KR101898519B1 - Ips lcd pannel - Google Patents

Abstract

The present invention relates to an IPS LCD panel using a polarizing plate which is resistant to moisture and has excellent thickness uniformity by using an acrylic film formed from a main dope liquid containing an acrylic resin and silica particles represented by the following formula 1 as a protective film, There is an effect that the excellent quality of appearance optical unevenness is maintained even after being left in the environment for a long time.
[Chemical Formula 1]
MMA-BA
Here, MMA represents methyl methacrylate unit and BA represents butyl acrylate unit.

Description

IPS LCD PANEL {IPS LCD PANEL}

The present invention relates to an IPS LCD panel of excellent quality free from appearance unevenness or deterioration even under severe conditions of high temperature and high humidity.

2. Description of the Related Art In recent years, a liquid crystal display device which consumes a small amount of power and operates at a low voltage and is lightweight and thin has been widely used in information display devices such as a cellular phone, a monitor for a portable information terminal computer, and a television. Such an information display device is required to have reliability under a severe environment depending on its use. For example, in a car navigation system liquid crystal display device, the temperature and humidity inside the vehicle in which it is placed may become extremely high, so that the required temperature and humidity conditions are strict as compared with a normal television or a personal computer monitor. A polarizing plate is used in a liquid crystal display device to enable the display. In a liquid crystal display device requiring such a strict temperature and humidity condition, a polarizing plate constituting it is required to have high durability.

Especially, IPS LCD has the following problems. First, PVA contracts and deforms by the external air including moisture and heat, and the glass part presses against the back light, thereby causing a locally elliptical stain Egg Mura. Second, as the panel is made thinner, the thickness of the glass part becomes thinner, and the PVA is more easily affected by the high temperature and high humidity environment, and it is bent so that the side of the panel is pressed. As a result, a phenomenon occurs in which light leaks from the mechanical part. Therefore, it is necessary to prevent the optical stain and light leakage of the IPS LCD by using a polarizing plate which is strong against water and heat and has excellent thickness uniformity.

The polarizing plate usually has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. Conventionally, triacetylcellulose (TAC) is widely used for this protective film, and this protective film is bonded to the polarizing film through an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin. However, the polarizing plate in which the protective film made of triacetylcellulose is laminated has a high moisture permeability of triacetyl cellulose, so that when the polarizing plate is used for a long time under a high humid environment, the polarization performance deteriorates or the protective film and the polarizing film peel off have. In order to solve these problems, attempts have been made to use a (meth) acrylic resin film having a lower moisture permeability as a protective film of a polarizing plate than a triacetylcellulose film.

Conventional acrylic films have been manufactured by melt casting method. However, Solvent Casting method has many advantages in terms of environment-friendliness such as thinning, mass production and recycling of resin. The solvent casting method is to melt the acrylic film in a solvent and extrude it into a T-die. Then, the solvent is dried in the belt to make a film. Optimized particles are added to increase impact strength and slip property for film transfer. The above process is possible. Also, the added particles should not be dissolved or deformed in the solvent.

Korean Patent No. 1265007 discloses a pressure-sensitive type polarizing plate in which light leakage of an image display device does not occur even by a change in use environment. In the pressure-sensitive adhesive type polarizing plate in which the acrylic polymer constituting the pressure-sensitive adhesive layer has an aromatic ring structure ) Acrylate monomer unit and its content is determined according to the value of the photoelastic coefficient X of the transparent protective film, and when the retardation value of the transparent protective film changes due to environmental changes such as heating, the pressure- It is proposed to adjust so as to cause a phase difference change of the opposite sign.

Korean Patent No. 1114354 discloses a protective film for an optical member having a pressure-sensitive adhesive layer containing a photopolymerizable acrylic polymer, an antistatic agent and a cured product of a polymerization initiator composition, wherein a crosslinking reaction is caused by a radical generated in the initiator An appropriate amount of an antistatic agent is added to a composition containing a photopolymerizable acrylic polymer into which a photoactivating group capable of causing photoinitiator is introduced and a polymerization initiator in a predetermined ratio so that the aging process at the time of curing can be omitted and the manufacturing process can be simplified , And a protective film excellent in antistatic property during peeling or use.

Korean Patent Laid-Open Publication No. 2015-0061591 discloses a composition comprising a first functional layer (low moisture-permeable layer) formed using a compound having a cyclic aliphatic hydrocarbon group and an ethylenically unsaturated double bond group, and a composition containing urethane acrylate thereon There is proposed a technique for obtaining a polarizing plate protective film having excellent interlayer adhesion and wind non-uniformity resistance by using a specific amount of a fluoroaliphatic group-containing copolymer having a second functional layer formed thereon and having a specific structure in the first functional layer .

