JP2016113467A - Interlaminar filler for touch panel, and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interlaminar filler for a touch panel which is excellent in: followability to a decorative printed part level difference or a wiring level difference in filling (in bonding) a space between layers therewith; and defoaming property of entrained air bubbles or air bubbles remaining in the vicinity of level differences in filling (in bonding) the space between the layers therewith, and which suppresses degradation of an ITO film formed in the touch panel.SOLUTION: An interlaminar filler 1 for a touch panel is used for filling a space between layers of the touch panel 2 and other members therewith or a space between layers of a plurality of transparent conductive films constituting the touch panel 2 therewith, which contains a plasticized polyvinyl acetal containing polyvinyl acetal and a plasticizer, and in which the plasticizer is triethyleneglycol di-2-ethylhexanoate (3GO), tetraethyleneglycol di-2-ethylhexanoate (4GO), triethyleneglycol dipivalate (3GT), or di-(2-buthoxyethyl) adipate (DBEA).SELECTED DRAWING: Figure 1

Description

The present invention is used for filling an interlayer between a touch panel and another member or between a plurality of transparent conductive films constituting the touch panel in the manufacture of a portable information terminal, etc. Deterioration of the ITO film formed on the touch panel, with excellent followability to decorative printed part steps or wiring steps and excellent defoaming of bubbles entrained during filling (bonding) between layers or bubbles remaining near the steps It is related with the interlayer filling material for touch panels which can suppress. Moreover, this invention relates to the laminated body manufactured using this interlayer filling material for touchscreens.

Touch panels are used in various fields. For example, in portable information terminals such as smartphones and tablets, a touch panel is disposed under a surface protection panel made of glass or the like, followed by a polarizing film or a display. In order.
In such a portable information terminal, the interlayer between the surface protection panel and the touch panel and the interlayer between the touch panel and the polarizing film are filled with a filling material that has a smaller refractive index difference with these members than air. In order to improve visibility, the display screen is improved in transparency, brightness, contrast, and the like.

As an interlayer filling material for a touch panel, an acrylic pressure-sensitive adhesive or pressure-sensitive adhesive tape is frequently used from the viewpoints of transparency, adhesiveness, coating property, and the like (for example, Patent Document 1).
However, when an acrylic pressure-sensitive adhesive or adhesive tape is pasted as a filling material, entrainment of bubbles may occur at the time of pasting, and bubbles may remain between the surface protection panel and the filling material. There is a problem of reducing the performance. In addition, a printing part is formed on the back side of the surface protection panel for the purpose of masking or the like, and a step formed by such a printing part or a boundary part of a wiring step formed on the touch panel In other words, bubbles remain in the surface, and the visibility or durability is deteriorated. In particular, with recent miniaturization, thinning, and weight reduction of portable information terminals, a thin filling material has been desired. In conventional acrylic adhesives or adhesive tapes, the thinness and the bubbles sufficiently follow the steps. It has been difficult to achieve both the property of not remaining (step following ability).

Moreover, the wiring formed on the touch panel is made of a transparent conductive film such as ITO (indium tin oxide), and the ITO film is in contact with the filling material when exposed to high temperature and high humidity. It is also a problem that is deteriorated. Since deterioration of the ITO film leads to deterioration of the performance of the touch panel, a filling material that can suppress such deterioration of the ITO film is desired.

JP 2013-119604 A

The present invention is used for filling an interlayer between a touch panel and another member or between a plurality of transparent conductive films constituting the touch panel in the manufacture of a portable information terminal, etc. Deterioration of the ITO film formed on the touch panel, with excellent followability to decorative printed part steps or wiring steps and excellent defoaming of bubbles entrained during filling (bonding) between layers or bubbles remaining near the steps An object of the present invention is to provide an interlayer filling material for a touch panel that can suppress the above. Moreover, an object of this invention is to provide the laminated body manufactured using this interlayer filling material for touchscreens.

