Touch panel

Abstract

Provided is a touch panel. The touch panel includes a base and a pressure-sensitive adhesive layer attached to the base and having a peel strength with respect to a polycarbonate sheet of 1,900 g/25 mm or more. The pressure-sensitive adhesive layer includes an acryl polymer compound containing an acryl polymer and a thiol polymer derived by binding a thiol compound into a chain, or a side chain or terminal end of a chain of the acryl polymer. Accordingly, penetration of oxygen, moisture or other impurities at an interface between the base film and the pressure-sensitive adhesive layer, or at an interface between a conductor thin film and a pressure-sensitive adhesive layer may be effectively inhibited, and degradation in optical properties such as visibility due to bubbles generated at a pressure-sensitive adhesive interface may be prevented. In addition, when the pressure-sensitive adhesive layer is directly attached to the conductor thin film and even exposed to severe conditions such as high temperature or high temperature and high humidity, the change in the resistance of the conductor thin film may be effectively inhibited, and thus the touch panel may be stably driven for a long time.

Claims

1. A touch panel, comprising: a base wherein an indium tin oxide (ITO) film is formed on at least one surface of the base; and a pressure-sensitive adhesive layer directly attached to the indium tin oxide (ITO) film on the base, which comprises an acryl polymer compound containing an acryl polymer derived from an acryl monomer and a thiol polymer derived from an acryl monomer and a thiol compound, wherein the pressure-sensitive adhesive layer completely covers the ITO film, wherein the acryl polymer compound has a polydispersity index from 5.0 to 6.9, wherein the acryl polymer compound has a weight average molecular weight of 630,000 to 2,500,000, wherein the thiol compound is at least one selected from the group consisting of n-dodecanthiol, t-butyl mercaptan, n-butyl mercaptan, 1-octadecanthiol, trimethylol propane tris(3-mercaptothiol), pentaerythritol tetrakis(3-mercaptopropionate) and glycol dimercaptoacetate, wherein the pressure-sensitive adhesive layer has a resistance change ratio of the indium tin oxide (ITO) film of 7% or less, and wherein the pressure-sensitive adhesive layer has a peel strength with respect to a polycarbonate sheet of 2,400 g/25 mm or more.

2. The touch panel according to claim 1, wherein the acryl polymer comprises a (meth)acrylic acid ester-based monomer in a polymerized form.

3. The touch panel according to claim 1, wherein the pressure-sensitive adhesive layer further comprises a multifunctional crosslinking agent crosslinking the acryl polymer compound.

4. A pressure-sensitive adhesive composition for a touch panel including a base wherein an indium tin oxide (ITO) film is formed on at least one surface of the base; and a pressure-sensitive adhesive layer directly attached to the indium tin oxide (ITO) film on the base, wherein the pressure-sensitive adhesive layer completely covers the ITO film, and the pressure-sensitive adhesive layer is formed from the pressure sensitive adhesive composition, wherein the pressure-sensitive adhesive composition comprises an acryl polymer compound containing an acryl polymer derived from an acryl monomer and a thiol polymer derived from an acryl monomer and a thiol compound, wherein the acryl polymer compound has a polydispersity index from 5.0 to 6.9, wherein the acryl polymer compound has a weight average molecular weight of 630,000 to 2,500,000, wherein the thiol compound is at least one selected from the group consisting of n-dodecanthiol, t-butyl mercaptan, n-butyl mercaptan, 1-octadecanthiol, trimethylol propane tris(3-mercaptothiol), pentaerythritol tetrakis(3-mercaptopropionate) and glycol dimercaptoacetate, wherein when a pressure-sensitive adhesive layer is formed by using the pressure-sensitive adhesive composition, the layer has a peel strength with respect to a polycarbonate sheet of 2,400 g/25 mm or more, and wherein the pressure-sensitive adhesive layer has a resistance change ratio of the indium tin oxide (ITO) film of 7% or less.

