JPS62258426A - Powder adhesive agent - Google Patents

Abstract

PURPOSE:To obtain an adhesive agent having excellent uniform sprayability to a substrate by using a mixture composed of spacer particles and adhesive particles having a specific relation between triboelectrostatic charge voltages. CONSTITUTION:This powder adhesive agent is the mixture composed of the spacer particles and adhesive particles having the relation ¦A-B¦>=30muc/g when the triboelectrostatic charge voltage of the spacer particles to iron powder is designated as Amuc/g and the triboelectrostatic charge voltage of the adhesive particles as Bmuc/g. The spacer particles to be used are exemplified by spherical org. polymer particles, spherical particles of an inorg. oxide, carbide or nitride, or the ground matter of fibers. The adhesive particles to be used are exemplified by spherical particles or shapeless particles of epoxy, polyolefin, ionomer, polyes ter and acrylic. The uniform distribution ratio of the spacer particles and adhe sive particles is obtd. in any part of the sprayed surface by using the adhesive agent in common use as the spacer for the liquid crystal electrooptic element in the above-mentioned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spacer and an adhesive for liquid crystal electro-optical elements (liquid crystal displays) and the like.

[Conventional technology]

It is common to use only spacer particles in liquid crystal electro-optical elements, or adhesive particles are also being used in combination with the demand for larger screens.

However, due to the state of the art, the optimal combination of spacer particles and adhesive particles is not yet known.

[Problem that the invention seeks to solve]

The conventional technique of separately dispersing spacer particles and adhesive particles has the disadvantage that the distribution ratio of the two tends to be uneven. Furthermore, even if uneven distribution occurs, it is not easy to detect it.

An object of the present invention is to provide a technique that can always keep the microscopic distribution ratio of spacer particles and adhesive particles constant and reduce uneven distribution.

(Means for solving problems) In order to achieve the above object, the present invention consists of the following configuration.

[Frictional charging voltage of spacer particles against iron powder is AμC/q
A powder adhesive, characterized in that it is a mixture of spacer particles and adhesive particles having the following relationship: IA-Bl≧30μC/g, where the frictional charging voltage of the adhesive particles is BμC/CI. ''The details of the present invention will be sequentially explained below.

Spacer particles preferably used in the present invention include spherical organic polymer particles, spherical particles of inorganic oxides, carbides, or nitrides, or crushed fibers. More specifically, crosslinked vinyl polymer particles such as poly-1-nosdyrene, crosslinked acrylic polymer particles such as polymethyl methacrylate, benzoguanamine/formaldehyde polymer particles, alumina spherical particles or pulverized fibers,
Preferable spacer particles include glass spherical particles or pulverized fibers.

It is preferred that the size distribution of the spacer particles used in the present invention be as sharp as possible. In the case of spherical particles, the particle size is 2r, in the case of crushed fibers, the diameter is 2r, and the particle size or diameter variation rate is 0.5μ.
The range of m≦2r≦20 μm and X510% is preferably used. Further, in the case of pulverized fibers, it is preferable that the average dimension in the longitudinal direction is 100 μm or less.

Examples of the adhesive particles used in the present invention include epoxy-based, polyolefin-based, ionomer-based, polyester-based, and acrylic-based spherical particles or amorphous particles. Specifically, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer of ethylene-acrylic acid copolymer and metal, isophthalic acid-neopendyl glycol-ruethylene glycol copolymer,
Examples include particles of epoxy resin as described below.

Adhesive particles can be suitably used in the present invention regardless of whether they are spherical or amorphous, but spherical particles are more preferable since they can be arranged into particles of the same shape by classification.

When the average particle diameter of the adhesive particles is 2R and its rate of variation is X, the present invention can be suitably achieved when the following formula is satisfied including the relationship with the spacer particles (2r).

r≦2R≦100μm Preferably 2r≦2R≦50μm I won't be able to accomplish it. Furthermore, if the adhesive particles or spacer particles become too large, they will become visible to the naked eye, resulting in a decrease in display quality.

