JP7160745B2 - Method for manufacturing image display device - Google Patents

Description

The present technology relates to a method for manufacturing an image display device.

In Patent Document 1, a first irradiation step (temporary curing step) of irradiating an adhesive applied to at least one of the display panel and the substrate with light, and a bonding of bonding the display panel and the substrate after the first irradiation step A manufacturing method of a display device is described which includes a bonding step and a second irradiation step (main curing step) of further irradiating the adhesive with light after the bonding step.

The hardened state of the outermost surface of the resin in the temporary hardening step is very important for maintaining the alignment at the time of bonding. Regarding the cured state of the outermost surface of the resin, the greater the influence of oxygen inhibition during temporary curing, the lower the curing rate, and the adhesive function tends to decrease accordingly. Therefore, it is preferable that the UV irradiation device has a wide range of wavelengths and a high output, such as a metal halide lamp or a high-pressure mercury lamp.

However, in recent years, due to the demand for long life performance of ultraviolet irradiation devices, UV-LEDs having a peak in the wavelength range of 360 to 430 nm, for example, tend to be widely used as light sources. Since such UV-LEDs are used with a single wavelength, there is a concern that the adhesion performance during temporary curing may deteriorate due to the influence of oxygen inhibition.

International publication WO2009/054168

The present technology has been proposed in view of such conventional circumstances, and provides a method of manufacturing an image display device with good adhesion performance during temporary curing.

A method for manufacturing an image display device according to the present technology includes a step A of forming a curable resin layer made of a photocurable resin composition on the surface of a front panel or an image display member, and applying a UV-LED to the curable resin layer. Step B of irradiating light to form a temporary hardening layer, Step C of bonding the front plate and the image display member through the temporary hardening layer, and irradiating the temporary hardening layer with light through the front plate. , and a step D of forming a cured resin layer. In step B, the curable resin layer is irradiated with the first light, and the portion of the curable resin layer where oxygen inhibition occurs is irradiated with the second light.

According to the present technology, it is possible to improve the adhesion performance during temporary curing.

FIG. 1 is a cross-sectional view for explaining an example of a process of forming a curable resin layer made of a photocurable resin composition on the surface of an image display member. FIG. 2 is a cross-sectional view for explaining an example of a process of forming a pre-cured layer by irradiating a curable resin layer with light from a UV-LED. FIG. 3 is a cross-sectional view for explaining an example of a process of forming a pre-cured layer by irradiating a curable resin layer with light from a UV-LED. FIG. 4 is a cross-sectional view for explaining an example of the process of bonding the front plate and the image display member together with the temporary hardening layer interposed therebetween. FIG. 5 is a cross-sectional view for explaining an example of a process of forming a cured resin layer by irradiating the temporarily cured layer with light through the front plate. FIG. 6 is a cross-sectional view showing an example of an image display device. FIGS. 7A to 7H are diagrams for explaining the procedure for preparing test samples. FIG. 8 is a perspective view for explaining a method of measuring the shear strength of the temporary hardening layer. FIG. 9 is a graph showing the measurement results of the shear strength of the temporarily hardened layer in the test samples obtained in Examples 1 to 6 and Comparative Examples 1 and 2. FIG. FIG. 10 is a graph showing the measurement results of the shear strength of the temporarily hardened layer in the test samples obtained in Example 7 and Comparative Examples 3-5. FIG. 11 is a graph showing the measurement results of the shear strength of the temporarily hardened layer in the test samples obtained in Example 8 and Comparative Examples 6-8. FIG. 12 is a graph showing the measurement results of the shear strength of the temporarily hardened layer in the test samples obtained in Example 9 and Comparative Examples 9-11. 13 is a graph showing the measurement results of the shear strength of the temporarily hardened layer in the test samples obtained in Example 10 and Comparative Example 12. FIG. 14 is a graph showing the measurement results of the shear strength of the cured resin layer obtained by fully curing the temporarily cured layer in the test sample obtained in Example 9. FIG.

Hereinafter, the details of the method for manufacturing an image display device according to the present technology (hereinafter also referred to as the present manufacturing method) will be described. In the following description, (meth)acrylate includes both acrylate and methacrylate. In addition, (meth)acryloyl group includes both acryloyl group and methacryloyl group.

