KR20170051455A - Method for manufacturing liquid crystal display protection plate - Google Patents

Abstract

The present invention provides a method of manufacturing a liquid crystal display protection plate in which an in-plane retardation value is controlled to a predetermined range. A thermoplastic resin laminate in which a methacrylic resin layer is laminated on at least one side of a polycarbonate resin layer is extruded from a T die 11 in a molten state to form a first cooling roll 12 and a second cooling roll 13, the thermoplastic resin laminate is sandwiched between the rolls 13, 13, and wrapped around the second cooling roll 13 and the third cooling roll 14 to cool the thermoplastic resin laminate to the take-up roll 15 And the resin plate 16 is formed. Thereafter, the resin plate 16 is heated at a temperature of 50 DEG C or more for 1 minute or more to manufacture a liquid crystal display protection plate. The in-plane retardation value of the liquid crystal display protective plate is 50 to 210 nm and the rate of decrease of the in-plane retardation value of the liquid crystal display protective plate to the in-plane retardation value of the resin plate 16 before heating is 5% or more.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a liquid crystal display protective plate,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a liquid crystal display protection plate using a resin plate. More specifically, the present invention relates to a method for manufacturing a liquid crystal display protection plate, which includes a step of processing a resin plate at a high temperature and in-plane retardation value is controlled within a preferable range.

In some cases, a protective plate is formed on the front side of the liquid crystal display in order to prevent scratches on the surface. It has been studied to use a resin plate in which various functional films are formed as protective plates. Various functional coatings can be used to prevent adhesion of a cured coating having scratch resistance (hard coat property) or low reflection, at least on one surface of a resin plate, an antiglare film for suppressing glare, and contaminants, An antistatic film for preventing adhesion of dust, and a transparent conductive film required for a touch panel.

For example, Patent Document 1 discloses that a methacrylic resin plate is used as a substrate, and a cured coating is formed on at least one surface of the methacrylic resin plate to be used as a shield for a display window of a liquid crystal type portable information terminal.

Patent Document 2 discloses that a laminated plate formed by laminating a methacrylic resin layer on one surface of a polycarbonate resin layer is used as a substrate and a cured coating is formed on the methacrylic resin layer to be used for a liquid crystal display cover Lt; / RTI >

As a method for forming the above-described functional film, there is a method of curing the ultraviolet-curing resin after lamination of the ultraviolet-curing resin such as the patent documents 1 and 2, a PET film (polyethylene terephthalate film) A method of applying a solution dispersed or dissolved in water or an organic solvent, followed by drying, a method of curing a laminated thermosetting resin on a substrate, and the like are known.

As a production method of the resin plate, an injection molding method, an extrusion molding method and the like are known.

The liquid crystal display protective plate is provided on the front side (viewer side) of the liquid crystal display. The viewer sees the screen of the liquid crystal display through the liquid crystal display shield plate. The conventional liquid crystal display protective plate hardly changes the polarization of the outgoing light from the liquid crystal display which is a polarized light. Therefore, depending on the angle formed by the polarization axis of the outgoing light and the transmission axis of the polarizing sunglasses, the image is sometimes invisible because the screen is dark. Therefore, a liquid crystal display shield plate capable of suppressing deterioration of the visibility of an image when a screen of the liquid crystal display is viewed through a polarizing filter such as polarizing sunglasses is being studied.

For example, Patent Document 3 discloses that an in-plane retardation value is set to 85 to 300 nm. In addition to the retardation value, the resin plate used for the liquid crystal display protective plate must satisfy a variety of required performance such as appearance quality, uniformity of thickness, shrinkability upon heating, direction of warpage, and size. For example, in the extrusion molding method, in order to satisfy the required performance, the resin temperature during molding, the main speed ratio (peripheral speed ratio) of a plurality of cooling rolls, the gap between the first cooling roll called the banks and the second cooling roll For example, the size of the resin layer to be formed, and various manufacturing conditions. However, there are many cases in which it is difficult to satisfy all the required performance.

In addition, the resin plate used for the liquid crystal display protective plate may be heated by being sandwiched between curved plates for the purpose of adjusting the state of warpage, etc., in the case of a drying process or for giving a warp shape.

Japanese Patent Application Laid-Open No. 2004-299199 Japanese Laid-Open Patent Publication No. 2006-103169 Japanese Laid-Open Patent Publication No. 2010-085978

If an extruded resin plate is manufactured by the in-plane retardation value of the resin plate and the production conditions satisfying the above-mentioned other required performance, and then, for example, a heat treatment is performed to adjust the state of bending, The in-plane retardation value may be lowered. Further, when the extruded resin plate is produced so that the in-plane retardation value of the resin plate does not decrease even if the above-mentioned heat treatment is performed, the above-mentioned other required performance other than the retardation value may not be satisfied.

