JP2017159506A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film that has high surface hardness, is resistant to a contaminant such as sebum, and has high scratch resistance.SOLUTION: A surface protective film 2 which is disposed on an outermost surface of a display or the like includes a transparent film 4 which is formed of an ultraviolet light curable acrylic resin 3 and has flexibility. A hard coat layer 9 including an antifouling component is disposed on the transparent film 4.SELECTED DRAWING: Figure 1

Description

  The present invention generally relates to a surface protective film such as a display or a touch panel, and more specifically relates to a surface protective film that is difficult to be attached with contaminants such as sebum and a method for producing the same.

  As shown in FIG. 4, conventionally, for example, the outermost surface of the touch panel 1 such as a navigation system or a mobile phone is easily scratched or scratched. Therefore, a surface protective film 2 in which a hard coat layer is laminated on a polyethylene terephthalate (PET) film is provided. Provide and protect. The surface protection film 2 is required to be transparent and preferably has a high total light transmittance. Furthermore, there is a need to make it difficult for contaminants such as sebum to adhere to the surface of the surface protective film 2.

  Japanese Unexamined Patent Publication No. 2011-201087 (Patent Document 1) discloses a technique for imparting antifouling properties to the surface of a surface protective film by adding a fluorine-based material to a hard coat agent.

JP 2011-201087 A

  The conventional surface protective film is formed as described above. However, the surface protective film disclosed in Patent Document 1 has a problem in that the pencil hardness on the film surface is about 3H, the scratch resistance is low, and it is used for a touch panel having a high frequency of rubbing.

  The present invention has been made in order to solve the above-described problems, and it is an object of the present invention to provide a surface protective film having a high surface hardness, being hardly attached with contaminants such as sebum, and having high scratch resistance.

The present invention is a flexible surface protective film provided on the outermost surface of a display or the like, which is provided on a transparent film formed of an ultraviolet curable acrylic resin, and on the transparent film. A hard coat layer formed of an ultraviolet curable resin containing at least one of the components, and the surface of the hard coat layer of the surface protective film has a pencil hardness (according to JISK5400). Measurement) is 8H or more, and in the steel wool sliding test (# 0000 steel wool, 1 kgf / cm ² , stroke width 6 cm, speed 9.6 cm / sec), the number of scratches confirmed is 1500 times or more and the initial The pure water contact angle is 100 degrees or more.

  According to a preferred embodiment of the surface protective film of the present invention, the ultraviolet curable acrylic resin contains a polyfunctional urethane (meth) acrylate having a number average molecular weight of 200 to 5,000, and a polyfunctional (meth) acrylate. It is a polymerizable composition. By this feature, it can be set as the surface protection film which has flexibility and is hard to break.

  According to a preferred embodiment of the surface protective film of the present invention, at least in the vicinity of the interface with the hard coat layer of the transparent film, the crosslinking rate of the ultraviolet curable acrylic resin contained in the transparent film is 40% or more and 65%. It is characterized by the following. With this feature, the adhesion between the surface protective film and the hard coat layer is enhanced, and a surface protective film having high surface hardness and high scratch resistance can be obtained.

  According to a preferred embodiment of the surface protective film of the present invention, the transparent film comprises a base material layer, and an adhesive layer provided on the upper side of the base material layer and in contact with the hard coat layer, and the adhesive layer The crosslinking rate of the ultraviolet curable acrylic resin contained in is 40% or more and 65% or less.

  According to the surface protective film according to the present invention, it is possible to provide a surface protective film that is difficult to be attached with contaminants such as sebum and has high scratch resistance.

It is a figure which shows the manufacturing method of the surface protection film which concerns on Embodiment 1 of this invention. It is a figure which shows the manufacturing method of the surface protection film which concerns on Embodiment 2 of this invention. It is a figure which shows the manufacturing method of the surface protection film which concerns on Embodiment 3 of this invention. It is a figure which shows the usage pattern of the surface protection film for touchscreens.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

  (Embodiment 1)

  In FIG. 1, the manufacturing process of the surface protection film using the ultraviolet curable acrylic resin based on Embodiment 1 of this invention is shown.

