JP5592445B2 - Production method of transparent film - Google Patents

Description

  The present invention relates to a method for producing a transparent film, and more particularly to a method for producing a transparent film suitable for optical use in which a liquid photocurable resin composition is cured by ultraviolet irradiation to form a transparent cured film. .

  Transparent resin films have been widely used in fields where glass has been used in recent years because they have excellent optical properties and are harder to break than glass. Resin films are roughly classified into thermoplastic films and curable films by heat or light, and curable resins are expected to be applied to new fields of use because of their high heat resistance. In particular, with the miniaturization of electronic devices and the like, development of a thin transparent film material has been desired.

  Until now, several methods have been proposed for the production of transparent plates and transparent films using photocurable resins. For example, JP-A-8-132455 (Patent Document 1) proposes a method for producing a methacrylic resin cast plate by injecting a polymerizable monomer into a cell. This method is a so-called cell casting method, but it is inefficient in that it cannot manufacture a plate continuously because of the batch method, and it is difficult to apply it to the production of thin film materials. It was.

  On the other hand, in JP-A-4-80007 (Patent Document 2) and JP-A-2002-22940 (Patent Document 3), a liquid polymer solution made of an ultraviolet curable resin is cast on a steel belt, and thereafter A method for producing an optical film to be irradiated with ultraviolet rays is shown. However, when photocuring resin on a steel belt is cured, the distribution of the reaction may cause a distribution of the curing rate in the thickness direction, resulting in non-uniform physical properties. When using a steel belt In some cases, when the film is separated from the film, if the strength of the cured film is weak, cracking may occur.

  In addition, a polyester film is used for the base material on which the photo-curable resin is applied, an ultraviolet curable resin is applied, and a sheet base material optionally subjected to surface treatment is overlapped with the polyester film, and ultraviolet rays are irradiated from both sides to cure. A method for peeling the polyester film later is disclosed in JP-A-60-1972270 (Patent Document 4). When photocuring is performed by this method, the uniformity of the curing rate of the cured film is achieved, and a film excellent in quality can be obtained. However, a base film such as a polyester film or a cover film (abbreviated as a base film) ) Has been pointed out to cause deflection and distortion (hereinafter also referred to as swell). The occurrence of such deflection and distortion makes it difficult to peel the base film and the like on one side, and it has been desired to improve it. In addition, it is conceivable that the material of the base film or the like is made of glass. However, since glass cannot be bent into a curved surface, it is difficult to apply it to a method for producing a continuous film in a band shape.

JP-A-8-132455 Japanese Patent Laid-Open No. 4-80007 JP 2002-22940 A JP 60-197270 A

  The present invention has been made in view of the above-described problems of the prior art. In the method for producing a transparent film using a photocurable resin, the uniformity of physical properties is maintained by making the curing reaction rate in the transparent film uniform. In addition, the base and cover film can be stably peeled and removed by removing the deflection and distortion generated during photocuring with a slitter device, and the product film has excellent winding stability thereafter. It aims at providing the method of manufacturing a transparent roll film continuously.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have cast a photocurable resin in the form of a film on a smooth transparent base film and laminated a smooth transparent cover film thereon. The present invention was completed by finding that the above-mentioned problems can be solved by irradiating ultraviolet rays and curing, and then cutting and removing the waviness portion of the film edge generated by the curing shrinkage of the photocurable resin with a slitting device. .

In the present invention, a liquid photocurable resin composition having a volume shrinkage of 3 to 10% between the start of the curing reaction and the end of the curing reaction with a reaction rate of 85% or more is formed on the transparent base film with a thickness of 0. A layer having a transparent layer formed on both sides of a photocurable resin layer by forming a photocurable resin layer by casting in a film form within a range of 0.03 to 0.4 mm and laminating a transparent cover film thereon. After forming the body, the photo-curable resin layer is cured by irradiating at least one surface of the layered body, and the end of the layered body is cut by a slitting device after the curing reaction is completed with a reaction rate of 85% or more. A method of producing a transparent film by cutting and removing,
The transparent cover film is the same material as the transparent base film, and is a film manufactured by a biaxial stretching method, and the temperature (T) at which the photocurable resin is cured by irradiating ultraviolet rays, The glass transition temperature (Tg) and melting temperature (Tm) of the transparent base film and the transparent cover film satisfy the condition represented by the formula: Tg + 50 ° C. ≦ T <Tm.
This is a method for producing a transparent film.

