JP5050960B2 - Release film and laminate - Google Patents

Description

  The present invention relates to a release film provided with a release layer on at least one surface of a film substrate, and more specifically, a release film for a display member such as a liquid crystal polarizing plate, a plasma display panel (PDP), or an organic EL, or an adhesive for external application. The present invention relates to a medical release film.

  Conventionally, a release film having a release layer provided on at least one surface of a film substrate is a protective film such as a ceramic green sheet, an adhesive label, an adhesive film, a liquid crystal polarizing plate, a PDP, an organic EL component with adhesive, such as an organic EL It is widely used as a separator film for medical films such as separator films and adhesive-type external medicines. The release film has a structure in which a release layer made of a silicone resin is applied and formed on at least one surface of a film substrate.

Japanese Patent Laid-Open No. 11-3008897 JP-A-9-156060

  In recent years, with the increase in size and definition of liquid crystal displays and the like, the required quality regarding foreign matters and appearance characteristics has become stricter, and a release sheet is used as a protective film for optical members such as an adhesive polarizing plate and a retardation film. In some cases, it is required that there is little foreign matter on the release film and no foreign matter. When foreign matter exists on the optical member, display failure may occur.

  In addition, even when a release film is attached to a medical sheet such as a patch-type external medicine, it is similarly required that there are few foreign objects on the release film and there are no foreign objects. Furthermore, even when a release film is bonded to an adhesive layer such as an adhesive label or an adhesive film, it is required that there are few foreign substances on the release film and there are no foreign substances.

  For the inspection of the foreign matter and defects of the release film, the foreign matter inspection by image analysis using a camera or the like is performed inline or offline after the step of applying a silicone release layer to the substrate and then heat-curing. In some cases, visual inspection is performed. In addition, foreign matter inspection and defect inspection may be performed in a state where a release film is stuck on an adhesive product.

  In this inspection, there has been a problem that a normal inspection cannot be performed when a foreign object inspection is performed by an inspection apparatus. In addition, in the case of a visual inspection by a person, problems such as an inspector causing sickness to inspection, fatigue of eyes, and work efficiency may occur.

  In the case of a release film, a print layer may be provided between the opposite surface of the film substrate or between the film substrate and the release layer, and display properties and design properties may be imparted, particularly in the case of a medical film, A printed layer may be provided to display the name of a drug, precautions, a logo mark, and the like. At this time, there is a problem that the display is difficult to read and the design property is remarkably deteriorated.

  The present invention is a release film in which a release layer is formed on at least one side of a film substrate, while exhibiting the release characteristics of the release film, allowing easy inspection of foreign matter defects, and providing a design layer when a print layer is provided. Another object is to provide an excellent release film.

  When the reflected light is strongly confirmed on the release layer side surface of the release film, or when the reflected light has a tint, or when the reflected light has color unevenness, the foreign matter inspection becomes difficult. The present inventors have found that the design properties are lowered and have solved the above problems.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a release film having a release layer on at least one surface of a film base material, wherein the refractive index of the release layer and the refractive index of the film base material The release film was characterized in that the difference was within 5% of the refractive index of the film substrate.

  The invention according to claim 2 is the release film according to claim 1, wherein the release layer contains metal oxide particles.

  The invention according to claim 3 is the release film according to claim 1 or 2, wherein the release layer contains a metal chelate compound.

The invention according to claim 4 is characterized in that the release film reflection hue on the side provided with the release layer has an ab chroma (C ^* _ab ) of 10 or less in the L ^* a ^* b ^* color system. It was set as the peeling film in any one of Claim 1 thru | or 3.

  The invention according to claim 5 is the release film according to any one of claims 1 to 4, wherein the release film includes a printed layer.

  According to a sixth aspect of the present invention, the release film according to any one of the first to fifth aspects and the substrate are provided, and the release layer surface of the release film and the substrate surface are in contact with each other. A laminated body was obtained.

  By setting it as the peeling film of the said structure, there was no color nonuniformity, the foreign material defect inspection was easy, and when the printing layer was provided, it was able to be set as the peeling film excellent also in the design property.

FIG. 1 shows an explanatory cross-sectional view of the release film of the present invention.
In the release film 1 of the present invention, a release layer 12 is provided on at least one surface of a film substrate 11. The release layer 12 is provided on the outermost layer of the release film.

