TWI606108B - Polarizer using light curable adhesive - Google Patents

Description

Polarizing plate using photocurable adhesive

The present invention relates to a photocurable adhesive and a polarizing plate using the photocurable adhesive; in particular, to a photocurable adhesive and a polarizing plate applied to a liquid crystal display panel.

The polarizing plate is an important component of the liquid crystal display panel, and only allows light of a specific vibration direction to pass through, converts the light source emitted by the backlight module into polarized light, and then controls the amount of light passing through the twist of the liquid crystal molecules, thereby achieving Control the brightness of the LCD panel.

Therefore, the appearance of the polarizing plate affects its function, and is the focus of material selection and process control.

The invention provides a photocurable adhesive, wherein the formed adhesive layer is not affected by the adhesion layer, and still maintains good adhesion and weather resistance, and further provides a polarizing plate which is bonded by using the photocurable adhesive, which can be improved. The phenomenon of red lines.

The present invention provides a photocurable adhesive agent in a total amount of 100 parts by weight, and the photocurable adhesive is contacted with an adhesion-promoting layer containing a salt-based epoxy resin component: 0.001 to 40 parts by weight Containing a monomer of the formula [Chemical Formula 1]: Wherein R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; Z represents an oxygen atom, an alkyl group having 1 to 6 carbon atoms, at least one ester group and at least one alkane having 1 to 20 carbon atoms; a divalent group in which a divalent group is bonded, or a divalent group in which at least one ether group is bonded to at least one alkanediyl group having 1 to 20 carbon atoms; and a photoionic polymerization initiator is 0.05 to 7 parts by weight.

The invention further provides a polarizing plate comprising a polarizing film and a compensation film, the compensation film being located on the first surface of the polarizing film, and coating the adhesion-supporting layer containing the salt on the surface close to the polarizing film. The compensation film is bonded to the first surface of the polarizing film by using the photocurable adhesive described above, and the photocurable adhesive is in contact with the adhesion promoting layer.

In summary, the present invention controls the ratio of the alicyclic epoxy resin in the photocurable adhesive, and the formed adhesive layer is not affected by the adhesion layer, and is not affected by the presence of salts therein. The specific performance of the polarizing plate still has better weather resistance in addition to cost saving.

1‧‧‧Polar plate

11‧‧‧ polarizing film

12‧‧‧Light curing adhesive

13‧‧‧Protective film

14‧‧‧Adhesive layer

15‧‧‧Compensation film

1 is a schematic view of a polarizing plate according to an embodiment of the present invention.

Some exemplary embodiments embodying the features and advantages of the present invention are described in detail in the following description. It is to be understood that the present invention is capable of various modifications in the various aspects of the present invention, and the description and the drawings are in the nature of the description and are not intended to limit the present invention.

The polarizing plate of the present invention mainly comprises a polarizing film, a protective film and a compensation film. The polarizing film and the two side protective films are bonded together by a photocurable adhesive, and the compensation film is attached to the protective film on one side thereof by an adhesion-promoting layer. In order to reduce the cost, the protective film between the compensation film and the polarizing film is sometimes omitted, and the protective film having the compensation property is used instead, but the compensation protective film coated with the adhesion-promoting layer is attached to the photocurable adhesive. After the polarizing film, during the curing process, the adhesion layer will incompletely react the photocurable adhesive and affect the polarizing film. In the weather resistance test, it will soon be in the direction of the polarizing film (machine direction, MD The appearance of red lines on the surface defects, affecting the performance of the polarizing plate and the display panel.

In order to solve the above problems, the polarizing plate 1 of the present invention comprises a polarizing film 11 coated with a photocurable adhesive 12 on both sides, a protective film 13 attached to one side, and a compensation film 15 attached to the adhesive layer 14 on one side. The adhesive layer 14 is in contact with the photocurable adhesive 12 on the side of the compensation film 15.

The polarizing film 11 is a main polarizing substrate of the polarizing plate 1, and converts light from non-polarizing light to polarized light. The polarizing film 11 is an iodine-based polarizing film, and is composed of a polyvinyl alcohol (PVA)-based resin film that adsorbs and distributes iodide ions (I ^- , I ₃ ^- , I ₅ ^- ), and can be made of polyvinyl acetate. The resin is obtained by saponification, and the polyvinyl acetate-based resin may be a copolymer containing vinyl acetate and another monomer, in addition to polyvinyl acetate polymerized from a homopolymer (vinyl acetate). Other monomers may be selected, for example, from unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like.

