JP2014167658A - Image display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device showing excellent visibility and comprising a transparent resin layer having excellent adhesion property to an image display panel and to provide a method for easily manufacturing the image display device with excellent productivity.SOLUTION: A manufacturing method comprises the steps of: placing a transparent resin sheet on either one panel of a display panel and a protective panel; placing UV curing liquid material on the transparent resin sheet; placing an image display panel or the protective panel to be the other panel on the UV curing liquid material; and curing the UV curing liquid material. According to the manufacturing method, an image display device where the transparent resin layer is disposed in close contact between the image display panel and the protective panel disposed in front of the image display panel is manufactured.

Description

  The present invention relates to an image display device and a manufacturing method thereof. Specifically, mobile display devices such as mobile phones, digital cameras and game consoles, mobile navigation device display devices such as car navigation televisions and various operation display panels, and home appliance display devices such as personal computers and flat-screen TVs. The present invention relates to a versatile image display apparatus and a manufacturing method thereof.

  A liquid crystal display device is illustrated as a typical image display device. A liquid crystal display device generally has a configuration including a liquid crystal panel and a backlight unit. As shown in FIG. 1A, the liquid crystal panel 10 includes a liquid crystal cell 12 and optical films such as polarizing plates 14a and 14b attached to both outer surfaces thereof. As shown in FIG. 1B, the liquid crystal cell 12 has a thickness of about several microns between a pair of glass substrates 16a and 16b having a thickness of about 1 mm, on which a transparent electrode, a pixel pattern, and the like are previously formed. The liquid crystal 18b is filled through the spacer 18a and sealed. A display device using a liquid crystal panel configured as described above is a thin display component that is easily damaged. Therefore, in particular, in applications such as mobile phones, game machines, digital cameras, and in-vehicle devices, a transparent protective plate is generally provided on the front surface of the liquid crystal panel via a certain gap.

  An example of a conventional liquid crystal display device having a protective plate on the front is shown in FIG. The liquid crystal display device shown in FIG. 2 includes a liquid crystal panel 10, a protective panel 30 disposed on the upper surface (viewing side) of the liquid crystal panel 10 via a gap 20, a reflector disposed on the lower surface of the liquid crystal panel 10, The backlight unit 40 includes a light guide plate and a diffusion sheet. The protective panel 30 is a transparent plate, and in general, transparent plastic such as glass or acrylic resin and polycarbonate resin is used. The air gap 20 is provided so that the influence of mechanical pressure applied from the outside of the apparatus does not directly affect the liquid crystal panel 10, and is a device that is assumed to be portable such as a mobile phone, a game machine, and a digital still camera. This is a configuration particularly required in the applied liquid crystal display device.

  In general, the refractive index of the transparent viewing portion of the protective plate is usually 1.4 to 1.6, and the refractive index of the transparent plastic film that is attached to the viewing side of the liquid crystal display cell and constitutes the outermost layer of the polarizing plate. Is usually 1.5 to 1.6. On the other hand, the gap is composed of air (air layer) and its refractive index is 1. When the protective plate is provided through the air layer in this way, reflection loss due to Fresnel reflection occurs at each interface, and the display characteristics tend to be greatly deteriorated. Therefore, in applications that require high image quality, such as televisions and monitors, it is not possible to provide a protective plate that degrades the display characteristics of the liquid crystal display device, and if the screen is pressed with a finger, the picture is distorted and commercialized. The current situation is.

  Under such circumstances, for the purpose of improving the visibility and strength of a liquid crystal display device, a structure in which a void portion is filled with a transparent material and a method for manufacturing such a device have been studied. However, filling the gap with a transparent material improves the display characteristics due to reflection loss, but the visibility is reduced due to entrainment of bubbles when the transparent material is interposed between the liquid crystal panel and the protective plate. Further development is being considered.

  In Patent Document 1, a space surrounded by a spacer or a molding frame is provided between an image display panel such as a liquid crystal panel and a protective panel, a liquid resin is supplied to the space, and then the liquid resin is cured, It is proposed to suppress entrainment of bubbles. Moreover, in patent document 2, the viscosity which does not swell and melt | dissolve the said sheet | seat between the transparent resin sheet and one or both of a liquid crystal display panel or a transparent protective plate through the transparent resin sheet which consists of a plasticizer containing polymer. A method has been proposed in which a viewing side of a liquid crystal display panel and a transparent protective plate are brought into close contact with a volatile liquid of 10 cP (0.01 Pa · s) or less.

JP-A-6-337411 JP-A-9-197387

  However, in the method described in Patent Document 1, even if the entrainment of bubbles can be solved, it takes a long time to supply the liquid resin precisely, and it is necessary to treat the resin that has exuded from the molding frame. There are problems to be solved, such as dents being easily generated by curing shrinkage (easily inferior in flatness). Moreover, although the method described in Patent Document 2 is excellent in workability and flatness, bubbles and interfacial delamination are likely to occur with the dissipation of volatile liquid that has penetrated near the interface of the transparent resin sheet immediately after bonding. Furthermore, there are problems to be solved, such as bubbles and interfacial detachment easily occurring due to changes in humidity and temperature of the use environment. Accordingly, the present invention solves such problems, provides an image display device provided with a transparent resin layer exhibiting excellent visibility and excellent adhesion to a panel, and such an image display device. An object of the present invention is to provide a method for easily producing a product with good productivity.

An image display device manufacturing method according to the present invention is directed to an image display device in which a transparent resin is closely disposed between an image display panel and a protective panel installed in front of the image display panel. A step of placing a transparent resin sheet on one of the display panel and the protective panel, a step of placing an ultraviolet curable liquid on the transparent resin sheet, and an upper surface of the ultraviolet curable liquid The method further comprises a step of placing the image display panel or the protective panel to be the other panel, and a step of curing the ultraviolet curable liquid material.

  Here, in the said manufacturing method, it is preferable that the said ultraviolet curable liquid is compatible with the said transparent resin sheet while swelling the said transparent resin sheet.

  Prior to the step of curing the ultraviolet curable liquid material, the method further includes the step of causing the ultraviolet curable liquid material to penetrate into the transparent resin sheet and closely attaching the other panel of the image display panel or the protective panel to the transparent resin sheet. It is preferable.

  Either one of the image display panel and the protection panel may include a frame member having an outer shape surrounding the transparent resin sheet on the surface thereof and a plurality of voids through which air can pass. preferable.

  The ultraviolet curable liquid has a viscosity of 10,000 cP (10 Pa · s) or less at 25 ° C., and contains a non-polymerizable volatile component having a boiling point of less than 120 ° C. present in the ultraviolet curable liquid. The amount is preferably 5% or less.

  In the step of placing the transparent resin sheet, the ultraviolet curable liquid material is dropped on one of the image display panel and the protective panel, and the transparent resin sheet is overlaid thereon, It is preferable to include developing the layer of the ultraviolet curable liquid at the interface between the transparent resin sheet and the panel.

  It is preferable that the image display device obtained by the manufacturing method described above does not include bubbles having a maximum diagonal length of 20 μm or more in the viewing portion.

  In the image display device according to the present invention, a transparent resin layer is disposed in close contact between an image display panel and a protective panel installed on the front surface of the image display panel. The resin sheet is swelled and has a cured product of an ultraviolet curable liquid compatible with the resin sheet, and bubbles having a maximum diagonal length of 20 μm or more are not present in the visual recognition part.