This production method includes a step A of forming a curable resin layer made of a photocurable resin composition on the surface of a front plate or an image display member, and irradiating the curable resin layer with light from a UV-LED to temporarily A step B of forming a cured layer, a step C of bonding the front plate and the image display member via the temporary cured layer, and irradiating the temporary cured layer with light through the front plate to form a cured resin layer. and a step D. The light irradiated in step B includes first light having a peak in the wavelength range of 360 to 430 nm and second light having a peak in the wavelength range of 200 to 345 nm. In step B, the curable resin layer is irradiated with the first light, and the portion of the curable resin layer where oxygen inhibition occurs is irradiated with the second light. The first light, which has a peak in the wavelength range of 360 to 430 nm, has less energy than the second light, which has a peak in the wavelength range of 200 to 345 nm, and reaches deep into the curable resin layer. On the other hand, the second light, which has a peak in the wavelength range of 200 to 345 nm, has higher energy than the first light, which has a peak in the wavelength range of 360 to 430 nm. reaches only the surface layer of the flexible resin layer. As the light to be irradiated in step B, a first light having a peak in the wavelength range of 360 to 430 nm and a second light having a peak in the wavelength range of 200 to 345 nm are used in combination to obtain a wavelength range of 360 to 430 nm. As compared with the case of irradiating only the first light having a peak at , the influence of oxygen inhibition can be reduced, and the adhesion performance during temporary curing can be improved.

<Process A>
In step A of this manufacturing method, as shown in FIG. 1, a curable resin layer 2 made of a photocurable resin composition is formed on the surface of an image display member 1 . For example, in step A, it is preferable to form the curable resin layer 2 by applying a photocurable resin composition evenly over the entire surface of the image display member 1 . The thickness of the curable resin layer 2 is preferably, for example, such that a step formed between the light shielding layer 3 described later and the surface of the front plate 4 on the light shielding layer formation side is canceled. It may be 2.5 to 40 times the thickness, may be 2.5 to 12.5 times, or may be 2.5 to 4 times the thickness. As an example, the thickness of the curable resin layer 2 may be 25-350 μm, and may be 50-150 μm. The number of times of application of the photocurable resin composition is not particularly limited as long as the required resin thickness is obtained, and may be one time or multiple times.

The image display member 1 is, for example, an image display panel in which a polarizing plate is formed on the viewing side surface of the image display cell. Examples of image display cells include liquid crystal cells and organic EL cells. Examples of liquid crystal cells include reflective liquid crystal cells and transmissive liquid crystal cells. The image display member 1 is, for example, a liquid crystal display panel, an organic EL display panel, a touch panel, or the like. A touch panel means an image display/input panel that combines a display element such as a liquid crystal display panel and a position input device such as a touch pad.

The photocurable resin composition for forming the curable resin layer 2 contains, for example, a photoradical reactive component, at least one of a plasticizer and a tackifying component, and a photopolymerization initiator. The photocurable resin composition may further contain other components as long as the effects of the present technology are not impaired.

<Photo-radical reactive component>
The photoradical-reactive component contains at least one of a (meth)acrylate oligomer and a (meth)acrylate monomer. The (meth)acrylate oligomer has polyisoprene, polyurethane, polybutadiene, or the like in its skeleton, and preferably has polyurethane in its skeleton (urethane (meth)acrylate oligomer). The (meth)acrylate oligomer preferably has 1 to 4 (meth)acrylic groups, more preferably 2 to 3 (meth)acrylic groups. Commercially available urethane (meth)acrylate oligomers include, for example, CN9014 (manufactured by Sartomer), EBECRYL 230, and EBECRYL 270 (manufactured by Daicel Allnex).

A (meth)acrylate monomer is used as a reactive diluent for imparting sufficient reactivity, coatability, etc. to the photocurable resin composition. The (meth)acrylate monomer may be a monofunctional (meth)acrylate, a bifunctional (meth)acrylate, or a polyfunctional (meth)acrylate. From the viewpoint of compatibility with other components, the (meth)acrylate monomer includes, for example, a (meth)acrylate monomer having a hydroxyl group (e.g., 4-hydroxybutyl acrylate), a (meth)acrylate monomer having a cyclic structure (e.g., iso bornyl acrylate, dicyclopentenyloxyethyl methacrylate), alkyl (meth)acrylate monomers having 5 to 20 carbon atoms (e.g., n-octyl acrylate, isodecyl acrylate, lauryl acrylate, isostearyl acrylate), polyfunctional (meth)acrylates It preferably contains monomers (eg, pentaerythritol (tri/tetra)acrylate, neopentylglycol hydroxypivalate diacrylate) and the like.

