WO2016038868A1

WO2016038868A1 - Method for manufacturing liquid crystal display protection plate

Info

Publication number: WO2016038868A1
Application number: PCT/JP2015/004522
Authority: WO
Inventors: 小野　陽二; 一男船崎
Original assignee: 株式会社クラレ
Priority date: 2014-09-08
Filing date: 2015-09-07
Publication date: 2016-03-17
Also published as: KR102365231B1; JP6542780B2; TWI683741B; CN106687278A; CN106687278B; JPWO2016038868A1; TW201613743A; KR20170051455A

Abstract

The present invention provides a method for manufacturing a liquid crystal display protection plate in which the in-plane retardation value is controlled so as to be within a predetermined range. The manufacturing method includes: extruding a thermoplastic resin laminated body in a molten state from a T-die (11), the thermoplastic resin laminated body being a polycarbonate resin layer on which a methacrylic resin layer is laminated on at least one surface of the polycarbonate resin layer; pinching the thermoplastic resin laminated body between a first cooling roll (12) and a second cooling roll (13) while forming a bank therebetween; cooling the thermoplastic resin laminated body by winding the thermoplastic resin laminated body around the second cooling roll (13) and a third cooling roll (14); and forming a resin plate (16) by taking up the thermoplastic resin laminated body with a take-up roll (15). Subsequently, after undergoing a process of heating the resin plate (16) for 1 minute or more at a temperature of 50°C or more, the liquid crystal display protection plate is manufactured. The in-plane retardation value of the liquid crystal display protection plate is 50 to 210 nm and the decreasing rate of the in-plane retardation value of the liquid crystal display protection plate with respect to the in-plane retardation value of the resin plate (16) before heating is 5% or more.

Description

Method for manufacturing LCD protective plate

The present invention relates to a method for manufacturing a liquid crystal display protective plate using a resin plate. More specifically, the present invention relates to a method for producing a protective plate for a liquid crystal display, which includes a step of processing a resin plate at a high temperature, and the in-plane retardation value is controlled within a suitable range.

∙ Liquid crystal displays may have a protective plate on the front side to prevent scratches on the surface. It has been studied to use a resin plate on which various functional films are formed as a protective plate. Various types of functional films are provided on at least one surface of the resin plate, such as a scratch-resistant (hard coat) and low-reflective cured film, an anti-glare film to prevent glare, and dirt. Alternatively, there are an antifouling film that makes it less noticeable, an antistatic film that prevents the adhesion of dust, a transparent conductive film required for a touch panel, and the like.

For example, Patent Document 1 discloses that a methacrylic resin plate is used as a substrate and a cured film is formed on at least one surface thereof and used as a display window protection plate for a liquid crystal 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, a cured film is formed on the methacrylic resin layer, and used for a liquid crystal display cover. It is disclosed.

As a method for forming the functional film described above, a PET film (polyethylene terephthalate film) in which a functional film is previously provided on the surface in addition to a method of curing an ultraviolet curable resin as described in Patent Documents 1 and 2 after being laminated on a substrate. There are known methods such as a method of bonding an adhesive with an adhesive or a pressure sensitive adhesive, a method of applying and dispersing a solution dispersed and dissolved in water or an organic solvent, and a method of drying after laminating a thermosetting resin on a substrate.

As a method for producing a resin plate, an injection molding method, an extrusion molding method and the like are known.
The liquid crystal display protective plate is installed 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 protective plate. The conventional liquid crystal display protective plate hardly changes the polarization of the light emitted from the liquid crystal display, which is polarized light. For this reason, when viewing the screen with polarized sunglasses, depending on the angle formed by the polarization axis of the emitted light and the transmission axis of the polarized sunglasses, the screen may be dark and the image may be difficult to see. In view of this, a liquid crystal display protective plate that can suppress a reduction in image visibility when a liquid crystal display screen is viewed through a polarizing filter such as polarized sunglasses has been studied.

For example, Patent Document 3 discloses that the in-plane retardation value is 85 to 300 nm. However, a resin plate used for a liquid crystal display protective plate must satisfy various required performances such as a retardation value, uniformity of appearance quality and thickness, shrinkage during heating, direction of warping and its size. For example, in the extrusion molding method, in order to satisfy the above required performance, the temperature of the resin being molded, the peripheral speed ratio of a plurality of cooling rolls, and the resin formed in the gap between the first cooling roll and the second cooling roll called a bank It is manufactured by adjusting various manufacturing conditions such as the size of the pool. However, in many cases, it is difficult to satisfy all of the required performance.

