Preparation method of thickening liquid and manufacturing method of optical film

Abstract

To provide a preparation method of thickening liquid capable of sufficiently removing a foreign matter while suppressing a change in a thixotropy value.SOLUTION: In a preparation method of thickening liquid according to the present invention, the thickening liquid has a thixotropy property. The method includes: a first filtration step of making the total amount of the thickening liquid before filtration processing to pass through a filter to obtain primary filtration liquid; and a second filtration step of making the primary filtration liquid to pass through the used filter that has been used in the first filtration step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for preparing a thickening adhesive and a method for manufacturing an optical film.

Background Art

[0002] Thickening adhesives are used in the manufacture of various products. For example, an image display device such as a liquid crystal display equipped with an antiglare film is known, and a thickening adhesive is used in the manufacture of this antiglare film. Specifically, the antiglare film usually has a coating film containing fine particles such as silica, and these fine particles form an uneven shape on the surface of the coating film. In an image display device equipped with such an antiglare film, light incident on the antiglare coating film is scattered by the fine particles, suppressing the reflection of light. And, a thickening adhesive is used to form such a coating film (for example, Patent Document 1).

[0003] In the preparation of such thickening adhesives, a filtration process is performed to remove foreign substances that can reduce the quality of the product. As a method commonly used for the purpose of removing foreign substances, a method of passing the thickening adhesive through a plurality of new filters can be mentioned.

[0004] In addition, a method of circulating the thickening adhesive before filtration using one filter can be mentioned. As a specific embodiment of the circulating method, a circulating system is constructed in which the thickening adhesive before filtration is stored in a tank, and one filter is interposed in a pipe capable of transferring the thickening adhesive from the discharge part of the tank to the supply part, and the thickening adhesive is circulated in this circulating system.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the preparation of the thickening agent, in order to make the product exhibit predetermined performance, the thixotropy value of the thickening agent may be adjusted to a predetermined value. For example, in the preparation of a thickening agent for forming a coating film of an antiglare film, the thixotropy value of the thickening agent is adjusted to a predetermined value in order to form a predetermined uneven shape due to fine particles on the surface of the coating film. Note that the adjustment of the thixotropy value may be performed on the thickening agent as a coating liquid containing fine particles such as silica, and may also be performed on the thickening agent as a material for preparing the coating liquid and not containing fine particles.

[0007] However, although the conventional method focuses on the removal of foreign substances in the thickening agent, it does not focus on the change in the thixotropy value. That is, it cannot be said that sufficient studies have been made so far on suppressing the change in the thixotropy value in the filtration process. And in the conventional preparation method, the thixotropy value of the thickening agent may change in the filtration process, and for this reason, there is a risk of being forced to readjust the thixotropy value or, in some cases, to re-prepare the thickening agent.

[0008] In view of the above circumstances, an object of the present invention is to provide a method for preparing a thickening agent that can sufficiently remove foreign substances while suppressing a change in the thixotropy value. Another object of the present invention is to provide a method for manufacturing an optical film containing particles, which can sufficiently exhibit the functions of the particles.

Means for Solving the Problems

[0009] The method for preparing a thickening agent according to the present invention is as follows: The thickening agent has thixotropy, It includes a first filtration step of passing the entire amount of the thickening agent before the filtration process through a filter to obtain a primary filtrate, and a second filtration step of passing the primary filtrate through the used filter used in the first filtration step.

[0010] According to such a configuration, in the first filtration step, by passing the entire amount of the thickened liquid before filtration through the filter, a used filter in which some of the pores are blocked by foreign substances contained in the thickened liquid can be obtained. In the second filtration step using such a used filter in a blocked state, the flow rate of the primary filtrate becomes faster and the shearing force on the primary filtrate increases compared to the case of using a new filter. As a result, since the viscosity of the primary filtrate decreases, it is considered that excessive capture of the thickening component is suppressed and a change in the thixotropy value is suppressed. Further, by performing a plurality of filtration steps including the first filtration step and the second filtration step, foreign substances can be sufficiently removed.

