JP2007231067A - Near-infrared radiation-absorbing adhesive and method for producing the same, and near-infrared radiation-absorbing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near-infrared radiation-absorbing adhesive excellent in moist heat resistance, capable of retaining the absorption effect of near-infrared radiation over a long period and also simple in composition, to provide a method for producing the adhesive, and to provide a near-infrared radiation-absorbing sheet. <P>SOLUTION: The near-infrared radiation-absorbing adhesive comprises a near-infrared radiation-absorbing coloring matter selectively absorbing rays of 820-1,000 nm wavelength zone, an adhesive resin and an organic solvent, wherein the above coloring matter to be used consists of multiple phthalocyanine-based dyes having respective maximum absorption wavelengths differing from each other in the above wavelength zone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a near-infrared absorbing adhesive, a method for producing the same, and a near-infrared absorbing sheet, and particularly, a near-infrared absorbing adhesive suitable for use as a near-infrared absorbing material for an optical filter provided on the viewing side of a plasma display panel (PDP). It is related with an agent, its manufacturing method, and a near-infrared absorption sheet.

Conventionally, there is a plasma display panel (PDP) as a large screen flat display (FPD) which does not take an installation place. This PDP has characteristics such as excellent color reproducibility and response speed, and natural gradation display.
This PDP discharges by applying a voltage to a rare gas (helium, neon, argon, xenon, etc.) sealed between two glass substrates, and excites the phosphor using ultraviolet rays generated by this discharge. Color display using the three primary colors (R), blue (B), and green (G) is performed.
By the way, this PDP generates visible light and at the same time generates harmful electromagnetic waves such as near infrared rays. Therefore, an optical filter for shielding harmful electromagnetic waves such as near infrared rays is provided on the front plate (viewing side) of the PDP. Therefore, these harmful electromagnetic waves are prevented.

As said optical filter, the optical film which shields 800-1100 nm near-infrared rays is proposed.
As this optical film, for example, on a transparent substrate such as polyethylene terephthalate (PET), a near infrared absorbing dye containing a near infrared absorbing dye such as a diimonium dye having a maximum absorption wavelength at 800 to 1100 nm, and a silicone adhesive. An optical film having an adhesive composition has been proposed (see, for example, Patent Document 1).
In addition, an infrared absorbing adhesive composition containing an infrared absorbent such as a diimonium compound having a maximum absorption wavelength at 700 to 1100 nm and an acrylic adhesive resin was laminated on one surface of a transparent film or a peelable film. An infrared absorbing sheet has also been proposed (see, for example, Patent Document 2).
JP 2005-62506 A JP 2001-207142 A

By the way, in a conventional optical film, a diimonium dye is used as a near-infrared absorbing dye. However, the weather resistance is easily deteriorated as compared with other near-infrared absorbing dyes. There was a problem that the shielding effect may be reduced.
In addition, since the silicone-based pressure-sensitive adhesive is expensive, there is a problem in that it increases the manufacturing cost of the PDP. Thus, since silicone adhesives are not suitable in terms of cost when mass-produced, there are adhesives that are relatively inexpensive and can be stably supplied, such as acrylic adhesives, and that have similar performance. It is desired.

On the other hand, in the conventional infrared absorbing sheet, a diimonium compound is used as a near-infrared absorbing dye of an acrylic pressure-sensitive adhesive. This diimonium-based compound has weather resistance in a general crosslinking reaction type acrylic pressure-sensitive adhesive. There was a problem that it was insufficient for practical use.
In addition, since the acrylic pressure-sensitive adhesive uses a cross-linking reaction, there is a problem that the pot life from the preparation of the paint to the use thereof is short and the storage is not effective.
In actual work, there is a limitation that the infrared absorbing adhesive once produced cannot be stored and the produced paint must be consumed on the same day. Further, after laminating the infrared absorbing adhesive layer, a certain aging period of several days to one week is required.

The acrylic resin constituting the pressure-sensitive adhesive has a number of cross-linking reactive groups (isocyanate group, hydroxy group, glycidyl group, carboxyl group, etc.), and this cross-linking reactive group reacts with the cross-linking agent or the like. However, since this curing takes time, a cross-linking reactive group may remain even after the infrared absorbing adhesive layer is formed. Therefore, there has been a problem that near-infrared absorbing pigments in the infrared-absorbing pressure-sensitive adhesive layer, particularly diimonium compounds, may deteriorate, and the durability, particularly heat resistance, of the resulting infrared-absorbing sheet may deteriorate.
In addition, the diimonium-based compound is sensitively affected by an alkali component contained in a glass plate used for the front surface of the PDP module or the front surface plate of the PDP filter. Therefore, when an adhesive layer containing a diimonium compound is sandwiched between a PDP filter film and a glass plate, the diimonium compound is deteriorated by an alkali component contained in the glass plate. This phenomenon becomes remarkable particularly in a high temperature and high humidity environment.

