JP2010204346A - Method of manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical film having a plurality of layers, which is excellent in productivity. <P>SOLUTION: The method of manufacturing the optical film includes a wet-on-wet step in which a first coating liquid 13a is applied from a first slit 12a to a light-transmissive base material 11a to form a first coated layer 24 and, thereafter, a second coating liquid 13b having a component different from the component of the first coating liquid 13a is applied from a second slit 12b onto the first coated layer 24 before drying the first coated layer 24 to form a second coated layer 25. Therein, when wet thickness of the second coated layer 25 is (a), distance in the vertical direction between the top end surface of a third lip 23 and the top end surface of a second lip 22 is D, viscosity at shear rate 100 s<SP>-1</SP>of the first coating liquid 13a is η1 and viscosity at shear rate 100 s<SP>-1</SP>of the second coating liquid 13b is η2, the following relations hold: 4.5 μm≤a≤30 μm, (0.5×a)μm≤D≤(3×a)μm, η1≥20mPa s, η2≤50mPa s, η2<η1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a multifunctional optical film formed from a plurality of layers.

  In recent years, development of high-definition and large-screen displays represented by a liquid crystal display (LCD), a plasma display panel (PDP), and the like has been rapidly progressing. In order to improve the visibility of the display surface of the display, it is necessary to dispose an optical film having an antireflection function on the surface in order to prevent reflection of external light such as a fluorescent lamp on the screen.

  As a method for producing an optical film, an inorganic metal is vapor-deposited or sputtered on the surface of a display, so-called dry coating method, a low refractive index material or the like is applied on a substrate in a solution or dispersion state, and is dried. There are known wet coating methods and the like which are produced by curing as necessary. With the recent increase in size of displays, a wet coating method that can be manufactured at low cost by roll-to-roll and is easy to cope with upsizing is now becoming mainstream.

  In addition, as a configuration of the optical film, for example, a hard coat layer and a low refractive index layer disposed on the substrate, a hard coat layer on the substrate, and a number of different refractive indexes on the hard coat layer. There are some in which a plurality of coating layers are formed on a substrate, such as those in which layers are arranged.

  In general, when an optical film is produced by a wet coating method, as a method for forming a coating layer, a coating solution for a high refractive index layer is coated on a substrate, dried, cured as necessary, and then further reduced in refractive index. A so-called sequential multilayer coating method is used in which a coating solution for the rate layer is applied thereon, dried and cured to form a plurality of coating layers.

  However, in the above-described sequential multilayer coating method, the coating process and the drying process are each required twice, resulting in poor productivity, high manufacturing costs, low adhesion between the two layers, and poor scratch resistance. Problems may arise. Therefore, a high refractive index layer containing inorganic fine particles and a low refractive index layer containing fluorine containing polymer are simultaneously formed by applying and curing a coating solution containing both the fluoropolymer and inorganic fine particles at once. A method of manufacturing an antireflection film has been proposed (Patent Document 1).

JP 2004-317734 A

  However, the method proposed in Patent Document 1 is to simultaneously produce a plurality of layers by phase separation in the drying process after coating, and it is difficult to determine the drying conditions and there is room for improvement from the viewpoint of productivity. It is believed that there is.

  The present invention relates to an improvement of a method for producing an optical film having a plurality of layers formed by applying at least two kinds of coating solutions to a substrate by a wet coating method, and an optical device having a plurality of layers having excellent productivity. A method for producing a film is provided.

The method for producing an optical film of the present invention is a method for producing an optical film in which a coating liquid is applied to a translucent substrate using a one-head type slot die including a first lip, a second lip, and a third lip. The slot die comprises a first slit between the first lip and the second lip, and a second slit between the second lip and the third lip, The first slit and the second slit are arranged in this order along the direction in which the coating liquid is applied, and the third lip is disposed at the end of the slot die, and the translucent substrate The first coating liquid is applied to the first coating layer to form the first coating layer, and then the first coating layer is dried on the first coating layer before the first coating layer is dried. Apply a second coating solution, which has a different component from the coating solution, A wet-on-wet process of forming a fabric layer, wherein the wet coating thickness of the second coating layer is a, the vertical distance between the tip surface of the third lip and the tip surface of the second lip is D, and the first When the viscosity of one coating solution at a shear rate of 100 s ⁻¹ is η1, and the viscosity of the second coating solution at a shear rate of 100 s ⁻¹ is η2, 4.5 μm ≦ a ≦ 30 μm, (0.5 × a) μm ≦ D ≦ (3 × a) μm, η1 ≧ 20 mPa · s, η2 ≦ 50 mPa · s, and η2 <η1.

