阅读说明：本技术 功能性片材 (Functional sheet ) 是由 木村英明 赤木雅幸 野中健太 藤井尊 村井克之 大野翔太朗 于 2018-07-05 设计创作，主要内容包括：本发明所要解决的技术问题在于：提供一种功能性聚酰胺片材和使用该片材而得到的功能性聚酰胺透镜,在将包含聚酰胺树脂的片材或膜作为保护层而制造偏光和/或调光功能性片材时,在该片材中不产生气泡或大幅度减少气泡。本发明用于解决技术问题的技术方案在于：提供一种聚酰胺功能性片材和使用其而得到的功能性聚酰胺透镜,该功能性片材的特征在于：在功能层的至少一个面隔着粘接层配置由透明塑料片材或膜形成的保护层,上述功能层为聚乙烯醇系偏光膜层、调光层或它们的组合,上述保护层为包含聚酰胺树脂的片材或膜,并且在23℃、85％RH的条件下,氧透过度为50cm<Sup>3</Sup>/m<Sup>2</Sup>·24hr·bar以上。(The technical problem to be solved by the invention is as follows: to provide a functional polyamide sheet and a functional polyamide lens obtained by using the same, in the case of producing a polarizing and/or light-modulating functional sheet using a sheet or film comprising a polyamide resin as a protective layerNo bubbles are generated or bubbles are greatly reduced in the sheet. The technical scheme of the invention for solving the technical problem is as follows: provided are a polyamide functional sheet and a functional polyamide lens obtained using the same, wherein the functional sheet is characterized in that: a protective layer made of a transparent plastic sheet or film is disposed on at least one surface of a functional layer via an adhesive layer, the functional layer is a polyvinyl alcohol-based polarizing film layer, a light modulation layer, or a combination thereof, the protective layer is a sheet or film made of a polyamide resin and has an oxygen permeability of 50cm at 23 ℃ and 85% RH 3 /m 2 24 hr. bar or more.)

1. A polyamide functional sheet characterized by:

the functional sheet is formed by arranging a protective layer formed by a transparent plastic sheet or a film on at least one surface of a functional layer through an adhesive layer,

the functional layer is a polyvinyl alcohol polarizing film layer, a light modulation layer or a combination of the polyvinyl alcohol polarizing film layer and the light modulation layer,

the protective layer is a sheet or film comprising a polyamide resin and has an oxygen permeability of 85% RH at 23 deg.C50cm³/m²24 hr. bar or more.

2. The polyamide functional sheet according to claim 1, wherein:

the polyamide resin of the protective layer is amorphous or microcrystalline polyamide resin.

3. The polyamide functional sheet according to claim 1 or 2, characterized in that:

the adhesive layer contains a urethane resin adhesive.

4. The polyamide functional sheet according to any one of claims 1 to 3, wherein:

the protective layer has a retardation value of 200nm or less or 2000nm or more.

5. A polyamide functional lens characterized by:

the functional sheet is obtained by using the functional sheet according to any one of claims 1 to 4.

6. A method for producing a polyamide functional lens, comprising:

a step of punching the functional sheet according to any one of claims 1 to 4 into a sheet for a single lens; and

and a step of subjecting the lens sheet to a thermal bending process.

7. A method for producing a polyamide functional lens, comprising:

a step of punching the functional sheet according to any one of claims 1 to 4 into a sheet for a single lens;

a step of subjecting the lens sheet to a thermal bending process; and

and a step of thermally fusing the thermoplastic resin to the concave side of the sheet after the hot bending process.

Technical Field

The present invention relates to a functional sheet for a sunglass and a functional lens for a sunglass, each of which is obtained by laminating a protective layer made of a transparent plastic sheet or film on at least one surface of a functional layer via an adhesive layer, wherein the functional layer is a polyvinyl alcohol-based polarizing film layer, a light modulation layer, or a combination thereof.

Background

A functional polycarbonate lens for a sunglass, which is an injection-molded lens produced by laminating a transparent plastic sheet or film, particularly an aromatic polycarbonate resin sheet, on a polarizing film obtained by dyeing a polyvinyl alcohol film (hereinafter referred to as PVA) with a dichroic dye, a light-controlling layer obtained by dispersing a light-controlling dye in a matrix resin, or a functional layer obtained by combining these, using a two-pack thermosetting resin or the like as an adhesive, and subjecting the functional sheet to a hot-bending process, and then molding the hot-bent product into an injection-molded lens by inserting the product into a mold, is generally widespread from the viewpoint of improving durability (patent document 1).