[0011] Further, a method for preparing a thickened liquid according to an aspect of the present invention The thixotropy value of the thickened liquid before the filtration treatment is 3 to 7.

[0012] According to such a configuration, since the object of the filtration treatment is a thickened liquid having a thixotropy value of 3 to 7, the above-described effects can be sufficiently obtained.

[0013] Further, a method for preparing a thickened liquid according to an aspect of the present invention In the first filtration step, the flow rate of the thickened liquid passing through the filter is set to 10 to 50 mm / min.

[0014] According to such a configuration, the used filter obtained through the first filtration step can be suitable for carrying out the second filtration step.

[0015] Further, a method for preparing a thickened liquid according to an aspect of the present invention In the second filtration step, the primary filtrate is stored in a tank, and filtration is performed while circulating the primary filtrate between the tank and the used filter.

[0016] According to such a configuration, by circulating the primary filtrate through the used filter, more foreign substances can be removed.

[0017] Further, a method for preparing a thickened liquid according to an aspect of the present invention When the implementation time of the second filtration step is T (minutes), the second filtration step is carried out so as to satisfy 2 ≦ T / t ≦ 4, (where t = V / r, V: the volume (L) of the primary filtrate, r: the filtration flow rate (L / min) of the used filter).

[0018] According to such a configuration, by stipulating 2 ≦ T / t, more foreign matters can be removed, and by stipulating T / t ≦ 4, the change in the thixotropy value can be suppressed.

[0019] Further, the method for preparing a thickening liquid according to one aspect of the present invention is During the implementation of the first filtration step, the thickening liquid before the filtration treatment is not stirred.

[0020] According to such a configuration, since the shearing force due to stirring is not applied to the thickening liquid before the filtration treatment, the change in the thixotropy value of the thickening liquid can be further suppressed.

[0021] Further, the method for preparing a thickening liquid according to one aspect of the present invention is The absolute filtration accuracy of the filter is 2 μm or more and 8 μm or less.

[0022] According to such a configuration, since the filtration accuracy of the filter is 2 μm or more, the capture of unnecessary thickening components can be suppressed. Also, since the filtration accuracy of the filter is 8 μm or less, the capture of unnecessary thickening components caused by the slow flow rate and the increase in the viscosity of the thickening liquid can be suppressed. That is, a filter with a filtration accuracy of 2 μm or more and 8 μm or less is appropriate for suppressing the change in the thixotropy value of the thickening liquid.

[0023] Next, the method for manufacturing an optical film according to the present invention is a method for manufacturing an optical film containing particles, Particles and a binder resin are dispersed in the thickening liquid obtained by any of the above preparation methods to prepare a coating liquid, and a coating film is formed using the coating liquid.

[0024] According to such a configuration, since dripping of the coating liquid is suppressed and particles are appropriately dispersed in the coating liquid, an optical film capable of sufficiently exhibiting the functions of the particles can be obtained.

Effect of the Invention

[0025] As described above, according to the present invention, it is possible to provide a method for preparing a thickening liquid that can sufficiently remove foreign substances while suppressing changes in the thixotropy value. Further, it is possible to provide a method for manufacturing an optical film capable of sufficiently exhibiting the functions of particles.

Brief Description of the Drawings

[0026]

Figure 1

Mode for Carrying Out the Invention

[0027] Hereinafter, with reference to the drawings, a method for preparing a thickening liquid according to a first embodiment of the present invention will be described.

[0028] The method for preparing the thickening liquid of this embodiment includes a mixing step of stirring a mixed liquid containing a thickening agent and a solvent to produce a thickening liquid having a predetermined thixotropy value, and a filtering step of filtering the thickening liquid using a filter. In the following, the thickening liquid before the filtering process in the filtering step, that is, the thickening liquid produced in the mixing step, may be referred to as the pre-treatment thickening liquid, and the thickening liquid after the filtering process in the filtering step may be referred to as the post-treatment thickening liquid.