  According to the present invention, even when two or more types of coating liquids discharged from adjacent slits are applied using a slot die in the wet-on-wet process, the adjacent coating liquids do not mix with each other. In addition, it is possible to provide a method for producing an optical film that can form a plurality of coating layers and is excellent in productivity.

FIG. 1 is a schematic side view showing an example of a step of applying a coating solution to a light-transmitting substrate by the simultaneous multilayer coating method of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of FIG. FIG. 3 is a scanning electron micrograph of the cross section of the optical film of Example 4. FIG. 4 is a scanning electron micrograph of the cross section of the optical film of Comparative Example 5.

  The method for producing an optical film of the present invention is a method in which a coating solution is applied to a translucent substrate using a one-head type slot die having at least a first lip, a second lip, and a third lip. . The slot die includes a first slit between the first lip and the second lip, and a second slit between the second lip and the third lip. Further, the first slit and the second slit are arranged in this order along the direction in which the coating liquid is applied, and the third lip is disposed at the end of the slot die.

  In the method for producing an optical film of the present invention, after forming the first coating layer by applying the first coating liquid from the first slit to the translucent substrate, before drying the first coating layer, A wet-on-wet process in which a second coating layer is formed by coating a second coating solution having a component different from that of the first coating solution from the second slit on the first coating layer.

  Thereby, application | coating of two or more types of coating liquids can be performed in one process, and productivity can be improved compared with the conventional sequential multilayer coating method. Further, since the second coating solution is applied before the first coating solution is dried, the adhesion between the first coating layer and the second coating layer is increased. The coating method according to the present invention is also referred to as a simultaneous multilayer coating method with respect to the conventional sequential multilayer coating method.

Furthermore, in the method for producing an optical film of the present invention, the wet film thickness of the second coating layer is a, the vertical distance between the tip surface of the third lip and the tip surface of the second lip is D, When the viscosity of one coating liquid at a shear rate of 100 s ^-1 is η1, and the viscosity of the second coating liquid at a shear rate of 100 s ^-1 is η2,
4.5 μm ≦ a ≦ 30 μm,
(0.5 × a) μm ≦ D ≦ (3 × a) μm,
η1 ≧ 20 mPa · s,
η2 ≦ 50 mPa · s,
η2 <η1.

  Thus, even when two or more types of coating liquids discharged from adjacent slits are applied in a wet-on-wet process using a slot die, a plurality of adjacent coating liquids are not mixed with each other. A coating layer can be formed, and a plurality of optical functional layers can be efficiently produced.

  The upper limit of η1 is preferably 10,000 mPa · s or less so as not to decrease the coating speed, and the lower limit of η2 is 0.5 mPa · s or more in order to maintain the coating conditions of 4.5 μm ≦ a ≦ 30 μm. It is preferable that

  Moreover, the said wet film thickness a means the film thickness before an application layer is dried with a dryer.

  Here, the two types of coating liquids having different components correspond to, for example, a case where one of the first coating liquid and the second coating liquid contains a filler.

  If the said translucent base material is formed with the material which has flexibility, the shape, a manufacturing method, etc. will not be specifically limited. For example, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethersulfone resin, triacetyl cellulose What processed the material, such as resin, into the film form or the sheet form can be used. Examples of the method for processing into a film or sheet include extrusion molding, calendar molding, compression molding, injection molding, and a method in which the above resin is dissolved in a solvent and cast. The thickness of the substrate is usually about 10 μm to 500 μm. Note that additives such as antioxidants, flame retardants, heat resistance inhibitors, ultraviolet absorbers, lubricants, and antistatic agents may be added to the above materials.

