JP2007058721A - Underlay material for touch panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underlay material for a touch panel, which can stably provide a feeling of soft touch to the touch panel stably with time and can prevent double touch on the touch panel by laying the underlay material under the touch panel. <P>SOLUTION: The underlay material for the touch panel comprises a sheet of segmented polyurethane gel obtained by reacting polyol liquid at room temperature and having an alkylene oxide segment, and/or a polyurethane polyol prepolymer liquid at room temperature and having an alkylene oxide segment and a polyurethane polyisocyanate prepolymer liquid at room temperature and having the alkylene oxide segment; where preferably, OH/NCO is 1.5 to 2.0, a Young's modulus is 40,000 to 150,000 Pa and the alkylene oxide segment is an EO-PO copolymer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an underlay material for a touch panel that can stably provide a soft touch friendly touch panel over time and can prevent double touch by laying under the touch panel. .

  2. Description of the Related Art Conventionally, a transparent touch panel mounting structure in which a transparent touch panel and a display are entirely mounted via a transparent re-peeling sheet made of an adhesive urethane gel sheet is known (Patent Document 1).

  In the mounting structure above, the space between the transparent touch panel and the display is replaced with a transparent re-peeling sheet, so light reflection is reduced and the impact force from the outside is reduced by the elasticity of the gel. It has the advantage that it can be easily performed.

However, since the urethane-based gel sheet used as the transparent re-peeling sheet is a hydrogel containing water, its elasticity and adhesiveness may decrease over time due to the volatilization of water, and at the interface with the touch panel and the display. There was a problem that air bubbles were generated. In addition, when the elasticity of the urethane gel sheet is reduced, the touch feeling of the touch panel becomes harder, and there is a problem that there are people who double-touch (double touch) by fingertip bounce on the surface of the touch panel when vigorously touched. It was.
JP-A-10-222305

  The present invention was made to cope with the above problem, and by laying under the touch panel, a soft touch friendly soft touch can be stably provided over time, and double touch can be prevented. The problem to be solved is to provide an underlay material for a touch panel.

  In order to solve the above problems, an underlay material for a touch panel according to the present invention includes a polyol having an alkylene oxide segment which is liquid at normal temperature and / or a polyurethane polyol prepolymer having an alkylene oxide segment which is liquid at normal temperature, and normal temperature. It consists of the sheet | seat of the segmented polyurethane gel which reacted with the polyurethane polyisocyanate prepolymer which has the segment of a liquid alkylene oxide.

  In the underlay material for a touch panel of the present invention, the ratio [OH / NCO] of the OH group at the terminal of the polyol or / and polyurethane polyol prepolymer before the reaction to the NCO group at the terminal of the polyurethane polyisocyanate prepolymer is 1.5. The Young's modulus of the reacted segmented polyurethane gel is preferably 40000 to 150,000 Pa. The alkylene oxide segment is preferably a segment composed of a copolymer of ethylene oxide and propylene oxide which is liquid at normal temperature. Particularly, the copolymer of ethylene oxide and propylene oxide which is liquid at normal temperature is 1000 to 1600. It is preferable that it is a block copolymer which has the weight average molecular weight of these, and the molar ratio of ethylene oxide and propylene oxide exists in the range of 30: 70-70: 30. The thickness of the segmented polyurethane gel sheet is preferably 0.1 to 2 mm.

  The segmented polyurethane gel that constitutes the underlay material for a touch panel of the present invention is a polyol having an alkylene oxide segment that is liquid at normal temperature and / or a polyurethane polyol prepolymer having an alkylene oxide segment that is liquid at normal temperature, and a liquid at normal temperature. This is a one-component segmented polyurethane gel obtained by reacting a polyurethane polyisocyanate prepolymer having an alkylene oxide segment, and does not contain a dispersion medium such as water as another component. Therefore, the underlay material for the touch panel of the present invention does not have a decrease in elasticity or adhesive strength over time due to volatilization of the dispersion medium, and can stably give a soft touch to the touch panel over time, and strongly touch It is possible to effectively prevent double touch by absorbing and relaxing the pressure at the time.