[0029] Examples of the thickening agent include organic clays such as smectite, talc, bentonite, montmorillonite, and kaolinite.

[0030] Examples of the solvent include monohydric alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, and 2-methoxyethanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ether solvents such as diisopropyl ether and propylene glycol monomethyl ether; polyol solvents such as ethylene glycol and propylene glycol; acyclic aliphatic hydrocarbon solvents such as hexane, heptane, and octane; cyclic aliphatic hydrocarbons such as cyclohexane and cycloheptane; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. The thickening agent may contain only one of these solvents or may contain a plurality of them.

[0031] The relative dielectric constant of the solvent is preferably from 2 to 6.

[0032] The content of the thickening agent in the pre-treatment thickening agent is preferably 4 to 10% by mass, more preferably 5 to 8% by mass, based on the total mass of the pre-treatment thickening agent. The content of the solvent in the pre-treatment thickening agent is preferably 90% by mass or more, more preferably 95% by mass or more, based on the total mass of the pre-treatment thickening agent.

[0033] In the mixing step of this embodiment, a stirring device is used. The stirring device of this embodiment includes a container for filling the thickening agent and the solvent, and a homomixer for stirring the mixture in the container.

[0034] In the mixing step of this embodiment, the thixotropy value of the pre-treatment thickening agent is adjusted to be from 3 to 7 by stirring the mixture with the stirring device. Here, the thixotropy value means a value obtained by dividing the viscosity at a low shear rate of 5 rpm by the viscosity at a high shear rate of 50 rpm when measuring the viscosity of the pre-treatment thickening agent under the measurement conditions of a temperature of 30 °C using an E-type viscometer.

[0035] Further, the pre-treatment thickening solution preferably has a viscosity of 30 mPa·s or more, more preferably 40 mPa·s or more, and even more preferably 50 mPa·s or more at low shear. Also, the pre-treatment thickening solution preferably has a viscosity of 10 mPa·s or less at high shear.

[0036] In the mixing step of the present embodiment, when the pre-treatment thickening solution having a predetermined thixotropy value is obtained, the stirring by the stirring device is terminated.

[0037] The filtration step of the present embodiment includes a first filtration step of passing the entire amount of the pre-treatment thickening solution through a filter to obtain a primary filtrate, and a second filtration step of passing the primary filtrate through the used filter used in the first filtration step to obtain the post-treatment thickening solution. The filtration step of the present embodiment aims to remove foreign matters having a particle size of at least 10 μm.

[0038] As shown in FIG. 1, the apparatus 1 used in the filtration step of the present embodiment includes a first tank 10 for storing the pre-treatment thickening solution, a second tank 20 for storing the primary filtrate or the post-treatment thickening solution, and a filter housing 40 provided in a first pipe 31 extending from the bottom wall portion of the first tank 10 to the upper wall portion of the second tank 20 to carry out the first filtration step. Further, the apparatus 1 includes a second pipe 32 extending from the bottom wall portion of the second tank 20 to the upper wall portion of the second tank 20 via the filter housing 40 to carry out the second filtration step. Furthermore, the apparatus 1 includes a first pump P1 provided on the upstream side of the filter housing 40 in the first pipe 31, and a second pump P2 provided on the upstream side of the filter housing 40 in the second pipe 32.

[0039] The filter of the present embodiment is a depth pleat type filter and is a laminate of a plurality of non-woven fabrics having different fiber diameters and has a pleated laminate. The filtration area of the filter used in the present embodiment is 0.15 to 0.20 m 2It is as follows. The absolute filtration accuracy of the filter used in this embodiment is 2 to 8 μm. Note that an absolute filtration accuracy of 8 μm means that the particle size that can be removed by 99.9% or more is 8 μm.

