JP5592111B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

  The present invention relates to a method for manufacturing a liquid crystal display device using a liquid crystal dropping method, and more particularly to a method for manufacturing a main seal around a substrate using a thermosetting resin composition.

  Conventionally, when assembling a relatively small liquid crystal display device (hereinafter also referred to as an LCD), two transparent substrates with electrodes are opposed to each other at a predetermined interval, and the periphery is sealed with a sealant. The liquid crystal was injected into the cell from a liquid crystal injection port provided in a part thereof, and the liquid crystal injection port was sealed with a sealant.

  In recent years, as large-sized LCDs have become widespread, the above-described manufacturing methods have caused various problems such as the time taken to inject liquid crystals and the poor productivity.

  Therefore, an LCD manufacturing method called a liquid crystal dropping method (ODF) is being studied and put into practical use as an efficient manufacturing method for large LCDs. In this method, first, a rectangular seal pattern is formed on one of two transparent substrates with electrodes by screen printing or the like. Next, fine droplets of liquid crystal are dropped and applied in a seal frame on a transparent substrate in an uncured state of the sealant, and after the other transparent substrate is overlaid, the sealant is cured to produce an LCD. If the substrates are bonded together under reduced pressure, an LCD can be manufactured efficiently.

  The sealing agent used in the liquid crystal dropping method is generally an ultraviolet curable type or an ultraviolet-heat combined curable type (see Patent Document 1). In the combined UV and heat type, after the two substrates are stacked, the sealant is cured in a short time to such an extent that no misalignment occurs due to UV irradiation, and further heated to heat the sealant to the final strength. Harden. However, when the size of the LCD is further increased, a special ultraviolet irradiation device is required, and measures for preventing deterioration of members such as liquid crystal and alignment film due to ultraviolet rays are also required.

  On the other hand, thermosetting resins, for example, one-pack type thermosetting epoxy resin compositions, are excellent in performance and easy to handle, and are used in various applications. For example, it is used for packaging of image sensors, assembling of image sensor modules, mounting of optical devices, and assembly / mounting of precision parts such as LCD main seals (conventional liquid crystal suction method).

  However, in general, the thermosetting resin composition may be misaligned when heated for curing because the resin viscosity rapidly decreases before curing. In the dripping method, a slight time lag occurs until the thermosetting resin is completely cured in the thermosetting process. During this time, the fluidity of the liquid thermosetting resin increases due to heating, and the shape of the seal part There is a problem that the liquid crystal leaks due to the collapse of the seal part or the liquid crystal leaks under reduced pressure. For this reason, the liquid crystal dropping method using a thermosetting resin composition has not been put into practical use at present.

  Therefore, Patent Document 2 describes that acrylic fine particles and sugar compound derivative fine particles are contained as a gelling agent (Patent Document 2, paragraph 0021, etc.). According to this document, the fluidity at high temperatures can be reduced by adding a gelling agent. However, the gelling agent referred to in Patent Document 2 is merely a solid particle and is considered to function to lower the fluidity, but is not a material that promotes the gelation reaction. And it remains in a hardened | cured material as it is and will affect the physical property.

  Therefore, it is extremely useful to provide a method that can utilize the excellent properties (for example, durability and reliability) of the thermosetting resin without using such a gelling agent.

JP 2002-342947 A JP 2005-308811 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of producing an LCD that is accurate and simple and excellent in durability without the need for a special ultraviolet irradiation device in producing an LCD by a liquid crystal dropping method.

  The present invention relates to the following matters.

1. A method of manufacturing a liquid crystal display device having a liquid crystal layer between a first substrate and a second substrate by a liquid crystal dropping method,
(A) A sealing region that includes an epoxy resin and a latent curing agent and that has a gelation time at 100 ° C. of 3 minutes or less and surrounds the substrate surface at the periphery of the first substrate surface Applying to
(B) dropping liquid crystal into a central region surrounded by the seal region on the first substrate surface;
(C) superimposing the second substrate on the first substrate;
(D) A heating step of curing the thermosetting resin composition.

