Electrophotographic belt and electrophotographic image forming apparatus

Abstract

The present invention relates to an electrophotographic belt and an electrophotographic image forming apparatus. The electrophotographic belt includes a biaxially-stretched cylindrical film as a base layer, wherein the biaxially-stretched cylindrical film contains a crystalline polyester, a non-crystalline polyester, and carbon black, the content of the carbon black is 2.0 mass% or more with respect to the biaxially-stretched cylindrical film, and a surface resistivity measured on a surface of the biaxially-stretched cylindrical film in an environment of 23°C and 50% RH is 1 x 10 3 Ω / □ or more and 1 x 10 13 Ω / □ or less, and A / B is 3.00 or less, wherein A (Ω / □) represents a surface resistivity of the biaxially-stretched cylindrical film after the biaxially-stretched cylindrical film is left to stand in an environment of 23°C and 50% RH for 24 hours, and B (Ω / □) represents a surface resistivity of the biaxially-stretched cylindrical film after the biaxially-stretched cylindrical film is left to stand in an environment of 30°C and 80% RH for 24 hours.

Description

Technical Field

[0001] This disclosure relates to an electrophotographic tape and an electrophotographic image forming apparatus including the electrophotographic tape. Background Technology

[0002] In electrophotographic image forming equipment, an annular electrophotographic tape made of thermoplastic resin is used as a transport transfer tape or intermediate transfer tape for conveying transfer material. Such electrophotographic tapes require high strength and, for example, a surface resistivity of 1 × 10⁻⁶. 3 Ω / □ (Ω / square) to 1×10 13 Conductivity within the range of Ω / □.

[0003] Japanese Patent Application Publication No. 2006-233150 discloses the problems of preforms containing a large amount of carbon black, namely, the reduced elongation when stretching the preform and the difficulty in biaxially stretching the preform. It then discloses that such problems can be solved by using thermoplastic resins and thermoplastic elastomers having specific constituent units.

[0004] Japanese Patent Application Publication No. 2006-233150 also discloses in its Examples 1 to 3 that even if a large amount of carbon black is contained (more than 10 parts by mass relative to 100 parts by mass of resin component), a preform can be biaxially stretched using a resin containing polyethylene naphthalate, polyethylene terephthalate, and two thermoplastic elastomers (trade names: Pelestat 6321; Sanyo Chemical Industries, Ltd., and trade names: Tuftec M1913; Asahi Kasei Corp.), and a biaxially stretched cylindrical film that can be used for an intermediate transfer belt can be obtained.

[0005] The thermoplastic elastomer "Pelestat 6321" used in this paper is a polyether ester amide and acts as an ionic conductive agent. Therefore, in some cases, the conductivity of the biaxially stretched cylindrical film obtained here varies depending on the surrounding environment. The inventors recognized that the variation in surface resistivity of the electrophotographic strip originating from the surrounding environment is a problem to be solved in order to form high-quality electrophotographic images more stably even under various environments. Summary of the Invention

[0006] At least one aspect of this disclosure aims to provide an electrophotographic tape that facilitates the stable formation of high-quality electrophotographic images under various conditions. Another aspect of this disclosure aims to provide an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images.

[0007] According to one aspect of this disclosure, an electrophotographic tape having a biaxially stretched cylindrical film as a base layer is provided. The biaxially stretched cylindrical film comprises crystalline polyester, amorphous polyester, and carbon black. The carbon black content is 2.0% by mass or more relative to the biaxially stretched cylindrical film, and the surface resistivity measured on the surface of the biaxially stretched cylindrical film at an environment of 23°C and 50% relative humidity is 1×10⁻⁶. 3 Ω / □ or higher and 1×10 13 Below Ω / □. Furthermore, A / B is below 3.00, where A(Ω / □) represents the surface resistivity measured on the surface of the biaxially stretched cylindrical membrane after standing for 24 hours at a temperature of 23°C and a relative humidity of 50%, and B(Ω / □) represents the surface resistivity measured on the surface of the biaxially stretched cylindrical membrane after standing for 24 hours at a temperature of 30°C and a relative humidity of 80%.

[0008] According to another aspect of this disclosure, an electrophotographic image forming apparatus is provided, which includes the electrophotographic tape as an intermediate transfer tape.

[0009] Further features of this disclosure will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 A schematic cross-sectional view illustrating an example of a panchromatic electrophotographic image forming apparatus using electrophotography is shown.

[0011] Figure 2 This is a schematic cross-sectional view of the injection molding equipment used in the embodiments.

[0012] Figure 3A , Figure 3B , Figure 3C and Figure 3D A schematic cross-sectional view of the blow molding apparatus used in the embodiment is shown.

[0013] Figure 4 A schematic cross-sectional view of the secondary blow molding equipment used in the embodiment is shown.

[0014] Figure 5A , Figure 5B-1 , Figure 5B-2 and Figure 5B-3 An explanatory diagram showing an example of the configuration of an electrophotographic tape according to the present disclosure is provided. Detailed Implementation

[0015] Preferred embodiments of this disclosure will now be described in detail (with reference to the accompanying drawings).

[0016] In this disclosure, unless otherwise stated, the expressions "above XX and below YY" and "XX-YY" indicating a numerical range mean a numerical range including both the lower and upper limits as endpoints. When describing a numerical range in segments, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, in this disclosure, "Ω / □" as a unit of surface resistivity means "Ω / square".

[0017] According to the invention disclosed in Japanese Patent Application Publication No. 2006-233150, biaxially stretched cylindrical films with excellent strength can be obtained even from preforms containing a large amount of carbon black. However, without using "Pelestat 6321" as a thermoplastic elastomer to suppress environmental changes in surface resistance, it becomes difficult to biaxially stretch the preform itself. On the other hand, when the carbon black content in the preform is reduced, biaxially stretched cylindrical films can be produced, but the surface resistance is extremely high, making it difficult to use this film as an intermediate transfer belt for electrophotography. This is believed to be due to the following reasons. The conductivity caused by electronically conductive agents such as carbon black is manifested by forming conductive paths with the help of these agents. However, in biaxially stretched cylindrical films obtained from preforms with a low carbon black content, the conductive paths of the electronically conductive agents are broken during the biaxial stretching of the preform in both the length and circumferential directions. As a result, it is believed that sufficient conductivity is not exhibited.

[0018] The inventors then conducted repeated studies to obtain a biaxially stretched cylindrical film with conductive paths due to an electronically conductive agent, while suppressing the content of the electronically conductive agent. As a result, it was discovered that using a combination of crystalline and amorphous polyesters as binders can form conductive paths due to carbon black in the biaxially stretched cylindrical film.

[0019] The inventors hypothesize that by using a combination of crystalline and amorphous polyesters as binders, conductive paths due to carbon black can be formed in biaxially stretched cylindrical films for the following reasons. Carbon black contained in preforms comprising crystalline thermoplastic resins acts as nuclei for the crystalline thermoplastic resin. Therefore, when carbon black is directly dispersed in the crystalline thermoplastic resin, it becomes a nucleus during biaxial stretching and promotes the formation of spherulites in the crystalline thermoplastic resin.

[0020] It is believed that the aggregation and growth of spherulites disrupts the conductive pathway of carbon black, making it difficult for it to exhibit conductivity.