[0040] The filter of this embodiment is formed in a cylindrical shape and provided in a filter cartridge. The filter cartridge includes a cylindrical core having a plurality of liquid passage holes on the side surface, the filter in a state of being inserted through the core, and a cover that is cylindrical and has a plurality of liquid passage holes on the side surface and through which the filter is inserted. Further, the filter cartridge includes end caps that seal both ends of the filter in a liquid-tight manner. The filter cartridge of this embodiment is used by being housed in a filter housing 40.

[0041] In this embodiment, the mixing step is carried out in the first tank 10 to obtain the pre-treatment thickened liquid in a state of being housed in the first tank 10.

[0042] In the first filtration step of this embodiment, the entire amount of the pre-treatment thickened liquid housed in the first tank 10 is transferred to the second tank 20 while passing through the new filter, and the primary filtrate housed in the second tank 20 and the used filter are obtained. In the first filtration step of this embodiment, the flow rate of the pre-treatment thickened liquid passing through the filter is set to 10 to 50 mm / min. According to such a flow rate, the viscosity of the pre-treatment thickened liquid can be suitable for the production of the primary filtrate and the used filter. Specifically, the change in the thixotropy value of the primary filtrate with respect to the pre-treatment thickened liquid is suppressed by suppressing the capture of the unnecessary thickening agent. Further, foreign matters having a particle size of 10 μm or more contained in the pre-treatment thickened liquid are captured by the filter, and the used filter suitable for the second filtration step can be produced.

[0043] Also, in the first filtration step of the present embodiment, during the filtration process, the pre-treatment thickened liquid stored in the first tank 10 is not stirred. By doing so, the volatilization of the solvent from the pre-treatment thickened liquid is suppressed, the concentration of the thickener does not inadvertently increase, and thus, the change in the thixotropy value of the primary filtrate with respect to the pre-treatment thickened liquid can be suppressed. Further, no excessive shearing force is applied to the pre-treatment thickened liquid, and the change in the thixotropy value of the primary filtrate with respect to the pre-treatment thickened liquid is suppressed. Also, although there is a possibility that some foreign matters with relatively large particle sizes may remain at the bottom of the first tank 10 or the like due to not stirring, the filter that has captured such foreign matters can unnecessarily increase the flow rate in the filter. Therefore, leaving foreign matters with relatively large particle sizes in the first tank 10 also contributes to making the used filter suitable for the filtration process in the second filtration step.

[0044] In the second filtration step of the present embodiment, in order to remove as many foreign matters as possible while maintaining the thixotropy value, the filtration process is carried out by circulating the primary filtrate between the second tank 20 and the filter housing 40 in which the used filter is accommodated.

[0045] Specifically, first, as follows: T: The implementation time of the filtration process in the second filtration step t: The theoretical implementation time of the filtration process in the second filtration step calculated by V / r V: The volume (L) of the primary filtrate r: The filtration flow rate (L / min) of the used filter Let the index of how many times the total amount of the primary filtrate passes through the used filter be defined as T / t. When T / t = 1, the number of times the total amount of the primary filtrate passes through the used filter is 1 time. When T / t < 1, the number of times the total amount of the primary filtrate passes through the used filter is less than 1 time. When T / t > 1, the number of times the total amount of the primary filtrate passes through the used filter is more than 1 time. And in the second filtration step of this embodiment, the filtration treatment is carried out so as to satisfy at least 1 ≦ T / t. More preferably, in the second filtration step, the filtration treatment is carried out so as to satisfy the following formula (1). 2 ≦ T / t ≦ 4 ···(1)

[0046] In addition, when producing the used filter having a predetermined filtration flow rate in the first filtration step, when the filtration flow rate of the new filter reaches the target value during the filtration treatment of the primary filtrate, it may be replaced with a separately prepared new filter to continue the filtration treatment, and the filter before replacement may be used as the used filter. Also, when the filtration flow rate of the new filter decreases below the target value during the filtration treatment of the primary filtrate, it may be replaced with a separately prepared new filter to continue the filtration treatment, and the used filter may be produced from this other filter.