The above-mentioned spacer particles and adhesive particles have l A-B l≧30 μC/CI, preferably≧≧, where the frictional charging voltage between them and the iron powder is Aμc/g and BμC/q, respectively.
The present invention is preferably applied when there is a relationship of 50 μC/g. When the value of +A-Bl is smaller than the above-mentioned number, the mutual electrostatic attraction between the two decreases, making it difficult to expect a uniform mixing state of the two. The most ideal mixed state of spacer particles and adhesive particles in the present invention is a state in which spacer particles electrostatically adsorbed are almost evenly distributed around adhesive particles larger than the spacer particles, and microscopically The mixing ratio of both is uniform from a macroscopic perspective. If the electrostatic attractive force between the spacer particles and the adhesive particles is weak, it will be quite difficult to achieve a uniform state of mixing of both particles even if they are sufficiently mixed.

Generally, the results of measurement of frictional charging voltage vary somewhat depending on the species, so in the present invention, values measured by the following method are used in all cases. That is, a Toshiba blow-off powder charge measuring device TB-200 model [manufactured by Toshiba Corporation] was used, and as the iron powder, TSSV-100 manufactured by Mitsui Kinzoku Co., Ltd. was used. Trial 0.6
Mix C1 and iron powder 20Q well, weigh out about 0.20% accurately, and place it in a Faraday cage with a 300 mesh stainless steel wire mesh attached to the bottom. Nitrogen gas of 1°0 kq/cm was blown onto the above mixture for 30 seconds from a nozzle with a diameter of 1 mm, and the amount of triboelectric charge on the iron powder was measured.

If the amount of frictional charge does not become constant within 30 seconds of blowing, repeat the blowing for another 30 seconds until it becomes constant. The indoor atmosphere at the time of measurement was approximately 23°C and 150% RH.

The adhesive particles most preferably used in the present invention are epoxy particles that have strong adhesive force and tend to have strong positive chargeability. Particles suitable for spacers are generally particles that exhibit negative chargeability or slightly positive chargeability, so if the adhesive particles are strongly positively charged,
This is because it is generally easier to achieve A−B l≧30 μC/Q.

The epoxy-based spherical particles containing the latent curing agent, which are most preferably used in the present invention, will be explained below.

The epoxy compound preferably contains two or more epoxy groups in the molecule. Examples include glycidyl etherified bisphenol A type compounds at both ends, diglycidyl ethers of polyethylene glycol, polyglycidyl ethers of phenol novolak type compounds, N, N, N'', N'-tetraglycidyl m-xylene diamine, etc. They can be used alone or in combination. If necessary, it is also possible to use a compound having one epoxy group in the molecule, such as 2-ethylhexyl glycidyl ether.

Before forming the above-mentioned epoxy compound into fine spherical particles, a latent curing agent is added to the epoxy compound. The latent curing agent used here is preferably a curing agent that exhibits a pot life of one day or more at room temperature in an optimal mixing ratio composition (composition with the fastest curing rate) with bisphenol A diglycidyl ether.

Examples of such curing agents include dicyandiamide,
imidazoles, Lewis acid complexes, phenols, phenol novolaks, polyvinylphenols, carboxylic acids, acid anhydrides, acidic polyesters,
Examples include carboxyl group-containing polymers such as styrene-maleic acid copolymers, polyamines, and modified polyamines.

Among these, preferred latent curing agents are polycondensation type compounds, and phenolic curing agents such as phenol novolacs, polyvinylphenols, and polybisphenol A are particularly suitable.

The epoxy compound and the latent curing agent are at least partially compatible, preferably not completely compatible, and are preferably used in combination. In order to make the epoxy compound and the latent curing agent compatible, the epoxy compound and the latent curing agent can be mixed by heating or dissolved in a common solvent for both, and if necessary, the solvent can be removed by drying under reduced pressure or the like.

The amount of the latent curing agent to be used is usually 0.05 to 1 equivalent per equivalent of the epoxy group of the epoxy compound, but as described later, partial curing with an amine-based curing agent is required to form spherical particles. In some cases, the optimal value may need to be a fairly small amount. Further, when a catalytic type latent curing agent is used, it is used in an amount of approximately 20% or less based on the weight of the epoxy compound.