  The present invention has been made in order to solve the above-mentioned problems, and is a near-infrared-absorbing pressure-sensitive adhesive that is excellent in moisture and heat resistance, can retain a near-infrared absorption effect for a long period of time, and has a simple configuration. It aims at providing an agent, its manufacturing method, and a near-infrared absorption sheet.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have maximized the near-infrared absorbing dye as a near-infrared absorbing dye in a wavelength band of 820 nm or more and 1000 nm or less. It has been found that by using a plurality of dyes having absorption, in particular, a plurality of phthalocyanine dyes in consideration of alkali resistance, the heat and moisture resistance is excellent, and the absorption effect of near infrared rays can be maintained for a long time. In addition, when the near-infrared absorbing dye that selectively absorbs light in the wavelength band of 820 nm or more and 1000 nm or less is dissolved in a solvent, the content of the near-infrared absorbing dye is 0.3 wt% or more and 15 wt% or less. By adjusting so that it is excellent in moisture and heat resistance, it is possible to keep the absorption effect of near infrared rays for a long time, and also the variation in near infrared absorption rate It found that the near infrared absorbing pressure-sensitive adhesive is obtained small, further, since it is one sheet-like, found to be easy construction is simple to handle, and have completed the present invention.

  That is, the near-infrared absorbing adhesive of the present invention comprises a near-infrared absorbing dye that selectively absorbs light in a wavelength band of 820 nm or more and 1000 nm or less, an adhesive resin, and an organic solvent. And

The near-infrared absorbing dye is preferably composed of a plurality of kinds of dyes having different maximum absorption wavelengths in the wavelength band of 820 nm or more and 1000 nm or less.
The pigment is preferably a phthalocyanine pigment.
The pressure-sensitive adhesive resin is an acrylic pressure-sensitive adhesive resin, and the near-infrared absorbing dye is preferably dispersed in the acrylic pressure-sensitive adhesive resin.
Moreover, it is preferable that the light transmittance in the wavelength range of 820 nm or more and 1000 nm or less when the thickness is 5 μm or more and 100 μm or less is 20% or less.

  In the method for producing a near-infrared absorbing pressure-sensitive adhesive of the present invention, a near-infrared absorbing dye that selectively absorbs light having a wavelength band of 820 nm or more and 1000 nm or less is dissolved in a solvent, and the content of the near-infrared absorbing dye is 0. Adjust to a solution of 3 wt% or more and 15 wt% or less, and then add a solution containing an adhesive resin to this solution to adjust the viscosity to 50 cP to 30000 cP and the non-volatile component to 70 wt% or less. It is characterized by doing.

The near-infrared absorbing sheet of the present invention is characterized in that an adhesive layer made of the near-infrared absorbing adhesive of the present invention is formed on a transparent substrate.
When the thickness of the pressure-sensitive adhesive layer is 5 μm or more and 100 μm or less, the light transmittance in the wavelength band of 820 nm or more and 1000 nm or less is preferably 20% or less.

  According to the near-infrared absorbing adhesive of the present invention, since it contains a near-infrared absorbing dye that selectively absorbs light in the wavelength band of 820 nm or more and 1000 nm or less, the near-infrared can be absorbed in a wide range, and the heat and moisture resistance is high. Can be improved. Therefore, the absorption effect of near infrared rays can be maintained for a long time.

  According to the method for producing a near-infrared-absorbing pressure-sensitive adhesive of the present invention, a near-infrared-absorbing dye that selectively absorbs light having a wavelength band of 820 nm or more and 1000 nm or less is dissolved in a solvent and the content of the near-infrared-absorbing dye is 0. Since the solution is adjusted so as to be 3 wt% or more and 15 wt% or less, the near-infrared absorbing dye can be uniformly dispersed in the solvent.

Further, a solution containing an adhesive resin is added to this solution to adjust the viscosity to 50 cP or more and 30000 cP or less and the non-volatile component to 70% by weight or less, so that the near-infrared absorbing dye and the adhesive resin can be uniformly dispersed. The near-infrared absorption characteristics of the adhesive layer obtained using this solution can be made uniform.
Therefore, it is possible to easily obtain a near-infrared absorbing pressure-sensitive adhesive having excellent wet heat resistance, excellent long-term persistence of the near-infrared absorption effect, and having uniform near-infrared absorption characteristics.

  According to the near-infrared absorbing sheet of the present invention, since the pressure-sensitive adhesive layer made of the near-infrared absorbing adhesive of the present invention is formed on the transparent substrate, the near-infrared ray can be absorbed in a wide range and the heat and humidity resistance can be improved. Can do. Therefore, it is possible to provide a near-infrared absorbing sheet having a simple configuration capable of maintaining the near-infrared shielding effect for a long period of time at a low cost.

The best form for implementing the near-infrared absorption adhesive of this invention, its manufacturing method, and a near-infrared absorption sheet is demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

The near-infrared absorbing adhesive of the present invention comprises a near-infrared absorbing dye that selectively absorbs light in a wavelength band of 820 nm or more and 1000 nm or less, which is a near infrared radiation (NIR) wavelength band, and an adhesive resin. And a near-infrared absorbing adhesive comprising an organic solvent.
Examples of the near infrared absorbing dye include inorganic pigments, organic pigments, organic dyes, and the like.
Examples of inorganic pigments include cobalt dyes, iron dyes, chromium dyes, titanium dyes, vanadium dyes, zirconium dyes, molybdenum dyes, ruthenium dyes, platinum dyes, tin-containing indium oxide (ITO) ) Dye, antimony-containing tin oxide (ATO) dye, aluminum-containing zinc oxide (AZO) dye, antimony-containing indium oxide (AIO) dye, and the like.

