Manufacturing method of liquid discharge head and liquid discharge head

Abstract

To provide a manufacturing method of a liquid discharge head which suppresses an increase in viscosity until pouring of a sealing material is completed, and is capable of extending a serviceable life.SOLUTION: A manufacturing method of a liquid discharge head includes the steps of: accommodating a substrate 2 having a discharge port 4 discharging liquid, in a recess of a member 3 provided with a recess 3a; filling gaps between walls 3b of the recess and the substrate 2 with a sealing composition; and hardening the composition to serve as a sealing material 5. The composition contains an isocyanate compound with an isocyanate group, and two kinds of polyol compounds. The composition is prepared according to: a primary mixing process in which a primary composition is obtained by mixing a part or all of a first polyol compound with an isocyanate compound; and a secondary mixing process in which the remainder of the first polyol compound and a second polyol compound having higher responsiveness to the isocyanate group than the first polyol compound are added to the primary composition, thereby obtaining a composition for the sealing material.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a liquid ejection head and a liquid ejection head. [Background technology]

[0002] An inkjet head, which is an example of a liquid ejection head, is composed of many parts, such as an inkjet head substrate having ink ejection ports and an electric wiring substrate. After assembling these parts, the gaps between the parts are filled with a sealant to prevent ink from entering the gaps between the parts. For this reason, a photocurable resin that is polymerized and hardened by light irradiation has been used as a sealant. However, in a large head such as a line-type head, the grooves that need to be sealed with a sealant become deep, and it becomes difficult for light to reach the deep parts to start polymerization. For this reason, there are cases where the sealant is not sufficiently hardened deep down and is not suitable as a sealant. In response to this, in recent years, a sealant containing a urethane resin obtained by reacting a polyol compound and an isocyanate compound, which are thermosetting resins, has come to be used.

[0003] In the inkjet head, a recovery operation is performed to wipe off the ink droplets with a rubber blade in order to remove the ink droplets adhering to the surface between the nozzle openings of the head. The inkjet head substrate is placed on a member having a recess for accommodating the substrate, and a sealant is often filled between the substrate and the wall of the recess. In this case, the sealant may come into contact with the blade during the recovery operation, and high blade resistance is required. However, the above-mentioned urethane resin generally has a problem of low blade resistance. Therefore, Patent Document 1 describes the use of a sealant containing a urethane resin obtained by reacting two types of polyol compounds having different reactivity to isocyanate groups with an isocyanate compound having an isocyanate group. As a result, phase separation occurs between the two types of polyol compounds, and an uneven structure called a sea-island structure is formed on the surface of the sealant. It is said that the formation of the sea-island structure reduces the contact between the urethane resin and the blade and disperses the force of the blade, thereby improving the blade resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-162839 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is said that the sea-island structure of Patent Document 1 has a larger difference in height as the difference in reactivity with the isocyanate group between the two types of polyol compounds becomes larger, and the contact area between the sealant and the blade can be reduced. However, a large difference in reactivity indicates that one of the two types of polyol compounds has a high reaction rate with the isocyanate compound. Therefore, in the case of a large-sized inkjet head such as a long head, it takes time to pour the sealant into the gap between the parts, and the reaction proceeds while the sealant is being poured, causing the viscosity of the sealant to increase, and there are cases where the sealant cannot be injected stably. Patent Document 1 states that the time from preparation of the sealant composition to completion of application (pot life) is preferably 30 minutes or less, but if this pot life can be extended, it will be easier to manufacture a larger liquid ejection head. In addition, Patent Document 1 evaluates the relationship between pot life and sealant abrasion by adding a filler such as silica, but adding a filler may cause blade abrasion on the contrary, and a sealant with high blade resistance even without a filler is desired.

[0006] Therefore, an object of the present invention is to provide a manufacturing method for a liquid ejection head that can suppress an increase in viscosity until the pouring (filling) of the sealant is completed and increase the usable time. Another object of the present invention is to provide a manufacturing method for a liquid ejection head sealed with a sealant that has excellent blade resistance, especially blade resistance even without a filler, and a liquid ejection head. [Means for solving the problem]

[0007] A method for manufacturing a liquid ejection head according to one aspect of the present invention includes the steps of: A step of accommodating a substrate having an ejection port for ejecting a liquid in a recess of a member having a recess; a filling step of filling a gap formed between a wall of the recess of the member and the substrate with a composition for sealing the gap; a curing step of curing the composition to form an encapsulant; A method for manufacturing a liquid ejection head comprising the steps of: The composition includes an isocyanate compound having an isocyanate group and a polyol compound that reacts with the isocyanate compound to form a urethane bond, the polyol compound includes a first polyol compound and a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound; The composition is characterized in that it is prepared by a primary mixing step of mixing a part or all of the first polyol compound with the isocyanate compound, and a secondary mixing step of adding the remainder of the first polyol compound and the second polyol compound to the primary composition obtained in the primary mixing step and mixing them.