Then, the polyvinyl alcohol-based resin film is immersed in a dichroic dye solution to be dyed, and the dichroic dye is usually a solution of iodine and potassium iodide, and then a uniaxially stretched polyvinyl alcohol-based resin film is about 4 to 8 times, The dichroic dye is arranged in an orderly manner, and finally, after being subjected to a drying treatment, a polarizing film 11 is obtained.

The formed polarizing film 11 is easily brittle or retracted in the direction of stretching, and the raw material is a hydrophilic polymer film, which is easily affected by moisture, and therefore needs to be bonded to the protective film 13 having a function of supporting and blocking moisture. The material of the protective film 13 can be selected, for example, from a cellulose resin, an acrylic resin, an amorphous polyolefin resin, a polyester resin, a polycarbonate resin, and a combination thereof.

The cellulose resin refers to a resin in which a part of the hydroxyl groups in the cellulose is acetated, or a mixed ester in which a part is acetated and a part is acidified. The cellulose resin is preferably a cellulose ester resin, more preferably an ethyl ketone cellulose resin such as triethyl fluorenyl cellulose, diethyl hydrazine cellulose, cellulose acetate propionate, cellulose. Acetate butyrate or the like, cellulose which is sufficiently esterified is called triacetate cellulose (TAC), has excellent supportability, optical uniformity and high transparency, and is resistant to acid and alkali and ultraviolet rays.

Other resins are simply exemplified as follows, but are not limited thereto, and those skilled in the art can cite the same types of resins as exemplified in the following description. The acrylic resin is, for example, polymerized or copolymerized from a monofunctional monomer containing methyl methacrylate (PMMA) and methyl acrylate. Non-crystalline polyolefin-based resins such as cycloolefin (co)polymers (COC/COP), from norbornene, cyclopentadiene, dicyclopentadiene, tetracyclic ten A ring-opening polymer such as a carbene or a copolymer with an olefin. A polyester resin such as a polymer of ethylene terephthalate or a copolymer of ethylene terephthalate and other dicarboxylic acid or diol. The polycarbonate resin is, for example, a polyester formed of carbonic acid and a diol or bisphenol. In some embodiments, the protective film 13 may be polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP).

Further, the protective film 13 may contain an ultraviolet absorber (for example, a diphenylketone compound or a benzotriazole compound) or a plasticizer (for example, a phenyl phosphate compound or a phthalate compound, etc.) ). Further, the protective layer may be further subjected to surface treatment such as anti-glare treatment, anti-reflection treatment, hard coating treatment, electrification prevention treatment or anti-fouling treatment.

The compensation film 15 is also called a retardation film, and can correct the phase difference generated by the liquid crystal at various viewing angles in various modes, and different compensation functions are given to the liquid crystal display mode by different manufacturing methods or processes, such as changing phase and chromatic aberration compensation. And the viewing angle is expanded, and the like, and the material thereof may be selected from the materials listed in the protective film 13, and will not be described again.

The adhesion-promoting layer 14 is coated on the compensation film 15 for subsequent bonding. The adhesion-promoting layer 14 may be an aqueous adhesive layer, wherein the adhesion-promoting layer 14 contains a salt base, and its composition is, for example, a salt-containing base [2 -hydroxy)-1-propyl]amine, 2-amino-2-methyl-1,3-propanediol (AMPD), 2-amino-2-hydroxymethyl-1,3-propane hydroxide Potassium, γ-aminopropyltriethoxydecane, dodecanedioic acid dioxime, and the like.

The composition of the photocurable adhesive 12 in contact with the adhesion promoting layer 14 mainly includes, but is not limited to, (A) alicyclic epoxy resin, (B) non-alicyclic epoxy resin, and (C) photoionic polymerization initiator. The composition will be described below, and the composition of the photocurable adhesive 12 on the other side of the polarizing film 11 may be the same as or different from the composition.

(A) alicyclic epoxy resin composition:

The monomer of the alicyclic epoxy resin is represented by [Chemical Formula 1], wherein R ₁ and R ₂ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and when the carbon number is 3 or more It may also have an alicyclic structure, Z is an oxygen atom or an alkanediyl group having 1 to 6 carbon atoms, and the alkanediyl group contains an alkylene group.