5. A double-sided pressure-sensitive adhesive tape for a touch panel, comprising a pressure-sensitive adhesive layer which is a cured product of the composition according to claim 4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 to 3 show a structure of a touch panel according to one exemplary embodiment of the present invention;

(2) FIG. 4 shows a double-sided pressure-sensitive adhesive tape according to an exemplary embodiment of the present invention; and

(3) FIG. 5 illustrates a method of measuring a resistance change ratio according to the present invention.

(4) 1, 2, 3: basic structure of the touch panel

(5) 11, 21, 31, 32, 41: pressure sensitive adhesive layer

(6) 23, 35: substrate

(7) 22, 33, 34: conductor thin film

(8) 12, 24, 36, 37: base

(9) 4: double-sided pressure-sensitive adhesive tape

(10) 42, 43: releasing film

(11) 10: PET film 20: ITO thin film

(12) 30: silver paste 40: pressure sensitive adhesive layer

(13) 51: releasing film 60: resistance measurer

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(14) Hereinafter, the present invention will be described in detail with reference to Examples according to the present invention and Comparative Examples not according to the present invention, but the scope of the present invention is not limited to the following examples.

(15) Physical properties in Examples were evaluated by the following methods:

(16) 1. Durability Test

(17) A sample was prepared by attaching a hard coating surface of a polyethylene terephthalate (PET) film (thickness: 100 μm) having hard coatings formed on both surfaces to a polycarbonate sheet (thickness: 1 mm) by means of a pressure-sensitive adhesive layer, cutting the resulting product to a size of 50 mm (width)×100 mm (length), and putting the cut product in an autoclave at 60° C. under 5 atm for 30 minutes. Afterward, the sample was left at 80° C. for 240 hours, and then durability was evaluated.

(18) The durability was evaluated by observing whether or not bubbles were generated and lift-off/peeling occurred when the sample was left under the above conditions, and specific measuring methods and criteria for evaluating respective properties are as follows:

(19) <Criteria for Evaluating Bubble Generation>

(20) O: When bubbles were not observed or it was observed that a small amount of bubbles having a diameter of 100 μm or less were dispersed at a pressure-sensitive adhesive interface through observation using an optical microscope

(21) X: When bubbles having a diameter of 100 μm or more, or groups of bubbles having a diameter of 100 μm or less were observed at a pressure-sensitive adhesive interface through observation using an optical microscope

(22) <Criteria for Evaluating Lift-Off/Peeling>

(23) O: When there was no lift-off/peeling at a pressure-sensitive adhesive interface

(24) X: When lift-off/peeling occurred at a pressure-sensitive adhesive interface

(25) 2. Resistance Change Ratio Test

(26) A resistance change ratio was measured by the method shown in FIG. 5. First, a PET film 10 (hereinafter, referred to as a “conductive PET” which is commercially available) having an ITO thin film 20 formed on one surface thereof, was cut into a size of 30 mm×50 mm (width×length). Subsequently, as shown in FIG. 5, a silver paste 30 was applied to both ends of the film to a width of 10 mm, and plasticized at 150° C. for 30 minutes. Afterward, a pressure-sensitive adhesive film having releasing films 51 attached to both surfaces thereof, as manufactured in Examples, was cut into a size of 30 mm×40 mm (width×length), the releasing film was removed from one surface of the pressure-sensitive adhesive film, and then a pressure-sensitive adhesive layer 40 was attached to the plasticized film by matching a center of the pressure-sensitive adhesive layer 40 with centers of the conductive PET 10. Then, an initial resistance R.sub.i was measured using a conventional resistance measurer 60. After measuring the initial resistance, a sample having the structure shown in FIG. 4 was left at 60° C. and 90% relative humidity for 240 hours, and a resistance (R) was measured using the measurer 60. Each value was put into Expression 1 to measure a resistance change ratio (P).
P=[(R−R.sub.i)/R.sub.i]×100  [Expression 1]

(27) 3. Peel Strength Test

(28) Peel strength was measured by preparing a double-sided pressure-sensitive adhesive tape previously manufactured to have a width of 1 inch and attaching the tape on a polycarbonate-stacked structure as an adherent by rolling the tape twice using a 2-kg roller. 30 minutes after the attachment, a 180-degree peel strength (peel rate: 300 mm/min) was measured at room temperature using a texture analyzer. The measurement was performed three times per each sample, and an average value was listed in Table 2.