An object of the present invention is to provide a method of manufacturing a protective plate for a liquid crystal display in which an in-plane retardation value is controlled to a predetermined range.

Means for Solving the Problems The present inventors have studied to achieve the above object, and as a result, they have found the present invention including the following aspects.

That is, the present invention includes the following aspects. An aspect of a method for manufacturing a protective plate for a liquid crystal display comprising a resin plate according to the present invention comprises at least the following steps.

 A step of extruding a thermoplastic resin laminate in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate resin layer, from a T die in a molten state.

And a step of sandwiching the thermoplastic resin laminate between the first cooling roll and the second cooling roll while forming a bank.

The step of cooling the thermoplastic resin laminate by winding the thermoplastic resin laminate on the second cooling roll and winding it on a third cooling roll.

And then drawing the thermoplastic resin laminate with a take-up roll to form the resin plate.

And then heating the resin plate at a temperature of 50 DEG C or more for 1 minute or more to manufacture a liquid crystal display protection plate.

The in-plane retardation value of the liquid crystal display protecting plate is 50 to 210 nm and the rate of decrease of the in-plane retardation value of the liquid crystal display protecting plate to the in-plane retardation value of the resin plate before the heating step is 5% Or more.

One aspect of the above-described liquid crystal display shielding plate may have appropriate in-plane retardation when viewing the liquid crystal display through the polarizing sunglasses. In other words, the liquid crystal display protective plate of the present invention is a substrate for a liquid crystal display protective plate, and even if it is a resin plate whose in-plane retardation value does not fall within a desired range, the resin plate is produced by performing a specific heating process, And can be preferably used. As a result, it is possible to adjust the manufacturing conditions in preference to the characteristics other than the retardation value.

In one embodiment of the method for manufacturing a protective cover for a liquid crystal display according to the present invention, the decrease rate is preferably 15% or more.

In one aspect of the method for manufacturing a protective plate for a liquid crystal display according to the present invention, when the main speed of the second cooling roll is V2 and the main speed of the third cooling roll is V3, the value of V3 / V2 is 1.000 or more . Further, when the main speed of the take-up roll is V4, the value of V4 / V2 is preferably 1.000 or more.

Hereinafter, in order to facilitate the explanation, the resin plate is produced by extruding a thermoplastic resin laminate, and unless otherwise specified, refers to a resin plate before the heating step. In addition, the liquid crystal display protective plate will be described as being obtained by adding a heating process to the produced resin plate. More specifically, the resin plate is a substrate before being subjected to various processes after being extruded, and the display protection plate is processed into a protection plate through various processes such as coating, bonding, and bending correction on the substrate. In at least one of the various processes, the substrate is heated. In other words, in the display protecting plate, the resin plate has passed through the above-described various processes to have an appropriate retardation value.

The method of manufacturing a protective plate for a liquid crystal display of the present invention can provide a liquid crystal display shield plate having an appropriate in-plane retardation value when a liquid crystal display is viewed through polarized sunglasses.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view showing a method of manufacturing a resin plate by co-extrusion according to an embodiment of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of clarity, the following description and drawings are properly omitted and simplified. In the drawings, the same reference numerals are given to constituent elements and substantial parts having the same constitution or function, and a description thereof will be omitted.

Embodiment 1

The resin plate used in the liquid crystal display protective plate of the present invention has a methacrylic resin layer laminated on at least one surface of the polycarbonate resin layer. Since the methacrylic resin layer is laminated on the polycarbonate resin layer, the transparency, impact resistance and scratch resistance of the plate are excellent.

The resin plate is manufactured by the extrusion molding method, so that the production efficiency is excellent.

Hereinafter, the " resin plate " may be appropriately described as " extruded resin plate ".

In one embodiment of the present invention, the methacrylic resin constituting the methacrylic resin layer contains a structural unit derived from methacrylic acid ester.

The content of the structural unit derived from methacrylic acid ester is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more. The content of the structural unit derived from methacrylic acid ester may be 100% by mass. When the content of the structural unit derived from methacrylic acid ester is within the above range, transparency is good.

Examples of the methacrylic esters include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, meta 2-hydroxyethyl ethyl acrylate, and 2-hydroxyethyl ethyl acrylate. Among them, it is preferable that 50 mass% or more of methyl methacrylate is contained in view of transparency.