Japanese Patent Application Laid-Open No. 2014-240905 discloses a polarizing plate having a film thickness and a modulus of elasticity within a specific range and having an acrylic resin as a main component in order to produce a polarizing plate excellent in adhesion with a polarizer, , A polarizer, and a retardation film B composed mainly of a cellulose derivative having at least an ether bond and a substituent in a glucose skeleton, and the film A and the film B are bonded together through an ultraviolet curable adhesive.

Therefore, there is a need to improve the technique for preventing optical unevenness on the IPS liquid crystal panel when used in a high temperature and high humidity environment.

Korea Patent No. 1265007 Korea Patent No. 1114354 Korean Patent Publication No. 2015-0061591 Japanese Laid-Open Patent Application No. 2014-240905

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an IPS liquid crystal display device, which is excellent in high temperature and high humidity, LCD panel.

The present invention relates to an acrylic resin composition comprising 80 to 98 parts by weight of methyl methacrylate units and 2 to 20 parts by weight of butyl acrylate units based on 100 parts by weight of an acrylic resin represented by the following formula (1) And an acrylic film formed by a solvent casting method from the main doping liquid containing the polarizer is bonded to both surfaces of the liquid crystal.

[Chemical Formula 1]

MMA-BA

Here, MMA represents methyl methacrylate unit and BA represents butyl acrylate unit.

 The present invention is an IPS panel in which an acrylic film is bonded to the front and back surfaces of a liquid crystal cell with polarizing plates provided on both sides of a polarizer, the main dope liquid includes silica particles, and the diameter of the particles is 100 to 300 nm desirable.

The solvent of the solvent casting of the present invention is preferably a mixture of a halogenated hydrocarbon and an alcohol.

It is preferable that the IPS panel of the present invention does not have Egg Mura which is optical unevenness on the screen and light leakage of the mechanism portion even after being left in a high temperature and high humidity environment of 60 ° C and 90% RH for 500 hours.

The IPS LCD panel manufactured by the present invention is able to maintain excellent quality without being stained or deteriorated in appearance due to long time in an extreme condition of high temperature and high humidity by using a polarizing plate made of an acrylic film which is strong against moisture and excellent in thickness uniformity .

Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited to these.

The inventors of the present invention have conducted research to develop an acrylic film which is easy to form a film and to transfer a film when a thin film acrylic film is manufactured by the solvent casting method. As a result, it has been found that the molecular weight of the resin is in the range of 300,000 to 2,500,000 g / The present invention has been completed on the basis of finding that a protective film which is easy to form and transfer can be obtained.

The polarizing plate of the present invention has an acrylic film formed on both sides of a stretched PVA formed from a main dope liquid containing an acrylic resin and silica particles represented by the following formula (1), and is disposed on the back surface and the front surface of the IPS mode liquid crystal panel, And is a polarizing plate for converting the progress axis.

[Chemical Formula 1]

MMA-BA

Here, MMA represents methyl methacrylate unit and BA represents butyl acrylate unit.

First, the acrylic resin of the present invention will be described. The acrylic resin of the present invention is an acrylic resin comprising a methyl methacrylate unit and a butyl acrylate unit and each of the monomer units is contained in the form of a repeating unit.

It is preferable that 80 to 98 parts by weight of methyl methacrylate units and 2 to 20 parts by weight of butyl acrylate units are added to 100 parts by weight of acrylic resin in consideration of optical properties, transparency, compatibility, workability, Is preferable.

When the content of methyl methacrylate units is in the above range, excellent retardation and optical characteristics can be obtained. When the methyl methacrylate unit content is less than 80 parts by weight, the optical performance of the acrylic film is deteriorated, and when it exceeds 98 parts by weight, the uniformity of the thickness of the acrylic film is decreased.

The content of the butyl acrylate unit is preferably 2 to 20 parts by weight based on 100 parts by weight of the acrylic resin. When the content of the butyl acrylate unit is within the above range, a preferable thickness uniformity property can be obtained.

In the present invention, by adding silica particles which are not soluble in a solvent and are not deformed to the acrylic resin, the impact strength of the film is increased, so that film formation and film transfer are facilitated. The silica particles of the present invention preferably have a diameter of 100 to 300 nm. When the diameter of the particles is less than 100 nm, the effect of the object of the present invention is not sufficiently exhibited, and when it exceeds 300 nm, the quality of the protective film becomes poor.

The molecular weight of the acrylic resin of the present invention is preferably 300,000 to 2,500,000 g / mol. If the molecular weight is less than 300,000 g / mol, the production efficiency of the film is lowered. If the molecular weight exceeds 2,500,000 g / mol, the molding process is not easy. The glass transition temperature (Tg) of the main dope of the present invention is preferably 110 ° or more. Even if the glass transition temperature is lower than the above-mentioned range, handling becomes poor, which is not preferable.