(29) 4. Evaluation of Weight Average Molecular Weight and Polydispersity Index

(30) Weight average molecular weight and polydispersity index of an acryl polymer were measured using GPC under the following conditions. To prepare a calibration curve, measurement results were converted using standard polystyrene produced by Agilent System.

(31) <Conditions for Measuring Weight Average Molecular Weight>

(32) Measurer: Agilent GPC (Agilent 1200 series, USA)

(33) Column: Two PL Mixed Bs connected

(34) Column Temperature: 40° C.

(35) Soluent: Tetrahydrofuran

(36) Flow Rate: 1.0 mL/min

(37) Concentration: Up to Approximately 2 mg/mL (100 μL injection)

Preparation of Acryl Polymer Compounds

Preparation Example 1: Preparation of Acryl Polymer Compound A

(38) 58 parts by weight of n-butyl acrylate (n-BA), 40 parts by weight of methyl acrylate (MA) and 2 parts by weight of hydroxyethyl acrylate (HEA) were put into a 1 L reactor in which a cooling apparatus was equipped to reflux a nitrogen gas and facilitate temperature control. Subsequently, 150 parts by weight of ethylacetate (EAc) was added as a solvent, and the reactor was purged with nitrogen gas for 60 minutes to remove oxygen. Temperature was maintained at 60° C., and 0.04 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator to initiate the reaction. Four hours after the reaction was initiated, 0.01 parts by weight of n-dodecanthiol was added as a thiol compound. After additional reaction for 1 hour, a reaction product was diluted with EAc, thereby obtaining an acryl polymer compound A having a solid content of 30 wt %, a weight average molecular weight of 700,000, and a polydispersity index (M.sub.w/M.sub.n) of 5.2.

Preparation Example 2: Preparation of Acryl Polymer Compound B

(39) An acryl polymer compound B having a solid content of 30 wt %, a weight average molecular weight of 710,000 and a polydispersity index of 5.8 was prepared by the same method as described in Preparation Example 1, except that 0.02 parts by weight of n-dodecanthiol was added as a thiol compound.

Preparation Example 3: Preparation of Acryl Polymer Compound C

(40) An acryl polymer compound C having a solid content of 30 wt %, a weight average molecular weight of 750,000 and a polydispersity index of 5.7 was prepared by the same method as described in Preparation Example 1, except that 0.04 parts by weight of n-dodecanthiol was added as a thiol compound.

Preparation Example 4: Preparation of Acryl Polymer Compound D

(41) An acryl polymer compound D having a solid content of 30 wt %, a weight average molecular weight of 730,000 and a polydispersity index of 6.9 was prepared by the same method as described in Preparation Example 1, except that 0.1 parts by weight of n-dodecanthiol was added as a thiol compound.

Preparation Example 5: Preparation of Acryl Polymer Compound E

(42) An acryl polymer compound E having a solid content of 30 wt %, a weight average molecular weight of 630,000 and a polydispersity index of 5.5 was prepared by the same method as described in Preparation Example 1, except that 0.04 parts by weight of n-dodecanthiol was added as a thiol compound 2 hours after the reaction was initiated.

Preparation Example 6: Preparation of Acryl Polymer Compound F

(43) An acryl polymer compound F having a solid content of 30 wt %, a weight average molecular weight of 690,000 and a polydispersity index of 5.1 was prepared by the same method as described in Preparation Example 1, except that n-octyl mercaptan was used as a thiol compound.

Preparation Example 7: Preparation of Acryl Polymer Compound G

(44) An acryl polymer compound G having a solid content of 30 wt %, a weight average molecular weight of 710,000 and a polydispersity index of 5.3 was prepared by the same method as described in Preparation Example 1, except that n-nonyl mercaptan was used as a thiol compound.

Preparation Example 8: Preparation of Acryl Polymer Compound H

(45) An acryl polymer compound H having a solid content of 30 wt %, a weight average molecular weight of 700,000 and a polydispersity index of 2.6 was prepared by the same method as described in Preparation Example 1, except that 0.04 parts by weight of n-dodecanthiol was added as a thiol compound together with a monomer.