[0008] A liquid ejection head according to one aspect of the present invention comprises: A liquid ejection head comprising: a substrate having an ejection port for ejecting liquid; and a member having a recess for accommodating the substrate; a gap formed between a wall of the recess of the member and the substrate is sealed with a sealant; the sealing material is a cured product containing a urethane bond formed by a reaction between an isocyanate compound having an isocyanate group and two types of polyol compounds, the urethane bond includes a first urethane bond formed by a reaction between a hydroxyl group of a first polyol compound and an isocyanate group, and a second urethane bond formed by a reaction with a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound; The surface of the sealing material has a sea-island structure in which the island portions are convex portions, The ratio of the average area of ​​the island portions to the standard deviation of the area of ​​the island portions is 63.5% or less. Effect of the Invention

[0009] According to the manufacturing method of a liquid ejection head of one aspect of the present invention, it is possible to suppress an increase in viscosity until the pouring (filling) of the sealant is completed, and to extend the usable time, so that it is possible to manufacture a larger liquid ejection head. Also, according to the manufacturing method of a liquid ejection head and the liquid ejection head of one aspect of the present invention, it is possible to provide a liquid ejection head sealed by a sealant having blade resistance even without a filler. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view of a liquid ejection head according to an embodiment of the present invention; [Diagram 2] 1A is a partially enlarged schematic view of a liquid ejection head, and FIG. 1B is a schematic cross-sectional view taken along line AA' shown in FIG. [Diagram 3] FIG. 2 is a conceptual diagram showing that a part of a first polyol compound has reacted with an isocyanate compound, resulting in an increase in molecular weight. [Figure 4] 1 is a graph showing the change in viscosity with respect to the standing time of the compositions for sealing material prepared in Examples 1 to 5 and the Comparative Example. [Diagram 5] 1 shows microscopic images of the appearance of the sea-island structure in the comparative example, example 2, and example 5. [Figure 6] 1 shows microscopic images of the cured products of the Comparative Example, Example 2, and Example 5 after scrubbing with a blade. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below with reference to preferred embodiments. The method for manufacturing a liquid ejection head according to an embodiment of the present invention includes a filling step of filling a gap formed between a substrate having an ejection port for ejecting a liquid and a wall of a member having a recess for accommodating the substrate with a composition for sealing the gap (hereinafter, also referred to as a sealant composition). The method also includes a curing step of curing the composition to form a sealant. The composition includes an isocyanate compound having an isocyanate group and a polyol compound that reacts with the isocyanate compound to form a urethane bond. The polyol compound includes a polyol compound (hereinafter, referred to as a first polyol compound) that has low reactivity with an isocyanate group and a polyol compound (hereinafter, referred to as a second polyol compound) that has higher reactivity with an isocyanate group than the first polyol compound. The method for manufacturing a liquid ejection head includes a primary mixing step of mixing a part or all of the first polyol compound with an isocyanate compound. The method further includes a secondary mixing step of adding the remainder of the first polyol compound and the second polyol compound to the mixture obtained in the primary mixing step and mixing them. In the primary mixing step, as shown in FIG. 3, a compound 8 is formed by the reaction of the first polyol compound 6 with the isocyanate compound 7. This compound 8 corresponds to a so-called prepolymer in which a urethane bond is formed by the reaction of the first polyol compound 6 with the isocyanate compound 7 and the molecular weight is increased. Since the reaction between the first polyol compound 6 and the isocyanate compound 7 proceeds slowly, many unreacted raw material compounds remain in the mixture. The composition (mixture) that has undergone the primary mixing step is called the primary composition. In the secondary mixing step, the second polyol compound and the remainder of the first polyol compound are added to this primary composition to prepare a sealant composition. The isocyanate compound may be added additionally in the secondary mixing step. In addition, the remainder of the first polyol compound in the secondary mixing step refers to the remainder when a part of the first polyol compound is added in the primary mixing step, and the remainder is 0 when the entirety of the first polyol compound is added. At this time, the first polyol compound to be mixed in the primary mixing step is preferably 25% or more in terms of mass ratio with respect to the entire first polyol compound to be blended in the encapsulant composition.

[0012] <Liquid ejection head> First, the configuration of a liquid ejection head according to one embodiment of the present invention will be described. Fig. 1 is a perspective view of one embodiment of the liquid ejection head of the present invention. Fig. 2(a) is a partially enlarged view of the liquid ejection head, and Fig. 2(b) is a cross-sectional view of the liquid ejection head taken along line A-A' shown in Fig. 2(a). As shown in Fig. 1, the liquid ejection head 1 has a substrate 2 and a member 3 that supports the substrate 2. As shown in Fig. 2(a), the substrate 2 has ejection ports 4 for ejecting ink, and further has therein an energy generating element (not shown) that generates energy for ejecting ink, and an electronic circuit element (not shown) that controls the energy generating element.