The present invention is an interlayer filling material for a touch panel used for filling an interlayer between a touch panel and another member or an interlayer of a plurality of transparent conductive films constituting the touch panel, and contains a polyvinyl acetal and a plasticizer. Containing plasticized polyvinyl acetal, the plasticizer being triethylene glycol di-2-ethylhexanoate (3GO), tetraethylene glycol di-2-ethylhexanoate (4GO), triethylene glycol di-pivalate ( 3GT) or an interlayer filling material for a touch panel, which is di- (2-butoxyethyl) adipate (DBEA).
The present invention is described in detail below.

The present inventor replaces an acrylic pressure-sensitive adhesive that has been widely used in the past in an interlayer filling material for a touch panel used for filling an interlayer between a touch panel and another member or a plurality of transparent conductive films constituting the touch panel. It has been found that plasticized polyvinyl acetal is effective as a material.
The inventor found that the interlayer filling material for a touch panel containing a plasticized polyvinyl acetal containing a polyvinyl acetal and a plasticizer has a storage elastic modulus and a loss elastic modulus at room temperature (around 20 ° C.) compared to an acrylic pressure-sensitive adhesive. On the other hand, the storage elastic modulus and loss elastic modulus are greatly reduced by heating (around 70 ° C.) at the time of filling (bonding) between layers, even if it is a thin filling material, It was found that bubbles remaining at the boundary of the step can be removed sufficiently following the wiring step. Furthermore, the present inventor has found that the deterioration of the ITO film formed on the touch panel can be suppressed by blending a specific plasticizer, and has completed the present invention.

The interlayer filling material for a touch panel of the present invention is used to fill an interlayer between a touch panel and another member or a plurality of transparent conductive films constituting the touch panel.
Although the said other member is not specifically limited, A surface protection panel (for example, a glass plate, a polycarbonate plate, an acrylic board) and a polarizing film are preferable. That is, the interlayer filling material for a touch panel of the present invention is preferably used for filling the interlayer between the surface protection panel and the touch panel and / or the interlayer between the touch panel and the polarizing film.

The interlayer filling material for a touch panel of the present invention contains plasticized polyvinyl acetal. In the present specification, the plasticized polyvinyl acetal means a resin containing polyvinyl acetal and a plasticizer.
By containing the plasticized polyvinyl acetal, the interlayer filling material for a touch panel of the present invention has a higher storage elastic modulus and loss elastic modulus at room temperature (around 20 ° C.) than an acrylic pressure-sensitive adhesive. When heated (at the time of bonding), the storage elastic modulus and loss elastic modulus are greatly reduced by heating (around 70 ° C.), and even if it is a thin filling material, it follows sufficiently the decorative printed part step or wiring step. Thus, bubbles remaining at the boundary between the steps can be removed.
In addition, the interlayer filling material for touch panel of the present invention can be easily filled between layers by sandwiching between layers (at the time of bonding) and then thermocompression bonding at around 70 ° C. Excellent.

The polyvinyl acetal can be prepared, for example, by acetalizing polyvinyl alcohol obtained by saponifying polyvinyl acetate with an aldehyde in the presence of a catalyst. The saponification degree of the polyvinyl alcohol is not particularly limited, but is generally in the range of 70 to 99.9 mol%, preferably 70 to 99.8 mol%, more preferably 80 to 99.8 mol%.
Although the average degree of polymerization of the polyvinyl alcohol is not particularly limited, it has a large molecular weight from the viewpoint of sufficiently suppressing the scattering of fragments such as glass when the portable information terminal is damaged by an impact such as dropping. Since polyvinyl acetal is suitable, it is preferable to use polyvinyl alcohol having a high average degree of polymerization. The preferable lower limit of the average degree of polymerization of the polyvinyl alcohol is 200, and the preferable upper limit is 4000. When the average degree of polymerization is less than 200, the mechanical strength of the plasticized polyvinyl acetal is lowered, and when the portable information terminal is damaged, the scattering of fragments may not be sufficiently suppressed. When the average polymerization degree exceeds 4000, when the polyvinyl alcohol is acetalized, the solution viscosity becomes abnormally high, and acetalization may be difficult, and it becomes difficult to mold an interlayer filling material for a touch panel. Sometimes. The more preferable lower limit of the average degree of polymerization is 600, the more preferable upper limit is 3800, the still more preferable lower limit is 800, and the still more preferable upper limit is 3600.