  In the present invention, in the method for producing a transparent film, after the photocurable resin layer is cured and the laminate end is cut and removed by a cutting slit device, one or both of the transparent base film and the transparent cover film are used. It is advantageous to further have a peeling step for continuously peeling the film, and it is also one of preferred embodiments to further have a step of continuously evaluating the physical properties of the obtained transparent film after the peeling step. . Here, as the photocurable resin composition, it is preferable to use a photocurable resin composition containing 3% by weight or more of a photocurable silicone resin.

  According to the method for producing a transparent film of the present invention, not only is the property and quality uniformity of the produced transparent film excellent, but also the undulating portion of the film edge generated by the curing shrinkage of the photocurable resin is cut and removed. Thus, the base and the cover film can be peeled and removed stably, and the product film is also excellent in winding stability. Therefore, the transparent film manufactured by this invention is used suitably as an optical film, a transparent substrate, etc., such as a liquid crystal display, a touch panel, a film with a transparent electrode, and a lens sheet. Therefore, the present invention capable of efficiently obtaining such a transparent resin film has extremely high industrial utility value.

It is the schematic which shows an example of the apparatus used for the manufacturing method of the transparent film of this invention.

  Hereinafter, a preferred embodiment of the method for producing a transparent film of the present invention will be described in detail with reference to the accompanying drawings as necessary.

  FIG. 1 is a schematic view showing an example of an apparatus used in the method for producing a transparent film of the present invention. In this invention, the liquid photocurable resin composition used as the raw material of a transparent film is cast on a transparent base film in a film form. In FIG. 1, for example, the photocurable resin composition is supplied from the coating head 2 to the transparent base film 1 by a certain amount. The transparent base film 1 is a rolled polyester film or the like, and can be made suitable for a continuous process by continuously pulling it out at a constant speed.

  As the photocurable resin used for the photocurable resin composition, a liquid resin having photocurability and fluidity or plasticity is used. The photocurable resin is a resin that can be cured by irradiating ultraviolet rays, and is not limited except that the curing shrinkage before and after curing is within a certain range. That is, the present invention casts a photocurable resin composition on a transparent base film, and suppresses and removes deflection and distortion that occur when curing, thereby producing a flat roll film. Therefore, it is necessary to use a photocuring resin having a volume shrinkage before and after curing in the range of 3 to 10%. When the value of the volume shrinkage rate is less than 3%, it is difficult to cause a problem, but since it is difficult for deflection and distortion itself to occur, the necessity of performing end cutting of the laminated body according to the present invention is low. On the other hand, if the value of the volume shrinkage rate exceeds 10%, not only the end portion of the laminated body but also the whole laminated body is deformed, so that it is impossible to stably produce a flat roll film. The volume shrinkage referred to in the present invention can be determined, for example, by measuring the density of the photocurable resin before and after curing. The volume shrinkage varies depending on the reaction rate of the photocurable resin, and the volume shrinkage defined in the present invention means a value with a reaction rate of 85% or more.

  A preferable photocurable resin composition is a photocurable resin containing 3% by weight or more, preferably 5 to 30% by weight, of a photocurable silicone resin. Examples of the photocurable silicone resin include siloxane resins having a functional group such as a double bond. Examples of other components include (meth) acrylate, polyfunctional (meth) acrylate, and epoxy. Furthermore, a filler additive may be added to the photocurable resin as long as the photocurability is not inhibited.

  A photopolymerization initiator is usually blended in the photocurable resin composition. In the present invention, an appropriate solvent can be used as a diluent, and the viscosity of the photocurable resin composition can be adjusted. However, in that case, it takes time to consider the solvent devolatilization process, and the production efficiency is reduced. Residual light is present in the cured film due to the presence of residual solvent and the like. In the curable resin composition, the content of the solvent is preferably kept at 5% or less, and it is preferable to use a material that does not substantially contain the solvent. That is, in the present invention, when the transparent cover film 3 is laminated, it is preferable that the photocurable resin layer is substantially free of a solvent.

