JP2012116894A - Zinc oxide dispersion liquid, coating liquid for primer layer formation and high durability uv cutoff plastic base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid for primer layer formation which has excellent ultraviolet absorptivity, maintains good adhesion to a transparent plastic base material and a hard coat layer, thereby improving outdoor durability, and exhibits excellent storage stability, and to provide a zinc oxide dispersion liquid applied to the preparation of the coating liquid, and the like.SOLUTION: The zinc oxide dispersion liquid contains: coated zinc oxide fine particles having a primary particle diameter of ≤100 nm, prepared by putting a silane compound comprising a silicone resin in a mill base comprising zinc oxide raw powder and a solvent, using a wet-type media agitation mill for grinding the zinc oxide raw powder and coating the surfaces of ground zinc oxide fine particles with the silane compound, without removing the solvent; a solvent; and further a clay mineral. The coating liquid for primer layer formation contains the zinc oxide dispersion liquid and an acrylic resin binder.

Description

  The present invention provides a highly durable UV-cut plastic substrate having a transparent plastic substrate excellent in durability, a primer layer formed on the transparent plastic substrate, and a hard coat layer formed on the primer layer. In particular, a zinc oxide dispersion used in a primer layer forming coating solution for forming a primer layer, a primer layer forming coating solution prepared using this zinc oxide dispersion, and this primer layer forming coating solution The present invention relates to a highly durable UV-cut plastic base material having a primer layer formed by using.

  Transparent plastic base materials such as polycarbonate resin are lightweight and excellent in transparency, impact resistance, and the like, and therefore are used as lighting materials for vehicles and buildings as members that replace glass. However, since it is inferior in practical properties such as scratch resistance and weather resistance as compared with glass, improvement in surface properties is required.

  As means for improving the weather resistance of transparent plastic substrates, polyorganosiloxane-based (silicone-based), melamine-based thermosetting resins, etc., or polyfunctional acrylic-based photocurable resins can be used. A coating method has been proposed, and among them, a hard coat material using a silicone-based thermosetting resin is applied in glazing applications for vehicles that require high wear resistance.

  However, silicone hard coat materials have been a major problem in the past because of their poor adhesion to plastic substrates. For this reason, generally, a method of modifying the surface of a plastic substrate by improving the adhesion by interposing a primer layer such as an acrylic resin coating between the plastic substrate and the silicone-based hard coat layer Has been adopted.

  However, in the article coated with the silicone hard coat layer through the primer layer, the primer layer is decomposed and deteriorated by ultraviolet rays irradiated from sunlight when exposed to the outdoors for a long time, and the entire primer layer shrinks in volume. As a result, microcracks are generated in the hard coat of the upper layer, and peeling at any of the interfaces of the transparent plastic substrate / primer layer / hard coat layer is known to have poor durability. Yes.

  Therefore, as a method for producing a transparent plastic substrate having both weather resistance and scratch resistance, JP-A-56-92059 (Patent Document 1), JP-A-1-149878 (Patent Document 2), and JP-A-Hei 3 No. 6282 (Patent Document 3) and the like propose a method of adding an organic ultraviolet absorber to the primer layer.

  However, when an organic ultraviolet absorber is added to the primer layer, there have been problems such as whitening of the film and deterioration of adhesion due to bleeding out of the organic ultraviolet absorber due to long-term outdoor exposure.

  On the other hand, there is a method in which an organic ultraviolet absorber is contained in the silicone hard coat layer. However, in this case, there is a problem that a large amount of the ultraviolet absorber cannot be added from the viewpoint of scratch resistance.

  For this reason, Japanese Patent Application Laid-Open No. 11-58654 (Patent Document 4) proposes a method in which an organic ultraviolet absorber and a light stabilizer are distributed and contained in both the hard coat layer and the primer layer. However, when a large amount of the organic ultraviolet absorber is contained to such an extent that the deterioration of the primer layer can be completely prevented, there is a problem that the mechanical strength of the hard coat layer and the primer layer is surely lowered.

  Furthermore, organic UV absorbers are excellent in compatibility with organic resins and solvents, but the compounds themselves that make up organic UV absorbers are easily decomposed and deteriorated by wet heat and UV rays. ) In many cases, the function cannot be imparted for a long time, and the weather resistance of the surface-coated plastic substrate itself is limited to about 10 years when exposed outdoors. In addition, some benzotriazole ultraviolet absorbers have restrictions on use due to concerns about safety to the human body.

  Under such circumstances, particularly in the construction and automobile fields where high durability is required, a surface-coated high-performance plastic substrate, particularly a surface using an inorganic ultraviolet absorber that hardly causes the above-described problems. A coated plastic substrate is required, and in Japanese Patent No. 3319326 (Patent Document 5), a primer composition and a transparent coated article in which an inorganic ultraviolet absorber of zinc oxide or titanium oxide is blended are proposed.

  Here, as representative examples of the inorganic ultraviolet absorber having a transparent wavelength region with respect to visible light (approximately in the range of wavelength 380 to 780 nm), the zinc oxide, titanium oxide, cerium oxide and the like are widely known. ing. However, the lifetime of these inorganic ultraviolet absorbers itself against ultraviolet irradiation is semi-permanent, but many exhibit strong photocatalytic activity, which promotes oxidative degradation deterioration of organic resin binders that are contacted by ultraviolet irradiation, such as choking Cause product trouble. For this reason, in order to apply and apply the inorganic ultraviolet absorber to the surface coating material, it is necessary to separately suppress the photocatalytic action on the surface of the inorganic ultraviolet absorber by surface treatment of the inorganic ultraviolet absorber itself. .

  Therefore, in order to suppress the photocatalytic action on the surface of the inorganic ultraviolet absorber, a hydrolyzable silane monomer such as a silane coupling agent or a reaction as disclosed in JP-A-2002-362925 (Patent Document 6). There has been proposed a method of forming a polysiloxane film on the surface of oxide particles such as zinc oxide using methyl hydrogen polysiloxane which is a kind of functional silicone oil.

  For example, titanium oxide particles having a polysiloxane film used in cosmetics or the like are directly mixed with titanium oxide particle powder and reactive silicone oil, or once dispersed in a solvent, It can be obtained by mixing the dispersion and reactive silicone oil, removing the solvent, and then drying by heating. In addition, when applied to a daylighting material application such as a window glass unlike a cosmetic application, the product base material is required to have high transparency without cloudiness. That is, in the matrix in which the particles are dispersed, it is necessary to maintain the dispersibility of the particles at a very high level, and the surface treatment technology of the inorganic ultraviolet absorber suppresses the aggregation of the inorganic ultraviolet absorber particles. At the same time, two aspects of sufficiently suppressing the photocatalytic activity are required. For this reason, generally, a method of finely crushing oxide particles such as zinc oxide formed with the polysiloxane film obtained by the above-described method using a medium stirring mill or the like is employed. It was done.

  However, as a result of studies by the present inventors, the following problems have been clarified.

  When forming a film on the surface of oxide particles, which are inorganic UV absorbers, using hydrolyzable silane monomers, hydrolyzable silane monomers are hydrolyzed and polycondensed by the sol-gel method to obtain oxide particle surfaces. A polysiloxane film is formed. However, in order to make the hydrolysis reaction proceed quickly, an acid catalyst such as hydrochloric acid or nitric acid, or an alkali catalyst such as sodium hydroxide, potassium hydroxide, or ammonia and water are required. The oxide particles are likely to aggregate due to pH fluctuations, and the aggregated oxide particles have a problem that the silane monomer is difficult to uniformly contact the individual oxide particles.

  In addition, condensation between surplus silane monomers easily occurs in the course of the reaction, and the generated oligomer reacts across a plurality of oxide particles, resulting in a coarse and strong condensation cluster interposing a silica component during solvent removal and drying. The problem that is easily formed occurs.

  In addition, since the mechanical strength of the coating formed on the oxide particles is low and the coating damage in the subsequent process such as crushing / dispersing treatment is large, as a result, the surface of the oxide particles such as zinc oxide is partially exposed. As a result, it became clear that it was difficult to obtain a reproducible effect.

  On the other hand, the reactive silicone oil disclosed in Patent Document 6 has a structure in which a linear polysiloxane is a main chain, and a side chain and a part of both ends are substituted with reactive groups. Yes. And since the reactive silicone oil is a high molecular weight substance, for example, it is easy to wet with respect to the oxide particle surface such as zinc oxide, and a highly active group such as Si-H can be introduced in a stable state. There is a merit that the reactivity to is high. However, since the reactive silicone oil is in the form of a series long chain, the influence of the steric factor is great, and the content of reactive groups present in the molecule is low, so that self-condensation is difficult. In addition, since it is difficult to form a three-dimensional bond between polymers, the film-forming property is low, and the surface of oxide particles such as zinc oxide is partially exposed due to film damage during pulverization treatment. There were problems such as low stability and low mechanical strength.

  Under such technical background, the present applicant has already proposed a method for producing surface-treated zinc oxide fine particles in which the photocatalytic action on the surface of the zinc oxide fine particles is suppressed (Patent Document 7).

  That is, this production method uses a silicone resin in place of the above-described reactive silicone oil and hydrolyzable silane monomer, and has a dispersion in which fine zinc oxide particles are dispersed in a solvent and at least one having a polysiloxane bond. A mixed solution containing the surface-treated zinc oxide fine particle precursor in which the above silicon atom is mixed with a silicone resin having a silanol group and / or an alkoxysilyl group to adsorb the silicone resin on the surface of the zinc oxide fine particle, and the above solvent And a first step of producing a dry solid by heat-treating the mixed solution to dryness, and a second step of producing surface-treated zinc oxide fine particles by crushing the dry solid.

  And since the silicone resin used in this method contains much more alkoxysilyl groups and silanol groups in the molecule than the reactive silicone oil, it has high self-condensation and excellent film-forming properties. In addition, there is no need to add an acidic (or basic) catalyst or water to promote the hydrolysis / polycondensation reaction unlike the hydrolyzable silane monomer, so that the pH change of the system is small during surface treatment. It does not impair the dispersibility of the zinc fine particles. For this reason, it becomes possible to apply a uniform and highly reproducible coating treatment to the surface of individual zinc oxide particles. Furthermore, silicone resins can be applied to cured coatings by introducing methyl groups or phenyl groups into the molecule. Since flexibility is imparted, film damage in the second step such as crushing / dispersing can be suppressed. Therefore, by the method described in Patent Document 7, it is possible to obtain a uniform surface-treated zinc oxide fine particle in which the surface of the zinc oxide fine particle can be uniformly coated with little damage and the photocatalytic action is suppressed. .