  Examples of organic pigments or organic dyes include anthraquinone dyes, cyanine dyes, merocyanine dyes, croconium dyes, squalium dyes, azulene dyes, polymethine dyes, naphthoquinone dyes, pyrylium dyes, and phthalocyanine dyes. Dyes, naphthalocyanine dyes, naphtholactam dyes, azo dyes, condensed azo dyes, indigo dyes, perinone dyes, perylene dyes, dioxazine dyes, quinacridone dyes, isoindolinone dyes, quinophthalone dyes, Examples include pyrrole dyes, thioindigo dyes, metal complex dyes, dithiol dyes, indolephenol dyes, triallylmethane dyes, and the like.

  The near-infrared absorbing dye is preferably composed of a plurality of kinds of dyes having different maximum absorption wavelengths in a wavelength band of 820 nm or more and 1000 nm or less, and a phthalocyanine dye is preferable as this dye.

  The adhesive resin is not particularly limited as long as it has good adhesion to the near-infrared absorbing dye and has adhesiveness, but the near-infrared absorbing dye is easily dispersed, and this near-infrared absorbing From the viewpoint of preventing the deterioration of the dye, an acrylic pressure-sensitive adhesive resin, particularly a pressure-sensitive adhesive resin containing an acrylic block copolymer is preferable.

  As the composition of this acrylic block copolymer, it contains two or more methyl methacrylate polymer blocks and one or more butyl acrylate polymer blocks. The ratio of these two types of polymer blocks is as follows: When the total amount of these two kinds of polymer blocks is 100 parts by mass, two or more methyl methacrylate polymer blocks are 20 parts by mass or more and 30 parts by mass or less, and the remaining one or more acrylics The acid butyl polymer block is 70 parts by mass or more and 80 parts by mass or less.

  The acrylic block copolymer preferably has a weight average molecular weight of 30,000 or more and 100,000 or less. Here, the reason why the weight average molecular weight is limited as described above is that when the weight average molecular weight is less than 30000, the cohesive force is insufficient as an adhesive, and thus the adhesiveness may be lowered when used for a long time. On the other hand, if the weight average molecular weight exceeds 100,000, the viscosity becomes high and the coatability is lowered.

  The alkali metal content in the acrylic block copolymer is preferably 10 ppm or less, and more preferably 3 ppm or less. Here, the reason why the alkali metal content is limited to 10 ppm or less is that when the alkali metal content exceeds 10 ppm, the near-infrared absorbing dye contained in the adhesive reacts with the alkali metal to cause discoloration or a decrease in weather resistance. It is because there is a possibility of producing.

The method for producing the acrylic block copolymer is not particularly limited as long as an acrylic block copolymer satisfying the conditions of the present invention is obtained. For example, a monomer as a constituent unit is subjected to living polymerization. Any method of (1) to (4) can be used.
(1) A method of polymerizing an organic rare earth metal complex as a polymerization initiator.
(2) A method of anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of a mineral salt such as an alkali metal or alkaline earth metal salt.
(3) A method of anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organic aluminum compound.
(4) Atom transfer radical polymerization method (ATRP).

In the present invention, it is preferable to use the method (3).
In this method, toluene or the like is used as a solvent in an inert gas atmosphere such as nitrogen or argon, and an organic aluminum compound such as triethylaluminum and a polar additive such as 1,2-dimethoxyethane are used. A method of synthesizing an acrylic block copolymer by sequentially adding and polymerizing methyl methacrylate and n-butyl acrylate under a temperature condition of −80 ° C. to 80 ° C. using an alkyl lithium compound as a polymerization initiator. is there.

In order to remove the remaining alkali metal from the acrylic block copolymer thus obtained, the acrylic block copolymer is purified.
Examples of the purification method include a method of subjecting the reaction solution after the anionic polymerization is stopped in the presence of an organoaluminum compound to a washing treatment or a purification treatment.
Examples of the washing treatment include a liquid separation extraction process using an acidic aqueous solution, a liquid separation extraction process using water, and the like. Examples of the acidic aqueous solution include dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid, acetic acid, aqueous propionic acid solution, and aqueous citric acid solution.

As purification treatment, adsorption treatment using an adsorbent such as ion exchange resin, silica gel or alumina, or re-precipitation of the acrylic block copolymer by pouring the above reaction solution into a poor solvent such as methanol. Examples include precipitation treatment.
In addition to the above method, for example, the obtained acrylic block copolymer may be redissolved in a solvent, and the above washing treatment or purification treatment may be performed on this solution. The solvent used for redissolving is not particularly limited as long as it can dissolve the acrylic block copolymer. For example, toluene, methyl acetate, ethyl acetate, n-butyl acetate, acetone, 2-butanone, cyclohexane And methylcyclohexane.

Although it does not specifically limit as a liquid separation extraction process, For example, the following methods can be used.
Using a reaction vessel with a stirrer, an acrylic block copolymer is dissolved in an organic solvent that can be separated from water such as toluene and ethyl acetate to prepare a polymer solution having a polymer concentration of 3 to 50% by mass. Next, an aqueous solution containing 0.01 to 20% by mass of an acid such as sulfuric acid and acetic acid is added to the polymer solution, and the mixture is stirred for 1 minute to 1 hour under a temperature condition of normal temperature (25 ° C.) to 80 ° C. Thereafter, stirring is stopped and the mixture is allowed to stand for 30 minutes to 1 hour, and the aqueous layer separated into the lower layer is extracted.
Thereby, the alkali metal component in an acrylic block copolymer can be reduced.