The total content of the (meth)acrylate oligomer and the (meth)acrylate monomer in the photocurable resin composition can be 95% by mass or less, and may be 90% by mass or less. Further, the total content of the (meth)acrylate oligomer and the (meth)acrylate monomer in the photocurable resin composition may be 20% by mass or more, may be 30% by mass or more, or may be 35% by mass. % or more. The (meth)acrylate oligomer and/or (meth)acrylate monomer may be used alone or in combination of two or more. When two or more (meth)acrylate oligomers and/or (meth)acrylate monomers are used in combination, the total content thereof is preferably within the range described above.

<Photoinitiator>
A known radical photopolymerization initiator can be used as the photopolymerization initiator. As the photopolymerization initiator, an alkylphenone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, an intramolecular hydrogen abstraction type photopolymerization initiator, or the like can be used. Specific examples include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 1-hydroxy-cyclohexyl-phenyl-ketone, methyl phenylglyoxylate and the like. Examples of commercially available products include LUCIRIN TPO, Irgacure 184, IRGACURE MBF (manufactured by BASF), and Esacure TZT (manufactured by Lamberti).

The total content of the photopolymerization initiator in the photocurable resin composition may be 10% by mass or less, may be 8% by mass or less, or may be 6% by mass or less. Further, the total content of the photopolymerization initiator in the photocurable resin composition may be 0.1% by mass or more, may be 1% by mass or more, or may be 2% by mass or more. good too. A photoinitiator may be used individually by 1 type, and may use 2 or more types together. When two or more photopolymerization initiators are used in combination, the total content thereof is preferably within the range described above.

<Plasticizer and tackifier>
The plasticizer and tackifier do not substantially react with the (meth)acrylate oligomer and the (meth)acrylate monomer upon irradiation with light. Examples of tackifier components include solid tackifiers and liquid oil components. Examples of solid tackifiers include terpene resins such as terpene resins, terpene phenolic resins and hydrogenated terpene resins, rosin resins such as natural rosin, polymerized rosin, rosin esters and hydrogenated rosins, and terpene hydrogenated resins. . Examples of liquid oil components include polybutadiene-based oils and polyisoprene-based oils. Examples of commercially available plasticizers and tackifiers include Clearon M105 (manufactured by Yasuhara Chemical Co., Ltd.), GI-1000 and GI-3000 (manufactured by Nippon Soda Co., Ltd.).

When the photocurable resin composition contains at least one of a plasticizer and a tackifier, the total content of the plasticizer and tackifier in the photocurable resin composition should be 70% by mass or less. may be 65% by mass or less, 60% by mass or less, or 58% by mass or less. The total content of the plasticizer and tackifier in the photocurable resin composition may be 0.5% by mass or more, may be 2% by mass or more, or may be 4% by mass or more. It may be present, may be 5% by mass or more, or may be 7% by mass or more. The plasticizer and/or tackifier may be used alone or in combination of two or more. When two or more plasticizers and/or tackifiers are used in combination, the total content of the plasticizers and/or tackifiers is preferably within the range described above.

<Other ingredients>
In addition to the components described above, the photocurable resin composition includes, for example, a polymer component (a polymer component other than the above-described photo-radical reactive component, plasticizer, and tackifier), oxidation It may further contain inhibitors, light stabilizers, silane coupling agents, and the like. As the polymer component, for example, Hitaloid 7927 (manufactured by Hitachi Chemical Co., Ltd.) can be used. This Hitaloid 7927 is an ultraviolet curable resin containing a polymer as a main component and an acrylic monomer as a reactive diluent, and the polymer as a main component functions as a tackifier. In the present invention, when the photocurable resin composition contains Hitaloid 7927, the content of Hitaloid 7927 in the photocurable resin composition is calculated as the content of the tackifier described above. As the antioxidant, for example, a hindered phenol-based antioxidant can be used. Commercially available antioxidants include, for example, IRGANOX1520L and IRGANOX1010 (manufactured by BASF). As the light stabilizer, for example, a hindered amine light stabilizer can be used. As a commercially available light stabilizer, for example, ADEKA STAB LA-52 (manufactured by ADEKA) can be used. For silane coupling, for example, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane can be used. Examples of commercially available silane coupling products include KBM5103, KBM503, and KBM803 (manufactured by Shin-Etsu Silicone Co., Ltd.).

<Step B>
In step B of this manufacturing method, the curable resin layer 2 is irradiated with light from a UV-LED as shown in FIG. 2 to form a pre-cured layer 5 as shown in FIG. In step B, the curable resin layer 2 formed in step A is irradiated with a first light having a peak in the wavelength range of 360 to 430 nm and a second light having a peak in the wavelength range of 200 to 345 nm. Irradiate.