  As shown in FIG. 1A, an ultraviolet curable acrylic resin 3 prepared in advance is applied onto a first base film 6 (PET film). The ultraviolet curable acrylic resin 3 is a polymer containing polyfunctional urethane (meth) acrylate and polyfunctional (meth) acrylate in order to produce a surface protective film having high surface hardness, flexibility, and resistance to cracking. It is preferable to use a composition. Since polyfunctional urethane (meth) acrylate is polyfunctional, it can be cured to form a crosslinked structure, and a resin molded body having high hardness can be obtained. The polyfunctional urethane (meth) acrylate, for example, is obtained by reacting a polyisocyanate compound and a hydroxyl group-containing (meth) acrylate, thereby imparting appropriate toughness by hydrogen bonding of urethane groups in the molecule, thereby increasing mechanical strength. It is preferable because it is excellent. The number average molecular weight of the polyfunctional urethane (meth) acrylate is preferably 200 to 5,000. If the number average molecular weight is less than 200, curing shrinkage increases and birefringence tends to occur. When the number average molecular weight exceeds 5,000, the crosslinkability is lowered and the heat resistance may be insufficient.

  It does not specifically limit as a polyisocyanate compound, For example, aliphatic polyisocyanate, aromatic polyisocyanate, and araliphatic polyisocyanate are mentioned, However, It is preferable to use aliphatic polyisocyanate at the point which can suppress yellowing. In addition, when a compound having no alicyclic structure is used as the polyisocyanate compound, it is possible to obtain the transparent film 4 having particularly excellent surface hardness, which is preferable. Aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate. 2,4,4-trimethylhexamethylene diisocyanate, lysine isocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,3-bis (diisocyanatemethyl) cyclohexane, 4,4′-dicyclohexylmethane diisocyanate and the like.

  The hydroxyl group-containing (meth) acrylate is not limited as long as it has a hydroxyl group and a (meth) acryloyl group in the molecule. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2 -Hydroxybutyl (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol tri (meth) Examples thereof include acrylate and tripentaerythritol heptaacrylate. In particular, it is preferable to use those having no alicyclic structure in the molecule from the viewpoint of suppressing the surface hardness and color change of the resin molding.

  Polyfunctional (meth) acrylates include bis (hydroxymethyl) tricyclo [5.2.1.02,6] decane = di (meth) acrylate, bis (hydroxy) tricyclo [5.2.1.02,6]. Decane = acrylate methacrylate, bis (hydroxy) pentacyclo [6.5.1.13,6.02,7.09,13] pentadecane = di (meth) acrylate, bis (hydroxy) pentacyclo [6.5.1.13 , 6.02, 7.09, 13] pentadecane = acrylate methacrylate, 2,2-bis [4- (β-methacryloyloxyethoxy) cyclohexyl] propane, 1,3-bis (methacryloyloxymethyl) cyclohexane, 1,3 -Bis (methacryloyloxyethyloxymethyl) cyclohexane, 1,4-bis Bifunctional (meth) acrylates such as methacryloyloxymethyl) cyclohexane and 1,4-bis (methacryloyloxyethyloxymethyl) cyclohexane, 1,3,5-tris (methacryloyloxymethyl) cyclohexane, 1,3,5-tris ( And trifunctional (meth) acrylates such as methacryloyloxyethyloxymethyl) cyclohexane. From the viewpoint of flexibility, it is preferable to use a bifunctional (meth) acrylate. Furthermore, it is preferable to use a bifunctional methacrylate from the viewpoint of heat resistance.

After the ultraviolet curable acrylic resin 3 is coated on the first base film 6 (PET film), the coated surface is covered with another second base film 7 (PET film). Then, the amount of light is controlled (250 to 600 mJ / cm ² ) so that the crosslinking rate is 40% or more and 65% or less (more preferably 45% or more and 60% or less), and the resin is cured by irradiation with ultraviolet rays. That is, it is characterized by leaving an uncrosslinked portion. The film thickness of the obtained transparent film 4 is set to 80 to 300 μm, more preferably 100 to 250 μm.