  In the peeling film of this invention, the difference of the refractive index of the film base material 11 and the refractive index of the peeling layer 12 is less than 5% of the refractive index of the said film base material, It is characterized by the above-mentioned. The present invention is characterized in that the refractive indexes of the film substrate and the release layer are substantially equal.

  When the difference in refractive index between the film substrate and the release layer exceeds 5%, the release layer functions as an optical interference layer. That is, interference between the light incident on the release film surface and the reflected light from the release layer surface and the reflected light from the release layer / base film interface occurs. And when a peeling layer functions as an optical interference layer, a peeling film will be tinged with color (interference color) by light interference.

  In the release film of the present invention, the release layer is formed by a wet film formation method. In the release layer formed by the wet film forming method, any in-plane film thickness variation occurs even if any wet film forming method is used.

  In the case of a release film when the release layer functions as an optical interference layer, the film has a tint (interference color) due to light interference, and the thickness of the release layer formed by the wet film formation method changes. The color changes accordingly. That is, in the case of a release film in which the difference in refractive index between the film substrate and the release layer exceeds 5% and the release layer functions as an optical interference layer, due to the film thickness variation of the release layer formed by the wet film formation method The color of the release layer (interference color) changes, resulting in a release film with interference unevenness and color unevenness. And the peeling film with uneven color becomes difficult to inspect for foreign matter defects, and the design is further deteriorated.

  In the release film of the present invention, the difference between the refractive index of the film substrate 11 and the refractive index of the release layer 12 is within 5% of the refractive index of the film substrate, whereby the release layer is colored (interference). Color) and a release film with less color unevenness (interference unevenness) due to fluctuations in the film thickness of the release film, easy foreign matter defect inspection, and excellent design A release film could be obtained.

  In the release film of the present invention, the difference in refractive index between the film substrate and the release layer is made substantially equal, so that the reflected light at the film substrate / release layer interface is reduced and the release film has less tint (interference color). Furthermore, it was possible to obtain a release film with little color unevenness (interference unevenness).

  In the present invention, the difference between the refractive index of the film substrate and the refractive index of the release layer is preferably as small as possible. Furthermore, the difference between the refractive index of the film substrate and the refractive index of the release layer is 3%. Is preferably within.

In addition, the refractive index difference of the refractive index ( _nsi ) of the peeling layer of this invention and the refractive index of a film base material ( _nf ) is calculated _| required by the following formula _| equation.

Refractive index difference (%) = (| n _si −n _f | / n _f ) × 100

  In the release film of the present invention, the refractive index of the release layer and the refractive index of the film substrate are determined by using a release film in which a matte black paint is applied to the surface of the film substrate on which the target release layer is not provided. The spectral reflectance curve can be measured with a spectrophotometer, and the film thickness of the release layer can be measured by cross-sectional observation, and the obtained spectral reflectance curve can be obtained by performing an optical simulation.

  Moreover, in this invention, it is preferable that a peeling layer contains metal oxide particle. In the release film of the present invention, the difference between the refractive index of the film base and the refractive index of the release layer is within 5% of the refractive index of the film base. Here, it is difficult to implement the present invention only by appropriately selecting the material used as the film substrate and the release layer forming material so that the difference in refractive index is within 5%. In the present invention, the difference between the refractive index of the film substrate and the refractive index of the release layer can be easily increased by using metal oxide particles as a refractive index adjusting agent in the release layer and increasing the refractive index of the release layer. It becomes possible to make it within 5% of the refractive index of the film substrate.

  In the release film of the present invention, the release layer preferably contains a metal chelate compound. As in the case of metal oxide particles, a metal chelate compound is added to the release layer as a refractive index adjusting agent, and the refractive index of the release layer is easily increased by increasing the refractive index of the release layer. Can be within 5% of the refractive index of the film substrate.

In the release film of the present invention, the release film reflection hue on the side provided with the release layer preferably has an ab chroma (C ^* _ab ) of 10 or less in the L ^* a ^* b ^* color system. . In the L ^* a ^* b ^* color system, ab chroma (C ^* _ab ) is obtained by the following equation.

_{^{C * ab = ((a *}} ) 2 + (b *) 2) 1/2

By setting the ab chroma (C ^* _ab ) to a release film of 10 or less, it is possible to obtain a release film with less color and less color unevenness.

