KR20080059879A - A filler for pressure sensitive adhesive, a pressure sensitive adhesive composition comprising the same, and an optical film for display device - Google Patents

Abstract

A filler particle for an adhesive is provided to impart excellent stress relieving property and resistance against residual stress to an adhesive composition for an optical film, and to realize excellent durability and shelf stability of an optical film. A filler particle for an adhesive comprises an acrylate group formed from an acrylate compound represented by the following formula 1 or a condensate thereof on the surface thereof. In formula 1, R1 is H or a C1-C5 alkyl; R2 is a C1-C10 alkylene. C6-C20 arylene, C6-C20 alkylarylene, or C6-C20 arylalkylene; and each R3 represents H or a C1-C5 alkyl. The filler particles have an average particle diameter of 5-100 nm.

Description

Filler for pressure-sensitive adhesive, pressure-sensitive adhesive composition comprising the same, and an optical film comprising the same {A FILLER FOR PRESSURE SENSITIVE ADHESIVE, A PRESSURE SENSITIVE ADHESIVE COMPOSITION COMPRISING THE SAME, AND AN OPTICAL FILM FOR DISPLAY DEVICE}

1 is a cross-sectional view showing the basic structure of a general polarizing film.

2 is a cross-sectional view showing an example of a polarizing film attached to both sides of the LCD liquid crystal cell.

Figure 3 is a cross-sectional view showing an example of the deformation of the shrinkage polarizing film and the resulting pressure-sensitive adhesive.

Figure 4 is a scanning electron micrograph of the filler particles prepared according to Example 1.

5 is an infrared spectral spectrum of the filler particles prepared according to Example 1. FIG.

6 is a tan δ graph of the pressure-sensitive adhesive composition prepared according to Examples 4, 5, and Comparative Example 1. FIG.

7 is a graph of G '(storage modulus), G ″ (loss modulus) of the pressure-sensitive adhesive composition prepared according to Examples 4, 5, and Comparative Example 1.

[Industrial use]

The present invention relates to a pressure-sensitive adhesive filler and a pressure-sensitive adhesive composition comprising the same, and more particularly, to a filler particle and a pressure-sensitive adhesive composition including the same to improve the resistance of the pressure-sensitive adhesive to residual stress, as well as the stress relief effect of the acrylic pressure-sensitive adhesive. will be.

[Private Technology]

The polarizing film for liquid crystal display (LCD) is a key component material of LCD that blocks or transmits the light from the backlight (BLU) so that the LCD which does not have self-luminous ability can be used as a display.

The basic structure of the polarizing film in the form of a multilayer thin film is shown in FIG. 1, and includes a polyvinyl alcohol (PVA) layer, a polymer medium for polarizing incident light, and triacetyl cellulose (TAC), a support thereof, for protecting the polarizing film. It has a structure of a protective film / TAC / PVA / TAC / adhesive layer / release film comprising a protective film, an adhesive layer for attaching the polarizing film to the LCD panel, and a release film for protecting the adhesive layer.

The polarizing film of this type is attached to both sides of the liquid crystal cell of the LCD as shown in FIG. 2, that is, the polarization axis intersects each other on the front part of the color filter glass and the rear part of the TFT (Thin Film Transister) substrate glass. At this time, in order to adhere the polarizing film and glass, an adhesive layer is required.

In general, the pressure sensitive adhesive for polarizing film includes a curable acrylic polymer having a low glass transition temperature as a main component, and the pressure sensitive adhesive has a great influence on the durability of the polarizing film. That is, the polarizing film is exposed to heat and moisture while the polarizer is used or during aging on the LCD manufacturing process, and at this time, the PVA film produced in the forcibly stretched state contracts. When the PVA film shrinks as described above, the polarizing film itself shrinks as shown in FIG. 3. If the pressure-sensitive adhesive layer does not adequately absorb the stress caused by the shrinking of the polarizing film, light leakage phenomenon of light leakage of BLU occurs and durability is improved. A problem arises.

