TW201930470A - Transparent film substrate for touch sensor panel, and touch sensor panel in which same is used - Google Patents

Abstract

The present invention also pertains to a touch sensor panel equipped with the transparent film substrate for a touch sensor panel, and with an element layer having a detection element formed on the transparent film substrate for a touch sensor panel. Specifically, the present invention pertains to a transparent film substrate for a touch sensor panel that contains a polyimide polymer and an inorganic component, has a yellowness of 5 or lower, has a thickness-direction retardation Rth of 200 nm or less, has a photoelastic coefficient absolute value of 30*10<SP>-12</SP> Pa-1 or less, and has a linear expansion coefficient of 50 ppm/DEG C or less.

Description

Transparent film substrate for touch sensor panel and touch sensor panel using the same

The invention relates to a transparent film base material for touch sensor panels and a touch sensor panel using the same.

Previously, glass has been used as the base material of touch panels. However, glass has shortcomings such as easy breakage and heaviness, and it has not had sufficient materials for the thinning, lightening, or flexibility of touch panels in recent years. Therefore, the industry is investigating the use of resin films such as polyimide films as substrate materials for touch panels instead of glass.

The polyimide used in the polyimide film is known as a resin excellent in heat resistance and dimensional stability. In particular, the aromatic polyimide obtained by the polycondensation reaction of aromatic tetracarboxylic dianhydride and aromatic diamines can also be used under high temperature conditions above 400 ° C and has excellent dimensional stability. However, aromatic polyimide is usually colored from light yellow to yellow, so it is not suitable for applications such as materials for electronic devices that require transparency (eg, materials for substrate films for transparent electrodes such as touch sensor panels, etc.) ). Therefore, in order to be applicable to such applications requiring transparency, an aliphatic polyimide excellent in transparency is studied, and a conductive laminate using a substrate film containing aliphatic polyimide is developed. For example, Patent Document 1 discloses a transparent conductive film excellent in transparency, heat resistance, and the like, which has a transparent conductive thin film laminated on a substrate containing aliphatic polyimide.
[Prior Technical Literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-111152

[Problems to be solved by the invention]

However, the above-mentioned previous polyimide film has a problem in visibility during bending, and does not have sufficient characteristics for use as a base material of a flexible touch panel. In addition, the substrate of the touch panel is also required to have excellent process characteristics during the manufacture of the touch panel, such as heat resistance and solvent resistance.

The present invention has been made in view of the circumstances described above, and its object is to provide a transparent film substrate for a touch sensor panel with excellent visibility during bending and process characteristics when manufacturing a touch panel and a touch using the same Sensor panel.
[Technical means to solve the problem]

To achieve the above object, the present invention provides a touch sensor panel with a transparent film substrate, comprising a polyimide-based polymer and an inorganic component, yellowness 5 or less, a thickness direction retardation R _th is 200 nm or less , the absolute value of photoelastic coefficient of 30 × 10 ^-12 Pa ^-1 or less, and a coefficient of linear expansion of 50 ppm / ℃ or less.

According to the above-mentioned transparent film substrate for touch sensor panel, by containing a polyimide-based polymer and an inorganic component, and yellowness, thickness-phase retardation R _th , absolute value of photoelastic coefficient, and linear expansion coefficient Within the above range, the process characteristics during the manufacture of a touch panel, such as visibility during bending, heat resistance, and solvent resistance, are excellent. In particular, excellent visibility during bending is difficult to obtain, for example, only because the transparency of the film substrate is high. In contrast, in the transparent film substrate for the touch sensor panel, the polyimide-based polymer and the inorganic component are used in combination, and the absolute value of the yellowness, the phase difference in the thickness direction R _th and the photoelastic coefficient The value is set to a specific range, and the contrast change and the hue change during bending can be sufficiently suppressed, and as a result, excellent visibility can be achieved. In addition, by using a polyimide-based polymer and an inorganic component together, and setting the linear expansion coefficient to a specific range, excellent process characteristics can be obtained.

The absolute value of the above-described touch sensor panel substrate of the light-transparent film can be an elastic coefficient of 23 × 10 ^-12 Pa ^-1 or less. If the absolute value of the photoelastic coefficient is 23 × 10 ^-12 Pa ^-1 or less, due to changes in the retardation film of the arising stress becomes smaller, more difficult to change the transmission characteristics of light occurs, so the transparent film substrate obtained More excellent visibility when bending.

In the transparent film substrate for the touch sensor panel, the inorganic component may be a silicon material containing silicon atoms. In addition, the silicon material may contain silicon dioxide particles. The inorganic material is a silicon material containing silicon atoms, and by containing silicon dioxide particles, the visibility and process characteristics during bending can be further improved.

In the transparent film substrate for a touch sensor panel, the content of the inorganic component may be 30 to 60% by mass based on the total solid content of the transparent film substrate. If the content of the inorganic component is within the above range, the transparent film base material for touch sensor panels becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics.

The thickness of the transparent film substrate for the touch sensor panel may be 20-50 μm. If the thickness of the transparent film substrate is within the above range, the transparent film substrate for a touch sensor panel becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics during touch panel manufacturing.

To the touch sensor panel with a transparent film substrate, in-plane retardation R ₀ may be 20 nm or less. If the in-plane retardation R ₀ is the above-mentioned range, the visibility can be more favorable when the bending.

Furthermore, the present invention provides a touch sensor panel comprising the transparent film substrate for a touch sensor panel of the present invention described above, and a detection device formed on the transparent film substrate for the touch sensor panel The component layer of the component. The touch sensor panel sufficiently suppresses the contrast change and hue change of the bent part at the time of bending, and becomes excellent in visibility.
[Effect of invention]

According to the present invention, it is possible to provide a transparent film substrate for a touch sensor panel excellent in visibility and process characteristics during bending and a touch sensor panel using the same.