The light irradiation in step B is preferably performed so that the reaction rate of the temporary hardened layer 5 is 10 to 90%, more preferably 40 to 90%, and more preferably 70 to 90%. It is more preferable to perform The reaction rate is a numerical value defined as the ratio (consumption ratio) of the amount of (meth)acryloyl groups after light irradiation to the amount of (meth)acryloyl groups in the curable resin layer before light irradiation. . The larger the value of this reaction rate, the more advanced the curing. Specifically, the reaction rate is the absorption peak height (X) from 1640 to 1620 cm ⁻¹ from the baseline in the FT-IR measurement chart of the curable resin layer before light irradiation, and the curable resin after light irradiation. It can be calculated by substituting the absorption peak height (Y) at 1640 to 1620 cm ⁻¹ from the baseline in the FT-IR measurement chart of the layer (cured resin layer 6) into the following formula.
Reaction rate (%) = [(XY) / X] × 100

In step B, a portion of the curable resin layer 2 where oxygen inhibition occurs by irradiating the curable resin layer 2 with a first light having a peak in the wavelength range of 360 to 430 nm, specifically the curable resin layer 2. It is preferable to irradiate the surface with a first light having a peak in the wavelength range of 360 to 430 nm and a second light having a peak in the wavelength range of 200 to 345 nm.

In step B, light is irradiated so that the integrated light intensity of the first light having a peak in the wavelength range of 360 to 430 nm is greater than the integrated light intensity of the second light having a peak in the wavelength range of 200 to 345 nm. is preferred. This makes it possible to improve the adhesion performance during temporary curing. As an example, the integrated light intensity of the first light having a peak in the wavelength range of 360 to 430 nm is in the range of 2000 to 5000 mJ/cm ² , and the integrated light intensity of the second light having a peak in the wavelength range of 200 to 345 nm is It is preferably in the range of 20 mJ/cm ² or more and less than 1000 mJ/cm ² . In step B, it is preferable to irradiate, for example, light having an emission wavelength of 365±5 nm as the first light having a peak in the wavelength range of 360 to 430 nm at an illuminance of 100 to 500 mW/cm ² . Further, in step B, it is preferable to irradiate, for example, light having an emission wavelength of 280±5 nm as the second light having a peak in the wavelength range of 200 to 345 nm under the condition of an illuminance of 10 to 100 mW/cm ² . As the UV-LED used in step B, for example, an LED having an emission peak wavelength in the range of 360 to 430 nm (e.g., an emission wavelength of 365±5 nm) and an emission peak wavelength of 200 to 345 nm (e.g., emission A device with an LED whose wavelength is 280±5 nm) can be used.

In step B, the first light having a peak in the wavelength range of 360 to 430 nm may be irradiated simultaneously with the second light having a peak in the wavelength range of 200 to 345 nm. Further, in step B, the second light having a peak in the wavelength range of 200 to 345 nm may be applied after the first light having a peak in the wavelength range of 360 to 430 nm is applied. In step B, the first light having a peak in the wavelength range of 360 to 430 nm may be applied after the second light having a peak in the wavelength range of 200 to 345 nm is applied.

In this manufacturing method, it is preferable to prevent the provisional hardening layer 5 from dripping or deforming during the bonding operation in step C, which will be described later. For example, in step B, before irradiating the curable resin layer 2 with a first light having a peak in the wavelength range of 360 to 430 nm and a second light having a peak in the wavelength range of 200 to 345 nm, It is preferable to irradiate the resin layer 2 with light so that the viscosity of the resin layer 2 becomes 20 Pa·S or more (cone plate rheometer, 25° C., cone and plate C35/2, number of revolutions 10 rpm).

<Process C>
In step C, the front plate 4 and the image display member 1 are bonded together with the temporary hardening layer 5 interposed therebetween, as shown in FIG. 4, for example. For example, in step C, the front plate 4 is attached to the image display member 1 from the temporary hardening layer 5 side. The lamination can be performed, for example, by applying pressure at 10 to 80° C. using a known crimping device.

The front plate 4 may be any material as long as it has optical transparency such that the image formed on the image display member 2 can be visually recognized. material and sheet material. These materials may be subjected to hard coating treatment, antireflection treatment, or the like on one or both sides thereof. Physical properties such as the thickness and elastic modulus of the front plate 4 can be appropriately determined according to the purpose of use. Also, the front plate 4 may be a laminate of various sheets or film materials such as a touch panel module.