[0021] However, when the binder contains amorphous polyester, the amorphous polyester phase causes the carbon black to be unevenly distributed within it. The carbon black in the amorphous polyester phase does not directly contact the crystalline polyester, thus inhibiting the spherulization of the crystalline polyester during biaxial stretching. On the other hand, while amorphous and crystalline polyesters are incompatible, both have ester bonds, resulting in relatively high affinity, and preventing breakage at the interface between the amorphous and crystalline polyester phases even during biaxial stretching. Consequently, the amorphous polyester phase is stretched biaxially while still containing carbon black. Therefore, it is believed that conductive paths for carbon black are formed in the biaxially stretched cylindrical film obtained through biaxial stretching, within the amorphous polyester phase stretched biaxially. This is believed to reduce the environmental dependence of surface resistivity. Furthermore, stretching the crystalline polyester along both the length and circumferential directions of the preform causes crystals to oriented in various directions, resulting in a biaxially stretched cylindrical film with excellent strength.

[0022] The following will describe in detail one aspect of the electronic photographic tape according to the present disclosure. Note that the present disclosure is not limited to the following aspects.

[0023] <Thermoplastic Resin Composition>

[0024] <Electronic photographic tape>

[0025] According to this disclosure, an electrophotographic tape has a biaxially stretched cylindrical membrane as a base layer.

[0026] Figure 5A A perspective view of an electrophotographic strip 500 having an annular strip shape according to one aspect of this disclosure is shown. Examples of layered structures are included in a cross-section taken along line A-A' of FIG. 5, such as... Figure 5B-1 The diagram shows a single-layer structure consisting only of a base layer 501. In this case, the outer surface 500-1 of the base layer becomes the toner carrier surface (outer surface) of the electrophotographic tape. Another example includes a structure having a cross-section taken along line A-A' as shown in the diagram. Figure 5B-2 The electrophotographic tape shown includes a laminated structure comprising a base layer 501 and a surface layer 502 covering the outer peripheral surface of the base layer. When the surface layer 502 is provided, its outer surface 500-1 becomes the toner carrier surface of the electrophotographic tape. Another example includes a tape having, for example... Figure 5B-3 The photographic tape shown includes a laminated structure comprising a base layer 501 and a back surface layer 503 covering the inner peripheral surface of the base layer. Furthermore, there are also photographic tapes with a three-layer structure (not shown) including a surface layer covering the outer peripheral surface of the base layer 501 and a back surface layer covering the inner peripheral surface of the base layer 501.

[0027] <Grassroots>

[0028] The biaxially stretched cylindrical membrane constituting the base layer comprises crystalline polyester, amorphous polyester, and carbon black. The carbon black content is 2.0% by mass or more relative to the biaxially stretched cylindrical membrane.

[0029] The surface resistivity measured on the outer surface of a biaxially stretched cylindrical membrane at 23°C and 50% relative humidity was 1.0 × 10⁻⁶. 3 Ω / □ or higher and 1.0 × 10 13 Below Ω / □. When using an electrophotographic tape as an intermediate transfer tape, for example, since the surface resistivity is set to 1.0 × 10⁻⁶... 3 With a surface resistivity of Ω / □ or higher, the transfer electric field during secondary transfer can be easily obtained. This effectively suppresses defects in the image originating from the secondary transfer (image loss or roughness, etc.). Furthermore, since the surface resistivity is set to 1.0 × 10⁻⁶, 13 With a voltage of Ω / □ or less, the transfer voltage can be more effectively suppressed from becoming too large, and the increase in power supply size and cost can be effectively suppressed.

[0030] Furthermore, A / B is 3.00 or less, where A (Ω / □) represents the surface resistivity measured on the outer surface of the biaxially stretched cylindrical film after it has been left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50%, and B (Ω / □) represents the surface resistivity measured on the outer surface of the biaxially stretched cylindrical film after it has been left to stand for 24 hours at a temperature of 30°C and a relative humidity of 80%. Therefore, in the biaxially stretched cylindrical film according to this disclosure, the environmental dependence of the surface resistivity on its outer surface is very small. As described above, in the electrophotographic tape according to this disclosure, the surface resistivity does not change significantly even in high-temperature and high-humidity environments or low-temperature and low-humidity environments, thus contributing to the stable formation of high-quality electrophotographic images. A / B is preferably 0.33 or more and 3.00 or less, more preferably 1.00 or more and 3.00 or less, and even more preferably 1.00 or more and 1.30 or less.

[0031] There is no particular limitation on the thickness of the biaxially stretched cylindrical film according to this disclosure. However, since the biaxially stretched cylindrical film is configured in a bent state within an electrophotographic image forming apparatus, it is preferable to control the thickness to 40 μm to 500 μm, and particularly to 50 μm to 100 μm, from the viewpoint of ensuring flexibility. Furthermore, it is preferable that the tensile modulus Ep in the circumferential direction and the tensile modulus Ea in the direction perpendicular to the circumferential direction of the biaxially stretched cylindrical film are both 1000 MPa or more. As described above, the electrophotographic belt is tensioned within the electrophotographic image forming apparatus by means of a predetermined tension caused by multiple rollers, but elongation and breakage can be prevented by setting Ep to 1000 MPa or more. Furthermore, due to the predetermined tension applied in the circumferential direction, a compressive force is applied in the direction perpendicular to the circumferential direction of the electrophotographic belt. However, by setting Ea to 1000 MPa or more, wrinkles on the outer surface of the electrophotographic belt formed in the circumferential direction due to the compressive force can be more reliably suppressed.

[0032] The tensile modulus of elasticity described above can be controlled by the orientation of the crystalline polyester along the circumferential direction and the direction perpendicular to the circumferential direction of the biaxially stretched cylindrical film. Furthermore, the degree of orientation of the crystalline polyester can be represented by the shrinkage rate αp along the circumferential direction of the biaxially stretched cylindrical film and the shrinkage rate αa along the direction perpendicular to the circumferential direction. Preferably, both αp and αa of the biaxially stretched cylindrical film are 2.0% or more. A biaxially stretched cylindrical film with αp and αa of 2.0% or more means that the crystalline polyester is sufficiently oriented along the circumferential direction and the direction perpendicular to the circumferential direction, and when the belt is tensioned, the shrinkage stress takes effect, thereby suppressing belt deformation. Furthermore, a biaxially stretched cylindrical film with such shrinkage rates can set the tensile modulus of elasticity Ep and Ea to 1000 MPa or more. For reference, methods for measuring Ep and Ea, as well as αp and αa, will be described in detail in the embodiments.

[0033] <Crystall Polyester>

[0034] Crystalline polyesters can be obtained by polycondensation of dicarboxylic acids and diols, polycondensation of hydroxycarboxylic acids or lactones, or polycondensation using multiple of these components. Further combination with multifunctional monomers is also acceptable. Crystalline polyesters can be homopolymers containing one ester bond or copolyesters (polymers) containing multiple ester bonds.

[0035] Preferred examples of crystalline polyesters include at least one selected from the group consisting of polyalkylene terephthalate and polyalkylene naphthalate, which have high crystallinity and exhibit excellent heat resistance. Furthermore, copolymers of polyalkylene naphthalate and polyalkylene isophthalate are preferred.