Hereinafter, the present invention will be described in detail based on its preferred embodiments.

[Transparent film substrate for touch sensor panel]
The transparent film substrate for touch sensor panels of the present embodiment (hereinafter, also simply referred to as "transparent film substrate") contains a polyimide-based polymer and an inorganic component, the yellowness is 5 or less, and the thickness direction The difference R _th is 200 nm or less, the absolute value of the photoelastic coefficient is 30 × 10 ^-12 Pa ^-1 or less, and the linear expansion coefficient is 50 ppm / ° C or less. In addition, the in-plane retardation R _{0 of the} transparent film substrate is preferably 20 nm or less.

The yellowness (YI value) of the transparent film substrate can be obtained in accordance with JIS K 7373: 2006. The yellowness of the transparent film substrate of this embodiment is 5 or less, preferably 3 or less. With a yellowness of 5 or less, the transparent film substrate can obtain excellent visibility when bent.

The transparent film substrate in the thickness direction retardation R _th line of the direction of the refractive index within the film plane is set to N _x, N _y and the refractive index of the set of N _x orthogonal direction, the direction of the thickness of the film of the refractive rate is set to N _z, the thickness of the film is set to be d (nm), by (A) calculated by formula. Here, the refractive index N _x lines of the slow axis direction, N _y based refractive index of the fast axis direction, and satisfies N _x> N _{y.
R th = {(N x +} N y) / 2-N z} × (nm) d ... (A)

The in-plane retardation R ₀ of the transparent film base material is to set the refractive index in one direction of the film surface to N _x , the refractive index in the direction orthogonal to N _x to N _y , and the thickness of the film to d (nm), and calculated by formula (B). Here, the refractive index N _x lines of the slow axis direction, N _y based refractive index of the fast axis direction, and satisfies N _x> N _y.
R ₀ = (N _x -N _y ) × d (nm)… (B)

The R _{th of the} transparent film substrate can be measured using a phase difference measuring device (trade name: KOBRA) manufactured by Oji Measuring Instruments Co., Ltd. The thickness direction phase difference R _th of the transparent film substrate of this embodiment is 200 nm or less, preferably 190 nm or less, more preferably 150 nm or less, and further preferably 120 nm or less, particularly preferably 50 nm or less, Preferably it is below 40 nm. When the phase difference R _{th in the} thickness direction is 200 nm or less, excellent visibility during bending can be obtained. From the viewpoint of the film-forming process, the R _{th of the} transparent film substrate may be 30 nm or more, and may also be greater than 50 nm, and may also be 100 nm or more.

The absolute value of the photoelastic coefficient of the transparent film substrate is obtained from the relationship between the stress applied to the transparent film substrate and birefringence. Here, the term "photoelasticity" means that if an external force is applied to an isotropic substance to cause internal stress, it will exhibit optical anisotropy and exhibit birefringence. When the stress (force per unit area) acting on the substance is set to σ and the birefringence is set to Δn, the stress σ is theoretically proportional to the birefringence Δn, which can be expressed as Δn = Cσ, where C is Photoelastic coefficient. In other words, if the stress σ acting on the substance is taken as the horizontal axis and the birefringence Δn of the substance when the stress is applied is taken as the vertical axis, the relationship between the two is theoretically a straight line, and the slope of the straight line is the photoelastic coefficient C . The photoelastic coefficient of the transparent film base material can be measured using a phase difference measuring device (trade name: KOBRA) manufactured by Oji Measuring Equipment Co., Ltd. The absolute value of photoelastic coefficient of the transparent film substrate of the present form of embodiment is 30 × 10 ^-12 Pa ^-1 or less, preferably 29 × 10 ^-12 Pa ^-1 or less, more preferably 25 × 10 ^-12 Pa ^-1 or less, further preferably 23 × 10 ^-12 Pa ^-1 or less, particularly preferably 20 × 10 ^-12 Pa ^-1 or less. When the absolute value of the photoelastic coefficient if of 30 × 10 ^-12 Pa ^-1 or less, the smaller the retardation film due to the stress generated by the variation of light transmission characteristics not easy to change, thus bending the transparent film substrate obtained Excellent visibility. In addition, the absolute value of the photoelastic coefficient of the transparent film substrate of this embodiment may be 0 Pa ^-1 or more, preferably 0.1 × 10 ^-12 Pa ^-1 or more, and more preferably 1 × 10 ^-12 Pa ^-1 or more It is further preferably 10 × 10 ^-12 Pa ^-1 or more, particularly preferably 14 × 10 ^-12 Pa ^-1 or more, and most preferably 15 × 10 ^-12 Pa ^-1 or more. Transparent film substrates with an absolute value of the photoelastic coefficient of 0.1 × 10 ^-12 Pa ^-1 or more are easy to produce in industry, and it is easy to obtain more excellent bendability.

The absolute value of optical elastic coefficient of the transparent film substrate is adjusted to the 30 × 10 ^-12 Pa ^-1 or less of the method is not particularly limited, for example, by the use of a solvent-soluble polyimide-based polymer, or improving the transparency film base The elastic modulus, or increase the content of inorganic particles, etc., can reduce the absolute value of the photoelastic coefficient of the transparent film substrate.

The linear expansion coefficient of the transparent film base material is based on JIS K7197, and is a value measured as an average linear expansion coefficient (also referred to as average linear expansion ratio) in an arbitrary temperature range. The linear expansion coefficient of this embodiment is set to a value within a temperature range of 90 to 150 ° C. The linear expansion coefficient of the transparent film substrate of this embodiment is 50 ppm / ° C or less, preferably 40 ppm / ° C or less. With a linear expansion coefficient of 50 ppm / ° C or less, the transparent film substrate can obtain excellent process characteristics during touch panel manufacturing.