A light shielding layer 3 may be provided on the periphery of the front plate 4 to improve the contrast of the image. The light shielding layer 3 can be formed, for example, by applying a paint colored black or the like by a screen printing method or the like, and drying and curing the paint. The thickness of the light shielding layer 3 is usually 5-100 μm.

<Process D>
In step D, for example, the temporarily cured layer 5 shown in FIG. 5 is irradiated with light through the front plate 4 to form a cured resin layer 6 as shown in FIG. The reason why the temporary hardening layer 5 is fully cured in the process D is to sufficiently harden the temporary hardening layer 5 to bond and laminate the image display member 1 and the front plate 4 . By performing the process D, as shown in FIG. 6, the image display device 7 having the image display member 1, the cured resin layer 6, and the front plate 4 in this order is obtained.

The main curing (light irradiation) in step D is preferably performed so that the reaction rate of the cured resin layer 6 is 90% or more, more preferably 97% or more. There are no particular restrictions on the type, output, illuminance, integrated light amount, etc. of the light source when performing the main curing, and known photoradical polymerization process conditions for (meth)acrylate using ultraviolet irradiation can be employed. For example, ultraviolet irradiation is preferably performed using an ultraviolet irradiation machine (metal halide lamp, high-pressure mercury lamp, UV-LED, etc.) under the conditions of illuminance of 50 to 300 mW/cm ² and integrated light intensity of 1000 to 6000 mJ/cm ² . In particular, in the step D, it is preferable to irradiate the first light having a peak in the wavelength range of 360 to 430 nm using a UV-LED in view of the requirement for long life performance of the ultraviolet irradiation device as described above.

In step D, if necessary, the temporary hardening layer 5 between the light shielding layer 3 of the front plate 4 and the image display member 1 may be irradiated with light to fully cure the temporary hardening layer 5. .

The cured resin layer 6 in the image display device 7 obtained by this manufacturing method preferably has a transmittance of 90% or more in the visible light region. By satisfying such a range, the visibility of the image formed on the image display member 1 can be improved. The refractive index of the cured resin layer 6 is preferably substantially the same as that of the image display member 1 and the front panel 4 . The refractive index of the cured resin layer 6 is preferably 1.45 or more and 1.55 or less, for example. Thereby, the brightness and contrast of the image light from the image display member 1 can be increased, and the visibility can be improved. The thickness of the cured resin layer 6 can be, for example, approximately 25 to 200 μm.

According to the present manufacturing method as described above, it is possible to improve the adhesion performance during temporary curing.

In step A, instead of applying the photocurable resin composition to the surface of the image display member 1, the photocurable resin composition is applied to the surface of the front plate 4 on which the light shielding layer 3 is formed. You may Alternatively, a front plate without the light shielding layer 3 may be used as the front plate.

Examples of the present technology will be described below. Note that the present technology is not limited to these examples.

<Preparation of photocurable resin composition>
A photocurable resin composition was prepared by uniformly mixing each component in the compounding amounts (parts by mass) shown in Table 1.

The abbreviations in Table 1 are the following compounds.
Urethane acrylate oligomer: number average molecular weight 20000
CN9014: urethane acrylate oligomer, Sartomer Hitaloid 7927: Hitachi Chemical 4HBA: 4-hydroxybutyl acrylate, BASF ISTA: isostearyl acrylate, Osaka Organic Chemical Miramer M210: neopentylglycol hydroxypivalate diacrylate, MIWON PETIA: pentaerythritol (tri/tetra) acrylate NOA: n-octyl acrylate IDA: isodecyl acrylate IBXA: isobornyl acrylate FA-512M: dicyclopentenyloxyethyl methacrylate LA: lauryl acrylate M105: terpene resin, product Name: Clearon M105, GI-1000 manufactured by Yasuhara Chemical Co., Ltd.: Hydrogenated polybutadiene at both ends, GI-3000 manufactured by Nippon Soda Co., Ltd.: Hydrogenated polybutadiene at both ends, Terpene resin manufactured by Nippon Soda Co., Ltd.: Number average molecular weight 800
TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, product name: LUCIRIN TPO, BASF Irg184D: 1-hydroxy-cyclohexyl-phenyl-ketone, product name; Irgacure184, BASF MBF: phenylglyoxyl Methyl acid, product name; IRGACURE MBF, TZT manufactured by BASF: Product name; Esacure TZT, manufactured by Lamberti