It may also be a copolymer of a monomer copolymerizable with methyl methacrylate. Examples of the monomer copolymerizable with methyl methacrylate include methacrylic acid esters other than methyl methacrylate. Examples of such methacrylic acid esters include ethyl methacrylate, butyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and the like. . Methacrylic monocyclic aliphatic hydrocarbon esters such as cyclohexyl methacrylate, cyclopentyl methacrylate, and cycloheptyl methacrylate; 2-norbornyl methacrylate, 2-norbornyl methacrylate, 2-methyl-2-norbornyl methacrylate, Isobornyl methacrylate, 2-ethyl-2-isobornyl methacrylate, 8-tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate, 8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate, 2- adamantyl methacrylate, 2- Ethyl methacrylate, 2-ethyl-2-adamantyl methacrylate, 1-adamantyl methacrylate, 2-pentyl methacrylate, 2- Methacrylic acid polycyclic aliphatic hydrocarbon esters such as pentyl methacrylate; And the like.

Examples of the monomer copolymerizable with methyl methacrylate include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate Styrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide, and the like. These monomers may be used alone or in combination of two or more.

When the methacrylic resin is a copolymer of methyl methacrylate and methyl acrylate, transparency is excellent. In this case, the monomer composition is preferably 80 mass% or more, more preferably 85 mass% or more, and even more preferably 90 mass% or more, based on 100 mass% of the total of the monomers. And methyl methacrylate may be 100% by mass.

The methacrylic resin used in one embodiment of the present invention preferably has a melt volume flow rate (MVR) of 0.5 to 20 (cm 3/10 min, 230 캜, 37.3 N) measured according to IS0-1133. When the MVR is in this range, the stability of the extrusion molding is good.

The methacrylic resin used in one embodiment of the present invention may contain known additives in order to improve impact resistance, light resistance, and the like. Examples of additives include antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, release agents, polymer processing aids, antistatic agents, flame retardants, salt pigments, light diffusers, organic pigments, polish remover, impact resistance modifiers, .

The polycarbonate resin to be used in one embodiment of the present invention is not particularly limited, but preferably has a melt volume flow rate (MVR) measured according to ISO-1133 of preferably 1 to 20 (cm < 3 & N). When the MVR is in this range, the stability of the extrusion molding is good.

The polycarbonate resin used in one embodiment of the present invention may contain known additives to improve the light resistance and the like. Examples of additives include antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, release agents, polymer processing aids, antistatic agents, flame retardants, salt pigments, light diffusers, organic pigments, polish remover, impact resistance modifiers, .

The resin plate in the embodiment of the present invention is preferable in that the methacrylic resin layer is laminated on both sides of the polycarbonate resin layer to thereby provide excellent scratch resistance and to prevent warpage due to humidity change.

The thickness of the resin plate in the embodiment of the present invention is preferably 0.4 to 2 mm, more preferably 0.5 to 1.5 mm. If it is too thin, the rigidity tends to become insufficient. If it is excessively large, the weight of the liquid crystal display device tends to be hindered.

The thickness of the methacrylic resin layer of the resin plate in the embodiment of the present invention is preferably 20 to 200 占 퐉. Within this range, the balance between scratch resistance and impact resistance is excellent. More preferably 25 to 150 占 퐉, and still more preferably 30 to 100 占 퐉.

The resin plate obtained by one embodiment of the present invention may be provided with a cured coating on at least one surface thereof. By forming a cured coating, functions such as scratch resistance and low reflectivity can be imparted.

For example, the thickness of the scratch-resistant (hard coat) cured coating is preferably 2 to 30 占 퐉, more preferably 3 to 10 占 퐉. If the thickness is too thin, the surface hardness becomes insufficient. If it is too thick, cracks may occur due to bending during the manufacturing process.

For example, the thickness of the low-reflective cured coating is preferably 80 to 200 nm, and more preferably 100 to 150 nm. Even if it is excessively thin or too thick, the low reflection performance becomes insufficient.

The resin plate in one embodiment of the present invention is produced by coextrusion. The polycarbonate resin and the methacrylic resin are heated and melted, extruded from a discharge port having a wide shape called a T-die, sandwiched by a pair of rolls composed of a first cooling roll and a second cooling roll, . The thermoplastic resin laminate is then cooled further by winding it on a second cooling roll and then winding it on a third cooling roll. Further, the thermoplastic resin laminate may be further cooled by further cooling rolls thereafter. Thereafter, the thermoplastic resin laminate is taken out with a take-up roll to form a resin plate. In such a process, the resin plate is produced by extruding a thermoplastic resin laminate, in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate resin layer, in a molten state from a T-die.

The manufactured resin plate is further subjected to a heating process to produce a liquid crystal display protective plate. The heating process will be described later.