(Polyimide polymer)
The transparent film substrate contains a polyimide-based polymer. In the transparent film base material, the content of the polyimide-based polymer is 40% by mass or more based on the total amount of the transparent film base material, preferably 40 to 70% by mass, more preferably 45 to 65% by mass It is further preferably 50 to 60% by mass. As a result, the transparent film base material becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics.

In this specification, the polyimide-based polymer refers to a polymer containing at least one type of repeating structural unit represented by formula (PI), formula (a), formula (a '), or formula (b). Among them, if the repeating structural unit represented by the formula (PI) is the main structural unit of the polyimide-based polymer, it is preferable from the viewpoint of the strength and transparency of the transparent film substrate. The repeating structural unit represented by the formula (PI) is based on all repeating structural units of the polyimide-based polymer, preferably 40 mol% or more, more preferably 50 mol% or more, and further preferably 70 mol More than 90% of ears, especially 90% of moles, and more preferably 98% of moles.

G in the formula (PI) represents a tetravalent organic group, and A represents a divalent organic group. In the formula (a) G ² represents an organic group of valency 3, A ² represents a divalent organic group of. In the formula (a ') G ³ represents the tetravalent organic group, A ³ represents a divalent organic group of. Of formula (b), the G ⁴ and A ⁴ each represent an organic group of divalent.

In the formula (PI), the tetravalent organic group represented by G (hereinafter, sometimes referred to as the organic group of G) may be selected from the group consisting of acyclic aliphatic groups, cyclic aliphatic groups, and aromatic groups The base of the group. From the viewpoint of transparency and flexibility of the transparent film substrate, G is preferably a tetravalent cyclic aliphatic group and a tetravalent aromatic group. Examples of the aromatic group include a monocyclic aromatic group, a condensed polycyclic aromatic group, and a non-condensed polycyclic aromatic group in which an aromatic group is directly connected or mutually connected by a bonding group. From the viewpoint of transparency of the transparent film substrate and suppression of coloration, the organic group of G may also be a cycloaliphatic group, a cycloaliphatic group having a fluorine-based substituent, or a monocyclic type having a fluorine-based substituent An aromatic group, a condensed polycyclic aromatic group having a fluorine-based substituent, or a non-condensed polycyclic aromatic group having a fluorine-based substituent. In this specification, the fluorine-based substituent refers to a group containing a fluorine atom. The fluorine-based substituent is preferably a fluorine group (fluorine atom, -F) and a perfluoroalkyl group, and more preferably a fluorine group and a trifluoromethyl group.

More specifically, the organic group of G is selected from, for example, saturated or unsaturated cycloalkyl, saturated or unsaturated heterocycloalkyl, aryl, heteroaryl, arylalkyl, alkylaryl, heteroalkylaryl A base, and a base having any two of the bases (which may be the same) and the bases are directly connected or mutually connected by a bonding base. Examples of the bonding group include -O-, alkylene having 1 to 10 carbon atoms, -SO _2- , -CO-, or -CO-NR- (R represents a carbon number such as methyl, ethyl, and propyl) 1 to 3 alkyl group, or hydrogen atom).

The carbon number of the tetravalent organic group represented by G is usually 2 to 32, preferably 4 to 15, more preferably 5 to 10, and still more preferably 6 to 8. When the organic group of G is a cycloaliphatic group and an aromatic group, at least one of the carbon atoms constituting these groups may be substituted with a heteroatom. Examples of heteroatoms include O, N, and S.

Specific examples of G include groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), and formula (26). The * in the formula represents the bond key. Z in formula (26) represents a single bond, -O-, -CH _2- , -C (CH ₃ ) _2- , -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C (CH ₃ ) ₂ -Ar-, or -Ar-SO ₂ -Ar-. Ar represents an aryl group having 6 to 20 carbon atoms, and for example, phenylene can be mentioned. At least one of the hydrogen atoms of these groups may be substituted with a fluorine-based substituent.

In the formula (PI), the divalent organic group represented by A (hereinafter sometimes referred to as the organic group of A) may be selected from the group consisting of acyclic aliphatic groups, cyclic aliphatic groups, and aromatic groups The organic base of the price of two groups. The divalent organic group represented by A is preferably a divalent cyclic aliphatic group and a divalent aromatic group. Examples of the aromatic group include a monocyclic aromatic group, a condensed polycyclic aromatic group, and a non-condensed polycyclic ring having two or more aromatic rings in which other rings are directly connected or mutually connected by a bonding group Type aromatic group. From the viewpoints of transparency of the transparent film substrate and suppression of coloring, it is preferable that a fluorine-based substituent is introduced into the organic group of A.

More specifically, the organic group of A is selected from, for example, saturated or unsaturated cycloalkyl, saturated or unsaturated heterocycloalkyl, aryl, heteroaryl, arylalkyl, alkylaryl, heteroalkylaryl A base, and a base having any two of the bases (which may be the same) and the bases are directly connected or mutually connected by a bonding base. Examples of the hetero atom include O, N, or S; examples of the bonding group include -O-, an alkylene group having 1 to 10 carbon atoms, -SO _2- , -CO-, or -CO-NR- ( R represents a C 1-3 alkyl group such as a methyl group, an ethyl group, a propyl group, or a hydrogen atom).

The carbon number of the divalent organic group represented by A is usually 2 to 40, preferably 5 to 32, more preferably 12 to 28, and still more preferably 24 to 27.