[Example 1]
<Preparation of test sample using resin A>
As shown in FIG. 7A, a photocurable resin composition 12 was applied from a slit nozzle 11 to a thickness of 33 μm from one end to the other end of the surface of a PET film 10 (thickness: 130 mm). After that, the applied photocurable resin composition 12 was irradiated with light having a peak at a wavelength of 365 nm from the UV-LED 13 so that the integrated amount of light was 500 mJ/cm ² . This light irradiation was performed to suppress dripping of the applied photocurable resin composition. Thus, the first curable resin layer 14A was formed. Next, as shown in FIG. 7B, the photocurable resin composition 12 is applied from the slit nozzle 11 onto the curable resin layer 14A so as to have a thickness of 33 μm, and then the applied photocurable resin composition A second curable resin layer 14B was formed by irradiating the article 12 with light having a peak at a wavelength of 365 nm from the UV-LED 13 so that the integrated amount of light was 500 mJ/cm ² . This light irradiation was also performed to suppress dripping of the applied photocurable resin composition. Next, as shown in FIG. 7(C), the photocurable resin composition 12 is applied from the slit nozzle 11 onto the curable resin layer 14B so as to have a thickness of 33 μm, and then the applied photocurable resin composition A third curable resin layer 14C was formed by irradiating the article 12 with light having a peak at a wavelength of 365 nm from the UV-LED 13 so that the integrated amount of light was 500 mJ/cm ² . This light irradiation was also performed to suppress dripping of the applied photocurable resin composition. As a result, a laminate was obtained in which a curable resin layer 14 having a thickness of about 100 μm was formed on the PET film 10 .

As shown in FIG. 7D, UV-LEDs (manufactured by CCS, a plurality of LEDs with an emission wavelength of 365 nm and a plurality of LEDs with an emission wavelength of 280 nm) are applied to the curable resin layer 14 of the laminate. from an irradiation range of 80 mm × 80 mm), light with an intensity of ²⁰⁰ mW/cm ² and a peak at a wavelength of 365 nm so that the integrated light amount is 5000 mJ/cm ² Light having a peak wavelength of 280 nm with an intensity of 20 mW/cm ² was irradiated. As a result, a laminate was obtained in which the temporary hardening layer 15 was formed on the PET film 10 . The curing rate of the temporary curing layer 15 was about 80 to 90% when the absorption peak height at 1640 to 1620 cm ⁻¹ from the baseline in the FT-IR measurement chart was used as an index.

As shown in FIG. 7(E), the laminate was cut to have a width of 25 mm. As shown in FIG. 7(F), the cut laminate was attached to a slide glass 16 (width 25 mm, thickness 1 mm). As shown in FIG. 7(G), pressure was applied using a 2 kg load roller 17 from the laminate side. As a result, the test sample 18 shown in FIG. 7(H), that is, the test sample in which the PET film 10 and the slide glass 16 are bonded via the temporary hardening layer 15 (10 mm × 25 mm, thickness 0.1 mm) 18 was obtained.

<Shear strength measurement of temporary hardened layer>
The shear strength of the temporarily hardened layer 15 in the test sample 18 was measured by the method shown in FIG. Specifically, using a desktop precision universal testing machine (manufactured by Shimadzu Corporation, Autograph), the PET film 10 positioned below the test sample 18 is fixed with a jig 19, and the slide glass positioned above The shear strength of the temporary hardened layer 15 was measured when the temporary hardened layer 16 was peeled off at a rate of 5 mm/min in the vertical direction via the jig 20 . The results are shown in FIG. 9 and Table 2.

[Examples 2 to 6, Comparative Examples 1 and 2]
A test sample was prepared in the same manner as in Example 1, except that the integrated amount of light irradiated to the curable resin layer 14 of the laminate was as shown in the table below, and the temporary cured layer in the test sample The shear strength of was measured. The results are shown in FIG. 9 and Table 2.

[Example 7, Comparative Examples 3 to 5]
A test sample was prepared in the same manner as in Example 1 except that resin B was used and the integrated amount of light irradiated to the curable resin layer 14 of the laminate was set as shown in the table below. The shear strength of the temporary hardening layer in the sample was measured. The results are shown in FIG. 10 and Table 3.

[Example 8, Comparative Examples 6 to 8]
A test sample was prepared in the same manner as in Example 1 except that resin C was used and the integrated amount of light irradiated to the curable resin layer 14 of the laminate was set as shown in the table below. The shear strength of the temporary hardening layer in the sample was measured. The results are shown in FIG. 11 and Table 4.