  In particular, the ratio [OH / NCO] of the OH group at the end of the polyol or / and polyurethane polyol prepolymer before the reaction to the NCO group at the end of the polyurethane polyisocyanate prepolymer is 1.5 to 2.0. The segmented polyurethane gel obtained has a Young's modulus of 40,000 to 150,000 Pa, and the alkylene oxide segment has a weight average molecular weight of 1,000 to 1,600, particularly a copolymer of ethylene oxide and propylene oxide which is liquid at room temperature. The underlay material, which is a segment made of a block copolymer having a molar ratio of oxide to propylene oxide in the range of 30:70 to 70:30, is soft and gentle because it has elasticity suitable for absorbing absorption of touch pressure. Add touch to touch panel Rukoto can, is also very effective in the prevention of double touch.

  Hereinafter, specific embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic cross-sectional view showing an example of use of an underlay material for a touch panel according to the present invention.

  The touch panel underlay material 1 of the present invention (hereinafter simply referred to as the underlay material) lays under the touch panel to provide a soft touch that is stable to the touch panel over time and prevents double touch. For example, when used for a touch panel of an electronic notebook or a cellular phone, as shown in FIG. 1, a touch panel 2 attached to a polarizing plate 3 on the display surface and a peripheral spacer 4 on the polarizing plate 3 as shown in FIG. And is assembled in close contact with the lower surface of the touch panel 2 and the upper surface of the polarizing plate 3 by its adhesive force.

  The underlay material 1 includes a polyol having an alkylene oxide segment that is liquid at normal temperature and / or a polyurethane polyol prepolymer having an alkylene oxide segment that is liquid at normal temperature, and a polyurethane polyisocyanate prepolymer having an alkylene oxide segment that is liquid at normal temperature. It is a one-component segmented polyurethane gel reacted with a polymer.

  More specifically, the segmented polyurethane gel constituting the underlay material 1 includes, for example, a polyurethane polyol prepolymer having an alkylene oxide segment (AO) that is liquid at room temperature shown in the following structural formula A as a polyol component. On the other hand, the polyol having the alkylene oxide segment (AO) which is liquid at room temperature shown in the following structural formulas B to D is used alone or in combination, and as an isocyanate component, for example, the following structural formulas E to I are used. It is obtained by using a polyurethane polyisocyanate prepolymer having an alkylene oxide segment (AO) which is liquid at room temperature as shown in FIG. 1 alone or in a mixture and urethane bonding the —OH group and —NCO group of both components. , Segment of the so-called Interpenetrated Network It is a polyurethane gel.

式中、Ｒ_１，Ｒ_２はアルキル化合物、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, R ₁ and R ₂ are any of an alkyl compound, an alicyclic compound, and an aromatic compound, and AO is an alkylene oxide segment.

式中、ＡＯはアルキレンオキサイドのセグメントであり、ｌは１または４の整数である。

In the formula, AO is an alkylene oxide segment, and l is an integer of 1 or 4.

式中、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, AO is an alkylene oxide segment.

式中、ＡＯはアルキレンオキサイドのセグメントであり、Ｒは水素原子もしくはアルキル化合物、脂環式化合物、芳香族化合物のいずれかである。

In the formula, AO is an alkylene oxide segment, and R is a hydrogen atom, an alkyl compound, an alicyclic compound, or an aromatic compound.

式中、Ｒはアルキル基、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, R is an alkyl group, an alicyclic compound, or an aromatic compound, and AO is an alkylene oxide segment.

式中、Ｒはアルキル基、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, R is an alkyl group, an alicyclic compound, or an aromatic compound, and AO is an alkylene oxide segment.