[0036] From the viewpoint of high crystallinity and heat resistance, the number of carbon atoms in the alkylene groups of poly(alkylene terephthalate), poly(alkylene naphthalate), and poly(alkylene isophthalate) is preferably 2 or more and 16 or less. More specifically, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene isophthalate, and copolymers containing these components are preferred as crystalline polyesters. These can be used alone or in combination of two or more of them. There is no particular limitation on the molecular weight of the crystalline polyester; however, for example, in the case of PET, a weight-average molecular weight of 50,000 (50,000) to 80,000 (80,000) is preferred. Furthermore, in the case of PEN, a weight-average molecular weight of 20,000 (20,000) to 80,000 (80,000) is preferred.

[0037] The content of crystalline polyester in the biaxially stretched cylindrical film is preferably 50.0% by mass or more, and more preferably 60.0% by mass or more, relative to the total mass of the thermoplastic resin composition. When the content of crystalline polyester is within the above range, sufficient crystalline polyester can be oriented along the circumferential direction of the biaxially stretched cylindrical film and in a direction perpendicular to the circumferential direction, and the mechanical strength of the biaxially stretched cylindrical film can be improved more reliably.

[0038] <Amorphous Polyester>

[0039] Examples of amorphous polyesters include polyesters having monomer units derived from at least one phthalic acid selected from the group consisting of terephthalic acid, phthalic acid and isophthalic acid, and monomer units derived from at least two diols selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol and cyclohexanediol.

[0040] Examples include: condensation polymers of copolymers having polyethylene terephthalate units and polyethylene phthalate units with the aforementioned diols, and condensation polymers of copolymers having polyethylene terephthalate units and polyethylene isophthalate units with the aforementioned diols. These copolymers can be either block copolymers or random copolymers. Furthermore, mixtures in which two or more copolymers are blended or alloyed are also acceptable.

[0041] Examples of suitable amorphous polyesters include those having monomer units derived from terephthalic acid, and monomer units of ethylene glycol and propylene glycol. Such amorphous polyesters are used, for example, as... GK640 and GK880" (both are trade names, manufactured by Toyobo Co., Ltd.) is commercially available.

[0042] The chemical structure of the amorphous polyester resin can be obtained by extracting the amorphous polyester from the substrate using suitable means such as dissolving it in a solvent such as toluene or methyl ethyl ketone. The extracted amorphous polyester is then separated and identified using thermal decomposition GC / MS, IR, NMR or elemental analysis.

[0043] Preferably, the content of amorphous polyester relative to the content of crystalline polyester is 10.0% by mass or more and 100.0% by mass or less, and particularly 15.0% by mass or more and 35.0% by mass or less. When the content of amorphous polyester relative to crystalline polyester is within the above range, an amorphous polyester phase containing a sufficient amount of conductive pathways due to carbon black can be formed in the biaxially stretched cylindrical film to exhibit the above-mentioned surface resistivity value.

[0044] <Carbon Black>

[0045] Examples of carbon blacks that may be used in this disclosure include, for example, acetylene black, furnace black, channel black, and thermal cracking black. These may be used alone or in combination of two or more thereof.

[0046] Among the aforementioned carbon blacks, carbon blacks that can form well-developed aggregate states, such as Ketjhen Black (registered trademark), are preferred. The aggregate state of the carbon black can be evaluated by its DBP absorption. DBP absorption is a parameter representing the complex aggregate form (structure) resulting from the chemical or physical bonding between carbon black particles, and is expressed as the amount (mL) of dibutyl phthalate (DBP) that can be contained in 100g of carbon black.

[0047] Carbon black with a high DBP absorption capacity has a more developed structure. Therefore, carbon black with a high DBP absorption capacity dispersed in the resin can improve the conductivity of the obtained resin composition. Furthermore, due to the more developed structure of the carbon black, the nucleation effect of carbon black crystallization is reduced, and the arrangement of crystalline polyester molecules is hindered. In other words, the crystallization of crystalline polyester can be relatively suppressed. Therefore, the inventors believe that by using carbon black with a high-grade structure, the formation of spherulites in crystalline polyester can be relatively suppressed, and the biaxial stretchability of the resin composition can be better maintained even when a high concentration of carbon black is included in the resin composition. For this purpose, it is preferable that the DBP absorption capacity of the carbon black is 300 mL / 100 g or more. The DBP absorption capacity of the carbon black in the base layer can be measured, for example, by dissolving the amorphous polyester from the base layer using a solvent or the like; extracting the carbon black present in the phase of the amorphous polyester; and measuring the carbon black using a known DBP absorption measurement device.

[0048] From the viewpoint of imparting a predetermined conductivity to the substrate, the carbon black content in the substrate should be 2.0% by mass or more relative to the mass of the substrate. From the viewpoint of the strength of the biaxially stretched cylindrical film, it is preferable to have an upper limit of 15.0% by mass or less. The carbon black content can preferably be from 2.0% to 15.0% by mass. Furthermore, it is preferable that the carbon black content is in the range of 8.0% to 35.0% by mass relative to the mass of the amorphous polyester in the substrate. Since the mass ratio of carbon black to amorphous polyester is set within the above range, conductive paths due to carbon black can be reliably formed in the phase of amorphous polyester, and the surface resistivity of the substrate can be easily adjusted within the above range.

[0049] <Additives>

[0050] Other components may be added to the thermoplastic resin composition without impairing the effects of this disclosure. Examples of other components include antioxidants, ultraviolet absorbers, organic pigments, inorganic pigments, pH adjusters, crosslinking agents, compatibilizers, release agents, coupling agents, and lubricants. These additives may be used alone or in combination of two or more thereof.

[0051] The amount of additives used can be set appropriately, and there are no particular restrictions.

[0052] Furthermore, the substrate may contain an ionic conductive agent without impairing one of the effects according to this disclosure, such as suppressing changes in surface resistance caused by the environment. For example, when the substrate contains an ionic conductive agent, it is preferable that the total amount of the ionic conductive agent is 2.0% by mass or less based on the mass of the substrate. Since the content ratio of the ionic conductive agent is set to 2.0% by mass or less, the environmental dependence of the surface resistance of the substrate can be controlled to a negligible level. However, in this disclosure, it is more preferable that the biaxially stretched cylindrical film does not contain an ionic conductive agent.

[0053] <Surface Layer>

[0054] Examples of surface layers include cured products containing active energy-curable (AE) resins and layers exhibiting excellent abrasion resistance. Such a second layer can be formed, for example, by coating the outer peripheral surface of a substrate with a composition containing an AE resin, such as a photocurable resin, and then curing the composition. There are no particular limitations on the thickness of the surface layer, but for example, 1 to 5 μm is preferred.

[0055] <Back layer>

[0056] Examples of back layers include: a resin layer for reinforcing the substrate; and a conductive layer for making the inner circumferential surface of the electrophotographic tape conductive. There is no particular limitation on the thickness of the back layer, but it is preferably, for example, 0.05 to 10 μm.

[0057] <Methods for producing base layers>

[0058] Biaxially stretched cylindrical membranes can be produced, for example, by the following steps (i) to (iii).

[0059] Step (i): Obtain a preform in the shape of a test tube formed from a resin mixture comprising crystalline polyester, amorphous polyester and carbon black.

[0060] Step (ii): The preform is stretched along its length and biaxially stretched in both the length and circumferential directions by introducing gas into the preform (biaxial stretch blow molding), and a biaxially stretched molded article (hereinafter also referred to as "bottle") is obtained.