When the latent curing agent is partially cured in the form of particles using an amine-based curing agent, it may be separated from the epoxy compound in the form of islands as the degree of polymerization of the epoxy compound increases, but in all cases the separated state is fine. Therefore, curing by the latent curing agent is not significantly affected, and this state is defined as "compatible" here.

Although it is possible to use as adhesive particles a pulverized composition of a compatible latent curing agent as described above or a partially cured composition with further addition of a general curing agent, the most preferable shape of the adhesive particles is This is the case of a spherical shape. The method of spheroidization will be described below.

Mechanically crushed particles of a mixture of an epoxy compound and a latent curing agent that are solid at around room temperature, or a mixture of an epoxy compound and a latent curing agent partially cured with a curing agent, are allowed to fall by gravity in a heating cylinder. There is a method to make it spheroidal (first
method).

Another method is to suspend a mixture of an epoxy compound and a latent curing agent in an aqueous liquid to form spheres (this is referred to as the second method).

The first method and the second method described above are not particularly limited, and the second method is particularly preferred from the viewpoint of particle uniformity, sphericity, etc. Among these, a method of emulsification using a surfactant or the like is preferred in terms of productivity.

There are various methods for suspending the mixture of the second method epoxy compound and latent curing agent in an aqueous liquid.

Typical methods are listed below, but these methods are not particularly limited.

(2) A method in which the mixture or its solution is continuously discharged from a nozzle that vibrates in the air or in the liquid, cutting it into droplets and collecting them in the liquid.

(2) A method in which the mixture or its solution is ejected in pulses from a nozzle in the air or in a liquid, and the mixture or its solution is collected in the liquid.

(2) A method of emulsifying using a combination of the mixture containing a surfactant and water.

■ A method of emulsifying using a combination of a powder emulsifier, the mixture, and water.

(2) A method of emulsifying using a combination of water containing a protective colloidal substance and the mixture.

Among the above methods, methods 1 to 2 are preferably used in the present invention from the viewpoint of productivity, but a combination of methods 1 to 2 is also preferably used.

What is important in the second method is that the mixture of the epoxy compound and the latent curing agent is liquid at room temperature, and if the product is used as a dry powder, it must be used, and if it is a solid, it can be used as necessary. This is achieved by partially curing the epoxy compound and keeping it in the state of solid spherical particles at least at room temperature.

For this purpose, hardeners other than latent hardeners may be used. The curing agent and curing method for this purpose are not particularly limited; ■ A method in which a mixture of an epoxy compound and a latent curing agent to which a curing agent has been added is suspended in an aqueous liquid and then partially cured as it is. and,
■There is a method of partially curing by adding a water-soluble amine curing agent to an aqueous suspension of a mixture of an epoxy compound and a latent curing agent.

Whichever method is used, in order to cure the suspended particles without bonding them to each other, it is preferable to cure at room temperature. agents often give favorable results.

In addition, if the mixture of the epoxy compound and the latent curing agent is solid at room temperature, the mixture is heated and suspended in an aqueous liquid in a liquid state, and then cooled to form solid spherical particles. Methods include (1) suspending a solution of the mixture in an organic solvent in an aqueous liquid and then removing the solvent to form solid spherical particles; ) In most methods, favorable results are likely to be obtained when an organic solvent that is soluble in an aqueous liquid is used.

A case in which a mixture of an epoxy compound and a latent curing agent is suspended in an aqueous liquid using a surfactant will be described below.

The surfactant used preferably has an HLB value of 10 or more. When the HLB value is lower than this, the stability of the emulsion is impaired and a good particulate cured product tends not to be obtained. Particularly suitable surfactants include ether-type nonionic surfactants such as polyoxyethylene/phenol-substituted ethers, polyoxyethylene/polyoxypropylene block polyethers, and higher fatty acid esters of polyethylene glycol. and ester-type nonionic surfactants such as fatty acid esters of polyhydric alcohols and alkoxylated rosins.

The amount of surfactant used is important. The above surfactant is
It is preferable that the amount is 2% by weight or more based on the mixture of the epoxy compound and the latent curing agent. When the amount of surfactant is less than this, the stability of the emulsion tends to decrease and it becomes difficult to obtain a good particulate cured product. The upper limit of the amount of surfactant to be used is not particularly limited, but it is generally preferred to use the surfactant in an amount of 30% by weight or less based on the mixture in order to prevent deterioration of the physical properties of the particles.