式中、Ｒはアルキル基、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントであり、ｌは１または４の整数である。

In the formula, R is an alkyl group, an alicyclic compound, or an aromatic compound, AO is an alkylene oxide segment, and l is an integer of 1 or 4.

式中、Ｒはアルキル基、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, R is an alkyl group, an alicyclic compound, or an aromatic compound, and AO is an alkylene oxide segment.

式中、Ｒはアルキル基、脂環式化合物、芳香族化合物のいずれかであり、ＡＯはアルキレンオキサイドのセグメントである。

In the formula, R is an alkyl group, an alicyclic compound, or an aromatic compound, and AO is an alkylene oxide segment.

  The polyol component of structural formulas A to D will be described. Structural formula A is a polyurethane polyol prepolymer that is a reaction product of a polyether polyol and a diisocyanate, both terminal components are made of polyether polyol, and the terminal is an -OH group. is there. The diisocyanate compound used here is the same as that in the polyurethane polyisocyanate prepolymer described later, for example, phenylene diisocyanate, 2,4-toluylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI). , Naphthalene-1,5-diisocyanate, hexamethylene diisocyanate (HMDI), tetramethylene diisocyanate (TMDI), lysine diisocyanate, xylylene diisocyanate (XDI), water-added TDI, hydrogenated MDI, dicyclohexyldimethylmethane-p, p'- Diisocyanate, diethyl fumarate diisocyanate, isophorone diisocyanate (IPDI) and the like can be arbitrarily used.

  Structural formula B is obtained by adding a polyether polyol to glycerol (l = 1) or sorbitol (l = 4), and structural formula C is obtained by adding a polyether polyol to trimethylolpropane. Similarly, 1,2,6-hexanetriol of the following structural formula J, trimethylolethane of the structural formula K, pentaerythritol of the structural formula L, polyglycerin of the structural formula M (n = 2 to 30), and Adducts of polyhydric alcohols such as partial esters and polyether polyols can also be used.

  Structural formula D is a polyether polyol having an alkylene oxide (AO) segment, both ends are —OH groups, and one end is blocked with an alkyl group, an aromatic group, etc. It can be easily obtained as a product.

  Next, the polyurethane polyisocyanate prepolymer represented by structural formulas E to I will be described. In structural formula E, two molecules of triisocyanate obtained by reacting diisocyanate with trimethylolpropane are converted into two molecules of alkylene oxide (AO). It is a quantified tetrafunctional tetraisocyanate. A prepolymer having the structural formula F is obtained by using glycerol instead of trimethylolpropane. Since this type of tetraisocyanate tends to dimerize triisocyanate with two or three molecules of (AO), it is necessary to finely control the reaction. Therefore, unreacted triisocyanate is mixed, but when reacting with polyol, the size of segmented polyurethane molecules varies, which is convenient for controlling the adhesiveness, flexibility, and elasticity of segmented polyurethane gel. It may act on the direction.

  Structural formula G is obtained by reacting a diisocyanate with the polyol of structural formula B, and is trifunctional or hexafunctional. Similarly, structural formula H is a trifunctional compound obtained by reacting a polyol of structural formula C with a diisocyanate. Structural formula I is a reaction product of polyether polyol and diisocyanate and is bifunctional.

In order to obtain a low modulus, low Young's modulus segmented polyurethane gel having soft elasticity, the alkylene oxide segment represented by (AO) in the above structural formulas A to I is liquid ethylene at room temperature. Oxide (EO) chain, propylene oxide (PO) chain that is liquid at normal temperature, EO-PO copolymer that is liquid at normal temperature [for example, a block copolymer represented by the following structural formula N, and-(PO-EO -EO-PO) _m -,-(PO-PO-EO) _m -,-(EO-EO-PO) _m -,-(EO-PO-EO-PO) _m- and the like (m Is a positive number of 1 or more) or a random copolymer of EO and PO. Moreover, the segment of (AO) may be a butylene oxide (BO) chain which is liquid at normal temperature, or a block or random copolymer of BO-PO which is liquid at normal temperature.