[0013] The liquid ejection head to which the present invention is applied is not particularly limited, but is preferably used for a large-sized liquid ejection head such as a serial head or a line-type head capable of high-speed printing. A serial head is a liquid ejection head that performs recording on a recording paper while scanning the recording head in the width direction of the recording paper. On the other hand, a line-type head is a liquid ejection head that has a width equal to or greater than the width of the recording paper and has multiple substrates 2 arranged in-line along the width direction. The multiple substrates 2 are arranged continuously on the liquid ejection head 1 with a length equal to or greater than the width of the recording paper so that the entire area in the width direction of the recording paper can be recorded by passing the recording paper once while the liquid ejection head is fixed. Here, the width of the recording paper is assumed to be the short side width of A4 paper.

[0014] At this time, as shown in FIG. 2(b), the substrate 2 is accommodated in a recess 3a provided in the member 3. A gap is formed between the substrate 2 and the wall 3b of the recess 3a, and there may also be gaps between the substrates 2. Therefore, a sealant 5 is used to fill these gaps. This sealant is formed by filling the gap between the substrate 2 and the wall 3b of the recess in the member with a sealant composition described later, and then curing it. In the case of a large-sized liquid ejection head such as a line-type head, the volume of this gap becomes large, and the amount of sealant required to be poured in also increases accordingly. Therefore, it takes a long time to complete filling of all the sealant.

[0015] The liquid ejection head according to the present invention is a liquid ejection head having a substrate having an ejection port for ejecting liquid, and a member having a recess for accommodating the substrate, and has a gap formed between the wall of the recess of the member and the substrate, and a sealant for sealing the gap. The sealant is a cured product containing a urethane bond formed by a reaction between an isocyanate compound having an isocyanate group and two kinds of polyol compounds. The sealant contains a first urethane bond formed by a reaction between the isocyanate compound and a first polyol compound, and a second urethane bond formed by a reaction between the isocyanate compound and a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound. Furthermore, the surface of the sealant on the side of the substrate on which the ejection port is formed has a sea-island structure formed by a portion having the first urethane bond and a portion having the second urethane bond. Here, the liquid ejection head according to the present invention is characterized in that the island portions included in the sea-island structure are convex portions, and the ratio of the average value of the area of ​​the island portions to the standard deviation of the area of ​​the island portions is 63.5% or less. This characteristic feature has been achieved with good reproducibility for the first time by the method for producing a liquid discharge head according to the present invention, in particular, the method for preparing a composition for a sealant, and is therefore a structure that has never been seen before.

[0016] <Composition for encapsulant> The composition for a sealant contains an isocyanate compound having an isocyanate group and a polyol compound having a hydroxyl group that reacts with the isocyanate group. The polyol compound contains a first polyol compound and a second polyol compound that is more reactive with the isocyanate group than the first polyol compound. The hydroxyl group in the polyol compound and the isocyanate group in the isocyanate compound react to form a urethane bond, which is cured as a urethane resin.

[0017] (First polyol compound) The first polyol compound is a compound having two or more hydroxyl groups that react with the isocyanate group of the isocyanate compound, and is a compound having a lower reactivity than the second polyol compound described below. In addition, the first polyol compound is preferably a compound having a polyolefin skeleton containing a carbon-carbon double bond, and the resulting urethane resin is less likely to absorb ink, and water resistance and rubber elasticity are improved. The carbon-carbon unsaturated bond may be an alkenylene group having 2 to 6 carbon atoms or an alkynylene group having 2 to 6 carbon atoms. The alkenylene group may be an ethenylene group, a propenylene group, a 1-butenylene group, a 2-butenylene group, a butadienylene group, or an isoprenylene group. The alkynylene group may be an isobutynylene group. The first polyol compound is not limited to compounds having these groups. In addition, the first polyol compound is more preferable when it has two or more types of carbon-carbon unsaturated bonds in the molecule, since the carbon-carbon double bonds are more likely to be uniformly distributed. The two or more types of carbon-carbon unsaturated bonds may be a combination of alkenylene groups or alkynylene groups having the same number of carbon atoms but different in cis-trans isomers or branched structures, or different numbers of carbon atoms in the repeating unit. Among them, butadiene-based polyols having a polybutadiene structure represented by the following formula (1) are preferred, and polybutadiene diols having hydroxyl groups at both ends are particularly preferred.

[0018] [ka] In the above formula (1), m, n, and o are 0 or an integer of 1 or more, and at least one of them is an integer of 1 or more.

[0019] In general, the larger the molecular weight of a substance, the lower the compatibility with other substances, so the smaller the molecular weight of the first polyol compound is, and in particular, from the viewpoint of ease of mixing with the isocyanate compound, the molecular weight of the first polyol compound is preferably 1500 or less.