When the polyvinyl alcohol is acetalized with an aldehyde in the presence of a catalyst, a solution containing the polyvinyl alcohol may be used. As a solvent used for the solution containing the said polyvinyl alcohol, water etc. are mentioned, for example.

Although the said aldehyde is not specifically limited, Generally, a C1-C10 aldehyde is used suitably.
The aldehyde having 1 to 10 carbon atoms is not particularly limited, and may be a linear aldehyde or a branched aldehyde such as n-butyraldehyde, isobutyraldehyde, n- Examples include valeraldehyde, 2-ethylbutyraldehyde, n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, benzaldehyde and the like. Of these, n-butyraldehyde, n-hexylaldehyde, and n-valeraldehyde are preferable, and n-butyraldehyde is more preferable. These aldehydes may be used alone or in combination of two or more.
That is, the polyvinyl acetal is preferably polyvinyl butyral (when the aldehyde is n-butyraldehyde, the polyvinyl acetal is referred to as polyvinyl butyral). By using the polyvinyl butyral, the adhesive force of the interlayer filling material for touch panel to glass is appropriately developed, and light resistance, weather resistance, and the like are improved. Moreover, you may use together 2 or more types of polyvinyl acetal as needed.

The preferable lower limit of the hydroxyl group content (hydroxyl group amount) of the polyvinyl acetal is 16 mol%, and the preferable upper limit is 45 mol%. When the amount of the hydroxyl group is 16 mol% or more, the adhesive force of the interlayer filling material for touch panel to glass is improved. If the amount of the hydroxyl group is 45 mol% or less, the flexibility of the polyvinyl acetal is increased, the handleability is improved, and the compatibility between the polyvinyl acetal and the plasticizer is increased, and the interlayer filling material for a touch panel is obtained. The step following ability is improved. The more preferred lower limit of the hydroxyl group content is 18 mol%, the still more preferred lower limit is 20 mol%, the particularly preferred lower limit is 22 mol%, the more preferred upper limit is 40 mol%, the still more preferred upper limit is 38 mol%, and the still more preferred upper limit. Is 36 mol%, and a particularly preferred upper limit is 35 mol%.
In addition, the hydroxyl group amount of polyvinyl acetal is the value which expressed the mole fraction calculated | required by dividing the ethylene group amount which the hydroxyl group has couple | bonded with the total ethylene group amount of a principal chain in percentage (mol%). The amount of ethylene group to which the hydroxyl group is bonded can be determined, for example, by a method based on JIS K6728 “Testing method for polyvinyl butyral”.

The preferable lower limit of the degree of acetylation (acetyl group amount) of the polyvinyl acetal is 0.1 mol%, and the preferable upper limit is 30 mol%. If the amount of the acetyl group is 0.1 mol% or more, the compatibility between the polyvinyl acetal and the plasticizer is increased, and the step following property of the interlayer filling material for touch panel is improved. When the amount of the acetyl group is 30 mol% or less, the moisture resistance of the polyvinyl acetal is improved. Moreover, when the said acetyl group amount exceeds 30 mol%, the reaction efficiency at the time of manufacturing the said polyvinyl acetal may fall. The more preferable lower limit of the amount of the acetyl group is 0.2 mol%, the still more preferable lower limit is 0.3 mol%, the more preferable upper limit is 24 mol%, the still more preferable upper limit is 20 mol%, and the still more preferable upper limit is 19. 5 mol%, and a particularly preferred upper limit is 15 mol%.
The amount of acetyl groups in polyvinyl acetal is the value obtained by subtracting the amount of ethylene groups to which acetal groups are bonded and the amount of ethylene groups to which hydroxyl groups are bonded from the total amount of ethylene groups in the main chain. This is a value expressed as a percentage (mol%) of the mole fraction obtained by dividing by the total amount of ethylene groups. The amount of ethylene group to which the acetal group is bonded can be measured, for example, according to JIS K6728 “Testing method for polyvinyl butyral”.