The acrylic film of the present invention preferably has a film thickness of 10 to 60 탆. When the thickness of the acrylic film is less than 10 mu m, sufficient retardation characteristics are not exhibited. When the thickness of the acrylic film exceeds 60 mu m, it is not suitable for use in a thin polarizer.

Hereinafter, a preferred manufacturing method of the present invention will be described in detail.

Manufacture of acrylic resin

In order to produce the acrylic film of the present invention, first, a copolymer resin solution of a methyl methacrylate monomer and a butyl acrylate monomer is prepared. There is no particular limitation on the method for producing the copolymer of these monomers, and the copolymer can be produced according to a method for producing a copolymer resin well known in the art such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization.

Preparation of main dope liquid containing acrylic resin and silica particles

In the present invention, a film is produced by a solvent casting method (solution film forming method). In the solvent casting method, a main dope liquid obtained by dissolving an acrylic resin in a casting solvent is cast on a support, and the solvent is evaporated to form a film. The main dope solution is prepared by mixing the acrylic resin and the auxiliary additive in the casting solvent.

When a film is produced by a solvent casting method, an organic solvent is preferred as the solvent for preparing the main dope solution. As the organic solvent, it is preferable to use halogenated hydrocarbons, and halogenated hydrocarbons include chlorinated hydrocarbons, methylene chloride and chloroform, among which methylene chloride is most preferably used.

If necessary, organic solvents other than halogenated hydrocarbons may be mixed and used. Organic solvents other than halogenated hydrocarbons include esters, ketones, ethers, alcohols and hydrocarbons. Examples of the ester include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acylate, ethyl acylate and pentyl acylate. Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, di Isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone and the like can be used. As the ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, Ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-butanol and the like can be used. 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2, -trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like Lt; / RTI >

More preferably, methylene chloride may be used as the main solvent, and alcohol may be used as the minor solvent. Concretely, a mixed solvent in which the mixing ratio of methylene chloride and alcohol is in the range of 80:20 to 95: 5 is preferable.

In the production of the acrylic film, auxiliary additives may further be used. To the main dope liquid, various auxiliary additives depending on the use in each production step, for example, an auxiliary additive such as an ultraviolet ray inhibitor, a fine particle, an infrared absorbent, and a releasing agent may be added. The specific kind of such additives can be used without limitation as long as they are commonly used in the field, and the content thereof is preferably used within a range that does not deteriorate the physical properties of the film. The timing of adding the additives depends on the type of additive. A step of adding an additive to the end of the main dope liquid preparation may be performed.

In the present invention, silica nanoparticles are used as an additive, and the diameter of the particles is preferably 100 to 300 nm.

The main dope liquid obtained as described above can be produced by an ordinary temperature, high temperature or low temperature dissolution method.

Film forming process

In the solvent casting method of the present invention, the main dope liquid is poured on a metal support from a nozzle of a pressure die and allowed to stand for a predetermined time to form a semi-dry film. Thereafter, the semi-dried film is peeled from the metal support, transferred to a drying system, and dried to remove the solvent. Then, a uniaxial stretching process or a biaxial stretching process is performed on the dried film. By this stretching process, it is possible to improve the film uniformity and the retardation value of the protective film.

Specifically, the main dope liquid obtained as described above is cast on a support through a casting die to form an acrylic sheet. Here, the support serves to evaporate the solvent present in the casting solution while casting the casting solution on the sheet extruded from the die, thereby forming an acrylic film. The support or the surface thereof is preferably made of a metal and has a mirror finished surface, and a steel belt such as a stainless steel belt is preferably used as the support. The surface temperature of the metal support is advantageous because it can accelerate the evaporation of the solvent present in the casting stock solution as the temperature is higher. However, if the temperature is too high, the casting stock solution tends to foam or deteriorate in planarity, But it is preferably 0 to 75 占 폚, more preferably 5 to 45 占 폚. As the support, a metal support in the form of a planar conveyor belt may be used.

The acrylic sheet thus formed is subjected to a stretching step in the tenter, and the preheating step is such that the glass transition temperature (Tg) of the acryl flake is 120 DEG or more. The acrylic film of the present invention may be completed in the dryer under the above conditions after having been subjected to the stretching step in the tenter and then the left and right ends of the film whose surface has been damaged by the clip or pin of the tenter are removed.