[0020] (Isocyanate compounds) From the viewpoint of reactivity with the first polyol compound, the isocyanate compound is preferably a polyisocyanate having two or more isocyanate groups in one molecule. Examples include, but are not limited to, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (DPMDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (HXDI), naphthalene diisocyanate (NDI), and norbornene diisocyanate (NDI). In particular, 4,4'-diphenylmethane diisocyanate (monomeric MDI) represented by the following formula (2) or polymethylene polyphenyl polyisocyanate (polymeric MDI) represented by the following formula (3) is preferred.

[0021] [ka]

[0022] [ka] In the above formula (3), n is an integer of 1 or more.

[0023] (Second Polyol Compound) The second polyol compound is a polyol compound having a higher reactivity with an isocyanate group than the first polyol compound, and is preferably a compound having a solubility parameter close to that of the isocyanate compound. For example, a polyol compound having fewer carbon-carbon unsaturated bonds per molecule than the first polyol compound or a polyol compound having no polyolefin skeleton is preferred. Furthermore, the second polyol compound is preferably a polyol compound having higher hydrophilicity than the first polyol compound. Here, the hydrophilicity of a polyol compound can be determined by the octanol / water partition coefficient. The octanol / water partition coefficient represents the ratio of the concentration of a compound in the octanol layer to the concentration of the water layer in a two-layer system of octanol and water. In other words, it is an index of whether a compound is fat-soluble or water-soluble, and a lower octanol / water partition coefficient indicates higher hydrophilicity. The greater the difference in hydrophilicity / hydrophobicity between the second polyol compound and the first polyol compound, the more likely phase separation occurs, and the easier it is to form an island structure. Specifically, polyol compounds having an ester, ketone, or amine skeleton are particularly preferred as the second polyol compound. Specific examples of the second polyol compound include polyester polyols, polycarbonate polyols, polyester polycarbonate polyols, and polyolamines such as triethanolamine.

[0024] The molecular weight of the second polyol compound is not particularly limited as long as it is compatible with the isocyanate compound, but a larger molecular weight is more preferable because it has a larger effect of delaying the reaction. Specifically, the molecular weight of the second polyol compound is preferably 750 or more. The amounts of the isocyanate compound and the polyol compound to be mixed are preferably amounts that give a molar ratio (NCO / OH) of isocyanate groups to hydroxyl groups of 0.6 to 1.5, and more preferably 0.7 to 1.3. If the molar ratio of isocyanate groups to hydroxyl groups is within this range, it is possible to prevent insufficient curing and reduced heat resistance of the resulting resin. The blending ratio of the first polyol and the second polyol correlates with the ratio of the sea-island structure to be formed, the hardness difference, etc., and may be set so as to minimize scraping during the recovery operation with a blade.

[0025] (Other additives) The composition for sealing material of the present invention may contain a component that can be added to a urethane resin sealing material within a range that does not impair the effects of the present invention. For example, a catalyst that adjusts the reaction between a polyol compound and an isocyanate compound, various fillers (such as silica filler), plasticizers, polymerization initiators, colorants, antioxidants, antistatic agents, etc. can be mentioned. In the present invention, excellent blade resistance may be obtained without using additives such as fillers to improve blade resistance, which may be advantageous in terms of cost and blade durability.

[0026] <Sea-island structure> By reacting two types of polyols (a first polyol compound and a second polyol compound) that have different reactivity to isocyanate groups with an isocyanate compound, a sea-island structure is formed on the surface of the encapsulant. The sea-island structure is also called a matrix-domain structure, and is a structure consisting of a continuous phase, the sea part, and a discontinuous phase, the island part. The reason why the sea-island structure is formed is thought to be that each polyol compound is phase-separated between the first polyol compound and the second polyol compound while the urethane reaction is progressing. In general, the mechanism by which the sea-island structure is formed (phase separation occurs) is that the compounds differ in their hydrophilicity / hydrophobicity or polarity, which leads to phase separation. In the present invention, it is believed that the first polyol compound having low reactivity is reacted with the isocyanate compound to a certain extent in the primary mixing to increase the molecular weight, which makes the phase separation due to the difference in molecular weight more pronounced, and thus enables the formation of a sea-island structure with little variation in the island parts.

[0027] In the sea-island structure of the sealant, a structure in which the islands become convex portions can be formed. If there is a height difference between the sea and the islands, there is an effect of reducing the contact area between the sealant and the blade when a blade is used for recovery operation to wipe off ink adhering to the ejection ports of the liquid ejection head. In this case, in a sea-island structure in which there is a height difference between the sea and the islands, it is preferable that the hardness of the sea is lower than that of the islands. This is because even if the sealant is scraped with a blade, the blade will come into contact with the relatively high and hard island parts, and most of the force of the blade moving is applied to the island parts. The force applied to the island parts is dissipated to the relatively soft sea parts, and as a result, scraping of the sealant can be suppressed. For this reason, the sea portion is preferably made of a urethane resin made of a polyol compound having a chemical structure that enhances rubber elasticity, i.e., the sea portion is preferably made of a first urethane resin made of a first polyol having many carbon-carbon unsaturated bonds, whereas the island portion is preferably made of a second urethane resin made of a second polyol having a smaller proportion of carbon-carbon unsaturated bonds per molecule than the first polyol compound that forms the sea portion.