  The thickness of the photocurable resin layer on the transparent base film 1 needs to be in the range of 0.03 to 0.4 mm. If the thickness of the photocurable resin layer is less than 0.03 mm, the uniformity of the coating thickness may be impaired, and the transparent film is easily damaged when the transparent base film or the like is peeled off. On the other hand, if the thickness of the photocurable resin layer exceeds 0.4 mm, the transparent film may be damaged during winding of the roll.

  Since the photocurable resin composition is in a liquid state, it can be applied with a known coating apparatus. However, if a curing reaction is caused in the coating head 2, gel-like deposits cause streaks and foreign matter. It is desirable not to be exposed to ultraviolet rays. Moreover, in order not to advance hardening of photocurable resin, it is preferable to perform this process in the range of 5-50 degreeC preferably. As the coating method, known methods such as gravure coating, roll coating, reverse coating, knife coating, die coating, lip coating, doctor coating, extrusion coating, slide coating, wire bar coating, curtain coating, extrusion coating, spinner coating, etc. is there.

  As the transparent base film 1, a film of polyester, polypropylene, polyethylene, acetate, acrylic, vinyl fluoride, polycarbonate, polyamide, polyarylate, cellophane, polyethersulfone, norbornene resin or the like alone or in combination of two or more types Can be used. Among these, a polyester film excellent in heat resistance and transparency and balanced in other characteristics is preferable.

  The light transmittance of the transparent base film is preferably 80% or more, and more preferably 85% or more. The thickness of the transparent base film is not particularly limited, but is preferably 10 to 400 μm, particularly preferably 50 to 300 μm. Even if the surface shape is flat, the surface may be uneven. However, a surface shape that does not hinder transparency is preferable. If the thickness of the transparent base film is less than 10 μm, it may not be able to withstand the tension for use in the production method of the present invention, and the deflection and distortion of the laminate produced in the production process will increase. Probability is high. On the other hand, if the thickness of the transparent base film exceeds 400 μm, the transmittance decreases, so the amount of ultraviolet energy applied to the photocurable resin decreases, and the photocurable resin may not be sufficiently cured.

  In this invention, after casting a photocurable resin composition to predetermined thickness on a transparent base film, the transparent cover film 3 is laminated | stacked on a photocurable resin layer before ultraviolet irradiation. Examples of the transparent cover film 3 that can be used include those listed as the transparent base film 1 described above, and the same film can be used. The transparent cover film 3 desirably has the same characteristics as the transparent base film 1, and from such a viewpoint, a polyester film having a light transmittance of 80% or more and a thickness of 10 to 400 μm is preferable.

Through the above steps, a laminated body in which the transparent base film 1, the photocurable resin layer, and the transparent cover film 3 are sequentially laminated is formed. In the present invention, the transparent base film or the like is subsequently applied to the photocurable resin layer. Then, ultraviolet rays are irradiated from at least one surface of the photocurable resin layer. Such ultraviolet irradiation is achieved by generating ultraviolet rays using the ultraviolet lamp 4 and irradiating the ultraviolet rays. Examples of the ultraviolet lamp 4 include a metal halide lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a pulse type xenon lamp, a xenon / mercury mixed lamp, a low-pressure sterilization lamp, and an electrodeless lamp, all of which can be used. Among these ultraviolet lamps 4, a metal halide lamp or a high-pressure mercury lamp is preferable. Irradiation conditions vary depending on individual lamps conditions, it is preferable that the amount of irradiation exposure is about 20~10000mJ / cm ^2, and more preferably about 100~10000mJ / cm ^2.

  The ultraviolet lamp 4 is preferably provided with an elliptical, parabolic, diffusing or the like reflecting plate for effective use of light energy. Further, a heat cut filter may be attached as a cooling measure.