Here, it is preferable that the transparent resin layer is surrounded by a frame material having a plurality of voids through which air can pass, and the ultraviolet curable liquid is impregnated in the voids of the frame material and further cured. .
The ultraviolet curable liquid has a viscosity of 10,000 cP (10 Pa · s) or less at 25 ° C., and contains a non-polymerizable volatile component having a boiling point of less than 120 ° C. present in the ultraviolet curable liquid. The amount is preferably 5% or less.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the image display apparatus which is excellent in visibility, an optical characteristic, and durability. In particular, the transparent resin layer is configured by using a transparent resin sheet and an ultraviolet curable liquid in combination, and by appropriately handling, the generation of bubbles having a maximum diagonal length of 20 μm or more in the visual recognition part is controlled, and the residual stress is reduced. It is possible to relax and reduce the occurrence of distortion. Further, by reducing the remaining volatile components, the generation of bubbles due to the gas due to the volatile components and the peeling due to the decrease in adhesive force are improved, and an image display device with excellent long-term reliability can be realized. . In addition, according to the method for manufacturing an image display device according to the present invention, by suppressing the generation of bubbles that can be visually identified, it is not necessary to perform defoaming treatment such as pressurization or decompression by an autoclave, and is excellent in visibility. In addition, it is possible to easily manufacture an image display device having a protective panel integrated structure. Furthermore, if bubbles or foreign substances are discovered by inspection before the completion of ultraviolet irradiation, repair can be easily performed before the ultraviolet curable liquid is completely cured, so that the image display device can be operated at a very high rate. Can be produced by distillation.

It is a figure explaining the liquid crystal panel applied to a liquid crystal display device, (a) is typical sectional drawing which shows the structure of a liquid crystal panel, (b) is typical sectional drawing which shows the liquid crystal display cell part in (a). FIG. It is typical sectional drawing which shows an example of the structure of the conventional liquid crystal display device with a protective plate. It is typical sectional drawing which shows an example of the structure of the image display apparatus by this invention. BRIEF DESCRIPTION OF THE DRAWINGS The outline of the manufacturing method of the image display apparatus by this invention is demonstrated, (a)-(d) is typical sectional drawing corresponding to each process. It is a front view explaining one Embodiment of the manufacturing method of the image display apparatus by this invention.

Details of the present invention will be described below.
An example of an image display device according to the present invention is shown in FIG. As shown in FIG. 3, in the image display device according to the present invention, the transparent resin layer 22 is closely disposed between the image display panel 10 ′ and the protective panel 30 installed on the front surface of the image display panel 10 ′. The transparent resin layer 22 has a structure, and includes a transparent resin sheet and a cured product of an ultraviolet curable liquid, and is identified by visual observation and reduces the visibility of the device, more specifically, It is characterized in that bubbles having an angular length of 20 μm or more are not included in the visual recognition part. The transparent resin layer 22 can be formed by providing a transparent resin sheet between the image display panel 10 ′ and the protective panel 30 via an ultraviolet curable liquid, but the ultraviolet curable liquid is a transparent resin. It is preferable that the sheet is swollen and compatible with the resin sheet. By using such an ultraviolet curable liquid, it is possible to form a transparent layer by absorbing and integrating the liquid into the transparent resin sheet and further curing by irradiation with ultraviolet rays.

  The terms “swelling” and “compatible” used in the present invention are the low molecular weight liquid components (various additives such as monomer compounds and plasticizers) in the liquid material, respectively, and the resin of the transparent resin sheet. It shows the property of being absorbed with affinity. More specifically, “swelling” means that a part or all of the medium is absorbed by the transparent resin sheet while the medium high molecular weight component (oligomer and polymer compound) in the liquid is dissolved in the low molecular weight liquid component. Means a state. “Compatible” means a state in which the components absorbed in the sheet are maintained after being uniformly finely dispersed in the transparent resin sheet. These states can be confirmed by visually observing changes in the appearance of the transparent resin sheet. Although liquid substances can be distinguished from resin sheets at the initial stage of observation, they penetrate into the sheet and become integrated with the sheet as they are absorbed. And when it is in a “swelled” state, it is accompanied by a change in appearance such as wetting of the sheet surface and expression of stickiness. Furthermore, the state in which the liquid material and the transparent resin sheet are “compatible” can be easily confirmed visually because they form a transparent layer. Even if the liquid material swells the transparent resin sheet, if they are not compatible, macroscopic phase separation occurs, resulting in a cloudy appearance, so that it can be easily distinguished from the previous state. it can. Thus, the state of “swelling” and “compatibility” can be easily confirmed from the appearance of the sheet, but more strictly speaking, as will be described later, a transparent resin layer having a total light transmittance of 50% or more is used. It is preferably sufficient to form.

  When a specific ultraviolet curable liquid is used as described above, when a transparent resin sheet is bonded to the panel as a single unit, or when a sheet is bonded via a volatile liquid that does not swell or compatible with the sheet In comparison, the stress and strain that tends to remain on the sheet are reduced by phenomena such as swelling of the liquid material and compatibility after curing. Compared to the case where a transparent resin layer is formed with a liquid material alone, the volume change accompanying the curing shrinkage of the liquid material is so small that it hardly becomes a problem, so there is no obstacle in structural design and almost no residual stress remains. . Furthermore, since the transparent resin layer in the image display device of the present invention has a low residual amount of volatile components, no bubbles are generated later due to the volatile components, and the adhesive strength is reduced and the transparent resin layer is reduced. Does not peel from the panel. As described above, according to the present invention, it is possible to prevent bubbles that can be visually identified with a maximum diagonal length of 20 μm or more from occurring in the visual recognition portion, and to realize an image display device that is excellent in optical characteristics, mechanical characteristics, and long-term reliability. can do.

  In the image display device according to the present invention, the total light transmittance of the transparent resin layer is 50% or more, preferably 75% or more. If the transmittance is less than 50%, the brightness and contrast of the image display panel may be impaired. The phase difference due to birefringence of the transparent resin layer is preferably 50 nm or less even when the transparent resin layer substantially serves also as a color tone fine adjustment function by phase difference control. If the phase difference exceeds 50 nm, the influence on a polarizing optical system such as a liquid crystal panel is increased, which is not preferable. The thickness of the transparent resin layer can be freely set according to the specifications of the image display device (for example, the size of the image display unit, the thickness of other members, etc.). For example, a preferable range is 0.1 to 10 mm. If the thickness is less than 0.1 mm, it tends to be difficult to absorb external stress, and if it exceeds 10 mm, the transparency and hue tend to decrease. Moreover, it is preferable from the point of visibility that the visual recognition part has a uniform thickness within ± 15%. The refractive index of the transparent resin layer is preferably 1.4 to 1.6 from the viewpoint of reducing the difference in refractive index between the adjacent panel surface and the protective panel surface and reducing the reflected light. Particularly preferred is 1.55.

