Photographic paper base and photographic paper

Abstract

This invention provides a photographic paper base and photographic paper. The photographic paper base includes a base paper layer and a plastic layer, with the plastic layer disposed on at least one side of the base paper layer. The base paper layer comprises pure wood pulp, an antistatic agent, a hygroscopic agent, and an anti-bleeding agent. The antistatic agent includes a sodium salt, and the hygroscopic agent includes a lithium salt. Therefore, in the photographic paper base of this invention, sodium salt is used as the antistatic agent, and lithium salt as the hygroscopic agent. The simultaneous use of both effectively reduces the volume resistivity of the paper base, thereby preventing the generation of static spots due to charge accumulation and discharge. It also reduces moisture loss from the cut edges of the paper base, thus preventing edge bleeding. Furthermore, sodium and lithium salts have strong solubility and do not interact with the base paper fibers and the anti-bleeding agent, therefore they do not exacerbate edge bleeding or affect the effectiveness of the anti-bleeding agent. Therefore, the photographic paper base of this invention has a low volume resistivity, avoids the generation of static sparks, and is less prone to edge bleeding and bleed.

Description

Technical Field

[0001] This invention belongs to the field of photographic printing technology, specifically, it relates to a photographic paper base and photographic paper. Background Technology

[0002] Color photographic paper is made by coating photographic base paper with PE (polyethylene) coating on both sides to form a coated paper base. This coated paper base is then further coated to form color photographic paper. The PE coating plays a crucial role in the use of photographic paper. It acts as a waterproof layer, protecting the paper base from liquids and moisture. Coating the base paper with PE is an essential process in photographic paper production; however, the double-sided coating directly increases the resistivity of the paper base, leading to excessive static electricity during production. This can cause electrical sparks during winding, unwinding, and cutting. For photosensitive photographic paper, static electricity is unacceptable; these sparks directly cause static spots on the paper, affecting its use and even rendering the product unusable.

[0003] Currently, the common method for reducing electrostatic sparks on paper substrates is to add a coating to the surface of the paper substrate's plastic layer. For example, patent DE4435350C2 mentions adding antistatic substances to the coating on the paper substrate surface, which can reduce the surface resistance of the paper substrate and reduce the impact of static electricity. However, this antistatic method has certain limitations. It can only reduce the surface resistance of the paper substrate, allowing static charge to be conducted through the surface layer. When the static charge increases suddenly, relying solely on the surface layer for conductivity results in a slow conductivity rate, which cannot effectively eliminate static electricity by discharging the charge in time. Furthermore, the surface resistance of the antistatic layer is greatly affected by ambient humidity; when the humidity is below 40% RH, the conductivity decreases significantly.

[0004] Furthermore, in existing technologies, to increase the conductivity of the paper base and prevent edge bleeding in low-humidity environments, highly absorbent conductive macromolecular conductive substances such as conductive starch and polyethylene glycol are typically added during the papermaking and pulping process. For example, patent DE3400125C2 mentions adding macromolecular conductive substances to increase the conductivity of the paper base. However, these macromolecular conductive substances can become entangled with the base paper fibers, causing the paper base to rapidly absorb water during wet processing, exacerbating edge bleeding. When edge bleeding is improved by adding anti-edge bleeding agents, these agents usually interact with both the base paper fibers and the hydrophilic groups in the macromolecular conductive substances, significantly damaging the conductivity and anti-edge bleeding effect of the paper base.

[0005] Therefore, existing coated paper bases still need further improvement. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in the related art. Therefore, one object of this invention is to provide a photographic paper base and photographic paper, wherein the photographic paper base has low volume resistivity, effectively avoiding the generation of electrostatic sparks, and is less prone to edge bleeding and edge bleed phenomena.

[0007] In one aspect of the invention, a photographic paper base is provided. According to an embodiment of the invention, the photographic paper base includes a base paper layer and a plastic layer, the plastic layer being disposed on at least one side of the base paper layer; wherein the base paper layer includes pure wood pulp, an antistatic agent, a hygroscopic agent, and an anti-bleeding agent, the antistatic agent including a sodium salt, and the hygroscopic agent including a lithium salt.