[0028] In addition, the height difference of the sea-island structure is preferably 100 nm or more. This is because if the height difference is 100 nm or more, the contact between the urethane resin and the blade is reduced, and the phenomenon of the sealant being scraped off by the blade can be suppressed. On the other hand, if the height difference is too large, it may lead to pressure loss during the recovery operation. For this reason, the height difference is preferably 1 μm (1000 nm) or less, and more preferably 500 nm or less. The heights of the sea and island parts are calculated using the average values ​​measured at 20 randomly distributed points, respectively. Furthermore, it is preferable that the standard deviation of the area of ​​each island is small (the size is uniform). This is to prevent the force of the blade from being applied locally during the recovery operation by uniformly distributing the force of the blade, which may cause scraping. Specifically, the surface of the encapsulant is observed under a microscope to determine the area of ​​any 20 islands included in the sea-island structure (hereinafter simply referred to as "area"). It is preferable that the ratio (As / Av) of the average value (Av) of the island area to the standard deviation (As) of the island area is 63.5% or less, because the force of the blade is more uniformly distributed and scraping is reduced. Furthermore, it is more preferable that the ratio is 60% or less. The lower limit of the ratio is not particularly specified because theoretically it can take a value where the standard deviation is 0, but in reality, the lower limit of the ratio is about 30%.

[0029] <Filling step and curing step of the encapsulant composition> As described above, the sealant composition prepared by the primary mixing and secondary mixing is filled into the gap formed between the substrate having a discharge port for discharging the liquid and the wall of the member having a recess for accommodating the substrate (filling step). In the filling step, the sealant composition is filled to a height that is approximately the same as the surface of the substrate. The filling method is not particularly limited, and a conventionally known method can be applied, and any method may be used as long as it can quickly fill a fine gap with an appropriate amount of the sealant composition using a dispenser or the like. The time from preparation of the sealant composition to completion of the filling step depends on the reactivity of the materials used, but it is preferable to quickly perform the filling work without waiting too long. In addition, in the present invention, since the primary mixing and the secondary mixing can be performed separately, the time required for preparation of the sealant composition can be adjusted, and the increase in viscosity can be suppressed more than before. Therefore, it is also possible to complete the process in a longer time than the case in which Patent Document 1 states that the time from preparation of the composition to filling is preferably 30 minutes or less, for example, 40 minutes or less.

[0030] In the curing step, the curing reaction can be accelerated by heating, but if the temperature is too high, the substrate may be deformed due to the difference in linear expansion coefficient between the substrate and the sealant, which may affect the discharge performance. The composition for the sealant according to the present invention undergoes a curing reaction without heating, but may be heated to 40 to 50°C to accelerate the curing reaction as necessary. The composition for the sealant can be cured at a relatively low temperature of 0°C or higher and 50°C or lower. In addition, from the viewpoint of reducing the variation in the area of ​​the islands in the sea-island structure, it is more preferable to leave the composition to cure without heating. In the preparation stage of the composition, the material may be heated and liquefied before handling, and the material itself may have heat, but the temperature in the curing step means the atmospheric temperature during the time when the composition is left to stand after filling.

[0031] <Curing mechanism of encapsulant> The reaction between the polyol compound and the isocyanate compound that constitute the urethane resin proceeds without the use of a polymerization initiator or heat, so as soon as the polyol compound and the isocyanate compound are mixed together, an increase in viscosity due to the reaction occurs. In the present invention, a part or all of the first polyol compound, which has low reactivity among the polyol compounds, is reacted with an isocyanate compound to generate a compound 8, which is composed of a first polyol compound 6 and an isocyanate compound 7 and has a larger molecular weight than the molecular unit, as shown in FIG. 3. In this way, the molecular mobility is reduced by increasing the molecular weight. This makes it possible to reduce the reaction rate after the addition of the second polyol compound, and to suppress the increase in viscosity. At this time, in order to further suppress the increase in viscosity, it is preferable to reduce the mobility and the reactivity. In order to reduce the mobility, it is preferable to react more of the first polyol compound with the isocyanate compound and convert it into a polymer compound. Furthermore, the presence of the reaction compound between the first polyol compound and the isocyanate compound before the addition of the second polyol compound makes it easier for the first polyol compound or the second polyol compound to react with the isocyanate compound to exist separately, which makes it easier for phase separation to occur and is expected to further improve blade resistance. EXAMPLES

[0032] Examples and comparative examples are shown below, but the present invention is not limited thereto. In the following description of the examples, "parts" are by weight unless otherwise specified.