Also, the resin plate used for the liquid crystal display protective plate may be heated by being subjected to a drying process in order to adjust the state of warping or the like and sandwiched between curved plates for giving a warped shape.

JP 2004-299199 A JP 2006-103169 A JP 2010-085978 A

When the extruded resin plate is manufactured under the manufacturing conditions satisfying the in-plane retardation value of the resin plate and the other required performance described above, and then subjected to heat treatment, for example, to adjust the state of warping, the surface of the resin plate In some cases, the retardation value may be lowered. In addition, when an extruded resin plate is manufactured so that the in-plane retardation value of the resin plate does not decrease even when the heat treatment is performed, the above-described 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 liquid crystal display protective plate whose in-plane retardation value is controlled within a predetermined range.

As a result of studies to achieve the above object, the present inventors have found the present invention including the following aspects.

That is, this invention includes the following aspects. One aspect of a method for producing a liquid crystal display protective plate comprising a resin plate according to the present invention includes 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.
A step of sandwiching the thermoplastic resin laminate while forming a bank between the first cooling roll and the second cooling roll.
The process of cooling by winding the said thermoplastic resin laminated body around a said 3rd cooling roll, after winding around the said 2nd cooling roll.
Then, the step of forming the resin plate by taking the thermoplastic resin laminate with a take-off roll.
Then, the process of manufacturing a liquid crystal display protective board through the process of heating the said resin board at the temperature of 50 degreeC or more for 1 minute or more.
In addition, the in-plane retardation value of the liquid crystal display protective plate is 50 to 210 nm, and the in-plane retardation value of the liquid crystal display protective plate with respect to the in-plane retardation value of the resin plate before the heating step is performed. The reduction rate of the retardation value is 5% or more.

One aspect of the liquid crystal display protective plate described above can have an appropriate in-plane retardation when viewing the liquid crystal display through polarized sunglasses. In other words, the liquid crystal display protective plate of the present invention is a substrate for a liquid crystal display protective plate, even if it is a resin plate whose in-plane retardation value does not fall within a desired range, a specific heating step for the resin plate It has been found that it can be suitably used as a protective plate for a liquid crystal display by manufacturing with the above. As a result, it is possible to adjust the manufacturing conditions by giving priority to characteristics other than the retardation value.

Moreover, in one aspect of the method for producing a liquid crystal display protective plate according to the present invention, the reduction rate is preferably 15% or more.

Furthermore, in one aspect of the method for manufacturing a liquid crystal display protective plate according to the present invention, when the peripheral speed of the second cooling roll is V2 and the peripheral speed of the third cooling roll is V3, the value of V3 / V2 is 1. It is preferable that it is 000 or more. In addition, when the peripheral speed of the take-up roll is V4, the value of V4 / V2 is preferably 1.000 or more.

Hereinafter, for ease of explanation, the resin plate is manufactured by extruding a thermoplastic resin laminate, and unless otherwise specified, refers to the resin plate before the heating step. Moreover, a liquid crystal display protective plate is demonstrated as what added the heating process to the manufactured resin plate. More specifically, the resin plate is a substrate that has been extruded and before undergoing various processes, and the display protection plate is protected through some of various processes such as coating, bonding, and warping correction. It is processed into a plate. In at least one of the various steps, the substrate is heated. In other words, the display protective plate is a resin plate having an appropriate retardation value through the various steps described above.

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

It is a figure which shows the manufacturing method of the resin board by the co-extrusion concerning one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Embodiment 1
The resin plate used for the liquid crystal display protective plate of the present invention has a methacrylic resin layer laminated on at least one surface of a 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.
A resin plate is excellent in production efficiency by being manufactured by an extrusion method.
Hereinafter, the “resin plate” may be described as “extruded resin plate” as appropriate.

In one embodiment of the present invention, the methacrylic resin constituting the methacrylic resin layer contains a structural unit derived from a methacrylic acid ester.
The content of the structural unit derived from the methacrylic acid ester is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The content of the structural unit derived from the methacrylic acid ester may be 100% by mass. When the content of the structural unit derived from the methacrylic acid ester is within the above range, the transparency is good.

Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate and the like. Among these, it is preferable in terms of transparency that methyl methacrylate is contained in an amount of 50% by mass or more.