  2. 2. The method according to 1 above, wherein the step (c) of superposing is performed in a state where the thermosetting resin composition has fluidity, and then heating is performed in the step (d) of heating.

  3. 2. The method according to 1 above, wherein the (d) heating step is started before the (c) superposing step is completed.

  4). 4. The method according to any one of 1 to 3 above, wherein the thermosetting resin composition further contains an additive selected from the group consisting of a filler, a thixotropic agent, and a silane coupling agent.

  5. 5. The method according to any one of 1 to 4 above, wherein the epoxy resin contains an epoxy resin selected from the group consisting of a bisphenol type epoxy resin, a novolac type epoxy resin, and a biphenyl type epoxy resin.

  6). 6. The method according to any one of 1 to 5 above, wherein the latent curing agent is selected from modified amine-based latent curing agents.

  7). A thermosetting resin composition for a liquid crystal dropping method, which is used in the method described in 1 above, contains an epoxy resin and a latent curing agent, and exhibits a gelation time at 100 ° C. of 3 minutes or less.

  According to the LCD manufacturing method according to the liquid crystal dropping method of the present invention, an LCD can be easily manufactured without requiring a special ultraviolet irradiation device and maintaining a precise alignment accuracy without any positional deviation. And since epoxy-type thermosetting resin excellent in durability and reliability can be used as a sealing agent, it is excellent in durability and reliability of LCD, especially the seal part.

The production method of the present invention generally comprises:
(A) applying a liquid thermosetting resin composition to a seal region surrounding the substrate surface at the periphery of the first substrate surface;
(B) dropping liquid crystal in a central region surrounded by the seal region on the surface of the first substrate;
(C) superimposing the second substrate on the first substrate, and (d) a heating step of curing the thermosetting resin composition.

  The first substrate and the second substrate used in the present invention are usually transparent glass substrates. Generally, transparent electrodes, active matrix elements (TFTs, etc.), alignment films, color filters, etc. are formed on at least one of the opposing surfaces of the two substrates. Is possible. The manufacturing method of the present invention is considered to be applicable to all types of LCDs.

  In the step (a), the thermosetting resin composition that is a sealing agent is made to make one round around the periphery of one substrate and the surface of the first substrate (the surface facing the other substrate). Apply to the frame. A portion where the sealant is applied in a frame shape is referred to as a seal region. At this point, the thermosetting resin composition is at least in a liquid state that can be applied, and can be applied by a known method such as screen printing or dispensing. The seal area is generally a rectangular frame, and an LCD display unit is provided in the center area of the seal area. Accordingly, the “peripheral portion” where the seal region is set generally means the outside of the display portion of the LCD, and does not necessarily mean the end portion of the substrate. On the substrate surface, outside the sealing region, there may be a space where an electrode and, if necessary, an electric / electronic element for driving the LCD are provided.

  Next, in a process (b), a liquid crystal is dripped at the center area | region enclosed by the frame-shaped sealing area | region of the 1st board | substrate surface. This step is preferably carried out under reduced pressure.

  Next, in the step (c), the second substrate is superposed on the first substrate, and in the step (d), the thermosetting resin composition is cured by heating to complete a seal. This completes the main part of the LCD panel.

  The heating in the step (d) is performed to cure the thermosetting resin composition. In one embodiment of the present invention, step (c) and step (d) are performed in order. That is, the overlapping step (c) is performed in a state where the thermosetting resin composition has fluidity, and then heated in the heating step (d), whereby the composition is gelled and cured.

  However, if the first substrate and the second substrate can be bonded together, the step of superimposing the second substrate on the first substrate in a state where the fluidity of the thermosetting resin composition is somewhat lowered. (C) may be implemented. That is, before the step (c) is completed, the heating step of the step (d) can be started. However, it is always after step (c) that the composition is finally cured in step (d).

  The curing in step (d) is generally heated by a heating profile such that the maximum temperature is preferably up to 150 ° C, more preferably up to 130 ° C. The heating time is appropriately selected, and is, for example, 3 hours or less, preferably 2 hours or less, more preferably 1.5 hours or less (typically 1 hour).

