KR20190015188A - Piezoelectric film - Google Patents

Abstract

A piezoelectric film (10) of the present invention comprises a laminate of a base film (11) and a coating layer (12) having piezoelectricity. The coating layer 12 having piezoelectricity contains a fluororesin. The fluororesin is a polymer of vinylidene fluoride or two or more kinds of copolymers (vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene). The coating layer 12 having piezoelectricity is obtained by applying a solution of a fluororesin to the base film 11 and drying it. The piezoelectric film (10) of the present invention realizes a piezoelectric film having a small haze value and a high total light transmittance.

Description

Piezoelectric film

The present invention relates to a piezoelectric film.

Generally, in a touch panel, a two-dimensional position on a surface of a touch panel or a finger to be touched is detected (hereinafter, "finger or pen" is simply referred to as "finger" Quot; finger XY coordinate "). In this case, the pressure to which the finger is touched can not be detected. (Hereinafter, it is assumed that the magnitude of pressure to be touched by the finger is held in the Z-axis direction, and is referred to as "Z-coordinate of the finger"). That is, regardless of the magnitude of the pressure (the Z-coordinate of the finger) that the finger touches, only the XY coordinates of the touch position of the finger are detected.

However, depending on the application used in the touch panel, it may be necessary to identify the pressure (finger Z coordinate) to be touched by the finger. In a conventional capacitive touch panel, by touching a finger, a touch position is selected and a command at a touch position is executed. In the case where the sensitivity of the capacitive touch panel is very high, the position closest to the finger is selected and the command at that position is executed, just because the finger is close to the capacitive touch panel (without touching the finger). However, for example, when the execution of erroneous commands is not allowed in the operation panel of the machine tool or the like, it is preferable that the selection and the execution are separated. That is, the command is selected by touching the finger (or the finger is brought closer), but it is preferable that the command is not executed by itself and that the command is executed only after the pressure is applied by the finger next .

A touch panel capable of detecting the pressure (finger's Z-coordinate) detected by the finger is described in, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-26938). In the touch panel of Patent Document 1, a laminate in which transparent electrodes are laminated on both surfaces of a piezoelectric layer containing a polyvinylidene fluoride-tetrafluoroethylene copolymer is used. The thickness of the piezoelectric layer containing the polyvinylidene fluoride-tetrafluoroethylene copolymer is 20 mu m to 300 mu m. Since the piezoelectric layer containing the polyvinylidene fluoride-tetrafluoroethylene copolymer of Patent Document 1 is manufactured by the casting method or the extrusion method, the self-sustaining film (a film not laminated on another film) .

In Patent Document 1, a haze value (fog value) of a piezoelectric layer containing a polyvinylidene fluoride-tetrafluoroethylene copolymer is 5% to 7% and a total light transmittance is 95%. The haze value and the total light transmittance of the embodiment of Patent Document 1 are the values of the piezoelectric layer alone containing the polyvinylidene fluoride-tetrafluoroethylene copolymer before the transparent electrodes are laminated.

According to the experiment of the present inventor, the visibility of the image of the display on the back surface of the touch panel is affected at least by the haze value of the piezoelectric film and the total light transmittance. The piezoelectric layer containing the polyvinylidene fluoride-tetrafluoroethylene copolymer of Patent Document 1 has a large haze value, so that the visibility of the image on the display on the back surface of the touch panel may be lowered.

Japanese Patent Application Laid-Open No. 2010-26938

According to the experiment of the inventor of the present invention, the decrease in the visibility of the image of the display on the rear surface of the touch panel has a larger influence on the haze value than the total light transmittance. Therefore, an object of the present invention is to realize a piezoelectric film having a small haze value and a high total light transmittance.

(1) The piezoelectric film of the present invention comprises a laminate of a base film and a coating layer having piezoelectricity.

(2) The piezoelectric film of the present invention includes an undercoat layer between a base film and a coating layer having piezoelectricity.

(3) The piezoelectric film of the present invention has at least one optical adjustment layer on the surface of the coating layer having piezoelectricity opposite to the base film. At least one optical adjustment layer means that the optical adjustment layer may be a multilayer film of two or more layers.

(4) The piezoelectric film of the present invention has at least one first optical adjustment layer between the base film and the coating layer having piezoelectricity. The first optical adjustment layer of at least one layer means that the first optical adjustment layer may be a multilayer film of two or more layers.

(5) The piezoelectric film of the present invention has at least one second optical adjustment layer on the surface of the coating layer having piezoelectricity opposite to the first optical adjustment layer. At least one second optical adjustment layer means that the second optical adjustment layer may be a multilayer film of two or more layers.

(6) The piezoelectric film of the present invention has at least one anti-blocking layer between the base film and the coating layer having piezoelectricity. At least one anti-blocking layer means that the anti-blocking layer may be a multilayer film of two or more layers.

