Substrate for cleaning sheet and manufacturing method thereof

Abstract

To provide a substrate for a cleaning sheet with a heat resistance property that can restrict degradation due to thermal oxidation of a cushioning property, followability and the like, when cleaning a cleaning object such as a probe, also in a high temperature region.SOLUTION: A substrate for a cleaning sheet includes a resin sheet with multiple tear-shaped air bubbles. The resin sheet comprises polyurethane urea resin, and a compound having a hindered phenol structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substrate for a cleaning sheet and a method for producing the same. [Background technology]

[0002] Probe cards equipped with probes (tipped needles) are used in tests to ensure the quality of semiconductor devices and the like. In such tests, the probes are brought into contact with the test object, so if there is any foreign matter attached to the tip of the probe, it can affect the test results. In order to remove any foreign matter that may be attached to the tip of the probe, the probe is cleaned using a member called a cleaning sheet.

[0003] As an example of such a cleaning sheet, Patent Document 1 discloses an abrasive sheet for needle-shaped workpieces, in which the surface of an elastic film made of a dried product of polyester-based urethane resin or ether-based polyurethane resin is coated with an abrasive layer made of a dried product of a mixed liquid in which abrasive grains are dispersed in an aqueous resin solution. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-006035 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, power devices, such as those made of silicon carbide (SiC) and gallium nitride (GaN), have become increasingly popular. Accordingly, cleaning sheets are expected to withstand use in higher temperature ranges. When a polishing sheet such as that disclosed in Patent Document 1 is used as a cleaning sheet in such high temperature ranges, its performance as a cleaning sheet tends to deteriorate due to insufficient heat resistance. Such deterioration in performance can lead to insufficient cleaning of probes, which may result in reduced yields and reduced quality in the manufacturing process of semiconductor devices, etc.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a substrate for a cleaning sheet that has heat resistance even in a high temperature range. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by applying a specific material to the substrate of a cleaning sheet, thereby completing the present invention.

[0008] That is, the present invention includes the following aspects. [1] a resin sheet having a plurality of teardrop-shaped bubbles; The resin sheet contains a polyurethane urea resin and a compound having a hindered phenol structure. Base material for cleaning sheets. [2] The content of the hindered phenol structure is 2.0×10 as the content of the compound relative to the polyurethane urea resin / molecular weight of the compound×number of the hindered phenol structures per molecule. -5 ~1.2×10 -4 equivalents / g, [1] The substrate for a cleaning sheet according to [1]. [3] When the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 175°C for 1 hour and the value Mp2 after heating is 40% or less as expressed as 100 × (Mp1 - Mp2) / Mp1. [1] or [2]. The cleaning sheet substrate. [4] When the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 200°C for 1 hour and the value Mp3 after heating is 70% or less as expressed as 100 × (Mp1 - Mp3) / Mp1. The substrate for a cleaning sheet according to any one of [1] to [3]. [5] For cleaning the probe, The substrate for a cleaning sheet according to any one of [1] to [4]. [6] a mixing step of mixing a polyurethane urea resin with a compound having a hindered phenol structure to obtain a polyurethane urea resin-containing solution; a coating step of coating the polyurethane urea resin-containing solution onto a film-forming substrate; and a solidification step of solidifying the polyurethane urea resin-containing solution to obtain a resin sheet. A method for producing a substrate for a cleaning sheet. [7] In the mixing step, the content of the hindered phenol structure is 2.0×10 as the content of the compound relative to the polyurethane urea resin / molecular weight of the compound×number of the hindered phenol structures per molecule. -5 ~1.2×10 -4 The compounds are mixed so that the amount is equivalent to 1 / g. [6] A method for producing a substrate for a cleaning sheet according to [6]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a substrate for a cleaning sheet that has heat resistance even in a high temperature range. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating one aspect of use of the substrate for a cleaning sheet of the present embodiment. [Figure 2] 1 is a schematic diagram showing an example of a cross section of a substrate for a cleaning sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. Note that the present embodiment is an example for explaining the present invention, and the present invention is not limited to the following embodiment.

[0012] [Cleaning sheet substrate] The cleaning sheet substrate of the present embodiment includes a resin sheet having a plurality of teardrop-shaped bubbles, and the resin sheet includes a polyurethane urea resin and a compound having a hindered phenol structure. Due to this configuration, the substrate for a cleaning sheet of this embodiment has heat resistance even in a high temperature range.

[0013] An example of the use of the cleaning sheet substrate of this embodiment will be described with reference to FIG. 1. In the example of FIG. 1, the cleaning sheet 20 has a coating layer 2, a cleaning sheet substrate 10, and an adhesive layer 3, in this order. The cleaning sheet 20 can be fixed to a holding platen by the adhesive layer 3. This also fixes the relative position of the cleaning sheet 20 with respect to the cleaning target W. Next, the surface 2a of the coating layer 2 is brought into contact with the cleaning target W, and the cleaning sheet 20 is slid over the surface of the cleaning target W to perform cleaning. The cleaning target W is not particularly limited, but a probe is preferably used, and in particular, a probe for testing continuity of chips on a semiconductor wafer, which requires cleaning at high temperatures, is particularly preferably used. That is, the cleaning sheet substrate 10 of this embodiment is preferably used for cleaning probes, and in particular, a probe for testing continuity of semiconductor elements (power devices) for power control, which requires cleaning at high temperatures.