The transparent resin sheet used for forming the transparent resin layer described above preferably has a total light transmittance of 50% or more. When the total light transmittance of the transparent resin sheet is less than 50%, the contrast tends to decrease or the visibility tends to decrease. The birefringence of the transparent resin sheet is preferably a phase difference of 30 nm or less and more preferably 10 nm or less in order to maintain an excellent hue of an image display panel such as a liquid crystal panel. If the birefringence is large, color unevenness is likely to occur when the image display panel is turned on. Furthermore, it is preferable that the storage elastic modulus in 25 degreeC of a transparent resin sheet is 10 < ⁴ > -10 < ⁷ > Pa. If the elastic modulus is too low, the protective panel cannot be supported, and the protective panel is easily broken when an impact is applied. On the other hand, if the elastic modulus is too high, the image display panel can be easily broken without being able to absorb the impact. The refractive index of the transparent resin sheet is preferably 1.4 to 1.6, and particularly preferably 1.45 to 1.55 from the viewpoint of reducing reflected light. Although the thickness of a transparent resin sheet can be freely set according to the specification of an image display apparatus, 0.1-5 mm is preferable. If the thickness of the sheet is less than 0.1 mm, it tends to be difficult to absorb external stress, and if it exceeds 5 mm, it is disadvantageous in terms of sheet manufacturing cost and handling properties.

  Specific examples of the transparent resin sheet include an acrylic resin, an epoxy resin, a silicone resin, a polyurethane resin, a polyolefin resin, a polycarbonate resin, a polyester resin, and a polystyrene resin. Any sheet that can be attached to the protective panel by heating, pressing, an adhesive, a pressure-sensitive adhesive, or the like may be used. Although not particularly limited, it is particularly preferable to use acrylic resin and polyurethane resin as constituent materials from the viewpoint of optical characteristics and compatibility with the ultraviolet curable liquid described later. Acrylic resin refers to acrylic monomers such as acrylic acid or methacrylic acid, and alkyl esters thereof, and, if necessary, styrene, acrylonitrile, methacrylonitrile, and other vinyl monomers. It means a resin obtained by polymerizing a monomer (mixture) containing it.

The method for producing the transparent resin sheet used in the present invention is not particularly limited. For example, a method of forming a resin synthesized by thermal polymerization such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization into a sheet shape by a melt processing method or a solution casting method can be applied. In addition, a known method such as a method of directly forming a resin material (monomer mixture) into a sheet shape in the form of a lump or a solution and forming it into a resin sheet by thermal polymerization, photopolymerization, or the like can also be applied. In particular, when applying the latter method, that is, a method in which a resin material (monomer mixture) is molded into a sheet shape in the form of a lump or solution and is made into a resin sheet by thermal polymerization or photopolymerization, etc. Another (co) polymer may be added to the body mixture in advance.
Examples of usable (co) polymers include polyurethane resins, urethane acrylate resins, (meth) acrylate resins, polycarbonate resins, polyolefin resins, and petroleum resins (tackifier resins). A method for producing a transparent resin sheet from such a blend of a (co) polymer and a monomer mixture is preferred in that it can adjust the viscosity and improve the mechanical properties of the cured product. In this case, the weight average molecular weight of the (co) polymer to be blended is preferably in the range of 100,000 to 600,000. In addition, the term “weight average molecular weight” used in the present specification indicates a value obtained by measurement by gel permeation chromatography using a standard polystyrene calibration curve. The suitable range of the amount of the (co) polymer is 10 to 60% by weight based on the mixture of the (co) polymer and the monomer. As a method for synthesizing the (co) polymer, known polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be applied, but solution polymerization or bulk polymerization is preferable.

  When the transparent resin sheet is formed from a resin material that can be polymerized by radical polymerization such as an acrylic resin, a polymerization initiator may be added to the resin material as necessary. As the polymerization initiator, any compound used in a normal radical polymerization reaction can be used. For example, benzoyl peroxide, lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-3,3,5- Organic peroxides such as trimethylcyclohexane; azo compounds such as azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, azodibenzoyl; potassium persulfate A water-soluble catalyst such as ammonium persulfate; a redox catalyst comprising a peroxide or a combination of a persulfate and a reducing agent; and 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2- Methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl fe Photopolymerization initiators such as ketone may be cited. The polymerization initiator is preferably used in the range of 0.01 to 10% by weight based on the total amount of monomers.

  The ultraviolet curable liquid used in the present invention can be placed in close contact between the image display panel and the protective panel, and swells the transparent resin sheet at the interface between the transparent resin sheet and both panels by ultraviolet irradiation, Those which can be cured in a state of being substantially compatible with the transparent resin sheet are preferable. That is, it is preferable that the ultraviolet curable liquid penetrates the transparent resin sheet, is absorbed and integrated with the sheet, and is further cured by ultraviolet rays to form a transparent layer together with the transparent resin sheet. By combining such an ultraviolet curable liquid and a transparent resin sheet, the stress and distortion remaining on the transparent resin sheet side can be eliminated, and transparency and low resistance can be achieved between the image display panel and the protection panel. It is possible to form a transparent resin layer excellent in optical homogeneity such as birefringence, mechanical properties, and long-term reliability. The cured product of the ultraviolet curable liquid need not be the same material as the transparent resin sheet. The mechanical properties and optical properties of the transparent resin layer are appropriately variably controlled by arbitrarily changing the properties of the transparent resin sheet and the cured product of the UV curable liquid according to the structure of the image display device and its use. It is possible.

The ultraviolet curable liquid has a viscosity of 10,000 cP (10 Pa · s) or less at room temperature (25 ° C.) from the viewpoint of suppressing air bubbles from being mixed when the image display panel and the protective panel are brought into close contact with each other. It is preferable to have. When the viscosity exceeds this range, the handleability tends to be inferior. Although there is no particular lower limit of viscosity, in general, those having a viscosity of 0.1 cP (1 × 10 ⁻⁴ ) or more are preferable in consideration of practical use. Further, the ultraviolet curable liquid material used in the present invention is obtained by bonding a transparent resin sheet between the image display panel and the protective panel by their curing, followed by heating and pressurization, vacuum degassing, drying, etc. In order to eliminate the post-treatment and improve long-term reliability, it is preferable that the content of the non-polymerizable volatile component is small. More specifically, the content of the non-polymerizable volatile component having a boiling point of less than 120 ° C. present in the ultraviolet curable liquid is preferably 5% or less. Examples of components that can be volatile components include organic solvents such as toluene, methyl ethyl ketone, methyl isobutyl ketone, and tetrahydrofuran, low molecular weight unreacted monomers, and photopolymerization initiator decomposition products. When such a volatile component is present in an ultraviolet curable liquid in an amount of more than 5%, generation of bubbles derived from the volatile component at the interface between the protective panel or the image display panel and the cured product of the ultraviolet curable resin and Problems such as peeling off at the interface are likely to occur.

  Specific examples of the ultraviolet curable liquid that can be used in the present invention are obtained by adding various additives such as a photopolymerization initiator to an ultraviolet curable monomer that swells a transparent resin sheet and is compatible with the resin sheet. Liquids to be produced. The liquid material may contain those oligomer and polymer compounds in addition to the above-mentioned ultraviolet curable monomer. Among such UV curable liquids, those containing a (meth) acrylate compound are preferable from the viewpoint that appropriate adhesive strength can be imparted for joining the protective panel and the image display panel, and light can be emitted in a shorter time. The thing containing an acrylate type compound from the point which can harden | cure is more preferable. Examples of the acrylate monomers include alkyl acrylates such as n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and stearyl acrylate. Among these, n-butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are preferable, and 2-ethylhexyl acrylate is particularly preferable. These acrylate monomers may be used alone or in combination of two or more.

