WO2011162414A1

WO2011162414A1 - Transparent planar body and transparent touch panel

Info

Publication number: WO2011162414A1
Application number: PCT/JP2011/064994
Authority: WO
Inventors: Atsushi Yamashita; Reiko Onodera; Daisuke Teraoka; Yoshinori Ishii; Yasunori Ii
Original assignee: Gunze Limited
Priority date: 2010-06-25
Filing date: 2011-06-23
Publication date: 2011-12-29
Also published as: JP5709311B2; TW201201225A; JP2012025158A

Abstract

The present invention provides a transparent planar body and a transparent touch panel which can reduce resistance and can enhance visibility. A transparent planar body (1) having a transparent conductive layer (11) subjected to patterning on one of surface sides of a transparent substrate (12), which includes a polarizing plate (13) on the other surface side of the transparent substrate (12), and in which the transparent substrate (12) is a phase difference film which is constituted by a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 :10, and an MVR(a melt volume rate) of 0.8 to 2.0 cm³/10 minutes and has a retardation of 100 nm to 150 nm.

Description

DESCRIPTION

TITLE OF THE INVENTION: TRANSPARENT PLANAR BODY AND TRANSPARENT TOUCH PANEL TECHNICAL FIELD

[0001]

The present invention relates to a transparent planar body and a transparent touch panel.

BACKGROUND ART

[0002]

Conventionally, touch panels are used in display devices such as a banking terminal (a cash dispenser), a ticket machine, a personal computer, an OA apparatus, an electronic organizer, a PDA and a portable telephone. The touch panel is a sensor for detecting a touched part without disturbing a screen display, and various systems are devised and utilized practically. The touch panel and the display device are usually separate parts, and two module components are combined (stuck together) and accommodated in a single case for use.

[0003]

As described in Patent Document 1, a typical touch panel of a resistive type has a structure in which two transparent planar bodies each having a transparent electrode (a transparent conductive layer) of ITO or the like formed on one of surfaces of a transparent base film are provided with the transparent conductive layers disposed opposite to each other at a certain interval.

[0004]

Fig. 13 is a sectional view showing a touch panel. A touch panel 100 includes an upper electrode film 110 and a lower electrode substrate 120, and a dot spacer 103 is provided in a space thereof. The upper electrode film 110 is constituted by a phase difference film 111 and an ITO electrode 112. The lower electrode substrate 120 is constituted by a glass substrate 121 and an ITO electrode 122. The phase difference film 111 and a polarizing plate 101 are stuck together through an adhesive layer 102. The glass substrate 121 and the phase difference film 105 are stuck together through an adhesive layer 104.

[0005]

In the touch panel 100, the polarizing plate 101 and the phase difference films 111 and 105 are used in combination in order to obtain a surface low-reflection touch panel in which an external light reflection is suppressed to enhance visibility (for example, see Patent Document 2).

[0006]

Conventionally, the phase difference film 111 is formed of polycarbonate, a cycloolefin polymer film or the like.

PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0007]

Patent Document l: Japanese Unexamined Patent Publication No. 2000-89914

Patent Document 2^'· Japanese Unexamined Patent Publication No. 10-48625

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008]

However, a phase difference film constituted by a material having a glass transition point (Tg) of 150°C or less, for example, a polycarbonate or cycloolefin polymer film has the following problem. More specifically, when a layer of ITO (indium tin oxide) is to be formed on the film 111, a retardation is reduced if a temperature of the film having a Tg of 150°C is set to be equal to or higher than 140°C, for example. For this reason, a temperature of layer formation or a temperature of a heat treatment (an annealing treatment) after the layer formation cannot be raised so that a degree of crystallization of ITO is low. As a result, it is hard to reduce resistance of an ITO layer.

[0009]

Moreover, in the case in which a transparent conductive layer is constituted to have a predetermined pattern shape (for example, the case in which a transparent conductive layer is constituted to be an aggregate of a plurality of band-shaped conductive portions), there is also a problem in that the pattern shape of the transparent conductive layer is remarkable, resulting in deterioration in visibility. As one of factors of the problem, it is supposed that insufficient crystallization of ITO causes an increase in absorption of light having a wavelength of 400 to 450 nm and the ITO layer thus has a deeply yellowish color.

[0010]

Furthermore, in order to cause the pattern shape of the transparent conductive layer to be less remarkable, it is necessary to reduce a thickness of the transparent conductive layer. However, there is also a problem in that a resistance value is increased if the thickness of the transparent conductive layer is reduced.

[0011]

The present invention has been made in order to solve the problems, and an object thereof is to provide a transparent planar body and a transparent touch panel in which resistance can be reduced and visibility can be enhanced.

MEANS FOR SOLVING THE PROBLEMS

[0012]

The object of the present invention can be achieved by a transparent planar body having a transparent conductive layer subjected to patterning on one of surface sides of a transparent substrate, including a polarizing plate on the other surface side of the transparent substrate, the transparent substrate being a phase difference film which is constituted by a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 ^'■ 20 to 90 ^'■ 10, and an MVR (melt volume rate) of 0.8 to 2.0 cm³/10 minutes and has a retardation of 100 nm to 150 nm.

[0013]

Moreover, in the transparent planar body, it is preferable that the transparent substrate has a shrinkage ratio through a heat treatment at 160°C for 30 minutes of equal to or lower than 0.5% in MD (a flow direction) and TD (a direction vertical to the flow direction).

[0014]

Furthermore, it is preferable that an undercoat layer is provided between the transparent substrate and the transparent conductive layer, and the undercoat layer is constituted by a laminate formed of at least two layers having different photorefractive indices and the transparent conductive layer is formed on a low refractive index layer side.