[0014] (resin sheet) Fig. 2 is a diagram schematically showing an example of a cross section of a cleaning sheet substrate of this embodiment. In the example of Fig. 2, a cleaning sheet substrate 10 includes a resin sheet 1. The resin sheet 1 has a plurality of teardrop-shaped bubbles P. The bubbles P may be formed by a wet film-forming method described below. An example of the wet film-forming method is, but is not limited to, a method in which a resin solution prepared by dissolving a resin such as a polyurethane urea resin in a water-miscible organic solvent is applied to a sheet-shaped film-forming substrate, and then the organic solvent is replaced with water in an aqueous coagulation liquid to obtain a resin sheet. When the resin sheet 1 is formed by a wet film-forming method, a skin layer (not shown) containing dense micropores may be formed on the surface 1a of the resin sheet 1. The surface of the skin layer tends to have fine flatness. The resin sheet 1 may have such a skin layer as it is, or at least a portion of the skin layer may be removed by grinding (buffing) or slicing to form openings on the surface 1a. A plurality of teardrop-shaped bubbles P are formed further inside the skin layer (inside the resin sheet). The bubbles P have a larger pore size than the micropores in the skin layer and are observed as rounded triangular pores (i.e., teardrop-shaped bubbles) along the thickness direction of the resin sheet. Of the plurality of bubbles P, the bubbles present on the surface 1a side of the resin sheet 1 may be smaller than the bubbles present on the surface 1b side of the resin sheet 1. In the resin sheet 1, pores (microbubbles; not shown) larger than the micropores of the skin layer but smaller than the bubbles P may be formed on the surface of the skin layer or further inside the skin layer. The resin sheet 1 may have interconnected pores in a three-dimensional network pattern. For example, the micropores, bubbles P, and microbubbles in the skin layer may be interconnected in a network pattern through interconnected pores. In the present embodiment, such a structure is easily obtained when the resin sheet is formed by a wet film-forming method, although this is not limited to the following.

[0015] In this embodiment, the resin sheet 1 itself may be used as the cleaning sheet substrate 10, or a laminate in which a plurality of resin sheets 1 are laminated may be used as the cleaning sheet substrate 10.

[0016] In this embodiment, the openings may be formed by buffing or slicing on the surface 1a side of the resin sheet 1, or by buffing or slicing on the surface 1b side of the resin sheet 1. When one surface is buffed or slicing, the other surface does not need to be buffed or slicing. When the resin sheet 1 has openings, it becomes easier to guide the cleaning target W into the resin sheet 1, which tends to improve the contact and followability between the cleaning sheet substrate 10 and the cleaning target W. When the cleaning sheet substrate 10 itself is used as the cleaning sheet 20, the surface that comes into contact with the cleaning target W may be surface 1a or 1b of the resin sheet 1. When a cleaning sheet 20 is used in which a coating layer 2 described below is formed on the cleaning sheet substrate 10, the surface that comes into contact with the cleaning target W may be surface 2a of the coating layer 2. In this embodiment, when buffing or slicing is performed on the surface 1a of the resin sheet 1, the openings formed on the surface 1a tend to be smaller than the openings formed on the surface 1b of the resin sheet 1 when buffing or slicing is performed on the surface 1b of the resin sheet 1. In this embodiment, whether to form the openings on the surface 1a or the surface 1b of the resin sheet 1 may be selected based on the size, shape, etc. of the cleaning target W.

[0017] (Polyurethane urea resin) The resin sheet contains a polyurethane urea resin as a matrix material constituting the resin sheet. The resin sheet may contain 80.0 to 100% by mass of polyurethane polyurea resin relative to the total amount of the matrix material. The polyurethane urea resin is not particularly limited as long as it contains a urethane bond and a urea bond in the molecule. For example, depending on the polyol component, polyether-based polyurethane urea resin, polyester-based polyurethane urea resin, polycarbonate-based polyurethane urea resin, etc. may be used. The polyurethane polyurea resin may be synthesized by a conventional method or may be commercially available. In this embodiment, the polyurethane urea resin may contain one type alone or two or more types in any combination and ratio. In this embodiment, the polyurethane urea resin preferably contains a polyether-based polyurethane urea resin, and more preferably consists of a polyether-based polyurethane polyurea resin.

[0018] The modulus of the polyurethane urea resin is not particularly limited, but is preferably 5 to 50 MPa, more preferably 10 to 45 MPa, and even more preferably 15 to 40 MPa. The modulus is an index representing the hardness of a resin, and is the value obtained by dividing the load applied when an unfoamed resin sheet is stretched 100% (stretched to twice its original length) by the unit area. The modulus can be adjusted appropriately by changing the types and ratios of the polymerization components of the polyurethane urea resin.