  In the present invention, it is preferable to appropriately use an acrylate having a polar group in addition to the above-mentioned alkyl acrylate as the ultraviolet curable liquid. By adding an acrylate having a polar group, it is possible to suppress white turbidity of the transparent resin layer during moisture absorption. Examples of acrylates having polar groups that can be used include 2-hydroxyethyl acrylate, 1-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 1-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3- Hydroxyl-containing acrylates such as hydroxyalkyl acrylates such as hydroxybutyl acrylate, 2-hydroxybutyl acrylate and 1-hydroxybutyl acrylate; monoacrylates of (poly) ethylene glycols such as diethylene glycol, triethylene glycol and polyethylene glycol; dipropylene glycol , Monopropylene of (poly) propylene glycols such as tripropylene glycol and polypropylene glycol Acrylate; monoacrylates of (poly) butylene glycols such as dibutylene glycol, tributylene glycol, and polybutylene glycol. Among them, 2-hydroxyethyl acrylate, 1-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 1-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, 2-hydroxybutyl acrylate, Hydroxyalkyl acrylates such as 1-hydroxybutyl acrylate are preferred, and 2-hydroxyethyl acrylate is particularly preferred. These acrylates may be used alone or in combination of two or more.

  As the photopolymerization initiator compounded in the ultraviolet curable liquid, a compound having sensitivity to light such as ultraviolet rays is used. For example, benzophenone, N, N′-tetramethyl-4,4′-diaminobenzophenone (Michler ketone), 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1- Phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) ) Phenyl) propanone) and the like. Examples of those that do not color the resin composition include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]- Α-hydroxyalkylphenone compounds such as 2-hydroxy-2-methyl-1-propan-1-one, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) Acylphosphine oxide compounds such as -2,4,4-trimethyl-pentylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, oligo (2-hydroxy-2-methyl-1- (4- (1 -Methylvinyl) phenyl) propanone) and combinations thereof It is preferred. In order to produce a particularly thick sheet, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, A photopolymerization initiator containing an acylphosphine oxide compound such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is preferable. In order to reduce the odor of the sheet, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) is preferable. A preferable blending amount of these photopolymerization initiators is 0.5 to 2% by weight with respect to the monomer mixture contained in the ultraviolet curable liquid, and a plurality thereof may be used in combination. Furthermore, when using a photopolymerization initiator, a photosensitizer such as benzophenone or naphthalene can be added as necessary. Furthermore, mercaptan compounds, thioglycol, carbon tetrachloride, α-methylstyrene dimer, etc. can be added as necessary as molecular weight modifiers.

  In this invention, you may mix | blend various additives with the constituent material of the above-mentioned transparent resin sheet, or an ultraviolet curable liquid as needed. For example, an additive having an antifoaming effect, a dye for adjusting light transmittance and color, an ultraviolet absorber and an antioxidant for improving long-term reliability of the apparatus, and a viscosity adjusting agent for adjusting the viscosity , A polymer additive (for example, tackifier) for enhancing adhesive strength, a surfactant for controlling wettability with the surface of the image display panel or the protective panel, a plasticizer with low volatility, etc. Is possible. In particular, the use of an additive having an antifoaming effect is preferable because it is possible to easily suppress the generation of bubbles during the manufacture of an imaging statutory apparatus and increase productivity. The amount of these various additives used is not particularly limited as long as the display performance and reliability of the image display device in which the transparent resin layer is closely disposed between the image display panel and the protective panel are not adversely affected.

  The protective panel applied to the image display device according to the present invention is preferably such that at least the transparent viewing portion has a phase difference of 50 nm or less due to birefringence and an ultraviolet transmittance of 1% or more at a wavelength of 365 nm. When the birefringence of the transparent viewing portion exceeds 50 nm, it is not preferable because it affects the excellent color tone of an image display panel such as a liquid crystal panel. Further, when the ultraviolet transmittance at a wavelength of 365 nm is less than 1%, when the ultraviolet curable liquid is cured to form a transparent resin layer, a sufficient exposure amount is obtained when ultraviolet rays are irradiated from the transparent visual recognition side. And problems such as odor due to insufficient curing are likely to occur. Examples of materials that can be used to form the transparent visual recognition portion of the protective panel in the present invention include glass and transparent resin with small optical distortion. Particularly preferred are acrylic resin sheets, olefin resin sheets, cycloolefin resin sheets, fluorine resin sheets, low birefringence polycarbonate resin sheets, low birefringence polyester resin sheets, and silicone resin sheets. The transparent resin sheet which is excellent in both the ultraviolet ray permeability and the low birefringence of the above.

  The protective panel and the transparent resin layer of the image display device of the present invention include phenolic, phosphite-based, thioether-based antioxidants, fats, and the like from the viewpoints of prevention of deterioration, thermal stability, moldability, workability, and the like. Group alcohols, fatty acid esters, phthalic acid esters, triglycerides, fluorine surfactants, release agents such as higher fatty acid metal salts, other lubricants, plasticizers, antistatic agents, UV absorbers, flame retardants, heavy metal deactivation Additives, fine particulate fillers such as alumina, silica, magnesium oxide, talc, barium titanate and barium sulfate, dyes such as Victoria Pure Blue, and colorants such as pigments such as phthalocyanine green may be used. .

  In the image display device according to the present invention, various display panels such as a plasma display panel (PDP), a liquid crystal display (LCD), an organic EL display (OLED), and a field emission display (FED) can be applied as the image display panel. It is. Moreover, you may comprise an apparatus by adding elements, such as a backlight unit, as needed. For example, when a liquid crystal display device is configured using a liquid crystal display panel, a backlight unit such as a reflector, a light guide plate, and a diffusion sheet is provided on the back surface of the liquid crystal display panel. The image display device according to the present invention is not limited to various image display devices for displaying moving images as exemplified above, but has a structure in which a protective layer is provided on the surface of a panel displaying still images such as photographs and paintings. Intended to include the body.

  Furthermore, the image display device according to the present invention is provided on the surface of the protective panel which is the front surface of the device, if necessary, such as an antireflection layer, an antifouling layer, an electromagnetic wave shielding layer, a near infrared shielding layer, and a color adjustment layer. It is good also as a structure which laminated | stacked the functional layer. When various functional layers are provided on the surface of the protective panel, one of the various functional layers may be laminated as a single layer, or a plurality of functional layers may be laminated. The functional layer may be laminated directly on the surface of the protective panel, or a member obtained by laminating a functional layer on a separate film may be bonded. Moreover, you may use the protection panel which incorporated various functions. From the viewpoint of improving the display characteristics of the device, it is preferable to provide an antireflection layer on the surface of the protective panel. The antireflection layer is not particularly limited as long as it has an antireflection function. For example, a commercially available antireflection film may be used. It is also preferable to provide an antifouling layer on the front surface of the image display device. By providing the antifouling layer, it becomes difficult for dirt to adhere to the apparatus or the dirt is easily removed, and the display characteristics and appearance of the apparatus are improved.