For this reason, studies to improve the stress relaxation ability of the adhesive have been mainly attempted so far to improve the durability of the LCD polarizing film (Masayuki, S .; Yasushi, T. Nitto Technical Report 2000, 38, 54, Japanese publication) Patent No. 07-301792, Korean Patent Publication No. 10-2001-0053399, Japanese Patent Publication No. 10-279907, and US Patent No. 5,795,650).

However, these patents and papers focus only on the stress-relaxation ability of the pressure-sensitive adhesive, and change the structure of the acrylic copolymer constituting the pressure-sensitive adhesive, add a low molecular weight plasticizer, or a low molecular weight acrylic polymer ( Molecular weight 30,000 or less) to lower the glass transition temperature to improve the stress relaxation ability of the material. In addition, by adjusting the concentration of the curing agent to reduce the degree of hardening to improve the stress relaxation ability.

However, the stress relaxation ability can be improved in this way, but this increases the flowability of the material, worsens the cutting property of the polarizing film, and prevents side contamination due to the flow of the adhesive during storage. There is a problem that occurs. In addition, since the physical properties of the pressure-sensitive adhesive deteriorates with time, the problem of reworkability may be accompanied.

The present invention is to solve the above problems, an object of the present invention to provide a filler particle for pressure-sensitive adhesive surface modified with acrylate.

Another object of the present invention is to provide an adhesive composition having excellent stress relaxation ability and excellent resistance to residual stress.

Still another object of the present invention is to provide an optical film for a display device including a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition.

The present invention provides a filler particle for a pressure sensitive adhesive (Pressure Sensitive Adhesive, PSA) comprising an acrylate compound represented by the following formula (1), or a condensate thereof, on the surface of the silica particles to achieve the above object do.

[Formula 1]

Wherein R ¹ is hydrogen or alkyl having 1 to 5 carbon atoms, R ² is alkylene having 1 to 10 carbon atoms, arylene having 6 to 20 carbon atoms, alkylarylene having 6 to 20 carbon atoms, or aryl having 6 to 20 carbon atoms. Alkylene and R ³ are each independently hydrogen or alkyl having 1 to 5 carbon atoms.

The present invention also provides a pressure-sensitive adhesive (PSA) composition comprising the filler particles for pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a curing agent, and a silane coupling agent.

The present invention also provides an optical film for display device, wherein the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is provided on one side or both sides of the optical film base material for display device.

The present invention also provides a display device including an optical film for display device, wherein the pressure-sensitive adhesive layer including the pressure-sensitive adhesive composition is provided on one or both surfaces of the optical film substrate for display device.

Hereinafter, the present invention will be described in more detail.

According to the researches of the present inventors, in order to obtain a durable pressure-sensitive adhesive formulation for polarizing film, not only the stress relaxation ability but also the resistance of the pressure-sensitive adhesive to residual stress, that is, to have a certain modulus of durability of the pressure-sensitive adhesive and polarizing film It was confirmed that it can be made good.

In the present invention, in order to improve the stress relaxation ability and modulus of the pressure-sensitive adhesive, a pressure-sensitive adhesive filler particle including an acrylate compound represented by Formula 1 below, or a condensate thereof, is formed on the surface of the silica particles.

[Formula 1]

Wherein R ¹ is hydrogen or alkyl having 1 to 5 carbon atoms, R ² is alkylene having 1 to 10 carbon atoms, arylene having 6 to 20 carbon atoms, alkylarylene having 6 to 20 carbon atoms, or aryl having 6 to 20 carbon atoms. Alkylene and R ³ are each independently hydrogen or alkyl having 1 to 5 carbon atoms.

Further, the most preferred examples of the acrylate compound are 3-trimethoxysilylpropyl methacrylate, 3-trimethoxysilylpropyl acrylate, 3-triethoxysilylpropyl methacrylate, 3-triethoxysilylpropyl And at least one member selected from the group consisting of acrylate, 3-trihydroxysilylpropyl methacrylate, and 3-trihydroxysilylpropyl acrylate.

Since the pressure-sensitive adhesive filler particles are used in the pressure-sensitive adhesive of the optical film, it is preferable that the average particle diameter of the silica particles is 100 nm or less in view of securing transparency, and considering the convenience of the process and the cost problem, the average particle size is 5 nm or more. desirable.