  By the way, including the manufacturing method of the surface treatment zinc oxide fine particle described in the said patent document 7, the above-mentioned wet surface treatment method using reactive silicone oil, a hydrolyzable silane monomer, etc. is (1) Raw material grinding | pulverization process, Each process such as (2) surface treatment process, (3) solvent removal / drying process, and (4) redispersion process is necessary, and the treatment process is complicated, resulting in problems in manufacturing cost and productivity.

  In particular, it is industrially difficult to apply the above-described conventional surface treatment method to inorganic ultraviolet absorbers in the paint and plastics industry, where the market price has been established with inexpensive organic ultraviolet absorbers. I can say that.

  That is, in a transparent plastic substrate having a primer layer formed on a transparent plastic substrate and a hard coat layer formed on the primer layer, while maintaining practical transparency and substrate adhesion, There is no known primer composition that can completely suppress cracking and peeling of the hard coat layer by outdoor exposure. In particular, in the method of adding an ultraviolet absorber to a primer layer, if a surface treatment technology for an inorganic ultraviolet absorber is established, which is inexpensive and industrial, stable performance as a primer layer forming composition can be ensured. It becomes easy and the durability of the transparent plastic substrate itself can be improved.

JP 56-92059 A JP-A-1-149878 Japanese Patent Laid-Open No. 3-6282 JP-A-11-58654 Japanese Patent No. 3319326 JP 2002-362925 A JP 2009-120721 A

  The present invention has been made paying attention to such problems, and the problem is that it has excellent ultraviolet absorption (shielding) ability and maintains good adhesion to a transparent plastic substrate and a hard coat layer. And providing a primer layer-forming coating solution (composition) that can form a primer layer that dramatically improves durability outdoors and has excellent long-term storage stability. Zinc oxide dispersion that can be used for the preparation of coatings and can also contribute to the storage stability of the coating solution, and also has a high durability UV in which a hard coat layer is formed via a primer layer formed on a transparent plastic substrate The object is to provide a cut plastic substrate by an inexpensive and industrial production method.

  Therefore, in order to achieve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, the silicone resin, which is a silane compound, is introduced into a mill base composed of zinc oxide raw material powder and a solvent, and zinc oxide is used using a wet medium stirring mill. Long-term storage stability that includes the coating of zinc oxide fine particles and solvent, and clay minerals, without pulverizing the raw material powder and coating the surface of the pulverized zinc oxide fine particles with silicone resin. A zinc oxide dispersion having excellent properties is prepared, and a primer layer-forming coating solution (composition) having excellent long-term storage stability can be easily obtained by mixing an acrylic resin binder with the zinc oxide dispersion. I found out. In addition, the primer layer formed by applying the primer layer-forming coating solution (composition) on a transparent plastic substrate and heat-curing has excellent ultraviolet absorption (shielding) ability and transparency. The resulting primer layer maintains good adhesion to the transparent plastic substrate and hard coat layer, making it a highly durable UV-cut plastic substrate with excellent outdoor durability by an inexpensive manufacturing method. I came to find what I could provide.

That is, the invention according to claim 1
In zinc oxide dispersion in which zinc oxide fine particles are dispersed in a solvent and an acrylic resin binder is added when preparing a primer layer forming coating solution,
A silane compound is charged into a mill base composed of zinc oxide raw material powder and a solvent, and the zinc oxide raw material powder is pulverized and the surface of the pulverized zinc oxide fine particles is coated with the silane compound using a wet medium stirring mill. Coating-treated zinc oxide fine particles having a primary particle diameter of 100 nm or less prepared without removal and a solvent are included, and the silane compound is mainly composed of polysiloxane composed of repeating siloxane bonds (Si—O—Si). One or more molecular ends are blocked with an alkoxysilyl group (Si-OR) and / or silanol group (Si-OH), and the hydrocarbon group having 1 to 18 carbon atoms and / or the phenyl group is organically substituted. It is composed of a silicone resin contained in the molecule as a group, and further contains a clay mineral.

The invention according to claim 2
In the zinc oxide dispersion according to the invention of claim 1,
Bentonite selected from quartz, cristopalite, feldspar, mica, zeolite, and / or smectite selected from montmorillonite, beidellite, nontronite, saponite, hectorite, soconite, stevensite. Including,
The invention according to claim 3
In the zinc oxide dispersion according to the invention of claim 2,
The clay mineral is characterized by being intercalated with an organic cation,
The invention according to claim 4
In the zinc oxide dispersion according to any one of claims 1 to 3,
The clay mineral contains 1 part by weight or more and 120 parts by weight or less with respect to 100 parts by weight of the zinc oxide fine particles,
The invention according to claim 5
In the zinc oxide dispersion according to any one of claims 1 to 4,
The silicone resin contains 5 to 300 parts by weight with respect to 100 parts by weight of zinc oxide fine particles.

Furthermore, the invention according to claim 6 provides
Primer for forming the above-mentioned primer layer of a highly durable UV-cut plastic substrate having a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat layer formed on the primer layer In the coating liquid for layer formation,
It contains the zinc oxide dispersion liquid in any one of Claims 1-5, and an acrylic resin binder, It is characterized by the above-mentioned.

Next, the invention according to claim 7 provides:
In a highly durable UV-cut plastic substrate having a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat layer formed on the primer layer,
The primer layer-forming coating solution according to claim 6 is applied onto a transparent plastic substrate, and the primer layer is formed by heating the coating film. The transparent plastic substrate, the primer layer, and the hard coat layer The UV-cut plastic substrate having a visible light transmittance of 85% or more and a haze value of 1.0% or less, and before and after being irradiated with 100 mW / cm ² ultraviolet rays for 500 hours, The change in visible light transmittance is 2.0% or less, the change in haze is 1.0% or less,
The invention according to claim 8 provides:
In the highly durable UV cut plastic substrate according to the invention of claim 7,
The hard coat layer is formed of a silicone resin,
The invention according to claim 9 is:
In the highly durable UV-cut plastic substrate according to the invention of claim 7 or 8,
The primer layer has a thickness of 1 μm or more and 5 μm or less,
The invention according to claim 10 is:
In the highly durable UV cut plastic substrate according to any one of claims 7 to 9,
The amount of zinc oxide fine particles in the primer layer is 1 part by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the acrylic resin binder,
The invention according to claim 11 is:
In the highly durable UV cut plastic substrate according to any one of claims 7 to 10,
The transparent plastic base material is polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, polyester resin, polyacetal resin, polysulfone resin, polyether sulfone resin, polyvinyl chloride resin, polyvinylidene chloride resin, epoxy resin, unsaturated polyester resin. , Polyurethane resin, diallyl phthalate resin, diethylene glycol bisallyl carbonate resin, acetyl cellulose resin, sulfur-containing urethane resin or cross-linked (meth) acrylic resin.

  The zinc oxide dispersion according to the present invention is obtained by adding a silane compound to a mill base composed of a zinc oxide raw material powder and a solvent, and pulverizing the zinc oxide raw material powder using a wet medium stirring mill and pulverizing the silane compound on the surface of the zinc oxide fine particles It contains a coating-processed zinc oxide fine particle and a solvent prepared without removing the solvent and a clay mineral that contributes to the dispersion stability of the coating-processed zinc oxide fine particle.

  According to the present invention, unlike the conventional wet surface treatment method for the surface of the zinc oxide fine particles, the above coating is not required without the above-mentioned (3) solvent removal / drying step and (4) redispersion step. A zinc oxide dispersion containing a clay mineral that contains treated zinc oxide fine particles and contributes to the dispersion stability of the fine particles can be easily obtained, and by adding an acrylic resin binder to the zinc oxide dispersion for a long period of time. A primer layer-forming coating solution (composition) with excellent storage stability can be easily obtained, so inorganic UV absorbers can be used in the paint and plastics industries, where market prices have been established with inexpensive organic UV absorbers. It can be used as an applied inexpensive primer layer forming coating solution.

  Furthermore, the primer layer formed using the above primer layer forming coating solution has excellent ultraviolet absorption (shielding) ability and transparency, and good adhesion to a transparent plastic substrate or hard coat layer. Therefore, it is also possible to provide a highly durable UV-cut plastic base material excellent in outdoor durability at low cost.

  Next, embodiments according to the present invention will be specifically described.

  First, the zinc oxide dispersion according to the present invention is prepared by adding a silane compound to a mill base composed of a zinc oxide raw material powder and a solvent, and pulverizing the zinc oxide raw material powder and pulverizing the surface of the zinc oxide fine particles using a wet medium stirring mill. And a coating-treated zinc oxide fine particle having a primary particle diameter of 100 nm or less and a solvent, which were prepared without removing the solvent, and the silane compound had a siloxane bond (Si- The main chain is polysiloxane composed of repeating O-Si), and one or more molecular ends are blocked with alkoxysilyl groups (Si-OR) and / or silanol groups (Si-OH), and the number of carbon atoms is 1-18. It is composed of a silicone resin having in its molecule hydrocarbon groups and / or phenyl groups as organic substituents, and further contains clay minerals. And wherein, also, the primer layer forming coating liquid according to the present invention is characterized by containing the above zinc oxide dispersion and an acrylic resin binder.

  Hereinafter, (1) zinc oxide fine particles and production method thereof, (2) zinc oxide dispersion and production method thereof, (3) primer layer forming coating solution, and (4) primer layer forming primer layer forming coating solution. Each will be specifically described in the order of forming method, (5) hard coat layer, (6) transparent plastic substrate, and highly durable UV-cut plastic substrate.

(1) Zinc oxide fine particles and production method thereof Ultraviolet light is classified according to wavelength region into UVC light of 280 nm or less, UVB light of 280 to 320 nm, and UVA light of 320 to 400 nm. In the highly durable UV-cut plastic substrate according to the present invention, the UVA light occupies 90% of the ultraviolet light reaching the ground.

  And as an inorganic material which has a transparent wavelength range with respect to visible light (380-780 nm) and absorbs ultraviolet light, the above-mentioned titanium oxide, cerium oxide, etc. other than the said zinc oxide are known. Among them, zinc oxide has the feature that it can selectively absorb UVA light without greatly reducing the visible light transmittance because the absorption edge is on the longer wavelength side compared to titanium oxide, cerium oxide, and the like. is doing.