(7) The piezoelectric film of the present invention has at least one anti-blocking layer on the surface of the base film opposite to the coating layer having piezoelectricity.

(8) The piezoelectric film of the present invention has at least one transparent adhesive layer on the surface of the coating layer having piezoelectricity opposite to the base film. The transparent adhesive layer of at least one layer means that the transparent adhesive layer may be a multilayer film of two or more layers.

(9) In the piezoelectric film of the present invention, at least one transparent adhesive layer is provided on the surface of the base film opposite to the coating layer having piezoelectricity.

(10) In the piezoelectric film of the present invention, the coating layer having piezoelectricity contains a fluororesin.

(11) In the piezoelectric film of the present invention, the fluororesin is a polymer of vinylidene fluoride or a copolymer of two or more of (vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene).

(12) In the piezoelectric film of the present invention, it is preferable that the fluororesin is a copolymer of vinylidene fluoride and trifluoroethylene, and the molar ratio of vinylidene fluoride and trifluoroethylene contained in the copolymer is 100 , (50 to 85): (50 to 15).

(13) In the piezoelectric film of the present invention, it is preferable that the fluororesin is a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene, vinylidene fluoride contained in the copolymer, trifluoroethylene and chlorotri Fluoroethylene is in the range of (63 to 65): (27 to 29): (10 to 6), where the molar ratio of fluoroethylene is 100 as a whole.

(14) In the piezoelectric film of the present invention, the coating layer having piezoelectricity is a coating layer obtained by applying a solution of a fluororesin to a base film and drying the base film.

(15) In the piezoelectric film of the present invention, the thickness of the coating layer having piezoelectricity is 0.5 mu m to 20 mu m.

(16) In the piezoelectric film of the present invention, the material of the base film is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyolefin, polycycloolefin, cycloolefin copolymer, polycarbonate, polyether sulfone, polyarylate, Polyamide, polystyrene, and polynorbornene.

(17) The piezoelectric film of the present invention has a haze value of 5% or less.

(18) The piezoelectric film of the present invention has a total light transmittance of 90% or more.

In the piezoelectric film of the present invention, since the piezoelectric layer is formed by coating, the thickness of the piezoelectric layer is thinner than the piezoelectric layer made of a conventional self-supporting film. Therefore, the haze value of the piezoelectric layer and the total light transmittance are lower than the piezoelectric layer made of the self-supporting film. By this effect, a piezoelectric film having a small haze value and a high total light transmittance can be realized. When the piezoelectric film of the present invention is used as a piezoelectric film for Z coordinate detection of a touch panel, the visibility of the display on the back surface of the touch panel is good, and a touch panel having a Z coordinate (finger pressing force) detecting function can be realized .

1 is a schematic view of a first basic structure of a piezoelectric film of the present invention.
2 is a schematic view of a second basic configuration of the piezoelectric film of the present invention.
3 is a schematic view of a third basic configuration of the piezoelectric film of the present invention.
4 is a schematic view of a fourth basic constitution of the piezoelectric film of the present invention.
5 is a schematic view of a fifth basic configuration of the piezoelectric film of the present invention.
6 is a schematic view of a sixth basic configuration of the piezoelectric film of the present invention.
7 is a schematic view of a seventh basic constitution of the piezoelectric film of the present invention.
8 is a schematic view of an eighth basic constitution of the piezoelectric film of the present invention.
9 is a schematic view of a ninth basic constitution of the piezoelectric film of the present invention.
10 is a schematic diagram showing a configuration in which a transparent electrode is formed on a piezoelectric film of the present invention.

[Basic Configuration of Piezoelectric Film]

Fig. 1 shows a first basic structure of a piezoelectric film of the present invention. The first basic structure of the piezoelectric film of the present invention is a piezoelectric film 10 in which a coating layer 12 having piezoelectricity is laminated on a base film 11. An easy adhesion layer (not shown) may be laminated between the base film 11 and the coating layer 12 having piezoelectricity.

Fig. 2 shows a second basic structure of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the first basic configuration. The second basic structure of the piezoelectric film of the present invention is a piezoelectric film in which an undercoat layer 13 is laminated on a base film 11 and a coating layer 12 having piezoelectricity is further laminated on an undercoat layer 13 Film 20. The undercoat layer 13 (or the anchor coat layer) has a function of increasing the adhesion between the base film 11 and the coating layer 12 having piezoelectricity.

3 shows a third basic structure of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the first basic configuration. The third basic structure of the piezoelectric film of the present invention is that a coating layer 12 having piezoelectricity is laminated on the base film 11 and at least one layer of the optical adjustment layer 14 is further laminated on the coating layer 12 having piezoelectricity, Is laminated on the piezoelectric film 30. The index matching layer (also referred to as a refractive index adjusting layer) has a function of adjusting the reflectance of the piezoelectric film 30. [ An easy adhesion layer (not shown) may be laminated between the base film 11 and the coating layer 12 having piezoelectricity.