Generally, the difficulty of emulsifying a compound is affected by its viscosity. When the mixture has a high viscosity or is solid at room temperature, it is difficult to emulsify it sufficiently using mechanical force alone. In such cases, there is a method of using a diluent of an epoxy compound together with a surfactant, or of heating and liquefying the material.

Diluents include ketones, alcohols, cellosolves,
Examples include dioxane, aromatic hydrocarbons, and esters such as ethyl acetate.

Although the emulsification method is not particularly limited, typical methods are shown below.

The above-mentioned epoxy composition containing a surfactant is heated at room temperature, cooled or heated, and water is gradually added thereto while stirring at high speed.

The adhesive particles may contain other additives within a range that does not impair the present invention. The most typical additives are organic and inorganic pigments and dyes used for coloring purposes. These are usually added before the epoxy composition is suspended in an aqueous liquid, but it is also possible to dye the epoxy composition after it is formed into spherical particles.

When the mixture of an epoxy compound and a latent hardener suspended in an aqueous liquid is liquid at room temperature, the hardener is added to the suspension of the aqueous liquid or before forming into suspended particles as described above.
It is preferable to solidify the suspended particles at room temperature.

For this purpose, particularly favorable results are often obtained when using a room-temperature-curing curing agent, especially the following amine-based curing agents.

The amine curing agent is an amine characterized by mixing a stoichiometrically calculated equivalent amount of amine with an epoxy compound at room temperature, and having a Shore A hardness of 50 or more after being left at room temperature for 8 hours. A type compound is preferable.

If the Shore A hardness is smaller than this value, the curability of the suspended particles will tend to decrease, making it difficult to obtain a good particulate cured product. Note that the normal temperature here refers to 20'C.

Examples of the curing agent that can be used in the present invention include the following compounds, but are not particularly limited thereto. These include polyethylene polyamines such as piperazine, hydrazine, ethylenediamine, diethylenetriamine, and triethylenetetramine, alcohol amines such as monoethanolamine, and N(2-aminoethyl)piperazine.

The curing method is particularly preferably achieved by adding an amine iating agent that satisfies the Shore A hardness conditions described above to an aqueous liquid suspension.

Monovalent amines such as diethylamine are also necessarily used for the purpose of lowering the degree of polymerization, but particularly good results are often obtained when used in combination with piperazines and hydrazines.

The amount of the above curing agent used varies depending on the average particle diameter of the target particles, the timing of adding the curing agent, the suspension concentration, etc.
If the amount is too small, particles that are solid at room temperature cannot be obtained, and if the amount is too large, the melting point (softening point) tends to be high and no adhesive strength is exhibited. Generally 0.1 to 0.1 for epoxy compounds
It is preferable to use about 0.6 equivalents, but when added to an aqueous liquid suspension, the curing reaction becomes a non-uniform reaction, resulting in poor reaction efficiency, and even if 1 equivalent or more is used, good results may not be obtained. There are things you can get.

The general method for adding an amine curing agent to an aqueous liquid suspension is to add the curing agent directly or in the form of an aqueous solution.

In the second method, if the curing agent is added to the mixture of the epoxy compound and the latent curing agent in advance to form an aqueous suspension, then the curing agent is added after the aqueous suspension; When adding the curing agent, it is preferable to allow the curing reaction to occur after the addition of the curing agent by allowing the curing agent to stand still or with gentle stirring.

When particles are prepared as an aqueous suspension, if necessary, neutralize the whole with mineral acid, etc., separate the particles from the aqueous liquid by a method such as filtration, and wash them by drying with variable air or low humidity. If so, it can be taken out as dry particles without losing adhesive strength.