[0015]

In addition, it is preferable that the low refractive index layer is formed of silicon oxide and the high refractive index layer is formed of a resin material containing a metal oxide particle having a photorefractive index of 2.0 to 2.8.

[0016] Moreover, the object of the present invention can be achieved by a transparent touch panel including at least one of the transparent planar bodies, the transparent conductive layer of the transparent planar body and a second transparent conductive layer which is different from the transparent conductive layer being disposed in opposite directions to each other or the same direction.

EFFECTS OF THE INVENTION

[0017]

According to the present invention, it is possible to provide a transparent planar body and a transparent touch panel in which resistance can be reduced and visibility can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]

Fig. 1 is a schematic sectional view showing a transparent touch panel according to an embodiment of the present invention.

Fig. 2 is a plan view showing a part of the transparent touch panel illustrated in Fig. 1.

Fig. 3 is a plan view showing another part of the transparent touch panel illustrated in Fig. 1.

Fig. 4 is a plan view showing a part of a variant of the transparent touch panel illustrated in Fig. 1.

Fig. 5 is a plan view showing another part of the variant of the transparent touch panel illustrated in Fig. 1.

Fig. 6 is a chart showing a result of measurement of a degree of crystallization of an ITO layer obtained in Example 1.

Fig. 7 is a chart showing a result of measurement of a degree of crystallization of an ITO layer obtained in Example 2.

Fig. 8 is a chart showing a result of measurement of a degree of crystallization of an ITO layer obtained in Example 3.

Fig. 9 is a schematic sectional view showing a variant of the transparent touch panel illustrated in Fig. 1.

Fig. 10 is a schematic sectional view showing another variant of the transparent touch panel illustrated in Fig. 1.

Fig. 11 is a schematic sectional view showing a transparent planar body sample used in a sensory test.

Fig. 12 is a graph showing a result of a variation confirmation experiment of a retardation value in the case in which a heat treatment (an annealing treatment) is carried out over a transparent substrate.

Fig. 13 is a schematic sectional view showing a conventional touch panel.

EMBODIMENT OF THE INVENTION

[0019]

An embodiment according to the present invention will be described below with reference to the accompanying drawings. For easy understanding of a structure, each of the drawings is partially enlarged or reduced in place of an actual dimensional ratio.

[0020]

Fig. 1 is a sectional view showing a schematic structure of a transparent touch panel according to an embodiment of the present invention. A transparent touch panel 100 is a touch panel of an electrostatic capacitance type, and includes a first transparent planar body 1 and a second transparent planar body 2. The first transparent planar body 1 includes a transparent substrate 12 having a patterned transparent conductive layer 11 on one of surface sides, and a polarizing plate 13 disposed on the other surface side of the transparent substrate 12. The polarizing plate 13 is usually stuck to the transparent substrate 12 through a general transparent adhesive such as an epoxybased or acrylic adhesive (not shown). The second transparent planar body 2 includes a transparent substrate 22 having a patterned transparent conductive layer 21 formed on one of surface sides. The first transparent planar body 1 and the second transparent planar body 2 are stuck together through an adhesive layer 3 in such a manner that the respective transparent conductive layers 11 and 21 are opposed apart from each other. The respective transparent conductive layers 11 and 21 may be disposed to be turned in the same direction.

[0021]

The touch panel 100 having the structure described above is attached to a display device of a banking terminal (a cash dispenser), a ticket machine, a personal computer, an OA apparatus, an electronic organizer, a PDA, a portable telephone or the like, for example, and is thus used. The touch panel 100 is attached to the display device through a transparent adhesive layer in such a manner that the polarizing plate 13 side serves as an exposed surface (a touch surface).

[0022] The transparent substrates 12 and 22 are formed of a phase difference film which is constituted by a cyclic olefin addition (co)polymer (a cyclic olefin copolymer^ COC) having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 : 10, an MVR (a melt volume rate) of 0.8 to 2.0 cm³/10 minutes, and a glass transition temperature of 170 to 200°C and has a retardation of 100 nm to 150 nm. The transparent substrates 12 and 22, that is, the phase difference films are disposed at such an angle that respective lag axes are orthogonal to each other.

[0023]

As the cyclic olefin copolymer (COC) as the addition copolymer of norbornene and ethylene, it is possible to use a product on the market, for example. Examples of the product on the market can include "TOPAS" (trade name) manufactured by TOPAS Advanced Polymers (TAP). It is preferable that the copolymerization ratio of norbornene to ethylene is 80 : 20 to 90 : 10 in a mass ratio. By setting such a copolymerization ratio, it is possible to obtain a cyclic olefin addition copolymer having a glass transition temperature (Tg) of 170 to 200°C. When a ratio of norbornene is set to be lower than 80% by mass, it is impossible to obtain a high glass transition temperature of 170°C or more as shown in Table 1. When the ratio of ethylene is set to be lower than 10% by mass, it is hard to endure a necessary posttreatment step (a coating step, a thin layer forming step, or the like) due to a reduction in a strength of a film to be obtained. The glass transition temperature (Tg) is a value measured by a differential scanning calorimeter (manufactured by SHIMADZU CORPORATION, DSC-60) in accordance with JIS K7121.

[Table l]

[0024]

As for the cyclic olefin copolymer (COC), four types of resins each having an MVR of 0.7 cm³/10 minutes, 1.8 cm³/10 minutes, 1.9 cm³/10 minutes or 2.2 cm³/10 minutes were used to be pelletized, and processability in formation into a film was then evaluated. As a result, as shown in Table 2, the resin having an MVR of 0.7 cm³/10 minutes was hard to be pelletized and hard to be formed into a film. As for the resin having an MVR of 2.2 cm³/10 minutes, the obtained film had a small strength and the resin was hard to be formed into a film. On the other hand, as for the resin having an MVR of 1.8 cm³/10 minutes and the resin having an MVR of 1.9 cm³/10 minutes, processability was excellent in both pelletization and formation into a film. Accordingly, it is preferable that the MVR of the cyclic olefin copolymer (COC) as the addition copolymer of norbornene and ethylene is 0.8 to 2.0 cm³/10 minutes, and it is more preferable that the MVR is 1.5 to 2.0 cm³/10 minutes. The MVR can be regulated through adjustment of a heat quantity in copolymerization or the like, for example.