Fig. 4 shows a fourth basic structure of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the first basic configuration. The fourth basic structure of the piezoelectric film of the present invention is such that at least one first optical adjustment layer 15 is laminated on the base film 11 and at least one first optical adjustment layer 15 is further laminated, And a coating layer 12 having piezoelectricity is laminated on the piezoelectric film 40.

5 shows a fifth basic configuration of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the fourth basic configuration. The fifth basic structure of the piezoelectric film of the present invention is such that at least one first optical adjustment layer 15 is laminated on the base film 11 and at least one first optical adjustment layer 15 is piezoelectric And at least one second optical adjustment layer 16 is laminated on the coating layer 12 having piezoelectricity. In addition, the piezoelectric film 50 is formed by laminating at least one layer of the second optical adjustment layer 16 on the coating layer 12 having piezoelectricity.

6 shows a sixth basic structure of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the first basic configuration. The sixth basic structure of the piezoelectric film of the present invention is such that at least one anti-blocking layer (17) is laminated on the base film (11), and furthermore, at least one antireflection layer And a coating layer 12 laminated on the piezoelectric film 60. [ The anti-blocking layer 17 has a function of preventing the piezoelectric films 60 that are overlapped or wound with each other from squeezing (blocking).

7 shows a seventh basic configuration of the piezoelectric film of the present invention. Elements common to the third basic configuration are assigned the same reference numerals. A seventh basic configuration of the piezoelectric film of the present invention is a piezoelectric film in which a coating layer 12 having piezoelectricity is laminated on one surface of a base film 11 and a coating layer 12 having piezoelectricity is further laminated on at least one layer of an optical adjustment layer 14 is laminated on the other surface of the substrate film 11 and at least one anti-blocking layer 17 is laminated on the other surface of the base film 11. An easy adhesion layer (not shown) may be laminated between the base film 11 and the coating layer 12 having piezoelectricity.

8 shows the eighth basic constitution of the piezoelectric film of the present invention. The same reference numerals are given to the elements common to the first basic configuration. The eighth basic structure of the piezoelectric film of the present invention is such that a coating layer 12 having piezoelectricity is laminated on a base film 11 and at least one transparent adhesive layer 18 is laminated on a coating layer 12 having piezoelectricity, And the piezoelectric film 80 is a laminated piezoelectric film. At least one transparent adhesive layer 18 may be a transparent adhesive layer of at least one layer. An easy adhesion layer (not shown) may be laminated between the base film 11 and the coating layer 12 having piezoelectricity.

9 shows a ninth basic constitution of the piezoelectric film of the present invention. Elements common to those of the eighth basic configuration are denoted by the same reference numerals. The ninth basic structure of the piezoelectric film of the present invention is such that a coating layer 12 having piezoelectricity is laminated on one surface of a base film 11 and at least one transparent adhesive layer 18 Is laminated on the piezoelectric film 90. At least one transparent adhesive layer 18 may be a transparent adhesive layer of at least one layer. An easy adhesion layer (not shown) may be laminated between the base film 11 and the coating layer 12 having piezoelectricity.

[Base film]

The base film 11 may be formed of a material such as polyethylene terephthalate, polyethylene naphthalate, polyolefin, polycycloolefin, cycloolefin copolymer, polycarbonate, polyether sulfone, polyarylate, polyimide, polyamide, polystyrene, poly Norbornene and the like. Although the material of the base film 11 is not limited to these materials, polyethylene terephthalate (PET) excellent in transparency, heat resistance, and mechanical characteristics is preferable.

The thickness of the base film 11 is preferably 10 탆 to 200 탆, but the thickness is not limited thereto. If the thickness of the base material film 11 is less than 10 占 퐉, handling may become difficult. If the thickness of the base film 11 exceeds 200 占 퐉, it may be difficult to roll the piezoelectric films 10, 20, 30, 40, 50, 60, 70, 80, 90 to roll. If the thickness of the base film 11 exceeds 200 占 퐉, there is a fear that the thickness becomes excessively thick when the piezoelectric films 10, 20, 30, 40, 50, 60, 70, 80, 90 are mounted on a touch panel or the like have.

[Coating layer having piezoelectricity]

The material of the coating layer 12 having piezoelectricity can be coated in the form of a thin film on the surface of the base film 11 and is not particularly limited as long as the thin film after the coating has piezoelectricity. It is preferable that the coating layer 12 having piezoelectricity exhibits piezoelectricity without performing poling (polarization treatment), but it may be a material showing piezoelectricity after poling.

There are non-contact polling and contact polling as polling (polarization treatment). In non-contact polling, for example, the coating layer 12 is corona discharge treated to polarize the coating layer 12. In the contact type polling, for example, two metal plates sandwich the coating layer 12, and a voltage is applied between the two metal plates to polarize the coating layer 12.