  Zinc oxide is particularly suitable when used as a raw material for a transparent substrate because zinc oxide is excellent in visible light transparency with respect to ultraviolet light absorption properties, although the hiding power as a white pigment does not reach that of titanium oxide. The primary particle diameter of the zinc oxide fine particles needs to be 100 nm or less in order to avoid the light shielding phenomenon due to scattering, and is more preferably 50 nm or less. In this case, the particle diameter is remarkably small with respect to the wavelength of visible light (380 to 780 nm), and Mie or Rayleigh scattering formula is applied to light scattering. In general, the smaller the refractive index of the material, It is known that the smaller the particle size, the smaller the scattering intensity. In this respect, since zinc oxide has a refractive index lower than that of titanium oxide or the like, the intensity of scattered light when compared with the same particle diameter is smaller than that of titanium oxide or the like. That is, zinc oxide has a smaller tendency to scatter incident light than other inorganic transparent ultraviolet absorbers, and as a result, higher transparency can be obtained when dispersed in a resin binder or plastic.

  Next, a method for producing zinc oxide fine particles will be described with an example.

  First, zinc oxide crystals are hexagonal (wurtzite type), and zinc atoms and oxygen atoms are tetrahedrally coordinated with each other by four atoms, and this is a framework for developing various physical properties. And, the industrial production method of zinc oxide is roughly divided into a dry method in which molten zinc is steam-oxidized and a wet method in which basic zinc carbonate is made by adding a soda ash solution to a zinc sulfate aqueous solution. In the present invention, wet powder from which crystals with a finer particle diameter are obtained is used as a raw material. Specifically, a precipitate is generated from an aqueous zinc solution and an alkaline aqueous solution, and this is aged and washed. The precipitate is moistened with alcohol to start drying, and a zinc oxide fine particle precursor is obtained. The zinc fine particle precursor is fired to form zinc oxide fine particles.

  Here, the zinc compound for preparing the zinc aqueous solution is not particularly limited, and examples thereof include zinc nitrate, zinc chloride, zinc acetate, and zinc sulfate. Nitrate is preferable because of easy removal of impurities.

  On the other hand, the alkaline aqueous solution is not particularly limited, and examples thereof include aqueous solutions of sodium hydroxide, potassium hydroxide, ammonium hydrogen carbonate, ammonia, and the like. The alkali concentration of sodium hydroxide or the like in the alkaline aqueous solution is preferably 1.0 to 1.5 times the chemical equivalent necessary for the zinc compound to become a hydroxide. This is because if the alkali is equal to or more than the chemical equivalent, the charged zinc compound can react, and if it is 1.5 times or less, the cleaning time for removing the residual alkali does not increase.

  Next, the formation and aging of the precipitate will be described.

  The precipitate is formed by dropping an aqueous solution of a zinc compound into an alkaline aqueous solution that is continuously stirred. By dropping the aqueous solution of the zinc compound into the alkaline aqueous solution, the supersaturation degree is instantaneously reached and a precipitate is generated, so that a precipitate of fine particles of zinc carbonate and zinc hydroxide carbonate having a uniform particle diameter is obtained. Precipitates of fine particles of zinc carbonate and zinc hydroxide carbonate with the same particle size as described above, whether an alkaline solution is dropped into an aqueous solution of zinc compound or a zinc compound solution and an alkaline solution are dropped in parallel It is difficult to get.

  Although the alkaline aqueous solution temperature at the time of the production | generation of a precipitate is not specifically limited, It is 50 degrees C or less, Preferably it is room temperature. The lower limit of the temperature of the alkaline aqueous solution is not determined, but if it is too low, a cooling device or the like is newly required. Therefore, it is preferable that the temperature is not required. The dropping time of the aqueous zinc compound solution in the alkaline aqueous solution is less than 30 minutes, preferably 20 minutes or less, more preferably 10 minutes or less from the viewpoint of productivity. After completion of the dropwise addition, aging is carried out with continuous stirring in order to make the system uniform. The aging temperature is the same as that during precipitation. The time for continuous stirring is not particularly limited, but is 30 minutes or less, preferably 15 minutes or less from the viewpoint of productivity.

  The precipitate obtained after the aging is washed by decantation, but is sufficiently washed until the conductivity of the washing liquid becomes 1 mS / cm or less. This is because a desired ultraviolet absorption (shielding) characteristic can be obtained if there are few impurities such as chlorine ions, nitrate ions, sulfate ions and acetate ions remaining in the fine particles. Therefore, it is preferable to sufficiently wash until the conductivity of the supernatant after washing becomes 1 mS / cm or less (corresponding to a residual impurity amount of 1.5% or less).

  Next, the washed precipitate is wet-treated with an alcohol solution to obtain a wet-processed product, and then the wet-processed product is dried to obtain a zinc oxide fine particle precursor. By performing the wet treatment, aggregation of the zinc oxide fine particle precursor after drying can be avoided.

  The alcohol concentration of the alcohol solution is preferably 50% by mass or more. This is because if the alcohol concentration is 50% by mass or more, the zinc oxide fine particles can be prevented from becoming strong aggregates and exhibit excellent dispersibility.

  The alcohol solution used in the wet treatment will be described. Although the alcohol used for the said alcohol solution is not specifically limited, Alcohol which melt | dissolves in water and whose boiling point is 100 degrees C or less is preferable. Examples include methanol, ethanol, propanol, and tert-butyl alcohol.

  The wetting process will be described. The wet treatment may be performed by adding the filtered and washed precipitate into the alcohol solution and stirring, and the time and stirring speed at this time may be appropriately selected according to the treatment amount. The amount of the alcohol solution when the precipitate is put into the alcohol solution may be a liquid amount that can easily stir the precipitate and ensure fluidity. The agitation time and agitation speed are appropriately selected on the condition that the precipitate containing the part that has been partially aggregated during the filtration and washing described above is uniformly mixed in the alcohol solution until the aggregated part is eliminated.

  In the wet treatment, the temperature is usually room temperature, but if necessary, it can be carried out while heating to such an extent that the alcohol is not lost by evaporation. Preferably, by heating at a temperature equal to or lower than the boiling point of the alcohol, disappearance of the alcohol during the wet treatment can be avoided, and the loss of the effect of the wet treatment can be avoided. By maintaining the presence of alcohol during the wet treatment, the effect of the wet treatment is obtained, and the precipitate does not become a strong aggregate after drying, which is preferable.

  The drying of the wet processed product will be described. Drying conditions such as drying temperature and time are not particularly limited, and it is only necessary to start heat drying in a state where the wet processed product is wet with alcohol. After the wet treatment, the precipitate does not become a strong agglomerate even if heat drying is performed. Therefore, the drying conditions may be appropriately selected depending on the treatment amount of the wet treated product, the treatment apparatus, and the like.

By the drying treatment, a zinc oxide fine particle precursor subjected to a wet treatment can be obtained. Examples of the precursor include ZnCO ₃ , Zn ₅ (CO ₃ ) ₂ (OH) ₆ , Zn ₄ CO ₃ (OH) ₆ H ₂ O, and a mixed phase thereof. The precursor may be fired to form zinc oxide fine particles.

  The dried zinc oxide precursor is baked to improve ultraviolet absorption (shielding) characteristics and hiding power. The calcination is performed in the atmosphere, in an inert gas such as nitrogen, argon, or helium, or in a mixed gas of the inert gas and a reducing gas such as hydrogen. The treatment temperature at this time is preferably lower than 350 ° C. and preferably 500 ° C. or lower from the viewpoint of desired ultraviolet absorption (shielding) characteristics. What is necessary is just to select the processing time at this time suitably according to the processing amount and baking temperature of a zinc oxide precursor.

(2) Zinc oxide dispersion and method for producing the same The zinc oxide dispersion according to the present invention is obtained by adding the silane compound to the mill base composed of the zinc oxide raw material powder and the solvent and using the wet medium stirring mill as described above. Zinc raw material powder is crushed and coated with a silane compound on the surface of the pulverized zinc oxide fine particles, and the coated zinc oxide fine particles and the solvent are prepared without removing the solvent. It includes a clay mineral that contributes to the dispersion stability of the fine particles.

  First, since the zinc oxide fine particles exhibit a stronger photocatalytic activity as the particle size becomes smaller, the deterioration of the coating binder and the resin base material, which serve as a dispersion medium, is promoted, causing product troubles such as chalking (chalking). Cause. In order to apply the zinc oxide fine particles to a coating material such as a primer layer for practical use, it is necessary to suppress the catalytic action of the zinc oxide fine particles by a surface treatment or the like.

  That is, the surface treatment technology for zinc oxide fine particles requires two aspects of suppressing the aggregation of the zinc oxide fine particles and at the same time sufficiently suppressing the photocatalytic activity as described above. The performance will be greatly affected.

  In the present invention, a non-desorbing integral blend method is employed as a method for coating (surface) treatment of zinc oxide fine particles. That is, the zinc oxide raw material powder is introduced into a mill base composed of a zinc oxide raw material powder and a solvent, and a wet medium stirring mill (eg, wet ball mill, wet bead mill, wet paint shaker, etc. is exemplified). And the surface of the pulverized zinc oxide fine particles are coated with a silane compound (surface), and the zinc oxide fine particles and the solvent are coated with a silane compound (silicone resin) without removing the solvent. Furthermore, the zinc oxide dispersion according to the present invention containing the clay mineral blended after the coating treatment of the zinc oxide fine particles is obtained.

  By the way, when preparing the primer layer-forming coating liquid described later, some acrylic resin binders blended with the zinc oxide dispersion have very poor compatibility with moisture, and the zinc oxide dispersion of the present invention It is preferable to keep the amount of water contained in the liquid below a certain level. For this purpose, when the above-mentioned wet medium stirring mill is used to pulverize the zinc oxide raw material powder and coat the surface of the pulverized zinc oxide fine particles with a silane compound (silicone resin), it prevents moisture from entering due to moisture and condensation. It becomes important. That is, the water content in the primer layer-forming coating solution (composition) obtained by blending the acrylic resin binder with the zinc oxide dispersion of the present invention is controlled to be 1.5% by weight or less. Is preferred.

  And in order to make the moisture content in the coating liquid for forming the primer layer 1.5% by weight or less, pulverization treatment of the zinc oxide raw material powder using the wet medium stirring mill and the silane compound on the surface of the pulverized zinc oxide fine particles The silicate coating treatment with (silicone resin) may be performed under a relative humidity of 50% RH or less and / or a dry gas or inert gas blowing condition, or may be performed by a closed wet medium stirring mill. That is, if a closed type wet medium stirring mill is used, it is possible to completely prevent moisture and condensation. As an example of a closed type wet medium stirring mill, there is a dyno mill KDL type 0.3 liter grinding container (batch type closed type) manufactured by Willy et Bacofen. Further, the same effect can be obtained even when the airtight container containing the grinding medium is reciprocated and moved left and right like a known paint shaker to stir the grinding medium in the airtight container. What is necessary is just to enclose dry gas etc. in the container which grind | pulverizes and coat | covers.