These functional polycarbonate lenses are pointed out to have the following technical problems: when used for a spectacle frame made of plastic containing a plasticizer such as cellulose acetate, the plasticizer in the spectacle frame bleeds out, and a lens made of a polycarbonate resin is cracked or the like. Under these circumstances, a polarizing laminate for sunglasses and the like in which a protective layer obtained by stretching a sheet containing a polyamide resin and imparting retardation is formed has been disclosed (patent document 2).

Disclosure of Invention

Technical problem to be solved by the invention

The technical problem to be solved by the invention is as follows: provided are a polyamide functional sheet and a polyamide functional lens obtained by using the same, wherein bubbles are not generated in the sheet or are greatly reduced when the sheet or the film containing the polyamide resin is used as a protective layer to manufacture a polarizing and/or light-modulating functional sheet. In this specification, a sheet and a film are not distinguished. That is, the sheet or the film is sometimes referred to as only the sheet or only the film, but they have the same meaning.

As described above, there is a demand for a functional sheet having a polyamide resin sheet as a protective layer due to the chemical resistance of polyamide resin. The present inventors have observed that, when a protective layer of a polycarbonate functional sheet which has been able to be produced so far is changed to a polyamide resin sheet to produce a functional sheet, the generation of bubbles is observed to the extent of impairing the appearance of the sheet.

The production conditions were the same except that the aromatic polycarbonate sheet was changed to a polyamide resin sheet. Since the bubbles are observed after the protective layer is bonded to the functional layer via the adhesive layer, it is considered that the bubbles are generated by a reaction of the components of the adhesive layer and the functional layer. The inventors of the present invention have studied the difference in physical properties between an aromatic polycarbonate sheet and a polyamide resin sheet, and as a result, have focused on the difference in gas barrier properties between the two sheets and conducted comparative studies. The results clearly show that: the polyamide resin sheet has a higher gas barrier property than the aromatic polycarbonate sheet, as indicated by its low oxygen permeability.

That is, it is considered that the generation of bubbles is caused as a result of gas generated by a reaction between the adhesive layer and the component of the functional layer being confined by the protective layer containing a polyamide resin having high gas barrier properties.

If the occurrence of bubbles can be recognized in the production process, it is considered that the occurrence of bubbles can be prevented by appropriately adjusting the bonding speed and stress of each layer to escape the gas, but it is difficult to find the point of time when bubbles are generated, and a production method that must take this point into consideration is not suitable for industrial production in terms of production efficiency.

In addition, as the adhesive, the adhesive used for producing the polycarbonate functional sheet invented by the inventors is a thermosetting resin. In the present invention, such an adhesive layer containing a thermosetting resin is preferably used if no air bubbles are generated because it can be stably used without peeling off in the thermal bending and injection molding steps.

Technical solution for solving technical problem

The present inventors have found that when a polyamide resin sheet exhibiting a predetermined oxygen permeability is used as a protective layer, problematic air bubbles can be reduced or prevented from being generated, and have completed the present invention. Namely, the present invention is as follows.

(1) A polyamide functional sheet characterized by: the functional sheet is formed by arranging a protective layer formed by a transparent plastic sheet or a film on at least one surface of a functional layer through an adhesive layer, wherein the functional layer is a polyvinyl alcohol polarizing film layer, a light modulation layer or a combination of the polyvinyl alcohol polarizing film layer and the light modulation layer, the protective layer is a sheet or a film containing polyamide resin, and the oxygen permeability is 50cm under the conditions of 23 ℃ and 85% RH³/m²24 hr. bar or more.

In the invention as recited in the above (1), the polyamide functional sheet is characterized in that:

(2) the polyamide resin of the protective layer is amorphous or microcrystalline polyamide;

(3) the adhesive layer is a polyurethane resin solvent adhesive;

(4) the retardation of the protective layer is 200nm or less or 2000nm or more.

In addition, the present invention also relates to:

(5) a polyamide functional lens obtained by using the functional sheet described in the above (1) to (4).

In addition, the present invention also relates to:

(6) a method of making a polyamide functional lens comprising: a step of punching the functional sheet described in any one of (1) to (4) into a sheet for a single lens; and a step of subjecting the lens sheet to a thermal bending process.

In addition, the present invention also relates to:

(7) a method of making a polyamide functional lens comprising: a step of punching the functional sheet described in any one of (1) to (4) into a sheet for a single lens; a step of subjecting the lens sheet to a thermal bending process; and a step of thermally fusing the thermoplastic resin to the concave side of the sheet after the hot bending process.

Detailed Description

(functional layer (polarizing film layer))

The polarizing film used for the functional layer is a film obtained by swelling a resin film as a substrate in water, stretching the resin film in one direction, and impregnating the resin film with a dyeing solution containing a dichroic organic dye to disperse the dichroic dye in the substrate resin in a state of being oriented in the substrate resin, thereby imparting polarization properties and a desired color tone.