[0061] Next, step (iii): cut off both ends of the bottle and obtain a biaxially stretched cylindrical membrane with an annular shape.

[0062] Regarding step (i), firstly, granules comprising a resin mixture of crystalline polyester, amorphous polyester, and carbon black are prepared.

[0063] At this point, it is preferable to prepare the granules of the resin mixture by first melt-blending an amorphous polyester and carbon black, thereby preparing an amorphous polyester mixture.

[0064] Then, the amorphous polyester mixture is mixed with the crystalline polyester, and

[0065] Further, the mixture is subjected to hot melt mixing.

[0066] This allows for a more reliable non-uniform distribution of carbon black within the amorphous polyester. Specifically, as described above, in the biaxially stretched cylindrical film according to this disclosure, it is preferable to make the carbon black non-uniformly distributed within the amorphous polyester phase and to prevent the carbon black from directly contacting the crystalline polyester. This prevents the formation of spherulites in the crystalline polyester during biaxial stretching, prevents the formation of conductive pathways for the carbon black from being hindered, and allows for a more reliable formation of conductive pathways for the carbon black within the amorphous polyester phase.

[0067] It should be noted that when using two or more crystalline polyesters as crystalline polyesters, it is preferable to heat and melt-blend the two or more crystalline polyesters to prepare a crystalline polyester mixture.

[0068] In the heated melt compounding of crystalline polyesters or blends of crystalline polyesters, and blends of amorphous polyesters, compounding at the following temperatures is preferred. Specifically, in order to fully compound the polyester with the highest melting point among the crystalline and amorphous polyesters to be included in the resin blend, it is preferable to compound the resulting blend at a temperature above the highest melting point. There are no particular limitations on the compounding method, and single-screw extruders, twin-screw compounding extruders, Banbury mixers, rollers, Brabenders, plastographs, and kneaders can be used.

[0069] The resulting resin mixture is used to form preforms in the shape of test tubes. There are no particular limitations on the method of forming the preforms, and examples include the following methods. Figure 2 As shown, a method is used to form a preform 205 having a predetermined shape by injecting a molten resin mixture into a preform forming mold including a cavity mold 203 and a core mold 207 using an injection molding apparatus 201 and allowing the molten mixture to solidify within the preform forming mold. For reference, at this time, for example, it is preferable to set the temperature of the preform forming mold into which the molten mixture is injected to be below 40°C. The molten mixture injected into the mold is cooled and solidified within the mold, and rapid cooling at this time can prevent the crystallization of the crystalline polyester.

[0070] Since the crystallization of crystalline polyester is suppressed within the preform, the crystallization orientation of the crystalline polyester along the biaxial direction can be controlled more accurately in the stretch blow molding in step (ii).

[0071] Next, in step (ii), the preform is subjected to biaxial stretch blow molding. First, as... Figure 3A As shown, the preform 205 is placed in a heating furnace 301 and heated to a temperature at which the preform 205 can be stretched. The heating time is preferably less than 1 minute. Since the heating time is set to less than 5 minutes, crystallization of the crystalline polyester within the preform during heating can be prevented. The heated preform is conveyed in the direction of arrow 305. Next, a blowdie 303 is lowered from directly above the heated preform 205 in the direction of arrow 307. The blowdie 303 has a cylindrical cavity 303-3 formed therein by a combination of a left mold 303-1 and a right mold 303-2. Then, as... Figure 3B As shown, the preform 205 is disposed at the opening of the blow molding die 303.

[0072] Preferably, the heated preform is placed at the mouth of the blow molding die for a short time (e.g., within 20 seconds) to prevent the temperature of the heated preform from dropping before the start of the next biaxial stretching step. This prevents the crystallization of the crystalline polyester within the preform due to slow cooling. As a reference, it is acceptable to calculate the heating temperature of the preform in advance by checking the endothermic peak or baseline shift of the resin mixture that constitutes the preform during heating using differential scanning calorimetry (DSC), or by determining the heating temperature from the glass transition temperature (Tg).

[0073] like Figure 3C As shown, the stretching rod 309 is driven in the direction of arrow 311, thereby stretching the heated preform 205 disposed within the blow molding head 303 along its length. This stretching is called primary stretching. Furthermore, synchronously with the driving of the stretching rod 309, gas flows into the preform 205 from its opening (arrow 313), causing the preform to expand circumferentially. This operation is called secondary stretching. Examples of gases to be blown in include air, nitrogen, carbon dioxide, and argon. As a result, the preform 205 expands along its length... Figure 3C The expansion occurs in each direction indicated by arrow 315, bringing the material into close contact with the inner wall of the mold cavity 303-3, where it cools and solidifies. Next, the left mold 303-1 and the right mold 303-2 of the blow molding head 303 are separated, thereby removing the molded article with the bottle shape (hereinafter also referred to as "blow-molded bottle") from the blow molding head 303.

[0074] Next, as Figure 3D As shown, the mouth-side portion and the upper portion opposite to the mouth-side of the obtained blow-molded bottle 317 are cut off, and a biaxially stretched cylindrical film 319 that becomes the base layer is obtained.

[0075] For reference, it is also acceptable to heat-treat the blow-molded bottle 317 as needed before cutting it, and to adjust the surface roughness of the outer circumference of the blow-molded bottle or fine-tune the crystallinity of the crystalline polyester. Specifically, for example, such as... Figure 4 As shown, a blow-molded bottle 317 is placed inside a cylindrical mold head 401, and then the blow-molded bottle is filled with gas. The upper and lower parts of the mold head 401 are then positioned such that an outer mold head is respectively installed thereto, preventing gas leakage from the inside of the blow-molded bottle. The mold head 401 is heated by a roller-shaped heater 403 that contacts the outer circumferential surface of the mold head 401, while the mold head 401 is rotated. The heating temperature is set, for example, to about 130 to 190°C, and the heating time is set, for example, to about 60 seconds, to uniformly heat the entire circumference of the blow-molded bottle.

[0076] The electrophotographic tape according to this disclosure is not limited to use as an intermediate transfer tape, but is also suitable for use as, for example, a transport transfer tape.

[0077] Electrophotographic image forming equipment

[0078] Examples of electrophotographic image forming apparatuses using an electrophotographic tape according to one aspect of this disclosure as an intermediate transfer tape will be described below. Figure 1 As shown, the electrophotographic image forming apparatus has a so-called tandem configuration in which electrophotographic stations of various colors are arranged side by side along the rotation direction of the intermediate transfer belt. In the following description, the suffixes Y, M, C, and k are appended to the reference numerals of the structures associated with the respective colors yellow, magenta, cyan, and black; however, in some cases, the suffixes are omitted for the same structures.

[0079] exist Figure 1 In this setup, charging devices 2Y, 2M, 2C, and 2k, exposure devices 3Y, 3M, 3C, and 3k, developing devices 4Y, 4M, 4C, and 4k, and an intermediate transfer belt (intermediate transfer body) 6 are respectively arranged around the photosensitive drum (photosensitive element, image carrier) 1Y, 1M, 1C, and 1k. The photosensitive drum 1 is driven to rotate at a predetermined circumferential speed (processing speed) in the direction of arrow F (counterclockwise). The charging devices 2 charge the circumferential surface of the photosensitive drum 1 to a predetermined polarity and potential (primary charging). The laser beam scanner, which serves as the exposure device 3, outputs a laser beam that is modulated on / off in response to image information input from an external device such as an image scanner or computer (not shown), and scans and exposes the charged surface on the photosensitive drum 1. Through this scanning and exposure, an electrostatic latent image corresponding to the target image information is formed on the surface of the photosensitive drum 1.