  The thermosetting resin composition used in the present invention is characterized in that gelation rapidly proceeds by heating. That is, in the present invention, a composition is selected which cures immediately before the viscosity decreases due to temperature rise and immediately reaches a state without fluidity. In the present invention, since the viscosity of the thermosetting resin composition does not rapidly decrease, there is no occurrence of positional deviation between the two substrates, and the positional relationship between the two substrates is fixed in the initial stage of heating.

  The thermosetting resin composition used in the present invention is specifically a thermosetting resin composition containing an epoxy resin and a latent curing agent and having a gelation time at 100 ° C. of 3 minutes or less. . The progress of curing of the thermosetting resin composition can be confirmed by pulling the composition with a wooden stick during heating (contacting). In the initial state, the composition is in a liquid state, and even if the composition is lifted by touching it with a stick, it does not pull the thread, but when curing progresses and fluidity is lost and stickiness increases, It will pull the thread. The state in which a thread of about 2 to 3 cm is pulled is defined as the gel time.

  When the thermosetting resin composition used in the present invention is placed at 100 ° C. and the gelation time is within 3 minutes, curing proceeds with a decrease in viscosity due to temperature increase and competitively. For this reason, the viscosity is not low enough to cause displacement. The gelation time at 100 ° C. is more preferably within 2 minutes, and most preferably within 1 minute.

  For this reason, in the heating profile for hardening of a thermosetting resin composition, a viscosity does not fall rapidly from an initial viscosity.

  The thermosetting resin composition used in the present invention is obtained by appropriately selecting an epoxy resin, a latent curing agent, and optionally added components so as to have the above-mentioned predetermined gelation time. be able to. In the present invention, it is not necessary to contain a gelling agent as defined in the above-mentioned Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-308811).

  It is preferable that the epoxy resin contained in the thermosetting resin composition is mainly composed of an epoxy resin having an aromatic ring, and in particular, component (a): 50% (by weight) or more of the thermosetting resin component, preferably Is 70% or more, particularly preferably 90% or more, and preferably 100%. If necessary, an epoxy resin having no aromatic ring may be contained.

  Examples of the epoxy resin having an aromatic ring include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol S type epoxy resin; novolak type epoxy resins such as phenol novolak type epoxy resin and cresol novolak type epoxy resin. A biphenyl-type epoxy resin such as trade name YX4000 manufactured by Japan Epoxy Resin Co., Ltd. can be used. The epoxy resin having an aromatic ring usually has one or more epoxy groups in the molecule, and the epoxy equivalent can be appropriately selected.

  As an epoxy resin having no aromatic ring, an alicyclic epoxy resin having an epoxy group having a ring strain such as a cyclohexene oxide structure and a cyclopentene oxide structure in the molecule (for example, in the following formulas (1) to (5) Compounds shown)

；水素化ビスフェノール型エポキシ樹脂（ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂およびビスフェノールＳ型エポキシ樹脂等のビスフェノール型エポキシ樹脂のベンゼン環が水素化されたもの）；ジシクロペンタジエンフェノールノボラックのグリシジルエーテル等のジシクロペンタジエン型エポキシ樹脂；シクロヘキサンジメタノールジグリシジルエーテル(cyclohexanedimethanol diglycidyl ether)、ブチルグリシジルエーテル、２−エチルヘキシルグリシジルエーテル、アリルグリシジルエーテル等の脂肪族アルキル−モノまたはジ−グリシジルエーテル；グリシジルメタクリレート、３級カルボン酸グリシジルエステル等のアルキルグリシジルエステル；スチレンオキサイド；フェニルグリシジルエーテル、クレジルグリシジルエーテル、ｐ−ｓ−ブチルフェニルグリシジルエーテル、ノニルフェニルグリシジルエーテル等の芳香族アルキルモノグリシジルエーテル；テトラヒドロフルフリルアルコールグリシジルエーテル等を挙げることができる。