The coating layer 12 having piezoelectricity can be obtained by, for example, dissolving the material of the coating layer 12 having piezoelectricity in a solvent to form a solution, and coating the substrate film 11 with a known coating apparatus such as a bar coater or a gravure coater Coated on the surface with a uniform thickness, and then dried.

[Material of the coating layer having piezoelectricity]

As the material of the coating layer 12 having piezoelectricity, for example, a material containing a fluororesin is preferably used. Specific examples of the material containing the fluororesin include polymers of vinylidene fluoride, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and trifluoroethylene and chlorotrifluoroethylene, hexafluoroethylene, Copolymers of propylene and vinylidene fluoride, copolymers of perfluorovinyl ether and vinylidene fluoride, copolymers of tetrafluoroethylene and vinylidene fluoride, copolymers of hexafluoropropylene oxide and vinylidene fluoride, And copolymers of hexafluoropropylene, tetrafluoroethylene and vinylidene fluoride. These polymers can be used alone or as a mixture.

The fluororesin-containing material is preferably a copolymer of vinylidene fluoride and trifluoroethylene, or a copolymer of vinylidene fluoride and trifluoroethylene and chlorotrifluoroethylene. A copolymer of vinylidene fluoride and trifluoroethylene is used as a binary copolymer. A copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene is used as the ternary copolymer.

When a copolymer (binary copolymer) of vinylidene fluoride and trifluoroethylene is used as the material of the coating layer 12 having piezoelectricity, the molar ratio of vinylidene fluoride and trifluoroethylene is 100 (50 to 85): (50 to 15) is appropriate.

When a copolymer (ternary copolymer) of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene is used as a material for the coating layer 12 having piezoelectricity, vinylidene fluoride and trifluoroethylene (63 to 65): (27 to 29): (10 to 6) is suitable as the molar ratio of chlorotrifluoroethylene to chlorotrifluoroethylene.

[Thickness of the coating layer having piezoelectricity]

The thickness of the coating layer 12 having piezoelectricity is not limited. However, considering the optical characteristics to be described later, the thickness is preferably 0.5 m to 20 m, more preferably 0.5 m to 10 m, and more preferably 0.5 m to 5 m desirable. If the thickness of the coating layer 12 having piezoelectricity is less than 0.5 占 퐉, the formed film may be incomplete. If the thickness of the coating layer 12 having piezoelectricity is more than 20 mu m, the optical characteristics (haze value and total light transmittance) may become inadequate.

[Transparent adhesive layer]

The transparent pressure-sensitive adhesive layer 18 is preferably made of an optical transparent pressure-sensitive adhesive. For example, a transparent adhesive layer 18 can be formed using a sheet of optical transparent pressure-sensitive adhesive. The transparent adhesive layer is preferably made of an optical transparent adhesive. For example, it is possible to form a transparent adhesive layer by applying a liquid optical transparent adhesive and curing by irradiating ultraviolet rays. The refractive index of the transparent adhesive layer 18 or the transparent adhesive layer is preferably an intermediate value of the refractive index of each of the materials laminated on both sides thereof. By selecting the refractive index of the transparent adhesive layer 18 or the transparent adhesive layer, reflection of light at the interface between the transparent adhesive layer 18 or the transparent adhesive layer and the material stacked on both sides of the transparent adhesive layer 18 can be suppressed.

[Optical properties of piezoelectric film]

Generally, even when the haze value of the piezoelectric film is increased, the light is not absorbed and scattered in some cases, so that the total light transmittance may not be lowered. However, even if the total light transmittance of the piezoelectric film is not lowered, the visibility of the display image is lowered as the haze value becomes larger. Therefore, the visibility of the display image can not be determined only by the value of the total light transmittance of the piezoelectric film. According to the experiment of the present inventor, in order to ensure the visibility of the display image, the haze value of the piezoelectric film is preferably 5% or less, more preferably 4% or less, still more preferably 3% , And particularly preferably 1% or less. The total light transmittance of the piezoelectric film is preferably 90% or more, more preferably 91% or more, and particularly preferably 92% or more. When the haze value of the piezoelectric film is more than 5% or the total light transmittance is less than 90%, the image of the display may not be clearly visible.

[Transparent electrode]

Further, a transparent electrode may be laminated on the piezoelectric film 10 of the present invention, and the change of the electric potential of the coating layer 12 having piezoelectricity can be detected by the transparent electrode. For example, as shown in Fig. 10, the optical adjusting layer 14 and the transparent electrode 20 are laminated on the piezoelectric film 10 of Fig. A hard coat layer 22 having an anti-blocking function is laminated on a surface of the base film 11 opposite to the surface of the coating layer 12 having piezoelectricity.