[Table 2]

O- Pelletization or formation into a film was possible

x^ Pelletization or formation into a film was impossible

[0025]

A phenomenon in which light incident on an anisotropic substance is separated into two light rays (an ordinary ray and an extraordinary ray) having perpendicular oscillating directions to each other is referred to as double refraction, and a retardation indicates a phase difference between the ordinary ray and the extraordinary ray. The retardation is also referred to as a phase delay. In the present invention, when a refractive index in an MD direction (a flow direction) in a film surface is represented by nx, a refractive index in a TD direction (a direction vertical to the flow direction) is represented by ny and a thickness of a film is represented by d, a retardation (Re) is expressed in Equation (l) based on a difference (Δη) between the refractive index (nx) in the MD direction and the refractive index (ny) in the TD direction, and the thickness (d) of the film and can be measured by means of an automatic double refraction meter KOBRA 21-ADH manufactured by Oji Scientific Instruments, for example. Although the retardation is controlled by drawing of the copolymer film of norbornene and ethylene, the drawing technique is not particularly restricted. If an external stress is greater, a double refraction is increased so that the retardation is also increased.

Re = And = | nx - ny | x d ··· Equation (l)

[0026]

Moreover, a shrinkage ratio obtained by a heat treatment at 160°C for 30 minutes is preferably equal to or lower than 0.5 % in both MD (the flow direction) and TD (the direction vertical to the flow direction). If the shrinkage ratio exceeds 0.5%, there is caused a drawback that a flat property of a film cannot be maintained to cause deformation, and furthermore, a crack occurs in an ITO layer formed on a surface when a sputtering processing is to be carried out at a high temperature of 150°C in order to form a highly crystalline transparent conductive layer (ITO layer), for example. Although a means for controlling the shrinkage ratio to be equal to or lower than 0.5% is not particularly restricted, such a same shrinkage ratio can be obtained by using a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 : 10, an MVR (melt volume rate) of 0.8 to 2.0 cm³/10 minutes, and a glass transition temperature of 170 to 200°C to carry out a drawing processing at 180°C or more, for example.

[0027]

Examples of materials of the transparent conductive layers 11 and 21 can include transparent conductive materials such as indium tin oxide (ITO), indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, aluminum- doped zinc oxide, potassium-doped zinc oxide, silicon-doped zinc oxide, a zinc oxide-tin oxide-based material, an indium oxide-tin oxide-based material, a zinc oxide-indium oxide-magnesium oxide-based material, zinc oxide and a tin oxide film, metallic materials such as tin, copper, aluminum, nickel and chromium, and metal oxide materials. Two or more of them may be used as a compound. Moreover, it is also possible to use, as a conductive material, a metallic element which is not resistant to an acid or an alkali.

[0028]

Moreover, a composite material obtained by dispersing an extra fine conductive carbon fiber such as a carbon nanotube, a carbon nanohorn, a carbon nanowire, a carbon nanofiber or a graphite fibril or an extra fine conductive fiber constituted by a silver material in a polymer material functioning as a binder can also be used as the materials of the transparent conductive layers 11 and 21. For the polymer material, it is possible to employ a conductive polymer such as polyaniline, polypyrrole, polyacetylene, polythiophene, polyphenylene vinylene, polyphenylene sulfide, poly p-phenylene, polyheterocyclic vinylene, or PEDOT: poly(3,4-ethylenedioxythiophene). Moreover, it is possible to employ a non-conductive polymer such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether ether ketone (PEEK), polycarbonate (PC), polypropylene (PP), polyamide (PA), polyacrylic (PAC), polyimide, an epoxy resin, a phenol resin, aliphatic cyclic polyolefin or a norbornene-based thermoplastic transparent resin.

[0029]

In the case in which a carbon nanotube composite material obtained by dispersing a carbon nanotube in a non-conductive polymer material is particularly employed as the material of the transparent conductive layers 11 and 21, the carbon nanotube rarely inhibits light transmission through a dispersion in the non-conductive polymer material one by one or every bundle since the carbon nanotube has a very small diameter of generally 0.8 nm to 1.4 nm (approximately 1 nm), which is preferred for ensuring transparency of the transparent conductive layers 11 and 21.

[0030]

Examples of a method of forming the transparent conductive layers 11 and 21 can include a PVD process such as a sputtering process, a vacuum deposition process or an ion plating process, a CVD process, a coating process, and a printing process. More specifically, the transparent conductive layer is formed, by the sputtering process or the like, on a transparent substrate (a phase difference film) having the feature described above with the temperature of the substrate maintained at equal to or higher than 140°C. Alternatively, the transparent conductive layer can be formed, through the sputtering process or the like, on a transparent substrate (a phase difference film) having the feature described above with the temperature of the film maintained at -10°C to 150°C and a heat treatment can be then carried out at a temperature of 140 to 180°C. In the case in which an ITO layer is formed by the sputtering process, for example, the thicknesses of the transparent conductive layers 11 and 21 is preferably equal to or smaller than 60 nm and more preferably equal to or smaller than 30 nm. If the thickness of the film is equal to or smaller than 5 nm, it is hard to form a continuous film. Consequently, it is difficult to form a stable conductive layer.