  Since the segment of (AO) composed of these EO chain, PO chain, EO-PO copolymer, BO chain, BO-PO copolymer and the like must be liquid at room temperature, the upper limit of the molecular weight is regulated. . If the molecular weight is too low even when it is liquid, the distance between the cross-linking points is shortened, the molecular motion of the segments is suppressed, the cross-linking density is increased, and the flexibility of the segmented polyurethane gel is lowered. Therefore, the lower limit of the molecular weight is also regulated. The molecular weight of the EO chain (weight average molecular weight MW, hereinafter the same) is suitably 150 to 1000, preferably 300 to 800. The PO chain is a liquid even if its molecular weight is tens of thousands, and the range of molecular weight that can be used is wide. However, the smaller the end group ratio, the lower the reaction probability, and in the case of an excessively long segment, the fluidity of the polyurethane gel is increased and the shape retention is poor, so a range of about 200 to several thousand is preferred.

  On the other hand, the fluidity (softness) and adhesiveness of an EO-PO copolymer are affected by the ratio and arrangement of EO and PO. That is, in the block copolymer, when the molar ratio of PO is high, it is liquid even if the molecular weight is high, but even if the molar ratio of PO is low, it is liquid if the molecular weight of EO is low. However, as described above, when the molecular weight of PO is high, problems such as shape retention occur, and when the molecular weight of the copolymer is low, molecular motion is suppressed and the flexibility of the polyurethane gel decreases. Therefore, the EO-PO polymer can be used in a wide molecular weight range of 60 to 8000, but in order to obtain a flexible and shape-retaining segmented polyurethane gel suitable for an underlay material, the molecular weight is 800. A block copolymer having a molecular weight of 900 to 3000, preferably 900 to 3000, particularly preferably 1000 to 1600, and a molar ratio of EO to PO of 30:70 to 70:30 is used. If the molar ratio of PO exceeds 70, the fluidity may increase and the shape retention may be reduced. If the molar ratio of PO is less than 30, the EO molecular weight must be kept low to form a liquid segment. Therefore, the segment length may be shortened and the elasticity may be reduced. A more preferred molar ratio of EO and PO is 50:50.

  Further, since the BO chain becomes solid when the degree of polymerization increases, it can be used in the molecular weight range of 200 to 1000, preferably 400 to 800. Since the BO-PO copolymer is liquid even if the molecular weight is high if the molar ratio of PO is high, it can be used in the molecular weight range of 800 to 6000, preferably 900 to 3000.

  In addition, polyethylene glycol (PEG) is used as the compound that forms the EO chain, polypropylene glycol (PPG) is used as the compound that forms the PO chain, and PEG-PPG copolymer is used as the compound that forms the EO-PO copolymer. However, polytetramethylene glycol (PTMG) is used as the compound that forms the BO chain, and PTMG-PPG copolymer is used as the compound that forms the BO-PO copolymer.

  A segmented polyurethane gel with soft elasticity suitable for underlaying materials has a relatively bulky molecular structure with a three-dimensional network chain structure, and a linear chain concentration that allows free movement of segments, It is important to have many (linear) free terminal molecules. Therefore, in order to obtain a three-dimensional network structure, if each of the polyol component and the polyisocyanate component is a single compound, one is a bifunctional combination and the other is a combination of three or more functional groups. It is necessary to make a combination of three or more functions. However, when those having a functional number of 3 or more are reacted with each other, the network chain concentration becomes too high, so that it is difficult to obtain a gel having soft elasticity unless a very long segment exists. Therefore, the preferred functional number of both components is a combination of 2 to 4, and in particular, a combination in which the functional number of the polyol component is 2 and the functional number of the polyisocyanate component is 3 has an appropriate network chain concentration. Segmentation with soft elasticity suitable for bulky gel underlays because a three-dimensional network chain structure is formed and, as will be described later, when the reaction ratio of the polyol component is large, a large number of linear free end molecules are generated. Ideal for obtaining polyurethane gels.