In addition, if necessary, the above aqueous solution is added to the polymer solution remaining in the reaction vessel with a stirrer, and the same separation and extraction operation is repeated a plurality of times to further reduce the alkali metal component in the acrylic block copolymer. Can be made.
In addition, the reprecipitation treatment is not particularly limited. For example, a polymer solution having a polymer concentration of 3 to 50% by mass is poured into a poor solvent such as methanol having a mass of 1 to 100 times the polymer solution and precipitated. A method of collecting the polymer by filtration can be used.

  Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Esters such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, acetone, Methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, etc. Amides, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and amides such as dimethylformamide, N, N-dimethylacetoacetamide and N-methylpyrrolidone are preferably used. One of these solvents or Two or more kinds can be used.

Next, the manufacturing method of the near-infrared absorption adhesive of this embodiment is demonstrated.
First, the near infrared absorbing dye described above is dissolved in an organic solvent, and the content of the near infrared absorbing dye is 0.3 wt% or more and 15 wt% or less, more preferably 1 wt% or more and 12 wt% or less, Preferably, the solution is adjusted to 3% by weight or more and 10% by weight or less.

The reason why the near-infrared absorbing dye is once dissolved in the organic solvent is that it is difficult to uniformly disperse the dye if it is directly added to a solution containing an adhesive resin described later.
Here, the reason for limiting the content of the near-infrared absorbing dye to 0.3% by weight or more and 15% by weight or less is that the concentration of the near-infrared absorbing dye in the pressure-sensitive adhesive is controlled by setting the content within the above range. This is because it can be made uniform. If the content of the near-infrared absorbing dye is less than 0.3% by weight, the organic solvent is in an excessive state, so that the near-infrared absorbing performance is lowered, and the coating becomes difficult when actually applied. . On the other hand, when the content exceeds 15% by weight, since the organic solvent is too small, the near-infrared absorbing dye is not sufficiently dissolved, and a solution in which the near-infrared absorbing dye is uniformly mixed cannot be obtained.

In particular, when the near-infrared absorbing dye is composed of a plurality of kinds of dyes, if at least one of them is less than 0.3%, it is necessary to reduce the transmittance at 820 to 1000 nm to 20% or less. When the dye solution is mixed with the infrared absorbing adhesive, the organic solvent in the near infrared absorbing adhesive becomes excessive, resulting in excessive decrease in viscosity, and a coating film having a desired thickness is obtained during film formation. Disappear.
In addition, if any one of these is 15% or more, the dye cannot be sufficiently dissolved, or the dye solubility is affected by the rise or fall of the room temperature when the dye solution is stored, so that the dye is stable. It becomes difficult to store in a dispersed state.

  Then, to this solution, a solution containing an adhesive resin, for example, a solution obtained by dissolving an acrylic adhesive resin in an organic solvent, particularly a solution obtained by dissolving an adhesive resin containing an acrylic block copolymer in an organic solvent, The viscosity and the content of nonvolatile components are adjusted to obtain a near-infrared absorbing adhesive.

The viscosity is preferably 50 cP or more and 30000 cP or less, more preferably 100 cP or more and 10000 cP or less, and further preferably 300 cP or more and 5000 cP or less.
Here, the reason why the viscosity of the near-infrared absorbing adhesive is 50 cP or more and 30000 cP or less is that when the viscosity is less than 50 cP, the viscosity is too low to sufficiently exhibit the function as an adhesive, If the viscosity exceeds 30000 cP, the viscosity is too high and the flowability of the near-infrared absorbing pressure-sensitive adhesive is lowered, so that the film cannot be formed by a normal coating method.

The content of the nonvolatile component is preferably 70% by weight or less, more preferably 20% by weight or more and 60% by weight or less, and further preferably 30% by weight or more and 55% by weight or less.
Here, the reason why the non-volatile component is 70% by weight or less is that when the non-volatile component exceeds 70% by weight, unevenness of the surface appears remarkably after the coating film is dried.

  This near-infrared absorbing adhesive has a light transmittance of 20% or less, more preferably 10% or less, in a wavelength band of 820 nm or more and 1000 nm or less when the thickness is 5 μm or more and 100 μm or less.

FIG. 1 is a cross-sectional view showing a near-infrared absorbing sheet according to an embodiment of the present invention. In the figure, 1 is a transparent base material, 2 is a near-infrared absorbing material of this embodiment formed on a transparent base material 1. A near-infrared absorbing adhesive layer 3 made of an adhesive is a release paper adhered on the adhesive layer 2.
The transparent substrate 1 may be in the form of a sheet having transparency and flexibility, especially considering that it is attached to the display surface of a flat panel display (FPD) such as a PDP, LCD, organic EL or the like. A transparent plastic sheet or transparent plastic film made of a flexible material is preferable.

The plastic is not particularly limited. For example, cellulose acetate, polystyrene (PS), polyethylene terephthalate (PET), polyether, polyimide, epoxy, phenoxy, polycarbonate (PC), polyvinylidene fluoride, acrylic, It can be appropriately selected from polyethylene (PE), nylon, polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyfluoroacetylene (PFA) and the like.
Also, the thickness of the plastic substrate is not particularly limited, and a film of about 50 to 250 μm can be used for a film, and a sheet of about 10 mm can be used for a sheet.