  Moreover, it is preferable to have the heating / cooling device 5 in the ultraviolet irradiation location. The heating / cooling device 5 heats and cools the laminated body together with the heat generated from the ultraviolet lamp 4, and controls the temperature (T) at which the photo-curable resin is cured by ultraviolet irradiation, so that a transparent base film, etc. The thermal deformation of can be suppressed. As the cooling method, there are known methods such as an air cooling method and a water cooling method.

  When the transparent base film and the transparent cover film are films produced by a biaxial stretching method, the temperature (T) for curing the photocurable resin by the ultraviolet irradiation is the glass transition of the transparent base film and the transparent cover film. It is necessary to satisfy the condition represented by the formula: Tg + 50 ° C. ≦ T <Tm with respect to the temperature (Tg) and the melting temperature (Tm).

  Furthermore, the transparent base film and the transparent cover film are required to be the same material in order to efficiently suppress thermal deformation such as swell during photocuring or after curing.

  When the temperature (T) for curing the photocurable resin by ultraviolet irradiation is less than 20 ° C., the curing rate of the photocurable resin becomes extremely slow, and an enormous amount of ultraviolet irradiation is required, which hinders productivity. That is not preferable. In addition, when the curing temperature (T) is within the range of Tg <T <Tg + 50 ° C., the difference in linear expansion coefficient (CTE) with the photocurable resin increases with the occurrence of thermal shrinkage in the transparent base film and the transparent cover film, In particular, it is not preferable because waviness is noticeably generated at the end of the width direction film.

  In addition, when the transparent base film and the transparent cover film are manufactured by the biaxial stretching method, thermal shrinkage of the transparent base film and the transparent cover film occurs when the curing temperature (T) is in the range of Tg + 50 ≦ T <Tm. However, as a result, the difference in the amount of deformation from the photocurable resin tends to be reduced, and in particular, the waviness at the end of the width direction film is suppressed. On the other hand, when the curing temperature (T) is equal to or higher than the melting temperature (Tm) of the transparent base film and the transparent cover film, the transparent base film or the transparent cover film is melt-ruptured, making the production of the transparent film difficult. .

  Since the ultraviolet curing reaction is a radical reaction, it is inhibited by oxygen. Therefore, the ultraviolet light irradiation zone, that is, the surface of the liquid photocurable resin as a raw material sandwiched and cast between the transparent base film and the transparent cover film has oxygen. The concentration is preferably 1% or less, and more preferably 0.1% or less. In order to reduce the oxygen concentration, it is necessary to employ a film having no pores on the surface such as a transparent base film and having a low oxygen permeability.

  Thus, although a photocurable resin layer is hardened and it is set as a transparent film, in this invention, since volatile components, such as a solvent, are hardly contained in a raw material, the transparent film of thickness equivalent to application | coating thickness is formed. Here, the end of the laminated body after photocuring has a non-uniform shape, and the film end is wavy due to curing shrinkage. In the present invention, the end of the laminate is cut and removed by the cutting slit device 6 in order to adjust the shape of the end of the laminate and remove the waviness. Such a phenomenon is more likely to occur as the width of the laminated body becomes wider, and the width of the laminated body is in the range of 50 to 1500 mm. And it is preferable to perform the cut of an edge part in the range of 1 to 10% of the whole width. In the present invention, it is possible to stably peel off the transparent base film and / or the transparent cover film on both sides of the laminated body by cutting and removing the end of the laminated body. It becomes favorable and can perform continuous manufacture of a transparent film smoothly.

  As a method for cutting the resin at the end of the laminated body, there are known methods such as a sawing method, a contour machine method, a shearing method, a lathe method, a gas cutting method, a laser cutting method, a plasma cutting method, and a water jet cutting method.

  The laminated body from which the end of the laminated body is cut and removed still has a transparent base film and a transparent cover film on both sides thereof, and a film (transparent base film) on at least one side of the laminated body for commercialization as a transparent film 10. And / or the transparent cover film) is preferably peeled off. Such peeling is preferably performed by an apparatus having a winding device mechanism and a mechanism for controlling the speed and tension at the time of peeling. For example, the transparent base film 1 peeled off from the transparent film can be wound into a roll via the base film winding unit 8. Similarly, the transparent cover film 3 peeled off from the transparent film can be wound up in a roll shape via the cover film winding portion 7.