Examples of a method for adjusting the amount of acetyl groups of the polyvinyl acetal within the above range include a method for adjusting the degree of saponification of the polyvinyl alcohol. That is, the amount of acetyl groups in the polyvinyl acetal depends on the degree of saponification of the polyvinyl alcohol. If polyvinyl alcohol having a low saponification degree is used, the amount of acetyl groups in the polyvinyl acetal increases and the degree of saponification is high. The amount of acetyl groups in the polyvinyl acetal is reduced.

The preferable lower limit of the degree of acetalization of the polyvinyl acetal is 50 mol%, and the preferable upper limit is 85 mol%. If the said acetalization degree is 50 mol% or more, the compatibility of the said polyvinyl acetal and the said plasticizer will become high. If the said acetalization degree is 85 mol% or less, reaction time required in order to manufacture the said polyvinyl acetal can be shortened. The more preferable lower limit of the degree of acetalization is 54 mol%, the still more preferable lower limit is 58 mol%, and the particularly preferable lower limit is 60 mol%. A more preferable upper limit of the degree of acetalization is 82 mol%, a further preferable upper limit is 79 mol%, and a particularly preferable upper limit is 77 mol%.
The degree of acetalization of polyvinyl acetal is a value obtained by dividing the amount of ethylene groups to which the acetal group is bonded by the total amount of ethylene groups in the main chain, as a percentage (mol%). . The degree of acetalization is determined by measuring the amount of acetyl groups and the amount of vinyl alcohol (hydroxyl content) by a method based on JIS K6728 “Testing methods for polyvinyl butyral”, and calculating the molar fraction from the obtained measurement results. Subsequently, it can be calculated by subtracting the amount of acetyl groups and the amount of vinyl alcohol from 100 mol%.

Examples of a method for adjusting the degree of acetalization of the polyvinyl acetal include a method for adjusting the amount of the aldehyde added. If the addition amount of the aldehyde is decreased, the degree of acetalization of the polyvinyl acetal is lowered, and if the addition amount of the aldehyde is increased, the degree of acetalization of the polyvinyl acetal is increased.

The plasticizer is triethylene glycol di-2-ethylhexanoate (3GO), tetraethylene glycol di-2-ethylhexanoate (4GO), triethylene glycol dipivalate (3GT), or di- ( 2-butoxyethyl) adipate (DBEA).
In recent years, there has been a problem that the ITO film in contact with the filling material deteriorates when exposed to high temperature and high humidity, whereas the interlayer filling material for touch panel of the present invention is a plasticizer of these. By containing the deterioration of the ITO film formed on the touch panel can be suppressed. In addition, general plasticizers other than these plasticizers (for example, organic acid ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, organic phosphoric acid plasticizers, organic phosphorous acid plasticizers, etc. In the case of using a phosphoric acid plasticizer), it is difficult to sufficiently suppress the deterioration of the ITO film.

Among the plasticizers, triethylene glycol di-2-ethylhexanoate (3GO) is particularly preferable because the step following property of the interlayer filling material for touch panels is excellent.

Although the content of the plasticizer with respect to the polyvinyl acetal is not particularly limited, a preferable lower limit with respect to 100 parts by weight of the polyvinyl acetal is 5 parts by weight, and a preferable upper limit is 75 parts by weight. If the content is within the above range, it is possible to suppress the bubbles from remaining in the steps when filling the layers (during bonding) and to suppress the deterioration of the ITO film formed on the touch panel. It becomes easy to do.
If the content is less than 5 parts by weight, the moldability of the interlayer filling material for a touch panel may be lowered. When the content exceeds 75 parts by weight, the transparency of the interlayer filling material for a touch panel may decrease, or the plasticizer may bleed out. The more preferred lower limit of the plasticizer is 10 parts by weight, the still more preferred lower limit is 15 parts by weight, the particularly preferred lower limit is 20 parts by weight, the more preferred upper limit is 65 parts by weight, the still more preferred upper limit is 55 parts by weight, and the particularly preferred upper limit is 45 parts by weight.