Moreover, the copolymer with the monomer which can be copolymerized with methyl methacrylate may be sufficient. Examples of monomers that can be copolymerized 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. Also, methacrylic acid monocyclic aliphatic hydrocarbon esters such as cyclohexyl methacrylate, cyclopentyl methacrylate, cycloheptyl methacrylate; 2-norbornyl methacrylate, 2-methyl-2-norbornyl methacrylate, 2-ethyl-2 -Norbornyl methacrylate, 2-isobornyl methacrylate, 2-methyl-2-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-methyl-2-adamantyl methacrylate, 2 Methacrylic acid polycyclic aliphatic hydrocarbon esters such as ethyl-2-adamantyl methacrylate, 1-adamantyl methacrylate, 2-fenkyl methacrylate, 2-methyl-2-fenkyl methacrylate or 2-ethyl-2-fenkyl methacrylate; Is mentioned.

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

If the methacrylic resin is a copolymer of methyl methacrylate and methyl acrylate, the transparency is excellent. A preferable monomer composition in this case is that the total amount of monomers is 100% by mass, and methyl methacrylate is preferably 80% by mass or more, more preferably 85% by mass or more, and 90% by mass or more. Even more preferably. Methyl methacrylate may be 100% by mass.

Methacrylic resin used in an embodiment of the present invention has a melt volume flow rate to be measured in accordance with IS0-1133 (MVR) is preferably 0.5 ~ 20 ^(cm 3/10 min, 230 ℃, 37.3N ). When the MVR is in this range, the stability of 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. Additives include antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes and pigments, light diffusing agents, organic dyes , Matting agents, impact resistance modifiers, phosphors and the like.

Is not particularly limited polycarbonate resin used in an embodiment of the present invention, melt volume flow rate to be measured in accordance with ISO-1133 (MVR) is preferably 1 ~ 20 ^(cm 3/10 min, 300 ° C., 11.8 N). When the MVR is in this range, the stability of extrusion molding is good.

The polycarbonate resin used in one embodiment of the present invention may contain a known additive in order to improve light resistance and the like. Additives include antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes and pigments, light diffusing agents, organic dyes , Matting agents, impact resistance modifiers, phosphors and the like.

The resin plate according to an embodiment of the present invention is preferable in that a methacrylic resin layer is laminated on both surfaces of a polycarbonate resin layer, so that it is excellent in scratch resistance and warpage due to humidity change is less likely to occur.

The thickness of the resin plate in one 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 be insufficient. If it is too thick, it tends to hinder weight reduction of liquid crystal display devices.

In the embodiment of the present invention, the thickness of the methacrylic resin layer of the resin plate is preferably 20 to 200 μm. Within this range, the balance between scratch resistance and impact resistance is excellent. More preferably, it is 25 to 150 μm, and further preferably 30 to 100 μm.

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 providing a cured film, functions such as scratch resistance and low reflectivity can be imparted.

For example, the thickness of the scratch-resistant (hard coat property) cured film is preferably 2 to 30 μm, more preferably 3 to 10 μm. If it is too thin, the surface hardness will be insufficient, and if it is too thick, cracks may occur due to bending during the production process.

Also, for example, the thickness of the low reflective cured coating is preferably 80 to 200 nm, more preferably 100 to 150 nm. This is because the low reflection performance is insufficient if it is too thin or too thick.

The resin plate in one embodiment of the present invention is manufactured by coextrusion. The polycarbonate resin and the methacrylic resin are heated and melted, extruded from a wide-shaped discharge port called a T die, and sandwiched between a pair of rolls including a first cooling roll and a second cooling roll to form a sheet-like thermoplastic resin laminate. It is formed. Thereafter, the thermoplastic resin laminate is further wound around the second cooling roll and then cooled by winding around the third cooling roll. Further, the thermoplastic resin laminate may be further cooled by a further cooling roll. Then, a resin plate is formed by taking up the thermoplastic resin laminate with a take-up roll. In such a process, the resin plate is manufactured by 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.

The manufactured resin plate is further subjected to a heating process to manufacture a liquid crystal display protection 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 one embodiment. The resin extruded from the T die 11 is sandwiched between a pair of rolls including a first cooling roll 12 and a second cooling roll 13 to form 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 composed of a pair of rolls, whereby the resin plate 16 is formed. The present invention is not limited to this form.