Preparation Example 9: Preparation of Acryl Polymer Compound I

(46) An acryl polymer compound I having a solid content of 30 wt %, a weight average molecular weight of 730,000 and a polydispersity index of 5.9 was prepared by the same method as described in Preparation Example 1, except that a thiol compound was not added.

Manufacture of Double-Sided Pressure-Sensitive Adhesive Tape

Example 1

(47) A pressure-sensitive adhesive composition was prepared by uniformly mixing 0.3 parts by weight of an isocyanate crosslinking agent (toluene diisocyanate (TDI); solid) with respect to 100 parts by weight of an acryl polymer compound obtained in Preparation Example 1 used as a pressure-sensitive adhesive resin (solid).

(48) A transparent pressure-sensitive adhesive layer having a coating thickness of 50 μm was formed by coating the pressure-sensitive adhesive solution on a releasing-treated surface of a PET film (thickness: 50 μm) and leaving the coated product at 120° C. for 3 minutes. Subsequently, a pressure-sensitive adhesive film was prepared by laminating the releasing-treated surface of the PET film having a thickness of 50 μm on the other surface of the pressure-sensitive adhesive layer.

Example 2

(49) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that the acryl polymer compound B in Preparation Example 2 was used.

Example 3

(50) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound C in Preparation Example 3 was used.

Example 4

(51) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound D in Preparation Example 4 was used.

Example 5

(52) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound E in Preparation Example 5 was used.

Example 6

(53) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound F in Preparation Example 6 was used.

Example 7

(54) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound G in Preparation Example 7 was used.

Comparative Example 1

(55) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound H in Preparation Example 8 was used.

Comparative Example 2

(56) A double-sided pressure-sensitive adhesive tape was prepared by the same method as described in Example 1, except that acryl polymer compound I in Preparation Example 9 was used.

(57) Compositions in Examples and Comparative Examples are shown in Table 1.

(58) TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 1 2 Acryl Polymer BA 58 58 58 58 58 58 58 58 58 (Parts by MA 40 40 40 40 40 40 40 40 40 Weight) HEA 2 2 2 2 2 2 2 2 2 Initiator AIBN 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 (Parts by Weight) Thiol n- 0.01 0.02 0.04 0.1 0.04 — — 0.04 0 Compound dodecanthiol (Parts by n-octyl — — — — — 0.01 — — — Weight) mercaptan n-nonyl — — — — — — 0.01 — — mercaptan Input Time 4 hrs 4 hrs 4 hrs 4 hrs 2 hrs 4 hrs 4 hrs Input with — monomer Crosslinking TDI 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Agent (Parts by Weight) BA: n-butyl acrylate MA: methylacrylate HEA: hydroxyethylacrylate AIBN: azobisisobutyronitrile TDI: toluene diisocyanate

(59) Conversion rates, weight average molecular weights, polydispersity indexes, and results of the durability and resistance change ratio tests, which were measured in Examples and Comparative Examples, are shown in Table 2.

(60) TABLE-US-00002 TABLE 2 Comparative Example Example 1 2 3 4 5 6 7 1 2 Acryl Polymer M.sub.w(10,000) 70 71 75 73 63 69 71 70 73 Compound Polydispersity 5.2 5.8 5.7 6.9 5.5 5.1 5.3 2.6 5.9 Index Inhibition of Bubble Generation ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Evaluation of Lift-off/Peeling ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Peel Strength(g/25 mm) 2400 2380 2450 2460 2500 2430 2410 1820 2420 Adherent PC Sheet Resistance Change Ratio(%) 7 6 5 5 7 7 7 5 18 M.sub.w: weight average molecular weight

(61) As shown in Table 2, the pressure-sensitive adhesive layer of the present invention satisfies all of various properties required for a touch panel, and particularly, the pressure-sensitive adhesive having an excellent resistance change ratio with respect to ITO and a double-sided pressure-sensitive adhesive tape using the same can be manufactured.