  The reflective hue of the surface of the release film on the side provided with the release layer in the present invention is measured with a spectrophotometer after applying a matte black paint on the surface of the film substrate on which the target release layer is not provided. The The reflection hue of the release film of the present invention is determined under the condition of a 2-degree visual field using a C light source as the light source, with the incident angle set to 5 degrees from the direction perpendicular to the antireflection film surface.

  FIG. 2 shows an explanatory cross-sectional view of another embodiment of the release film of the present invention. In the release film of the present invention, as shown in FIG. 2A, the print layer 13 may be provided on the surface of the film base 11 on the side where the release layer 12 is not provided. Moreover, in the peeling film of this invention, as shown in FIG.2 (b), you may provide the printing layer 13 between the peeling layer 12 and the film base material 11. FIG.

  When the release film of the present invention is provided with a printed layer as shown in FIGS. 2A and 2B, a particularly great effect can be obtained. In other words, the release film provided with the print layer of the present invention has less color caused by optical interference of the release layer, so that the design of the print layer is not deteriorated, and the release layer is formed by a wet film formation method. Since there is little color unevenness generated by the in-plane variation of the film thickness, it is possible to obtain a release film having high designability without deteriorating the design of the printed layer.

  FIG. 3 shows an explanatory sectional view of another embodiment of the release film of the present invention. In the release film of the present invention, an anchor layer 14 may be provided between the release layer 12 and the base film 11 to improve adhesion as shown in FIG. The anchor layer is formed by a wet film formation method in the same manner as the release layer.

  However, in providing the anchor layer in the release film of the present invention, it is preferable to provide the anchor layer so as not to affect the optical properties of the release film. In other words, for light incident on the release film surface, color (interference color) and color unevenness (interference unevenness) due to interference between reflected light at the peel layer / anchor layer interface and reflected light at the anchor layer / film substrate interface. It is preferable to provide an anchor layer so that there is little. Specifically, the difference between the refractive index of the release layer and the refractive index of the anchor layer is within 5% of the refractive index of the anchor layer, and the difference between the refractive index of the anchor layer and the refractive index of the film substrate is the refractive index of the film. By setting it within 5% of the rate, it is possible to suppress the occurrence of color and color unevenness due to the provision of the anchor layer. Alternatively, the thickness of the anchor layer is set to 3 nm or more and 30 nm or less, and the occurrence of color and color unevenness due to the provision of the anchor layer by reducing the thickness of the anchor layer can be suppressed.

  FIG. 4 is a cross-sectional explanatory view of the laminate of the present invention. In the laminate of the present invention, the surface of the release layer 13 of the release film is in contact with one surface of the substrate 2. Examples of the substrate include those having an adhesive layer on the surface, and the adhesive layer of the substrate 2 is bonded to the release layer of the release film 1 in order to maintain the adhesiveness.

  As the substrate, a pressure-sensitive adhesive tape, a pressure-sensitive adhesive sheet, a liquid crystal polarizing plate having a pressure-sensitive adhesive layer, a plasma display panel (PDP), a display member such as an organic EL, a medical sheet such as a sticking external medicine, a medical film, or the like is used. be able to.

  FIG. 4 shows a cross-sectional explanatory view of the laminate of the present invention. In the laminate of the present invention, the surface of the substrate 2 formed by contacting the release film surface 1 of the release film and one surface of the substrate 2 maintains its adhesiveness or prevents foreign matter from adhering to the substrate surface. In order to prevent this, it is bonded to the release layer of the release film 1.

  As the substrate, a pressure-sensitive adhesive tape and a pressure-sensitive adhesive sheet, a liquid crystal polarizing plate, a plasma display panel (PDP), a display member such as an organic EL, a medical sheet such as a patch-type external medicine, a medical film, or the like can be used. The release sheet of the present invention can be used as a protective film for maintaining the adhesiveness of the substrate and a protective film for preventing foreign matter from adhering to the surface of the substrate.

  Next, the manufacturing method of the peeling film of this invention is demonstrated.