As the resin of the substrate of the polarizing film used in this case, a polyvinyl alcohol may be used, and as the polyvinyl alcohol, polyvinyl alcohol (hereinafter referred to as PVA), a product having an acetate structure in which a small amount of PVA remains, polyvinyl formal, polyvinyl acetal, ethylene-vinyl acetate copolymer saponified product, or the like which is a PVA derivative or the like is preferable, and PVA is particularly preferable.

In addition, as for the molecular weight of PVA, from the viewpoint of stretchability and film strength, the weight average molecular weight is preferably from 50,000 to 350,000, more preferably from 100,000 to 300,000, and particularly preferably 150,000 or more. The ratio of the stretching ratio to the stretching ratio is 2 to 8 times, preferably 3.5 to 6.5 times, and particularly preferably 4.0 to 6.0 times, from the viewpoint of the dichroic ratio and the film strength after stretching. The thickness of the PVA film after stretching is 10 μm or more, and from the viewpoint of enabling handling without integrating with a protective film or the like, the thickness is preferably 20 μm or more and 50 μm or less.

A typical production process using a PVA film as a base film can be produced by the following steps: (1) swelling and washing the PVA film in water to properly remove impurities; (2) properly stretching; and (3) dyeing in a dyeing bath; (4) carrying out crosslinking or chelation treatment in a treatment tank by using boric acid or a metal compound; (5) drying is carried out. The steps (2) and (3) (if necessary, (4)) may be performed simultaneously with the above steps by changing the order as appropriate.

First, the swelling and washing step of step (1) can uniformly soften and stretch the PVA film, which is easily broken in a dry state at room temperature, by absorbing water. The step of removing the water-soluble plasticizer used in the step of producing the PVA film, or the step of appropriately pre-adsorbing the additive is also used. In this case, the PVA film does not sequentially swell uniformly, and therefore, unevenness is inevitably generated. In this state, it is also important to try to uniformly apply as small a force as possible in order not to cause local elongation or local insufficient elongation, and to suppress the occurrence of wrinkles and the like. In addition, in this step, it is most desirable that only uniform swelling and excessive stretching are not uniform, and therefore, it is preferable to avoid them as much as possible.

The step (2) is a step of stretching the film by a factor of 2 to 8.

In the present invention, it is important that the workability is good, and therefore, the stretching ratio is selected from 3.5 to 6.5 times, particularly 4.0 to 6.0 times, and the orientation is preferably maintained in this state.

In the state of being stretched and oriented, if the time in which the stretching treatment is carried out is long and the time until drying is long, the orientation tends to relax, and therefore, from the viewpoint of maintaining higher performance, it is preferable to set the stretching treatment to a shorter time, and after stretching, to remove moisture as quickly as possible, that is, to immediately introduce the stretching treatment into a drying step, and to dry the stretching treatment while avoiding an excessive heat load.

The dyeing in the step (3) is carried out by adsorbing or depositing the dye onto the polymer chain of the oriented polyvinyl alcohol resin film. According to this mechanism, although it can be performed before, during, and after uniaxial stretching without a large change, a surface having a large restriction such as an interface is most easily oriented, and it is preferable to select conditions that can exhibit this.

From the viewpoint of high productivity, the temperature is usually selected from high temperatures of 40 to 80 ℃, and in the present invention, the temperature is usually selected from 25 to 45 ℃, preferably 30 to 40 ℃, and particularly 30 to 35 ℃.

The step (4) is performed to improve heat resistance, water resistance and organic solvent resistance.

The former treatment with boric acid improves heat resistance by crosslinking between PVA chains, and can be performed before, during, and after uniaxial stretching of the polyvinyl alcohol resin film without any significant change. The latter metal compounds are stabilized mainly by forming chelate compounds with dye molecules, and are usually carried out after dyeing or simultaneously with dyeing.

As the metal compound, among transition metals belonging to any of the 4 th cycle, the 5 th cycle, and the 6 th cycle, there are compounds whose metal compounds can confirm the above-described heat resistance and solvent resistance effects, but metal salts such as acetates, nitrates, sulfates, and the like of the 4 th cycle transition metals such as chromium, manganese, cobalt, nickel, copper, zinc, and the like are preferable from the viewpoint of price. Among these, compounds of nickel, manganese, cobalt, zinc and copper are more preferable because they are inexpensive and have excellent effects as described above.

The content of the metal compound and boric acid in the polarizing film is preferably 0.2 to 20mg, more preferably 1 to 5mg, of the metal compound as a metal per 1g of the polarizing film, from the viewpoint of imparting heat resistance and solvent resistance to the polarizing film. The boric acid content is preferably 0.3 to 30mg, more preferably 0.5 to 10mg, in terms of boron.