[0047] In the filtration step of this embodiment, the temperature of the pre-treatment thickened liquid and the primary filtrate is adjusted to 15 to 50 °C to carry out the filtration treatment.

[0048] According to the method for preparing the thickened liquid of this embodiment, a thickened liquid having a thixotropy value substantially the same as that produced in the mixing step can be prepared. That is, according to this embodiment, a thickened liquid having a thixotropy value of 3 to 7 can be obtained.

[0049] The thickening solution obtained by the preparation method of the present embodiment can be used as a material for manufacturing various products. Examples of such products include an antiglare film which is an optical film having a functional layer containing particles. The antiglare film usually includes a base material and an antiglare layer formed on one surface of the base material. The coating film for forming the antiglare layer contains particles and a binder resin. And the thickening solution obtained by the preparation method of the present embodiment can be used to form the coating film.

[0050] In the formation of the coating film, a coating liquid in which the particles and the binder resin are dispersed in the thickening solution is used. And this coating liquid is also adjusted to a predetermined thixotropy value in order to disperse the particles and the binder resin to exhibit antiglare property in the coating film. Also, this coating liquid can be filtered for removing foreign matters. And for the filtration treatment of the coating liquid, the methodology of the filtration step of the preparation method of the thickening solution of the above embodiment can be adopted. That is, the thickening solution of the present invention includes one containing materials such as the particles that exhibit an essential function for products such as the antiglare film, and a previous stage one that does not contain the essential materials of such products.

[0051] Therefore, next, as a second embodiment of the present invention, a method for preparing the coating liquid, which is an aspect of the thickening solution, will be described.

[0052] The method for preparing the coating liquid (thickening solution) according to the second embodiment includes a dispersion step of obtaining a coating liquid in which the particles and the binder resin are dispersed in the thickening solution obtained by the preparation method of the first embodiment, and a filtration step of filtering the coating liquid using a second filter.

[0053] Examples of the particles include inorganic particles and organic particles. Examples of the inorganic particles include silicon oxide particles, titanium oxide particles, aluminum oxide particles, zinc oxide particles, tin oxide particles, calcium carbonate particles, barium sulfate particles, talc particles, kaolin particles, calcium sulfate particles, and the like. Examples of the organic particles include polymethyl methacrylate resin particles (PMMA particles), silicone resin particles, polystyrene resin particles, polycarbonate resin particles, acrylic styrene resin particles, benzoguanamine resin particles, melamine resin particles, polyolefin resin particles, polyester resin particles, polyamide resin particles, polyimide resin particles, polytetrafluoroethylene resin particles, and the like. These may be used alone or in combination of multiple types.

[0054] The particle diameter of the particles is usually 1.5 to 5 μm. Here, the particle diameter means the median diameter in the volume-based particle size distribution measured by the laser diffraction scattering method.

[0055] Examples of the binder resin include thermosetting resins and photocurable resins. Examples of the thermosetting resins include polyfunctional acrylic monomers such as tricyclodecane dimethanol diacrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol tetra(meth)acrylate, dimethylolpropane tetraacrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol (meth)acrylate, 1,9-nonanediol diacrylate, 1,10-decanediol (meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, dipropylene glycol diacrylate, tri(meth)acrylate isocyanurate, ethoxylated glycerin triacrylate, ethoxylated pentaerythritol tetraacrylate, and monofunctional monomers such as ethoxylated o-phenylphenol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isooctyl acrylate, isostearyl acrylate, cyclohexyl acrylate, isophoronyl acrylate, benzyl acrylate, 2-hydroxy-3-phenoxy acrylate, acryloyl morpholine, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and hydroxyethyl acrylamide.