The pressure-sensitive adhesive layer 2 has a light transmittance of 20% or less, more preferably 10% or less in a wavelength band of 820 nm or more and 1000 nm or less when the thickness is 5 μm or more and 100 μm or less.
The release paper 3 is attached to protect the surface of the pressure-sensitive adhesive layer 2 and maintain the pressure-sensitive adhesive property, and has an adhesive strength that can be easily peeled off during use with the pressure-sensitive adhesive layer 2. Any material may be used as long as it is present, but a release paper having a surface laminated is preferably used.

In order to produce this near-infrared absorbing sheet, first, the near-infrared absorbing adhesive of this embodiment is applied to a predetermined location on the transparent substrate 1. As a coating method, for example, a usual method such as a spin coating method, a spray coating method, an ink jet method, a dip method, a roll coating method, a screen printing method, or the like is used.
Subsequently, this coating film is dried to form an adhesive layer 2. Since this coating film contains an organic solvent immediately after it is applied, it is dried at room temperature in the atmosphere, or by drying at a predetermined temperature, for example, 50 ° C. to 80 ° C. The organic solvent contained in the membrane can be dissipated.

Next, the release paper 3 is overlaid on the adhesive layer 2 and pressed from above to bring the adhesive layer 2 and the release paper 3 into close contact.
By the above, the near-infrared absorption sheet of this embodiment can be produced.
When this near-infrared absorbing sheet is used for FPD such as PDP, LCD, organic EL, etc., a flexible transparent plastic sheet or transparent plastic film is used as the transparent substrate 1, and the release paper 3 is placed on the adhesive layer 2. After sticking, the adhesive layer 2 may be supplied to the FPD production line as it is without peeling off the transparent substrate 1.

  According to the near-infrared absorbing adhesive of this embodiment, it contains a near-infrared absorbing dye that selectively selects and absorbs light in the wavelength band of 820 nm or more and 1000 nm or less, an adhesive resin, and an organic solvent. Since the absorbing dye is a plurality of types of phthalocyanine dyes having different maximum absorption wavelengths in the wavelength band of 820 nm or more and 1000 nm or less, it can absorb near infrared rays in the wavelength band of 820 nm or more and 1000 nm or less, Moisture and heat resistance can be improved. Therefore, the near infrared absorption effect can be maintained over a long period of time.

  According to the method for producing a near-infrared-absorbing pressure-sensitive adhesive of this embodiment, a near-infrared-absorbing dye is dissolved in an organic solvent. Therefore, the near-infrared absorbing dye can be uniformly dispersed in the solvent.

Further, a solution containing an adhesive resin such as an acrylic adhesive resin is added to this solution to adjust the viscosity to 50 cP or more and 30000 cP or less, and the non-volatile component to 70 wt% or less. Can be uniformly dispersed, and the near-infrared absorption characteristics of the adhesive layer obtained using this solution can be made uniform.
Therefore, it is possible to easily obtain a near-infrared absorbing pressure-sensitive adhesive having excellent wet heat resistance, excellent long-term persistence of the near-infrared absorption effect, and having uniform near-infrared absorption characteristics.

  According to the near-infrared absorbing sheet of this embodiment, the near-infrared absorbing adhesive of this embodiment is applied to a predetermined location on the transparent substrate 1, and this coating film is dried to form an adhesive layer 2. This adhesive layer 2 The release paper 3 is overlaid and pressed from above to bring the adhesive layer 2 and the release paper 3 into close contact with each other, so that it is possible to absorb near infrared rays over a wide range, improve the heat and moisture resistance, and handle it. It becomes easy. Therefore, it is possible to provide a near-infrared absorbing sheet that can maintain a near-infrared shielding effect for a long period of time and is easy to handle at low cost.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
A main agent solution was prepared by mixing 20 parts by mass of toluene and 2.5 parts by mass of methyl ethyl ketone with 27.5 parts by mass of acrylic pressure-sensitive adhesive resin LA2140e (trade name) (manufactured by Kuraray Co., Ltd.).
On the other hand, four types of dyes IR-10A (maximum absorption wavelength: λmax = 840 m), IR-12 (λmax = 870 m), 906B (λmax = 928 m), 910B (λmax = 968 m) (all of which are Nippon Shokubai) And an IR-10A 8% toluene solution, an IR-12 5% toluene solution, a 906B 8% toluene solution, and a 910B 10% methyl ethyl ketone solution.

  Subsequently, 26.5 parts by mass of methyl ethyl ketone, 2.2 parts by mass of 8% toluene solution of IR-10A, 0.8 parts by mass of 5% toluene solution of IR-12, 8% of 906B Example 1 A mixture of 0.9 parts by mass of a toluene solution and 2.6 parts by mass of a 10% methyl ethyl ketone solution of 910B and further 5 parts by mass of Tackfire ARUFON UP-1000 (trade name) (manufactured by Toagosei Co., Ltd.) The near-infrared absorbing adhesive A was prepared. The non-volatile component in the adhesive A at this time was 36.9%, and the viscosity was 100 cP.

Next, the pressure-sensitive adhesive A was applied on a polyethylene terephthalate (PET) film Lumirror U-94 (trade name) (manufactured by Toray Industries, Inc.) having a thickness of 100 μm with a bar coater so that the dry thickness was 25 μm. It dried at 5 degreeC for 5 minute (s), and the optical film sheet with the near-infrared absorption adhesion layer of Example 1 was produced.
Thereafter, the near-infrared absorbing adhesive layer of this optical film sheet was bonded to a 2 mm thick soda glass plate to produce a sample piece of Example 1.