Further, Z may be a divalent group in which at least one ester group or at least one alkanediyl group having 1 to 20 carbon atoms (linear, branched or alicyclic structure) is bonded to form an alicyclic epoxy group. The monomer of the resin forms an ester, a diester or a polyester, and the monomer of the alicyclic epoxy resin can be selected, for example, from a 3,4-epoxy ring of 3,4-epoxycyclohexanecarboxylic acid. Hexyl methyl ester, 3,4-epoxy-1-methylcyclohexanecarboxylic acid 3,4- Epoxy-1-methylcyclohexylmethyl ester, 3,4-epoxy-3-methylcyclohexanecarboxylic acid 3,4-epoxy-3-methylcyclohexylmethyl ester, 3,4 An ester such as 3,4-epoxy-6-methylcyclohexylmethyl ester of epoxy-6-methylcyclohexanecarboxylic acid.

Further, Z may be a divalent group in which at least one ether group or at least one alkanediyl group having a carbon number of 1 to 20 (linear, branched or alicyclic structure) is bonded to form an alicyclic epoxy group. The monomer of the resin forms an ether, and the monomer of the alicyclic epoxy resin may be, for example, an etherified product of 3,4-epoxycyclohexylmethanol.

The monomer of the alicyclic epoxy resin may comprise one kind or a mixture of a plurality of monomers. When the total amount of the photocurable adhesive agent 12 is 100 parts by weight, the alicyclic epoxy resin component is 0.001 to 40 parts by weight, preferably. When the ratio is 0.001 to 20 parts by weight, the hardening property is increased, but when the reaction is incomplete, the remaining monomer attacks the polarizing film 11 at a high temperature and a high humidity to form the following reaction: The monomer of the alicyclic epoxy resin is exemplified by the monomer 3,4-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl ester, and the iodide ion on the polarizing film 11 is formed as follows reaction: Because the iodine ions that absorb red light are reduced, in the weather resistance test (60 ° C / 90%), red lines are quickly observed in the extending direction, resulting in abnormal color and unevenness of the liquid crystal display panel, and also Since the reaction is incomplete, affecting the adhesion of the photocurable adhesive, the proportion of the alicyclic epoxy resin component must be strictly controlled, and the excessive unreacted residue after curing due to the salt-based intervening in the adhesion-promoting layer 14 can be reduced. Epoxy epoxy resin monomer.

(B) Non-alicyclic epoxy resin composition:

The monomer of the non-alicyclic epoxy resin is represented by [Chemical Formula 2], wherein X is an alkanediyl group having 1 to 9 carbon atoms, the alkanediyl group is an alkylene group, and an ether group, an ester group, or -SO can be interposed therebetween. ₂ -, -SO- or -CO-, a monomer of a non-alicyclic epoxy resin, for example, may be selected from: ethylene glycol diepoxypropyl ether, propylene glycol diepoxypropyl ether, 1,3-propanediol II Epoxypropyl ether, 1,4-butanediol diepoxypropyl ether, 1,6-hexanediol diepoxypropyl ether, and the like. The monomer of the non-alicyclic epoxy resin may comprise one kind or a mixture of a plurality of monomers in a total amount of 60 to 99.999 parts by weight, and the non-alicyclic epoxy resin component may increase the viscosity of the photocurable adhesive 12.

(C) Photoionic polymerization initiator:

The photocurable adhesive 12 of the present invention uses a photoionic polymerization initiator to generate a cationic substance or a Lewis acid by irradiation of visible light, ultraviolet rays, X-rays, or an energy beam of an electron beam, and initiates an alicyclic ring in the photocurable adhesive 12. Monomers such as epoxy resins and non-alicyclic epoxy resins undergo polymerization. Since the photoionic polymerization initiator absorbs light for catalysis, even if it is mixed with the aforementioned monomer, it has storage stability even when it is not irradiated with an energy ray. The photoionization polymerization initiator used in the present invention may be an aromatic diazonium salt, an aromatic onium salt, an aromatic onium salt, an iron-aromatic arene complex or the like.

The aromatic diazonium salt can be selected, for example, from diazobenzene hexafluoroantimonate, diazobenzene hexafluorophosphate, diazobenzene hexafluoroborate or the like.