Fig. 1 shows an outline of a method for producing a resin plate by a co-extrusion apparatus comprising a T die 11, first to third cooling rolls 12 to 14, and a take-up roll 15 as an embodiment. The resin extruded from the T die 11 is sandwiched between a pair of rolls composed of the first cooling roll 12 and the second cooling roll 13 and formed into a sheet-like thermoplastic resin laminate. Thereafter, the thermoplastic resin laminate is further cooled by the third cooling roll 14 and taken up by the take-up roll 15 constituted by a pair of rolls, whereby the resin plate 16 is formed. Further, the present invention is not limited to this embodiment.

The T die 11 can use both a single manifold type and a multi-manifold type, but a multi-manifold type is preferable in that the thickness precision of each layer is excellent.

As the cooling roll, both of a metal rigid roll and a metal elastic roll can be used.

The term retardation refers to the phase difference between light in the molecular main chain direction and light in the direction perpendicular thereto. It is known that a polymer can be formed into an arbitrary shape by heat molding in general, but a certain stress is generated in the heating and cooling process, and molecules are oriented to cause retardation. Therefore, in order to control the retardation, it is necessary to control the orientation of the molecules. The orientation of the molecules is caused by, for example, stress at the time of molding at a temperature near the glass transition temperature of the polymer.

In extrusion molding, the in-plane retardation value of the resin plate, the uniformity of the appearance quality and the thickness, the direction of the warp, and the magnitude of the deflection are controlled by variously adjusting the manufacturing conditions. Hereinafter, the influence of the bank, the influence of the main speed ratio, the influence of the thickness of the resin plate, and the heating process will be described as factors related to the control of the manufacturing conditions. In addition, for ease of explanation, the configuration shown in Fig. 1 is suitably used.

* About influence of bank

The bank is a resin coating formed on the gap between the first cooling roll 12 and the second cooling roll 13.

As a result of evaluating the relationship between the bank amount and the in-plane retardation value, it was found that the in-plane retardation value increases as the bank amount increases.

The reason is that when the molten resin flows to the minimum gap between the first cooling roll 12 and the second cooling roll 13 at the position where the resinous molten resin is generated, Is oriented.

By increasing the supply of resin to the roll, or by lowering the speed of the roll, the bank becomes larger and adjustable. In the following examples, the amount of the bank was adjusted by changing the resin supply amount, and the magnitude of the amount was evaluated by visual observation.

* About influence of main speed ratio

The main speed ratio is the ratio of the main speed of any other cooling roll and take-up roll to the second cooling roll 13.

The relationship between the main speed ratio and the in-plane retardation value of the third cooling roll 14 with respect to the second cooling roll 13 was evaluated. As a result, it was found that the in-plane retardation value was increased as the main speed ratio was increased.

This is because when the resin temperature at the time when the resin contacts the third cooling roll 14 is close to the glass transition temperature of the polycarbonate, the ratio of the main speed of the third cooling roll 14 is large, It is believed that when stress is applied, the molecules of the resin are oriented.

As a result of evaluating the relationship between the main speed ratio and the in-plane retardation value of the take-up roll 15 with respect to the second cooling roll 13, it was found that the in-plane retardation value increases as the main speed ratio increases.

The reason is that when the resin temperature at the time of peeling off the resin from the third cooling roll 14 is in the range of about +5 to +40 DEG C relative to the vicinity of the glass transition temperature of the polycarbonate, It is believed that when the tensile stress is applied, the molecules of the resin are oriented because the ratio is larger.

Further, the main speed ratio between the second cooling roll 13 and the take-up roll 15 is preferably 0.98 or more, more preferably 1.000 or more. The reason is that if the ratio of the primary cooling rate of the second cooling roll 13 to that of the take-up roll 15 is less than 0.98, the tensile strength of the thermoplastic resin laminate is insufficient and the thermoplastic resin laminate in contact with the third cooling roll 14 The contact state can not be maintained and the film is peeled off from the roll, and there is a possibility that a clean surface can not be maintained.

The temperature at which the third cooling roll 14 is peeled off is preferably in the range of +5 占 폚 to -40 占 폚 than the vicinity of the glass transition temperature of the polycarbonate. The reason is that a clean surface can not be obtained even if the temperature is excessively higher or lower than the vicinity of the glass transition temperature.

Next, the degree of reduction of the in-plane retardation value when the extruded resin plate was heated was examined.

When the main speed ratio is constant and the bank amount is gradually increased, the in-plane retardation value gradually increases, but the rate of decrease of the in-plane retardation value after heating is gradually decreased.

When the bank amount is constant and the main speed ratio of the second cooling roll 13 and the third cooling roll 14 is gradually increased, the in-plane retardation value gradually increases, and the in-plane retardation value And it was found that it gradually grew.