The composition of the treating liquid used for the treatment is set so as to satisfy the above content, and generally, the concentration of the metal compound is preferably 0.5 to 30g/L, and the concentration of boric acid is preferably 2 to 20 g/L.

The content of the metal and boron in the polarizing film can be analyzed by an atomic absorption spectrometry.

The temperature is usually the same as that of dyeing, and is usually selected from 20 to 70 ℃, preferably 25 to 45 ℃, more preferably 30 to 40 ℃, particularly 30 to 35 ℃. The time is usually selected from 0.5 to 15 minutes.

In the step (5), the dyed uniaxially stretched PVA film after stretching, dyeing, and treatment with boric acid or a metal compound as appropriate is dried. The PVA film exhibits heat resistance according to the amount of water contained therein, and when the temperature is increased in a state where a large amount of water is contained, disorder or the like occurs in a shorter time to be out of the uniaxially stretched state, resulting in a decrease in the dichroic ratio.

Drying is carried out from the surface, preferably from both surfaces, preferably by removing water vapor by blowing dry air. It is known that, from the viewpoint of avoiding excessive heating and from the viewpoint of drying which can suppress temperature rise, a method of immediately removing evaporated moisture to promote evaporation is preferable, and the temperature of the drying air is generally dried at a temperature of 70 ℃ or more, preferably 90 to 120 ℃ for 1 to 120 minutes, preferably 3 to 40 minutes, within a range of not more than the temperature at which the polarizing film in a dried state is not substantially discolored.

The dried PVA is usually produced at a water content of 1 to 4 wt%.

(functional layer (light control layer))

As the functional layer of the present invention, a polyurethane film can be also applied to a light-adjusting film or the like containing a light-adjusting pigment. Further, a light control dye may be incorporated into the adhesive layer described later, and for example, a light control layer formed of a thermosetting urethane resin layer containing a photochromic compound can be produced by the following method. The light-controlling coloring matter (photochromic compound) is not particularly limited as long as it has good compatibility with the polyurethane prepolymer, and a commercially available organic photochromic compound can be used. From the viewpoint of photochromic properties, spiropyran-based compounds, spirooxazine-based compounds and naphthopyran-based compounds are preferably used.

A method for manufacturing a light-adjusting film used for a light-adjusting layer is exemplified. A solution obtained by diluting a polyurethane prepolymer with a specific organic solvent is added with a photochromic compound in an amount of 0.2 to 5 wt% relative to the solid content of the resin, and then with an additive such as a hindered amine light stabilizer and/or an antioxidant in an amount of 0.1 to 5 wt% relative to the solid content of the resin, and the mixture is uniformly stirred and mixed. Then, the curing agent is added in such a manner that the ratio I/H of the isocyanate group (I) to the hydroxyl group (H) of the curing agent is 0.9 to 20, preferably 1 to 10, and then the mixture is stirred to form a solution. The concentration of the polymer in the solution is preferably 40 to 90% by weight. The solution is applied to the back surface of a transparent polycarbonate sheet having a coating film layer provided on the surface thereof, using a doctor blade, so that the coating thickness is 50 to 1000 μm. After the coating, the coated surface was dried by heating to a state substantially free from a solvent, and the back surface of a transparent polycarbonate sheet having a coating film layer provided on the other surface was laminated to the coated surface of the synthetic resin sheet to form a laminate, followed by drying after leaving to obtain a light-adjusting film.

(adhesive layer)

In order to form a functional sheet by laminating a functional layer and a protective layer, an adhesive layer is interposed between the functional layer and the protective layer. In general, as a material used for an adhesive of a functional sheet, there are a polyvinyl alcohol resin material, an acrylic resin material, a polyurethane resin material, a polyester resin material, a melamine resin material, an epoxy resin material, a silicone material, and the like.

In the present invention, a thermosetting material is preferable in view of stability in the hot bending process and the injection molding process, and a two-liquid type thermosetting polyurethane resin composed of a polyurethane prepolymer and a curing agent is particularly preferable as the polyurethane resin material.

The polyurethane prepolymer is a compound obtained by reacting a diisocyanate compound and a polyoxyalkylene glycol at a certain ratio, and has isocyanate groups at both ends. As the diisocyanate compound used for the polyurethane prepolymer, diphenylmethane-4, 4 ' -diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4 ' -dicyclohexylmethane diisocyanate, lysine isocyanate, hydrogenated xylylene diisocyanate, preferably diphenylmethane-4, 4 ' -diisocyanate, can be used. As the polyoxyalkylene glycol, polypropylene glycol, polyethylene glycol, polyoxytetramethylene glycol can be used, and polypropylene glycol having a polymerization degree of 5 to 30 is preferably used. The molecular weight of the polyurethane prepolymer is not particularly limited, but is usually 500 to 5000, preferably 1500 to 4000, and more preferably 2000 to 3000 in number average molecular weight.