[0033] <Preparation of Encapsulant Composition> First polyol compound As the first polyol compound, a polybutadiene diol represented by the following formula (4) (product name: G-1000, manufactured by Nippon Soda Co., Ltd., number average molecular weight: 1400, solubility parameter: about 8.3) was used.

[0034] [ka]

[0035] The first polyol compound of the above formula (4) has 15% or less of carbon-carbon unsaturated bonds in the main chain (1,4-trans structure, not shown) and 85% or more in the side chain (the above structure), and has a hydroxyl value of 68 to 78 mg / g (median value 73 mg / g). 1.82 molecules of calcium hydroxide react with one molecule of polybutadiene diol.

[0036] Second polyol compound As the second polyol compound, polyester polyol (product name: Nipporan 4042, manufactured by Tosoh Corporation, average molecular weight 2000) was used.

[0037] The second polyol compound has a hydroxyl value of 56.0 mg / g, and reacts with 2.01 molecules of calcium hydroxide per molecule of the compound.

[0038] ·Isocyanate compounds As the isocyanate compound, monomeric MDI (trade name: Millionate MT, manufactured by Tosoh Corporation, molecular weight 250, solubility parameter: about 11.6) was used. The isocyanate compound has a hydroxyl value of 448.1 mg / g, and 2.00 molecules of calcium hydroxide react with one molecule of the isocyanate compound.

[0039] [Comparative Example] <Preparation of Encapsulant Composition> First, the materials shown in Table 1 below were heated at 60°C for 3 hours to liquefy them, and then all the raw materials were placed in a plastic cup and stirred by hand with a spoon for 1 minute, and then stirred for 2 minutes at 1200 rpm in a vacuum stirring / defoaming mixer to obtain a composition.

[0040] [Table 1]

[0041] Examples 1 to 5 The materials were placed in a plastic cup in the amounts shown in "Primary Mixture" in Table 2, and mixed by hand using a spoon for 1 minute, and then mixed for 2 minutes in a vacuum mixing and degassing mixer at 1200 rpm. In order to react the materials in the cup, the mixture after being put in the vacuum mixing and degassing mixer was further stirred by hand using a spoon at room temperature for 15 minutes to obtain a primary composition. Next, materials were added to the obtained primary composition in the amounts shown in "Secondary Mixing" in Table 2, and the mixture was stirred by hand using a spoon for 1 minute, and then stirred for 2 minutes in a vacuum stirring and degassing mixer at 1200 rpm to obtain a composition for an encapsulant. Before mixing, each material was liquefied by heating at 60°C for 3 hours.

[0042] [Table 2]

[0043] <Evaluation> -Changes in viscosity of sealant composition over time The viscosity of the obtained sealing material compositions of the examples and comparative examples was measured with a viscometer (product name: TVE-25H, manufactured by Toki Sangyo Co., Ltd.). The temperature of the circulating water during the viscosity measurement was 40°C. In consideration of the time from the end of blending to transferring the sample to the viscometer, the viscosity measurement was started 1 minute after the end of mixing with the vacuum stirring and degassing mixer. At this time, the measurement mode of the viscometer was set to manual stop mode, and the viscosity change was observed over time without stopping the measurement midway. FIG. 4 is a graph showing the relationship between the standing time and the viscosity of the compositions of Examples 1 to 5 and Comparative Example. In Examples 1 to 5, the viscosity rise is slower than in Comparative Example. In addition, it was confirmed that the viscosity rise is slower in Examples 1 to 5 as the amount of the first polyol reacted in the primary mixing increases. This is considered to be because the molecular weight of the reactant consisting of the first polyol compound and the isocyanate compound increases as the amount of the first polyol reacted in the primary mixing increases, and the reactivity with the first polyol compound decreases. In this example, the viscosity at 30 minutes in Comparative Example and the viscosity at 40 minutes in Example 5 are almost the same, which means that the time from the preparation of the composition to the filling of the composition (pot life) can be extended by about 10 minutes.

[0044] Microscopic image of the island structure Immediately after obtaining the composition, it was poured into a mold made of fluororesin (registered trademark "Teflon") with a coin-shaped hole formed therein, and then left to stand at room temperature (22°C) for 48 hours to allow hardening to proceed, yielding a coin-shaped sample. The surface structure of the obtained sample was observed with a laser scanning microscope (product name: VK-9700, manufactured by KEYENCE). The diameter of each island was measured with this microscope and converted into the area of ​​the island. In this case, the average island area and the standard deviation of the island area were calculated by determining the areas of any 20 islands observed in the microscope field (in the image). In this way, the ratio (%) of the average island area to the standard deviation of the island area observed in the microscope field was calculated. Microscopic images of the appearance of the sea-island structure in the comparative example, Example 2, and Example 5 are shown in Figure 5.