Hydrogenated bisphenol type epoxy resin (hydrogenated benzene ring of bisphenol type epoxy resin such as bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol S type epoxy resin); glycidyl ether of dicyclopentadienephenol novolac Dicyclopentadiene type epoxy resin such as cyclohexanedimethanol diglycidyl ether, aliphatic alkyl-mono or di-glycidyl ether such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether; glycidyl methacrylate, Alkyl glycidyl esters such as tertiary carboxylic acid glycidyl ester; styrene oxide; phenyl glycidyl ether, cresyl g Aromatic alkyl monoglycidyl ethers such as ricidyl ether, p-s-butylphenyl glycidyl ether, and nonylphenyl glycidyl ether; tetrahydrofurfuryl alcohol glycidyl ether and the like.

  The epoxy resin component may contain other known diluents.

  The latent curing agent contained in the thermosetting resin composition used in the present invention cures the epoxy resin when heated. The latent curing agent is appropriately selected from one or more types of commercially available latent curing agents so that the gelation time at 100 ° C. of the thermosetting resin composition is 3 minutes or less, It is preferable to appropriately set the addition amount of the latent curing agent in consideration of the epoxy equivalent of the epoxy resin.

  Specifically, the latent curing agent preferably contained in the thermoplastic resin composition used in the present invention is preferably a heat curing type latent curing agent, particularly a fine powder modified amine system or a modified imidazole system. A latent curing agent is preferred, a modified amine latent curing agent is more preferred, and a modified amine latent curing agent containing active hydrogen is most preferred. Modified amine-based and modified imidazole-based latent curing agents include core-shell type curing agents in which the surface of the core of an amine compound (or amine adducts) is surrounded by a shell of a modified amine (such as surface adduct), and the like Is included in a masterbatch type curing agent in a state of being mixed with an epoxy resin.

Examples of amine compounds having heat-curable latent potential include aromatic primary amines such as diaminodiphenylmethane and diaminodiphenylsulfone;
2-heptadecylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellito, 2,4-diamino-6- [2-methylimidazolyl- (1)]-ethyl-S-triazine, 1-dodecyl-2- Imidazoles such as methyl-3-benzylimidazolium chloride, 2-phenylimidazolium isocyanurate, 2-phenyl-4-methyl-5-hydroxymethylimidazole;
Boron trifluoride-amine complex;
Dicyandiamide, and derivatives of dicyandiamide such as o-tolylbiguanide and α-2,5-methylbiguanide;
Organic acid hydrazides such as succinic acid dihydrazide and adipic acid dihydrazide;
Diaminomaleonitrile and its derivatives;
Mention may be made of melamine derivatives such as melamine and diallyl melamine.

  The modified amine-based latent curing agent is a finely powdered solid reaction product of an amine compound and an epoxy compound, an isocyanate compound and a urea compound. The modified imidazole-based latent curing agent is usually a fine powdered solid reaction product obtained by an adduct reaction between an imidazole compound and an epoxy resin.

Representative examples of commercially available modified amine-based latent curing agents include, for example, “ADEKA HARDNER EH-3615S” (trademark of ADEKA Corporation), “ADEKA HARDNER EH-4070S” (trademark of ADEKA Corporation). ), “Adeka Hardener EH-4357S” (trademark of ADEKA), “Amicure MY-24” (trademark of Ajinomoto Co., Inc.), “Fujicure FXE-1000” (trademark of Fuji Kasei Kogyo Co., Ltd.), "Fujicure FXR-1036" (trademark of Fuji Chemical Industry Co., Ltd.), Aradur 939 (Huntsman
A trademark of Advanced Materials).

  Typical examples of commercially available modified imidazole-based latent curing agents include “ADEKA HARDNER EH-3293S” (trademark of ADEKA), ““ ADEKA HARDNER EH-4344S ”(trademark of ADEKA). , “Amicure PN-23” (trademark of Ajinomoto Co., Inc.), “Cureduct P-505” (trademark of Shikoku Kasei Kogyo Co., Ltd.), and Sanmide LH-210 (trademark of Air Products). .