  As described above, the coating (surface) treatment method of the present invention removes the solvent, which is an essential step in the conventional wet surface treatment method, and then removes and dries (fires) [(3) Solvent removal and drying described above. Step] and dispersion (disintegration) treatment of the coated (surface) treated powder [(4) redispersion step described above] without pulverization of the zinc oxide raw material powder and crushed zinc oxide fine particle surface silane compound It becomes possible to obtain a dispersion of zinc oxide which has been subjected to coating (surface) treatment by the above and before the clay mineral is blended in only one step. In addition, the solvent which concerns on the said mill base is not specifically limited, For example, various kinds of common solvents and organic solvents, such as alcohol, ether, ester, a ketone, an aromatic compound, can be used.

[A] Silicone Resin Next, the silane compound applied to the coating (surface) treatment of zinc oxide fine particles in the zinc oxide dispersion of the present invention is a silicone resin (silane oligomer) made of a silicone polymer having a polysiloxane bond. A silanol having a polysiloxane composed of repeating siloxane bonds (Si-O-Si) as the main chain and one or more molecular ends hydrolyzed by alkoxysilyl groups (Si-OR) and / or alkoxysilyl groups It is necessary to be a high molecular weight molecule blocked with a group (Si—OH) and having a hydrocarbon group having 1 to 18 carbon atoms and / or a phenyl group as an organic substituent in the molecule, and the molecular structure shown below [ 1] A silicone resin having [2] is exemplified.

［但し、Ｒは、炭素原子数１〜１８のアルキル基またはフェニル基である。各末端基におけるＲは、分子中内において全て同じ基であっても、異なった基であってもよい。］

[However, R is a C1-C18 alkyl group or a phenyl group. R in each terminal group may be the same group or different groups in the molecule. ]

  Silicone resins, unlike linear silicone reactive silicone oils based on dimethylpolysiloxane, have alkoxysilyl groups and silanol groups in their molecules and are self-condensing, so they have film-forming properties. high. In addition, since it has a three-dimensionally crosslinked siloxane skeleton, rapid self-condensation is unlikely to occur, and it is acidic (or basic) to promote hydrolysis and polycondensation reactions like hydrolyzable silane monomers. Since there is no need to add a catalyst or water, the pH variation of the system is small during the surface treatment, and the dispersibility of the zinc oxide fine particles is not impaired, so the surface of each zinc oxide fine particle is uniformly and highly reproducible. (Surface) treatment is possible, and an excellent coating (surface) treatment effect can be obtained in inactivating the photocatalytic activity of the zinc oxide fine particles. In addition, by changing the molecular weight and the introduction rate of methyl and phenyl groups, which are organic substituents in the molecule, it is possible to increase compatibility with various solvents and resin media, and to adjust the polarity. It is also possible to function as an excellent polymer dispersant for zinc fine particles.

  The total weight of the silicone resin used for the coating (surface) treatment of the zinc oxide fine particles is desirably 5 parts by weight or more and 300 parts by weight or less, more desirably 100 parts by weight with respect to 100 parts by weight of the zinc oxide fine particles. Hereinafter, it is more desirably 75 parts by weight or less. That is, when the silicone resin is less than 5 parts by weight, the coating amount of the silicone resin on the surface of the zinc oxide fine particles may not be sufficient, and it becomes difficult to sufficiently suppress the photocatalytic activity of the zinc oxide fine particles. This is because when contained in the layer, the organic resin binder or resin base material may be oxidatively deteriorated to cause problems such as choking. In addition, the dispersion stability of the zinc oxide fine particles tends to be low, and sufficient transparency may not be imparted to the resulting primer layer. On the other hand, when the silicone resin exceeds 300 parts by weight, the silicone resin reacts across a plurality of zinc oxide fine particles in the process of coating (surface) treatment, or condensation or aggregation of excess silicone resin tends to occur. As a result, the zinc oxide fine particles cannot be highly dispersed, and it may be difficult to impart sufficient transparency to the resulting primer layer.

  Furthermore, the molecular weight of the silicone resin is preferably 100 to 100,000, more preferably 500 to 10,000. If the molecular weight is 100 or more, sufficient film-forming properties can be obtained, and if it is 100,000 or less, the viscosity does not become too high, and the efficiency and dispersibility of the zinc oxide raw material powder during the coating (surface) treatment process are improved. A decrease can be avoided.

[B] Clay mineral The above-mentioned clay mineral added after the zinc oxide fine particle coating treatment in the zinc oxide dispersion of the present invention contributes to the dispersion stability of the silicate-coated zinc oxide fine particles in the zinc oxide dispersion. And also has a function of improving the pot life of the primer layer forming coating solution (composition) prepared using the zinc oxide dispersion.

  The clay mineral is selected from bentonite selected from quartz, cristopalite, feldspar, mica, zeolite, and / or montmorillonite, beidellite, nontronite, saponite, hectorite, soconite, stevensite. It is desirable to include smectite. Among them, clay minerals in which a plate-like crystal has a laminated structure (layered structure) with interlayer ions such as sodium ions and potassium ions are suitable, such as mica and montmorillonite.

Further, as the clay mineral, it is desirable to replace the interlayer ions with an organic cation such as a quaternary ammonium cation so as to easily dissolve in a water-insoluble solvent and improve the compatibility with the resin. Here, the quaternary ammonium cation, which is an organic cation, preferably includes four carbon chains having 1 to 50 carbon atoms and 3 to 101 hydrogen atoms centering on N ⁺ . Further, this carbon chain may have a linear structure, a branched structure, or a cyclic structure. The clay mineral obtained by intercalating the interlayer ions with an organic cation such as a quaternary ammonium cation is subjected to vibration treatment in one or more solvents selected from ketones, esters, hydrocarbons, ethers and alcohols. It is most preferable to use a primer layer-forming coating solution that is dispersed by stirring treatment and ultrasonic treatment so as not to adversely affect the haze of the resulting primer layer.

  The present inventors consider the action of the clay mineral added to the primer layer forming coating solution as follows. A clay mineral in which an organic cation such as a quaternary ammonium cation is intercalated between layers easily swells with an organic solvent due to the presence of the organic cation between the layers. And it is thought that it contributes to the dispersion stability of the silicate coating | coated process zinc oxide fine particle in a zinc oxide dispersion liquid as a result of suppressing aggregation of the filler which is a zinc oxide fine particle by the steric hindrance of the swollen clay mineral. Furthermore, it is thought that the surface-active effect by the said organic cation intercalated between layers also contributes.

  And it is preferable that the total weight of the said clay mineral shall be 1 to 120 weight part with respect to 100 weight part of zinc oxide fine particles. When the amount is less than 1 part by weight, the amount of clay mineral relative to the coated zinc oxide particles is insufficient, and it becomes difficult to improve the dispersion stability of the coated zinc oxide fine particles. It may be difficult to improve the storage stability of the primer layer-forming coating solution (composition) prepared by using the primer layer. On the other hand, if it exceeds 120 parts by weight, the viscosity of the primer layer forming coating solution may increase due to the swollen clay mineral, and the coating property may be greatly deteriorated.

(3) Primer layer forming coating solution (composition)
The primer layer-forming coating solution (composition) according to the present invention comprises a silicate-coated zinc oxide fine particle having a primary particle size of 100 nm or less, a solvent and a clay mineral, and the zinc oxide dispersion described above. Contains an acrylic resin binder blended in

[A] (Meth) acrylic resin binder The primer layer-forming coating solution according to the present invention is one in which the silicate-coated zinc oxide fine particles are highly dispersed in a liquid medium. In addition, the primer layer forming coating liquid contains an organic binder resin in the liquid medium as a film-forming component in order to finally form a primer layer that is a solid medium on a plastic substrate. And as organic binder resin for paints, styrene resin, acrylic resin, cellulose derivative, urethane resin, melamine resin, epoxy resin, phenol resin, etc. are widely used and are selected according to the purpose as appropriate. Examples of the organic binder resin contained in the primer layer forming coating liquid according to the invention include dispersibility of the silicate-coated zinc oxide fine particles, adhesion to the plastic substrate and the upper hard coat material, transparency of the material itself and processing. In consideration of properties and the like, a (meth) acrylic resin obtained by polymerizing an alkyl acrylate monomer or an alkyl methacrylate monomer is applied.

  Further, the blending amount of the zinc oxide fine particles can be arbitrarily set according to the thickness of the primer layer, required optical characteristics, and mechanical characteristics, but (meth) acrylic resin binder (acrylic resin binder) 100 It is preferable to be in the range of 1 to 40 parts by weight with respect to parts by weight. If the blending amount of the zinc oxide fine particles is within the above range, within the thickness (1-5 μm) range of the predetermined primer layer, the high durability of the target transparent plastic substrate can be achieved, and Since the aggregation of the zinc oxide fine particles in the resin matrix can be avoided, it is possible to maintain good transparency.

[B] Other components The primer layer-forming coating solution (composition) according to the present invention may contain known additives, diluents, and curing catalysts in addition to the above components.

[B-1] Organic UV Absorbing Material The primer layer forming coating liquid according to the present invention uses zinc oxide fine particles as the UV absorber, and the lifetime as the UV absorber is semi-permanent. It can be used throughout. However, for the purpose of further enhancing the ultraviolet absorption (shielding) ability, an organic ultraviolet absorbing material selected from the following group can be appropriately blended in the primer layer forming coating solution. The organic UV-absorbing material is not particularly limited, but it is at least one selected from benzophenone derivatives, benzotriazole derivatives, triazine derivatives and cyanoacrylate derivatives from the viewpoint of availability and cost. Is desirable.

  As the organic ultraviolet absorbing material, specifically, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2- (2-hydroxy- 5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-octylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 4- (2 -Acryloxyethoxy) -2-hydroxybenzophenone polymer, 2- (2-hydroxy-4-hexyloxyphenyl) -4,6-diphenyltriazine and the like can be exemplified. It is not limited.

[B-2] Hindered amine light stabilizer (HALS)
The primer layer forming coating solution according to the present invention suppresses ultraviolet deterioration of organic components such as an organic binder resin in the primer layer over a long period of time by using zinc oxide fine particles as an ultraviolet absorber. For the purpose of further extending the lifetime of the organic component, a hindered amine light stabilizer (HALS) can be blended in the primer layer forming coating solution.

