Cellulose triacetate Solvent: Mixed solvent of methyl acetate, ethanol, cyclohexanol Plasticizer: Triacetin Additive: Colloidal silica, anti-degradation agent, UV absorber Viscosity: 400 poise

(2) Dope retention from the above high viscosity dope and low viscosity dope using the feed block type resin solution merging device having notched pins shown in FIGS. By changing the time, a three-layer resin film having a total thickness of 200 μm was produced. And the thickness precision (ratio) of the obtained three-layer resin film was measured using the continuous thickness meter. The results are shown in Table 2.

[Comparative Examples 3 to 4]
A three-layer resin film having a total thickness of 200 μm was produced using the same high viscosity dope and low viscosity dope as in Example 3 and Example 4, and the same feed block type resin solution merging device except that the dope residence time was changed. . And the thickness precision (ratio) of the obtained three-layer resin film was measured using the continuous thickness meter. The results are shown in Table 2.

Table 2 ─────────────────────────────────────────
Pin groove depth Residence time Thickness accuracy (judgment)
────────────────────────────────────────
Example 3 0.2 mm 12 seconds 0.98 (pass)
Example 4 3.5 mm 20 seconds 1.01 (pass)
────────────────────────────────────────
Comparative Example 3 0.2 mm 3 seconds 0.80 (failed)
Comparative Example 4 3.5 mm 30 seconds 1.10 (failed)
────────────────────────────────────────

  That is, as is apparent from the results of Tables 1 and 2, in the case of producing a multilayer resin film using the solution casting method, a multilayer with high thickness accuracy can be obtained by utilizing the production conditions of the present invention. It can be seen that a resin film can be obtained.

  In the above description, the case of a three-layer structure has been described as an example. However, the method for producing a multilayer resin film of the present invention can be suitably implemented even for a film having a multilayer structure other than three layers. .

The perspective view which illustrates schematically the structure and operation | movement of an apparatus containing the casting die provided with the feed block type resin solution merging apparatus. It is sectional drawing which shows in more detail the structure of the co-casting die provided with the feed block type | mold resin solution confluence | merging apparatus. It is a perspective view which shows the state of the resin solution flow discharged in the multilayer state from the co-casting die to the surface of a support body, and the state of the multilayer cast resin film produced | generated on the surface of a support body from the resin solution flow. It is a schematic sectional drawing explaining the internal structure of the feed block type | mold resin solution merging apparatus which can be advantageously used for implementation of the manufacturing process of the multilayer cast resin film according to this invention. It is a perspective view which shows the structure of the notch groove pin described in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feed block type resin solution (dope) confluence apparatus 2 Co-casting die 3 Support body 4 Multilayer cast resin film 5 Stripping roll

Claims (6)

From the intermediate layer flow path for circulating the dope forming the central resin layer of the multilayer cast resin film, and the two outer layer flow paths for flowing the dope forming the outer resin layer formed on both sides of the central resin layer The notch groove pin for adjusting the flow rate of the dope that merges from the outer layer flow path is provided at the joining portion, and the notch groove depth of the notch groove pin is 0.1. A feed block type resin solution merging device characterized by being in a range of ˜5 mm .   The dope forming the central resin layer is a relatively low viscosity resin solution having a viscosity in the range of 50 to 700 poise, and the dope forming the outer resin layer has a viscosity of the dope forming the central resin layer. 2. The feed block type resin solution merging device according to claim 1, wherein the feed block type resin solution merging device is a relatively high viscosity resin solution having a viscosity in a range of 500 to 2500 poises at 2 to 10 times.   A feed block type casting solution die comprising a feed block type resin solution joining device and a co-casting die, wherein the feed block type resin solution joining device is the feed block type resin solution joining device according to claim 1. Feed block type casting die.   In the feed block type resin solution merging device, the dopes are joined to form parallel resin solution flows in contact with each other at the interface, and then introduced into the co-casting die, and the resin solution parallel flow is supported from the die lip through the flow channel of the casting die. The feed block type casting die according to claim 3, wherein a multilayer casting resin film is formed by discharging on a body.   The feed block type casting die according to claim 4, wherein the thickness of the multilayer cast resin film after drying is 20 to 500 µm.   The feed block type casting die according to claim 3, wherein discharge from the casting die is performed for 5 to 25 seconds calculated from the time when the dopes are joined.

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