[0019] The content of the polyurethane urea resin in the resin sheet is not particularly limited, but from the viewpoint of improving cleaning performance, it is preferably 70.0 to 99.9 mass% relative to the total amount of the resin sheet, more preferably 80.0 to 99.0 mass%, even more preferably 85.0 to 97.0 mass%, and even more preferably 87.0 to 95.0 mass%.

[0020] (Compounds having a hindered phenol structure) The resin sheet contains a compound having a hindered phenol structure (hereinafter also referred to as "compound A"). The hindered phenol structure refers to a structure having a phenol skeleton in which an alkyl group R having a tertiary carbon atom is bonded to at least one of the carbon atoms (adjacent carbon atoms) adjacent to the carbon atom to which a phenolic hydroxyl group is bonded among the carbon atoms constituting the aromatic ring. The alkyl group R is preferably a t-butyl group. One of the adjacent carbon atoms may be bonded to a hydrogen atom or an alkyl group other than the alkyl group R. In this embodiment, it is preferable that an alkyl group having a tertiary carbon atom is bonded to both adjacent carbon atoms, and it is more preferable that a t-butyl group is bonded to both adjacent carbon atoms. In this embodiment, compound A can function as an antioxidant. Note that deterioration of the cleaning sheet that may occur at high temperatures is presumed to be due to thermal oxidation of the resin sheet constituting the cleaning sheet substrate when exposed to high temperatures. In particular, it is presumed that the physical properties of the resin sheet change due to decomposition of urethane bonds in the polyurethane urea resin contained in the resin sheet due to thermal oxidation. Here, in this embodiment, since the resin sheet contains compound A, thermal oxidation can be suppressed even at high temperatures. However, the mechanism of action of this embodiment is not limited to the above, and as long as the resin sheet contains compound A, it tends to have heat resistance even in a high temperature range.

[0021] In the present embodiment, the content of the hindered phenol structure is not particularly limited, but is preferably 2.0×10 as the content of compound A relative to the polyurethane urea resin / molecular weight of compound A×number of hindered phenol structures per molecule. -5 ~1.2×10 -4 It is preferable that the content of the hindered phenol structure is 2.0×10 equivalents / g. -5 When the content of the hindered phenol structure is 1.2×10 equivalents / g or more, the heat resistance of the substrate for the cleaning sheet tends to be further improved. -4 When the content is equal to or less than equivalents / g, the cleaning performance of the substrate for the cleaning sheet tends to be improved. From the above viewpoint, the content of the hindered phenol structure is 2.0 × 10 -5 ~1.0×10 -4 More preferably, it is 1.0 x 10 equivalents / g. -5 ~1.0×10 -4 Equivalents / g are even more preferred.

[0022] In calculating the content of the hindered phenol structure, when multiple types of polyurethane urea resins are contained in the resin sheet, the content of compound A is calculated based on the total amount of polyurethane urea resin. Similarly, when multiple types of compound A are contained in the resin sheet, the content of compound A is calculated based on the total amount of compound A. Furthermore, when multiple types of compound A are contained in the resin sheet, the "molecular weight of compound A" and the "number of hindered phenol structures per molecule" are calculated based on average values.

[0023] The content of the hindered phenol structure can be specifically measured by the method described in the Examples below. The content of the hindered phenol structure can be adjusted to the above-mentioned range by, for example, changing the types and compounding ratios of the polyurethane urea resin and compound A used to form the resin sheet.

[0024] In this embodiment, the content of compound A is not particularly limited, but is preferably 0.10 to 5.00 mass %, more preferably 0.30 to 4.00 mass %, and even more preferably 0.50 to 3.50 mass %, relative to the total amount of polyurethane urea resin.