[0080] The developing devices 4Y, 4M, 4C, and 4k each contain toners comprising yellow (Y), magenta (M), cyan (C), and black (k) color components, respectively. Then, based on image information, the developing device 4 to be used is selected, and the developer (toner) is developed on the surface of the photosensitive drum 1, visualizing the electrostatic latent image as a toner image. In this embodiment, a reversal developing system is used, which attaches the toner to the exposure portion of the electrostatic latent image in this manner and develops the electrostatic latent image. Furthermore, the charging device, exposure device, and developing device constitute an electrophotographic image forming unit.

[0081] Furthermore, the intermediate transfer belt 6 is composed of an annular electrophotographic belt. The intermediate transfer belt 6 is tensioned by multiple rollers 20, 21, and 22 so that its outer peripheral surface contacts the surface of the photosensitive drum 1. In this embodiment, roller 20 is a tension roller configured to control the tension of the intermediate transfer belt 6 to maintain a constant tension; roller 22 is a drive roller for the intermediate transfer belt 6; and roller 21 is a counter-rotating roller for secondary transfer. Then, driven by roller 22, the intermediate transfer belt 6 rotates in the direction of arrow G. Furthermore, primary transfer rollers 5Y, 5M, 5C, and 5k are respectively arranged at the primary transfer position facing the photosensitive drum 1, while the intermediate transfer belt 6 is held between them.

[0082] Using a primary transfer bias voltage (not shown) applied to the primary transfer roller 5, having a polarity opposite to that of the toner, the unfixed toner images of each color formed on the photosensitive drum 1 are sequentially electrostatically transferred onto the intermediate transfer belt 6. Then, a panchromatic image of four colors of the unfixed toner images is obtained on the intermediate transfer belt 6. The intermediate transfer belt 6 rotates while carrying the toner images transferred from the photosensitive drum 1 in this manner. Each rotation of the photosensitive drum 1 after a primary transfer cleans the surface of the photosensitive drum 1 of any residual toner using a cleaning device 11, and the resulting surface is then repeatedly subjected to the image forming step.

[0083] Furthermore, at the secondary transfer position of the intermediate transfer belt 6 facing the transport path of the recording material 7 used as the transfer medium, a secondary transfer roller (transfer section) 9 is press-fitted onto the toner image bearing surface side of the intermediate transfer belt 6. Additionally, on the back side of the intermediate transfer belt 6 at the secondary transfer position, a counter roller 21, forming the counter electrode of the secondary transfer roller 9 and subjected to a bias voltage, is disposed. When the toner image on the intermediate transfer belt 6 is transferred to the recording material 7, a bias voltage (e.g., -1000 to -3000V) with the same polarity as the toner is applied to the counter roller 21 by the transfer bias voltage application unit 28, and a current of -10 to -50μA flows through the counter roller 21. The transfer voltage at this time is detected by the transfer voltage detection unit 29. Furthermore, a cleaning device (with cleaner) 12 for removing residual toner from the intermediate transfer belt 6 after the secondary transfer is provided downstream of the secondary transfer position.

[0084] Recording material 7 is conveyed via conveying guide 8 in the direction of arrow H and introduced to the secondary transfer position. Recording material 7 introduced to the secondary transfer position is clamped and conveyed there; at this time, a constant bias voltage (transfer bias voltage) controlled to a predetermined value is applied from the secondary transfer bias voltage application unit 28 to the opposing roller 21 of the secondary transfer roller 9. Due to the transfer bias voltage applied to the opposing roller 21, which has the same polarity as the toner, a full-color image (toner image) of four colors overlapping on the intermediate transfer belt 6 is transferred to the recording material 7 in one step at the transfer section, forming a full-color unfixed toner image on the recording material. The recording material 7 with the toner image transferred onto it is introduced to a fixing device (not shown), where it is heated; and the toner image is fixed.

[0085] According to one aspect of this disclosure, an electrophotographic tape that facilitates the stable formation of high-quality electrophotographic images under various environments can be obtained. According to another aspect of this disclosure, an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images can be obtained.

[0086] [Example]

[0087] The present disclosure will now be described in detail with reference to embodiments and comparative examples, but the disclosure is not limited thereto. Materials used in producing the electrophotographic tapes according to the embodiments and comparative examples are shown below.

[0088] [Table 1]

[0089]

[0090] [Table 2]

[0091]

[0092] [Table 3]

[0093]

[0094] (Methods for measuring and evaluating characteristic values)

[0095] Methods for measuring and evaluating the characteristic values ​​of the electrophotographic tape according to the embodiments and comparative examples are as follows (1) to (5).

[0096] (Evaluation 1) Evaluation of surface resistivity (A, B)

[0097] The surface resistivity of the base layer of the electrophotographic tape was measured according to the method of JIS-K6911. As the measuring equipment, a high-resistivity meter (trade name: Hiresta UP MCP-HT450, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) was used, with an inner diameter of 50 mm for the main electrode, an inner diameter of 53.2 mm for the guard ring electrode, and an outer diameter of 57.2 mm for the probe (trade name: UR-100, manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Surface resistivity was expressed as per unit area (1 cm²) of the electrophotographic tape. 2 The surface resistance value is expressed as [Ω / □], and the unit is expressed as [Ω / □].

[0098] The substrate of the produced electrophotographic tape was left to stand for 24 hours in an environmental test chamber with the temperature controlled at 23°C and the relative humidity controlled at 50%. Afterward, at the same temperature and humidity, a voltage of 250V was applied to the electrophotographic tape for 10 seconds, and the surface resistivity of the substrate was measured at four points along the circumference. The average value of the obtained surface resistivity was defined as index A of the surface resistivity under normal temperature and humidity.

[0099] Similarly, the substrate of the produced electrophotographic tape was left to stand for 24 hours in an environmental test chamber with the temperature controlled at 30°C and the relative humidity controlled at 80%. Afterward, at 30°C and 80% relative humidity, a voltage of 250V was applied to the substrate for 10 seconds, and the surface resistivity of the substrate was measured at four points along the circumference. The average value of the obtained surface resistivity was defined as index B of the surface resistivity under high temperature and high humidity conditions.

[0100] In addition, A / B (times) is calculated from the obtained A and B, and is used as an indicator of the change in surface resistivity due to temperature and humidity.

[0101] (Evaluation 2) Evaluation of tensile modulus of elasticity (Ep, Ea)

[0102] The tensile modulus of elasticity was measured using a low-load universal testing machine (trade name: 34TM-5, manufactured by Instron) equipped with a 5kN load sensor at an environment of 23°C and 50% relative humidity. Sample pieces of 100mm circumferential x 20mm length and 20mm circumferential x 100mm length were cut from the manufactured electrophotographic tape and held in a pneumatic clamp with a chuck spacing of 50mm. The clamped sample pieces were stretched at a constant speed of 5mm / min, and the tensile modulus of elasticity was calculated based on the stress value at 0.25% strain from the obtained stress-strain curve and the thickness of the electrophotographic tape. The average value was determined from the measurements of five sample pieces cut from the same electrophotographic tape; the tensile modulus of elasticity along the circumferential direction of the electrophotographic tape was defined as Ep, and the tensile modulus of elasticity in the direction perpendicular to the circumferential direction was defined as Ea.