[0056] Further, examples of the binder resin include urethane (meth)acrylate obtained by reacting a hydroxy (meth)acrylate obtained from (meth)acrylic acid or a (meth)acrylic acid ester and a polyol with a diisocyanate. Examples of the polyol include ethylene glycol, 1,3 - propylene glycol, 1,2 - propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3 - butanediol, 1,4 - butanediol, 1,6 - hexanediol, 1,9 - nonanediol, 1,10 - decanediol, 2,2,4 - trimethyl - 1,3 - pentanediol, 3 - methyl - 1,5 - pentanediol, neopentyl glycol hydroxypivalate, tricyclodecane dimethylol, 1,4 - cyclohexanediol, spiroglycol, hydrogenated bisphenol A, ethylene oxide - added bisphenol A, propylene oxide - added bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 3 - methylpentane - 1,3,5 - triol, pentaerythritol, dipentaerythritol, tripentaerythritol, glucose - like substances, and the like.

[0057] In the dispersion step of the present embodiment, the stirring device is used to adjust the thixotropy value of the coating liquid to be 3 to 7.

[0058] In the filtration step of the present embodiment, the device 1 shown in FIG. 1 is used. And the filtration step of the present embodiment includes a first filtration step of passing the total amount of the pre - treatment coating liquid through the second filter to obtain a primary filtrate, and a second filtration step of passing the primary filtrate through the used second filter used in the first filtration step to obtain a post - treatment coating liquid.

[0059] The filter used in the present embodiment may be the same filter as that in the first embodiment. Further, so that the particles (particle diameter 1.5 to 5 μm), which are the active ingredients of the coating liquid, are not captured, the absolute filtration accuracy of the filter used in the present embodiment may be 8 μm or more and 20 μm or less.

[0060] In the first filtration step of this embodiment, the entire amount of the pre-treatment coating liquid stored in the first tank 10 is transferred to the second tank 20 while passing through a new second filter, and the primary filtrate stored in the second tank 20 and the used second filter are obtained. In the first filtration step of this embodiment, the flow rate of the pre-treatment coating liquid passing through the second filter is set to 10 to 50 mm / min. Also, in the first filtration step of this embodiment, during the filtration process, the pre-treatment coating liquid stored in the first tank 10 is not stirred.

[0061] In the second filtration step of this embodiment, the filtration process is carried out by circulating the primary filtrate between the second tank 20 and the filter housing 40 containing the used second filter. In the second filtration step of this embodiment, the filtration process is carried out so as to satisfy at least 1 ≦ T / t. More preferably, in the second filtration step, the filtration process is carried out so as to satisfy the above formula (1).

[0062] The coating liquid obtained by the preparation method of this embodiment has suppressed dripping and is excellent in the dispersibility of the particles, and thus is suitable for forming an antiglare coating film. Further, the antiglare layer exhibits sufficient antiglare properties.

[0063] In the formation of the antiglare layer, for example, the coating film may be formed on the substrate using the coating liquid, and the binder resin contained in the coating film may be cured by heat or light to form the antiglare layer. Thereby, an antiglare film in which the antiglare layer is laminated on the substrate can be obtained. In addition, the coating liquid may be used in the production of an optical film having a plurality of functional layers. That is, the optical film is a laminate including the antiglare layer as the first layer and a second layer on which the antiglare layer is laminated, and the coating film is formed on the second layer using the coating liquid, and the binder resin contained in the coating film is cured by heat or light to form the antiglare layer on the second layer.

[0064] Note that the method for preparing the thickening liquid according to the present invention is not limited to the above embodiments. Further, the method for preparing the thickening liquid according to the present invention is not limited by the above-described effects. The method for preparing the thickening liquid according to the present invention can be variously modified without departing from the gist of the present invention.