In the present invention, the spacer particles and adhesive particles are in a mixture state. A common method for making a mixture is to put the two dry powders together in a mortar, homogenizer, ball mill, or pulverizer. However, secondary or tertiary agglomeration tends to occur during the dry powder process, so even if macroscopic mixing of the two is possible, it may be quite difficult to release the agglomerated state and perform microscopic mixing. Therefore, the most preferable method for mixing spacer particles and adhesive particles is in a wet state. Among these, when the spacer particles and adhesive particles are prepared by a wet method, particularly a water wet method, it is most preferable to use them in the mixing step in a slurry state without drying them. When both or one of them is a dry powder, there is a method in which they are sufficiently dispersed in a surfactant, particularly a nonionic surfactant, or water containing the same, and then mixed. In any case, when mixing the spacer particles and adhesive particles in a wet state, it is easy to obtain the best mixing state.

The mixing ratio of spacer particles and adhesive particles varies depending on the particle size and the adhesive force of the adhesive particles, but generally it is preferably in the range of 0.001 to 100 adhesive particles to 1 spacer particle. It tends to be able to perform functional and adhesive functions.

〔Example〕

Example 1 Adhesive particles were prepared in the following manner. 50% of Epicote 82B, which is a commercially available bisphenol A diglycidyl ether type epoxy resin, and 50% of Epicote 1001 (both manufactured by Yuka Shell Epoxy) were placed in a 100CC polycup, and a commercially available polyoxyethylene/phenol-substituted ether type resin with an HLB of 13 was placed in a 100CC polycup. Tens of Noigun FA-137 (manufactured by Dai-Kogyo Seiyaku Co., Ltd.), a surfactant, was added.Furthermore, Epicure 171N (a phenolic latent curing agent) was added.
1Q (approximately 0.12 equivalents) of Yuka Shell Epoxy) was added, and the whole was heated to 90°C and stirred quickly to form a transparent compatible solution. Immediately, the mixture was kneaded at 800 rpm for 1 minute using a stirrer equipped with a Teflon plate blade at the tip so as not to lower the temperature. Next, add 1.5c of 6cc of water to the syringe.
c at 1 minute intervals while stirring at 800 rpm. A milky white emulsion was obtained in the polycup.

Add 8 CC of 0.44 equivalents of piperazine to this emulsion.
A hardening solution diluted with water was added and stirred gently to homogenize.

After being left at 25°C for 6 days, a slurry containing spherical particles with an average particle diameter of about 4.9 μm was obtained.

Wet classification yields an average particle size of 5 μm and a particle size variation rate of 42%.
After adjusting the distribution, some of the particles were filtered and dried, and the thermal meltability, adhesive strength, and frictional charging voltage against iron powder were measured using the method described above.

That is, place the particles after filtering and drying on a slide glass.
After processing 40'Cff1, it became transparent and integrated. Also, place 10 of these particles on a glass slide (75mm x 25mm, 1mm thick). The TIg was weighed and evenly spread 3 Qmm from one end, then the same area was covered with another glass slide, and both glass slides were fixed with cellophane tape. After processing in a hot air dryer at 140°C for 8 hours, the adhesive strength was observed by hand after taking it out and cooling it.
The glass slide in other parts was destroyed without breaking the adhesive part.

Further, the frictional charging voltage against iron powder TSSV-100 measured with a Toshiba blow-off powder charge measuring device TB=200 type was +60 μC/Q.

Alumina spherical particles with an average particle size of 3 μm and a particle size variation rate of 4.5% were used as spacer particles. The frictional charging voltage of these particles was +60 μC/Q.

The above alumina particles were sufficiently dispersed in water containing a surfactant Neugen EA-137 to form a water slurry.

The adhesive particle slurry and the spacer particle slurry were mixed at a ratio of about 1:1 (number ratio) and then over-dried.

The adhesion particles and spacer particles were in a very good mixing state, the chargeability of the powder as a whole was low, and the dispersibility over the liquid crystal electro-optical element substrate was very good, so it was possible to scatter it extremely evenly.

After spraying approximately 1000 particles/C♂ on the substrate as adhesive particles, the four peripheries were fixed with a sealant and cured at 150'C for 8 hours. When the liquid crystal was sealed between the boards, it worked stably.