[Example 9, Comparative Examples 9 to 11]
A test sample was prepared in the same manner as in Example 1 except that resin D was used and the integrated amount of light irradiated to the curable resin layer 14 of the laminate was set as shown in the table below. The shear strength of the temporary hardening layer in the sample was measured. In Comparative Example 10, only light having a peak at a wavelength of 365 nm with an intensity of 600 mW/cm ² was irradiated from the UV-LED so that the integrated light amount was 6000 mJ/cm ² . The results are shown in FIG. 12 and Table 5.

[Example 10, Comparative Example 12]
A test sample was prepared in the same manner as in Example 1 except that resin E was used and the integrated amount of light irradiated to the curable resin layer 14 of the laminate was set as shown in the table below. The shear strength of the temporary hardening layer in the sample was measured. The results are shown in FIG. 13 and Table 6.

From the results of Examples 1 to 10 and Comparative Examples 1 to 12, the light irradiated in the process of forming a temporary cured layer by irradiating the curable resin layer with light from a UV-LED has a peak in the wavelength range of 360 to 430 nm. and the second light having a peak in the wavelength range of 200 to 345 nm, the shear strength of the temporary cured layer is good, that is, the adhesive performance during temporary curing is good. It turns out there is. Further, from the results of Example 9 and Comparative Example 11, it was found that in Example 9, it was possible to achieve adhesion performance during temporary curing that was equal to or higher than that during irradiation with a metal halide lamp. Furthermore, from the results of Examples 1 to 10, it was found that the tendency of improvement in adhesion performance during temporary curing does not depend on the composition ratio of the photocurable resin composition.

From the results of Examples 1 to 6, when resin A was used, in the step of forming a temporary cured layer by irradiating the curable resin layer with light from a UV-LED, a peak was observed in the wavelength range of 360 to 430 nm. The integrated light amount of the first light is in the range of 2000 to 5000 mJ/cm ² , and the integrated light amount of the second light having a peak in the wavelength range of 200 to 345 nm is in the range of 20 mJ/cm ² or more and less than 1000 mJ/cm ² and more preferably, the integrated light quantity of the second light having a peak in the wavelength range of 200 to 345 nm is in the range of 500 mJ/cm ² or more and less than 1000 mJ/cm ² .

In Example 8 and Comparative Examples 6 and 8, since resin C containing a photopolymerization initiator exhibiting relatively mild reactivity and having a large proportion of plasticizer was used, compared to the case of using other resins Although there was a tendency that the shear strength at the time of temporary curing was difficult to develop, it was found that Example 8 exhibited a shear strength that was at least twice that of Comparative Examples 6-8.

In Comparative Examples 1 to 12, the light irradiated in the step of irradiating the curable resin layer with light from the UV-LED to form a temporary cured layer has a peak in the wavelength range of 360 to 430 nm. It was found that since only light with a peak in the range of 200 to 345 nm was included, the adhesion performance during temporary curing was not good.

In Comparative Example 4, the integrated light quantity of light having a peak in the wavelength range of 360 to 430 nm from the UV-LED was increased to 8000 mJ/cm ² , but the light having a peak in the wavelength range of 200 to 345 nm was not irradiated. , the shear strength was found to be extremely low compared to Example 7. Moreover, in Comparative Example 5 in which only light having a peak in the wavelength range of 200 to 345 nm was irradiated, the shear strength was found to be significantly lower than that in Example 7. From these results, considering the curability of the deep part of the curable resin layer, in the step of forming the temporary cured layer, light having a peak in the wavelength range of 360 to 430 nm and light having a peak in the wavelength range of 200 to 345 nm It turned out that it is essential to use light together.

In Comparative Example 10, the illuminance of light having a peak in the wavelength range of 360 to 430 nm from the UV-LED was increased to 600 mW/cm ² and the integrated light amount was increased to 6000 mJ/cm ² , but the wavelength was 200 to 345 nm. It was found that the measurement result of the shear strength was inferior to that of Example 9 because light having a peak in the range of was not irradiated.

<Measurement of shear strength of cured resin layer>
[Example 9-1]
The temporarily cured layer of the test sample in Example 9 was irradiated with light having an intensity of 200 mW/cm ² using a metal halide lamp with a conveyor (manufactured by USIO) so that the integrated light amount was 5000 mJ/cm ² . As a result, the temporary hardened layer was completely hardened to form a hardened resin layer. The curing rate of the cured resin layer was 97%. The shear strength of this cured resin layer was measured by the same method as for the temporarily cured layer described above. The results are shown in FIG. In addition, N1 to N4 in FIG. 14 represent the measurement results of the shear strength of four test samples prepared for each test. The average (*) in FIG. 14 represents the average value of the shear strength measurement results of N1 to N4.