  As described above, the image display device according to the present invention comprises a transparent resin layer and a transparent resin layer using an ultraviolet curable liquid material that swells or is compatible with the transparent resin sheet. As long as it is a feature and an appropriate transparent resin layer can be formed, any method may be applied in the production thereof. However, by applying the manufacturing method for the image display device according to the present invention described below, an image display device having excellent visibility, optical characteristics and durability, and excellent long-term reliability can be obtained simply and with a high yield. It is possible to produce.

  An image display device manufacturing method according to the present invention is directed to an image display device in which a transparent resin layer is disposed in close contact between an image display panel and a protective panel installed in front of the image display panel. A step of placing a transparent resin sheet on one of the display panel and the protective panel, a step of placing an ultraviolet curable liquid on the transparent resin sheet, an ultraviolet curable liquid on the other, The method includes a step of placing an image display panel or a protection panel to be a panel, and a step of curing the ultraviolet curable liquid material. According to such a method, generation | occurrence | production of a fine bubble can be suppressed at the time of formation of a transparent resin layer. That is, in the production method of the present invention, the transparent resin sheet is allowed to penetrate into the resin sheet and the ultraviolet ray is irradiated after being brought into close contact with the protective panel and the image display panel through an compatible ultraviolet curable liquid. Therefore, the bubbles at the interface can be easily discharged by the liquid filled in the gap between the two panels without performing defoaming treatment such as pressurization or decompression by an autoclave. In addition, the UV curable liquid penetrates the transparent resin sheet and is compatible with each other, so that the protective panel, the image display panel, the transparent resin sheet, It is possible to adhere to the interface without leaving stress strain. As a result, it is possible to realize an image display panel integrated with a protection panel that is free from air bubbles and has little residual distortion and is excellent in visibility and long-term reliability.

  4A and 4B illustrate a method for manufacturing an image display device according to the present invention, and FIGS. 4A to 4D are schematic cross-sectional views corresponding to respective steps. Hereinafter, the manufacturing method of the present invention will be specifically described with reference to the drawings. The details of the image display panel, the transparent resin sheet, the ultraviolet curable liquid material, and the protection panel constituting the image display device are as described above.

  First, a transparent resin sheet is placed on one of the image display panel and the protective panel. FIG. 4A shows a case where the transparent resin sheet 50 is placed on the protective panel 30. The transparent resin sheet is preferably the same size as the panel on which the sheet is placed or is smaller than the panel. The method for placing the transparent resin sheet is not particularly limited, but it is preferable that the transparent resin sheet is pasted so that air bubbles and dust are not caught between the panel surface and the transparent resin sheet. For example, by applying a conventionally known method using a roll laminator or a sheet laminating machine, it can be stuck without leaving bubbles. Also, an ultraviolet curable liquid is dropped on the panel on which the sheet is placed, and a transparent resin sheet is overlaid on the panel to spread the layer of the ultraviolet curable liquid over the entire interface between the transparent resin sheet and the panel. Depending on the situation, a transparent resin sheet may be attached. The method described later is preferable because it can easily make the interface completely free of bubbles.

  Next, an ultraviolet curable liquid material is placed on the transparent resin sheet. FIG. 4B shows a case where the ultraviolet curable liquid material 52 is placed at the center of the transparent resin sheet 50. The placement method is not particularly limited as long as it can be dropped and applied so that the liquid material reaches the entire surface of the sheet. It is also possible to provide a frame material on the surface of either the protective panel or the image display panel on which the transparent resin sheet is mounted so as to prevent excessive liquid material from flowing out. FIG. 5 shows a case where a frame member is provided on the upper surface of the protective panel as an embodiment of the manufacturing method according to the present invention. The frame member 60 shown in FIG. 5 has an outer shape surrounding the transparent resin sheet 50. However, the shape and material of the frame material that can be used in the present invention are not particularly limited as long as the ultraviolet curable liquid can be prevented from excessively spreading.

  In one embodiment of the present invention, it is preferable to use, for example, an ultraviolet cured product of the same type as the ultraviolet cured product obtained by curing an ultraviolet curable liquid as the material of the frame material. It is more preferable to use a cured product obtained by curing a paste-like curable liquid or an ultraviolet curable liquid having an extremely high viscosity with ultraviolet rays. In particular, it is possible to easily improve the adhesion and optical homogeneity between the frame material and the UV-cured product by using the same UV-cured product as the UV-curable liquid material. It becomes. As a result, it is possible to suppress the vicinity of the boundary between the frame material and the ultraviolet cured product from becoming cloudy or discoloring.

  Moreover, it is also preferable that the frame material is configured using a material that can be impregnated with an ultraviolet curable liquid. Such a frame material can suppress the occurrence of peeling near the boundary. Furthermore, it is also preferable that the frame material is configured using a material having a large number of voids through which air can pass. Since the frame material has a large number of gaps through which air can pass, air bubbles can be prevented from being mixed into the transparent resin (ultraviolet cured product) between the image display panel and the protection panel. An image display device free from bubbles and having excellent visibility can be easily manufactured. Such a frame material can be configured using, for example, an open-cell PVA sponge sheet, a PP nonwoven fabric sheet, or the like as a material. In addition, the outflowing liquid substance is impregnated in the space | gap of a frame material. Therefore, when a frame material having voids is used, the liquid material impregnated in the voids of the frame material is preferably cured in the same manner as the liquid material impregnated in the transparent resin sheet. That is, it is preferable that the space | gap of the frame material surrounding a transparent resin layer contains the hardened | cured material of an ultraviolet curable liquid material.

The amount of UV curable liquid used to fill the gap between the transparent resin sheet and the protective panel or image display panel stacked as the other panel on the transparent resin sheet when the image display panel and protective panel are bonded together However, it is sufficient that the amount is sufficient to discharge the bubbles to the outside. When the amount of the ultraviolet curable liquid used exceeds the amount corresponding to the volume of the transparent resin sheet, the curing shrinkage of the ultraviolet curable liquid cannot be ignored in the subsequent steps. On the other hand, when the amount used is too small, the bubbles tend to be absorbed by the transparent resin sheet before the bubbles are completely discharged. The appropriate range for the amount of UV-curable liquid used varies depending on the compatibility with the transparent resin sheet or the thickness of the sheet. It is preferable to do. Although it does not restrict | limit in particular, In one Embodiment of this invention, it is preferable to set it as 0.1-1.0 by volume ratio with a transparent resin sheet. For example, when the resin sheet is 1 mm × 100 mm × 100 mm (= 10 cm ³ = 10 ml), the amount of the liquid material used is preferably 1 to 10 ml.

  Next, an image display panel or a protection panel to be the other panel is placed on the ultraviolet curable liquid. FIG. 4C illustrates a case where the other panel is the image display panel 10. Although there is no restriction | limiting in particular in the mounting method, Carry out mounting carefully so that a bubble may not be involved. For example, it is preferable to place the image display panel from the center so that air bubbles do not enter after the transparent resin sheet is once swollen with the ultraviolet curable liquid. You may add the process of closely_contact | adhering the mounted panel and a transparent resin sheet, making a transparent resin sheet penetrate | infiltrate an ultraviolet curable liquid. When infiltrating the liquid material, heating may be accompanied as necessary in order to increase the permeability. Such a process is preferable because it is possible to more effectively suppress bubble entrainment. At the stage where the panel is placed and brought into close contact as described above, it is possible to inspect for entrainment of bubbles and contamination of foreign matter, and repair as necessary before curing the UV curable liquid. is there. Repair work is easy before the UV curable resin liquid is completely cured, and therefore it is possible to manufacture an image display device with an extremely high yield by adding such an inspection process. .