  The plurality of layers is not particularly limited as long as it is a functional layer that imparts a specific function to the optical film. For example, the first coating layer is a hard coat layer, and the second coating layer is a low refractive index layer. In some cases, in the simultaneous multi-layer coating method of the present invention, an optical film (such as an antireflection film) can be produced in a single coating process without the first coating liquid and the second coating liquid being mixed. Become. Further, the first coating layer or the second coating layer may be a near infrared absorption layer, a diffusion layer, an antiglare layer, or the like.

  The method for adjusting the viscosity of the coating solution used in the present invention is not particularly limited, and the viscosity can be adjusted by adjusting the type and content of each component contained in the coating solution. For example, when two types of acrylic resins (acrylic monomers) are included in the coating liquid, the above-mentioned η1 ≧ 20 mPa · s is obtained by adjusting the content ratio of two types of acrylic resins having different numbers of functional groups. It can adjust to (eta) 2 <= 50mPa * s and (eta) 2 <(eta) 1. Moreover, when the acrylic resin and the organic solvent are contained in the coating liquid, the viscosity can be similarly adjusted by adjusting the content ratio of the acrylic resin and the organic solvent. Furthermore, when the coating liquid contains an acrylic resin, an organic solvent, and a filler, the viscosity can be similarly adjusted by adjusting the content ratio of the acrylic resin, the organic solvent, and the filler.

In the present specification, the viscosity of the coating liquid means the viscosity at a shear rate of 100 s ⁻¹ , and the viscosity is measured with a viscometer (rheometer). Therefore, hereinafter, “viscosity at a shear rate of 100 s ⁻¹ ” is simply referred to as “viscosity”.

  The present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing an example of a process of applying a coating solution to a light-transmitting substrate by the simultaneous multilayer coating method of the present invention, and FIG. 2 is an enlarged cross-sectional view of the main part of FIG. FIG. 1 shows a part of it in a cross section, but hatching indicating the cross section is not attached so as not to disturb the understanding of the drawing. In FIG. 1, first, the first coating liquid 13a is applied from the first slit 12a of the slot die 12 to the surface of the translucent substrate 11a supplied from the unwinding roll 10a, and then the first coating liquid 13a is dried. Before the second coating liquid 13b is applied, the second coating liquid 13b is applied from the second slit 12b of the slot die 12 onto the base material 11a coated with the first coating liquid 13a.

  The base material 11a is bridged between a pair of support rolls 14a and 14b, and the slot die 12 is disposed between the support rolls 14a and 14b so as to face the base material 11a. Therefore, a certain pressure is applied to the slot die 12 by the tension applied to the base material 11a.

  Then, it dries with the dryer 15, produces the optical film 11b of a multilayer structure, and winds up on the winding roll 10b.

  In FIG. 2, the slot die 12 is a one-head type, and includes a first lip 21, a second lip 22, and a third lip 23. Further, the slot die 12 includes a first slit 12 a between the first lip 21 and the second lip 22, and a second slit 12 b between the second lip 22 and the third lip 23. Further, the first slit 12 a and the second slit 12 b are arranged in this order along the direction in which the coating liquid is applied, and the third lip 23 is disposed at the end of the slot die 12.

  In FIG. 2, the first coating layer 24 is formed on the substrate 11 a by applying the first coating solution 13 a from the first slit 12 a to form the first coating layer 24, and then before the first coating layer 24 is dried. A second coating layer 25 is formed by applying a second coating solution 13b having a component different from that of the first coating solution 13a from the second slit 12b.

Further, in FIG. 2, the wet film thickness of the second coating layer 25 is a, the vertical distance between the tip surface of the third lip 23 and the tip surface of the second lip 22 is D, and the shear rate of the first coating solution 13a. When the viscosity at 100 s ⁻¹ is η1, and the viscosity at the shear rate 100 s ⁻¹ of the second coating liquid 13b is η2,
4.5 μm ≦ a ≦ 30 μm,
(0.5 × a) μm ≦ D ≦ (3 × a) μm,
η1 ≧ 20 mPa · s,
η2 ≦ 50 mPa · s,
η2 <η1,
Is set to

The width L of the third lip 23 may be L ≦ 1.0 × 10 ⁴ μm, and the wet film thickness b of the first coating layer 24 may be 0.5 μm ≦ b ≦ 100 μm.