  In the present invention, after peeling the transparent base film or the like, it is advantageous to continuously measure (physical property evaluation) the physical properties and quality of the transparent film formed of the photocurable resin before winding the transparent film. . As a result, it is possible to continuously perform processes from manufacturing to product quality control. The physical property evaluation device 9 used for the measurement includes a reaction rate measuring device using an infrared absorption device, a light transmittance measuring device using a spectrophotometer, a surface defect detecting device using laser reflection, a film thickness detecting device using a laser displacement meter, and the like. Yes, as long as it is a physical property and quality measuring device for the film, it is not limited to these. Here, when measuring the light transmittance of the transparent film itself, the transparent cover film or the like hinders the measurement, so that the transparent base film and the transparent cover film on both sides are previously peeled off by the peeling step. Is preferred.

  In the present invention, from the above-described drawing of the transparent base film and the like, starting with the application of a photocurable resin, it is possible to continuously perform the cut and removal of the end of the laminate, preferably the physical property evaluation. It can be set as the product of the transparent film wound up by roll shape. In addition, although this invention is characterized by being able to manufacture a transparent film continuously, it is not disturbed once winding in roll shape in arbitrary positions and moving to another process. That is, in the present invention, for example, a laminate in which the photocurable resin layer is cured from the transparent base film drawn out can be manufactured, and this can be achieved by winding it into a roll. In this case, it is necessary to draw the laminate again from the roll, cut and remove the end of the laminate, and wind it up. As the installation environment of the manufacturing apparatus used in the present invention, a clean room environment is preferable because there is a concern of foreign matter contamination, but it is sufficient if consideration is given to exhaust and intake environment such as foreign matter contamination around the device. is there.

  Hereinafter, although the manufacturing method of the transparent film of this invention is demonstrated in detail based on an Example, this invention is not limited to the following Example. In the examples, “part” represents “part by weight”.

(Reference Example 1)
80 parts of trimethylolpropane triacrylate (KS-TMPTA manufactured by Nippon Kayaku Co., Ltd.), 20 parts of phenylsilsesquioxane oligomer containing methacrylic group, 2.5 parts of hydroxycyclohexyl phenyl ketone (IRGACURE 184 manufactured by Ciba Specialty Chemicals) After uniformly stirring and mixing, defoaming was performed to obtain a liquid photocurable resin composition. In addition, it was 5.0% when the cure shrinkage rate of the photocurable resin composition was measured. A transparent base film (polyethylene terephthalate biaxially stretched film, width 600 mm, thickness 100 μm, light transmittance of 90% or more) which is charged into a coating apparatus using this photocurable resin composition as a raw material and unwound at a rate of 1 m / min. , Tg 80 ° C., Tm 250 ° C.). A transparent cover film (polyethylene terephthalate biaxially stretched film, width 600 mm, thickness 100 μm, light transmittance 90% or more, Tg 80 ° C., Tm 250 ° C.) is pressure-bonded to the coating resin, and then kept at 45 ° C. The lamp was irradiated with ultraviolet rays at a rate of 500 mJ / cm ² . The cured transparent film had a thickness of 200 μm and a width of 500 mm.

  Then, the deflection | deviation at the time of hardening generate | occur | produced in the area | region to 25 mm from the transparent film edge part of the three-layer film of a transparent base film-transparent film-transparent cover film, The deflection | deviation generation | occurrence | production part was removed by the laser cutting method. And the transparent base film and the transparent cover film were peeled from the transparent film with those winding apparatuses, and the desired transparent film (photocuring resin film) without a bending was obtained. Then, in the pre-process which winds up the obtained transparent film in roll shape, the light transmittance measurement was performed with the spectrophotometer, and the transparent film was wound up in roll shape after the measurement. As a result of evaluating the obtained transparent film, the light transmittance was 85% or more. Moreover, the reaction rate measurement with an infrared absorption device was 85% or more, and the reaction rate profile result in the depth direction of the transparent film by Raman spectroscopic measurement was 85% or more, and a uniform result was obtained.