Specific examples of A include the groups represented by formula (30), formula (31), formula (32), formula (33), and formula (34). The * in the formula represents the bond key. Z ¹ to Z ³ each independently represent a single bond, -O-, -CH _2- , -C (CH ₃ ) _2- , -SO _2- , -CO-, or -CO-NR- (R represents a methyl group , Ethyl, propyl and other C 1-3 alkyl groups, or hydrogen atoms). In the following groups, Z ¹ and Z ² and Z ² and Z ^{3 are} preferably located in the meta or para position with respect to each ring, respectively. Moreover, the single bond of Z ¹ and the terminal, the single bond of Z ² and the terminal, and the single bond of Z ³ and the terminal are preferably in the meta position or the para position, respectively. An example of A is that Z ¹ and Z ³ are -O-, and Z ² is -CH _2- , -C (CH ₃ ) _2- , or -SO _2- . One or more hydrogen atoms of these groups may be substituted with fluorine-based substituents.

Regarding at least one of A and G, at least one hydrogen atom constituting these hydrogen atoms may be selected from the group consisting of a fluorine-based substituent, a hydroxyl group, a sulfonyl group, and a C 1-10 alkyl group At least one functional group. Moreover, when the organic group of A and the organic group of G are respectively a cycloaliphatic group or an aromatic group, it is preferable that at least one of A and G has a fluorine-based substituent, and it is more preferable that it is A and G Both have fluorine-based substituents.

G ² in formula (a) is a trivalent organic group. The organic group may be selected from the same groups as the organic group of G in the formula (PI) except that it is trivalent. As an example of G ² , the formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), and formula ( 26) Any one of the four bonding bonds of the indicated group is substituted with a hydrogen atom. A ² in formula (a) may be selected from the same groups as A in formula (PI).

In the formula (a ') G ³ selected from the same as in the formula (PI) G group. In the formula (a ') A ³ may be selected from the same as in the formula (PI) A group.

G ⁴ in formula (b) is a divalent organic group. The organic group may be selected from the same groups as the organic group of G in the formula (PI) except that it is a divalent group. Examples of G ⁴ include formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), and formula (2) listed as specific examples of G. 26) A group in which any two of the four bonding bonds of the represented group are replaced with hydrogen atoms. A ⁴ in formula (b) may be selected from the same group as A in formula (PI).

The polyimide-based polymer contained in the transparent film substrate may also be composed of diamines, tetracarboxylic acid compounds (including tetracarboxylic acid compound analogs such as acetyl chloride compounds and tetracarboxylic dianhydrides), or three A condensation-type polymer obtained by polycondensation of at least one carboxylic acid compound (including tricarboxylic acid compound analogs such as an acetyl chloride compound and a tricarboxylic anhydride). Furthermore, a dicarboxylic acid compound (including an acetyl chloride compound and the like) may be polycondensed. The repeating structural unit represented by formula (PI) or formula (a ') is usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by formula (a) is usually derived from diamines and tricarboxylic acid compounds. The repeating structural unit represented by formula (b) is usually derived from diamines and dicarboxylic acid compounds.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds, alicyclic tetracarboxylic acid compounds, and acyclic aliphatic tetracarboxylic acid compounds. Two or more tetracarboxylic acid compounds may be used in combination. The tetracarboxylic acid compound is preferably tetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride include aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and acyclic aliphatic tetracarboxylic dianhydride.

From the viewpoints of the solubility of the polyimide-based polymer in a solvent and the transparency and flexibility when forming a transparent film substrate, the tetracarboxylic acid compound is preferably an alicyclic tetracarboxylic acid compound and aromatic Group tetracarboxylic acid compound. From the viewpoints of transparency of the transparent film substrate and suppression of coloration, the tetracarboxylic acid compound is preferably an alicyclic tetracarboxylic acid compound having a fluorine-based substituent and an aromatic tetracarboxylic acid compound having a fluorine-based substituent, Furthermore, an alicyclic tetracarboxylic acid compound is preferable.

Examples of the tricarboxylic acid compounds include aromatic tricarboxylic acids, alicyclic tricarboxylic acids, non-cyclic aliphatic tricarboxylic acids, and similar acetyl chloride compounds, acid anhydrides, and the like. The tricarboxylic acid compound is preferably an aromatic tricarboxylic acid, an alicyclic tricarboxylic acid, an acyclic aliphatic tricarboxylic acid, and similar acetyl chloride compounds. Two or more tricarboxylic acid compounds may be used in combination.

From the viewpoints of the solubility of the polyimide-based polymer in a solvent and the transparency and flexibility when forming a transparent film substrate, the tricarboxylic acid compound is preferably an alicyclic tricarboxylic acid compound or aromatic Group tricarboxylic acid compounds. From the viewpoints of transparency of the transparent film substrate and suppression of coloration, the tricarboxylic acid compound is preferably an alicyclic tricarboxylic acid compound having a fluorine-based substituent and an aromatic tricarboxylic acid compound having a fluorine-based substituent.

Examples of the dicarboxylic acid compounds include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, non-cyclic aliphatic dicarboxylic acids, and similar acetyl chloride compounds, acid anhydrides, and the like. The dicarboxylic acid compound is preferably an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, an acyclic aliphatic dicarboxylic acid, and similar acetyl chloride compounds. Two or more dicarboxylic acid compounds may be used in combination.

From the viewpoints of the solubility of the polyimide-based polymer in the solvent and the transparency and flexibility when forming a transparent film substrate, the dicarboxylic acid compound is preferably an alicyclic dicarboxylic acid compound and an aromatic Group dicarboxylic acid compound. From the viewpoints of transparency of the transparent film substrate and suppression of coloration, the dicarboxylic acid compound is preferably an alicyclic dicarboxylic acid compound having a fluorine-based substituent and an aromatic dicarboxylic acid compound having a fluorine-based substituent.

Examples of the diamines include aromatic diamines, alicyclic diamines, and aliphatic diamines. Two or more diamines may be used in combination. From the viewpoints of the solubility of the polyimide-based polymer in a solvent, and the transparency and flexibility when forming a transparent film substrate, the diamines are preferably alicyclic diamines and have a fluorine-based substitution Aromatic diamine.