In addition, since the cohesive force is generated by the polyvinyl acetal, it is preferable that the content of the plasticizer is small. That is, it is preferable to increase the compatibility between the polyvinyl acetal and the plasticizer to reduce the content of the plasticizer. Thereby, scattering prevention property can be improved.
As a method for increasing the compatibility between the polyvinyl acetal and the plasticizer, for example, a method for increasing the degree of acetalization of the polyvinyl acetal and a method for increasing the amount of acetyl groups are preferable. Also preferred is a method of removing the blocking property of the hydroxyl group of the polyvinyl acetal. As a method of suppressing the blocking of the hydroxyl group, a method of lowering the aging temperature is preferable.

In the interlayer filling material for a touch panel of the present invention, the content of the plasticized polyvinyl acetal is preferably 50% by weight or more. When the content is less than 50% by weight, when the portable information terminal is damaged, scattering of fragments cannot be sufficiently suppressed, or air bubbles may remain in a step when filling (bonding) between layers. There is. The more preferable lower limit of the content is 60% by weight, the still more preferable lower limit is 70% by weight, the still more preferable lower limit is 80% by weight, and the particularly preferable lower limit is 90% by weight.
The upper limit of the content of the plasticized polyvinyl acetal is not particularly limited, and may be 100% by weight.

The interlayer filling material for a touch panel of the present invention, if necessary, within a range that does not impair the transparency and does not hinder the effects of the present invention, an adhesive strength modifier, a tackifier resin, a plasticizer, an emulsifier, a softener, fine particles, You may contain well-known additives, such as a filler, a pigment, dye, a silane coupling agent, antioxidant, surfactant, and wax.

The shape of the interlayer filling material for a touch panel of the present invention is not particularly limited, and examples thereof include a sheet shape, a film shape, and a liquid (dispersed liquid, emulsion), and the like is preferable. Even if the interlayer filling material for a touch panel of the present invention is a thin filling material, it can sufficiently follow the decorative printed portion step or the wiring step and remove bubbles remaining at the step boundary.
In the case of a sheet form, the thickness of the interlayer filling material for a touch panel of the present invention is not particularly limited and is set depending on the application, but a preferable lower limit is 5 μm and a preferable upper limit is 800 μm. When the thickness is less than 5 μm, bubbles may easily remain in the step during filling between layers (during bonding). The more preferred lower limit of the thickness is 10 μm, the more preferred upper limit is 400 μm, the still more preferred lower limit is 25 μm, the still more preferred upper limit is 300 μm, the still more preferred lower limit is 50 μm, the still more preferred upper limit is 200 μm, and the particularly preferred lower limit. Is 75 μm, and a particularly preferred upper limit is 100 μm.

The method for producing the interlayer filling material for a touch panel of the present invention is not particularly limited. In the case of a sheet form, for example, a composition containing a plasticized polyvinyl acetal and an additive blended as necessary, an extrusion method, a coating method And a method of forming a film into a sheet by a normal film forming method such as a casting method, a calendar method, and a press method.