The crosslinking rate was calculated by calculating the peak area in the vicinity of 810 cm ⁻¹ derived from the (meth) acryloyl group by FT-IR (manufactured by Perkin Elmer, model number: Spectrum 100) and comparing it with the unreacted raw material. The ultraviolet irradiation conditions for obtaining a predetermined crosslinking rate were set based on prior test data on the crosslinking rate and the amount of ultraviolet irradiation.

  In addition, the ultraviolet curing in the state sandwiched between the two first and second base films 6 and 7 is that the transparent film 4 having a predetermined film thickness is formed smoothly and the ultraviolet curable acrylic resin 3 is formed. This is to prevent oxygen from being affected by oxygen inhibition during UV curing.

  As shown in FIG. 1 (B), the two first and second bases 6 and 7 are peeled off to obtain a transparent film 4. In Embodiment 1, the overall crosslinking rate (related to the crosslinking density) of the obtained transparent film 4 is controlled to 40% or more and 65% or less. That is, the feature is that 35% to 60% of the uncrosslinked portion remains. After forming the transparent film 4 by performing the above control, an unreacted (meth) remaining on the surface of the transparent film 4 when the ultraviolet curable resin 8 is applied on the transparent film 4 and cured by irradiation with ultraviolet rays. It is considered that the adhesion is improved because the acrylate component and the crosslinking component such as acrylate in the ultraviolet curable resin 8 are subjected to photo-radical polymerization and bond formation proceeds at the interface. Even if uncrosslinked portions remain, it has been confirmed in a prior test that the surface of the obtained transparent film 4 is not sticky when the crosslinking rate is 40% or more.

  Next, as shown in FIG. 1 (C), an ultraviolet curable resin 8 that contains a fluorine-based or silicone-based antifouling component and becomes a hard coat layer on the transparent film 4 has a film thickness after curing. It is applied with a bar coater so as to be several μm and dried (80 ° C., 2 minutes).

  The ultraviolet curable resin 8 is not particularly limited as long as it has antifouling properties (water repellency and oil repellency) and has a functional group that forms an ultraviolet crosslink. For example, a silicone compound such as silicone-containing (meth) acrylate, or a fluorine-based compound such as fluorine-containing (meth) acrylate compound or fluorinated epoxy acrylate can be used. Only 1 type may be used for a silicone type compound and a fluorine-type compound, and 2 or more types may be used together.

  As shown in FIGS. 1C and 1D, the ultraviolet curable resin 8 was irradiated with ultraviolet rays and cured to form a hard coat layer 9. Thereby, the surface protection film 2 which consists of the transparent film 4 and the hard-coat layer 9 was completed. The surface protective film 2 itself can be used as a substitute for a glass cover such as a display or a touch panel.

  Example 1

  The ultraviolet curable acrylic resin 3 of the example was prepared as follows. As a polyisocyanate compound, an isocyanurate type trimer (130 g) of 1,6-hexane diisocyanate was prepared. Moreover, dipentaerythritol pentaacrylate (870g) was prepared as a hydroxyl-containing (meth) acrylate. These, 0.8 g of hydroquinone methyl ether as a polymerization inhibitor, and toluene as a solvent were charged into a glass reactor equipped with a stirrer, a cooling tube, and a thermometer. The —OH group / —NCO group of 1,6-hexane diisocyanate isocyanurate type trimer and dipentaerythritol pentaacrylate was 1/1. Furthermore, after adding 0.3 g of dibutyltin dilaurate as a urethanization catalyst and reacting at 85 degrees for 6 hours, the solvent was distilled off to prepare a polyfunctional urethane (meth) acrylate.