The filler particles may be prepared by mixing the compound represented by Formula 1 or a condensate thereof with silica particles in the presence of alcohol and water, and then condensation or hydrolysis-condensation under acidic conditions. Specific examples of the reaction are the same as in Scheme 1 below, but are not necessarily limited thereto.

Scheme 1

The pressure-sensitive adhesive composition of the present invention includes the filler particles in a conventional acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive may be used in the present invention as long as it is all widely used acrylic pressure-sensitive adhesives, and is not particularly limited in the present invention.

However, the acrylic pressure-sensitive adhesive preferably contains an acrylic polymer, which is a base resin, and a curing agent, and may further include a silane coupling agent as necessary.

The acrylic polymer is more preferably an acrylic copolymer obtained by further copolymerizing an acrylic monomer for controlling glass transition temperature based on an alkyl acrylate component, and a monomer including a hydroxy group is added to facilitate bonding with a curing agent as necessary. It may be in the form copolymerized with.

In addition, the acrylic copolymer may be an acrylic copolymer in which a monomer including an acid group is further copolymerized to facilitate a reaction with a silane coupling agent as necessary.

As the curing agent, an isocyanate curing agent, an epoxy curing agent, an aziridine curing agent, or the like may be used alone or in combination of two or more. Among them, an isocyanate curing agent may be mainly used, and an epoxy curing agent may be further mixed and used. have.

In addition, in order to improve the adhesive strength of the pressure-sensitive adhesive to the glass plate, one or two or more known silane coupling agents may be mixed and used, and the present invention is not limited to the type of silane coupling agent.

However, the filler particles are preferably included in an amount of 3 to 40 parts by weight based on 100 parts by weight of the acrylic pressure sensitive adhesive to ensure a stress relaxation effect and modulus in an optimal range, and the curing agent may be included in an acrylic pressure sensitive adhesive in an amount of 0.01 to 5% by weight. Preferably, the silane coupling agent is preferably contained in 0.01 to 2% by weight in the acrylic pressure-sensitive adhesive.

The pressure-sensitive adhesive composition is mainly suitable for the polarizing film, but is not necessarily limited to the polarizing film, it can be used in all applications requiring the pressure-sensitive adhesive in a display device such as a liquid crystal display device, a plasma display panel.

The pressure-sensitive adhesive composition is preferably in the form of a coating thin film, film, or sheet, it is more preferable that the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is provided on one side or both sides of the optical film substrate for display devices to form part of the optical film. Do.

The outer surface of the pressure-sensitive adhesive layer provided on one side or both sides of the optical film substrate can be commercialized in a state attached to the release film, when used to remove the release film.

The optical film to which the pressure-sensitive adhesive composition of the present invention can be applied includes a polarizing film, a reflective polarizing film, a retardation film, or an oval polarizing film in which a retardation film is laminated, and may be applied to other optical films as needed.

The optical film may be applied to a general CRT, a liquid crystal display (LCD), an organic light emitting display, a plasma display, or the like, and may be preferably applied to a liquid crystal display.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Example 1 (Preparation of Filler Particles)

To 200 ml of isopropyl alcohol (IPA) was added 100 g of colloidal silica (30 wt% in IPA, average particle diameter of 15 nm), to which 100 g of 3-trimethoxysilyl propyl methacrylate (MSMA) was added, water 22 g was mixed. The initial acidity of the mixture was pH 4-4.5 immediately after mixing.

Hydrochloric acid was added to the mixture to pH 2.5.

The mixed solution was reacted with stirring for 12 hours while maintaining the reactor temperature at 60 ° C. After the stirring reaction, water and the solvent were removed by a rotary evaporator, and dried in a vacuum oven at 80 ° C. for 1 hour to prepare a filler particle for pressure-sensitive adhesive.