[0103] (Evaluation 3) Evaluation of shrinkage rate (αp, αa)

[0104] As an indicator of the shrinkage stress of electrophotographic tape, the shrinkage rate is measured using the following method. The shrinkage rate is measured using a thermomechanical analysis instrument (trade name: TMA / SDTA841; manufactured by Mettler Toledo) under the following measurement conditions, while varying the distance between the chucks with changes in sample size.

[0105] Sample pieces measuring 5mm in the circumferential direction and 20mm in the length direction of the tape, and 20mm in the circumferential direction and 5mm in the length direction of the tape, are cut from the produced electrophotographic tape and used.

[0106] Clamp the sample piece so that the distance between the chucks becomes 10 mm and the load becomes 0.01 N. Hold it at 25°C for 10 minutes, heat it at 5°C / min to a temperature 10°C higher than the glass transition temperature of the thermoplastic resin composition, hold it for 30 minutes, and then cool it down to 25°C again at 5°C / min.

[0107] When the distance between the chucks before heating is represented by x1 and the distance between the chucks at the end is represented by x2, the shrinkage rate α (unit: %) is calculated according to the following equation.

[0108] α=(x1-x2) / x1×100

[0109] The average value was determined by measuring five sample pieces cut from the same electrophotographic tape, and the average value was defined as the shrinkage rate αp along the circumference of the electrophotographic tape and the shrinkage rate αa along the direction perpendicular to the circumference. For reference, the shrinkage rate value was recorded as a negative number when expansion occurred.

[0110] (Evaluation 4) Evaluation of DBP absorption

[0111] The DBP absorption of the carbon black contained in the produced electrophotographic tape was measured by the following method: 100 2mm × 2mm sample sheets were cut from the electrophotographic tape and pulverized; the product was immersed in toluene heated to 50°C and allowed to stand for 48 hours; this dissolved the amorphous polyester in the sample sheets and extracted the carbon black contained in the amorphous polyester phase. The carbon black was filtered from the solution and the DBP absorption was measured using an absorbance measuring device (trade name: S-500; manufactured by ASAHISOUKEN CORPORATION). Specifically, 10g of the collected carbon black was added to the measuring chamber, the DBP (dibutyl phthalate) dropping rate was set to 4mL / min, the rotor blade rotation speed was set to 125rpm, and the torque was measured. The DBP absorption can be defined by the amount of DBP added when the torque reaches 70% of the peak torque value and the sample volume.

[0112] It should be noted that if the amount of carbon black required to measure DBP absorption cannot be obtained from 100 sample sheets, it is acceptable to increase the number of samples to be collected and perform the above operation to obtain the required amount of carbon black.

[0113] (Evaluation 5) Digital reproducibility of electrophotographic image forming equipment (evaluation of scattering images)

[0114] Use with Figure 1 The electrophotographic image forming apparatus shown has an intermediate transfer belt, used as an electrophotographic belt, installed within it. The resulting apparatus is then placed in a test chamber with a controlled temperature of 30°C and a relative humidity of 80% for 24 hours. Subsequently, an unfixed image is output, showing the transfer of fine-line images (30 lines / 5mm) onto paper. This unfixed image is then fixed in a 100°C oven without pressure to obtain an image. The image is observed using a magnifying glass, and the number of fine-line images showing toner scattering is evaluated.

[0115] [Example 1]

[0116] (Production at the grassroots level)

[0117] <Preparation of Amorphous Polyester Blends>

[0118] A premixed sample was prepared by mixing aPES1 ​​and CB1 from Table 2 at the mixing ratio shown in Table 4. The premixed sample was then melt-blended using a twin-screw extruder (trade name: TEX30α, manufactured by Japan Steel Works, Ltd.) to prepare an amorphous polyester blend. The melt-blending temperature was adjusted to be between 190°C and 270°C, and the melt-blending time was set to 3 to 5 minutes. The resulting amorphous polyester blend was granulated and dried at 90°C for 10 hours.

[0119] <Preparation of Crystalline Polyesters>

[0120] The cPES1 granules in Table 1 were dried at 140°C for 10 hours.

[0121] Next, cPES1 granules and granules of the amorphous polyester blend were fed into an injection molding machine (trade name: SE180D, manufactured by Sumitomo Heavy Industries, Ltd.) according to the mixing ratios described in Table 4. Then, the molten resin of the mixed granules was injected into a mold having a test tube shape, with the temperature of the mold controlled at 30°C and the temperature of the mold barrel set to 250 to 300°C, to produce a preform. The obtained preform had a test tube shape with an outer diameter of 50 mm, an inner diameter of 46 mm, a length of 150 mm, and a thickness of 2 mm.

[0122] Next, the preform is stretched biaxially along both the length and circumferential directions using a biaxial stretching forming apparatus. First, as... Figure 3A As shown, the preform 205 is placed in a heating device 301 equipped with a non-contact type heater (not shown) for heating the preform 205, and is heated by means of the heater to make the outer surface temperature of the preform 120 to 160°C.

[0123] Next, the blow molding die 303, with the die head temperature maintained at 30°C, descends toward the heated preform 205 in the direction of arrow 307, and the heated preform 205 is positioned at the opening of the blow molding die 303. Figure 3B Next, as Figure 3C As shown, the tension rod 309 is driven in the direction of arrow 311, and the drive of the tension rod begins simultaneously, as indicated by... Figure 3C As indicated by arrow 313, air at a temperature adjusted to 23°C is introduced into the preform 205 through its opening. In this manner, the preform 205 is stretched along a biaxial direction and brought into close contact with the inner wall of the blow molding die. For reference, the drive speed of the stretching rod 309 is set to 2.0 m / sec, and the pressure of the air introduced into the blow-molded bottle is set to 0.5 MPa.

[0124] Next, the left mold 303-1 and the right mold 303-2 of the blow molding head 303 are separated, thereby removing the molded article (blow-molded bottle) 317 with the bottle shape from the blow molding head 303.

[0125] Next, the obtained blow-molded bottle 317 will be set up in a process that produces it by electroforming, using nickel and as... Figure 4 The cylindrical die head 401 is shown, and the outer die head 405 is mounted thereto. An air pressure of 0.1 MPa is applied to the blow-molded bottle to prevent air leakage to the outside, thereby ensuring that the outer circumferential surface of the blow-molded bottle 317 is in close contact with the inner circumferential surface of the cylindrical die head. Furthermore, the entire circumference of the blow-molded bottle is uniformly heated at 130 to 190°C for 60 seconds using a heater 403, while the nickel cylindrical die head 401 is rotated at a constant speed of 2 revolutions per second.

[0126] Subsequently, air at a temperature of 25°C is blown onto a cylindrical die made of nickel to cool the die to room temperature (25°C), and the pressure of the air applied to the inside of the blow-molded bottle 317 is released, resulting in a blow-molded bottle 317 with dimensions improved through annealing. Regarding the biaxial stretch ratio, considering the dimensions of the preform 205 and the blow-molded bottle 317, the transverse stretch ratio (circumferential direction) Lp is 4.0 times, and the longitudinal stretch ratio (perpendicular to the circumferential direction) La is 4.3 times.