  Examples of the hindered amine light stabilizer (HALS) include 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy. -1,2,2,6,6-pentamethylpiperidine, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine Bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis (2,2,6,6- Tetramethyl-1-octoxypiperidinyl) sebacate, 4- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl Xy} -1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] -2,2,6,6-tetramethylpiperidine, bis (1,2 , 2,6,6-pentamethyl-4-piperidinyl) 2-butyl-2- (3,5-di-t-butyl-4-hydroxybenzyl) malonate, 8-acetyl-3-dodecyl-7,7,9 , 9-Tetramethyl-1,3,8-triazaspiro [4.5] decane-2,4-dione, tetrakis (2,2,6,6-tetramethyl-4-piperidinyl) 1,2,3,4 -Butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) 1,2,3,4-butanetetracarboxylate, tridecyltris (2,2,6,6-tetra Methyl -Piperidinyl) 1,2,3,4-butanetetracarboxylate, tridecyltris (1,2,2,6,6-pentamethyl-4-piperidinyl) -1,2,3,4-butanetetracarboxylate, Ditridecyl bis (2,2,6,6-tetramethyl-4-piperidinyl) 1,2,3,4-butanetetracarboxylate, ditridecyl bis (1,2,2,6,6-pentamethyl-4- Piperidinyl) 1,2,3,4-butanetetracarboxylate, 3,9-bis [1,1-dimethyl-2- {tris (2,2,6,6-tetramethyl-4-piperidinyloxycarbonyl) ) Butylcarbonyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-bis [1,1-dimethyl-2- {tris (1, 2,2,6,6-pentamethyl-4-piperidyloxycarbonyl) butylcarbonyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 2,2,4,4-tetra Methyl-20- (β-lauryloxycarbonyl) -ethyl-7-oxa-3,20-diazadispiro [5.1.1.12] heneicosan-21-one, 2,4,6-tris {N-cyclohexyl- N- (2-oxo-3,3,5,5-tetramethylpiperazino) ethyl} -1,3,5-triazine and the like. Preferably, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis (2,2,6, 6-tetramethyl-1-octyloxy-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) 2-butyl- (3,5-di-t-butyl-4 -Hydroxybenzyl) malonate, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro [4.5] decane-2,4-dione, 2,2,4 , 4-Tetramethyl-20- (β-lauryloxycarbonyl) -ethyl-7-oxa-3,20-diazadispiro [5.1.1.1.2] heneicosan-21-one, tetrakis (1,2,2 6,6-pentamethyl-4-piperidinyl) 1,2,3,4-butanetetracarboxylate, tridecyl tris (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3 4-butanetetracarboxylate, 4- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} -1- [2- {3- (3,5-di-t-butyl) -4-hydroxyphenyl) propionyloxy} ethyl] -2,2,6,6-tetramethylpiperidine, more preferably bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, Bis (2,2,6,6-tetramethyl-1-octyloxy-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) 2-buty Ru- (3,5-di-t-butyl-4-hydroxybenzyl) malonate, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro [4.5 Decane-2,4-dione, 2,2,4,4-tetramethyl-20- (β-lauryloxycarbonyl) -ethyl-7-oxa-3,20-diazadispiro [5.1.1.12] Heneicosan-21-one, tridecyl-tris (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, 4- {3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionyloxy} -1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} ethyl] -2,2,6 , 6-Tetramethyl Piperidine, and the like. Moreover, these can use 1 type (s) or 2 or more types.

  More preferably, a hindered amine light stabilizer (HALS) selected from 2,2,6,6-tetramethylpiperidine derivatives or 1,2,2,6,6-pentamethyl-4-piperidine derivatives. There should be. In particular, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, or bis (1,2,2,6, 6-pentamethyl-4-piperidyl) sebacate is preferred in that it is excellent in solubility in (meth) acrylic resin binders and in the effect of suppressing deterioration due to radical oxidation.

[B-3] Diluent The primer layer-forming coating solution according to the present invention is applied to the above-described silicate-coated zinc oxide fine particles, acrylic resin binder, organic ultraviolet absorbing material, and hindered amine light stabilizer (HALS). In addition, a diluent can be blended. For example, an organic solvent can be used as the diluent, and examples of the organic solvent include alcohols, ketones, esters, ethers, and the like. Specifically, methanol, ethanol, isopropanol, isobutanol and the like Alcohols, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and isobutyl acetate, aromatic compounds such as toluene and xylene, and mixed solvents thereof.

(4) Method for forming primer layer using primer layer forming coating solution The primer layer forming coating solution (composition) according to the present invention is a coating layer (hard coat layer) made of a silicone-based coating agent on a transparent plastic substrate. It is used for the primer treatment when forming.

  When the primer layer is formed on the transparent plastic substrate using the primer layer forming coating solution according to the present invention, the primer layer forming coating solution is spray coated, roll coated, dip coated on the transparent plastic substrate. It may be applied by an appropriate method such as spin coating.

  When applying the primer layer-forming coating solution (composition) according to the present invention, in order to suppress white turbidity due to moisture at the time of application, the environmental atmosphere to be applied is 25 ° C./50% RH or less in the primer layer. It is preferable to apply so that no moisture is contained.

  Thereafter, the coating film can be leveled at room temperature for 10 minutes and heated at 110 to 130 ° C. for 10 minutes to 1 hour to cure the binder resin. The lower limit temperature, heating time, and heating atmosphere (including vacuum) are not particularly limited as long as the solvent evaporates and the coating layer (coating film) is cured. In this case, the thickness of the primer layer is 1 to 5 μm. When the film thickness is less than 1 μm, the blending amount of the zinc oxide fine particles with respect to the resin binder becomes excessive in order to obtain a predetermined UV-resistant light, and as a result, sufficient adhesion strength may not be obtained. On the other hand, if the film thickness exceeds 5 μm, cracking or peeling of the upper hard coat layer may easily occur due to curing shrinkage of the primer layer.

(5) Hard coat layer A highly durable UV-cut plastic substrate according to the present invention comprises a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat formed on the primer layer. It is preferable that the hard coat layer is made of a silicone resin. The silicone resin is a silicon compound having a polysiloxane bond, and examples thereof include a hard coat layer containing an inorganic silane compound and / or a polyorganosiloxane compound as a main component.

This inorganic silane compound, polyorganosiloxane compound, or a mixed system thereof can be produced by various methods as described below. For example, the following general formula [3]
R ¹ _n Si (OR ² ) _4-n [3]
[However, R ¹ in the above general formula is a non-hydrolyzable group, and is an alkyl group, a substituted alkyl group (substituent: halogen atom, epoxy group, (meth) acryloyloxy group etc.), alkenyl group, aryl group. Or an aralkyl group, R < ² > is a lower alkyl group, n is an integer of 0 or 1-3. When there are a plurality of R ¹ and OR ² , the plurality of R ¹ may be the same or different, and the plurality of OR ² may be the same or different.] Hydrolysis using a catalyst such as nitric acid or acetic acid, and polycondensation is used. In this case, an inorganic silane-based binder can be obtained by hydrolyzing a compound of n = 0, that is, tetraalkoxysilane, and a polyorganosiloxane-based binder or a mixture of an inorganic silane-based and polyorganosiloxane-based can be partially hydrolyzed. A system binder is obtained. On the other hand, since a compound with n = 1 to 3 has a non-hydrolyzable group, a polyorganosiloxane-based binder can be obtained by partial or complete hydrolysis. In the above case, an appropriate organic solvent may be used for the purpose of controlling the hydrolysis reaction.

  Examples of the alkoxysilane compound represented by the general formula [3] include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, Tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, Butyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, γ-methacryloyl Trimethoxysilane, dimethyl dimethoxysilane, methylphenyl dimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, divinyl dimethoxysilane, divinyl diethoxy silane, trivinyl silane, trivinyl silane, and the like. These may be used alone or in combination of two or more.

  In the hard coat layer, since hard coat performance is regarded as important, a layer containing as much inorganic silane compound as possible is preferable as long as necessary adhesion is maintained. In addition, the hard coat layer may contain an organic ultraviolet absorber, a hindered amine light stabilizer, and the like similar to those of the primer layer as desired, as long as the scratch resistance is not impaired.

  This hard coat layer is obtained by applying a hard coat agent-containing coating solution to the primer layer using a known method such as a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method, or a gravure coat method. It can be formed by coating on, leveling at room temperature for 10 minutes, and heating and curing at 110 to 130 ° C. for 30 minutes to 2 hours.

  The thickness of the hard coat layer thus formed is preferably in the range of 1 to 20 μm, particularly preferably in the range of 1 to 10 μm, more preferably 2 from the viewpoints of uniform coatability and adhesion, film strength and the like. A range of ˜5 μm is more preferable.

(6) Transparent plastic substrate and highly durable UV-cut plastic substrate The transparent plastic substrate according to the present invention is not particularly limited, but it is a transparent organic resin molded product according to the present invention. This is preferable from the viewpoint of obtaining a highly durable UV-cut plastic substrate.

  And the base resin of a transparent plastic base material is not specifically limited, According to a use, it can select suitably. Specifically, polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, polyester resin, polyacetal resin, polysulfone resin, polyether sulfone resin, polyvinyl chloride resin, polyvinylidene chloride resin, epoxy resin, unsaturated polyester resin, polyurethane Resin, diallyl phthalate resin, diethylene glycol bisallyl carbonate resin, acetyl cellulose resin, sulfur-containing urethane resin or cross-linked (meth) acrylic resin, etc. are mentioned, but polycarbonate resin is particularly preferred because of its excellent strength, heat insulation, and durability. Preferably there is.

  The highly durable UV-cut plastic substrate according to the present invention includes a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat formed on the primer layer as described above. Each layer and base material, such as yellowing and peeling, because it has excellent transparency and ultraviolet absorption (shielding) ability, and the lifetime of ultraviolet absorption (shielding) ability contained in the primer layer is semi-permanent. Can be used for a long period of time.

  Next, examples of the present invention will be described in detail with reference to comparative examples. In addition, this invention is not limited to a following example.

  A series of operations were performed in an atmosphere air-conditioned at 23 ° C. and a relative humidity of 40% RH. The measurement of the visible light transmittance was in accordance with JIS R3106. The haze value was measured according to JIS K7105.

  Furthermore, the average particle diameter of ZnO (zinc oxide) fine particles was measured with a measuring device using a dynamic light scattering method (Nanotrac 150 manufactured by Nikkiso Co., Ltd.).

[Example 1]
In a 70 ml glass container, 4.0 g of ZnO fine particles (specific surface area 75 m ² / g), 12.67 g of methyl isobutyl ketone, and silicone resin (“KR-311” manufactured by Shin-Etsu Chemical Co., Ltd.), active ingredient 60 wt. %) Was added and mixed to prepare 20 g of a raw material solution. Further, 80 g of zirconia beads having a diameter of 0.3 mm (manufactured by Toray Industries, Inc.) were added, and the glass container was sealed. did.