In addition, even when the amount of bank is constant and the ratio of the main speed of the second cooling roll 13 and the take-up roll 15 is gradually increased, the in-plane retardation value gradually increases. However, the rate of decrease of the in-plane retardation value after heating becomes very large .

Hereinafter, in order to facilitate the description, it is assumed that the main speed of the second cooling roll is V2, the main speed of the third cooling roll is V3, and the main speed of the take-up roll is V4, The speed ratio may be expressed as (V3 / V2), and the main speed ratio of the take-up roll and the second cooling roll may be described as (V4 / V2).

Next, the influence on the in-plane retardation value in the case of using a metal rigid roll or a metal elastic roll as the second cooling roll 13 was evaluated, and as a result, it was found that the in-plane retardation value was smaller in the case of using the metal elastic roll . The reason for this is considered to be that the metal elastic roll generally has a small amount of bank in many cases, and that the molecular orientation by bank formation is small. Therefore, it is found that it is necessary to adjust the main speed ratio of the second cooling roll 13 and the third cooling roll 14 in order to control the in-plane retardation proper to the metal elastic roll.

* About influence of thickness

The thickness control in the width direction orthogonal to the extrusion direction in the extrusion molding is generally performed by controlling the gap between the first cooling roll 12 and the second cooling roll 13 and the amount of extrusion accompanying the amount of resin supplied, The main speed, and the bank amount.

Generally, the larger the amount of the bank, the greater the pressure applied to the first cooling roll 12 and the second cooling roll 13, and the cooling roll is pressed and bent. Therefore, the thickness distribution in the width direction orthogonal to the flow direction along with the increase in the bank amount tends to be thicker at the center in the north, and thinner at both ends.

As a method of flattening the thickness distribution in the width direction, for example, the amount of the bank at both ends in the width direction may be made larger than the amount of the bank near the center. In this case, the retardation values at both end portions in the width direction become large.

Therefore, in order to control the deviation of the retardation value in the width direction and the rate of decrease of the retardation value to an appropriate value, it is necessary to appropriately adjust the thickness distribution in the width direction.

In view of this, it is preferable that the thickness ratio (TC / TS) of the average thickness (TS) at the both ends in the width direction perpendicular to the extrusion direction and the average thickness (TC) there was. The average thickness TC in the vicinity of the center may be calculated at the center 100 mm in the width direction perpendicular to the extrusion direction of the resin plate 16 and the average thickness TS at both ends may be calculated in the width direction perpendicular to the extrusion direction An average thickness of 100 mm from a position 100 mm away from the end to a position 200 mm away from the end was defined as the thickness of one end and an average thickness of 100 mm from a position 100 mm away from the other end to a position 200 mm away And the average thickness at the both ends of 100 mm (the average thickness of 200 mm in total) is calculated as the thickness of the other end.

Here, the width direction is a direction orthogonal to the direction in which the resin plate is conveyed in the extrusion apparatus, and the part in the width direction refers to a region including an arbitrary length of the width of the resin plate.

When the in-plane retardation value after heating was 50 to 210 nm and the rate of decrease of the in-plane retardation value before and after heating was 5% or more as a result of measuring the selected point in this order, the obtained resin plate exhibited the effect of the present invention . Further, it is more preferable that the rate of decrease of the in-plane retardation value before and after heating is 15% or more. Here, the decrease rate of the in-plane retardation value before and after the heating can be said to be the rate of decrease of the in-plane retardation value of the liquid crystal display protection plate to the in-plane retardation value of the resin plate before the heating step.

When the thickness ratio (TC / TS) exceeds 1.05, the amount of the bank becomes too large to be stably produced. On the other hand, when the ratio is less than 1.0, the amount of the bank is too small, .

(Bank amount) of the bank is controlled so that the ratio of the thickness of the extruded resin plate produced is greater than 1.00 and equal to or smaller than 1.05 in the production process of the extruded resin plate, . If the control of the thickness is insufficient, for example, a region where the retardation value deviates from the intended numerical range is formed at the end in the width direction of the extruded resin plate, which may not be suitable as a product. Therefore, in order to stably produce a good product, it is preferable to control the thickness of the resin plate.

In the resin plate (extruded resin plate) according to the embodiment of the present invention, the rate of decrease of the in-plane retardation value in the heating step is 5% or more. If it is attempted to adjust to less than 5%, for example, the amount of the bank may be increased. However, if the amount of the bank is excessively large, there is a case that the retardation value of the resin plate becomes excessively large. In addition, for example, it is conceivable to reduce the main speed ratio V3 / V2 or V4 / V2 of the roll, but if it is too small, the cooling roll and the molten resin are not smoothly released, There is a case that the surface property of the resin plate is deteriorated.