On the other hand, the curing agent is not particularly limited as long as it is a compound having 2 or more hydroxyl groups, and examples thereof include polyurethane polyols, polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polycarbonate polyols, and the like, and among them, polyurethane polyols having hydroxyl groups at the terminals obtained from a specific isocyanate and a specific polyol are preferable. Particularly preferred are polyurethane polyols having hydroxyl groups at least at both ends derived from a diisocyanate compound and a polyol. As the diisocyanate compound, diphenylmethane-4, 4 '-diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, lysine isocyanate, hydrogenated xylylene diisocyanate can be used, and tolylene diisocyanate is preferably used. The polyol may be a compound obtained by reacting ethylene oxide or propylene oxide with trimethylolpropane or the like, and is preferably a polypropylene glycol derivative having a polymerization degree of 5 to 30. The molecular weight of the curing agent is not particularly limited, but the number average molecular weight is usually 500 to 5000, preferably 1500 to 4000, more preferably 2000 to 3000.

Solvents such as ethyl acetate and tetrahydrofuran for viscosity adjustment can be used for these polyurethane prepolymers and curing agents. In addition, when a light-controlling function is provided to the adhesive layer, it is effective to use a solvent in order to uniformly disperse the photochromic compound in the polyurethane resin.

(protective layer)

The functional sheet of the present invention has a protective layer (or a protective film for a polarizing film) containing a polyamide resin formed on at least one surface thereof.

From the viewpoint of transparency and molding processability, the polyamide resin is preferably a polyamide called an amorphous polyamide or a microcrystalline polyamide, and is preferably injection-moldable as described later. That is, it is preferably used as long as it is thermoplastic, exhibits melt fluidity enabling molding at a temperature not higher than the thermal decomposition temperature, and has an appropriate Tg (glass transition temperature).

When the amorphous property is used as a condition, the amount of the repeating unit forming the crystalline property is limited, and examples of the molecular structure inhibiting the crystalline property include a structure imparting a steric barrier property, and a bulky molecular structure such as a cyclic alkane or introduction of a branched structure or a substituent can be used.

Under the condition of appropriate heat resistance, a structure having a large enthalpy among the repeating units (unit molecular chain length) or a structure that restricts the molecular movement within the repeating units and between the repeating units is required, and the former is typically aromatic, and when the latter is a synthetic product, cycloalkane, cycloolefin, or the like having a structure obtained by hydrogenating an unsaturated bond of an aromatic nucleus can be used. Further, as described above, since the compound having an alicyclic structure has heat resistance and a molecular structure which inhibits crystallinity, it can be said that the compound is a useful material for forming a functional sheet for a sunglass which uses a polyamide as a protective layer for hot bending processing or the like.

The polyamide generally has a structural unit derived from a monomer such as a diamine, a dicarboxylic acid, or an aminocarboxylic acid. From the principle viewpoint, the aromatic polyamide or alicyclic polyamide can be produced by converting a structural unit derived from at least one monomer constituting the fully aliphatic polyamide into an aromatic or alicyclic structure. In the present invention, a partially aromatic polyamide, an aromatic partially alicyclic polyamide, a partially alicyclic polyamide, or a combination thereof can be used by making all or part of these monomers aromatic or alicyclic, and a polyamide having an alicyclic structure is preferably used as one of typical examples of amorphous polyamides having amorphous properties and appropriate heat resistance. In consideration of optical characteristics such as retardation described later, it is preferable that the aromatic moiety is included.

Of course, additives such as lubricants and antioxidants can be suitably used in the polyamide resin used in the present invention in order to cope with oxidative deterioration of the polyamide and processing defects.

When the functional sheet of the present invention is produced as a sheet for a single lens, and is subjected to a hot bending process, and if necessary, a thermoplastic resin is integrated with the concave surface side thereof by injection fusion to form a polyamide functional lens, optical distortion may occur, that is, when the polyamide functional lens is observed as a "color unevenness" of rainbow color in oblique viewing, or when the polyamide functional lens is observed as a curved polarizing plate by being superimposed on a planar polarizing plate arranged so that the polarizing axes thereof are orthogonal to each other, so-called "polarized light leakage" of light transmission may be observed, because the resin used for the protective layer has a large birefringence, that is, an intrinsic birefringence or a photoelastic coefficient is large, and the retardation value (defined as a birefringence △ n × thickness d) (for example, 300nm to 1200nm or the like) is large due to the stress at the time of melt extrusion molding or at the time of the above-mentioned hot bending process, and the above-mentioned "polarized light" is disturbed, and when the lens is observed as a "color unevenness" convex stripe "in oblique viewing.