[0127] Next, as Figure 3D As shown, the portion of the blow-molded bottle 317 on the mouth side and the portion opposite to the mouth side are cut off, and a base layer for an electrophotographic tape is produced, which has a circumference of 630 mm, a width of 250 mm and a thickness of 70 μm.

[0128] (Preparation of coating solution for surface layer)

[0129] The acrylic resin composition described in Table 3 was weighed according to the ratio of AN / PTFE / GF / SL / IRG = 66 / 20 / 1.0 / 12 / 1.0 (mass ratio based on solid content), and the coarsely dispersed solution was dispersed using a high-pressure emulsification dispersion device (trade name: Nanovater, manufactured by Yoshida Kikai Co., Ltd.). This dispersion treatment was carried out until 50% of the average particle size of the contained PTFE became 200 nm. The obtained dispersion was used as a coating liquid for the surface layer.

[0130] (Formation of the surface layer)

[0131] The substrate is adhered to the outer circumference of a cylindrical die head (630 mm in circumference), and its ends are sealed. The resulting die head is then immersed in a container filled with a surface coating liquid, and lifted to maintain a constant relative speed between the liquid surface of the curing composition and the substrate of the electrophotographic tape. In this manner, a coating film formed by the coating liquid is formed on the surface of the substrate of the electrophotographic tape. The lifting speed (the relative speed between the liquid surface of the curing composition and the substrate of the electrophotographic tape) and the solvent ratio of the curing composition can be adjusted according to the desired film thickness of the surface layer.

[0132] In this embodiment, the lifting speed is set to 10 to 50 mm / sec, and the film thickness of the surface layer is adjusted to approximately 3 μm. In this embodiment, the coating direction refers to the direction opposite to the direction in which the substrate of the electrophotographic tape is lifted. In other words, the position where it is first lifted from the coating solution is the upstream position. The substrate of the electrophotographic tape coated with the coating solution is removed from the cylindrical die and dried at 23°C under exhaust for 1 minute. The drying temperature and drying time are appropriately adjusted according to the solvent type, solvent ratio, and film thickness.

[0133] Subsequently, the coating was irradiated with ultraviolet light using a UV irradiation machine (trade name: UE06 / 81-3, manufactured by Eye Graphics Co., Ltd.) until the cumulative light intensity reached 600 mJ / cm². 2 This allows the coating to cure.

[0134] The thickness of the surface layer is measured by such destructive testing: the base layer of an electrophotographic tape produced separately under the same conditions is cut off, and the cross-section is observed using an electron microscope (trade name: XL30-SFEG, manufactured by FEI Company Japan Ltd.).

[0135] As a result of the destructive testing, the thickness of the surface layer was 2.8 μm. Thus, an electron radiograph tape with a surface layer formed on the outer peripheral surface of the substrate was obtained. The electron radiograph tape was subjected to the above-described (Evaluation 1) to (Evaluation 5).

[0136] [Examples 2 to 6, 10 and 11]

[0137] Except for the types and blends of cPES, aPES, and CB described in Table 4, the electrophotographic tape was produced and evaluated in the same manner as in Example 1.

[0138] [Examples 7 to 9]

[0139] <Preparation of Crystalline Polyester Blends>

[0140] Premixed samples according to each embodiment were prepared, wherein cPES1 and ES1 were mixed in accordance with the mixing ratios described in Table 4. Each premixed sample was heated and melt-blended using a twin-screw extruder (trade name: TEX30α, manufactured by Japan Steel Works, Ltd.) to obtain crystalline polyester blends according to each embodiment. The temperature for heating and melting blending was adjusted to a range of 220°C to 300°C, and the heating and melting blending time was set to 3 to 5 minutes. Each obtained crystalline polyester blend was granulated and dried at 140°C for 10 hours.

[0141] <Preparation of Amorphous Polyester Blends>

[0142] Except for changing the types and blending ratios of aPES and CB to comply with the blending ratios described in Table 4, the granules of the respective amorphous polyester mixtures according to Examples 7 to 9 were prepared in the same manner as the amorphous polyester mixture of Example 1.

[0143] Except for using granules of crystalline polyester blends and non-crystalline polyester blends according to each embodiment, the preforms were produced in the same manner as in Example 1. Furthermore, except for using the obtained preforms, the base layer and surface layer were produced in the same manner as in Example 1, and electrophotographic tapes according to each embodiment were produced. The obtained electrophotographic tapes were evaluated from Evaluation 1 to Evaluation 5.

[0144] [Examples 12 to 16]

[0145] <Preparation of Crystalline Polyester Blends>

[0146] Premixed samples according to each embodiment were prepared, wherein cPES1 and cPES2, or cPES1, cPES2 and ES1, were mixed in accordance with the mixing ratios described in Table 4. These premixed samples were heated and melt-blended using a twin-screw extruder (trade name: TEX30α, manufactured by Japan SteelWorks, Ltd.) to obtain crystalline polyester blends according to each embodiment. The temperature for heating and melting was adjusted to be above 220°C and below 300°C, and the heating and melting time was set to 3 to 5 minutes. Each obtained crystalline polyester blend was granulated and dried at 140°C for 10 hours.

[0147] <Preparation of Amorphous Polyester Blends>

[0148] Except for changing aPES1 ​​and aPES2 and CB1 or CB2 to comply with the blending ratios described in Table 4, the granules of the amorphous polyester mixtures according to each embodiment were prepared in the same manner as the amorphous polyester mixture of Example 1.

[0149] Next, preforms were produced in the same manner as in Example 1, except that granules of crystalline polyester blends and granules of non-crystalline polyester blends according to each embodiment were used in accordance with the mixing ratios described in Table 4. Furthermore, except that the obtained preforms were used, a base layer and a surface layer were produced in the same manner as in Example 1, and an electrophotographic tape according to each embodiment was produced. The obtained electrophotographic tapes were evaluated from Evaluation 1 to Evaluation 5.

[0150] [Examples 17 to 19]

[0151] <Preparation of Crystalline Polyester Blends>

[0152] Premixed samples according to each embodiment were prepared, in which cPES1 and IC were mixed according to the mixing ratios described in Table 4. Each premixed sample was heated and melt-blended using a twin-screw extruder (trade name: TEX30α, manufactured by Japan Steel Works, Ltd.) to obtain crystalline polyester blends according to each embodiment. The temperature for heating and melting was adjusted to be above 220°C and below 300°C, and the heating and melting time was set to 3 to 5 minutes. Each obtained crystalline polyester blend was granulated and dried at 140°C for 10 hours.

[0153] <Preparation of Amorphous Polyester Blends>

[0154] Granules of the non-crystalline polyester mixture were prepared in the same manner as in Examples 1 to 3.

[0155] Next, except that granules of crystalline polyester blends and non-crystalline polyester blends according to each embodiment are used, preforms are produced in the same manner as in Example 1. Furthermore, except that the obtained preforms are used, a base layer and a surface layer are produced in the same manner as in Example 1, thereby producing an electrophotographic tape according to each embodiment. The obtained electrophotographic tape is evaluated from Evaluation 1 to Evaluation 5.

[0156]

[0157] [Compare Examples 1 and 2]

[0158] Prepare a premixed sample in which cPES1 and CB1 are mixed in the proportions described in Table 5. Except for using these premixed samples, obtain granules of the crystalline polyester blend in the same manner as in Example 7. Next, produce a preform in the same manner as in Example 1, except that only the granules of the crystalline polyester blend are used. Next, perform biaxial stretching of the preform in the same manner as in Example 1.