  A trifunctional or higher polyfunctional polyester acrylate was charged into a 677.6 g glass container. Furthermore, the polyfunctional urethane (meth) acrylate 193.6g prepared as mentioned above in the said glass container; 96.8g of tricyclodecane dimethanol dimethacrylate of bifunctional (meth) acrylate; 1- 1 as a photoinitiator 9.7 g of hydroxycyclohexyl phenyl ketone; 0.97 g of 2-hydroxy-4- (acryloylethoxy) benzophenone as an ultraviolet absorber; 19.4 g of a thiol compound as a sensitizer were added.

  These were mixed and stirred in a glass container under conditions of 40 ° C. for 2 hours to prepare an ultraviolet curable acrylic resin 3.

The obtained UV curable acrylic resin 3 is coated with a bar coater on an untreated surface (surface on which an easy adhesion layer is not formed) of a PET film (A4100 manufactured by Toyobo Co., Ltd.) so that the dry film thickness becomes 200 μm. (# 75). The coated surface is covered with another PET film (A4100 manufactured by Toyobo Co., Ltd.), and 450 mJ from above using a UV lamp (model number CV-110Q-G manufactured by FUSION UV SYSTEM) so that the crosslinking rate of the transparent film 4 is 60%. The transparent film 4 was obtained by irradiating UV light of / cm ² and then peeling the PET films on both sides.

HS coating 001 (DSP Gokyo Food & Chemical Co., Ltd.) was used as the UV curable resin 8 and coated on one side of the transparent film 4 with a bar coater and then dried (80 ° C., 2 minutes). Then, the surface protection film 2 of Example 1 is formed by irradiating an ultraviolet ray of 1200 mJ / cm ² with a UV lamp (model number CV-110Q-G manufactured by FUSION UV SYSTEM) to form a hard coat layer 9 (thickness: 4 μm). Got.

  (Example 2)

  Except that the surface of the transparent film 4 to which the UV curable resin 8 is applied has been previously subjected to corona treatment (a corona treatment machine manufactured by enercon, model number: LM3214-11, treatment condition: 1 kW, 1 round trip at 100 mm / sec) In the same manner as in Example 1, a surface protective film 2 of Example 2 was obtained.

(Example 3)
As in the case of Example 1, except that X-12-2464B (Shin-Etsu Chemical Co., Ltd.) was used as the ultraviolet curable resin 8 and the ultraviolet ray was cured under an irradiation condition of 1200 mJ / cm ² . A surface protective film 2 was obtained.

(Comparative Example 1)
Comparative Example 1 was carried out in the same manner as in Example 1 except that the ultraviolet curable acrylic resin 3 was ultraviolet-cured under irradiation conditions of 1500 mJ / cm ² so that the cross-linking rate of the transparent film 4 was 75%. Surface protection film 2 was obtained.

  (Comparative Example 2)

Comparative Example 2 was carried out in the same manner as in Example 2 except that the ultraviolet curable acrylic resin 3 was UV-cured under irradiation conditions of 1500 mJ / cm ² so that the cross-linking rate of the transparent film 4 was 75%. Surface protection film 2 was obtained.

  (Comparative Example 3)

Comparative Example 3 was carried out in the same manner as in Example 3 except that the ultraviolet curable acrylic resin 3 was UV-cured under irradiation conditions of 1500 mJ / cm ² so that the cross-linking rate of the transparent film 4 was 75%. Surface protection film 2 was obtained.

  Table 1 shows the physical property values of the obtained surface protective films 2. The measuring method of each measured value is as follows.

[Steel wool (SW) sliding test (scratch resistance)]
A sample of 10 cm × 4 cm is fixed on a glass plate with tape, and using a # 0000 steel wool of 2 cm × 1 cm, a stroke width of 6 cm at a load of 1 kg / cm ² and a speed of 9.6 cm / second (48 reciprocations per minute) ) Was conducted. The surface was confirmed every 100 reciprocations of sliding, and the number of times the scratch was visually confirmed under a fluorescent lamp was defined as the number of scratch confirmation.