[0065] For example, the thickening liquid according to the present invention may be used in the production of various optical films that exhibit functions by particles. Examples of the optical film include an antireflection film. Examples of the antireflection film include those having a base material, a hard coat layer laminated on the base material, and an antireflection layer laminated on the hard coat layer. And, as the hard coat layer, those containing inorganic particles such as silicon oxide particles are known, and the thickening liquid according to the present invention may be used in the preparation of a coating liquid for forming such a hard coat layer. Further, examples of the antireflection film include those having a base material and a plurality of refractive index layers laminated on the base material with different refractive indexes. And, those containing inorganic particles such as silicon oxide particles in at least a part of the plurality of refractive index layers are known, and the thickening liquid according to the present invention may be used in the preparation of a coating liquid for forming such a refractive index layer.

[0066] In addition, examples of the optical film include a light diffusion film having a base material and a light diffusion layer laminated on the base material. And, those containing organic particles such as polymethyl methacrylate resin particles and silicone resin particles in the light diffusion layer are known, and the thickening liquid according to the present invention may be used in the preparation of a coating liquid for forming such a light diffusion layer.

[0067] Furthermore, the thickening liquid according to the present invention may be used in the preparation of a coating liquid for forming a film containing conductive particles.

[0068] The present disclosure includes the following. (1) A method for preparing a thickening liquid, wherein the thickening liquid has thixotropy, A method for preparing a thickening solution, comprising: a first filtration step of passing the total amount of the thickening solution before filtration through a filter to obtain a primary filtrate; and a second filtration step of passing the primary filtrate through the used filter used in the first filtration step. (2) The method for preparing a thickening solution according to (1) above, wherein the thixotropy value of the thickening solution before the filtration treatment is 3 to 7. (3) The method for preparing a thickening solution according to (1) or (2) above, wherein in the first filtration step, the flow rate of the thickening solution passing through the filter is 10 to 50 mm / min. (4) The method for preparing a thickening solution according to any one of (1) to (3) above, wherein in the second filtration step, the primary filtrate is stored in a tank, and filtration is performed while circulating the primary filtrate between the tank and the used filter. (5) When the implementation time of the second filtration step is T (minutes), The second filtration step is performed so as to satisfy 2 ≦ T / t ≦ 4, (where t = V / r, V: the volume (L) of the primary filtrate, r: the filtration flow rate (L / min) of the used filter), the method for preparing a thickening solution according to (4) above. (6) The method for preparing a thickening solution according to any one of (1) to (5) above, wherein the thickening solution before the filtration treatment is not stirred during the implementation of the first filtration step. (7) The method for preparing a thickening solution according to any one of (1) to (6) above, wherein the filtration accuracy of the filter is 2 to 8 μm. (8) A method for manufacturing an optical film containing particles, comprising: dispersing particles and a binder resin in the thickening solution according to any one of (1) to (7) above to prepare a coating solution, and forming a coating film using the coating solution.

Example

[0069] Hereinafter, the present invention will be further described by showing examples.

[0070] [Example 1] Smecton as a thickener and toluene as a solvent were measured into a container and stirred using a homomixer to prepare a thickened liquid A before filtration with a viscosity of 54 mPa·s at low shear, a viscosity of 9.0 mPa·s at high shear, and a thixotropy value (TI value) of 6. Next, using a filter cartridge equipped with a depth pleats type filter (manufactured by Nippon Pall Co., Ltd., product number PUY1UY045, filtration area 0.19 m 2 ), the thickened liquid A was filtered under the condition E1 of the filtration process shown in Table 1 to prepare a thickened liquid B after filtration.

[0071] [Example 2] A thickened liquid B was prepared in the same manner as in Example 1 except that a filter with an absolute filtration accuracy of 2 μm was used.

[0072] [Comparative Example 1, Comparative Example 2] A thickened liquid B was prepared in the same manner as in Example 1 except that the conditions of the filtration process were changed to C1 or C2 shown in Table 1.