[0031]

As shown in Figs. 2 and 3, the transparent conductive layers 11 and 21 are formed as aggregates of band-shaped conductive portions 11a and 21a extended in parallel respectively, and the band-shaped conductive portions 11a and 21a of the transparent conductive layers 11 and 21 are disposed to be orthogonal to each other. The transparent conductive layers 11 and 21 are connected to an external driving circuit (not shown) through a run-around circuit constituted by a conductive ink or the like (not shown). Pattern shapes of the transparent conductive layers 11 and 21 are not restricted to those in this embodiment and an arbitrary shape can be taken as long as a contact point such as a finger can be detected. For example, as shown in Figs. 4 and 5, the transparent conductive layers 11 and 21 may be set to have such a structure that rhombic conductive portions lib and 21b are coupled rectilinearly, and may be disposed in such a manner that coupling directions of the rhombic conductive portions lib and 21b in the transparent conductive layers 11 and 21 are orthogonal to each other and the upper and lower rhombic conductive portions lib and 21b seen on a plane do not overlap with each other. As for operation performance such as a resolution of the transparent touch panel 100, it is better to employ a structure in which regions having no conductive portion are lessened in the case in which the first transparent planar body 1 and the second transparent planar body 2 are caused to overlap with each other. From this viewpoint, as the pattern shapes of the transparent conductive layers 11 and 21, a structure in which the rhombic conductive portions lib and 21b are coupled rectilinearly is more desirable than a rectangular structure.

[0032]

It is possible to carry out patterning of the transparent conductive layers 11 and 21 by forming a mask portion having a desirable pattern shape on surfaces of the transparent conductive layers 11 and 21 provided on a silicon-containing layer or a transparent substrate respectively and removing an exposed part through etching with an acid solution or the like, and then dissolving the mask portion in an alkali solution or the like. [0033]

The polarizing plate 13 has a structure in which a layer obtained by drawing polyvinyl alcohol (PVA) and carrying out coloring with iodine is used as a polarizer and cellulose triacetate layers (TAC layers) as protective layers are superposed on both sides thereof, for example. If a transmittance in a direction of a transmission axis is high and a transmittance in a direction of an absorption axis is low, the polarizing plate 13 may be constituted by using a hydrophilic polymer film in addition to PVA, a dichromatic pigment in addition to iodine and a transparent film material in addition to TAC. The polarizing plate 13 is stuck in such a manner that a transmission axis thereof and a lag axis of the transparent substrate 12 as a phase difference film form an angle of 45 degrees. Moreover, in order to protect an exposed surface of the polarizing plate 13, it is also possible to provide a covering layer 4 on the exposed surface as shown in Fig. 1. The covering layer 4 is preferably constituted by a material having high transparency. More specifically, examples can include a flexible film of polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether ether ketone (PEEK), polycarbonate (PC), polypropylene (PP), polyamide (PA), polyacrylic (PAC), acrylic, an amorphous polyolefin-based resin, a cyclic polyolefin-based resin, aliphatic cyclic polyolefin or a norbornene-based thermoplastic transparent resin, a laminate formed of two or more of them, glass and the like. In order to enhance mar-proofness, abrasion resistance, fingerprint resistance, an antireflection property and a non-glare property, a surface treatment processing may be carried out over the exposed surface of the polarizing plate 13 or the covering layer 4. Moreover, the covering layer is usually stuck to the polarizing plate 13 through a general transparent adhesive such as an epoxybased or acrylic adhesive (not shown).

[0034]

For the adhesive layer 3, it is possible to use a general transparent adhesive such as an epoxybased or acrylic adhesive. It is also possible that the adhesive layer 3 include a core material formed of a transparent film of a norbornene-based resin. Moreover, the adhesive layer 3 may be formed by superposing a plurality of sheet-like adhesive materials. In addition, the adhesive layer 3 may be formed by superposing plural kinds of sheet-like adhesive materials. Although the thickness of the adhesive layer 3 is not particularly designated, it is preferably equal to or smaller than 200 μπι practically. Moreover, a photorefractive index of the adhesive layer 3 is preferably 1.40 to 1.70 and is further preferably 1.46 to 1.57. If a refractive index of the adhesive layer is approximated to that of the transparent conductive layer (increased), a difference between the refractive indices on an interface is reduced so that an effect of making a pattern shape unremarkable is enhanced. However, there is a problem in that it is necessary to add a fine particle of a highly refractive material in order to increase the refractive index of the adhesive layer 3 and a transmittance of a transparent planar body is reduced. Moreover, the adhesive layer 3 is provided in contact with the transparent conductive layer and a substance containing a material which damages the transparent conductive layer, for example, an acid is not preferable.

[0035]

It is preferable that the copolymer of norbornene and ethylene which is a material of the transparent substrates 12 and 22 according to the present invention usually has a coefficient of water absorption (23°C/24 hours) of approximately 0.005 to 0.1%. When the coefficient of water absorption (in accordance with ISO 62, 23°C/24 hours) exceeds 0.1%, dimensional stability of an obtained substrate tends to be deteriorated. Usually, the photorefractive index (in accordance with JIS K7142) of the copolymer of norbornene and ethylene which is used in the transparent substrates 12 and 22 is approximately 1.49 to 1.55 and a light transmittance (in accordance with JIS K7361-1 (measured by means of a haze meter NDH5000 manufactured by NIPPON DENSHOKU CO., LTD.)) is approximately 90.8% to 93.0%. Various well-known additives such as an ultraviolet absorber, an inorganic or organic anti-blocking agent, a lubricant, an antistatic agent and a stabilizing agent may be suitably added to the copolymer of norbornene and ethylene. It is preferable that the MVR (melt volume rate) has a discharge volume (cm³) per 10 minutes at a temperature of 260°C and a load of 2.16 kg of 0.8 to 2.0 cm³/10 minutes. If the discharge volume (cm³) per 10 minutes is smaller than 0.8 cm³/10 minutes, a pressure in a molding machine becomes excessively high in manufacture of a raw material or manufacture of a film so that the manufacture cannot be carried out. If the discharge volume (cm³) per 10 minutes is larger than 2.0 cm³/10 minutes, a strength of an obtained phase difference film is excessively reduced so that it is impossible to endure a necessary processing (sputtering or the like) step for a touch panel or the like.