The T die 11 can be either a single manifold type or a multi-manifold type, but the multi-manifold type is preferable because the thickness accuracy of each layer is excellent.
As the cooling roll, both a metal rigid roll and a metal elastic roll can be used.

Retardation is the phase difference between the light in the molecular main chain direction and the light perpendicular to it. In general, a polymer can be formed in an arbitrary shape by thermoforming. However, it is known that a certain stress is generated in the heating and cooling processes, and the molecules are oriented to cause retardation. Therefore, in order to control retardation, it is necessary to control molecular orientation. The orientation of the molecules is generated by, for example, stress at the time of molding near the glass transition temperature of the polymer.

In extrusion molding, the in-plane retardation value, appearance quality and thickness uniformity, warpage direction and size of the resin plate are controlled by adjusting various manufacturing conditions. In the following, as the elements related to the control of the manufacturing conditions, the influence of the bank, the influence of the peripheral speed ratio, the influence of the thickness of the resin plate, and the heating process will be described separately. For ease of explanation, the configuration shown in FIG. 1 is used as appropriate.

* About the influence of a bank A bank is a resin pool formed in 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 increased as the bank amount increased.

The reason is that when the molten resin flows from the position where the resin pool is generated to the minimum gap between the first cooling roll 12 and the second cooling roll 13, molecules are aligned due to a difference in flow velocity inside the resin as the resin cools. It seems to do.

The bank becomes larger and can be adjusted by increasing the amount of resin supplied to the roll or decreasing the roll speed. In the examples described later, the bank amount was adjusted by changing the resin supply amount, and the magnitude of the amount was visually evaluated.

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

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

The reason for this is that when the resin temperature when the resin contacts the third cooling roll 14 is near the glass transition temperature of the polycarbonate, the peripheral speed ratio of the third cooling roll 14 is large and the thermoplastic resin laminate has a large tensile stress. This is probably because the molecules of the resin are oriented.

And as a result of evaluating the relationship between the peripheral speed ratio of the take-up roll 15 to the second cooling roll 13 and the in-plane retardation value, it was found that the in-plane retardation value increased as the peripheral speed ratio increased.

The reason is that when the resin temperature when the resin is peeled from the third cooling roll 14 is in the range of about + 5 ° C. to −40 ° C. from the vicinity of the glass transition temperature of the polycarbonate, the peripheral speed ratio of the take-up roll 15 is larger. This is probably because the resin molecules are oriented when a large tensile stress is applied.

Further, the peripheral speed ratio between the second cooling roll 13 and the take-up roll 15 is preferably 0.98 or more, and more preferably 1.000 or more. The reason is that when the peripheral speed ratio between the second cooling roll 13 and the take-off roll 15 is less than 0.98, the thermoplastic resin laminate is insufficient in tension and is in contact with the third cooling roll 14. This is because there is a possibility that the body cannot maintain a close contact state and peels off from the roll, so that a beautiful surface state cannot be maintained.

Furthermore, the temperature for peeling from the third cooling roll 14 is preferably in the range of + 5 ° C. to −40 ° C. from the vicinity of the glass transition temperature of polycarbonate. The reason is that a clean surface shape cannot be obtained if the temperature is too high or too low near the glass transition temperature.

Next, the extent to which the in-plane retardation value when the extruded resin plate was heated was examined.
It was found that when the bank amount was gradually increased while the peripheral speed ratio was constant, the in-plane retardation value gradually increased, but the reduction rate of the in-plane retardation value after heating gradually decreased.

When the peripheral speed ratio between the second cooling roll 13 and the third cooling roll 14 is gradually increased while the bank amount is constant, the in-plane retardation value gradually increases, and the in-plane retardation value decreases during heating. It was found that the amount gradually increased.

In addition, when the peripheral speed ratio between the second cooling roll 13 and the take-up roll 15 is gradually increased with the bank amount being constant, the in-plane retardation value gradually increases, but the in-plane retardation value after heating decreases. The rate was found to be very large.

Hereinafter, for ease of explanation, the peripheral speed of the second cooling roll is V2, the peripheral speed of the third cooling roll is V3, the peripheral speed of the take-up roll is V4, and the third cooling roll and the second cooling roll The peripheral speed ratio may be described as (V3 / V2), and the peripheral speed ratio between the take-up roll and the second cooling roll may be described as (V4 / V2).