The scanning electron microscope (Scanning Electron Microscope, SEM) photograph of the prepared filler filler particles is shown in FIG. As can be seen in Figure 4, the silica particles used in Example 1 has an average particle size of 15nm, while the filler particles prepared according to Example 1 has an acrylate-based organic material attached to the surface, thereby Since the surface of the surface appears to be reduced, it can be seen that it appears to have a particle diameter of about 5 to 15 nm.

Example 2 (Preparation of Filler Particles)

The same procedure as in Example 1 was conducted except that 150 g of colloidal silica (30 wt% in IPA, 15 nm in average particle diameter) was used.

Example 3 (Preparation of Filler Particles)

Filler particles were prepared in the same manner as in Example 1, except that 50 g of colloidal silica (30 wt% in IPA, 15 nm in average particle diameter) was used.

Example 4 (Preparation of pressure-sensitive adhesive composition for polarizing film)

An acrylic pressure-sensitive adhesive comprising an acrylic copolymer (206 B / M, manufactured by Ace Digitech), a curing agent (toluene diisocyanate, TDI), and a silane coupling agent (γ-glycidoxypropyltrimethoxy silane, Glymo); The filler particles prepared according to Example 1 were uniformly mixed in the content according to Table 1 below to prepare an acrylic pressure-sensitive adhesive composition.

The obtained acrylic pressure-sensitive adhesive composition was cast on a release film and dried, and then aged at 35 ° C. and R.H. 45% for 5 days to prepare an adhesive film.

Example 5 (Preparation of pressure-sensitive adhesive composition for polarizing film)

The pressure-sensitive adhesive film was prepared in the same manner as in Example 4, except that the filler particles for the pressure-sensitive adhesive prepared in Example 2 were mixed in the same amounts as in Table 1 below.

Example 6 (Preparation of pressure-sensitive adhesive composition for polarizing film)

The pressure-sensitive adhesive film was prepared in the same manner as in Example 4, except that the pressure-sensitive adhesive filler particles prepared according to Example 3 were mixed in the same amounts as in Table 1 below.

Comparative Example 1 (Preparation of pressure-sensitive adhesive composition for polarizing film)

A pressure-sensitive adhesive film was prepared in the same manner as in Example 4, except that the filler particles for the pressure-sensitive adhesive were not used and were mixed in the same amount as in Table 1 below.

TABLE 1

206B / M (g) TDI (g) Glymo (g) Filler (g) Example 4 100 0.318 1.46 20 (Manufacture of Example 1) Example 5 100 0.318 1.46 20 (Manufacture of Example 2) Example 6 100 0.318 1.46 20 (Manufacture of Example 3) Comparative Example 1 100 0.31 1.42 0

[Property evaluation]

(Infrared spectroscopy)

Infrared spectroscopic analysis (Thermonicolet Corp. NEXUS) was performed to confirm that the acrylate group was introduced into the filler particles prepared according to Example 1, and the 3-trimethoxysilyl propyl methacrylate used in Example 1 for comparison. The same analysis was carried out for (MSMA) and colloidal silica. At this time, the filler particles and the colloidal silica sample were applied to the KBR window in a solution state, and then dried in an oven and measured.

The infrared spectroscopic analysis results are shown in FIG. 5.

As shown in Figure 5, it can be seen that the filler particles prepared according to Example 1 of the present invention exhibits the property that the hydroxyl group of the silica particles is substituted with an acrylic group.

In the spectrum of the silica particles used in the reaction, due to the Si-O-Si structure, a strong absorption peak near 1100 cm ^-1 and a broad peak near 3300-3500 cm ^-1 due to the hydroxyl group (-OH) present on the surface are shown. Can be observed.

In comparison, the spectrum of MSMA shows C = C, C = O, CH absorption peaks around 1600cm ^-1 , 1700cm ^-1 , and 2950cm ^-1 .

On the other hand, in Example 1. In the infrared spectrum of the produced filler particles according to (1) a silica inorganic particles caused by the organic functional groups of acrylic groups created on the surface of ^{1600cm -1, 1700cm -1, 2950 cm} -1 (broad peak It can be seen that the organic-inorganic hybrid filler particles of the present invention are well formed through the peak generation at) and (2) a reduced surface OH functional peak by reaction with MSMA.