[Pencil hardness test]
The pencil hardness was measured with a pencil scratch tester (manufactured by Dazai Equipment Co., Ltd.) according to JIS-K5400. The pencil was evaluated using products of hardness 8H and 9H.

[Tape peeling test]
After scratching the surface of the hard coat layer 9 of the surface protective film 2 with a cutter knife, a tape (manufactured by Nichiban Co., model number: CT-18) is applied and pulled vertically to check the state of the surface film. did. In the case where film peeling is not recognized, it is marked as ◯, and in the case where it is recognized, it is marked as x.

From the above results, by setting the crosslinking rate to 60%, the scratch resistance is remarkably improved as compared with the case of the crosslinking rate of 75%, and by reducing the crosslinking rate of the transparent film 4, the transparent film 4 and It was confirmed that the adhesion with the hard coat layer 9 was improved. On the other hand, regarding the corona treatment, when the crosslinking rate was 60% (Examples 1 and 2), no difference was observed in each performance. In addition, as an alternative index of antifouling properties, the initial pure water contact angle is preferably 100 ° or more, but the initial pure water contact angle of the surface protective film 2 of Examples 1 and 3 is determined by a contact angle meter (manufactured by KRUS, When the tangential measurement was performed using a model number: DSA20E), all showed 109 °, and it was confirmed that they also had sufficient antifouling properties.
(Embodiment 2)

  In FIG. 2, the manufacturing process of the surface protection film which concerns on Embodiment 2 of this invention is shown.

  As shown in FIG. 2A, an ultraviolet curable acrylic resin 3 prepared in advance was applied on the first base film 6. Thereafter, the coated surface is covered with another second base film 7 and cured by irradiation with ultraviolet rays. At this time, ultraviolet irradiation is performed under the condition that the ultraviolet curable acrylic resin 3 is sufficiently cured. After the curing, as shown in FIG. 2B, the two first and second base films 6 and 7 are peeled off to obtain the base material layer 11. The base material layer 11 is a part of the transparent film 4 on which the hard coat layer 9 described later is provided. The film thickness of the base material layer 11 is 80 to 300 μm, more preferably 100 to 2500 μm.

  Next, as shown in FIG. 2 (C), an ultraviolet curable acrylic resin 5 is applied onto the base material layer 11, and the crosslinking rate is 40% or more and 65% or less (more preferably 45% or more and 60% or less). 2), the adhesive layer 10 is formed as shown in FIG. 2D. The ultraviolet curable acrylic resin 5 may be different from the ultraviolet curable acrylic resin 3 of the base layer 11, but the same material is preferable. The adhesive layer is preferably formed to have a thickness of 5 μm or less. The structure combined with the adhesive layer 10 and the base material layer 11 corresponds to the transparent film 4 of the first embodiment. The cross-linking rate of the adhesive layer 10 is preferably in the same range as in the first embodiment. For the ultraviolet curable acrylic resin 3 or 5, the same material as in the first embodiment can be used.

  Next, as shown in FIG. 2 (E), an ultraviolet curable resin that becomes a hard coat layer containing a fluorine-based or silicone-based antifouling component on the adhesive layer 10 has a film thickness after curing of several. A hard coat layer 9 is formed by applying with a bar coater to a thickness of μm, drying (80 ° C., 2 minutes), and curing by irradiating with ultraviolet rays. Thereby, the surface protection film 2 provided with the base material layer 11, the adhesive layer 10 (two correspond to the transparent film 4 of Example 1), and the hard-coat layer 9 is obtained. The same material as in Embodiment 1 can be used for the ultraviolet curable resin.