The transparent electrode 20 may be an indium based composite oxide, typically indium tin oxide (ITO), or an indium zinc composite oxide. However, the transparent electrode 20 may be a metal oxide or a metal oxide, (In2O3). The indium based composite oxide is characterized in that the transmittance is as high as 80% or more at the visible light region (380 to 780 nm) and the surface resistance per unit area is low (30 to 1000? /?).

The surface resistance value of the indium based composite oxide is preferably 300 Ω / □ (ohms per square) or less, more preferably 150 Ω / □. The transparent electrode having a small surface resistance can be obtained by forming an amorphous layer of an indium based composite oxide on a cured resin layer by, for example, a sputtering method or a vacuum deposition method and then heat-treating the amorphous layer at a temperature of 100 to 200 ° C to form a crystalline Layer.

The transparent electrode 20 is not limited to the above materials, but may be a transparent conductive oxide such as tin zinc oxide, zinc oxide, or fluorine-doped tin oxide, or a conductive polymer such as polyethylene dioxythiophene.

The thickness of the coating layer 12 having piezoelectricity of 0.5 to 10 占 퐉, the thickness of the optical adjustment layer 14 of 80 to 160 nm and the thickness of the transparent electrode 20 of 20 nm or more. The refractive index of the coating layer 12 having a piezoelectric property is 1.40 to 1.50, the refractive index of the optical adjustment layer 14 is 1.50 to 1.70, and the refractive index of the transparent electrode 20 is 1.90 to 2.10. The base film 11 has a thickness of 2 to 100 占 퐉 and a refractive index of 1.50 to 1.70. Or more and the refractive index, the difference in reflectance between the transparent electrode 20 and the optical adjusting layer 14 becomes 2.0% or less, and the appearance becomes better.

Example

[Example 1]

The piezoelectric film 10 of the first embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 1 was obtained by firstly forming an unshown adhesive property on the surface of the base film 11 (polyethylene terephthalate film), and then forming a copolymer of vinylidene fluoride and trifluoroethylene 2-type copolymer). The thickness of the base film 11 (polyethylene terephthalate film) was 23 占 퐉.

In producing the coating layer 12 having piezoelectricity, first, a copolymer (binary copolymer) of vinylidene fluoride and trifluoroethylene is dissolved in methyl ethyl ketone by ultrasonic wave, and a mixture of vinylidene fluoride and tri A solution of a copolymer of fluoroethylene (binary copolymer) was prepared. The molar ratio of vinylidene fluoride to trifluoroethylene contained in the copolymer (binary copolymer) of vinylidene fluoride and trifluoroethylene was 70/30.

Next, a solution of a copolymer (binary copolymer) of vinylidene fluoride and trifluoroethylene was coated on the surface of the base film 11 (polyethylene terephthalate film) by a bar coater. Next, the base film 11 (polyethylene terephthalate film) and the non-dried coating layer were dried at 60 DEG C for 5 minutes to obtain a coating layer 12 having piezoelectricity. The thickness of the coating layer 12 having piezoelectricity after drying was 1 mu m.

[Example 2]

The piezoelectric film 10 of the second embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 2 was produced in the same manner as the piezoelectric film 10 of Example 1 except that the thickness of the coating layer 12 having piezoelectricity after drying was 5 占 퐉.

[Example 3]

The piezoelectric film 10 of the third embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 3 was produced in the same manner as the piezoelectric film 10 of Example 1 except that the thickness of the coating layer 12 having piezoelectricity after drying was 10 占 퐉.

[Example 4]

The piezoelectric film 10 of the fourth embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 4 was produced in the same manner as the piezoelectric film 10 of Example 1 except that the thickness of the coating layer 12 having piezoelectricity after drying was 20 占 퐉.

[Example 5]

The piezoelectric film 10 of the fifth embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 5 was obtained in the same manner as the piezoelectric film 10 except that the molar ratio of vinylidene fluoride to trifluoroethylene contained in the copolymer (binary copolymer) of vinylidene fluoride and trifluoroethylene was 75/25 Was produced in the same manner as the piezoelectric film 10 of Example 1.

[Example 6]

The piezoelectric film 10 of the sixth embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 6 was manufactured in the same manner as the piezoelectric film 10 of Example 5, except that the thickness of the coating layer 12 having piezoelectricity after drying was 5 占 퐉.

[Example 7]

The piezoelectric film 10 of the seventh embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 7 was produced in the same manner as the piezoelectric film 10 of Example 5 except that the thickness of the coating layer 12 having piezoelectricity after drying was 10 占 퐉.

[Example 8]

The piezoelectric film 10 of the eighth embodiment is composed of the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 8 is the piezoelectric film 10 of Example 5 except that the thickness of the coating layer 12 having piezoelectricity after drying is 2 占 퐉 and the drying condition is 135 占 폚 for 5 minutes. ).