Next, as a result of evaluating the influence on the in-plane retardation value when the metal cooling roll or the metal elastic roll is used as the second cooling roll 13, the in-plane retardation value is smaller when the metal elastic roll is used. I understood that. The reason seems to be that the metal elastic roll generally has a small bank amount and the molecular orientation by the bank forming is small. Thus, it has been found that the peripheral speed ratio between the second cooling roll 13 and the third cooling roll 14 needs to be adjusted in order to control proper in-plane retardation with the metal elastic roll.

* Influence of thickness Thickness control in the width direction orthogonal to the extrusion direction in extrusion molding is generally performed by the gap between the first cooling roll 12 and the second cooling roll 13, the extrusion amount associated with the resin supply amount, and the second cooling. It is controlled by the peripheral speed of the roll and the bank amount.

Here, generally, the larger the bank amount, the greater the pressure applied to the first cooling roll 12 and the second cooling roll 13, and the cooling roll is pushed and bent. Therefore, as the bank amount increases, the thickness distribution in the width direction perpendicular to the flow direction tends to be thick near the center and thin at both ends in a drum shape.

As a technique for flattening the thickness distribution in the width direction, for example, the bank amount at both ends in the width direction may be made larger than the bank amount near the center. In that case, the retardation values at both ends in the width direction are increased.
Therefore, in order to control the variation of the retardation value in the width direction and the decrease rate of the retardation value to an appropriate value, it is necessary to optimize the thickness distribution in the width direction.

Therefore, the thickness ratio (TC / TS) between the average thickness (TS) at both ends within the effective range in the width direction orthogonal to the extrusion direction and the average thickness (TC) near the center exceeds 1.0. It has been found that it is preferable to set it to 1.05 or less. The average thickness (TC) near the center may be calculated at the center 100 mm in the width direction orthogonal to the extrusion direction of the resin plate 16, and the average thickness (TS) at both ends is one end in the width direction orthogonal to the extrusion direction. The average thickness for 100 mm from the position 100 mm away from the position to the position 200 mm away is the thickness of one end, and the average thickness for 100 mm from the position 100 mm away from the other end to the position 200 mm away Is the thickness of the other end, and the average thickness for each end of 100 mm (average thickness of 200 mm in total) may be calculated.

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

As a result of measuring the location selected in such a procedure, the in-plane retardation value after heating is 50 to 210 nm, and the reduction rate of the in-plane retardation value before and after heating is 5% or more. In this case, the obtained resin plate is preferable because the effects of the present application are exhibited. In addition, the reduction rate of the in-plane retardation value before and after heating is more preferably 15% or more. Here, the rate of decrease in the in-plane retardation value before and after heating is the rate of decrease in the in-plane retardation value of the liquid crystal display protection plate relative to the in-plane retardation value of the resin plate before the heating step. be able to.

When the thickness ratio (TC / TS) exceeds 1.05, the bank amount becomes too large and may not be stably manufactured. When the thickness ratio is 1.0 or less, the bank amount is too small. Therefore, the in-plane retardation value is small.

Since the influence of the thickness as described above was discovered, in the manufacturing process of the extruded resin plate, the thickness ratio of the manufactured extruded resin plate is set to be larger than 1.00 and within a numerical range of 1.05 or less. It is preferable to control the formation (bank amount). If the thickness control 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, it is preferable to control the thickness of the resin plate in order to stably produce a good product.

The resin plate (extruded resin plate) according to an embodiment of the present invention has a reduction rate of the in-plane retardation value in the heating process of 5% or more. In order to adjust to less than 5%, for example, it is conceivable to increase the bank amount. However, if the bank amount is too large, there may be a problem that the retardation value of the resin plate becomes too large. Further, for example, it is conceivable to reduce the peripheral speed ratio V3 / V2 or V4 / V2 of the roll, but if it is too small, the cooling roll and the molten resin do not release smoothly, and a fine surface called a release mark There may be a problem that unevenness occurs and the surface property of the resin plate is inferior.

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

The reduction rate of the in-plane retardation value in the heating process is preferably 90% or less. If it is larger than this, the shrinkage rate when the resin plate is heated tends to increase. For example, the heating of the process of laminating and curing a photocurable resin may cause wrinkles in the laminated resin layer, or before and after the heating. There may be a problem that the dimensional change becomes too large and the handling ease such as transporting and fixing the plate is poor. For example, it is conceivable to reduce the bank amount. However, if it is too small, the bank may not be temporarily formed due to slight temperature unevenness of the bank, etc., and the first cooling roll or the second cooling roll does not adhere to the molten resin, and the surface property of the resin plate is There may be a problem that it is inferior or thickness unevenness becomes large. Further, the reduction rate of the retardation value is more preferably 85% or less, and still more preferably 80% or less.