[0036]

A method of obtaining a film for the transparent substrates 12 and 22 from the copolymer of norbornene and ethylene is not particularly restricted and examples can include a solution casting process, an extrusion process, and a calender process. The thickness of the copolymer film of norbornene and ethylene is preferably 20 to 300 μιη and is further preferably 40 to 200 μιη. If the thickness is excessively small, the strength of the film tends to be insufficient. If the strength of the film is sufficient, it is not necessary to increase the thickness excessively.

[0037]

In order to enhance wettability and an adhesive property of a surface of the copolymer film of norbornene and ethylene, it is also possible to carry out a surface modification treatment such as a flame treatment, an ultraviolet irradiation treatment, a corona discharge treatment, a plasma treatment, an itro treatment, a primer treatment or a chemical treatment. The corona discharge treatment and the ultraviolet irradiation treatment can be carried out in air, a nitrogen gas, a rare gas or the like. A wet tension of a surface of a cyclic ole fin-based resin film is preferably set to be equal to or higher than 450 μΝ/cm (23°C) and is more preferably set to be equal to or higher than 500 μΝ/cm (23°C) by the surface modification treatment.

[0038]

The shrinkage ratio is measured as follows. Lengths of four sides of a film cut out into a size of 100 χ 100 mm were measured on a unit of 0.001 mm by using a length measuring machine and the measured film was then put into an oven set to 160°C for 30 minutes. The film was thereafter taken out, and the lengths of the four sides of the film were measured on the unit of 0.001 mm by using the length measuring machine again to obtain respective variations in the lengths of the four sides. The measurement was carried out every two sheets and an average value was obtained as the shrinkage ratio in each of the MD and TD directions. A negative value implies shrinkage and a positive value implies expansion.

[0039]

A technique for drawing the copolymer film of norbornene and ethylene to control a retardation is not particularly restricted and examples can include a roll drawing process, a tenter clip drawing process, and a rolling process.

[0040]

The present inventors formed the transparent conductive layer (the ITO layer) on the transparent substrate 12 (22) and measured the degree of crystallization of the transparent conductive layer in order to evaluate the transparent substrate 12 (22) having the structure described above. The results will be described.

[0041]

First, a film was fabricated by melt-extruding a copolymer having a copolymerization ratio of norbornene to ethylene of 82 : 18, a glass transition temperature of 180°C and an MVR of 1.5 so that the film has a thickness of 100 μιη at a resin temperature of 300°C and a take-up roll temperature .of 130°C through a melt extrusion process. Subsequently, the film was caused to run between two metal rolls different in circumference respectively having roll circumferential speeds of 7.0 m/min and 14.0 m/min in a state in which a temperature of the film was maintained at 190°C. Consequently, there was obtained a phase difference film having a draw ratio of 2.0, a retardation of 138 nm, an Nz coefficient of 1.0, and a film thickness of 86 μηι. The Nz coefficient is one of indices representing a relationship among refractive index components nx, ny and nz and is defined by Equation (2). nx and ny indicate refractive indices in a film surface and nz indicates a refractive index in a perpendicular direction to the film surface.

Nz = (nx - nz) / 1 nx - ny I ··· Equation (2)

A dimensional change rate at 160°C over 30 minutes of the obtained phase difference film was MD = -0.46% and TD = 0.22%. The obtained phase difference film had a strength sufficient for use.

[0042]

Next, a hard coat layer was provided on both sides of the obtained phase difference film by using an ultraviolet curable acrylic coating material in order to obtain a thickness of 6 μιη on a surface and a back face, respectively. The surface of the obtained film had a pencil hardness of HB.

[0043]

An ITO transparent conductive layer having a resistance value of 256 Ω/D was formed on one of the surfaces of the obtained film by the sputtering process in a state in which a temperature of the film was maintained at 150°C. Fig. 6 shows a result of measurement of a degree of crystallization of the obtained ITO layer (Example l).

Moreover, an ITO transparent conductive layer having a resistance value of 450 Ω/D was formed on one of the surfaces of the obtained film by the sputtering process in a state in which the temperature of the film was maintained at 90°C. Furthermore, a heat treatment was carried out at a temperature of 165°C for one hour to form an ITO transparent conductive layer having a resistance value of 240 Ω/D. Fig. 7 shows a result of measurement of a degree of crystallization of the obtained ITO layer (Example 2).

[0044]

Moreover, a film was fabricated by melt-extruding a copolymer having a copolymerization ratio of norbornene to ethylene of 82 ^'■ 18, a glass transition temperature of 180°C and an MVR of 1.5 so that the film has a thickness of 200 μιη at a resin temperature of 300°C and a take-up roll temperature of 130°C through a melt extrusion process. Subsequently, lateral drawing was carried out at a speed of 1.0 m/min, a draw ratio of 2.0 and a temperature of the film of 185.5°C by means of a tenter clip type drawing machine so that a phase difference film having a retardation of 138 nm, an Nz coefficient of 1.5 and a film thickness of 95 μιη was obtained. A dimensional change rate at 160°C over 30 minutes in the obtained phase difference film was MD = -0.06% and TD = -0.12%. The obtained phase difference film had a strength sufficient for use .