"Example 2"
The near-infrared absorbing adhesive and sample piece of Example 2 according to Example 1 except that the amount of methyl ethyl ketone mixed in the main agent solution was changed to 35.4% non-volatile component in the adhesive and the viscosity was 55 cP Was made.

"Example 3"
The near-infrared absorbing adhesive and sample piece of Example 3 according to Example 1 except that the amount of methyl ethyl ketone mixed in the main agent solution was changed to 52.9% non-volatile component in the adhesive and the viscosity was 2000 cP. Was made.

Example 4
The near-infrared absorbing adhesive and sample piece of Example 4 according to Example 1 except that the amount of methyl ethyl ketone mixed with the main agent solution was changed to 68.2% non-volatile component in the adhesive and the viscosity was 26000 cP. Was made.

“Comparative Example 1”
A main agent solution was prepared by mixing 20 parts by mass of toluene and 2.5 parts by mass of methyl ethyl ketone with 27.5 parts by mass of acrylic pressure-sensitive adhesive resin LA2140e (trade name) (manufactured by Kuraray Co., Ltd.).
Next, to 50 parts by mass of this base solution, 26.1 parts by mass of methyl ethyl ketone, 3.1 parts by mass of a 10% methyl ethyl ketone solution of diimonium dye CIR-RL (trade name) (manufactured by Nippon Carlit), IR-as phthalocyanine dye 3.8 parts by mass of 10A 8% toluene solution was mixed, and 5 parts by mass of Tackfire ARUFON UP-1000 (trade name) (manufactured by Toagosei Co., Ltd.) was mixed. Produced. The non-volatile component in the adhesive B at this time was 36.9%, and the viscosity was 70 cP.

  Next, this adhesive B was applied on a polyethylene terephthalate (PET) film Lumirror U-94 (trade name) (manufactured by Toray Industries, Inc.) having a thickness of 100 μm with a bar coater so as to have a dry thickness of 25 μm. The optical film sheet with a near-infrared absorbing adhesive layer of Comparative Example 1 was produced by drying at 5 ° C. for 5 minutes. Thereafter, the near-infrared absorbing adhesive layer of this optical film sheet was bonded to a 2 mm thick soda glass plate to prepare a sample piece of Comparative Example 1.

"Comparative Example 2"
12.5 parts by mass of toluene and 12.5 parts by mass of methyl ethyl ketone were mixed with 25.0 parts by mass of acrylic pressure-sensitive adhesive resin LA2140e (trade name) (manufactured by Kuraray Co., Ltd.) to prepare a base solution.
Next, 50 parts by mass of the main agent solution, 26.5 parts by mass of toluene, 12.6 parts by mass of methyl ethyl ketone, 2.0 parts by mass of an 8% toluene solution of four types of dyes IR-10A as phthalocyanine dyes, A mixture of 0.7 parts by weight of 5% toluene solution, 0.8 parts by weight of 8% toluene solution of 906B, and 2.4 parts by weight of 10% methyl ethyl ketone solution of 910B was further added. Tackfire ARUFON UP-1000 (trade name) 5 parts by mass) (manufactured by Synthetic Co., Ltd.) were mixed to prepare a near infrared absorbing adhesive C of Comparative Example 2. The non-volatile component in the adhesive C at this time was 30.0%, and the viscosity was 25 cP.

  Next, this pressure-sensitive adhesive C was tried to be coated on a polyethylene terephthalate (PET) film Lumirror U-94 (trade name) (manufactured by Toray Industries, Inc.) having a thickness of 100 μm with a bar coater so as to have a dry thickness of 25 μm. The adhesive C flowed because of low viscosity at the time of application, and the dry thickness of the obtained near-infrared absorbing adhesive layer was about 10 μm, and the near-infrared absorbing adhesive layer having a predetermined thickness could not be formed. .

“Comparative Example 3”
Acrylic pressure-sensitive adhesive resin LA2140e (trade name) (manufactured by Kuraray Co., Ltd.) 50.0 parts by mass, toluene 11.3 parts by mass, and phthalocyanine dyes 4 types of dyes IR-10A 8% toluene solution 4.1 parts by mass , 1.4 parts by mass of a 5% toluene solution of IR-12, 1.6 parts by mass of an 8% toluene solution of 906B, and 9.6 parts by mass of a 5% toluene solution of 910B, and further, tackifier ARUFON UP-1000 ( Product name) 10 parts by mass (manufactured by Toagosei Co., Ltd.) were mixed to prepare a near-infrared absorbing adhesive D of Comparative Example 3. The non-volatile component in the adhesive D at this time was 68.2%, and the viscosity was 35000 cP.

Next, this pressure-sensitive adhesive D was applied on a polyethylene terephthalate (PET) film Lumirror U-94 (trade name) (manufactured by Toray Industries, Inc.) having a thickness of 100 μm with a bar coater so as to have a dry thickness of 25 μm. An optical film sheet with a near-infrared absorbing adhesive layer of Comparative Example 3 was produced by drying at 5 ° C. for 5 minutes.
Since this optical film sheet had a high viscosity of the pressure-sensitive adhesive D, a smooth coating film could not be produced, and the surface was extremely rough and the coating film was extremely rough.