As described above, it is desirable that a protective layer having a retardation value (for example, 300nm or less, preferably 200nm or less, and more preferably 100nm or less) of such a degree that the function of the polarizing film layer provided in the inner layer is not impaired be disposed at least at a position where the lens is convex after processing.

When the retardation is as low as this, the thickness of the protective layer is preferably 100 μm or less, preferably 80 μm or less. Further, a film produced by a casting method or the like in which molecular orientation is more difficult to promote can be suitably used as the protective layer, and in the casting method, it is necessary to pay attention not to cause unnecessary stress at the time of drawing and to increase the retardation value.

In addition, when the cast film is produced so as to have a thickness of 100 μm or less and a retardation of the above small value, the intrinsic birefringence value is easily kept small when the polyamide resin does not contain an aromatic component, and the increase in retardation value is easily suppressed even in a thermal bending process or the like described later.

Alternatively, in a method other than keeping the retardation value small, on the contrary, a protective layer having a retardation value extremely large, for example, 1300nm or more, preferably 2000nm or more, more preferably 3000nm or more is disposed on a convex surface after processing of the lens, and the phenomenon of "color unevenness" or "polarized light leakage" is made to be a problem hardly visible to the naked eye, and thus it is possible to cope therewith.

When the retardation value is extremely high in this manner, it is necessary to subject the protective layer containing a polyamide resin to a stretching treatment. In this case, a method of forming a protective film having a desired retardation value and thickness by stretching the sheet after molding to a certain thickness, for example, a thickness of 100 μm or more, preferably 150 μm or more, more preferably 200 μm or more, and still more preferably 300 μm or more by melt extrusion or the like is desired. In the present invention, the retardation value is an in-plane retardation value. It is within the knowledge of those skilled in the art to derive an in-plane retardation value from the refractive index in the slow axis direction, and the film thickness when splitting incident linearly polarized light into a slow axis and a fast axis. Wherein, in the present invention, the retardation value is a value measured at 590 nm. As the measurement apparatus, there is a delay measurement apparatus for an Otsuka type electronic measurement: RETS-100, and the like.

As a method for increasing the retardation value by stretching a film formed by the melt extrusion method, there are a drawing method in which the film is drawn while being stretched at the time of drawing, and an off-line stretching method in which the film is formed, wound into a roll, and then stretched.

In the melt extrusion molding method, the polyamide resin or the resin constituting the protective layer is melt-mixed by, for example, an extruder, and is extrusion-molded from a die (for example, a T die) and cooled to produce a polyamide sheet. The resin temperature at the time of melting and molding (melt molding) the polyamide resin or the resin constituting the protective layer may be selected from a temperature range of about 120 to 350 ℃, for example, about 130 to 300 ℃, preferably about 150 to 280 ℃, and more preferably about 160 to 250 ℃. In this case, the drawing speed is increased as compared with the speed of the cooling roll, thereby enabling the stretching process.

The specific method of stretching is not particularly limited as long as the performance of the functional sheet of the present invention is not impaired. In order to suppress uneven stretching, it is preferable that the rolls in the stretching section be heated appropriately by a die temperature controller or the like and the resin temperature be maintained at a constant level. Generally, stretching is performed in the vicinity of Tg of the polyamide resin to maintain the desired appearance of a sheet suitable for use as a solar mirror. When stretching is performed at a temperature lower than the Tg of the polyamide resin used, stretching unevenness, which tends to cause uneven stretching, occurs, and uneven patterns are generated in the stretched portions and the unstretched portions. Further, when stretching is performed in a temperature range higher than Tg, there are problems such that the polyamide film or sheet is easily welded to a roll, and a mark remains when the film or sheet is peeled from the roll. It is also necessary to select the conditions of the rolls and other temperature regulators by appropriately considering the relationship with the delay described later.

In addition, Tg as referred to herein means a temperature at the start point, the middle point, within the end point temperature, or at the middle point of a Tg curve measured by DSC.

The resin temperature of the protective layer sheet during stretching is also related to the retardation. When the stretching treatment is performed in a temperature range where the resin temperature of the film or sheet at the time of stretching is lower than Tg of the resin used, a higher retardation is easily imparted, and the retardation is less easily expressed as the temperature is higher. Further, it is preferable to cool the film as quickly as possible after the stretching, thereby making it possible to fix the retardation and the angle between the slow axis and the fast axis.