  Finally, the ultraviolet curable liquid is cured to form a transparent resin layer, thereby constituting an image display device. Curing of the ultraviolet curable liquid is achieved by irradiation with ultraviolet rays. As shown in FIG. 4D, the irradiation with ultraviolet rays is preferably performed from the front surface of the image display device, that is, the transparent protective panel 30 side that can transmit ultraviolet rays. Curing conditions such as the intensity of ultraviolet light and the curing time can be appropriately selected. In the production method according to the present invention, the ultraviolet curable resin liquid material can be completely cured by irradiating ultraviolet rays from the ultraviolet transmissive protective panel side. Furthermore, it is preferable to promote curing of the liquid material at a site that is difficult to be exposed to the ultraviolet rays irradiated from the protective panel side by irradiating ultraviolet rays from a place other than the protective panel or by performing a post cure.

  As an apparatus for irradiating ultraviolet rays, a commercially available general ultraviolet irradiation apparatus can be used. The light source may be, for example, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, and an LED, but a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, and a metal halide lamp are more preferable. Moreover, even if the irradiation apparatus is a continuous apparatus conveyed with a conveyor, any of the batch type apparatuses which irradiate one sheet at a time may be used. When curing only a specific part, it is preferable to use a spot irradiation device using a bundle fiber.

  In the manufacturing method according to the present invention, in addition to the above-described steps, a step of providing various functional layers such as an antireflection layer and an antifouling layer incorporated in the image display device as necessary is added. When various functional layers are laminated on the surface of the protective panel, they may be laminated directly on the surface of the protective panel, or a member obtained by laminating a functional layer on a separate film may be bonded. In addition, for example, when manufacturing a backlight type liquid crystal display device, an additional step of forming a backlight unit such as a reflective layer, a light guide layer, and a diffusion layer provided on the lower surface (back surface) of the liquid crystal display panel is added. Is done.

  A liquid crystal display device which is an embodiment of an image display device according to the present invention forms a unit in which a protective panel and a liquid crystal panel are bonded via an ultraviolet curable liquid according to the above-described method, and the unit is further a backlight unit. At the same time, the liquid crystal module can be manufactured by being placed in a metal frame and then incorporated into the exterior of the display device. Such a configuration is easily adapted to a display device that is conventionally configured without using a protective panel, such as a liquid crystal television. Alternatively, a liquid crystal module in which a liquid crystal panel and a backlight unit are arranged in a metal frame is bonded to an exterior of a mobile phone, a digital still camera or the like, or an ultraviolet curable liquid material is applied to an integrally molded protective panel. It is also possible to manufacture by joining via. Such a configuration is easily adapted to the case of a device using a protective panel such as a mobile phone.

  The manufacturing method of the image display device according to the present invention is not limited to a small liquid crystal display device of about 2 inches used for, for example, a cellular phone, but a large size of 32 inches, 42 inches, 50 inches or more. It can also be applied to other liquid crystal display devices. Further, the present invention is not limited to the liquid crystal display panel exemplified above, and can be similarly applied to the manufacture of an image display device including other various image display panels such as a plasma display panel and an organic EL display panel. By applying the manufacturing method according to the present invention, it is possible to produce various image display devices that are excellent in visibility, optical characteristics, durability, and long-term reliability with a simple and high yield.

  Hereinafter, an image display device and a manufacturing method thereof according to the present invention will be described with reference to examples. However, the present invention is not limited to the following examples, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

In addition, evaluation of various characteristics in the following examples and comparative examples was performed according to the following methods.
(Total light transmittance)
The total light transmittance was measured using a color difference / turbidity measuring device COH-300A (manufactured by Nippon Denshoku Industries Co., Ltd.).

(Phase difference due to birefringence)
The phase difference (single pass) of the transparent resin sheet was measured with an ellipsometer (AEP-100 manufactured by Shimadzu Corporation) using a He—Ne laser, and the degree of birefringence was evaluated.

(Storage modulus)
The transparent resin sheet was cut into a width of 3 mm and a length of 20 mm, and the cut piece was measured by a tensile test method using RS Instruments-III manufactured by TA Instruments. The measurement frequency was 1 Hz.

(viscosity)
Using an E-type viscometer (Tokyo Keiki TV-33), the viscosity at a temperature of 25 ° C. was measured.

(Weight average molecular weight)
Measurement was performed by gel permeation chromatography using THF as a solvent and polystyrene as a standard substance. The used apparatus is Hitachi L6000 type high performance liquid chromatograph manufactured by Hitachi, Ltd., and the columns are Gel Packs R400, R450 and R400M (trade name) manufactured by Hitachi Chemical Co., Ltd.

Example 1
(Preparation of transparent resin sheet A)
In a reaction vessel equipped with a cooling tube, a thermometer, a stirring device, a dropping funnel and a nitrogen injection tube, 84.0 g of 2-ethylhexyl acrylate, 36.0 g of 2-hydroxyethyl acrylate, and 150. 0 g was weighed, and heated from room temperature to 70 ° C. over 15 minutes while purging with nitrogen at a flow rate of 100 ml / min. Thereafter, while maintaining the temperature at 70 ° C., 21.0 g of 2-ethylhexyl acrylate and 9.0 g of 2-hydroxyethyl acrylate were weighed as additional monomers, and 0.6 g of lauryl peroxide was dissolved in the solution. And the solution was added dropwise over 60 minutes. After completion of the dropwise addition, the reaction was continued for another 2 hours. From the obtained reaction mixture, methyl isobutyl ketone was distilled off to obtain a copolymer of 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate (weight average molecular weight 250,000).
Next, the following compounds:
44.50 g of the previously prepared copolymer,
38.25 g of 2-ethylhexyl acrylate,
16.25 g of 2-hydroxyethyl acrylate,
1,6-hexanediol diacrylate 1.00 g and 1-hydroxy-cyclohexyl-phenyl-ketone 0.50 g
Were weighed, added to the reaction vessel, and stirred and mixed in a nitrogen atmosphere at 35-40 ° C. until the copolymer and photoinitiator were completely dissolved, thereby preparing a resin material constituting the transparent resin sheet. The obtained resin material is poured into a molding frame having a width of 100 mm, a depth of 100 mm, and a depth of 0.5 mm, and an ultraviolet ray is irradiated at 2,000 mJ using an ultraviolet irradiation device in a state where the upper part of the molding frame is covered with an ultraviolet transmissive glass. Was obtained to obtain a transparent resin sheet A. The cure shrinkage of the resin material was 5.5%, the total light transmittance of the sheet A was 92%, the birefringence was 0.5 nm, and the storage elastic modulus at 25 ° C. was 1.8 × 10 ⁵ . The thickness of the sheet A was 250 μm.