[Example 9-2]
The temporary cured layer of the test sample in Example 9 was surface irradiated with light having a peak at a wavelength of 365 nm with an intensity of ²⁰⁰ mW/cm using a UV ^- LED so that the integrated light amount was 5000 mJ/cm . . As a result, the temporary hardened layer was completely hardened to form a hardened resin layer. The curing rate of the cured resin layer was 97%. The shear strength of this cured resin layer was measured by the same method as for the temporarily cured layer described above. The results are shown in FIG.

[Comparative Example 9-1]
The shear strength of the cured resin layer was measured in the same manner as in Example 9-1, except that the test sample in Comparative Example 9 was used. The results are shown in FIG.

[Comparative Example 9-2]
The shear strength of the cured resin layer was measured in the same manner as in Example 9-2, except that the test sample in Comparative Example 9 was used. The results are shown in FIG.

From the results of Examples 9-1 and 9-2 and Comparative Examples 9-1 and 9-2, it was found that the strength of the cured resin layer was almost the same. It is considered that this is because the difference in physical adhesive strength (the influence of oxygen inhibition) is noticeable during temporary curing, while the difference in chemical adhesive strength is added after main curing.

1 image display member, 2 curable resin layer, 3 light shielding layer, 4 front panel, 5 temporary hardening layer, 6 hardening resin layer, 7 image display device, 10 PET film, 11 slit nozzle, 12 photocurable resin composition, 13 UV-LED, 14 curable resin layer, 15 temporary hardened layer, 16 slide glass, 17 load roller, 18 test sample, 19 jig, 20 jig

Claims (9)

A step A of forming a curable resin layer made of a photocurable resin composition on the surface of the front plate or the image display member;
The curable resin layer is irradiated with light from a UV-LED device having an LED with an emission peak wavelength of 360 to 430 nm and an LED with an emission peak wavelength of 200 to 345 nm to form a temporary cured layer. a step B;
A step C of bonding the front plate and the image display member together via the temporary hardening layer;
A step D of irradiating the temporary cured layer with light through the front plate to form a cured resin layer,
The light to be irradiated in step B includes a first light having a peak in the wavelength range of 360 to 430 nm and a second light having a peak in the wavelength range of 200 to 345 nm,
In the step B, the method of manufacturing an image display device, wherein the curable resin layer is irradiated with the first light, and a portion of the curable resin layer where oxygen inhibition occurs is irradiated with the second light. In the step B, the curable resin layer is irradiated with the first light and the second light so that the integrated light amount of the first light is larger than the integrated light amount of the second light. 2. The method of manufacturing an image display device according to claim 1. 3. The method of manufacturing an image display device according to claim 1, wherein in the step B, the surface of the curable resin layer is irradiated with the first light and the second light. 4. The method for manufacturing an image display device according to claim 1, wherein the curable resin layer has a thickness of 25 to 350 μm. In the step B, the integrated light amount of the first light is in the range of 2000 to 5000 mJ/cm ² , and the integrated light amount of the second light is in the range of 20 mJ/cm ² or more and less than 1000 mJ/cm ² . Item 5. A method for manufacturing an image display device according to any one of Items 1 to 4. The photocurable resin composition according to any one of claims 1 to 5, which contains a photoradical reactive component, a photopolymerization initiator, and at least one of a plasticizer and a tackifier component. A method for manufacturing an image display device. 7. The method of manufacturing an image display device according to claim 6, wherein the photo-radical reactive component contains at least one of a (meth)acrylate oligomer and a (meth)acrylate monomer. The photopolymerization initiator contains at least one of an alkylphenone photopolymerization initiator, an acylphosphine oxide photopolymerization initiator, a benzophenone photopolymerization initiator, and an intramolecular hydrogen abstraction type photopolymerization initiator. Item 8. A method for manufacturing an image display device according to Item 6 or 7. The photocurable resin composition contains a total of 30 to 90% by mass of the photoradical reactive component, 2 to 6% by mass of the photopolymerization initiator, and at least one of the plasticizer and the tackifier component. The method for manufacturing an image display device according to any one of claims 6 to 8, containing 5 to 58% by mass.

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