The aromatic phosphonium salt can be selected, for example, from diphenylphosphonium (pentafluorophenyl) borate, diphenylphosphonium hexafluorophosphate, diphenylphosphonium hexafluoroantimonate, bis(4-mercaptophenyl) ) hexafluorophosphate and the like.

The aromatic phosphonium salt can be selected, for example, from triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4'-bis[ Phenylhydrazine]diphenyl sulfide dihexafluorophosphate, 4,4'-bis[bis(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide dihexafluoroantimonate, 4,4'- Bis[di(β-hydroxyethoxy)phenylhydrazine]diphenyl sulfide dihexafluorophosphate, 7-[bis(p-tolyl)indole]-2-isopropylthioxanthone hexafluoroantimony Acid salt, 7-[bis(p-tolyl)fluorene]-2-isopropylthioxanthone oxime (pentafluorophenyl)borate, 4-phenylcarbonyl-4'-diphenylfluorene-di Phenyl sulfide hexafluorophosphate, 4-(p-tert-butylphenylcarbonyl)-4'-diphenylphosphonium-diphenyl sulfide hexafluoroantimonate, 4-(p-butyl butylbenzene) Alkylcarbonyl)-4'-bis(p-tolyl)indole-diphenyl sulfide quinone (pentafluorophenyl) borate.

The iron-aromatic complex may, for example, be selected from the group consisting of: xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene- Cyclopentadienyl iron (II) ginseng (trifluoromethylsulfonyl) methanide and the like.

The photoionic polymerization initiator may comprise one or a mixture of a plurality of photoionic polymerization initiators in a total amount of 0.05 to 7 parts by weight, and the photoionic polymerization initiator may sufficiently harden the photocurable adhesive 12, so that the obtained polarizing plate has a high Mechanical strength and adhesion strength, but when the amount used is too large, the ionic substance in the cured adhesive increases, and the hygroscopic property becomes high, which may lower the durability of the polarizing plate.

In addition to the above composition, the photocurable adhesive 12 may optionally comprise (D) an unsaturated monomer polymer component which is polymerized from an ethylenically unsaturated monomer and has a weight average molecular weight of from 5,000 to 100,000. The ethylenically unsaturated monomer has a vinyl group, an externally bonded alkyl group having 1 to 7 carbon atoms, an aromatic group having 6 to 12 carbon atoms or an alicyclic hydrocarbon group having 6 to 10 carbon atoms. Alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, tbutyl, butyl, isobutyl, pentyl, isopentyl, pentyl, hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 4-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, isoheptyl, 3hheptyl, etc.; aryl, but not limited to phenyl, Methylphenyl, naphthyl and the like; alicyclic hydrocarbon groups include, but are not limited to, cyclohexyl, methylcyclohexyl, norbornyl, bicyclopentyl, bicyclooctyl, trimethylbicycloheptyl, tricyclooctyl, tri Cyclodecyl, spirooctyl, spirobicyclopentyl, adamantyl, isodecyl and the like. Besides, these alkyl, aryl or alicyclic hydrocarbon groups may additionally have at least one substituent such as a free epoxy group, an oxetane group, a hydroxyl group and a carboxyl group.

The unsaturated monomer polymer can be polymerized from the foregoing one or a mixture of a plurality of unsaturated monomers, and the total amount is from 0 to 100 parts by weight, and the addition of the unsaturated monomer polymer component can further improve the polarizing film 11 and the protective film 13 / compensation The adhesion between the films 15.

In addition to the above composition, the photocurable adhesive 12 may optionally contain (E) a photosensitizer, which improves the photosensitivity and expands the range of coloration, thereby increasing the curing hardness of the photocurable adhesive 12. The photosensitizer may include, but is not limited to, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9,10-dibutoxyanthracene, 9,10-dipentyloxy fluorene, 9,10-dihexyloxy fluorene, 9,10-bis(2-methoxyethoxy)anthracene, 9,10-bis(2-ethoxyethoxy)anthracene, 9,10-bis(2-butoxyethoxy)anthracene 9,10-bis(3-butoxypropoxy)indole, 2-methyl or 2-ethyl-9,10-dimethoxyanthracene, 2-methyl or 2-ethyl-9, 10-diethoxy hydrazine, 2-methyl or 2-ethyl-9,10-dipropoxy fluorene, 2-methyl or 2-ethyl-9,10-diisopropoxy fluorene, 2 -methyl or 2-ethyl-9,10-dibutoxyanthracene, 2-methyl or 2-ethyl-9,10-dipentyloxy oxime, 2-methyl or 2-ethyl-9 An anthraquinone compound such as 10-dihexyloxyanthracene, in a total amount of 0.05 to 7 parts by weight.