Further, when stretching is performed in a temperature range lower than Tg, there may be a problem that shrinkage or the like after sheet molding is affected, and therefore, it is necessary to select stretching temperature conditions in consideration of this point. Conversely, when stretching is performed at a resin temperature higher than Tg, the effect of sheet necking during stretching becomes large, which affects the thickness distribution and increases the variation in retardation and phase axis angle, and therefore care must be taken not to excessively increase the stretching magnification or the like.

When the protective layer is formed by stretching a polyamide resin molded by a melt extrusion method, it is desirable to use a polyamide resin containing an aromatic component. This increases the intrinsic birefringence of the resin, makes it easy to express a high retardation with a lower stress, and makes it easy to maintain the retardation even when the resin is stretched at a resin temperature higher than Tg.

As described above, the intrinsic birefringence value varies depending on the composition of the polyamide resin and also depends on the desired retardation value, and therefore, the stretching ratio in the stretching treatment must be appropriately adjusted. In general, the minimum amount is 1.1 times, preferably 1.2 times, and more preferably 1.3 times or more. Further, the higher the magnification, the more the necking is promoted, or the risk of breaking is generated, etc., and for these reasons, the upper limit is determined from the viewpoint of the production efficiency. Usually about 2.2 times, preferably about 2.0 times or less.

In the present invention, it was found that the gas barrier property of the protective layer comprising a polyamide resin has a large relationship with the generation of bubbles. As described in the technical problem, it is considered that the main cause of the generation of bubbles is presumably gas generated after the protective layer, the adhesive layer, and the functional layer are laminated.

The protective layer comprising a polyamide resin has a high gas barrier property as compared with an aromatic polycarbonate resin which has been conventionally used as a protective layer for a polarizing sheet for a sunglass. In particular, the structure of the polyamide resin is a polyamide containing a polymer having high regularity, for example, terephthalic acid (1, 4-benzenedicarboxylate) or 1, 4-diaminobenzene as a monomer, and the polyamide resin is bonded in a flat plate shape and arranged on the same plane, and tends to have high gas barrier properties because it is easy to produce an aggregate having high regularity and small gas permeability. The composition of the polyamide resin sheet must also be selected in consideration of this point.

Further, the gas barrier properties of the protective layer are, of course, greatly influenced by the thickness of the protective layer and the conditions of the stretching treatment. Even in a protective layer having gas barrier properties to the extent that bubbles are not generated in an unstretched state, the higher the stretch ratio, the more the molecular orientation is promoted, and in a protective layer cooled and fixed in such a state, gas barrier properties such as bubbles are generated in some cases.

Further, the gas barrier properties include several indexes in addition to the oxygen permeability and the water vapor permeability, and in the present invention, the oxygen permeability is adopted in the present invention because the correlation between the oxygen permeability and the generation of bubbles is found. The evaluation method of oxygen permeability is based on DIS/ISO 15105-1.

From the above description, it is important in the present invention to use a protective layer exhibiting a certain or more oxygen permeability, and the thickness of the protective layer and the degree of stretching may be determined in consideration of the specification and oxygen permeability of the final product.

In the present invention, the oxygen permeability of the protective layer is 10cm at 23 ℃ and 85% RH³/m²When the pressure was about 24 hr/bar, generation of bubbles was remarkable, and the sheet could not be used as a functional sheet.

In suppressing the generation of bubbles, it is desirable that the oxygen permeability of the protective layer is 50cm³/m²60cm at a height of more than 24hr and bar³/m²70cm at a length of more than 24hr and bar³/m²More than 24hr and bar, 90cm³/m²Over 24hr bar, 110cm³/m²130cm at a height of over 24hr bar³/m²24 hr. bar or more, 150cm³/m²24 hr. bar or more. Alternatively, it may be 400cm³/m²More than 24hr and bar, 410cm³/m²420cm at least 24hr bar³/m²More than 24 hr.bar, 430cm³/m²24 hr. bar or more. However, the upper limit of the oxygen permeability of the protective layer is not particularly important as long as the protective layer can form a good lens according to the gist of the present invention. The resin composition, the thickness of the protective layer, the stretching treatment, and other conditions need to be selected in consideration of these points.

(preparation of functional sheet)

The functional sheet can be formed by applying the adhesive layer using the polarizing film layer as a functional layer by gravure coating or die coating, bonding the protective layer to both surfaces, and cutting the sheet to a desired length. The laminating method is not particularly limited, and a sufficient discharge amount is maintained in order to avoid entrainment of air bubbles due to insufficient coating liquid when the adhesive is applied. Further, it is desirable to appropriately adjust the tension at the time of bonding, the nip pressure of the bonding roller, and the like in consideration of the warp state of the sheet after bonding and the like.

(production of functional lens)

Next, the functional sheet is punched into individual lens sheets, the obtained individual lens sheets are subjected to curved surface processing, and if necessary, the lens sheets are inserted into an injection molding machine, and a thermoplastic resin is injected into the concave surface side of the individual lens sheets to form functional lenses.