[0025] Compound A is not particularly limited, and a conventionally known compound can be used. Specific examples thereof include, but are not limited to, tetrakis[methylene-3(3'5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane (melting point 110-130°C, molecular weight 1178), commercially available as IRGANOX 1010 (product name of BASF), IRGANOX 1010 FF (product name of BASF), Adeka STAB AO-60 (product name of ADEKA), SUMILIZER BP-101 (product name of Sumitomo Chemical Co., Ltd.), and Tominox TT (product name of Yoshitomi Pharmaceutical Co., Ltd.); 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (melting point 110-120°C, molecular weight 741), commercially available as GA-80 (product name, manufactured by Sumitomo Chemical Co., Ltd.) and Adeka Stab AO-80 (product name, manufactured by ADEKA Co., Ltd.); 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, commercially available as SUMILIZER GS (product name, manufactured by Sumitomo Chemical Co., Ltd.); IRGANOX 1035 (product name, manufactured by BASF), IRGANOX 1035 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (melting point >63°C, molecular weight 643), commercially available as FF (BASF product name), etc.; n-ocladecyl-3(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate (melting point 51-54°C, molecular weight 531), commercially available as IRGANOX 1076 (BASF product name), IRGANOX 1076 FD (BASF product name), IRGANOX 1076 DWJ (BASF product name), Adeka STAB AO-50 (ADEKA product name), SUMILIZER BP-76 (Sumitomo Chemical product name), Tominox SS (Yoshitomi Pharmaceutical product name), etc.; IRGANOX N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide] (melting point: 151 to 161°C, molecular weight: 637), commercially available as 1098 (BASF product name), etc.3-(4-hydroxy-3,5-diisopropylphenyl)octylpropionate (melting point <10°C, molecular weight 390), commercially available as IRGANOX 1135 (BASF product name); 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene (melting point 243-245°C, molecular weight 775), commercially available as IRGANOX 1330 (BASF product name) and Adeka STAB AO330 (ADEKA product name); 2,4-bis(dodecylthiomethyl)-6-methylphenol (melting point 28°C, molecular weight 525), commercially available as IRGANOX 1726 (BASF product name); and IRGANOX 1425. Calcium bis[3,5-di(tert-butyl)-4-hydroxybenzyl(ethoxy)phosphinate] (melting point 90-300°C, molecular weight 695), commercially available as IRGANOX WL (product name, manufactured by BASF); 2,4-bis(octylthiomethyl)-6-methylphenol (melting point 14°C, molecular weight 425), commercially available as IRGANOX 1520 L (product name, manufactured by BASF); bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)] (melting point 76-79°C, molecular weight 587), commercially available as IRGANOX 245 (product name, manufactured by BASF) and IRGANOX 245 FF (product name, manufactured by BASF); 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (melting point 104-108°C, molecular weight 639), commercially available as IRGANOX 259 (BASF product name), etc.; tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanate (melting point 220-226°C, molecular weight 784), commercially available as IRGANOX 3114 (BASF product name), etc.; bis[4-(1,1,3,3-tetramethylbutyl)phenyl]amine, commercially available as IRGANOX 5057 (BASF product name), etc.; IRGANOX 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol (melting point 91-96°C, molecular weight 589), commercially available as 565 (BASF product name), etc.Examples include diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate (melting point 116-121°C, molecular weight 356), which is commercially available as IRGAMOD 295 (product name, manufactured by BASF), and 1,3,5-tris[[4-(1,1-dimethylethyl)-3-hydroxy-2,6-dimethylphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (melting point 159-162°C, molecular weight 699), which is commercially available as IRGANOX 3790 (product name, manufactured by BASF) and CYANOX 1790 (product name, manufactured by Cytec Industries Inc.). These may be used alone or in combination of two or more.

[0026] The molecular weight of compound A is not particularly limited, but is preferably 200 or more, more preferably 500 or more, even more preferably 700 or more, and even more preferably 1000 or more. From the viewpoint of dispersibility in a resin solution, the molecular weight of compound A is preferably 2000 or less, more preferably 1500 or less. Here, the molecular weight can be measured by field desorption mass spectrometry or the like.

[0027] (optional ingredient) In addition to the polyurethane urea resin as a matrix material, the resin sheet may contain other resin components as long as the effects of the present invention are not impaired. In addition to the polyurethane polyurea resin, other resins such as polyurethane resin, polysulfone resin, and polyimide resin may be contained. The polyurethane resin may be synthesized by a conventional method or may be commercially available. Examples of commercially available products include CRISVON (trade name, manufactured by DIC Corporation), SANPREN (trade name, manufactured by Sanyo Chemical Industries, Ltd.), and LEZAMIN (trade name, manufactured by Dai-Nippon Fine Chemicals Co., Ltd.). The polysulfone resin may be synthesized by a conventional method or may be commercially available. Examples of commercially available products include Udel (trade name, manufactured by Solvay Advanced Polymers). The polyimide resin may be synthesized by a conventional method or may be commercially available. Examples of commercially available products include AURUM (trade name, manufactured by Mitsui Chemicals, Inc.). These may be used alone or in any combination and ratio of two or more types.

[0028] The resin sheet may contain other antioxidants in addition to compound A. The other antioxidants are not particularly limited, and conventionally known antioxidants can be used. For example, phosphorus-based antioxidants that serve to capture radicals generated from compound A can be mentioned. By using compound A and a phosphorus-based antioxidant in combination, it is expected that the effect of imparting heat resistance to the cleaning sheet substrate can be further improved.

[0029] The phosphorus-based antioxidant is not particularly limited, and any known phosphorus-based antioxidant can be used. Specific examples thereof include, but are not limited to, tris(2,4-di-t-butylphenyl)phosphite (melting point 146 to 152°C, molecular weight 583) commercially available as ADK STAB 2112 (product name of ADEKA), IRGAFOS 168 (product name of BASF), JP-650 (product name of Johoku Chemical Co., Ltd.), etc.; a 1:1 blend of IRGANOX B 225 or IRGAFOS 168 (product name of BASF) and IRGANOX 1010 (product name of BASF); a 2:1 blend of IRGANOX B 215 or IRGAFOS 168 (product name of BASF) and IRGANOX 1010 (product name of BASF); a 2:1 blend of IRGANOX B 220 or IRGAFOS 168 (product name of BASF) and IRGANOX a 3:1 blend of bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite (melting point 89-92, molecular weight 514) commercially available as IRGAFOS 38 (BASF); a mixture commercially available as IRGASTAB PUR 68 (BASF); 2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-N,N-bis[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-ethyl]ethanamine commercially available as IRGAFOS 12 (BASF); SUMILIZER 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]-2-methylphenol (melting point ≥ 115°C, molecular weight 661), commercially available as GP (product name, manufactured by Sumitomo Chemical Co., Ltd.); 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus (melting point 146-152°C, molecular weight 583), commercially available as ADK STAB HP-10I (product name, manufactured by ADEKA Corporation);Examples include hydrogenated bisphenol A pentaerythritol phosphite polymers, commercially available as JPH-3800 (product name, manufactured by Johoku Chemical Co., Ltd.). These may be used alone or in combination of two or more.