  As a film base used for the release film of the present invention, a polyethylene film, a polypropylene film, a polyolefin film such as a stretched polypropylene (OPP) film, a polyethylene terephthalate (PET) film, a polyester film such as a polyethylene naphthalate film, Cellulose films such as triacetyl cellulose film, diacetyl cellulose film, cellophane film, polyamide films such as 6-nylon and 6,6-nylon, acrylic films such as polymethyl methacrylate film, polystyrene film, polyvinyl chloride film, Made of organic polymer such as polyimide film, polyvinyl alcohol film, polycarbonate film, ethylene vinyl alcohol film Things can be used. Among these, a polyethylene terephthalate (PET) film and a polypropylene film can be suitably used from the viewpoint of processing stability, heat resistance, and adhesion.

  Moreover, these film base materials may have a laminated structure. Moreover, an antioxidant, dye, a pigment, etc. can be added to a film base material as needed.

  In the release film of the present invention, the release layer is formed by applying a release layer forming material, which is a coating solution, onto a film substrate.

  As the release layer forming material of the present invention, a silicone-based material can be suitably used from the viewpoints of adhesion to a film substrate, processability, and release performance. As the silicone material, it is possible to use a curing reaction type silicone coating material for a release film such as an addition curing type or a UV curing type. Specifically, SRX211, LTC750A, LTC760A, BY24-510, manufactured by Toray Dow Corning Co., Ltd., KS774, KS847, KS5508, manufactured by Shin-Etsu Chemical Co., Ltd. Although chemical industry Co., Ltd. product UV-POLY200, UV-POLY201 etc. can be used, these are not limited. Further, as the release layer forming material, a fluorine-based material can also be used.

  In the release layer forming material, various curing catalysts and photoinitiators are used according to the curing type, and are appropriately added. For example, when using a silicone coating material as a release layer forming material, Momentive Performance Materials such as SRX212, NC-25, BY24-835 manufactured by Toray Dow Corning Co., Ltd., PL-50T manufactured by Shin-Etsu Chemical Co., Ltd. CM-670, UV9380, etc. manufactured by KK and UV-CATA211 manufactured by Arakawa Chemical Industries, Ltd. can be used as a curing catalyst and a photoinitiator.

  Moreover, a solvent is added to the release layer forming material as necessary. By adding a solvent, coating suitability can be improved. Solvents include aromatic hydrocarbons such as toluene, xylene, cyclohexane and cyclohexylbenzene, hydrocarbons such as n-hexane, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, dioxane, dioxolane, and trioxane. , Ethers such as tetrahydrofuran, anisole and phenetole, and ketones such as methyl isobutyl ketone, methyl butyl ketone, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and methylcyclohexanone , Ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate It is appropriately selected in consideration of the coating proper and the like from the esters such as acetic acid n- pentyl, and γ- butyrolactone.

  The refractive index of the silicone coating material and fluorine-based material used as the release layer forming material is lower than that of general-purpose plastic films, so the release layer forming material has a smaller refractive index difference from the film substrate. A refractive index adjusting agent can be added to.

  As the refractive index adjusting material, metal oxide particles such as alumina particles, titanium oxide particles, and zirconium oxide particles can be used. For metal oxide particles, the refractive index of the release layer can be adjusted without degrading other properties such as the peelability that is the original property of the release layer and the adhesion between the film substrate and the release layer. Since it can be used, it can be preferably used. In addition to alumina particles, titanium oxide particles, and zirconium oxide particles, zinc oxide, tin oxide, and the like can be used as the metal oxide particles, but the metal oxide particles are not limited to these. The particle diameter of the metal oxide particles is preferably in the range of 3 nm to 200 nm. When the particle diameter of the metal oxide particles exceeds 200 nm, the transmitted light is scattered, and thus transparency may be impaired. On the other hand, when the particle size of the metal oxide particles is less than 3 nm, it takes a lot of time to manufacture the fine particles, and the stability of the coating liquid may decrease.

  As the refractive index adjusting material, a metal chelate compound can also be used. The metal chelate compound is a compound that can be used as an anchor layer for improving the adhesion between the film substrate and the release layer. By adding a chelate compound to the release layer forming material, not only the refractive index of the release layer can be improved, but also the adhesion between the release layer and the film substrate can be improved. Examples of chelate compounds include aluminum tris (acetylacetonate), aluminum monoacetylacetonate bis (ethyl acetoacetate), aluminum diisopropoxy monomethyl acetoacetate, titanium diisopropoxybis (acetylacetonate), titanium tetraacetylacetonate, Titanium diisopropoxybis (ethylacetoacetate), zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium dibutoxybis (acetylacetonate), etc. can be used, but are not limited thereto.