“Comparative Example 4”
Acrylic adhesive resin LA2140e (trade name) (manufactured by Kuraray Co., Ltd.) 40.0 parts by mass, toluene 0.6 parts by mass, methyl ethyl ketone 3.6 parts by mass, 8% of four types of dye IR-10A as a phthalocyanine dye 5.4 parts by mass of toluene solution, 1.9 parts by mass of 5% toluene solution of IR-12, 2.1 parts by mass of 8% toluene solution of 906B, 6.4 parts by mass of 10% methyl ethyl ketone solution of 910B were mixed, and 40 parts by mass of Tackfire ARUFON UP-1000 (trade name) (manufactured by Toagosei Co., Ltd.) was mixed to prepare a near infrared absorbing adhesive E of Comparative Example 4. The non-volatile component in the adhesive E at this time was 80.0%, and the viscosity was 20000 cP.

Next, this pressure-sensitive adhesive E was applied on a polyethylene terephthalate (PET) film Lumirror U-94 (trade name) (manufactured by Toray Industries, Inc.) having a thickness of 100 μm with a bar coater so as to have a dry thickness of 25 μm. The film was dried at 5 ° C. for 5 minutes to produce an optical film sheet with a near-infrared absorbing adhesive layer of Comparative Example 4.
Since this optical film sheet had a high content of non-volatile components in the pressure-sensitive adhesive E, the surface unevenness was remarkable and a smooth coating film could not be produced.
Table 1 shows the nonvolatile components and viscosity of the adhesives of Examples 1 to 4 and Comparative Examples 1 to 4 and the properties of the adhesive layer of the optical film sheet.

"Evaluation of optical properties and heat and humidity resistance of sample pieces"
The optical properties and wet heat resistance of each sample piece of Example 1 and Comparative Example 1 were evaluated.
The evaluation method is as follows.

(1) Optical characteristics Evaluation was made based on two items of color values (a ^* , b ^* ) and spectral transmittance.
For the color values (a ^* , b ^* ), the a ^* value and b ^* value of the L ^* a ^* b ^* color system standardized by the CIE (International Commission on Illumination) of each sample piece are used as the color analyzer TOPSCAN TC. -1800-MKII (manufactured by Tokyo Denshoku Industries Co., Ltd.) was used for measurement.

  Spectral transmittance was measured using a spectrophotometer V-570 (manufactured by JASCO Corporation), and the transmission spectrum of each sample piece was measured in the wavelength range of 400 to 1200 nm. Here, the spectral transmittance (T820, T880, T950, T1000) at each wavelength of 820 nm, 880 nm, 950 nm, and 1000 nm in the near infrared region was measured.

(2) Heat and humidity resistance Samples of Examples 1 to 4 and Comparative Example 1 in which color values (a ^* , b ^* ) and spectral transmittance were measured as described above using a constant temperature and humidity chamber KCH-1000 (manufactured by EYELA). The piece was left for 48 hours in a constant temperature and humidity at a temperature of 80 ° C. and a humidity of 95%, and then the color values (a ^* , b ^* ) and spectral transmittance were measured at room temperature in the same manner as described above. Color values (a ^* , b ^* ) and spectral transmittance were evaluated.
Table 2 shows the optical properties and wet heat resistance of the sample pieces of Example 1 and Comparative Example 1.
Further, FIG. 2 shows a near infrared transmission spectrum before and after the wet heat resistance test of Example 1, and FIG. 3 shows a near infrared transmission spectrum before and after the wet heat resistance test of Comparative Example 1.

"Evaluation of color change, near-infrared absorption ability and adhesiveness of sample piece"
Each sample piece of Example 1 and Comparative Example 1 was evaluated for changes in color tone, near-infrared absorptivity, and adhesiveness before and after the moisture and heat resistance test.
The evaluation method is as follows.
(1) Color tone change The case where at least one of the color values (a ^* , b ^* ) changed by 3.0 or more was designated as “X”, and the case where only less than 3.0 was designated as “◯”.

(2) Near-infrared absorptivity If at least one of the four points of T820, T880, T950, and T1000 fluctuates by 3.0% or more, “x” and all four points fluctuate by less than 3.0%. In this case, “○” was assigned.
(3) Adhesiveness It was performed in accordance with Japanese Industrial Standards JIS Z 0237 “Testing method for adhesive tape and adhesive sheet”. However, in this evaluation, a soda glass plate was used as a test plate, and the adhesive force between the surface of the soda glass plate and the near infrared absorbing adhesive layer was measured.
In the evaluation of adhesiveness, those having an adhesive strength of 3.0 N / 25 mm or more were evaluated as “◯”, and those having an adhesive strength of less than 3.0 N / 25 mm were evaluated as “X”.
Table 3 shows the color tone change, near-infrared absorption ability, and adhesiveness of each sample piece of Example 1 and Comparative Example 1.

"Example 5"
Four types of dyes IR-10A (maximum absorption wavelength: λmax = 840 m), IR-12 (λmax = 870 m), 906B (λmax = 928 m), 910B (λmax = 968 m) (all manufactured by Nippon Shokubai Co., Ltd.) And each of these dyes is dispersed in an organic solvent using an ultrasonic disperser, and as shown in Table 4, a solution having a dye content of 0.3 wt% or more and 15 wt% or less is prepared. Produced. For comparison, a solution having a content rate outside the range was also prepared.
As the organic solvent, toluene was used for IR-10A, IR-12, and 906B, and methyl ethyl ketone was used for 910B.