Example 2 Adhesive particles were prepared in the following manner. 40 g of Epicote 828 used in Example 1 was placed in a 300 cc polycup, and Emuljit 9 (manufactured by Dai-Kogyo Seiyaku Co., Ltd.) 4C1, a polyoxyethylene nonylphenyl ether surfactant with an HLB of 16.2, and the latent type used in Example 1 were added. Add curing agent Epicure 171N 12Q (approximately 0.26 equivalent) and
Heating to 0'C resulted in a transparent compatible solution. After cooling to room temperature,
An emulsion was obtained in the same manner as in Example 1 using 24 cc of water.

Approximately 0.31% of this emulsion was dissolved in 32cc of water.
When an equivalent amount of piperazine aqueous solution was added and hardened in the same manner as in Example 1, a slurry containing spherical particles with an average particle diameter of 19.2 μm was obtained.

Wet classification resulted in an average particle size of 13 μm and a particle size variation rate of 15.
After preparing the particles to 5%, some of the particles were filtered and dried, and the adhesive strength was measured by the method of Example 1, and the same results as in Example 1 were obtained. Also, the frictional charging voltage is +110μ
It was C/Ω.

As spacer particles, crushed glass fibers with a diameter of 7 μm were used. This product had a frictional charging voltage of +20 μC/g.

As in Example 1, spacer particles were sufficiently dispersed in water containing a surfactant to form a water slurry.

The adhesive particle slurry and the spacer particle slurry were mixed at a ratio of approximately 1:5 (number ratio) and then over-dried. The mixing state of both was very good, and the dispersibility to the substrate was very good.

As a liquid crystal electro-optical element, it exhibited good performance similar to that of Example 1.

24 Example 3 The wet-classified epoxy spherical particle slurry obtained by the method of Example 2 was used as adhesive particles.

Crosslinked polystyrene spherical particles with a diameter of 6.5 μm were used as spacer particles. The particle size variation rate of this particle is 4.9%
The frictional charging voltage was -5 μC/q. Example 1
Similarly, the mixture was sufficiently dispersed in water containing a surfactant to form a water slurry.

The adhesive particle slurry and spacer particle slurry were mixed at a ratio of approximately 1:2 (number ratio), and filtered and dried.

The mixing state of both was very good, and the dispersibility to the substrate was also good.

Approximately 500 adhesive particles were sprinkled onto the substrate, and then cured in the same manner as in Example 1. When the liquid crystal was sealed between the substrates and operated, a high-quality liquid crystal electro-optical device was obtained.

〔Effect of the invention〕

The powder according to the present invention can be used as a spacer/adhesive for liquid crystal electro-optic elements, etc., and has excellent uniformity in spreading onto a substrate, and can make the distribution ratio of spacer particles and adhesive particles uniform everywhere on the spreading surface. As a result, it was possible to improve the quality of liquid crystal display devices and the like.

Claims (9)

[Claims] (1) The frictional charging voltage of spacer particles against iron powder is Aμc
A powder adhesive characterized in that it is a mixture of spacer particles and adhesive particles having the following relationship: |A-B|≧30μc/g, where Bμc/g is the frictional charging voltage of the adhesive particles. (2) The spacer particles are one or more types selected from spherical organic polymer particles, spherical particles mainly composed of inorganic oxides, carbides, and nitrides, and pulverized fibers. The powder adhesive described in (1). (3) The powder adhesive according to claim (1), wherein the adhesive particles are one or more types selected from epoxy, polyolefin, anonomer, polyester, and acrylic polymer particles. (4) The powder adhesive according to claim (3), wherein the adhesive particles are epoxy particles containing a latent curing agent in a compatible manner inside the particles. (5) The powder adhesive according to claim (4), wherein the latent curing agent is a polycondensate type compound. (6) The powder adhesive according to claim (4), wherein the latent curing agent is a phenolic compound. (7) Claim No. 4, characterized in that the adhesive particles are prepared in the form of spherical particles by suspending an epoxy compound containing a latent curing agent in an aqueous liquid.
Powder adhesive as described in section. (8) The adhesive particles are particles of an epoxy compound suspended in an aqueous liquid and partially cured with a water-soluble amine curing agent. A powder adhesive according to claim (4). (9) The powder adhesive according to claim (1), wherein the spacer particles and adhesive particles are mixed by a wet method.