  Moreover, in the peeling film of this invention, a metal oxide particle and a metal chelate compound can also be used together as a refractive index regulator. In addition, it is preferable that a refractive index modifier is added within the range of 5 wt% or more and 30 wt% or less with respect to the solid content of the release layer forming material. When the addition amount of the refractive index adjusting agent with respect to the solid content of the release layer forming material is less than 5 wt%, the refractive index difference from the base material cannot be within 5% and color unevenness may not be suppressed. On the other hand, when the addition amount of the refractive index adjusting agent exceeds 30 wt%, the refractive index may be too higher than the refractive index of the base material, and the refractive index may exceed 5%. Similarly, color unevenness cannot be reduced. Sometimes.

  Further, a surface conditioner, a leveling agent, an adhesion improver, a photosensitizer, and the like can be added as additives to the release layer forming material that is a coating liquid.

  The release layer forming material of the present invention is applied onto a film substrate by a wet film forming method in an application step. At this time, if necessary, a drying process for removing the solvent is provided after the coating process, and an ionizing radiation irradiation process and a heating process are provided as the curing process. As a coating method of the release layer forming material in the coating process, use a coating method using a roll coater, reverse roll coater, gravure coater, micro gravure coater, knife coater, bar coater, wire bar coater, die coater, dip coater. Can do.

  A known ink can be used as the printing layer forming material provided in the present invention. In the case of multicolor printing, a plurality of inks can be used. As a method for forming the printing layer, a printing method such as a relief printing method, a gravure printing method (intaglio printing method), an offset printing method, a screen printing method, and an inkjet printing method can be used.

  In addition, as an anchor layer forming material provided as necessary between the leaf film substrate and the release layer, epoxy-based, polyester urethane-based, acrylic urethane-based, silane coupling agent-based, titanium chelate-based chelate compounds, etc. What is used as a primer of a plastic film can be selected suitably. Specific examples include: Seikadine PET primer manufactured by Dainichi Seika Kogyo Co., Ltd., G588 gloss manufactured by Dainippon Ink, BLS-PC50 manufactured by Toyo Morton, Byron UR1350 UR3200 manufactured by Toyobo, etc. A combination with an isocyanate curing agent can be used. Examples of silane coupling agents include BY24-846 manufactured by Toray Dow Corning (3-part system of B, C, and E), glycidoxypropyltrimethoxysilane, methacryloxytrimethoxysilane, and aluminum chelate mixed primer. Examples of the titanium chelate-based anchor layer forming material include Matsumoto Fine Chemical Co., Ltd. Olga-Tix TC-100.

  Moreover, a solvent is added to the anchor layer forming material as necessary. By adding a solvent, coating suitability can be improved. Solvents include aromatic hydrocarbons such as toluene, xylene, cyclohexane and cyclohexylbenzene, hydrocarbons such as n-hexane, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, dioxane, dioxolane, and trioxane. , Ethers such as tetrahydrofuran, anisole and phenetole, and ketones such as methyl isobutyl ketone, methyl butyl ketone, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and methylcyclohexanone , Ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate , Esters such as n-pentyl acetate, and γ-ptyrolactone, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate, alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and ethylene glycol It is selected as appropriate from the viewpoint of coating suitability, etc.

  The anchor layer forming material of the present invention is applied onto a film substrate by a wet film formation method in an application step, thereby forming an anchor layer. At this time, if necessary, a drying process for removing the solvent is provided after the coating process, and a heating process and an ionizing radiation irradiation process are provided. As a coating method of the anchor layer forming material in the coating process, use a coating method using a roll coater, reverse roll coater, gravure coater, micro gravure coater, knife coater, bar coater, wire bar coater, die coater, dip coater. Can do.