[0045] -Evaluation of blade durability of cured material The coin-shaped sample obtained by the above-mentioned method was rubbed ten times by hand with a blade (made of acrylonitrile butadiene rubber), and the degree of scraping at the rubbed area was visually compared for evaluation. Microscopic images of the cured products after rubbing with the blade in the comparative example, example 2, and example 5 are shown in FIG. 6. The rubbed area is clearly visible in the comparative example, but the rubbed area is faint in example 2, and the rubbed area is almost invisible in example 5.

[0046] [Table 3]

[0047] In all of Examples 1 to 5, the ratio of the average island area to the standard deviation of the island area was smaller than in the comparative example, and the ratio became smaller as the amount of the first polyol reacted in the primary mixing increased. This is considered to be because the higher the conversion rate of the compound generated after the primary mixing, the higher the molecular weight, and the more the phase separation of the second polyol compound during the secondary mixing was promoted. It was also confirmed that the more the first polyol reacted during the primary mixing and the smaller the standard deviation of the island area, the less scraping there was. This is believed to be because the smaller the variation in the island area, the more uniformly the force of the blade can be distributed during the blade recovery operation, preventing scraping caused by localized force. In particular, it was confirmed that when the ratio of the average island area to the standard deviation of the island is 54.2% or less, the scraping is "very small," and scraping of the sealant by the blade can be further suppressed.

[0048] The present invention includes the following methods. [Method 1] A step of accommodating a substrate having an ejection port for ejecting a liquid in a recess of a member having a recess; a filling step of filling a gap formed between a wall of the recess of the member and the substrate with a composition for sealing the gap; a curing step of curing the composition to form an encapsulant; A method for manufacturing a liquid ejection head comprising the steps of: The composition includes an isocyanate compound having an isocyanate group and a polyol compound that reacts with the isocyanate compound to form a urethane bond, the polyol compound includes a first polyol compound and a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound; The method for manufacturing a liquid ejection head is characterized in that the composition is prepared by a primary mixing process in which a part or all of the first polyol compound is mixed with the isocyanate compound, and a secondary mixing process in which the remainder of the first polyol compound and the second polyol compound are added to and mixed with the primary composition obtained in the primary mixing process. [Method 2] The method for producing a liquid ejection head according to [Method 1], wherein the molecular weight of the first polyol compound is 1,500 or less. [Method 3] The method for producing a liquid ejection head according to [Method 1] or [Method 2], wherein the first polyol compound is a polyol compound having a polyolefin skeleton containing a carbon-carbon double bond. [Method 4] The method for producing a liquid ejection head according to [Method 3], wherein the first polyol compound is a polyol compound having two or more types of carbon-carbon unsaturated bonds in the molecule. [Method 5] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 4], wherein the first polyol compound is a butadiene-based polyol. [Method 6] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 5], wherein the first polyol compound is polybutadiene diol. [Method 7] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 6], wherein the isocyanate compound is a polyisocyanate having two or more isocyanate groups in one molecule. [Method 8] The method for producing a liquid ejection head according to [Method 7], wherein the isocyanate compound is 4,4'-diphenylmethane diisocyanate or polymethylene polyphenyl polyisocyanate. [Method 9] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 8], wherein the second polyol compound has fewer carbon-carbon unsaturated bonds per molecule than the first polyol compound. [Method 10] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 9], wherein the second polyol compound does not have a polyolefin skeleton containing a carbon-carbon unsaturated bond. [Method 11] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 10], wherein the second polyol compound is a compound having higher hydrophilicity than the first polyol compound. [Method 12] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 11], wherein the second polyol compound has a skeleton of any one of an ester, a ketone, and an amine. [Method 13] The method for producing a liquid ejection head according to any one of [Method 1] to [Method 12], wherein the molecular weight of the second polyol compound is 750 or more. [Method 14] The method for manufacturing a liquid ejection head according to any one of [Method 1] to [Method 13], wherein the first polyol compound is a butadiene-based polyol, and the second polyol compound has a skeleton of any one of an ester, a ketone, and an amine. [Method 15] The method for manufacturing a liquid ejection head described in [Method 1], wherein the first polyol compound to be mixed in the primary mixing step is 25% or more by mass ratio with respect to the total amount of the first polyol compound to be blended in the sealing material composition.