  The reaction ratio of each prepolymer of the polyol component and the polyisocyanate component can be regulated by the ratio of terminal functional groups, that is, the value of OH / NCO. Since OH / NCO must be 1 or more because post-reaction occurs when unreacted -NCO remains. And the segmented polyurethane gel which has favorable adhesiveness as 1 <= OH / NCO <= 5 is obtained. In a state where OH / NCO is 1 or more and 5 or less, it can be imagined that a straight-line segment having an OH group at the end in a group of bulky molecules is moving freely with a tail. The closer it is, the longer the free tails are, and the larger the number of free tails. In addition, such free tails have a large effect on the fluidity and elasticity of the gel. When OH / NCO exceeds 2.0 and the number of free tails increases, the fluidity of the gel increases more than necessary. When the OH / NCO is below 1.5 and the free tail is reduced, the elasticity of the gel becomes stronger than necessary. Therefore, in order to obtain an adhesive segmented polyurethane gel having soft elasticity suitable for the underlay material, OH / NCO is adjusted to a range of 1.5 to 2.0 to obtain soft elasticity. It is preferable to control so that the number of free tails is suitable.

  The molecular weight range of the polyol component and the polyisocyanate component varies in a wide range depending on the kind of AO or isocyanate, the molecular shape, and whether the AO is a homopolymer or a copolymer. 10,000, about 150 to 6000 for polyol, and about 500 to 10,000 for polyurethane polyisocyanate prepolymer. Preferably, each can be selected in the range of about 1000 to 6000, about 300 to 3000, and about 1000 to 6000.

  The segmented polyurethane gel used as the underlay material 1 of the present invention is prepared by mixing the polyol component and the polyisocyanate component so that the ratio of OH / NCO becomes the above-mentioned ratio and, if necessary, an appropriate amount of catalyst (for example, dibutyltin). Prepare a material solution by mixing a tertiary amine such as dilaurate, trialkylamine, triethylenediamine, etc., cast it into a sheet and react it at room temperature or under heating. By controlling the kind and molecular weight of AO, the combination of the functional numbers of both components, OH / NCO, etc. as described above, the gel has a Young's modulus of 40000 to 150,000 Pa suitable for an underlay material. It is a thing. This segmented polyurethane gel with a Young's modulus of this level absorbs and relaxes the touch pressure sufficiently and has a moderate elasticity, so it can give the touch panel a soft and gentle touch feeling, effectively preventing double touch. It can also be prevented. If the Young's modulus is less than 40,000 Pa, the gel becomes too flexible, so the feeling of sinking when touched becomes large, and if it exceeds 150,000 Pa, the elasticity becomes strong and double touch tends to occur. .

  Although the thickness of the gel sheet used as the underlay material 1 is not specifically limited, For example, when laying under the touch panel of an electronic notebook or a mobile telephone, it is preferable to set it as 0.1-2 mm. If the thickness is less than 0.1 mm, the absorption of the touch pressure may be insufficiently reduced. If the thickness is greater than 2 mm, in addition to increasing the sinking when strongly touched, the transparency of the gel sheet decreases. This is not preferable because the display may be hard to see. A more preferable thickness is 0.5 to 1 mm.