The use of the interlayer filling material for a touch panel of the present invention is not particularly limited. For example, a flat or flexible image display device using an image display panel such as a portable information terminal (for example, a smartphone or a tablet), LCD, EL, or PDP ( For example, in electronic paper, PDA, TV, game machine, etc., it is selected from the group consisting of an interlayer between a surface protection panel and a touch panel, an interlayer between a touch panel and a polarizing film, and an interlayer between a plurality of transparent conductive films constituting the touch panel. It is preferably used between at least one layer.
If the interlayer filling material for touch panels of the present invention is sandwiched between layers and then thermocompression bonded at around 70 ° C., the layers can be filled easily. In addition, after laminating | stacking the said transparent adhesive agent and the said polarizing plate by a normal pressure, you may perform the autoclave (ACV) process which pressurizes simultaneously with a heating. Further, after laminating the transparent adhesive and the polarizing plate and heating them to around 70 ° C. to adhere the transparent adhesive to the surface of the polarizing plate, it is further 70 ° C. at 1 atm, for example, with a vacuum laminator. Air bubbles can be more easily removed by performing autoclave (ACV) treatment in which pressurization is performed simultaneously with heating for 30 minutes at 85 ° C. and 0.5 MPa or more after performing pre-heat pressure bonding for 30 minutes.

FIG. 1 is a cross-sectional view schematically showing an example of a method of using the interlayer filling material for a touch panel of the present invention. In FIG. 1, the interlayer between the surface protection panel 3 and the touch panel 2 and the interlayer between the touch panel 2 and the polarizing film 4 are filled with the interlayer filling material 1 for a touch panel of the present invention.
In FIG. 1, a decorative printing portion 5 is formed on the peripheral portion of the back side of the surface protection panel 3 for the purpose of masking or the like, but the interlayer filling material 1 for a touch panel of the present invention is such a decorative printing. Air bubbles remaining at the boundary of the step at the time of filling (bonding) between the layers sufficiently following the step formed by the part 5 and the step (not shown) of the wiring formed on the touch panel 2. Can be removed.

At least one kind of interlayer selected from the group consisting of an interlayer between a surface protection panel and a touch panel, an interlayer between a touch panel and a polarizing film, and an interlayer between a plurality of transparent conductive films constituting the touch panel is an interlayer for a touch panel of the present invention. A laminate that is filled with a filling material is also one aspect of the present invention.
The said surface protection panel is not specifically limited, For example, what is normally used for a portable information terminal, a flat type, or a flexible image display apparatus, such as a glass plate, a polycarbonate plate, an acrylic plate, can be used.
The said touch panel is not specifically limited, For example, what is normally used for a portable information terminal, a flat type, or a flexible image display apparatus, such as a touch panel having a plurality of layers such as an ITO film, can be used. The configuration of the touch panel is not particularly limited, and examples thereof include an out-cell type, an in-cell type, an on-cell type, a cover glass integrated type, and a cover sheet integrated type. The touch panel system is not particularly limited, and examples thereof include a resistance film type, a capacitance type, an optical type, and an ultrasonic type.
It does not specifically limit as said polarizing film, The thing normally used for a portable information terminal, a flat type, or a flexible image display apparatus etc. can be used.

According to the present invention, it is used for filling an interlayer between a touch panel and another member or a plurality of transparent conductive films constituting the touch panel in the manufacture of a portable information terminal, etc. ITO film formed on the touch panel with excellent followability to decorative printed part steps or wiring steps and the defoaming property of bubbles entrained during filling (bonding) between layers or bubbles remaining near the steps It is possible to provide an interlayer filling material for a touch panel that can suppress deterioration of the touch panel. Moreover, according to this invention, the laminated body manufactured using this interlayer filling material for touchscreens can be provided.

It is sectional drawing which shows typically an example of the usage method of the interlayer filling material for touchscreens of this invention. It is a figure which shows typically the test method of deterioration suppression (ITO deterioration property) of the ITO film | membrane under the high temperature, high humidity of the sheet-like interlayer filling material obtained by the Example and the comparative example.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Production of polyvinyl butyral resin (1))
A reactor equipped with a stirrer was charged with 2700 mL of ion-exchanged water, 300 g of polyvinyl alcohol having an average polymerization degree of 1800 and a saponification degree of 99.3 mol%, and was heated and dissolved while stirring to obtain a solution. Next, 35% by weight hydrochloric acid as a catalyst was added to this solution so that the hydrochloric acid concentration was 0.2% by weight, the temperature was adjusted to 15 ° C., and n-butyraldehyde (n-BA) was stirred. 21 g was added. Thereafter, when 145 g of n-butyraldehyde (n-BA) was added, white particulate polyvinyl butyral resin was precipitated. 15 minutes after the precipitation, 35 wt% hydrochloric acid was added so that the hydrochloric acid concentration was 1.8 wt%, heated to 50 ° C., and aged at 50 ° C. for 2 hours. Then, after cooling and neutralizing the solution, the polyvinyl butyral resin was washed with water and dried to obtain a polyvinyl butyral resin (1). The amount of hydroxyl groups was 31.0 mol%, the amount of acetyl groups was 0.7 mol%, and the degree of butyralization (degree of Bu formation) was 68.3 mol%.