  Next, the sealed glass container is stirred for 18 hours by a paint shaker (manufactured by Asada Tekko Co., Ltd., vibration frequency: 640 rpm), and the ZnO fine particles in the glass container are crushed and the surface of the crushed ZnO fine particles is coated with the silicone resin. A dispersion liquid (A liquid) was prepared in which ZnO fine particles were dispersed without performing the coating treatment and removing the solvent (methyl isobutyl ketone). The average particle diameter of the ZnO fine particles dispersed in this dispersion (liquid A) was measured and found to be as small as 80 nm, indicating that it was a good dispersion.

Next, 15.0 g of the above dispersion (Liquid A) and 0.9 g of surface-treated (intercalated) clay mineral are sufficiently mixed, and the coated ZnO fine particles are dispersed and the clay mineral is dispersed. A zinc oxide dispersion (solution B) according to Example 1 was prepared. The clay mineral includes sodium silicate / magnesium (hectorite), polyoxypropylene methyldiethylammonium (chemical formula: [CH ₃ (C ₂ H ₅ ) ₂ N (CH ₂ CH (CH ₃ ) O) ₂₅ H ] ⁺ ) And intercalated.

  Next, 20.00 wt% of this zinc oxide dispersion (liquid B), acrylic primer (“Primer PH-91” manufactured by Momentive Performance Materials Japan GK, solid content 4 wt%) 79. A coating solution (composition) for forming a primer layer according to Example 1 containing ZnO fine particles, which were sufficiently mixed at a rate of 00 wt%, coated, an acrylic resin binder, and a clay mineral was obtained.

  Then, the primer layer-forming coating solution (composition) according to Example 1 was flow-coated on a polycarbonate plate (“Lexan” manufactured by SABIC) containing an organic ultraviolet absorber, and leveled at room temperature for 10 minutes. A “primer layer” was formed by thermosetting at 125 ° C. for 20 minutes. Next, on this “primer layer”, a polyalkylsiloxane-based hard coat solution (“Tosguard 510” manufactured by Momentive Performance Materials Japan GK) is flow-coated and leveled at room temperature for 10 minutes. A “hard coat layer” was formed by thermosetting at 30 ° C. for 30 minutes to produce a highly durable UV-cut plastic substrate (coated polycarbonate plate) according to Example 1.

  And when the "visible light transmittance" and the "haze value" of the highly durable UV cut plastic substrate according to Example 1 were measured, the visible light transmittance was 89.4%, and the haze value was It was 0.3%, and it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high.

Furthermore, “durability evaluation” of the highly durable UV-cut plastic substrate according to Example 1 was performed. That is, using an ultraviolet irradiation device [“SUV-W131” manufactured by Iwasaki Electric Co., Ltd.], ultraviolet irradiation was performed for 500 hours under the condition of 100 mW / cm ² .

The optical properties of the highly durable UV-cut plastic substrate after UV irradiation were measured in the same manner as described above. The visible light transmittance was 88.3% and 100 mW / cm ² UV was irradiated for 500 hours. It was confirmed that the change in visible light transmittance (that is, Δvisible light transmittance) due to this was as small as “89.4-88.3 = 1.1%”. In addition, the haze value was 0.6%, and it was confirmed that the change in haze value (Δhaze) after irradiation with ultraviolet rays for 500 hours was as small as “0.6−0.3 = 0.3%”. . Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Next, the primer layer-forming coating solution (composition) according to Example 1 was stored at 25 ° C. for 60 days, and the appearance of the primer layer-forming coating solution (composition) after storage was observed. Etc. were not seen, and the storage stability was good.

  Further, using the primer layer-forming coating solution (composition) after storage, a highly durable UV-cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the resulting highly durable UV was obtained. When the haze value of the cut plastic substrate was measured, it was confirmed that the transparency was extremely high at 0.3%, and the storage stability of the primer layer forming coating liquid (composition) according to Example 1 was good. It was.

  In addition, "average particle diameter (nm) of coated ZnO fine particles", "clay mineral", "surface treatment agent", "clay mineral content (parts by weight)", "silicone resin content (parts by weight) according to each example and comparative example ) ”“ Visible light transmittance (%) ”“ Haze (%) ”“ Δ visible light transmittance (%) after UV irradiation ”“ Δ Haze (%) after UV irradiation ”and“ 25 ° C. × 60 days haze ” (%) ”(That is, the haze of the highly durable UV cut plastic substrate obtained using the primer layer-forming coating solution after storage at 25 ° C. for 60 days) is shown in Tables 1 to 4 below. Here, each numerical value of “clay mineral content (parts by weight)” and “silicone resin content (parts by weight)” indicates parts by weight with respect to 100 parts by weight of the ZnO fine particles.

[Example 2]
An implementation in which 15.0 g of the above dispersion (liquid A) and 0.9 g of surface-treated (intercalated) clay mineral were sufficiently mixed to disperse the coated ZnO fine particles and contain the clay mineral A zinc oxide dispersion (solution C) according to Example 2 was prepared. The clay mineral used was sodium silicate / magnesium (hectorite) intercalated with [Chemical formula: (CH ₃ ) ₂ (C ₁₈ H ₃₇ ) ₂ N ⁺ ].

  Next, 21.00 wt% of this zinc oxide dispersion (C liquid) and “Primer PH-91” manufactured by Momentive Performance Materials Japan GK mentioned above were mixed thoroughly at a ratio of 79.00 wt%. In the same manner as in Example 1, except that the primer layer-forming coating solution (composition) according to Example 2 containing the coated ZnO fine particles, the acrylic resin binder, and the clay mineral was obtained. A highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 2 was prepared.

Then, when “initial characteristics” and “durability evaluation” of the highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 2 were performed in the same manner as in Example 1, “initial characteristics” were obtained. The visible light transmittance was 89.6% and the haze value was 0.3%, and it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as “durability evaluation” after irradiation with ultraviolet rays for 500 hours under the condition of 100 mW / cm ² is 88.4%, and the change in visible light transmittance (that is, Δvisible light transmittance). Was as small as 1.2%, the haze as the “durability evaluation” was 0.6%, and the change in haze value (Δhaze) was also confirmed to be as small as 0.3%. Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Next, the primer layer-forming coating solution (composition) according to Example 2 was stored at 25 ° C. for 60 days, and the appearance of the primer layer-forming coating solution (composition) after storage was observed. Etc. were not seen, and the storage stability was good.

  Further, using the primer layer-forming coating solution (composition) after storage, a highly durable UV-cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the resulting highly durable UV was obtained. When the haze value of the cut plastic substrate was measured, it was confirmed that the transparency was extremely high at 0.3%, and the storage stability of the primer layer forming coating solution (composition) according to Example 2 was also good. It was.

[Example 3]
An implementation in which 15.0 g of the above dispersion (liquid A) and 0.9 g of surface-treated (intercalated) clay mineral were sufficiently mixed to disperse the coated ZnO fine particles and contain the clay mineral A zinc oxide dispersion (solution D) according to Example 3 was prepared. The clay mineral used was sodium silicate / magnesium (hectorite) intercalated with [Chemical Formula: (CH ₃ ) (C ₈ H ₁₇ ) ₃ N ⁺ ].

  Next, 21.00 wt% of this zinc oxide dispersion (D solution) and "Primer PH-91" manufactured by Momentive Performance Materials Japan GK mentioned above were mixed thoroughly at a ratio of 79.00 wt%. In the same manner as in Example 1, except that the primer layer-forming coating liquid (composition) according to Example 3 containing the coated ZnO fine particles, the acrylic resin binder, and the clay mineral was obtained. A highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 3 was produced.

  Then, when “initial characteristics” and “durability evaluation” of the highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 3 were performed in the same manner as in Example 1, “initial characteristics” were obtained. The visible light transmittance was 89.5% and the haze value was 0.3%, and it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 88.5%, and the change in visible light transmittance (Δvisible light transmittance) is as small as 1.0%. It was confirmed that the haze as the “durability evaluation” was 0.6% and the change in haze value (Δhaze) was as small as 0.3%. Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Next, the primer layer forming coating solution (composition) according to Example 3 was stored at 25 ° C. for 60 days, and the appearance of the primer layer forming coating solution (composition) after storage was observed. Etc. were not seen, and the storage stability was good.

  Further, using the primer layer-forming coating solution (composition) after storage, a highly durable UV-cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the resulting highly durable UV was obtained. When the haze value of the cut plastic substrate was measured, it was confirmed that the transparency was extremely high at 0.3%, and the storage stability of the primer layer forming coating liquid (composition) according to Example 3 was also good. It was.

[Example 4]
In a 70 ml glass container, 4.0 g of ZnO fine particles (specific surface area 75 m ² / g), 15.33 g of methyl isobutyl ketone, and silicone resin (“KR-311” manufactured by Shin-Etsu Chemical Co., Ltd.), active ingredient 60 wt. %) Was added and mixed to prepare 20 g of a raw material solution. Further, 80 g of zirconia beads having a diameter of 0.3 mm (manufactured by Toray Industries, Inc.) were added, and the glass container was sealed. did.

  Next, the sealed glass container is stirred for 18 hours by a paint shaker (manufactured by Asada Tekko Co., Ltd., vibration frequency: 640 rpm), and the ZnO fine particles in the glass container are crushed and the surface of the crushed ZnO fine particles is coated with the silicone resin. A dispersion liquid (E liquid) in which ZnO fine particles were dispersed was prepared without performing the coating treatment and removing the solvent (methyl isobutyl ketone). In addition, when the average particle diameter of the ZnO fine particles dispersed in this dispersion (E liquid) was measured, it was as small as 61 nm and confirmed to be a good dispersion.

Next, 15.0 g of the above dispersion liquid (E liquid) and 0.9 g of surface-treated (intercalated) clay mineral are sufficiently mixed, and the coated ZnO fine particles are dispersed and the clay mineral is dispersed. A zinc oxide dispersion liquid (F liquid) according to Example 4 was prepared. As the clay mineral, a material obtained by intercalating sodium silicate / magnesium (hectorite) with [chemical formula: (CH ₃ ) (C ₈ H ₁₇ ) ₃ N ⁺ ] was used.

  Next, 15.00 wt% of this zinc oxide dispersion (F solution) and "Primer PH-91" manufactured by Momentive Performance Materials Japan GK mentioned above were mixed thoroughly at a rate of 85.00 wt%. In the same manner as in Example 1, except that the coating liquid (composition) for forming the primer layer according to Example 4 containing the coated ZnO fine particles, the acrylic resin binder, and the clay mineral was obtained. A highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 4 was prepared.