[0030] The resin sheet may contain a surfactant as a film-forming stabilizer or foaming adjuster, and the type of surfactant is not particularly limited. Examples of anionic surfactants include sodium lauryl sulfate, carboxylates, sulfonates, sulfates, and phosphates. Examples of nonionic surfactants include ester compounds, ether compounds, ester-ether compounds, amide compounds, and polyether-modified silicone oils.

[0031] The resin sheet may contain inorganic fillers such as carbon black in addition to the above components, but it is preferable that they not be contained from the viewpoint of cleaning properties.

[0032] In this embodiment, from the viewpoint of heat resistance, when the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 175°C for 1 hour and the value Mp2 after heating, expressed as 100 x (Mp1 - Mp2) / Mp1, is preferably 40% or less, more preferably 30% or less. When the reduction rate of the peak top molecular weight is 40% or less, decomposition of the urethane bond of the polyurethane urea resin in the resin sheet tends to be suppressed before and after heating in the high temperature range of 175°C. The reduction rate can be measured based on the method described in the examples below. The reduction rate can be adjusted to fall within the above range by, for example, adjusting the types and compounding ratios of the polyurethane urea resin and compound A used when forming the resin sheet.

[0033] In this embodiment, from the viewpoint of heat resistance, when the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 200°C for 1 hour and the value Mp3 after heating, expressed as 100 × (Mp1 - Mp3) / Mp1, is preferably 70% or less, more preferably 60% or less. When the reduction rate of the peak top molecular weight is 70% or less, decomposition of the urethane bond of the polyurethane urea resin in the resin sheet tends to be suppressed before and after heating in the high temperature range of 200°C. The reduction rate can be measured based on the method described in the examples below. The reduction rate can be adjusted to fall within the above range by, for example, adjusting the types and compounding ratios of the polyurethane urea resin and compound A used when forming the resin sheet.

[0034] The thickness of the cleaning sheet substrate of this embodiment is not particularly limited, but when buffing or slicing is performed to form openings on the surface, the thickness is preferably 100 to 1500 μm, more preferably 150 to 1000 μm, even more preferably 200 to 800 μm, and even more preferably 250 to 750 μm from the viewpoint of conformability as a cleaning sheet. When a skin layer is left, the thickness is preferably 50 to 1000 μm, more preferably 75 to 750 μm, even more preferably 100 to 650 μm, and even more preferably 120 to 600 μm from the viewpoint of flatness as a cleaning sheet. The thickness is measured in accordance with the measurement method described in JIS K 6505. That is, the thickness is measured by applying an initial load of 1 cm in the thickness direction of the resin sheet. 2 This is the thickness when a load of 100g is applied (stressed) per unit area.

[0035] The density of the cleaning sheet substrate of this embodiment is not particularly limited, but from the viewpoint of ease of handling as a cleaning sheet, it is preferably 0.100 to 0.500 g / cm 3 is preferable, and 0.150 to 0.450 g / cm 3More preferably, 0.200 to 0.400 g / cm 3 is more preferable. The density can be measured based on the method described in the examples below. The density can be adjusted to the above range by, for example, employing a manufacturing method for a cleaning sheet substrate described below, for example, by adjusting the amount of additives used in the manufacturing process of the resin sheet in this embodiment.

[0036] [Method for producing substrate for cleaning sheet] The method for producing a cleaning sheet substrate of this embodiment includes a mixing step of mixing a polyurethane urea resin with a compound having a hindered phenol structure to obtain a polyurethane urea resin-containing solution, an application step of applying the polyurethane urea resin-containing solution to a film-forming substrate, and a solidification step of solidifying the polyurethane urea resin-containing solution to obtain a resin sheet.

[0037] (Mixing process) The mixing step is a step of mixing a polyurethane urea resin with compound A to obtain a polyurethane urea resin-containing solution. In the mixing step, in addition to the polyurethane urea resin and compound A, other additives such as the above-mentioned other resins, other antioxidants, and surfactants may be mixed. The polyurethane urea resin may also be mixed with an organic solvent in which it can be dissolved. The organic solvent is not particularly limited and may be, for example, N,N-dimethylformamide (hereinafter abbreviated as "DMF").