When the rate of decrease of the in-plane retardation value in the heating step is 10% or more, particularly 15% or more, occurrence of the above problem can be suppressed.

The rate of decrease of the in-plane retardation value in the heating step is preferably 90% or less. If it is larger than the above range, the shrinkage ratio when the resin plate is heated tends to increase. For example, wrinkles may occur in the laminated resin layer due to heating in the step of laminating and curing a photo-curing resin or the like, There is a case that the dimensional change becomes too large, and the ease of handling such as conveyance and fixing of the plate is deteriorated. It is also conceivable to reduce the amount of the bank, for example. However, if it is too small, the bank may not be formed temporarily due to a slight temperature unevenness of the bank, and the first cooling roll or the second cooling roll and the molten resin are not in close contact with each other, Or the thickness irregularity becomes large. In addition, the rate of decrease of the retardation value is more preferably 85% or less, and still more preferably 80% or less.

* About the heating process

The heating step in the embodiment of the present invention is to heat the resin plate at 50 DEG C or more for 1 minute or more. The heating process includes, for example, the following processes.

A step of allowing the resin plate to stand in an oven heated to 50 ° C or more for 1 minute or more in order to dry the liquid coated on the surface of the resin plate.

A step of placing the resin plate in an oven heated to 50 ° C or more for 1 minute or more for thermosetting the thermosetting resin laminated on the surface of the resin plate.

A step of sandwiching a resin plate between a pair of metal plates bent to the same degree in a pair of the same direction heated to 50 占 폚 or more and adjusting the warping shape of the resin plate.

An annealing process in which a resin plate is sandwiched between a pair of flat metal plates heated to 50 占 폚 or more to reduce molding deformation of the resin plate.

A resin plate annealing step in which one side of a resin plate is held by a jig and is suspended in a heating furnace heated to 50 DEG C or more for 1 minute or more in order to reduce molding deformation of the resin plate.

In the step of irradiating light with a xenon lamp or the like in order to cure the photo-curing resin laminated on the surface of the resin plate, heat generated by infrared rays contained in light beams emitted from the lamp or heat due to reaction of the photo- A process in which the time required for the surface of the resin plate to become 50 ° C or more becomes 1 minute or more.

The above-described process is an example of a process performed to process a resin plate into a display protecting plate. The process described above is included in the heating process of one embodiment if it is a process of heating at 50 ° C or more for 1 minute or more .

In a method of manufacturing a resin plate according to an embodiment, a heating step is included. The heating step is carried out, for example, by one or more of the above-described steps.

The length of the heating time is determined in accordance with each of the above-described steps, and it is preferable to heat the heating time for a period of time in which the effect of each step occurs.

In addition, when the in-plane retardation value of the liquid crystal display protective plate exceeds 210 nm, the difference in transmittance of each wavelength of the visible light range in the case of viewing through a polarizing filter such as polarizing sunglasses becomes large, and various colors are hardly visible. On the other hand, if it is less than 50 nm, the transmittance at the entire wavelength in the visible light range is greatly reduced, resulting in a blackish image, which makes visibility difficult. In the range of 50 nm to 210 nm, the larger the value, the brighter the image, and the smaller the value, the less the color. Particularly, when the in-plane retardation value is from 60 nm to 200 nm, the balance of brightness and color is good and visibility is excellent, more preferably from 80 nm to 180 nm, and more preferably from 100 nm to 150 nm Is more preferable.

As described above, one aspect of the liquid crystal display protective plate of the present invention is a resin plate that is an in-plane retardation value which is not necessarily appropriate as a substrate for a liquid crystal display protective plate, or when a resin plate is manufactured through a specific heating process , It can be preferably used as a liquid crystal display shielding plate.

According to the manufacturing method of the liquid crystal display protective plate of one embodiment, even if the in-plane retardation value of the resin plate is larger than the predetermined range, the heat treatment can be performed to provide a liquid crystal display having an appropriate range of retardation value. Therefore, the manufacturing method of the liquid crystal display of one embodiment and the protective plate of the liquid crystal display manufactured have priority to adjustment of the manufacturing conditions in preference to characteristics other than the retardation value, such as appearance quality, thickness uniformity, So that it is excellent in various characteristics and productivity.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited at all by these examples.

The physical properties of the resin and the resin plate were measured by the following methods.

[MVR]

The measurement was carried out in accordance with ISO-1133 using a melt indexer ("TAKARA L241-153", manufactured by Techno Seven Co., Ltd.).

[Methacrylic resin]

"Parapet (registered trademark) HR" (MVR: 2.0 cm < 3 > / 10 min) manufactured by Kuraray Co., Ltd. was prepared as a methacrylic resin.