[Example 9]

The piezoelectric film 10 of the ninth embodiment has the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 9 is the same as the piezoelectric film 10 except that the material of the coating layer 12 having piezoelectricity is a copolymer of vinylidene fluoride and trifluoroethylene and chlorotrifluoroethylene , And the piezoelectric film 10 of the first embodiment.

In producing the coating layer 12 having piezoelectricity, first, a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene (ternary copolymer) is added to methyl isobutyl ketone at room temperature by ultrasonic wave , And a solution of a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene (ternary copolymer) was prepared. The molar ratio of vinylidene fluoride to trifluoroethylene and chlorotrifluoroethylene contained in the copolymer (ternary copolymer) of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene was 64.2 / 27.1 / 8.7 .

Next, a solution of a copolymer (ternary copolymer) of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene was coated on the surface of the base film 11 (polyethylene terephthalate film) by a bar coater . Next, the base film 11 (polyethylene terephthalate film) and the non-dried coating layer were dried at 60 DEG C for 5 minutes to dryness to prepare a coating layer 12 having piezoelectricity. The thickness of the coating layer 12 having piezoelectricity after drying was 1 mu m.

[Example 10]

The piezoelectric film 10 of the tenth embodiment is composed of the first basic structure of the piezoelectric film of the present invention. The piezoelectric film 10 of Example 10 was produced in the same manner as the piezoelectric film 10 of Example 9, except that the thickness of the coating layer 12 having piezoelectricity after drying was 5 占 퐉.

[Comparative Example 1]

The piezoelectric film of Comparative Example 1 is composed of a self-supporting film (without a base film) having a thickness of 40 占 퐉 of a vinylidene fluoride polymer (polyvinylidene fluoride). The piezoelectric film of Comparative Example 1 was obtained by dissolving a polymer of vinylidene fluoride (polyvinylidene fluoride) in isobutyl ketone at room temperature by ultrasonic waves to a surface of a polyethylene terephthalate film with a thickness of 40 mu m after drying , Dried, and then peeled off from the polyethylene terephthalate film.

Table 1 shows the composition of the piezoelectric film of Examples and Comparative Examples of the piezoelectric film of the present invention, the molar ratio and thickness of the piezoelectric layer having the piezoelectric property, the haze value of the piezoelectric film and the total light transmittance. In Table 1, VDF represents vinylidene fluoride, TrFE represents trifluoroethylene, CTFE represents chlorotrifluoroethylene, and PET represents polyethylene terephthalate. P () represents a copolymer. Therefore, "P (VDF-TrFE)" means "a copolymer of vinylidene fluoride and trifluoroethylene". "P (VDF-TrFE-CTFE)" means "a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene". "P (VDF-TrFE) / PET base film" means "a copolymer of vinylidene fluoride and trifluoroethylene was coated on the surface of the base film 11 made of polyethylene terephthalate". The "P (VDF-TrFE-CTFE) / PET base film" is a film obtained by coating a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene onto the surface of a base film 11 made of polyethylene terephthalate "It means. PVDF means a polymer of vinylidene fluoride (polyvinylidene fluoride).

The piezoelectric films of Examples 1 to 4 have the same constitution and materials but differ in the thickness of the coating layer 12 having piezoelectricity. Comparing Examples 1 to 4, the haze value tends to increase as the thickness of the coating layer 12 having piezoelectricity increases. However, the haze value and the total light transmittance of the piezoelectric films of Examples 1 to 4 are all at a level of no problem.

The piezoelectric films of Examples 5 to 7 have the same constitution and materials but differ in the thickness of the coating layer 12 having piezoelectricity. Comparing Examples 5 to 7, the haze value tends to increase slightly as the thickness of the coating layer 12 having piezoelectricity increases. However, the haze value and the total light transmittance of the piezoelectric films of Examples 5 to 7 are all at a level at which no problem occurs.

The piezoelectric film of Example 8 is the same in constitution and material as the piezoelectric film of Example 5, and the thickness of the coating layer 12 is close, but the haze value is greatly different. The reason why the haze value of the piezoelectric film of Example 8 is great is that the drying temperature is 135 ° C (the drying temperature in the other Examples is 60 ° C). As described above, when the drying temperature of the coating layer 12 is increased, the haze value of the piezoelectric film tends to increase.

The piezoelectric films of Examples 9 and 10 have the same constitution and materials but differ in the thickness of the coating layer 12 having piezoelectricity. From Examples 9 and 10, the haze value tends to increase as the thickness of the coating layer 12 having piezoelectricity increases. However, the haze value and the total light transmittance of the piezoelectric films of Example 9 and Example 10 are all levels at which no problem occurs.