[0038] In the mixing step, the content of the hindered phenol structure is not particularly limited, but is preferably 2.0×10 as the content of compound A relative to the total amount of polyurethane urea resin / molecular weight of compound A×number of hindered phenol structures per molecule. -5 ~1.2×10 -4 It is preferable to mix Compound A so that the compound A is mixed at a concentration of 2.0×10 equivalents / g. -5 ~1.0×10 -4 equivalents / g, more preferably 1.0×10-5 ~1.0×10 -4 equivalents / g. The content of hindered phenol structure is 2.0 x 10 -5 When the content of the hindered phenol structure is 1.2×10 equivalents / g or more, decomposition of the urethane bond of the polyurethane urea resin in the resin sheet of the cleaning sheet substrate tends to be suppressed in the high temperature range, and the heat resistance of the cleaning sheet substrate tends to be improved. -4 By ensuring that the content is equal to or less than equivalents / g, the film-forming properties of the resin sheet can be sufficiently ensured, and a substrate for a cleaning sheet having a smooth surface tends to be obtained.

[0039] In the mixing step, the mixing method for obtaining the polyurethane urea resin-containing solution is not particularly limited, and a general stirring device can be used, and can be appropriately selected depending on the properties of the polyurethane urea resin-containing solution.

[0040] (coating process) The coating step is a step of coating the polyurethane urea resin-containing solution obtained in the above step onto a film-forming substrate. The temperature conditions are not particularly limited, but room temperature is preferred.

[0041] In the coating step, the method for coating the polyurethane urea resin-containing solution is not particularly limited, and any known method can be used, including methods using coating devices such as a knife coater, blade coater, bar coater, roll coater, gravure coater, screen coater, curtain coater, spray coater, etc. Among these, it is preferable to use a knife coater from the viewpoints of controlling variations in coating thickness and improving work efficiency.

[0042] In the coating step, the thickness of the polyurethane urea resin-containing solution to be applied can be adjusted appropriately so that the thickness of the resin sheet to be finally obtained becomes the desired thickness.

[0043] In the coating step, the material of the film-forming substrate is not particularly limited, and examples thereof include resin films such as PET films, fabrics, nonwoven fabrics, etc. Among these, resin films such as PET films are preferred because they can increase the rigidity of the cleaning sheet substrate even when they are thin.

[0044] (solidification process) This is a process for solidifying a polyurethane urea resin-containing solution to obtain a resin sheet. In the solidification process, first, a coating of the polyurethane urea resin-containing solution applied to a film-forming substrate is continuously introduced into a solidification liquid containing a poor solvent for the polyurethane urea resin (e.g., water) as a main component. To adjust the resin regeneration rate, an organic solvent such as a polar solvent, such as the solvent in the resin-containing solution, may be added to the solidification liquid. The temperature of the solidification liquid is not particularly limited as long as it can solidify the resin, and may be, for example, 15 to 65°C.

[0045] In the coagulation liquid, a coating (skin layer) first forms at the interface between the resin-containing solution coating and the coagulation liquid, and numerous dense micropores form in the resin immediately adjacent to the coating. Subsequently, the solvent contained in the resin-containing solution diffuses into the coagulation liquid, and the poor solvent penetrates into the resin, resulting in the regeneration of a resin preferably having an open-cell structure. If the film-forming substrate is impermeable to liquids (e.g., PET film), the coagulation liquid does not penetrate the substrate, and the solvent in the resin solution is replaced by the poor solvent preferentially near the skin layer. This tends to result in the formation of multiple teardrop-shaped bubbles as larger bubbles in the inner region than near the skin layer. In this way, a precursor sheet is formed on the film-forming substrate.

[0046] Next, the obtained precursor sheet is peeled from the film-forming substrate and then subjected to a washing and drying process. The washing and drying process removes the solvent remaining in the precursor sheet formed by the washing process, thereby obtaining a resin sheet. Water can be used as the washing liquid. The washed resin sheet is then dried. The drying process of the resin sheet can be performed by a conventional method, for example, by drying in a dryer at 80 to 150°C for about 5 to 60 minutes. The obtained resin sheet can also be wound into a roll. In this way, a substrate for a cleaning sheet is obtained.

[0047] In addition to the above steps, a grinding / removal step may be included. In the grinding / removal step, surface 1a and / or surface 1b of resin sheet 1 are ground and / or partially removed by buffing or slicing. Buffing or slicing can improve the uniformity of the thickness of the resin sheet, and air bubbles in the resin sheet are exposed to the surface to form openings, which tends to further improve contact and followability with the object to be cleaned.

[0048] [Cleaning sheet] The cleaning sheet of the present embodiment includes the cleaning sheet substrate of the present embodiment. In the present embodiment, the cleaning sheet substrate itself may be used as the cleaning sheet, or a cleaning sheet substrate having a coating layer formed on the surface thereof may be used as the cleaning sheet.

[0049] 1, the cleaning sheet 20 includes a coating layer 2 formed on a cleaning sheet substrate 10. The coating layer 2 can be formed, for example, by applying a solution of abrasive particles (abrasive grains) and a resin to the surface of the cleaning sheet substrate 10, followed by drying.

[0050] The abrasive particles in the coating layer are not particularly limited, and examples thereof include diamond, white alumina, silicon carbide, boron carbide, cerium oxide, zirconium oxide, chromium oxide, iron oxide, titanium oxide, silicon dioxide, manganese dioxide, manganese trioxide, zirconium silicate, barium carbonate, glass, boron nitride, titanium nitride, etc. These can be used alone or in combination of two or more.