If such a polyimide-based polymer is used, it is particularly easy to obtain excellent bendability and high light transmittance (for example, 85% or more, preferably 88% or more for light at 550 nm), and A transparent film substrate having a low yellowness (for example, a YI value of 5 or less, preferably 3 or less) and a low haze (for example, 1.5% or less, preferably 1.0% or less).

The polyimide-based polymer may be a copolymer containing a plurality of repeating units of different types. The weight average molecular weight of the polyimide-based polymer is usually 10,000 to 500,000. The weight average molecular weight of the polyimide-based polymer is preferably 50,000 to 500,000, and more preferably 70,000 to 400,000. The weight average molecular weight is the standard polystyrene converted molecular weight measured by GPC (Gel Permeation Chromatography). Although the weight average molecular weight of the polyimide-based polymer is larger, the tendency to obtain higher flexibility is easier, but if the weight average molecular weight of the polyimide-based polymer is too large, the viscosity of the varnish becomes high, and the processability The tendency to decline.

The polyimide-based polymer may contain a halogen atom such as a fluorine atom that can be introduced through the fluorine-based substituent or the like. Since the polyimide-based polymer contains halogen atoms, the elastic modulus of the transparent film substrate can be increased, and the yellowness can be reduced. Thereby, the occurrence of scratches, wrinkles, etc. on the transparent film substrate is suppressed, and the transparency of the transparent film substrate can be improved. The halogen atom is preferably a fluorine atom. The content of halogen atoms in the polyimide-based polymer is based on the total mass of the polyimide-based polymer, preferably 1 to 40% by mass, and more preferably 1 to 30% by mass.

The polyimide-based polymer is preferably formed into a film (layer) having a thickness of 50 μm including the polyimide-based polymer, and the total light transmittance of the polyimide-based polymer film is 85 %, And the transparent polyimide-based polymer with a yellowness (YI value) of the polyimide-based polymer film of 10 or less. The above-mentioned total light transmittance is preferably 90% or more. The aforementioned yellowness is preferably 5 or less. By using the transparent polyimide-based polymer, a transparent film substrate with high transparency can be obtained. Furthermore, the total light transmittance of the polyimide-based polymer film is more preferably 91% or more, and still more preferably 92% or more. The yellowness is more preferably 3 or less, and particularly preferably 2.5 or less. Here, the polyimide-based polymer film can be formed by applying and drying the polyimide-based polymer dissolved in a solvent. The total light transmittance of the polyimide-based polymer film can be obtained in accordance with JIS K7105: 1981. The yellowness YI of the polyimide-based polymer film can be obtained in accordance with JIS K 7373: 2006.

(Inorganic component)
The transparent film substrate further contains inorganic components. By including an inorganic component, the strength of the transparent film substrate can be improved, and the process characteristics of the touch panel during heat resistance and solvent resistance can be improved.

The inorganic component is preferably a silicon material containing silicon atoms. In addition, the inorganic component preferably contains inorganic particles. Examples of inorganic particles are particles containing silicon atoms. An example of particles containing silicon atoms are silicon dioxide particles. Other examples of inorganic particles are titania particles, alumina particles, and zirconia particles.

The average primary particle diameter of the inorganic particles may be 200 nm or less, preferably 10-100 nm, and more preferably 20-50 nm. The reason why the average primary particle diameter of the inorganic particles is preferably within the above range is that if the average primary particle diameter is 200 nm or less, the transparency of the film is improved, and if the average primary particle diameter is 10 nm or more, the strength of the film is increased . The measurement of the primary particle diameter can be set to a fixed diameter using a transmission electron microscope (TEM). The average primary particle size can be measured by TEM observation to determine the primary particle size at 10 locations, and the average value can be obtained.

When the transparent film base material contains inorganic particles, the content ratio of the polyimide-based polymer to the inorganic particles can be 1: 9 to 9: 1, preferably 3: 7 to 8: 2 in terms of mass ratio. . If the blending ratio of the polyimide-based polymer and the inorganic particles is within the above range, the transparency or mechanical strength tends to increase.

The inorganic particles can also be bonded to each other by molecules having a siloxane bond (-SiOSi-).

The inorganic component may also contain an organosilicon compound such as quaternary alkoxysilane such as orthosilicate or an inorganic component derived from a metal alkoxide such as a metal alkoxide having an amine group. Such an inorganic component may be, for example, a molecule having SiO ₂ or a siloxane bond (-SiOSi-). When inorganic particles and organosilicon compounds are mixed in the varnish used to form the transparent film substrate, the obtained transparent film substrate has a structure in which inorganic particles are bonded to each other by molecules having a siloxane bond . By having such a structure, the transparent film base material becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics.

In the transparent film base material, the content of the inorganic component is based on the total solid content of the transparent film base material and can be 30 to 60% by mass, preferably 35 to 55% by mass, more preferably 40 to 50% by mass . As a result, the transparent film base material becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics.

The transparent film base material may further contain other components within a range that does not impair transparency and flexibility. Examples of other components include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants or lubricants, and leveling agents.

The thickness of the transparent film substrate is appropriately adjusted depending on the application, for example, it can be 20-50 μm, preferably 22-45 μm, and more preferably 25-40 μm. If the thickness of the transparent film substrate is within the above range, the transparent film substrate becomes more excellent in transparency, flexibility, visibility during bending, and process characteristics during the manufacture of a touch panel.

The total light transmittance of the transparent film substrate according to JIS K7361-1: 1997 can be 85% or more, preferably 90% or more. In addition, the haze (Haze) of the transparent film substrate according to JIS K 7136: 2000 may be 1.5% or less, preferably 1.0% or less.