  When the base material 1 made of a segmented polyurethane gel sheet as described above is mounted between the touch panel 2 and the polarizing plate 3 on the display surface as shown in FIG. 1, the base material 1 is touched by the adhesive force of the gel. 2 and the upper surface of the polarizing plate 3. As described above, when the space portion between the touch panel 2 and the polarizing plate 3 is replaced with the base material 1 made of a segmented polyurethane gel sheet, the light refractive index of the gel of the base material 1 is changed to that of the touch panel 2 or the polarizing plate 3. Since it approximates the optical refractive index, light reflection is reduced and the display on the display is easy to see. And, when touching the touch panel 2 with a fingertip, the touch pressure is absorbed and relaxed by the segmented polyurethane gel sheet of the base material 1 having a Young's modulus of 40000 to 150,000 Pa, and when the fingertip is raised, it is instantly restored with an appropriate elasticity. A soft and gentle touch feeling can be obtained, and double touch can be effectively prevented even when strongly touched. In addition, the segmented polyurethane gel constituting the underlay material 1 is a one-component gel that does not contain other dispersion media and the like, and changes in elasticity and tackiness due to volatilization of the dispersion media do not occur over time. As a result, it is possible to continue to provide the touch panel 2 with a soft and gentle touch feeling that does not change from the original even if time passes, and to maintain the double touch prevention effect that does not change from the original.

  Next, more specific examples of the present invention will be described.

[Example 1]
Bifunctional composed of 100 parts (parts by weight, the same applies hereinafter) of a PEG-PPG block copolymer (MW 1500) which is a liquid at normal temperature in which polyethylene glycol and polypropylene glycol in an equimolar ratio are randomly bonded, and 1.1 parts of an antioxidant. A triisocyanate prepolymer having a trifunctional structural formula G obtained by reacting hexamethylene diisocyanate (HMDI) with a compound obtained by adding the above PEG-PPG block copolymer to glycerin to the polyether polyol of the structural formula D. 50 parts of a polymer (MW 2600) and 0.01 part of dibutyltin laurate as a catalyst were added and mixed with good stirring.

  Next, this mixed solution is degassed under reduced pressure, poured into a predetermined vessel, casted, and left to react at 50 ° C. for 17 hours, whereby the EO-PO copolymer that is liquid at room temperature is segmented. A transparent and flexible 2.0 mm thick segmented polyurethane gel sheet was obtained. The OH / NCO of this polyurethane gel is 2.1 as shown in Table 1 below.

  The obtained segmented polyurethane gel sheet was measured for Young's modulus using an apparatus of Biosensor “Venustron” manufactured by AXIOM, and as shown in Table 1 below, it was 31000 Pa. Further, this gel sheet was allowed to stand at 30 ° C. for 9 days, and the Young's modulus was measured in the same manner. As a result, it was 30000 Pa as shown in Table 1 below, and substantially no change over time was observed.

  In addition, as shown in FIG. 1, this segmented polyurethane gel sheet is attached to a space between the touch panel 2 and the polarizing plate 3 of the electronic notebook, and 100 people randomly selected operate the touch panel 2, I checked the touch feeling and double touch. As a result, as shown in Table 1 below, there were 65 people who answered yes (soft and good touch feel) and 35 people who answered △ (too soft and not very good touch feel). Also, there were 0 people who double touched.

[Example 2]
EO-PO which is liquid at room temperature in the same manner as in Example 1 except that the mixing amount of the triisocyanate prepolymer of Example 1 is changed to 65 parts and the reaction temperature and reaction time are changed to 30 ° C. and 24 hours, respectively. A transparent and flexible 2.0 mm-thick segmented polyurethane gel sheet having a copolymer as a segment was obtained. The OH / NCO of this polyurethane gel is 1.6 as shown in Table 1 below.

  About the obtained gel sheet, it carried out similarly to Example 1, and measured the Young's modulus immediately after and the Young's modulus after nine-day progress, and the quality of the touch feeling and the presence or absence of the double touch were investigated. The results are listed in Table 1 below.

[Example 3]
EO-PO which is liquid at room temperature in the same manner as in Example 1 except that the mixing amount of the triisocyanate prepolymer of Example 1 is changed to 55 parts and the reaction temperature and reaction time are changed to 30 ° C. and 24 hours, respectively. A transparent and flexible 2.0 mm-thick segmented polyurethane gel sheet having a copolymer as a segment was obtained. The OH / NCO of this polyurethane gel is 1.9 as shown in Table 1 below.