In the case of using the tenter stretching device, it is preferable to use a device capable of controlling the holding length of the film from the left and right by the left and right gripping means of the tenter. The stretching operation may be carried out by dividing into a plurality of steps or biaxially stretching in the machine direction and the width direction. When biaxial stretching is carried out, simultaneous biaxial stretching may be carried out or may be performed stepwise. In this case, the stepwise means that the stretching in different stretching directions can be performed sequentially, the stretching in the same direction can be divided into multiple steps, and the stretching in the other direction can be added to any one of them. The simultaneous biaxial stretching may include stretching in one direction and relaxation of the other stretch by shrinking. The preferred stretching magnification of the simultaneous biaxial stretching can be in the range of 1.01 to 2.0 times in both the width direction and the longitudinal direction.

The drying means generally blows hot air on both sides of the web, but there is also a means of heating the micro web in place of the wind. Too rapid drying tends to impair the planarity of the finished film.

The acrylic film of the present invention produced in accordance with the above method was produced under the conditions of an in-plane retardation Ro defined by the following formula (1) and a retardation Rth in the thickness direction of 23 ° 55% RH under an environment of 23 ° humidity and 55% RH 10 nm or less.

[Equation 1]

Ro = (nx-ny) x

Rth = (nx + ny) / 2-nz x

Ny represents a refractive index in a direction perpendicular to the slow axis, nz represents a refractive index in a film thickness direction, and d represents a film thickness (nm) of the film, respectively .

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by the following examples.

Example  One

≪ Step 1 >

For acrylic, acryl represented by the following formula 2 was used.

(2)

≪ Step 2 > Preparation of main dope liquid

The main doping solution was composed of 64.17 parts by weight of methylene chloride, 7.13 parts by weight of methanol, 27.94 parts by weight of acrylic resin, 0.72 parts by weight of Tinvuin 928 (manufactured by BASF) and 0.04 parts by weight of Silica.

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≪ Step 3 > Production of acrylic film

The main dope liquid was uniformly plied to a stainless steel band support having a width of 2000 mm by using a belt softener. The solvent was evaporated on the stainless steel band support and peeled off from the stainless band support. Then, both ends of the web were held with a tenter and stretched so that the stretching magnification in the TD direction was 1.5 times in a temperature environment of 130 °. After the stretching, the stretching was maintained for a few seconds, the tension in the width direction was relaxed, the stretching was performed in the width direction, the stretching was continued for 35 minutes in the drying section set at 90 DEG, An acrylic film having a thickness of 40 m and a knurling width of 10 mm and a height of 8 m was produced.

<Step 4> Polarizing plate production

PVA was laminated on both sides using the acrylic film to prepare a polarizing plate.

<Step 5> Manufacture of IPS LCD

The prepared polarizing plate was coated with a pressure-sensitive adhesive on the polarizing plate protective film surface, and an IPS LCD was manufactured by attaching an up / down polarizing plate so that the polarizing plate protective film was directed to the IPS panel side.

Comparative Example 1 A TAC protective film

A triacetyl cellulose resin having an average degree of acetyl substitution (DS) of 2.86 was used to make a dope under the same conditions as in Example 1 above. The film was formed in the same manner and the retardation was measured. However, the stretching was performed at 130% at a temperature of 170 ° C. A polarizing plate was prepared using the thus prepared TAC protective film, and an IPS LCD was manufactured in the same manner.

Appearance optical quality evaluation before and after applying reliability environment

The thus prepared Example 1 and Comparative Example 1 were allowed to stand in a high-temperature and high-humidity chamber for 500 hours under conditions of a reliability environment of 60 and 90% RH, The appearance and appearance of the optical image were observed under the same conditions, and the results are shown in Table 1.

division
Picture Presence or absence of optical stains
(Egg Mura, Light Emitter)

Example 1

none


Comparative Example 1

has exist

 As can be seen from the results shown in Table 1, the IPS LCD panel of the present invention is superior in appearance optical unevenness quality before and after the reliability.

Claims (4)

1. A photosensitive resin composition comprising, as essential components, 100 parts by weight of an acrylic resin represented by the following formula (1): 80 to 98 parts by weight of methyl methacrylate units and 2 to 20 parts by weight of butyl acrylate units; A polarizing plate provided on both sides of the polarizer was bonded to both sides of the liquid crystal by an acrylic film formed by solvent casting method,
60 ° C, 90% RH An IPS panel characterized by having no optical uneven egg (Egg Mura) on the screen and no mechanical light leakage even after being left in a high temperature and high humidity environment for 500 hours.
[Chemical Formula 1]
MMA-BA
Here, MMA represents methyl methacrylate unit and BA represents butyl acrylate unit. The method according to claim 1,
Wherein the main doping liquid comprises silica particles having a diameter of 100 to 300 nm. The method according to claim 1,
Wherein the solvent of the solvent casting is mixed with a halogenated hydrocarbon and an alcohol. delete