(Manufacturing method)
Next, an example of the method for manufacturing the transparent film substrate of this embodiment will be described.

A solvent-soluble polyimide-based polymer obtained by polymerization using a well-known synthetic method of polyimide-based polymer is dissolved in a solvent to prepare a polyimide-based varnish. As the solvent, any solvent that dissolves the polyimide-based polymer may be used, for example, DMAc (Dimethylacetamide), DMF (dimethylformamide), DMSO (dimethyl) Dimethyl sulfoxide, γ-butyrolactone, or a combination of these. The polyimide-based polymer may be any polyimide-based polymer that is soluble in a solvent, and preferably contains an alicyclic tetracarboxylic dianhydride, an aromatic diamine, and an alicyclic diamine. A structure obtained by using two or more kinds of amines and non-cyclic aliphatic diamines alone or in combination.

Polyimide-based varnishes may contain water in addition to the above-mentioned solvents. By varnish containing water, readily available yellowness, a thickness direction retardation R _th, the absolute value of photoelastic coefficient, and the linear expansion coefficient of the transparent film substrate satisfy the above conditions.

The polyimide-based varnish may further contain the above-mentioned inorganic particles. In addition, the polyimide-based varnish may contain an organic silicon compound such as a quaternary alkoxysilane such as tetraethyl orthosilicate.

When the polyimide-based varnish contains inorganic particles, the varnish may further contain a linking group for bonding the inorganic particles to each other through a siloxane bond. Examples of linking groups are metal alkoxides such as alkoxysilanes. Examples of metal alkoxides are metal alkoxides having an amine group, examples of which are 3-aminopropyltriethoxysilane and 3- (2-aminoethylamino) propyltrimethoxysilane . The amine group of the linking group can catalyze the reaction between the inorganic particles and the linking group.

The addition amount of the linking group can be 0.1 to 100 parts by mass, preferably 0.5 to 50 parts by mass with respect to 100 parts by mass of the solid content of the polyimide varnish (polyimide polymer and inorganic particles) Quality parts.

Furthermore, additives may be further added to the polyimide-based varnish, for example, antioxidants, mold release agents, stabilizers, bluing agents, flame retardants or lubricants, and leveling agents may be added as additives.

Then, using a known roll-to-roll or batch method, the above-mentioned polyimide-based varnish is coated on a PET (Polyethylene Terephthalate) substrate, SUS tape, or glass substrate and A coating film is formed, the coating film is dried, and peeled from the substrate, thereby obtaining a film.

The coating film is dried by evaporating the solvent at a temperature of 50 to 350 ° C under an inert gas or reduced pressure. The drying of the coating film can also be carried out in multiple stages by changing the temperature conditions. In this case, the temperature can be increased as the process proceeds to the later stage.

In addition, the coating film may be dried after being peeled off from the substrate. That is, the coating film can be dried on the substrate as the first drying, and then peeled off from the substrate, and then dried to be the second drying. The second drying can be performed by attaching a metal frame to the coating film peeled from the substrate. The second drying may be performed at a higher temperature than the first drying, for example, the first drying may be performed at 50 to 150 ° C, and the second drying may be performed at 180 to 350 ° C. Furthermore, both the first drying and the second drying can be performed in multiple stages while changing the temperature conditions.

[Touch sensor panel and display device]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a display device provided with a touch sensor panel. The display device 100 shown in FIG. 1 includes an organic EL (Electroluminescence) device 50, a touch sensor panel 70, and a front panel 90, and is housed in a casing (not shown). The organic EL device 50 and the touch sensor panel 70 and between the touch sensor panel 70 and the front panel 90 are adhered by, for example, an optical clear adhesive (OCA) (not shown).

The organic EL device 50 includes an organic EL element 51, a first substrate 55, a second substrate 56, and a sealing material 59.

The organic EL element 51 has a pair of electrodes (first electrode 52 and second electrode 53) and a light-emitting layer 54. The light emitting layer 54 is arranged between the first electrode 52 and the second electrode 53.

The first electrode 52 uses a light-transmitting conductive material as a forming material. The second electrode 53 may have translucency. As the first electrode 52 and the second electrode 53, well-known materials can be used.

The light-emitting layer 54 can use a well-known light-emitting material constituting an organic EL element as a forming material, and both low-molecular compounds and high-molecular compounds can be used.

In the organic EL device 50, when power is supplied between the first electrode 52 and the second electrode 53, carriers (electrons and holes) are supplied to the light-emitting layer 54 to cause the light-emitting layer 54 to generate light. The light generated by the light-emitting layer 54 is emitted to the outside of the organic EL device 50 through the first electrode 52 and the first substrate 55.

The first substrate 55 uses a light-transmitting material as a forming material. The second substrate 56 may have translucency. The first substrate 55 and the second substrate 56 are bonded together by a sealing material 59 disposed so as to surround the organic EL element to form a sealing structure that seals the organic EL element inside.

As a material for forming either or both of the first substrate 55 and the second substrate 56, a known transparent resin such as acrylic resin can be used.

The touch sensor panel 70 has a substrate 71 and an element layer 72 having a detection element formed on the substrate 71.

The substrate 71 uses the transparent film base material for the touch sensor panel of this embodiment.

A well-known detection element including a semiconductor element, wiring, and resistance is formed on the element layer 72. As the configuration of the detection element, a configuration that realizes a well-known detection method such as a matrix switch, a resistive film method, and an electrostatic capacitance type can be adopted.

The touch sensor panel 70 using the transparent film base material for a touch sensor panel of the present embodiment on the substrate 71 sufficiently suppresses the contrast change and hue change of the bent portion during bending, and is excellent in visibility.

The front panel 90 uses a light-transmitting material as a forming material and functions as a protective base material for protecting the display device. As the front panel 90, a well-known transparent resin such as acrylic resin can be used.