* About a heating process The heating process in one Embodiment of this invention heats a resin board 50 degreeC or more and 1 minute or more. As a heating process, the following processes are included, for example.
A step of allowing the resin plate to stand for 1 minute or longer in an oven heated to 50 ° C. or higher in order to dry the liquid applied to the surface of the resin plate.
A step of allowing the resin plate to stand for 1 minute or longer in an oven heated to 50 ° C. or higher in order to thermoset the thermosetting resin laminated on the surface of the resin plate.
A step of adjusting the warp shape of the resin plate by sandwiching the resin plate between a pair of metal plates that are heated to 50 ° C. or more and curved in the same direction.
An annealing process in which the resin plate is sandwiched between a pair of flat metal plates heated to 50 ° C. or higher in order to reduce molding distortion of the resin plate.
In order to reduce molding distortion of the resin plate, a resin plate annealing step in which one side of the resin plate is suspended by being held by a jig and left in a heating furnace heated to 50 ° C. or higher for 1 minute or longer.
In order to cure the photo-curing resin laminated on the resin plate surface, in the process of irradiating light with a xenon lamp or the like, by heating with infrared rays contained in the light emitted from the lamp, or by heat of reaction of the photo-curing resin, The process in which the time for the resin plate surface to be 50 ° C. or higher is 1 minute or longer.

The above-described process is an example of a process that is performed to process a resin plate into a display protection plate. Even if it is a process other than the above-described process, as long as it is a process of heating at 50 ° C. or more and 1 minute or more, one embodiment It is included in the heating process.

In the manufacturing method of the resin board of one Embodiment, a heating process is included. In the heating step, for example, one or more of the steps described above are performed.
In addition, the length of the heating time is determined according to each process mentioned above, and it is preferable to heat for the time which the effect of each process produces.

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 in the visible light range becomes large when viewed through a polarizing filter such as polarized sunglasses. Is difficult to see. On the other hand, when the thickness is less than 50 nm, the transmittance at all wavelengths in the visible light range is greatly reduced, and a black image is obtained, which is difficult to visually recognize. Within 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. In particular, when the in-plane retardation value is 60 nm to 200 nm, the balance between brightness and color is good and the visibility is good.

As described above, one aspect of the liquid crystal display protective plate of the present invention is a resin plate having an in-plane retardation value that is not necessarily appropriate as a substrate for a liquid crystal display protective plate. On the other hand, when manufactured through a specific heating process, it discovered that it could be used conveniently as a liquid crystal display protective plate.

According to the method for manufacturing a protective plate for a liquid crystal display according to one embodiment, the resin plate has a retardation value in an appropriate range by performing heat treatment even if the in-plane retardation value is larger than a predetermined range. A display can be provided. Therefore, the manufacturing method of the liquid crystal display and the manufactured liquid crystal display protective plate of one embodiment give priority to characteristics other than the retardation value, such as appearance quality, uniformity of thickness, direction of warping and its size, and other manufacturing conditions. Since it can be adjusted, it excels in various characteristics and productivity.

EXAMPLES Hereinafter, an Example is shown and this invention is demonstrated in detail. However, this invention is not limited at all by this Example.
The physical properties of the resin and the resin plate were measured by the following method.

[MVR]
A melt indexer (“TAKARA L241-153”, manufactured by Techno Seven Co., Ltd.) was used, and measurement was performed according to ISO-1133.
[Methacrylic resin]
Produced by Kuraray Co., Ltd. "Parapet (registered trademark) HR" (MVR: 2.0cm ^3/10 minutes) was prepared as methacrylic resin.
[Polycarbonate resin]
Sumitomo scan Tyrone polycarbonate Co., Ltd. "SD polycarbonate (registered trademark) PCX" (MVR: ^8cm 3/10 min., And a glass transition temperature: 151 ℃) was prepared as a polycarbonate resin.