  About the obtained gel sheet, it carried out similarly to Example 1, and measured the Young's modulus immediately after and the Young's modulus after nine-day progress, and the quality of the touch feeling and the presence or absence of the double touch were investigated. The results are listed in Table 1 below.

[Example 3]
EO-PO which is liquid at room temperature in the same manner as in Example 1 except that the mixing amount of the triisocyanate prepolymer of Example 1 is changed to 47 parts and the reaction temperature and reaction time are changed to 30 ° C. and 24 hours, respectively. A transparent and flexible 2.0 mm-thick segmented polyurethane gel sheet having a copolymer as a segment was obtained. The OH / NCO of this polyurethane gel is 2.2 as shown in Table 1 below.

  About the obtained gel sheet, it carried out similarly to Example 1, and measured the Young's modulus immediately after and the Young's modulus after nine-day progress, and the quality of the touch feeling and the presence or absence of the double touch were investigated. The results are listed in Table 1 below.

注）〇はソフトでタッチ感触が良いこと、△は柔らかすぎてタッチ感触があまり良くないことを示す。

Note) ○ indicates soft and good touch feeling, and △ indicates soft touch and poor touch feeling.

  As can be seen from Table 1, in any of the gel sheets of Examples 1 to 4, there is no substantial difference between the Young's modulus immediately after and the Young's modulus after 9 days. From this, it can be seen that the one-component gel sheets of Examples 1 to 4 do not substantially change over time. Further, when the gel sheets of Examples 1 to 4 are compared, OH / NCO and Young's modulus have a negative correlation, and as OH / NCO increases, Young's modulus decreases, flexibility increases, and elasticity decreases. I understand. The gel sheets of Examples 1 and 4 in which OH / NCO exceeds 2.0 and Young's modulus is less than 40000 Pa have a touch feeling of Δ (not too good because the touch feeling is too soft). There are more than 35 people who answered), and it turns out that the dissatisfaction remains as the underlay material for the touch panel. On the other hand, the gel sheets of Examples 2 and 3 in which OH / NCO is in the range of 1.5 to 2.0 and Young's modulus is in the range of 40000 to 150,000 Pa are 0 people who double touched. There are as many as 95 or more people who answered that the touch feeling was ◯ (soft and good touch feeling), and it can be seen that it is suitable as an underlay material for a touch panel.

It is a schematic sectional drawing which shows the usage example of the base material for touchscreens which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Underlay material for touch panels 2 Touch panel 3 Polarizing plate on display surface 4 Spacer

Claims (6)

  A polyol having an alkylene oxide segment which is liquid at normal temperature and / or a polyurethane polyol prepolymer having an alkylene oxide segment which is liquid at normal temperature and a polyurethane polyisocyanate prepolymer having an alkylene oxide segment which is liquid at normal temperature were reacted. An underlay for touch panels made of segmented polyurethane gel sheets.   The ratio [OH / NCO] of the OH group at the terminal of the polyol or / and polyurethane polyol prepolymer before the reaction to the NCO group at the terminal of the polyurethane polyisocyanate prepolymer is 1.5 to 2.0. The underlay material for a touch panel as described.   The underlay material for a touch panel according to claim 1 or 2, wherein the segmented polyurethane gel has a Young's modulus of 40,000 to 150,000 Pa.   The underlay material for a touch panel according to any one of claims 1 to 3, wherein the alkylene oxide segment is a segment made of a copolymer of ethylene oxide and propylene oxide which is liquid at normal temperature.   A block copolymer in which a copolymer of ethylene oxide and propylene oxide, which is liquid at normal temperature, has a weight average molecular weight of 1000 to 1600, and the molar ratio of ethylene oxide to propylene oxide is in the range of 30:70 to 70:30. The underlay material for a touch panel according to claim 4, wherein the underlay material is a combined body.   The underlay material for a touch panel according to any one of claims 1 to 5, wherein a thickness of the segmented polyurethane gel sheet is 0.1 to 2 mm.

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