The punching process may generally use a punching blade formed of a thomson blade. A plurality of individual lens sheets are generally obtained from 1 functional sheet by press working. The shape of the sheet for an individual lens is appropriately selected depending on the shape of the final product (sunglasses, goggles, etc.). The standard lens-shaped product for binocular use is a disk having a diameter of 80mm or a strip shape in which both ends are cut to have the same width in a direction perpendicular to the polarizing axis.

In the above-mentioned press working, it has been studied to prevent the polarizing film layer, the adhesive layer, the protective layers on both surfaces, and the protective films on both surfaces from being largely broken, to prevent the occurrence of fine broken sheets, cracks propagating in the stretching direction, excessive strain elongation, and the like, and to have appropriate toughness. In this case, a method of appropriately using a material after moisture absorption is also recommended in order to prevent the polarizing film layer from being broken by drying and pressing and to generate a finely broken sheet.

Next, the single lens sheet is subjected to a preliminary drying treatment, and then thermally bent into a spherical surface or an aspherical surface under heating to form a thermally bent sheet. In the pre-drying, conditions under which the color does not change are selected after the individual lens sheet is subjected to the thermal bending process. The air-drying is usually carried out at 60 to 80 ℃ and preferably 65 to 75 ℃ for 8 hours or more and preferably about 24 hours.

The individual lenses are bent along the mold surface by a thermal bending process of the sheet material. The mold may also be a mold for injection molding. The thermal bending process generally forms a planar sheet for a single lens into a three-dimensional curved surface such as a partially spherical surface or an ellipsoidal surface as required. Since such processing with the minimum energy accompanying deformation is processing accompanied by shrinkage, and if smooth shrinkage of the sheet is hindered, waviness and wrinkles occur, and a good product cannot be produced, it is preferable to control the temperature, load, and the like by a gradual excessive load in order to ensure smooth shrinkage of the sheet.

The heating temperature is selected to be not less than 50 ℃ (Tg-50 ℃) lower than the glass transition temperature of the polyamide resin used for the protective sheet, but less than the glass transition temperature (Tg) as the processing temperature. Preferably, the temperature is not lower than 25 ℃ lower than the glass transition temperature of the polyamide resin (Tg-25 ℃), more preferably not lower than 20 ℃ lower than the glass transition temperature of the polyamide resin (Tg-20 ℃) and not higher than 5 ℃ lower than the glass transition temperature of the polyamide resin (Tg-5 ℃).

The processing conditions during injection molding must be such that a lens having excellent appearance can be produced. Therefore, injection conditions, such as injection pressure, holding pressure, metering, molding cycle, etc., under which a lens molded article having a high filling rate can be obtained without flash are appropriately selected. The resin temperature also depends on the melting temperature of the polyamide resin and the composition of the polyamide resin, and is usually appropriately selected from 230 to 320 ℃, preferably 250 to 300 ℃. The injection pressure is suitably selected from 50 to 200 MPa.

The mold temperature is selected from a temperature not lower than 100 ℃ lower than Tg of the polyamide resin (Tg-100 ℃) and lower than Tg, and is preferably 70 to 120 ℃.

The thermoplastic resin used for injection molding is preferably a polyamide resin, more preferably a polyamide resin called amorphous polyamide. The thermoplastic polyamide resin may be any one that exhibits melt fluidity enough to be molded at a temperature not higher than the thermal decomposition temperature and has an appropriate Tg (glass transition temperature), but it is preferable to select a polyamide resin having a refractive index equal to or close to that of the polyamide resin used for the functional sheet so as not to impair the appearance of the interface with the functional sheet.

The functional lens manufactured as described above is subjected to a hard coating treatment as appropriate, and then subjected to a mirror coating, an antireflection coating, or the like to produce a product.

The hard coat layer is preferably fired at a temperature which is 50 ℃ or higher and lower than the glass transition temperature of the polyamide resin, more preferably 40 ℃ or higher and lower than the glass transition temperature by 15 ℃ (Tg-15 ℃) and most preferably at a temperature as low as 30 ℃ (Tg-30 ℃) from the viewpoint of the appearance, the polyamide resin used as a substrate, and the inorganic layer such as a mirror coating layer or an antireflection coating layer to be applied next. The hard coating layer is fired for about 0.5 to 2 hours.

The functional lens manufactured as described above is manufactured by a lens manufacturer into sunglasses, goggles, and the like as final products and sold, and lens processing for various products such as grinding, punching, and bolt fastening is performed in individual sales stores (retail stores) to manufacture sunglasses, goggles, and the like and sell them.