[Measurement of thickness of resin plate and evaluation of thickness unevenness in width direction]
The average thickness of the center 100 mm in the width direction orthogonal to the extrusion direction of the resin plate is the thickness (TC) of the center, and the average thickness for 100 mm from the position 100 mm away from one end to the position 200 mm away. Is the thickness of one end, the average thickness of 100 mm from the position 100 mm away from the other end to the position 200 mm away is the thickness of the other end, and the average of the average thickness of each 100 mm at both ends The value was the end thickness (TS). The thickness ratio (TC / TS) between the end thickness (TS) and the center thickness (TC) was used 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 liquid crystal display protective plate was cut with a running saw to prepare a 100 mm square. The retardation value was measured with WPA-100 (-L) manufactured by Photonic Lattice Co., Ltd. after leaving the test piece in an environment of 25 ° C. ± 3 ° C. for 10 minutes or more. The measurement position was measured near the center of the test piece.
Further, the reduction rate of the retardation value was a value obtained by the following formula.
(Rate of decrease in retardation value)
= {(Retardation value of resin plate)-(Retardation value of liquid crystal display protective plate)} / (Retardation value of resin plate) × 100 (%)

[Visual evaluation method when wearing polarized sunglasses]
The test piece of the liquid crystal display protective plate was cut with a running saw to produce a 100 mm square.
Next, an image was displayed by placing a liquid crystal display device at a position 35 cm away from the eyes. And the test piece concerning an Example and a comparative example was arrange | positioned in parallel with the screen of the display apparatus in the position 30 cm away from the eyes between the liquid crystal display device and eyes.

First, without wearing polarized sunglasses, the image was visually observed through the thickness direction of the test piece.
Next, wearing polarized sunglasses, the neck was tilted left and right with the face facing the image, and the image was visually observed in the same manner as described above.
○: The image appearance did not change significantly depending on whether or not the polarized sunglasses were worn, and the image could be visually recognized without any problem.
X: The image was viewed in a darker image when the neck was tilted at a certain angle when the sunglasses were worn, or when the sunglasses were worn, dark coloring was seen and the image was difficult to see.

[Appearance evaluation method of resin plate]
The surface of the resin plate was visually evaluated. The evaluation was made by observing an image of an indoor illumination light source reflected on the surface of the resin plate and determining whether the image was fluctuating or not.
Placement of resin plate: Placed on the methacrylic resin side surface of the resin plate in parallel with the floor surface. Illumination light source: Straight tube type 40W white fluorescent lamp illumination: Placement about 2m upward from the resin plate, about horizontal direction Illumination angle of 2 m away: Direction that is about 45 ° above the surface of the resin plate Direction of illumination: Direction that the longitudinal direction of the fluorescent lamp moving to the surface of the resin plate and the direction of extrusion of the resin plate are about 45 ° ○: Good without fluctuations.
Δ: Slight fluctuation but not noticeable.
X: There is fluctuation and it stands out.

[Example 1]
(Production method of resin plate)
A methacrylic resin was melted with a 150 mmφ single screw extruder (manufactured by Toshiba Machine Co., Ltd.) and a polycarbonate resin was melted with a 150 mmφ single screw extruder (manufactured by Toshiba Machine Co., Ltd.). Three layers were laminated in the order of methacrylic resin, polycarbonate resin, and methacrylic resin. The laminated resin (thermoplastic resin laminate) was sandwiched between a first cooling roll 12 and a second cooling roll 13 as shown in FIG. 1 to produce a resin plate. Here, all the 1st cooling roll 12, the 2nd cooling roll 13, and the 3rd cooling roll 14 were made into the metal rigid roll.

Further, the bank amount is kept small, the peripheral speed ratio (V3 / V2) of the second cooling roll 13 and the third cooling roll 14 is adjusted to 1.000, and the peripheral speed of the second cooling roll 13 and the take-up roll 15 is adjusted. The ratio (V4 / V2) was adjusted to 1.011. Moreover, the result of having measured the temperature of the whole thermoplastic resin laminated body with the infrared radiation thermometer in the position which peels from the 3rd cooling roll 14 was 130 degreeC. The thickness of each layer was 75 μm for one methacrylic resin layer, 850 μm for the polycarbonate resin layer, and 75 μm for the other methacrylic resin layer. The thickness of the entire laminate was molded and cooled so that the average thickness (TC) near the center was 1 mm. The width of the obtained resin plate was about 1500 mm.