(Production of polyvinyl butyral resins (2) and (3))
Based on the formulation and conditions shown in Table 1, polyvinyl butyral resins (2) and (3) were produced in the same manner as polyvinyl butyral resin (1).

(Examples 1-16, Comparative Examples 1-16)
(Manufacture of sheet-like interlayer filling material)
Using the obtained polyvinyl butyral resins (1) to (3), the following film formation was performed with the plasticized polyvinyl acetal formulation shown in Table 2.
The plasticizer is added in the types and blending amounts shown in Table 2 with respect to 100 parts by weight of the obtained polyvinyl butyral resin (having the butyralization degree (Bu degree), hydroxyl group amount, and acetyl group amount shown in Table 1). And kneaded sufficiently to obtain a kneaded product. The obtained kneaded material was press-molded by a press molding machine to form a sheet, and a sheet-like interlayer filling material having a film thickness shown in Table 2 was obtained.

<Evaluation>
The following evaluation was performed about the sheet-like interlayer filling material obtained by the Example and the comparative example.

(1) Defoaming property The following evaluation was performed about the sheet-like interlayer filling material obtained in Examples 1-4.
One side of the sheet-like interlayer filler material cut to the same size as the white plate glass is pasted on 76 mm × 52 mm and a white plate glass (S9112 made by Matsunami Glass) having a thickness of 1.0 to 1.2 mm, and the other side of the sheet-like interlayer filler material The surface was affixed to an ITO-PET film (polyethylene terephthalate (PET) film coated with ITO) whose surface was cut to the same size as white plate glass to prepare a glass / sheet-like interlayer filler / ITO-PET film structure. At this time, bubbles were sealed at the interface between the glass and the sheet-like interlayer filling material. Next, this structure was preliminarily heat-pressed with a vacuum laminator at 70 ° C. and 1 atm for 30 minutes, and then heated in an autoclave at 70 ° C. and 0.5 MPa for 30 minutes. A layered product filled with the interlayer filler material was obtained.
When the obtained laminate was observed with a digital microscope (manufactured by Keyence Corporation), no bubbles remained in any of Examples 1 to 4.

(2) Step following ability The following evaluation was performed about the sheet-like interlayer filling material obtained in Examples 1-4.
A single-sided adhesive with a frame shape of a square shape of outer frame 76 mm x 52 mm and inner frame 56 mm x 32 mm is applied to white plate glass (S9112 made by Matsunami Glass) of 76 mm x 52 mm and thickness 1.0-1.2 mm. Affixed to make a step.
Sheet-like interlayer filling material is cut to 76 mm x 52 mm, and is pasted on the surface of a white sheet glass with a square-shaped frame-shaped step, and further ITO coated polyethylene terephthalate film (ITO-PET, Sekisui Nanocoat Technology Co., Ltd.) was cut into 76 mm × 52 mm and attached to the sheet-like interlayer filling material. Air bubbles were prevented from entering as much as possible when each was bonded. After pressure bonding with a vacuum laminator at 70 ° C. for 30 minutes and 1 atm, the sample was treated with an autoclave at 70 ° C. and 0.5 MPa for 30 minutes, and the pressure was reduced to 30 ° C. or less to prepare a sample for evaluation.
When observed with a digital microscope (manufactured by Keyence Corporation), no bubbles remained at the interface of the steps in any of Examples 1 to 4.