Next, dispersibility and suitability as an adhesive were evaluated for each of the above solutions.
Regarding dispersibility, the dye was dispersed in an organic solvent using an ultrasonic disperser, and then allowed to stand naturally for 48 hours to evaluate the presence or absence of sedimentation and the possibility of redispersion.
Here, “○” indicates that no sedimentation occurred, “△” represents sedimentation that could be redispersed, and “x” represents sedimentation that could not be redispersed. .

Regarding the suitability as an adhesive, one of the four dye solutions of Example 1 was replaced with the above solution, and a near-infrared absorbing adhesive and a sample piece were prepared according to Example 1, and the wavelength: 400 to 1200 nm. When the minimum transmittance of the spectral transmittance in the range of 20% is 20%, the one with the minimum transmittance of 20% or less is set as “O” within the appropriate range, and the minimum transmittance is over 20% Was outside the proper range. In addition, the thing which could not produce a pigment solution by precipitation is set as "-".
Table 4 shows the dispersibility and suitability as an adhesive.

According to the above evaluation results, the following was found.
In Example 1, there was almost no change in color tone before and after the wet heat resistance test, and it was found that the color tone was very stable even in a high temperature and high humidity environment. Similarly, no deterioration was observed in the near infrared absorption ability.
Moreover, in Examples 2-4, it turned out that the adhesive layer with the smooth surface is obtained in the range of the non-volatile component and viscosity of an adhesive.

Further, in Example 5, a solution having a dye content of 0.3 wt% or more and 15 wt% or less is prepared once, and a near infrared absorbing adhesive is prepared using this dye solution. It was found that a near-infrared absorbing adhesive having a uniform concentration can be easily obtained.
Moreover, if the content rate of the pigment | dye is less than 0.3%, the organic solvent in a near-infrared absorption adhesive will be in an excess state, and it was unsuitable for coating. Further, when the pigment content exceeded 15%, the pigment dispersion was insufficient, and a near-infrared absorbing adhesive having a uniform concentration could not be produced.

On the other hand, in Comparative Example 1, it was found that the color was remarkably changed after the heat and humidity resistance test, the near-infrared absorption ability was deteriorated, and the diimonium dye was altered in a high temperature and high humidity environment.
In Comparative Example 2, the viscosity of the near-infrared absorbing pressure-sensitive adhesive is too low, so that the pressure-sensitive adhesive layer flows immediately after coating until drying, the thickness is not stable, and the thickness of the obtained coating film is also desired. It was very different from the thickness and was unsuitable for coating.

In Comparative Example 3, it was difficult to produce a smooth adhesive layer because the viscosity of the near-infrared absorbing adhesive was too high, and it was unsuitable for coating.
In Comparative Example 4, it was difficult to produce a smooth adhesive layer because the amount of nonvolatile components in the near-infrared absorbing adhesive was too large, and it was unsuitable for coating.

  The near-infrared-absorbing pressure-sensitive adhesive of the present invention is excellent in moisture and heat resistance because it contains a near-infrared-absorbing dye that absorbs light having a wavelength band of 820 nm or more and 1000 nm or less, an adhesive resin, and an organic solvent. In addition, since it is possible to maintain the absorption effect of near infrared rays for a long period of time, not only near infrared absorption in PDP but also members and parts that require near infrared absorption function other than PDP It is very effective and its industrial utility value is very large.

It is sectional drawing which shows the near-infrared absorption sheet of one Embodiment of this invention. It is a figure which shows the near-infrared transmission spectrum before and behind the wet heat resistance test of the sample piece of Example 1 of this invention. It is a figure which shows the near-infrared transmission spectrum before and behind the wet heat resistance test of the sample piece of the comparative example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Near-infrared absorption adhesion layer 3 Release paper

Claims (8)

  A near-infrared absorbing adhesive comprising a near-infrared absorbing dye that selectively absorbs light in a wavelength band of 820 nm or more and 1000 nm or less, an adhesive resin, and an organic solvent.   The near-infrared-absorbing pressure-sensitive adhesive according to claim 1, wherein the near-infrared-absorbing dye comprises a plurality of kinds of dyes having different maximum absorption wavelengths in the wavelength band of 820 nm or more and 1000 nm or less.   The near-infrared absorbing adhesive according to claim 2, wherein the dye is a phthalocyanine dye.   The near-infrared absorbing adhesive according to claim 1, 2 or 3, wherein the adhesive resin is an acrylic adhesive resin, and the near-infrared absorbing dye is dispersed in the acrylic adhesive resin. .   5. The near infrared ray according to claim 1, wherein a transmittance of light in the wavelength band of 820 nm or more and 1000 nm or less when the thickness is 5 μm or more and 100 μm or less is 20% or less. Absorbent adhesive. A near-infrared absorbing dye that selectively absorbs light having a wavelength band of 820 nm or more and 1000 nm or less is dissolved in a solvent to obtain a solution having a content of the near-infrared absorbing dye of 0.3 wt% or more and 15 wt% or less. Adjust so that
Next, a solution containing an adhesive resin is added to this solution to adjust the viscosity to 50 cP or more and 30000 cP or less, and the non-volatile component to 70% by weight or less.   A near-infrared absorbing sheet, comprising an adhesive layer made of the near-infrared absorbing adhesive according to any one of claims 1 to 5 formed on a transparent substrate.   The near-infrared absorbing sheet according to claim 7, wherein a transmittance of light in the wavelength band of 820 nm to 1000 nm when the thickness of the adhesive layer is 5 μm to 100 μm is 20% or less.

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