(Dynamic kinematic viscoelasticity measurement)

For the pressure-sensitive adhesive film prepared according to Examples 4 to 6, and Comparative Example 1, tan δ value and G '(storage modulus), G "(under oscillatory shear deformation) using a dynamic rheometer (Rheometric Scientific, RMS-800). loss modulus) was measured.

The geometry of the sample used in this experiment is a parallel plate (plate diameter: 25mm, gap spacing: 1mm), and the characteristics in the low frequency region are varied at room temperature while varying the frequency from 0.1 to 1rad / s under 5% constant strain. Among them, the tan δ value of 0.1 to 1 rad / s section, which is related to the stress relaxation behavior of the adhesive film, is shown in FIG. 6, and G 'is related to the deformation resistance of the adhesive polymer to residual stress. (storage modulus) is shown in FIG.

As shown in Figure 6 and 7, the pressure-sensitive adhesive composition of Examples 4 and 5 to which the filler particles of the present invention is added, the value of tan δ and G '(storage modulus) are simultaneously increased for stress relaxation ability and residual stress. It can be seen that the deformation resistance of the polymer increases at the same time.

On the other hand, the pressure-sensitive adhesive composition of Comparative Example 1, which does not include a filler, has a lower G 'value than the composition of Example, indicating that the deformation resistance to residual stress is poor.

 The filler particles of the present invention improve not only the stress relaxation effect of the acrylic pressure-sensitive adhesive, but also the resistance of the pressure-sensitive adhesive to residual stress, and the acrylic pressure-sensitive adhesive composition comprising the same has excellent durability and storage properties when applied to a polarizing film or the like.

Claims (11)

Filler particles for pressure-sensitive adhesive on the surface of the silica particles comprising an acrylate compound represented by the following formula (1), or an acrylate group formed from a condensate thereof: [Formula 1]

Wherein R ¹ is hydrogen or alkyl having 1 to 5 carbon atoms, R ² is alkylene having 1 to 10 carbon atoms, arylene having 6 to 20 carbon atoms, alkylarylene having 6 to 20 carbon atoms, or aryl having 6 to 20 carbon atoms. Alkylene, R ³ are each independently hydrogen or alkyl having 1 to 5 carbon atoms. The method of claim 1, The filler particles are pressure-sensitive adhesive filler particles having an average particle diameter of 5 to 100 nm. The method of claim 1, The acrylate compound is 3-trimethoxysilylpropyl methacrylate, 3-trimethoxysilylpropyl acrylate, 3-triethoxysilylpropyl methacrylate, 3-triethoxysilylpropyl acrylate, 3-tri A filler particle for pressure-sensitive adhesive which is at least one member selected from the group consisting of hydroxysilylpropyl methacrylate, and 3-trihydroxysilylpropyl acrylate. An adhesive composition comprising the filler particles according to claim 1 and an acrylic adhesive. The method of claim 4, wherein The filler particles are included in the pressure-sensitive adhesive composition 3 to 40 parts by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive. The method of claim 4, wherein The acrylic pressure-sensitive adhesive comprises an acrylic copolymer, and a curing agent, the content of the curing agent is an adhesive composition of 0.01 to 5% by weight. The method of claim 6, The acrylic pressure-sensitive adhesive further comprises a silane coupling agent, the content of the silane coupling agent is 0.01 to 2% by weight pressure-sensitive adhesive composition. The method of claim 4, wherein The pressure-sensitive adhesive composition of the pressure-sensitive adhesive composition has a coating thin film, film, or sheet form. The optical film for display device provided with the adhesive layer containing the adhesive composition of any one of Claims 4-8 on the one or both surfaces of the optical film base material for display devices. The optical film for display device according to claim 9, wherein the optical film is a polarizing film, a reflective polarizing film, a retardation film, or an oval polarizing film in which a retardation film is laminated. A display device comprising an optical film for a display device, wherein the pressure-sensitive adhesive layer including the pressure-sensitive adhesive composition according to any one of claims 4 to 8 is provided on one or both surfaces of the optical film substrate for a display device.

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