  Then, when “initial characteristics” and “durability evaluation” of the highly durable UV-cut plastic substrate (coated polycarbonate plate) according to Example 4 were performed in the same manner as in Example 1, “initial characteristics” were obtained. The visible light transmittance was 89.3% and the haze value was 0.3%, and it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 88.4%, and the change in visible light transmittance (Δvisible light transmittance) is as small as 0.9%. It was confirmed that the haze as the “durability evaluation” was 0.7% and the change in haze value (Δhaze) was as small as 0.4%. Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Next, the primer layer forming coating solution (composition) according to Example 4 was stored at 25 ° C. for 60 days, and the appearance of the primer layer forming coating solution (composition) after storage was observed. Etc. were not seen, and the storage stability was good.

  Further, using the primer layer-forming coating solution (composition) after storage, a highly durable UV-cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the resulting highly durable UV was obtained. When the haze value of the cut plastic substrate was measured, it was confirmed that the transparency was extremely high at 0.3%, and the storage stability of the primer layer forming coating solution (composition) according to Example 4 was also good. It was.

[Example 5]
15.0 g of the above dispersion (liquid A) and 0.15 g of surface-treated (intercalated) clay mineral were sufficiently mixed, and the coated ZnO fine particles were dispersed and contained clay mineral A zinc oxide dispersion (solution G) according to Example 5 was prepared. The clay mineral used was sodium silicate / magnesium (hectorite) intercalated with [Chemical Formula: (CH ₃ ) (C ₈ H ₁₇ ) ₃ N ⁺ ].

  Next, 17.00 wt% of this zinc oxide dispersion (G solution) and "Primer PH-91" made by Momentive Performance Materials Japan GK mentioned above were mixed thoroughly at a rate of 83.00 wt%. In the same manner as in Example 1 except that the coating solution (composition) for forming a primer layer according to Example 5 containing ZnO fine particles subjected to coating treatment, an acrylic resin binder, and clay mineral was obtained. A highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 5 was produced.

  Then, when “initial characteristics” and “durability evaluation” of the highly durable UV cut plastic substrate (coated polycarbonate plate) according to Example 5 were performed in the same manner as in Example 1, “initial characteristics” were obtained. The visible light transmittance was 89.0%, the haze value was 0.3%, and it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 87.8%, and the change in visible light transmittance (Δvisible light transmittance) is as small as 1.2%. It was confirmed that the haze as the “durability evaluation” was 0.6% and the change in haze value (Δhaze) was as small as 0.3%. Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Next, the primer layer-forming coating solution (composition) according to Example 5 was stored at 25 ° C. for 60 days, and the appearance of the primer layer-forming coating solution (composition) after storage was observed. Etc. were not seen, and the storage stability was good.

  Further, using the primer layer-forming coating solution (composition) after storage, a highly durable UV-cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the resulting highly durable UV was obtained. When the haze value of the cut plastic substrate was measured, it was confirmed that the transparency was extremely high at 0.3%, and the storage stability of the primer layer forming coating solution (composition) according to Example 5 was also good. It was.

[Comparative Example 1]
An acrylic resin binder ("Primer SPH-91" manufactured by Momentive Performance Materials Japan GK) was applied as the primer layer forming coating solution (composition) of Comparative Example 1, and this coating solution was organic A polycarbonate plate (“Lexan” manufactured by SABIC) containing a UV absorber was flow-coated, leveled at room temperature for 10 minutes, and then thermally cured at 125 ° C. for 20 minutes to form a “primer layer”. Next, on this “primer layer”, a polyalkylsiloxane-based hard coat solution (“Tosguard 510” manufactured by Momentive Performance Materials Japan GK) is flow-coated and leveled at room temperature for 10 minutes. A “hard coat layer” was formed by thermosetting at 30 ° C. for 30 minutes to produce a UV cut plastic substrate (coated polycarbonate plate) according to Comparative Example 1.

  And when the "visible light transmittance" and "haze value" of the obtained UV cut plastic substrate (coated polycarbonate plate) according to Comparative Example 1 were measured in the same manner as in Example 1, the visible light transmittance was 89. 0.7% and haze value of 0.2%, it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 64.6%, and the change in visible light transmittance (Δvisible light transmittance) is as large as 25.1%. It was confirmed that the haze as the “durability evaluation” was 3.0% and the change in haze value (Δhaze) was as large as 2.8%. Furthermore, when the film appearance after ultraviolet irradiation was observed, it was confirmed that the film turned yellow, became cloudy and deteriorated in transparency, and cracks were also generated.

  Further, the primer layer-forming coating solution (composition) of Comparative Example 1 composed of the above “Primer PH-91” was stored at 25 ° C. for 60 days, and the primer layer-forming coating solution (composition) after storage was stored. When the appearance was observed, no cloudiness or sedimentation was observed, and the storage stability was good.

  Furthermore, using the primer layer-forming coating solution (composition) after storage, a UV cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the haze of the obtained UV cut plastic substrate was obtained. When the value was measured, it was confirmed that the transparency was extremely high at 0.2%.

[Comparative Example 2]
In a 70 ml glass container, 4.0 g of ZnO fine particles (specific surface area 75 m ² / g), 14.0 g of methyl isobutyl ketone, and 2.0 g of acrylic polymer dispersant were charged and mixed. 20 g of a raw material solution was prepared, and 80 g of zirconia beads having a diameter of 0.3 mm (manufactured by Toray Industries, Inc.) were added, and the glass container was sealed.

  Next, the sealed glass container is stirred for 18 hours by a paint shaker (manufactured by Asada Tekko Co., Ltd., vibration frequency: 640 rpm), and ZnO fine particles in the glass container are pulverized to disperse the fine particles (K Liquid). When the average particle diameter of the ZnO fine particles dispersed in this dispersion (liquid K) was measured, it was as small as 90 nm and confirmed to be a good dispersion.

  Next, 15.50 wt% of this dispersion (K liquid) and the above-mentioned Momentive Performance Materials Japan GK “Primer PH-91” were sufficiently mixed at a ratio of 84.50 wt%, A UV-cut plastic substrate according to Comparative Example 2 in the same manner as in Example 1 except that a primer layer-forming coating solution (composition) according to Comparative Example 2 containing ZnO fine particles and an acrylic resin binder was obtained. (Coated polycarbonate plate) was produced.

  And when the "visible light transmittance" and the "haze value" of the obtained UV cut plastic substrate (coated polycarbonate plate) according to Comparative Example 2 were measured in the same manner as in Example 1, the visible light transmittance was 89. 0.5% and a haze value of 0.3%, it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 83.3%, and the change in visible light transmittance (Δvisible light transmittance) is as large as 6.2%. It was confirmed that the haze as “durability evaluation” was 14.5%, and the change in haze value (Δhaze) was also very large at 14.2%. Furthermore, when the film appearance after ultraviolet irradiation was observed, it became cloudy and the transparency was greatly deteriorated. The reason for the cloudiness is that the acrylic resin binder has deteriorated due to the photocatalytic activity of the ZnO fine particles.

  In addition, when the primer layer forming coating solution (composition) according to Comparative Example 2 was stored at 25 ° C. for 60 days and the appearance of the primer layer forming coating solution (composition) after storage was observed, sedimentation occurred. It was confirmed that the storage stability was extremely poor.

[Comparative Example 3]
15.5 wt% of the dispersion (solution A) according to Example 1 in which the ZnO fine particles subjected to the coating treatment of the silicone resin were dispersed, “Primer PH-” manufactured by Momentive Performance Materials Japan GK described above. 91 ”was thoroughly mixed at a ratio of 84.50 wt%, and the coating liquid (composition) for forming the primer layer according to Comparative Example 3 containing the coated ZnO fine particles and the acrylic resin binder was obtained. Produced a UV-cut plastic substrate (coated polycarbonate plate) according to Comparative Example 3 in the same manner as in Example 1.

  And when the "visible light transmittance" and "haze value" of the obtained UV cut plastic base material (coated polycarbonate plate) according to Comparative Example 3 were measured in the same manner as in Example 1, the visible light transmittance was 89. 0.6% and a haze value of 0.3%, it was confirmed that the light in the visible light region was sufficiently transmitted and the transparency was extremely high. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 88.4%, and the change in visible light transmittance (Δvisible light transmittance) is as small as 1.2%. It was confirmed that the haze as “durability evaluation” was 0.6% and the change in haze value (Δhaze) was as small as 0.3%. Furthermore, when the film appearance after ultraviolet irradiation was observed, there was no discoloration, white turbidity, cracks, etc., and no change in the film appearance was observed.

  Further, the primer layer-forming coating solution (composition) of Comparative Example 3 was stored at 25 ° C. for 60 days, and the appearance of the primer layer-forming coating solution (composition) after storage was observed. It was done.

  Furthermore, using the primer layer-forming coating solution (composition) after storage, a UV cut plastic substrate (coated polycarbonate plate) was produced in the same manner as described above, and the haze of the obtained UV cut plastic substrate was obtained. It was confirmed that the storage stability of the primer layer forming coating solution was poor because the transparency was poor at 1.4% when the value was measured.

[Comparative Example 4]
In a 70 ml glass container, 4.0 g of ZnO fine particles (specific surface area 75 m ² / g), 12.67 g of methyl isobutyl ketone, and silicone resin (“KR-311” manufactured by Shin-Etsu Chemical Co., Ltd.), active ingredient 60 wt. %) Was added and mixed to prepare 20 g of a raw material solution. Further, 80 g of zirconia beads having a diameter of 0.3 mm (manufactured by Toray Industries, Inc.) were added, and the glass container was sealed. did.

  Next, the sealed glass container is stirred for 9 hours by a paint shaker (manufactured by Asada Tekko Co., Ltd., vibration frequency: 640 rpm), and the ZnO fine particles in the glass container are pulverized and the crushed ZnO fine particle surface is coated with the silicone resin. A dispersion liquid (Liquid L) in which ZnO fine particles were dispersed was prepared while performing the coating treatment and without removing the solvent (methyl isobutyl ketone). In addition, when the average particle diameter of the ZnO fine particles dispersed in this dispersion (Liquid L) was measured, it was confirmed to be as large as 150 nm.

A comparison in which 15.0 g of the above dispersion (Liquid L) and 0.9 g of surface-treated (intercalated) clay mineral were sufficiently mixed to disperse the coated ZnO fine particles and contained clay mineral A zinc oxide dispersion (solution M) according to Example 4 was prepared. The clay mineral includes sodium silicate / magnesium (hectorite), polyoxypropylenemethyldiethylammonium (chemical formula: [CH ₃ (C ₂ H ₅ ) ₂ N (CH ₂ CH (CH ₃ ) O) ₂₅ H ] ⁺ ) And intercalated.