The photocurable adhesive 12 having the above composition can be cured by irradiation with a UV curing amount of 150 to 250 mJ/cm ² , but is not limited thereto, and the results of the weather resistance test of the obtained polarizing plate are shown in Table 1.

It can be seen from Table 1 that when the proportion of the alicyclic epoxy resin component is less than 40%, the condition of the red grain can be improved or the red grain can not be observed, and the interlayer adhesion can be increased to 1.9 N/25 mm or more, if almost No alicyclic epoxy resin component is added, and even if the interlayer adhesion is too high, the film may be broken.

In summary, the present invention controls the proportion of the alicyclic epoxy resin component in the photocurable adhesive, even if it must be used in combination with the adhesion promoting layer, and does not affect the specificity of the formed polarizing plate due to the presence of salts therein. Performance (such as appearance, interlayer adhesion, etc.) still has better weatherability in terms of cost savings.

1‧‧‧Polar plate

11‧‧‧ polarizing film

12‧‧‧Light curing adhesive

13‧‧‧Protective film

14‧‧‧Adhesive layer

15‧‧‧Compensation film

Claims (10)

A polarizing plate comprising: a polarizing film; and a compensation film on a first surface of the polarizing film, the compensation film coating an adhesion-promoting layer containing a salt base on a surface of the polarizing film; wherein the compensation layer The film is adhered to the first surface of the polarizing film by using a photocurable adhesive, and the photocurable adhesive contacts the adhesion promoting layer, wherein the total amount of the photocurable adhesive is 100 parts by weight, comprising: an alicyclic ring The epoxy resin component is 0.001 to 40 parts by weight, and contains a monomer of the formula [Chemical Formula 1]: Wherein R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; Z represents an oxygen atom, an alkyl group having 1 to 6 carbon atoms, at least one ester group and at least one alkane having 1 to 20 carbon atoms; a divalent group in which a diradical group is bonded, or a divalent group in which at least one ether group is bonded to at least one alkanediyl group having 1 to 20 carbon atoms; and a photoionic polymerization initiator is 0.05 to 7 parts by weight. The polarizing plate according to claim 1, wherein the photocurable adhesive further comprises a non-alicyclic epoxy resin component containing a monomer of the formula [Chemical Formula 2]: [Chemical Formula 2] Wherein X is an alkanediyl group having 1 to 9 carbon atoms. The polarizing plate of claim 1, wherein the alicyclic epoxy resin component is 0.001 to 20 parts by weight. The polarizing plate according to claim 1, wherein the photoionic polymerization initiator is an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic sulfonium salt or an iron-aromatic hydrocarbon complex. The polarizing plate of claim 1, wherein the photocurable adhesive further comprises an unsaturated monomer polymer component containing an ethylenically unsaturated monomer having a vinyl group and an external carbon number of 1 An alkyl group of ~7, an aromatic group having 6 to 12 carbon atoms or an alicyclic hydrocarbon group having 6 to 10 carbon atoms. The polarizing plate of claim 1, wherein the photocurable adhesive further comprises 0.05 to 7 parts by weight of a photosensitizer, and comprises a lanthanide compound. The polarizing plate of claim 1, wherein the adhesion-promoting layer comprises a salt-containing tris[(2-hydroxy)-1-propyl]amine, 2-amino-2-methyl-1, 3-propanediol (AMPD), 2-amino-2-hydroxymethyl-1,3-propane potassium hydroxide, γ-aminopropyltriethoxydecane or dodecanedioic acid dioxime. The polarizing plate of claim 1, wherein the photocurable adhesive has an interlayer adhesion of 1.9 N/25 mm or more. The polarizing plate of claim 1, wherein the monomer of the alicyclic epoxy resin and the polarized light are unreacted when the monomer of the alicyclic epoxy resin of the photocurable adhesive is incompletely reacted. The iodide ions on the membrane form the following reaction: The polarizing plate according to claim 1, wherein the material of the compensation film is selected from the group consisting of a cellulose resin, an acrylic resin, a non-crystalline polyolefin resin, a polyester resin, and a polycarbonate resin. And their combinations.