In addition, the display device 100 may be provided with a layer to which various functional layers such as an ultraviolet absorbing layer, a hard coat layer, an adhesive layer, a hue adjustment layer, and a refractive index adjustment layer are added as part of the above-mentioned substrates or other substrates.

Since the display device 100 includes the touch sensor panel 70 using the transparent film substrate for the touch sensor panel of the present embodiment, the contrast change and the hue change of the bent portion during bending are sufficiently suppressed to become an organic EL device The visibility of 50 is excellent.
[Example]

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1]
(Preparation of Polyimide Varnish)
20% by mass of polyimide with a glass transition temperature of 390 ℃ ("Neopulim" manufactured by Mitsubishi Gas Chemical Co., Ltd., a polyimide-based polymer containing a repeating structural unit of formula (PI)) Butyrolactone solution, dispersion of silica particles (average primary particle size 30 nm) with 30% by mass solids dispersed in γ-butyrolactone, and dimethyl alkoxysilane The ethylacetamide solution was mixed and stirred for 30 minutes, thereby preparing a polyimide-based varnish.

Here, the formulation amount of each component is based on the total content of silica particles and the total amount of silica particles and polyimide-based polymer (solid content of polyimide-based varnish) (100 mass %) Adjust to become 50% by mass. In addition, in the polyimide-based varnish, the amount of the alkoxysilane having an amine group is relative to that of the silica particles and the polyimide-based polymer (solid component of the polyimide-based varnish). The total amount is 100 parts by mass, which is set to 1.5 parts by mass.

(Manufacture of transparent film substrates for touch sensor panels)
The polyimide-based varnish was applied to the glass substrate, heated at 50 ° C for 30 minutes, and then heated at 140 ° C for 10 minutes, and then further heated at 210 ° C for 1 hour, and peeled from the glass substrate, thereby A polyimide-based film with a thickness of 25 μm was obtained. This polyimide-based film was used as a transparent film base material for touch sensor panels.

[Example 2]
In the preparation of polyimide-based varnishes, the formulation amount of each component is adjusted so that the content of silicon dioxide particles is 55% by mass based on the total amount of silicon dioxide particles and polyimide-based polymers. Except for this, a polyimide-based varnish was prepared in the same manner as in Example 1 and a transparent film base material for a touch sensor panel using the same was prepared.

[Example 3]
In the preparation of polyimide-based varnishes, the formulation amount of each component is adjusted so that the content of silica particles is 30% by mass based on the total amount of silica particles and polyimide-based polymers Except for this, a polyimide-based varnish was prepared in the same manner as in Example 1 and a transparent film base material for a touch sensor panel using the same was prepared.

[Example 4]
An 18% by mass γ-butyrolactone solution of polyimide "KPI-MX300F (100)" manufactured by Kawamura Industries Co., Ltd. was dispersed in γ-butyrolactone with a solid content concentration of 30% by mass of dioxide A dispersion liquid of silicon particles (average primary particle diameter of 30 nm) and a dimethylacetamide solution of an alkoxysilane having an amine group are mixed and stirred for 30 minutes, thereby preparing a polyimide-based varnish.

Here, the formulation amount of each component is adjusted so that the content of silicon dioxide particles is 50% by mass based on the total amount of silicon dioxide particles and polyimide-based polymer. In addition, in the polyimide-based varnish, the addition amount of the alkoxysilane having an amine group is 1.5 parts by mass relative to 100 parts by mass of the total amount of silica particles and the polyimide-based polymer.

(Manufacture of transparent film substrates for touch sensor panels)
The polyimide-based varnish was applied to the glass substrate, heated at 50 ° C for 30 minutes, and then heated at 140 ° C for 10 minutes, and then further heated at 210 ° C for 1 hour, and peeled from the glass substrate, thereby A polyimide-based film with a thickness of 25 μm was obtained. This polyimide-based film was used as a transparent film base material for touch sensor panels.

[Comparative Example 1]
During the preparation of the polyimide-based varnish, silicon dioxide and alkoxysilane having an amine group were not added, except that the polyimide-based varnish was prepared and used in the same manner as in Example 1. Transparent film substrate for touch sensor panel.

[Comparative Example 2]
The thickness of the transparent film substrate for the touch sensor panel was set to 50 μm, except that the polyimide varnish was prepared in the same manner as in Example 3 and the touch sensor panel using the same Transparent film substrate.

[Comparative Example 3]
During the preparation of the polyimide-based varnish, silicon dioxide and alkoxysilane having an amine group were not added, except that the polyimide-based varnish was prepared and used in the same manner as in Example 4. Transparent film substrate for touch sensor panel.

[Comparative Example 4]
In the preparation of polyimide-based varnishes, the formulation amount of each component is adjusted so that the content of silicon dioxide particles is 40% by mass based on the total amount of silicon dioxide particles and polyimide-based polymers. Except for this, a polyimide-based varnish was prepared in the same manner as in Example 4 and a transparent film substrate for a touch sensor panel using the same was prepared.

[Determination of a thickness direction retardation R _th of]
Using a phase difference measuring apparatus (Oji Scientific Instruments (shares), trade name: KOBRA), of a thickness direction retardation R _th Examples and Comparative Examples of the transparent film base of the embodiment was measured. The results are shown in Table 1.

[Measurement of photoelastic coefficient]
The transparent film substrates of Examples and Comparative Examples were cut into a width of 20 mm and a length of 150 mm as test pieces. In a state where tensile stresses of 0 MPa, 3 MPa, 6 MPa, 9 MPa, and 12 MPa were applied to the longitudinal direction of the test piece, in-plane retardation R ₀ was measured respectively. The quotient obtained by dividing the in-plane phase difference R ₀ by the thickness of the test piece is the birefringence Δn. Plot the tensile stress σ as the horizontal axis and the birefringence Δn when the stress acts on the test piece as the vertical axis, and find the slope C of the approximation by the least square method so that the relationship between the two becomes Δn = Cσ Absolute value, and use it as the photoelastic coefficient. The results are shown in Table 1.