[Polycarbonate resin]

"SD Polycar (registered trademark) PCX" (MVR: 8 cm 3/10 min, glass transition temperature: 151 캜) manufactured by Sumikastar Theory Polycarbonate Co., Ltd. was prepared as a polycarbonate resin.

[Evaluation of thickness of resin plate and evaluation of thickness unevenness in width direction]

The average thickness of 100 mm at the center in the width direction orthogonal to the extrusion direction of the resin plate was defined as the thickness TC of the center portion and the average thickness of 100 mm from the position of 100 mm away from the one end to the position 200 mm away, And an average thickness of 100 mm from a position 100 mm away from the other end to a position 200 mm away from the other end is defined as the thickness of the other end and the average value of the average thicknesses at both ends 100 mm is defined as the thickness of the end Thickness (TS). The thickness ratio (TC / TS) of the thickness of the end portion (TS) and the thickness of the central portion (TC) was taken as an index of thickness unevenness in the width direction. The thickness was measured using a micrometer.

[Measurement of retardation value]

The test piece of the resin plate or the protective plate of the liquid crystal display was cut by a runner to produce a test piece of 100 mm square. The retardation value was measured by WPA-100 (-L) manufactured by Photonic Lattice Co., Ltd. for 10 minutes or more under the environment of 25 캜 3 캜. The measurement position was measured near the center of the test piece.

The lowering rate of the retardation value was set to a value obtained by the following formula.

(Reduction rate of the retardation value)

= {(Retardation value of resin plate) - (retardation value of liquid crystal display protective plate)} / (retardation value of resin plate) 100

[Method for evaluating visual observation at the time of attaching polarized sunglasses]

The test piece of the protective plate for the liquid crystal display was cut by a running piece to produce a test piece of 100 mm square.

Next, a liquid crystal display was disposed at a position 35 cm away from the eye to display an image. The test pieces related to Examples and Comparative Examples were arranged in parallel with the screen of the display device at a position 30 cm away from the eye between the liquid crystal display device and the eye.

First, the polarizing sunglasses were not mounted, passed through the thickness direction of the test piece, and the images were visually observed.

Next, the polarized sunglasses were attached, the left and right necks were tilted with the face facing the image, and the image was observed with naked eyes in the same manner as described above.

&Amp; cir &: There was no significant change in the manner in which the image was seen depending on the presence or absence of polarized sunglasses, and the image could be visually recognized without any problem.

X: The image is visible, the image is dark when the neck is tilted at an angle, or the dark color is seen, and the image is not visible, when the polarizing sunglasses are attached.

[Appearance evaluation method of resin plate]

The surface of the resin plate was evaluated by visual observation. The evaluation was made by observing the image of the illumination light source of the room reflected on the surface of the resin plate, and judging whether the image was shaky or not.

Arrangement of resin plate: Arranging the surface of the resin plate on the methacrylic resin side as the upper side and parallel to the bottom surface

Lighting light source: straight tube 40 W white fluorescent light

Arrangement of illumination: Approximately 2 m upward from the resin plate, about 2 m in the horizontal direction

Angle of illumination: Direction that is about 45 degrees upward from the resin plate surface

Direction of illumination: The length direction of the fluorescent lamp on the surface of the resin plate and the direction in which the extrusion direction of the resin plate is about 45 degrees

○: There is no fluctuation and is good.

?: There is slight fluctuation, but it is not conspicuous.

X: There is a shake and it stands out.

[Example 1]

(Manufacturing method of resin plate)

The methacrylic resin was melted with a 150 mmφ single screw extruder (Toshiba Machine Co., Ltd.), a polycarbonate resin with a 150 mm single screw extruder (Toshiba Machine Co., Ltd.), and both were melted through a multi-manifold die Methacrylic resin, polycarbonate resin and methacrylic resin were stacked in this order from the side in three layers. The laminated resin (thermoplastic resin laminate) was sandwiched between the first cooling roll 12 and the second cooling roll 13 shown in Fig. 1 to manufacture a resin plate. Here, the first cooling roll 12, the second cooling roll 13 and the third cooling roll 14 were all made of a metal rigid roll.

In addition, the amount of the bank is kept small, the main speed ratio (V3 / V2) of the second cooling roll 13 and the third cooling roll 14 is adjusted to 1.000, The main speed ratio (V4 / V2) of the roll 15 was adjusted to 1.011. The temperature of the entire thermoplastic resin laminate at the position of peeling from the third cooling roll 14 was measured by an infrared radiation thermometer at 130 占 폚. The thickness of each layer was 75 占 퐉 for one methacrylic resin layer, 850 占 퐉 for a polycarbonate resin layer, and 75 占 퐉 for the other methacrylic resin layer. The total thickness of the laminate was molded and cooled such that the average thickness (TC) in the vicinity of the center was 1 mm in thickness. The width of the obtained resin plate was approximately 1500 mm.