The self-supporting film of the vinylidene fluoride polymer (polyvinylidene fluoride) of Comparative Example 1 has a significantly larger haze value than that of the piezoelectric films of Examples 1 to 10 of the present invention. Therefore, the visibility of the image on the display is likely to be lowered. However, the total light transmittance of the piezoelectric film of Comparative Example 1 is not substantially different from that of the piezoelectric films of Examples 1 to 10 of the present invention. From Comparative Example 1, it can be understood that the total light transmittance can not be reduced even if the haze value is increased.

[How to measure]

(thickness)

The thickness of the film less than 1 mu m was measured by observing a cross section using a transmission electron microscope (H-7650, Hitachi, Ltd.). The thickness of the film or film exceeding 1 mu m was measured using a film thickness meter (digital dial gauge DG-205 manufactured by Peacock).

[Haze value, total light transmittance]

The haze value and the total light transmittance were measured using a Direct Reading Haze Computer (HGM-ZDP manufactured by Suga Test Instruments).

[Examples 11 to 16]

10, assuming that the transparent electrode 20 is laminated on the piezoelectric film 10 of the present invention, the optical adjusting layer 14 is disposed between the piezoelectric film 10 and the transparent electrode 20 The thickness and the refractive index of the coating layer 12, the optical adjusting layer 14, and the transparent electrode 20 having the piezoelectric properties were measured. The piezoelectric film 10 is the same as the above embodiment, and a PET film is coated with a copolymer of vinylidene fluoride and trifluoroethylene.

The optical adjustment layer 14 may have refractive indexes of 1.54, 1.62, and 1.7 as shown in Table 2 below. Since the manufacturing method differs depending on the refractive index, the refractive index will be described for each refractive index. (Refractive index n = 1.54 of light) of a melamine resin: alkyd resin: organosilane condensate in a weight ratio of 2: 2: 1 on the surface of one side of the coating layer 12 having piezoelectricity when the refractive index is 1.54, The optical adjustment layer 14 having a thickness of 120 nm was formed.

47 parts by mass of an ultraviolet curing resin, 57 parts by mass of zirconia oxide particles (median diameter 40 nm), and an optical adjusting composition containing PGME (manufactured by JSR Corporation) were laminated on one surface of a coating layer 12 having piezoelectricity, , "Opsta Z7412", solid content: 12 mass%) was applied using a gravure coater, and immediately dried in a no-wind condition (less than 0.1 m / s) at 60 ° C for 1 minute. Thereafter, a curing treatment was carried out by irradiating with a high-pressure mercury lamp an ultraviolet ray having an accumulated light quantity of 250 mJ / cm 2. By this method, an optical adjustment layer 14 having a thickness of 90, 120, or 150 nm and a refractive index of 1.62 was formed on the coating layer 12 having piezoelectricity.

If the refractive index of 1.7, a thermosetting resin composed of a melamine resin, an alkyd resin and an organosilane condensate of TiO ₂ (refractive index = 2.35) to (a weight ratio of melamine resin: alkyd resin: 1 organic silane condensate = 2: 2) Based on the total weight of the resin composition. At this time, the mixing amount of the TiO ₂ fine particles was adjusted so that the refractive index of the resin composition became 1.70. Then, the resin composition was coated on the coating layer 12 having piezoelectricity and cured to form an optical adjustment layer 14 (refractive index: 1.70) having a thickness of 150 nm.

The transparent electrode 20 was formed by sputtering indium tin oxide. The results are shown in Table 2, where the "first layer" is the coating layer 12 having piezoelectricity, the "second layer" is the optical adjustment layer 14, and the "third layer" is the transparent electrode 20.

In each embodiment, the thickness of the coating layer 12 having piezoelectricity is 0.5 to 10 占 퐉, the thickness of the optical adjustment layer 14 is 80 to 160 nm, and the thickness of the transparent electrode 20 is 20 nm or more as described above . The refractive index of the coating layer 12 having piezoelectricity is 1.40 to 1.50, the refractive index of the optical adjustment layer 14 is 1.50 to 1.70, and the refractive index of the transparent electrode 20 is 1.90 to 2.10. The difference in reflectance between the transparent electrode 20 and the optical adjusting layer 14 was 2% or less, and the appearance was good.

In addition, the transparent electrode 20 is etched to become a desired electrode or the like, if necessary. When obtaining the refractive index, the refractive index of the optical adjustment layer 14 was the portion from which the transparent electrode 20 was removed by etching. Therefore, the reflectance ratios of the air, the transparent electrode 20, and the air and the optical adjusting layer 14 were determined from the respective refractive indices, and the reflectance difference was obtained.

[Comparative Examples 2 to 3]

As a comparative example for Examples 11 to 16, Comparative Example 2 in which the optical adjusting layer 14 was not provided (Comparative Example 3) was performed when the refractive index of the optical adjusting layer 14 was smaller than 1.5. In the absence of the optical adjustment layer 14, the reflectance difference is a difference between the transparent electrode 20 and the coating layer 12 having piezoelectricity. The reflectance difference was larger than 2%, and the appearance was deteriorated.