Example 1
A transparent film having a thickness of 200 μm and a width of 500 mm was obtained in the same manner as in Reference Example 1 except that ultraviolet rays were irradiated with a metal halide lamp while maintaining the temperature during ultraviolet irradiation at 160 ° C. The amount of ultraviolet irradiation at this time was 500 mJ / cm ² . The reaction rate measurement was 85% or more, and a uniform transparent film was obtained with a reaction rate profile of the photocured resin film in the depth direction measured by Raman spectroscopy.

(Comparative Example 1)
A transparent film having a thickness of 200 μm and a width of 500 mm was obtained in the same manner as in Reference Example 1 except that ultraviolet rays were irradiated with a metal halide lamp while maintaining the temperature during ultraviolet irradiation at 95 ° C. The amount of ultraviolet irradiation at this time was 500 mJ / cm ² . The reaction rate measurement was 85% or more, and a uniform transparent film was obtained with a reaction rate profile of the photocured resin film in the depth direction measured by Raman spectroscopy.

(Evaluation of deflection)
About the transparent film produced in Example 1, Reference Example 1 and Comparative Example 1 (however, the one in which the transparent base film and the transparent cover film were peeled off without removing the deflection portion) was used from both ends in the width direction. The shape was observed as follows until the transparent film was judged as an acceptable product with no waviness deformation while being cut by 5 mm. That is, when the transparent film with both ends cut is left on a smooth surface and observed from the side, the transparent film at the time when the floating from the smooth surface becomes invisible is not swelled (bent) and is a product (accepted product). ) And the maximum width was examined. The results are shown in Table 1 below.

  As described above, according to the method for producing a transparent film of the present invention, not only the physical properties and quality uniformity of the produced transparent film are excellent, but also the film end portion generated by the curing shrinkage of the photocurable resin. By cutting and removing the waviness portion, the base and the cover film can be peeled and removed stably, and the product film is also excellent in winding stability. Therefore, the present invention is effectively used when a thin optical film or the like of 0.4 mm or less is continuously produced using a photocurable resin. Further, the transparent film produced according to the present invention has many fields where transparency, surface hardness, heat resistance, and smoothness are required. Specifically, a lens, a display substrate, an optical waveguide, a solar cell substrate, Used for various applications such as optical disks.

  1: base film unwinding part, 2: coating head, 3: cover film unwinding part, 4: ultraviolet lamp, 5: cooling device, 6: edge slit device, 7: cover film winding part, 8: base Film winding part, 9: physical property evaluation apparatus, 10: transparent film winding part.

Claims (4)

On the transparent base film, a liquid photocurable resin composition having a volume shrinkage of 3 to 10% between the start of the curing reaction and the end of the curing reaction with a reaction rate of 85% or more is formed in a thickness of 0.03 to 0. After forming a photocurable resin layer by casting in the form of a film in the range of 4 mm and laminating a transparent cover film thereon to form a laminate having transparent layers on both sides of the photocurable resin layer The photocurable resin layer is cured by irradiating at least one surface of the laminate with an ultraviolet ray, and after completion of the curing reaction to achieve a reaction rate of 85% or more, the end of the laminate is cut and removed by a cutting slit device. A method for producing a transparent film,
The transparent cover film is the same material as the transparent base film, and is a film manufactured by a biaxial stretching method, and the temperature (T) at which the photocurable resin is cured by irradiating ultraviolet rays, The glass transition temperature (Tg) and melting temperature (Tm) of the transparent base film and the transparent cover film satisfy the condition represented by the formula: Tg + 50 ° C. ≦ T <Tm.
A method for producing a transparent film.   The method further comprises a peeling step of continuously peeling one or both of the transparent base film and the transparent cover film after curing the photocurable resin layer and cutting and removing the end of the laminated body with a cutting slit device. The method for producing a transparent film according to claim 1.   The method for producing a transparent film according to claim 2, further comprising a step of continuously evaluating the physical properties of the obtained transparent film after the peeling step.   The production of a transparent film according to any one of claims 1 to 3, wherein the photocurable resin composition contains 3 wt% or more of a photocurable silicone resin. Method.

Images