  Next, 21.00 wt% of this zinc oxide dispersion (M solution) and "Primer PH-91" made by Momentive Performance Materials Japan GK mentioned above were mixed thoroughly at a rate of 79.00 wt%. In the same manner as in Example 1 except that the coating liquid (composition) for forming the primer layer according to Comparative Example 4 containing ZnO fine particles subjected to the coating treatment, the acrylic resin binder, and the clay mineral was obtained. A UV cut plastic substrate (coated polycarbonate plate) according to Comparative Example 4 was produced.

  And when the "visible light transmittance" and the "haze value" of the obtained UV cut plastic substrate (coated polycarbonate plate) according to Comparative Example 4 were measured in the same manner as in Example 1, the visible light transmittance was 88. 0.5% and haze value of 1.8%, which sufficiently transmits light in the visible light region, but was confirmed to be low in transparency and cloudy. Further, the visible light transmittance as the “durability evaluation” after irradiation with ultraviolet rays for 500 hours is 85.0%, and the change in visible light transmittance (Δvisible light transmittance) is as large as 3.5%. It was confirmed that the haze as the “durability evaluation” was 5.4% and the change in haze value (Δhaze) was as large as 3.6%. Furthermore, when the film appearance after ultraviolet irradiation was observed, it was further clouded and the transparency was deteriorated.

  Further, the primer layer-forming coating solution (composition) according to Comparative Example 4 was stored at 25 ° C. for 60 days, and the appearance of the primer layer-forming coating solution (composition) after storage was observed. It was confirmed that the storage stability was poor.

"Evaluation"
(1) In Example 1 to Example 5, a primer layer forming coating solution (composition) containing zinc oxide fine particles having an average particle diameter of 100 nm or less coated with a silicone resin, clay minerals, and an acrylic resin binder is provided. Since it is applied, the visible light transmittance of the highly durable UV cut plastic base material (coated polycarbonate plate) manufactured as can be seen from the “Initial characteristics” column of Table 2 is 89.0% or more in the visible light region. It is confirmed that the light is sufficiently transmitted and the haze is 0.3% or less and the transparency is extremely high.

  Further, as can be seen from the column of “After SUV-500 hours irradiation” in Table 2, Δvisible light transmittance before and after UV irradiation of 500 hours is 0.9% to 1.2%, and Δhaze is 0.3% to 0%. It is also confirmed that the rate of change is as small as 4%.

  Furthermore, even when using the primer layer-forming coating solution (composition) after storage at 25 ° C. for 60 days, as can be seen from the “storage stability” column in Table 2, the haze is 0.3% and the transparency is high. It is confirmed that the storage stability of the primer layer forming coating solutions according to Examples 1 to 5 is good.

(2) On the other hand, in Comparative Example 1, a UV-cut plastic base material is applied by applying a primer layer-forming coating solution (composition) containing the acrylic resin binder and not containing zinc oxide fine particles, clay mineral, and silicone resin. (Coated polycarbonate plate) is manufactured, and as can be seen from the column “After SUV-500 hours irradiation” in Table 4, the Δvisible light transmittance around 500 hours of ultraviolet irradiation is 25.1%, and Δhaze is 2 It is confirmed that the rate of change is significantly larger than that of Examples 1 to 5.

  Moreover, the film | membrane external appearance after ultraviolet irradiation changes to yellow, and it is cloudy, its transparency is bad, and generation | occurrence | production of a crack is also confirmed.

(3) In Comparative Example 2, a primer layer forming coating solution (composition) containing zinc oxide fine particles not coated with a silicone resin and the acrylic resin binder and containing no clay mineral is applied. This is an example in which a UV cut plastic substrate (coated polycarbonate plate) is manufactured.

  In Comparative Example 2, since the photocatalytic activity of the zinc oxide fine particles is not inactivated, as can be seen from the “After SUV-500 hours irradiation” column of Table 4, the Δvisible light transmittance at around 500 hours of ultraviolet irradiation is 6 .2% and Δhaze are 14.2%, confirming that the rate of change is significantly greater than in Examples 1-5.

  In addition, it was confirmed that the film appearance after UV irradiation was white turbid, and that the primer layer forming coating solution after being stored at 25 ° C. for 60 days had sedimentation and the storage stability was poor. Is done.

(4) In Comparative Example 3, a UV-cut plastic is applied by applying a primer layer forming coating solution (composition) containing zinc oxide fine particles coated with a silicone resin and the acrylic resin binder, and containing no clay mineral. This is an example in which a substrate (coated polycarbonate plate) is manufactured.

  As can be seen from the “Initial characteristics” column in Table 4, the visible light transmittance is 89.6%, which sufficiently transmits light in the visible light region, and the haze is 0.3%, which is extremely high in transparency. It is confirmed.

  Further, in Comparative Example 3, since the photocatalytic activity of the zinc oxide fine particles is inactivated, as can be seen from the column “After SUV-500 hours irradiation” in Table 4, the Δvisible light transmittance at around 500 hours of ultraviolet irradiation is 1 .2% and Δhaze are 0.3, which is confirmed to be small as in Examples 1-5.

  However, since the clay layer is not contained in the primer layer forming coating solution, as can be seen from the “storage stability” column of Table 4, the primer layer forming coating solution after being stored at 25 ° C. for 60 days is used. The haze of the manufactured UV cut plastic substrate (coated polycarbonate plate) is 1.4%, which is significantly higher than those of Examples 1 to 5, and the dispersion (storage) stability of the primer layer forming coating solution is poor. That is confirmed.

(5) In Comparative Example 4, a primer layer-forming coating solution (composition) containing zinc oxide fine particles having an average particle diameter of 150 nm coated with a silicone resin, clay minerals, and an acrylic resin binder is applied and UV is applied. This is an example in which a cut plastic substrate (coated polycarbonate plate) is manufactured.

  And since the average particle diameter of zinc oxide fine particles is as large as 150 nm, as can be seen from the “initial characteristics” column in Table 4, the initial haze is 1.8%, which is higher than in Examples 1 to 5, and the transparency is low. It is confirmed that it is cloudy.

  Moreover, as can be seen from the column “After UV irradiation for 500 hours” in Table 4, the Δvisible light transmittance before and after 500 hours of UV irradiation is 3.5%, and the Δhaze is 3.6%. Is significantly larger than

  Furthermore, the film appearance after UV irradiation was confirmed to be more cloudy, and precipitation occurred in the primer layer forming coating solution after storage at 25 ° C. for 60 days, which was stored in comparison with Examples 1-5. It is confirmed that the stability is also poor.

  According to the present invention, unlike the conventional wet surface treatment method on the surface of the zinc oxide fine particles, the storage stability to which the inorganic ultraviolet absorber is applied without the need for solvent removal / drying step, redispersion step, etc. is excellent. Because it can provide a coating solution for forming a primer layer, it can also be used as an inexpensive coating solution for forming a primer layer using an inorganic UV absorber even in the paint and plastics industry, where market prices have been established with inexpensive organic UV absorbers. Has industrial applicability.

Claims (11)

In zinc oxide dispersion in which zinc oxide fine particles are dispersed in a solvent and an acrylic resin binder is added when preparing a primer layer forming coating solution,
A silane compound is charged into a mill base composed of zinc oxide raw material powder and a solvent, and the zinc oxide raw material powder is pulverized and the surface of the pulverized zinc oxide fine particles is coated with the silane compound using a wet medium stirring mill. Coating-treated zinc oxide fine particles having a primary particle diameter of 100 nm or less prepared without removal and a solvent are included, and the silane compound is mainly composed of polysiloxane composed of repeating siloxane bonds (Si—O—Si). One or more molecular ends are blocked with an alkoxysilyl group (Si-OR) and / or silanol group (Si-OH), and the hydrocarbon group having 1 to 18 carbon atoms and / or the phenyl group is organically substituted. A zinc oxide dispersion comprising a silicone resin in a molecule as a group and further containing a clay mineral.   Bentonite selected from quartz, cristopalite, feldspar, mica, zeolite, and / or smectite selected from montmorillonite, beidellite, nontronite, saponite, hectorite, soconite, stevensite. The zinc oxide dispersion according to claim 1, which is contained.   The zinc oxide dispersion according to claim 2, wherein the clay mineral is intercalated with an organic cation.   The zinc oxide dispersion according to any one of claims 1 to 3, wherein the clay mineral is contained in an amount of 1 part by weight to 120 parts by weight with respect to 100 parts by weight of the zinc oxide fine particles.   5. The zinc oxide dispersion according to claim 1, wherein the silicone resin is contained in an amount of 5 to 300 parts by weight with respect to 100 parts by weight of the zinc oxide fine particles. Primer for forming the above-mentioned primer layer of a highly durable UV-cut plastic substrate having a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat layer formed on the primer layer In the coating liquid for layer formation,
A coating solution for forming a primer layer, comprising the zinc oxide dispersion according to any one of claims 1 to 5 and an acrylic resin binder. In a highly durable UV-cut plastic substrate having a transparent plastic substrate, a primer layer formed on the transparent plastic substrate, and a hard coat layer formed on the primer layer,
The primer layer-forming coating solution according to claim 6 is applied onto a transparent plastic substrate, and the primer layer is formed by heating the coating film. The transparent plastic substrate, the primer layer, and the hard coat layer The UV-cut plastic substrate having a visible light transmittance of 85% or more and a haze value of 1.0% or less, and before and after being irradiated with 100 mW / cm ² ultraviolet rays for 500 hours, A highly durable UV-cut plastic substrate characterized by a change in visible light transmittance of 2.0% or less and a change in haze of 1.0% or less.   8. The highly durable UV-cut plastic substrate according to claim 7, wherein the hard coat layer is formed of a silicone resin.   The highly durable UV-cut plastic substrate according to claim 7 or 8, wherein the primer layer has a thickness of 1 µm or more and 5 µm or less.   The amount of zinc oxide fine particles in the primer layer is 1 part by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the acrylic resin binder. Durable UV cut plastic substrate.   The transparent plastic base material is polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, polyester resin, polyacetal resin, polysulfone resin, polyether sulfone resin, polyvinyl chloride resin, polyvinylidene chloride resin, epoxy resin, unsaturated polyester resin. A polyurethane resin, a diallyl phthalate resin, a diethylene glycol bisallyl carbonate resin, an acetyl cellulose resin, a sulfur-containing urethane resin, or a cross-linked (meth) acrylic resin. High durability UV cut plastic substrate.