The optical adjustment layer 14 in the case where the refractive index was 1.46 (Comparative Example 4) was prepared by diluting silica sol (Colcoat P, manufactured by Colcoat Co., Ltd.) with ethanol so as to have a solid concentration of 2% (SiO ₂ film, refractive index of light: 1.46) was formed on one side of the coating layer 12 having a thickness of 120 nm by applying silica coating method at 150 캜 for 2 minutes, The adjustment layer 14 was formed. The manufacturing method of the other constitution in the comparative example is the same as that of the embodiment.

The transparent electrode 20 may be provided on the coating layer 12 having piezoelectricity, so that the transparent electrode 20 may be colored yellow or brown, thereby deteriorating the appearance. The optical adjustment layer 14 is formed and the thickness and the refractive index of the transparent electrode 20, the optical adjustment layer 14, and the coating layer 12 having piezoelectricity are adjusted to be within the range described above, , The reflectance difference can be made small as shown in Table 2, and the appearance is not impaired. It has been found that the appearance of the display is not hurt well even if a configuration in which the optical adjusting layer 14 and the transparent electrode 20 are laminated on the piezoelectric film 10 is disposed on the front surface of the display.

Industrial availability

The use of the piezoelectric film of the present invention is not particularly limited, but is particularly preferably used as a piezoelectric film for detecting the Z coordinate (pressure at which a finger touches) of the touch panel.

10, 20, 30, 40, 50, 60, 70, 80, 90:
11: base film
12: Coating layer having piezoelectricity
13: Undercoat layer
14: Optical adjustment layer
15: first optical adjusting layer
16: second optical adjusting layer
17: Anti-blocking layer
18: transparent adhesive layer
20: Transparent electrode
22: Hard coat layer having anti-blocking function

Claims (18)

A piezoelectric film comprising a laminate of a base film and a coating layer having piezoelectricity. The method according to claim 1,
A piezoelectric film having an undercoat layer between the base film and the coating layer having piezoelectricity. The method according to claim 1,
Wherein at least one layer of the optical adjustment layer is provided on a surface of the coating layer having piezoelectricity opposite to the base film. The method according to claim 1,
Wherein at least one first optical adjustment layer is provided between the base film and the coating layer having piezoelectricity. 5. The method of claim 4,
Wherein at least one second optical adjustment layer is provided on a surface of the coating layer having piezoelectricity opposite to the first optical adjustment layer. The method according to claim 1,
And at least one anti-blocking layer between the base film and the coating layer having piezoelectricity. The method of claim 3,
Wherein at least one anti-blocking layer is provided on the surface of the base film opposite to the coating layer having piezoelectricity. The method according to claim 1,
Wherein at least one transparent adhesive layer is provided on a surface of the coating layer having piezoelectricity opposite to the base film. The method according to claim 1,
Wherein at least one transparent adhesive layer is provided on a surface of the base film opposite to the coating layer having piezoelectricity. 10. The method according to any one of claims 1 to 9,
Wherein the coating layer having piezoelectricity contains a fluororesin. 11. The method of claim 10,
Wherein the fluororesin is a polymer of vinylidene fluoride or a copolymer of two or more of (vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene). 12. The method of claim 11,
Wherein the fluororesin is a copolymer of vinylidene fluoride and trifluoroethylene, and the molar ratio of the vinylidene fluoride and the trifluoroethylene contained in the copolymer is 100: (50 to 85): (50 to 15). 12. The method of claim 11,
Wherein the fluororesin is a copolymer of vinylidene fluoride, trifluoroethylene and chlorotrifluoroethylene, wherein the molar ratio of the vinylidene fluoride contained in the copolymer to the trifluoroethylene and the chlorotrifluoroethylene is , And the total is 100, and (63 to 65): (27 to 29): (10 to 6). 14. The method according to any one of claims 10 to 13,
Wherein the piezoelectric layer is a coating layer obtained by applying a solution of the fluororesin to the substrate film and drying the coating layer. 15. The method according to any one of claims 1 to 14,
Wherein the thickness of the coating layer having the piezoelectric property is 0.5 mu m to 20 mu m. 16. The method according to any one of claims 1 to 15,
Wherein the material of the base film is selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyolefin, polycycloolefin, cycloolefin copolymer, polycarbonate, polyether sulfone, polyarylate, polyimide, polyamide, polystyrene, polynorbornene Wherein the piezoelectric film is selected from at least one kind. 17. The method according to any one of claims 1 to 16,
And a haze value of 5% or less. 18. The method according to any one of claims 1 to 17,
A piezoelectric film having a total light transmittance of 90% or more.

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