[0045]

A hard coat layer was provided on both sides of the obtained phase difference film by using an ultraviolet curable acrylic coating material in order to obtain a thickness of 6 μιη on a surface and a back face, respectively. The surface of the obtained film had a pencil hardness of HB. An ITO transparent conductive layer having a resistance value of 236 Ω/D was formed on one of the surfaces of the obtained film by the sputtering process in a state in which a temperature of the film was maintained at 150°C. Fig. 8 shows a result of measurement of a degree of crystallization of the obtained ITO layer (Example 3).

[0046]

As shown in Figs. 6 to 8, based on a result of measurement of a degree of crystallization of an ITO layer through an X ray, it was confirmed that an X-ray intensity peak through a peculiar (222) orientation to ITO in the vicinity of 2Θ = approximately 30° is high and the degree of crystallization of the obtained film is high in all of Examples 1 to 3.

[0047]

In the transparent touch panel 100 having the structure described above, a method of detecting a touch position is the same as that of a conventional touch panel of an electrostatic capacitance type. When an arbitrary position on a surface side of the first transparent planar body 1 is touched with a finger or the like, the transparent conductive layers 11 and 21 are grounded through an electrostatic capacitance of a human body in the contact position to detect a value of a current flowing through the transparent conductive layers 11 and 21 so that coordinates of the contact position are calculated.

[0048]

The transparent planar bodies 1 and 2 according to the present invention include the transparent substrates 12 and 22, that is, the phase difference films which are constituted by a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 : 10, an MVR (a melt volume rate) of 0.8 to 2.0 cm³/10 minutes, and a glass transition temperature of 170 to 200°C and has a retardation of 100 nm to 150 nm. In the formation of the transparent conductive layers 11 and 21 on the transparent substrates 12 and 22 or the heat treatment (annealing) after the formation of the film, therefore, it is possible to set the temperatures of the transparent substrates 12 and 22 to be equal to or higher than 140°C, thereby increasing the degrees of crystallization of the transparent conductive layers 11 and 21 to be formed. As a result, it is possible to reduce the resistance of the transparent conductive layers 11 and 21.

[0049]

Moreover, the degrees of crystallization of the transparent conductive layers 11 and 21 can be increased so that the ITO layer can be prevented from taking a deeply yellowish color and the pattern shape of the transparent conductive layer can be made less remarkable, resulting in an enhancement in the visibility of the transparent planar body and the touch panel. Furthermore, it is possible to increase the degrees of crystallization of the transparent conductive layers 11 and 21, thereby reducing the resistance. Therefore, the thickness of the transparent conductive layer can be reduced still more and the visibility can further be enhanced.

[0050]

In addition, the transparent planar body 1 according to this embodiment includes the polarizing plate 13 on the other surface side of the transparent substrate 12, that is, the phase difference film (an opposite side to a surface on which the transparent conductive layer 11 is formed). Therefore, external light incident from the polarizing plate 13 side is reflected by the surfaces of the transparent conductive layers 11 and 21 subjected to patterning and can be effectively prevented from passing through the polarizing plate 13 again. Specific description will be given. External light incident on the touch panel 100 (external light incident from the covering layer 4 side in Fig. l) is polarized into horizontal straight polarized light in the passage through the polarizing plate 13 and is thus incident on the transparent substrate 12 formed of the phase difference film. The horizontal straight polarized light incident on the transparent substrate 12 is polarized into clockwise circularly polarized light and is reflected by the surfaces of the patterned transparent conductive layers 11 and 21 or the surfaces of the transparent substrates 12 and 22 on which the transparent conductive layers 11 and 21 are not formed. The clockwise circularly polarized light thus reflected is changed into counterclockwise circularly polarized light upon reflection and is thus incident on the transparent substrate 12, that is, the phase difference film again. The counterclockwise circularly polarized light incident on the transparent substrate 12 is polarized into vertical straight polarized light in the passage through the transparent substrate 12 and is thus incident on the polarizing plate 13. The vertical straight polarized light incident on the polarizing plate 13 cannot pass through the polarizing plate 13. For this reason, it is impossible to visually recognize the light reflected by the surfaces of the patterned transparent conductive layers 11 and 21 or the surfaces of the transparent substrates 12 and 22 on which the transparent conductive layers 11 and 21 are not formed. By including the circularly polarized light structure, thus, it is possible to prevent the reflection of the external light. As a result, the pattern shapes of the patterned transparent conductive layers 11 and 21 can be made unremarkable, and furthermore, character information or image information displayed by a display device on which the touch panel is to be disposed can be seen more easily.

[0051]

Although the embodiment of the transparent planar bodies 1 and 2 according to the present invention and the transparent touch panel 100 using them have been described above, the specific structure is not restricted to the embodiment. For example, as shown in Fig. 9, it is also possible to constitute the transparent touch panel by forming the transparent substrate 22 possessed by the second transparent planar body 2 through a light isotropic film constituted by a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 : 10, an MVR (a melt volume rate) of 0.8 to 2.0 cm³/10 minutes, and a glass transition temperature of 170 to 200°C, and furthermore, drawing a polycarbonate (PC) film or a polyvinyl alcohol (PVA) film to dispose the phase difference plate 5 to which double refraction is provided.

[0052]

In this embodiment, moreover, it is possible to employ a structure in which undercoat layers 14 and 24 are provided between the transparent substrates 12 and 22 and the transparent conductive layers 11 and 21 as shown in Fig. 10. The undercoat layers 14 and 24 are constituted by laminates of low refractive index layers 14a and 24a and high refractive index layers 14b and 24b having a higher photorefractive index than the low refractive index layers 14a and 24a respectively, and are disposed in such a manner that the transparent conductive layers 11 and 21 are formed on the low refractive index layers 14a and 24a side.