The obtained resin plate was cut at a length of 1000 mm in the extrusion direction, and 100 mm at both ends in the width direction was cut off to obtain a rectangular resin plate having a size of approximately 1000 mm x 1300 mm.

In order to correct warpage, the obtained rectangular resin plate was put in an oven controlled at 100 ° C ± 3 ° C for 5 hours and taken out, and a rectangular resin plate after the heat treatment was used as a liquid crystal display protective plate. Inside the oven, a rectangular resin plate was placed in a state of being tied with a string with its short sides side up. The string was tied to two clips fixed at two points at the ends of the upper triangular section. The string was fixed to the hanging tool to be vertical.

Table 1 shows the manufacturing conditions and evaluation results of the obtained resin plate and protective plate for liquid crystal display.

[Examples 2 to 5]

The kind of the second cooling roll, the amount of the bank, the main speed ratio V3 / V2 of the second cooling roll 13 and the third cooling roll 14, A resin plate and a liquid crystal display protective plate were prepared in the same manner as in Example 1, except that the speed ratio (V4 / V2) was changed in accordance with Table 1. Table 1 shows the evaluation results of the obtained resin plate and the liquid crystal display protective plate.

[Comparative Examples 1 to 4]

The kind of the second cooling roll, the amount of the bank, the main speed ratio V3 / V2 of the second cooling roll 13 and the third cooling roll 14, A resin plate and a liquid crystal display protective plate were prepared in the same manner as in Example 1, except that the speed ratio (V4 / V2) was changed in accordance with Table 1. Table 1 shows the evaluation results of the obtained resin plate and the liquid crystal display protective plate.

From the comparison of the examples and comparative examples in Table 1, it can be seen that the retardation value of the protective plate of the liquid crystal display protective plate of the present invention is appropriate even if the rate of decrease of the retardation value of the resin plate is large. Good visibility.

Particularly, in Examples 1, 3 and 4, the retardation value of the resin plate is larger than the range of the appropriate retardation value. However, by passing through the heating process, it was possible to produce a resin plate excellent in the visibility of images in the state in which polarized sunglasses were mounted.

In Comparative Example 1, a resin plate satisfying a retardation value before and after heating was produced in which the rate of decrease in the retardation value was 0%. This shows an example of producing a resin plate satisfying the retardation value before and after the heat treatment. The comparative example 1 is excellent in the visibility of images in the state in which polarized sunglasses are mounted. On the other hand, it can be seen that the value of TC / TS is 1.05 and the thickness irregularity in the width direction is large. In addition, the image of the illumination light source is noticeable, and the appearance is not excellent. Therefore, the liquid crystal display protection plate is not sufficient and it is difficult to adjust the other requirements while satisfying the requirements of the retardation value.

Industrial availability

The liquid crystal display shield plate of the present invention is preferable as a liquid crystal display shield plate for use in, for example, a vehicle-mounted display device, a cellular phone, a smart phone, a PC, a television,

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

This application claims priority based on Japanese Patent Application No. 2014-181902 filed on September 8, 2014, the entire disclosure of which is hereby incorporated by reference.

11: T die
12: first cooling roll
13: second cooling roll
14: Third cooling roll
15: Draw roll
16: resin plate

Claims (4)

A method of manufacturing a protective plate for a liquid crystal display comprising a resin plate,
A thermoplastic resin laminate in which a methacrylic resin layer is laminated on at least one surface of a polycarbonate resin layer is extruded from a T die in a molten state,
The thermoplastic resin laminate is sandwiched between the first and second cooling rolls while forming a bank,
The thermoplastic resin laminate was wound around the second cooling roll, and cooled by being wound around a third cooling roll,
Thereafter, the thermoplastic resin laminate is taken out with a take-up roll to form the resin plate,
Thereafter, the resin plate is heated at a temperature of 50 DEG C or more for 1 minute or more to manufacture the liquid crystal display protective plate,
Plane retardation value of the liquid crystal display protective plate is 50 to 210 nm,
Plane retardation value of the liquid crystal display protective plate to the in-plane retardation value of the resin plate before the step of heating is 5% or more. The method according to claim 1,
Wherein the rate of decrease is 15% or more. 3. The method according to claim 1 or 2,
Wherein a value of V3 / V2 is 1.000 or more when the main speed of the second cooling roll is V2 and the main speed of the third cooling roll is V3. 4. The method according to any one of claims 1 to 3,
Wherein the value of V4 / V2 is 1.000 or more when the main speed of the second cooling roll is V2 and the main speed of the take-up roll is V4.

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