[0073] [Evaluation of foreign matter capture ability of filtration treatment] The thickened liquid B after each filtration treatment was applied to a transparent acrylic film and photocured, and the cured film was visually observed to evaluate the capture ability according to the following evaluation criteria. The results are as shown in Table 2. (Evaluation criteria) ◎: Less than 1 foreign matter (50 μm or more) per 1 m 2 ×: 1 or more foreign matters (50 μm or more) per 1 m 2

[0074] [Performance evaluation of thickened liquid after filtration treatment] ​​Using each of the prepared thickening liquids B, a coating liquid for forming an antiglare coating film was prepared. In addition to the thickening liquid B, the coating liquid used tec polymer SSX-103DXE (manufactured by Sekisui Chemical Co., Ltd.) as particles, NK oligomer UA-53-80BK (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a binder resin, Biscoat #300 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) as monomers, Omnirad 907 (manufactured by IGM Resin) as a photoinitiator, and GRANDIC PC4100 (manufactured by DIC Corporation) as a surface tension modifier. The ratio of the thickening liquid to the total mass of the coating liquid was 1.5 parts by mass, tec polymer SSX-103DXE was 0.5 parts by mass, NK oligomer UA-53-80BK was 50 parts by mass, Biscoat #300 was 50 parts by mass, 4-hydroxybutyl acrylate was 20 parts by mass, Omnirad 907 was 5 parts by mass, and GRANDIC PC4100 was 1 part by mass. Each coating liquid was applied to a substrate, and the coating liquid was cured to form a coating film on the substrate. Then, regarding the antiglare property of the coating film, the average roughness (average roughness Ra of the roughness curve element) defined in JIS B 0601:2013 was measured, and the performance of the thickening liquid B was evaluated according to the following evaluation criteria. The results are as shown in Table 2. (Evaluation Criteria) ◎: The Ra of the coating film is 0.05 μm or more ○: The Ra of the coating film is 0.03 μm or more ×: The Ra of the coating film is less than 0.03 μm

[0075] [Table 1]

[0076] [Table 2] [Explanation of Symbols]

[0077] 1: Device, 10: First tank, 20: Second tank, 31: First pipe, 32: Second pipe, 40: Filter housing, P1: First pump, P2: Second pump

Claims

1. A method for preparing a thickening solution, wherein the thickening solution has thixotropy, the method for preparing a thickening solution comprises: a first filtration step of passing the total amount of the thickening solution before filtration through a filter to obtain a primary filtrate; and a second filtration step of passing the primary filtrate through the used filter used in the first filtration step.

2. The method for preparing a thickening solution according to claim 1, wherein the thixotropy value of the thickening solution before filtration is 3 to 7.

3. The method for preparing a thickening solution according to claim 1 or 2, wherein in the first filtration step, the flow rate of the thickening solution passing through the filter is 10 to 50 mm / min.

4. The method for preparing a thickening solution according to claim 1 or 2, wherein in the second filtration step, the primary filtrate is stored in a tank, and filtration is performed while circulating the primary filtrate between the tank and the used filter.

5. When the implementation time of the second filtration step is T (minutes), the second filtration step is implemented so as to satisfy 2 ≤ T / t ≤ 4, where t = V / r, V: the volume (L) of the primary filtrate, r: the filtration flow rate (L / min) of the used filter), the method for preparing a thickening solution according to claim 4.

6. The method for preparing a thickening solution according to claim 1 or 2, wherein the thickening solution before filtration is not stirred during the implementation of the first filtration step.

7. The method for preparing a thickening solution according to claim 1 or 2, wherein the absolute filtration accuracy of the filter is 2 to 8 μm.

8. A method for manufacturing an optical film containing particles, wherein a coating liquid is prepared by dispersing particles and a binder resin in the thickening solution obtained by the preparation method according to claim 1 or 2, and a coating film is formed using the coating liquid, the method for manufacturing an optical film.

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