[0008] Therefore, in the photographic paper base of this invention, the base paper layer is made of pure wood pulp, an antistatic agent, a hygroscopic agent, and an anti-bleeding agent. Sodium salt is used as the antistatic agent. When the plastic layer away from the base paper layer accumulates charge due to friction, the opposite charge accumulates on the side of the plastic layer adjacent to the base paper layer. Since the base paper layer typically contains 5wt%-8wt% moisture, the addition of sodium salt allows it to move freely in the base paper layer as ions. The free sodium salt in the base paper layer redistributes the charge, thus preventing static spots caused by charge accumulation and discharge, effectively providing an antistatic effect. The photographic paper base of this invention utilizes lithium salt as a hygroscopic agent. Lithium salt has strong water absorption properties, and the combined use of sodium and lithium salts effectively reduces the volume resistivity of the paper base. Furthermore, it helps retain moisture at the cut edges of the paper base under high temperature and low humidity conditions, reducing moisture loss and thus preventing edge bleeding. On the other hand, sodium and lithium salts have strong solubility and do not interact with the base paper fibers. They dissolve rapidly from the base paper layer during wet processing and do not participate in the reaction between the anti-bleeding agent and the base paper fibers. Therefore, adding sodium and lithium salts to the base paper layer does not exacerbate edge bleeding or affect the effectiveness of the anti-bleeding agent. Thus, the photographic paper base of this invention, using the above-described composition of the base paper layer, effectively reduces the volume resistivity of the photographic paper base, avoids electrostatic sparks, and is less prone to edge bleeding and edge bleed phenomena.

[0009] In addition, the photographic paper base according to the above embodiments of the present invention may also have the following additional technical features:

[0010] According to an embodiment of the present invention, the base paper layer comprises: 80-90 parts by weight of pure wood pulp; 0.01-5 parts by weight of antistatic agent; 0.01-3 parts by weight of hygroscopic agent; and 0.01-3 parts by weight of anti-bleeding agent. This effectively prevents tight edges and bleeding in the photographic base paper, reduces the volume resistivity of the photographic base paper, and avoids the generation of electrostatic sparks.

[0011] According to embodiments of the present invention, the sodium salt includes at least one of sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate.

[0012] According to embodiments of the present invention, the lithium salt includes at least one of lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate.

[0013] According to an embodiment of the present invention, the anti-sagging agent comprises RM-R', wherein R and R' each independently comprise a hydrocarbon group, at least one of R and R' comprises a hydrocarbon group with not less than 10 carbon atoms, and M comprises at least one of lactone, acid anhydride, epoxy group, and isocyanate. Therefore, the addition of the above-mentioned anti-sagging agent can effectively reduce the hydrophilicity of the base paper fibers, thereby achieving better anti-sagging effect.

[0014] According to embodiments of the present invention, the anti-seepage agent comprises at least one of alkyl ketene dimers, olefinic amber, epoxy resin, and polyurethane prepolymer.

[0015] According to an embodiment of the present invention, the thickness of the base paper layer is 150μm-200μm. Therefore, the photographic paper base has a low volume resistivity and superior performance.

[0016] According to an embodiment of the present invention, the density of the base paper layer is 0.95 g / cm. 3 -1.05g / cm 3 Therefore, this photographic paper base is less prone to edge bleeding and has better performance.

[0017] According to an embodiment of the present invention, the smoothness of the base paper layer is 90-110 seconds. Therefore, the photographic paper base has superior performance.

[0018] According to embodiments of the present invention, the plastic layer comprises at least one of HDPE (high-density polyethylene), LDPE (low-density polyethylene), and LLDPE (linear low-density polyethylene).

[0019] According to an embodiment of the present invention, the thickness of the plastic layer is 15μm-35μm. This provides good impermeability and waterproofing, protecting the base paper from being soaked by liquids and moisture.

[0020] According to an embodiment of the present invention, the photographic paper base further includes an antistatic layer, which is disposed on the side of the plastic layer away from the base paper layer. This further prevents the photographic paper base from generating electrostatic sparks.

[0021] According to an embodiment of the present invention, the antistatic layer comprises at least one of alkyl sulfonates, sulfates, betaine, sodium polystyrene sulfonate, and sodium polyethylene sulfonate.

[0022] According to an embodiment of the present invention, the thickness of the antistatic layer is 0.1 μm-1 μm. This further prevents electrostatic sparks from forming on the photographic paper substrate.

[0023] In another aspect, the present invention provides photographic paper. According to an embodiment of the invention, the photographic paper comprises the photographic paper base described above.

[0024] Therefore, the photographic paper of the present invention has a low volume resistivity, effectively avoiding the generation of electrostatic sparks, and is less prone to edge tightness and edge bleeding during wet processing. Those skilled in the art will understand that this photographic paper possesses all the characteristics and advantages of the photographic paper base described above, and will not be elaborated upon further here.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0027] Figure 1 This is a schematic diagram of the structure of photographic paper base in one embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the photographic paper base in another embodiment of the present invention. Detailed Implementation

[0029] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0030] In one aspect of the invention, a photographic paper base is provided. According to an embodiment of the invention, referring to... Figure 1 The photographic paper base includes: a base paper layer 1 and a plastic layer 2, wherein the plastic layer 2 is disposed on at least one side of the base paper layer 1.