[0053]

As materials of the low refractive index layers 14a and 24a, examples can include an inorganic oxide such as silicon-tin oxide, silicon oxide or aluminum oxide, a composition constituted by their combination, a fluorine -based organic matter material, a silicon oxide -based sol/ gel material, and a silicon oxide-based or fluorine-based microporous material. In respect of enhancement in visibility and productivity, the material having a photorefractive index of 1.3 to 1.5 is particularly preferable. The low refractive index layers 14a and 24a can be formed by a sputtering process, a resistive deposition process, an electron beam evaporation process, various wet coating processes, or the like.

[0054] It is desirable that the high refractive index layers 14b and 24b have photorefractive indices of 1.60 to 1.80 and it is more desirable that they have photorefractive indices which exceed 1.65 and are equal to or lower than 1.80. If the refractive index is lower than 1.60, it is hard to approximate optical characteristics of a portion having the transparent conductive layer and a portion having no transparent conductive layer, and the pattern shape of the transparent conductive layer is remarkable so that excellent visibility is hardly obtained. If the photorefractive index exceeds 1.65, very excellent visibility can be obtained. In the case in which the photorefractive index exceeds 1.80, a difference between the refractive indices of the transparent substrates 12 and 22 and the adhesive layer 3 is increased so that an interference spot greatly occurs due to light interference caused by light reflected by an interface between materials and light reflected by an interface between the high refractive index layers 14b and 24b and the low refractive index layers 14a and 24a. As a result, the pattern shapes of the transparent conductive layers 11 and 21 are apt to be seen so that the visibility is deteriorated, which is not preferable. There is also a fact that it is hard to obtain a material or technique capable of industrially forming a layer having a refractive index exceeding 1.8 and such a hardness and thickness as to enable an improvement in a damaging property efficiently. As a hard coat material for the high refractive index layers 14b and 24b having a refractive index which exceeds 1.65 and is equal to or lower than 1.80, examples can include a resin material such as an acrylic ultraviolet curable or thermosetting resin. Moreover, examples can include the resin material to which a fine particle of a metal oxide having a high refractive index such as titanium oxide (refractive index: 2.5 to 2.8), zirconium oxide (refractive index: 2.4), cerium dioxide (refractive index: 2.2) or antimony oxide (refractive index: 2.0 to 2.3). In this case, it is required that the fine particle of the metal oxide to be added has a particle size of approximately several tens of nanometers in order not to inhibit transparency. It is preferable that the thicknesses of the high refractive index layers 14b and 24b are equal to or greater than 3 μπι. If the thicknesses are smaller than 3 μπι, an interference spot greatly occurs due to the light interference caused by the light reflected by the interface between the .transparent substrates 12 and 22 and the adhesive layer 3 and the light reflected by the interface between the high refractive index layers 14b and 24b and the low refractive index layers 14a and 24a. As a result, the pattern shapes of the transparent conductive layers 11 and 21 are apt to be seen, resulting in deterioration in the visibility, which is not preferable.

[0055]

By providing the undercoat layers 14 and 24 having such a structure between the transparent substrates 12 and 22 and the transparent conductive layers 11 and 21, it is possible to reduce a difference between a transmission spectrum of light transmitted through a portion in which the transparent conductive layers 11 and 21 are formed (a pattern forming region) and a transmission spectrum of light transmitted through a portion in which the transparent conductive layers 11 and 21 are not formed (a non-pattern forming region) in 450 nm to 700 nm to be a visible range wavelength of light. Thus, it is possible to obtain the transparent planar bodies 1 and 2 and the transparent touch panel 100 in which the pattern shapes of the transparent conductive layers 11 and 21 are less remarkable and visibility is excellent. The same effects can be obtained with a structure in which the difference between the transmission spectrum of the light transmitted through the pattern forming region and the transmission spectrum of the light transmitted through the non-pattern forming region is reduced in the visible range wavelength of the light in addition to the thin layer structure.

[0056]

The present inventors carried out a sensory test for deciding whether the pattern shape of the transparent conductive layer 11 is remarkable or not and measurement of a sheet resistance value in the case of producing a sample having a structure shown in Fig. 11 in which the undercoat layer 14 is provided between the transparent substrate 12 and the transparent conductive layer 11 and irradiating the sample with transmitted light.

[Example 1]

The sample has the structure shown in Fig. 11, and the low refractive index layer 14a and the high refractive index layer 14b which constitute the undercoat layer 14 were formed of a thin S1O2 layer (refractive index: 1.46) formed by sputtering and a high refractive index hard coat layer (refractive index^ 1.65) formed by coating the substrate with a hard coat agent containing a fine particle of zirconium oxide (LIODURAS manufactured by TOYO INK CO., LTD.), respectively. The transparent conductive layer subjected to patterning was formed by etching an ITO layer formed through sputtering. A thickness of the low refractive index layer 14a (the thin S1O2 layer) was set to be 7.5 nm, a thickness of the high refractive index layer 14b (the high refractive index hard coat layer) was set to be 5 μιη and a thickness of the transparent conductive layer (the ITO layer) was set to be 20 nm. Moreover, a thickness of the adhesive layer 3 was 25 μπι and a refractive index of the adhesive layer 3 was 1.47. Furthermore, the transparent substrate 12 was formed as follows. A film was fabricated by melt-extruding a copolymer having a copolymerization ratio of norbornene to ethylene of 82 : 18, a glass transition temperature of 180°C and an MVR of 1.5 so that the film would have a thickness of 100 μιη at a resin temperature of 300°C and a take-up roll temperature of 130°C through a melt extrusion process. Subsequently, the film was caused to run between two metal rolls different in circumference respectively having roll circumferential speeds of 7.0 m/min and 14.0 m/min in a state in which a temperature of the film was maintained at 190°C. Consequently, the transparent substrate 12 was formed of a phase difference film having a draw ratio of 2.0, a retardation of 138 nm, an Nz coefficient of 1.0, and a film thickness of 86 μπι. A dimensional change rate at 160°C over 30 minutes in the obtained phase difference film was MD = -0.46% and TD = 0.22%. The phase difference film (the transparent substrate 12) had a refractive index of 1.53. Moreover, a hard coat layer 6 formed of an acrylic UV curable resin was disposed on the other surface of the transparent substrate 12 (a surface on a side on which the transparent conductive layer 11 was not formed). The hard coat layer had a thickness of 5 μιη.