  Further, the core-shell type curing agent is obtained by modifying the surface of the amine compound (or amine adducts) by further treatment with an acidic compound such as a carboxylic acid compound and a sulfonic acid compound, an isocyanate compound, and an epoxy compound. (Adduct etc.) shell is formed. In addition, the masterbatch type curing agent is a state in which a core-shell type curing agent is mixed with an epoxy resin.

  Examples of commercially available masterbatch type curing agents include “Novacure HX-3722” (trademark of Asahi Kasei Epoxy Co., Ltd.), “Novacure HX-3742” (trademark of Asahi Kasei Epoxy Co., Ltd.), and “Novacure HX-3613”. (Trademark of Asahi Kasei Epoxy Co., Ltd.) and the like.

  Even those not described above can be used in the present invention as long as they can be combined with an epoxy resin so that the gelation time at 100 ° C. is 3 minutes or less.

  In the thermosetting resin composition, the ratio of the epoxy resin and the latent curing agent can be appropriately set depending on the type of the latent curing agent. For example, the latent curing agent is used with respect to 100 parts by weight of the epoxy resin. Is 0.5 to 500 parts by weight, preferably 2 to 200 parts by weight.

  The thermosetting resin composition can further contain additives, resin components, and the like in order to improve or change properties such as fluidity, coating properties, storage stability, curing properties, and physical properties after curing.

  Examples of components that can be contained as necessary include organic or inorganic fillers, thixotropic agents, silane coupling agents, diluents, modifiers, colorants such as pigments and dyes, surfactants, storage stabilizers, Examples include, but are not limited to, plasticizers, lubricants, antifoaming agents, and leveling agents. In particular, it is preferable to contain an additive selected from the group consisting of a filler, a thixotropic agent and a silane coupling agent.

  The filler is not particularly limited, for example, silica, diatomaceous earth, alumina, zinc oxide, iron oxide, magnesium oxide, tin oxide, titanium oxide, magnesium hydroxide, aluminum hydroxide, magnesium carbonate, barium sulfate, gypsum, calcium silicate, Examples thereof include inorganic fillers such as talc, glass beads, sericite activated clay, bentonite, aluminum nitride, and silicon nitride.

  The thixotropic agent is not particularly limited, and examples thereof include talc, fine silica, ultrafine surface-treated calcium carbonate, fine alumina, plate-like alumina; layered compounds such as montmorillonite; acicular compounds such as aluminum borate whisker. Can be mentioned. Of these, talc, fine silica, fine alumina, etc. are suitable.

  The silane coupling agent is not particularly limited, but γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, SH6062, SZ6030 (above, Toray Dow Corning Silicone Co., Ltd.), KBE903, KBM803 (above, Shin-Etsu Silicone Co., Ltd.) and the like.

  In addition, the thermosetting resin composition used by this invention is used suitably for the use as which the precision assembly without a position shift is requested | required besides the liquid crystal dropping method of this invention.

<Material>
The materials used in the examples and comparative examples are as follows.

  Epoxy resin: bisphenol A type epoxy resin, manufactured by Nippon Kayaku Co., Ltd., RE-310S, liquid at 25 ° C. (viscosity 13,000 to 17000 mPa · s), epoxy equivalent 175 to 190 g / eq.

Latent curing agent EH4357 Adeka Co., Ltd. Modified polyamine-based latent curing agent;
EH4070S Adeka Co., Ltd. Modified polyamine-based latent curing agent;
Amicure PN-23 manufactured by Ajinomoto Co., Inc .;
Novacur HX-3722 Asahi Kasei Epoxy Co., Ltd.

<Example 1>
After stirring and mixing 64.5 parts of epoxy resin RE-310S (manufactured by Nippon Kayaku Co., Ltd.) and 35.5 parts of latent curing agent EH-4357S (manufactured by ADEKA Co., Ltd.), the mixture was dispersed in a ceramic three roll mill. The resin composition of Example 1 was obtained.