[0031] According to an embodiment of the present invention, the base paper layer 1 includes pure wood pulp, an antistatic agent, a hygroscopic agent, and an anti-seepage agent, wherein the antistatic agent includes a sodium salt and the hygroscopic agent includes a lithium salt.

[0032] In the base paper layer 1 of the photographic paper base of this invention, sodium salt is used as an antistatic agent. When the side of the plastic layer 2 away from the base paper layer 1 accumulates charge due to friction, the opposite charge accumulates on the side of the plastic layer 2 adjacent to the base paper layer 1. Since the base paper layer 1 usually contains 5wt%-8wt% moisture, after adding sodium salt to the base paper layer 1, the sodium salt will move freely in the base paper layer 1 in the form of ions. The free sodium salt in the base paper layer 1 will redistribute the charge, thereby avoiding static spots caused by charge accumulation and discharge, and effectively playing an antistatic role. At the same time, lithium salt is used as a hygroscopic agent. Lithium salt has relatively high moisture absorption properties. The strong water absorption of sodium and lithium salts, when used together, can effectively reduce the volume resistivity of the paper base, prevent the generation of electrostatic sparks, and maintain the moisture at the cut edges of the paper base under high temperature and low humidity environments, reducing the loss of moisture at the cut edges and thus avoiding the phenomenon of tight edges. On the other hand, sodium and lithium salts have strong solubility and do not interact with the base paper fibers. They can be quickly dissolved from the base paper layer 1 during the wet processing of photographic paper and do not participate in the interaction between the anti-smudging agent and the base paper fibers. Therefore, adding sodium and lithium salts to the base paper layer 1 will neither aggravate edge seepage nor affect the function of the anti-smudging agent.

[0033] As an example, in this invention, the sodium salt may include at least one of sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate; the lithium salt may include at least one of lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate; and the pure wood pulp may be at least one of hardwood pulp and softwood pulp.

[0034] In the base paper layer 1 of the photographic paper base of the present invention, the addition of an anti-sagging agent can effectively prevent edge bleeding at the cut edges of the paper base due to water absorption by the base paper fibers during wet processing. In some embodiments of the present invention, the anti-sagging agent may include RM-R', wherein R and R' each independently include a hydrocarbon group, and at least one of R and R' includes a hydrocarbon group with not less than 10 carbon atoms, and M includes at least one of lactone, acid anhydride, epoxy group and isocyanate. Using the above-mentioned anti-sagging agent, the long-chain hydrocarbon groups R and R' in its structure can be intertwined with the base paper fibers, and the reactive group M can react with the carboxyl groups in the base paper fibers, thereby effectively reducing the hydrophilicity of the base paper fibers, thereby achieving a better anti-sagging effect. As an example, in the present invention, the anti-sagging agent may include at least one of alkyl ketene dimer, olefinic amber, epoxy resin and polyurethane prepolymer.

[0035] Therefore, the photographic paper base of the present invention, using the above-described composition of the base paper layer 1, can effectively reduce the volume resistivity of the photographic paper base, avoid the generation of electrostatic sparks, and also prevent edge bleeding and edge bleed phenomena. In some embodiments of the present invention, by using the base paper layer 1 of the above-described composition to prepare the photographic paper base, the volume resistivity of the photographic paper base can be reduced to the range of 1E+07Ω·cm-1E+09Ω·cm.

[0036] In some embodiments of the present invention, the weight percentage of pure wood pulp in the base paper layer 1 can be 80-90, such as 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, etc.; the weight percentage of antistatic agent can be 0.01-5, such as 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.; and the weight percentage of hygroscopic agent... The weight percentage of the agent can be 0.01-3, such as 0.01, 0.05, 0.1, 0.4, 0.8, 1.2, 1.5, 1.8, 2, 2.4, 2.6, 2.8, 3, etc.; the weight percentage of the anti-bleeding agent can also be 0.01-3, such as 0.01, 0.05, 0.1, 0.4, 0.8, 1.2, 1.5, 1.8, 2, 2.4, 2.6, 2.8, 3, etc. Using the above-described composition of the base paper layer 1 can achieve better anti-bursting and anti-bleeding effects, and can further reduce the volume resistivity of the photographic base paper, avoiding the generation of electrostatic sparks.