[0057]

In the sample, the transparent conductive layer 11 (the ITO layer) was formed by sputtering at a temperature of 140°C and a heat treatment (an annealing treatment) was then carried out at the temperature of 140°C for 30 minutes.

[0058]

In the case in which the sample was irradiated with transmitted light, there was obtained a result that a pattern shape of the transparent conductive layer 11 was not confirmed and visibility was excellent. In the confirmation of the pattern shape, transmitted light was emitted by means of a three band fluorescent lamp (27 W) and a distance between the sample and eyes was set to be 20 cm. A determination was made in such a manner that the three band fluorescent lamp had a white background.

[0059]

The sheet resistance value was equal to or smaller than 200 Ω/D and resistance of a transparent planar body was reduced (see Table 3). The sheet resistance value was measured by means of a resistivity meter Loresta EP four point probe manufactured by Mitsubishi Chemical Corporation.

[0060]

[Comparative Example l]

As a comparative example of the sample, there was produced a comparative sample in which a transparent substrate was replaced with ZEONOR Film [manufactured by ZEON CORPORATION, ZM series] in the structure of the transparent planar body shown in Fig. 11. The transparent conductive layer 11 (the ITO layer) was formed at a temperature of 120°C by a sputtering process and a heat treatment (an annealing treatment) was then carried out at the temperature of 120°C for 30 minutes. There was also carried out a sensory test for deciding whether the pattern shape of the transparent conductive layer 11 is remarkable or not in the case in which transmitted light was irradiated. In Comparative Example 1, however, there was obtained a result that the pattern shape of the transparent conductive layer 11 was confirmed and the visibility was deteriorated (see Table 3). It is supposed that a deeply yellowish color taken by the ITO layer due to insufficient crystallization thereof caused visual recognition of a pattern.

[Table 3]

[0061]

Moreover, the present inventors executed an experiment for confirming a' change in a retardation value in the case in which a heat treatment (an annealing treatment) was carried out for 30 minutes at each predetermined temperature for the transparent substrates according to Example 1 and Comparative Example 1. The result will be described below. Fig. 12 shows the result of the experiment. The following is apparent from Fig. 12. In the transparent substrate according to Example 1, the retardation value was great, that is, approximately 134 nm even when an annealing temperature was 150°C. On the other hand, in the transparent substrate according to Comparative Example 1, the retardation value was drastically reduced and was approximately 128 nm at the annealing temperature of 150°C when the annealing temperature exceeded 140^'°C.

[0062]

Thus, it is apparent that the transparent substrate 12 constituting the transparent planar body according to the present invention can maintain the retardation value even in a high temperature environment exceeding 140°C. As a result, the temperatures of the transparent substrates 12 and 22 can be set to be equal to or higher than 140°C in the formation of the transparent conductive layers 11 and 21 on the transparent substrates 12 and 22 or the heat treatment (annealing) after the formation of the layers. Consequently, the degrees of crystallization of the transparent conductive layers 11 and 21 to be formed can be enhanced so that the resistance of the transparent conductive layers 11 and 21 can be reduced.

DESCRIPTION OF REFERENCE SIGNS

[0063]

100 transparent touch panel

1 first transparent planar body

2 second transparent planar body

11, 21 transparent conductive layer

12, 22 transparent substrate

13 polarizing plate

14, 24 undercoat layer

14a, 24a low refractive index layer

14b, 24b high refractive index layer

3 adhesive layer

Claims

1. A transparent planar body having a transparent conductive layer subjected to patterning on one of surface sides of a transparent substrate, comprising:

a polarizing plate on the other surface side of the transparent substrate, wherein

the transparent substrate is a phase difference film which is constituted by a cyclic olefin addition (co)polymer having a copolymerization ratio of norbornene to ethylene of 80 : 20 to 90 ^'■ 10, and an MVR (a melt volume rate) of 0.8 to 2.0 cm³/10 minutes and has a retardation of 100 nm to 150 nm.

2. The transparent planar body according to claim 1, wherein the transparent substrate has a shrinkage ratio through a heat treatment at 160°C for 30 minutes of equal to or lower than 0.5% in MD (a flow direction) and TD (a direction vertical to the flow direction).

3. The transparent planar body according to claim 1 or 2, wherein an undercoat layer is provided between the transparent substrate and the transparent conductive layer, and

the undercoat layer is constituted by a laminate formed of at least two layers having different photorefractive indices and the transparent conductive layer is formed on a low refractive index layer side.

4. The transparent planar body according to claim 3, wherein the low refractive index layer is formed of silicon oxide, and

the high refractive index layer is formed of a resin material containing a metal oxide particle having a photorefractive index of 2.0 to 2.8.

5. A transparent touch panel comprising at least one transparent planar body .according to any of claims 1 to 4, wherein the transparent conductive layer of the transparent planar body and a second transparent conductive layer which is different from the transparent conductive layer are disposed in opposite directions to each other or the same direction.