[Measurement of optical properties]
(Yellowness)
The yellowness (Yellow Index: YI) of the transparent film substrates of Examples and Comparative Examples was measured using an ultraviolet-visible and near-infrared spectrophotometer V-670 manufactured by JASCO Corporation. After performing background measurement without a sample, the transparent film substrate is set in the sample holder, and transmittance measurement for light of 300 to 800 nm is performed to obtain tristimulus values (X, Y, Z). From this tristimulus value, YI is calculated based on the following formula. The results are shown in Table 1.
YI ＝ 100 × (1.2769X－1.0592Z) / Y

(Full light transmittance)
Regarding the total light transmittance of the transparent film substrates of Examples and Comparative Examples, the ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by Japan Spectroscopy Co., Ltd. was used to measure the transmittance for light of 300 to 800 nm. The total light transmittance (Tt) of the transparent film substrates of Examples and Comparative Examples exceeded 90%.

[Measurement of linear expansion coefficient]
The transparent film substrates of Examples and Comparative Examples were cut into a width of 5 mm and a length of 20 mm as test pieces. According to JIS K7197, a thermomechanical analyzer (Thermo-Mechanical Analyzer: TMA) "EXSTAR-6000" manufactured by SII NanoTechnology Co., Ltd. was used, and the temperature was raised from 25 ° C to 180 ° C at a rate of 10 ° C / min. The amount of deformation at temperature. The coefficient of linear expansion (average coefficient of linear expansion) of the test piece was determined from the amount of deformation in the temperature range of 90 to 150 ° C. In addition, the case where the film size becomes larger (expansion) as the temperature rises is taken as plus (Plus), and the case where the film size becomes smaller (shrinkage) as the temperature rises as negative (Minus). The results are shown in Table 1.

[Determination of glass transition temperature]
Using the DSC Q200 manufactured by TA Instruments, to measure the sample volume: 5 mg, the temperature range: from room temperature to 400 ° C, and the heating rate: 10 ° C / min, the glass of the transparent film substrates of Examples and Comparative Examples The transition temperature (Tg) is measured. The results are shown in Table 1. The higher the glass transition temperature, the higher the heat resistance of the transparent film substrate, which can be said to be excellent in process characteristics. (P14L2)

[Determination of Elastic Modulus]
As a measuring device for elastic modulus, Autograph AG-IS manufactured by Shimadzu Corporation was used. Prepare a short strip of transparent film substrate with a width of 10 mm and a length of 100 mm as a test piece. A tensile test was conducted under the conditions of a distance between chucks of 50 mm and a tensile speed of 20 mm / min to determine the tensile modulus of elasticity of the transparent film substrate. The results are shown in Table 1.

[Evaluation of solvent resistance]
The transparent film substrates of Examples and Comparative Examples were cut into a width of 50 mm and a length of 50 mm as test pieces. The test pieces were immersed in a large excess of methyl ethyl ketone (MEK) and left at 25 ° C for 1 hour, and then the change of the test pieces was observed. Those who did not find any change in the test piece were evaluated as "A", and those who found that the test piece was dissolved or whitened were evaluated as "B". The results are shown in Table 1. If the evaluation result is A, it is considered that the transparent film substrate has high solvent resistance and excellent process characteristics.

[Evaluation of visibility during bending]
The transparent film substrates of Examples and Comparative Examples were cut into a width of 10 mm and a length of 100 mm as test pieces. The test piece was bent 180 ° at the center in the longitudinal direction, and the presence or absence of changes in contrast and hue in the bent portion was visually observed. Those with a small change in contrast and hue in the curved part and good visibility were evaluated as "A", and those with a large change in contrast and hue in the curved part and poor visibility were rated as "B". The results are shown in Table 1.

[Table 1]
※ The content of silicon dioxide particles means the content based on the total amount of silicon dioxide particles and polyimide-based polymer (100% by mass).

50‧‧‧ organic EL device

51‧‧‧ organic EL element

52‧‧‧First electrode

53‧‧‧Second electrode

54‧‧‧luminous layer

55‧‧‧ First substrate

56‧‧‧Second substrate

59‧‧‧Sealing material

70‧‧‧Touch sensor panel

71‧‧‧ substrate

72‧‧‧Element layer

90‧‧‧Front panel

100‧‧‧Display device

FIG. 1 is a schematic cross-sectional view showing an embodiment of a display device provided with a touch sensor panel.

Claims (5)

A touch sensor panel with a transparent film substrate, comprising a polyimide-based polymer and an inorganic component, yellowness 5 or less, a thickness direction retardation R _th is 200 nm or less, the absolute value of photoelastic coefficient 30 × 10 ^-12 Pa ^-1 or less, and a coefficient of linear expansion of 50 ppm / ℃ or less. The requested item of the touch sensor panel using the transparent film substrate 1, the absolute value of photoelastic coefficient is 23 × 10 ^-12 Pa ^-1 or less. The transparent film substrate for a touch sensor panel according to claim 1 or 2, wherein the inorganic component contains silicon dioxide particles, and the content of the inorganic component is 30 based on the total solid content of the transparent film substrate ~ 60% by mass. The transparent film substrate for touch sensor panels according to any one of claims 1 to 3 has a thickness of 20 to 50 μm. A touch sensor panel provided with the transparent film substrate for a touch sensor panel according to any one of claims 1 to 4, and formed on the transparent film substrate for the touch sensor panel An element layer with detection elements.