[0037] In some embodiments of the present invention, the thickness of the base paper layer 1 can be 150μm-200μm, such as 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, 200μm, etc. The base paper layer 1 of the above thicknesses can give the photographic paper base a lower volume resistivity, resulting in better performance.

[0038] Furthermore, the density of the base paper layer 1 can be 0.95 g / cm³. 3 -1.05g / cm 3 For example, 0.95g / cm³ 3 0.96g / cm 3 0.97g / cm 3 0.98g / cm 3 1.02g / cm 3 10.4 g / cm 3 1.05g / cm 3 Therefore, this photographic paper base is less prone to edge bleeding and has better performance.

[0039] Furthermore, the smoothness of the base paper layer 1 can be between 90 and 110 seconds, for example, 90 seconds, 94 seconds, 98 seconds, 102 seconds, 106 seconds, 108 seconds, 110 seconds, etc. Therefore, this photographic paper base has good performance characteristics.

[0040] In some embodiments of the present invention, the plastic layer 2 is disposed on at least one side of the base paper layer 1. Therefore, by providing the plastic layer 2 on one side or both opposite sides of the base paper layer 1, it can achieve the functions of seepage prevention and waterproofing, protecting the paper base from being soaked by liquids and moisture. As an example, in the present invention, the plastic layer 2 may include at least one of HDPE (high-density polyethylene), LDPE (low-density polyethylene), and LLDPE (linear low-density polyethylene). The plastic layer 2 with the above-mentioned components can effectively achieve the functions of seepage prevention and waterproofing.

[0041] In some embodiments of the present invention, the thickness of the plastic layer 2 can be 15μm-35μm, for example, 15μm, 17μm, 20μm, 24μm, 28μm, 30μm, 33μm, 34μm, 35μm, etc. The plastic layer 2 described above can provide good seepage and water resistance, protecting the original paper layer 1 from being soaked by liquids and moisture. It can also prevent the photographic paper base from having excessive resistance, thus avoiding the generation of electrostatic sparks. It should be noted that the thickness of the plastic layer 2 mentioned here refers to the thickness of the plastic layer 2 on one side of the original paper layer 1.

[0042] In some embodiments of the present invention, reference is made to... Figure 2 The photographic paper base may further include an antistatic layer 3, which is disposed on the side of the plastic layer 2 away from the original paper layer 1. For example, the antistatic layer 3 may be provided as a single layer, i.e., the antistatic layer 3 is provided only on one side of the plastic layer 2, or two layers may be provided, i.e., the antistatic layer 3 is provided on one side of the plastic layer 2 on both sides of the original paper layer 1.

[0043] By setting an antistatic layer 3, the antistatic layer 3 works in conjunction with the antistatic agent and hygroscopic agent in the base paper layer 1 to quickly and effectively eliminate the charge accumulated in the photographic paper base during processing and unwinding. This further enhances the antistatic effect and prevents the photographic paper base from generating static sparks. Furthermore, the antistatic layer does not affect edge bleeding during wet processing.

[0044] As an example, in this invention, the antistatic layer 3 may include at least one of alkyl sulfonates, sulfates, betaine, sodium polystyrene sulfonate, and sodium polyethylene sulfonate.

[0045] In some embodiments of the present invention, the thickness of the antistatic layer 3 can be 0.1μm-1μm, such as 0.1μm, 0.3μm, 0.5μm, 0.7μm, 0.9μm, 1μm, etc. The antistatic layer 3 of the above thickness can provide excellent antistatic protection, thereby further preventing electrostatic sparks from being generated on the photographic paper substrate.

[0046] In another aspect, the present invention provides photographic paper. According to an embodiment of the invention, the photographic paper comprises the photographic paper base described above.

[0047] Therefore, the photographic paper of the present invention has a low volume resistivity, effectively avoiding the generation of electrostatic sparks, and is less prone to edge tightness and edge bleeding during wet processing. Those skilled in the art will understand that this photographic paper possesses all the characteristics and advantages of the photographic paper base described above, and will not be elaborated upon further here.

[0048] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0049] Example 1

[0050] In Example 1, the base paper layer contained 85 wt% broadleaf pulp, 1 wt% antistatic agent, 0.05 wt% hygroscopic agent, and 0.5 wt% anti-seepage agent, and the thickness of the base paper layer was 170 μm.

[0051] The front and back sides of the base paper layer are coated with PE film to form a plastic layer on both sides of the base paper layer, with each plastic layer having a thickness of 30μm.