(Preparation of UV curable liquid a)
In a reaction vessel equipped with a cooling tube, thermometer, stirring device, dropping funnel and nitrogen injection tube, 38 g of 2-ethylhexyl acrylate, 16 g of 2-hydroxyethyl acrylate, 1.0 g of 1,6-hexanediol diacrylate, An ultraviolet curable liquid a was obtained by weighing 0.5 g of 1-hydroxy-cyclohexyl-phenyl-ketone and stirring until the solution was uniform while purging with nitrogen at an air volume of 100 ml / min. In addition, the viscosity of the obtained liquid a was 10 cP (0.01 Pa · s). Moreover, when the content of the non-polymerizable volatile component having a boiling point of less than 120 ° C. in the liquid material a was confirmed by a heat loss method, it was less than 1%.

(Production of liquid crystal display device)
The previously produced transparent resin sheet A is cut into an outer shape of 40 mm × 50 mm, and the cut piece is a transparent acrylic resin protective plate having a thickness of 1 mm, a pencil hardness of 4H, a birefringence of 15 nm, and a transmittance of 25% at a wavelength of 365 nm. These were laminated together using a roll laminator. Next, 0.7 ml of ultraviolet curable liquid a is dropped into the center of the transparent resin sheet A with a dropper, and a 2-inch size liquid crystal panel is placed thereon, and the liquid crystal panel and the sheet A do not contain bubbles. So that they face each other. Thereafter, 2,000 mJ of ultraviolet light was irradiated from the main surface side of the protective plate using an ultraviolet irradiation device to cure the liquid material a, and the protective plate and the liquid crystal panel were completely joined to produce a liquid crystal display device. . About the obtained liquid crystal display device, when the liquid crystal panel portion was turned on, no visible bubbles or vacancies due to interfacial peeling were found in the visual recognition portion, and no defects such as a decrease in contrast and color unevenness occurred. In addition, good visibility was shown. When the visibility of the liquid crystal display device was examined again after 6 months, no bubbles that could be visually identified or voids due to interface peeling were found in the viewing portion.

(Example 2)
(Preparation of transparent resin sheet B)
The following compounds,
20.00 g of 2-ethylhexyl acrylate,
20.00 g of 2-hydroxyethyl acrylate,
60.00 g of dicyclopentanyl acrylate,
1,6-hexanediol diacrylate 1.00 g and 1-hydroxy-cyclohexyl-phenyl-ketone 0.50 g
Were weighed, added to the reaction vessel, and stirred and mixed in a nitrogen atmosphere at 35-40 ° C. until the copolymer and photoinitiator were completely dissolved, thereby preparing a resin material constituting the transparent resin sheet. The obtained resin material is poured into a molding frame having a width of 100 mm, a depth of 100 mm, and a depth of 0.5 mm, and an ultraviolet ray is irradiated at 2,000 mJ using an ultraviolet irradiation device in a state where the upper part of the molding frame is covered with an ultraviolet transmissive glass. The transparent resin sheet B was obtained by irradiating. The cure shrinkage of the resin material was 7.5%, the total light transmittance of the sheet B was 92%, the birefringence was 1.0 nm, and the storage elastic modulus at 25 ° C. was 7.8 × 10 ⁶ . Further, the thickness of the sheet B was 250 μm.

(Preparation of UV curable liquid b)
The UV curable liquid described in Example 1 except that 44.50 g of a copolymer of 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate prepared for the transparent resin sheet A in Example 1 was added. In the same manner as the preparation method of a, an ultraviolet curable liquid material b was prepared. In addition, the viscosity of the obtained liquid material b was 3500 cP (3.5 Pa * s). Moreover, when the content of the non-polymerizable volatile component having a boiling point of less than 120 ° C. in the liquid material b was confirmed by a heat loss method, it was less than 1%.

(Production of liquid crystal display device)
The previously produced transparent resin sheet B is cut into an outer shape of 40 mm × 50 mm, and the cut piece is a transparent acrylic resin protective plate having a thickness of 1 mm, a pencil hardness of 4H, a birefringence of 15 nm, and a transmittance of 25% at a wavelength of 365 nm. These were laminated together using a roll laminator. Next, 0.7 ml of the ultraviolet curable liquid material b is dropped with a dropper on the center of the transparent resin sheet A, and a 2-inch liquid crystal panel is placed thereon, and the liquid crystal panel and the sheet B do not contain bubbles. So that they face each other. After that, the liquid material b was cured by irradiating ultraviolet rays with 2,000 mJ from the main surface side of the protective plate using an ultraviolet irradiation device, and the protective plate and the liquid crystal panel were completely joined to produce a liquid crystal display device. . About the obtained liquid crystal display device, when the liquid crystal panel portion was turned on, no visible bubbles or vacancies due to interfacial peeling were found in the visual recognition portion, and no defects such as a decrease in contrast and color unevenness occurred. In addition, good visibility was shown. When the visibility of the liquid crystal display device was examined again after 6 months, no bubbles that could be visually identified or voids due to interface peeling were found in the viewing portion.

(Example 3)
(Preparation of transparent resin sheet C)
A solution in which 1-hydroxy-1,1-dimethoxy-1-vinylsilane (20 g) and a platinum catalyst (0.02 g) are mixed is poured onto a surface release-treated glass plate provided with a forming frame along the outer periphery. And allowed to cure in an oven heated to 100 ° C. After confirming the curing of the solution, a transparent resin sheet C was obtained by removing the molding frame. The forming frame had an inner dimension of 180 mm × 250 mm, an outer dimension of 190 mm × 260 mm, and a thickness of 1 mm. The cure shrinkage of the resin material was 10%, the total light transmittance of the resin sheet C was 92%, the birefringence was 12 nm, and the storage elastic modulus at 25 ° C. was 1.8 × 10 ⁷ . The thickness of the sheet was 1 mm.

(Production of liquid crystal display device)
On the glass polarizing plate provided on the viewing side of the liquid crystal panel, 9 g of the ultraviolet curable liquid material a prepared in the previous Example 1 is dropped, and the transparent resin sheet C is overlaid thereon, thereby ultraviolet curable. The layer of the liquid material a was spread over the entire interface between the transparent resin sheet C and the glass polarizing plate, and was brought into close contact with no bubbles. Next, 9 g of UV curable liquid a is again dropped on the surface of the remaining transparent resin sheet, and a protective plate with a thickness of 2.8 mm, a pencil hardness of 7 H, a birefringence of 30 nm, and a transmittance of 83% at a wavelength of 365 nm. The glass plates were superposed and the layer of the ultraviolet curable liquid a was spread over the entire interface between the transparent resin sheet C and the glass plate and adhered in the absence of any bubbles to form a laminate. Next, a liquid crystal display device in which a transparent resin layer was closely disposed between the liquid crystal panel and the protective plate was produced by irradiating ultraviolet rays with 2,000 mJ using an ultraviolet irradiation device from the glass plate side of the laminate. About the obtained liquid crystal display device, when the liquid crystal panel portion was turned on, no visible bubbles or vacancies due to interfacial peeling were found in the visual recognition portion, and no defects such as a decrease in contrast and color unevenness occurred. In addition, good visibility was shown. When the visibility of the liquid crystal display device was examined again after 6 months, no bubbles that could be visually identified or voids due to interface peeling were found in the viewing portion.