[0051] The resin in the coating layer is not particularly limited, and any conventionally known resin can be used, and can be appropriately selected depending on the desired performance, etc. Examples include polyester resin, polyurethane resin, etc.

[0052] In addition to the abrasive particles and resin, the coating layer may contain other known additives. Examples of additives include curing accelerators, catalysts, dyes, pigments, water repellents, hydrophilic agents, and antistatic agents. These may be used alone or in combination of two or more.

[0053] 1, the cleaning sheet 20 may have an adhesive layer 3. The material of the adhesive layer is not particularly limited, and any material may be selected from conventionally known double-sided tapes and adhesives, with heat resistance being preferred.

[0054] At least one surface of the cleaning sheet substrate 10 may be buffed or sliced ​​to form openings. In the example of FIG. 2, when the resin sheet 1 is buffed or sliced ​​to form openings on the surface 1a and used as the cleaning sheet substrate 10, the coating layer can be formed on the surface 1a, and the adhesive layer 3 can be formed on the surface 1b. In the example of FIG. 2, when the resin sheet 1 is buffed or sliced ​​to form openings on the surface 1b and used as the cleaning sheet substrate 10, the coating layer can be formed on the surface 1b, and the adhesive layer 3 can be formed on the surface 1a. In either case, the cleaning target W can be more easily guided into the resin sheet 1, which tends to improve the contact and tracking ability between the cleaning sheet substrate 10 and the cleaning target W.

[0055] 2, the openings formed on the surface 1b of the resin sheet 1 by buffing or slicing the surface 1b tend to be larger than the openings formed on the surface 1a when the surface 1a of the resin sheet 1 is buffed or sliced. Therefore, when the surface 1b of the resin sheet 1 is buffed or sliced ​​to form openings on the surface 1b and used as the cleaning sheet substrate 10, the contact and / or tracking ability tend to be improved even if the cleaning target W (e.g., a probe) has a complex shape. Furthermore, when the openings on the cleaning sheet substrate 10 are large, the surface area near the surface that is susceptible to heat tends to be large, making the sheet more susceptible to thermal oxidation, and therefore the effect of imparting heat resistance by the compound A tends to be more pronounced. [Example]

[0056] Hereinafter, the present embodiment will be described in more detail based on examples and comparative examples, but the present embodiment is not limited to these.

[0057] [Example 1] A polyurethane urea resin-containing solution was obtained by mixing 100 parts by mass of a polyether-based polyurethane urea resin solution (30 parts by mass of polyether-based polyurethane urea resin) with 50 parts by mass of DMF, 3 parts by mass of polyether-modified silicone, and 0.5 parts by mass of a compound having a hindered phenol structure (tetrakis[methylene-3(3'5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane; molecular weight 1178; hereinafter also referred to as "compound a") with 100 parts by mass of a 100% modulus 26 MPa polyether-based polyurethane urea resin solution. Next, a PET film was prepared as a film-forming substrate, and the polyurethane urea resin-containing solution was applied to the PET film using a knife coater. The PET film coated with the polyurethane urea resin-containing solution was immersed in a coagulation bath containing water as a coagulation liquid to coagulate the polyurethane resin-containing solution. The PET film was then peeled off, washed, and dried to obtain a resin sheet. The resulting resin sheet was used as a measurement sample and subjected to the following evaluations.

[0058] (Hindered phenol structure content) The content of compound a in the polyurethane urea resin was calculated from the amounts of polyurethane urea resin and compound a having a hindered phenol structure charged when preparing a polyurethane urea resin-containing solution. Using this content, the molecular weight of compound a, and the number of hindered phenol structures per molecule of compound a, the content of the hindered phenol structure was calculated using the following formula. Content of hindered phenol structure = Content of compound a in polyurethane urea resin / Molecular weight of compound a × Number of hindered phenol structures per molecule of compound a That is, in Example 1, the content of the hindered phenol structure was 5.7 × 10 -5 Calculated as equivalents / g.

[0059] (Thickness) The thickness of the resin sheet was measured in accordance with the measurement method described in JIS K 6505. That is, the resin sheet was subjected to an initial load of 1 cm in the thickness direction. 2The thickness was measured when a load of 100 g was applied (loaded) per unit area.

[0060] (density) The density was calculated from the volume and mass of a sample cut out from the resin sheet.