  As a result, even when two types of coating liquid discharged from the adjacent first slit 12a and second slit 12b using the slot die 12 are applied in the wet-on-wet process, the adjacent first coating liquid is used. The first coating layer 24 and the second coating layer 25 can be formed without causing mixing of the first coating liquid 13a and the second coating liquid 13b, and a plurality of optical functional layers can be efficiently produced.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to a following example. Further, “parts” in the following examples and comparative examples means parts by weight.

  In the following examples and comparative examples, the viscosity of the coating liquid depends on the ratio of the 10-functional acrylate resin “UA510H” (viscosity 27000 mPa · s) and the trifunctional acrylate resin “PE3A” (viscosity 550 mPa · s), or these acrylate resins. And the ratio of the solvent “isobutanol”. That is, increasing the ratio of the resin to the solvent or increasing the ratio of the 10 functional acrylate resin to the trifunctional acrylate resin increases the viscosity. When the filler is contained in the coating solution, the viscosity varies depending on the filler content, and basically the viscosity increases as the filler content increases. The photopolymerization initiator is used for curing the coating film and is not used for viscosity adjustment.

(Examples 1-4)
<Preparation of first coating solution>
The following components of the first coating solution were mixed and stirred to prepare the first coating solution. The viscosity η1 of the first coating solution was 613 mPa · s.

(1) Acrylate resin “UA510H” (manufactured by Kyoeisha Chemical Co., Ltd.): 28 parts (2) Acrylate resin “PE3A” (manufactured by Kyoeisha Chemical Co., Ltd.): 18 parts (3) Isobutanol: 49 parts (4) Photopolymerization initiator “ IRGCURE184 "(Ciba Specialty Chemicals): 5 parts

<Preparation of second coating solution>
After mixing and stirring the components of the following second coating solution, the second coating solution was prepared using a bead mill (“Picomill” manufactured by Asada Tekko Co., Ltd.) with a residence time of 60 minutes. The viscosity η2 of the second coating solution was 1.6 mPa · s.

(1) Silica fine powder “Aerosil” (produced by Nippon Aerosil Co., Ltd.): 1.5 parts (2) Acrylate resin “UA510H” (produced by Kyoeisha Chemical Co., Ltd.): 0.6 parts (3) Acrylate resin “PE3A” (Kyoeisha Chemical Co., Ltd.) Manufactured): 0.4 part (4) Isobutanol: 97.3 parts (5) Photopolymerization initiator “IRGCURE184” (manufactured by Ciba Specialty Chemicals): 0.1 part (6) Dispersant “DISPERBYK110” (BIC Chemie): 0.1 part

<Production of optical film>
The first coating solution is applied on a polyethylene terephthalate biaxially stretched film ("Lumirror" manufactured by Toray Industries Inc., thickness 100 μm) using a slot die shown in FIG. 2 to form a first coating layer. Before drying one coating layer, the second coating solution was further coated on the first coating layer to form a second coating layer (wet-on-wet process). At that time, the vertical distance D between the tip surface of the third lip and the tip surface of the second lip and the wet film thickness a of the second coating layer were set as shown in Table 1. Then, the drying zone of each condition of drying temperature 60 degreeC-80 degreeC-100 degreeC-100 degreeC was passed by each drying time 10 seconds or more, and it dried. Subsequently, the obtained coating film is irradiated with ultraviolet rays (dose: 700 mJ / cm ² ) to cure the coating film, and the optical film for evaluation of Examples 1 to 4 having the first coating film and the second coating film Was made.

  The wet film thickness a of the second coating layer was calculated based on the coating liquid supply flow rate / (coating speed × coating width).

(Comparative Examples 1-3)
Examples 1-4 except that the vertical distance D between the tip surface of the third lip and the tip surface of the second lip and the wet film thickness a of the second coating layer were set as shown in Table 1. Similarly, optical films for evaluation of Comparative Examples 1 to 3 were produced.

(Example 5, Comparative Examples 4 to 6)
<Preparation of first coating solution>
The following components of the first coating solution were mixed and stirred to prepare the first coating solution. The viscosity η1 of the first coating solution was 216 mPa · s.