The obtained resin plate was cut into an extrusion direction of 1000 mm, and 100 mm at both ends in the width direction were cut and removed to obtain a rectangular resin plate of approximately 1000 mm × 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 then taken out, and the rectangular resin plate after the heat treatment was used as a liquid crystal display protective plate. In the oven, the rectangular resin plate was hung with a string with the short side up. The string was tied to two clips that were respectively fixed at two ends of the position where the upper short side was equally divided into three. Moreover, the string was fixed to the hanging tool so as to be vertical.
Table 1 shows the manufacturing conditions and the evaluation results of the obtained resin plate and liquid crystal display protective plate.

[Examples 2 to 5]
The type of the second cooling roll, the bank amount, the peripheral speed ratio (V3 / V2) between the second cooling roll 13 and the third cooling roll 14, and the peripheral speed ratio (V4 / V2) between the second cooling roll 13 and the take-up roll 15 A resin plate and a liquid crystal display protective plate were produced in the same manner as in Example 1 except that the change was made according to Table 1. Table 1 shows the evaluation results of the obtained resin plate and liquid crystal display protective plate.

[Comparative Examples 1 to 4]
The type of the second cooling roll, the bank amount, the peripheral speed ratio (V3 / V2) between the second cooling roll 13 and the third cooling roll 14, and the peripheral speed ratio (V4 / V2) between the second cooling roll 13 and the take-up roll 15 A resin plate and a liquid crystal display protective plate were produced in the same manner as in Example 1 except that the change was made according to Table 1. Table 1 shows the evaluation results of the obtained resin plate and liquid crystal display protective plate.

From the comparison of the examples in Table 1 and the comparative example, the liquid crystal display protective plate of the present invention has a proper retardation value as a protective plate even if the retardation value decrease rate relative to the resin plate is large. Excellent image visibility when worn.

Particularly in Examples 1, 3 and 4, the retardation value of the resin plate is larger than the appropriate retardation value range. However, through the heating process, it was possible to produce a resin plate having excellent image visibility with the polarized sunglasses attached.

In Comparative Example 1, the rate of decrease in retardation value is 0%, and a resin plate that satisfies the retardation value before and after heating is manufactured. This shows an example of producing a resin plate that satisfies the retardation value before and after the heat treatment. The comparative example 1 is excellent in the visibility of the image in the state where the polarized sunglasses are worn. On the other hand, the value of TC / TS is 1.05, and it can be seen that the thickness unevenness in the width direction is large. In addition, the fluctuation of the image of the illumination light source is conspicuous and the appearance is not excellent. Therefore, it is not sufficient as a protective plate for a liquid crystal display, and shows the difficulty of adjusting other requirements while satisfying the requirement of retardation value.

The liquid crystal display protective plate of the present invention is suitable as a liquid crystal display protective plate used for, for example, an in-vehicle display device, a mobile phone, a smartphone, a personal computer, a television, and the like.

Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit 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 incorporated herein.

11 T die 12 1st cooling roll 13 2nd cooling roll 14 3rd cooling roll 15 Take-off roll 16 Resin plate

Claims

A method of manufacturing a liquid crystal display protective plate made of a resin plate,
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 in a molten state,
While sandwiching the thermoplastic resin laminate while forming a bank between the first cooling roll and the second cooling roll,
After the thermoplastic resin laminate is wound around the second cooling roll, it is cooled by winding around the third cooling roll,
Thereafter, the resin plate is formed by taking the thermoplastic resin laminate with a take-off roll,
Thereafter, the liquid crystal display protective plate is manufactured through a process of heating the resin plate at a temperature of 50 ° C. or more for 1 minute or more,
The in-plane retardation value of the liquid crystal display protective plate is 50 to 210 nm,
A method for producing a liquid crystal display protective plate, wherein a reduction rate of the in-plane retardation value of the liquid crystal display protective plate with respect to the in-plane retardation value of the resin plate before undergoing the heating step is 5% or more.
The method for manufacturing a liquid crystal display protective plate according to claim 1, wherein the rate of decrease is 15% or more.
3. The liquid crystal display according to claim 1, wherein the value of V3 / V2 is 1.000 or more, where V2 is the peripheral speed of the second cooling roll and V3 is the peripheral speed of the third cooling roll. A manufacturing method of a protection plate.
The value of V4 / V2 is 1.000 or more, where the peripheral speed of the second cooling roll is V2, and the peripheral speed of the take-up roll is V4. The manufacturing method of the liquid crystal display protective plate of description.