[0159] However, the preform has high hardness and cannot be stretched along its length and circumference. For reference, the DBP absorption of carbon black in this comparative example was analyzed in the same manner as described in Evaluation 4 of Example 1, except that pulverized material from a sample collected from a preform that had undergone biaxial stretching was used.

[0160] [Compare Examples 3 and 4]

[0161] Premixed samples according to each comparative example were prepared, in which aPES1 ​​and CB1 were mixed in the mixing ratios listed in Table 5. Except for using these premixed samples, granules of the amorphous polyester blend were obtained in the same manner as in Example 1. Pre-forms were produced in the same manner as in Example 1, except that only the granules of the amorphous polyester blend were used. Next, the pre-forms were biaxially stretched in the same manner as in Example 1.

[0162] As a result, the preform was stretched along both the length and circumferential directions, but localized overstretching occurred, and the preform broke in these areas. Therefore, blow-molded bottles could not be obtained. This was believed to be because the binder resin was composed of a non-crystalline polyester, making the preform too soft. For reference, the DBP absorption of carbon black in this comparative example was analyzed in the same manner as described in Evaluation 4 of Example 1, except that pulverized material from samples collected from biaxially stretched molded articles that broke as a result of biaxial stretching was used.

[0163] [Comparative Examples 5 to 8]

[0164] Granules of the non-crystalline polyester blend were prepared in the same manner as in Examples 1 and 3.

[0165] Except that the cPES1 granules and the granules of each amorphous polyester blend are used in accordance with the mixing ratios described in Table 5, the preforms are produced in the same manner as in Example 1. Furthermore, except that the obtained preforms are used, the base layer and surface layer are produced in the same manner as in Example 1, thereby producing electrophotographic tapes according to each comparative example. The obtained electrophotographic tapes are evaluated from Evaluation 1 to Evaluation 5.

[0166] [Comparative Example 9]

[0167] Prepare a premixed sample in which cPES1, aPES1, IC, and ES2 are mixed in the proportions listed in Table 5. Melt-mix the premixed sample using a twin-screw extruder (trade name: TEX30α, manufactured by Japan Steel Works, Ltd.). Adjust the melting-mixing temperature to a range of 220°C to 300°C, and set the melting-mixing time to 3 to 5 minutes. Granulate the resulting polyester mixture and dry it at 140°C for 10 hours.

[0168] Except for using only polyester blend granules, the preform was produced in the same manner as in Example 1. Next, except for using the obtained preform, the base layer and surface layer were produced in the same manner as in Example 1, thereby producing the electrophotographic tape according to Comparative Example 9. The obtained electrophotographic tape was evaluated from Evaluation 1 to Evaluation 5.

[0169] [Table 5]

[0170]

[0171] The evaluation results of Examples 1 to 19 and Comparative Examples 1 to 9 are shown in Tables 6 to 8. For reference, in Tables 6 to 8, when a blow-molded bottle can be formed by biaxial stretching of the preform, "Y" is recorded in the "Possibility of Biaxial Stretching". On the other hand, when a blow-molded bottle cannot be formed due to damage to the preform during biaxial stretching, "N" is recorded in the "Possibility of Biaxial Stretching".

[0172] [Table 6]

[0173]

[0174] [Table 7]

[0175]

[0176] [Table 8]

[0177]

[0178] In Comparative Examples 1 or 2, non-crystalline polyester was not included. Therefore, it is believed that heating the preform during a single blow molding process promotes spheroidization of the carbon black used as nuclei, thereby hardening the preform and making stretch blow molding impossible.

[0179] In Comparative Examples 3 or 4, crystalline polyester was not included. Therefore, it was assumed that when the preform was biaxially stretched, no increase in strength due to orientation crystallization occurred, and the preform broke from the locally thinned portion.

[0180] In Comparative Examples 5 to 8, ionic conductive agents or polyether ester amides were included in large quantities. When crystalline and amorphous polyesters were used in combination, biaxial stretching could be achieved even when carbon black was included. However, in the obtained electrophotographic tape, the surface resistivity in an environment of 23°C and 50% relative humidity differed by more than three times from that in an environment of 30°C and 80% relative humidity. Furthermore, in an environment of 30°C and 80% relative humidity, a large amount of scattering was observed in image evaluation.

[0181] While this disclosure has been described with reference to exemplary embodiments, it should be understood that this disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be accorded the broadest interpretation, thereby covering all such modifications and equivalent structures and functions.

Claims

1. A tape for electrophotography, comprising a biaxially stretched cylindrical film as a base layer, characterized in that, The biaxially stretched cylindrical membrane comprises crystalline polyester, amorphous polyester, and carbon black. The carbon black content relative to the biaxially stretched cylindrical membrane is 2.0% by mass or more and 15.0% by mass or less, and The surface resistivity measured on the surface of the biaxially stretched cylindrical membrane at a temperature of 23°C and a relative humidity of 50% was 1×10⁻⁶. 3 Ω / □ or higher and 1×10 13 Ω / □ or less, and A / B is less than 3.00, where A represents the surface resistivity measured on the surface of the biaxially stretched cylindrical membrane after it has been left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50%, and the unit of A is Ω / □. B represents the surface resistivity measured on the surface of the biaxially stretched cylindrical membrane after it has been left to stand for 24 hours at a temperature of 30°C and a relative humidity of 80%, and the unit of B is Ω / □.

2. The electrophotographic tape according to claim 1, wherein A / B is 0.33 or more and 3.00 or less.

3. The electrophotographic tape according to claim 1, wherein A / B is 1.00 or higher and 3.00 or lower.

4. The electrophotographic tape according to claim 1, wherein the biaxially stretched cylindrical film comprises an ion-conductive agent, and the total amount of the ion-conductive agent is less than 2.0% by mass relative to the biaxially stretched cylindrical film.

5. The electrophotographic tape according to claim 1, wherein the biaxially stretched cylindrical film is free of ionic conductive agents.

6. The electrophotographic tape of claim 1, wherein the crystalline polyester comprises at least one selected from the group consisting of polyalkylene terephthalate, polyalkylene naphthalate, polyalkylene isophthalate, and copolymers comprising these components.

7. The electrophotographic tape according to claim 1, wherein the amorphous polyester comprises monomer units derived from at least one phthalic acid selected from the group consisting of terephthalic acid, phthalic acid and isophthalic acid, and at least two diols selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol and cyclohexanediol.

8. The electrophotographic tape according to claim 1, wherein the content of the amorphous polyester is 100% by mass or less relative to the content of the crystalline polyester.

9. The electrophotographic tape according to claim 1, wherein the carbon black has a DBP absorption of 300 mL / 100 g or more.

10. The electrophotographic tape according to claim 1, wherein the tensile modulus Ep along the circumferential direction and the tensile modulus Ea in the direction perpendicular to the circumferential direction of the biaxially stretched cylindrical film are both 1000 MPa or more.

11. The electrophotographic tape according to claim 1, wherein the shrinkage rate αp along the circumferential direction and the shrinkage rate αa along the direction perpendicular to the circumferential direction are both 2.0% or more.

12. An electrophotographic image forming apparatus, characterized in that, It includes an electrophotographic tape as an intermediate transfer tape according to any one of claims 1 to 11.

Images