[0049] The present invention includes the following configurations. [Configuration 1] A liquid ejection head comprising: a substrate having an ejection port for ejecting liquid; and a member having a recess for accommodating the substrate; a gap formed between a wall of the recess of the member and the substrate is sealed with a sealant; the sealing material is a cured product containing a urethane bond formed by a reaction between an isocyanate compound having an isocyanate group and two types of polyol compounds, the urethane bond includes a first urethane bond formed by a reaction between a hydroxyl group of a first polyol compound and an isocyanate group, and a second urethane bond formed by a reaction with a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound; The surface of the sealing material has a sea-island structure in which the island portions are convex portions, A liquid ejection head, wherein a ratio of an average value of the area of ​​the island portions to a standard deviation of the area of ​​the island portions is 63.5% or less. [Configuration 2] The liquid ejection head according to [Configuration 1], wherein the ratio of the average area of ​​the island portions to the standard deviation of the area of ​​the island portions is 60% or less. [Explanation of symbols]

[0050] 1 Liquid ejection head 2. Board 3. Materials 3a Recess 3b Recess wall 4 outlet 5. Encapsulating material

Claims

1. a step of accommodating a substrate having a discharge port for discharging a liquid in a recess of a member provided with the recess; a filling step of filling a gap formed between a wall of the recess of the member and the substrate with a composition for sealing the gap; a curing step of curing the composition to form an encapsulant; A method for manufacturing a liquid ejection head, comprising: The composition includes an isocyanate compound having an isocyanate group and a polyol compound that reacts with the isocyanate compound to form a urethane bond; the polyol compound includes a first polyol compound and a second polyol compound that is more reactive with an isocyanate group than the first polyol compound; A method for manufacturing a liquid ejection head, characterized in that the composition is prepared by a primary mixing step in which part or all of the first polyol compound is mixed with the isocyanate compound, and a secondary mixing step in which the remainder of the first polyol compound and the second polyol compound are added to and mixed with the primary composition obtained in the primary mixing step.

2. The method for manufacturing a liquid ejection head according to claim 1 , wherein the molecular weight of the first polyol compound is 1,500 or less.

3. 2. The method for manufacturing a liquid ejection head according to claim 1, wherein the first polyol compound is a polyol compound having a polyolefin skeleton containing a carbon-carbon double bond.

4. 4. The method for manufacturing a liquid ejection head according to claim 3, wherein the first polyol compound is a polyol compound having two or more types of carbon-carbon unsaturated bonds in the molecule.

5. The method for manufacturing a liquid ejection head according to claim 1 , wherein the first polyol compound is a butadiene-based polyol.

6. The method for manufacturing a liquid ejection head according to claim 1 , wherein the first polyol compound is polybutadiene diol.

7. The method for manufacturing a liquid ejection head according to claim 1 , wherein the isocyanate compound is a polyisocyanate having two or more isocyanate groups in one molecule.

8. 2. The method for manufacturing a liquid ejection head according to claim 1, wherein the isocyanate compound is 4,4'-diphenylmethane diisocyanate or polymethylene polyphenyl polyisocyanate.

9. 2. The method for manufacturing a liquid ejection head according to claim 1, wherein the second polyol compound has fewer carbon-carbon unsaturated bonds per molecule than the first polyol compound.

10. 2. The method for manufacturing a liquid ejection head according to claim 1, wherein the second polyol compound does not have a polyolefin skeleton containing a carbon-carbon unsaturated bond.

11. The method for manufacturing a liquid ejection head according to claim 1 , wherein the second polyol compound is a compound having higher hydrophilicity than the first polyol compound.

12. The method for manufacturing a liquid ejection head according to claim 1 , wherein the second polyol compound has a skeleton of any one of an ester, a ketone, and an amine.

13. The method for manufacturing a liquid ejection head according to claim 1 , wherein the second polyol compound has a molecular weight of 750 or more.

14. 2. The method for manufacturing a liquid ejection head according to claim 1, wherein the first polyol compound is a butadiene-based polyol, and the second polyol compound has a skeleton of any one of an ester, a ketone, and an amine.

15. The method for manufacturing a liquid ejection head according to claim 1 , wherein the first polyol compound mixed in the primary mixing step is 25% or more by mass relative to the total amount of the first polyol compound blended in the composition.

16. A liquid ejection head comprising: a substrate having an ejection port for ejecting a liquid; and a member having a recess for accommodating the substrate, wherein a gap formed between a wall of the recess of the member and the substrate is sealed with a sealant; the sealing material is a cured product containing a urethane bond formed by a reaction between an isocyanate compound having an isocyanate group and two types of polyol compounds, the urethane bond includes a first urethane bond formed by a reaction between a hydroxyl group of a first polyol compound and an isocyanate group, and a second urethane bond formed by a reaction with a second polyol compound having a higher reactivity with an isocyanate group than the first polyol compound; The surface of the sealing material has a sea-island structure in which island portions are convex portions, A liquid ejection head, wherein the ratio of the average area of ​​the island portions to the standard deviation of the area of ​​the island portions is 63.5% or less.

17. 17. The liquid ejection head according to claim 16, wherein the ratio of the average area of ​​the island portions to the standard deviation of the area of ​​the island portions is 60% or less.

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