Example 4
(Production of liquid crystal display device)
All implemented except using a transparent cycloolefin resin (product name: ZEONOR1060R, manufactured by Nippon Zeon Co., Ltd.) with a thickness of 1 mm, pencil hardness H, birefringence of 15 nm, and a transmittance of 75% at a wavelength of 365 nm. A liquid crystal display device in which a transparent resin layer was disposed in close contact between the liquid crystal panel and the protective plate was produced in the same manner as in Example 1. About the obtained liquid crystal display device, when the liquid crystal panel portion was turned on, no visible bubbles or vacancies due to interfacial peeling were found in the visual recognition portion, and no defects such as a decrease in contrast and color unevenness occurred. In addition, good visibility was shown. When the visibility of the liquid crystal display device was examined again after 6 months, no bubbles that could be visually identified or voids due to interface peeling were found in the viewing portion.

(Example 5)
Toluene 5 g was added to the ultraviolet curable liquid a prepared in Example 1 to prepare an ultraviolet curable liquid c. A liquid crystal display device in which a transparent resin layer was disposed in close contact between the liquid crystal panel and the protective plate was produced in the same manner as in Example 1 except that this ultraviolet curable liquid c was used. When the obtained liquid crystal display device was examined, it was found that about 5 to 10 bubbles having a maximum diagonal length of 20 μm or more that can be visually recognized were generated in the region serving as the visual recognition portion.

  As described above, in the first to fifth embodiments, the liquid crystal display device is taken as an example to describe the image display device and the manufacturing method thereof according to the present invention. However, the present invention is not limited to the liquid crystal display device, but can be applied to other display devices such as a plasma display device in the same manner. According to the present invention, excellent visibility and adhesion to the image display panel can be obtained. It should be easily understood that various image display devices having an excellent transparent resin layer can be easily manufactured with high productivity.

(Comparative Example 1)
A liquid crystal display device in which a transparent resin layer was closely disposed between the liquid crystal panel and the protective plate was produced in the same manner as in Example 1 except that methyl ethyl ketone was used instead of the ultraviolet curable liquid a. Methyl ethyl ketone showed swelling and compatibility with the transparent resin sheet, but it was not polymerized and therefore it was not cured by UV irradiation. Therefore, the actually produced liquid crystal display device has an uncured transparent resin sheet which is in a swollen and compatible state between the liquid crystal panel and the protective plate. As a result of examining the visibility of such a device, it was found that bubbles having a maximum diagonal length of 20 μm or more that can be visually identified and vacancies due to interfacial peeling occurred in at least 10 locations in the region that becomes the visual recognition portion. .

(Comparative Example 2)
A liquid crystal display device in which a transparent resin layer was closely disposed between the liquid crystal panel and the protective plate was produced in the same manner as in Example 2 except that pure water was used instead of the ultraviolet curable liquid material b. Pure does not show swelling and compatibility with the transparent resin sheet, and is not polymerized and therefore does not cure by irradiation with ultraviolet rays. Therefore, the actually produced liquid crystal display device has a transparent resin sheet between the liquid crystal panel and the protective plate, and pure water remains at the interface. When the visibility of such a liquid crystal display device was examined, bubbles could not be confirmed in a region to be a visual recognition portion at the time of production. However, after leaving the device in the room for several days, when the visibility was confirmed again, it was found that bubbles with a maximum diagonal length of 20 μm or more that could be visually identified and vacancies due to interfacial peeling occurred at least 10 locations. It was.

Table 1 shows the evaluation results of various characteristics of each example and each comparative example.

(Note)
Evaluation criteria for the liquid crystal display device are as follows.
“◯”: In the appearance inspection immediately after manufacturing the liquid crystal display device and in the inspection after 6 months, the occurrence of bubbles, interface peeling, contrast, and color unevenness that can be visually identified are not observed.
“Δ”: In the appearance inspection immediately after manufacturing the liquid crystal display device, no bubbles or interfacial peeling that can be visually identified are observed. However, in the inspection after 6 months, generation of bubbles and interface peeling that could be visually identified were observed.
“X”: In the appearance inspection immediately after the production of the liquid crystal display device, bubbles and interface peeling that could be visually identified were observed.
“-”: Not measured

DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 10 'Image display panel 12 Liquid crystal display cell 14a, 14b Optical film (polarizing plate)
16a, 16b Glass plate 18a Spacer 18b Liquid crystal 20 Air gap (air layer)
22 Transparent resin layer 30 Protection panel 40 Backlight unit 50 Transparent resin sheet 52 Ultraviolet curable liquid 60 Frame material

Claims (10)

A method of manufacturing an image display device in which a transparent resin is disposed in close contact between an image display panel and a protective panel installed in front of the image display panel,
A step of placing a transparent resin sheet on one of the image display panel and the protective panel;
Placing an ultraviolet curable liquid on the transparent resin sheet;
An image display device comprising: a step of placing the image display panel or the protective panel, which is the other panel, on the ultraviolet curable liquid material; and a step of curing the ultraviolet curable liquid material. Manufacturing method.   The method for producing an image display device according to claim 1, wherein the ultraviolet curable liquid swells the transparent resin sheet and is compatible with the transparent resin sheet.   Prior to the step of curing the ultraviolet curable liquid material, the method further includes the step of causing the ultraviolet curable liquid material to permeate the transparent resin sheet and closely attaching the other panel of the image display panel or the protective panel to the transparent resin sheet. The method of manufacturing an image display device according to claim 1 or 2.   Either one of the image display panel and the protective panel includes a frame member having an outer shape surrounding the transparent resin sheet and a plurality of air gaps through which air can pass. The method for manufacturing an image display device according to claim 1.   Content of a non-polymerizable volatile component having a viscosity of 10,000 cP (10 Pa · s) or less at 25 ° C. and having a boiling point of less than 120 ° C. present in the ultraviolet curable liquid. 5 is 5% or less, The manufacturing method of the image display apparatus in any one of Claims 1-4 characterized by the above-mentioned.   The step of placing the transparent resin sheet includes dropping the ultraviolet curable liquid on one of the image display panel and the protective panel, and superimposing the transparent resin sheet thereon, The method for manufacturing an image display device according to claim 1, further comprising developing the layer of the ultraviolet curable liquid material at an interface between the transparent resin sheet and the panel.   An image display device obtained by the manufacturing method according to claim 1, wherein a bubble having a maximum diagonal length of 20 μm or more is not included in the visual recognition unit.   An image display device in which a transparent resin layer is disposed in close contact between an image display panel and a protective panel installed in front of the image display panel, wherein the transparent resin layer includes a transparent resin sheet and the resin sheet. An image display device comprising: a cured product of an ultraviolet curable liquid material that swells and is compatible with the resin sheet, wherein no bubbles having a maximum diagonal length of 20 μm or more are present in the viewing portion.   The transparent resin layer is surrounded by a frame member having a plurality of voids through which air can pass, and the ultraviolet curable liquid is impregnated in the voids of the frame member and further cured. Item 9. The image display device according to Item 8. The ultraviolet curable liquid has a viscosity of 10,000 cP (10 Pa · s) or less at 25 ° C. and contains a non-polymerizable volatile component having a boiling point of less than 120 ° C. present in the ultraviolet curable liquid. The image display device according to claim 8 or 9, wherein the amount is 5% or less.