(3) Suppression of deterioration of ITO film under high temperature and high humidity (ITO degradation)
The following evaluation was performed about the sheet-like interlayer filling material obtained in Examples 1-16 and Comparative Examples 1-16.
FIG. 2 is a diagram schematically showing a test method for suppressing deterioration (ITO deterioration) of the ITO film under high temperature and high humidity of the sheet-like interlayer filling material obtained in Examples and Comparative Examples.
As shown in FIG. 2, first, a silver paste is applied to both ends 15 mm in the length direction of a conductive film (width 25 mm, length 120 mm) 6 having an ITO film formed on the surface, dried by heating, and then a silver layer ( Silver electrode part) 7 was formed. Thereafter, the conductive film 6 on which the silver layer 7 was formed was attached to the glass plate 8. Next, a sheet-like interlayer filling material (30 mm in width, 100 mm in length) 9 was applied so as to be in contact with both silver layers 7, and processed for 30 minutes in an autoclave at 70 ° C. and 0.5 MPa to prepare a sample for evaluation. .
In addition, the sample for evaluation is comprised from the electroconductive film 6, the silver layer 7, the glass plate 8, and the sheet-like interlayer filling material 9, as shown in FIG.
The resistance value between the two silver layers 7 of the sample for evaluation was measured by the tester 10, and this was designated as “ITO resistance value A” (initial). Thereafter, the sample for evaluation was put in an environment of a temperature of 100 ° C. and a humidity of 90% and treated for 250 hours. After the treatment, the resistance value between the two silver layers 7 of the sample for evaluation was measured by the tester 10, and this was designated as “ITO resistance value B” (after 100 ° C.-90% 250 h). The value of “ITO resistance value B” / “ITO resistance value A” was determined.

According to the present invention, it is used for filling an interlayer between a touch panel and another member or a plurality of transparent conductive films constituting the touch panel in the manufacture of a portable information terminal, etc. ITO film formed on the touch panel with excellent followability to decorative printed part steps or wiring steps and the defoaming property of bubbles entrained during filling (bonding) between layers or bubbles remaining near the steps It is possible to provide an interlayer filling material for a touch panel that can suppress deterioration of the touch panel. Moreover, according to this invention, the laminated body manufactured using this interlayer filling material for touchscreens can be provided.

DESCRIPTION OF SYMBOLS 1 Interlayer filling material for touch panels of this invention 2 Touch panel 3 Surface protection panel 4 Polarizing film 5 Decorative printing part 6 Conductive film 7 Silver layer (silver electrode part)
8 Glass plate 9 Sheet-like interlayer filling material (width 30 mm, length 100 mm)
10 Tester

Claims (5)

An interlayer filling material for a touch panel that is used to fill an interlayer between a touch panel and another member or an interlayer of a plurality of transparent conductive films constituting the touch panel,
Containing a plasticized polyvinyl acetal containing a polyvinyl acetal and a plasticizer;
The plasticizer is triethylene glycol di-2-ethylhexanoate (3GO), tetraethylene glycol di-2-ethylhexanoate (4GO), triethylene glycol di-pivalate (3GT), or di- ( An interlayer filling material for a touch panel, which is 2-butoxyethyl) adipate (DBEA). The interlayer filling material for a touch panel according to claim 1, wherein the content of the plasticized polyvinyl acetal is 50% by weight or more. The interlayer filling material for a touch panel according to claim 1 or 2, wherein the polyvinyl acetal is polyvinyl butyral. The interlayer filling material for a touch panel according to claim 1, 2 or 3, wherein the other member is a surface protective panel and / or a polarizing film. Claims 1, 2, wherein at least one layer selected from the group consisting of an interlayer between a surface protection panel and a touch panel, an interlayer between a touch panel and a polarizing film, and an interlayer of a plurality of transparent conductive films constituting the touch panel. A laminate comprising the touch panel interlayer filling material according to 3 or 4.

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