(1) Acrylate resin “UA510H” (manufactured by Kyoeisha Chemical Co., Ltd.): 24 parts (2) Acrylate resin “PE3A” (manufactured by Kyoeisha Chemical Co., Ltd.): 17 parts (3) Isobutanol: 55 parts (4) Photopolymerization initiator “ IRGCURE184 "(Ciba Specialty Chemicals): 4 parts

  Except that the first coating liquid was used and the vertical distance D between the tip surface of the third lip and the tip surface of the second lip and the wet film thickness a of the second coating layer were set as shown in Table 1. Produced optical films for evaluation of Example 5 and Comparative Examples 4 to 6 in the same manner as in Examples 1 to 4.

[Evaluation of optical film]
The optical films for evaluation in Examples 1 to 5 and Comparative Examples 1 to 6 are pretreated by irradiating gallium (Ga) ions with a focused ion beam (FIB), and then a scanning electron microscope (SEM). The cross section of the coating film was observed and evaluated. In the evaluation, a case where the boundary between the first coating film and the second coating film could be confirmed was accepted, and a case where the boundary could not be confirmed was rejected. The results are shown in Table 1 with A as pass and B as fail. In Table 1, Examples 1 to 5 and Comparative Examples 1 to 6 are shown as actual 1 to 5 and ratios 1 to 6, respectively.

  Moreover, the SEM photograph of the cross section of the optical film of Example 4 is shown in FIG. 3, and the SEM photograph of the cross section of the optical film of Comparative Example 5 is shown in FIG.

From Table 1, Examples 1 to 5, for example, as shown in FIG. 3, when all the boundaries between the first coating film and the second coating film can be confirmed, and two types of coating liquids having different components are applied almost simultaneously. Even so, it can be seen that mixing of the adjacent coating liquids does not occur. On the other hand, from Table 1, in Comparative Examples 1 to 6, for example, as shown in FIG. 4, the boundary between the first coating film and the second coating film becomes unclear, and mixing of adjacent coating liquids occurs. I understand that.
3 and 4, the white thin film visible on the second coating film is a pretreatment protective film at the time of SEM photography.

  As described above, according to the present invention, even when at least two kinds of coating liquids having different components are applied substantially simultaneously, mixing of adjacent coating liquids does not occur, and thus the plurality of layers are surely provided. An optical film can be produced and an optical film manufacturing method excellent in productivity can be provided. By using this optical film, a front filter suitable for various displays, particularly PDPs can be provided.

10a Unwinding roll 10b Take-up roll 11a Base material 11b Optical film 12 Slot die 12a First slit 12b Second slit 13a First coating liquid 13b Second coating liquids 14a and 14b Support roll 15 Dryer 21 First lip 22 Second Lip 23 Third lip 24 First coating layer 25 Second coating layer

Claims (5)

A method for producing an optical film in which a coating liquid is applied to a translucent substrate using a one-head type slot die including a first lip, a second lip, and a third lip,
The slot die includes a first slit between the first lip and the second lip, and a second slit between the second lip and the third lip,
The first slit and the second slit are arranged in this order along the direction in which the coating liquid is applied, and the third lip is disposed at the end of the slot die,
After the first coating liquid is applied to the translucent substrate from the first slit to form the first coating layer, the first coating layer is dried on the first coating layer before the first coating layer is dried. Including a wet-on-wet process of applying a second coating solution having a component different from that of the first coating solution from two slits to form a second coating layer;
The wet film thickness of the second coating layer is a,
The vertical distance between the tip surface of the third lip and the tip surface of the second lip is D,
The viscosity of the first coating solution at a shear rate of 100 s ⁻¹ is η1,
When the viscosity of the second coating liquid at a shear rate of 100 s ⁻¹ is η2,
4.5 μm ≦ a ≦ 30 μm,
(0.5 × a) μm ≦ D ≦ (3 × a) μm,
η1 ≧ 20 mPa · s,
η2 ≦ 50 mPa · s,
A method for producing an optical film, wherein η2 <η1.   The manufacturing method of the optical film of Claim 1 in which any one of a said 1st coating liquid and a said 2nd coating liquid contains a filler.   The method for producing an optical film according to claim 1, wherein the first coating layer is a hard coat layer.   The method for producing an optical film according to claim 1, wherein the second coating layer is a low refractive index layer.   The method for producing an optical film according to claim 1, wherein the first coating layer or the second coating layer is a near-infrared absorbing layer.

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