Example 1
A biaxially stretched polyethylene terephthalate film (Melinex S manufactured by Teijin Limited) with a thickness of 75 μm is used as a film substrate, a release layer forming material (coating solution) having the following composition is applied by a bar coater, dried and cured at 140 ° C. for 1 min, and peeled off. A film was prepared. The thickness of the release layer of the obtained release film was 98 nm.
<Peeling layer forming material (coating solution)>
LTC750A (silicone base agent: manufactured by Toray Dow Corning Co., Ltd.) 10 parts by weight NC-25 (curing catalyst: manufactured by Toray Dow Corning Co., Ltd.) 0.1 parts by weight Toluene 60 parts by weight n-hexane 30 parts by weight ZrO ₂ Ultrafine particles (average particle size 30nm / solid content 3wt% / toluene dispersion)
25 parts by weight

(Example 2)
Using the release layer forming material of Example 1, a release film was produced by changing the thickness of the release layer to be formed. The thickness of the release layer of the obtained release film was 495 nm.

(Example 3)
A biaxially stretched polyethylene terephthalate film (Melinex S manufactured by Teijin Limited) with a thickness of 75 μm is used as a film substrate, a release layer forming material (coating solution) having the following composition is applied by a bar coater, dried and cured at 140 ° C. for 1 min, and peeled off. A film was prepared. The thickness of the release layer of the obtained release film was 498 nm.
<Peeling layer forming material (coating solution)>
LTC750A (silicone base agent: manufactured by Toray Dow Corning Co., Ltd.) 10 parts by weight NC-25 (curing catalyst: manufactured by Toray Dow Corning Co., Ltd.) 0.1 parts by weight Toluene 60 parts by weight n-hexane 30 parts by weight Titanium Di Isopropoxybis (acetylacetonate)
(3 wt% solid content / toluene dispersion) 25 parts by weight

(Comparative Example 1)
A biaxially stretched polyethylene terephthalate film (Melinex S manufactured by Teijin Limited) with a thickness of 75 μm is used as a film substrate, a release layer forming material (coating solution) having the following composition is applied by a bar coater, dried and cured at 140 ° C. for 1 min, and peeled off. A film was prepared. The thickness of the release layer of the obtained release film was 500 nm.
<Peeling layer forming material (coating solution)>
LTC750A (silicone base agent: manufactured by Toray Dow Corning Co., Ltd.) 10 parts by weight NC-25 (curing catalyst: manufactured by Toray Dow Corning Co., Ltd.) 0.1 parts by weight Toluene 60 parts by weight n-hexane 30 parts by weight

  The following evaluation was performed on the release films obtained in (Example 1) to (Example 3) and (Comparative Example 1).

-Measurement of spectral reflectance The surface opposite to the release layer forming surface of the obtained release film was applied in black by a black matte spray. After spray coating, an automatic spectrophotometer (manufactured by Hitachi, Ltd., U-4000) is used to measure the spectral reflectance at an incident angle of 5 ° with respect to the low refractive index layer forming surface under the condition of a C light source and a 2-degree field of view. Hue (a ^* , b ^* ) was calculated from the obtained reflectance curve to obtain C ^* _ab .

-Evaluation of color unevenness of release film The surface opposite to the release layer forming surface of the obtained release film was applied to black by a black matte spray. After coating, the release film was visually observed (30 cm directly under the fluorescent lamp stand and 1.5 m under the ceiling fluorescent lamp), and the occurrence of color unevenness was observed. The evaluation criteria are shown below.
Double circle mark: Color unevenness is hard to see even directly under the stand Circle mark: Color unevenness is slightly under the stand, but color unevenness is not visible under the ceiling Triangle mark: Color unevenness is easily confirmed under the ceiling Cross mark: Color unevenness is clearly confirmed even under the ceiling

・ Evaluation of color unevenness and design properties of printed release film The color of the obtained release film on the opposite side of the release layer forming surface using Toyo Ink's gravure ink, white, indigo and black. A sample was prepared, and the peeled film was visually observed (30 cm directly under the fluorescent lamp stand and 1.5 m under the ceiling fluorescent lamp) in the same manner as the color unevenness evaluation, and the occurrence of color unevenness was observed. The evaluation criteria are shown below.
Double circle mark: Color unevenness is hard to see even under the stand, and the design is extremely high. Circle mark: Color unevenness is slightly under the stand, but color unevenness cannot be confirmed under the ceiling.
Designability is high. Triangle mark: Color unevenness is easily confirmed even under the ceiling, and designability is low. Cross: Color unevenness is clearly confirmed even under the ceiling, and the designability is extremely low.