The transparent film 4 of Embodiment 1 has a configuration in which the overall crosslinking rate is lowered, whereas the transparent film 4 of Embodiment 2 has an adhesive layer 10 having a low crosslinking rate at the interface with the hard coat layer 9. It can be said that the configuration is provided. With this configuration, the majority of the transparent film 4 can be cured sufficiently to obtain a stable material state, and the adhesion to the hard coat layer 9 can be improved to improve the scratch resistance.
(Embodiment 3)

  In FIG. 3, the manufacturing process of the surface protection film based on Embodiment 3 of this invention is shown. As shown in FIG. 3 (A), after preparing the ultraviolet curable acrylic resin 3 and applying it on the first base film 6, the ultraviolet light is not covered with another second base film. Irradiate to cure. At this time, when the coated surface is covered with another second base film, ultraviolet irradiation is performed under the condition that the ultraviolet curable acrylic resin 3 is sufficiently cured. The ultraviolet curable acrylic resin 3 can use the same material as in the first embodiment. After the curing, as shown in FIG. 3B, the first base film 6 is peeled off to obtain the transparent film 4. The film thickness of the transparent film 4 is 80 to 300 μm, more preferably 100 to 250 μm. At this time, the surface of the transparent film 4 that is not covered with the PET film is not sufficiently cross-linked by the ultraviolet curable acrylic resin 3 due to oxygen inhibition of the ultraviolet curable acrylic resin 3 (low crosslinking rate). A surface 4a is formed. The ultraviolet irradiation is controlled so that the amount of crosslinking on the surface is 40% or more and 65% or less (more preferably 45% or more and 60% or less).

  Next, as shown in FIG. 3 (C), an ultraviolet curable resin 8 that becomes a hard coat layer containing a fluorine-based or silicone-based antifouling component on the surface 4a of the transparent film 4 having a low crosslinking rate is provided. The hard coat layer 9 is formed by coating with a bar coater such that the film thickness after curing is several μm, drying (80 ° C., 2 minutes), and curing by irradiation with ultraviolet rays. The same material as that of the first embodiment can be used for the ultraviolet curable resin 8. Thereby, the surface protection film 2 provided with the transparent film 4 and the hard-coat layer 9 is obtained.

  The third embodiment can be said to be a configuration in which a layer having a low crosslinking rate is provided at the interface with the hard coat layer 9 of the transparent film 4 as in the second embodiment, but the manufacturing process is simpler than that of the second embodiment. There is a certain feature.

  The embodiments disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the surface protective film according to the present invention, it is a high-hardness film, it is difficult to be attached with contaminants such as sebum, and the surface is not peeled off.

DESCRIPTION OF SYMBOLS 1 Display 2 Surface protection film 3 Ultraviolet curable acrylic resin 4 Transparent film 4a Surface with low cross-linking rate 5 Ultraviolet curable acrylic resin 6 First base film 7 Second base film 8 Ultraviolet curable resin 9 Hard coat layer 10 Adhesive layer 11 Base material layer

Claims (4)

A transparent film formed of an ultraviolet curable acrylic resin;
A hard coat layer provided on the transparent film and formed of an ultraviolet curable resin containing at least one component of silicone and fluorine, and a surface protective film comprising:
The surface of the hard coat layer of the surface protective film is
Pencil hardness (measurement based on JISK5400) is 8H or more,
In the steel wool sliding test (# 0000 steel wool, 1 kgf / cm ² , stroke width 6 cm, speed 9.6 cm / sec), the number of scratches confirmed is 1500 times or more and the initial pure water contact angle is 100 degrees or more. Some surface protection film.   The ultraviolet curable acrylic resin is a polymerizable composition containing a polyfunctional urethane (meth) acrylate having a number average molecular weight of 200 to 5,000 and a polyfunctional (meth) acrylate. The surface protective film as described.   The surface protection according to claim 1 or 2, wherein the transparent film has a cross-linking ratio of 40% or more and 65% or less of the ultraviolet curable acrylic resin contained in the transparent film at least in the vicinity of the interface with the hard coat layer. the film.   The transparent film includes a base material layer and an adhesive layer that is provided on the base material layer and is in contact with the hard coat layer, and a cross-linking ratio of an ultraviolet curable acrylic resin contained in the adhesive layer is 40%. The surface protective film according to claim 1 or 2, wherein the content is 65% or less.