<Example 2>
After stirring and mixing 64.5 parts of epoxy resin RE-310S (manufactured by Nippon Kayaku Co., Ltd.) and 35.5 parts of latent curing agent EH-4070S (manufactured by ADEKA Co., Ltd.), the mixture was dispersed in a ceramic three roll mill. The resin composition of Example 2 was obtained.

<Comparative Example 1>
After stirring and mixing 83.3 parts of epoxy resin RE-310S (manufactured by Nippon Kayaku Co., Ltd.) and 16.7 parts of latent curing agent Amicure PN-23 (manufactured by Ajinomoto Fine Techno Co., Ltd.), in a ceramic three roll mill The resin composition of Comparative Example 1 was obtained by dispersing.

<Comparative example 2>
76.9 parts of epoxy resin RE-310S (manufactured by Nippon Kayaku Co., Ltd.) and 23.1 parts of latent curing agent Novacure HX-3722 (manufactured by Asahi Kasei Epoxy Co., Ltd.) are mixed with stirring, and then dispersed in a ceramic three roll mill. Thus, a resin composition of Comparative Example 2 was obtained.

<Characteristic measurement experiment>
The characteristics of the resin compositions of the above examples and comparative examples were measured as follows. The measurement results are shown in Table 1.

  Pot life: The time when the viscosity within the measurement period reaches twice the initial viscosity is defined as the pot life.

  Gelation time: Hot plate method The composition samples of Examples and Comparative Examples were placed on a hot plate at 100 ° C. according to the gel time measurement method, and the gelation time was defined as the time when the composition gelled. As described in the text, gelation is performed by putting a wooden stick into a composition being heated and pulling it up, and pulling a thread of about 2 to 3 cm into a gelling time.

  Seal shape stability: 1% of the spacer was mixed and defoamed in the obtained sealing agent, and after filling the syringe, a rectangular frame was applied on the glass substrate. Next, an appropriate amount of liquid crystal is appropriately placed in a rectangular frame, and another glass substrate is placed under vacuum. Release the vacuum and heat cure at 100 ° C. for 1 hour. The seal state after curing is observed, and a state similar to that before curing is determined to be good.

  The compositions of Example 1 and Example 2 satisfy the characteristics of the thermosetting resin composition used in the present invention in terms of pot life, gelation time, and seal shape stability.

  As is apparent from the above, various modifications can be made without departing from the spirit of the present invention. Therefore, the form described here is an example, and the scope of the present invention described in the claims is not limited thereto.

  The LCD manufacturing method according to the liquid crystal dropping method of the present invention can easily manufacture an LCD while maintaining a precise alignment accuracy without the need for a special ultraviolet irradiation device and without positional deviation. And it is excellent in durability and reliability of LCD, especially the seal part. Therefore, it is useful as an LCD manufacturing method.

Claims (5)

A method of manufacturing a liquid crystal display device having a liquid crystal layer between a first substrate and a second substrate by a liquid crystal dropping method,
(A) A sealing region that includes an epoxy resin and a latent curing agent and that has a gelation time at 100 ° C. of 3 minutes or less and surrounds the substrate surface at the periphery of the first substrate surface Applying to
(B) dropping liquid crystal into a central region surrounded by the seal region on the first substrate surface;
(C) superimposing the second substrate on the first substrate;
(D) have a heating step for curing the thermosetting resin composition,
The method, wherein the latent curing agent is selected from modified amine-based latent curing agents .   The method according to claim 1, wherein the step (c) of superposing is performed in a state where the thermosetting resin composition has fluidity, and then heating is performed in the (d) heating step.   The method according to claim 1, wherein (d) the heating step is started before the (c) superposing step is completed.   The method according to claim 1, wherein the thermosetting resin composition further contains an additive selected from the group consisting of a filler, a thixotropic agent, and a silane coupling agent.   The method according to claim 1, wherein the epoxy resin contains an epoxy resin selected from the group consisting of a bisphenol type epoxy resin, a novolac type epoxy resin, and a biphenyl type epoxy resin.