・ Peeling force A polyester adhesive tape (31B made by Nitto Denko) was attached to the release layer-forming surface of the obtained release film, and it was crimped with a load of 20 g / cm ² between glass plates and left for 5 hours. The resistance value when peeled 180 degrees at a speed of 300 mm / min was measured (test piece 25 mm × 100 mm).

  In addition, in the release films of (Example 1) to (Example 3) and (Comparative Example 1), the thickness of the release layer was measured by performing cross-sectional observation with a transmission electron microscope (TEM). Moreover, about the refractive index of a base material and a peeling layer, it calculated | required by performing optical simulation about the obtained spectral reflectance curve.

  The evaluation results of the release films obtained in (Example 1) to (Example 3) and (Comparative Example 1) are shown in (Table 1). Moreover, the spectral reflectance curve by the side of the peeling layer of the peeling film obtained by (Example 1)-(Example 3) and (comparative example 1) is shown in FIGS.

The release films of (Examples 1 to 3) have sufficient release performance, the reflection hue is in the range of C ^* _ab of 10 or less, the color is small, and in-plane color unevenness is difficult to be confirmed. A release film could be obtained.

  On the other hand, the release film of (Comparative Example 1) was able to be a film having sufficient release performance, but the spectral reflectance curve in the wavelength range of 400 nm to 800 nm had several maximum and minimum values. It becomes a steep type with respect to the wavelength change. The peeling film of (Comparative Example 1) was confirmed to have a non-uniform color unevenness with a blue to red-purple color unevenness. The release film provided with the printed layer on the back surface was also affected by the uneven color of the release layer, resulting in poor design.

  Moreover, about the peeling film of (Example 1)-(Example 3) and (Comparative Example 1) which provided the printing layer in the back surface, the foreign material confirmation test | inspection was visually performed in the room provided with the fluorescent lamp of a ceiling. As a result, the release films of (Example 1) to (Example 3) were able to easily confirm foreign matters. On the other hand, in the peeling film of (Comparative Example 1), it is necessary to stare at the surface of the peeling film while adjusting the angle between the peeling film and the fluorescent lamp in order to check the foreign matter. could not. That is, in the release films of (Example 1) to (Example 3), it was possible to obtain a release film with little tint and color unevenness and easy foreign matter inspection.

  The release film of the present invention can provide a release film with less color unevenness, facilitates inspection of foreign matters, and is used for manufacturing display members such as optical displays where medical problems are regarded as important due to foreign matter adhesion. It is suitable as a release film. Even when a release layer is provided on the release film of the present invention, the release film has low reflectance on the release layer surface and less color unevenness, which may impair the content display, design, and design of the target adhesive product. And a peelable film having high display properties and design properties can be obtained.

FIG. 1 is a schematic cross-sectional view of the release film of the present invention. FIG. 2 is a schematic cross-sectional view of a release film provided with the printing layer of the present invention. FIG. 3 is an explanatory diagram of a spectral reflectance curve (model) of the release film. FIG. 4 is a cross-sectional explanatory view of the laminate of the present invention. FIG. 5 is a spectral reflectance curve of the release film obtained in (Example 1). FIG. 6 is a spectral reflectance curve of the release film obtained in (Example 2). FIG. 7 is a spectral reflectance curve of the release film obtained in (Example 3). FIG. 8 is a spectral reflectance curve of the release film obtained in (Comparative Example 1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release film 11 Film base material 12 Release layer 13 Print layer 14 Anchor layer 2 Base | substrate

Claims (6)

A release film having a release layer on at least one surface of a film substrate,
The difference between the refractive index of the said peeling layer and the refractive index of the said film base material is less than 5% of the refractive index of the said film base material, The peeling film characterized by the above-mentioned.   The release film according to claim 1, wherein the release layer contains metal oxide particles.   The release film according to claim 1, wherein the release layer contains a metal chelate compound. The release film reflection hue on the side provided with the release layer has an ab chroma (C ^* _ab ) of 10 or less in the L ^* a ^* b ^* color system. Release film.   The release film according to claim 1, wherein the release film includes a printing layer.   A laminate comprising the release film according to any one of claims 1 to 5 and a substrate, wherein the release layer surface of the release film is in contact with the substrate surface.

Images