[0061] (molecular weight measurement) The peak top molecular weight Mp1 of the resin sheet was measured by the following gel filtration chromatography. (Sample preparation) 0.05 g of the resin sheet was dissolved in DMF to prepare a 1% by mass solution, which was then shaken overnight at room temperature. After shaking, 0.5 g of the supernatant was weighed out and further diluted with DMF to prepare a solution with a final concentration of 0.2%. The resulting solution was filtered through a 45 μm mesh filter to prepare a measurement sample. (Measurement method) The measurement sample was subjected to gel filtration chromatography measurement under the following measurement conditions to measure the peak top molecular weight (Mp) in terms of polyethylene glycol / polyethylene oxide (PEG / PEO). (Measurement conditions) Column: Shodex OHpak KB-805HQ (exclusion limit 2,000,000) Mobile phase: 5mM LiBr / DMF Flow rate: 0.75mL / min (21kg / cm 2 ) Oven: 60℃ Detector: RI 40℃ Sample volume: 30 μL

[0062] (heating test) The resin sheet was placed in a thermostatic bath and heated at 175°C for 1 hour. The heated resin sheet was subjected to the above-mentioned molecular weight measurement, and the obtained peak top molecular weight was designated Mp2. Separately, a resin sheet was placed in a thermostatic bath and heated at 200°C for 1 hour. The heated resin sheet was subjected to the above-mentioned molecular weight measurement, and the obtained peak top molecular weight was designated Mp3.

[0063] (reduction rate of peak top molecular weight) Using the peak top molecular weights Mp1, Mp2 and Mp3 obtained in the above measurement, the reduction rate of the peak top molecular weight was calculated according to the following formula. Reduction rate of peak top molecular weight by heating at 175°C = 100 × (Mp1 - Mp2) / Mp1 Reduction rate of peak top molecular weight due to heating at 200°C = 100 × (Mp1 - Mp3) / Mp1 In Example 1, the reduction rates of the peak top molecular weight due to heating at 175°C and 200°C were 26% and 60%, respectively.

[0064] [Examples 2 to 3 and Comparative Example 1] A resin sheet obtained in the same manner as in Example 1 was used, and evaluation was carried out in the same manner as in Example 1, except that the amount of compound a in Example 1 was changed to the amount shown in Table 1.

[0065] The compositions and evaluation results of the resin sheets in Examples 1 to 3 and Comparative Example 1 are shown in Table 1.

[0066] [Table 1]

[0067] Comparing Examples 1 to 3 with Comparative Example 1, the reduction rates of the peak top molecular weight before and after heating at 175°C and 200°C are lower in Examples 1 to 3. This demonstrates that the cleaning sheet substrates of Examples 1 to 3 have sufficient heat resistance and are useful even in high temperature ranges.

[0068] [Structure and appearance of resin sheet] When the cross sections of the resin sheets in Examples 1 to 3 were observed with a scanning electron microscope, it was confirmed that each had a plurality of teardrop-shaped bubbles. When the cross-sectional structures of the resin sheets in each example were compared in this way, it was evaluated that the resin sheets in Examples 1 and 2 had bubbles arranged more regularly than the resin sheet in Example 3. Furthermore, when the appearances of the resin sheets obtained in Examples 1 to 3 were compared visually, the resin sheets of Examples 1 and 2 were evaluated to have smoother surfaces than the resin sheet of Example 3. Furthermore, the resin sheets of Examples 1 and 2 were evaluated to have less waviness as a whole than the resin sheet of Example 3. The above comparison suggests that when the resin sheets of each example are used as substrates for probe cleaning sheets, the resin sheets of Examples 1 and 2 tend to have better cushioning and / or conformability than the resin sheet of Example 3, i.e., tend to have better cleaning performance. [Explanation of symbols]

[0069] 1...resin sheet, 2...coating layer, 3...adhesive layer, 10...cleaning sheet substrate, 20...cleaning sheet, W...object to be cleaned

Claims

1. a resin sheet having a plurality of teardrop-shaped bubbles; The resin sheet contains a polyurethane urea resin and a compound having a hindered phenol structure. Base material for cleaning sheets.

2. The content of the hindered phenol structure is 2.0×10 as the content of the compound relative to the polyurethane urea resin / molecular weight of the compound×number of the hindered phenol structures per molecule. -5 ~1.2 × 10 -4 equivalents / g, The substrate for a cleaning sheet according to claim 1 .

3. When the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 175°C for 1 hour and the value Mp2 after heating is 40% or less as expressed as 100 x (Mp1 - Mp2) / Mp1. The substrate for a cleaning sheet according to claim 1 .

4. When the peak top molecular weight of the resin sheet is measured by gel filtration chromatography, the reduction rate of the peak top molecular weight calculated from the value Mp1 before heating the resin sheet at 200°C for 1 hour and the value Mp3 after heating is 70% or less as expressed as 100 x (Mp1 - Mp3) / Mp1. The substrate for a cleaning sheet according to claim 1 .

5. For cleaning the probe, The substrate for a cleaning sheet according to any one of claims 1 to 4.

6. a mixing step of mixing a polyurethane urea resin with a compound having a hindered phenol structure to obtain a polyurethane urea resin-containing solution; a coating step of coating the polyurethane urea resin-containing solution onto a film-forming substrate; and a solidification step of solidifying the polyurethane urea resin-containing solution to obtain a resin sheet. A method for producing a substrate for a cleaning sheet.

7. In the mixing step, the content of the hindered phenol structure is 2.0×10, as expressed by (content of the compound relative to the polyurethane urea resin / molecular weight of the compound)×(number of the hindered phenol structures per molecule). -5 ~1.2 × 10 -4 The compounds are mixed so that the equivalent weight per gram is obtained. A method for producing the substrate for a cleaning sheet according to claim 6.

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