[0052] Sodium polystyrene sulfonate antistatic liquid is coated on the side of one of the plastic layers away from the base paper layer, thereby forming an antistatic layer on one side of the plastic layer with a thickness of 0.1 μm.

[0053] The similarities between the photographic paper base in Examples 2-9 and Comparative Examples 1-4 and the photographic paper base in Example 1 will not be repeated here. The differences are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] The photographic paper bases from Examples 1-9 and Comparative Examples 1-4 were subjected to performance tests:

[0058] 1. Resistance test: The volume resistance was tested using a ZC36 high resistance meter at a temperature of 25℃ and a humidity of 40%RH.

[0059] 2. Edge bleeding test: Immerse the paper base in a developer solution (pH 11-12) at 38.5℃ for 15 minutes. Remove the paper and use a magnifying glass with a scale to measure the distance the developer has penetrated. The distance at which the developer has penetrated is recorded as the test result; a distance ≤3mm is considered no edge bleeding. (The developer solution used in the edge bleeding test is commercially available and includes sulfuric acid, nitric acid, benzene, methanol, silver halide, boric acid, hydroquinone, etc.)

[0060] 3. Tight edge test: At a temperature of 25℃ and a humidity of 40%RH, take a 1.5m piece of paper along the longitudinal axis of the paper base and place it naturally on the test table. Gently press one side against a flat wall and measure the distance between the paper edge and the wall. Take the average of the three points with the largest distance as the measurement result. If the distance is ≤0.5cm, it is judged as no tight edge.

[0061] The performance test results of the photographic paper base in Examples 1-9 and Comparative Examples 1-4 are shown in Table 2.

[0062] Table 2

[0063]

[0064] As can be seen from the test results in Table 2, in Examples 1-9, the synergistic effect of the antistatic agent, hygroscopic agent, and anti-bleeding agent resulted in a low volume resistivity of the photographic paper base, exhibiting excellent antistatic effects, while preventing edge bleeding and tight edge phenomena. Notably, the photographic paper base in Example 5 lacked an antistatic layer. Compared to Examples 1-4 and 6-9, the volume resistivity of the photographic paper base in Example 5 was relatively high, indicating that adding an antistatic layer could further reduce the volume resistivity of the photographic paper base and improve the antistatic effect.

[0065] As can be seen from the tight edge test results in Table 2, compared with Comparative Examples 1, 2 and 4, Examples 1-9 and Comparative Example 3 effectively avoided the tight edge phenomenon of the photographic paper base through the synergistic effect of sodium salt and lithium salt.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A photographic paper base, characterized in that, It includes a base paper layer and a plastic layer, wherein the plastic layer is disposed on both sides of the base paper layer; The base paper layer includes: 80-90 parts by weight of pure wood pulp; 0.01-5 parts by weight of antistatic agent; 0.01-3 parts by weight of desiccant; 0.01-3 parts by weight of anti-seepage agent; The antistatic agent includes sodium salt, and the hygroscopic agent includes lithium salt; The sodium salt includes at least one of sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate; The lithium salt includes at least one of lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate; The anti-seepage agent comprises RM-R', wherein R and R' each independently comprise a hydrocarbon group, at least one of R and R' comprises a hydrocarbon group with not less than 10 carbon atoms, and M comprises at least one of lactone, acid anhydride, epoxy group and isocyanate.

2. The photographic paper base according to claim 1, characterized in that, The anti-seepage agent includes at least one of alkyl ketene dimers, olefinic amber, epoxy resin, and polyurethane prepolymer.

3. The photographic paper base according to claim 1, characterized in that, The thickness of the base paper layer is 150μm-200μm; Optionally, the tightness of the base paper layer is 0.95 g / cm 3 - 1.05 g / cm 3 ; Optionally, the smoothness of the base paper layer is 90-110 seconds.

4. The photographic paper base according to claim 1, characterized in that, The plastic layer includes at least one of HDPE, LDPE and LLDPE; Optionally, the thickness of the plastic layer is 15μm-35μm.

5. The photographic paper base according to claim 1, characterized in that, It also includes an antistatic layer, which is disposed on the side of the plastic layer away from the base paper layer.

6. The photographic paper base according to claim 5, characterized in that, The antistatic layer comprises at least one of alkyl sulfonates, sulfates, betaine, sodium polystyrene sulfonate, and sodium polyethylene sulfonate; Optionally, the thickness of the antistatic layer is 0.1 μm-1 μm.

7. A photographic paper, characterized in that, The photographic paper base includes any one of claims 1-6.

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